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

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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
Page 1 and 2: RADIO BROADCASTVOLUME XIMAY, 1927,
Page 3 and 4: INDEX.ContinuedPAGEThreshold of Hea
Page 5 and 6: RADIO BROADCAST ADVERTISERALUMINUMB
Page 7 and 8: RADIO BROADCAST ADVERTISERfIA REALA
Page 9 and 10: :RADIO BROADCASTVOLUME XI NUMBER 1M
Page 11 and 12: MAY, 1927WITH MACMILLAN TO THE ARCT
Page 13: THE MARCHInterpretation of Current
Page 16 and 17: 18volved the law in precarious lega
Page 20 and 21: 22 RADIO BROADCAST MAY, 1927type of
Page 22 and 23: A Balanced Short-Wave ReceiverA Des
Page 24 and 25: What About the A BatteryThe Importa
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Page 28 and 29: 30 RADIO BROADCAST MAY, 1927NO STRA
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Page 34 and 35: AS THE BROADCASTER SEES ITDrawings
Page 36 and 37: 38 RADIO BROADCAST MAY, 1927Interes
Page 38 and 39: Some Facts About Coil DesignThe Osc
Page 40 and 41: 42 RADIO BROADCAST MAY, 1927Shows e
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Page 44 and 45: ''Measuring TubeCharacteristicsA Pa
Page 46 and 47: 48 RADIO BROADCAST MAY, 1927MUTUAL
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Page 50 and 51: RADIO BROADCAST ADVERTISERThe Radio
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Page 54 and 55: 56 RADIO BROADCAST ADVERTISERNo. 94
Page 56 and 57: .58 RADIO BROADCAST ADVERTISERTJour
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Radio Broadcast - 1927, May - 61 Pages, 4.9 MB ... - VacuumTubeEra

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