Radio News for October, 1928 289

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www.americanradiohistory.com Radio News for October, 1928 289

EARNED $500 SPARE TIME &syWays WITH RADIO tontake 3an how' ín YoiiïSpaïe.?ime Coplay, Pa., June 4- (RA)- During the few months that Frank J. Deutsch has been a member of the Radio Association of America, he has made over $500 out of in Radio in his spare time. INDIO "Four super -hetrodyne sets of my own construction brought me a profit of $60.00 each, and the other profit was from sales EACH of these plans, developed by the Radio Association of supplies purchased through the Whole- of America, is a big money- maker. Set owners everywhere want to get rid of static, to sale Department of the Association," he have their sets operate from the electric light socket, said. "The Association certainly has the tone improved, and the volume increased, and great plan for ambitious men." transformed into single -dial controls. Phonograph owners In a neighboring state, Werner Eichler, want their machines electrified and radiofied. If you learn to render these services, you can easily Rochester, N. Y., another member of the make $3.00 an hour for your spare time, to say nothing Association, has been making $50 a week of the money you can make installing, servicing, during his spare time. repairing, and building radio sets, and selling supplies. They are only two of the hundreds of Over $600,000,000 is being spent yearly for sets, Radio Association members who are making supplies, service. You can get your share of this money out of Radio in their spare time. business and, at the same time, fit yourself for the big -pay opportunities in Radio by joining the Association. BECOMES RADIO ENGINEER IN Join the ONE YEAR Radio Association Toronto, Canada, May 20- (RA) -Onc of the newly admitted associate members of America of the Institute of Radio Engineers is A membership in the Association offers you the Claude DeGrave, a member of the engi- easiest way into Radio. It will enable you to earn neering staff of the DeFbrest Company of .$3.00 an hour upwards in your spare time -train you to install, this city. "I knew nothing repair, and build all kinds of sets - about Radio start you in business without capital or finance an and started from the ground up," Mr. invention -train you for the $3,000 to $10..000 big - DeGrave stated, "when I enrolled a year pay radio positions -help secure a better position at ago in the Radio Association. Its easy bigger pay for you. A membership need not cost you u cent! lesson's and superb training made it possible for me to become a Radio Expert in less The Association will give you a comprehensive' than a year's time. My income is now practical, and theoretical training and the benefit about 225% more than of our Employment Service. You earn while you at the time I joined learn. Our cooperative plan will make it possible for the Association." you to establish a radio store. You have the privilege The Institute of Radio Engineers is a very of buying radio supplies at wholesale from the very first. ' exclusive 'organization, and its membership requirements are very rigid, so that Mr. DeGrave has reason to be proud of his ACT NOW election. -If you wish No -Cost Membership Plan Clerk Doubles To a limited number of ambitious men, we will give Income In Special Memberships that may not -need nqt -cost Six Months Through Radio you a cent. To secure one, write today. We will MODERNIZE OLD SETS send you details and also our book, "Your Opportunity Chicago, Ill., May 9 -Even though his WITH ONE DIAL CONTROL in the Radio Industry:" It will open your eyes to membership in the Radio Association has the looney -making possibilities of Radio. 'resulted in W. E. Thon securing the manager- ship of a Radio Department in a large COUPON Chicago store, his ambition was not satisfied. RADIO ASSOCIATION OF AMERICA Six months later, he started his own store. Dept. RN -10, 4513 Ravenswood Ave., "The Radio Association has an excellent Chicago, III. ,plan for the man who wants to get out of Gentlemen: the rut and succeed," Please send me by return maid full details of your says this man who Special Membership Plan, and also copy of your quickly rose from clerkdom to the pro- book, "Your Opportunity in the Radio Industry." prietorship of a profitable radio store. "I Name attribute my success entirely to the Radio Association of America. Six months after Address I had enrolled, I bad doubled my income City State through its help." INA

l'leose soy you saw it in RADIO Nrws

www.americanradiohistory.com Radio News for October, 1928

Volume 10 OCTOBER, 1928 Number 4

HUGO GERNSBACK, Editor -in -Chief ROBERT HERTZBERG, Managing Editor BERYL B. BRYANT, Laboratory Director C. P. MASON, Associate Editor Technical Editor FRED H. CANFIELD, Technical Editor C. WALTER PALMER, Assistant

