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www.americanradiohistory.com 506 Radio News for November, 1928 0)THFR coWYEW 'k Dr.Lee 4 With the same creative enthusiasm that produced the first radio vacuum tube (1906) Dr. DeForest has now developed the perfected Audion. V When you replace your tubes with DeForest Audions you will experience a new enjoyment in clarified reception. Send today for your free copy of the interesting booklet by the "Father of Radio." Deforest Radio Co. JERSEY CITY ^. N.J. FOUÑDED 1899 Learn to Earn $60 to $200 a week! Learn on Actual Electrical Machinery in 90 Days Get into Electricity in 90 days. Learn by work In the Brat roaring shops of Coyne. Nactual ot Corres onaence School. All experience on practical full-elm electrical machinery. 92000.000 New school with vast t new chinery. electrical ma- You don't a need eededuatioo experience. We Will Assist You To Part. Time hl Job aarning And Free Employment Service Life For Graduation. Special offer for omot Cores Act extra now -get big free book. COYN EPaulina lintr t ELECTRICAL SCHOOL e ©pt 88 777. H. C. Lewis, Pres. ÑCoyne Electrical School, Dept.88.77 South Paulina St. Chicago. 111. ar H. . C.: Please send me free your big ratan log and full particulars of your special offer. a k Name li b Address B C Torn[ St of*. Elections have brought back Custom Set building. Business is booming. Thousands of old -timers are cleaning up. Let Barawlk show you thei way to bigger profits, more sales. Send today for Barawlle's Big Bargain Book - the radio man's bible. BARAWIK CO. 2118 CHICAGO, Ü A, A, quality and sufficient sensitivity. A variable grid leak may be used; but most of them are unsuitable because of their tendency to make the set noisy, and set owners usually try to avoid adding another adjustment. If the grid leak has too high a resistance, the receiver will howl and block without much provocation. The blocking is indicated by a series of popping noises either fast or slow, depending on the value of the leak and the other constants of the circuit. If the resistance of the grid leak is too low, the distant stations will be weak, or entirely absent. It may also be found difficult to make the set regenerate and, when the regeneration point is reached, the set will suddenly drop into oscillation. \\'ith the "bard" tubes (such as the 201A, 199, and 112A) a grid leak with a value of between 2 and 5 megohms will usually be found satisfactory, at wavelengths in the broadcast range. The gaseous tubes (of the 200A type) will also use a value within this range; while the old -style soft tube (similar to the L' \'-200) required a value of about %- megobm. However, the best value for the grid leak in a particular receiver can only be found by experiment. Grid Leaks in Amplifiers Grid leaks, or grid resistors, are used also in amplifiers of certain types. In the choke -coil- and resistance- coupled amplifiers, in which the stages are coupled through transformers, the grid must be supplied with the correct bias. In order to keep the "signal" (-\.F. or, sometimes, R.F.) in the correct channel, - it is necessary to use an arrangement which will allow the direct -current potential of the "C" battery to be placed on the grid, but will not short- circuit the signal current. This may be accomplished by the use of either a choke coil or a resistor of the correct value. Since the latter is much simpler and cheaper, it is used more frequently. The bias applied to the grid is determined by the value of the leak and method in which the resistor is connected to the filament circuit. If it is connected to a "C" battery, the biasing voltage depends on the potential of this battery, of course, as well as on the resistance of the grid leak. When the grid return is connected to the negative terminal of the filament circuit, the bias is derived from the "A" battery, and it is necessary to use the correct resistance in the grid leak in order to have the tube correctly biased. The latter method is often employed in the first stages of an amplifier where the grid voltage does not have to be very high. I Our OM November er Issue: The World at Bay, by B. and G. Wallis. Part I. Application of the fourth dimension, in this story, enables the travelers to make a journey to the moon and back and around the earth in an astoundingly short space of time. Our new authors have given us a carefully studied treatment of the subject of interplanetary travel, cleverly interwoven with romance and human psychology. The Ananias Gland, by W. Alexander, What determines the extent of our truth - fullness.'