June 22d, 1929 15 Cents BYPASS CONDENSERS OFTEN INEFFECTIVE

REG. U.S. PAT. OFF, EXPERIMENTS WITH SPACE CHARGE GRID

CONDENSER SPEAKER The First and Only National Radio Weekly 378th Consecutive Issue-Eighth Year PROMISES MUCH

A FISTFUL OFPOWER. SEE PAGES6 AND 7. RADIO WORLD, owned and published by Hennessy Radio PublicationsCorporation, Hennessy, President and Treasurer, 145 West 45th Street,New York, N. 145 West 45thStreet, New York,N. Y.Roland Burke Y.; Herman Bernard, Secretary, 145 West45th Street, New 4Zork, N, Y. RADIO WORLD June 22, 1929 How About Short Waves ? Individual Have you been troubled with tricky regeneration control?Does the detector suddenly burst into METERS oscillation,before you can reachasatisfactory pointof maximum sensitivity ?Ifso,try the For Portable or Panel Use VOLUME CONTROL CLA_ROSTAT inthe B plus detector lead,asthe regenerationcontrol. You'd be surprised! Askyourdealerto show youthe VOLUME CONTROL CLAROSTAT as wellas otheritemsofthisline. Or 15,4, Sotgli 5441101 Sit write for our literature. 2v5 5,50 Rut* humane) Sit CLAROSTAT MFG. CO., Inc. 4 501 PODelli, 44414 Sam S., Specialists in Radio Aids 4 Till 5,,,.e6,14 .341 291 N. 6th St.,Brooklyn, N. Y. 3 T. Ill can Sn (20 to $5415 11-E11enncoe for I C Cureert cLAROSTAT

By JOHN F. RIDER " The Mathematics of Radio " The Latest Book on High resistance 0-800 Voltmeter, accurateto1%. Measures any Fourteen Circuits DC voltage to 300,including B 5 0 This Important Subject eliminators. Provided with 80" Each Shown in Colored Picture Diagram, cord, with luxurious lack tips and Colored Schematic Diagram and Front banger. Meterfullnickelde Price $2.00 luxe finish.No. 348F. Hereisthefirstradio Panel Layout No.34717,sameasabove,but0-600volts, 111.011 bookthatcoversthefield betweenthebeginnerand Get This FREE Book! thecollegeprofessor. POCKET AND PORTABLE VOLTMETERS Itisthefirstpractical Complete AC electric receivers, with B elimin- Ne. 8-For testing A batteries, dry or storage. interpretation of radio atorsincluded,also AC receiverswithout is technique and is written in eliminators, also battery operated models, all easy 0-8volts DC scale $1.10 a practical manner forthe - No. 10-For testingAbatteries, dry or storage, practical man.Itisnon- to -build circuits, using your own parts. 0-10volts DC scale 1.61 technical,yetitisnot No. 13-For testingAbatteries,dry orstor- written for the veriest be- age,0-16 volts DC scale 1.011 ginneralthough he,too, RADIO WORLD, 145 W. 45th St.,N. Y. City. may obtain much valuable (Just East of Broadway) No. 50-For testing B batteries,dry orstor- assistance and information. Gentlemen: Enclosed please find $1.00 for which please age,butnotfor B eliminators,0-50volts ItisthefirstbookIn send me Radio World each week for eight weeks (regular DC scale LOS which thelatestdataare Na 89-Far testing B batteries,dry orstor- Price,$1.20)and besides send me a FREE copy of the volts converted into actual prac- 1929 edition of The Radio Blueprint Library ofAC sad agebut notfor B eliminators.0-100 tical examples, examples Battery Hookups. DO scale 1.25 which apply to your tubes. No. 40-For testing A and B batteries,dry receiver,amplifier,elimin- or etorage, but notfor B eliminators; double ator. Name reading, 0-8 volts and 0-100 volts DC scale 1.75 128pages. 8% x11". 119illustrations. Printed and No. 42-For testing B batteries,dry orstor- bound inaflexiblecover. age,but netfor B eliminators; 0-150 alts Address DC scale 1.10 TABLE OF CONTENTS: No. 348-For testingACcurrentsupply line, OHM'S LAW: IR drop, DC and AC circuits, peak and City State portable,0 -150volts 4.01 effective AC voltages. PANEL AO VOLTMETERS RESISTANCES: Basisforresistancevariation,atomic Note: Present mail subscribers may take advantage of structure,temperaturecoefficient,calculationofresist- this offer by putting a cross in this square. 0 Your sttb- (Panel meters take 2-5/64" hole) ancevariation,expressionofampere,voltand Ohm sedation will be extended eight weeks. No. 351-For reading 0-15 volts AC $2.25 fractions,applicationofvoltagedrop,platecircuits, filamentcircuits,filamentresistances,gridbiasre- No. 852-For reading 0-10 volts AC ...... r2,25 sistances. Parallel,series,wattagerating,maximum No. 353-For reading 0-6volts AO ...... 2.211 permissible current flow,distributionofcurrent,calcu- (See No. 348 under 'Packet and Portable lationsofresistance inparallel,inseries, C bias re- 0-600 V. AC and DC Voltmeters.") sistancesin filament circuits,in B eliminators. DC FILAMENT CIRCUITS: Calculationofresistances. PANEL VOLTMETERS AC FILAMENT CIRCUITS: Transformers, wattagerat- ing,distributionofoutputvoltages,voltagereducing High Resistance Meter No. 995-For reading DC voltages, 0-6 volts, $1.91 resistances,linevoltage reduction. No. 810-For reading DC voltages, 0-10volts, 1.00 CAPACITIES:Calculationofcapacity,dielectriccon- Same Meter Reads Both AC and DC No. 318-For reading DC voltages, 0-16 volts, 1.00 stant, condensers in parallel,condensersinseries,volt- No. 326-For readingDCvoltages,II -6 volts, 1.00 age of condensers in parallel, in series, utility of paral- Accurate to I per cent. No. 837-Far readingDCvoltages, 0-50volts, 1.00 lelcondensers,seriescondensers. No. 839-For reading DC voltages, 0-100 volts,2.25 VOLTAGE DIVIDER SYSTEMS FOR B ELIMINATORS: No. 842-For reading DC voltages, 0-150 volts.2.25 Calculation of voltage divider resistances, types of volt- No. 340-For readingDCvoltages, double read- age dividers, selection of resistances, wattage ratingof 1-8volts,0-100 141 resistances. ing, volts ...... INDUCTANCES: Aircoreandironcore,typesofair VOLTAMMETERS core inductances, unitofinductance, calculationofin- ductance. No.18-For testingamperageofdrysell A INDUCTANCE REQUIRED IN RADIO CIRCUITS: batteriesandvoltageofdryorstorageA Relation ofwavelength and productofinductance and batteries,double reading, 0-8volts,and capacity,shortwavecoils,coilsforbroadcastband, 0-40amperes DC $1.25 coupling and mutual inductance,calculationofmutual No. 95-For testingamperageofdrysell A inductanceand coupling. batteriesand voltageof B batteries(not B REACTANCE AND IMPEDARCE: Capacityreactance, eliminators); double reading, 0-60 volts, 0-40 inductance reactance,impedance. amperes DC 1.51 RESONANT CIRCUITS:Seriesresonance,parallelre- sonance,coupledcircuits,bandp assfiltersforradio PANEL MILLIAMMETERS frequency circuits. No, 911-For reading 0-10milliamperesDC $1.75 IRON CORE CHOKERS AND TRANSFORMERS: De- No. 391-For reading 0-20 and 0-100 ma.DC 1.50 sign ofchokes,core,a irgap, inductance, reactance, im- VOLTAGE REGULATOR pedance, transformers, half wave, full wave windings. No. 218-For preventingexcesevoltage on the VACUUM TUBES: Two element filament type,electronic filamentand cathodeof AC tubes,by com- emission,limitations,classificationsoffilaments,struc- pensating for excels line voltage $5.00 ture,two element rectifying tubes, processof rectifica- tion,tun gar bulb. POCKET AMMETER THREE ELEMENT TUBES: Structure of tube,detector, No. 1-For testing drycells,0-60 ampere DO gridbias,gridleakandcondenser,amplifiers,tube scalepocketmeter $ .75 constants,voltage amplification,resistance coupling, reactancecoupling,transformercoupling,variationof impedance of load with frequency, tuned plate circuit. Immediate Shipment POWER AMPLIFICATION: Square law,effectofload, calculationofoutputpower,undistortedoutput power, GUARANTY RADIO GOODS CO., parallel tubes, push-pull systems, plate resistance. 145 West 45th Street, New York City. GRAPHS AND RESPONSE CURVES: Typesof paper, JustEast of Broadway utility of curves, types of curves, significance of curves, voltageamplification,poweramplification,powerout- Send me the following individual meters (quantity in put, radio frequency amplification. square): MULTIPLE STAGE AMPLIFIERS: Resistance coupling, The 0-600 volt AC and DC meter (Cat. No. 600), design, calculation of values,effect of resistance,calcu- with 3 -ft. card, de luxe tips and hanger $7.00. ID Cat. No. 0 Cat. No. 0 Cat. Es. lation of couplingcapacity,effectofplate load,effect ofinput tubecapacity,calculation,reactancecoupling, 0 Cat. Ne. 0 Cat. No. 0 Cat. No. tuned double impedance amplification, underlying princi- THE outputvoltagesofall B eliminators,thevoltages ples,transformercoupling, ofall B batteries, as well as the house eurrent line turnsratio,voltageratio, AC DC, typesofcores,platecurrentlimitation, voltage, whether or and the voltage across power NAME I im itat ion. gridcurrent transformersecondaries,canbeaccuratelymeasuredby ALTERNATING CURRENT TUBES: Temperaturevari- this meter.The full scaleis 0-600 volts,and this same ADDRESS ationhum,voltagevariationhum,relationbetween meter measures bothACendDC. Sinceitisahigh grid and filament, filamentcircuit center tap, types of resistance meter,of extraordinary range, andaccurateto AC tubes. 1% plusor minus,itIsadvisable toget this meterfor CITY STATE SCREEN GRID TUBE: Structuraldesign,application, your testing purposes, sinceitislike two meters in ens amplification,associated tuned circuits, DC. amplification, radio frequency -AC and YoucanAndtroublemorequickly. TEN-DAY MONEY -BACK ABSOLUTE GUARANTY! audiofrequencyamplification. Withoutityou can'ttellifapower transformer second A AND B ELIMINATORS: Voltageregulation sections of eliminator, rectifying systems, gaseouscurves, recti- aryisdeliveringvoltage. 10 -daY money -backguaranty. fier,sulphide rectifier,power B units,power A units. GUARANTYRADIO GOODS CO., 145 West 46thStreet, N Y.City. (Just Eastof Broadway) RADIO WORLD, 145 West 45thSt.,New York, (JustEastofBroadway). N. Y. Enclosed please find $2.00for which please send me at RADIO WORLD, a weekly paper, published by RADIO WORLD, published every Wednesday, once one copyof "MathematicsofRadio," HennessyRadioPublicationCorporation,from dated Saturday of same week, from publication PublicationOffice,145West 45thStreet, New office, Hennessy Radio Publications Corporation, Vame York, N.Y. Phone: BRYant 0558 and 0559. 145 West 45th Street, New York, N. Y., just east 15c per copy, $6 per year.This issueisdated of Broadway. Roland Burke Hennessy, President; Address June 22d, 1929, and is Vol. XV, No. 14.Whole M. B. Hennessy, Vice -President; Herman Ber- No. 378.Entered as second-class matter, March, nard, Secretary.Roland Burke Hennessy, Editor; City State 1922, at the post office at New York, N. Y., un- Herman Bernard, Managing Editor; J. E. Ander- der Act of March, 1879. son, Technical Editor: Anthony Sodaro. Art Editor. June 22, 1929 RADIO WORLD 3 Leaders224 and 245! What These Marvelous Tubes Do

The Radio Trade Show in Chicago established the 224 AC Screen Grid Tube and the245 AC Power Tube, both new, as by far the leading tubes for1930.The master designersof circuits have chosen these tubes, the 224 for radio frequency amplification, the 245 for output tube.They merely confirmed what experimenters already hadestablished -extremesensitivity, great distance and finestability are possiblewiththe224,while main- tainingneedle -pointselectivity. The 224 is capable of RI' amplifi- cationofahigherorderthanen- gineers are able to capitalize in fulL The tube can easily be worked at a gain as compared with 8for hen201of A.60, This Great New Book Indirect heating is used.The fila- ment, called heater, requires 2.5 volts tells you how to build and draws1.75ampere. The plate voltage should be 180, the screen grid voltage (G post of socket)75 volts. The control grid connectionis made MARVELOUS tothecapattopoftube. The cathode is the electronemitter. POWER Negativebias,1.5volts. Typeof socket required: UY (five -prong). AMPLIFIERS Ordinarycoilsmay be used with this tube by doubling the number of LTERE'S the latest, greatest and most help- turns on the primary. ful Book on POWER AMPLIFIERS, If still greater amplification is de- Audio Amplification, and Adaptation of sired a larger primary may be used, and ifstill greater selectivity isde- Dynamic Speakers. Contains diagrams with sired,the primary may be reduced, butshouldhaveatleastone-third components for building 10 hookups, includ- more turns than for ordinary tubes. ing U X 245 and U X 250 Push Pull Power 224Screen Grid AC Tube "Look for the Green Box" Amplifie-s .. powerful, realistic amplifiers The 245 has a low filament voltage, 2.5 OTHER SPECIAL PURPOSE TUBES which will outperform any you ever heard. 222 Screen Grid, for battery or AC eliminator operation; volts,at a relatively high current,1.25 3.3 voltfilament, @ .132ampere;135 voltsplate Endorsed by leading technical writers, pro- 22 to 45 volts screen grid; negative bias1.5 volts -53.50 fessional ampere.This eliminates the objection- 240 high mu tube, for detector or audio circuits, where builders, musicians and others. able hum.The tube requires only 250 aresistororimpedancecoilisintheplatecircuit; Send Coupon today. amplification factor,31. Filament 5volts, @ .25 ampere; volts on the plate to be able to handle plate 135 to 180 volts, negative bias 1.3 to 3 volts$1.25 FERRANTI, Inc. 280full -wave rectifier,125 milsat300 voltsorless; about as great undistorted power as the 5 -voltfilament @ 1.25amperes $2.50 130W. 42nd St Desk 25 New York City 210 does at 350 volts. A single 245 output 281 half -way rectifier,7.5 -volt filament $3.50 227detectorandamplifierfor ACcircuits,indirect COJPON tube will handle, without overload, the heating type; 2.5voltsfilament @ 1.75 amperes; 90to FERRANTI, INc.. 180 volts plate, negative bias 1.5to 6 volts; excellent for largest input to a last stage as would be powerdetection $2.25 130 W. 42nd St., Dept. 28. NewYork, N.Y. It works well into 226 AC amplifier;1.5volts filament @ 1.05 amperes; Gentlemen : Enclosed find lq coin, for which send me required in any home. 90 to 150 plate volts; negative bias 2.5 to 4.5 volts .$1.25 a dynamic speaker, or, by filtering the 112A output tube for battery or AC operation; filament Ferranti POWER AMPLIFIER Instruction Book, post- 5volts @ .25 ampere; 135 plate volts;9 volts negative paid. Money to be refunded if I ask it. output, into a magnetic speaker.In push- bias 171A power tube for battery or AC operation; 5 volts$1.50 pull two 245s give superb tone at doubled filament @ .25 ampere; 180 plate volts @ 40 volts nega- Name power handling capacity.The 250 re- tivebias $1.50 250 -power tube, 7.5 -volt filament @ 1.25 amperes; 450 Address quires 50 volts negative bias at 250 volts plate volts; 80 volts negative bias $6.00 on the plate and draws 32 milliamperes 210power tube $4.50 GENERAL PURPOSE TUBES City State under those conditions.The direct fila- 201A, 5 -volt filament @ .25 ampere; 45 to 135 volts on plate, 5 -volt positive for detector to 4.5 negative bias, ment heating method isused.Type of foramplifier $1.00 socket, UX (four -prong). 199,3.3 -volt filament @ .06ampere; 45to 90volts on plate; 3.3 -volt positive bias for detector, to 4.5 nega- tiveforamplifier $1.25 New Junior Model There never was apower tubesoexcellently PUSH -PULL PAIRS suited to home use -one that handles such large The250,245,171A and 112Aaresoldinmatched inputwithoutstrain,yet whicn operates on a pairsforpush-pull,insuringbalanced,symmetrical plate voltage now regarded as in the "medium" cuits. Order MP 250, MI' 245, MP I71A or MP 112A.cir- The matched tubes are of equal mutual conductance. They POLO UNIT $4 class.Use this power tube and know supreme are boxed together and bear "Matched Pair" identification performance. _stickers. - -No extra- charge- -. for matching.- --- Kelly Tube Company, 57 DeyStreet, New York City. (Walter J.McCord, Manager.) Gentlemen: Please send me the following tubes: Quantity Type Quantity Type Quantity Type O 224 0 222 0 280 O 245 0 201A 0 281 O 226 0 240 0 250 O 227 0 199 0 210 O 112d. 0 171A 0 MP. If ordering C.O.D. put a cross here 0 If enclosing remittance with order put acrosshere 0 On prepaid orders we Day cartage. On C.O.D./ orders you pay cartage plus postoffice money -order fee. itame

Address

City State 71k METALLIZED ±1A., Barawik offers set builders bigger Standohm-The "Self -Supporting"Resistor. In- bargains - bigger opportunities to make sulatedbase,designedtopermitmountingon money this season.New sets, new kit The famous twin magnet principlefor metal surfaces.Mocierate in, price. Efficientin ideas, all the leading parts, dynamic operation. speakers, supplies, etc. Lowest rock - double sensitivity, large magnets forgreat bottom prices. Bigger stocks, quicker flux, permanently adjusted armature, all ARTHUR H, LYNCH, Inc. , service. Send for Big Bargain Book today -free. are in the new junior model Polo Unit. 1775 Broadway New York, N.Y. gickanaluS.t.A. Write for complete information. loBARAWIK CO., Weight, 2Y4. lbs.Stands 150 volts unfil- 4 tered.Stands up to 250 push-pull filtered. Works any output tube,power or other- wise.Supplied with 10 -ft.cord.Order A COMPLETE I unit now. Five-day money -backguarantee. CATALOG THE RESEARCH WORKER containing detailed in- A E RIO VOX Acoustical Engineering will keep you abreast Associates formation on conden- BUILT Et ETTER of developments in sers and resistors may CONDENSERS AND RESISTORS 143 West 45th Street be had free on request. radio. It may be had 741/2 Washington St., Bklyn., N. Y. free on request. New York City (Just Past of 4 RADIO WORLD June 22, 1929 ARISTOCRAT FREE! FLOOR SPEAKER Filament With Molded Weed Horn of tt. tone travel(exponential tYpe)With baffle 2000 andhorn motorbuilt In. Extraordinarybargain. Transformer

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Send $6 for year's omumomoimmoi Radio World Subscription The heater type tube draws 1.75 ampere at 2.5 volts.If several such tubes are used a heavy- And Obtain duty filament transformer is necessary.The top 2.5 -volt windingofthisfilamenttransformer easily carries NINE AMPERES, or enoughcur- rent for five heater type tubes.The bottom 2.5 - Unit FREE! voltwindingstandsfouramperes,orenough current to heat TWO MORE such tubes, a total Radio World for one year of SEVEN TUBES!The power tube, ifof the (52 numbers, one each week) The speaker cabinetis walnut finish, 33" high, 5 -volt type, may be heated from the 5 -voltcen- will of 243(".wide,.171/2".deep,.with.carved.legs. tralwinding. 5 -voltpower tubesinpush-pull keep you abreast Golden cloth grille covers front opening..Built may be heated from this winding. latestcircuitsandnews. inside is No. 595 molded wood horn with baffle Act now.Offerrevocable and No. 203 driving motor unit that stands SO All threewindingsaretappedattheexact without notice. voltswithoutfiltration. Horn and motorre- electricalcenter. Thisprecisionlocation, made movable. Tablealoneisworthpriceasked. with the aid of an impedance bridge, accountsfor If renewal put cross here. Remit with order and we pay cartage on Aristo- absence of bum otherwise caused by the last tube crat Floor Speaker. when heated directly with AC.The heater type Radio World, 145 West 45th St., tubesareindirectlyheatedby AC,sincethe N. Y. City. Acoustical Engineering Associates filament that glows is fed by AC butcommuni- Enclosedpleasefind$6for one 143 WEST 45th STREET cates heat to the cathode or electron emitter. year's subscription for Radio NEW YORK CITY World (52 numbers).Send your The heater type tube is represented by the 227, "superb unit" free. (Just East of Broadway) excellentas radio amplifier and audio amplifier, and the exclusive type of AC detector tube. the new AC screen grid tubes, with theAlso Name Recent Issues of RADIO WORLD, 15 cents each. filament voltage and current, are of thename Any number publishedin1928availablefora type. heater short while.Six issues 75 cents, 10 issues $1.00. Address Send stamps, coin or money order NOW, before The theissuesaresold. RADIO WORLD,145 West transformer is beautifullyfinishedIn crackledglossyblack,withbakelitefront, and City State 45th Street, New York City. comes equipped with 52 -inch AC cable with plug. Sixrivetedmountingholesforbaseboard subpanel.Size, 3% in. high, 2% in. wide, 3or deep.Shipping weight, 6 lbs. in.

Cat. F226A1 for 50 -to -60 cycles, 105 AC, Net Price -to -120 volt. Cash in on ThisOffer Now! $6.00 rpm full year's subscription for any TWO of the followingmagazines given to you-RADIO Guaranty Radio Goods Co. vv NEWS or SCIENCE AND INVENTION or RADIO (San Francisco) or BOYS' LIFE or CITIZENS RADIO CALL BOOK AND SCIENTIFIC DIGEST orRADIO ENGINEERING. 145 West 45th St. Select any TWO of these four publications, each of whichwill be sent to you (at only one address, however) each month for twelvemonths- in other words, 24 issues-if you will send in now your subscription for RADIO WORLD for two years(104 numbers) at $10.00. N. Y. City RADIO WORLD'S subscription price for one year is $6.00, so yougain the extra 2 dollars by taking advantage of the liberal offer for two-year subscriptions;and, besides, you get a sub- scription for each of the TWO other magazines selected from theenumerated list, making a total of 128 numbers for $10.00. If you want to select only one from among the four other magazines, you mayobtain this one for TWO years, so that you will be subscribingfor RADIO WORLD for two years and for the other magazine for TWO years, all for only $10.00 (bothmailed to one address only). All Parts for These offers are rightly regarded as among the most liberal evermade, but as they are limited as to expiration date (see notice below) you must act now. PUSH-PULL DIAMOND Please use the attached coupon. Mershon Electrolytic ------Condensers, four inone SPECIAL TWO -FOR -PRICE -OF -ONE COUPON Copper Container RADIO WORLD, 145 West 45th Street, New York City (Just East of Broadway): Inclined please tlnd $10.00, for which send me RADIO WORLD each week for two Nan (104 ambers). andalso send me, without extra cost, 'soh month for one year each of the following TWOmagaidaes--tetal. 8-8-18-18 mfd. 54 issues-grandtotal, 128 numbers: (SanFranolsoe) List price, $9.60 $5.76 0 0 RADIO El RADIO NEWS Net O 0 SCIENCE AND INVENTION 0 0 BOYS' LIFE O 0 CITIZENS RADIO CALL BOOK, ETC. 0 0 RADIO ENGINEERING 10-10-10-10 mfd. Ityou want ens of each, put a cross in a square next to the name of each ofthe two other =gestate. List price, $7.75 If you want a two-year subscriptionfor ONE ofthe above magazines, withthe two-yearsubscriptionfor $4.65 RADIO WORLD (same grand totalof 128 numbers), puttwotresses before the name ofOne magazine. Net If you prefer to pay $8.00 for only one year's subscription for RADIO WORLD (52 numbers) and get Filament Transformer, 2%, 5, 2%v., one of the other Magazines for .2.1 year,without extra est, put one Mal in one square in front of the name of we magazine. net$4.01 Power Transformer, 2%,5,2%, 300. Present RADIO WORLD 300 v., net 10.84 e absoribers may resew ander Name S M Unichoke 331, net 4.84 this offer. Ifrenewing. ant a erns barsa Street Address Guaranty Radio Goods Co. 145 West 45th Street City State New York City THIS OFFER EXPIRES AT NOONON AUGUST 15TH, 1929 (Just Eaat of Broadway) .0b1PILM -7F

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/14t. - I__2_ :.;. ,10 ...147..e-..'4.x., 1 .. .7.NWillifill it .r.1,2-:;;,.gg. w-. 4....--e,:i.eziutg4e .-...,..,..:Imsoommi, 111111..l.' ---f, =11PI, al mahmaitai,.. muaomat alismamavolami .whioliofiti ;Ia. 11WI1= Vol. XV, No. 14 Whole No. 378 June 22d,1929 Technical Accuracy Second to None A Weekly Paper published by Hennessy 15c per Copy, $6.00 per Year Latest Circuits and News RadioPublicationsCorporation,from Publication Office, 145 West 45th Street, [Entered as second-class matter, March, New York, N. Y. 1922, at the Post Office at New York, Telephone, BRYant 0558 and 0559 N.Y.,under ActofMarch,1879.] EIGHTH YEAR (Just East of Broadway) Bypass YesandNo The Relative Reductionof Impedance Counts By J. E. Anderson Technical Editor