Contents of This Issue

What Is Coining in Television e Television in Natural Colors Demon- By Hugo Gernsback 299 strated By Ronald F. Tiltman 320 l'he Radio Laboratory Takes Wings How to Build from the Schematic- By S. R. Winters 300 Part II By Fred H. Canfield 321 "Wired Wireless" -What It Is and Why The Radio Beginner -"The Milk- Shaker By J. E. Smith 302 Special" Receiver -By the Staff of RADlo NEws Laboratories 324 The Photoelectric Cell-Radio's "Eye" By Dr. Lewis lt. Koller 30.5 'l'he "Combine" Receiver -a $100 Prize Winner By W. H. Scheppele 328 The Listener Speaks By Himself 308 A Completely -Shielded Short-Wave Re- ceiver By Herndon Green 334 Broadcastatics 309 The Search for the Perfect Amplifier What's New in Radio 310 By Sydney P. O'Rourke 338 Interesting New European Screen-Grid Radio Wrinkles 340 Tubes By Major R. Raven -Hart 313 Radiotics 342 Television-"Seeing" Music with a Tele- vision Receiver 314 On the Short Waves 343 Radio -Picture Equipment for Police List of Broadcast Station Calls 344 Noaek 316 By Dr. F. The Radio Constructor's Own Pages 346 The F'ultograph Radio Picture -Broadcast RADIO NEws Laboratories 348 System 317 I Want to Know By C. W. Palmer 350 The Radio Bean Sorter -A Novelty By Herbert W. Augustaclt 318 Adjusting and Operating the Screen - Grid Strobodyne By R. E. Lacault 380 RADIO NEWS Free Blueprints Available 383 for the Asking 319 Terms of Prize Awards

Reproduction of articles 10th of each preceding month. Then are 12 obtained from the publishers. Copyrighted in Germany. RADIO NEWS is published on the in Germany is reserved for Radio, Berlin 42. Subscription price is $2.50 a year in U. S. and possessions. United States and Canada, numbers per year. U. S. Coin as well as U. 8. Stamps RADIO NEWS is for sale at all newsstands in the Canada and foreign countries, $3.00 per year. and and at Brentano's. Are. de L'Opera. Paris, France. European agents: S. J. Wise (no foreign coins or stamps). Single copies. 25 cents each. Checks accepted of EXPERIUIENTER PUBLISHING Et Cie. 40 Place Cerce. Antwerp, Belgium. money orders should be drawn to order HOW TO SUBSCRIBE FOR RADIO NEWS. Send your name. address and re- INC. Are., New York. Mention the CO., to mittance to Experimenter Publishing Co., 230 Fifth All communications and contributions to this journal should be addressed name of the magazine you arc ordering. We also publish SCnìNCE AND INVEN- Ace., New York, N. Y. 'Unaccepted contribu- GUIDE, AMAZING STORIES and TIDBITS. Editor, RADIO NEWS, 230 Fifth con- TION, RADIO LISTENERS' tions cannot be returned unless Rol postage has been included. All accepted Write clearly. tributions are paid far on publication. A special rate is paid for novel experi- RATES AND TEEMS. The subscription rate for RADIO. NEWS is $2.50 per accompanying them are highly desirable. Publishers are When remitting do no by check. money order, or registered ments: good photographs is taken with year. (12 numbers). not responsible for loss of manuscripts, although every precaution letter if cash is enclosed. Avoid sending cash through the mail if possible. Sub- such manuscripts, upon receipt thereof. scriptions for less than one year are not accepted. Subscription may be made in the combination with SCIENCE & INVENTION, RADIO LISTENERS' GUIDE, RADIO NEWS. Monthly. Entered as second -class matter. July 12. 1924. at the AMAZING STORIES and TIDBITS. Post Office N. One POSTAGE. We prepay in all parts of the United States, Mexico and Francso Cli.fMarch Title regis ereU.d7 S. dtetPan lre postage in r J aknd n ic, Publishing Co., Inc., 230 Fifth Ave.. island possessions. For foreign or Canadian subscriptions we require 50 cents Copyright, 1928, by The Experimenter must not be to the subscription price for additional postage charge. York. The contents of this magazine are copyrighted and addition New States without giving full credit to the publication. CHANGE OF ADDRESS. Notify us as far in advance as possible. It requires reproduced in the United permission Is several weeks to malle an address change on our records. Always write clearly. Translation into foreign languages must not be made unless The contents of RADIO NEWS are Indexed in the Industrial Arts Index. copies of which can be found In every library.

