Radio Broadcast - 1927, May - 61 Pages, 4.9 MB ... - VacuumTubeEra

RADIO BROADCASTVOLUME XIMAY, 1927, to OCTOBER, 1927GARDEN CITY NEW YORKDOUBLEDAY, PAGE & COMPANY1927

INDEX("Illustrated Articles.Editorials in Italics)PAGE*A B, C Device, A lamp Socket (Gilrl,bert Edgar) 153*A, B, C Power-Supply Unit for 201-AType Tubes, An (Roland F. Beers) . . 155*A Battery? What About the (Edgar H.Felix) 26Advertising Over the Air from Corsets toCalliopes, Direct 81*A. C. Filament Supply, Problems of(Roland F. Beers) 101*A. C. Mains, Filament Lighting fromthe (Roland F. Beers) 33*A. C. Operation, Receiver Design for(Howard E. Rhodes) 157*A. C. Set, Your (Edgar H. Felix) 374"A. C. Supply" Units, A New Termfor 19*A. C. Vacuum Tubes, Three-Element(B. F. Miessner) 302*Amplification, Use of Tubes HavingHigh (A. V. Loughren) 238,* Analyzing the Power Amplifier (D. E.Harnett)Ill* Antenna, How to Design a Loop(Homer S. Davis) 104*As the Broadcaster Sees It (Carl Dreher)36, 106, 167, 235, 293, 376Aurora and Fading, The (Austin G.Cooley) 135Australia, Radio Control Unsettled in ... 141*r> SOCKET power Device, Perfecting-D the (Howard E. Rhodes)*Balanced Short-Wave Receiver, A43(Frank C. Jones) 24*Balsa Wood Loud Speaker, The (TheLaboratory Staff) 211*Battery Charger, A Low-Cost (JamesMillen) 143Book Reviews:Practical Radio Constructionand Repairing, by Moyer andWpstrel (Edgar H. Felix) ... 416Radio Encyclopedia, The, by S.Gernsback (Edgar H. Felix) 110Theory of Vibrating Systemsand Sound, by Irving B.Crandall (Carl Dreher) 110Using Radio in Sales Promolion,by Edgar H. Felix (CarlDreher) 369Broadcasters in New York Organise 268Broadcasting Situation, Stabilizing the 79. .*Building an Electrical Phonograph(James Millen) 86*Building the Laboratory "Super"(Ernest R. Pfaff) 280CANADIAN Demand for More Wave-Ls lengths? What About the 80"Canned" Programs Good and Bad 206*Causes of Poor Tone Quality (EdgarH.Felix) 296*Charger, A Low-Cost Battery (JamesMillen) 143" Christian " Mud Throwing 18*Coil Design, Some Facts About (RossGunn) 40Combined Push-Pull Power AmplifierPAGEand Socket B Device, A (The LaboratoryStaff) 163Commission Regulates Broadcasting forthe Broadcasters Not the Listener, The 204*Condenser, Coil, Antenna Measurements(Keith Henney) 227Conditions for Long-Distance ReceivingDo Vary*Cone, How to Build a 36-Inch (Warren81T. Mithoff) 148*Constructing a Five-Tube Neutrodyne(Howard E. Rhodes) 232*Constructing Transformers and Chokesfor Power Supply Devices, Home(Homer S. Davis) 274, 379*Crvstals, Piezo-Electric (M. ThorntonDow) 271T\ANGER of Direct Advertising on theLJ Air, The 346Davis Resigns, Judge 269*Description of a Short-Wave Station(C. R. Runyon, Jr.) 171Direct Advertising Over the Air fromCorsets to Calliopes 81Directory of Manufactured Receivers,"Radio Broadcast's" 316, 402Discovering Ore Deposits by Radio 267*Discovery That Newton Missed, A(James Stokley) 263DX Listening, What Commissioner BellowsThinks About 205*T^LECTRICAL Phpnograph, Build-ing an (James Millen)*Electrical Phonograph, The (James86Millen) 20*"Equamatic" Receiver, The 1928 (JulianKay) 364*Equipment for the Home Constructor(The Laboratory Staff) 58, 120, 182T^ILAMENT Lighting from the A. C.C Main (Roland F. Beers) 33*Filament Supply, Problems of A. C.(Roland F. Beers) 101*Five-Tubs Neutrodyne, Constructing a(Howard E. Rhodes) 232*Five-Tube Receiver, A Super-SensitiveShielded (Herbert J. Reich) 229*Flexible Short-Wave Transmitter, A(Howard E. Rhodes) 213Freedom of Speech Impossible, Radio . . . 138Frequent Misuse of the Word "Broadcasting,"The 141"TTAVEYouReflex?(John B. Brennan) ............*"Hi-Q" Has an Extra R. F. Stage, The(John B. Brennan) ................*Home Constructing Transformers andChokes for Power Supply Devices(Homer S. Davis) ............... 274, 379*Home Constructor, Equipment for the(The Laboratory Staff) ....... 58, 120, 182*Home Laboratory, An Instrument forthe (Keith Henney) ............... 92*How to Build a 36-Inch Cone (WarrenT. Mithoff) ...................... 148*How to Design a(Homer S. . .Davis)LoopPAGEAntenna104*INSTRUMENT for the Home Lab-1 oratory, An (Keith Henney) 92Interference, Suppressing Radio (A. T.Lawton) 299International Short-Wave Test 60/T UDGE DA JudgingVIS ResignsTone Quality (Edgar H.269Felix) 224to Recent Radio Articles, AKEY(E. G. Shalkhauser)60, 126, 255, 326, 398Kit Shall I Buy? What125, 190, 254, 324, 396"TABORATORY Information Sheets,1^, "Radio Broadcast's:"A Battery Chargers 246Analysis of Voice Frequencies. 56Audio Amplifiers 246Audio Amplifying Systems. .54, 116Audio Transformers 119. 390B Power Units 312Care of Power Supply Units .Carrier Telephony 392Characteristics of the 171 TypeTube 310Circuit Diagram of the "Universal" Receiver 118Closely Coupled Circuits 392Condenser Reactance 312Condenser Reactance Table. .. 312Curves of the 171 Type Tube. 310Data on Honeycomb Coils. . . . 388Data on the "Universal" Receiver118Dry-Cell Tubes 180Efficiency of Amplifying Systems119Hertz Antenna, The 308High Voltage Supply for 210Type Tube 178Index 180Lightning Arresters 118Loop Antennas 52Loud Speaker Horns 392Measuring R. F. Resistance ofa Coil... 176Methods of Generating High-Frequency Energy 116Morse Code, The 310Neutralization 178Periodical Output Circuits 242208Principles of Reflexing, The. . . 56Radio-Frequency Choke Coils. 216348Resistance-Coupled Amplifier. 390Resistance-Coupled AmplifierCircuit 330Short-Wave Coils 52Simple Tube Tester, A 54Socket Power Units 119Static 244Storage Batteries 56Super-Heterodynes 244Testing Radio Receivers 308MA 26 '

INDEX.ContinuedPAGEThreshold of Hearing and Feelingin the Ear, The 178Transmission Unit. The 242Type 874 Glow Tube, The. ... 388Ux-240 Type Tube, The 176Wave Traps 244'Laboratory, "Strays" from the146, 222, 284'Laboratory "Super," Building the(Ernest R. Pfaff) 280*Lamp Socket A, B, C Device, A (GilbertEdgar) 153Latest Television Developments 81Law, A Profound Study of Radio 345"Light Socket, Servants of Your 356Listeners' Organizations? Where are the141, 269'Listeners' Point of View, The (JohnWallace) 29, 97, 159, 218, 286, 372Listeners, Why We Need More 206Listening to World-Wide Broadcasting isNear 345Long- Distance Receiving Do Vary, Conditionsfor 81'Long-Wave Receiver, A Portable(Keith Henney) 165'Loop Antenna, How to Design a(Homer S. Davis) 104'Loud Speaker, The Balsa Wood (TheLaboratory Staff) 211'Loud Speakers, 1928 370'Low-Cost Battery Charger, A (JamesMillen) 143Radio Installations Safe(Edgar H. Felix) 410MAKINGManufacturers' Booklets Available61, 123, 186, 248, 314, 394'Manufactured Receivers for the ComingSsason 351Manufactured Receivers, "RadioBroadcast's" Directory of.. ..250, 316, 402'March of Radio, The15, 78, 138, 203, 266, 344'Measurements, Condenser, Coil, Antenna(Keith Henney) 227'Methods of Measuring Tube Characteristics(Keith Henney) 46Methods Which Fail to Materialize, Revolutionary203Modern Radio Receivers Are a Good Investment344Month in Radio, The19, 82, 142, 206, 269, 346Mud Throwing, "Christian" 18'\TEUTRODYNE, Constructinga1M Five-Tube (Howard E. . .Rhodes) 232'Neutrodyne Group, The 354Never Again Without Radio ! 206'New Offerings for the 1928 Season,Ssme 360'New Principle of R. F. Tuning, A(David Grimes) 367'New Receiver Offerings for the Fall(The Laboratory Staff) 298'New Regulator Tube, A (James Millen) 363New Term for "A. C. Supfly" Units, A 19'1928 "Equamatic" Receiver, The(Julian Kay) 364'1928 " Hi-Q " Has an Extra R. F. Stage,The (John B. Brennan) 348'1928 Loud Speakers 370'1928 Radio Receivers of Beauty andUtility 352'Now You Can Receive Radio Pictures(Keith Henney) 341/ABJECTIONS.to the Radio Law 17DATENT Licensing Points to a Bright-i Radio Future 79Patent Tangle, Unsnarling the 206'Perfecting the B Socket Power Device(Howard E. Rhodes) 43'Phonograph, Building an Electrical(James Millen) 86'Phonograph, The Electrical (JamesMillen) 20'Pictures by Radio 279PAGE'Pictures, Now You Can ReceiveRadio (Keith Henney) 341'Piezo-Elcctric Crystals (M. ThorntonDow) 271Please for a Blue Radio Sunday 80'Poor Tone Quality, Causes of (EdgarH.Felix) 296'Portable Long-Wave Receiver, A(Keith Henney) 165'Problems of A. C. Filament Supply(Roland F. Beers) 101Profound Study of Radio Law, A 345Programs, Good and Bad "Canned" . . . . 206Prosperous Radio Year Forecast, A 267'Push-Pull Power Amplifier and SocketB Device, A Combined (The LaboratoryStaff) 163'/DUALITY, Causes of Poor ToneVJ (Edgar H. Felix) 296Question of Vested Rights, The. ... 17Broadcast's" Directory ofManufactured Receivers . . .250, 316, 402RADIO'"Radio Broadcast's" Laboratory InformationSheets (See Laboratory)52, 116. 176, 242. 308. 388Radio Commission Is Accomplishing,What the 138Radio Control Unsettled in A.ustralia. . . . 14119Radio Engineers. There Are NoRadio Freedom of*R. F. Tuning,Speech Impossible.A New Principle. .of. 138(David Grimes) 367'Radio Interference, Suppressing (A. T.Lawton) 299Radio Installations Safe, Making(Edgar H. Felix) 410Radio Law, Objections to the 17Radio Needs No Yearly Models 266'Radio Pictures, Now You Can Receive(Keith Henney) 341Radio Receivers Are a Good Investment,Modern 344'Radio Receivers of Beauty and Utility,1928 352Radio Reception Is No Longer Seasonal. . 141'Radio Waves in Transit? What Do WeKnow About (R. W. King) 75'Radiolas for 1928 358Recent Radio Articles, A Key to (E. G.Shalkhauser^ 60. 126, 255, 326, 398'Receiver Design for A. C. Operation(Howard E. Rhodes) 157Receiver Offerings for the Fall, New(The Laboratory Staff) 298'Receivers for the Coming Season, Manufactured351'Regulator Tube, A New (James Millen) 363Revolutionary Methods Which Fail toMaterialize 203'Roberts Reflex? Have You a (John B.Brennan) 208*0 ALESMEN, We Need Better RadioO (Carl Dreher) 283'Servants of Your Light Socket 356'Shielding? Why (Edgar H. Felix) 83'Short-Wave Receiver, A Balanced(Frank C. Jones) 24'Short-Wave Station, Description of a(C. R. Runyon, Jr.) 171Short-Wave Test, International 60'Short-Wave Transmitter, A Flexible(Howard E. Rhodes) 213'Short Waves? Why Not Try the (KeithHenney) 290'Should the Small Station Exist? (JohnWallace) 372'Single Control, Something About(Edgar H. Felix) 151'Socket Power Device, Perfecting the B(Howard E. Rhodes) 43'Some Facts About Coil Design (RossGunn) 40'Some New Offerings for the 1928 Season360Stabilizing the Broadcasting Situation. . . 79Standards, Unnecessary Duplication ofRadio 140PAGEStations Shall Be Eliminated? What .... 139'"Strays" from the Laboratory.146, 222, 284'"Super," Building the Laboratory(Ernest R. Pfaff) 280'Super-Sensitive Shielded Five-TubeReceiver, A (Herbert J. Reich) 229'Suppressing Radio Interference (A. T.Lawton) 299Survey of Radio Conditions, A 19TELEVISIONDevelopments, Latest. 81-There Are No Radio Engineers .... 19'Three-Element A. C. Vacuum Tubes(B. F. Miessner) 302'Tone Quality, Causes of Poor (EdgarH.Felix) 296'Tone Quality, Judging (Edgar H .Felix) 224'Transformers and Chokes for PowerSupply Devices, Home Constructing(Homer S. Davis) 274, 379'Tube Characteristics, Methods ofMeasuring (Keith Henney) 46'Tubes Having High Amplification, Useof (A. V. Loughren) 238'Tuning, A New Principle of R. F.(David Grimes) 367T TNNECESSARYUDuplications ofRadio Standards 140Unsnarling the Patent Tangle 206'Use of Tubes Having High Amplification(A. V. Loughren) 238*\ 7ACUUM Tubes, Three-Element A.V C. (B. F. Miessner) 302Vested Rights, The Question of 17'TXTE NEED Better Radio SalesmenVV (Carl Dreher) 283'What About the A Battery? (Edgar H.Felix) 26What About theCanadian Demand forMore Wavelengths? 80What Commissioner Bellows ThinksAbout DX Listening 205'What Do We Know About RadioWaves in Transit? (R. W. King) .... 75What Does the Listener Want? Let HimSpeak 15What Kit Shall I Buy?125, 190, 254, 324, 396What Stations Shall Be Eliminated? .... 139What the Radio Commission Is Accomplishing138Where Are the Listeners' Organizations? 141Where Are the Listeners' Organizations?. 269Why Important Events Can't Always BeBroadcast 141'Why Not Try the Short Waves? (KeithHenney) 290Why Radio Home Construction Continuesto be Fascinating 78'Why Shielding? (Edgar H. Felix) 83Why We Need More Listeners 206Which Stations Shall Broadcast? 16Will Telephotography Be the Experimenters'Next Field? 266Wisely Chosen Radio Commissioners, The 80'With Macmillan to the ArcticG. Cooley)(AustinHWorld-Wide Broadcasting is Near, Listeningto 345AUTHORSBeers, Roland F 33, 155Brennan, John B 208. 348Cooley, Austin G 11, 135Davis, Homer S 104. 274, 379Dow, M. Thornton 271Dreher, Carl36, 106, 167, 232, 283. 293. 369. 376Edgar, Gilbert 153Felix, Edgar H.26, 83, 151, 224, 296, 374, 410, 414

INDEXContinuedPAGEGrimes, DavidPAGE367PORTRAITSHeerman, Emil 288Wallace, John . . 29, 97, 159, 218, 286, 372 . .Gunn, Ross 40(*Portraits in "The March of Radio")Harriett, D. E.. . . IllAhkla, Trixie 373Henney, Keith 46, 92, 165, 227, 290, 341Atkinson, Eva Gruninger 30Jones, Frank C 24 *Baker, L. S 142Blackford, Frank 30Kay, JulianKing, R. W364Blight, Arthur 3075Bushman, Annette R 287Lawton, A. TLoughren, A. VCoates, D. R. P 289299 "Cohen, Louis 269238 Combs, R. H 30Cook, Lucile 288Miessner, B. F 302 Cook, Nell 288Millen, James 20, 86, 143, 199, 363 *Crandall, Irving Bardshar 141Mithoff, Warren T 148 Crosley, Powel 288Pfaff, Ernest R 280Damonte, Jerome 160 .Dobbs, Hugh Barrett 218Dozier, Lydia 288Reich, Herbert J... 229Rhodes, Howard E 43, 157, 213, 232 *Edwards, C. P... 142Runyon, C. R. Jr 171 Edwards, C. P 346Shalkhauser, E. G 60, 126, 255, 326, 398Grimes, David 367Stokley, James 263Harper, Clair.. 289*Hartley, Herbert 268Hogan, Park VPAGE221Holub, Josephine 30Katzman, Louis 99King, Mildred '. 160La Pee, Honarine""Lindbergh, Charles . . .30344McKee, Mickey 219McLeod, Keith 30Mallory, Walter. 221*Manley, Edward 347*Manson, Ray H.'. 82Olson, Vivian 289Pearson, James 30Pellettieri, Vito 160Rianhard, Conrad 29*Rice, Martin P 344Shannon, Marguerite 289*Shinn, B. L 18*Shumaker, Edward E 19Stockman, Edward 160*Waller, Alfred E... 207Watt, Lillian 160Weagant, Roy A 237Wessell, Isaac 286White, Lee 289Copyright, 1927, byDOUBLEDAY, PAGE & COMPANY

RADIO BROADCAST ADVERTISERALUMINUMBOX SHIELDSMade of "Alcoa Aluminum'Consist of:Top, Bottom, Sides4 Extruded Corner Posts8 Aluminum ScrewsEETING the highest radio standards shipped toyou in the most convenient knocked-down formfor easy assembly These Box Shields are madeof heavy aluminum (.080" No. 12 B. & S.) and are supplied5"x9" x6", which will cover most requirements. Ifthe size does not meet your exact needs, change it Aluminumis easy to work.CT'HE ordinary typeof low resistance volt'J. meter cannot be used to measure the out'put of battery eliminators because mosteliminators cannot deliver sufficient cur'rent to operate the voltmeter and stillmaintain their voltage. For this serviceWeston now offers a special voltmeterwith an exceptionally high self-con'tained resistance of 1,000 ohms pervolt Model 489 Battery EliminatorVoltmeter. This new instrument,because of its high resistance, re'quires a current of only one milli'ampere to produce full scale de'flection. It is made in twodouble range combinations of200/8 and 250/50 volts. Thelatter range can be suppliedwith an external multiplierto increase it to 500 volts.Ask your dealer or ad'dressManufacturers can obtain these shields made to their exactspecifications or they can secure the necessary corner-postmoulding and sheet to manufacture under their own supervision.Those who use Aluminum have ample proof of its advantages.Insist on "Alcoa Aluminum," ask your dealer orwrite us."ALCOA ALUMINUM" is furnished to manufacturersin the following forms:ALUMINUM INSheet: for shields, chassis, variable condensers,cabinets.Panels finished in walnut and mahogany.Die and Sand Castings.Screw Machine Products.Foil for fixed condensers.High Purity Rods for rectifiers.Stamping, rod, wire, rivets.EVERY COMMERCIAL FORMALUMINUM COMPANY of AMERICA2320 OLIVER BUILDING, PITTSBURGH, PA.ALUMINUM ItWESTON ELECTRICALINSTRUMENT CORPORATION179 Weston Avenue, Newark, N. J.STANDARD THE WORLD OVERWESTONPioneers since 1888

RADIO BROADCASTMAY, 1927WILLIS K. WING, EditorKEITH HENNEYJOHN B. BRENNANDirector of the LaboratoryTechnical EditorEDGAR H. FELIX, Contributing EditorVol. XI, No. 1AMOA[G OTHER THINGS...Cover DesignFrontispieceFrom a Painting by Fred }. EdgarsThe Towers of Station WOW, at Omaha, NebraskaWith MacMillan to the Arctic-The March of Radio -What Does the Listener U'ant? Let Him SpeakQuestionnaire: Which Stations Shall Btoad'cast?Objections to the Radio LawThe Question of Vested RightsThe Electrical PhonographA Balanced Short-Wave ReceiverWhat About the A Battery?The Listeners' Point of ViewHow Long Will Radio Broadcasting Prosper?Why a Good Program Was GoodThumb Nail ReviewsFilament Lighting from the A. C. MainsAs the Broadcaster Sees ItOne Explanation of the Plethora of BroadcastingStationsBroadcasting and Social UpheavalsGlad Tidings From the WestAustin G. Cooley"Christian" Mud ThrowingA New Term for "A. C. Supply" UnitsThere Are no Radio EngineersA Survey of Radio ConditionsThe Month in Radio--James MillenFran\ C. JonesEdgar H. FelixJohn WallaceMicrophone MiscellanyCommunicationsWhat the Listener Likes and How He Likes ItSome Facts About Coil Design - The Radio Club of AmericaRoland F. BzersCarl DreherTechnical Operation of Broadcasting Stations(Volume Indicators)Something About Gain ControlRoss GunnPerfecting the B Socket Power Device -Howard E. RhodesMethods of Measuring Tube Characteristics- -Keith Henney"Radio Broadcast's" Laboratory Information SheetsNo. 89 Short-Wave CoilsNo. 93 Audio Amplifying SystemsNo. 97 Circuit Diagram of Tube Tester No. 96 Analysis of Voice FrequenciesNo. oo Loop AntennasNo. 94 The Principle of Re6exingNo. 91 A Simple Tube TesterNo. 95 Storage BatteriesEquipment for the Home ConstructorA Key to Recent Radio ArticlesInternational Short-Wave Test- -10nAn Editorial Interpretation 1526293336404346E. G. Shall{hauser 60Manufacturers' Booklets Available - - 6160V\ T^TH this issue, RADIO BROADCAST starts its sixth year of* *publication. The five years just concluded have seenmany changes in the radio industry and among radio experimentersand fans. American radio magazines of to-day are quitedifferent from those of 1922; RADIO BROADCAST has changedconsiderably, both in physical appearance and in type of contents,since those days. We believe the changes are improvements,for certainly our files are filled with countless letters ofapproval. The aim of Doubleday, Page 6? Company has been topublish the highest class radio magazine possible. This we haveattempted to do, first, in setting the standard of physical appearanceof the magazine where now it is, and secondly, tospare no pains or expense in making our technical material ascompletely accurate and helpful as possible. Two large laboratoriesare maintained in Garden City where practical andtheoretical experiments are constantly under way; and our advertisingpages are carefully supervised."\ X"ANY editorial features in RADIO BROADCAST have given-" -1 the magazine a unique position in its field. The "Marchof Radio" provides an editorial comment and suggestion aboutall branches of radio. "The Listeners' Point of View" standsalone as a national review of broadcasting, particular andgeneral. "As the Broadcaster Sees It" has turned out to be aunique department (prepared, incidentally, by one of the ablestbroadcast engineers in the country) where engineer, programdirector, listener, and general reader alike, may meet. The reviewof current radio periodicals, the Laboratory Data Sheets,the listing of informative manufacturers' booklets, all furnishvaluable information for our readers. Our constructional articlesare chosen carefully for accuracy and greatest help and interestfor the reader. We are at work on an editorial schedule nowwhich holds much for everyone interested in radio in all itsbranches. Unfortunately there is insufficient space here tooutline that schedule, but we prefer to let each issue of RADIOBROADCAST speak for itself in that connection.in its tabulation of advertising lineage1 for March magazines, shows that RADIO BROADCAST ledthe field with a total of 20,621 lines, followed by Radio Newswith 18,930 lines, Popular Radio with 14,872, Radio with12,770, and Radio Age with 4395.IN THE June RADIO BROADCAST, a fine story for the homeexperimenter is scheduled, describing the construction anduse of a modulated oscillator. Other articles deal with shortwaves, the problems of series filament connection for 2OI-A typetubes, how to use new apparatus, technical problems for broadcastoperators and others, and many other features of unusualinterest.WILLIS K.WING.Doubleday, Pagefir Co.MAGAZINESCOUNTRY LIFEWORLD'S WORKGARDEN & HOME BUILDERRADIO BROADCASTSHORT STORIESEDUCATIONAL REVIEWLE PETIT JOURNALEL EcoFRONTIER STORIESWESTDoubleday, Page fir Co.BOOK SHOPS(Books of all Publishes)LORD & TAYLORNEW YORKPENNSYLVANIA TERMINAL (2 Shops)GRAND CENTRAL TERMINAL38 WALL ST. and 520 LEXINGTON AVE.848 MADISON AVE. and 166 WEST 32ND ST.ST Louis: 223 N. STH ST. and 4914 MARYLAND AVE.KANSAS CITY: 920 GRAND AVE. ana 206 W. 47TH ST.CLEVELAND: HIGBEE CoSPRINGFIELD, MASS.: MEEKINS, PACKARD & WHEATDoubleday, Page & Co.OFFICESGARDEN CITY, N. Y.NEW YORK: 285 MADISON AVE.BOSTON: PARK SQUARE BUILDINGCHICAGO: PEOPLES GAS BUILDINGSANTA BARBARA, CAL.LONDON: WM. HEINEMANN LTD.TORONTO: OXFORD UNIVERSITY PRESSDoubleday, Page 5* Co.OFFICERSF. N. DOUBLEDAY, PresidentNELSON DOUBLEDAY, ^ice-PresidentS. A. EVERITT, V'ice -PresidentRUSSELL DOUBLEDAY, SecretaryJOHN J. HESSIAN, TreasurerL. A. COMSTOCK, Assl. SecretaryL. J. McNAUGHTON, Asst. TreasurerDOUBLEDAT, 'PAGE & COMPACT, Garden &ty,Copyright, 2927, in the United Statei, Newfoundland, Great Britain, Canada, and other countries by Doubleday, PageTERMS: $4.00 a year; single copies 35 cents.Company. All rights reserved.

RADIO BROADCAST ADVERTISERfIA REALABUSE TEST; .sO many peopleruntheir batteries up too highthat, having made goodRadiotrons for carefulusers, RCA set about tomake Radiotrons thatwould stand abuse.A year ago, an RCARadiotron could standabout twenty hours ofrunning under too heavya current. Now it willoutlive a hundred hoursof such abuse.!Many very minutechanges brought aboutthrough laboratory studyhave effected this improvement.Ifyou have children whoare aptto turn up therheostats carelessly, ofcourse it is hard on thetubes. No tubes can beproof against ruin, but ifyou are usingRCA Raknow atdiotrons, youleast that they'll standmore than ordinary tubes.Look for that RCA mark!You'll find iton Radiotronsfor every purpose.RADIO CORPORATIONOF AMERICANew YorkChicagoSan FrinciscoThe stations are thereget them !You're not gettingthe most out of that storage batteryset of yours. The set has a bigger distance reach... all it needs is a different tube in the detectorsocket. Put in the RCA super-detectorRadiotronUX-200-A. You'll get more stations getthe farawayones more regularly and more easily!small change, but itbrings big results.Bring your storage battery set up-to-date -withapower RADIOTRON ux-171 or ux-112a detector RADIOTRON ux-200-Aand RADIOTRONS ux-201-A for all-round quality.Bring your dry battery set up-to-date witha power RADIOTRON ux-120and RADIOTRONS ux-199 for all-round quality.It's aRCA-RadiotronMADE BY THE MAKERS O F T H E RADii ||1O L*

a1*90"> ^^i 3131 111311"^ ^ *" 1- ,TOWERS OF STATION WOW, oAT OMAHA, ^EBRASKAFormerly known as WOAW, this station has enjoyed a -wide national popularity. In April,thisstation celebrates its fourth anniversary. The illustration shows the hoisting of a large sectionofplate glass, which now forms the front of a unique studio atop this 19-story building.The studioisarranged as a stage, properly insulated against sound inside, but with a front panel of glassto allow those seated in a small auditorium to watch and to hear the broadcasting as it occurs

:RADIO BROADCASTVOLUME XI NUMBER 1MAY, 1927With MacMillan to the ArcticTales from the Pen of the Sachem's Radio OperatorNot so Stupid, These EskimoFlappers Some Notes on the Aurora, Mirages, and Radio Abe Puts One Over.'BAKING up the threadsof our storyfrom where we dropped them lastmonth, we on the Sacbcm and ourfriends on the Bowdoin find ourselvesat Godhaven, Disko Island, thenorthernmost port of call of the expedition.Let us deviate a little, though, to tellof the inhabitants of these arctic regions, foran account of an expedition into the landof the Eskimos is not complete withoutsome mention of these most interestingpeople. Although the full-blooded Eskimosare few and far between, their habits andmethods of living are preserved by thosewho possess considerable Danish blood.They are all wards of the Danish Governmentand are well cared for, and everyeffort is made to preserve their native customsand practices.The Eskimo flappers are not sostupid; in fact, they have many ofthe same instincts that are commonamong the American beauties. In thematter of short skirts, they are yearsahead of the best of our stenographers.The complete absence of skirtsis due in a large measure to the Danishrulings that prevent them fromchanging from their native customof sealskin pants and boots. Theytake great pride in making theirboots the most attractive in thesettlement. Generally they are dyedwith a brilliant white or bright red.The girls all make large bead collarsfor themselves of their own design,with beads imported from Denmark.Ordinarily it is very difficult to obtainthese collars but this year afew were purchased for thirty kronerMany of the girls,(Danish money).ifthey have considerable Danishblood in them, are quite pretty;otherwise they look too much likeEskimos.By AUSTIN G.COOLEYA few of the Eskimos live in small framehouses or shacks while the others have theirhomes built of sod. These houses, or igloos,are built very scientifically with a selectedsod that is a good heat insulator. The wallsare built very thick and the doors all havetunnel approaches built of sod, entering atan angle to the door. Each igloo has a bedconsisting of a raised platform large enoughto accommodate the entire family. TheGreenland Eskimos, and the igloos thatwe saw, were very clean.Many of the expedition found itgreatsport trading with the Eskimos for souvenirs,such as harpoons, bird spears, modelkyaks, etc. In Sukkertoppen, Mrs. Metcalfwanted to get a model of a woman's skinboat. She asked some of the Eskimos intheir language if they had any "coumiaks."CAPTAIN "MAC" AND ABEThe latter was the Eskimo interpreter of the Expedition. Hereturned with the others to America when the Sachem andBowdoin came back and, among many other things, saw atrain for the first time in his lifeConsiderable laughter among the Eskimosimmediately resulted. Abe Bromfield, CommanderMacMillan's interpreter, had tocome to her assistance. It was an "umiak"she wanted. "Coumiak" is the Eskimoword for "lice"!For exchange, the Eskimos generallywanted tobacco and calico, although someasked for kroner which could be used atthe stores run in the large settlementsby the Danish government. The Danishmoney used in Greenland bears pictures ofanimals, such as polar bears, whales, seals,and ducks, so that the value may be recognizedby the Eskimos.During certain seasons, the Eskimoswork in fisheries operated by the Government,and at other times they are busysealing and hunting. The womens' workincludes the chewing of seal skinsso as to soften them, and the makingof boots and clothing.Anyone espied walking ashore witha camera was sure to have a largefollowing, for the Eskimo girls are asanxious to have their pictures takenas are some American girls to appearin the movies. When preparing for ashore trip with the cameras, I alwaysconsidered a supply of gum and cigarettesas important as the films.After taking pictures, these wouldbe passed around to the eager natives,who were especially anxiousfor cigarettes; even the babies intheirmother's arms made manifesta desire to smoke. They seemed toenjoy smoking as much as theirgrandmothers.The Eskimo's Santa Claus is moreof a fact than a myth. His phaseangle displacement is 80 1 degreesfrom ours! He comes from thesouth in the summer time in a whiteschooner, and brings toys and candyfor the bad little boys and girls as

12 RADIO BROADCAST MAY, 1927well as the good ones. He is known to them faded out completely at times. While goingas "Captain Mac." Captain Mac's own across to Baffin Land it was hardly possiblegenerosity is always backed up by various to get through any amount of traffic tocandy manufacturers who see that the expeditiondoes not leave American shores Radio i AAY (Kenneth M. Gold, Holyoke,the States because of complete fading.without a plentiful supply of all kinds of Massachusetts) was worked a couple ofcandy for the natives. The toys distributed times but it was only possible to get oneby Captain Mac are generally of the nickel complete message of about fifty wordsand dime variety, but some of the most from him. Other stations were worked butdeserving Eskimo men receive presents communications only lasted a few minutesof excellent jack knives.before they faded out completely.Some of the unfortunate Eskimos receivepresents of lemons and a pleasant publicity as being a "blind spot" becauseDavis Straits had received considerablevisit by the expedition's doctor Doctor it so happened that short-wave radio communicationcould not be established fromThomas of Chicago. Doctor Thomas treateda number of cases among the Labrador this location on the previous year. On theEskimos and in one instance performed an recent outward trip, Paul J. McGee, theoperation.operator at WNP, the Bowdoin, succeededAt practically all of the settlements at in transmitting to the States a 2OO-wordwhich we stopped, Captain Mac put on message when going north through themovie shows for the natives. The attendancewas always one hundred per cent. the signals from the States were comingStraits. At the same time I observed that"Robbie," the mate of the Bowdoin, was through with good intensity. Why the conditionson our return trip were so poorskilled in packing whole settlements intoa small room so as to give each Eskimo a seemed to have some connection with thegood view of the screen.aurora because strong displays of thenorthernWE lights were visible as we leftSTART OUR TRIP HOMESukkertoppen/COMMANDER at 2 A.M. on Friday, AugustMacMillan planned the thirteenth.^-" on running south from Godhaven, On the return trip, both McGee and IGreenland, to Holsteinborg, then across seemed to have considerable trouble withto Baffin Land, but the problem of replenishingour fuel supply required some fields off the Labrador coast we wereswinging waves. When we reached the icechanges in the schedule. We went south to hardly able to get through any communicationsalthough, after considerable ef-a whaling station at Edgesminde whereten barrels of fuel oil were obtained, but fort, we exchanged position messages. Thethis was not enough to take us home. ice was fairly heavy but we considered itUsing the engines seemed more desirable not too bad to prevent us from makingthan the sails, so we went further on, to Cape Murchison. About 8 P.M. on theSukkertoppen, where a larger supply could fourteenth, we sighted the cape throughbe had.the fog about a half mile off.This southbound trip included a few The weather kept getting thicker anddays' stop at Holsteinborg, formerly a centerfor American halibut fisheries. In the creased the danger of navigating these un-colder and a strong gale came up that in-cemetery were found a number of graves of charted waters. The harbor where weGloucester fishermen. All foreign fishermen were to meet the Bowdoin was full of ice.are now barred from the coast of Greenland The storm became more severe and theand the Danish Government isoperating night was very dark, so it was consideredthe halibut fishing industry at Holsteinborgwith great success. During our stay ship even though we could find a harbor.too much of a risk to try to anchor theat this port, we enjoyed many meals of halibut.It was delivered to the ship at a price The entire crew stood watch that night.A broken reverse gear added to the hazards.corresponding to one cent a pound. We all wore all the clothes we hadExcept for the fog at sea, the weather we aboard under our oilskins, together withexperienced in Greenland was of the best. hip boots so as to offer maximum resistanceto the cold rain, sleet, and snow thatDuring the day, the temperature generallyran around 70 degrees. This weather, on was driven hard by the gale.the middle western Greenland coast, is Radio communication was establisheddue to a warm ocean current which preventsthe winters from being any more to give our position to the Bowdoin if hewith radio iAAY, and as I was asking himsevere than they are in Maine.could, all signals faded out completely.Our call at Sukkertoppen for fuel lasted At frequent intervals 1 called WNP, theonly a few hours. Before leaving, plans were Bowdoin, but I received no answer.made to set a course for Cape Murchison, As the day started to break, two harborswere located. One was well shelteredBevoort Island. If the ice was not tooheavy, we planned to run up Robinson but we could not get in because the entrancewas blocked by a few large icebergs.Sound, between Bevoort Island and BaffinIsland, and anchor in a harbor that was The other was full of rocks and bergs but,dotted in on the chart. The dots meant: with the skillful handling of the ship, a"Harbor about here."reasonably safe place was located and thenThe radio conditions during our last the hook dropped. Dropping the hook wasfew days in Greenland were very poor. not so easy. The gale was still strong andEven the powerful commercial stations the water twelve fathoms deep, and we hadto let out about forty fathoms of anchorchain. The last twenty fathoms came outof the chain locker in installments of oneand two feet at a time while it was beinguntangled and untwisted.Communication was established withWNP that afternoon on a schedule. Hiswave was swinging badly but I was ableto learn his position and that he washeaded for Hall Island, near the southernend of Baffin Island. Apparently the Bowdoingot the worst of the storm as theystayed at sea and rode it out, for CommanderMacMillan considered the ice tooheavy to attempt to run into the Sound.The danger of the ice was that, if the windchanged, it might pack in on us and pushthe vessel on to the beach.The following morning we pulled in our40 fathoms of anchor chain and headed forHall Island.While passing through the ice, we sawmany seals, and after clearing it, walruseswere plentiful. After quite an exciting timewith artillery, harpoons, and killing irons,we managed to get one of the latter aboardthat weighed about i s pounds.Upon arriving at Hall Island that evening,a radio message was received from theCommander advising us that he had goneon and that we should meet him at SaglekBay, Labrador. At four o'clock the followingmorning, we started out on this longtrip across the Hudson Straits. Fair weatherpermitted us to make Saglek Bay by sixP.M. the following day.OBSERVATIONS ONRADIO FADINGOUR activities at Saglek Bay deserveconsiderable mention. The Bowdoinhad gone up far into one arm of the bay sothat the scientists could make a collectionof some kind of field mice that exist there.Some of the other boys found sport huntingcaribou but they did not enjoy thesuccess the scientists had.McGee planned on setting up a receiv-so that Kennetting set ashore that nightRawson, a member of the Bowdoin crew,could hear his father who was scheduled tobroadcast from WJAZ, Chicago. An elaborateinstallation was made with the help" of" Ken, who was so strong he stretched theantenna wire enough to break The it.heavyequipment had been carried about twomiles up into the hills to an "ideal" location.All this work did not even result ina squeal from WJAZ. This was most disappointingas reception in Greenland fromthis station had been quite successful attimes.good,During the time that McGee was tryingto receive WJAZ, was I trying to receive anyoneI could. At times signals seemed fairlyand then they would fade out completely.Someone informed me that theaurora was quite strong.I went on deck toinvestigate. Never before had I ever seensuch a violent and brilliant display of thenorthern lights.At times we were completely surroundedby the bright blue bands of aurora, andstreamers from all around the horizon