45 / 3 5

lA IB 2A 2B FIG. I (A.)-A BY-PASS CONDENSER CONNECTEDACROSS A RESISTOR. (B.)-A CONDENSER, R2, CONNECTEDIN SERIES WITH A GRID BIAS RESISTOR RI TO MAKE THE CONDENSERC RELATIVELY MORE EFFECTIVE AS A BY-PASS. FIG. 2 (A.)-SCREEN GRID RADIO FREQUENCYAMPLIFIER IN WHICH TWO BY-PASS CONDENSERS Cl AND C2 ARE USED. (B.)-C1 MUST BE SMALL BECAUSEIT IS ACROSS THE LINE AND ACROSS A HIGH IMPEDANCE. BY -PASS condensers are used in largenumbers in radio 1+C2W2. Since unity is negligible in comparison with 10,000 frequency circuits, audio frequency amplifiersand currentwe may put 100 equals Cw. We know that w is equal to 6.28 supply filters.In the radio frequency portion of the cir- times 550,000. Hence C must be equal to 23.4 microfarads. cuit itis seldom that such condensers exceed .5 mfd. In audio A condenser of this size is never used in the radio frequency frequency amplifiers and filtersthey often are as high as amplifier. Indeed, it is rarely used in audio frequency amplifiers 18 mfd. or current supply filters,If there is a resistance of one ohm What determines the size of a condenser that should be usedin the radio frequency amplifier that needs bypassing,a com- in a given position? Why are condensers smaller in radiofre- mon size of condenser is .001 mfd. Just how much does this quency sections of a receiver than in the audio amplifier and reduce the impedance at 550 kc?Substitution in the formula in current supply filters ? shows that the impedance is reduced from one ohm to .999994 The first thing that enters into the choice of size ofcon- ohm, which is only six parts in a million. denser is the purpose of that condenser. Thencomes the fre- quency at which itisto work, and finally the resistance or other impedance across which itis connected. Reduction Greater at .1500 kc The reduction in the impedance is a little greaterat 1,500 kc. Formula for Impedance Indeed, itis reduced by 45 parts in one million. Hence itis obvious that a condenser of .001 microfarad does little In most instances a bypass condenser is connectedacross a good resistance to lower the impedance of the circuit, when connected across a resistance of one ohm. This factmay as in Fig. 1A. explain why bypass condensers sometimes fail tosuppress oscil- The effective value of a resistance anda condenser in parallellation in radio frequency amplifiers. is R divided by the square root of thequantity (1+C2W2R2), Now let us see how effective bypass condensers in which C is the capacity of the condenserconnected across are when the resistance R, and w is 628 times the frequency they are connected across 1,000 ohms, first at 550 kc andthen of the cur- at1,500 kc. We substitute in the same formula, using1,000 rent flowing through the parallel circuit. ohms. This formula tellsdirectly how much agivencondenser The impedance of the parallel combination of 1,000 ohmsand reduces the impedance of a resistor and it also tellshow effec- a .001 mfd. condenser is 277 ohms at 550 kc and 106 at 1,500 kc. tive the condenser is.Suppose the resistance is onlyone ohm and thatitisin such a critical position that the impedanceThe reduction is substantial. Now if there isa one ohm grid bias resistor which must be bypassed to prevent oscillationit is must be reduced to one per cent. of the value of theresistance. quite feasible to connect a 1,000 ohm resistor in series That is, the impedance isto be reduced 'to .01 ohm. Let the with it so frequency at which it is to work be 550,000 cycles. as to make the .001 mfd. condenser more effective and yetnot ing in the formular given above Substitut-alter the grid bias. How this can be, done is shownin Fig. 1B. we find that 10,000 equalsR1 is the low value resistance to be bypassedand R2 is the 6 RADIO WORLD June 22, 1929 high value resistance which is used to make C relatively more effective. The value of R2 is not limited to 1,000 ohms.It could well be 10,000 ohms. Bypassing Across Plate Frequently a bypass condenser of about .01 mfd. is connected Fistful across a resistor in the plate circuitofaradio frequency amplifier. Just how effective is it?The resistance to be by- passed may be 1,000 ohms. The question is to determine how the impedance of the parallel combination of 1,000 ohms .01 mfd. Let us consider 550 kc. since the reduction in the impedance at that frequency will he the least in the broadcast band. Substituting in the formula we find that the impedance is 289 ohms. That is a substantial reduction. The reduction is approximately the same for the same con- in denser and at the same frequency when the condenser is con- Each 2 nected from -the screen gridtothefilament, because the resistance to be bypassed is of the same order of magnitude. Obviously it is better to use much larger condensers even at Why This Valve Has Become radio frequency when resistances of 1,000 ohms or less are to be bypassed when theresistancesareincriticalpositions. Hence the condensers Cl and C2in Fig. 2A should be no of Its Use As Amp smaller than .01 mfd. and it would be preferable if they were as large as 1 mfd. When a resistor or a radio frequency choke coil is connected in series with the screen grid or plate the Space Charge lead the condensers may be smaller. By Capt. Pete) Bypassing at Audio Frequency Contributing Condensers of 2 mfd. are often used for bypassing at audio THE AC screen grid tube is destined to be the most popular frequencies. Just how effective is such a condenser when con- of all radio frequency amplifier tubes, because it has more nected across a one ohm grid bias resistor at a frequency of 50 favorable characteristics than any other tube.Also it will cycles?It reduces the impedance by two parts in ten million.be used as a detector in many futk.ire receivers, as well as audio In other words, it serves no purpose. Even at 5,000 cyclesit frequency amplifier. reduces the impedance by only 9 per cent. Hence if there is a The technique for this tube as a radio frequency amplifier one ohm grid bias resistor in a circuit there is no object ofhas been worked out sufficiently,so that already many re- putting a 2 mfd. condenser across it unless there is a much ceivers now on the market embody this tube.The use of the larger resistor in series with the condenser which is not a part tube as a detector is now being discussed both from theoretical of the grid bias resistor. and practical viewpoints.The use of the tube as an audio But a grid bias resistor is often 1,000 ohms or more. How amplifier is merely being suggested as possibly desirable. effective is the 2 mfd. condenser in reducing the impedance at Why is this tube becoming the most popular tube with such 50 and 5,000 cycles ?At 50 cycles the reduction is about 18 per rapidity?Because it has a greater amplification constant than cent., and at 5,000the impedance is only 159 ohms instead of any other tube that has been offered the public, because it has 1,000 ohms. a higher mutual conductance than any other high mu tube, be- Condenser C2 in Fig. 2B may be assumed to be across 1,000 cause is ohms, thereforetheconclusions applyasdetermined with it operated with alternating current on the heater, respect to the grid bias resistor just discussed. They do not because it has a very low grid -to -plate capacity. apply, however, if a resistor be connected in the plate lead to The heater voltage is 2.5 volts, either AC or DC, the heater B plus. Suppose we insert a 10,000 ohm resistor in series withcurrent1.75 amperes.Thus the tube has the same heater this lead. The total resistance now' is 11,000 ohms and C2 will characteristics as the 227 type tube, and can be connected to be relatively more effective. At 50 cycles the total impedance the same transformer winding as these tubes. is 4,583 ohms, a substantial reduction at this frequency. Voltages Needed Apparent Discrepancy It requires a plate voltage not in excess of 180 volts and a screen voltage of 75 at this plate voltage. Lower voltage may be Now some one may ask the purpose of adding a 10,000 ohm used provided that the screen and plate voltages are reduced resistor when that increases the actual impedance a 50 cyclesin proportion.The plate current is about 4 milliamperes and from 847 ohms to 4,583 ohms. 'The object of the condenser inthe screen current one-third as much.These values are for the first place is to prevent signal current from flowing intonormal values of heater, plate, screen and grid potentials, and the plate voltage supply, assumed in the above to be 1,000for no external load. ohms. The added 10,000 ohm resistor aids greatly in preventing The required grid bias on the control grid with 180 volts on the current from reaching the 1,000 ohm resistor and forces it the the plate and 75 volts on the screen is 1.5 volts.The amplifica- through the condenser.Itistherelative reductionin tion constant of the tube is420. Itisclear that the signal impedance that counts. voltage cannot swing 1.5 volts in either direction without dis-. A bypass condenser across the primary of an audio trans- tortion.If it did the amplitude of the signal voltage in the plate former such as Cl in' Fig. 2B must be small when consideredcircuit would be 630 volts, and there are only 180 volts DC in from the view point of audio frequencies and large when con- the plate circuit. sidered from the view point of radio frequency. Let the value The mutual conductance of the tube itself is 1,050 micromhos of Cl be .0005 mfd. At 550 kc the reactance is 578 ohms. This which compares with 350 for the DC screen grid tube.The isnegligible in comparison with the plate resistance of the plate resistance is only 400,000 ohms, which compares with 850,000 tube, which may be of the order of 20,000 ohms. Hence thisohms for the DC tube.The mutual conductance in any tube is condenser is satisfactory. the quotient of the amplification constant by the resistance. The inductance of the primary of the transformer may be Suppose the load resistance of the -AC screen grid tube is assumed to be100 henries, sothatits reactance at10,000 500,000 ohms.The total resistance in the plate circuit is then cycles is 6.28 million ohms. The reactance of Cl at 10,000 cycles 900,000 ohms, and the amplification is 5/9 of 420, or 233.If the is 31,800 ohms. Hence the reactance of the condenser is onlytube is used in an audio frequency amplifier preceding a. 245 1/200 of the reactance of the primary. Hence the condenser type tube requiring a maximum input of 50 volts a voltage of will act as a short circuit and the amplification on 'the 10,000only 50/233 volt is needed tp load up the power tube.That is, cycle frequency will be very low.If a smaller condenser is it used the detection will not be so good.The .0005 mfd. con- is only necessary to impress -.214 volt on the control grid of denser is a fair compromise between detection and audio sup- have the same plate voltage. There are then three apparent pression at the high frequencies.' places where condensers may be connected to advantage. Then Consider now the bypass condenser Cl in Fig. 3. Assume that if the detector isalso connected to the same voltage source the effective plate load resistance is 100,000 ohms. Let Cl bethere is another place where a condenser may be put. Actually .0005 mfd. At 10,000 cycles the reactance, as before, is 31,800the four condensers are in parallel and a single condenser could ohms, or about one-third of the value of the resistance. Therebe used just as well. A single condenser of the same capacity is much reduction in the amplification due to the condenser,as the sum of the capacities of the four separate condensers and therefore the capacity must be kept small. Again aboutwould not cost so much as the four smaller condensers, and it .0005 mfd. is a good compro.mise. would not take up so much room. It would be much easier to put into the circuit, with less chance of making a mistake. Common, Bypass And the single condenser would perform the same function as the f our. There are many instances in which condensers are distributed in the receiver when they are actually connected in parallel. [In some instances in push-pull circuits the bypass condenser across There is no good reason for this practice. For example, sup- a biasing resistor is not only unnecessary, but injurious, as will be pose there is an audio amplifier having three tubes, all of which explained in an article next week, issue of June 29th.] June 22, 1929 RADIO WORLD 7 the plate -to -cathode capacity is only 12 mmfd.These compare with 6 and 15, respectively, for the DC tube. Operation from Common Transformer One of the advantages of the AC screen grid tube is that it has the same filament voltage as the 227 and 245 type tubes. ofPower Thus it is practical to use a single transformer winding for all the tubes in an AC receiver.This materially simplifies the construction.Of course, it is not practical to use a low -power 2.5 volt winding to supply the heaters.The current required by each tube of the heater type is 1.75 amperes. Many trans- formers now on the market will not carry much more than this. Hence if two or more tubes are put on the winding the trans- former will heat up dangerously and the voltage on each tube will not be the rated 2.5.It is necessary to use a transformer Tube which has been designed to carry a very heavy current.For 24 example, if there are 5 heater tubes in the circuit, the total current will be 8.75 amperes.Certainly the transformer should he Most Popular- Discussion be designed to carry at least 9 amperes in this case. There is only one fact that makes it inadvisable to use the same heating winding for an AC screen grid tube as for a tube lifier or Detector, of the 245 type.If the power tube is given a bias, by means of the usual voltage drop in a resistor, of 50 volts, there will be a positive voltage of this amount on the heater with respect Method Included to the cathode on the heater type tubes.The AC screen grid tube's heater requires a negative voltage of 9 volts or less. Any higher voltage, whether positive or negative, endangers the tube.This does not apply to the case where the bias on the V. O'Rourke power tube is obtained with a liattery or battery substitute not Editor depending on a drop in the plate circuit of the power tube, Even if all the heater type tubes are put on one winding and the screen grid tube.It appears, then, that one of the things the power tube on another, there is considerable simplification the tube will do is to eliminate tubes from the amplifier. On of the main advantages of the screen grid tube is that itof the transformer.Itisbetterto have only two filament has a very low plate -to -grid capacity.In the AC tube thiswindings than four. capacity is only .01 mmfd. At a frequency of 10,000 cycles this has an impedance of 1.59 billion ohms, compared with the load Space Charge Tube resistance of 500,000 ohms.Thus there will be no appreciable suppression of the high frequency audio notes.In the three - The AC screen grid tube, like the DC tube, can be used in the element tube one of the limitations is the suppression of highspace charge connection.When this is done the screen, grid notes due to the plate -to -grid capacity. becomes the control grid and the inner grid (cap) is given a positive voltage. In the space charge connection the tube immediately loses Stable RF Amplification some of its valuable characteristics.The capacity between the The small grid -to -plate capacity also permits the tube to beplate and the screen grid, now the control grid, is high, the used efficiently at high radio frequencies without oscillation. amplification factor is greatly reduced, and it is no longer self - Indeed, the tube was especially designed for this purpose.It neutralizing.But the mutual conductance remains high because is quite feasible to design a radio frequency amplifier with this the internal resistance is low.The object of giving the inner tube at a step-up of 50 per stage without the use of anygrid a positive voltage is to accelerate the electrons from the neutralization.The only precaution that must be taken is tocathode and thus to overcome retarding effect of the space shield the stages so that. there will be no feedback by external charge, or the electrons distributed in the space between the coupling, electric or magnetic.The fact that the step-up is so cathode and the plate.It is this acceleration which reduces the high requires more thorough shielding than in a circuit using internal resistance. ordinary tubes. The space charge connection can be used in detector circuits The plate -to -cathode and grid -to -cathode capacities are also and in audio frequency amplifiers where suppression of the smaller in the AC screen grid tube than in the DC, and this highest audio notes is relatively immaterial. fact adds further to the efficiency of the tube at high radio When this connection is used it is best to employ resistance frequencies.The grid -to -cathode capacity is only 5 mmfd. and or impedance coupling.

L 0 ANT T2

.,C> C 2 L C> C1 L1 p .1:43 1.1 7 Co pL2 Co /C> R vo' C3

C8

Ch2 Ch3

INN C12 di11-7 0.01 ow 03 0.9 ,040,

/AO vf7C FIG. 1 THIS CIRCUIT EMPLOYS ONE AC SCREEN GRID TUBE AND TWO 227 TYPE TUBES ON ONE HEATER WINDING.THE TWO 245 TYPE TUBES ARE ON A SEPARATE 2.5 VOLT WINDING FOR REASONS EXPLAINED IN THE TEXT. 8 RADIO WORLD June 22, 1929 Space ChargeorNot Screen Grid ExperimentsInvited SimpleAudio By Herman Bernard Managing Editor FIG. 2 CA SA8,,® 0 ae SPACE CHARGE SA - DETECTOR. F 0 R SPA THIS HOOKUP IN- CREASE THE CAP VOLTAGE TO 67 En JS OR 90.BY THE OTHERMETHOD. traltmwm A 8 C THE G POST GETS A POSITIVE VOLT- AGE INSTEAD C,9/. TO C.- 4.1- BUT OF A LOWER 45# To So* FIG. 1 ORDER. TWO SCREEN GRID TUBES ARRANGED INA TUNERlation at radio frequencies.However, the lead may be lifted THAT FEEDS AN AUDIO AMPLIFIER WELLABLE TOto +45 on the batteries as an experiment, especiallyas the REPRODUCE SPEAKER VOLUME. THE DETECTORIS Avolume control (25,000 ohm Clarostat)is an oscillation stifler. SCREEN GRID OF NEGATIVE BIAS TYPE. Compare results obtained thisway with those obtained when the space charge method is used, \a,s in Fig.2. Louder signals, but not purer ones, may result when the THE use of the screen grid tubehasnot beenfully grid return is to A-, rather than space charge tube's explored.This applies even to the 222 battery model, is fully justified. to C-41/2, but the extra bias which soon will have been on the market twoyears, and, of course, to the recently. introduced 224 AC type. The two models are similar in use and performance, but by no means identical. Pointers on Parts Some may take the viewpoint they are dissimilar, although The last tube is a 112A, with 9 volts negativebias, and requires related.Either way, they are different.It depends on howno output filter for any speaker whatsoever. much importance you assign to the difference. Certainlyeven Constants not previously statedare: Cl, a midget condenser, the standard voltages do not agree: adjusted once and left thus; R1, 10ohms; R3, a 112 amperite Type Plate Vats S. G. Volts. Bias Volts or 2 ohms; R5, 5 to 8 meg.; C7, C8, .02 mfd.; C6,as large as you 222 135 45 -1.5 have ;C5, .0005 mfd. 224 180 75 -1.5 The circuit should be built with tube 1at left, tube 4 next, Even the grid biases do not agree. Thesame bias prevailstube 3 next, tube 2 at right, all in line.A 7x17" subpanel is for a 33 1-3% difference in plate voltage. large enough.The coils are near the front panel,extreme On the operational side there is a difference, too. Thescreen left and right. A double condenser (twosections, each .0005 grid tube of either type may be used (a)as a screen grid tube,mfd.) may be used, with flat type dial, by thismethod of layout. as shown in Fig. 1, or (b) as a space charge tube, as shown inA Hammarlund MLD 23 is suggested.If factory -made coils Fig. 2. The screen grid method, with cap to the tuned circuit,are desired use Screen Grid Coil Company's RF5 for L1L2and is the only one desirable for radio frequency and amplification. R5 for L3L4. For .00035 mfd. these coilsare RF3 and R.3. The space charge method lends itself to detectionor audio amplification, where a resistor or an impedance coil ison the Experimental Suggestions plate circuit. As a space charge detector the tube functions well as a grid bias detector. In audio circuits the problem of In using the tube asa grid bias detector in screen grid fashion stability arises when the tube is usedas a space charge grid microphone effects will be present, butwhen the space charge tube. grid method is used theseare absent.To cure microphonism put a metal shield over the tube, the type of shieldthat simulates the shape of the tube and fitsover the socket. Chance to Experiment stage shield is not meant. The box type Thespacechargegriddevelopshighergrid -to -filament Fig. 1 lends itself to experimentation.The two screen gridcapacity and requires readjustment ofthe equalizing condenser, tubes are of the battery -operated type, 222, .both used inscreen by use of more capacity.This detail must be attended to in grid fashion. L1L2 is an antenna coupler, of standard design.switching from screen grid tospace grid detection.If the L3L4 is special, in that the primary L3 has about twiceas many change -overismade ih the other direction ofcourseless turns as would be used for general purpose tubes. Ona 21/2' equalizing capacity is needed. diameter tubing L1L2 would consist of 12 and 48 turns, L2L3 When the space grid method is used thedetector plate bypass of 24 and 48 turns, both on .0005 mfd. The wire is No. 24condenser may be omitted,as the capacity in the plate circuit insulated. is automatically enlarged. Note how the negative biasisobtained. Tube 1gets 1.7 The leak -condenser method of detectionis not shown, but volts, because the grid return is made to negative filament ofa may be tried.The grid condenser should be about.0001 mfd., 5 -volt tube fed from a 6 -volt battery, while the 222 filamentor less than half the capacity otherwise used.The leak value gets 3.3 volts.Negative filament of the first 222 tube is -2.7should be more than .5meg.The higher the value of the in respect to the A battery minus (6-3.3). The negative fila-louder signals, up to overload. Thegrid return (coil connection ment of the 5 -volt tubes is1volt negative in respect to Aonly) would go to A+ when the leakcondenser method is tried. battery, minus. As -2.7 was measured from A minus, ifitis It is to be expected that the grid biasmethod will prove more measured from Fl of a 5 -vole tube the difference is1volt satisfactory under actualcircuit conditions, althougha dis- less, or 1,7.This measurement is correct when the grid returnsociated tube under test mightseem to provide good detection is made as shown. by the leak -condenser method.The operating circuit changes this situation. RotOr Connection Common Good AudioChannel The rotor of the tuning condenser C4goes to the same point Excellent tone at moderate volumeis reproducable b'y the as the rotor of C2 and the. end of L2. But the detector grid audio amplifier in Fig. 1, although thedetector output is indeed coil IA goes to C--41/2, for grid bias detection, which takesmodest, due to the tuner.But locals will be plenty loud place when 135 voltsare applied to a .5 to 1 meg. resistor R4.If a more sensitive tuner is used, enough. The audio amplification is enough tooperate a speaker if atuned radio frequency amplification,say two or more stages of high mu tube, 240, is used in socket 3, with R6a .25 to .5 meg.and the fine quality of which the audioall signals will be louder, resistor. R7 has to be small to prevent audio gurgling.Aboutnot be invalidated. amplifier is capable will .5 meg will work well, ora little lower resistance value may be The audio amplifier will not motorboat used. a well -filtered B supply. on B batteries, nor on Both G posts of sockets holdingscreen grid tubes in Fig. 1 What seems to be motorboating,if any disturbance arises, will prove to be RFoscillation.R2. will are shown connected to B+221/2. This is to prevent self-oscil-control that. , June 22, 1929 RADIO WORLD 9 Condenser Speakers Have Preponderance of Good Points By James H. Carroll Contributing Editor THE outstanding radio developments during the 1929 seasoncan be used, the power to operate the speaker can be made up are the application of the heater type tube, the placing ofof low current and high voltage, rather than high current and the AC screen grid and the 245 power tubes on the market, low voltage.This fact will make filtering of the plate voltage the perfection of the inductor -dynamic speaker, and the an- supply a simpler matter. nouncement of the condenser type speaker.Push-pull audio But the condenser speaker has disadvantages too.It is not amplification and power detection have also been emphasizedso' effective on the high audio notes.This is not because it is during the season. a poor sound radiator on the high frequencies. It is as good in The trend seems to be in the direction of eliminating all butthis respect as any other radiating surface of the same size. the heater type tubes, except in the power stage and toward a The loss of the high notes results from the capacity of the con- wider use of push-pull amplification.Most of the receiversdenser, an unavoidable feature if the speaker is to be made announced for the coming season have this form of amplification. large enough to radiate the bass, as INell as sensitive enough to In most instances the receivers of the 1930 season will be sold radiate much power on any frequenty. with the loudspeaker built in, so that the complete radio instal- Since the size of the radiating surface determines the effec- lation will be in compact and convenient form.The dynamic tiveness at the bass frequencies as well as the capacity which speaker leads at the present time, but there is no doubt that reduces the response at the high, it is possible to proportion the the new inductor -dynamic will figure prominently in the nearradiating surface so that the response will be good at both the future, because it has certain inherent advantages which lend high and the low frecipencies.Any lack of bass can be com- simplicity to the receiver assembly. . pensated for by using a baffle board. The baffle will aid in the radiation of the bass but it will not increase the capacity which The Electro-static Speaker cuts down the high notes.Indeed, the baffle will help the The so-called electro-static speaker has been announced, and radiation of sound on the high frequencies too. the public is keenly interested in its possibilities It is well known that dynamic speakers require an external But since the electro-static, or more logically, the condenserpower source for polarizing the field.This has always been type speaker has been announced, occasionally an individual isused by magnetic speaker proponents as an argument against found who has heard one in operation.He reports splendid dynamics. In a sense it is a disadvantage, but this is 'more than results, irreproachable quality.Such reports keep the interestoffset by the results. alive and may induce many to tolerate their present loudspeaker Inthe condenser speaker,too,a polarizing potentialis a while longer until they will be able to procure one of the needed. No current is required, however, only potential.And condenser speakers.Some suspicious individual has suggestedthe DC voltage needed is rather high, from 600 volts upward. that those rare persons who go around reporting having heard Many objections are raised against this.Itis inconvenient a condenser speaker in operation are the emissaries of theto provide an extra source of potential.The voltage is so manufacturers, and, that the sole object of their enthusiasm is high that it may be dangerous.And extra expensive equip- in the direction of sales. ment is needed. The idea of a condenser speaker is not new.It is much older than radio as we know it.The principle upon which it works Potential Not Dangerous is as old -as electricity.Indeed, it was one of the first things worked out when knowledge of electricity was as new as radio These objections have no weight when balanced against su- is today.Yet there has been no commercial application of itperior performance.In the first place it is no more inconven- until the present.But that is not against the speaker, for theient to supply the required voltage than to use the speaker dynamic was known for at least thirty years before it came to itself.The voltage supply readily can be built into the speak- be applied commercially.When that came, it came with aer assembly, and it will take very little room. As to the dan- rush.It may be the same with the condenser speaker.If it hasger, there is none.Suppose the voltage is, 1,000 volts.If this all the virtues that are claimed for it, there is no doubt aboutwe're a battery, or a generator, it would be dangerous to life. the rush. If it were an eliminator such as is used for power amplifiers, F. K. Vreeland iscredited with a patent on a condenserit might result in an unpleasant shock.But for a condenser speaker as far back as 1907, the year of the birth of the three- speaker neither of these sources is required. The high voltage element vacuum tube, and it is said that a successful model ofsupply can be designed so that no appreciable powercan be it has been perfected recently.Working models of condenser taken from it.And then it would be quite harmless.Possibly speakers have also been made in Germany by Hans Vogt anda shock from the device would, not feel pleasant but it would others.Condenser headphones made in Germany have been innot be more than a severe tickle. this country for several years and are capable of unexcelled Battery eliminators are already available for supplying the quality as long as they stand up, which is not long.Theypotential to condenser speakers, when and if promisesare sub- deteriorate rapidly whether or not in use. stantiated.One of these is a compact little device employing a single 201A tube for rectification.High and low voltage Deterioration a Problem windings, as well as chokes and condensers, are built in, and It is this difficulty of deterioration which has held up progressthe whole device can be held in one hand. of condenser loudspeaker development. There are two types of condenser speaker, unilateral and bi- It may be that this lateral.The unilateral has two plates, one fixed and onemov- explains why we had nothing until ,now in this or any other able.The signal and the polarizing voltages are impressed country. As soon as this problem has been solved satisfactorilybetween these two plates.As the signal voltage varies, the we shall be able to use condenser speakers, and we may havemovable plate vibratesjustas any other loudspeaker dia- something exceptionally good to listen to. phragm ,orpiston. There is no doubt of the possibilities of the condenser speaker. The bilateral type of speaker contains two fixed platesand It works essentially on the same principle as the condenser one movable,the movable plate being placed midway between microphone, and there does not exist a practical microphone the two fixed plates. The polarizing voltage is impressedbe- which is superior to this.But the microphone is, not subjecttween the center plate and the two fixed plates.That is, to deterioration to the same extent as the speaker.This is the center plateis made positive and the two fixed plates because in the microphone the dielectric between the two plates negative, potential difference between the center plateand the of the condenser is air while in the loudseaker itis an elastic fixed plates being the same.The .signal voltage is impressed membrane, usually rubber.It is the rubber which deterioratesbetween the center and the fixed plates simultaneously in with time. such The condenser speaker will be practical as soonmanner that when the totaleffective voltage betweenone as somebody discovers a substitute for the rubber membranepair is increased by a certain amount itis decreased by the which will hold up. There is a great fortune in that discovery.same amount between the other two.That is, the bilateral type The condenser speaker is particularly effective on the bass speaker is a push-pull speaker.The moving plate in the center is frequencies, one reason for which is that it has a relatively held in an unstrained position when no signal is impressed,or in a large radiating surface.Another 'advantage isthatit has a balanced position.The signal voltage upsets the balanced inpro- comparatively high impedance and so can be used in -conjunction portion to the strength of the signal. with tubes having a high output impedance.It will not require The effect of the push-pull arrangement is to make thespeaker any step-down output transformer.Since high impedance tubes more sensitive and free from distortion. 10 RADIO WORLD June 22, 1929 POWER AMPLIFIERS By J. E. Anderson and Herman Bernard [A notable series of expository articles on power amplifiers, by J. E. Anderson and Herman Bernard, was begun in the June 1st issue, in which the components of battery, DC and AC power am- plifiers were analyzed, and illustrated with fifteen diagrams.Types of audio couplers were also described and compared.In the June FIG. 18 8th issue loudspeaker coupling devices and battery -operated ampli- (A)-CIRCUIT OF A FULL -WAVE RECTIFIER SHOWING fiers were explained. A special analysis of resistance -coupled audioTHE DIRECTION OF CURRENT AND VOLTAGES DURING was included.There were nine illustrations.Last week, in theTHE HALF -CYCLE WHEN THE PLATE L IS ACTIVE. June 15th issue, the exposition was carried forward to the DC sup- (B)-THE SAME CIRCUIT DURING THE HALF -CYCLE ply of A, B and C voltages, e.g., for operation from 110 -volts DC WHEN PLATE R IS ACTIVE. obtained from the convenience outlet.Ohm's law was explained in conjunction with the design of a DC supplyThen the part was,part time from the condensers.The property of the coil is to begun that treats of AC fully, with rectifier and filter analysis ex-resist changes in the current, increases as well as decreases. ceptionally well set forth. The AC topic is continued this week.InThe value of the steady current is the mean value of the cur- the June 25th issue next week will be another fine instalment ofrent during a complete cycle, or .318 of the peak value of the this notable series.The articles will continue from week to week.current. Follow them closely.-Editor.] The current output of a rectifier and filter is steady only if the filtering is very good.If the filtering is not adequate there will be ripples in the current.In a half -wave -rectifier the frequency of the main ripple will be the same as the frequency of the supply current, but there will also be ripples at harmonic frequencies, that is,two, three, four, and so on, times the frequency of the supply.But these will be very small. The effectiveness of the filter in removing the ripple depends on the capacity of the condenserand the inductance of the chokes.The larger they are the ripple will remain in the output.Also, the more condensers and more chokes used, FIG. 16 the steadier will the output current be.Again, the smaller the (A)-CIRCUIT OF A HALF -WAVE, VACUUM TUBE TYPEcurrent that is drawn from the rectifier -filter, the less rinnb, RECTIFIER DURING THE ACTIVE HALF -CYCLE. for any given filter and type of rectification. During the half -cycle in which no current flows the voltage (B)-THE SAME CIRCUIT AS IN A DURING THE INAC-rises to a higher value than during the half -cycle in which TIVE HALF -CYCLE. current does flow, and since the average value of the current Suppose the current in the primary flows in the direction in-is only .318 of the maximum, a higher input voltage is required dicated by the arrow (a) in Fig. 16A.There will then be ain order to get the required value of steady current.There- current in the filament circuit in the direction indicated by thefore the filter condensers used must be designed to withstand arrow (b).There will also be a voltage induced in the high comparatively high voltages. voltage winding in the direction indicated by the arrow (c). But will there be a current? ' The direction of the voltage is Full -Wave Rectifier such that the plate is positive with respect to the filament. Hence electrons will be attracted from the hot filament to the A more satisfactory rectifier is one in which current flows plate. This is equivalent to an electric current from the plate every half -cycle.This type is known as full -wave rectifier and to the filament, and there will be a current through the external is shown in Figs. 18A and 18B, and the corresponding rectified circuit as indicated by the arrows (d). current curve is shown in Fig. 19.It will be observed that the While the plate is positive with respect to the filament, thefull -wave rectifierisessentially the same asthe half -wave direction of the current is such that the filament end of therectifier, except that the tube has two equal plates and the load resistance ispositive and the plate end of the load ishigh voltage winding is center -tapped. negative. Consider the half -cycle durinc, which the primarycurrent The primary current will flow as indicated by arrow (a)flows in the direction indicated' byarrow (a)in Fig. 18A. for only half cycle, which for 60 -cycle current has a durationThe high voltage is then in the direction indicated by the long of 1/120th part of a second. The current will rise and fall asarrows (c).This voltage makes plate L positive, and plate R indicated by the first loop in Fig. 17. negative, with respect to the filament.Therefore current flows At the end of the first half -cycle the current will reverse inbetween plate L and the filament, and the direction of this the primary as well as in the heater winding, as indicated bycurrent in the external circuit is indicated by the shortarrows. the arrows in Fig. 16B.The voltage in the plate winding willThe portion of the circuit containing plate L is active because also reverse and ad in the direction indicated by the dotted current flows.The portion containing plate R is inactive for arrow. Now the plate of the tube is negative with respect to no current is produced by the voltage, indicated by the dotted the filament, and therefore no electrons are attracted from the arrow. filament to the plate.Indeed, they are driven back to the The active portion of this circuit corresponds with Fig. 16A filament.Hence there will be no current through the external and the inactive portion corresponds with Fig. 16B. circuit,or through theload.The arrow representing the When the current in the primary of the transformerreverses, voltage has been dotted to show that the voltage produces no thecurrentflowsasindicatedinFig.18B. The portionof. current, and the second loop in Fig. 17 also has been dottedthe circuit containing plate L isnow inactive while that con- to indicate the absence of current. taining plate R is active.The important thing to note is that During the third half -cycle all the events of the first half - the current in the external circuit flows in thesame direction cycle are repeated, and therefore the loop in Fig. 17 repre- in both instances.Therefore there will be no time during which senting the current in this phase has been drawn in a solid the rectifier as a whole is inactive, butcurrent will flow every line.The process is continued as long as there is an alternating half -cycle. current in the primary of the transformer, current pulses be- The filament current has not been indicated inA or B in ing producedinone direction only withtotal absence of Fig. 18, because the current is equally effectivein heating the current half of the time. filament whether it is flowing inone direction or the other. It is the function of the filter to smooth out the pulsations In Figs. 18A and 18B the positive terminalhas been con- into a steady, direct current. The condensers inthefilter nected to the center of the filament heatingtransformer, where- store up part of the electricity from the pulses, and they dis-as in Figs. 16A and 16B it has been connected toone side. charge thiselectricity during the half -cycles when the tubeIt makes practically no difference whether theconnection is does not supply any.The choke coils in the filter maintain amade to the center or one side in either the full-wave or half - steady flow, part time taking the current from the tube andwave rectifier. Fig.19 shows the current pulses contributedby the two sides of the full -wave rectifier. STEADY The loops are marked L and CURREA/7) R according to which plate contributes them. The filtered current from the full-wave rectifier is the mean current of a half -wave rectifier multiplied by 2. SEC. -Pi SEC. ,' 7342; I .6367 FIG. 17 R L R APPROXIMATE FORM OF THE RECTIFIED CURRENT BEFORE FILTERING AS PRODUCED BY A HALF -WAVE FIG. 19 RECTIFIER.THE DOTTED LOOP INDICATES NO CUR- THE FORM OF THE RECTIFIED CURRENT FROM A FULL- RENT. WAVE RECTIFIER BEFORE FII.TARIN( June 22, 1929 RADIO WORLD 11 But it does mean that for a given current output, the maximum current in one instance is twice the maximum in the other. And from thisitfollows that the output from a full -wave ro rectifier is more easily filtered, for the fluctuations to start with 1, ro are not so great.The half -wave rectifier for a given current RFC TlrIER C output has the greater maximum current peaks 1 to The frequency of the main ripple component from a full - O wave rectifier is twice the frequency of the supply current.For example, if the supply is 60 -cycle current, the main ripple will A B have a frequency of 120 cycles.There will be a ripple com- PIG. 21 ponent at60cycles and othercomponentsatthehigher (A)-SIMPLE FILTER CIRCUIT CONSISTING OF A SINGLE harmonics of 60, but these will be very small compared with CONDENSER ACROSS THE OUTPUT OF THE RECTIFIER the 120 -cycle ripple. AND ACROSS THE LOAD Not only is the output of the full -wave rectifier easier to (B)-THE -FORM OF THE FILTERED CURRENT AFTER filter than that of a half -wave rectifier because the originalIT HAS PASSED BY THE CONDENSER IN A. IIS THE fluctuations are smaller, but also because the ripple frequency is AMPLITUDE OF THE RESIDUAL RIPPLE. higher.Condensers and chokes of given values will be just twice as effective at 120 cycles as at 60 cycles. rent is flowing, but tha;t when the mean output current is flowing in Taking into consideration that the ripple frequency is twice the coil.This is considerably less inductance, for the larger the cur- as great in the full -wave rectifier as in the half -wave, and that rent the lower the inductance.The filtering is also more thorough the original fluctuations are only half as great, it would seem, the larger condenser C2 is.The wavy curve in Fig. 22B represents other conditions being equal, that the output of the full -wave the form of the output current after it has passed by the filter com- rectifier is four times more easily filtered than the output of the prising the two condensers C and C2 and through the choke L. half -wave rectifier.And soitis. to as before, represents the mean value of the current and I repre- Another advantage of the full -wave rectifier is that its volt- sents the amplitude of the residual ripple.The amplitude of this age regulation is better.That is, the output voltage does not ripple has been exaggerated to emphasize it.Actually the ampli- fluctuate so much when the amount 'of current drawn from it tude may not be greater than one per cent: of the mean current. is changed.There are two reasons for this.First the rec- Although the ripple is as small as one percent. of the steady tifier tube has a lower resistance because it is conductive duringcurrent, it is too large for use on an amplifier.Hence it is neces- both half -cycles, and second, because the filter chokes need not sary to add another filter section consisting of a choke coil L2 and a condenser C3, Fig. 23A.If the first filter section reduced the be so largeand,therefore have less resistance. ripple to one per cent.of the steady current, and if the second section is just like the first, the residual ripple is reduced to one The Gaseous Type Rectifier per cent. of one per cent.This is so small that the current may be A typical circuit of a full -wave gaseous type rectifier is given in considered to be pure DC. The undulations in the output current Fig. 20.The current to be rectified is supplied by a voltage step- up transformer T, the secondary of which is center -tapped.There are two rectifying elements inside the tube composed of the cen- I} Tz CURRENT tral plate Mind the two points K.Current can flow only from the points K to the plate A and not in the opposite direction.Hence the plate A is the anode, or positive terminal, and the Ks take turns being the cathode, or negative terminal. ' The functioning of this tube is similar to that of the filament type rectifier.Consider the half -cycle during which the primary A B current flows in the direction indicated by arrow (a).The sec- FIG.. 22 ondary voltage is then in the direction of the long arrows placed, (A) near the center -tapped winding.Current then flows around the SIMPLE FILTER CONSISTING OF TWO CONDENSERS current as indicated by the short arrows, because it can flow only C AND C2 ACROSS THE LINE AND A CHOKE COIL L IN from K to A. SERIES WITH THE LINE When the primary current reverses, the upper half of the center - (B)-THE FORM OF THE FILTERED OUTPUT AFTER tapped winding becomes active, but the current in the external cir- IT HAS PASSED BY THE TWO CONDENSERS- AND cuit does not change direction.Therefore the rectified output cur- THROUGH THE COIL IN A. IIS THE AMPLITUDE OF rent has the form indicated in Fig. 19.Condensers C, C across the THE RESIDUAL RIPPLE. two halves of the high voltage winding are called buffer condensers are so small that the wavy curve does notappreciably deviate from and they serve to improve the rectification characteristic of thethe mean current curve, as shown in Fig. 23B. tube.The -value of each is usually .02 mfd. to .1 mfd. When the ripple is as low as one per cent. of oneper cent, the current may be used for audio frequency amplifiers without any Filtering Rectified Output noticeable hum resulting.It also can be used to supply a radio frequency amplifier and detector without hum, provided that there Since the output current of every type of rectifier contains con-is no oscillation or excessive regeneration in the radio circuit.It siderable ripple,itis necessary to employ filtersto remove the is assumed that there is no oscillation or regeneration in the audio fluctuations and to make the current truly steady and continuous. amplifier.if there is, even a very small residual hum will become The simplest filter, shown in Fig. 21A, consists of a single con- noticeable.But if a circuit oscillates, or regenerates excessively, at denser C across the output of the rectifier and across the load. audio frequencies, the amplifier is not satisfactory, and it becomes If the condenser has a large capacity, and if the load resistance is necessary to treat the circuit so as to stop the regeneration. high, this type of filter takes out a large proportion of the ripple. The filter given in Fig. 23A has come to be regarded as standard, The output current from a full -wave rectifier may be represented and it is the one most frequently used.But there are other forms. by a curve such as that in Fig. 21B.Io represents the mean value Fig. 24, for example, shows a two -section filter in whichone of of the partly filtered current, and I represents the amplitude of the choke coils is tuned with a condenser C4, the ripple.The frequency of the ripple is twice the frequency of The inductance of L2 and the capacity of C4 are proportioned so that L2C4 formsa the current supplied to the rectified by the step-up transformer. tuned circuit at the principal ripple frequency, that is, at 120 cycles More thorough filtering can be effected by inserting a high in- in a full -wave rectifier using 60 -cycle current supply. ductance choke coil L in series with the line, as shown in Fig. L2 and C4 form a parallel tuned circuit at the resonant frequency, 22A.This coil tends to keep the current steady, opposing both in- and one characteristic of such a circ'hit is that its impedance at the creases and decreases.But if the coil works into a high resistance resonant frequency is extremely high.Hence if L2 and C4 are ad- itis not effective, and therefore itis desirable to connect another justed to resonate at the principal ripple frequency, say 120 cycles, condenser C2 across the load resistance.The coil then works into the ripple is almost completely suppressed. the comparatively low impedance of the condenser C2, rather than into the high resistance of the load. C4 admits the higher harmonic ripple frequencies, but theseare The greater the inductance of L the more complete is the filtering. The effective inductance is not that of the coil when no direct cur- //lEAN ICURRENT 7-