Published by Experimenter Publishing Company, Inc. H. GERNSBACK, President S. GERNSBACK, Vice. President and Treasurer C. E. ROSENFELT, Secretary Member: Audit Bureau of Circulations Radio Magazine Publishers Association Advertising Representatives: RHODES & LEISENRING New York Offices: 624 Graybar Building Chicago Offices: 307 North Michigan Ave. Editorial and General Offices 230 Fifth Avenue, New York City

www.americanradiohistory.com 291. Radio News for October, 1928

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The PACKARD Engineers have invented this most unusual, powerful SUPER - Eight Tube Radio. Astonishing volume and tone quality. Remarkable selectivity and long -distance reception. Leading radio engineers unanimously agree that there is no better radio made - regardless of price. Let us prove this by shipping a set to your home on 30 days' trial. Examine the set from A to Z. Let the most WORLD'S GREATEST RADIO exacting critics pass on its merits. And if, after the 30 Genuine Walnut Console Cabinet the Packard day trial period, you are convinced that tubes and one genuine full- of any console Eight powerful A. C. Eight -tube El.ctric is fully the equal wave rectifying tube -nine tubes in all. Supreme radio set selling up to $250 -then, and only then, need quality throughout. Simple to operate. Connect the you decide to keep it at our factory price of only $99 plug to electric socket and turn switch. Only one -otherwise, return it.. dial to tune. One hundred per cent electric. Hand- some walnut cabinet- two -tone genuine DUCO fin- This marvelous set combines every new scientific de- ish. Metal trimming finished in old gold. Marvel- velopment in receiving sets-possessing beauty, refine- ous built -in, powerful speaker. Size of cabinet is 54 ment, durability. Gets everything on the air from coast inches high, 27 inches wide. to coast -from Mexico into Canada, loudly, clearly, and distinctly. Only one dial to tune in all stations. You Save the Jobbers', Dealers' and Salesmen's Profits The PACKARD Radio is shipped direct from our factory. All the in- between profits are deducted from the price of the Packard Radios are also set and instead of paying $250 you pay only $99. Quantity production, economy in selling, and only a small profit made for BATTERY OPERATION for the manufacturer makes this astounding offer possible.. PRICED AS LOW AS S53 MAIL COUPON NOW FOR I. Packard Radio Company 30 days' free trial offer gar 2323 Milwaukee Ave., Dept. 320, Chicago, Ill. Mail coupon at once for complete inform- I am interested in Packard Radios and your $5,000.00 Don't miss this opportunity. guarantee. Send ation about the PACKARD A. C.- 8 TUBE ELECTRIC RADIO and Bonded 30 days' free trial offer and our liberal 30 days' free trial offer. No obligation on your part. Our full details. cash bond backs up our guarantee. $5,000.00 Name

PACKARD RADIO CO. Address..... ------_ -_ -- 2323 Milwaukee Ave. Dept. 320 Chicago, Ill. City._-___ - State Please say you saxe it in RADIO NEWS www.americanradiohistory.com 29 2 Radio News for October, .1928