MAY, 1927WITH MACMILLAN TO THE ARCTIC 13would shoot up to the zenith, making a five or six degrees as the bands of auroracomplete umbrella of aurora. In places, the passed over us.bands were fringed with a dark red. We were following the Bowdoin alongUntil making this Itrip, felt that no the half-charted coast of northern Labradorwhen our engines stopped. The chiefrelation existed between the aurora andradio conditions, as I had made rough engineer found the fuel pipe lines full ofobservations during the part of one winter water. A little over an hour was requiredin Alaska and was able to detect no connectionsbetween the two on wavelengths a barrel of water out of the fuel tank thatto take down all the lines and drain aboutof six hundred meters or higher (500 kc. had been filled at Sukkertoppen. Theor less). No one seemed to really know Bowdoin was a mile or two ahead of uswhether any relation existed although some when we stopped and her lights soonwere quite certain that it did and others dropped out of sight altogether. Therewere more positive that it did not.was a light breeze up so we were able toAn excellent opportunity was offered keep clear of the rocks with the use of theme to gather some data that might throw sails. Nain was no easy place to find as ita little light on the subject, so I started was hidden away somewhere among awork, but in a rather crude fashion. My great conglomeration of islands and baysnotes consisted of brief descriptions of theaurora together with a log of the stationsthat were coming through and remarks asto intensity. For three hours Ikept runningup and down the companionway takingnotes on the aurora and then listening tothe radio. I was thoroughly convinced afterthese notes had been gone over that a definiterelation did exist between the auroraand radio conditions.The following night we were at sea, boundfor Nain. The aurora appeared in thinbands sweeping across the sky from thenortheast. 1 took data as on the night before.Mr. Warren was at the wheel at thetime and noticed compass variations ofnot appearing on the charts with which wewere supplied.The following afternoon we ran into anentrance that appeared to be the correctone for Nain. After hours of sailing aroundislands and into bays that all looked alike,we came to anchor. Commodore Metcalf,the Captain, and the Chief immediatelyset to chasing a large bear we sighted alongthe shore.One time that afternoon, while we weresailing up a wide clear channel at fullspeed, we hit a rock. The ship lurched alittle to one side as we slid over it and wentright on. The hull was well built and especiallyconstructed to stand any shockof hitting rocks or running on to ice, sowe were none the worse for the mishap.Locating Nain was no problem for CommanderMacMillan on the Bowdoin ashe knew the Labrador coast equally as wellas the streets of his home town, but whileoriginally acquiring his familiarity of thecountry he tells how he spent two weekslocating this settlement.The Moravian missionaries here had amotive in locating their station in a placeso difficult to find. Before the fishermenbegan intruding upon this coast, the Eskimoswere a strong healthy lot of peoplemaking a prosperous living from fishingand hunting. Fighting took place betweenthe Eskimos and fishermen at their firstappearance. To protect the Eskimos andSOME PICTURES TAKEN IN ARCTIC REGIONSThe upper circle shows an Eskimo boy in his kayak at Sukkertoppen, Greenland. The top left "snap" was taken at the northernmost port of call ofthe Expedition Godhaven. The Eskimo girls are interested in the camera and are not a bit bashful. The pile of sod in front of them is being dried for usein the construction of an igloo. This material is also used for fuel. The Bowdoin and Sacbem are shown at anchor at the foot of the towering rocky coast-Sine at Godhaven in the top right-hand picture. The inner circle depicts Maude Fisher at the wheel of the Sackem, cheerful despite a painfully swollen face-caused by Labrador mosquitoes. The Sachem is at anchor in Battle Harbor, Labrador, in the lower left-hand picture. The group of three to the right includes:Captain Crowell, skipper of Commodore Metcalf's Sachem; Marion Smith; and Maude Fisher

14 RADIO BROADCAST MAY, 1927prevent their annihilation, Moravian missionariesfrom Germany risked and sacrificedtheir lives for the cause. They havebeen able to keep the race alive for over ahundred and forty years by their persistent,self sacrificing work. Protection fromthe diseases of the fisherman has been oneof the most important problems they faced,and their station at Nain was hiddenaway so as to make its approach by thewhite man very difficult.In hunting for Nain, Commodore Metcalfhad given way to the opinions of othersas to where we should head the Sachem.His good sense of direction finally won thecourage of his convictions when he informedus that we would hoist anchor atfive A. M. and arrive at Nain at eight.At 8:20 we dropped the hook alongsidethe Bvwdoin at Nain.In going south from Nain to Battle Harbor,we stopped nearly every night. Wehad two days at Jack Lane's Bay whereAbe Bromfield lived. Arrangements weremade to take him to the States for thewinter. We were all as much interested inhis trip to civilization as Abe himself. Abehad never seen a railroad train, an automobile,a horse, or many of the other thingsthat are so common to us. Just how hewould be impressed by all these things wasa matter of much speculation on our part.Some of our stops on the Labrador coastandrepresented agony because of the fliesmosquitoes. At one placeIarranged to setup some apparatus for measuring earthcurrents that exist during aurora displays.I soaked myself with Flit and went ashoreto locate a suitable place. The effect of theFlit did not last long. I was compelled toretreat to the ship with all the speed Icould put behind the Idory was in. Theswellings and itching from the fly biteslasted for days.In comparison with what the three womenwho were with us on the Sachem sufferedfrom the flies, I had no reason tocomplain. They went ashore, protectedby head nets, but the flies easily workedtheir way through. Miss Fisher's face wasswollen up like a toy balloon while MissSmith suffered with hundreds of bites butwas not affected by such swelling.I was able to get additional data on therelation between the aurora and radioevery night. In addition to the aurora data,notes were taken on the barometer readingsand on the mirages that were so common.At times we were able to get photographsof the ice mirages. After reporting to RADIOBROADCAST about the mirages, the editorsent me a message quoting a press reportthat read as follows: "Captain Rose, ofSteamer President Adams, at 8 P.M. July15, in Mediterranean Sea, bound for PortSaid, states they saw 'large field of floatingice cakes suspended above horizonand presently a number of small piecesdrifted into view followed by a large one.The latter was so clear we could see blueand green veins in the ice.'"Early in the trip, Commander MacMillansaid that if conditions were right, itwould be possible to see mirages of images table phonograph with a large number ofcrew. I held back on the broadcast music success as the ticket taker almost passedbecause we had an excellent Sonora por- out while Abe walked on in.half way around the earth. Considering records and because the reception up tolight and radio waves to be the same thing, that time did not have much entertainmentexcept for difference in frequency,it seemed value. It was possible to hear broadcastthat there might be some connection betweenstations faintly as they faded in and outthe mirages and radio phenomena. but to try to get them regularly seemedIn the data collected, there appeared tobe a rather definite relation between barometriconly a waste of time.I noticed that many of the missionariespressure, mirages, aurora, magnetic in Labrador and governors in Greenlandstorms, and radio fading. The data is by have receivers that had been given themno means complete but the observations the previous year by Commander E. F.substantiate the following statements: MacDonald. With their large antennas,they are able to hear stations in the States1. and aurora only occur with heavyMirages pressure.reasonably well in the summer. Winter reception2. The relation between the aurora and radiois reported as excellent.fading depends upon the following:The 63-meter (476o-kc.) signals from(a). Formation of aurora and its location in KDKA came in well during most of the summerrespect to the approaching radio wave andbut were subject to bad fading. Thethe receiving station,325-meter (9225-^.) signals from WGY(b.) Frequency of the radio signal.appeared very steady and fairly strongIn accounting for the fading, the temperaturewhile we were in Greenland.is an important factor in the for-mulas already worked out for mirages. ABACK TO CIVILIZATIONmore detailed account of the data and the conclusions drawn will be taken up in a IF want to find out how great a finebig juicy beef steak can taste, just takelater article.a three months' trip into the north and liveIt might be well to mention here that on canned goods as we did. When wecommunication between the Bowdoin and up with fresh supplies on our arrivalSachem was never hampered due to "skip Sydney, Nova Scotia, we all ate like wilddistance" effect. The distance between the men. With the crew fed up on red meat,two ships varied between three feet and the captain was afraid to let the men handlethree hundred miles during the trip and the lines for fear of breaking all we had.we always communicated on waves betweenOn the last leg of the voyage beforethirty-two and forty-two meters reaching the States, we ran into some very(9370 and 7140 kc.).heavy weather off the Nova Scotia coast.We found Battle Harbor filled up tight Most of us on the Bowdoin and Sachem experiencedseasickness but it did not lastwith eighteen fishing vessels, and we werecompelled to anchor in what is known as long on the Sachem as Commodore Metcalf"Outer Harbor." We had prepared to put aboard a supply of "seasick pills" atwait there until the mail boat arrived on Sydney which served their purpose nicely.name the following day hoping that a new reverseI believe their trade is "Sea Oxyl."gear would be aboard for us. Ac-This is not a free advertisement it iscording to calculations, the chances seemed sympathetic advice.very poor and the next boat was not due Our arrival at Wiscasset on Septemberfor two weeks.the eleventh does not end the story. AbeThe story about the reverse gear, however, Bromfield has to be accounted for. Atdisplays the efficiency of modern means of Sydney, Abe appeared to be mostcommunication. The extent of the damage interested in the railroad whistle and adone to the gear which was caused when long train of cars. At Wiscasset, he couldwe ran aground on the Arctic Circle, was not understand why they had small lighthousesin the middle of the streets.not determined until an examination wasmade at Holsteinborg. A radiogram was Commander MacMillan was engaged tosent through on the night of the examinationto the offices of John G. Alden, the went with him. In a day and a half Com-speak at the New York Radio Show. Abeship's designers, in Boston. This message mander E. F. MacDonald showed Abewas received by them when the offices more of New York than I had seen in awere opened at nine in the morning. A wire year and a half. Abe remembers every detailwas sent from there to the makers of theof this trip, for his memoryis remarkable.Reporters all shot the stock questiongear but not knowing the type used, theywired the builders of the engine in Columbus,at him: "What do you think of AmericanOhio, for this information. By noon a flappers?" Abe's confidential report is thatwire was received at the Alden offices from the Wiscasset girls are much prettier thanthe makers of the gear that a new one had the ones in New York.been shipped express, special handling. Abe is a great one for shaking hands. IOnly by a margin of a few hours, the gear am sure he would enjoy exchanging placesreached the mail steamer before sailing, with President Coolidge at times. On oneand we received it the morning after arrivingBattle Harbor.MacDonald into the New York Radiooccasion, Abe was following CommanderIt was not until we reached Battle Harborthat IShow when the ticket taker put out hisput any broadcast music on the hand. Abe shocks hands with him. Thisloud speaker for the entertainment of the first attempt at crashing gates was a grand

THE MARCHInterpretation of Current ''Radio EventsWhat Does the Listener Want? Let Him SpeakTHERadio Act of 1927 providesthat "the licensing authority shallmake such a distribution of licenses,bands of frequency orwavelengths, periods of time for operation,and of power among the different states andcommunities as to give fair, efficient, andequitable service to each of the same."Licenses shall be issued and renewed only"if public interest, convenience, or necessityare served thereby."These are the sole bases in the new radiolaw upon which broadcasting stations shallbe distributed and licensed. The criterion,then, by which a station's right to broadcastis to be judged is its service value to thelistening public in its own service area andthe effect of its operation upon broadcastingin other areas.What a trail of broken hearts must followin the wake of that formula! Even now wecan hear the groans and lamentations of thedisappointed, who have pleaded in vainbefore the relentless Commission. Here isa reformer, who spent the hard-earnedmoney of generous contributors, to broadcastmessages of uplift to an immense aud-The illustration forming the heading shows a general view ofthe first international radio telegraph station at Alfragide,nine miles west of Lisbon, Portugal. On December 5, 1926,direct high-speed service to London opened.I he station willJao communicate with Kast and West Africa, and with SouthAmerica. The short-wave "beam" is used.ience, an enthusiastic audience whichcontributions fornecessity for listener organization. Wenoted, for instance, in a recent issue of theNorthwest Radio News, the official organ ofthe Northwest Radio Trade Association, aa cause depending uponbought so many of his expensive little revenue, a commodity feeding its salespamphlets in the past; we see his bowed through goodwill, or a community encouragingcapital and population to its territorialform as he staggers dizzily out of the officesof the Radio Commission, realizing that limits.his work of saving the public soul can no The most important evidence to guidelonger be continued behind the comfort of the commissioners in determining what isthe microphone. There is a philanthropic fair, efficient, and equitable service to thebusiness man who, out of the goodness of different states and communities will be thehis great heart, has spent thousands and expressions of the listening public of theirthousands of his excess profits to spread desires. The broadcast listener must becomegladness and cheer and advertising, to a articulate if this wise provision in the lawreceptive public. And here is a little fellow, is to have the opportunity to mean whatso he says, who has erected a modest little it says.station, but a nice little station nevertheless,just to make folks happy but, he sobs,Already there has been recognition of thethe accursed monopoly has bought the soulsof the Radio Commission; they get theirplace in the ether without a struggle; hemust put his tubes and condensers back in strong plea that the trade support radiostock now and sell them to his unsuspecting listener organizations. It urges such listenercustomers, not without a little free monopolypublicity in the home groups to consider questions of receiveroperation and repair, to conduct settown paperthough, to help him on his way.building contests, to give opportunity forGentlemen of the Radio Commission, let unbiased demonstration of commercial setsbut one voice rule you! The voice of the and accessories, to criticize, condemn, orbroadcast listener! Give him fair, efficient, commend sales methods and radio advertising,to encourage new uses for radio, toand equitable service! Remember, not oneof those who seek to broadcast has anything improve radio reception conditions by exposingbroadcasting station interference,but a selfish purpose, however disguised, inseeking a place in the ether. Big and little, discouraging radiating receivers, and locat-alike, have something to sell, whether it being power line leaks, and, most important

MAY, 1927PAST OBJECTIONS TO THE RADIO LAWprotests came in such numbers that thesevery vocal Senators were forced to capitulate.But there was no truly organized listeneropinion represented. Indeed, Senatorsclutched upon the feeblest ray of evidenceto cite listener opinion in support of theirvarious arguments. For example, referencesappear in the Congressional Record to aprotest against the Radio Bill made byone C. Wood Arthur, speaking for aso-called Radio League of America.Letters from this magazine addressedto Mr. Arthur have receivedno acknowledgment or reply. Norhave we been able to learn fromany other source who Mr. Arthurrepresents beside himself. In theabsence of a recognized listener organization,anyone, however unknownand unrepresentative, may take itupon himself to influence the courseof legislation and the future actionof the Commissioners. The lack oforganizationof broadcast listenersis a menace to their interests, acondition which would be quicklyalleviated by the formation of a trulynationwide listener organization.Objectionsthe Radio Act was the sub-of debate in the House andSenate, certain objections werejectWHILEto the Radio Lawbrought to its provisions which, were theyvalid, would undoubtedly be serious reflectionsupon the soundness of the Act.It is worth while to consider some of thesepoints lest confidence in the Radio Law beundermined.The radio listener has every reason to becongratulated on the fine piece of legislationwhich Senator Dill so ably marshalledthrough the Senate. We regret, of course,that the original White Bill, which did notprovide the cumbersome and expensiveradio commission, was not passed, but theingenious compromise worked out is thebest law which could be hoped for. Thecommission, we fear, is a permanent expense.It will probably remain in sessionpractically all the time even after the firstyear, since anyone questioning the Departmentof Commerce's rulings automaticallybrings his case before the Commission.Some of the objectors to the billapparentlyfailed to read it carefully or theyhave no adequate understanding of theEnglish language. One provision of the Actstates that broadcasters cannot acquire orconstruct wire lines of their own for thepurpose of securing unfair advantage overrival broadcasters. Senator Copeland (D.New York) spoke harshly against this provision,stating that the telegraph and telephonecompanies (against whom this provisionis directed) make so much moneynow out of telegrams sent in response toradio programs that they fear broadcastersmight take away this business by meansof a communication system of their own!He also stated that light, heat, and powerwould "soon be transmitted bv radio" andthat, therefore, licenses should not be a splutter by insisting that, as soon as thegranted for three years. The Act specifically "interests" were licensed under the newprovides that a station's license may be Act, they might begin transmitting scrambledprograms, so that the listener wouldrevoked if it is used for a service differingin any way from that for which the license have to pay for them or else junk his set.was granted. This same provisionis adequateprotection against the transmission without express permission of the Com-Such transmission could not be undertakenof "scrambled" programs for which the mission, which would be derelict in itsdutylistener would be compelled to use a special if itgranted that permission without publicdemand for it.I he Question of Vested RightsHE only serious criticism ofthe Act in the Senate centeredT:upon the point that no declarationwas made in the law to the effectthat the ether is owned by thepeople. The law ignores the matterof ether ownership but asserts unequivocallythe full power of thegovernment to regulate its use.EtherTHE ORIGINAL MAGNETIC DETECTORownershipis a subject ofconsiderableUSED BY MARCONIlegal complexity, sincewe cannot accurately define what theether is. The "ether" is internationalpatented receiver. The Commission has full and hence cannot be owned by any onepower to limit and prescribe the kind of nation or any individual. If the ether wereequipment to be used in transmission. Fortunately,no specific barrier to charging for station of itsconsidered as "property," divestment of afrequency would automaticallymake it a matter of property confisca-programs was incorporated in the law becauseit isquite conceivable that there tion. As a matter of fact, had broadcastingmay, some day, be demand for high-grade stations, by any legal interpretation, possessedvested rights prior to the passing ofprograms for which the listener might beasked to pay. On the other hand, such a privateservice could not be undertaken, under gress that they did not possess such rightsthe Radio Act, the mere statement by Con-the Act, if it did not meet the requirement would not automatically dissolve them.that it was fair and equitable service to the The inclusion of a declaration of ownershiplistener. One Representative created quite of the ether by the"people would have in-TWO WELL-KNOWN RADIO EXECUTIVESPowel Crosley, jr., President of the Crosley Radio Corporation, and his newly appointed assistant,R. H. Langley. For the last six years, Mr. Langley has been in charge of receiving set developmentfor the General Electric Company and iswidely known in radio engineering circles. The first Americanairplane transmitter is credited to Mr. Langley

18volved the law in precarious legal entanglements.Confinement of the Act's scope toregulation of any and every device usingether waves in no way jeopardizes or weakensits effectiveness. If you have entire controlof the use of a thing, its technicalownership becomes of minor importance.If the government can prescribe when,where, and for what purpose you may useyour motor car, it, in effect, can exert allof the advantages of complete ownership.Legal experts state that a vested rightcould be secured to a wavelength, providedunrestricted ownership had been exercisedfor a period of many years. In historic coveredwagon days, a prospector had only tostake out his claim and to occupy his propertyto obtain a good title to it. His occupationand improvement thereof eventuallygave him legal possession. Complete possessionand utilization, without existenceof any rights conflicting with it, might intime bring about the establishment of avested right to a radio frequency. But nosuch condition obtains with respect tobroadcasting frequencies. The right of thegovernment to regulate interstate radiocommunication is clearly given in the Constitutionand the government asserted andexercised that right long before the firstbroadcasting station went on the air. Nobroadcasting station at any time has operatedwithout first securing a governmentlicense and, in so doing,it has recognizedthe government's power to regulate the useof the ether.Undoubtedly there will be efforts on thepart of disgruntled stations to prove thattheir investment in radio transmittingequipment is, in effect, confiscated iftheyare not allowed on the air. They will thereforedemand compensation as is guaranteedunder the Constitution when private propertyis confiscated. But they will be wastingtheir time and money in seeking compensationbecause the government's power torevoke a license for the general good, evenif it involves depreciation or destruction ofprivate property, has been abundantly establishedby endless court decisions. Oneneed only recall the actions brought manyyears ago when local option closed saloons.Although a license to sell intoxicating liquorwas property so tangible that it could besold, mortgaged, and subjected to execution,the courts decided that a license to sellliquor is not a vested right and the statecould, in the exercise of its police power,revoke it.Revoking broadcasting licensesis not different. Although revocation of alicense may involve making a radio transmittervalueless, the license is neverthelesssubject to revocation for the good of thepeople as a whole. It is extremely unlikely,particularly since broadcasting stationswere officially warned that the ether laneswere overcrowded, that any of the existingstations whose licenses must be revokedwill be able to obtain compensation on thegrounds of confiscation.We are indebted to the Hon. S. H.Rollinson, an eminent New Jersey lawyer,who has made a thorough study of the legaliRADIO BROADCASTB. L. SHINN-New York City-Associate Director, National [Setter BusinessBureau. Especially written for RADIOBROADCAST:"Many radio firms as well as radio dealersand manufacturers have written to the NationalBetter Business Bureau to expressappreciation of its work in promoting theaccurate retailing, advertising, and selling ofradio storage batteries. This appreciation ismost welcome, and in acknowledging it, 1take the occasion to point out that this is butone of a number of instances in which theBureau has worked out, with the engineeringand advertising leaders in the radio industry,methods of selling, which have assisted thepublic to obtain accurate and dependablefacts regarding radio products. El-en the woodsappearing on exposed surfaces of radio cabinetsand consoles are now accurately describedby most manufacturers, instead of byonly a few, because of the activities of thisBureau." The Better Business Bureau's service toindustry and the public, however, is by nomeans limited to radio. There is scarcely animportant item of merchandise in your homein whose advertising, branding, and marketingthe influence of the Bureau s recommendationsare not felt. If you have saved moneyfor investment, the National Better BusinessBureau and forty-three local Bureaus standready to supply reliable and disinterestedinformation upon the security which you areconsidering."r ||||(| ll]m[1|llr rrrllmlll1n n ,., , r | llm , LI,,!,,!,!,,,,!! , 11 , ,aspects of the broadcasting stituation, forother examples of a governmental policepower, the exercise of which has involvedwhat amounts to, but is not, confiscation ofproperty. The State of New Jersey passeda law prohibiting the use of repeating firearmscapable of firing more than two shots.This rendered useless repeating rifles possessedby many sportsmen and, in the legalaction which followed as a result, broughtby sportsmen and manufacturers of firearms,the state proved its complete rightto regulate the matter of firearms underthe law. Likewise, the government may orMAY, 1927may not grant charters to national banks,as its chooses. If it does not consider it inthe public interest to license an additionalnational bank in any locality, it need notdo so. It is empowered to revoke the charterof a national bank in the public interest. Areckless automobile driver may have hislicense revoked in the maintenance of lawand order, even though, in effect, it makesa valuable and expensive piece of propertyuseless to him. The regulation of the etheris a police power which cannot be overthrownupon any grounds of vested rightsand cannot be hampered by demands forcompensation. We are convinced that theactions brought by broadcasting organizationsfor compensation or broadcastingrights will be unsuccessful, unless and onlyif they can show that failure to license themis denying the public fair, efficient, andequitable radio service.The case of the disgruntled broadcastingstation must be overwhelming proof thatclosing it down is contrary to the publicinterest. The personal desire of those maintainingthe station is of absolutely no valueunder the law. The Radio Act of 1927 haswiped the broadcasting slate clean for theRadio Commission. At this writing, nobroadcasting station is licensed for morethan sixty days. Let the Commission havecourage! The vast majority will support itto the limit in its difficult task of reducingthe number of broadcasting stations by atleast sixty per cent. A noisy and selfishminority will always oppose and criticize it.Let the clamoring be outweighed by anorganized and powerful listener sentimentand there will be no difficulty in decidingwhat is meant by fair, efficient, and equitableradio service."Christian" Mud Throwingto receive a com-WE WERE pleasedpletedisclaimer from the ChristianScience Mother Church inBoston,stating that the destructive propagandasent out by WHAP in New York is in no waysanctioned by and does not in any way representthe views of that organization. StationWHAP has used its broadcasting stationto disseminate large quantities of mud,trained largely against Catholicism. Theaction of WHAP has disgusted listeners ofevery shade of religious belief. Broadcasting,fortunately, has been very largely freeof intolerance, every kind of religious beliefhaving free access to the microphone tospread its thought constructively. BroadcasterWHAP, disregarding its obligation tothe diversified radio audience, has chosen acourse of intolerance and villification. Itsattacks on Catholicism can not be condoned,and tend to undermine the faith of impressionable persons in any religion. For the goodof radio, let us hope that it will no longer beused as a means of breaking down anyone'sbelief, be it Catholicism, Protestantism,Buddhism, Christian Science, or atheism.A cardinal virtue of Christianity is tolerance.No doubt we will be suspected byintolerant WHAP of being subsidized by the

MAY, 1927 A SURVEY OF RADIO CONDITIONS 19Pope, but this item is written by a non-Catholic who resents, as do all liberals, thebesmirching of any religious belief, his ownor some one else's. Let us have no more ofA New Term for "A. C. Supply"UnitsNational Better Business Bureauhas endorsed the use of the termTHE"socket power unit" to describe devicesfor the purpose of furnishing A or Bpower for radio sets. The term "A eliminator"or "B eliminator" is declared as obsoleteas the term "horseless carriage,"which was at first applied to the motor car."Socket power" may be applied to describedevices employing combined storage batteriesand chargers, thus powering the setindirectly rather than directly from thelight socket. It thereby covers the numeroustrickle charging storage battery combinationunits now being so widelyWe sold.suggest the general acceptance of aterm such as "electric set" in order thatone may differentiate between receiversusing trickle charger storage battery devicesand those powered directly from thelight socket through filtering devices withoutthe aid of a secondary battery.Our attention has been called to advertising,having wide publication, describingA battery devices which "banish the storagebattery forever," "eliminate A batterytroubles," and similar claims. Investigationhas proved that these devices frequentlycomprise storage batteries combined withtrickle chargers. The implication of theseminimum but we believe the declarationthat they completely eliminate it is bothexaggerated and misleading.There Are No Radio EngineersFROMphrases in advertisingis that the deviceeliminates the storage battery. Combinationtrickle chargers and A batteries reducemaintenance attention to a very desirableD. A. Johnston of New Britain,Connecticut, we receive a commenton our item in a previous issue, urgingthat the education of radio engineersbe better balanced with respect to economicand commercial phases of their work:"Insofar as radio engineers are concerned, Iam not quite convinced that there isany suchthing. Engineering is very nearly an exact scienceand an engineer should be able to tell on paperwhat his product will do so that another engineercan tell exactly whether his productis better ornot. Did you ever see any firm producing radioapparatus who would give you information comparingto that which you would expect in buyingan electric motor? For example, how many engineersworking on sets know what the curves oftheir particular set look like? I doubt if manyof those producing simple articles like batterychargers do know what actual efficiency is. Thefew who do know these things are not sufficientlysatisfied with the product to be willing to saymuch about them."This comment is often made by engineersin fields better established than radio. TheEDWARD E.New YorkSHUMAKERPresident of the Victor Talking MachineCompany:" The question as to who is to pay for radiobroadcasting appears to have been temporarilysolved. The bills are being met by those whobenefit directly fromit. While I do not believethat the broadcasting of radio entertainmentcan be made to take the place of otherestablished forms of advertising, it is an additionalmedium for creating demands forsome products, and a good-will builder whenproperly used. We have found that the broadcastingof Victor recording artists results inan immediate and traceable demand for theirrecords. We are convinced, also, that anythingwe may do to raise the standards of radioprograms will be reflected in a healthier conditionin our business and in other branchesof the music industry."Radio and the talking machine may atlimes appear to overlap somewhat. In actualpractice they do not overlap. Each has its ownplace as an instrument for home entertainment.This is borne out by the experience ofmore than 6000 Victor dealers in the UnitedStales. It is also a fact that thousands of newtalking machines which are not equipped withradio receiving sets are being sold annuallyin homes which also contain radio sets." In 11)24, ""d the early part of 1925, whenthe talking machine industry was at a lowebb due to its failure to improve its products,the general impression was that recordedmusic was being replaced by radio broadcasting.Subsequent developments have demonstratedclearly that such was not the case."fact is that we have no standardized methodof rating the efficiency or selectivity of receivingsets, which nets down to a figure ofmerit of standardized valuation.A Survey of Radio ConditionsT\ADIO RETAILING has issued a/Y report on the broadcasting situa-"tion based upon telegraphic summariesfrom 21 cities, scattered throughoutthe United States and Canada. Washington,District of Columbia, and Portland,Oregon, were the only two districts reportingsatisfactory conditions, but it wasnoted that almost every center of populationhas one or two high-grade stationswhich are not being interfered with seriously.The most enterprising leadership inhandling the situation was demonstratedon the Pacific Coast, where the PacificRadio Trade Association not only securedpledges from broadcasting stations thatthey would abide by the district radioinspector's decisions as to changes in wavelengths,but exerted strong influence inhaving them observed. Twenty-five percent, of the midwest stations conflict withlocal wavelengths in San Francisco on setsof average sensitiveness. From this reportand other sources, we learn that among theimportant stations seriously heterodynedare KOA, wcco, WOR, WEAF, WTAM, WHN,WEEI, WNAC, CKCL, and KFKX. Radio Retailingis to be congratulated upon theexcellence and thoroughness of its survey.The Month In RadioTHE sales of combination radio and talkingmachine instruments made by the VictorCompany during 1926 had a retail value ofsomething over seventeen million dollars andamounted to one sixth of the total business of thecompany.FROMMr. C. R. Cuchins, Vice Prlsident ofthe First National Bank of Bessemer, Alabama,we learn that the Birmingham News decided,upon suggestion from broadcast listenerswho forwarded copies of RADIO BROADCAST'Seditorial on the subject, to resume running radioprograms in its columns in a manner whichmakes them intelligible to the listener.PORTLAND, Oregon, has passedan ordinance1making it unlawful to operate without a permitany apparatus generating high-frequencyoscillations which interfere with broadcast reception.Violet ray machines, quenched sparkdevices, and X-ray machines must be licensed andmay not be used, except in emergencies, betweenthe hours of seven and eleven. Power interference,being a local matter, appears to be suitedto local regulation.ANEWtransmitter for WEAF will be erectedat Bellmore, Long Island. Bellmore is on thesouth shore of Long Island, the nearest townsbeing Freeport, Hempstead, and Farmingdale.An advantage of this location is the relativelysmall population which suffers from proximityto the station and the fact that the new stationwill impress the strongest signal where ship interferenceis most likely to mar its programs.Plans for the new station have been drawn byDr. Alfred N. Goldsmith, Chief Research Engineerof the Radio Corporation of America,Dr. E. F. W. Alexanderson, of the General ElectricCompany, and Frank Conrad, AssistantChief Engineer of the Westinghouse Company.This station may be in operation by October,1927.beacons have been installed atRADIO McCook Field, Dayton, and at the DetroitFord airport for the guidance of the Stout-Fordcommercial airplane between those two points.

The ElectricalA Non-Technical Explanation of thePrinciples Involved in Electrical Recordingand Reproduction The New"Panatrope" and "Electrola" Datafor the Home-Constructor Wishing toBuild His Own Electrical PhonographByJAMES MILLENTHE "PANATROPE"An entirely electrically operatedphonograph. Provision is madeso that the amplifier system, includingthe baffleboard loud speaker, may be usedfor radio purposes after the detector in any radiocircuit. This photograph was taken in the RADIOBROADCAST LaboratoryMOST fascinating experience for one interestedin radio especially one whohas long been connected with its developmentis to spend an evening with the earlyissues of some of the older radio magazines.A study of the advertisement section not onlyrecalls the queer contraptions that were lookedupon in their day as the acme of engineeringperfection, but also throws light upon the foundingand first products of small companies, regardednow as leaders in the radio industry. Notonly do large things often develop from a humblestart, but also large concerns of one decade oftenpass into oblivion by the next.Aside from this,also read what thewe may"prophets" of but just a few years ago outlinedfor the future of the radio industry. For instance,in the November, 1922, issue of this magazine,appeared an -article entitled: "Will Radio Replacethe Phonograph:"Apparently there existed some doubt in themind of the public as to whether the new novelty,radio, could ever reach the "perfection" of thephonograph as regards tone quality, service,and reliability. Now, on the other hand, thereappearsto be some doubt in the mind of thepublic regarding the same question, but from adifferent angle: "Can today's phonograph competewith the radio in tone quality, service, andreliability r"But, why not, from comparisons of the two.draw one's own conclusions? It is not at alla difficult or costly task to construct a trulyfineelectric phonograph. Before going intothe construction of such devices, however,let us first find out just what this new instrument,known commercially as the "Panatrope"and "Electrola," really is, and justhow it works.The grooves in a phonograph record are socut as to cause the needle to vibrate from sideto side. In the old phonograph these transversevibrations of the needle were conveyed mechanicallyby a system of multiplying levers toa mica diaphragm located at the small endof a horn. The vibration of the needle causedvibration of the diaphragm which set the aircolumn in the horn moving, and thus producedsound.Such a system, while low in manufacturingcost and reliable in operation, resulted in considerabledistortion. The horn was resonant atcertain frequencies and the diaphragm at othersThus some notes were greatly over-emphasizedwhile others were entirely missing.The new electric system depends for its operationupon the vibrations of the needle to producea constantly varying electric voltage. Theminute electric voltage generated by the movementof the needle is amplified by a high-qualityaudio-frequency amplifier, such as is a componentpart of the better radio sets, and thenconverted into sound by a loud speaker.While the new phonograph will play the oldrecords, the results are not the same as whenthe new Orthophonic (correct-tone) type records,made especially for the purpose, are used. Informer years, records were made mechanicallyby a machine much resembling the old-stylephonograph, into the horn of which orchestrasplayed while closely and uncomfortably huddledtogether.Now, however, studios much the same as thoseof modern broadcast stations, are employed forrecord making. Standard radio microphones,as many as needed, are so placed as to properlyblend all the instruments of even a large symphonyorchestra. No longer must the player infront play softer than natural in order not to"drown out" those in back. Everyone plays asifgiving a regular recital, and the various microphonesare so placed as to produce the properresults.In fact, the output of the electric phonograph,when one gets right down to the matter, is buta standard broadcast program which, instead ofbeing sent over the air, is recorded and deliveredto the consumer without picking up static,heterodyne whistles, and other disturbances enroute.The acoustical difference between the samepiece played by the same orchestra over a highgradebroadcast station on a quiet night andplayed on an electric phonograph, is nil, assuming,of course, that the same quality audiofrequencyamplifier and loud speaker are used inboth instances.With these improvements, and one otherthe elimination of the record scratch the modernphonograph becomes a highly desirablecompanion to the modern radio receiver. Staticand sos signals no longer need spoil an evening'sentertainment. Favorite selections, beautifullyrendered and reproduced, are availableat a moment's notice when the radio programis not tempting.Even the inconvenience of constantly changingrecords seems soon to be done away withaccording to recent announcements, of some ofthe leading phonograph concerns.But do not understand this article to be anargument in favor of the phonograph over theradio. The phonograph can never take the placeof the radio. First, the radio brings news andentertainment into the home as it is actually occurringbanquets, speeches, sporting eventsand many others; and second, radio suppliesits own program; its repertoire is not limited bythe number of records in the album.But, as a companionto modern radio, thereis a distinct service to be performed by theelectrically operated phonograph.THE NEW PHONOGRAPHBEFORE considering the re-vamping of theold-style phonograph, perhaps a briefsemi-technical description of the "Panatrope"or the "Electrcla" may not be amiss. In orderto make such a description more clear and tobetter "tie itup" with what is to follow, thecomplete device will be divided into its varioussub-units.