1 0 A B FIG. 23 (A)-A FILTER CONSISTING OF THREE CONDENSERS C, C2 AND C3- AND TWO CHOKES L I AND L2.THIS IS A TWO -SECTION FILTER. (B)-THE FORM OF THE FILTERED CURRENT AFTER HAVING PASSED THROUGH THE TWO -SECTION FILTER FIG. 20 IN A. THE RESIDUAL RIPPLE IS NOW SO SMALL THAT CIRCUIT OF A FULL -WAVE RECTIFIER EMPLOYING ,A THE ACTUAL CURRENT CURVE COINCIDES WITH THE GASEOUS TYPE TUBE MEAN CURRENT CURVE. 12 RADIO WORLD June 22, 1929 400 350 300 FIG. 24 FIG. 25 B-. A TWO -SECTION FILTER IN WHICH THE SECONDCHOKE COIL, L2, IS TUNED TO THE PRINCIPAL RIPPLEFRE- 250 QUENCY BY MEANS OF CONDENSER C4. BETTER RIPPLE c. SUPPRESSION AND BETTER REGULATION CAN BE SE- CURED WITH THIS CIRCUIT THAN WITH THE CIRCUIT 200 IN FIG. 23A A TWO -SECTION FILTER IN WHICH THE FIRST BY-PASS CONDENSER HAS BEEN OMITTED.BETTER REGULA- TION AND LONGER LIFE OF THE RECTIFIER TUBE ARE TWO OF THE ADVANTAGES CLAIMED FOR THIS CIRCUIT /00 almost completely suppressed by the untuned filtersection com- 20 40 60 . 80. /00 /20 prising C and Ll, as well as by the other condensers, C2 andC3, across the line.Therefore the gain by the use of a tuned section DC OUTPUT" (MILLI AMPERES) is considerable. There is another advantage gained by theuse of a tuned filter = 300 Y. AC PER PLATE section.Ordinarily, L2 would have to be a high inductance choke coil, which is necessarily wound with comparatively fine wire.This = 260 V. AC PER PLATE means that the resistance of L2 would be high, which would impair C = 220 V. AC PER PLATE the voltage regulation of the filter.When L2 is tuned, a much lower inductance value must be used, whichmeans .that for a given FIG. 26 size of core only a small amount of heavy wiremay be used. The TYPICAL REGULATION CURVES OFA FULL WAVE REC- resistance of the coil will then be lower and the regulationof the TIFIER -FILTER EMPLOYING 280 TYPETUBE WORKING voltage better.Indeed, if the tuned filteris to be as effective as INTO A FILTER LIKE THAT IN FIG. 23A. possible in eliminating the ripple at the resonant frequencythe re- sistance of L2 must be very low, for the lower it is the higher is drop.Itis only the voltage dropacross the load resistance the impedance of the tuned circuit at the resonant frequency. which is useful. The voltages droppedin the other resistors de- If L2 is not tuned its inductance should be 30 henriesor more. crease the total useful voltage. When the load isshort-circuited Ifitis tuned, and ifa 1 mfd. condenser is used, the coil should all the voltage is dropped in thetransformer, the tube and the have an inductance or about 1.75 henries.This coil may be made chokes, and hence there isno output. to have a very low resistance, keeping the physical dimensions the A regulation curve ofa rectifier -filter is the relation, graph- same as those for the 30 henry coil. ically shown, between theoutput voltage and the output cur- Another special filter is given in Fig. 25. tent for a fixed value of AC input voltage.Three such curves This is essentially the for a 280 rectifier tube workinginto a filter like that in Fig. same as that in Fig. 23A, except that condenser C has been omitted. 23A are shown in Fig. 26. The omission has been recommended by the enginers of E. T.Cun- The ordinates give the DC voltage ningham, Inc., as a means of protecting the filament type rectifier across the load resistance and the abscissas thecurrent drawn tube. from the circuit.The AC voltages associated with thethree The argument against the use of a condenser nextto the curves are effective values and equal to one-half of rectifier tube is that it offers a very low impedanceto the tube so effective voltages across the the total that for every half -cycle a large current pulse is demandedof the center -tapped winding when no tube for charging the condenser. current is drawn. Some of the advantages claimed for the circuit without condenser If these curves were horizontal,or parallel with the current C are: (a) improved regulation; (b) improved efficiency, (c)re- axis, the regulation would be perfect.The slope of any curve duced emission demand on the rectifier tube; (d) reduced heating isa measure of the regulation.The greater the slope the of the tube; and (e) increased life of the tube. poorer the regulation. It is clear that the slope ofany curve does not remain con- Advantages gained by the use of the condenserare : (a) greater output voltage with a given fixed transformer voltage and (b) bet- stant but decreases as the current drawnincreases. Thus the ter filter action. regulation improves as the current isincreased.Unfortunately, When condenser C is omitted from the position next this improvement in the regulation isaccompanied by a decrease to the rec- in the effective filtration, anincrease in the power loss, and shorten- tifier tube, it should not be omitted from the filter circuit, but should ing of the life of the rectifier tube. be added to the final condenser C3. Poor regulation of The first condenser should not be omitted ina half -wave rec- a current supply, or B battery eliminator, tifier because the charge on the condenser is needed invariably results in distortionof the signal. When the signal to supply cur- is strong there is a sudden increasein the current requirements rent during the half -cycle when the tube is inactive. and this causes a decrease in the Any method that promises better regulation is always interesting will not be amplified output voltage.The signal because better uniformity of results obtain. What regulationmeans, as much as it should.The distortion is and how its importance uses, constitutesan important branch of largely of the wave form type, whichis harmonic distortion. the study of power amplifiers, andwe proceed to discuss it. Poor regulation also indicates that thecurrent supply has a high internal resistance to directcurrent. Suppose the power transformer supplying therectifieris not indicate a high resistance to alternating It may or may wound for an effective voltage of. 300 volts.The current is current.Usually, if rectified and sent through a given filter and the resistance is high for directcurrent it is also high for alter- a variable load.nating current, especially for lowfrequencies. What isthe rectified output voltage across the load?Itis Good filtering does not necessarily not a fixed quantity but varies with the load.The higher the mean that the AC resist- load resistance, that is, the lower. the rectifiedcurrent that is ance of the current supply device is low, looking fromthe am- drawn from the rectifier -filter, the higher is the voltage plifier, but it does mean that theresistance to AC is low, look- across ing from the rectifier.If the last condenser, C3 in Fig. 23A, the load.As the resistance of the load is decreased, that is,as is very large, the AC resistance the current drawn is increased, the voltage falls.The variation low. looking from the amplifier is in the voltage across the load as the current changes is referred This resistance is lowered stillfurther by the voltage di- vider which is associated with theload. to as the regulation.If the output voltage_ varies much as the A low AC resistance for all frequencies currentisvaried through a definite range, the regulationis looking from the am- poor; if the voltage varies just a little, or not at all, the regula-plifier is essential for good performanceof the rectifier -filter. tion is good. If the resistance is lowsome of the effects of poor regulation The output voltage may be considerably higher than thewill be annulled. Ifitis high, feedback will result in the amplifier, and this willcause frequency distortion or actual effective AC voltage across each half of the center -tapped wind-cillation at some frequency. The AC os- ing in a full -wave rectifier. For no load, that is, forno output resistance of the filter- current, the voltage may be about 41 per cent. higher than the rectifier, looking from the amplifier,is a large part of the com- effective voltage across each half of the transformer. mon impedance among the tubes served.The other part of But the common impedance isthe reactance due to the various when current is drawn the voltage is always lower than this.chokes and condensers, and this When the output terminals are short-circuited there isno output reactance may be either induc-. voltage at all.Hence the voltage may vary from zero to 1.41 tive or capacitive, dependingon the frequency. times the effective AC voltage impressedon each plate of the full -wave rectifier. The Voltage Divider What causes the voltage delivered to drop as the current is Every rectifier -filter designed to deliver increased?Resistance in the rectifier and the filter.First there current at different is the DC resistance in the high voltage windings of the voltages must have a voltage divider,which usually consists of trans- a resistor across the output, with oneor more taps on it. former, then the plate to filament resistance of the rectifier tube, To design properly a voltage divider it is and finally the resistance in the filter choke coils. Whencurrentthe current distribution as well necessary to know flows in the circuit there is a voltage drop in all of thesere- as the voltages desired.It is sistances, and the greater the current, the greater the voltageimpossible to say what the value of theresistance between any two voltage taps should be if the voltage alone isknown, because June 22, 1929 RADIO WORLD 13 the voltage difference between the two points is the product of the current and the resistance.Also', it is not practical to adjust the position of the taps with the aid of a voltmeter, because the 534 voltmeter takes current, so that the voltage will not be the same when the meter is removed as it was when the meter was in /80 position.A voltmeter of 1,000 ohms per volt can be used to get a close approximation to the voltage, for such a meter /35 takes only a small current, but a less sensitive voltmeter will 45 take possibly more current than that which flows in the re- sistor itself.With such a meter not even a rough approximation to 0 the correct voltage can be obtained. A simple voltage divider is shown in Fig. 27A, which consists of two resistances R1 and R2 in series, with a tap X at the junc- tion.If it is assumed that no curent flows into the tap the total FIG. 27 voltage between the positive and negative sides of the line is divided in proportion to the values of the resistors, that is, the (A)-A VOLTAGE DIVIDER HAVING A SINGLE TAP voltage between X and plus is to R1 as the voltage between WHICH IS ASSUMED TO TAKE NO CURRENT. minus and X is to R2. This holds because the same current flows in Ri and R2.The current i,flowing in the main load does (B)-A TYPICAL VOLTAGE DIVIDER DESIGNED TO SUP- not affect the division but it does affect the total voltage across PLY A CIRCUIT USING 245 POWER TUBES, AC SCREEN R1 and R2.The larger this current the slower the total volt- GRID TUBES AND OTHER TUBES REQUIRING THE VOLT- age, as was explained in connection with voltage regulation. AGES INDICATED. Referring again to Fig. 27A, suppose that the total voltage (C)=A VOLTAGE DIVIDER DESIGNED FOR A CIRCUIT across R1 and R2 is 180 volts and that R1 is15,000 and R2 USING 250 POWER TUBES, BATTERY TYPE SCREEN is 10,000 ohms. The total resistance is then 25,000 ohms. Hence GRID TUBES, AND OTHER TUBES REQUIRING THE VOLT- the current through the resistors is 180/25,000 amperes, or 7.2 AGES GIVEN. milliamperes.The voltage drop in R1 is therefore 108 volts and the drop in R2 is 72 volts. The current flowing through the voltage divider is known as the "bleeder current" because it flows whether or not the recti- ing 250 power tubes, battery type screen grid tubes (222) and fier -filterisdelivering any useful power. other amplifier tubes requiring voltages from 45 to 180 volts. There are three objects of the bleeder current.First, it pre- The placement of the taps is determined in the same way as, in vents a sudden and high rise of the voltage across the con-the preceding example. The first thing to do is to determine densers in the filter when the load is removed, that is, when the value of the bleeder current, making it large enough to the filaments in the amplifier are turned off or when the line permit simplifying assumptions, yet' not so large as to lower the Second, it provides a means for total available voltage excessively or to affect adversely the fil- to the amplifier is opened. tering.When the bleeder current has been determined, and obtaining lower voltages than the maximum, that is, it enables neglecting the current to the 45 -volt tap, R3 and. R4 may be de- the voltage divider to function.Third, it brings the current termined. The 45 volt tap should be adjustable, as indicated by operating point of the rectifier -filter to a place where the regu-the arrow termination.Next the current to the 135 -volt tap lation is better,The first two of these functions are the More should be measured so that R2 may be determined.Then the important. current to the 180 -volt tap should be measured to give data for Only infrequently may it be assumed that no current flows in determining Rl. a tap on the voltage divider.The only case where this assump- tion is justified is when the tap is used to supply a grid po- It is well to use a voltage divider strip with adjustable taps tential.When the tap is connected to a plate of a tube, or to so that there will be no limitation on the resistance values that a screen grid, some current flows, and this must be taken into may be selected.But if strips of fixed taps are used itis account in determining the positions of the taps on the voltage possible to use the tap which gives the voltage nearest to that divider resistance. desired, and then adjust the grid bias on the tubes served to Fig. 27B shows a voltage divider suitable for an amplifier in-suit the plate voltage actually obtained. volving 224 AC screen grid and 245 type tubes. The maximum If a high resistance voltmeter, one of 1,000 ohms per voltage, voltage is 300 volts, which provides the plate and grid voltages is used, fair accuracy may be attained without measuring the for the 245 tube or tubes.The next lower voltage is 180, which current in the various taps.It should be remembered that even provides voltage for the plate of the screen grid tube, or for a 1,000 ohms per volt reads lower than the actual voltages. But any other tubes which may be operated at this voltage.The the discrepancy is small and should not seriously affect the op- lowest voltage is 75 volts, intended primarily for the screen grid erations of the amplifier. (G post of socket) of the 224 tube. The 75 -volt tap terminates in The suggestion was made that the current drawn from a certain an arrow on the resistor strip, indicating that the voltage is ad-tap be measured under normal operating conditions.This is not justable. always easy to comply with, for the object of the adjustment is to Current is taken by all of the taps in Fig. 27B, as is indicatedbring about normal operating conditions, and the normal current by the arrows.But the amount of current taken by any tap is cannot be Measured before normal conditions have been brought not known, for it depends on the filament temperature of the about. tubes, on the grid bias on the tubes, on the number of tubes The current that will be drawn from any tap can be determined on a given tap, and on the nature of the coupling devices used quite accurately without any measurement at all.Let us illustrate in the amplifier. Hence the current in any section of the volt- how this May be done. age divider is unknown. Let us suppose that two 201A tubes are connected to the 135 volt However, in section R1 all the plate current flows, as well tap and that these tubes are properly biased and that they are work- as the bleeder current of the amplifier, except the plate current ing into primaries of audio transformers.Under these conditions of the tubes on 300 volts.In section R2 the bleeder current the current taken by each tube is known.Let us say that the bias and the current taken by the 75 -volt tap flo'vs.In section R3 is such that each tube takes 6 milliamperes.Therefore 12 milliam- only the bleeder current flows. peres will flow from the 135 volt tap.That figure can be used in In the design of a voltage divider certain simplifying assump- place of the result of measurement, at least for purposes of calcu- tions sometimes may be made.Suppose the bleeder current is lating the resistances in the voltage divider. large, so that the current taken by the screen grids is small in In the same manner the current from any tap can be estimated. comparison.Then itis permissible to assume that the same It is only necessary to count the number of tubes of various types current flows in- both R2 and R3, and that this is the bleederserved by a given tap and then take from tube tables the normal current.Let the bleeder current be 20 milliamperes.The 180 current for each, tap for the plate voltage in question.If there are volts equals .020 x (R2+ R3).Hence the sum of the two lowerany other conductors taking current from the same tap the current resistors should be 9,000 ohms.A 10,000 -ohm potentiometer should be estimated and added to the total. could then be used for R2 and R3, with the 75 -volt tap connected to the slider.The bleeder current' would be 18 milliamperes. It will be noted that the highest voltages in Figs. 27A and Hence both the 180- and 75 -volt potentials would be adjusted27B are higher than the rated plate voltages for the tubes.The regardless of how much current were drawn from the 180- anddifference is the grid bias intended for the power tubes.For 300 -volt taps. example, the 534 volts are divided in the ratio of 450 for the Now it remains to determine the value of RI. We might find plates and 84 for the grids.The bias on the tubes served by by measurement in the 180 -volt lead that the current is 15 mil- the other taps is so small that allowance need not be made liamperes.This measurement should be made after the 180 - for it. volt potential and the grid and filament voltages on the tubes No by-pass condensers are shown in Fig. 27, A, B, or C, be- served by the 180 -volt tap have been adjusted to the desired values. cause only DC voltages were considered.When the voltage Having determined the current to be 15 milliamperes under divider is used with an amplifier there will also be signal cur- normal operating conditions, we know that the current in R1 rents flowing in the various taps and resistors, and each of these is33 milliamperes. The voltage drop inthis resistorisalso currents must be provided with a low impedance path to the negative known, being the difference between 300 and 180 volts. There- side of the line, or to the filament.Hence a by-pass condenser fore we know that Ri must, have a value of 3,636 ohms.For should be connected from every tap to the negative side.These con- a different current distribution the resistance would have an- densers may be connected either in the amplifier or in the volt- other value. age divider. Fig. 27C shows a voltage divider suitable for a circuit compris- (Part V 'next week, issue of Tune 29th) 14 RADIO WORLD June 22, 1929

A Question and Answer Annual subscriptions are Department conducted by acceptedat$6for52 Radio World's Technical numbers, with the privil- Staff. OnlyQuestions ege of obtaining answers sentinbyUniversity to radio questions for the Club Members are ans- 1 ADO iRS1TYperiod of the subscrip- wered.Those not ans- tion, but not if any other wered in these columns premium is obtained with are answered by mail. the subscription.