INDEX TO ADVERTISERS

Page Page Page Page

A F M S

Acme Wire Co., The 375 Fanspeaker Radio Co. 381 M & II Sporting Goods Co 396 School of Engineering of Aerovox Wireless Corp 389 Fergus Co., The 372 Massachusetts Radio & Milwaukee 396 Aero Products, Inc. 378 Freshman Co., Inc., Chas 381 Telegraph School 383 Scott Transformer Co., Allied Radio Corp., Master Engineering Co 368 Back Cover Sce Jay 356 -358- 372-374 -393- Metro Electric Co.. . Battery Co 370 400- 385 -386 -38 Inside Front Cover Setbuilders Supply Co...358 -391 Aluminum Company of MidWest Radio Corp'n 355 Shanklin Mfg. Co. G 393 359 America Shieldplate Tube Corp. 397 American Radio & Merc General Radio Co. 391 Silver -Marshall, Inc. 294 Co. 388 Gernsback, S. 380 Smith, B. I-Iawley 395 American Sales Co. 378 -382 Gray & Danielson Mfg. Co 386 Southern Toy Co. 385 Amrad Corporation, The.... 383 Starrett Mfg. Co. 391 Arcturus Radio Co. 399 N

H National Company, Inc 388 B National Electrical School 388 Hammarlund Mfg. Co 381 National Radio Institute 293 -373 T Barawik Co., The, 356 -358 High Frequency Labs. 387 National School 360- 368- 370 -374 -378 -381 -383 -385 of Visual Education 386 Teleplex Co. 356 386-388-391-392-395-396-398-399 New England Mills Co 378 Televocal Corp. 356 Belden Mfg. Co. 368 Thordarson Elec. Mfg. Co 353 Co 356 Benjamin Electric Mfg. I Townsend Labs. 389 Transformer Corporation Illinois Transformer Co. 356 of America 385 C Independent Elec. Works 396 Tyrman Electric Corp. 399 Interstate Electric Co 374 Carborundum Co., The 370 Carter Radio Co. 368 P Ceco Mfg. Co. 354 Pacard Radio Co. 291 Central Radio Labs. 362 J Pathfinder Publishing Co 391 Chemical Institute of New U Penn Co., Geo. R. 395 York, Inc. 394 J. M. P. Mfg. Co., Inc 372 Pilot Electric Co.. Inc., Underground Aerial System, Chicago Radio Apparatus Jewell Electrical Instru- 296- 297 -298 Inside Back Cover Co. 389 ment Co. 357 Potter Mfg. Co. 360 Cloverleaf Mfg. Co. 396 Press Guild. Inc. 362 Consumers Radio Co. 391 Craftsman Radio Products 372 Cunningham, Inc., E. T 360 X V

Maras Electric Co. 362 Van Asche Radio Co. 392 D Knapp Electric Co. 379 367 R Daven Corp., The 392 Kodel Radio Corp. Denver Optic Co. 305 Radiali Co. 395 Directory Section of Radio Radio Association of w News 364 -365 America 289 L Dresner Radio Mfg. Corp. 386 Radio Directory Section of Walker Co., The Gco. W... 378 RADIO NEws 364 -363 Lacault, Inc.. R. E 377 Western Radio Mfg. Co., Radio Doctors, Inc. 387 Lacey and Lacey 386 295 -374 Radio Equipment 372 E Lafayette Hotel 358 Co. Wirt Co. 388 Radio of America 367 Leutz, Inc., C. R. 363 Institute Eby Mfg. Co., Inc., H. H... 392 Lynch, Inc.. Arthur H 372 Radio Manufacturers Show Electrad, Inc. 370 -393 Ass'n 397 Electric Specialty Co. 391 Radio Products Labora- Electro- Chemical Co. of tories 369 SY 383 Radio Specialty Co. 366 America Mc Elkon, Inc. 358 -371 Raytheon Mfg. Co. 358 X -L Radio Labs 362 Excello Products Corp 399 McAlpin Hotel 391 Rowan Co., Walter 395 Yaxley Mfg. Co.' 389 Please say you saw it in RADIO Nees.

www.americanradiohistory.com Radio News for October, 1928 293

If all the Radio sets I've "fooled" with in my time were piled on top (f each other, they'd reach about halfway to Mara. The trouble with me was that I thought I knew so much about Radio that I really didn't know the first thing. I thought Radio was a plaything - that was all I could see in it for me.