MAY, 1927THE ELECTRICAL PHONOGRAPHDetails of a home-made pick-up. It consists radio headset. The headset should be of fairly greater must be the dampingif transient freeessentially of a permanent horse-shoe magnet, high impedance and good make.vibrations are to be quickly checked. The elasticityvery small by pivoting thean armature, and two small electromagnets. The armature should also be made of hardenedThe armature is reduced in cross section at itsupper end by grinding. The steel, and may either be pivoted or spring mounted.In order that there may be no sustained res- sensitivity is lowered by the consequent re-reed, but if the mass is too much reduced, thepurpose of this isto provide a hinge-like action at this pointduction of the iron circuit. Rubbermanent magnet to the ends of which are attachedpole pieces carrying coils of fine wire.Between the pole pieces is the reed, or armature,Grind so that bendingoccurs herePermanentwhich carries the needle.The permanent magnet should be made fromtool steel, cut, drilled, and formed, before beingMagnethardened. The larger the cross section of the-Armaturemagnet, the more volume, within RADIO BROADCAST Photographlimits, thatwill be obtained from the pick-up. An excessivelyTHE "MEROLA" PICK-UP(Must be connectedso aslarge magnet will press too heavily upon the An adapter makes possible the use of this devicerecord. To magnetize, when a magnetizing machinein combination with any good quality amplifier.Coils.tois not available, wind about a hundred Merely plug the adapter into the detector tube'ssocket in the receiver and connect a second leadturns of heavy cotton-covered wire around theto the B battery 4S-volt poststeel horse-shoe and connect the ends of the wire! electrically'aid")Pole Piecesacross a six-volt storage battery for a few minutes.Fewer turns of wire than specified will onance effect from the armature or reed, it is necessaryNeedleFIG.draw an excessive current from the battery.The pole pieces and coils may be taken from a that it should be mechanically damped.The greater the mass and stiffness of the reed, theImay be used for damping.Proper adjustment of the completedpick-up is important. TheFirst there is the turntableupon which the record is placed.faces of the two pole pieces andAs all of the present modelsthe armature must be parallel.are designed solely for a. c. operation,the motor employed tobetween the pole pieces, and theThe armature must be centereddrive the turntable is generallypole pieces must be as close togetherof the induction type, which,as possible without dangerdue to lack of the sparkingof the armature hitting. Dampingbrushes and commutator of theshould not be greater thanmotor, will not cause any pseudonecessary.static disturbances in the loudELIMINATING NEEDLE SCRATCHspeaker.Then there is the pick-up,which converts the mechanicalA SI DE from tone quality, oneof the outstanding achievementsvibrations imparted by the recordof the new phonographvibrations isto the needle into electrical impulses.the elimination of surface noisesand needle "scratch." The useAs will be seen from Figs,iof a new material for the manufactureand 2, the pick-up consists of aof records has done muchpermanent magnet, to which isto eliminate this annoyance ofbolted two pole pieces, two smallthe past but the final and completeelectromagnets, and a movableelimination is accomplishedarmature. Movement of theby means of an electrical filterarmature, at one extremity ofA COMBINATION OF RADIO AND PHONOGRAPHcircuit so tuned as to suppresswhich is located the needle, resultsin a variation of the elec-This " Electrola " frequencies in the neighborhoodRepresenting the ultimate in luxury so far as home entertainment is concerned.retails for a sum not considerably below a thousand dollars. of the scratch frequency. Suchtromagnetic flux passing through The reproduction from the records is by electrical pick-up, electrical amplification,and a cone loudan electrical filter is quite simple,the cores of the electromagnets.speakerThis variation in flux induces avarying or alternating voltage in the coils ofMernalB Supply to Radio Setthe electromagnets. The home constructed pickup+90V.-I-45V.illustrated in Fig.iclearly indicates theform of construction employed in several highgradeunits. Some commercial pick-ups employvariations of the design, such as the use of butone coil, that coil being wound on the armaturerather than the pole pieces of the permanentmagnet.Although but few readers will have the facilitiesfor making their own pick-ups, a brief descriptionof an electromagnetic unit shouldprove interesting to even those who intend purchasinga unit.A pick-up, as will be seen from Fig. i, consistsof a special shape and size horse-shoe type per-FIG. 2The circuit diagram of the "Panatrope." The purposeof the five tubes isemployed as follows:The two ux-2i6-n's are wired to form a fullwaverectifier system. The ux-8y6is a ballasttube connected in the a. c. line to compensate linevoltage variations. The ux-ipg is the first stageOutputaudio amplifier while the ux-2io is a power out-Transformertube the second audio

22 RADIO BROADCAST MAY, 1927type of Rice- Kellogg cone loud speakeris usedas the filter choke for the B supply.Third, the necessity of a ground connectionis eliminated by the use of a 2-mfd. condenserbetween one side of the I lo-volt line and thecenter-tap of the power tube filament winding.In inserting the lo-volt plug in a socket or otherioutlet, the plug should first be tried one wayand then the other as best results are generallysecured when the grounded side of the line is theside to which the condenser is connected.RADIO BROADCAST PhotographTHE HANSCOM "SUPERUNIT"This pick-up is constructed froma Baldwin phone unitRADIO BROADCAST PhotographTHE GRIMES PICK-UPAn excellent exampleThe rear of the baffleboard loud speaker is seen in the center of this picture.A metal funnel is placed over the UV-876 tube qual-to deflect the heat ity of the radio set is poor.phonographare at least four different types of1 pick-ups. The electro-magnetic and theof theelectro-magnetic type of crystal types function by generating voltages,pick-upwhile the condenser and the carbon forms operateby variations of impedance.as will be seen from Fig. 3, and is connectedOf these four, the only one of commercialbetween the pick-up and the amplifier. Theimportance, and, it would seem, the most practical,is the electromagnetic form. To this classfilter is so located before, rather than after theamplifier, in order to prevent unnecessary overloadingtrope," andbelongs those used in the " Electrola," " Pana-amplifier."Vitaphone." This latter is inThe volume is controlled by a wire-wound reality a potentiometerspecial electric phonograph designedwhich permits the audio-frequencyfor synchronization with a motion picture pro-voltage supplied to the amplifier to be made jector.anydesired fraction of the One of the pick-up output.large corporations interested in theThe amplifiers employed in the present commercialdevelopment of radio isexperimenting with amodels of the electric phonograph oper-FIG. pick-up of the crystal type but as yet this 3uniqueate entirely from a. c. The circuit, as will bedevice is still inThe experimental stage.seen from Fig. 2, comprises a stage of electrical connections of the pick-up, scratchvoltagePick-upsamplification, using a filter, volume control, and adapter. The scratchtype have been in existencefor a number rectified a. c., and approximately a 4600years but only recentlyux-igg tube with filament filter as shown is tunedlighted from stage of has onepowercapable ofcycleshigh-quality reproduction"amplification using a ux-2io tube with filamentbeen perfected. This is the Bristophone,"and to adapt the complete phonograph to power The loud speaker, as unitalready mentioned, telephone receiver.islines of various voltages located in different sectionsof the country.the amplifier due to the use of its field emphasize certain notes and, unless used inof the cone type and is electrically "tied into" Generally, however, such devices tend to over-windingSecond, the field winding of the baffleboard as a filter inductance.connection with a "trick" amplifier, will sound"flat." An exception is the unit from the Western540 AW cone loud speaker. Thislighted from raw a. c. This power tube shown inissuppliedpotential of close to 400 volts, andThisa photograph on page 23.A special input jack makes the pick-up, whichamplifierloudspeaker unit available for operation di-upon the change of its electrical resistance withdepends for its operationthe requisite negative grid bias. Transformercoupling is employed between the two stages of rectly from the detectoramplification as well as between output of any radio vibrations of the needle,set,in a somewhat differentclassthe amplifier or better yet, a small two- orthan the others as it isthree-tube set, suchdesigned to operatea speaker.as the two-tube R. B. "Lab." receiver, de-speaker without the use of an ampli-output and the loudThe power supply, which is the same as that scribed in the fier.January RADIO BROADCAST byemployed in the RCA-IO4 loud speaker, embodiesunique features.used in the construction of anJohn B. Brennan, may be built just for the Some pick-ups are made of the samepurpose.ordinary radioparts asFirst, a line ballast tube isemployed to compensatevoltage so as to pregraphcase isTerminals are also provided on the type headphono-telephone. That such should be thesupplying B power to the radio receiver.pick-up is exactly the reverse of the loud speakerquite reasonable, for the function of thevent changes in filament current of the 199 tube,unit can be converted into a very fine, but needlesslyexpensive, pick-up. One of the tricks tosuch a conversion is the counter balancing of thetone-arm so that the unit, which isquite heavy,does not press too hard on the record.As a rule, however, for best results, a unit designedfrom the "ground-up" as a high gradepick-up should be used. Several units of thistype are now being manufactured.USING A PICK-UP WITH ANY SETREMOVING the base from an old 2OI-ABYtube (this may readily be accomplishedby heating over a gas flame to melt the cementin the base and the solder on the prongs), andconnecting the leads from a pick-up to the plateand filament prongs, as shown in Fig. 3, thehome-made pick-up shown in iFig. may beused with the amplifier in any radio set. Merelyremove the detector tube and in its place insertthe "adapter." Fig. 3 also shows the inclusionof a scratch filter and volume control.The audio amplifier channels of many radiosets in use to-day are so poor as to make sucha system of using the pick-up most undesirable.RADIO BROADCAST Photograph There is little goodWITHIN THE "PANATROPE"purchasing or constructinga pick-up for obtaining the same quality from a

MAY, 1927 THE ELECTRICAL PHONOGRAPH 23AHOME-CONSTRUCTED PHONOGRAPH-RADIO COMBINATIONBuilt by the author. A more detailed description of this particularinstrument is scheduled to appear in RADIO BROADCAST for next monthA desirable thing to do is to constructa new high-quality lamp socketoperated audio channel of the type describedby the writer in recent issues ofRADIO BROADCAST so as to secure wellnigh perfect phonograph and radioquality.Where the amplifier in the radio setis to be used with a pick-up, the fol-RADIOlowing essentials of good quality shouldbe kept in mind:1. Use of high-grade coupling mediums. Theuse of the new large-size audio transformers,resistance coupling, or impedance coupling, is tobe recommended.2. Use of a power tube in last audio stagewith proper B and C voltages to prevent overloading.~).Use of an output device. Inductancecapacityunits are, in the author's opinion, preferableto the transformer units.4. Use of a high-grade loud speaker.SCRATCH FILTERSan electrical filter circuit of theWHILEtype indicated in Fig. ^ will remove allobjectionable scratch from the music issuingfrom the loud speaker, it will not prevent onehearing the un-amplified scratch noise directlyfrom the record. For this reason the lid of theturntable compartment should be kept closedwhile records are playing.A high-resistance potentiometer, such as theCentralab or the type L Electrad Royalty unit,makes a very excellent volume control, whenwired as indicated in Fig. ->,.As a rule, it willgenerally be found rather convenient to mountthis volume control on a small square or discof bakelite in the turntable compartment of theRADIO BROADCASTphonograph. This same panelPhotographmay also wellcontain the amplifier control switch.To get the full benefit from a home-constructedelectric phonograph,it is essential to use thenew electrically cut records and a good loudspeaker of the cone type. Of course the pick-upand amplifier must be good, but generally, afterdevoting much attention to them, the finalresults are spoiled by failure to use a good loudspeaker.In the June RADIO BROADCAST, details of aconsole phonograph cabinet in which a two-tubeR. B. "Lab" receiver, baffleboard loud speaker,and lamp-socket powered amplifier with recordBROADCAST Photographpick-up, will be described. Data on the constructionof a special amplifier, entirely lamp-socketTHE "BRISTOPHONEoperated and designed primarily for use with aA pick-up of the carbon type which operatespick-up device, will also be given.a loud speaker without using an amplifierR

A Balanced Short-Wave ReceiverA Description, by the Designer of the Best Receiver Submitted in RadioBroadcast's Recent Contest, of a Short-Wave Receiver That Won't Radiateshort-wave receiver described byTHE theauthor in the September, 1926, issue ofRADIO BROADCAST was an effort towardthe design of a short-wave receiver whichwould not radiate and interfere with othernear-by receivers. Although it had many desirablefeatures, it was not as sensitive as a standardshort-wave receiver. The receiver describedin this article is the result of further experimentsand calculations carried along thesame lines. If made carefully, it does not radiateat all and is, in the author's opinion, just assensitive as the ordinary carefully built shortwavereceiver. The improvement over the firstreceiver described is considerable; in fact, thereis no comparison between the two, both as tonon-radiating qualities and sensitivity.The receiver, as shown in the accompanyingpictures, was a model built up after the circuitwas conceived and not in its final form, since athorough job of shielding had not been donewhen the photographs were taken. Imperfectthough the photographed receiver was, it waspossible to copy New Zealand amateurs on asecond receiver while this incompleted one wasconnected to the same antenna and ground system and permitted to oscillate on the samefrequency as the distant station. No interferencewhatsoever was apparent from the oscillatingset during the reception of the NewZealand stations. The writer has never seenany other short-wave receiver which could approachthat mark for non-radiating qualitiesWhen listening to the same New Xealand stationon the balanced receiverdescribed here, the standardreceiver could notbe tuned to the samefrequency without absolutelyswampingeverything with itswhistling. In fact, itwould ruin any attemptto receive anything excepta local stationwhen it was oscillatingon the same frequencyas the received station.Capacity coupling tothe same antenna wasused by both receivers,one being the balancedand the other a standardReinartz receiver.The circuit of thebalanced receiver isshown in Fig. I, and, ascan be readily seen, isa form of Wheatstonebridge. It is absolutelynecessary to use someform of a bridge withthe antenna and groundacross zero potentialpoints of the oscillatingcircuit or circuits.In Fig. i. the midgetBy FRANK C.Amateur Station 6 AJFJONEScoupling condensers, Q and d, form the twocapacitive arms of the bridge and Li,Ca,Csand LjCiCr form the essential arms on theother side of the bridge. Both of these latterarms are tune.l simultaneously to the same frequency,i.e., that of the incoming frequency andplus or minus say 1000 cycles for heterodyningpurposes, and Ci and C2 are left set in a certainnlation to each other. Cs is a resultant capacityfrom the combination of Ci and the gridfilamentcapacity, C ?. The condensers Cs andQ are on the same shaft and should be exactlysimilar so that the two circuits will be tuned tothe same frequency or wavelength at any pointof the tuning scale. The tickler coils, L2 and L4,are coupled inductively to their respective coils,Li and LS, in the proper phase relation to causethe oscillatory currents in the bridge to justneutralize each other, or balance out. L? is coupledto Li so that the detector will oscillate, andLt is reversed with respect to direction of windingto La. Cj is a very small neutralizing typecondenser which is set to the same capacity asGi. This latter setting is easy to determine inpractice. Ce is simply a "throttle" condenserto control the amount of regeneration or oscillationin the detector circuit, such as is used inpractically all modern short-wave receivers.Thus the balanced receiver has one tuning controland one feed-back control, the latter beingadjusted only once or twice throughout the wholetuning range of the receiver. Simplicity and easeof tuning have been accomplished in this receiver.Now for some simple theory as to why the receiverdoes not radiate when properly balanced.The energy of the incoming signal at any oneinstant can be represented by the dotted arrows.This energy splits and part of itgoesthrough each coupling condenser, Ci and C;.The tuning circuits associated with LI and U,are tuned to the frequency of the desired incomingsignal energy and so offer an extremelyhigh impedance to this energy. This means thatmost of the signal energyisimpressed equallyacross the grid-filament capacity of the detectortube and the small capacitance C?. The actionthus far is the same as for any receiver. Theenergy component in the plate circuit of the detectorthrough the tickler coils L. and L, induceenergy in the coils Li and L3 respectively, thatin Li in a direction as indicated by the singleheadedsolid arrow, and in Ls in a direction asshown by the double-headed solid arrow. Thisis obtained by having the direction of the windingsof the coils in reverse directions. The energyinduced in Li adds to the incoming signal energyof the same frequency. and this continuous feedbackcauses the detector to oscillate. Unfortunately,part of this feed-back energy, as shownby the single solid arrows, splits at the top ofthe bridge, part of itgoing across the grid andthe rest through Ci to the antenna, which can,for our purposes, be represented as an inductance,resistance, and capacitance acrossthe points A and G, as shown in Fig. I.The energy induced in Ls, however, is in sucha direction as to be opposite to that inducedin Li in its effectacross the points A andG. The net effect in theantenna circuit is zerooutput from the receiver.Thus we have aone way circuit, theantenna gives energyto the detector but doesnot take any away.Since the circuitCiLsCv is tuned to thedesired frequency, as isalso LiC3Cs, these twoarms of the bridge offerhigh impedance to thefeed-back energy fromthe opposite tickler coilsrespectively, and mostof the energy finds itsway across the pointsA and G. The reactanceor impedance of theantenna circuit is comparativelylow so thatthe main components ofenergy are as shown bythe arrows. The minutequantities, in comparisonwith those shownthe arrows, can bebySHOWING THE DISPOSITION OF PARTS WITHIN THE CABINETautomatically eliminatedor compensated

andMAY, 1927 A BALANCED SHORT-WAVE RECEIVER 25in adjusting the values of Ci and and C2the relative positions of the tickler coilsLj and L< with respect to their associatedcoils, Li and L3 .In order to simplify as much as possiblethe explanation of this receivercircuit, values of energy were spoken ofinstead of induced currents and effectivevoltages. In speaking of induced energy,it was meant that portion of energywhich was available at the points of thetuned circuits which would cause aradiation in the antenna system. Intracing through the circuit using currentsand voltages, all of the phasedifferences must be taken into account,which would make it a very complicatedexplanation of the functioning of thiscircuit.CONSTANTS OF THh CIRCUITA DIAGRAM which maybe somewhateasier to follow in wiring upsuch a receiver is shown in Fig. 2. Thecoils LI and L 3 should be exactly similar,with preferably spaced winding on aform about 2\ inches in diameter. Forcovering the 4O-meter (ysoo-kc.) band, 9 turnsfor use with the 199 type of tubes and 8 turns if2OI-A type tubes are used, is about right. Inthe original receiver, an old ly-plate condenserwas rebuilt so that there were two separatecondensers in the one unit, each with four plates.This set tunes from about 30 up to 50 meters(about 10,000 tofxjookc.) when using ux-igg typetubes. The tickler coils, L2 and Li, are similarand are wound with about No. 26 wire on a 2-inch form with 7 turns apiece. Celluloid dissolvedin acetone was used in holding these coils inshape and makes a minimum amount of dielectricin the field of the coils, L, and L3 ,where thelosses should be kept as low as possible. Thecoils LI and U were space wound with No. 18wire on a 22-inch cardboard tube. Four narrowstrips of celluloid were laid at equal distancesaround the cardboard tube and the wire woundover them. Where the wire touches the strips,it was painted with the acetone celluloid solutionand allowed to dry, after which the cardboardcould be torn out leaving the four stripsof cemented celluloid to support the coil turns.The two coil mountings for the four coils weremade from strips of hard rubber acting as clampsover the coils, and the whole unit was screweddown to the baseboard of the receiver. This arrangementmakes it possible to mount theFIG.-The Facts About this Receiver.N[ame of Receiverof Circuitand Kind ofTubesWavelength RangeBalanced Short-Wave Receiver (Non-Radiating).The circuit is of the autodyne type inwhich the detector acts as an oscillator.The local oscillations are preventedfrom going out on the antennaby a special Wheatstone Bridge arrangement.Two tubes are used, one as an oscillatorand detector, and the other in astage of audio frequency. Either 199or 20 1 -A type tubes can be used, aslight change in the number of turnsin the tuning coils being required forthe different tubes, as explained in thetext.jo to 50 meters(0994 to 5996 kc).This receiver is the result of further work on the part of Mr.Jones in his efforts to develop a truly non-radiating short-wavereceiver which may be used by the average amateur. His firstattempt was described in RADIO BROADCAST in September,1926. The present receiver is more sensitive and radiates far lessthan the first because of refinements in the bridge circuit.tickler coils about an inch from the filamentends of the coils Li and Ls, and to vary thecoupling to Li and LS, which is necessary inbalancing the receiver. Incidentally, plug-incoils could be used in order to cover the otheramateur bands, providing exactly similar coilswith their associated ticklers were obtainablewith plug-in mountings.The feedback controlcondenser, Ce, can be ofany type of some valuenear 0.00025 m fd. maximum,and could as wellb; controlled by a smallknob as a large dial sinct;ithas practically no effectat all on the tuning of thisreceiver. The radiofrequencychoke, in serieswith the primary of theaudio-frequency transformer,is in this case amidget honeycomb coil ofabout 400 or 500 turns offine wire. Any kind of asmall r.f. choke coil canbe used here, though onewith a very small externalfield should be used. Therenothing new or different in the audio amplifier,isthough a peaked transformer could be used toadvantage here, say with a resonant peak somewherebetween 600 and 1000 cycles. The couplingcondensers, Ci and C2 are midget variablecondensers of very low capacity, of which thereare numerous types on the market. The grid condenser,C5 , should be about o.oooi mfd . thegrid leak, R, of about 8 or 10 megohms in value.The detector socket should be well cushioned, apiece of sponge rubber being used in the receiverdescribed.In balancing the receiver, a separate shortwavereceiver should be set up, preferablyusing separate batteries, but coupled tothe same antenna and ground. By listening-inon the regular short-wave receiver, a loud squealwill probably be heard when the two sets aretuned to the same wavelengths. It is a good planto use about 45 volts on the plate of the detectorin the balanced receiver in order to make surethat the oscillations will be quite strong. Ci andC2, together with C;, are then varied until thebridge is balanced, which condition will be indicatedby there being no interferencein the regular receiver when the two aretuned to the same frequency. If thesame relative setting of Ci and C2holds true for the whole tuning rangeof the receivers, then the receiver isnicely balanced and the tickler coils arecoupled to coils LI and Ls correctly,and the small capacity C? is correctlyadjusted. If the condensers Ci and C2have to be changed, then try readjustingCT, and also the tickler coil couplings,until a correct balance is obtained.In order to improve the receivershown, the coupling condensers Ci andC2 should be shielded from the rest of theset so that there is no capacitive couplingto the antenna on the antenna sideof the condensers. In this set, the antennalead was brought into the set in abunch of battery leads, which actuallyshield it to some extent until it reachesthe condensers Ci and Q. A goodarrangement would be to have the commonconnection point to the antenna asnear as possible to the place where thetnonJI down lead comes through the shieldedbox. Another better arrangement wouldbe to have the twin condenser placed in the centerof the front panel and the two circuits placedsymmetrically on each side of it instead of in the+22 '/>+ 45FIG. 2arrangement as shown in the photograph.The set should of course becompletely shielded, in order thatno radiation will take place fromthe coils, etc.. of the set itself.

What About the A BatteryThe Importance of Balance in Trickle Charging Those Misleading"Statements About A Battery Elimination" Comparing the Methodsof Charging and Their Costs The Best Rate and When to ChargeBy EDGAR H. FELIXfails to function because of a APower is a term used to describeWith charging rates as high as two amperesgradually until the set at last comparatively few who manufacture such a device supplying B current also most simplicity and, by observingdischargeddevices which enable aSOCKETreceiving set to draw battery. In this case, unless the trickle charger available, the danger of grave overcharge,its power directly from the electric light has a high charging adjustment which permits resulting in quick destruction of the battery, ismains. To the uninformed enthusiast, it usually bringing back the battery from its discharged constantly present. On the other hand, a fewimplies a complete elimination of all the elements state to full charge quickly, it is difficult to restore hours a week with a high charging rate, and a lowof the power supply system which require care it to good working order without the assistance of trickle charge for the balance of the time, willand attention.a high-rate charger. When a user experiences a keep the battery in the best of condition.Socket power devices now on the market fall run-down A battery, he naturally increases the There are always occasions when a set is used aslightly short of accomplishing this desirable trickle charging rate to the maximum, which great deal for a few days for special reasons, andresult. They do, however, reduce to the very should bring the battery back to full efficiency in this case a higher charging rate istemporarilyminimum the care and attention required to in several days. But often, he considers such an necessary to bring the battery back to full charge.keep the receiver's power supply at full efficiency.experience as evidence that the charging rate The table on page 27 shows the chargingThe storage battery and rectifier, which should permanently be kept at maximum. For adjustments recommended by Philco. This tablethese devices invariably combine in a single a long time, perhaps even two or three months, gives the average number of hours a dayunit, do nevertheless require a little intelligent this rate gives satisfaction because the battery is a set may be used at various current drains andcare, and, given that care, are both reliable and always kept fully charged, but, sooner or later, the charging rates. For example, with a five-tube setconvenient.battery breaks down completely from prolonged used 3.02 hours a day, each tube drawing aThe most advanced types of socket power and continued overcharging, Active material quarter of an ampere, the trickle charger at theequipment comprise a charging device and storagestarts to fall out of the plates and, also, the speci-0.2 ampere adjustment will keep the battery upbattery so designed that the battery is left fic gravity of the electrolyte may rise to a high to full charge. If the set is used but two hours aon charge at a slow or trickle rate during the value and the distilled water of the solution day, the trickle charger should be shut off byentire time the set is not in use. Therefore the requires renewal every few days. Usually the removing the attachment plug occasionally sostorage battery is either discharging through the manufacturer is condemned for these misfortunes, that constant overcharging is avoided.tubes of the receiver or being charged by the while the cause issimply incorrect setting of the On the other hand, such a five-tube receivertrickle charger. Theoretically, the only attention trickle charging rate.may be used for twelve hours within two dayswhich must be given such socket power devices Different socket power devices use different because of some special broadcasting event,is the occasional addition of distilled water to combinations of charging rate. Philco, for example,and this would draw a total of fifteen amperethe storage battery and the trickle charger.has three adjustments, low, medium, and hours from the battery. For example, the setEven when turning on and off the set, it is not high, giving 0.2, 0.33, and o.6-ampere charging may be in use from eight o'clock until one a. m.necessary to think about the trickle charger connectionsrates respectively. Willard uses a low and a high on one evening and from six o'clock to one a. m.because, by the use of an automatic adjustment, giving 0.5 and 2.0 amperes, while on the next, drawing a total of fifteen amperedevice, the receiver's "on-off" switch disconnectsGould offers no less than five adjustments, 0.2 hours from the storage battery. Between thesethe charger when the switch is turned on, to 0.25 ampere, 0.275 to 0.320 ampere, o 350 to two periods of listening, and between the secondand connects it when in the "off" position. 0.425 ampere, 0.450 to 0.750 ampere, and 0.9 to period and a third period which we shall supposeWith most devices provision is also made for 1.5 amperes, according to line voltage.commences at eight o'clock on the thirdconnecting the power line to a Bevening, the battery is rechargedsupply device when the controlfor thirty-six hours at the lowswitch is in the "on" position.rate, which gives it back 7.2A minimum of attention is indeedampere hours. Now, if the cur-attained, provided that therent drain, after this experiencetrickle chargeis of the correctof twelve hours' use in two days,rate to offset the current drawnis continued at its normalwhen the set is used. But, alas,average for about three hoursthis condition of perfect balancedaily, and the normal chargingof input to output is not alwaysrate of 0.2 ampereis maintained,happily secured. Therefore thethe battery may never be restoredfilament current require mentsto full charge.of the receiver and the number ofUnderstanding these conditions,hours a dayit is used must beit is not difficult to under-determined fairly accurately, andstand the correct charging rate.the charging rate by the trickleEstimate the average needs ofcharger adjusted to meet them.your set in ampere drain andFor this reason, A power combinationshours of use and adjust the trickleare equipped with meanscharging rate recommended byof adjusting the trickle chargethe manufacturer for that load. Ifrate to suit the power requirementsyou depart from this average useof different receivingby extended use on special oc-sets.casions, use a higher chargingThe importance of balancingrate for a few days to counterbalanceit. On the other hand,charge and discharge becomesapparent when we consider theif the receiver is subject to longeffects of undercharge and overchargeRADIO BROADCAST Photograph periods of disuse, disconnect theupon the life and con-attachment plug for a few daysdition of the storage battery.A THREE-IN-ONE SOCKET POWER DEVICEwhen you estimate the batteryIf the trickle charge rate is tooCombining trickle charger, storage battery, and B power supply in one unit. Althoughmany manufacturers combining the first two in one unit, there These are operations of theto be in a fully charged condition.low, the battery voltage will fallut-

MAY, 1927 WHAT ABOUT THE A BATTERY? 27them, you getthe true convenience of socketpower.The only other attention required to keep asocket power device in working order is to keep itconstantly filled with fresh distilled water. TheGould "Unipower" has an ingenious method ofreminding you of this water matter because therectifier cell is so designed that the rectifier cutsoff just before the storage battery needs renewalof water. Hence the battery will go dead beforeits plates have been unduly exposed because oflack of water. Philco supplies a convenient hydrometerwith certain of its larger storage batteries,fastened in the top of the cell case. If the wateris at the proper level, squeezing the hydrometerbulb draws electrolyte into the charge indicator.If it fails to do so, you are plainly warned that thewater must be renewed. Philco and others alsouse built-in charge indicators which permit one tosee the electrolyte level through the glass wallsof the cell, simple markings indicating the dangerpoint.MISLEADING STATEMENTSWE HAVE observed the advertising andliterature of several concerns purportingto describe A-battery eliminators or insinuatingthat their devices eliminate A-battery troubles,storage battery attention, etc. A number of thesedevices which we have examined, are simply storagebatteries with trickle chargers. To imply"elimination of storage battery troubles" withsuch devices is plain deception. If manufacturersare not above using such deception in theiradvertising, dealers can hardly be blamed forextending this misrepresentation to the consumer.Readers are therefore warned to examine socalledA-battery eliminators carefully beforepurchase, lest they prove to be only the conventionaltrickle charger-storage battery combination.They then require the simple attentionsherein recommended and will fail in service ifthey are not given it.The condition of a storage battery, whetherused in connection with a trickle charging deviceor otherwise, is not difficult to check so long asit receives fairly normal treatment. Voltmeterreadings, however, should not be relied uponunless a very accurate, high-grade instrument isused.A hydrometerisvery useful for the purpose,because it isinexpensive and somewhat moreaccurate in its indications than a voltmeter.However, it too is subject to certain slightdiscrepancies which, when understood, are notdifficult to account for.When a battery is fully charged, the specificgravity is at its maximum. Constantovercharge produces boiling,reducing the water in the solutionand accordingly increasing the specificgravity. Extended and continuedovercharging (such as thatresulting from an excessive tricklecharging rate) tends to force thesulphuric acid to the top of the cellso that we sometimes get a highspecific gravity reading althoughthe battery goes mysteriously deadafter a few minutes of use.Another misleading state is manifestwhen an unusually strong sulphuricacid solution is used. Thissubterfuge is sometimes employedto make a storage battery appearbetter than it really is. In automobileservice, where extremely heavycurrent is drawn for a few seconds,it is of advantage to use a strongsolution because an electric startersometimes draws as much or morethan ninety amperes from the battery but, with aradio battery, no such heavy loads are drawn.The only advantage gained by the use of a strongsolution is a little higher terminal voltage andbetter specific gravity reading; on the otherhand, it causes more rapid deterioration of theplates. The specific gravity reading for a radiostorage battery at full charge should be between1225 and 1300, depending upon the recommendationsof the maker. The majority of radioTo110V. iov. JA.C, .C. _