by coiling. L2 Inductance is a property of the wire that relates to the numberoflines of 8+ PWR. force in the magnetic field of thewire under stated conditions. Nobodyever saw inductance, but its manifestations have beenstudied and measured.Defining inductance isasdifficult as defining electricity.An extended exposition isrequired.Itwill surprise many to learn 0 that inductanceis measured in linear length. 7.7 0 C2 Europeans express it directly interms of the 0 meter.We use an equivalent method, with the henry as the unit. *** C8 I DESIRE TO USEa 245 output tube incor- porated in a B supply with 281rectifier. Please show diagram.-A. L. Fig. 762 shows the wiring. The OUTPUT secondaries of (5 PE- 471(ER) the power transformer T1'are, top to bottom, Z 71/2 volts, 300 volts, 21/2 volts. 0_ O L1L2 are a SM Unichoke 331. Cl, C2, C3are 2 mfd. each, 600 - volt AC rating.C2I\ C5, C6 are 2 mfd. each, C7 and C8, 4 mfd. each.T2 is an audio trans- former to which detector plate and B+detector are connected. L3 isan output filter choke. The output potentiometer isan Aerovox Pyrolim type A, 1,500 ohms being used from C-to C -I-. FIG. 762 ** B SUPPLY WITH ONE -STAGE AUDIO, USING A HALF -WAVE THE LID of my table modelcabinet rests RECTIFIER. on top of the 281rectifier tube, because in building thesetIdidnot IN BUILDING my present receiver I used ample radio fre-room, not having counted the thickness allowsufficient quency amplification, power detector and two stages of impe-connection with the unusual height of the baseboard in dance coupled audio amplification, as therewas enough detector of the rectifier tube. How output to enable loading up the last two stages of can I avoid this situation, so that if thecabinet lid should fall moderate -amplification audio. it won't break another 281tube?-M. C. However, when I turn the set on Remove the 281 socket.Drill a 1" hole through the baseboard it sounds like a clocking hen until the heatertype tubes get at this point. Then elevate the warm enough to function.This sounds like incipient motor- mounting the socket baseboard sufficiently to permit boating, and while it disappears about the time when the on bottom of the baseboard, so that the pro- socket prong holesare accessible through the 1" opening. The gram starts to become audible, some visitors commented on the filament and plate wiring of preliminary knocking sound, and I should like to do somethingthe top of the baseboard throughthe rectifier can be broughtto to avert their criticisms.-M. L. B. ply by bringing the wires holes specially drilled,or sim- This condition results primarily from the fact thatyour audio around the back of the baseboard. circuit is capable of good low -note reproduction, and to the high * *' value of voltage actually applied to the plates of the heater tubes IF THE WATTAGE is known, during theheaters' warming -upprocess. The preliminary F. O'B. is the current known?-C. motorboating is not a vice, since it disappears before the pro- No. The wattage is the productof the current and the volt- gram begins to be audible.This proves the interference's re- age.Infinite combinations of lationship to the proper functioning of the tube.As the plate the same wattage. current and voltage would produce current begins to flow at near its normal value, the voltage drop Often, however, when the wattage isstated the current is known becausethe voltage is known fromex- in the plate loads increases proportionately, and reduces the perience, reputation,or other disclosure.Thus a 25 -watt lamp effective voltage on the plates commensurately.This increase draws 208 ampere, since the voltageat which the wattage rat- in current flow also reduces the voltage at the B plus terminals ing was established is imprintedon the glass, with the wattage, of the eliminator, on the basis of the regulation of the rectifier thus : 25 watts, 120 volts. Thetest voltage of 120 is used because tube and its associated circuit.The heavier natural drain pulls thisis the highest voltage usuallyobtained in practice froni the voltage down. The only remedy would be heater tubes of AC or DC lines ratedat 110 volts.However, with radio de- instantaneous action, but none such tubes exist. vices, other than tubes, thewattage gives no clue to the current, * * because the current dependson the voltage, and nobody knows WHEN IS A GROUND an aerial? My set works well when what voltage will be used, and therange of useful voltages is the aerial is left off, the ground connected to theantenna post large. of the receiver, and nothing connected to the ground. I should *** say it works as well that way as if the aerial were used in the OUR BABY is just beginningto walk. What type of cabinet accustomed place and the ground in its regular position. Howor console would you suggest that would be immune come?-J. J. K. attacks by said infant during the three from all A self -grounding effect is produced by the A battery and B-L. G. trying years to come? batteries,ifused, or by the power transformer in AC sets. A cabinet or console of such perfect Thus when seemingly nothingisconnected tothe groundattacks by an infant futile is impossiblesecurity as to render all post, B minus, which isself -grounded, actually isconnected armor -plating. of attainment except by there, so that an external ground lead, especially if rather long, This from one who knows. may be at a higher radio frequency potential than the self - ** *- ground. In that instance you simply havean antenna, one end IS IT NECESSARY touse a large coupling condenser between of which goes to external ground, the other end to the set.the plate of a tube and the grid ofthe next tube in a resist- Hence you have aerial and ground.But an outdoor aerial,ance -coupled audio amplifier ?-S. M. connected to the antenna post, anda short ground lead from That depends on whatyou conSider large. The product of a cold water pipe or a radiator, with all connections securelythe grid leak and the grid condenser,where the capacity is in made, will give better results.Compare stations that come inmicrofarads and the resistance in megohms,should be at least weakly, rather than strong ones, since on loud stations itis .02.Therefore with a high value of grid leakthe capacity may sometimes hard for the ear to tell there is any volume difference be less than otherwise.Thus the condensed may be .02 mfd. at all, though that difference may be nearly 50 per cent. How- if the leak is1 meg. or more.The condenser that you mis- ever, use any method that you, think works your set best. takenly refer to as a coupling condenser doesnot couple one * ** tube to the next, but is simplya stopping condenser used for IS A COIL of wire an inductance?-T. M. keeping the positive plate voltage off the grid ofthe succeeding No.That is a popular definition, but not a scientific one.tube, which grid must be maintained negative.For a detailed A coil is no more an inductance than a steam engine is a puffdiscussion of this entire topic see the secondinstalment of of steam or a pistol is a bullet.All wire, coiled or straight or"PowerAmplifiers,"publishedintheJune8thissueof twisted, has inductance.Inductance is more compactly obtained RADIO WORLD, page 13, column 1. June 22, 1929 RADIO WORLD 15 IS IT BETTER to incorporate the coils and the condensers in separate shields in building a shielded receiver, or should one use a large can and place all the parts in it?I notice that in several descriptions of shielded receivers, the front por- tions of the can are left off.Wouldn't it be better to place them on?Must the cans be grounded?If so, does it matter whether the plus A or the minus A is also brought to the ground?-M. A. The separate shields should be used for best results.Using a common shield does only one thing, and that is to prevent the coils from acting as miniature antennas, thus making the set a bit more selective.There is no shielding unless the can is complete.If the front is left off the shielding may as well be omitted.Ground the shields. A minus is the usual connec- tion to the shields in battery sets. ** * MY SUPER -HETERODYNE is extremely selective yet it does not' cut all interference.It heterodynes with certain stations. What can I do to remedy this condition?The receiver was built of the very best parts throughout but still I do not like the quality.The signals are muffled and throaty. What is the reason?-A. D. The cause of the interference is lack of selectivity in the radio frequency level.Another tuner and radio frequency amplifier C2 will remedy this condition. The cause of the muffled or throaty FIG. 763 signalsistoo great selectivity in the intermediate frequencyHOW THE CAPACITY EFFECT OF THE GRID AND PLATE filter. ELEMENTS OF A TUBE IS BALANCED OUT. C2 AT TOP * ** NEUTRALIZESClAT BOTTOM,C2 AT BOTTOM IS THERE ANY ADVANTAGE in using an output filter con-NEUTRALIZES Cl AT TOP.THE OUTPUT IS RESIST- sisting of a choke and a condenser over an output transformer? What should be the inductance of the choke coil and the ca- ANCE -COUPLED, A NOVELTY IN PUSH-PULL. pacity of the condenser in an output filter?What should theif this is accomplished that the effect that even a small capacity ration of the transformer be if this method of output is em-may have upon frequency response would be nullified.This ployed ?-S. W. small capacity, due to the height of the amplification, must Each method has advantages over the other but perhaps the have an attenuating effect upon the higher frequencies, par- choke and condenser method hag the more.Thereisless ticularlyifthe load isresistive.Is there not some way of danger of saturating the core, the inductance used can be larger,taking the output from a detector through resistors for push- and itis possible to shunt the AC component of the output pull input to the first audio stage, and can not a commensurate around the B voltage source.The inductance of the choke push-pull resistance coupled output be obtained from the first used across the speaker should be about 100 henrys when work- audio ?-A. B. L. ing with normal plate current in its winding.Good results will The capacity effect between the grid and plate exists, as you be obtained even if the inductance is as low as 35 under thesay, and it may be balanced out by the introduction of neutraliz- same conditions.The condenser should have a capacity of at ing condensers.See Fig. 763. The two neutralizing condensers least 4 mfd.The type of transformer depends on the type ofare C2, each connected from plate of one tube to grid of the tube and on the type of speaker. The primary impedance should other.The inter -electrode capacityisshown by the small be somewhat larger than the impedance of the tube and thesymbols, both marked Cl.Therefore lower C2 balances out secondary impedance should be the same as the impedance of the capacity of upper Cl, and the others the same. The diagram the speaker.Often that means a ratio of 1 -to -1. also shows a resistance coupled push-pull output, where the *** plate load is an electrically center -tapped resistor of a total WHY DO CERTAIN transformer manufacturers recommend resistance of about 200,000 to 300,000 ohms. The electrical center the use of a low ratio transformer next to the detector and- amust be accurately established, and itisadvisable to use a somewhat higher ratio in the amplifier stage when the rule has potentiometer with a movable arm to B plus, so that differences long been just the opposite.Is there any advantage in the in the plate resistances of the two tubes may be compensated. newer method 'and is it worth while to switch the transformers The isolating condensers must be equal also.There is no way around in my old set?-J. L. of satisfactorily taking the output of a detector through push- The detector has a higher impedance than the amplifier tube, pull resistance coupling, as the circuit works one-sidedly, that hence the transformer coupled to the detector should have a is, the other side is inactive. A coil is necessary, and a push- higher impedance.The lower ratio transformer has a higher pull output transformer may be used, as shown in the diagram. impedance.The newer method gives a little better ,amplifica- tion on the low notes. * * * WHY DOES the resistance of a coil increase with frequency? Join I understand that the resistance of a wire is directly propor- tional to its length and inversely and proportional to its cross- Radio World's section.Don't these remain the same as the frequency varies?. -D. M. There are two reasons why the resistance of a coil goes up with the frequency.The first is that the effective area of the cross-section of the wire does not remain the same as the NIIVERSIITY CIL13 frequency is increased, but decreases rapidly.The second is And Get Free Question and Answer Service for the Coming that at the higher frequencies there are greater losses due to 52 Weeks.This Service for Yearly Subscribers Only eddy currents in surrounding metal bodies, as well as greater dielectric losses.The decrease in the effective area is known Subscribe for RADIO WORLD for one year (52 numbers). as the skin effect.The current travels in a thin layer on the Use the coupon below. Your name will be entered on our sub- surface of the wire and the higher the frequency the thinner scription and University Club lists by special number. When the layer in which current flows.The increase in radio fre- sending questions, put this number on the outside of the for- quency resistance with frequency, that is the skin effect, depends warding envelope (not the enclosed return envelope) and also on the conductivity of the wire, on the diameter and on the put it at the head of your queries.If already a subscriber. permeability of the material of which the wire is made.For send $6 for renewal from close of present subscription and magnetic metals of high permeability such as iron the skin your name will be entered in Radio University. effectis very large.Even for comparatively low frequencies the current travels on the surface to such an extent that theNO OTHER PREMIUM GIVEN WITH THIS OFFER resistance of the wire is several times the direct current resis- [In sending in your queries to the University Department please tance. For fine wires the skin effect is not nearly so pronounced as for heavy wires.It is for this reason that radio frequencyparagraph and number them.Write on one side of sheet only. conductors are frequently stranded, that is, made of a large Always give your University Club Number.] number of very fine wires.The foregoing applies to resistanceRADIO WORLD, 145 West 45th Street, New York City. to radio frequencies.The direct current resistance is propor- Enclosed find 46.00 for RADIO WORLD for one year (52 nos.) tional to the length of the wire.Do not confuse the AC and and also enter my name on the list of members of RADIO DC resistances. WORLD'S UNIVERSITY CLUB, which gives me free answers * * * to radio queries for 52 ensuing weeks, and send me my number SEVERAL QUESTIONS REGARDING PUSH-PULL have indicating membership. been puzzling me and therefore I ask you kindly to answer them.First, there is the capacity effect'between the grid and Name plate of a tube, and if two tubes are used in push-pull this capacity must be present to an added extent.As this capacity Street may be one reason for unbalance sometimes encountered in City and State push-pull circuits, I am wondering whether there is not some way of counteracting this effect directly?It seems to me that If renewing subscription, put cross here. 16 RADIO WORLD June 22, 1929 Harry Buchman, 817 Court. Scranton. Pa. Harold Palladino, 2923 No. Stillman, Phila, Pa. Vern G. Mathiesen,P.0. Box 604,Lindsay, Calif. G. C. Broun, Box 2, Leechburg, Pa. E. F. Woodrow, 8 St. Angle St., Quebec City, Edward F.Berry, 3009 Golden Ave., Bronx, Que.. Can. N. Y. City. Alex Gyorfi, 4 Hollywood St., New Brunswick, Literature Wanted R. White, 193 Geenesee Ave., Paterson, N. J. W. S.Perry, 1638 W. Louden St., Phila., Pa- N. J. J. C. Cushman, 905 Randolph, Neosho, Mo. M. R. Galvin, 20 Harding Rd.. Buffalo. N. Y. THE names and addresses of read- Boston Music House, Brilliant, Ala. G. D. Mohundoo, 230 N. Market St., Shawnee, ers of RADIO WORLD who Radio Engineering & equipmentCo.,E.E. Okla. desireliterature on parts and sets Erickson, Pres., 420 Manufacturers Exch., Kansas Joel Lucyn, 2734 Lawrence Ave., Chicago,Ill. from radio City, Mo. Louis Fowler, 8119 Ingleside Ave., Chicago, Ill. manufacturers, jobbers, L. M. Jenkins, 3508 CaliforniaSt., San Fran- Chas. C. Flynn, 16190 Wark Ave., Detroit, Mich. dealers and mail order houses are cisco, Calif. Robert W. Marks, 132 Charles St., New York published in RADIO WORLD on re- Thos. C. Ellis, Cedar Grove, No. Car, City. quest of the reader. W. G. Strabala, Lohrville, Ia. A. J.Alger, 449 Corbett Ave., San Francisco, The blank at J. W. Keifer,Jr., Bostwick. Nebr. Calif. bottom may be used. or a post card Andor Gazdah, Main St., Expedit, Pa. L. W. Mateyka, 608 Thomas St.. Edwardsville, or letter will do instead. Virgil E. Lewis, 792 Commercial Ave., El Cen- Ill. tro,Calif. Chas. Coombs, Jr., 14 Gilman St., Holyoke, Mass. RobertPeres, 245 Wanaque D. L. Boak, 533 Cora St., Wilkinsburg, Pa. RADIO WORLD, Lakes, N. J. Ave.,Pompton T. W. Bossung, 1265 Preston St., Louisville, Ky. 145 West 45th St., N. Y. atY Chas, F. Tomas, Jr., 2715S. Komensky Ave., Carl Lindgren, 62 Front St., Fargo. N. Dak. I desire to receive radio literature. Chicago, F.X. Mackasey,124 BarringtonSt.,Halifax, The Radio Window Cleaning Co., 200 East 72nd N. S., Can. St., New York City. Charles A.Schehl,4200 Hartford Ave..Balti- Name T. E. Jordan, 3434 Birdie Ave., St. Louis, Mo. more, Md. F. W. Stroehle, 2112 32nd St., Rock Island, Ill. M. G. Gossard, 8077 Beverly Blvd., Los Angeles, Address H. L. Wilson, 415 Sixth Ave., St. Charles, Ill. Calif. 0. A. Welling, 625 No. Orlando Ave.. Los An- Baker & StevensRadio Service,301 3rdSt., geles,Calif. Braddock, Pa. City or town R.J.Thatcher,Serv.Mgr.,407 W. School Clark -Warner. Box 160,Glenside, Pa. Lane, Germantown, Penna Harrison P. White, 450 High St., Newark, N. J. State Enrico Peck, Via Nicola Piccinni No. 5, Milano P. W. Richards, 1409 No. Felton St., Phila. Pa. 132, Italy N. Crews, 7609 Champlain Ave.. Chicago, Ill. J. Geo. Burton, 3915 61st St., Huntington Park, Charles Harvey, 2915 West St.. Wilmington. Del. Calif. C. Ramsay, 650 Main St., New Rochelle. N. Y. Overland Radio Service,2513Woodson Road, Harry L.Williams. Jr.,Gen'lDel'y., Blooms- H.Koskiuen,144-03123dAve..South Ozone Overland, Mo. burg, Pa. Park, L. I. W. M. Smith, R. No.4,Frankfort, N. Y. Charles E. McGrew, 416 N. Maple, Newkirk, R. W. Walton, Lake & High Rock Ayes., Sara. Okla. G. T. Burch, 3710 Ridgecroft Rd., Gardenville, toga Spgs., N. Y. Chas. H. Hager, Box 193. New Butler. Wis. Baltimore, Md. W. G. Amdur, 47 W. 63rd St., N. Y. City. Frank P. Surdyk, 838 Pearl St., Milwaukee, Wis. J. W. Hanlon, 24 Darina Pl., Milford, Conn. Henry D. Byseit, 14831 Rockdale Ave., Detroit, A. Skeiner,14 Dean St.. Toronto No.2,Ont., Otto Lee, Burns. Tenn. Mich. Can. Horace M. Duncan, 731 Moro St., Manhattan, E. E. Gilcrease, 5357-A Union Ave., St. Louis, S. Jacobs. 2118 76th St.. Brooklyn, N, Y. Kans. Mo. H.C.Bidinger,17917 Lumkin Ave.,Detroit, E. R. Hoover, 1110 Maryland Ave., S. W.. Can- Norman H. Kutz, 117 So, 10th St., Allentown, Mich. ton, Ohio. Pa. John C. Hagan. Cairo, Ill. F. W. McKenney, Box 79. Haverhill, Mass. Julio C. Montaluo, Box 664, Mayaguez, Puerto Francis J. Holland, 520 3rd Ave., Brooklyn, N. Y. H. P. Covington, 1315 N. Calvert St., Baltimore, Rico. Harry Haskell, 10823 Magnolia Drive. Cleveland, Md. E. C. Appeller, 3839 Lafayette Blvd., Detroit, Ohio. New England Stock Co., Box 79, Haverhill, Mass. Mich. Roy P. Norton, 1317 Dolores St., San Francisco, Al. Gill, Seaview Hospital, Staten Island, N. Y. Louis C.Stark,57 Home Ave., Terre Haute, Calif. Frank C. Bayer, 9 So. Geo. St.. York, Pa. Ind. James Nash, 8022 Normal Ave.. Chicago, Ill. Del Gillespie, 2049 E. Clearfield St., Phila, Pa. Anthony Tubbiolo, 7 MadelineAve.,Clifton. R. Dawson. 1926 Highland Ave.. Detroit. Mich. R. G. Floyd, Jr.,Sabina], Texas. NAJ. . Hunter, "The Radio Nut," Box 63,Prosperity, Kenneth Breen, 126 CharlesSt.,Painted Post, N. Y. W. Seidler, 217 Bridge St., Berea, Ohio. So. Car. Jas.G.Burton, 3915E.61stSt.,Maywood, L. F. Heller, 40 No. Dearborn, 2nd Floor, Chi- W. G. Burdick, 624 Academy St., Watertown, Calif. cago,Ill. N. Y. A. A. Busby, Goodsprings, Ala. S. Kittle, 1321 N.W. 27th St.. Miami, Fla. William Ryan, 744 Franklin Ave., Brooklyn, N. E. M. Gerstenfeld, 350 Stone Ave., Brooklyn, W. L. Rutledge, Elkport, Iowa. Y. N. Y. Ray Schroder, Box 453, Chelsea. Mich. M. Geo. Hassar, 4405 Ashland Ave.,Detroit, DonaldB.Ocamb,5326 BondSt., H. F. Brockman, 18425 So. Morris Ave., Home- Mich. Calif. Oakland, wood, Ill. Henry H. Graef, 3110 N. Damen Ave.. Chicago, N. V. Hardy, 209 Akron Savings & LoanBldg., Acorn Radio & ElectricCo.,482416thAve., Ill. Akron, Ohio. Brooklyn. N. Y. G. W. Neill, 25 Howard St.. Newark. N. J. Emil F. Gaspard, 459 E.115thSt.,Cleveland, Atlee W. Vance, 948 Fallon St., Phila, Pa. William H. Shuey, Box 218, Oak Point,Ill. Ohio. R. B. Carmody. 121 Julian St., Providence, R. I. D. Heath, 21 No. Dewhurst Blvd., Toronto, Ont., H. G. Osburn, 418 E. Oliver St., Owosso, Mich. S. Patrette. 240 No. 15th St.. San Jose, Calif. Can. Joseph Willis Co., 443 Third Ave., Kingston, Pa. George L. Klingler, 6349 Gifford Ave.. Bell, Calif. George Neuschafer, P. 0. Box 5, Kerrville, Texas. L. T. McCampbell, 847 Ransom St., S. Thomas Fisher,12210 RoselawnSt.,Detroit, Alex C. Ruble, Chapel Hill, N. C. lanta,Ga. W., At- Mich. C. E. Coon, 123 Laurel Ave., Binghamton, N. Y. Henry Ouillette, Box 222, JewettCity, Conn. A. Prestwood. 557 110th St.. Whiting, Ind. J. M. Morgan. Madisonville. La. Frank H. Fredericks, R. R. 3, Box 9 G, Racine, A. Helming, 109 Pape St.. San Francisco, Calif. A. Bartolomei, 315 Orange Rd.. Montclair. N. J. Wis. R.E. Brown, Box 713,Bellows Falls,Vt. Geo. A. Plinske, 1108 Hamilton St., Manitowoc, IraWinbigler,OrmsbyatSt.Joseph,Mt. John Hamilton, 29 Pear St.. Palmyra, N.J Wis. - Clemens, Mich. August H. Hoffman, 2207 Grand Ave.. Butte, John Lamhofer, 834 Brown's Ave., Erie, Pa. F. Linden Thaler, 820 E. 175th St., N. Y.City. Mont. L. W. Bale, 1168 E. 114th St., Cleveland. Ohio. Hoke Brown, 504 Likley St., Waycross, Ga. Mat. Spooner, Jr.. 511 1st St., Albany, N. Y. Arthur N. Etz, P. 0. Box 126, Santa Monica, Roy C. Letno, 707 Jefferson St., N. E., Charley Schmidt, 2820 Lafayette. St. Louis. Mo. Calif. apolis, Minn. Minne- A. C. McClure, 640 S. 39th St., Louisville, Ky. Geo. C. Fultz, 3038 Prospect Ave.. Kansas City, L. B. Shaughnessy, 5079 UnderwoodAve., De- Mo. L. G. Smith, 3601 No. Miami Ave., Miami, Fla. troit,Mich. Oscar E. Malech, 323 Woolsey St., San Fran- G. S. Lawrence, Hillsdale, Okla. H. Vinson (manufacturets only), cisco,Calif. Theo. W. Epfeld, 1115 Flushing Rd..Flint, Mich. Moo. Carrollton, H. M. Sutterfield, Iowa Park, Texas. Raymond D. Sherman, 5 Hubbard St., Saratoga W. F. Lambert, Temple, Ga. M. George Hassar, 4405 Ashland Ave., Detroit, Springs, N. Y. M. R.Mantelman, Mich. J. P. Nelson, 2325 Chester Ave., Cleveland, Ohio. N. Y. 185374thSt.,Brooklyn. James W. Burns, 2113 E. Lombard St.,Balti Russell Crosby, 12166 Broadstreet, Detroit, Mich. Ed. Morris, 610 Baker St., Lansing, more, Md. Julian J. Schaefer. 81 Linden St., Brooklyn, N. Y. W. H. Couch, 108 Shelton Ave.. NewMich. Clark Radio Shop, Gastonville, Pa. Geo. E. Ingalls, 1729 Melrose Ave., Seattle, Wash. Conn. Has en, A. E. Albrecht, 633 W. 52d St., Phila., Pa. North Side Auto & Machine Co., Louis Geissler, G.F. Roberts, 4707 Glenshade Ave. Wayne Storch, Radio Service, Beecher.Ill. 1146 South Side Ave., N. S.. Pittsburgh, Pa. ville), Cincinnati, Ohio. (Madison- H. A. Sterling, 1107 Third Ave., New York, N. Y. W. A. West, care Dept. of Works and Mines, Crescent Radio Shop, 5048 Eagle Robt. E. Wilson, 1812 3rd Ave., N.. Birmingham, Halifax, N. S. Eagle Rock, Calif. Rock Blvd., Ala. Frank Winfrey, 2010 St. Aubin, Detroit. Mich. Abraham Tietler, F. M. Wilson. 8006 Loomis St., Chicago. Ill. Chas. F. King, Box 54, Rachel, W. Va. N. Y. 442LorimerSt.,Brooklyn, J.J. Cronin, care Hotel Statler, Park Square, JosephB.Alloway,6426 NorwoodSt.,Gtn., Tom W. Searle, Cascade, Mont. Boston, Mass. Phila.,Pa. R. V. Glaudel, 2226 Scott St., C. Fred Vollmer, P. 0. Box 175, Bucyrus, Ohio. Linred L.Sterling,25 Noe St.,Apt.2,San J. C. Elder, 4931 N. Rorer St.,Davenport, Phila., Iowa, Hyman Koltman, 514 Williams Ave., Brooklyn, Francisco.Calif. A. C. Hall, 275 Rutledge St., Pa. N. Y. Victor Rocco, 174 W. Parmenter St., Newburgh, H. Cramer, Brooklyn, N. Y. W. G. Barlow, Pittsville, Md. N. Y. 12 Boyden Ave.,Beverly, Mass. F. E. Delk, 932 Park Ave.,Manning, Iowa. G.M. Wright.45S.FranklinAve.,Valley P. W. Wright,1404 Maryland Ave.,Steuben- Geo.Maxwell, Watrous, Stream, N. Y. ville, Ohio. T. F. Hall, Laceyville, Pa.Pa. F. E. Titus, Box 126, Middleport, Ohio. A. S. Connor, 1127 Harford Ave.. Baltimore, Md. Marvin Storm, 411 E. Dayton O. H. Pedersen, 1132 N. Mayfield Ave., Chicago, H. A. Allen, Brookston, Ind. Ind. St., South Bend, Eli Goldberg. 386 Penna. Ave.. Brooklyn. N. Y. J. A. Bradley, Box 722, Cobourg, Ont., Can. Otto Heuer. 279 Linden St., Brooklyn, N. Y. Earl Milla, R. No.2,Boise, Idaho. E. M. LeFevre, 11 Beech St.. Nutley, N. J. W. B. Bradshaw, 223 Conn. Ave., New London. C. C. Irvin, 710 S. Vermont,Royal Oak, Mich. L. E. G. Suiter,1003 Franklin Ave.. Wilkins - P. B. Lovegren, 7846 EuclidAve., Chicago, Ill. burg, Pa. Conn. A. W. Looking, 2nd & Penn, G. A. Zeltvay, 134-20 Grand St., Ozone Park, Britz, c/o Journal of Commerce,Greensburg, Pa. William H. Shuey, Box 218. Oak Park. Ill. N. Y. bia St., 83 Colum- W. Wallace Wyllie,Corning,Calif. Dr. Ashton B. Heyl, N. W. Cor. Madison Rd. Seattle, Wash. Ira B. Valentine, Box 22, Sq. HillSta., Pitts- and Wold Ave., Cincinnati, Ohio. J. G. Franklin, 954 Belmont Ave.,Phila., Pa. burgh, Pa. H. B. Hallenback, 136 Cascadilla Park,'Ithaca. C. Goggin,171 Maple St.,Bangor, Me. Martin johanesen, 330 W 95th St., N. Y. City. N. Y. Wm. C. Edwards, P. 0. Box106, Powell River, H.B.Krause, 699 Hudson Ave., West New R. E. Wansor. The Valley Radio & Elec. Lab- B. C., Can. York, N. J. oratory, Locust Valley, L. I. M. A. Murphy, Box 310, Leesburg,Fla. Geo. A. Clark, 434 So, Grand Ave.. Los Angeles, Cyril Forry. Remington, Ind. F. E, Leeger, Freeport, Pa. Calif. James D. Huckaby, 1810 Madison Ave., Mont- K. Gott, c/o Sneible-TavernettiCo., Gonzales. H. Barker. 1711 30th Ave.. West, Seattle, Wash. gomery, Ala. Calif. R. A. Willis, 128 Ely St..Alma. Mich.. Frank Strasser. Soldiers' Home, Lafayette, Ind. H. W. Batty, 88 Oak, Battle Creek,Mich. W. C. Thompson, Cor. Mills & Baldy Roads, Elmer E. Bretthauer, Box 105, KAW Station, J. A. Koutnik, 2837 So.St. Louis Ave., Chi- Claremont.Calif. cago, Ill. Kansas City, Kans. F. E. Drake, 8739 Point Ave., Niagara W. M. Simpson, 1315 Second Ave.. Rockford, Ill. Harry Briggs,13706Glenside Rd.,Cleveland, N. Y. Falls, Chas. D. Freeman. West Hickory. N. C. Ohio. H. R. Shelden, 2509 GarfieldAve., Bay City, G. C. Watson. P. 0. Box 301, Americus, Ga. Edwin Bodner, 3906 So. 3rd St.,Louisville, Ky. Mich. Edw. Roth, 1736 fraud St., Los Angeles, Calif. Sam'l Watkinson, Schodack Landing,N. Y. Henry Fox, 37 Thomas St., Newark,N. J. June 22, 1929 RADIO WORLD 17