I Thought Radio Was a Plaything But Now My Eyes Are Opened, And I'm Making Over $100 a Week!

$50 a week! Alan alive, just one year usually stayed home in the evenings after day I sent for their eye- opening book, I'd ago a salary that big would have been the work, because I didn't make enough money been wailing "I never had a chance!" height of my ambition. to go out very much. And generally during Now I' E making, as:I told you before, Twelve months ago I was scrimping the evening I'd tinker a little with Radio - over $100 a week. And I know the future along on starvation wages, just barely mak- a set of my own or some friend's. I even holds even more, for Radio is one of the ing both ends meet. It was the same old made a little spare chane this way, which most progressive, fastest -growing busi- story-a little job, a salary just as small as helped a lot, but I didn't know enough to nesses in the world today. And it's work the job-while I myself had been dragging go very far with such work. that I like -work a man can get interested along in the rut so long I couldn't see over And as for the idea that a splendid Radio in. the sides. job might be mine, if I macle a little effort Here's a real tip. You may not be as bad If you'd told me a year ago that in twelve to prepare for it -such an idea never en- off as I was. But think it over-are you months' time I would be making $100 and tered my mind. When a friend suggested satisfied? Are you making enough money, more every week in the Radio business - it to me one year ago, I laughed at him. at work that you like? Would you sign a whew! I know. I'd have thought you were "You're kidding me," I said. contract to stay where you are now for the crazy. But that's the sort of money I'm "I'm not," he replied. "Take a look at next ten years-making the same money? pulling down right now -and in the future this ad." If not, you'd better be doing something I expect even more. Why only today - He pointed to a page ad in a magazine, about it instead of drifting. But I'm getting ahead of my story. I an advertisement I'cl seen many times but This new Radio game is a live -wire field was hard up a year ago because I was kid- just passed up without thinking, never of golden rewards. The work, in any of ding myself, that's all -not because I had dreaming it applied to me. This time I read the 20 different lines of Radio, is fascinat- to be. I could have been holding then the the ad carefully. It told of many big op- ing, absorbing, well paid. The National same sort of job I'm holding now, if I'd portunities for trained men to succeed in Radio Institute -oldest and largest Radio only been wise to myself. If you've fooled the great new Radio field. With the adver- home -study school in the world -will train around with Radio, but never thought of it tisement was a coupon offering a big free you inexpensively in your own home to as a serious business, maybe you're in just book full of information. I sent the coupon know Radio from A to Z and to increase the same boat I was. If so, you'll want to in, and in a few days received a handsome your earnings in the Radio field. read how my eyes were opened for me. 64 -page book, printed in two colors, telling Take another tip-No matter what your all about the opportunities in the Radio plans are, no matter how much or how little When broadcasting first became the rage, field, and how a man can prepare quickly you know about Radio -clip the coupon be- several years ago, I first began my dabbling and easily at home to take advantage of low and look their free book over. It is with the new art of Radio. I was "nuts" these opportunities. Well, it was a revela- filled with interesting facts, figures, and about the subject, like many thousands of tion to me. I read the book carefully, and photos, and the information it will give you other fellows all over the country. And no when I finished it I macle my decision. is worth a few minutes of anybody's time. wonder! There's a fascination -something What's happened in the twelve months You will place yourself under no obligation that grabs hold of a fellow -about twirling since that day, as I've already told you, -the book is free, and is gladly sent to any- a little knob and suddenly listening to a seems almost like a dream to me now. For one who wants to know about Radio. Just voice speaking a thousand miles away! ten of those twelve months, I've had a address J. E. Smith, President National Ra- Twirling it a little more and listening to Radio business of my own. At first, of dio Institute, Dept 22S, Washington, D. C I the mysterious dots and dashes of steamers course, started it as a little proposition on O- =MO far at sea. Even today I get a thrill from the side, under the guidance of the National - - - -- I iJ. E. SMITH, President, this strange force. In those days, many Radio Institute, the outfit that gave me my National Radio Institute, times I stayed up almost the whole night Radio training. It wasn't long before I I Dept. 22S, Washington, D. C. trying for DX. Many times I missed sup- was getting so much to do in the Radio line I Dear Mr. Smith: per because I couldn't be dragged away that I quit my measly little clerical job, and Please send me your 64 -page free book, from the latest circuit I was trying out. devoted my full time to my Radio business. I printed in two colors, giving all information I about the opportunities in Radio and how I I I never seemed to get very far with it, Since that time I've gone right on up, can learn quickly and easily at home to take though. I used to read the Radio maga- always under the watchful guidance of my I advantage of them. I understand this' request zines and occasionally a Radio book, but I friends at the National Radio places me under no obligation, and_that no Institute. I salesman will call on me. never understood the subject very clearly, They would have given me just as much and lots of things I didn't see through at all. help, too, if I had wanted to follow some I Name So, up to a year ago, I was just a dabbler line of other Radio besides building my own I Address -I thought Radio was a plaything. I never retail business-such as broadcasting, man- i realized what an enormous, fast -growing ufacturing, experimenting, sea operating, ITown State...... I industry Radio had come to he- employing or any one of the score of lines they pre- Occupation thousands and thousands of trained men. I pare you for. And to think that until that =MI _.- .1 Please say you saw it in Rauto NEWS www.americanradiohistory.com Radio News for October, 1928 294