. It might very well be glandular action of some kind. Mr. Alexander cleverly works up an idea of extreme interest. The Psychophonic Nurse, by D. H. Keller, M.D. Instead of contenting himself with the conception of new mechanical laborsaving devices -generally involved in the human scheme of life -Dr. Keller always goes further. He gives us, in a perfectly natural manner, the ultimate psychological effect of his mechanical innovations, on the human being. Though he never destroys-or even temporarily puts out of commission -his newly developed apparatus, we are glad, when we finish the story, that we are still a little ahead of the invention. The Eye of the Vulture, by Walter Kately. The human eye is limited in its vision of the colors of the spectrum, just as the ear is limited in its range of sound appreciation, and it must differ drastically from that of animals, birds, insects, etc. A bird, for instance, may not see all we do; on the other hand, many things within the bird's visual range may be completely out of ours. In this story, a number of theories, novel and interesting, but seemingly founded on scientific grounds, are introduced. And Others. -against 30 seconds to a minute for other tubes -the Arcturus 127 A -C Detector Tube! Put an Arcturus A -C Long Life Tube in every socket for quicker action, better tone, better volume, longer life and immunity to line surge. Complete line of Arcturus low voltage Tubes : 126H, 126, 071H, 071, 127 and 180. Mea.' Arcturus Radio Company 255 Sherman Ave., Newark, N. J. Vrfe.awwr; " ' Less Static Sharper Tuning Bring Your Set to P S Maximum Sharpness IN EVERY HIGH GRADE CIRCUIT TODAY MODEL "N" VARIO- DENSER -Micrometer adjustment easily made, assures exact oscillation control. Quick, easy tuning, more volume, clearness and sta- bility. Capacity range 1.8 to 20 micro-microfarads. Price 81.00. ModelO Made fn 3 sortable capacity ranges; fnfee. each. S1 50. F REE of all lead, guiWrite today for ecopy. XLAadio Laboratories Dept. A, 1224 Belmont Ave., Chicago, III. 1000 HOURS -of the Best Fun You Ever Had -Get Your Copy Of SAM LOYD'S Tricks and Puzzles The year's most unique book, contains 120 pages that are crammed full of all kinds of tricks, puzzles, games, conun- drums, etc. Please say you saw it in RA110 NEWS Size, 9 x 12 inches -illustrations on every page. Fun for every member of the family. 50e On All Newsstands EXPERIMENTER PUBLISHING CO., Inc. 230 Fifth Avenue, New York, N. Y.
www.americanradiohistory.com Radio News for November, 1928 NEW! -. 90 Volt _-_ Ir .t4 Positively Eliminates 1 Hums, Line Noises, etc. Greater Volume and Clarity Guaranteed Non -arid and noiseless. All detector and intermediate voltages plainly marked. Simpler to hook up than dry ills. Operates 1 to 12 tubes. If not thoroughly satisfied return after using 30 days for complete refund. t :uaranteed further 2 years. For 110 -120 volts A.C. 25 to 60 cycle current. 90 volts. $12.75: 1125¢, 315.25; 185. 517.50: 157iy. $19.50: 180, 324.00:2025 326.00. Uso built for D.C. current 110 and 32 volts at only S:S.00 additional, any size above. Ample stocks -same day shipments. Simply say-ship C.O.D. or write for my interesting literature, testimonials, etc. arter Radio Col Ce-tiCAGO .75 B. HAWLEY SMITH 334 Washington Ave., Danbury, Conn., U.S.A. ARTE PARTS FOR NEW A. C. CIRCUITS USED BY LEADING SET MANUFACTURERS Carter Center Tapped Resistors Small, compact, rugged. Guaranteedwithin 3 per cent. 8 different types. 6 to 60 ohms. Carter Adjustable Resistors. 'rho Ideal A. C. Hum adjustor for mounting on sub - panel. 6 to 20 ohms. Carter IMP Power Switch. Self-contained. double contact, post Uve, for 6 volts fila - ment or 110 volt A.C. Circuit. Write for Catalog of Complete Line Any dealer mn supply Wholesale Prices Here you will find a new up -todate stock of kits, parts, accessories and sets -everything you want in radio. Write for catalog "B -1" quoting special dealer's wholesale prices. AIIied CORPcJoR.CCI-ION 711 W. LANE STREET, CHICAGO S incotho dew of Itedio. Barawik lase been known the world e hendoeortere for .et builder, and luna alas. under one cool, u everything ;thine you seed -let e. parte. au optdayyour arrivduet s -reed oehip to youths ,p y. Barewik ui semi. imam. me. Baraw,k chnndieealw Y ales A rmali neatisaed B pleases. is Best." Let us send you tihecBig ydarawik Book tree and prove it to zisee CANAL STA., B11. ARAW I K CO. cwICA60. u. s. A Radio News Laboratories (Continued from page 461) vides a resistance of approximately 150.000 ohms in the plate circuit of the tube. A high value of inductance is used in the grid circuit of the succeeding tube, which gives a step -up ratio through the use of the grid inductor as an auto -transformer. The plate output of the preceding tube is cou pied to the primary tap of the auto -transformer -coupled grid inductor through a capacity of such size than excellent amplification is obtained between 30 to 5,000 cycles. The iron -core inductor, plate resistor and coupling condenser are encased in an iron housing of black enameled finish, 4 inches high. with a base 3!i x 31 inches. Excellent quality and volume, with great amplification, was obtained when the unit was tested in a screen -grid, space - charge A.F. amplifier. A WARDED THE RADIO NEWS LABORA- TORIES CERTIFICATE OF MERIT NO. 2435. GRAPHITE (IN SUSPENSION) ".