28 RADIO BROADCAST MAY, 1927The cases of storage batteries are now so welldesigned that they are usually quite sanitary.Hydrometers are equipped with non-drip pointsso that keeping the battery clean is reduced toa small labor. Another convenient form of hydrometer,as stated previously isdesigned aspart of the vent caps, to be screwed permanentlyinto the top of the cell cases. This type eliminatesthe risk of dripping electrolyte, whichdamages carpets and furniture. If acid sometimesgets on the outside of the battery, it canbe taken up with blotting paper or witha cloth which has first been soaked in ammonia.Local chemical action forms a coating onthe terminals of the battery as a resultof moisture or spray from overcharging. Thisshould be carefully removed by means of sodawater applied with an old tooth-brush, followedby final cleaning with a file or scraper. Thisprecaution is apt to be slighted and is often thecause of receiving set noises. After cleaning theterminals and connecting clips, cover them withvaseline. It will keep them uncorroded for aperiod of several months.When a trickle charger or A-battery socketpower unit is not employed, other types of chargersare available. Those of the vibrator typeare the least expensive. They have the disadvantageof causing noise and, if the vibratorcontacts stick, feeding alternating current intothe storage battery. New contacts are easilyinstalled at low cost and a fine file can be usedto keep the contacts smooth and fairly silent.Electrolytic chargers of various kinds can bepurchased separately or in combination withsmall storage batteries, forming a socket powerunit. These require the addition of distilled waterabout as frequently as the storage battery itselfneeds it and, generally after a year or two of use,renewal of the active electrode. Occasionally newacid is needed for the rectifier and that is best renewedat a battery service station, usually at thecost of a dollar or two.Bulb rectifiers are generally of the two-ampereor five-ampere type. A bulb is usually good fortwo thousand or three thousand hours of charging.For example, a set which requires a twentyfiveampere-hour storage battery supply a weekcan be recharged and maintained by five hourscharging a week from a five-ampere charger. Thisis the average A power requirement of a fourtubestorage battery set used about three hours aday. A charger bulb used in this modest servicewould last for many years. In trickle chargerservice, however, the bulb would be in use about140 hours a week instead of but five and wouldtherefore last only five or six months. The bulbdepreciates as rapidly when furnishing halfan ampere as when furnishing two amperes.Some trickle charger outfits are fitted withbulb chargers. Only when the current drainfrom a storage battery is so large, by the use of amulti-tube set for many hours a day, is a tricklecharger of such large capacity necessary. Otherwisethe overcharge danger, towhich we have already referredat length, occurs, and the lifeof the charger bulb is reduced toa matter of months, unless thetrickle chargeris disconnectedfrom the line a good part ofthe time. For example, a halfampererate, supplied fortyhours a week, instead of theentire time the set is not inuse, may tenfold the life of therectifier tube, cut the electricpower required to one tenth,and greatly increase the life ofthe storage battery, by avoidingcontinued overcharging.Since the crux of the whole matter of storage tery, supplies about half an ampere; four suchwatt lamp, connected with a six-volt storage bat- observing the following:battery life and economyis a matter of correct lamps in parallel will deliver two amperes.charging rate so as to assure ample current in the The circuit diagram on this page shows thebattery when you need it but not at the cost of correct circuit connections.continued and damaging overcharging, it may be Two precautions should invariably be observedwhen charging storage batteries. First, beof advantage to suggest a simple charging policywhich meets the requirements of the average certain that the positive or plus, charger lead isindivijual.connected with the red, plus, or positive A-With bulb type chargers (whether combined incharger units or not) it is preferable to usebattery terminal and that the negative chargerlead is connected with the minus A-battery terminal.Second, disconnect the radio set fromthe two-ampere rate on the required number ofovernight charges per week necessary to keep the the A battery terminals, unless you are absolutelystorage battery in condition. Experience willcertain that the power line is not short-determine whether one night a week or two circuited through the charger.nights a week is sufficient to keep the battery in To determine the polarity of the power linegood condition, showing full charge at the end of leads when charging through a bank of lampsthe charging period and still giving reasonable plunge the terminals to be connected withservice voltage before charging is begun again. the battery into a glass of salt water solution.Five-ampere chargers bring the battery back Bubbles will rise from the negative terminal.into condition quickly, but they offer a rate Rectifiers of the electrolytic and bulb type havewhich is generally a little high for radio receiving plain markings, usually employing a red wire forrequirements. A high charging rate means more the positive lead.intensive chemical action with consequently Many misleading statements have been madeintensified deterioration of the plates.as to the cpst of battery maintenance.ServiceWith chemical types, low charging rates are stations charge from fifty cents to one dollar forgenerally available. Perhaps the easiest policy to charging a radio battery and, if this service ispursue is to use a low charging rate during the required twice a month, the cost comes to one orweek, which seems to keep the set going satisfactorilytwo dollars a month, plus inconvenience andunder ordinary conditions, without "time out" because the set is not in service.permitting the storage battery to reach a nearly Chargers of various types are generally advertiseddischarged condition at any time. It may beas drawing negligible current from thebelow full charge a good part of the time without line but this is not always true. The most efficientdanger so long as it is not showing a specific way tochargea battery is with a standard chargergravity below 11503! any time. Then, over the capable of supplying several amperes say twoweek-end, give it a high charging rate, Such chargers draw 25 or 30 watts from the lineif that isnecessary to bring it to the full charge condition. so that, if used five hours a week, only about oneIf the set is used for prolonged periods, one or seventh of a kilowatt, costing from two to threetwo nights during the week, so that the balanced cents depending upon the locality, will be used.condition is upset, restore the battery to its Trickle chargers draw from 5 to 20 watts fromnormal condition by a few hours at a high chargingthe line, the average being about 10 watts.rate.Assuming you use a set three hours a day, thisThere may be occasions when a low trickle means about 630 hours of non-use a monthcharge rate keeps the battery constantly at full which, at 10 watts, means 6.3 kilowatt hourscharge and the renewal of distilled water is found The average rate is ten cents a kilowatt hour sinecessary more frequently than once a month. that the upkeep cost for electric power is aboutThis indicates continued overcharging and sixty three cents a month. The chemical type ofshould be avoided by disconnecting the trickle charger is somewhat more efficient than the bulbcharger from the set one or two days a week. type when they are used for trickle charging and,When some such formula, which gives the balancedfor this reason, from the standpoint of economy,condition, is established, storage battery the electrolytic type is preferable although thismaintenance becomes a simple and easy matter.advantage is offset by the fact that the chemicaltype requires more care in its upkeep than doesCONCLUSION ABOUT CHARGINGthe bulb type.Since it isadvantageous to disconnect theTHOSE few areas served by direct current,IN charger if it subjects the battery to overrectifiers are not suited to storage battery charge, we find in power economy an addedcharging. The only thing requiredis some form argument for disconnecting the trickle chargerof resistance so as to reduce the current supplied two or three days a week. In this way currentto the battery during charge to the value which it cost, with practically any type of charger, mayrequires for the purpose. A convenient form of be reduced to less than a dollar a month.resistance is an electric light bulb connected in We therefore find that A power satisfaction,series with the battery, of a wattage determined with due consideration to convenience, economy,by the battery's charging requirements. A fifty-and reliability, is most readily attained byCHARGING WHERE D. C. IS AVAILABLEFour 50-Watt Bulbs >Phis is a very simple arrangement, no rectifier ortransformer being necessary. The charging rate dependsupon the number of lamps. An ideal arrangementof trickle charging where d. c. is used would beto connect the storage battery in series with an ordinary5O-watt lamp used for illuminating purposes inthe living room. This would give an half-amp, rate.2 Amp' charging rats1. Use a charging system.whether trickle or high-rate,which balances the loadfrom the battery.2. Keep the electrolyte levelof rectifier and storage batteriescorrect by the additionof distilled water.I he first rule may requireoccasional disconnection of thetrickle charger or the use of ahigher charging rate for limitedperiods. The reward for obeyingthese most simple precautionsis unfailing and reliable Abattery service at low cost.

THE LISTENERS' POINT OF VIEWConducted by John WallaceHow Long Will Radio Broadcasting Prosper?kOPING out what isgoing to happen inthe future isalways a pleasurable, ifhardly ever a profitable, pastime. Mostdopesters of radio's future are extravagant intheir prophecies of ever-widening influence andever-increasing prosperity. We are inclined toagree with them, providing they do not attemptto push therr claims too far into the future. Forit is our conjecture that radio will arrive at itsfullmaturity in a very few years. From then onits course will be no more sensational than isthat of the talking machine at the present time.And in a decade or so will come some new contraptionthat will relegate radio to as exciting andvaried career as that of a telephone operator.But this inevitable cycle could, conceivably,be nipped in the bud (astounding mixed metaphor)by the failure of radio to keep up with theexactions of a public which has already becomeinured to it;-novelty. Concerning this possibilitywe have an interesting letter from a reader,I. R. Coolidge jrd, of Brookline, Massachusetts,which presents a good analysis of the factorswhich will determine radio's longevity. Mr.Coolidge says in part:"Answering your questionnaire has promptedme to go further intothe fundamental questionswhich affect thefuture of radio inthiscountry, questionswhich radio enthusiastsdiscuss eagerlywhenever they meetand for some strangereason rarely put onpaper."Without havingany statistics at myIdisposal will assumethat there is one radioreceiver in use for 50nt. of the familiesin America, and thatB C. L.'s may be dividedinto three importantclasses:"i. Average normalhealthy citizens whobuy standard sets ingood looking cabinetsas an investment inentertainment and as-ipiece of furniturefor the living roomand because theirneighbors have one.This class spends from^i to $300.00 onan outfit once in aboutlive years and then.ihout 825 oo per yearinupkeep" For them, this investment cannot be worthwhile in the long run if most of the 'entertainment'is dance music, jazz, cheap popular songs,etc., because the same amount of money wouldpermit them to hear the original performancesat frequent intervals and to go to the dancehalls, etc., where this class of music is current.If this is to be the prevailing type of program,the majority will cease to use their receiversafter the novelty wears off. To hold the interestof this large class permanentlyit will be necessaryto provide music of very high quality indeed,not necessarily heavy classics only butany good music played by well trained orchestras,organ recitals by the most skilled players,good instrumental solos, etc., in the field ofmusic. In other fields, such as politics, education,religion, athletics, and radio plays, the samestandards must be maintained ifbroadcastingis to be permanent. Give the B. C. L. somethingat home which would be expensive or impossibleto obtain outside, and his receiver will be in useevery night."2. Invalids, shut-ins, convalescents, agedpeople, those who are hard of hearing, and thosewho have poor sight. This class is not nearlyAN INFANT PRODIGY AT WRVAConrad Rianhard, aged nine years, who is said to have mastered,to an incredible degree, many difficult piano compositionsso large numerically as the first but it is veryimportant because nearly every family has atleast one member. To this class, the radio is morethan mere entertainment; it is their constantcompanion. Instead of mere 'news flashes' agood reader could read them in detail extractsfrom the morning papers every morning, includingthe best editorial comment. The same couldbe pursued with regard to magazines and popularnovels (a chapter a day). For this class a certainamount of popular music, etc., could beworked in at appropriate intervals before thehealthy members of the family returned fromtheir daily occupations. This class does not buyradio receivers, but uses the family receiver hardand constantly. Often it is because of them thatthe receiver ispurchased."}. The smallest class, the enthusiasts andexperimenters, who buy radio parts and buildand rebuild their own receivers, constantly strivingto improve the quality, the selectivity andsensitivity of reception, always spending morethan they can afford, whether it be in tens,hundreds, or even thousands of dollars, on theirequipment. Most of the readers of RADIOBROADCAST must belong to this group, becausethey alone, among B.C. L.'s, are interestedin technical questionsand details of construction."This group hasspecial requirementsIt wants high gradeprograms just as muchas the first group, butin addition it musthave DX because DXis a definite measureof comparison betweenreceiving sets in thematter of sensitivity."The writer's classificationof radio listenersseems to us anaccurate one, as doesalso his outline of theirrespective demands.The first group, hesays, must be guaranteedfirst class entertainmentor they willgradually lose interestand finally abandonradioaltogether. Thereneed be no grave fearson this score however,for this fact is realizednumberby a sufficientof radio station operators.Of course it is notrealized byall. But thatis their hard luck. The

30 RADIO BROADCAST MAY, 1927NO STRANGERS TO THE MICROPHONEThe first is Eva Gruninger Atkinson, contralto, who sings from KPO; next is Keith McLeod, studio manager and pianist at wjz; the third is MissHonarine La Pee, a "syncopating pianist" at KMOX. Miss La Pee recently won a contest as the most popular artist on the staff of this St. Louisstation. The fourth photograph shows Miss Josephine Holub, violinist on the "Pilgrim" program, heard from KGO on Tuesday nightslisteners, instead of abandoning their receiving boring, in fact, because the musician knowssets, will abandon the inferior stations, whereuponthe inferior stations will Mr.what he is in for.go out of business.Aylesworth might have followed the etherealThe service which radio can perform for Mr. "Lohengrin" prelude with the equally etherealCoolidge's second preludegroupis undeniable. However,to "Parsifal" and by doing so alienateit is a service. That is, it is a department whichthe radio fans from Wagner forever. Instead,can bring the broadcaster no demonstrable financialreturn. Evidently, in this day of cut throatoperation, no station manager can afford to devotemuch time and thought to a group which isnumerically small. But when time and theoperation of the 1927 Radio Law has winnowedthe existing number of stations down to a comparativefew, these stations will find it not onlypossible, but advisable, to provide features forminority groups.Why a Good Program Was Goodinaugural program of the NationalBroadcasting Company, which tookTHEplacelast winter, has come in for quite a lotof praise. Perhaps the most authoritative testimonialto it was that of Samuel Chotzinoff,music critic of the New York World in his column:"Concert Pitch." Commenting on the arrangementof the program, Mr. Chotzinoff said.If Mr. Aylesworth constructed this masterpieceof program making he proves himself abetter psychologist than all the orchestra conductorswe have ever listened to. Mr. Aylesworthknows that the untutored radio ear can-The "Newsboy" at KFNF, Shenandoah, Iowa.JAMES PEARSONnot be much different from the sophisticated Mr. Pearson gives a digest of the news at 7:45concert ear. Four Beethoven sonatas on the same p. M. "The Newsboy"is also heard in a healthprogram are as boring to the trained musician talk atas they are to the public at large, even more 7:50 A. M. On Sundays, Mr. Pearsongives religious talkshe isolates the "Lohengrin" piece by followingits last pianissimo with the lustful, mundanechorus from "Tannhauser." Who but Mr.Aylesworth, ever thought of presenting only thefirst movement of Schumann's concerto? Thismovement contains the best of Schumann'sinspiration the other two are anti-climax.During the intermezzo of this concerto, peoplehave a tendency to scan the ads. in the program.Mr. Aylesworth must have noticed this and decidednot to take any chances. Even the firstmovement demands the listeners' closest attention,so Mr. Aylesworth gives his invisible audiencea chance to relax by bringing on MaryGarden at once. Mary chooses her own songs,but her personality is intriguing, whether shedecides to sing Bach or Irving Berlin. Bear inmind that it is Mr. Aylesworth's purpose to keephis twenty millions from straying out of earshotof the loud speaker.Those who feel that the Chorale from " DieMeistersinger" is a little too steep will stay tchear the "Lost Chord," which follows it. WillRogers follows the "Lost Chord." etc.Compare this amazing program with, let ussay, that of the Cleveland Orchestra, whichpaid us a visit last week. The Clevelandersplayed a Mozart symphony, the Stravinsky"Fire Bird," and three new American compositions.With the exception of the symphony, fpiwhich Mr. Aylesworth can match the Schumannconcerto and the Wagner numbers, the highbroworchestra gave us nothing near as good as anynumber on the radio program.As I see it, it isn't the radio that needs encouragement.Mr. Aylesworth should be consoled,The so-called legitimate musical events get thegreat volume of critical comment because theyneed it. The radio seems to be getting alongbeautifully without it.AT STATION CKNC, TORONTOFrank Blachford, violinist of the Toronto Conservatory of Music Instrumental Trio; R. H. Combs, general manager of CKNC,which is owned by the Canadian National Carbon Company; Arthur Blight, baritone, frequently heard from this Toronto station

MAY, 1927 THUMB NAIL REVIEWS 31Thumb J^ml ReviewsWEBH (and others) The last act of "IITrovatore" by the Chicago Civic Opera Companyfrom the Auditorium stage. This was thesecond trial at broadcasting the Chicago Operaand itproved an incredible improvement on thefirst job. The voices, which in the first attemptwere blurred and echo-y, came out clear and undistorted.The orchestra, as before, was wellpicked up. In fact the whole broadcast made usreconsider our statement that we had little faithin theater broadcasts. It was in every way asuccess, and to our taste vastly more pleasantthan watching the same opera. An unforeseendelay brought this act on almost an hour late.The attempt of the broadcasters to fill in thiswait without specially prepared "filler" was indeeda sorry one.WMAQ The Woman's Symphony Orchestraof Chicago playing the Caesar Franck symphony,which is heard all too infrequently byradio. The first movement of this symphony,full as it is of luscious tunes, could be made quiteas popular as the hackneyed William Tell overtureif radio orchestras would give it sufficientairings. And as real music goes, it would constitutea large improvement on the Tell piece.WBAP Jazz, pre-war jazz of a vintage wethought entirely exhausted. But evidently it ismaking a last stand in the hinterlands. Jigglyjazz with stops, panting jazz with a hurry-uptempo, noisy jazz with neither rhyme nor reason.WHT Al and Pat, the ultra-lowbrow Hellofolkers-ersof a super-lowbrow station, supplyingus with one of the very few stomach laughswe have ever got out of radio. With Al at theorgan, Pat commenced reeling off the weatherreports in delightful burlesque of our old friendthe Pianologue. While Pat improvised a melodramaticand quavering accompaniment on theorgan, Al recited, in the manner of one depictinglittle 'Liza's flight across the ice: "For Iowaincreasing cloudiness and rising temperatureSaturday (sob). Rain Saturday night (tremolo).Sunday cloudy to p-p-p-partly c-c-c-cloudy(blubber), preceded by rain or snow (tears anda complete breakdown)."WLS Haymaker's Minstrels. Oh how sad!Minstrel Shows just naturally don't get overby radio. Even the best of minstrel jokes needthe reinforcement of a clowning End Man andthe cooperation of a lenient For-the-Benefit-of-Charity audience. As for the worst of minstreljokes well those were the type essayed by theHaymakers. F'rinstance: A long discussion betweentwo End Men as to the definition of a newmoon, capped after many minutes of futileintroduction with the side splitting climax "Ifa man by the name of Moon had a son he'd bea new Moon!"KOA Monologue by a Mrs. (or was it Miss?)Harrison. First rate, and in excellent style forradio delivery. Mrs. (Miss?) Harrison is acquaintedwith one of the principal secrets of successin humorous broadcasting, to wit that ofnot pausing after each wise crack for a laugh.Nobody laughs out loud at a radio joke anywayso such pauses are simply flat. This monologistrushed through with her lines at top speedand without underscoring her jokes by a changedinflection of the voice. The ludicrous laugh whichpunctuated her remarks lost nothing of itsmirth in the broadcasting. The sketch was originaland had to do with a club woman's busyday.WJZ and Blue Network A new radio team,Vernon Dahlhart, Carson Robinson, and MaruyKellner, specializing in light popular selections,comedy numbers, and songs of the South. Dahlhart,the singer and spokesman, has a non-old time fiddling. Followed by a trio playingKMA Henry Powell doing some excellentobnoxious Southern accent, striking a happy conventional, uninspired jazz.mean between the orthodox "number" and theSouthern "numbah." The accompanying instrumentsare a guitar and a violin. Rather good.WHT Microphone MiscellanyAl Barnes and Pat Carney again; thistime in the "Your Hour," presenting "A TripThrough the Dials." Highly comical in a boisterous,infectious way. Why, we ask ourself,have we been missing these perfectly elegant WE ARE eternally deluged with printedmatter telling us how this feature drewthree thousand telegrams of commendationand how that artist receives 'em at the ratelow-brows all these years? To those of you whobecome wearied at the lofty pomposity of Doctor of three a minute while his concert is in progress.Damrosch, we heartily recommend the artfully While we frequently scoff, there must be someartless Al Barnes as an antidote.truth in the matter. If so, it is only reasonableWJZ and associates The First National To- to surmise that the advent of radio has broughtBe-Weds issuing propaganda for various pictureshows in the guise of a controversy on the in revenue. Then if this be so, we suggest, withthe telegraph companies an enormous increasemerits of a movie just witnessed. Terrible! no very valid argument to back up the suggestion,that the telegraph companies return someWEAF, WJZ, WEEI, WBZ, WTIC, WJ4R, WTAG,WCSH, WCR, WGY, WLIT, WRC, WCAE, KDKA, of this gold to the people by sponsoring a weeklyWTAM, WSAI, WLW, WWJ, WON, WMAQ, KYW, KSD, program. If the reports of large telegraphic returnsmade by radio press agents are veritable,WOC, WCCO, WDAF, WFAA, WSM, WMC, WSB,KFKX, KVOO, KOA, KSL, KPO, KGO, KFI, KGW, KOMO, which the telegraph companiesKFOA, KHQ, WJAX, WHAS A will probablyspeech by one Calvin now deny, we can see no reason why theyCoolidge on the occasion of Washington's Birth- shouldn't spend several grand a week dishing outON THE AIRAT WBBM, CHICAGOHoward Osburn's International Radio Orchestra. Left to right: C. Mason, P. Beckler, H. Osburn(leader), G. Moorehead, and N. Sherrday. But of course you heard it, so write your ownreview. This issimply for purposes of record.WAIU Celebrating the installation of a new5OOo-watt transmitter by reading a lot of telegramsand sending the best regards of the chiefengineer to some personal friend of his in Florida.WAAT Nut Club at 2 A. M. Oh well, it wasour own fault for staying up that late.KOIL A radio play "The Scoop." Good inthat it was easy to follow and had a quick movingplot. But the lines were amateurishly writtenand read in a none too convincing manner.WFAK (or WFAD or WFA| or wpcx!?)Clearwater, Florida. A garrulous announcer whotook up at least as much time between numbersas the numbers themselves, and in spite of all hiswordiness never succeeded in pronouncing his callletters so they could be deciphered by any oneother than a magician. In striking contrast toKFI whose announcers, realizing, no doubt,that they represent the most sought after DXstation, call their letters with a pause betweeneach one making the signal intelligible througheven the worst static disturbances.a first rate program. And if their programs weregood enough they might receive enough of telegramsto pay the entire cost of said programswhich issomething like the worm devouringhimself.TpHE KFI-KPO-KGO network has been broad-* casting a series of concerts by the Los AngelesPhilharmonic Orchestra. The final concertwill be on April 23 from 9:10 to 10:45 p. M.Walter Henry Rothwell is conductor.CommunicationsSIR:The National broadcasts form 95 per cent,of what's worth while on the air to-day and theyare making, or rather saving, radio, but unlessone goes up and down the dials on the hour andthe half-hour he's liable to miss much that isreally good and worth while, for nowhere arethese programs all listed the chaff winnowed

32 RADIO BROADCAST MAY, 1927from the wheat. Many metropolitan newspapers altogether, or keeps well hidden in tho background,even the name of the advertiser.bos who keep time with a pick handle. I am in-the flatted and fluttery vocalists, or the jazz-own or are affiliated with some one broadcastingstation, and labor under the short-sighted policy These great, national broadcasts can't continueunless they bring their sponsers at least a KDK A in daylight, or 4 QG at night, then 1 knowradio programs of any big event that isterested in DX because if the set will bring inthat they should make no mention in their dailygoing out fair return, and they are not going to bring such that the machine iskeeping step in a halfheartedmanner, and will bring home enter-Year's Day, for instance, the Chicago Tribune amount of definite publicity for the advertiser tainment if the weather will let it.through stations other than their own. On New return unless they are tied up with a certainfeatured the fact that it would put on the air in question, both in the news and over the air. Even in this stationless part of the countrythat afternoon, through its station, WGN, aR. H. J. nearly every wave carries two stations and atelegraphic report of the Leland StanfordMILWAUKEE, Wisconsin. pack of coyotes. It is to weep.Alabama football game in Pasadena, "with theROBERT T. POUND.WGN Quartet singing college songs and furnishingthe local color." Thousands of fans in this Your fourth question on the enclosed ques-SIR:LAVINA, Montana.part of the country listened to Quin Ryan's tionnaire has been answered in a general mannerSIR:"kiss-proof-lip-stick" voice broadcast this big because I think American people tend to judgegame from Of the ticker, not knowing that KYW the quality of their cigars by the all the "technical" journal's articles 1 likeprice. ("Whatyour facetious articles best of all. Your selfadmittedignoranceand the wjz Chain was puttingit on the air directfrom the Rose Bowl!the fourth question in the recent RADIO BROAD-are the six best broadcasts you have heard?" wasis refreshing, as is yourstyleAnd one other thing in this connection: If I CAST questionnaire). As a simple matter of writing.of factP. L.were a national advertiser, spending from $1000 I believe it can be demonstrated that there areSAN FRANCISCO.to $10,000 a week in creating good-will by giving hundreds of voices as good as the best advertisedthe radio public the splendid programs that such ones, dozens of comparatively unknown orchestrasthat should be ranked near the top,real I think there is too much constructive criticismSIR:advertisers are giving, I'd see to it that I hadcooperation from certain participating stationsand the of theand so on.newspapers which own them. What 1 desire in radio is entertainment. destructive type in your dept. "As theIfBroadcaster Sees It" isStation WON never misses an opportunity of I wish education it can be secured from booksmy preference.F. H. S.cutting off the New York announcer; and the and magazines in a fresher, more interesting, andChicago Tribune does all it can to create the impressionthat it, The World's Greatest, at great like to hear a few great men talk over the radiomore permanent form than by radio. I shouldPITTSBURGH, Pennsylvania.expense, out of pure love, is furnishing this wonderfulprogram to its Dear Readers. It hides others can't ride on my electrons. Neither canjust to discover how human they are but the There seems to be some difference of opinionhere!WHAT THE LISTENER LIKES AND HOW HE LIKES ITIN THE January and February RADIO BROAD-CAST a full page questionnaire appeared inthis department which was answered in greatdetail by readers of the magazine. More than1000 answers were received and the results aretabulated below.It is difficult to interpret the results fairly, becausewe had answers from city dwellers in congestedradio districts and from listeners in remotepoints, many miles from the nearest broadcastingstation. Many answers were not definite but wereinterestingly qualified. It will be seen that thereplies are classified according to the district fromwhich they came. Metropolitan centers, such asNew York, Chicago, and San Francisco, wereseparated from the others in the tabulation.Among the many important conclusions to bedrawn from this survey, perhaps the most impor-tant is that, under present radio conditions, thecity listener, especially in the large city, relieson his local stations for the most part, while thoseliving some distance from the so-called "keystations" rely on DX. The comparatively fewlisteners who answered our specific question: Isthe DX listener disappearing? gave conclusivereply that the DX listener is here now and forevermore. Another interesting conclusion is that"instrumental music" is favored as above allother classifications by more than 60 per cent.Serious music, so called, was most popular, althoughnot overwhelmingly so.The fourth question about the six most popularbroadcasts received a variety of answers,which fell into three classes, as the tabulationshows. Our purpose was to discover what sixbroadcasts had attained great popularity. TheThe Resultstabulation of this question shows that the regularfeature or "hour" of greatest popularity wasalways the one which was broadcast over thelargest number of stations. But the comparativepopularity of broadcasts such as that of theHappiness Boys and Sam 'n' Henryis remarkable,for each feature is broadcast over but onestation. In special events, sports broadcasts topthe list. Among individual artists, the name ofJohn McCormack appears most often, althoughthat of Walter Damrosch is a close second.After this tabulation was completed a largenumber of questionnaires were received whicharrived too late to be tabulated and we regretthat these could not be included. And to allthose who sent in letters of comment and appreciationand the filled-out questionnaire, we offerour hearty thanks. THE EDITOR.IDo you listen to your radio evenings as you would toa regulal show, or do you simply turn it on and useit as a background to other activities?New York Chicago San NationalFranciscoAs a background 10 3 4 91As a showAs a backgroundexcept for features4580)O 18 370448Vocal MusicRadio PlaySpeechEducational LectureMiscellaneous NoveltiesWhat are the six best broadcasts you have heard?Hours or Regular EventsDo you regularly tune-in on distant stations or do youregularly rely on your local stations?Locals onlyRegularly rely ondistance'6s2?1927314423Distance occasionally187(They tell us that the DX hound is a fast-disappearingbreed. Is he?)Yes I o 6 36No 3 3 3 92If you had a hundred minutes to listen to all, or any3part of the following broadcasts, how would you apportionyour time?Instrumental Music:Serious 26.3% 30.1% 28.5% 23.3'';,Light 18. 18.2 14.3 18.4Popular 16.6 14.8 16. i17.4Silvertown 19Tioldv and Dustv . 185-34-77-69-513.61.74.28.29.28.03-4.612.3.2.67.012.8Atwater Kent 228Victor Hour 128N. Y. Symphony 93Eveready 89Boston Symphony 76Maxwell Hour 53A. & P. Gypsies 49N. Y. Philharmonic 48Whitall Anglo-Persians 47Clicquot Club 44Capitol Theatre 44Ipana 40Goldman's Band 38San Francisco Symphony 33Happiness Boys 31Roxy -30Royal Hour 28George Olsen 28Sam 'n' Henry 26Zippers 26KDKA Symphony 25Balkite 22Cook's Travelogue 19Little Jack LilileMarine BandRecord BoysDavis Saxophone Octette .Special EventsDemps'-y-Tunney FightInaugural N. B. CWorld's SeriesArmy-Navy GameCoohdge's Inaugural ....Radio Industries BanquetDemocratic ConventionPershing's Farewell ....Alabama-Stanford Game .Dempsey-Firpo Fight ....Election 1924John McCormack .Walter Damrosch .Schumann-Heinck .Calvin CoolidgeVincent Lope/ .Joseph HoffmanWill RogersRev. CadmanHeinald WairenrathMadame HomerMarian Tailey.Godfrey LudlowMary Lewis .Mary GardenRev. Fosdick . .Wendell HallIndividuals181615"53131124833920133913302818111614

'Filament Lighting from the A. C. MainsA Discussion of a Practicable Method for Batteryless ReceiverDesign The Advantages of Series Connection of FilamentsBy ROLAND F.BEERSA NATURAL query when discussingwhy such an arrangement iscrease the values of the constants untilFig 2, may in- thecircuit shown in I- 1C.. 2subject of series filaments is to inquire we obtain the same degree ofrequiredfiltering for 23either necessaryamperes at 6 volts. Our structure will then lookor desirable. This inquiry ably illustrates like Fig The i. weight of such a device would bethat growth of tradition which radio is rapidly approximately 300 pounds, and its cost, on theaccumulating. With a few exceptions, modern same basis as previously assumed, would averageradio receivers up to the present time have $i 500.00! For the reason of its weight^and cost,employed the parallel filament connection. The it is therefore not feasible to effect A-batteryfilaments of the radio tubes have been operated elimination at 2\ amperes.from a constant 6-volt source, and variations of There are two main reasons why the seriesindividual tube filaments have been made by filament connection is so much more desirablechanging the applied voltage.from the power standpoint. The first reason isIt is not difficult to trace the reason for the that the total current to be filtered is very muchprevalence of the parallel filaments scheme. In less than with the parallel system. With anythe beginning, audion filaments often required number of tubes in series, the maximum currentone or two amperes for each tube. A multi-tube required is only that taken by one filament, andset would therefore require 3 to 6 amperes. as the size and cost of filter chokes increasesWhat better source of power was there, then, rapidly with the increase in the amount of currentthan the familiar 6-volt storage battery a lowvoltage,they are required to pass, we realize the economyhigh current capacity affair? Its availa-possible by a reduction of current.bility through the regular channels of distributionWe are somewhat assisted by the fact that thewas assured, and everyone was acquaintedwith its operation and maintenance. As the firstuses of the vacuum tube were determined bythe amateurs, so were its tendencies bound tofollow along their pioneer activities. It did nottake long, therefore, for the 6-volt parallel filamentscheme to become firmly entrenched in theminds of those who were to become radio setdesigners and builders of later periods.In answer to the query concerning the systemwherein radio tube filaments are arranged consecutivelyC 2000 to 8000 mfd. for 6 Volts, 2.5 Amps.in series, it is first necessary to showwhy A batteries have not yet been completelyFIG. Ieliminated by the use of the parallel filamentscheme. Let us first consider the general principlesfiltering efficiency of a choke coil increases withof power supply, illustrated by the modern the current through it; therefore, we should beB-power unit. Here we have the customary able to design a more efficient filter system for Atransformer, rectifier, and filter circuit, as shown supply than for B supply, as far as the chokes arein Fig. 2. The current and voltage capacity of concerned. The amount of energy that can besuch a device is of the order of 85 mA. and 200 stored in a given choke coil isequal to one halfvolts d. c. The degree of filtering of high-grade the inductance times the square of the current.units of this type In spite of this fact, however, there are otheris such that a variation orripple of but o. i per cent, is attained in the currentconsiderations which work to our disadvantageoutput.in the design of a high-current choke coil. ForIf high-quality reproduction is desired, with example, on account of the direct-current satura-freedom from hum and "motor-boating," it is tion of the steel core it is necessary to includeabsolutely necessary that the variation in current large air gaps in high-current chokes. These airsupply be of this order. In order to achieve this gaps reduce the effective permeability of the coredegree of smoothing in plate supply devices, to low values, makingitnecessary to increasea filter structure of such design as is shown in the amount of copper and iron to large quantities,Fig. 2 is used. The retail cost of a structure of in order to attain sufficient inductance at highthis type is approximately $20.00.direct-current saturations. We are also limitedIf we are to adhere to the same standard of in this consideration by the amount of copperquality with regard to the A powersupplysource, it is also necessarythat the current ripple shall not exceedo.i percent. This statement has _ Tbeen theoretically demonstrated andexperimentally verified, using anaverage radio receiver with no po- ^tentiometers which may be used tojbalance out any hum. With such areceiver the storage battery mightbe replaced with this theoretical Afjpower-supply unit. Basing our judgmentupon the design ofwethe filterthat can be used in a choke coil, on account ofthe d. c. resistance. If the choke coils havehigh d. c. resistance, the voltage output of apower unit intended for parallel filament supplywould be much too large on a j-tube set, forexample, if the unit were designed to supplysufficient voltage for a 6- or 8-tube set. A powerunit having sufficiently low regulation for parallelfilament operation would therefore requiremonstrous inductances.A second reason why the series filament connectionis desirable is that higher voltages areavailable for filtering. For example, a j-tube receiverwith 100 tubes in series requires 15 voltsfor the filament supply, and an additional 15volts may be advantageously employed for gridbias. Therefore, the total voltage required is 30volts instead of 3 volts (grid bias is obtainedfrom external batteries) for the parallel filamentconnection. Additional voltageis also availableat the filter circuit by virtue of the fact thatthe A current is obtained through a series rheostat,the voltage drop through which may rangefrom 100 to 150 volts (Regulation in this circuithas not the same importance as in the parallelfilament scheme, because it is a constant-currentsystem and not a constant-voltage system). Thetotal voltage applied to the filter circuit isequalto the sum of these values or approximately200 volts.Now it is a matter of common knowledge thatcondenser efficiency in a filter circuit is muchgreater at high voltages than at low voltages.The amount of energy stored in a condenser isequal to one-half the capacity times the squareof the voltage applied. Therefore, from thisstandpoint alone, a great saving is gained. Forexample, if a total capacity of 12 mfd. is requiredfor a given degree of smoothing at 200 volts, thecapacity required for the same degree of smoothingat 3 volts would be in excess of 50,000 mfd.The saving in inductance and capacity affectedby the use of the series filament scheme is thereforeenormous.Fig 3 shows a typical filter circuit for use inconnection with IQQ type tubes in series. Thisarrangement actually gives the same degree offiltering found in IFigs. and 2. Its cost is withinreasonable limits, in comparison with othermethods of power supply, while its size is notbeyond the scope of average radio cabinets.One obvious way in which to attack the problemof series filament connections is to place thevacuum tubes consecutively in sequence, in thesame order in which they normallyoccur. That is, we may begin withthe radio-frequency stages and runthrough the detector and audiostages. While this method may appearto be the most straightforward,it isopen to several criticisms.In the first place, it has been demonstratedthat less difficulty with humwill be experienced if the detector isplaced nearest the B-minus or groundconnection. Several different theorieshave been advanced to explain thissituation, but the important fact to