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AU of the models here Where A.C. filament power is desired, sign and S-M 247 or 325 transformer is readily built Are you receiving "The mentioned use standard tubes (not included Radiobuilder" regularly? in the kit price)and are supplied either in kit into the amplifier. The 681-210 (push-pull. given, or completely wired at $87.00) is the most powerful single -stage Published every month; form, at prices amplifier made. The 681-250 at $81.50 uses this little magazine pro- slightly higher prices. Complete information two. Type is in the big new S-M catalog. only one power tube instead of vides you with the earliest given 682 -210 (2 -stage push -pull, $102.00) uses a B, type 670B information on forthcom- For sets requiring 180 volts 226 tube in a stage preceding its push -pull ing developments and Reservoir Power Unit ($40.50) will deliver super-power stage. Type 682.250 at $96.50 is S-M up to 60 ma. of current, with 22, 90, and 135 similar, but with one super -power tube only with operating hints and volts also available, besides 22 -90 variable. in the last stage. Type 685 ($125.00) is the kinks that will help you to The 670ABC ($43.00) is similar but supplies popular Public Address Unipac, using three get the most out of radio. also 1M, 2 t/ and 5 volt A.C. filament current. stages for the amplification of microphone, To S -M Authorized Service Type 675ABC ($54.00) gives 450 maximum radio, or record pick -ups to cover crowds up Stations, "The Radio - voltage instead of 180, and has an adapter to 10,000 people. 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S-M will gladly refer your inquiry to IIÏÍ11i,. ::üleeäcÇ.. A _...z+..M. .ú.ir, y -Y. Serv- . Please send me, free of charge, the an Authorized Silver -Marshall fft5tt!-t-r,alrrf°Gai complete S-M Catalog. ice Station near you. If, on the other =curTs!iióBUil. i:"s ...mil faammarl For enclosed in stamps. send me the r ® uInl following: I hand, you build sets professionally, !!líi!iíl !! of THE RADIOBUILDER . ' ts iiiúiiri .. (50e) Next 12 issues and are interested in learning whether b° e i 7 iu1 Next 25 issues of THE RADIOBUILDER 1 fa .... ($1.00) there are valuable Service Station .. 3 816., ..t..l S-M DATA SHEETS as follows, at 2c each: yet open in your territory, i=Ir. n annwmm ....No. 1. MOB. 670ABC Reservoir Power Units I franchises Unipac ....No. 2. 685 Public Address please write us. 11® , II 111111111111milli ....No. 3. 730, 731, 732 Round- the -World" Short " w +, m ,a ,a, so m,... Wave sets raw..,. c., ....No. 4. 223, 225. 226. 2S5, 256. 251 Audio Trans- formers I ....No. 5. 720 Screen Grid Six Receiver ...No. 6. 740 "Coast-to-Coast" Screen Grid Four 848 S . A. ....No. 7. 675ABC Power Supply and 676 Dynamic SILVER - MARSHALL, In öU Speaker Amplifier I .... (50c) Sargent -Rayment Instruction Booklet Name mss s- Add ress ly.ea of vna rnm it in RADIO NEWS www.americanradiohistory.com Radio News for October, 1928 797