\quadag," submitted by the Acheson t liblac Company. Port Huron, Mich., is a concentrated colloidal solution of artificial (electric -furnace) graphite in water. which has found successful use ill the manufacture of resistance elements for gridleaks and variable resistors. It has been used also as a dry lubricant for condenser bearings and for the drawing of tungsten wire. It has been used ill tube manufacture as a "Getter." as an opaque coating in the manufacture of photoelectric cells, and has been found, as well, useful in establishing positive electrical contacts, and as a conductive coating for electroplating. It has many other applications, and is suitable for uses of the manufacturer, either the above- named, or wherever conductive material of this type is needed. AWARDED THE RADIO NEWS LABORA- TORIES CERTIFICATE OF MERIT NO. 2436. R.F. CHOKE The R.F. choke coil shown, submitted by the Hammarlulul Manufacturing Co.. 424 W. 33rd Street, New York, N. Y., is of the helical -winding type. It was found to have an inductance within 10% of its rated value, 85 millihenries, when meas. tired at 1,000 cycles. The D.C. resistance, as measured, is 2,000 ohms. The distributed capacity was found to be extremely small, in comparison with the inductance. The coil is contained in a molded black bakelite housing, 1y, inches high, and requires a base space 1% x 2 inches. AWARDED THE RADIO NEWS LABORA- TORIES CERTIFICATE OF MERIT NO. 2437. SHORT -WAVE TUNING CONDENSER The short -wave condenser (Type ML -7) shown, submitted by the same manufacturer, is a 7 -plate condenser of the midline- frequency low -loss type. It has a sturdy cast -aluminum frame supporting the stator, and drilled for base -board or sub -panel mounting; two flat -head screws are provided on the front of the frame for panel mounting also. The stator plates are soldered to plate- spacing mounting brackets which, in turn, are fastened to the Bakelite insulating strip. The stator plates are provided with a spacing bar and the entire stator assembly is supported from the bottom of the frame. The rotor is of the "floating type"; which allows the removal of the shaft, and the operation of the condenser in a gang. The bearings are of the cotte type, and the rotor - is provided with maximum and minimum THE MIRACLE OF 507 THE RADIO WORLD! Newest Guaranteed 7 -Tube 1 -Dial Console S_ et -Worth $200 BUY 1929 DIRECT A a MODEL A BIG VALUE COMES COMPLETE ALL ELECTRIC RADIO 30 DAYS' FREE TRIAL! A Wonder Bargain! Buy direct from factory. 9200 VALUE Outperforms sets selling at 2 and 3 times our low price. Includes con. sole shown, made of combination walnut; A. C. electric set, all tubes, built -in magnetic speaker and aerial equipment, COMPLETE Nothing Else to Buy Powerful Reception- Amazing Tone! Remember -30 days free trial. , You be the judgct W orth 5200 and looks Itt Only one dial to tune- uluminatedl Marvelous mellow tone. Selective and gets distance easily. The radio sensation for quality. price and performance. Mail coupon today for our big, Money-Saving Free Catalog, befor you uy any radio accessories! Battery Sets Our low factory prices on the complete line of Diamond Electric and battert, operated radios shown in catalog will amaze youi Our New FREE Catalog -Just Published -Shows You How To SAVE HALF! Diamond Radio Company 1 Dept. =IS w 1120S. Clinton St., Chicago, III. MAIL THIS COUPON TODAY! Diamond Radio Company, Dspt.2114 820 S. Clinton St., Chicago, III. Please Send me your Free Catalog of Diamond radios and details of your 30 Day FREE Trial offer Name Address , City State Newest - Radio Hook - - Ups Free Send now for the newest radio hook -up book. Shows how easy it is to bs lid remarkable new A.C. and D.C. receivers of longest range, greatest volume, purest, clearest tone, and super -selective. Also shows how to make short -wave receivers and adapters, how to use new screen grid tube In A.C. and D.C. circuits, how to build power amplifiers and A -B-C eliminators. Latest information on all new radio wrinkles. Send for free copy now. KARAS ELECTRIC COMPANY 4038L3 N. Rockwell St., Chicago. U. S. A. Name St. and No City and State Please sap you saur it in RADIO NEU'S IN VENTORSwho derive largest profits know and heed certain simple but vital facts before applying for Patenta. Our book Patent -Sense gives those facts: sent tree. Write LACEY & LACEY, 631 F St. Washington, D.C. Established 1663 1
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