34 RADIO BROADCAST MAY, 1927the average set constructor is that a real advantage Examination of the other filament circuits bias, the number of available biases was insufficient.A receiver wired in this manner veryisgained by this position of the detector tube. would indicate similar overloading.A second difficulty frequently encountered On account of these various difficulties involved,frequently blocked completely in one or morea study of the stages on account of improper grid bias. Whenin this method of series connection is that theproper values of negative grid bias are not always errors which existed in the straight series connectionand to makestages, amplification was again at normal values,C batteries were inserted in these troublesomeavailable. In certain commercial receivers, notablythe Western Electric 4-6 super-heterodyne, such alterations asbut as this receiver was intended to be a batterylessset, other means of grid biasing were sought.it is common practice to connect the grid return were required to bringlead of those tubes requiring negative grid bias the radio receiver toThe second difficulty was encountered in theto some preceding filament in the series. This its normal operatingr.f. stages, where regeneration often occurred.connection takes advantage of the voltage dropIn this situation the operator is unable to controlhis receiver on account of the incessant squealso B+ Max.and whistles of heterodyned carrier waves. Asimilar situation may also exist in a.f. stages.In this case it may cause an audio howl that willB+ Int. completely prevent reception.The means^^finally adopted in obtaining correctgrid biases was to place a 60- to 75-ohm adjustableresistance in series with each-4-0 filament, for3+ Det.199 type tubes, as shown in Fig. 5.This methodentirely satisfactory and has been used to someextent in Western Electric receivers. If adjustableresistances are used, the plate current of eachtube can be set at the right value when final testsare made on the receiver. Fixed resistances maybe used, however, if the constructor does notwant to make this refined adjustment. The platecurrent of each 199 type amplifier tube can bereducedA.C. Filament to about 2.2 mA., with 90 volts on theSupplyplates.For Power Amplifier TubeWhen the 6o-ohm resistances were placed inposition in the filament circuit, it was found thatthere was noFIG. tendency to regenerate, as out-3in the filament circuit, and employsit as a gridbias. It can be readily demonstrated that whilesome of the tubes in the series will be benefitedby such a connection, there will always be atleast one of the tubes for which the requirednegative grid bias is not available. The thirdobjection to the straight series connection is thatall of the 199 tube filaments, with the exceptionof the first, must have some current overload inthem, if the applied plate voltage exceeds 40volts. For an analysis of this situation, see Fig.4-In this diagram, with no potential applied toany of the plates, the filament current ammeter,A, could be adjusted to read 60 mA., and thecorrect current would then be passing througheach tube filament. However, when B voltageis applied to the plates, current flows in all theplate circuits, as indicated by the plate milliammeter,B. This current must return to the negativeB. If we check the current in the filament fortube No. 3 at the point (b) we would find that itwas carrying the regular filament current plusthe plate current of tubes Nos. i and 2, because,as stated above, these plate currents must returnto the negative B, and the most direct path isthrough the filaments. Consequently, the filamentof tube No. 3 would be overloaded by anamount dependingupon the plate currentof tubes Nos. i and 2.The data printed onthe diagram, Fig. 4,give the amount of currentin the filaments ofeach of the first fivetubes. The amount ofoverload depends onthe plate current of thepreceding tubes. Thus,in the case of tubs No.3 (the 2nd audio stage).the overload isequalto the sum of the platecurrents of tubes Nos.i and 2.1st. R.F. 2ndR.F. 2nd.A.F. 1st. A.F. DET. 3rd. A.F.Tube No. 1 -IfTube No. 4- lj-t-IP,+IP2+ IP 3-Tube No. 2- Ip- IP,TubeNo.5- If-t+ IP -t IP 1P, 2 3Tube No. 3- lf tlP,+ IFIG. 4Ir* Normal FilamentCurrentIP. Plate CurrentThe first step in this direction was to place the lined above. From a study of Fig. 5 it may benormal grid bias on each tube, with 90 volts on seen that r.f. currents in tube No. i must traversethe plates of the amplifier tube and 45 volts on the filament of tube No. 2; likewise, those currentsin tube No. 2 must pass through the fila-detector plates. It was frequently found that, ifthe various filament voltage drops were relied ment of tube No. 5.The question might ariseupon as the only source of grid bias, three difficultiesarose. First, because of the need of a tube ation. It was found, however, that the inclusionwhether or not this would be a source of regener-in the series ahead of each one requiring grid of the 6o-ohm resistances in the grid circuit ofthe respective tubeswas of the propervalue to eliminate thetendency tooscillation.This phenomenon is awell known fact, andin many modern radioreceivers a resistance isdeliberately includedin the grid circuit forthe purpose of stabilizingthe tendency tooscillate. The principleinvolved here is that,if the resistance of anoscillatory circuit is ofsufficiently large value,sustained oscillations

MAY, 1927 FILAMENT LIGHTING FROM THE A. C. MAINS 35FIG. 6resistances6o-ohm resistor ahead of each amplifier tube forcannot be produced therein. Such a circuit is saidseries, including i. Wire all filaments in ato have a high decrement.grid bias, (see Fig. 5).2.When the series filament receiver had beenChoose the proper order of wiring the filaments,so that the detector is next to the B minusprovided with proper grid biasing, as described,or ground connection.it was found that its performance was at least3. Place shunt resistances across each filament,equal to that of a similar set with parallel filaments.as shown in Fig. 5.This particular receiver had two stagesof tuned r.f., detector, and three stages of The foregoing discussion is based upon a plateresistance-coupled a.f. amplification. Five ux- voltage of 90 volts on all amplifier tubes, so that199 tubes and one ux-i 12 power tube were used. large signal voltages may be applied without distortion.Under this condition it is necessary thatA filament battery of 36 volts was employedfeeding 60 mA. to the set. A plate battery of 157 a negative grid bias be obtained in some mannervolts delivered a total current of 22 mA.for these tubes, such as by the use of the 6o-ohmIf the results of Fig. 4 are now applied to theset in consideration, it is readily seen that thefilaments of all the 199 tubes in series, with theexception of tube No. i, will carry a currentwhich is in excess of 60 mA. The excessive currentin the last tube in the series may rise to a valuewhich is30 per cent, above the normal value.The actual current overloads may be computedby reference to the table on this page. In thistable, the overload figures are obtained by deducting6ofrom the filament-current figures givenin the second column of figures. These data arebased on the assumption that all tubes haveproper grid bias, that amplifier tubes are providedwith 90 volts on the plates, and that detectortubes have 45 volts on the plates. Thisarrangement will give a plate current in eachamplifier tube of approximately 2.2 mA., whilethat of the detector tubes will average i.o mA.A very simple and satisfactory method of reducingthe filament current overload is to shunta bypass resistance across each filament, asshown in Fig. 5.These resistances do not allhave the same values, and their proper size, for199 tubes, is determined as follows :-.R = IExcess Filament Current, Amperes.For example, the last tube in a 6-tube serieswas measured, and its filament current wasfound to be 71 mA. The excess filament currentis therefore 1 1mA.,oro.oi amperes. The correctIvalue of the bypass resistance is then equal to,. or 273 ohms.The table shows the correct values of bypassresistance to be used in various combinations of199 tubes.When the receiver has been provided withthe correct biasing resistances and filamentshunts, it is now ready to be connected up foruse. If the receiver is to be used in connectionwith an electric power supply device, it may benecessary to take additional precautions to prevent"motor-boating."For the present discussion, the following rulessummarize the procedure in laying out a seriesfilament receiver using 199 tubes:in series with each amplifier filament.It is entirely possible, however, to build a satisfactoryseries filament radio receiver withoutthe use of these 6o-ohm resistances, for use onmoderate volumes. In this case it is essentialthat the amplifier plate voltage shall not exceed50 volts, so that the average plate current willlie between 2.0 and 2.5 mA. This situation frequentlyprevails in radio-frequency stages wherethe signal voltage is low enough not to warrantthe use of a high negative grid bias, and also inresistance-coupled a.f. stages where the actualvoltage on the plates is frequently of the orderof 40 volts.In such cases as these a very simple proceduremay be followed that of connecting the gridreturn leads to the negative leg of the respectivefilaments, as shown in Fig. 6. It is, of course,apparent that the use of shunt resistors acrosseach filament isalways necessary, in order toprevent current overload. It will also be advisableto provide some means of stabilizing the r.f.amplifier, thus preventing the tendency to oscillation.The inclusion of the 6o-ohm biasing resistancesreduces this tendency to a very lowdegree, but without their use, difficulties are athand. A satisfactory means of overcoming thissituation is to bypass these r.f. currents througha o.i -i .o mfd. condenser shunted across each filament,as shown in Fig. 6. The use of these bypasscondensers insures complete control over thereceiver at all times and affords a greater possibilityof high-quality reproduction.

AS THE BROADCASTER SEES ITDrawings by Frantyyn F.StratfordOne Explanation for the Plethora of Broadcasting StationslOR some time, as the number of breadthalthough it is actually losing in "HE ALSO WANTS TO SHINE AT HIScasting stations in the United States Some of them are even willing to holddollars and cents. The boosters must broadcast.||* bagmounts toward the thousand mark,I for a while, as a matter of civic pride.have been wondering where they all came from, In some cases the stations actually receiveand what process caused them to multiply. Did community support through the localthey reproduce by simple cell division, like the of Commerce or some other semi-official oramoeba? Did they cast spores over the countryside,official agency. Then, of course, there arewhich, falling on fertile soil, took root and municipally owned and operated transmitters,became new transmitters? Or was itnecessary to such as those of Atlantic City, New Jersey (WPG),mate a pair of them in order to produce a third? and New York City (WNYC). Whether municipallyWhatever the mechanism,maintained or not, broadcasting stationsI have found oneof the sources of their nourishment, which heretoforetend to function as the mouthpieces of theirI had overlooked. In small towns, it may respective communities "The Voice of What-well be the principal urge leading to expression ever-It-Is" being a common slogan derived fromin kilocycles. It is the booster spirit, the " Bigger this role.and Better Blattville" pressure which all but Of course there are very definite limits, economicblows off the safety valve in the would-be metropoliand electrical, to this process of com-of the inland states. Among other activities, munity-magnification by radio. The towns maybuilds broadcasting stations.compete all they like in fire engines, railroaditThe rivalry between country towns, while ticket sales, and fraternal orders; such mattersusually good-natured, is exceedingly intense. are their own business. But radio knows noWhen itgoes so far as to lead to the posting of county lines, and there is no such thing as one'ssigns about the town, urging the citizens to buy own business when it comes to letting looseround-trip tickets at the local railroad station, ether waves of frequencies between 10 andin order that the total for the year may be 50,000 kilocycles per second. Furthermore, tohigher than the ticket sales of some rival settlementdown the line, it is apt to extend to all the is about as rational a procedure, economically,plant a broadcasting station in every townshipother activities of community life. One of these as maintaining a dozen telephone systems. Inis broadcast reception and transmission. Some wire telephone systems, for reasons too elementaryvillage of 2000 out on the plains possesses ato require statement, unity is the aim. Andbroadcasting station, perhaps by accident. A right there we have the answer to the broadcastingmanufacturer of babies' diapers, say, has erectedproblem as it affects the civic ambitionsit to advertise his product. Incidentally, he of the smaller towns. Instead of Podunk havingadvertises the town. The next village, with 4000population and a natural feeling of superiority,feels an irresistible impulse to have a broadcastingstation bigger than the diaper broadcastingstation. The local manufacturer ofvarnished pretzels thinks he might take a whackat it. His primary object is, ofcourse, to advertise his varnishedpretzels. But he alsowants to shine at his luncheonclub among his fellow businessmen. He wants to be slappedon the back by the Presidentof the Chamber of Commerce.He wants to be pointed out asa benefactor of the town. Theseconsiderations weigh with himas much as his itch for gold.No doubt they are the determiningfactor in many caseswhere a station stays on the airLUNCHEON CLUBits own precious twenty-watt squeaker manipulatedby one of the local apprentice electricians,and Peadunk, fifteen miles away, competingdesperately with a twenty-five waiter,let Podunk and Peadunk and a few others, ifthey must broadcast, contribute toward a commontransmitter, and maintain studios connectedto itby wire lines. There is plenty of No. 12copper running on poles over the countryside,and, at any rale, one Iransmitter with a halfdozenstudios is better than six transmitterswith one studio apiece.Broadcasting and Social UpheavalsAOUT a year ago the British general strikeflared up, ran its course, and came to anend. Maybe it was the last general strikeof this industrialized world, but it takes a confirmedoptimist to believe that. If it should cometo pass again, whether in the British Isles or onsome other portion of the globe, what parl willbe played by radio broadcasting, the latest andmost rapidly developing of all the means ofmass communication?The British conflict afforded some indicationsof what may be expected to happen in the future.Once the battle was on, the regular newspaperseither ceased publication or were reduced to litllemore than handbills. The government publisheda newspaper of its own, the British Gazette, in oppositionto the British Worker, representing theLabor side. Judged by normal newspaper standards,neither paper was a shining star. But theywere about all that remained of British journalism.Piling transportation difficulties on to theconfusion in the newspaper plants themselves,the strike raised hurdles too high to surmount.Had it not been for the chain of the BritishBroadcasting Company, withits principal stations at Aberdeen,Belfast, Birmingham,Bournemouth, Cardiff, Glasgow,London, Manchester,Newcastle, and Daventry, thepublic would have been practicallyuninformed during theearly days of the strike. Atsuch times the tide towardpanic runs swiftly. In theabsence of reliable information,sensational rumors spring upand circulate rapidly, gaininghorrors, by a well-known processof accretion, as they go

,menMAY, 1927BROADCASTING AND SOCIAL UPHEAVALSalong. An agency which helps to keep people'sfeet on the ground, at such a time, is performingno small service. This is substantially whatradio broadcasting did in England during thecrisis of May, 1926.Let it be emphasized that our discussion isconcerned with the function of broadcastingduring times of grave social disturbance in industrialcommunities. During normal periods,broadcasting occupies a field quite distinct fromthat of journalism. Since fairly normal periods,until the world gets a good deal worse, may beexpected to cover 0.999 f 'he total time, thenewspapers are in a secure position. Their facilitiesfor news-gathering and catering to the interestsof great masses of people are in a class bythemselves. Broadcasting, in quiet times, interfereswith the newspapers about as much asthe theatres do; that is to say, not at all. If aman intends to go to a show in the evening, or tolisten to his radio, he reads his morning andevening papers just the same.But when there is an acute industrial crisis,the tables may be turned temporarily, as theBritish strike showed. The reason lies in the contrastingconditions of news dissemination byradio telephony and by printing. Publishing amodern newspaper of large circulation is a formidableproject. We do not realize what a hugeundertaking it is merely because we are accustomedto it. The thing has been organized andbuilt up on such a scale that we feel it mustcome around every morning, like the sun. Thatis a palpable mistake. The newspaper is producedby the concerted action of hundreds orthousands of men. If the men quit, there is nonewspaper.Even if the newspaper is produced,it meansnothing unless the distribution system remainsintact. Modern newspapers are bulky. One copydoes not weigh much, but try lifting fifty andthen visualize the motor trucks and mailcars required to transport fifty thousand.Reduce the size, and you have amelioratedthe difficulty, but you cannot removeit.Paper is gross matter, subject tothe physical limitations of physical things.Contrast the radio telephone station.Instead of hundreds of workers, it requiresonly a handful of men. A station of 1000watts output is considered fairly large;its night program coverage in an urbandistrict is, in fact, comparable with thatof a good sized newspaper's circulationsay 100,000 listeners. Plenty of 500- andlooo-watt stations with the studios, controlroom, and power plant in closeproximity can be, and are, run by onetechnician. One of the largest broadcastingplants in the world, with forty or fiftyfield points, and the studios and radio powerplant separated by thirty-five miles, isoperatedby a technical staff of sixteen men. In apinch, with the field work tossed overboard, thetwo engineers in charge, whose functions innormal times are mainly administrative, couldrun the whole plant alone. They might need awire chief for the lines connecting the studio andradio station, but a telephone engineer couldsubstitute for the wire chiefs if the latter all wentout on strike. In short, three or four professionalmen, who are likely to be on the "White" sidein a serious industrial conflict, can operate thelargest broadcasting stations, and one or twoeach can take care of the rest. They mightnot turn out a one hundred per cent, transmissionjob, but that is beside the point. The stationwould radiate and say what the proprietors'wanted it to say.The second factor, that of transportation,presents an even more striking contrast. A broadcastingstation generates its own "carrier," asthe high frequency wave is aptly termed. Itscontent is not printed on a few ounces of paperor other tangible medium. It is of the nature ofradiation weightless, impalpable, invisible, and,once released, itpenetrates to every point withinrange of the station without the aid of a singleman or vehicle. In distribution, even more thanin production, the radio is free where the newspaperis shackled, when the men walk out.Not very many powerful radio stations arerequired to cover a country of moderate area. InGreat Britain a single high-power station, Daventry,of twenty-five kilowatts rating, can coverthe entire island kingdom. Countries like Franceand Germany are similarly protected. Even inthe United States a single fifty-kilowatt stationlocated in the North-East can provide usableservice, in daylight,for South-Eastern Canada,New England, New York, Pennsylvania, NewJersey, Maryland, Delaware, the District ofColumbia, and the Virginias, with a possibilityof service to regions beyond. The daylight rangeof such a transmitter is about 400 miles. Thepopulation of the area of a circle of this radius,in this part of the United States, is of the orderof thirty millions. Three or four such stationsstrategically placed over the country, getting"OUR LISTENING WILL BE DONE ATTHE ORIFICES OF LOUD SPEAKERS"news over telephone or telegraph lines remainingin service, or by airplane if the worst comes tothe worst, could solve the problem even in theUnited States. Of course, not every family, evenin such industrialized countries as the UnitedStates and Great Britain, owns a radio receiver.But millions of them do, and each set is potentiallya focus of information when information ishard to get by other means.The weaknesses of radio distribution of newsfall under two heads: First, physical vulnerabilityanalogous to, but less serious than that of thenewspaper; second, the limitations of the spokenword, as such. The first division may in turn beconsidered under two subheads: Power supplyand wire connections. A broadcasting stationrequires electric power, normally obtained fromcentral stations. During a general strike thispower might not be available. But the amountisrequired not excessive, being in the ratio offive or six times the energy output of the transmitter.Ten horsepower would be an ample supplyfor a joo-watt station. A gasolene drivenalternator of two hundred and fifty kilowattscapacity would supply the largest broadcastingstation in existence at the present time. Such amachine is readily obtainable, and might beincluded as an integral part of broadcastingplants whose continuance in operation is vital.As for the telephone lines connecting studio andpower plant, the former being located in the cityand the latter rurally, a detachment of infantrywith a few motor cyclists, could safeguard twentymiles of aerial cable without special difficulty.And in many instances the stretch of wire isshort. In New York City, for example, there aretwo five-kilowatt stations with studios practicallyadjacent to the power rooms. The assailabilityof radio stations, even if overt force is employed,is not greater than that of water worksand similar utilities, and far less than that ofnewspapers. As for the telegraph circuits onwhich the radio stations would have to depend,in the main, for news armies and naviesusually maintain very effective radio telegraphsystems. In the United States there would beno insurmountable difficulty on that score.But, itmay be objected, when the radiospeaks, its words go in at one ear and out at theother; it lacks the relative permanency of theprinted phrase. This defect is of only moderateconsequence. For the general public thenewspaper certainly contains no elementof permanency; it lasts a morning or eveningand goes into the fire. The readersremember principally the headlines of thearticles which interest them. These salientpoints are impressed just as well by oralcommunication, and, by frequent repetition,or by some coordination of printingwith radio, the defect may be overcomeentirely. For example, in New York City,several hundred police booths and precinctstation houses are being fitted outwith receiving apparatus capable of respondingselectively to the municipalradio broadcasting station. During periodsof civil disturbance, these official receivingposts could be utilized as secondary distributionpoints for news, with no moreadditional equipment than simple letteringmaterials for printing bulletins. Suchideas have their ramifications, which weneed not trace in this sketch; the developmentswill follow when the necessity forthem arises.Against the limitations of radio broadcasting,even admitting them to be moreserious than they actually are, we mustbalance the directness and speed of thisform of communication. When the radioaudience receives blow-by-blow descriptions ofprize fights, the impulse of pain has scarcelypassed along the nerve paths of the man struckbefore the radio listeners know as much about itas he does. This quality of immediate contact,as opposed to the tedious mechanical interventionsof printing,is of special importance at timeswhen event follows event and conditions changefrom hour to hour.The next general strike, wherever it bobs up,will provide food for further reflection. It is aplausible guess that we shall hear more than weshall see, and that our listening will be done atthe orifices of loud speakers.Glad Tidings from the WestA CLIPPING kindly contributed by Mr.Zeh Bouck to this department revealsastounding leaps forward in the progressof the radio art, as set down for posterity in theSanta Cruz Morning Sentinel. It is entitled: "Of

38 RADIO BROADCAST MAY, 1927Interest to All DX Fans." Only one paragraphneed be lifted :The inventor's claims regarding the applicationof polarized harmonics was (sic) a little toodeep for the writer but to demonstrate what hemeant he tuned in KYW where Mr. Meehan wassinging an Indian song and by manipulation ofthe loop he entirely eliminated the accompaniment,also reversing the situation by bringing theaccompaniment up so loud that it interferedwith the singer. Another demonstration on anorchestra was the elimination or making ofthe string instruments predominate at will.On a mixed duet the soprano could be almostcompletely tuned out leaving the tenor singerpredominating and vice versa. Altogether, thedemonstration was very remarkable.The only commentbet!"Ican think of is: "YouThe Radio Club of Americaone evening each month, in the largelecture room of Havemeyer Hall, at ColumbiaUniversity, the portrait of the vener-FORable James Renwick,LL. D., Professor ofNatural Philosophyand Chemistry, 1820-1854, looks down on agroup of young men,and some older ones,gathered to discuss asubject which did notexist during his life.There are a hundredof these young men,more or less. They talkabout power packs,loud speakers, shortwavetransmitters,tendencies in modernradio receivers. Theportraitof ProfessorRenwick, who livedwhile Clerk Maxwellwas evolving theelectro -magneticseems to bear atheory,slightly puzzled frown.Seated at the table, from left to right: George H. Clark, E. E. Bucher,But the members ofGano Dunn, Edwin H. Armstrong, Michael I.Pupin, E. V. Amy, George J.the Radio Club ofEltz, Jr., David Sarnoff, George Burghard, John L. Hogan, Paul F. GodleyAmerica never look upat him. He is too far back for them. Theirthe members of the Club werethoughts sometimes regress to the early days ofradio, to the year 1909, say, when the Club wasfounded. In radio that is a long time. Radio menthink mainly in the present; they find plentythere to occupy them.The Club has two principal objects oneconcerned with the engineering aspects of theradio art, the other with the perpetuation ofthe amateur tradition. The Year Book for 1926states: "The Club now has among its membersmany prominent scientists, inventors, and engineers,as a glance at the membership list willshow. However, it is always anxious to embraceamateurs of the present day, in order that itsmembership shall never lack the renewed lifegiven by embryo scientists." It is primarily anamateur association, as the Institute of RadioEngineers is fundamentally a professional body.Amateurs and professionals belong to both organizations,but the Radio Club members neverforget that they were or are radio amateurs,while the members of the I. R. E., carrying theburden of radio scholarship, seldom forget thatthey are professionals.The Club now has some 400 members, ofwhom 108 are of Fellow grade. Fellows qualifyby five years of membership in the Club or bycontributions to the radio art, at the discretionof the Board of Directors, the governing body.It consists of a President, Vice-President,Treasurer, Corresponding Secretary, RecordingSecretary, and thirteen Directors. The officersand seven Directors are elected annually by themembership; the remaining six Directors areelected by a majority vote of the newly constitutedBoard of Direction at its first meeting.This year, the President of the Club is Ernest V.Amy; C. R. Runyon, Jr. is Vice-President. PastPresidents are W. E. D. Stokes, Jr., Frank King,George J. Eltz, Jr., Edwin H. Armstrong (1916-1920), and George E. Burghard (1921-1925).Mr. Amy was re-elected in 1926 for the presentyear.Among the authors who have presented papersbefore the Radio Club of America are includedArmstrong, Farrand, Van Dyck, Weagant,Hazeltine, W. C. White, Godley, Conrad,Heising, Aceves, Clement, Morecroft, Grebe,John Stone Stone, Lowenstein, Dubilier, Goldsmith,Marriott, Logwood, Pacent, and Hogan.The completelist is a formidable one, and thenames above represent it only partially. AsAT A RADIO CLUB BANQUETThe Radio Club of America has the name. It is agoing concern. It has a membership of 400 at thiswriting. An inspection of the 1926 Year Bookreveals that 78 per cent, of the members thereinlisted reside in New York City or its suburbs.But it is not a club, as yet. It maintains an officeat 55 West 42nd Street, New York City, but ithas no lounging rooms where the members canguzzle bottles of cool ginger ale, boast abouttheir distance records of fifteen years ago, recallfondly the days when Doc. Hudson called FNKwith a service on 600 meters to remind John V. L.Hogan that he had left his pipe at the Doctor'shouse the night before, and consummate milliondollar deals. If half the present membershipwanted a club, it could be started on a modestthis year or next. Such a development, ofscale,course, would not interfere with the monthlytechnical sessions, and technical membershipon the present order, with dues of $3 and $5 ayear, could be retained for those not interestedin the proposed aspect of the Club's activities.No one who has attended meetings of the Club,or been entertained at one of its annual banquets,can doubt that the organization has the vitalityand energy necessaryto take the lead in thisenterprise. Steps havealready been taken inthis direction. It is interestingto note thatthe Club has recentlyappointed a special" House Committee"for the purpose of investigatingthe desirabilityof such anunderstanding and tosubmit recommendationsfor organizationand financing. A modestClub House, withcomfortable loungingroom or rooms, isplanned. The radiomen in and aroundNew York will awaitdevelopments withmuch interest, nowthat the wheels haveactually begun toturn.permanent quarters, is obviously within reach. may be designed and calibrated to measure tele-early as 1912 Technical Operation of Broadcastingsquare-law variable condensersand directional radio transmission. The value oftalking about Stationsthe papers presented, to the radio art as a whole,75. Volume Indicatorshas been inestimable. They form a contributionto the engineering literature second only to the 1HE collected Proceedings of the Institute of RadioEngineers. Incidentally, these papers are printedTsight of a milliammeter in the platecircuit of an overloaded tube, its needlefluctuating violently, is familiar to everyin RADIO BROADCAST.broadcast operator and engineer. When the tubeThe discussions following the presentation of is in the speech circuits of the transmitter thepapers are lively and informal. Nobody tries to sight, for obvious reasons, is a deplorable one,display his knowledge and no one is afraid to but the principle, or something on its order, isshow his ignorance. The attitude issimply that valuable for preventing the very overloadingof a group of men vastly interested in radio, which the fluctuating milliammeter shows. Thiswhether or not they are making any money out is when it is embodied in the instrument calledof it, who meet once a month to talk about the "volume indicator," much used in broadcastingthe subject which happens to entertain themas a visual guide in setting energymost.levels.And now, what course is to be charted for the Before going into the description of one typefuture? Will the Club remain a sort of junior of volume indicator I should like to make itengineering society, or will it become a club clear that it is an indicator, as the name implies,literally? One plausible guess is that the organizationrather than a measuring instrument. Basically,will become a club in fact as well as the instrument is an alternating current volt-in name, within the next few years, but without meter, and in certain forms it may be calibratedsacrificing its technical status. The two roles as an accurate low-reading instrument of thisare in no way incongruous. The formation of class, extremely useful in telephone and radiosome sort of radio club in New York City, with work for measuring audio potentials. Again, it

MAY, 1927phone levels in TU's. The form shown in Fig.i, however, is intended primarily as an indicator.The input transformer shown may be an audioamplifying transformer, preferably with a highstep-upratio (1:10 or 1:5). The primary impedancemust be sufficiently high sothat, even at low frequencies, theinstrument will not affect circuits ofabout 500 ohms impedance, acrosswhich it is bridged. This means that at100 cycles the primary of the transformershould have an impedanceInputof20,000 ohms, which requires 40 henrysinductance, approximately. The secondaryof this step-up transformerfeeds a vacuum tube, which may be ofthe UX20I-A type, or its equivalent.The grid of this tube is biased negativelyto about 10 volts, so that theplate current, measured on a milliammeter,MA., of o-io range, is onlyabout 0.5 milliampere with 90 voltsplate potential. A filament voltmeteris provided to keep the voltage acrossthe filament constant.The theory of operationis as follows:Through the negative biasing ofthe grid, the tube is being worked sofar down on the curve that when thetransformer secondary contributes afurther negative potential to the gridInputthe plate current is only insignificantlyreduced. See the characteristic curveof Fig. 3. On the other hand, positive potentialscarry the current up on to the steep portionof the curve once more, resulting in a flickupward of the milliammeter pointer. The amplitudeof this movement indicates the magni-VOLUME INDICATORSshort of transmitter overloading, is 5.0. Then itis the control operator's business not to allowhis peaks on the volume indicator meter to hitmore than 5.0, and, even if he does not know theabsolute value of the r. m. s. audio voltage heFIG.STATIC CHARACTERISTICUX-201 -A90 V. PlateImfd.Reacta nee (Am plifyingTransformer with Primary& Secondary in series, additively )sufficiently on the second tube, which is thevolume indicator proper. Both in the one- andtwo-tube outfits, various combinations oftransformers, tubes, and indicating instrumentsmay be utilized. An ordinary amplifying transformerof i :3 or i .-5 ratio, a highmutube, and a galvanometer ofabout 1.5 milliamperes full scalereading, is a good single-tube combination.The voltages may be aboutthe same as with the high ratioinput transformer, ux-2oi-A tube, ando-io milliammeter described below.Mr. W. K. Aughenbaugh sends ina sketch of a volume indicatorusing two ux-i I2's, 45 volts plate, noGRIDVOLTSgrid bias, ordinary amplifying transformers,and a o-io d.c. voltmeter asan indicator. A swing from 2 to 6 onthe meter gives him the proper modulationon the WFBG transmitter, whichhe runs. This is not really an orthodoxvolume indicator, and it wouldbe improved with the negative biasfeature, but it serves the purpose. Sincethe instrument is used only as a leve'indicator, the proper limits of operationhaving been established by listeningchecks on quality and overloadobservations in the amplifiers andtransmitter, the operators at eachMA. D.C.0-10 =; .Milliamperes s90V.3FIG. 2tude of the alternating potential impressed onthe grid, and hence, divided by the transformervoltage ratio, the audio potential on the lineacross which the volume indicator has beenbridged. The device ismerely a special form ofrectifier. Fig. 4 is a table, in which columns i and2 are taken from the characteristic curve ofFig. 3, showing the variation of plate currentwith grid potential. Column 3 shows the plusrise in voltage calculated from the base point,which is the negative grid bias potential, 10volts in this case. Column 4is this figure dividedbythe transformer ratio, assumed as 10; thisgives us a rough measure of the audio voltageacross the input of the instrument. By tappingvarious potentials along the grid bias batteryone may calibrate a volume indicator, for comparativepurposes, in this way. The results shouldnot be taken as absolute values, because theresponse characteristic of the meter, the terminalconditions in the circuit being measured, andother factors, all affect the readings. However,these unknowns may be disregarded when onlyindications are required. For example, with atube of normal emission in the volume indicator,and proper filament and plate voltages, it mayhave been ascertained that, when the volumeindicator isbridged across the line leading tothe radio station, with given settings there,the maximum allowable deflection of the meter,

Some Facts About Coil DesignThe Oscillating Circuit as a Form of Voltage AmplifierThe "Qain"in the BroadcastSpectrum of Some Typical Coils The Essentials for a Well-Designed CoilBy ROSS GUNNTHE oscillating circuit, as applied to radio of a magnetic field, the capacity serves to store when one potential reaches its instantaneousreception, has been so thoroughly discussedin the past that itthe energy in the form of an electrostatic field, maximum, the other potential isgoing throughmight appear and the resistance serves to transform this stored its instantaneous zero value. These two potentialshave a certain interesting relation in termscertain point of view is always most fruitful in happens as the energy shifts from the condenser of the circuit constants. One of these potential?the matter has been completely exhausted. A energy into heat. The physical picture of whatthe consideration of oscillating circuits, especiallyin giving one a thorough understanding of familiar to the reader, and will not be given at and the other as the generated potential. Theto the coil, and back again, is undoubtedly will be referred to as the applied potentialthe physical phenomena that take place. In this time. In case the reader is unfamiliar with applied potential is the potential introduced intothe first part of the present paper an approach tothe circuit from some outside influence, such asthe problem is made from a particular angle, andan oscillator or an antenna. This applied potentialisit will be shown that an oscillating circuit is notD OSS GUNN,only a device to select a given frequency butthe author of this in phase with the high-frequency currentarticle,*may also be considered which is the first of two on as a type of the flowingsubjectin the oscillating circuit. The other potential,or the generated potential, is producedamplifier.of receivingIn the second part of the paper, the set radio-frequencyinductance and research within the its relation to engineer for the United States Aircircuit, by the action of the oscillat-inductors, was formerly a radioselectivity Service. Mr. Gunn is now attached to the Shane ing current, and is 90 degrees out of phase withand gain in a tuned amplifier, considering theLaboratoryoscillating circuit, is discussed. Finally, theat Yale the current and theUniversity and has devotedapplied potential.Theconsiderable attention toprime factors that should be considered to makethe currentproblems invokedflowing in any alternating currentcircuit is determined byinup the the ideal coil are design and use of coils in high-frequencythe applied potentialand the circuitgiven.oscillatingThe resistance or "loss" in an circuits. The present article doesconstants, in the mannernotoscillatingcircuit is made up of several components, and pretend to be revolutionary, for the basic given by the well known equation:theoryinvolved is atit is convenient to divide the circuit resistanceleast 50 years old. The author,instead of discussing power factor and= 1decrement,which have littleinto two parts, namely, the part due to coil resistance,and the part due to condenser to many read-resis-meaningers, has chosen to use atance. Modern factor which has a simplecondensers are relatively efficientsince they have resistances of only a fraction physical interpretation. The idea that there are where I is the current, Ea is the applied potential,L is the inductance, C the capacity, R thetwo potentials in anof an ohm oscillating circuit and thatat broadcast frequencies, while theordinary coils have resistances of from 5 to their ratio is the power factor, is of course well50equivalentknown, but the useohms. It is then obvious that, even if a manufacturerof the bestof the factor "G" series resistance, f the frequency,to explain and it is a numerical constant of value 3.1416.good condensers would succeed ratio of inductance to capacity, has If the circuit is resonated to ainrarely been pointed out. The definite frequency,casual reader willcutting the resistance of his condenserthe reactances arein balanced andhalf,equation (i)findthe total circuit resistance would be but this story an excellent discussion of circuitslightlyproblems whichaffected since the condenser resistance are is, in by no means reduces to:abstract, andgeneral,but a small percentage of the total circuitbetter informed should be (2)those who are interestedin the work Mr. Gunn and his assistantsresistance. On the other hand, if the coil resistancewere cut in half, the circuit resistancein which where I, Ea, and R are the same it is pre-as previouslyhave done, and in the waymentioned.sented. THETheEDITOR.greatest interest, however, iswould be cut almost in half, and the signal impressedon the grid of the amplifier will beduced by the applied potential. Considering nownot in the current flowing, but in the signal pro-double what it would be with the original poorthe application of the oscillating circuit to acoil. An improvement of this magnitude would this process, he is referred to almost any good radio set, it is assumed to be connected to a vacuumtube as shownbe well worth while, and may be accomplished elementary textbook on physics or electricity.by giving sufficient attention to the design of When in Fig. i, and so neutralizedthat there is no appreciable regeneration.the theory of oscillating circuits is examined,it is found that, in any series resonant Since the vacuum tube is a device controlledthe coil used in the oscillating circuit. Attentionis directed to the coil particularly, because the circuit, there may be considered to be two highfrequencypotentials which are approximately are able to apply to the grid, the greater will besolely by potential, the greater the potential wegood modern condensers are so much betterthan the best coils that there is no particular 90 degrees out of phase with each other. That is, the output signal from the tube.gain made by the use of the highestTHE "GAIN" OF A COILgrade condensers. The coil, then, shouldbe the object of considerable attentionT^HK diagram of connections in Fig.*and study until its losses are reducedi shows that the condenser and theto a minimum.inductance are in parallel across theIn the following discussion it isgrid and filament of the amplifyingshown that an oscillating circuit tube.mayTherefore, any potential thatbe considered as a type of voltageappears across the inductance or condenserwill be impressed on the gridamplifier, and a physical interpretationof the relation of the circuit constantsto the gain or desirability of01when an alternating current flowsof the tube. It is well known that,any given circuit will be C3given. TheLJthrough an inductance, there is generateda potential which is deter-physical interpretation that thismethod leads to, simplifies to a greatmined by the following equation:extent the perplexing questions thatEg = 2TfLI (3)arise, when one tries to state definitelywhere Egjust what is desired in an is the potential generatedoscillatingacross the coil,1 is the current in thecircuit.coil, L the inductance, and f the frequency.Similarly, the potential gener-Every electrical oscillating circuitLOOSE COUPLINGconsistsof an inductance, capacity, anda resistance (with usually an ated across the condenser is given by:oversupplyof the latter). The inductanceserves to store the energy in the form FIG. I where the symbols are as before.