NEW STATIONS Dill Asks Census LABOR STATION Include Receivers Washington. ARE REGARDED Senator Dill, of the State of Washing- GOES TO COURT ton, has promulgated a bill to have the number and class of radio sets counted inconjunction with the1930 personal census.Opposition to the measure de- AS HINDRANCEveloped in the House. FOR FULL TIME Washington. Washington. Improvement in radio reception, which The Chicago Federation of Labor, op- has resulted fromthereallocationof erating WCFL, at Chicago, as the organ- broadcasting facilities effected November izedlaborbroadcastingstation,has 11th, shouldnotbejeoparded by theSTORMS BRING petitioned the Court of Appeals of the licensing of addi- District of Columbia to reverse the de- tionalbroadcast- cision of the Federal Radio Commission ingstationsand denying ita cleared channel and full- further .crowding LOUD SIGNALStime operation with 50,000 watts power. of the broadcast The petition,filed by E. M. Nockels, band, William D. Washington. secretary, and Hope Thompson, attorney, L. Starbuck, The Bureau of Standards of the De-contended that the' Commission's decision Radio Commis-partment of Commerce made the follow-was contrary to the law, against public sioner, said. ing announcement : interest, convenience and necessity, and Calling atten- "A study of the variation in long -wavecontrary to the evidence in the record. tiontothein- daylight signal intensity observed at the Seeks Wider Scope creasingnumberlaboratory for special radio transmission of applicants fromresearch at the Bureau of Standards, at The petition sets forth that the station all sections of theWashington, and of the disturbances inis operated in the interests of the entire country forper-terrestrial magnetism, reveals a markedmembership 6f organized labor. The im- mission to oper-increaseinthe intensityof long -waveproved assignmentisdesired,itisas- atestations,hesignals following severe magnetic storms.serted, to permit the promulgation of the W. D. L. Starbuck saidthat the "In the case of long distance reception"policies, principles and ideals of the Fed- broadcast bandisovercrowded. Therefrom European stations, there is a gen- eration." are now more than 600 stations on theeral tendency for the signal intensity to "The Federal Radio Commission, by air. be below normal for several days beforeits decision, denies to this vast body of "It is a fact, in spite of the overcrowd-the maximum of the magnetic disturb-citizens any adequatefacilitiesinthis ing of broadcasting stations which nowance, and to show a definiteincreasegreat new field of communication, partly exists, that the listening public is enjoying from one to three days after the passageon the theory that radio should not be better reception than was possible beforeof the storm. used for propaganda purposes, and partly, the allocation of November, 1928. "Observations taken on stations at mod-no doubt, for other reasons to be assigned "The Commission desires to maintain erate distances, i.e., the Radio Corpora-by the Commission,"thepetition sets this condition and to improve 'it, and totion stations at Tuckahoe and New Bruns- forth. "In so denying one single frequency this end does not encourage the estab-wick, N. J., and Rocky Point, L. I., giveto organized labortheFederal Radio lishment of new stations.It is not be- Commission, inits lieved that new stations contribute to asomewhat different results. While the in- decision, disregarded tensity of signal from these stationsis the public interest,necessity and con- condition of good reception but ratherhigh from two to four days after the venienceindenying theappellant the that they are detrimental in greatly in-storm, as in the case of the distant sta-means and opportunity to render this ser- creasing interference and reducing the vice." service area of existing stations." tions, there is also a decided increase in signal strength from two to four days Wants 770 kc Exclusively before the magnetic disturbance." The station now op'erates on the 970- Inventor Sues Over kilocycle channel with 1,500 watts in day- light hours only. It sought assignment on Majestic's "B" DesignRichmond is Elected the 770 -kilocycle channel, now occupied by KFAB, Lincoln, Nebr., and WBBH, Chicago. President of R. M. A.Chicago, Ill., with unrestricted hours of Suit has been brought against Hartman operation and the maximum power of Furniture & Carpet Company in Dan- Chicago. 50,000 watts. ville, 'Illinois,forthe H. B. Richmond, treasurer of General saleof Majestic Radio Corporation, has been elected presi- Officials of the American Federation of radio sets made by Grigsby Grunow Com- Labor, includingitspresident, William pany, of Chicago, for alleged infringe-dent of the Radio Manufacturers Asso- Green, appeared in favor of the WCFL ment of three patents of Philip E. Edel-ciation, succeeding Herbert H. Frost, who served three terms. Major Frost is a vice- application at hearings held by the Com- man. One patent relatestoa voltagepresident of mission last April. divider for use in B eliminator packs. Kolster. A sterlingsilver The Chicago Federationalsosought Another covers the use of two choke coils plaque was presented to the Major as atwo or more short-wave channels to be whose fields are set so as to buck eachtoken of esteem. employed in rebroadcasting programs of other for the elimination of hum from the T. K. Webster, Jr., president of theWCFL throughoUt the United States and circuit. The third covers an arrangementEkko Company, was elected treasurer. to foreign countries. of rectifier and filter circuits with a regu- Mr. Richmond is the first president to lator for compensating for the voltagecome fromtheengineering profession. drop as the output current is increased.He is a graduate of Massachusetts Insti- These are said to be controlling patentstute of Technology. U. S. Offers Afternoon covering the use of AC power packs for Although he joined the ranks of Gen- radio sets. eral Radio Company as engineer- in 1919 Programs to Europe Edelman is the author of several booksmost of hisactivities have been along on radio, the first of which was copy- administrative lines.He is a member of Schenectady, N. Y. righted in 1912.His attorneys are Ban-the Institute of Radio Engineers and of To provide Europeans with an Ameri- ning & Banning. the American Institute of Electrical En-can radio program at a convenient hour, gineers. At M. I. T. he was president ofWGY's short-wave station W2XAF has the Electrical Engineering Society, one of inaugurated a series of afternoon broad- the student branches, and vice-presidentcasts on two different frequencies: These Pilot Corporate Name of the Radio Society. programs alsoafford engineersofthe Mr. Richmond is an expert rifleman. British Broadcasting Company an oppor- Undergoesa ChangeDuring his first year at college he wontunity to carry on experiments in 'recep- the freshman rifle -shot medal. tion and rebroadcasting of trans -Atlantic The name of the Pilot. Electric Manu- programs. facturing Company has been changed to The afternoon scheduleof W2XAF, thePilot Radio & TubeCorporation. NEW 60 -STATION CHAIN effective at once, follows: Sunday, 2:30 The organization will continue to func- A. coast -to -coast chain of sixty stations to 5 :30 p. m., 15,340 kilocycles ; Monday, tion as before, no changes in either, man-is planned by the American Broadcasting 2:00 to 4:00p.m., 13,660kilocycles ; agement or policy being contemplated. . Company of Seattle, Wash.. The com-Tuesday, 2:00 to 3:00 p. m., 15,340 kilo- The officers of the corporation are Isi-pany plans to add New York and Wash-cycles; Thursday, 2:00to4:00p.m., dor Goldberg, president ;Henri Sadacca,ington (D. C.) stations to the chain and 13,660 kilocycles ;Friday,2 :00to 3:00 vice-president,and James I. Benjamin,have the sixty stations in operation within p. m., 15,340 kilocycles.All time refer- secretary and treasurer. a year. ences are Eastern Daylight Saving Time. 18 RADIO WORLD June 22, 1929 Compact Condenser NEW WARNING New Flechtheim ItemHOTEL HAS NEW