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Unequalled tone quality, and an appearance (in vidually shielded in neat copper cans -and finally the the cabinet) identical with the 720 Six, -yet the price is marvelous new audio transformers, described on the only $51.00 for the complete approved kit, with the 700 opposite page. Then you will have some idea of the 720's cabinet $9.25 extra. The 740 goes together easily and overwhelming superiority in actual reception. simply, and will out -demonstrate ready-made sets selling Try it. See these three screen -grid r.f. stages cut past a at twice its price. powerful local and reach out after a feeble signal a thousand miles away on the next channel (only 10 kilocycles difference!) and deliver it with loud speaker volume. And The 730 "Round- the -World" tone quality -well, it takes a vivid imagination indeed to Have you had your taste of the "thrill band"-the short get from the mere amplification curve on the preceding wave band from 17 to 200 meters? Down there you can page, remarkable as it is, any idea of the glorious beauty hear European broadcasting stations; chain programs which transformers like these impart to radio music. through heavy static; television -the low -wave band is its 740 Coast -to -Coast So -when we get hold of a set carrying the S-M guar- busy nursery. You can hear amateurs in almost every Four: Best Money's antee, and are able to offer it at a list price of only $72.50 country, all in one evening -if you have this neat, trim, Worth in the Fifty- for the complete kit (the 700 cabinet is $9.25 extra) -or snappy little receiver -four-tube regenerative (non -radi- Dollar Class the entire set custom -built in this cabinet and tested in the ating) -with one screen grid r.f. stage and two of the S-M S-M laboratories at $102.00 -then we say it's a bargain. high -gain audio stages. Four plug -in coils fit instantly into And while we hope to keep 720's always in stock, scarcity a 5 -prong socket on top of the aluminum cabinet. The corn. is coming-so we urge you to order yours now! plete 730 kit, including cabinet, is $51.00; the 731 (same kit without the two audio stages, at $36.00) converts any 710 set to long- distance short -wave reception. The 732 Essential The Sargent -Rayment Seven Kit, at only $16.50, contains the two tuning and tickler A station tuned in for every ten kilocycles -a hundred condensers, the four plug -in coils, coil socket, and three stations heard in one summer evening, in the heart of r.f. chokes, with full instructions. Chicago interference -that is the performance record of Choose whichever of the three kits you prefer, and step the 710 Sargent-Rayment Seven-latest masterpiece of out into the "thrill band "! the inventors of the "lnfradyne." The 710 is a precision laboratory instrgqment for the veteran fan. The thick aluminum shielding and chassis, finished in satin silver, The 1929 Laboratory Receiver give beauty of a strikingly appropriate type. Other features Three stages of screen grid radio frequency amplification, responsible for this unusual performance include five a screen grid first detector, two stages of 65 kc. screen grid sharply tuned circuits in a four -stage screen grid r.f. ampli- intermediate frequency stages, and a super-powered second fier, all tuned by a single illuminated drum, and provided detector -all copper -shielded- working into an audio with individual verniers. One knob controls volume from stage using the new S-M audio system -selectivity that Five Continents in _ero to maximum. There are no other controls. Each circuit makes stations literally snap in and snap out -and all One Evening: 730 is individually shielded, bypassed, and isolated from all under the control of two vernier drum dials, and a "vol- Short -Wave Set others. New S-M transformers insure unbeatable tone ume" and a "sensitivity" knob. Just imagine a 65 kc. i.f. quality. The set is a joy to build, so workmanlike is its super, with all the tremendous amplification that this design and layout. frequency (plus screen -grid tubes) gives! With the The approved 710 Sargent -Rayment kit, manufactured ultra -fine tone that can be gotten only with the exclusively by S-M, is priced at $120.00 with cabinet. new S-M audio transformers and a stage of external light -socket, push -pull 210 or 250 Unipac amplification-the highest- powered, finest -toned A Station Every 10 Kilocycles: amplification money can buy! The Sargent- Raymenc Six The parts for this super, mostly of S-M manufacture, cost but $95.20 complete, less cabinet at $9.25 list. Outstandingly the finest superhetro- dyne money can buy.