MAY, 1927 SOME FACTS ABOUT COIL DESIGN 41the usual one. The fact that the of aequivalent in every way toIf we eliminate the unknown current from theThis definition ishigher than for telephony.equations (3) and (4) by substituting the relationselectivitycircuit and the gain go hand in hand is indeed aexpressed in (2), we obtain the following very pleasant one since, if one increases, the otherresults:automatically increases also.'_Eg_ = rrcfl^_ __L l/LTHE EKFICIENCY(5)Ea ~TT~ 2-icfCR R C'"THE expression for the efficiency of an os-or rewriting in the more convenient form, we 1 dilating circuit may be easily obtained byhave, due to inductance:defining the efficiency in the following manner:Eg = Ea(6)ENERGY SUPPLIED PER HALF :CYCLE= EfficiencyThis for convenience may be written as:Eg(7)= EfficiencyENERGY SUPPLIEDor simply:Now, the energy supplied per half cycle is theEg = maximumG Eaenergy stored in the inductance which(8)isgiven by the well known equation:where G is either of the factors given above andalways has a value greater than I. I''unity. That is,Energy = max.the potential applied to the grid of the amplifiertube is always greater than the applied potentialwhere L is the inductance and I max. is the maximumcurrent. Moreover, the energy lost perby a factor "G". The factor "G" is thereforeof the nature of an amplifying factor, and the half cycle is :writer has usually referred to it as the "circuitR lvoltage amplifying factor."i fIt has been suggested that this factor be calledwhere"gain" and since this is a much more R isconvenientterm, we shall now call "G" meanthe equivalent series resistance, I isthe rootthe square current, and f is the frequency.gaindue to the oscillating circuit. Obviously then,Making use of the relation betweenrootthe factor "G," or the gain, should be mademeanassquare current and maximum current,large as possible for any given circuit. To illustratenamely:this idea, suppose we had two oscillatingcircuits, one with a value for "G" of 50 and theother a value of 200. Suppose further, that therewas such an antenna current and such couplingthe efficiency may be written as follows:in both cases that the applied potential was sVof a volt. Then since Kg = LG I max_ R 2 maxIx Ea, the potential~'' 2applied to the grid of the tube (that is the Efficiency 4fJfgeneratedpotential) would be 50 x fa = L I' maxi volt inthe first case and 200 x ^ (4 volts) in the secondObviously then, the coil with a high value and canceling out the common factors, theefficiency reduces to:of "G" would be the best. It may then be said,that in an oscillating circuit, the potential impressedon the grid of an associated tube Efficiency= R IT . 2 x f LI r-ri since G = --dependson the potential applied to the oscillating circuit,and depends equally on a gain factor "G,"which in turn isdependent for its value on theEfficiency = G rc _ G 3.1416circuit constants only.Before considering the application of the above or for per cent, efficiency:results to the determination of the proper coil,it will be valuable to point out the intimate relation,00%between this factor "G" and other char-acteristics of the oscillating circuit. Consider Thus, if the gain is known for any given circuit,the efficiency may readily be computed.first, the relation between the factor "G" andthe selectivity of the circuit. The selectivity, or This equation gives the efficiency of the circuitthe "sharpness of resonance," of an oscillatingin the strict engineering sense and shouldthe circuit is directly proportional to the factor not be construed loosely as a measure of the"G," and if we define selectivity or sharpness of general performance of a coil. The poorest coilsresonance as the ratio of the natural frequency and condensers yield efficiencies of 90 per cent.of the tuned circuit at resonance to the differenceand better while the best coils show efficienciesof the natural frequencies of the circuit of 99 per cent., an apparent increase of but 9when on each side of resonance, such that the per cent. The increase in performance would,oscillating energy on each side or resonance is however, amount to approximately 1300 perjust one half the energy at resonance, then the cent, for the good coil in comparison to the poorselectivity so defined isexactly equal to the factor"G" or:Other things must be considered in radio tele-one.phony besides the intensity of the receivedSelectivity (9) signal. The quality of the received signal is ofgreat importance and if we should increasewhere fr is the natural frequency of the oscillating"G" indefinitely we would soon have a circuitcircuit when in resonance with the incoming that would be so selective that the only fre-wave, f 2 the natural frequency of the tuned circuitquency that would be amplified would be theat a point above resonance, such that the carrier frequency, and the side bands, whichoscillating current is 70.7 per cent, of the current give rise to the speech or music, would be cutat resonance, and fi is the natural frequency of off or, at the least, badly mutilated. There is anthe tuned circuit at a point below resonance, such upper limit to the value of the "gain"if thethat the oscillating current is 70.7 per cent of quality of the speechis to be maintained. Inthe current at resonance.the case of telegraphy, the upper limit is muchCalculations which would be tiresome andout of place in a discussion of this type, showthat if all voice frequencies are to be faithfullyreproduced up to 4000 cycles at a mean wavelengthof 450 meters (666 kc.) the value of thefactor "G" should not materially exceed avalue of 250. This puts a definite upper limit tothe gain or selectivity that can be used in theordinary radio set.Up to this point the discussion relates to thenon-regenerative oscillating circuit as a whole.Now if the condenser used with the inductanceis a good one, having a low resistance, then thelosses of the condenser may, in comparison withthe losses of the coil, be neglected. With thisassumption, which is perfectly legitimate in theaverage case, we may then talk about the "gain"due to the coil, and understand by this, thatthis is the gain that would be obtained if thecoil were used with any condenser of negligibleresistance. These conditions have been met within all experimental data given in this article sincea precision condenser was used which was insulatedwith amber and which had a resistanceof not over 0.2 ohm at 1000 cycles. Thus, at300 meters (1000 kc.), the resistance would beentirely negligible.Considering how the application of the principlesjust discussed are applied to an inductance,we may say that the inductance for any givencircuit should be so chosen that the factor "G,"which, as we have shown, is a measure of theselectivity and the gain, should be as large aspossible, provided it does not greatly exceedthe limiting value for good quality.Returning now to the factors that determinehow large the "gain" will be in any case, equation(5) shows how this factor varies with theinductance, associated capacity, resistance, andthe frequency. It is impossible to examine theequation and say off hand that the ratio of theinductance to the capacity should be very large,as equation (7) would seem to indicate, because,as the inductance of the coil is increased, theresistance increases, perhaps very rapidly, dependingon the physical structure of the coil.On the other hand, if the capacity of the condenseris increased the circuit resistance will decrease,but at a relatively slow rate. It wouldthen appear that in order to determine justwhat combination of inductance and capacityto use or to determine what types of coils arethe best, it will be necessary to make measurementsof this factor "G" and determine experimentallyits values under different circumstances.The factor for the "gain" may be determinedin several different ways. The ratio of the generatedpotential to the applied potential maybe measured directly by means of a vacuumtubevoltmeter, and since by definition thisratio is the "gain," we have a simple methodof getting its value for different coils. The factormay also be determined by use of the definitionfor selectivity as given in equation (9) whichcan be transformed so that known condensersettings may be used instead of frequencies.The values for "G " in this paper were computedfrom the known values of the resistance, inductance,and frequency, since these data werealready available in some cases from previouswork.SOME COILEXPERIMENTSA GREAT many measurements on different'* types of coils have been made during the lastyear in an attempt to obtain sufficient informationto point the way to the design of still bettertypes of coils. Curves showing the "gain" ofvarious representative coils are included in thispaper. In every case but one, the coils were

42 RADIO BROADCAST MAY, 1927Shows effect of changingratio of L to C150200 300 400WAVELENGTH -METERSFIG. 2purchased on the open market, and may be takenas reasonably representative of the commercialcoils now available.One of the first things investigated, in thelight of the previous discussion, was the effectof changing the ratio of inductance to capacityin any circuit using coils of nearly identicalconstruction. A single-layer solenoid, consistingof 45 turns of No. 24s. c. c. wire was wound ona cardboard form of 3!! inches in diameter.The values for the gain of this coil over thebroadcast range, using a condenser with maximumcapacity of 35ommfd., were plotted as shown inFig. 2, labeled I_o= 0.250 mh. Wire was thentaken off this coil until the coil resonated to 550meters (545 kc.) with a maximum capacity of485 mmfd. The values for the gain were againdetermined over the broadcast band and plottedas shown in the curve Fig. 2, labeled = Lo 0.178mh. These curves, with others, seem to show thatthe gain in any given oscillating circuit does notchange greatly with moderate changes in theratio of inductance to capacity. There does,however, seem to be some slight advantage inusing the higher values of inductance.Fig. 3 shows the value for the gain for a certaincommercial "figure eight" coil. It was woundin the conventional manner, the winding beginningat one end and progressing in a seriesof "figure eights" to the other end. The coil wasmade up of 80 complete loops of No. 26 s. s. c.wire and had an inductance of 0.250 mh approximately.The coil was if inches long and ifby 4 inches in the other directions. The gainfor this type of coil was surprisingly low, as itvaried from 100 to 130, as shown by the curve.The curve for a typical commercial typecoil is shown in Fig. 3 (b). This coil was a singlelayeropen solenoid of 0.245 mh. It was madeup of 58 turns of No. 23 s. s. c. wire closely woundso it could be made self supporting with the aidof a binder. It was 3!" in diameter and if"long. The curve shows that the coil is not whatone would call a bad coil.Recent work of the Bureau of Standards hasshown that in general the best type of solenoidconstruction is the type known as the "loosebasketweave." The curve, Fig. 3 (c), shows thegain for such a coil. It was wound with 53 turnsof No. 24s. c. c. wire, and was 35 inches in diameter.This coil is a very good coil and would givethe best of results if it is not placed too close toother apparatus.Much better coils can, of course, be built by500 600the use of litzendraht wire, but the writer hasonly considered the solid wire-wound coil sofar. A graduate student getting his Master's degreeat Yale in 1926 succeeded in building asolenoid out of "litz" with which he obtainedan average value for the gain of over 450 for theentire broadcast band. Such coils are, of course,exceptional and are more or less laboratory curiositiesbecause of their size and large externalfield. They cannot be used in the vicinity ofother apparatus without increasing the lossesand hence decreasing the value for the "gain."This is because their field sets up either eddycurrents in the metal parts, or causes dielectriclosses in insulators. These losses naturally decreasethe value of the gain.THE IDEAL COILTHIS brings up consideration of the ideal coilor high-frequency inductance. Considerablethought has been given to this question andthose points consideredthe most important, ornecessary, are tabulated below. The requirementsin their order of importance follow:(a) The "gain" of the coil as previously defined,and hence also, its selectivity, should ingeneral, be made as large as possible but shouldnot exceed the limit of 250 for good quality.This item in itself says a great deal, implicitly,since in order for the gain factor to beeven as large as 200, say, all known methods tokeep the coil losses down must be employed.This would mean, in general, that the coil wouldbe self supporting, it would be wound with relativelysmall wire since small wire serves to keepthe eddy current losses down, and it would beso wound that individual turns were reasonablywell separated. It seems to have been prettydefinitely established that the best coil is obtainedwhen the wire is spaced by an amountabout equal to the wire diameter. It would meana great many other smaller things which canall be grouped under the statement given in thepreceding paragraph.(b) The exterior field of the coil should bezero or, certainly, very small. This is essentialin order that there shall be as little stray energyexchange within the various circuits of the radioreceiver as possible. Putting an ordinary coilhaving an exterior field in a metal can is to bediscouraged, since it will greatly reduce the valuefor the "gain." For the same reason, the gainof an ordinary coil may be greatly reduced bymounting the coil in the vicinity of metal or poordielectric.(c) The distributed capacity of the coilshould be very low, and the high- and lowpotentialends of the coil should be well separated.The terminals of the coil should be wellseparated so that connecting wires to the coilwill not introduce an excessive amount of distributedcapacity into the circuit.(d) Mechanically the coil should be strongand able to withstand a reasonable amount ofabuse.(e) Its physical structure should not be excessivelylarge taking into account item (a).(f) A commercial coil should have some markingwhich would give its "gain" over the broadcastband.200 300 400500 600WAVELENGTH - METERSFIG. 3

.manent1shadowPerfecting theHow the Oscillograph Is Utilized to Obtain Visual Indication ofthe Voltage Characteristics at Different Points of the CircuitTheConstruction of a Better B Device with Uniform Output PropertiesSOCKET power units are now in theirsecond or third year of popularity, andBy HOWARD E.RHODES;variations through the wire,causing the latter to vibrate in THEaccordance with these current variations, andthe way in which it vibrates will therefore indicateduring this time many excellent unitsthe character of the current flowing throughhave been designed. Some of the first models it. It is possible to connect an oscillograph atwere described in this magazine as far back as various points in a circuit and in this waySeptember, 1924, but it was not until the determine the nature of the current whetherpresent gaseous and thermionic type rectifiers it is alternating or direct, or whether it is abecame available that B power from the light combination of the two.socket became really practical for home use. It In analyzing the a. c. line voltage at the inputis surprising that since these rectifiers first becameof the power device, the oscillograph, indicatedavailable there have been no important by the circle with an "X" in it in Fig. I, was con-advances in design over the first models.nected across the primary of the transformer ofPower supply units are simple devices, employingthe B power unit, as shown at "A," and at "B"principles that have been known manyis a copy of the picture that was seen. The lineyears, although their special application to radio marked "zero" indicates the position of theiscomparatively recent. Many construction vibrator when there is no voltage applied. Thearticles have appeared in the various magazines voltage starts at zero, rises to a maximum in onebut in these articles there has been little or no direction, decreases to zero, and rises to ainformation as to how the devices function. It maximum in the opposite direction, decreases towill be worth while to devote some space to a zero, and then starts the same cycle over again.brief explanation of the fundamentals underlying The voltage across the secondary of the transformerthe operation of any ordinary power unit.has the same form but it is larger.the For the purposes of our description we will use Across the secondary of the transformer wethe power unit illustrated and described in this have a high a. c. voltage and the next thing to doarticle. Sufficient information will be given to is to change it to d. c. In the particular unit weenable anyone to construct the unit and it is are working with, this isaccomplished with a cxhopedthat many will do so because this particular3 1 3 double-wave rectifier tube. This rectifier hasdevice gives very good results and has two plates and two paralleled filaments so thatseveral design features, explained in this article, both the halves of the wave above and belowto particularly commend it.the zero line in " B" can be utilized. The cx-3 13B socket power units are devices intended to tube was arranged as shown at "C" in Fig. i,take power from an ordinary lo-volt 6o-cycle only one of the i plates being connected, and thea. c. house lighting system and convert it into oscillograph was connected as indicated. We nowhigh-voltage direct current suitable for the operationof a radio receiver. In order to accomplish we get a current through the circuit for eachget a wave as shown in Fig. at " D." Notice thatithis it is first of all necessary to transform the positive half of the a. c. voltage but nothing duringI io-vo!t a. c.power into energy of the same typethe negative half, because the rectifier willbut of higher voltage. This is accomplished by only conduct current when the plate is positive,means of a transformer, a device which merely while during the half cycle when the plate isconsists of two coils of wire wound on an iron negative, no conduction occurs. If we connectcore. If these two windings havea turn ratio of i to 2, placing1 10 volts across the smaller, orTUICCONDENSER BANI\RECTIFIERprimary winding, would give 220CX-313volts across the other, or secondarywinding; with a i to 3 ratiotransformer the voltage acrossthe secondary would be 330,and so on.What does this voltage looklike? We cannot see it directly,but with the aid of an instrumentcalled the oscillograph, weare able to obtain a visual pictureof it. The oscillograph consistsof a thin wire, or vibrator,strung between two strong permagnets.A light is'thrown on this wire and theof the wire, by means ofrevolving mirrors, is thrown on'a screen. If a current is passedthrough the wire, the magneticlines of force set up by the magnetswillIreact with the currentthe other plate, as shown in " E," we will be ableto take advantage of each half wave because,during the half cycle when terminal No. 5 ofthe transformer is negative, terminal No. 7 ispositive, and thus, during the half cycle whenno conduction is taking place from terminalNo. 5, there will be current flowing at terminalNo. 7. Consequently, we get a wave form in theoscillograph as shown in diagram "F" of Fig. I.Now, for each half cycle of the original a. c.voltage shown in" B," we get a correspondingimpulse in the oscillograph. But because of therectifying action of the tube, which will conductcurrent only one way, all the impulses shown in"F" are in the same direction. We now have acircuit in which the current flows in only onedirection, and this is the essential characteristicof a direct current. But, althoughCHOKE UNITLthe currentis unidirectional, it is pulsating; that is,itgoes from zero to its maximum value andthen drops to zero again, and then repeats thesame thing over again. Such direct current is notsuitable for application to radio purposes for itmust be perfectly constant for this use.THE FILTER CIRCUITTHIS brings us to the third part of a B powerunit the filter. In Fig. i, at "G," we haveadded a filter to the output of the rectifier. Thefilter consists of choke coils Li and Lj and condensersCi, d, and Ca. The function of thechoke coils is to block any sudden changes incurrent while the function of the condensers isto act as storage tanks or reservoirs. Energy isdelivered to the filter in the form shown in "F"and the filter serves to smooth out these impulsesand to allow non fluctuating direct current to bedrawn from its output. The oscillograph wasfirst connected at Xi, and the curve obtained isshown at "H." Here we notice a great change.The ripple is not nearly as greatas in the preceding picture andit never goes down to the zeroline. Through the ripple we showa dotted line indicating the averagevalue of the ripple current.What the curve means is thatwe now have a direct current,ADCAST PhotographTEXTIdci with a small a. c. ripple init, lac. The ripple must be gottenrid of so we pass the outputthrough another filter section.The oscillograph drawing "I"was obtained by connecting theinstrument in the circuit at thepoint marked \2 in "G". Noticehow much smaller the ripple is.The filtration is almost complete.Connecting the oscillograph onthe other side of the last filtercondenser, Ca, at the pointmarked Xj, we obtain the drawingshown at "J," and the rippleis entirely absent. This meansthat the voltage at the end ofthe filter is satisfactory to applyto a receiver.

44 RADIO BROADCAST MAY. 1927The filter is one of the most important partsof a B socket power device, and it is essentialthat it be carefully designed if it is to give bestoperation. The best filter will, of course, be thatone which gives the least hum in the output consistentwith reasonable cost. It is preferable toaccomplish the filtration with a filter as smallas is feasible because, in this way, it is possibleto keep the resistance of the filter circuit at alow value. In " F" the filter issupplied withenergy at the rate of 120 cycles per second. Ittherefore seems logical to design the first sectionof the filter to eliminate this ISO-cycle rippleand to then use one additional filter stage toeliminate any other harmonic frequencies orany residual ripple that gets through the firstsection. A selective filter of this type has beenpatented by Kendall dough and is used in theSilver-Marshall 331 Unichoke and also is incorporatedin this unit because, with such acircuit,excellent filtering action can be obtainedand, at the same time, it is possible to keep thefilter resistance down to a fairly low value.At the output of the filter we obtain thethe device. Amaximum voltage delivered byreceiver, however, requires several differentpotentials for its operation. In most cases a highvoltagetap, say about 180 for a 171 power tube,a go-volt tap for the first audio amplifier and ther. f. stages, and a 45-volt tap for the detector, areresistance of the rectifier, the poorer the voltage the B power unit will be called upon to supply aregulation. In the case of batteries in good varying load. If its regulation curve is not flat,condition, the internal resistance being very low, any variation in the milliampere load will causethe voltage remains substantially constant under a change in the voltage supplied to the receivernormal current loads and a regulation curve for and this will produce another surge in the receiveragain affecting the average plate currenta battery is substantially a straight line. In itself,a falling characteristic may not, at first, appear and repeating the process. "Motor-boating" dueto be a disadvantage so long as the curve indicatesthat the device is capable of supplying curve of the power unit be made substantiallysufficient voltage at the particular load at which flat, and this has been accomplished in theto this cause will be preventedif the regulationit is to be used, but, a poor regulation curve, particular unit illustrated on page 43 by connectinginto the output circuit a glow tube, asindicating a high internal resistance, is doubtlesslyan important contributory cause of shown in Fig. 2. The problem of eliminating"motor-boating" in a receiver."motorboating" is complicated and for this reason"Motor-boating" can also be produced by RADIO BROADCAST Laboratory expects to makeoverloading, which causes a change in the averageplate current drawn by the receiver. If the the exact causes of the trouble. These dataa series of tests in an endeavor to determineaverage current drawn by the receiver varies. will be published in a later article.required.To obtain the various voltages it is necessaryto equip the device with an output potentiometer,which merely consists of a resistance, orseveral resistances, connected in series acrossthe output, as will be seen in drawing "G," Fig.I. This circuit diagram is similar to many powerunits in use to-day. It has one important disadvantage,which is that the voltage obtainedfrom the various terminals depends upon theload. If one tube issupplied from the tap markedgo-volts it might really receive 1 10 volts, twotubes 90 volts, and three tubes only 70 volts,and so on. This is one important respect in whicha B power unit differs from a dry battery. Froma battery we obtain the same voltage at allreasonable loads, but from an ordinary powerunit we obtain voltages that depend on the milliamperedrain."MOTOR BOATING" CAUSESTHAT the output of most B power unitsvaries with load isimportant because it isvery likely that one of the causes of "motorboating"is to be found in this fact."Motor-boating" is seldom experienced (althoughit is not an impossibility) when anamplifier is operated from good new B batteries.Ordinary B batteries must be discarded as thevoltage runs down, the actual reason for thisbeing that the internal resistance of a batterygoes up as the voltage goes down, with the resultthat the high resistance, being common to thecircuits of all the tubes in a receiver, may causeoscillation, and most certainly distortion.Considering a B power supply from this angle,we find a comparatively high internal resistanceunavoidable with standard rectifying devices,and we further find a comparatively high resistanceis necessary for the mechanical constructionof satisfactory filter chokes. The net resultispoor voltage regulation; that is, as the currentdrawn from the B supply increases, the voltagedoes not remain constant as with a battery but,instead, falls off at a fairly rapid rate. Curve A,Fig. 3, indicates the regulation that may be expectedfrom a standard B supply with an extremelylow-resistance filter. The higher thefilter choke resistance, the poorer the voltageregulation; and, likewise, the higher the internalZero LineFIG.IZero Line

MAY, 1927 PERFECTING THE SOCKET POWER DEVICE 45entire unit. No particular care is necessary inthe way in which the wires are run since thereis little danger of feed-back. Just run thewires in the most convenient way to the variousterminals. By reference to the circuit diagram itwill be noted that a switch, marked Sw., isindicated in the primary of the power transformer.This switch is part of the glow tubebase. The terminals in the glow tube correspondingplate and minus A (minus A as indicatedon the Silver-Marshall socket) are shortcircuitedinside of the tube base wiring. Therefore,the lead from the unit that connects to the1O -8 10 volts a. c. is cut and one end connected toto glow tube theColor code on Condenser Bank . Cplate terminal of the glow tube socket (righthandBlue -2 mid Green - 1 midsocket) and the other end connected toHed - 4 mid. Black = commothe negative filament terminal of this samesocket. With this connection, the powerFIG. 2thereby automatically cut off if the glow tube ispulled out of its socket. This is necessary because,The use of a glow tube to improve the regulationof a socket power device is a comparatively used in the model constructed in the Laboratory practically 180 volts at the go-volt tap.The parts mentioned in the above list were with the glow tube removed, there will berecent development. The effectiveness of this and are known to give good results. There is no operation, there are practically no precautionsto be observed; the unit is foolproof. Thetube can be readily seen by referring to the reason why the parts of other manufacturerscurves B, C, and D in Fig. 3, and noticing that might not be substituted provided care is taken four B-battery leads from the receiver arethe voltage at the go-volt tap varies only 5 volts to make certain that the electrical characteristics simply connected to the similarly marked postsBetween a load of o milliamperes to 45 milliamseres.The tube also affects the regulation of the The Amsco type 125 resistance was not used on, and reception obtained by tuning the receiverof the substituted parts are equivalent.on the B unit, the receiver and B unit turnedother voltage taps on the device so that all of in the model made up and illustrated in the in the usual fashion. The 175 volts at 20 milliamperes,obtainable from the i8o-volt tap, willthe taps show a comparatively small variation photograph on page 43. It will be found thatvoltage with change in load. The voltage regulationat the go-volt tap is most important since resistance shown in the photograph.go-volt tap will supply up to 45 mils, at thisthis tap generally supplies a majority of the Satisfactory block condensers are also made by voltage; the 45-volt tap up to 10 mils., as shownthe type 125 unit is one inch longer than the operate a ux-171 type tube to perfection. Thetubes in a receiver. The use of a glow tube with Silver-Marshall, Tobe Deutschmann, Aerovox, by Fig. 3. There is no danger of damaging tubesthe concomitant improvement in the regulation Sangamo, Muter, Faradon, and the resistors that and condensers in the receiver due to highvoltagesurges from the B unit, since the voltagecurve will eliminate a factor (poor regulation) are used may be the products of any reputablewhich certainly has a very definite tendency to manufacturer provided they are capable of of the high tap can never rise above 190 volts.cause "motor-boating," and it is suggested that, carrying the currents that are specified. The In use, the two lighted filaments of the cxti3rectifier tube will cause the tube to getwith any B power unit that iswhere possible, the tube be used in conjunction S-M 653 resistor (Ward Leonard S 1 1500), costing82.50, can be used in place of the Amsco rather warm; at no time should the plates evercausing a gr^-atdeal of trouble.resistors and mounts.become red due to heating. The glow tube willAs was mentioned at a previous point in this The construction of the unit isvery simple. glow with a bluish or pinkish light, and thisarticle, an important feature of the socket power Upon the 7" by 10" wood base, beginning at the may possibly flicker when a very strong signal isunit illustrated herein is that it may be connectedto any standard receiver drawing normal down with the Dubilier condenser bank along of the tube. If too great current more than 45left-hand rear, the power transformer is screwed being received, due to the reciprocating actioncurrent with the certainty that the voltages will side of it, and the Unichoke at the right-hand milliamperes is drawn from the go-volt tap ofFall within the practically required operating end. The socket for the type 313 tube isplaced the unit, the glow tube may cease to glow. Turningimmediately result in thislimits, by virtue of the fact that a glow tube is directly in front of the transformer, while thatemployed. In an ordinary B unit, variable high for the 374 glow tube is placed directly in front tube re-lighting, after which the set mayresistances are used to control the output voltage,and it is seldom that the user has any de-are lined up in front of the sockets, and then, in is drawn by the go-volt receiver circuit, it shouldof the Unichoke. The three resistance mounts again be turned on. If more than 45 milliamperesfinite idea what voltages are being applied to his front of the resistance mounts, are placed four be examined for trouble. The brilliancy of thereceiver.Fahnestock clips. The left-hand clip is negative, glow in the cx-374 regulator tube will vary withThe parts necessary to build a B socket power and progressing to the right, we have the plus different loads.employing the principles outlined in this article, 45-, plus 90-, andare listed below:3coplus i;8o-volttaps. WiringLIST OF PARTSmost of the unitsR Cunningham cx-3 13 Rectifier Tube $ 5.00 can be done withoutsoldering, ifG Cunningham cx-374 Glow Tube 5.50T S-M 329 Power Transformer, withdesired, by simply5-volt balanced filament winding,two 2oo-volt secondaries,fastening thescraped ends ofand electrostatic shield . . . o.oo the connectingL S-M 331 Unichoke .... H.oo wire under theC Dubilier Type PL 381 Condens-jrterminal screws ofBank 14.00 those units whichTwo S-M 5 1 1 Tube Sockets . . i .00 are so equipped.Ri Amsco ijoo-Ohm Resistor withThe circuit diagramgiven in Fig.Mounts . .5oMA. Type 125 2.R-2 Amsco 4ooo-Ohm Resistor loMA.2 is marked withCapacity.QO terminal numbersR Amsco 6ooo-Ohm Resistor loMA.which correspondCapacity .90 to those on theTwo Amsco Resistor Mounts ..30 parts that wereFour Fahnestock Clips. . . .087" x 10" Wood used in this Base with 17 No.particularmodel,6, \", R. H., wood screws, and 15and this will aidfeet of Kellogg fabric insulatedin making it a20 25 30LOAD CURRENT IN MILLIAMPEREShook-up wire .50 simple matter toTOTAL 47.18 correctly wire the FIG. 3

''Measuring TubeCharacteristicsA Paper Delivered Before the Radio Club of America Discussing the SeveralBridge and D. C. Systems for Use in Obtaining Tube CharacteristicsBy KEITH HENNEYDirector, Radio Broadcast Laboratoryr T IS neither the desire nor purpose of the size and relativewriter to burden position, tubes differ inthis characteristics.There grid voltages thearticlefactors.with anAt low eulogyon the vacuum must, then, be tube. some amplificationmeansNearly every articleby factor falls offwhichsomewhat,that has engineers can rising toappeared on the tube incompare tubes just as a maximum atthe popularradio rate they zero grid voltage, andgenerators and press hasmotors doneor remaining constant thereafter,orother electricalthat, pointing out that it isfalling gently in some tubes.a mostapparatus.wonderful device, the modernThe Aladdin'splate impedance depends upon a lot ofLamp, and a number of other TUBE superlatives thatCONSTANTSthings, the filament efficiency, the amplificationfillup space. There can be no doubt constant,thatandthetheIN TUBE grid and platetube isimportant. Witness our engineering, there voltages. Noare two present broadcastingstructure, ourvery one curveimportant factors which, when or graph can show how it varies.known, define To long-distance telephone the properlytube representservice, our communication in it wouldexactly the same require a threedimensionalby telephone acrossmodel, such asmanner that weused has beenthe Atlantic, and to say in constructedschool that the United States isby high frequencies and exceedinglylow powers to all parts of the north by Doctor Chaffee and others. Somebounded on the by Canada, on photographsthe eastworld.bythe of All of these Atlantic very beautiful models of this natureOcean, etc. The two may beconstantsthings depend upon theseen in the tube.which Proceedings of the I. R. E.No really are not study of theconstants at alltube can beare the After the complete withouttube is sealed and a amplification factor placed inandknowledge oftheits varied services. For plate impedance, the operation!impedance example,changes with each change in in-',it is possible with a tube to convert directstantaneouscurrentplate or grid voltage all of whichfrom a set of batteries to alternating currentmakes the oftheory of the tube more or less com-all frequencies from as near zero as one likesplicated.upto 60,000 or more kilocycles. It is thenThese three possible,elements, the filament, the grid.with another tube exactly similar to theand the first, toplate, cause any current flowing in theconvert these extremely high frequencies backplate circuit to change, making itgo throughto direct current. It is also possible to very wide fluctuations.amplifyThe plate current is definedby the equation:both direct and alternating currents, and henceamplify power. It is also possible to = separateIP f (E P + jAEg)what is placed on the input of the tube intoBy maintaining constantdirect andany one of the threealternating currents ofpracticallyvariables in this equation andany ratio desired. varying the otherAll of these varied functionstwo, we arrive at theare carried out without relation between the plateany moving parts, withoutgrid orcurrent and the voltage on thenoise, with plate thatpractically no loss of power, andwe usually know aswith so little fuss that tubes now characteristic curves, and itexist that areisby means of these curves thatcapable of the giving serviceimportantfor 20,000 hours, a lifetube factors are defined. Forgreater than that of example, boththe gridcircuit in which they areand plate potential have some effect on theused. There can be no doubt gridabout the importanceof the tube is relatively morevoltage, but the gridin the importantfield of electrical engineering.In itthan the plate. In Fig.iaddition, tubes and may be seen that attheir associatedzero grid bias, changing thecircuits are now plate voltage frombeing used to measure the of rate90 to 135 changes the plate currentgrowth ofby 5.2 milliamperes,while changing the grid biasplants, to measure extremely smalldifferences of by 5 voltsthickness, the strength and rapiditywill do the same thing.of a man's pulse, and from this latter, to determineThe amplification factor is then defined as thewhether he is a lover, a thief, a liar.ratio ofThe tube the changehas been in plate potential to theharnessed and trained to do anda every function that thevast number tubeof performs andchange in grid potential which produces the sameinteresting tricks.itsNow efficiencythis in doing little assembly of glass and so may bemetaldiscovered by aeffect in plate current. In this case the amplificationknowledge of these factors and factorthe constantsperforms its ofis 9:multitudinous functions with the the circuits into which the tubeaid of threeworks... _ AEp l35-oo4i;elements. TheH-first and most importantof theseT-p = = =Another factor is the mutual conductanceAEg Q5-0 5elements is the filament. This which, contraryfilament has to popular opinion, is not so The other factor of importance, theundergone rather remarkableplateiimportant as itchanges since tubes may seem. The term isfirst somewhat impedance, is the ratio betweencame into the change inexistence. difficult toThe picturefirst ones were made physically. It has the dimensionsofplate voltageof to the resultant tungsten whichoperated with a change in platea conductance, i.e., a current divided current. In thishigh temperature, thenbycase it is45 voltsgoing to a voltage, but divided bythe current exists inlow one circuit 0.0052 amperes, or temperatureroughly oxide-coated8700 ohms:filaments manufacturedby a in another, with the tube ascomplicated and difficult process, the Rpand the voltagethence connecting link. It is due = AE P= _J15-oo_ ._i5_ =8toto our mostProfessorAlp 0.0116-0.0064 0.0052recent filament, the thoriated Hazeltine.wire. The measure of efficiency of the Now, as has beenfilament is These indicated constants, orby the Greekits emission per watt factors, are variable letter expended inA in theheating it, within definitions, these factors arerather wide definedby changes, andand limits.the Fornewest thoriated wire isexample, theexceedingly amplification factorefficient. Pure may range from for accuracy the changes3 to tungsten filaments 30, mustoperate at a whilevery high temperature. Oxide the be small.impedance varies, as someone has The filamentsmutual consume said, from conductance, defined as theHell to Peru. The ratioconsiderable current at low amplification factor between voltage and at amuch lower is pretty well determined when a change in piate current andthe tube the changeis sealedtemperature. Thoriated filamentsare somewhere and in grid voltagepumped; that that produced it, is also the ratiois, itdepends to withinbetween.very between thenarrow amplification factor limits and theThe other upon thetwo elementsgeometry of platethe tube.are the grid and impedance, as can be seen plate, The from themesh of the mathematicsand grid andbecause these elements can be its spacing with respectto the other comparing tubes underbelow. Forchanged inelements are the exactly thegoverning same conditions, this factor is somewhat import-

MAY, 1927 METHODS OF MEASURING TUBE CHARACTERISTICS 47AMPLIFICATION FACTORBGRID20181614!2108642

48 RADIO BROADCAST MAY, 1927MUTUAL CONDUCTANCEINPUT CONDUCTANCEFIG. 8FIG. 9There arc two sources of error in the bridgesshown so far. One is in the drop in plate voltagedue to the plate current flowing through thebalancing resistance. The other is the resistancedrop of the indicating device, whether this be apair of receivers or the primary of a transformer.Trouble from this source may be avoided bymaking certain that the actual plate-filamentvoltage is of the value desired after the balanceis obtained, and by the use of a low-resistancetransformer, such as a modulation transformer,to connect the bridge with the associated audioamplifier. On the Laboratory bridge, a pushbutton connects the plate voltmeter when itsreading is desired. Otherwise it is out of thecircuit.In practice, the normal filament, grid, andplate potentials are appliedto the tube, and alooo-cycle current of about one to two milliamperesflows through the bridge arms. To obtaina balance in measuring mu, the resistancein the grid circuit is set at 10 ohms and the plateresistance and variometer varied for balance.Thus, a tube whose mu is 8 requires 80 ohms inthe plate side. In a quiet room, and with leadsfrom the oscillator well separated from the amplifiermu can be read to the seconddecimal place. When tubes of highamplification factor, say 20 to 30,are measured, it is well to reducethe input grid resistance so thata smaller resistance is placed inTypeconditions, itprovides a useful instrument forthe laboratory or tube manufacturer, or evendealer. This is shown in Fig. 8. It will be seen thatit differs but little from the other arrangements.Another set-up of apparatus will measure theinput characteristics of the tube at low frequencies.It is shown in Fig. 9. At balance, the gridconductance (the inverse of the input impedance}isgiven by:RiRi R,and in practice, with normal tubes, all balancingis done with RI, since R2 is held constant at 100ohms, and Rs at 10,000 ohms. With soft tubesthe conductance may change sign at high platepotentials, and it is then necessary to give theinput a positive conductance by actually connectingacross the grid and filament a highresistance, say of 50,000 ohms. The tube conductancemay be obtained by subtracting fromthis known value, that determined by the bridge.Data given in Fig. 10 on a soft tube show theeffect of ionization in giving the input circuita negative conductance.TABLE NO.Ithe plate circuit.To measure plate impedancewith the Miller bridge, the switchis closed and a new balance obtained,when the factor desired isobtained as a function of mu. Inboth this bridge and in the Laboratorybridge, the resistance, R,against which the tube impedanceiscompared, may be fixed exactlyat 10,000 ohms, although the valueas it isis not important as longdefinitely known. On the Laboratorybridge the plate resistance isset at 100 ohms and the grid resistancevaried for balance. If theimpedance is 12,000 ohms, R Kwill be 120.MUTUAL CONDUCTANCE BR1DGRIPHEREare a number of other*bridge schemes for measuringthe various factors in which engineersare interested. Ballantine hasdescribed several in the Proceedingsof the I. R. E. One of theseis a method of measuring the mutualconductance di*"""""/, and forcomparing a great many tubes ofthe same sort under the same