ON TRANSFERS GUEST TUNERS Washington. A new system fordistributingradio The Federal Radio Commission held a programs to individual rooms inhotels, hearing on the application of the Clarke hospitals,apartment houses andstate- Electrical Company, of Danville, Va., for rooms on ships was announced recently permission toestablishabroadcasting and demonstrated in the Hotel Lincoln, station in that city. New York City, where the system is now Thomas F.Little,of Newport News, NON-INDUCTIVE in operation. owner of WGH in that city, had entered FILTER At present the system comprises six re- into an agreement with the Clarke Com- Con denser, ceivers of conventional design located in pany to transfer the WGH station license the "studio room" on the 29th floor of the for $2,700 payment for station equipment. CapacityMid hotel.Each of these receivers is tuned Ira E. Robinson, Commission chairman, Working Voltage, to a different station, and all receivers declared that under the law astation are operated from the same antenna on license may not be transferred by the 1000V DC the roof of the hotel.The six receivers licensee without authority of the Com- are battery -operated and are completely mission. shielded except for their connection to the "Thelawspecificallyprohibitsthe ACTUAL SIZE ILLUSTRATION OF common antenna. transfer ofa stationlicense from one NEW 1 MFD. CONDENSER, 1,000 The output of these receivers is carried partytoanother without authorityof VOLTS DC, 750 VOLTS AC TEST to the transmission room on the floor be- this Commission," he said."When this low, where a monitor operator issta- Commission granted youthisvaluable A. M. Flechtheim & Co., Inc., of 136 tioned.The function of this operator is franchise it was for your use as a trusteeLiberty Street, New York City, announces to listen in and to select the programs of the public, and when you decided thata high voltage condenser of small physi-and to control the volume and modula- you had no further use for the licensecal size. "We have succeeded in makingtion of the transmitted signals. it must revert back to the Commission.a 1,000 volt DC continuous working con- In the transmission room are six mina- It is not within your province to allocatedenser in a metal container 2" high, 11/8" ture transmitters which receive the sig- stationsandwavelengthsinVirginia. wide and deep, considerably less than nals from the six receivers.The oscilla- That is one of the problems before theone -quarter of the size of present stand-tors for these transmitters operate at dif- Commission." ards for a 1 mfd. 1,000 volt condenser," ferentfrequenciesfromthoseofthe Mr. Little voluntarily relinquished hissaid Leon L. Adelman, chief engineer. carriersof the signals selected.When license to WGH after examination by the "This new unit is wound in non -induc-the signals have been impressedon the Commission. He explained he had madetive manner, and had an accuracy ofnew frequencies they are impressed on a practice of leasing or selling stationscapacity within 5% plus or minus of rat-the steel framework of the building. but that he now proposes to operate one ing.Ithas a power factor appreciably Receivers located in the rooms can be station himself. less than 1%.It has an insulation resist-tuned in to any one of the six programs ance of more than 600 megohms perby a simple switching arrangement.No microfarad and its breakdown voltage isantenna isusedforthe individualre- three times its safe rating of 1,000 voltsceivers because all that is necessary is to Engineer Tours U. S. DC (750 rms AC)." connect a single wire to the radiator in the room, or to any other metal which is to Study Reception in electrical contact with the framework W2XCL Is Licensed of the building. Schenectady, N. Y. The entire system is carefully shielded K. B. Hoffman, maintenance engineer of so that the signals on the new frequencies WGY, began a national survey of the for Television Tests do not get outside the building. United States to ascertain facts concern- W2XCL, 323 Berry Street, Brooklyn, The new distributing system was in- ing average reception of WGY and theN. Y., operating since March 27th under vented by Dr. F. L. R. Satterlee, long a other General Electric Company stationsa construction permit issued by the Fed-prominent figure in the X-ray and radio KGO, of Oakland, Calif., and KOA, of eral Radio Commission, has been licensed fields ;Louis Kalozsy, a Hungarian engi- Denver, Colo., since November 11th, 1928, as an experimental visual broadcastingneer and inventor, and Samuel Saltzman, when the reallocationorderedbythe station to transmit in the 2,000-2,100 kilo-chief electrician for the Chanin Theatres Federal Radio Commission was put into cyclechannel(142.9-150meters).The Corporation. effect. Pilot Radio & Tube Corporation owns Mr. Hoffman travels in a car especiallythe installation. equipped with radio.His western route Televisionbroadcasting ona regularWEBC Asks Court takes him through Chicago, Denver andschedule will begin soon from W2XCL, Salt Lake City to San Francisco, and onsaid James I. Benjamin, treasurer. A new To Grant Full Time his return he will travel by slow stagessystem of disc scanning andasimple Washington. throughLosAngeles,Phoenix,Fort methodofmaintainingsynchronization The Head -of -the -LakesBroadcasting Worth, New Orleans and Montgomery. will be used. Co., Inc., operating WEBC, at Superior, The investigation willdeal more espe- Wis., filed with the Court of Appeals' of cially with reception in small cities, vil- NEW RESISTANCE FOLDER the District of Columbia a petition for lages and in rural sections which have no A new folder on resistance in radio,review of the Federal Radio Commis- local station from which to get radio en-ranging from an adjustable grid -leak of sion's decision denying it full-timeopera- tertainment. 1/10 to10 megohms toa super -power tion. Mr. Hoffman will invite listeners, radiovariable resistor of 250 watt rating, has The notice of appeal states that the editors and radio dealers to fill out ques-just been issued by the Clarostat Manu-station was denied its application for full- tionnaires. The radio survey car in whichfacturing Company, Inc., 291 North Sixthtime operation on the 1,280 kilocycle chan- Mr. Hoffmanis makinghistouris Street, Brooklyn, N. Y. A copy will benel, which it now shares with WDAY, at equipped with a long wave and a shortsent to any interested person upon re-Fargo, N. D.The Commission's finding wave receiver and a loudspeaker. quest. Mention RADIO WORLD. that the publicinterest would not be served by granting the application "is not SCHNELL IS GENERAL MANAGER supported by the testimony before the Home Talkies Planned Lieut. Commander F. H. Schnell has Commission," the petition contends. been made general managerofAero Products,Inc.,Chicago.James Barnes, NAMES N. Y. REPRESENTATIVE With Radio Receiverformerly of Thordarson Mfg.Co.,has The Automatic Radio Manufacturing The Vision Tone Sales Company, ofjoined Aero Products as radio engineer. Co., of Boston, Mass., manufacturers of Texas, with headquarters at Dallas, an- Tom Thumb Portable Radio,announces nounces a new invention combining a A THOUGHT FOR THE WEEK the appointment of the Friedman -Snyder radio, a phonograph and a motion picture ACERTAIN announcer in a Mid -West Co., 15 Park Place, New York City,as its machine, with records and films synchron- broadcasting station has one of thoserepresentatives in the Metropolitanarea. ized tocreatetalking picturesinthe soft voices that occasionally go off into a home. diminuendo that threatens at times to reach GRIMES JOINS PILOT Films with synchronized records will be the point of disappearance.Surely in these David Grimes, radio inventor, has been rented at 10 cents a night on the circu- days it would not be nice to refer to himappointed chief research engineer of the lating lifirary plan. Pilot Radio & Tube Corporation, I. Gold- as a speakeasy, would it, nowt berg, president of the firm,announced. June 22, 1929 RADIO WORLD 19 List of Stations by Frequency With Wavelength Conversion [REVISED AND CORRECTED FROM THE RECORDS OF THE FEDERAL RADIO COMMISSION, TO NOON, JUNE 12TH] Canadian shared WMC-Memphis, Tenn. KNX-Los Angeles, Calif.WEBS -Cambridge, Ohio WRBI-Tifton, Ga. s* Canadian exclusive KELW-Burbank, Calif. S -Hollywood, Calif. WBAX.Wilkes-Barre, Pa. WSAJ-Grove City, Pa. WBBC-Brooklyn, N. Y. S -Studio KTM-Santa Monica,Cal. 1060 KC, 282.8 METERS WJBU-Lewisburg, Pa. WBRE-Wilkes-Barre, Pa. Kw0cmCWA--Cchuhrrickeas, ha, Okla. 550 KC1 545.1 METERS S -Los Angeles, Calif.WBAL-Glen Morris, Md. WTAZ-Riclumxtd, Va. WMBL-Lakeland, Fla. WEAN -Providence, R.I. 790 KC, 379.5 METERS S -Baltimore,Md. WMBG-Richmond, Va. WKBC-Birmingham, Ala. IM. WGR-Buffalo, N. Y. WGY-Schenectady, N. Y.WTIC-Hartford, Conn. WSIX-Springfield, Tenn. KGHG-McGehee, Ark. W14K101)KF-c.Ind2imaneapiotliirraitss, WEAO-Columbus, 0. KGO-Oakland, Calif. WJAG-Norfolk,Nebr. WRBU-Gastonia, N. C. WOBT-Union City, Tenn. cinttoray, mIdialajek. WKRC-Cincinnati, 0. 800 KC, 374.8 METERSKWJJ-Portland, Ore. WJBY-Gadsden, Ala. WNBJ-Knoxville, Tenn. KFUO-Clayton, Mo. WBAP-Ft. Forth, Tex. 1070 KC, 280.2 METERS WMBR-Tampa, Fla. KRMD-Shreveport,La. KGRS-Amarillo, 'Tex. S -St.Louis, Mo. KTHS-Hot Springs Nat'lWAAT-Jersey City,N.J. WRBQ-Greenville, Miss. KTSL-Cedar Grove, La. WDAG-Amarillo, Tex. KSD-St. Louis, Mo. Park, Ark. WTAM-Cleveland, Ohio WGCM-Gulfport, Miss. S -Shreveport,La. Kr LV-Rockford, 113. KFDY-Brookings, S. D. 810 KC 370.2 METERSWEAR -Cleveland, Ohio KWEA-Shreveport, La. KFPM-Greenville, Tex. WHBL-Sheboygan, Wis. KFYR-Mismark, N.D. WPCH-Hoboken, N. J. WCAZ-Carthage, Ill. KDLR-Devils Lake, N. D. WDAH-El Paso, Tex. WSGP-Savannah, Ga. KTAB-Oakland,Calif. S -New York, N. Y. WDZ-Tuscola, Ill. KGCR-Watertown, S. D.KGFI-Corpus Christi, Tex. 560 KC, 535.4 METERSWCCO-Anoka, Minn. KJBS-San Francisco KFOR-Lincoln,Neb. KFPL-Dublin, Tex. KC, 211.1 METERS WDGY-Minneapolis, Minn. S -Minneapolis. 1080 KC, 277.6 METERS WHBU-Anderson, Ind. KFXR-Okla. City, Okla. WHDL-Tupper Lake, N.Y. WHDI-Minneapolis, Minn. 820 KC 365.6 METERSWBT-Charlotte, N. C. KFVS-CapeGirardeau, WKBS-Galesburg,Ill. WHIS-Bluefield, W. Va. WIOD-Miami, Fla. WHAS-Jeffersontown, Ky.WCBD-Zion, III. Mo. WEIIS-Evanston,Ill. WLBH-Patchogue, N. Y. WLIT-Philadelphia S -Louisville, Ky. WMBI-Chicago, Ill. WEBQ-Harrisburg,Ill. WCLS-Joliet, Ill. WMRJ-jamasca, N Y. WEI-Philadelphia 830 KC, 361.2 METERS 1090 KC, 257.1 METERSWSBC-Chicago, 111. WKBB-Joliet, Ill. WLEY-Lexuagton, Mass. KFDM-Beaumont, Tex. WHDH-Gloucester, Mass.KMOX-KFOA-Kirkwood WCRW-Chicago, Ill. WKBI-Chicago,Ill. WTBO-Cumberland, Md. WNOX-Knoxville, Tenn. KOA-Denver, Colo. S -St.Louis, Mo. WEDC-Chicago, Ill. WHFC-Cicero, Ill. WSSH-Boston, Mass. WOI-Ames, Iowa **840 KC, 356.9 METERS 1100 KC, 272.6 METERS WCBS-Springfield,Ill. KWCR-Cedar Rapids, Ia.WPOE-Patchogue, N. Y. KFEQ-St. Joseph, Mo. 850 KC, 352.7 METERSWPG-Atlantic City, N.J. WTA,X-Streator,Ill. KFJY-Ft. Dodge, Ia. WIBR-Steubenville, 0. KOAC-Corvallis, Ore. KWKH-Kestrionwood, La.WLWL-Kearny, N.j, WHBF-Rock Island,Ill.KFGQ-Boone, Ia. WILM-Wilmington, Del. RL7-Dupont, Colo. WWL-New Orleans, La. S -New York, N. Y.WIBA-Madison, Wis. WBOW-Terre Haute, Ind. WEDH-Erie, Pa. 570 KC, 526 METERS 860 KC, 348.6 METERSKGDM-Stockton,Calif. WOMT-Manitowoo, Wis. WJAK-Marion, Ind. WMBC-Detroit, Mich. WNYC-New York, N. Y.WABC-WBOQ-N. Y. City1110 KC, 270.1 METERS KPQ-Seattle, Wash. WLBC-Muncie, Ind. WKBP-Battle Creek, Mich WMCA-Hoboken, N. J. KFQZ-Hollywood, Calif. WRVA-Richmond, Va. KPCB-Seattle, Wash. WIBU-Poynette,WQBZ-Weirton Wis.W., Va. S -New York, N. Y. 070 KC, 344.6 METERSKSOO-Sioux Falls, S. D.1220 KC, 245.8 METERS KFBK-Sacramento,Calif.KGFF-Alva, Okla. WSYR-Syracuser N. Y. WLS-Crete, Ill. *1120 KC, 287.7 METERS WCAD-Canton, N. Y. KGEZ-Kalispell, Mont. KTAP-San Antonio, Tex WMAC-Cazenovia, N. Y. S -Chicago, WDEL-Wilmington, Del. WCAE-Pittsburgh, Pa. KFUP-Denver, Colo. KTUE-Houston, Tex. WS11K-Dayton, O. WENR-WBOIN-Chicago WCOA-Pensacola, Fla. WREN-Lawrenoe, Kan. KFXJ-Edgewater, Colo. KFYO-AbileneTex. WKBN-Youngstown, 0. *880 KC, 340.7 METERSWTAW-College Sta., TeX. KFKU-Lawrence, Kan. KMED-Medford, Ore. KICK -Red Oats,Iowa WWNC-AshevilleN. C. WQAN- anton,Pa. KUT-Austin, Tex. 1230 KC, 243.8 METERS WJDZ-Winston. Salem, N.WIAS-Ottumwa, Iowa KGKO-WichitaFalls, Tex. WGBI-Scranton, Pa. WISN-Milwankee, Wis. WNAC-Boston C. WLBF-Kansas City, Kan. WNAX-Yankton, S. D. WC0C-Colnmbus, Miss. WHAD-Milwaukee, Wis. WBIS-Boston 1320 KC, 272.1 METERS WMBH-lionlin, Mo. WPCC-Chicago, IL KLX-Oakland, Calif. KFSG-Los Angeles,Calif. WPSC-StateCollege,Pa. WADC-Akron, Ohio kriz-F-onadvellisatas LaNc. ob. WIBO-Desplaines, Ill. KPOF-Denver, Colo. KRSC-Seattle, Wash. WSBT-South Bend, Ind.WSMB-New Orleans, La. S -Chicago,Ill. KFKA-Greeley, Colo. 1130 KC, 285.3 METERS WFBM-Indianapolis,Ind. KGIO-Idaho Falls, Idaho KFXY-Flagstaff, Ariz.WJJD-Mooseheart, KUOM-MissoulaMont. "890 KC, 330.9 METERS Ill. KYA-San Francumo, Calif. KGIQ-Twin FallsIdaho KGFJ-LQU-oa Angeles,Calif. KXA-Seattle,Wash. WJAR-Providence,R.I.WOV-Secaucus, N.J. KFIO-Spokane Wash. KGHF-Pueblo, Colo. KF HolyCitya Calif. KMTR-Hollywood, Cal. WKAQ-San Juan, P. R. S -New York, N. Y. KFQD-Anchorlge,Alaska KID -IdahoFalls,Idaho KG GC-San Franctsoa. *580 KC, 516.9 METERS WMMN-Fairmont, W. Va.KSL-Salt Lake City, Utah.1240 KC, 241.8 METERS 1330 KC, 225.4 METERS KFXD-Jercane,Idaho WTAG-Worcester, Mass. WMAZ-Macon, Ga. 1140 KC, 263METERS WGHP-Fraser, Mich. WDRC-New Haven, Conn.KGIW-TrinidadColo. WOBU-Charleston, W. Va. WGST-Atlanta, Ga. WAPI-Birmingham, Ala. S -Detroit, Mich. WSAI-Harrison, Ohio KGCX-Vida, M WSAZ-Huntington, W. Va. KGJF-Little Rock, Ark KV00-Tulsa, Okla. KTAT-Ft. Worth, Tex. S -Cincinnati KFIF-Portland,Ore. KGFX-Pierre, S. D. WILL -Urbana;Ill. 1150 KC, 260.7 METERS WJAD-Waco, Tex. WTAQ-Washington, Wis.KORK-Eugene, One. KSAC-Manhattan, Kans. KUSD-Vermillion, S. D. WHAM -Victor Township WQA11-Miami,. Fla. S -Eau Claire, Wis. KFQW-Seattle, Wash. WSUI-Iowa City, Iowa KFNF-Shenandoah, Iowa S -Rochester, N. Y. VVRBC-Valparaiso, Ind. KSCJ-Sioux City, Iowa KX_RO-Abardeea, Wash. 590 KC 508.2 METERS 900 KC, 131.1 METERS 1160 KC, 258.5 METERS 1250 KC, 239.9 METERS 1340 KC, 223.7 METERS wurRLIC: WEEI-N.Weymouth, Mass. WFBL-Syracuse, N. Y. WWVA-Wheeling, W. Va. WGCP-Newark, N.J. WSPD-Toledo, Ohio C'llaTchas7 MEter,TfIRS.R. WEMC-BerrienSpgs.,Mich. WMAK-Martinsville, N. Y.WOWO-Ft. Wayne, Ind. WODA-Paterson,N.J.KFPW-Siloam Springs, wWHPIt.Harlarrirsisburbarg,g,Dl.. WCAJ-Lincoln, Nebr. S -Buffalo, N. Y. 1170 KC, 256.3 METERS WAAM-Newark, N. J. Ark. Pa. WOW -Omaha, Nebr. WRY -Okla. City, Okla. WCAU-Byberry, Pa. WLB-WGMS-Minneapolis K110 -Tacoma, Wash. WCAH-Columbus, Ohio KHQ-Spokane, Wash. WFLA-WSUN- S -Philadelphia, Pa. WRFIM-Fridley, Minn. 1350 KC, 221.1 METERS WGBC-Memphis, Testa. *600 KC, 499.7 METERS Clearwater, Fla. KTNT-Muscatine, Iowa KFMX-Northfield, Minn. WBNY-New York, N. Y. WNBR-Memphis, Tens. WTIC-Hartford, Conn. WLBL-Stevens Point, Wis.KEJK-Beverly Hills, Calif. WCAL-Northfield, Minn. WMSG-New York, N. Y.1440 KC, 208.2 METERS WCAC-Storrs,Conn KHJ-Los Angeles, Calif. 1180 KC, 254.1 METERS KFOX-Long Beach,Calif. WCDA-New York, N. Y.WHEC-W.ABO- WCAO-Baltimore, Md. KS22-Pocatello, Idaho WDGY-Minneapolis, Minn. KXL-PortlandOre. WKBQ-New York, N. Y. Rochester, N. Y. WREC-Whitehaven, Tenn. KGBU-Ketchikan, AlaskaWHDI-Minneapolis, Minn. KILO -Boise, Idaho KWK-St. Louis, 11o. WOXO-Mt. Beacon N. Y WOAN-Lawrenceburg,Tenn **Ste KC, 329.5 METERSWGBS-Astoria, L.I. 1260 KC, 238METERS 1360 KC, 220.4 METERS S-Poughkeeail;' 16.Y. WEBW-Beloit, Wis. 920 KC, 325.9 METERS S -New York City. WLBW-Oil Qty,, Pa. WLEX-Lexington, Mass. WCBA-Allentown, KFSD-San DiegoCalif. WWJ-Detroit, Mich. KE.X-Portland,Ore. WJAX-Jacksonville,Fla. WIIAMFalso.uthDartmouth, WSAN-.Allentown,Pa. KWYO-Laramie, Wyo. KPRC-Houston, Tex. KOB-State College, N. M. KVOA-Tucson, Ariz. VVNRC-Greensboro, N. C. 610 KC, 491.5 METERS WAAF-Chicago,Ill. 1190 KC, 252METERS KWWG-Brownsville, Tex. WQBC-Utica, Miss. . WFAN-Philadelphia KOMO-Seattle, Wash. WICC-Easton, Conn. KRGV-Harlingen, Tex. WJKS-Gary, Ind. WMBD-Peoria Eta., Ill. WIP-Philadelphia *930 KC, 322.4 METERS S -Bridgeport, Coml. KOIL-Council Bluffs,Ia.WGES-Chicago, Ill. KLS-Oakland, Calif. WDAF-Kansas City, Mo. WIBG-Elkins Park, Pa. WOAI-San Antonio, Tex. 1270 KC, 236.1 METERS KFBB-Great Falls, Mont. WOQ-Kansas City, Mo. WDBJ-Roanoke Va. *1200 KC, 249.9 METERS WJDX-Jackson, Miss. KGIR-Butte, Mont. 149015.4.-,,-- 2062 METERS KFRC-San Francisco WBRC-Birrniniiiam, Ala.WABI-Bangor, Maine. WEAI-Ithaca, N. Y. KGB -San Diego, Calif. WBMS-Fort Lee. N. J. 620 KC, 483.6 METERS KGBZ-York, ebr. WNBX-Springfield, Vt. WFBR-Baltimore, Md. 1370 KC, 218.8 METERS WNJ-Newark N WLBZ-Bangor, Maine KMA-Shenandoth, Iowa WEPS-Gloucester, Mass. WASH -Grand Rapids, WMBO-Auburn, N. Y. ing lizabeth WDBO-Orlando, Fla. KFWM-Oakland, Calif. WKBE-Webster, Mass. Mich. WSVS-Buffalo, N. Y. is?..J. WDAE-Tampa, Fla. KFWI-San Francisco WIBX-Utica, N.Y. WOOD-Furnwood,Mich. WCBM-Baltimore, Md. WSAR-Fall River, Mass. WJAY-Cleveland, 0. 940 KC, 319.0 METERSKGW-Stockton, Calif. S -Grand Rapids, Mich. WBBL-Richmond, Va. WFJC-Akron, Ohio WTMJ-Brookfield, Wis. WCSH-Portland, Maine WHBC-Canton, Ohio. WDSU-New Orleans, La.WHBD.Bellefacitaine, O. KTBS-Shreveport, La. . KGW-Portland, Ore. WFIW-Hopkinsville,Ky.WLAP-Louisville, Ky. KWLC-Decorah, Iowa WHDF-Calumet, Mich. WTFI-Toccoa, Ga. KFAD-Phoenix,Ariz. WHA-Madison, Wis. WLBG-Ettrick, Va. KGCA-Decorah, Iowa WJBK-Ypsilanti, Mich. 1460 KC, 205.4 METERS *630 KC, 475.9 METERS KOIN-Sylvan, Ore.W WNBO-Washington, Pa. KTW-Seattle, Wash. WJDW-Emory, Va. WJSV-Mt. Vernon, Va. WMAL-ashington, D. C.- S -Portland, Ore. WPRC-Harrisburg, Pa. KOL-Seattle, Wash. VnBM-Jackson, Mich. KSTP-Westeott, WW1. WOS-Jefferson City, Mo.KGU-Honolulu, T. H. WK C-LanCaster,Pa. KFUM-Colo. Springs, Col. WRAK-Erie, Pa. Minn.TR.S KFRU-Columbia, Mo. KFEL-Denver, Colo. WNBW-Carbondale, Pa. 1280 KC,234.2 METERSWELK-Philadelphia. 1470SK-C,St.zop4allIME, WGBF-Evansville, Ind. KFXF-Denver, Cobb. WABZ-New Orleans, La. WCAM-Camden, N. J. W BO -New Orleans,La.WKBW-Amherst, X Y 640 KC, 468.5 METERS 950 KC, 315.6 METERSWJBW-New Orleans, La. WCAP-Asbury Park, N.J. W BQ-Menaphis, Tenn. S -Buffalo, N. Y. WAIU-Columbus, 0. WRC-Washington, D. C.WBBY-Charleston,S.C.WOAX-Trenton, N.J. WRBT-Wilmington, N. C. KFJF-Okla. City,Okla. KFI-Los Angeles, Calif. KMBC-Independence, Mo.WBBZ-Ponca City,Okla. WDOD-Chattanooga, Term. KGFG-Okla. City, Okla. WRUF-Gainesville, Fla. 090 KC, 461.3 METERS WHB-Kansas Qty, Mo. WFBC-Knoxville, Tenn. WRR-Dallas, Tex. K148GA0 -IcSoco.kan2027.. WSM-Nashville, Tenn. KFWB-Hollywood, Calif. WRBL-Cloltnbust,Ga. WDAY-Fargo, N. D. KGCI-SanKCRC- Antal;Tex. 660 KC, 454.3 METERS KPSN-Pasadena, Calif. KGCU-Mandan, N. D. WEBC-Superior, Wis. KGRC-San Antonio, Tex. WEAF-Bellmore, N. Y. KGHL-Billings, Mont. WJBC-LaSalle,Ill. S -Duluth, Minn. KFJZ-Ft. Worth, Tex. WJAZ-Mt. Prospect. Ill. S -New York City "960 KC, 312.3 METERSWJBL-Decatur,Ill. 1290 KC, 232.4 METERSKGKL-San Angelo, Tex. S -Chicago, 11.1.- WAAW-Omahs. Nebr. 970 KC, 309.1 METERSWWAE-Hammond, Ind. WNBZ-Saranac Lake, KFLX-Galveston, Tex. WSOA-Deerfield,saticago. inI1.1. 670 KC, 447.5 METERS WCFL-Chicago, EL WRAF -Laporte, Ind. N. Y. WFBJ-Collegeville, Minn. WMAQ-Addison,Ill. KJR-Seattle, Wash. WMT-Waterloo, Iowa WJAS-Pittsbnrgh,Pa. WGL-Ft. Wayne, Ind. WORD -Batavia,Ill. S -Chicago, Ill. 980 KC, 305.9 METERSKFJB-Marshalltown, Iowa KTSA-San Antonio, Tex.KGDA-Dell Rapids,S. D. ss.-Covington, 080 KC, 440.0 METERS KDKA-Wilkins Township.WCAT-Rapid City,S.D, KFUL-Galveston, Tex. KFJM-Grand Forks, N. D.WCKY-Villa Madonna Ky n WPTF-Raleigh, N. C. S -Pittsburgh,Pa. KGDY-Oldham, S.D. KLCN-Blytheville, Ark. KWKC-Kansas City, Mo. ; KPO-San Francisco 990 KC, 302.8 METERSWIL-St. Louis, Mo. KDYL-Salt Lake City KGBX-St. Joseph, Mo. 11v4B9OAKwC,-Nrahvi,2012 ME.TTEenR.S.. "090 KC, 434.5 METERS WBZ-E. Springfield, Mass.KFWF-St. Louis, Mo. 1300 KC, 230.6 METERSWRJN-Racine, Wis. 700 KC, 428.3 METERS S -Boston, Mass. KFKZ-Kirksville,Mo. WBBR-Rossville, N.Y. KGAR-Tucson, Ariz. WLAC-Nashyllle, Tenn. WLVV-Mason, Ohio WBZA-Boston, Mass. KGDE-Fergguus Falls, Minn. WHAP-Carlstadt N.J. KIT -Yakima, Wash. KPWF-Westminster, Calif. 710 KC, 422.3 METERS 1000 KC, 299.8 METERSKGFK-Hal oek, - Minn. S -New York, N. Y.KOH-Reno, Nev. 1560 KC, 1999. METERS WOR-Kearny, N.J. WHO -Des MoinesIowa WCLO-Xenosha, Wis. WEVD-Woodhaven, N. Y. KZM-Hayward, Calif. WMBA-Newport, R.I. S -Newark, N. J. WOC-Davenport, Iowa WHBY-West DePere, Wis. S -New York, N. Y.KRE-Berkeley,Calif. WL0E-Chelsea. Mass. KFVD-Culver City,Calif.KPLA-Los Angeles, Calif.KFWC-Ontario, Calif. WHAZ-Troy, N. Y. KGER-Long Bead.,Calif. wWNMBBnESF:Biosittonha,mtMon:Mass. 720 KC, 413 METERS *1010 KC, 296.9 METERS S -Pomona, Calif. KFH-Wichita, Kan. KLO-Ogden, Utah Y, WGN-WLIB-Elgin, Ill. WQAO-WPAP- KPPC-Pasadena,Calif. WIBW-Topeka, Kan. KOOS-Marshfield, Ore. S-Chicago, Ill. WMBQ-Brooklyn, N. Y. CliffsideN.J. KX0-E1 Centro,Calif. KGEF-Los Angeles KFBL-Everett, Wash. wWLcIBBX.-LoneL. I. Qty, N.. Y: Y. C: **730 KC, 413 METERS S -New 'York, N. Y.KMJ-Fresno,Calif. KTBI-Los Angeles KVL-Seattle, Wash. 740 KC 4052 METERS WHN-New York, N. Y. KSMR-Santa Maria, Calif. KFJR-Portland, Ore. KFJI-Astoria,Ore. WWRL-Woodside, N. Y. WSB-Atlanta, Ga. WRNY-Coytesville, N. J.KGEK-Yuma, Colo. KTBR-Portland, Ore. KGFL-Raton, N. M. WAFD-Detroit. Mich. KMMJ-Clay Center, Nebr. S -New York, N. Y.KGEW-Ft. Morgan, Colo.1310 KC, 228.3 METERSKGGM-Albuquerque, N.M. WKBZ-Ludington, Mich, 750 KC, 399.8 METERS KGGF-Picher, Okla. KFHA-Gunnison, Colo. WKAV-Laconia, N. H. 1380 KC, 217.3 METERS WMPC-Lapeer, Mich. WJR-Silver Lake, Mich. WNAD-Norman, Okla. KVOS-Bellingham, Wash. WEBR-Buffalo, N. Y. WCSO-Springfield, Ohio. VV-MBJ-rittilsbukinsrbgtz Pag,P.a. S -Detroit, Mich. KQW-San Jose,Calif. KGY-Lacey, Wash. WNBH-New Bedford, KQV-Pittsburgh, Pa. 760 KC, 394.5 METERS 1020 KC, 293.9 METERS*1210 KC, 247.8 METERS KSO-Clarinda,Ia. WOPI-BristolTenn. WJZ-Boundbrook,N.J.VVRAX-Philadelphia. WJBI-Red Bank, N. 3. WOL-Washington, D. C.WKBH-LaCrosse, Wis. WPSW-Philadelphia. S -New York, N. Y. KYW-KFKX-Chicago. WGBB-Freeport, N. Y. WGH-Newport News, Va.1300 KC, 215.7 METERS KGIH-Little Rock, Ark. WEW-St. Louis, Mo. KYWA-Chicago. WINR-Bayshore, N. Y. WRK-Hamilton, Ohio WHK-Cleveland, 0. WRBJ-HattiesburgMiss. KVI-Des Moines, Wash. **1030 KC, 291.2 METERSWCOH-Greenville, N. Y. WAGM-Royal Oak, Mich. KLRA-Little Rock, Ark. KGKB-Brownwood; Tex. S -Tacoma 1040 KC, 238.3 METERS S -Yonkers, N. Y. WFDF-Flint, Mich. KOY-Phoenix, Ariz. KGDR-San Antonio, TV....x. 770 KC" 389.4 METERS 'WKEN-Grand Island, N.Y.WOCL-jamestown, N. Y.WNAT-Philadelphia, Pa. KUOA-Fayetteville, Ark. KGHX-Richmond, Tea. KFAB-Lincoln, Nebr. S -Buffalo, N. Y. WLCI-Ithaca, N. Y. WFKD-Frankford,, Pa. BOW -Denver, Colo. WKBV-Brook-ville, Ind. WBBM-WJBT-Glenview, WKAR-E. Lansing, Mich.WPAW-Pawtucket, R. I. S -Philadelphia. KWSC-Pullman, Wash. KPJM-Prescott, Ariz. S -Chicago, Ill. WFAA-Dallas, Tex. WDWF-WLSI- WHBP-Johnstown, Pa. KFPY-Spokane, Wash. KWBS-Portland, Ore. *780 KC, 384.4 METERS KRLD-Dallas, Tex. Cranston, R. I. WFBG-Altoona, Pa. 1400 KC, 214.2 METERS KVVTC-Santa Ana, Calif. WBSO-VVellesley, Mass. 1050 KC, 285.5 METERSWMAN-Columbus, Ohio WRAW-Reading, Pa. WCGI.J-Coney Isl., N. Y.KDB-Santa Barbara, Calif. WTA.R-WPOR-Norfolk, Va. KFKB-Milford, Kans. WJW-Mansfield, Ohio WGAL-Lancaster, Pa. WSGH-WSDA-Bklyn, N Y KUJ-Long View, Wash. 20 RADIO WORLD June 22, 1929 Alphabetical List of Stations by CallLetters; Location and Frequency [FROM FEDERAL RADIO COMMISSION LIST REVISED UP TONOON, JUNE 12TH] Station Location FrequencyStation Location Frequency Station Location FrequencyStation Location WAAF-Chicago, Ill.,920 FrequencyStation Location Frequency WGCP-Newark, N. J., 1250 WMAF-Dartmouth, Mass., 1360WTAM-Cleveland, O.1070 KGHL-Billings, Mont., 950 WAAM-Newark, N. J.,1250 WGES-Chicago, Ill.,1360 WMAK-Buffalo, N. Y., 900 WTAQ-Eau Claire, Wis., 1330KGHX-Richmond, Tex., 1500 WAAT-Jersey City, 1070 WGH-Newport News, Va., 1310 WMAL-Washington, D.C., 630WTAR-WPOR-Norflk, Va., 780KGIQ-Twin Falls, Idaho, 1320 WAAW-Omaha, Nebr., 660 WGHP-Detroit, Mich., 1240 WMAN-Columbus Ohio, 1210 WTAW-College Station, 1120 KGIR-Butte, Mont., 1360 WABC-WBOQ-N.Y. City, 860WGL-Ft. Wayne, Ind., 1370 WMAQ-Chicago, 'Ill.,670 WABI-Bangor, Me., 1200 WTAX-Streator,Ill.,1210 KGIW-Trinidad, Colo.. 1420 WGMS-See WLB-WGMS WMAZ-Macon, Ga., 890 WTBO-Cumberland, Md., 1420KGIX-Las Vegas,Nev., WABZ-New Orleans, La., 1200WGN-WLIB-Elgin, Ill.,720 WMBA-Newport, R.I.,1500 1420 WADC-Akron, 0., 1320 WGR-Buffalo, N. N., 550 WTFI-Toccoa, Ga., 1450 KGJF-Little Rock, Ark., 890 WAFD-Detroit, Mich., 1500 WMBC-Detroit, Mich, 1420 WTIC-Hartford, Ct.,600,1060KGKB-Brownwood, Tex., 1500 WGST-Atlanta, Ga., 890 WMBD-Peoria Hts.,Ill.,1440 WTMJ-Milwaukee, Wis., 620 KGKL-San Angelo, Tex., 1370 WAGM-Royal Oak, Mich., 1310WGY-Schenectady, N.Y., 790 WMBG-Richmond, Va., 1210 WWAE-Hammond, Ind., 1200 WAIU-Columbus, 0., 640 WHA-Madison, Wis., 940 WMBH-Joplin, Mo., 1420 WWJ-Detroit, Mich., 920 KGKO-Wichita, Falls, Tex 570 WAPI-Birmingham, Ala., 1140WHAD-Milwaukee, Wis., 1120 KGKX-San Point, Idaho, 1420 WMBI-Addison, Ill.,1080 WWL-New Orleans, La., 850 KGO-Oakland, Calif.,790 WASH-Gd. Rapids, Mich., 1270WHAM-Rochester, N. Y., 1150 WMBJ-Pittsburgh, Pa., 1500 WWNC-Asheville, N. C., 570 KGRC-San Antonio, Tex., 1370 WBAK-Harrisburg, Da., 1430 WHAP-N. Y. City,1300 WMBL-Lakeland, Fla.,1310. WWRL-Woodside, N.Y., 1500KGRS-Amarillo, Tex., WBAL-Baltimore, Md., 1060 WHAS-Louisville, Ky.,820 WMBO-Auburn, N. Y., 1370 1410 WBAP-Fort Worth, Tex., 800WHAZ-Troy, N. Y., 1300 WWVA-Wheeling, W.Va., 1160KGU-Honolulu, Hawaii, 940 WMBQ-Brooklyn, N. Y., 1500KCRC-Enid, Okla., 1370 KGW-Portland, Ore.,620 WBAW-Nashville, Tenn., 1490WHB-Kansas City, Mo., 950 WMBR-Tampa, Fla., 1210 KDB-Santa Barbara, Cal.,1500KGY-Lacey, Wash., 1200 WBAX-Wilkes-Barre, Pa., 1210WHBC-Canton, Ohio,1200 WMC-Memphis, Tenn., 570 KDKA-Pittsburgh, Pa., 980 KHJ-Los Angeles, Calif., 900 WBBC-Brooklyn, N. Y., 1400 WHBD-Bellefontaine, 0., 1370WMCA-New York, N.Y., 570 KDLR-Devils Lake, N.D., 1210KHQ-Spokane, Wash., 590 WBBL-Richmond, Va.,1370 WHBF-Rock Island, Ill.,1210 WMES-Boston, Mass., 1500 KDYI,-Salt Lake, Utah, 1290 KICK-Red Oak, Iowa, 1420 WBBM-WJBT-Chicago, Ill., 770WHBL-Sheboygan, Wis., 1410WMMN-Fairmont, W. Va., 890KEJK-Beverly Mils, Calif., 1170KID-Idaho Falls, Idaho, 1320 WBBR-Rossville, N. Y., 1300 WHBP-Johnstown, Pa., 1310 WMPC-Lapeer, Mich., 1500 KELW-Burhank, Calif., 780 KIDO-Boise, Idaho, 1250 WBBY-Charleston, S. C., 1200WHBQ-Memphis, Tenn., 1370WMRJ-Jamaica, N. Y. 1420 WBBZ-Ponca City, Okla., 1200 KEX-Portland, Ore., 1180 KIT-Yakima, Wash., 1370 WHBU-Anderson, Ind., 1210 W7&SG-New York, N. Y., 1350KFAB-Lincoln, Nebr., 770 KIBS-San Francisco, Cal., 1070 WBCM-Bay City, Mich., 1410 WHBW-Philadelphia, Pa.,1500 WMT-Waterloo, Iowa, 1200 KFAD-Phoenix, Ariz., 620 WBIS-See WNAC WHBY-W. De Pere, Wis., 1200 WNAC-WI3LS-Boston, KJR-Seattle, Wash, 970 WBMS-Fort, Lee., N. J., 1450 1230 KFBB-Great Falls, Mont., 1360KLCN-Blytheville, Ark., 1290 WHDF-Calumet, Mich., 1370 WNAD-Norman, Okla., 1010 KFBK-Sacramento, Calif.,1310KLO-Ogden, Utah, 1370 WBNY-New York, N. Y., 1359WHDH-Gloucester, Mass., 830 WNAT-Philadelphia,Pa.,1310KFBL-Everett, Wash., 1370 KLRA-Little Rock, Ark., WBOQ-See WABC WHDI-Minneapolis, Minn. 1180 WNAX-Yankton, S. D.570 1390 WBOW-Terre Haute, Ind., 1310 KFDM-Beaumont, Tex., 560 KLS-Oakland,Calif.,1440 W1HDL-Tupper Lake, N.Y.,1420 WNBF-Binghamton, N.Y., 1500KFDY-Brookings, S.Dak., 550KLX-Oakland, Calif.,880 WBRC-Birmingham, Ala.,930WHEC-WABO-Rooh'st'r,NY.1440 WNBH-N'w Bedf'rd, Mass.,1310KFEL-Denver, Colo., 940 KLZ-Dupont, Colo., 560 WBRE-Wilkes-Barre,Pa., 1310WHFC-Cicero, Dl., 1310 WNBJ-Knoxville, Tenn., 1310WFEQ-St. Joseph, Mo., 560 KMA-Shenandoah, Iowa, 930 WBRL-Tilton, N. H., 1430 WHIS-Bluefield, W. Va., 1420WNBO-Washington, Pa., 1200KFGQ-Boone, Iowa, 1310 KMBC-Independence, Mo., WBSO-Wellesley H., Mass., 780WHK-Cleveland, Ohio, 1390 WNDR-Memphis, Tenn., 1430 KFH-Wichita, Kans., 1300 950 WBT-Charlotte, N. C., 1080 WHN-New York, N.Y., 1010 KMED-Medford, Ore., 1310 WNBW-Carbondale, Pa., 1200KFHA-Gunnison, Colo., 1200 KMIC-Inglewood, Calif.,1120 WBZ-Springfield, Mass., 990 WHO-Des Moines, Ia., 1000 WNBX-Springfield, Vt., 1200 KFI-Los Angeles, Calif., 640 KMJ-Fresno, Calif., 1200 WBZA-Boston, Mass., 990 WHP-Harrisburg, Pa., 1430 WNBZ-Saranac Lk., N.Y. 1290KFIF-Portland, Ore., 1420 KMMJ-Clay Center, Nebr., 740 WCAC-Storrs, Conn 600 WIAS--Ottumwa, Iowa, 1420 WNJ-Newark, N. J., 1450 KFIO-Spokane, Wash., 1230 WCAD-Canton, N. 'v., 1220 A-Madison, Wis., 1210 WNOX-Knoxville, Tenn., 560 KFIZ-Fond du Lac, Wis., 1420KMO-Tacoma, Wash., 1340 WCAE-Pittsburgh, Pa.,1220 W1BG-Elkins, Park, Pa., 930 KMOX_KFQA-St. Louis, 1090 WNRC-Greensboro, N.C., 1440KF B-Marshalltown, Ia., 1200KMTR-Hollywood,Calif.,570 WCAH-Columbus, Ohio, 1430 WIBM-Jackson, Mich., 1370 WNYC-New York, N.Y., .570 KF F-Okla.., City.,Okla.,1470KNX-Hollywood, Calif., WCAJ-Lincoln, Nebr., 590 WIBO-Chicago, Ill., 570 WOAI-San Antonio, Tex., 1190KF I-Astoria, Ore., 1370 1050 WCAL-Northfield, Minn., 1250WIBR-Steubenville0., 1420 KOA-Denver, Colo., 830 WOAN-Lawrenceburg, Tenn. 600K M-Gd. Forks., N.D., 1370KOAC-Corvallis, Ore.,560 WCAM-Camden, N. J., 1280 WIBS-Elizabeth, I4. J., 1450 WOAX-Trenton, N. J., 1280 KF R-Portland, Ore., 1300 KOB-State College, N.M., WCAO-Baltimore, Md., 600 WIBU-Poynette, Wis., 1310 WOBT-Union City, Tenn., 1310KFJY-Fort Dodge, Iowa, 1310KOCW-Chickasha, Okla.,1180 WCAP-Asbury Pk., N. J., 1280WIBW-Topeka, Kan., 1300 WOBU-Charlestown, W.Va., 580KFJZ-Fort Worth, Tex., 1370KOH-Reno, Nev., 1370 1400 WCAT-Rapid City, N.D., 1200WIBX-Utica, N. Y., 1200 WOG-Davenport, Ia.,1000 KFKA-Greeley, Colo., 880 ROIL-Council Bluffs, WCAU-Philadelphia, Pa., 1170WICC-Bridgeport, Conn., 1190 Ia.,1260 WOCL-Jameatown, N. Y., 1210KF'KB-MiMord, Kans.;1050 KOIN-Portland,Ore.,940 WCAZ-Carthage, Ill.,1070 WIL-St. Louis, Mo., 1200 WODA-Paterson, N. J., 1250 KFKU-Lawrence, Kans., 1220 KOL-Seattle, Wash., 1270 WCBA-Allentown, Pa., 1440 WILL-Urbana, Ill..890 WOI-Ames, Iowa, 560 KFKX-KYW-See KYW WCBD-Zion, Ill., 1080 1420 KOMO-Seattle, Wash, 920 WILM-Wilmington, Del. WOK-WMBB-See WMBB KFKZ-Kirksville, Mo., 1200 KOOS-Marahfield, Ore., 1370 WCBM-Baltimore, Md., 1370 WINR-Bay Shore, N. Y., 1210 WOKO-Poughkeepale, NY., 1440KFLV-Rockford, In.,1410 1210 KORE-Eugene, Ore.,1420 WCBS-Springfield, Ili. WIOD-Miami Beach, Fla., 560WOL-Washmgton, ]i.C., 1310KFLX-Galveston, Tex.,1370 KOY-Phoenix, Ariz., 1390 WCCO-Minneapolis, Minn., 810WIP-Philadelphia, Pa., 610 WOMT-Manitowoc, Wis., 1210 WCDA-Cliffside, Pk., N.J., 1350 KFMX-Northfield, Minn., 1250KPCB-Seattle, Wash., 1210 WISN-Milwaukee, Wis., 1120 WOOD-Gd. Rapids, Mich., 1270KFNF-Shenandoah, Iowa, 890KPJM-Prescott, Ariz.,1500 WCFL-Chicago, Ill., 970 WJAD-Waco, Texas, 1240 WOQ-Kansas City, Mo., 610 KFOR-Linooln, Nebr., 1210 KPLA-Los Angeles, Calif., WCGU-Coney Island, N.Y..1400WJAG-Norfolk, Nebr., 1060 WOR-Newark, N. J., 710 KFOX-Long Beach,Calif, 1250KPO-San Francisco, 1000 1480 W AK-Kokomo, Ind., 1310 Cal, 680 WCKY-Covington, WORD-Chicago, El.,1480 KFPL-Dublin, Tex.1310 KPOF-Denver, 880 WCLB-Lg. Beach, N.Y., 1500 W AR-Providence, R.I., 890 WOS-Jefferson City, Mo., 630KFPM-Greenville, ex.,1310 KPPC-Pasadena, Calif., WCLO-Kenosha, Wis., 1200 WJAS-Pittsburgh, Pa. 1290 WOV-New York, N.Y., 1130KFPW-Siloam Spgs., Ark.,1340 1200 WCLS-Joliet, Ill., 1310 WJAX-Jacksonville, Fla.. 1260 KPQ-Seattle, Wash., 1210 WOW-Omaha, Nebr., 590 KFPY-Spokane, 1390 1CPRC-Houston, Tex. 920 WCMA-Culver, Ind., 1400 WJAY-Cleveland Ohio, 620 WOWO-Ft. Wayne, Ind., 1160 Wash.KMOX KPSN-Pasedena, WCOA-Pensacola, Fla.,1120 WJAZ-Chicago,Ill., 1480 WPAP-WQAO-See WQAO Calif.,950 WCOC-Columbus, Miss., 880 KF D-Anchorage, Alaska, 12.30KPWF-Westminster,Calif.1490 WJBC-La Salle, Ill., 1200 WPAW-P'awtucket, R.I.,1210 KF U-Holy City,Calif.,1420 KOV-Pittsburgh, Pa., 1380 WCOH-Yonkers, N.Y., 1210 WJBI-Red Bank, N. J., 1210 WPCC-Chicago, 570 KFQW-Seattle, Wash., 1420 WCRW-Chicago, Ill.,1210 WJBK-Ypsilanti, Mich., 1370 KQW-San Jose, Calif., 1010 WPCH-New York, N.Y., 810 KFQZ-Hollywood, Calif.,860 KRE-Berkeley, Calif.,1370 WCSH-Portland, Maine, 940 WJBL-Decatur, Ill., 1200 WPG-Atlantic City, N.J.,1100 KFRC-San Francisco, Cal., 610KRGV-Harlingen, Tex., 1260 WCSO-Springfield, 0., 1380 WJBO-New Orleans, La., 1370WPOE-Patchogue, N. Y., 1420KFRU-Columbia, Mo., 630 KRLD-Dallas, Tex., WDAE-Tampa, Fla., 620 WJBU-Lewisburg, Pa. 1210 WPOR-WTAR-See WTAR KFSD--San Diego, Calif., 600 1040 WDAF-Kansas City, Mo., 610WJBW-New Orleans, La., 1200 WPRC-Harrisburg, Pa., 1200 KRMD-Shreveport, La.,1310 WDAG-Amarillo, Tex., 1410 KFSG-Los Angeles,Calif., 1120KRSC-Seattle, Wash., 1120 WJBY-Gadsden, Ala., 1210. WPSC-State College, Pa., 1230KFUL-Galveston, Tex.,1290 KSAC-Manhattan, Kans., 580 WDAH-E1 Paso, Tex., 1310 WJDW-Emory, Va., 1370 WPSW-Philadelphia, Pa., 1500KFUM-Colo. Springs, Col.,1270KSCJ-Sioux City, Ia., 1330 WDAY-W. Fargo, N. D., 1280WJDX-Jackson, Miss.,1270 WPTF-Raleigh, N. C., 680 WDBJ-Roanoke, Va., 930 KFUO-Clayton, Mo., 550 KSD-St. Louis, Mo., 550 WJDZ-W. Salem, N. C., 1310WQAM-Miami, Fla., 1240 KFUP-Denver, Colo.. 1310 K.SEI-Poeatello, Idaho,900 WDBO-Orlando, Fla. 620 WITD-Mooseheart, 111.,1130 WQAN-Scranton, Pa., 880 KFVD-Culver City, Calif., 710 KSL-Salt Lake City, LT., 1130 WDEL-Wilmington,Ind., 1120WYKS-Gary, Ind., 1360 WQAO-WPAP-N.Y.C., 1010 KFVS-Cape Girardeau, 1, o.1210KSMR-Santa Maria, Calif, 1200 WDGY-Minneapolis, Minn., 1180WJR-Detroit, Mich., 750 WQBC-Utica, Miss., 1360 KFWB-Hollywood, 950 WDOD-Chattanooga, Tenn., 1280 Calif., KSO-Clarinda, Iowa, 1380 WTSV-Mt.Vernon HIlls,Va., 1460 WQBZ-Weirton, W.V., 1420 KFWC-S. Pomona, Calif.,1200KSOO-Sioux Falls, S. D., 1110 WDRC-New Haven, Conn.,1330WJW-Mansfield, O., 1210 WRAF-LaPorte, Ind.,1200 WDSU-New Orleans, La., 1870 KFWF-St. Louis, Mo., 1200 KSTP-St. Paul, Minn., 1460 WJZ-New York, N. Y., 760 WRAK-Erie, Pa., 1370 KFWI-San Francisco,Cal., 930KTAB-Oakland,Calif.,550 WDWF-WLSI-Censt'n,R.I.1210WKAQ-San Juan, P. R., 890 WRAW-Reading, Pa., 1310 KFWM-Oakland, Calif., 930 KTAP-San Antonio, Tex., 1420 WDZ-Tuscola, Ill.,1070 WKAR-E. Lansing, Mich., 1040 WRAX-Philadelphia, Pa.,1020KFXD-Jerome, Idaho,1433 KTAT-Ft. Worth, Tex., 1240 WEAF-New York, N.Y., 600 WKAV-Laconia N. H., 1310 WRBC-Valparaiso, Ind., 1240 KFXF-Denver, Colo., 940 WEAL-Ithaca, N. Y., 1270 WKBB-Joliet,Ill., 1310 WRBI-Tifton, Ga., 1310 KTBI-Los Angeles, Calif., 1300 WEAN-Providence, R.I., 550 KFXJ-Edgewater, Colo., 1310 KTBR-Portland, Ore., 1300 WKBC-Birmingham, Ala., 1310 WRBJ-Hattiesburg, Miss., 1500KFXR-Okla. City, Okla., 1310KTBS-Shreveport, La., 1450 WEAO-Columbus, 0., 550 WKBE-Webster, Mass., 1200 WRBL-Columbus, Ga.,1200 KFXY-Flagstaff, Ariz.,1420 KTHS-Hot Springs, Ark., 800 WEAR-Cleveland, 0., 1070 WKBF-Indianapolis, Ind., 1400WRBQ-Greenville. Miss.,1210 KFYO-Abilene, Tex., 1420 KTM-Los Angeles, Calif.,780 WEBC-Duluth, Minn., 1280 WKBH-La Crosse, Wis., 1380WRBT-Wilmington, N. C., 1370KFYR-Bismarck, N.D., 550 KTNT-Muscatine, Iowa, WEBS-Cambridge, 0., 1210 WKBI-Chicago, Ill.,1310 WRBU-Gastonia, N.C., 1210 1170 WEBQ-Harrisburg III., 1210 KGA-Spokane, Wash., 1470 KTSA-San Antonio, Tex., 1290 WKBN-Youngstown, O.570 WRC-Washington, D. C., 950 KGAR-Tnscon, Ariz., 1370 KTSL-.Shreveport, La., 1310 WEBR-Buffalo, N. Y., 1310 WKBO-Jersey City, N.J., 1450WREC-Memphis, Tenn., 600 KGB-San Diego, Calif., 1360 KTUE-Houston, Tex., 1420 WEBW-Beloit, Wis., 600 WKBP-Battle Creek, Mch.,1420 WREN-Lawrence, Kans., 1220KGBU-Ketchikan, Alaska, 900KTW-Seattle, Wash., 1270 WEDC-Chicago, Ill.,1210 WKBQ-New York, N. Y., 1350 WRHM-Friedley, Minn., 1250 KGBX-St. Joseph,Mo.,1370 WEDH-Erie, Pa., 1420 WKBS-Galesburg, Ill.,1310 KUJ-Longview, Wash., 1500 WRJN-Racine, Wis. 1370 KGBZ-York, Nebr., 930 KUOA-Fayetteville, Ark.,1390 WEEI-Boston, Mass., 590 WKBV-Brookville, Ind., 1500 WRK-Hamilton, Ohio, 1310 KGCA-Decorah, Iowa, 1270 KUOM-Missoula, Mont., 570 WEHS-Evanston, Ill.,1310 WKBW-Buffalo, N. Y., 1470 WRNY-New York, N.Y., 1010KGCI-San Antonio, Tex., 1370KUSD-Vermillion, S.D., 890 WELK-Phila, Pa., 1370 WKBZ-Ludington, Mich., 1500WRR-Dallas, Tex., 1280 KGCR-Watertown, S.D., 1210 KTJT-Austin, Tex., 1120 WEMC-Berrien Spgs., Mch. 590WKEN-Buffalo, N. Y., 1040 WRUF-Gainesville, Fla., 1470 KGCU-Mandan, N. D., 1200 KVI-Tacoma, Wash., 760 WENR-WBCN-Chico, III., 870WKJC-Lancaster, Pa., 1200 WRVA-Richmond, Va., 1110 KGCX-Vida, Mont., 1420 KVL-Seattle, Wash., 1370 WEPS-Gloucester, Masgos.1200WKRC-Cincinnati, 0., 550 WSAI-Cincinnati, 0., 1330 KGDA-Dell Rapids, S.D., 1370 WEVD-New York N.Y'.,1300 KV0A-Tucson, Ariz., 1260 WRY-Okla. City, Okla., 900 WSAJ-Grove City, Pa., 1310 KGDE.-Fergus Falls,Minn,1200KVOO-Tulsa, Okla.,1140 WEW-St. Louis, Mo., 760 WLAC-Nashville, Tenn.,1490 WSAN-Allentown, Pa., 1440 KGDM-Stockton, Calif.,1100 KVOS-Bellingham, Wash., 1200 WFAA-Dallas, Texas, 1040 WLAP-Louisville, Ky.,1200 WSAR-Fall River, Mass., 1450KGDR-San Antonio, Tex., 1500KWBS-Portland, Ore., WFAN-Philadelphia, Pa., 610 WLB-WGMS-Minneapolis, 1250 WSAZ-Huntington, W.V., 580KGDY-Oldham, S. D., 1200 1500 WFBC-Knerville, Tenn., 1200 KWCR-Cedar Rapids, Ia.,1310 WLBC-Muncie, Ind., 1310 WSB-Atlanta, Ga.. 740 KGEF-Los Angeles, Calif., 1300KWEA-Shreveport,La., 1210 WFBG-Altoona, Pa., 1310 WLBF-Kansas City, Mo., 1420 WSBC-Chicago, 1210 KGEK-Yuma, Colo.,1200 KWG-Stockton, Calif., 1200 WFBJ-Collegeville, Minn., 1370WLBG-Ettrick, Va., 1200 WSBT-South Bend, Ind., 1230KGER-Lg. Beach, Calif.,1370 KWH-Portland, Ore., 1060 WFBL-Syracuse, N. Y., 900 WLBL-Stevens Pt.Wis., 900 WSDA-WSGH-See WSGH KGEW-Ft. Morgan, Colo., 1200KWK-St. Louis WFBM-Indianapolis, Ind., 1230WLBW-Oil City, Pa., 1260 WSGH-WSDA-Bklyn.,NY. 1400KGEZ-Kalispell, Mont., 1310 Mo., 1350 WFBR-Baltimove Md., 1270 KW-KC-Kansas -City, Mo., 1370 WLBX-L. I. City, N.Y., 1500 WSGP-Savannah, Ga., 1410 KGFF-Alva., Okla., 1420 KWKH-Kennonwood, La.,850 WFDF-Flint, Mich.,1310 1210 WLBZ-Bangor, Maine, 620 WSIX-Springfield, Tenn., KGFG-Okla. City, Okla., 1370KWLC-Decorah, Iowa,1270 WFI-Philadelphia, Pa., 560 WLCI-Ithaca, N. Y., 1210 WSM-Nashville, Tenn., 650 KGFI-Corpus Christi, Tex.,1500 WFIW-Hopkinsville, Ky., 940WLEX-Lexington, Mass., 1360 WSMB-New Orleans, La., 1320KGFJ-Los Angeles, Calif., 1420KWSC-Pullman, Wash., 1390 WFJC-Akron, 0.,1450 KWTC-Santa Ana, Calif.,1500 WLEY-Lexington, Mass., 1420 WSMK-Dayton, Ohio, 570 KGFK-Ilallock, Minn., 1200 KWWG-Brownsville,Tex.,1260 WFKD-Philadelphia, Pa., 1310WLIB-WGN-See WGN-WLIB WSOA-Deerfield, Ill., 1480 KGFL-Raton, N. Mex., 1370 KWYO-Laramie, Wyo., 600 WFLA-WSUN-Clrw'tr Fla, 900WLIT-Philadelphia, Pa., 560 WSPD-Toledo, Ohio, 1340 KGFW-Ravenna, Nebr., 1420 WGAI,-Lancaster, Pa., 1310 WLOE-Chelsea, Mass., 1500 WSSH-Boston, Mass., 1420 KGFX-Pierre, S. D., 580 KXA-Seattle, Wash., 570 WGBB-Preeport, N. Y., 1210 WLS-Chicago, Ill., 870 WSUI-Iowa City, Ia., 580 KGGC-San Francisco, Cal.,1420KXL-Portland, Ore. 1250 WGBC-Memphis, Tenn., 1430 KXO-El Centre, Calif.,1200 WLSI-WDWF-See WDWF WSUN-WFLA--See WFLA KGGF-Picher, Okla., 1010 KXRO-Aberdeen, Wash.,1420 WGBF-Evansville, Ind.,630 WLTH-Brooklyn, N. Y., 1400WSVS-Buffalo, N. Y., 1370 KGGM-Albuquerque, N.M., 1370KYA-San Francisco, Ca1.,1230 WO-AI-Scranton. Pa.. 880 WLW-Mason, Ohio, 700 WSYR-Syracuse, N. Y., 370 KGEF-Pueblo, Colo., 1320 WGBS- New York City, 1180 KYW-KFKX-Chicago,Ill., 1020 WLWL-New York, N. Y., 1100 WTAD-Quincy, Ill.,1440 KGFIG-McGehee, Ark., 1310 KYWA-Chicago, Ill.,1020 WGCM-Gulfport, Miss., 1210WMAC-Cazenovia, N. Y., 570WTAG-Worcester, Mass., 580KGHI-Little Rock, Ark., 1500 KZM-Hayward, Calif., 1370 [IF YOU WANT TO CONVERT THE FREQUENCIES TO WAVELENGTHS, CONSULTPRECEDING PAGE] June 22, 1929 RADIO WORLD 21 DIAMOND CONE YOU MUST GET ASSEMBLY THIS BOOK! Pair WITH DOUBLE DRAKE'S RADIO MAGNET UNIT CYCLOPEDIA (New Edition) hasbeendeveloped to $6.00 answerthequestion,of servicemen,customset builder,and home con- structors,ofexperiment - era, students, salesmen and operators of receiving equipmentandtoMice all theseto have instant access to the Information theywant. Theauthor. HaroldI'.Manly, has collectedandtranslated IntoplainEnglish Use materiel formerly obtain- able only from dozens et scattered sources. Each rule, fort, method, plan, layout and diagram 11 Instantlypickedant BOOKIS2'/a"THICK, and separated from every - WEIGHS 33/4LBS..1,025 thing ales by platingall ILLUSTRATIONS. subjecteinalphabetise' ACS ....$1.50 orderwithcrossrefer- An excellent magnetic type speaker for installa- encesfor every imagina- Highly selective antenna coil for any dr- tion in any cabinet.The unit is a double -magnet blenameunderwhichtheinformationmightbe euit, and interstage coilfor AC circuits, Paratone,withtwo magnetcoils,farutmost classed. Step-upratio,1 -to -8. Tunes with .811115 sensitivity.Each horseshoe magnet is IV thick. Thisalphabetical arrangement letstheexperienced mfd. The magnet coilsare forever protected against workerreferdirectlytotheone thinginwhich ho Model AC3, for.00035 mfd $1.75 Isinterested atthe moment without hunting through dust and other foreign, injurious substances, by non -essentials. The needsofthe beginner are eared specialbakelitehousings. The pinisreverse for. drive.The cone frame ismetal.The 9" cone The important articles deal primarily with receivers is specially treated buckram. and reception.Thry do not stop with theelectrical end,butgoalsoIntothe mechanicsofconstruction. Every new thingn radio is covered In detail. All assembled, with long cord, ready 1,660 Alphabetlial Headings from A -battery is toplay,Shippingweight II lbs. .00 Zero Beat (Cat. CAS) Net 1,025Illustrations,Diagrams,LayoutsandGraphs 020 Pages, Each 8 by 9 Inches 240 CombinationsforReceiver Layeuth The unitalone(cord included). It OF THE PRINCIPAL ARTICLES will operate any type sounding sur- 159Concern service men,129 helpthesetbuilder, face, including paper, cloth, wood, etc. 162helpthe experimenter, 155interestthestudent. Shipping weight4lbs.(Cat. UA) $3,5050 75 assistInsales work, 73Interestset owners. Net GUARANTY RADIO GOODS 00., 145 W. 45th St., New York, N. Y. (lustE.sf B'way) Guaranty Radio Goods Co. Gentlemen: Please mall me atoncethe new (sec- ond) edition of"Drake'sRadioCyclopedia," by 145 West 45th St., New York City Harold P. Manly, just published, with allthelatest technicalinformationInit. Iwill pay the postman