MAY, 1927 METHODS OF MEASURING TUBE CHARACTERISTICS 49the statement that mutual conductance is notthe determining factor in a tube's goodness orunfitness for particular tasks.In receivers, as we have them to-day, the firsttube generally acts as a radio-frequency amplifierwith inductance in both plate and gridcircuits. It is necessary that the plate-gridcapacity be small and that a given make andtype of tube will be uniform. It is also necessarythat the input impedance be high and the outputimpedance be low, for maximum gain. Forexample, the maximum possible gain from anamplifier is given by the well known expression:K __t X T/^t\ / A 5v RP iand a little mathematics will show that when theproper load is inserted into the plate circuit of ahigh-frequency amplifier that the maximumthe formula:amplification will be given byUoi/Rwhere L is the inductance of the secondary coiland R the effective resistance of the circuit. TubeCeCo TYPE K

50 RADIO BROADCAST MAY, 1927whose base is fixed at three units and whosevertical leg is, when R P= Ro, equal to 1.5. Itis then only necessary to plot the voltages developedacross known resistances in the platecircuit of the detector tube and to form the abovetriangle on this curve. Some data on detectorimpedance measured by several methods will beavailable later. Table No. 3 is the result of bridgemethods.TpHEPOWER OUTPUTfinal measurement in which we shall be* interested at present is that of undistortedpower output. With the advent of tubes of the112, the 171, and the 210 class, honest-togoodnessamplifiers have been possible, andmany strange misconceptions have arisenfrom a none too clear understanding of theirnature. Some people think that a great increasein volume will result from the substitutionof a 171 for a 20I-A. Of course sucha result is impossible. As a matter of fact the201 A, with its larger mu, will produce twiceas much voltage amplification as a 171,providedthe proper impedances are used, butit is certain that more power, with lessTube10 12 14 16 18 20OUTPUT RESISTANCEFIG. 15distortion, will be delivered to the loudspeaker when a true power tube is used.In the first place it may be said thatmeasurement of undistorted power outputfrom present-day tubes seems impossible,for the simple fact that there is no suchthing. The question is one of allowabledistortion, which involves not only mattersof opinion but the particular amplifierand loud speaker used.It is simple enough to measure the powerfrom a tube. It isonly necessary to measurethe current through a known resistance,and if the tube constants are knownto within ten per cent., and if the griddoes not take over 10 microamperes in350,000 ohms, approximately, the measuredpower will check the mathematicalvalue to within 10 per cent.The power developed in the load resistancein Fig.1 6 is:(tfEg' Ro(Ro + Rp)*And when R = R p this simplifies to:

RADIO BROADCAST ADVERTISER 51FUTURE PERFECTION OF RADIO RECEPTION DEMANDSRADIO TUBES DESIGNED FOR EACH RADIO FUNCTION.Lik^ the Bcnvenutiflfi from the Altman collection ofthe Metropolitan Museum in55 New York, the De Forest Audiamare fine examples of craftsmanshipand pain&oking skill.35S1~\E FOREST engineers^"^recognized certainacteristics in the functioningtubes in all radio units.laboratories have laboredadvance these characteristicsradio reception, and now,elements have been developedons for specific operationsreception departments.Fans who are keen tothe highest degree of efficiencythese Specialist Audions,long been appreciatedThese new De Forestnow available for detectoramplification and use intaking up to 500 voltsTo demonstrate theand the improvementperformance tune in a havechar'ofOurlong tothat so improvethese highly desirablein De Forest Audi'in the various radiobring their radios up towill eagerly adoptthe idea of which hasEngland.Specialist Audions arework, radio frequencystages in typesplate.advantages of this ideapossible in your radioesor turn down the volume of a local until you canjust barely hear it in the loud speaker. Substi'tute De Forest DL'4 Specialist radio frequencyAudions in place of the RF amplifiers you havebeen using. Note the remarkable increase involume how much louder the distant stationand how the music of a local is raised to roomfilling proportion.Radio amateurs will appreciate the character'istics of these efficient tubes. We must remem'ber that regardless of RF circuits, tubes for bestresults must be uniform. The rigid limits, bothelectrical and mechanical, to which De ForestAudions are held assure a high standard of uni'formity. With a very constant grid'plate ca'pacity and high mutual conductance the volumethese Audions obtain from distant receptionisboth amazing and satisfying.These DL'4's are recommended for trial beforeyou change all the tubes in your set.De Forest Audions have been standardsince 1906. The same genius who hasmade the broadcasting of voice and musicpossible is still hard at work for greaterperfection and greater achievement in radioreception.Of course, De Forest has designed ageneral purpose Audion. It is a good oneand where price is a consideration theDOI'A Audion is an unequalled value at $1.65.This tube is built to the same high standards ofquality that mark all De Forest Audions.De Forest dealers are pretty much everywhere.Look for displays of the brilliant black and orangeAudion containers in shop windows. (Metalboxes in which De Forest Specialist Audions arepacked insure their safety and dependability.)If dealer is not available write for booklet whichdescribes characteristics of each Audion and forchart indicating proper replacements for allstandard makes of radio.DE FOREST RADIO COMPANYPowell Crosley, jr. m*J PresidentJERSEY CITY, N.J.

RADIO BROADCAST ADVERTISERThe Radio BroadcastDubiliercondenser blockTYPE: PL-381as specified byRADIO BROADCASTType PL-38i condenser unit has beenselected by Radio Broadcast becauseof its long life and general adaptability.It is the ideal eliminator condenserbecause of the improved dielectricmaterial used. Each unit mustwithstand severe tests in order to passour rigid inspection standards. Dubiliernigh quality workmanship andreputation protect your investmentand eliminate trouble.Note the Flexible, Rubber -Covered Leadsand convenient mounting tabs. Metallic containersprotect condenser element from moistureand mechanical injury.Capacities 2,2,4,4,1, 1 mfd. operating voltageand nowDUBILIERBUFFERCondensersFor satisfactoryservice using theRaytheon rectifiertube, the newDubilier buffercondenser is absolutely essential. Made of two.1 mfd. condensers electrostatically shielded fromeach other and from external capacity effects.Flexible rubber-covered leads. Metallic containerswith mounting tabs. Two types: PL-91for 400 volts D.C.; PL-340 for 600 D.C. volts.At all DealersWrite For Booklet(^4 new booklet "17 Ways to Improve yourSet" will be mailed on receipt of ten cents.Tells how to use fixed condensers and givescircuit details. Be sure to get your copy.)DubilierCONDENSER CORPORATION4377 BRONX BLV'D NEW YORK, N.Y.SHEETSTNQUIRIES sent to the Questions and Answers department of RADIO BROADCAST were at one time* answered either by letter or in " The Grid." The latter department has been discontinued, and allquestions addressed to our technical service department are now answered by mail. In place of " TheGrid," appears this series of Laboratory Information Sheets. These sheets contain much the same typeof information ax formerly appeared in " The Grid," but we believe that the change in the method of presentationand the wider scope of the information in the sheets, will make this section of RADIO BROADCASTof much greater interest to our readers.The Laboratory Information Sheets cover a wide range of information of valu-e to the experimenter, andthey are so arranged that they may be cut from the magazine and preserved for constant reference. Wesuggest that the series of Sheets appearing in each issue be cut out with a rajor blade and pasUd on 4" by 6"filing cards, or in a notebook. The cards should be arranged in numerical order. Several times during theyear an index to all sheets previously printed will appear in this department. The first index appearedin November.Those who wish to avail themselves of the service formerly supplied by " The Grid," are requested to sendtheir questions to the Technical Information Service of the Laboratory, using the coupon which appearson page 60 of this issue. Some of the former issues of RADIO BROADCAST, in which appeared the firstsets of Laboratory Sheets, may still be obtained from the Subscription Department of Doubleday, Page &Company at Garden City, New York.No. 89 RADIO BROADCAST Laboratory Information SheetMay, 1927Short-Wave CoilsSOME DATA ON THEIR RESISTANCE'THIERE are, at present, a great many excellent* coils on the market for use in short-wave receivers.They are generallyof the "plug-in" typeso that different coils are used to obtain the variousranges required.These coils should have as low a radio-frequencyresistance as is possible, consistent with a constructionsufficiently rugged to prevent their being damagedif they are handled somewhat roughly. Itwould be preferable if the coils could be wound onsome solid form but the question then arises whetheror not a form can be used without increasing theresistance of the coil to a considerable extent.The General Radio Company has conductedsome experiments along this line to determine justhow much the form used affects the coil's resistanceand also to determine what size wire is bestto use. Tests were made using a standard bakeliteform having a diameter of 2J". The curve given onthis Sheet indicates how the radio-frequency resistanceof the coil varies with the size of the wireused. Evidently, from the curve, the wire size is notespecially critical but best results are obtained witha wire size of about No. 12 or 14 gauge.It was found that the use of good binders to holdthe turns in place has no appreciable effect upon theresistance. A coil was wound in such a manner thata form could be slipped in and out of it withoutdisturbing the wire. Measurements on the coil withand without the form indicated that the differencein efficiency was negligible.Tests were also made with regard to shieldingNo. 90SOME OF THEIR ADVANTAGESoperation of a transformer is usually ex-* plained by saying that the current flowing inthe primary sets up an alternating magnetic fieldwhich in turn causes a current to flow in the secondary.This is also the simplest way to explain theoperation of a loop antenna, the only differencebeing that the alternating magnetic field thatcauses the current to flow in the loop is in the formof radio waves.The number of volts induced in a loop by the passageof radio waves is:2 TC f n A H x 10-swhere H is the amplitude of the wave, f the frequency,n the number of turns in the loop, and A thearea of the loop. The voltage calculated from thisformula is only correct when the plane of the loopis vertical and perpendicular to the direction of themagnetic field. That is, the loop must be pointingtoward the transmitting station. If rotated abouta vertical axis only a quarter of a turn, no voltagewill be induced.This feature is the most important advantage ofa loop, for two stations using exactly the same wavelengthmay often satisfactorily be separated (providedthey do not lie in the same or exactly oppositedirections) by simply turning the loop at rightRADIO BROADCAST Laboratory Information Sheetand it was found that the shielding could be placedvery near the coil and have no appreciable effect.The result of the tests may be summed up as follows:When designing a coil for use on the 40-meter2.01.5J.flLoop Antennas14 16 18 20 22B&S WIRE GAUGE(7500-kc.) short-wave band (all these tests weremade at this frequency), it is well to (1.) use aboutNo. 12 to 14 wire; (2.) use a coil form if desired;(3.) use any good dope as a binder; (4.) use anyreasonable amount of shielding where advantageous;(5.) keep the form factor (diameter dividedby length) around 1 to 2. 5.These data are taken from the February, 1927,issue of the General Radio Experimenter.May, 1927angles to the interfering station. Loops are cominginto greater use as transmitting stations becomemore powerful, and they will probably ultimatelybe used almost exclusively on account ofthe small space required, ease of installation, portability,lack of necessity to safeguard against lightning,and the improvement of the ratio of signalstrength to interfering noises, due to their directionalproperties.If a loop is compared in size to an antenna of theordinary type it would appear that the amount ofenergy intercepted by the loop would be exceedinglysmall indeed. The fact is, however, that a goodloop antenna, tuned with a condenser having lowinsulation losses, will pick up signals much betterthan might be expected from a comparison of itssize to that of an outdoor antenna. This is due tothe fact that the loop has a very much lower resistancethan an elevated antenna.The loop type antenna has been used most frequentlyin conjunction with super-heterodynes because,with this type of receiver, it is easy to obtaina large amount of radio-frequency amplification.During the last year, however, several receivers ofthe neutrodyne type have been placed on the marketdesigned for use with a loop. These receiversare generally completely shielded so as to preventinteraction between the loop and the coils in thereceiver.

RADIO BROADCAST ADVERTISER 53Model AC-97-Tube, 2-Dial, Battery lessThis two-dial control set ts designedespecially for AC power, for use with theAmrad A B & C Power Unit. Easilyoperated, marvelous selectivity. Furnishedwith Power Unit but without tubes.142Console Model 192Model S-7337-Tube, 2-Dial, Battery TypeOwners of this Amrad Neutrodyne reportcomplete satisfaction. High ratio verniercontrols simplify tuning. Volume Is controlledby a single adjustment. Beautifullydesigned cabinet finished in twotonedmahogany. Without accessories.#77Console Model 1271 tube 'Neutrody ^ties a^yAMRADNeutrodynes are built with the greatestskill and precision. Each set must pass certainhigh standard tests before it leaves the factory.The great skill and engineering feats of the AmradLaboratories are manifest in thecircuit as well as in the beautifully designedcabinets.Produced tinder mass productionmethods influenced by Powel Crosley,Jr., combined with Amrad's engineeringskill, these genuine neutrodynes arethe greatest values on the market.The console model AC-g-C is an unusualvalue. It is a 7-tube set withtwo-dial control. All the necessarypower is furnished by the Amrad A Band& C Power Unit, an efficient power sup-tested under actual home conditionsply"B" ELIMINATOR"Will furnish B current voltages22%, 30 or 4 5. 69. 90, 135 or 180.Maximum volts. 180 at 50 mils.Unit is housed In a metal cabinetand finished in black enamel.#35'Precisionfor more than a year and operating from AC current.100-120 volts, 60 cycle. No trickle charger is concealedin this unit. No more power supply troubles.Just snap the switch and set is in full operation. Thecabinet is of beautiful two-toned mahoganyfinish, with the genuine Crosleymusicone built in. This is a wonderfulvalue at $192, with the powerunit,but without the tubes.Write Dept. 2E? for descriptive literatureand information.AMRAD CORPORATIONMedford Hillside, Mass.'Efficienl ^iube genuineltyutrodynes, unsurpassedin /he radio market anywhere at this price /60 125Model S-5225-Tube, 3-Dial, Battery TypeAmnd quality is again exemplified inthis beautifully made and proportionedset. The simple, yet elegant lines ofthis set are pleasing to the eye. Actualreports of performance are remarkable.Simple to tune and easy to operate. Alsomade in console model at $110.Model AC-55-Tube, 3-Dial, Battery lessA compact, rllli ictit si-t delivering theutmost in radio enjoyment at the lowestpossible cost. No batteries to fuss with.Operates direct from light current. Unusualselectivity, volume, and tone mattethis the greatest neutrndyne value on themarket. Ctusric Mrtel 1175.

54 RADIO BROADCAST ADVERTISERA BetterTuning UnitWas NeverDevisedNo. 91RADIO BROADCAST Laboratory Information SheetA Simple Tube TesterMay, 1927HOW TO GET CHARACTERISTICS OF TUBESbefore (2 mA.). The new reading of plate voltagemay be 82. We now have all the necessary data to/CONTRARY to the opinion of many experi- calculate the constants of the tube.^ menters, a set-up of instruments to measure The amplification constant will be equal to thethe characteristics of vacuum tubes is not excessivelycostly nor is it complicated. The diagram of divided by the difference of the two grid voltages,difference of the two plate voltages, 90-82, or 8,connections of a tester is shown on Laboratory 4.5 3.5 = 1. The amplification constant is therefore8. The plate impedance is equal to the differ-Sheet No. 92; this Laboratory Sheet will explainhow to measure tube characteristics using the tester. ence of the plate voltages divided by the differenceThe procedure can be explained most easily by in the plate currents, or 8 divided by 0.001 . The quotientis 8000, which is the plate impedance. The mu-taking an actual example.Suppose we desire to measure the characteristics tual conductance is the plate current differenceof a 201-A tube. We would first place the tube in divided by the grid voltage difference, or 0.001the socket and then, with switch No. 2 in position divided by 1 = 0.001 mhos or 1000 micromhos.B and switch No. 3 in position A, the rheostat In measuring tube factors with this apparatus,would be adjusted until the filament voltage, as care must be taken that the actual changes in voltagesand the corresponding current changes areread on the voltmeter, is correct. In this case thecorrect voltage would be 5. Then, with switch No. small. If the plate-current meter, and the gridvoltagemeter, can be read with sufficient accuracy,3 in position B the plate voltage is adjusted to 90volts. The grid bias is next adjusted to 4.5 volts very small changes should be made say a plate voltagechange of 5 volts. This, however, would make itby throwing switches Nos. 1 and 2 to the A positionsand adjusting the potentiometer P. The rrrilliammeterwill now read about 0.002 amperes (2 m A.). volt. The investigator, then, is between two firesnecessary to read grid bias changes of less than aNote down the plate voltage, the grid voltage, and in his endeavor to measure his tubes accurately.the resulting plate current.If he takes plate current readings resulting fromNow adjust the potentiometer until the grid large voltage changes, he gets a factor which representsworking the tube over a large part of its char-bias is, say 3.5., and read the plate current. It shouldread about 0.003 amperes {3 mA.). Leaving the grid acteristic curve. On the other hand, if he uses smallbias at 3.5, next adjust the switches to read the voltage changes, the accuracy depends upon theplate voltage. Reduce the plate voltage so as to accuracy of his meters and his ability to readmake the milliammeter read exactly the same as them.No. 92RADIO BROADCAST Laboratory Information SheetMay, 1927Circuit Diagram, of Tube TesterOfficially Specifiedfor theHammarlundRoberts"Hi-Q"ReceiverTHE Hammarlund "Auto-Couple" Unitcombines scientifically the Hammarlund"Midline" Condenser with the HammarlundSpacewound Coil to give automaticvariable primary coupling at everycondenser setting. This arrangementmakes for maximum signal strength andselectivityjat all wave-lengths and lessensthe tendency of radio-frequency circuits tooscillate at the higher frequencies.The "Midline" condenser has a full-floatingrotor, with removable shaft. A longershaft permits coupling together any numberof condensers for single control.No. 93RADIO BROADCAST Laboratory Information SheetAudio Amplifying SystemsMay, 1927The Hammarlund "Auto-Couple" Unit(condensers and coils may be purchased separately)is readily adapted to any radiofrequencycircuit and when combined withHammarlund Shields, Equalizers, and BalancingCondensers, will make your receiverthe last word in modern radio reception.Write for folder describing HammarlundProducts officially specified bytwenty-eight prominent designers fortheir newest receivers.HAMMARLUND MFG. CO.424-438 W. 33rd Street New York City'tGkyu Batlft^, RxxoLLcyHamma r I u n dPRODUCTSDUAL-IMPEDANCE COUPLED AMPLIFIERSpears possible to overload the power stage of animpedance amplifier to a considerable extent, withoutintroducing very objectionable distortion. ThisTHIS Sheet we give some facts regardingONdual-impedance coupled amplifiers. A circuit comes about in the following way.diagram of such an amplifier will be found on LaboratorySheet No. 87 (April, 1927).signal that can be placed on the grid is limited byIn a transformer-coupled amplifier the maximumDouble-impedance amplifiers are capable of givingexcellent results if care is taken in the selection current will flow in the grid circuit of the powerthe fact that, if the signal voltage is too large, gridof the apparatus and in the layout of the parts. tube. This current flowing through the secondaryThe plate impedances should have an inductance ot the transformer saturates the core and preventsaround 100 henries; if the inductance is much less, the transformer from properly amplifying the signal.In an impedance amplifier there are no trans-the low frequencies will be lost. Well-made 0.1-mfd.blocking condensers are essential to prevent leakageslightly lowering the inductance of the impedanceformers, and the grid current only has the effect ofṪhe amplification of each stage is generally equal unit in the power tubes's grid circuit. Slight overloadingis therefore less noticeable in an impedanceto about nine tenths of the amplification constantof the tube. If we lose one tenth on each stage, amplifier than in a transformer-coupled 9ne.then the total amplification in three stages will be As stated above, the amplification obtained at lowequal to 0.9 x 0.9 x 0.9 = 0.73 times the product frequencies depends upon the use of high-inductanceot the amplification constants of the three tubes concerned.Suppose two 201 -A's, each with an plate and grid circuits. There hasimpedances in theamplificationof eight, and one 171 with an amplifica-double-impedance amplifiers by which it is possiblehowever been a recent development in the design oftion of three, are used. Then the total amplification to obtain very good low-note amplification withoutwill be equal to 8 x 8 x 3 x 0.73 = 140.16. This value using very large coils. This design feature consists inis rather too low for best results, and for this reason so determining the inductance of the plate and gridhigh-mu tubes, having an amplification constant coils and the capacity of the coupling condenser, thatof anything up to about thirty, are generally used the entire combination tunes or resonates at about 30in this type of amplifier.cycles, with the result that the amplification of theseFrom some tests made in the Laboratory, it ap- low frequencies is unusually good.

RADIO BROADCAST ADVERTISERsafeThe heart of the socketpower unit is the variableresistor. Don't experimentwith that importantorgan. Use CLARO-STAT. Its ability tocover the entire rangeand its current carryingcapacity of 20 watts isessential if your unit is tofurnish quiet, uniformpower year after year.CAUTION! CLAROSTATis being imitated. Don't bemisled. Insist on seeing thename which isstamped onevery genuine QLAROSTAT.25c never bought more value!"The Gateway to BetterRadio" 32 pages of interestingreading, diagrams andillustrations covering everythingin radio-amplification,transmission, socket powerunit construction.Send 25c in stamps or coin toAmerican Mechanical Labs., Inc.roi-32 pageillustrated book283 N. 6th Si, Brooklyn, N.Y.RADIO PANELSOF GENUINE BAKELITECut, drilled and engraved to order. Send rough sketchfor estimate. Our complete Catalog on Panels, Tubes andRods all of genuine linkelite mailed on request.STARRETT MFG. CO.521 S. Green Street Chicago, 111.GoodrichRadioPanelsBlack, Mahogany and Walnut.Standard thickness 3-16" and ^4".High softening point preventswarping.Low free sulphur content preventsdiscoloration.Machine easier and are better electricallythan any other material incommon use.Your radio dealer has them or willget them for youif not, write tous and we will see that you aresupplied.Also hard rubber for coils, spaghettitubing and miscellaneous rubberitems for radio manufacturers.Radio Sales DivisionThe B. F. Goodrich Rubber CompanyEstablished 1870Akron, OhioThousands of Fains Saythe Biggest Value in Radiocan Build It, Too 11CYoii and Save $50 to $100 JfMEN who take a real Scotch pride ingetting the last penny's worth ofvalue out of a radio set are themen we want to build theHi-Q Shielded Receiver, forit is now a universally establishedfact that this set representsthe fullest value inradio.Thousands of these remark'able receivers have been builtat home by novices, amateursand professional radio men.Universally the verdict isSuccess. There is no more(VGet complete illustrated instructionbook from anygood dealer or send 25 centsefficient circuit at any price. Its performancepleases even those radio expertswho demand almost the impossible..McimmarlundR.OB ER.TSHiQ"Any one can build theHi-Q easily and successfullyand save at least $50to $100 over factory madesets of anythinglike similarefficiency. The approvedparts (less cabinet)cost only $63.05 includingthe simplified foundationunit.High Ratio of Reactance to Resistance. High Ratio Great Selectivity Loud Signals.HAMMARLUND-ROBERTS, Inc.Benjamin Elec. Mfg. Co.Carter Radio CompanyInternational Resistance Co.(Durham Resistors)ASSOCIATE MANUFACTURERSEby Mfg. CompanyHammarlund Mfg. Co.Radiall Co. (Amperite)1 182-A Broadway, New York CityMartin-Copeland Co.Samson Electric Co.Sangamo Electric Co.Westinghouse MicartaRADIO ROTARY METERThe Radio Dealer who services his customers'sets the most quickly and thoroughly, gainsthe most good will and profit. This HOYTRadio Rotary Meter gives him in one rugged,compact and accurate instrument, all the necessary5 meter scales required for prompt andsure Radio service, by a simple rotation ofthe meter case.Send for 8-pdge boolj describing20 Radio service tests with [theHOTT Radio Rotarjp Meter.BURTON-ROGERS CO.Sales Dept. for HOYT Electrical Instrument Works857 Boylston Street Boston, Mass.Send for booklet, "Hoyt Meters for Radio"

56 RADIO BROADCAST ADVERTISERNo. 94 RADIO BROADCAST Laboratory Information Sheet \^3.V. 1927AmplionConeCabinet Model A C 12 ... $30Even the best radioset depends onthe reproducer forits quality of tone.In every test or comparison,the AmplionCone quickly demonstrateshow much thequality of reception isimproved by this fineinstrument.Especially vocalbroadcastingthe supreme test of aradio reproducer.Withan Amplion Cone, allreproduction soundsnatural and distinct.Other Amplionsfrom $12 to $135Write for Amplion literaturewhich illustrates and describesall modelsTHE AMPLIONCORPORATION OFAMERICADept. L, 280 MadisonAvenue, New York CityTHE AMPLIONCORPORATION OFCANADA, LTD.Toronto, OntarioAN EXPLANATION OF THE ACTIONTXTHEN a tube capable of amplifying a fairly* * strong signal is used to amplify a very weakone, it is evident that its power amplifying ability isnot being made use of to the fullest possible extent."Reflexing" is a system for getting more out ofa tube by making it amplify two things the incomingsignal, which is a radio-frequency current,and the detected signal, which is an audio-frequencycurrent. The accompanying diagram indicatesa simple receiver using one stage of reflexedamplification.In this receiver, the radio-frequency current entersthe receiver via the antenna and is impressedon the tube by the tuned circuit, A. It then passesthrough the tubes and into the tuned transformer,B, the output of which is impressed on a crystaldetector. The audio-frequency currents resultingfrom the detecting action of the crystal pass throughthe primary of the audio transformer, T. The voltageinduced in the secondary of this transformer isimpressed on the grid of the tube and is amplified.A pair of phones is used in the plate circuit of thetube for receiving the signal.So long as the variations of potential due to thesetwo different signals do not cause the tube to overload,neither interferes with the other. Some circuitsuse a reflex principle consisting of severalstages of radio-frequency amplification and severalstages of audio-frequency amplification. In suchsets it is advantageous to use the system due toDavid Grimes and known as the Inverse DuplexNo. 95NECESSARY CAREThe Principle of ReflexingRADIO BROADCAST Laboratory Information Sheet'"PHE storage battery has been developed to a-*remarkable degree of perfection so that it willfunction over a long period of time with only asmall amount of attention. Such attention consistsmore than anything else in keeping the batteryproperly filled with pure distilled water and correctlycharged at all times. The efficiency and thelife of the battery will decrease considerably if thesetwo points are not carefully watched. The chargingrate should be as close as possible to that recommendedby the manufacturer, this information generallybeing given on the name plate of the battery.Although the state of charge of a battery can bemeasured with some accuracy by means of a voltmeterif the proper precautions are taken, the readingsmade in this way are not generally to be reliedupon. A better method for use in testing a storagebattery is to determine the state of charge by meansof a hydrometer. The specific gravity, which iswhat the hydrometer measures, will be found toincrease the reading of the hydrometer as the batteryis charged, up to a certain point. The specificgravity reading for full charge is not the same forall batteries. For this reason, an endeavor should beNo. 96Storage BatteriesRADIO BROADCAST Laboratory Information SheetAnalysis of Voice Frequenciessystem. In this system, the tube handling the smallestamount of radio-frequency energy is made tohandle the largest amount of audio-frequency energyand, vice versa, the tube handling the greatestCrystalamount of radio energy handles the smallest amountof audio energy. In this way the point of overloadingis not reached as quickly, and it is possible toobtain high efficiency from such a receiver.May, 1927made to obtain from the manufacturer of the batteryinformation regarding the hydrometer readingwhich should be obtained using his battery when itis fully charged and when it is fully discharged.Frequently, but not always, these same data willbe found on the name plate. In the event that thisinformation cannot be obtained, it is a safe rule tocharge the battery until the hydrometer readingdoes not change during a period of one hour. Whenthis condition holds true, the battery has absorbedall the charge possible. It will generally be foundalso that, when this condition of constant specificgravity reading throughout an hour is reached,the electrolyte will also begin to gas or bubble.Care should be taken in charging the batteryto make certain that its positive terminal is connectedto the positive terminal of the source beingused for charging purposes. If the battery is chargedin the opposite direction the plates will be reversedin chemical character, and if the charging is continuedfor any great length of time, the Battery willbe destroyed. If a battery has only been chargedin the wrong direction for a short length of time itcan generally be brought back to normal by chargingin the right direction for a very long time at alow charging rate.May, 1927RELATIVE IMPORTANCE OF LOW AND HIGH FRE-QUENCIESATANY investigations have been made to de-*" termine the relative importance of the variousIrequencies that are found in the human voice.For these investigations a high-quality audioamplifying system must be employed over which itis possible to hear equally as well as by direct transmissionthrough the air.Tests have been made by the Western ElectricCompany using such an amplifying system to determinethe relative importance of different frequenciesin the voice frequency range, and the re-These curves indicate, then, that the lower frequenciesfurnish most of the energy in the voiceand that the higher frequencies are most importantfor proper articulation. If frequencies below 500cycles are eliminated the energy is reduced 60 persults of these tests are shown in the curves on thissheet. These curves were obtained by inserting inthe circuit low-pass (L.P) filters, which will onlypass low frequencies, and high-pass (H. P.) filtersdesigned to pass no frequencies below a certainpoint. First of all let us consider the curve marked1000 2000 3000 4000 5000"Articulation H. P." The curve shows that thearticulation was 40 per cent, when a high-pass filterFREQUENCYwas used that eliminated all frequencies below 2000 cent., and the articulation is only reduced 2 percycles. The articulation rises to 70 per cent, when cent. Eliminatinga high-pass filter was all frequencies above 400 cyclesused to cut off all frequencies leaves remaining 60 per cent, of the total energybelow 1400 cycles. The curve marked "Energy but the articulation is only about 5 per cent.L.P." shows that 60 per cent, of the total energy The curves on this sheet were traced from an excellentbook by K. S. Johnson entitled: Tram-in the voice remained when a low-pass filter wasused to cut off frequencies above 500 cycles. mission Circuits for Telephone Communication.