$8.00 plus few cents extraforpostage. IfIam not delighted,I may return the hook infive days and HAVE AN EXPERT PUT you will promptly refund my purchase money. YOUR SET IN SHAPE! If your receiver or amplifier, no matter of what Name SGTS . ..$275 kind,is not giving proper results, send itto us, Tuner to work out of a screen grid tube. prepaid. We will test it FREE and let you know Address The largeprimaryisfixedandiscon- what's wrong, telling you costofrepairs.Our nected inthe platecircuitofthescreen charges are very reasonable.Six years' experi- City State grid tube.Tunes with.0005 mfd. ence.Loudspeakers and units repaired. Burnt -out 5 -DAY MONEY -BACK GUARANTY! Model SGT3. for.00035mfd $3.00 coilsreplaced. JaynxonLaboratories, 57 Dey Street, New York City. UNIVERSAL TwiceasMuch for Your Money! Pair Send $6.00 for one year's mail subscription for RADIO WORLD (52 numbers, one each week), and you will be

TPS $3000 Interstage coupler to work out of a screen given one full year's subscription for any one of the fol- grid tube, where the primary in the plate circuit is tuned, the secondary, in the next lowing six magazines: gridcircuit,untuned.Tunes with.0005. Model TP3, for .01035 mfd $325 Radio News (monthly) Radio Engineering (monthly) Science and Invention (monthy) Youth's Companion (weekly) RFS....$1 50 Radio, San Francisco (monthly) Boys' Life (monthly) Excellently selective antenna coil for any circuit, and interstage coil for any battery E Citizens Radio Call Book and Scientific Digest operatedreceiver,exceptingoutput of 11=0. WA= 10E0 =MI =MO .1= =NM ,11= screen grid tube.Tunes with .0005mfd. .000 Model RF3, for .00035 mfd $1.71 SPECIAL TWO -FOR -PRICE -OF -ONE COUPON RADIO WORLD, 145 West 45th Street. New York CHY (Just East of Broadway): Enclosed please find$8.00,for which send me RADIO WORLD each week for one year.52numbers, and also send me, without errta cost, for one year ONE of the following magazines as indicated: D RADIO NEWS O RADIO ENGINEERING O SCIENCE AND INVENTION 10 YOUTH'S COMPANION O RADIO (San Francisco) O BOYS' LIFE CITIZENS RADIO CALLBOOK AND SCIENTIFIC DIGEST (PutacressIntheproper square above. FIIIout coupon and send$6.00. Ifyouare asubscriber for RADIO WORLD or for the other magazine youselect, or both, check oft squares below. e'left.]

PresentRADIO WORLD subscribers may renew under thisoffer. Itrenewing.put Name acrosshere C. Itrenewingfortheother Street Address magazineyouselect,put VIM herealso 0. City State AS $1.75 THIS OFFER EXPIRES AT NOON JULY 30TH, 1929 Conductively coupled antennacoil,for maxi- mum pickup, where selectivity is not the main consideration. Continuouswindingin two colors.Tunes with .0005 mfd. Model A3, for .00035 mid $2.00 Look at the date of the label pasted on the wrapper containing your Model T5 screen grid Transformer for .0005, subscription copies.If this date on wrapper is older than the date of the $1.50; T3 for .00035, $1.75. issue received, then your subscription has expired and should be renewed. ScreenGridCoilCo., 143W. 45thSt.,N.Y.City 20 RADIO WORLD June 22, 1929 Alphabetical List of Stations by CallLetters; Location and Frequency [FROM FEDERAL RADIO COMMISSION LIST REVISED UPTO NOON, JUNE 12TH] Station Location FrequencyStation Location FrequencyStation Location FrequencyStation Location WAAF-Chicago, III.,920 WGCP-Newark, N. J., 1250 FrequencyStation Location Frequency WAAM-Newark, N. I., 1250 WMAF-Dartmouth, Mass., 1360WTAM-Cleveland, 0., 1070 KGHL-Billings, Mont., 950 WGES-Chicago, Ill.,1360 WMAK-Buffalo, N. Y., 900 WTAQ-Eau Claire, Wis., 1330KGHX-Richmond, Tex., 1500 WAAT-Jersey City, NJ., 1070WGH-Newport News, Va., 1310WMAL-Washington, D.C., 630WTAR-WPOR-NorPlk, Va., 780KGIQ-Twin Falls, Idaho, 1320 WAAW-Omaha, Nebr., 660 WGHP-Detroit, Mich., 1240 WMAN-Columbus, Ohio, 1210 WTAW-College Station, 1120 KGIR-Butte, Mont., 1360 WABC-WBOQ-N.Y. City, 860WGL-Ft. Wayne, Ind., 1370 WMAQ-Chicago, Ill., 670 WABI-Bangor, Me., 1200 WGMS-See WLB-WGMS WTAX-Streator,Ill.,1210 KGIW-Trinidad, Colo..1420 WMAZ-Macon, Ga., 890 WTBO-Cumberland, Md., 1420KGIX-Las Vegas,Nev.,1420 WABZ-New Orleans, La., 1200WGN_WLIB-ElginIll.,720 WMBA-Newport, R. 1500 WADC-Akron, 0., 1320 WGR-Buffalo, N. 4., 550 I., WTFI-Toccoa, Ga.. 1450 KGJF-Little Rock, Ark., 890 WAFD-Detroit, Mich., 1500 WMBC-Detroit, Mich, 1420 WTIC-Hartford, Ct.,600,1060KGKB-Brownwood, Tex., 1500 WGST-Atlanta, Ga., 890 WMBD-Peoria Hts.,Ill.,1440 WTMJ-Milwaukee, Wis., 620 KGKL-San Angelo. Tex., 1370 WAGM-Royal Oak, Mich., 1310WGY-Schenectady, N. Y., 790WMBG-Richmond, Va., 1210 WWAE-Hammond, Ind., 1200KGKO-Wichita, Falls, Tex 570 WAIU-Columbus, 0., 640 WHA-Madison, Wis., 940 WMBH-Joplin, Mo., 1420 WWJ-Detroit, Mich., 920 KGKX-San Point, Idaho, 1420 WAPI-Birmingham, Ala.,1140WHAD-Milwaukee, Wis., 1120WMBI-Addison, Ill., 1080 WWL-New Orleans, La., 850 WASH-Gd. Rapids, Mich., 1270WHAM-Rochester, N. Y., 1150 KGO-Oakland, Calif.,790 WBAK-Harrisburg, Pa., 1430 WMBJ-Pittsburgh, Pa., 1500 WWNC-Asheville, N. C., 570 KGRC-San Antonio, Tex., 1370 WHAP-N. Y. City,1300 WMBL-Lakeland, Fla.,1310. WWRL-Woodside, N.Y., 1500KGRS-Amarillo, Tex., 1410 WBAL-Baltimore, Md., 1060 WHAS-Louisville, Ky.,820 WMBO-Auburn, N. Y., 1370 WWVA-Wheeling, W.Va., 1160KGU-Honolulu, Hawaii, 940 WBAP-Fort Worth, Tex., 800WHAZ-Troy, N. Y., 1300 WMBQ-Brooklyn, N. Y., 1500KCRC-Enid, Okla., 1370 KGW-Portland, Ore., 620 WBAW-Nashville, Tenn., 1490WHB-Kansas City, Mo., 950 WMBR-Tampa, Fla., 1210 KDB-Santa. Barbara, Cal.,1500 KGY-Lacey, Wash., 1200 WBAX-Wilkes-Barre, Pa., 1210WHBC-Canton, Ohio,1200 WMC-Memphis, Tenn., 570 KDKA-Pittsburgh, Pa., 980 KHJ-Los Angeles, Calif., 900 WBBC-Brooklyn, N. Y., 1400 WHBD--Bellefontaine, 0., 1370WMCA-New York, N.Y., 570 KDLR-Devils Lake, N.D., 1210KHQ-Spokane, Wash., 590 WBBL-Richmond, Va.,1370 WHBF-Rock Island, Ill.,1210 WMES-Boston, Mass., 1500 KDYL-Salt Lake, Utah, 1290 WBBM-WJBT-Chicago, Ill., 770WHBL-Sheboygan, Wis., 1410WMMN-Fairmont, W. Va., 890 KICK-Red Oak, Iowa, 1420 WBBR-Rossville, N. Y., 1300 KEJK-Beverly Mlle, Calif., 1170KID-Idaho Falls, Idaho, 1320 WHBP-Johnstown, Pa., 1310 WMPC-Lapeer, Mich., 1500 KELW-Burbank, Calif., 780 KIDO-Boise, Idaho.1250 WBBY-Charleston, S. C., 1200WHBQ-Memphis, Tenn., 1370 WMRJ-Jamaica, N. Y., 1420 KEX-Portland, Ore., 1180 KIT-Yakima, Wash., 1370 WBBZ-Ponca City, Okla., 1200WHBU-Anderson, Ind., 1210 WI4SG-New York, N. Y., 1350KFAB-Lincoln, Nebr., 770 KJBS-San Francisco, Cal., WBCM-Bay City, Mich., 1410 WHBW-Philadelphia, Pa., 1500WMT-Waterloo, Iowa, 1200 KFAD-Phoenix, Ariz., 620 1070 WBIS-See WNAC WHBY-W. De Pere, Wis., 1200 KJR-Seattle, Wash, 970 WBMS-Fort, Lee., N. J., 1450 WNAC-WBIS-Boston, 1230 KFBB-Great Falls, Mont., 1360KLCN-Blytheville. Ark., 1290 WHDF-Calumet, Mich., 1370 WNAD-Norman, Okla., 1010 KFBK-SacramentoCalif.,1310KLO-Ogden, Utah, 1370 WBNY-New York, N. Y., 1350WHDH-Gloucester, Mass., 830WNAT-Philadelphia,1'a.,1310KFBL-Everett,Wash., 1370 KLRA-Little Rock, Ark., WBOQ-See WABC WHDI-Minneapolis, Minn. 1180WNAX-Yankton, S. D. 570 KFDM-Beaumont, Tex., 560 1390 WBOW-Terre Haute, Ind., 1310WHDL-Tupper Lake, N.Y.,1420 KIS-Oakland, Calif.,1440 WNBF-Binghamton, N.Y., 1500KFDY-Brookings, S.Dak., 550KLX-Oakland,Calif.,880 WBRC-Birmingham, Ala., 930WHEC-WABO-Roch'aer,NY.1440WNBH-N'w Bedf'rd, Mass.,1310KFEL-Denver, Colo., 940 KLZ-Dupont, Colo., 560 WBRE-Wilkes-Barre,Pa., 1310WRFC-Cicero, Ill.,1310 WBRL-Tilton, N. H., 1430 WNBJ-Knoxville, Tenn., 1310 WFEQ-St. Joseph, Mo., 560 KMA-Shenandoah, Iowa, 930 WHIS-Bluefield, W. Va., 1420WNBO-Washington, Pa., 1200KFG Boone, Iowa, 1310 KMBC-Independence, Mo., 950 WBSO-Wellesley H., Mass., 780WHK-Cleveland, Ohio 1390 WNBR-Memphis, Tenn., 1430KF -Wichita, Kans.1300 KMED-Medford, Ore., 1310 WBT-Charlotte, N. C., 1080 WHN-New York, N.Y., 1010 1200 WNBW-Carbondale, Pa., KFHA-Gunnison, Colo., 1200 KMIC-Inglewood, Calif.,1120 WBZ-Springfield, Mass., 990 WHO-Des Moines, Ia., 1000 WNBX-Springfield, Vt., 1200 KFI-Los Angeles, Calif., 640 KMJ-Fresno, Calif., 1200 WBZA-Boston, Mass., 990 WHP-Harrisburg, Pa., 1430 WNBZ-Saranac Lk., N.Y. 1290KFIF-Portland, Ore.,1420 KMMJ-Clay Center, Nebr., 740 WCAC-Storrs, Conn., 600 WIAS--Ottumwa, Iowa, 1420 WNJ-Newark, N. J., 1450 KFIO-Spokane, Wash., 1230 KMO-Tacoma, Wash., 1340 WCAD-Canton, N. Y., 1220 WIXA-Madison, Wis., 1210 WNOX-Knoxville, Tenn., 560 KFIZ-Fond du Lac, Wis., 1420 WCAE-Pittsburgh, Pa., 1220 WTBG-Elkins, Park, Pa., 930 KMOX-KFQA-St. Louis, 1090 WNRC-Greensboro, N.C., 1440KF B-Marshalltown, Ia., 1200 KMTR-Hollywood,Calif.,570 WCAH-Columbus, Ohio, 1430 WIBM-Jackson, Mich., 1370 WNYC-New York, N.Y., 570 KF F --Okla..,City.,Okla.,1470KNX-Hollywood, Calif., WCAJ-Lincoln, Nebr., 590 WIBO-Chicago, Ill.,570 WOAI-San Antonio, Tex., 1190KF I-Astoria, Ore., 1370 1050 WCAL-Northfield, Minn., 1250WIBR-Steubenville, 0., 1420 KOA-Denver, Colo., 830 WOAN-Lawrenceburg Term. 600K M-Gd. Forks., N.D., 1370KOAC-Corvallis, Ore.,560 WCAM-Camden, N. J., 1280 WIBS-Elizabeth, N. J., 1450 WOAX-Trenton, 1280 KF R-Portland, Ore., 1300 KOB-State College, N.M., WCAO-Baltimore, Md., 600 WIBU-Poynette, Wis., 1310 WOBT-Union City,enn., 1310KF Y-Fort Dodge, Iowa, 1310KOCW-Chickasha, Okla., 1180 WCAP-Asbury Pk., N. J., 1280VVIBW-Topeka., Kan., 1300 WOBU-Charlestown, W.Va., 580KF Z-Fort Worth, Tex., 1370KOH-Reno, Nev., 1370 1400 WCAT-Rapid City, N.D., 1200WIBX-Utica, N. Y.. 1200 WOC-Davenpert, Ia.,1000 KFKA-Greeley, Colo., 880 ROIL-Council Bluffs, Pa.,1170WICC-Bridgeport, Conn., 1190 Ia.,1260 WCAU-Philadelphia, WOCL-Jamestown, N. Y., 1210KFKB-Milford, Kans.,1050 KOIN-Portland,Ore., 940 WCAZ-Carthage, 1070 WIL-St. Louis, Mo., 1200 WODA-Paterson, N. J., 1250 KFKU-Lawrence, Kans., 1220 KOL-Seattle, Wash., 1270 WCBA-Allentown, Pa., 1440 WILL-Urbana, Ill..890 WOI-Ames, Iowa, 560 KFKX-KYW-See KYW KOMO-Seattle, Wash, 920 WCBD-Zion, Ili., 1080 WILM-Wilmington, Del.1420 WOK-WMBB-See WMBB WCBM-Baltimore, Md., 1370 WINR-Bay Shore, N. Y., 1210 KFKZ-Kirksville, Mo., 1200 KOOS--Marshfield, Ore., 1370 WOKO-Poughkeepsie, NY., 1440KFLV-Rockford, In.,1410 KORE-Eugene, Ore.,1420 WCBS-Springfield, Ili, 1210 WIOD-Miami Beach, Fla., 560WOL-Washington, D.C., 1310KFLX-Galveston, Tex.,1370 KM-Phoenix, Ariz., 1390 WCCO-Minneapolis, Minn., 810WIP-Philadelphia, Pa., 610 WOMT-Manitowoc, Wis., 1210KFMX-Northfield, Minn., 1250 WCDA--Cliffside, Pk., N.J., 1350WISN-Milwaukee, Wis., 1120 KPCB-Seattle, Wash., 1210 WOOD-Gd. Rapids, Mich., 1270KFNF-Shenandoah, Iowa, 890KPJM-Prescott, Ariz..1500 WCFL-Chicago, Ill., 970 WJAD-Waco, Texas, 1240 WOQ-Kansas City, Mo., 610 KFOR-Linooln, Nebr., 1210 KPLA-Los Angeles, Calif., WCGU-Coney Island, N.Y.,1400WJAG-Norfolk, Nebr., 1060 WOR-Newark, N. J., 710 KFOX-Long Beach,Calif, 1250KPO-San Francisco, Cal, 6801000 WCKY-Covington, 1480 WJAK-Kokomo, Ind., 1310 WORD-Chicago, M.,1480 KFPL-Dublin, Tex., 1310 KPOF-Denver, WCLB-Lg. Beach, N.Y., 1500 WJAR-Providence, R.I., 890 WOS-Jefferson City, Mo., 630KFPM-Greenville, Tex., 1310 KPPC-Pasadena, Calif.,880 WCLO-Kenosha, Wis., 1200 WJAS-Pittsburgh, Pa. 1290 WOV-New York, N.Y., 1130KFPW-Siloam Spgs., Ark.,1340 1330 WCLS-Joliet, Ill., 1310 WJAX-Jacksonville. Fla., 1260 KPQ-Seattle, Wash., 1210 WOW-Omaha, Nebr., 590 KFPY-Spokane, Wash., 1390 KPRC-Houston, Tex.,920 WCMA-Culver, Ind., 1400 WJAY-Cleveland Ohio, 620 WOWO-Ft. Wayne, Ind., 1160 KFKF K.MOX KPSN-Pasedena, WCOA-Pensacola, Fla.,1120 WJAZ-Chicago,Ill., 1480 Calif.,950 VVPAP-W0A0--See WQAO D-Anchorage, Alaska, 1230KPWF-Westminster,Calif.1490 WC0C-Columbus, Miss., 880 WJBC-La Salle, III.1200 WPAW-Pawtucket, R. 1210KF U-Holy City,Calif.,1420 KOV-Pittsburgh, Pa., 1380 WCOH-Yonkers, N.Y., 1210 WJBI-Red Bank, N. J.1210 WPCC-Chicago, Ill..570 KFQW-Seattle, Wash., 1420 WCRW-Chicago, Ill.,1210 WJBK-Ypsilanti, Mich., 1370 MOW-San Jose, Calif., 1010 WPCH-New York, N.Y., 810 KFQZ-Hollywood, Calif.,860 KRE--Berkeley, Calif.,1370 WCSH-Portland, Maine, 940 WJBL-Decatur, HI., 1200 WPG-Atlantic City. N.J.,1100KFRC-San Francisco, Cal., 610KRGV-Harlingen, Tex., 1260 WCSO-Springfield, 0., 1380 WJBO-New Orleans, La., 1370WPOE-Patchogue, N. Y., 1420KFRU-Columbfa, Mo., 630 KRLD--Dallas, Tex., WDAE-Tampa, Fia., 620 WJBU-Lewisburg, Pa.,1210 1040 WPOR-WTAR-See WTAR KFSD-San Diego, Calif., 600 KRMD-Shreveport, La.,1310 WDAF-Kansas City, Mo., 610WJBW-New Orleans, La., 1200WPRC-Harrisburg, Pa., 1200 KFSG-Los Angeles,Calif., 1120KRSC-Seattle, Wash., 1120 WDAG-Amarillo, Tex., 1410 WJBY-Gadsden, Ala., 1210. WPSC-State College, Pa., 1230KFUL-Galveston, Tex., 1290 KSAC-Manhattan, Kans., 580 WDAH-E1 Paso, Tex., 1310 WJDW-Emory, Va., 1370 WPSW-Philadelphia, Pa., 1500KFUM-Colo. Springs, Col.,1270KSCJ-Sioux City, Ia., 1330 WDAY-W. Fargo, N. D., 1280WJDX-Jackson, Miss.,1270 WPTF-Raleigh, N. C., MO KFUO-Clayton, Mo., 550 WDBJ-Roanoke, Va., 930 WJDZ-W. Salem, N. C., 1310 KSD-St. Louis, Mo., 550 WQAM-Miami, Fla., 1240 KFUP-Denver, Colo.. 1310 K.SEI-Pocatello, Idaho,900 WDBO-Orlando, Fla. 620 WTJD-Mooseheart, Ill.,1130 WQAN-Scranton, Pa., 880 KFVD-Culver City, Calif., 710KSL-Salt Lake City, U., 1130 WDEL-Wilmington,Ind.. 1120WYKS-Gary, Ind., 1360 WQAO-WPAP-N.Y.C., 1010 REVS-Cape Girardeau, Mo.1210KSMR-Santa Maria, Calif, 1200 WDGY-Minneapolis, Minn., 1180WJR-Detroit, Mich., 750 WQBC-Utica, Miss., 1360 KFWB-Hollywood, 950 WDOD-Chattanooga, Tenn., 1280 Calif., KSO-Clarinda, Iowa, 1380 WJSV-Mt.Vernon Hills,Va., 1460WQBZ-Weirton, W.V., 1420 KFWC-S. Pomona, Calif.,1200KSOO-Sioux Falls, S. D., 1110 WDRC-New Haven, Conn.,1330WJW-Mansfield, 0., 1210 WRAF-LaPorte, Ind.,1200 KFWF-St. Louis, Mo., 1200 WDSU-New Orleans, La., 1279 1370 KSTP-St. Paul, Minn., 1460 WJZ-New York, N. Y., 760 WRAK-Erie, Pa., KFWI-San Francisco,Cal., 930KTAB-Oakland,Calif.,550 WDWF-WLSI-Censen,R.I.1210WKAQ-San Juan, P. R., 890 WRAW-Reading, Pa., 1310 KFWM-Oakland Calif., 930 KTAP-San Antonio, Tex., 1420 WDZ-Tuscola, III.,1070 WKAR-E. Lansing, Mich., 1040WRAX-Philadelphia, Pa.,1020KFXD-Jerome,Idaho, 143) KTAT-Ft. Worth, Tex., 1240 WEAF-New York, N.Y., 660WKAV-Laconia., N. H., 1310 WRBC-Valparaiso, Ind., 1240 KFXF-Denver, Colo., 940 KTBI-Los Angeles, Calif., 1300 WEAI-Ithaca, N. Y., 1270 WKBB-Joliet, Ill.,1310 WRBI-Tifton, Ga., 1310 KFXJ-Edgewater, Colo., 1310 KTBR-Portland, Ore., 1300 WEAN-Providence, R.I., 550 WKBC-Birmingham, Ala., 1310WRBJ-Hattiesburg, Miss., 1500KFXR-Okla. City, Okla., 1310KTBS-Shreveport, La., 1450 WEAO-Columbus, CI.,550 WKBE-Webster, Mass., 1200 WRBL-Columbus, Ga.,1200 KFXY-Flagstaff, Ariz., 1420 KTHS-Hot Springs, Ark., 800 WEAR-Cleveland, 0., 1070 WKBF-Indianapolis, Ind., 1400WRBQ-Greenville. Miss.,1210KFYO-Abilene, Tex., 1420 WEBC-Duluth, Minn., 1280 WKBH-La Crosse, Wis., 1380 KTM-Los Angeles, Calif.,780 WRBT-Wilmington, N. C., 1370KFYR-Bismarck, N.D., 550 KTNT-Muscatine, Iowa,1170 WEBE-Cambridge, 0., 1210 WKBI-Chicago, 1310 WRBU-Gastonia, N.C., 1210 KGA-Spokane, Wash., 1470 KTSA-San Antonio, Tex., 1290 WEBQ-Flarrisburg, III., 1210 WKBN-Youngstown, 0., 570 WRC-Washington, D. C., 950KGAR-Tuscon, Ariz., 1370 KTSL-Shreveport, La., 1310 WEBR-Buffalo, N. Y., 1310 WKBO-Jersey City, N.j., 1450WREC-Memphis, Tenn., 600 KGB-San Diego, Calif., 1360 KTUE-Houston, Tex., 1420 WEBW-Beloit, Wis., 600 WKBP-Battle Creek, Mch.,1420WREN-Lawrence, Kans., 1220KGBU-Ketchikan, Alaska, 900KTVir-Seattle, Wash., 1270 WEDC-Chicago, Ill.,1210 WKBQ-New York, N. Y., 1350WRHM-Friedley, Minn., 1250 KGBX-St. Joseph,Mo.,1370 WEDEI-Erie, Pa., 1420 WKBS-Galesburg, Ill.,1310 KUJ=Longview, Wash., 1500 WRJN-Racine, Wis. 1370 KGBZ-York, Nebr., 930 KUOA-Fayetteville, Ark.,1390 WEEI-Boston, Mass., 590 WKBV-Brookville, Ind., 1500 WRK-Hamilton, Ohio, 1310 KGCA-Decorah, Iowa, 1270 KUOM-Missoula, Mont., 570 WEHS-Evanston, III.,1310 WKBW-Buffalo, N. Y., 1470 WRNY-New York, N.Y., 1010KGCI-San Antonio, Tex., 1370KUSD-Vermillion, S.D., 890 WELK-Phila, Pa., 1370 WKBZ-Ludington, Mich., 1500WRR-Dallas, Tex., 1280 KGCR-Watertown, S.D., 1210 KUT-Austin, Tex., 1120 WEMC-Berrien Spgs., Mch. 990WREN-Buffalo, N. Y., 1040 WRUF-Gainesville, Fla., 1470 KGCU-Mandan, N. D., 1200 KVI-Tacoma, Wash., 760 WENR-WBCN-Chicago, M., 870WKJC-LancasterPa., 1200 WRVA-Richmond, Va.,1110 KGCX-Vida, Mont., 1420 KVL-Seattle, Wash., 1370 WEPS-Gloucester, Mass.1200 WKRC-Cincinnati, 0., 550 WSAI-Cincinnati, 0., 1330 KGDA-Dell Rapids, S.D., 1370 WEVD-New York, N.Y'.,1300 KVOA-Tucson, Ariz.,1260 WKY-Okla. City, Okla., 900 WSAJ-Grove City, Pa., 010 KGDE-Fergus Falls,Minn,1200KVOO-Tulsa, Okla.,1140 WEW-St. Louis, Mo., 760 WLAC-Nashville, Tenn.,1490 WSAN-Allentown, Pa., 1440 KGDM-Stockton, Calif.,1100 KVOS-Bellingham, Wash., 1200 WFAA-Dallas, Texas, 1040 WLAP-Louisville, Ky., 1200 WSAR-Fall River, Mass., 1450KGDR-San Antonio, Tex., 1500KWBS-Portland, Ore., WFAN-Philadelphia, Pa., 610 WLB-WGMS-Minneapolis, 1250WSAZ-Huntington, W.V., 580KGDY-Oldham, S. D., 1200 1500 WFBC-Knexville, Tenn., 1300 WLBC-Muncie, Ind., 1310 KWCR-Cedar Rapids, Ia.,1310 WSB-Atlanta, Ga., 740 KGEF-Los Angeles, Calif., 1300KWEA-Shreveport,La., 1210 WFBG-Altoona, Pa., 1310 WLBF-Kansas City, Mo., 1420WSBC-Chicago, 1210 KGEK-Yuma, Colo.,1200 KWG-Stockton, Calif., 1200 WFBj-Collegeville, Minn., 1370WLBG-Ettrick, Va., 1200 WSBT-South Bend, Ind., 1230KGER-Lg. Beach, Calif.,1370K WJJ-Portland, Ore., 1060 WFBL-Syracuse, N. Y., 900 WLBL-Stevens Pt.Wis., 900WSDA-WSGH-See WSGH KGEW-Ft. Morgan, Colo., 1200 Louis. Mo., 1350 WFBM-Indianapolis, Ind., 1230WLBW-Oil City, Pa., 1260 WSGH-WSDA-Bklyn.,NY. 1400KGEZ-Kalispell, Mont., 1310 KWKC-Kansas City, Mo., 1370 WFBR-Baltimore, Md.. 1270 VVLBX-L. I. City, N.Y., 1500 WSGP-Savannah, Ga., 1410 KGFF-Alva., Okla., 1420 KWKH-Kennonwood, La., 850 WFDF-Flint, Mich.,1310 WLBZ-Bangor, Maine, 620 WSIX-Springfield, Tenn.,1210KGFG-Okla. City, Okla., 1370 WFI-Philadelphia, Pa.. 560 WLCT-Ithaca, N. Y., 1210 KWLC-Decorah, Iowa, 1270 WSM-Nashville, Tenn., 650 KGFI-Corpus Christi, Tex.,1500KWSC-Pullman, Wash., 1390 WFIW-Hopkinsville, Ky., 940WLEX-Lexington, Mass., 1360WSMB-New Orleans, La., 1320KGFJ-Los Angeles, Calif., 1420 WFJC-Akron, 0.,1450 KWIC-Santa Ana, Calif.,1500 WLEY-Lexington, Mass., 1420WSMK-Dayton, Ohio, 570 KGFK-Hallock, Minn., 1200 KWWG-Brownsville,Tex.,1260 WFKD-Philadelphia, Pa., 1310WLIB-WGN-See WGN-WLIBWSOA-Deerfield, Ill., 1480 KGFL-Raton, N. Mex., 1370 KWYO-Laramie, Wyo., 600 WFLA-WSUN-C1rw'tr Fla, 900WLIT-Philadelphia, Pa., 560 WSPD-Toledo, Ohio, 1340 KGFW-Ravenna, Nebr., 1420 WGAL-Lancaster, Pa., 1310 WLOE-Chelsea, Mass., 1500 WSSH-Boston, Mass., 1420 KGFX-Pierre, S. D., 580 KXA-Seattle, Wash., 570 WGBB-Freeport, N. Y., 1210 WLS-Chicago, HI., 870 WSUI-Iowa City, Ia., 580 KGGC-San Francisco, Cal.,1420KXL-Portland, Ore. 1250 WGBC-Memphis, Tenn., 1430 KX0-E1 Centre, Calif.,1200 WLSI-WDWF-See WDWF WSUN-WFLA-See WFLA KGGF-Picher, Okla., 1010 KXRO-Aberdeen Wash.,1420 WGBF-Evansville, hid.,630 WLTFI-Brooklyn, N. Y., 1400 WSVS-Buffalo, N. Y., 1370 /MGM-Albuquerque, N.M., 1370KYA-San Francisco, Ca1.,1230 WGBT-Scranton. Pa.. 880 WLW-Mason Ohio, 700 WSYR-Syracifse, N. Y., 370 KGHP--Pueblo, Colo., 1320 KYW-KFKX-Chicago, WGBS- New York City, 1180WLWL-New York, N. Y., 1100 1440 III., 1020 WTAD-Quincy, Ill., KGEG-McGehee, Ark., 1310 KYWA-Chicago, Ill.,1020 WGCM-Gulfport, Miss., 1210WMAC-Cazenovia, N. Y., 570WTAG-Worcester, Mass., 580KGHI-Little Rock, Ark., 1500 KZM-Hayward, Calif., 1370 [IF YOU WANT TO CONVERT THE FREQUENCIES TO WAVELENGTHS, CONSULTPRECEDING PAGE] June 22, 1929 RADIO WORLD 21 DIAMOND CONE YOU MUST GET ASSEMBLY THIS BOOK! Pair WITH DOUBLE DRAKE'S RADIO MAGNET UNIT CYCLOPEDIA (New Edition) has been developed to $6.00 answerthequestionsof servicemen,customset builder,and home con- structers,ofexperiment- ers. students, salesmen and operators of receiving equipmentand toallow alltheseto have instant scenes to the Information theywant. The author, Harold P. Manly, has collected and transtatad intoplainEnglish the materiel formerly obtain- able only from dozens of scattered source.. Each rule, feet, method. plan, layout and diagram le instantlypickedslut BOOKIS 21/2" THICK, and separated from every - WEIGHS 3% LBS.,1,025 thing else by placingall ILLUSTRATIONS. subjects In alphabotteal ACS ....$1.50 orderwith cress refer- An excellent magnetic type speaker for Installa- encesforevery Imagina- Highly selective antenna coil for any cir- tion in any cabinet.The unit is a double -magnet ble nameunderwhich the informationmight be cuit, and interstage coilfor AC circuits. Paratone,withtwo magnetcoils,forutmost classed. Step-upratio,l -to -8. Tunes with .0113 sensitivity.Each horseshoe magnet is 3/4" thick. Thisalphabetical arrangementletstheexperienced mfd. The magnet coilsare forever protected against workerreferdirectlytotheone thinginwhich be Model AC3, for.00035 mfd $1.75 IsInterestedatthe moment without hunting throne) dust and other foreign, injurious substances, by non-essentlals. The needsofthe beginner are eared specialbakelitehousings. Thepinisreverse for. drive.The cone frame ismetal.The 9" cone The important art'cles deal primarily with receivers is specially treated buckram. andreception. They do not stop with theelectrical end,but goalsoI Itothe mechanics ofconstruction. Every new thing 11 radio is severed in detail. All assembled, with long cord, ready 1,68.0 Alphabetical H ead lags from A -battery to toplay,Shippingweight II lbs. .00 Zero Beat (Cat. CAS) Net 1,025Illustrations, D la grams, Layoutsend Graphs 920 Pages, Each 8 by 9 Inches 240 CombinationsforReceiver Layeuth The unit alone(cord included).It OF THE PRINCIPAL ARTICLES will operate any type sounding sur- 159 Concern service men,129 helptheset builder, face, including paper, cloth, wood, etc. 182 helpthe experimenter. 155 Interestthestudent, Insaleswork, 73Interestset owners. Shippingweight 4 lbs.(Cat_ UA). .50 75 assist GUARANTY RADIO GOODS 00., 145 W. 45th St., New York, N. Y. (lustE. ef13' way) Guaranty Radio Goods Co. Gentlemen: Please mail me atoncethe new(sec- ond)edition of "Drake'sRadio Cyclopedia," by 145 West 45th St., New York City Harold P. Manly, just published, withallthe latest technical informationInIL Iwill pay the postman