RADIO BROADCAST ADVERTISERRadio Reception'betterthan poor tubeswithout Amperite. Utmostperformance andlongest life reQuires theperfect automatic filamentcontrol of each individualtube, affordedonly by Amperite. Insiston this variable filamentresistance and look forthe. name. Eliminates hand rheostats. SimplifiesrmgRadiall Book-FREEExplains fully Amperite principle and operation.Gives season's best Hook-Ups and ConstructionData. Send for it today to Dept. RB5Radiall Co., SO Franklin St., New YorkNewestlnformaMTO SET BUILDERS *Price $1.10mounted (U.S.A.)Sold EverywhereOne of the outstanding developments oithe present radio season is Cftmfield'xSuptr-Seto-tic* AYn*, a receiver teahiredby the Citizens Radio Call BookJo their latest issue and tested in the greatest laboratoryin the country. The Super-Selt

.58 RADIO BROADCAST ADVERTISERTJour AerialisSubject toLightningInduction7/iis Qrrester Carries$100-JREE INSURANCESafetvjDemands aBRACHStormKingARRESTERBECAUSE~It Gives MaximumProtectionItWill Not GroundItWill Not AffectReceptionIt Carries $100Free Insurance120 Years Standard on\I America's LeadingRailways\OVER 2,000,000 RADIOSARE PROTECTED BYBRACH ARRESTERSBracliRadio ProductsLS. BRACH MFG. CO..NEWARK.N.J.TORONTO, CAN.Equipment forConstructorthe Home*How to Use Some of the New Equipment Tested andApproved by the " Radio Broadcast " LaboratoryINTERFERENCEBy THE LABORATORY STAFFELIMINATORSas well as the natural sort ofMAN-MADE, "static," will hinder the reception of radiosignals. Fortunately, however, the former can beeliminated in almost all cases. Any kind of electricalspark will set up high-frequency oscillationssimilar to thpse used for broadcasting, the differencebetween the two being that the electricalspark from a motor or other household applianceis of an intermittent and varying intensity, whichresults only in noise in the receiver. There aremany classes of electrical apparatus which cancause interference, such as oil burners, batterychargers, violet ray apparatus, etc. The commutatortype of motor commonly used in connectionwith household appliances is one of the mostcommon offenders. The spark takes place at thecommutator, but the high-frequency oscillationsmay be carried along wires for a block or moreand blanket reception over a large area.FIG.IGround frarolMoloiA combination of fixed condensers and chokecoils, placed in the electric line near the offendingapparatus, will usually eliminate, or at leastgreatly reduce, the interference from this source.The common connections of such a filter apparatusare shown in Fig. i. A choke coil isplaced in each leg of the line supplying the motoror other apparatus. These coilshave a high impedance to highfrequencyoscillations, and are usuallyof approximately 200 millihenriesinductance. They shouldbe wound with wire heavy enoughto carry the current requiredwithout undue heating.l Chokesof this character may be constructedby winding 175 turns ofNo. 16 d.c.c. on a porcelain tubeI inch in diameter and 12 incheslong. The condensers act as a bypathto ground for the high-frequencycurrent. The value of thesecondensers may be from I to 2microfarads, depending upon thenature of the interference. Sometimesanother condenser, shownby the dotted lines, is placedacross the line side of the filter.These condensers should have ahigh enough working voltage totake care of any voltage whichmay be impressed on them. THEThere are several interferencefilters on the market, two ofwhich are shown in the photograph.While the circuit diagram given may notbe exactly that used in the commercial type offilter, these latter are all based on the samegeneral principle. In each device there are fivewires leading out of the case, two of which go tothe electric line, two to the motor or other apparatus,and the fifth to the grounded frame ofthe motor. The Tobe Interference Filter No. I ismade by the Tobe-Deutschmann Company, ofCambridge, Massachusetts, and sells for $15.00.This filter is designed for household appliancesand will work effectively on motors up to J horsepower,and may be used on d.c. or a.c. lines. Itis understood that these filters may be obtained,by special order, for installations of as high as5Oo-kilowatts and 1000 volts potential. The Day-Fan Electric Company, of Dayton, Ohio, alsomake a filter, known as the "Quietus," which isobtainable in two models, one, the No. 6001, forgeneral use in the home, which sells for $10.00,and another, the No. 6003, for use with a householdlighting plant, such as the Delco-Light,which is priced at $8.00.RESISTORSFOR SOCKET-POWER DEVICESRESISTORS designed for use in socket-powerdevices may be of the wire-wound type orof the metallic filament type, but in every case,they must be designed to dissipate the heat generatedfast enough so that they will not burn out.Some manufacturers rate their resistors accordingto how much current may be carried withsafety, while others rate them in watts. To choosethe correct resistance when the rating isgiven incurrent, the amount of current which is to flowin the circuit must be known. This may be measuredor it may be calculated by Ohm's Law. Forinstance, if the resistance is 1000 ohms and thevoltage 100, the voltage divided by resistancewill give the amount of current which will flow,which in this case is o. 10 amperes (100 milliamperes).The current-carrying capacity of the resistorshould therefore be rated at 100 or moremils. In the case of the resistor rated in watts,the procedure is slightly different. The wattage isfound by multiplying the voltage by the current,or in the case of the above resistor, the voltage(100) times the current (o. 10) gives us 10 watts.That is, a looo-ohm resistor having a rating of10 watts would carry the 100 milliamperes with-RADIO BROADCAST Photograph"QUIETUS" AND TOBE-DEUTSCHMANN INTER-FERENCE FILTERSout overheating. Another way in which the carryingcapacity may be figured is by the formula inwhich watts are equal to the current squaredtimes the resistance. Transposing the formula weget:where I is the current, w is the watts rating, andR is the resistance. Substituting the actual values

RADIO BROADCAST ADVERTISER 59where R = 1000 ohms and w = 10, in the aboveformula, we have Iequal to the square root of10 + looo. Taking the square root, we obtain thesafe carrying capacity in current as o.i amperes,or 100 milliamperes.The resistances of various units as measuredin the Laboratory by means of the Wheatstonebridge were found to differ by about 3 per cent,from the rated value, which is close enough forall ordinary purposes. Resistors of this type aremade by Amsco Products, Incorporated, NewYork City; Ward-Leonard Electric Company,Mount Vernon, New York; the Tobe-DeutschmannCompany (Veritas), Cambridge, Massachusetts;Arther H. Lynch, Inc., New York, andthe C. E. Mountford Company (Kroblak), NewYork City.SHIELDSA RGUMENTS still continue among engineers,f\ experimenters, and home-constructors, re-'garding the shielding of radio broadcast receivers.Some say that coils, condensers, etc., if properlydesigned and properly spaced in the receiver, willneed no shielding, while others claim that shieldingis an absolute necessity.Until quite recently the home-constructor washampered in the use of shielding, because he hadno tools for working the material; besides, thelatter was hard to get. Several types of aluminumbox shields can now be had, and they may easilybe incorporated in almost any receiver requiringa shield. These shields usually come in knock-RADIO BROADCAST PhotographINDIVIDUAL STAGE SHIELDSdown form, and may easily be assembled bymeans of ingeniously designed corner strips.Their size is sufficient to allow a tube, radiofrequencytransformer, and variable condenserto be mounted within them without coming tooclose to the sides. If the size is not exactly rightthey may be cut down before assembly, as theyare in flat pieces. An accompanying photographshows one of these shield boxes, made by theAluminum Company of America, both inknocked-down and assembled form. The AluminumCompany's box is 12 gauge, 6 inches high, 5inches wide, and 9 inches deep, and is sold for$3.00. The Hammarlund Manufacturing Company'sbox shield is 22 gauge, 5^ inches high, 6inches wide, and 9 inches deep, and sells for $2.00.The Silver-Marshall Company makes a shield ofthis type which, however, is not knocked down.The box is 21 gauge, 5 inches high, 3 J incheswide, and yj inches deep. The price is $2.00.SOCKET-POWER UNITSTHE Balkite socket-power B units are all ofthe electrolytic type, having eight cells inseries which rectify the a.c. current from the line.THE BALKITERADIO BROADCAST Photograph"Kx" UNITThese cells are of the acid type having one electrodeof lead and the other of a special material.As a rule, this type of rectifier, combined withthe proper transformers, chokes, and condensersgives very quiet operation, and the only attentionrequired is the addition of pure water at intervalsof several months to take care of the evaporationwhich naturally takes place.In the instructions accompanying the apparatus,it is stated that the formation of a brown orwhite sludge in the bottom of the cell is a normalcondition and no attention should be paid to it.The solution sometimes turns pink, and this alsomay be regarded as natural. It should never benecessary to replace the electrolyte except incase of accident when the solution is spilled. Anew solution should be obtained from the manufactureror from the dealer who sold the unit. Ifthe electrolyte gets spilled in the metal case, thewhole unit should be shipped back to the factoryimmediately for a thorough cleaning, otherwisethe acid may cause considerable damage to theelectrical mechanism in the device and cause itto cease functioning.Sometimes when the electrolytic type of rectifieris left for some time without being operated,a thin film of sulphate will form on the surface ofthe electrodes which will materially lower theoutput voltage. There are two methods of bringingthe unit back to normal. For ordinary cases,the unit should be disconnected from the receiverand a short circuiting wire connected across theoutput terminals marked "High" and "Negative."The line current is then turned on for half anhour, after which the jumper wire is disconnectedand the unit is again hooked up to the receiver,and normal operation should be obtained.Another method which may be used is to put ajumper across the output as before and then shortout half of the rectifier cells at a time for a periodof about thirty seconds. In the Laboratory thebreaking down of the sulphate film was tried out,the voltage, in one case, being raised from 125 to140 volts. On one of the smaller units, the voltagewas raised from 105 to 120 volts. Both units hadbeen standing for some time. One model, the typeKX, which includes a trickle charger in the samecase, is shown in the accompanying photographon this page.A table of the price list and capacities is appendedat the bottom of this page. All ofthese Balkite units are for use with 1 10 to120 volts a.c. Models are sold for either 50 or 60cycles. They are manufactured by FansteelProducts, Incorporated, of North Chicago,Illinois.

60 RADIO BROADCAST ADVERTISERMire's WoUSThatisAlmiisiEARNBIGMONEY*RADIOGet into the great new BIG Pay IndustryRadio. If yqu'ie earning a penny less than$50 a week, clip coupon now.Send for 64-page FREEBOOK. Be a Radio Expert,and draw down bigmoney for this easy, fascinatingwork. Positionseverywhere. Need for RadioExperts in every community.Short hours. BIGPAY. Free Book givesall the facts.Learn Quickly andEasily at HomeSkilled Radio Engineers willshow you how to qualify, quicklyand easily at home, for Radio'sfine job*. We train you completelyand thoroughly. Hundredsof N. R. I. trained menare today down holding1 goodbig jobs fn the Radio field. Hundredsofopportunitiesnow awaitingthe trained man. FREEEMPLOYMENT SERVICE.Many other big features. Getthe facts-CLIP COUPON."My charges forconsultation $2.50per hour. All successdue to you.''R. W. Blackhill,BrooklynRadio a goldmine yourcourse worththousands."A. R. Herke,WinnipegGet This FREE BOOK!Send coupon below forFREE BOOK "Rich Rewardsin Radio." Readfor yourself. No previousexperience needed. Commonschooling enough.WRITE NOW.Materials for building up-to-date receiving srts and toconstruct 50 well-known Radio circuits included to helpyou learn. An UNEQUALLED OFFER. Other specialfeatures now being offered, so Act Quick!NATIONAL RADIO INSTITUTEDept. E-94. Washington, D. C.MAIL COUPONNational Radio Institute,Dept. E-94, Washington, D. C.Without obligating me in any way, pleasesend me your free book, "Rich Rewards inRadio." also complete information on yourpractical, home study Radio course.NameAddressTown. .StateA KEY TO RECENTRADIO ARTICLESBy E. G. SHALKHAUSERTHISis the nineteenth installmentof referencesto articles which have appeared recently in variousradio periodicals. Each separate referenceshould he cut out and pasted on 4" x 6" cards forfiling, or pasted in a scrap book either alphabeticallyor numerically. An outline of the DeweyDecimal System (employed here) appeared lastin the January RADIO BROADCAST.Rsso. BROADCASTING.BROADCASTINGPopular Radio. Jan., 1927. Pp. Il-ff. Who Pays for,"Who Pays the Broadcaster?" O. E. Dunlap. Jr.The problem of supporting radio broadcast programs,either through actual contributions by the listening public,or through indirect channels, such as advertising, and thuscreating good will and deriving publicity, is discussed. Alist of sponsors of various program featurfes, and the stationsbroadcasting, is tabulated, showing what is beingdone to-day in furnishing entertainment. A chart is alsoappended stating the toll charges of the various stations forgiven periods of time on the air.Ri4i.2. .. RESONANCE. .RESONANCE,Popular Radio. Jan., 1927, Pp. 3i-ff..Tuning."What Happens When You Tune Your Set," Sir OliverLodge.A simple treatise on the conversion of radio waves intoelectrical impulses in the tuning circuits of the radio setand its analogy to mechanical or sound resonance is givenin this second of a series of articles. The function of the detectortube is clearly outlined.R62o.o8. INSTALLATIONS.INSTALLATIONS,Bureau of Standards Handbook No. 9. Safety Rules."Safety Rules for Radio Installations."The material contained herein is a reprint of Part 5 ofthe National Electrical Safety Code, dealing with properradio installations as approved by the American EngineeringStandards Committee.ROQO. HISTORY.HISTORYRadio Service Bulletin. Dec. 31, 1926., Pp. 24-32."Important Events in Radio-Peaks in the Waves ofWireless Progress."A brief outline of the important happenings in the historyof radio, opposite the year in which these events occurred,is given. Starting with the year 1827, when the principleof magnetism was first discovered, and leading downthrough the year 1926, the progress made in radio is presented.R$50. BROADCASTING;BROADCASTING,Radio Service Bulletin. Dec., 31, 1926.Pp. 9-21. List of Stations."Broadcasting Stations, Alphabetically by Call Signals."A list of broadcasting stations, giving call signals, locationof station, owner of station, power, wavelength, andfrequency, is presented. The list is complete up to December31, 1926. This publication may be procured fromthe Superintendent of Documents, Government PrintingOffice, Washington, District of Columbia, at five cents percopy.R330. ELECTRON TUBES. ELECTRON TUBES,Radio. Jan., 1027, Pp. 2O-ff. 4 Element."The Shieldea Grid Vacuum Tube," E. E. Turner, Jr.By placinga second grid between the plate and the controlgrid of a vacuum tube. Doctor Hull, of the GeneralElectric Company, has succeeded in reducing inter-electrodecapacity between the elements of the tube. This secondgrid is said to act as an electrostatic shield when positivelycharged. It is composed of a number of flat circular discs,or rings, 3 mm. wide and spaced 3 mm. apart. The characteristicsof the tube are discussed.R344.5 ALTERNATING CURRENT SUPPLY.Radio. Jan., 1927. Pp. 23-24.SOCKET-POWERDEVICE,A Battery."A Home-Built A Battery Eliminator," G. M. Best.Constructional data concerning a 2-ampere A batteryeliminator employing a transformer, chokes, two tungar 2-ampere bulbs, and electrolytic condensers or rheostats,are presented.R382. INDUCTORS. INDUCTORS,Radio. Jan., 1927. Pp. 26-27. Chart."A Reversible Inductance Chart," A. C. Kulmann.A very comprehensible and useful inductance chart forsingle-layer solenoids, giving either the inductance of a coilor the coil size required for a given inductance, is shown.The range in inductance is from 4 to 20,000 microhenries.The use of the chart is illustrated.Ri34.8. REFLEX ACTION. REFLEXRadio. Jan., 1927. Pp. 290*. ACTION."More About the New Inverse Duplex," D. Grimes.In this second of a series of articles on the new InverseDuplex System, complete data on the construction of theseparate coils, data on wiring and assembly, and eliminationof trouble that might occur, are given.R343. ELECTRON-TUBE RECEIVING SETS. RECEIVER,Ra" .tadio. ' Jan., 1927. Pp. 3off. Infradyne."How and Why the Infradyne Works," R. B. Thorpe.The writer discusses theoretically the operation of thenew infradyne receiving circuit, analyzing the action takingplace within the various parts of the circuit. Various diagramsand graphs are shown, in order to explain clearlythe arrangement employed.R344-3. TRANSMITTING SETS.TRANSMITTERS,Proc. I. R." E.Jan., 1927. Pp. 9-36. Crystal-Controlled.Piezo-EIectnc Crystal-Controlled Transmitters," A.Crpssley.A discussion of piezo-electric crystals and the early historyof the development of the art are given.The development of crystal-controlled vacuum-lubeoscillators by the Naval Research Laboratory is outlined,and various means of amplifying the output of a crystalcontrolledoscillator are cited, the best method being described.This method consists of balancing or neutralizingthe various stages of amplification and also observing properprecautions for reducing grid circuit losses by using highvalues of biasing voltage.A complete high-power low-frequency crystal-controlledtransmitter is described, and a schematic wiring diagramof the circuits employed in this transmitter is shown. Aschematic wiring diagram, and illustrations of one type oflow-power high-frequency transmitter, complete the subjectmatter covered in this paper.R344. ELECTRON-TUBE GENERATORS. ELECTRON-TUBEProc. I. R. E. Jan., 1927. Pp. 37-39. GENERATOR."Simultaneous Production of a Fundamental and aHarmonic in a Tube Generator," H. J. Walls.A method whereby a single generator tube may be usedto transmit two frequencies simultaneously, thus eliminatingthe necessityof using two separate tubes, is described.In addition to the fundamental, some harmonic is amplifiedin a separate oscillating circuit. A broadcasting station maythus send put the same modulated energy on two frequenciesusing but one transmitter.Rii3.i. FADING. FADING.Proc. I. R. E. Jan., 1927. Pp. 41-47.Recorder lor,"An Automatic Fading Recorder, T. A. Smith and G.Rodwin.A device for automatically recording signal intensitiesis described, with the method employed to amplify the signalsufficiently to operate a commercial type graphic meter,Sample fading records of various transmissions are alsopresented.R33i. CONSTRUCTION; EVACUATION ELECTRON TUBES,OF TUBES.Proc. I. R. E. Jan., 1927. Pp. 40-55. Alkali" Vapor.Behavior of Alkali Vapor Detector Tubes," H. A. Brownand C. T. Knipp.The comparative efficiency of gas-filled tubes now onthe market, and certain potassium sodium alloy tubes, isdescribed. It is shown how the operation of gas-filled tubesdepends on the temperature of the gas and the tube walls.It is also shown how these K Na tubes compare with the2OI-A and the 200 type tubes, and that the K Na tubesare ideal for durability, true tone reproduction, and noncriticaladjustment of plate and filament voltage.International Short-WaveTestCROM April i8th to joth, short-wave testson yooo-kc. (43 meters) will be conductedfrom WAQ-2 XAI, the Westinghouse experimentalstation at Newark, New Jersey. The schedule is:8 to 8 :3O P. M. (Eastern Standard Time) " A BC de2 XAI" sent automatically on a crystal-controlledtransmitter. From 8:30 to 9, amateurs will beworked and other tests made. The manager ofthe station, E. Gundrum, Westinghouse Electric& Manufacturing Company, Plane and OrangeStreets, Newark, New Jersey, welcomes reportson audibility, fading, and keying, from listenersthroughout the world. Reports should be forwardedeither to RADIO BROADCAST or directlyto the station.TECHNICAL INFORMATION INQUIRYBLANKTechnical Service,RADIO BROADCAST LABORATORY,Garden City, New York.GENTLEMEN:Please give me fullestinformation on theattached questions.I enclose a stampedaddressed envelope.C] I am a subscriber to RADIO BROADCAST, Iand therefore will receive this information (free of charge.HH I am not a subscriber and enclose $1 to jcover cost of the answer.NAMEADDRESS .. . .R. B. M.

11 ;iitRADIO BROADCAST ADVERTISER 61Manufacturers'BookletsA Varied List of Books Pertaining to Radioand Allied Subjects Which May Be ObtainedFree by Using the Accompanying CouponTrade Mark Reg'd. U. S. Vat. OfficeASAN additional service to RADIO BROAD-CAST readers, we print below a list of bookletson radio subjects issued by various manufacturers.The publications listed below caver awide range of subjects, and offer interesting readingto the radio enthusiast. The manufacturersissuing these publications have made great effortto collect interesting and accurate information.RADIO BROADCAST hopes, by listing these publicationsregularly, to keep its readers in touchwith what the manufacturers are doing. Everypublication listed below is supplied free. In ordering,the coupon printed on page 62 must beused. Order by number only. THE EDITOR.1. FILAMENT CONTROL Problems of filament supply,voltage, regulation, and effect on various circuits. RADIALLCOMPANY.2. HARD RUBBER PANELS Characteristics and propertiesof hard rubber as used in radio, with suggestions onhow to "work" it. B. F. GOODRICH RUBBER COMPANY.3. TRANSFORMERS andA booklet giving data on inputoutput transformers. PACENT ELECTRIC COMPANY.4.RESISTANCE-COUPLED AMPLIFIERS A general discussionof resistance coupling circuit diagrams.with curves andCOLE RADIO MANUFACTURING COMPANY.5. CARBORUNDUM IN RADIO A book giving pertinentdata on the crystal as used for detection, with hook-ups,and a section giving information on the use of resistors.THE CARBORUNDUM COMPANY.6. B-ELIMINATOR CONSTRUCTION Constructional dataon how to build. AMERICAN ELECTRICAL COMPANY.TRANSFORMER AND CHOKE-COUPLED AMPLIFICA-7.TION Circuit diagrams and discussion. ALL-AMERICANRADIO CORPORATION.8. RESISTANCE UNITS A data sheet of resistanceunits and their application. WARD-LEONARD ELECTRICCOMPANY.VOLUME A leaflet circuits for9. CONTROL showingdistortionless control of volume. CENTRAL RADIO LABORA-TORIES.10. VARIABLE RESISTANCE As used in various circuits.CENTRAL RADIO LABORATORIES.1 1. RESISTANCE COUPLING Resistors and their applicationto audio amplification, with circuit diagrams.DEjuR PRODUCTS COMPANY.12. DISTORTION AND WHAT CAUSES IT Hook-ups ofresistance-coupled amplifiers with standard circuits. ALI.EN-BRADLEY COMPANY.1 5. B-ELIMINATOR AND POWER AMPLIFIER Instructionsfor assembly and operation using Raytheon tube.GENERAL RADIO COMPANY.53. B-ELIMINATOR AND POWER AMPLIFIER Instructionsfor assembly and operation using an R. C A. rectifier.GENERAL RADIO COMPANY.16. VARIABLE CONDENSERS A description of the functionsand characteristics of variable condensers with curvesand specifications for their application to complete receivers.ALLEN D. CARDWELL MANUFACTURING COMPANY.17. BAKELITE A description of various uses of bakeliteradio, its manufactuie, and its properties. BAKELITEinCORPORATION.IQ. POWER SUPPLY A discussion on power supply withparticular reference to lamp-socket operation. Theoryand constructional data for building power supply devices.ACME APPARATUS COMPANY.20. AUDIO AMPLIFICATION A booklet containing dataon audio amplification together with hints for the constructor.ALL-AMERICAN RADIO CORPORATION.21. HIGH-FREQUENCY DRIVER AND SHORT-WAVE WAVE-METER Constructional data and application. BURGESSBATTERY COMPANY.46. AUDIO-FREQUENCY CHOKES A pamphlet showingin the ciicuit where audiopositionsfrequency chokes maybe used. SAMSON ELECTRIC COMPANY.47. RADIO-FREQUENCY CHOKES Circuit diagrams illustratingthe use of chokes to keep out radio-frequencycurrents from definite points. SAMSON ELECTRIC COMPANY.48. TRANSFORMER AND IMPEDANCE DATA Tablesgiving the mechanical and electrical characteristics oftransformers and impedances, together with a short descriptionof their use in the circuit. SAMSON ELECTRIC COMPANY.4(>. BYPASS CONDENSERS A description of the manufactureof bypass and filter condensers. LESLIE F. MUTERCOMPANY.50. AUDIO MANUAL Fifty questions which are oftenasked regarding audio amplification, and their answers.AMERTRAN SALES COMPANY, INCORPORATED.51. SHORT-WAVE RECEIVER Constructional data on areceiver which, by the substitution of various coils, may bemade to tune from of a frequency 16,660 kc. (18 meters) to1099 kc. (150 meters). SILVER-MARSHALL, INCORPORATED.52. AUDIO QUALITY A booklet dealing with audiofrequencyamplification of vaiious kinds and the applicationto well-known circuits. SILVER-MARSHALL, INCOR-PORATED.$6. VARIABLE CONDENSERS A bulletin giving ananalysis of various condensers together with their characteristics.GENERAL RADIO COMPANY.>7. FILTER DATA Facts about the filtering of directcurrent supplied by means of motor-generator outfits usedwith transmitters. ELECTRIC SPECIALTY COMPANY.50. RESISTANCE COUPLING A booklet giving somegeneral information on the subject of radio and the applicationof resistors to a circuit. DAVEN RADIO CORPORATION.60. RESISTORS A pamphlet giving some technical dataon resistors which are capable of dissipating considerableenergy; also data on the_ordinary resistors used in resistance--coupled amplification. THE CRESCENT RADIO SUPPLYCOMPANY.62. RADIO-FREQUENCY AMPLIFICATION Constructionaldetails of a five-tube receiver using a special design of radiofrequency transformer. CAMFIELD RADIO MANUFACTURINGCOMPANY.63. FIVE-TUBE RECEIVER Constructional data onbuilding a receiver. AERO PRODUCTS, INCORPORATED.64. AMPLIFICATION WITHOUT DISTORTION Data andcurves illustrating the use of various methods of amplification.ACME APPARATUS COMPANY.65. RADIO HANDBOOK A helpful booklet on the functions,selection, and use of radio apparatus for better recepion.BENJAMIN ELECTRIC MANUFACTURING COMPANY.66. SUPER-HETERODYNE Constructional details of aseven-tube set. G. C. EVANS COMPANY.70. IMPROVING THE AUDIO AMPLIFIER Data on thecharacteristics of audio transformers, with a circuit diagramshowing where chokes, resistors, and condensers can be used.AMERICAN TRANSFORMER COMPANY.71. DISTORTIONLESS AMPLIFICATION A discussion ofthe resistance-coupled amplifier used in conjunction with atransformer, impedance, or resistance input stage. Amplifierciicuit diagrams and constants are given in detail for theconstructor. AMSCO PRODUCTS INCORPORATED.72. PLATE SUPPLY SYSTEM A wiring diagram and layoutplan for a plate supply system to be used with a poweramp.ifier. Complete directions for wiling are given. AMER-TRAN SALES COMPANY80. FIVE-TUBE RECEIVER Data are given for the constructionof a five-tube tuned radio-frequency receiver.Complete instructions, list of parts, circuit diagram, andtemplate are given. ALL-AMERICAN RADIO CORPORATION.81. BETTER TUNING A booklet giving much general informationon the subject of radio reception with specific illustrations.Primarily for the non-technical home constructor.BREMER-TULLY MANUFACTURING COMPANY.82. SIX-TUBE RECEIVER A booklet containing photographs,instructions, and diagrams for building a six-tubeshielded receiver. SILVER-MARSHALL. INCORPORATED.83. SOCKET POWER DEVICE A list of parts, diagrams,and templates for the construction and assembly of socketpower devices. JEFFERSON ELECTRIC MANUFACTURING COM-PANY.84. FIVE-TUBE EQUAMATIC Panel layout, circuit diagrams,and instructions for building a five-tube receiver, togetherwith data on the operation of tuned radio- frequencytransformers of special design. KARAS ELECTRIC COMPANY.85. FILTER Data on a high-capacity electrolytic condenserused in filter circuits in connection with A socketpower supply units, are given in a pamphlet. THE ABOX COM-PANY.ACCESSORIES22. A PRIMER OF ELECTRICITY Fundamentals ofelectricity with special reference to the applicationof drycells to radio and other uses. Constructional data on buzzers,automatic switches, alarms, etc. NATIONAL CARBON COMPANY.2}. AUTOMATIC RELAY CONNECTIONS A data sheetshowing how a relay may be used to control A and B circuits.YAXI.EY MANUFACTURING COMPANY.25. ELECTROLYTIC RECTIFIER Technical data on a newtype of rectifier with operating curves. KODEL RADIOCORPORATION. .26. DRY CELLS FOR TRANSMITTERS Actual testsgiven, well illustrated with curves showing exactly whatmay be expected of this type of B power. BURGESS BATTERYCOMPANY.27. DRY-CELL BATTERY CAPACITIES FOR RADIO TRANS-MITTERS Characteristic curves and data on discharge tests.BURGESS BATTERY COMPANY.28. B BATTERY LIFE Battery life curves with generalcurves on tube characteristics. BURGESS BATTERY COM-PANY.20. How TO MAKE YOUR SET WORK BETTER A nontechnicaldiscussion of general radio subjects with hints onhow reception may be bettered by u^ing the right tubes.UNITED RADIO AND ELECTRIC CORPORATION.30. TUBE CHARACTERISTICS A data sheet giving constantsof tubes. C. E. MANUFACTURING COMPANY.31. FUNCTIONS OF THE LOUD SPEAKER A short, nontechnicalgeneral article on loud speakers. AMPLION COR-PORATION OF AMERICA.32. METERS FOR RADIO A catalogue of meters used inradio, with connecting diagrams. BURTON-ROGERS COM-PANY.33. SWITCHBOARD AND PORTABLE METERS A bookletgiving dimensions, specifications, and shunts used withvarious meters. BURTON-ROGFRS COMPANY.14. COST OF B BATTERIES An interesting discussionof the relative merits of various sources of B supply. HART-FORD BATTERY MANUFACTURING COMPANY.TINYTOBESThe TINYTOBECondenser, shown inactual size here, la aru-tv product and isavailable In capacitiesfrom .00007 to .02 MM,For1 in nous operationat voltages up to1000 volts D.C. It is; * small and light thatIt can be soldered directly into the circuitwithout other support.Prices range from 35c for .00007 Mfd. toGOc for the .02 Mfd.A special-purpose condenser made for theRadlola No. 104 Loud Speaker, and made toM .rM up In continuous use. It fits the spaceprovided exactly. Price. $7.00.illThe first condenserB-BLOCK specificallydesigned for use withthe Thordarson PowerCompact Type R- 1 7 1is the TOBE B BLOCKType R-171. Theterminals are arranged-so that they come closeto those on the Thordarson Power Compact,for minimum time and length of wiring.Short-path, non-inductive condensers are usedfor increased efficiency. The price is $12.00.Thordarson makes a 210 unit also, andthere is the TOBE B-BLOCK Type B-210to go with It. Price. $13.00.The TOBE 6OO LineHfgh-vnH-ige condensers for AroerTran andsimilar high-voltage packs. Big. husky 1000-volt D.C. continuous-operating voltage condensersmade to stand the gaff.wilh TOBE safety terminals.EquippedPricesXo. 6T.O 0.5 Mfd $2 OnXo. 601 1.0 MM 2 :.i>No. 602 2.0 Mfd 3.50Xo. 604 4.0 Mfd >i OilWrite us for information on the TOBERadio Interference Filters. They are madeto reduce man-made static. Ask for PamphletB-S.Tobe DeutscKmannCo*Engineers & Manufacturers ofTechnical Apparatus^Cambridge

''. ..RADIO BROADCAST ADVERTISERin testing them. THE CARBON PRODUCTS COMPANY.68. CHEMICAL RECTIFIER Details of assembly, withwiring diagrams, showing how to use a chemical rectifier forcharging batteries. CLEVELAND ENGINEERING LABORA-TORIES COMPANY.69. VACUUM TUBES A booklet giving the characteris-35. STORAGE illustratedbooklet on the care and operation of the storage battery.GENERAL LEAD BATTERIES COMPANY.36. CHARGING A AND B BATTERIES Various ways ofconnecting up batteries for charging purposes. WESTING-HOUSE UNION BATTERY COMPANY.37. CHOOSING THE RIGHT RADIO BATTERY Advice onwhat dry cell battery to use; their application to radio,with wiring diagrams. NATIONAL CARBON COMPANY.rejuvenate53. TUBE REACTIVATOR Information on the care ofvacuum tubes, with notes on how and when they should bereactivated. THE STERLING MANUFACTURING COMPANY.54. ARRESTERS Mechanical details and principles of thevacuum type of arrester. NATIONAL ELECTRIC SPECIALTYCOMPANY.your55. CAPACITY CONNECTOR Description of a new devicefor connecting up the various parts of a receiving set,hard-workedat the same time providing bypass condensers between theleads. KURZ-KASCH COMPANY.61. DRY CELLS Information on the construction andtubes!operation of dry cells with a description of the methods usedtube with short oftics of the various types a descriptionwhere they may be used in the circuit. RADIO CORPORA-TION OF AMERICA.77. TUBES A booklet for the beginner who is interestedin vacuum tubes. A non-technical consideration of thevarious elements in the tube as well as their position in thereceiver. CLEARTRON VACUUM TUBE COMPANY.86. SHORT-WAVE RECEIVER A booklet containing dataon a short-wave receiver as constructed for experimentalpurposes. THE ALLEN D. CARDWELL MANUFACTURINGCORPORATION.87. TUBE TESTER A complete description of how tobuild and how to operate a tube tester. BURTON-ROGERSCOMPANY.MISCELLANEOUSNIGHT after night for hours at atime those tubes of yours havebeen hard at it. Now they are getting alittle jaded, in no shape to make goodin the coming months of "not sogood" radio reception. But just plugthem into a Sterling Meter EquippedTube Reactivator, turn on the currentfor a few minutes and your tubes willbe restored to their normal strength.The Sterling Reactivator workswonders with old tubes so long as thefilament isn't burned out.Model R-403 for large and small58. How TO SELECT A RECEIVER A commonsensebooklet describing what a radio set is, and what you shouldtubes, $12.50.expect from it, in language that any one can understand.DAY-FAN ELECTRIC COMPANY.67. WEATHER FOR RADIO AOrvery interesting bookleton the relationship between weather and radio reception,with maps and data on forecasting the probable results.TAYLOR INSTRUMENT COMPANIES.test themfor performancewith the Sterling"Home" Tube TesterKnowingwhat'swrong ismote thanhalf thebattle forthe use of electrical testing instruments in automotive workperfectcombined with aradio description of the cadmium test for storagebatteries. Of interest to the owner of storagereception.BURTON ROGERS COMPANY.And more79. INSULATION Aoften thancomprehensive book giving valuableinformation on all types of insulating material used innot thetroublecomes fromthe tubes.The onlyway to find this out is to have a reliable tubetester on hand when you need it. The SterlingTube Tester tells you at a glance theUSE THIS COUPONexact condition of your tubes. In simpleRADIO BROADCAST SERVICE DEPARTMENTlanguage too. No computations to make.RADIO BROADCAST, Garden City, New York.Just plug in and read "good", "fair" orPlease send me (at no expense) the following bookletsindicated"poor".by numbers in the published listModel R-411 for large tube $7.50for small tube $8.50See your dealer about these two essentialradio devices.I1RADIO NECESSITIESSend for booklet "7" tellingName. .Addressabout the complete line of(Number)(Street)Sterling Radio EquipmentTHE STERLING MFG. Co.(City)(Stat.')38. LOG SHEET A list of broadcasting stations withcolumns for marking down dial settings. 0. S. L. RADIO,INCORPORATED.41. BABY RADIO TRANSMITTER OF QXH-QEK Descriptionand circuit diagrams of dry-cell operated transmitter.BURGESS BATTERY COMPANY.42. ARCTIC RADIO EQUIPMENT Description and circuitdetails of short-wave receiver and transmitter used inArctic exploration. BURGESS BATTERY COMPANY.43. SHORT-WAVE RECEIVER OF QXH-QEK Completedirections for assembly and operation of the receiver.BURGESS BATTERY COMPANY.44. ALUMINUM FOR RADIO A booklet containing muchradio information with hook-ups of basic circuits, withinductance-capacity tables and other pertinent data.ALUMINUM COMPANY OF AMERICA.45. SHIELDING A discussion of the application ofshielding in radio circuits with special data on aluminumshields. ALUMINUM COMPANY OF AMERICA.73. RADIO SIMPLIFIED A non-technical booklet givingpertinent data on various radio subjects. Of especial interestto the beginner and set owner. CROSLEY RADIO COR-PORATION.74. THE EXPERIMENTER A monthly publication whichgives technical facts, valuable tables, and pertinent informationon various radio subjects. Interesting to the experimenterand to the technical radio man. GENERAL RADIOCOMPANY.75. FOR THE LiSTENER-^-General suggestions for theselecting, and the care of radio receivers. VALLEY ELECTRICCOMPANY.76. RADIO INSTRUMENTS A description of variousmeters used in radio and electrical circuits together with ashort discussion of their uses. JEWELL ELECTRICAL IN-STRUMENT COMPANY.78. ELECTRICAL TROUBLES A pamphlet describingelectrical work. More for the technical man than for theaverage set owner. MITCHELL-RAND MANUFACTURINGCOMPANY.ORDER BY NUMBER ONLYThis coupon must accompany every request. RB 527UsePoforat fullSimply adaptto your set withConnectproldsFor UX 171, and UX 112 Tubes, Na-AW 112Connectoralds are recommended for maximumvolume with storage battery sets. These tubeswill deliver without distortion several times thevolume of the regular 2OI A. Price $1.50.120 Tubes in UV 2OiA sockets, the Na-Ald No. 1 20 Connectorald should be used. Toconvert a storage battery set to drybatteries withi^ample loud speaker volume, use a UX 120 tube inthe last audio stage with the 1 20 Connectorald andUX 199 tubes with 4igX Adapters in the othersockets. Price $i 25.~ vfviFor the UX 120 Tube in UV 199 sockets, ampleloud speaker volume without distortion itobtainable from any set equipped for UV 199tubes by means of the UX i2Oor equivalent tubewith the Na-Ald No.J92O Connectorald. Thetube is raised slightly, but provides for its use inmost sets with limited headroom. Price $I.2JJ.For UX 120 tubes in the UV 199 sockets ofthe Radiola Superheterodyne Semi- Portable,and Radiola Super VIII. These excellent Superjheterodynes will deliver ample volume for loud|speaker operation when equipped with theUX 1 20 Iused with the Na-Ald No. 420 Connectorald. Price $1.25.!ALDEN MANUFACTURING GO.Dept. B-25Springfield, Mass.To get the utmostfrom those new High-Mu tubesDESIGNED to official specificationsfor usewith the new Radiotron and CunninghamResistance-coupled High-Mu tubes, the newLynch Metallized Resistance Coupled AmplifierKit will give you perfect tone with full volume.May be used with any receiver. At all gooddealers' or by mail, prepaid $9.00. Write forliterature.ARTHUR H. LYNCH, Inc.Member RMA250 West 57th St. New York, N. Y.This is a good time to subscribe JorRADIO BROADCASTThrough your dealer or direct, by the year only $4.00DOUBLEDAY, PAGE & CO. GARDEN CITY, NEW YORKType A$28.50Not a traceon thePACENTCONEEvery note everyword is true andfaithful in reproduction.PACENT RADIO CORP.156 West 16th Street New York

RADIO BROADCAST ADVERTISER 71TfcPower tubeamp. IP 2O1%iocKetiRadio's sensationalwithoutstartling than the new ZP 201 A,oxide filament, 14 amp. PowerTube the Zetka Process powertube for every stage.Now for the first time, can power tubesbe used in every socket of your set. Now additional C's but what an improvementin tone, in volume, in sensitivity.you can enjoy real power. And withoutchanging a single wire!Only $2.50 each at your nearest dealerReplace your old 201 A's with a set ofputsthese new ZP a complete Power tube set well within201 A's and enjoy the moststartling achievement your radioin tube budget. And then, and thenhistory.only, you'll enjoy real radio satisfactionThe current drain is small in bothA with power tubes of longer life, thatand B it is not necessary to hook up increase in efficiency as you use them.developmenthas seen nothing moreAsk your Zetka dealer tometer test.show you the Zetka WestonYou'll want nothing but Zetka thereafter.YOUR SET DESERVES THIS FINEREQUIPMENT PRICES NO HIGHERZETKAThe Clear Glass Tubere-wiringyour setZETKA LABORATORIES INC.73 Winthrop Street Newark, New Jersey