$6.00 plus few cents extraforpostage. IfIam not delighted,I may return the hook Intee days and HAVE AN EXPERT PUT you will promptly refund my purchase money. YOUR SET IN SHAPE! If your receiver or amplifier, no matter of what Name SGT5 ....$2.75 kind,is not giving proper results, send itto us, Tuner to work out of a screen grid tube. prepaid. We will test it FREE and let you know Address The largeprimaryisfixedandiscon- what's wrong, telling you costofrepairs.Our nected in the platecircuitofthescreen charges are very reasonable.Six years'experi- City State grid tube.Tunes with.0005 mfd. ence.Loudspeakers and units repaired. Burnt -out 5 -DAY MONEY -BACK GUARANTY! Model SGT3. for.00035 mfd $3.00 coilsreplaced. JaynxonLaboratories, 57 Dey Street, New York City. UNIVERSAL TwiceasMuch for Your Money! Pair Send $6.00 for one year's mail subscription for RADIO WORLD (52 numbers, one each week), and you will be TFS $3000 Interstage coupler to work out of a screen given one full year's subscription for any one of the fol- grid tube, where the primary in the plate circuit is tuned, the secondary, in the next lowing six magazines: gridcircuit,untuned.Tunes with.0005. Model TP3, for .00035 mfd $325 Radio News (monthly) Radio Engineering (monthly) Science and Invention (monthy) Youth's Companion (weekly) RFS $150 Radio, San Francisco (monthly) Boys' Life (monthly) Excellently selective antenna coil for any circuit, and interstage coil for any battery Citizens Radio Call Book and Scientific Digest operatedreceiver,exceptingoutput of 1111=MMI screen grid tube.Tunes with.0005mfd. MM. MIN MN IN= 1MMI TM/ 111, Model RF3, for .00035 mfd $1.71 SPECIAL TWO -FOR -PRICE -OF -ONE COUPON RADIO WORLD, 145 West 45th Street, New York City (Just East of Broadway) : Enclosed please find $6.00,for which send me RADIO WORLD each week forone year, 52 number., and also send me, without carte cost, for one year ONE of the following magazines as indicated: O RADIO NEWS 0 RADIO ENGINEERING O SCIENCE AND INVENTION 0 YOUTH'S COMPANION RAD 10 (San Francisco) 0 BOYS' LIFE fl CITIZENS RADIO CALL BOOK AND SCIENTIFIC DIGEST [Put acrossInthe proper square above. Fillout coupon and send56.00. Ifyouar' a subscriber for RADIO WORLD or for the other magazine you select, or both, check off squares below. a'let t.]

Present RADIO WORLD subscribers may renew under thisoffer. Ifrenewing,put Name a crosshere C. Ifrenewingfortheother Street Address magazine youselect,put a crossherealso 0. City State AS $1.75 THIS OFFER EXPIRES AT NOON JULY 30TH, 1929 Conductively coupled antennacoil,for maxi- mum pickup, where selectivity is not the main consideration. Continuouswindingintwo colors.Tunes with .0005 mfd. Model A3, for .00035 mid $2.00 Look at the date of the label pasted on the wrapper containing your Model T5 screen grid Transformer for .0005, subscription copies.If this date on wrapper is older than the date of the $1.50; T3 for .00035, $1.75. issue received, then your subscription has expired and should be renewed. ScreenGridCoilCo., 143 W. 45thSt., N.Y.City 22 RADIO WORLD June 22, 1929 VICTOREEN Super Coils Learn All About Write forFree Blueprints of SOCKET WRENCH New Vietoreen Circuits Geo. W. Walker Co. Power Amplifiers 2825 Chester Avenue in Dept. B Cleveland, 0. The First Complete Treatise on This Important and F Fascinating Subject NEWEST BOOK Now appearing serially in RADIO WORLD -a fine,biginstallmenteach week ! ON VACUUM TUBES Written for the novice, but worth any R "RADIORECEIVING expert's time to read! TUBES,"byJamesA. Moyer and John F. Wos- J. E. ANDERSON, Technical Editor, and trcl,firstedition justoff Herman Bernard, Managing Editor,are the the press.No radio serv- authorsofthissplendidexpositionofthe ice man, experimenter or known facts and previously unknown mys- E student of radio should be teries of power amplifiers. withoutthisauthoritative Nowhere else can you get the correlated book on the principles and information, the liberal education, on this sub- applications of vacuum iect,forthisseries traversesa virginfield, tubes.It answers all your blazes the way, and reaches a high goal in questionsrelatingtore- instructional literature. ceiving, amplifyingand Service men Must know power amplifiers rectifyingtubes.Itisa if they are to prosper-indeed, even survive. complete discussion of tube Custom -setbuilders must have anequally principles,functionsand thorough understanding of the subject. Home uses,thoroughly up-to- constructors,experimenters,students,teach- Push out control lever with knob (as at left) date. ers-all need followthis amazinglyskillful, and put wrench on nut.Push down on handle Inthisbooktheessential yetsimplified,expositionofanabsorbing only (at right), then turn nut left or right. principles underlying the oper- subject. ation of vacuum tubes are ex- ONE of the handiest tools for a custom set plainedinasnon -technical a builder, mannerasisconsistentwith YOUR OPPORTUNITY! service man or home constructor accuracy.The book covers the The series started inthe June1stissue isa BERNARD socket wrench. construction, action,reactiva- of RADIO WORLD.Itwillcontinueforat tion, testing and use of vacuum least It consists of a 6%" long metal tubing is tubesaswellasspecifications three months fromthen.Send $1.50 whichisaplunger,controlledbyaknob. for vacuum tubes and applica- forathree -monthsmailsubscriptionfor The plunger has a gripping terminal (called a tionsfor distant control of in- RADIO WORLD and youwillreceiveRADIO histrial processes and precision socket, hence the name "socket wrench") that WORLD every week for 13 weeks (3 months), may be expanded orcontracted measurements. andbesidesreceive FREE theissuesbe- tofit6/32, Price $2.50 ginning June 1st when the Power Amplifier 8/32 and 10/32 nuts,the most popular sized series started. nuts in radio. RADIO WORLD Use the knob to push out the plunger, press 145 West45thStreet,New YorkCity down on the handle to grip the nut, then turn (JustEastofBroadway) PLEASE USE THIS COUPON RADIO WORLD, the nut to left for removal or to right for fast- 145 West 45th St., New York City. ening down.Total length, distended, including Gentlemen: Enclosed please find $1.50, for stained wooden handle, 10".Gets nicely into which please send me RADIO WORLD each week tight places.Send $1 for 8 weeks' mail sub- for13 weeks, beginning at once.Also send scriptionfor RADIO WORLD and getthis issues beginning June 1st and up to the issue wrench FREE. with which my subscriptionstarts,without No other premium with this offer.Present DYNAMIC BAFFLE extra charge. extend subscription by stating Completelybuiltup,faranytypedy- he isone, and entitle himself to namic chassis.State what make dynamic Name this FREE you wantitfor.Cane sides, apes bask. Premium. making $1 remittance. De luxe finish.Size. 24:24 leshas...... 2.00 Address City RADIO WORLD GUARANTY RADIO GOODSCO. State. 145 WEST 45Th ST., N. Y. CITY 145 West 45tb Street.Now York CRY This offer expires July 6th, 1929.

BLUEPRINT of the FrontPanelandSubpanel LACAULT'S BOOK for the "Super -HeterodyneConstructionandOperation," New, Highly Selective givingthemaster'smostmasterfulexposition ofthetheory,performanceandconstruction of Screen Grid DIAMOND thisfascinatingtypeofcircuit,isanecessity Screen Grid Universal toevery seriousradio experimenter.More than (AC MODEL) Bakelite front panel alone,drilled....$2.3.5 100 pages and more than 50 illustrations.Buck- Drilled aluminum subpanel alone, with ram cover.This book by R.E.Lacault,FREE self - bracketing feature, built - in ifyousend$1.00foran8 -weekssubscription $ 1.00 sockets,extrawashersandhard- for Radio World.Present subscribers may accept ware 3.00 willbeextended. thisoffer. Subscription RADIO WORLD Both front and subpanel together 5.00 145 W. 45th St., N.Y. City 145 West 45th Street New York City RADIO WORLD Just East of B'way Few Doors East of Broadway GUARANTY RADIO GOODS CO. 145 West 45th Street, New York City (Just East of Broadway) Equip Yourself Now With Necessary Meters! Todo your radio work properly you need meters. Hero is your opportunity toget them at no extra cost.See the list of nine meters at left.Heretofore we have offered thechoice SUBSCRIBERS! of any one of these meters free with an 8 -weekssubscription forRADIO WORLD,at$1,theregularpriceforouch subscription. Now we extendthisoffer. Forthe first time you are permitted to obtain any one or moreorallof these metersfree,by sending in$1for8 -week's subscription, en- Look at the Expiration titling you to one meter; $2for16 weeks, entitlingyou to two meters; $3for26 weeks,entitling you to three meters; $4 for 35 weeks, entitling you to four meters; $5 for44 weeks, Date on Your entitling you to 5 meters; $6for52 weeks,entitling you to six meters. Return this offer with remittance, and cheek off desired metersinsquaresatleft. Wrapper RADIO WORLD willhelp youinyour radio work,so youwillbeabletousethemetersmost valuably. abreast ofall the new circuits, intimate details on perfectingKeep Please look at the subscription existingsets,and getinsidetrackonsensitivity, reception, tonal quality, and news of radio, technical anddistance non- date stamped on your lastwrap- technical.Enjoy the writings of Dr. Lee De Forest, McMurdo Silver,J.E.Anderson, Herman Bernard andahost of other per, and ifthat date indicates radio engineers who contribute their knowledge to you through the medium of RADIO WORLD, the first and only illustrated that your subscription is about national radio weekly.You can find no magazine that better caterstoyour needsthan RADIO WORLD. Short waves? toexpire,please sendremit- RADIO WORLD willtellyouallabout them. Extremely sensitive broadcast receivers?Their construction and operation tance to cover your renewal. Your Choice of arefully discussed with confident regularity. Power supplies - -push-pull or otherwise?AC receivers?Screen grid tubes? These Nine Meters FREE! Large receivers that giveasuper -abundance of performance- In this way you will get your small,economicalreceiversthat giveperformance out 0-6 Voltmeter D.0 No. 328 comparison to their size?Are you interested in these?ofall copies without interruption and 0-50VoltmeterD.0 No. 337 you're interested in RADIO WORLD. Then 6 -Volt Charge Tester D.0 Ne. 23 Present mall subscribers may renew their subscription under keep your file complete. 0-10 AmperesD.0 No. 338 thisremarkablygenerousoffer.Putacross 0-23 Milliamperes D.0 No. 325 insquare. 0 0-50 Milliamperes D.0 No. 350 SUBSCRIPTION DEPARTMENT 0-100MilliamperesD.0 No. 390 RADIO WORLD 0-300MilliamperesD.0 No. 399 145W. 45th St.. N. Y.City-Published Weekly. RADIO WORLD 0.400MilliamperesD.0 AllNewsstands. No. 394 15e per espy-$3, six months -88 ayear 145 WEST 45TH ST., N. Y. CITY June 22, 1929 RADIO WORLD

PLUG AND CABLE for anySHORT WAVE ADAPTER All Parts Handiest thing for ANY short-wave adapter. May also be used as a 5 -Lead Bat- Put detector tube of your present setin for socketof anyshort-waveadapteryou tery Cable and Plug, inconjunction build, put plug in detector socket of your with a 5 -prong (AC227) socket. broadcastreceiver. Cable: 34".Leads identified both by color scheme and tags MB -29 5 -prongplugand5 -lead cable for AC short wave adapter. May as describedand specified beused as 5 - lead bat- tery cableby J.E. Anderson-$40. plugwith Also UY socket (C a t. No. 21AC) 151.54 Velvetone 245 P -P GREEN {-prong wen' plugonly aecessary ad - Power Amplifier-$55 YELLOW dittonto otherforbatteryshort- GUARANTY RADIO GOODS CO. waveadapter(Cat.No. 21 -BAT) $0.50. ' 145 West 45th Street Cat. No. Z1AC and n -BAT ordered together$1.75. N. Y. 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RADIO WORLD, published every Wednesday, If your receiver or amplifier, no matter of what dated Saturday of same week, from publication kind,is not giving proper results, send itto us, office,Hennessy Radio PublicationsCorporation, AGENTS AND SALESMEN WANTED prepaid. We will test it FREE and let you know 145 West 45th Street, New York, N. Y., put east what's wrong,telling you costofrepairs.Our of Broadway.Roland Burke Hennessy, President, Sell $5.00 Men's Daily Necessity for 50c. Cost charges are very reasonable. Six years' experience. M. B. Hennessy, Vice -President; Herman Ber- quantities20c. Samplepostpaid30c. Catalog Loudspeakers and units repaired.Burnt -out coils nard, Secretary.Roland Burke Hennessy, Editor; hundreds household articles free.Mills Sales Co., replaced.Jaynxon Laboratories,57 Dey Street, Herman Bernard, Managing Editor; J. E. Ander- 901 Broadway, New York. New York City. son, Technical Editor; Anthony Sodaro, Art Editor. RADIO WORLD June 22, 1929 New Style DeLuxeLeatherette Carrying Case FREE with each Jiffy Tester! This combination of meterstests all standard tubes, including thenew AC screen grid tubes and the new 245 tube, making thirteen tests in 41/2 minutes! Instruction sheet gives these tests in detail.

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A PORTABLE testinglaboratoryisyours mHE newcarrying 11 you case, whichis when possessacombinationJiffy -I- furnished FREE with each order Tester, for then you can measure the filament and for a Combination Jiffy Tester, platevoltagesofallstandardtubes,including AC the entire outfit, including contains tubes, and all standard battery -operated or AC screen grid cable and plug, and three the three meters, tubes; also plate voltages up to 500 volts on a high re- prong tubes, two for 199 tubes).adapters (one for 4 - sistance meter that is 99% accurate; also plate current. 704x3%" and has nickel This case is 1054x lock.The case is made of corner pieces and protective snap- The Jiffy Tester consists of a 0-20, 0-100 milliammeter, with change- strong wood, with black leatheretteoverlay. over switch and a 0-10 volt AC and DC voltmeter (same meter reads To operate, removea tube from the receiver, place both), with two sockets, one for 5 -prong, the other for 4 -prong tubes; in the vacant receiver socket, the cable plug agridbiasswitch and two binding poststo which areattached the Tester, connect the high put the tube in the proper so,ketof the cords of the high resistance voltmeter; also built-in cable with 5 - and you're all set to makeresistance meter to the twobinding poste, prong plug and 4 -prong adapter, so that connections in a receiver are the thirteen vital tests in41A minutest transferred to the Tester automatically.Not only can you test tubes, The Combination Jiffy Testeris just the thing for service but also opens or shorts in a receiver, continuity, bias, oscillation, etc. tom set builders, experimenters, men, cus- The instruction sheet tells all about these tests. "Jiffy 500."The price is only $14.50.students, teachers and factories.Order In addition you can test screen grid tubes by connecting a special Ifa0-600 AC and DC high cable, with clip to control grid (cap of tube) and other end of special desired, so house electricity line resistance meter (99%accurate)is cable to the clip in the set that went to the cap before the tube was can be measured, as well asvoltage and power transformervoltages transferred to the tester. plate voltage, instead voltmeter, order "Jiffy 600"at $15.50. of the 0-500 DC

GUARANTY RADIO GOODS CO., 145 W. 45 St., N. Y. City.(Just East of Broadway). 0 Please ship at once on 5 -day money -back guaranty one "Jiffy 500," at $14.50, consisting of (1)One Two -in -One 0 to 10 voltmeter for AC and DC.Same meter reads both.Scale especially legible at PA to PA volts.This meter reads the AC and DC filament voltages. (2) One DOUBLE reading DC milliammeter, 0 to 20 and 0 to 100 milliamperes, with change aver switch.This reads plate current. - (3) One 0-500 volts high resistance voltmeter, 99% accurate; with tipped 30" cord B voltages. to measure (4) One 5 -prong plug with 30" cord for AC detector tubes, etc., and other tubes. one 4 -prong adapter for (5 One grid switch to change bias. (9) One handsome moire metal case. ( One 5 -prong socket. (10) One instruction sheet. ( One 4 -prong socket. (11) One de luxe carrying case. (8 Two binding posts. (12) One screen grid special cable. 13 If 0-300 DC high tesistance 99% accurate voltmeter is preferred Price is same, $14.50. to 0-500, put check here. Cl Same as above, except substitutea 0 -600 -volt AC and DC high resistance 99% accurate voltmeter (same meter reads both) for the 0-500 DCmeter.Price $15.50.

NAME

ADDRESS

CITY STATE The new de luxe leatherette compact and handy. carrying case it FIVE-DAY MONEY -BACK GUARANTY wide, 335" deep. Size 10%" long, 7%"