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Addre. State L----l'ltl' _._.-- R.N 10-28 Pfease .cot' vnu .vin, it ix RAMCI NF W!' www.americanradiohistory.com Editorial and General Offices, 230 Fifth Avenue, New York Vol. 10 OCTOBER, 1928 No 4

What is Corning in Television By HUGO GERNSBACK

NOW that television has actually arrived, and a number radio of Particularly with television, a great deal of caution is necessary stations are already broadcasting television as a before any material regular thing, it behooves us to is put out at all. Manufacturers should not look into the future and rush into the market with half -baked production see what is likely to happen during the next few months and with material and the next few years. that is not scientifically and correctly designed. Radio during It is a foregone conclusion that history the broadcast will repeat itself, and that we shall have boom came in for a good deal of adverse criticism; a boom in television, because, seemingly, every shoemaker just as there was a boom in radio in 1921 and 1922. became a radio manufacturer There are, over night and turned out the most impossible however, certain differences that should not be overlooked and, and incredible con- if these differences traptions, which dici not last for more than two months. are carefully studied, we will avoid the pitfalls probably It will and the disappointments which be the same with television. the radio industry had to contend Already, in with in the broadcast boons period. New York and other cities, small temporary booms To begin with, have been created artificially by irresponsible retail establishments I cannot repeat too strongly my previous admoni- who tion that television at the present sold "television" ( ?) material which is, in the first place, time, and for some months to unfitted for use, and secondly, come, is not for the public at large. It is doubtful whether, for even though it had been all right, some years could not have been used because no one was broadcasting to come, television sets will be sold as radio sets are vision impulses tele- now sold, direct to the public. at that time. These practices only react against The problem of the merchants synchronization has not, as yet, been solved com- themselves, because, when a legitimate pletely, although mach valuable demand comes along, those who have been previously work along these deceived lines has already been accomplished. The and disappointed will probably be most idea of TELEVISION cautious in Investing "You push the button, we have done the rest," is their money in new devices. not yet true in television. 'l'he public at large should know that television MEANS is purely an Television just now is in its earliest stages of experimental art at the present time infancy, and may be compared INSTANTANEOUS and only those handy with tools and proficient to radio at its coherer radio in and spark -coil stage in 1903. took almost and general science should attempt to build It twenty a television years from that period for broadcasting to come SIGHT receiver. Pretty soon, many television kits will be offered about. Of course, the cycle at this time will be for sale; but even such kits, no shortened considerably; but AT A matter how well made, are only for the experienced even the most optimistic radio constructor today doubt whether television will be ripe for the and those mechanically and elec- general public within two years, at least. DISTANCE trically inclined and handy with tools, and not for In the meanwhile, it will be paradise the general public. for the ex- The perimenter and the amateur who will "build their television fan should know, without being own "; who will experiment, who will told, that results to start with will not be any too improve and do a thousand good. Unless you are within and one things to make television practical from the public's twenty miles of a transmitter, con- point. For stand- ditions are not apt to be favorable. Such a thing some time we will have the rotating disc and the neon DX television, as receiving lamp with us. As I have said before, for the time being, seems doubtful; unless you can editorially, this is only a be satisfied to receive only transitory stage during the development and, in the end, occasional snatches of an image, or the disc when it is impossible to distinguish a with its motor will not prevail. But at the present time we have mans hand from a woman's nothing better; and the face. In television today, we require a strong impulse disc really does give results and is making, then, and, even at least for the present, television practicable reproductions are apt to he not too good. for us. What In the reception of radio broadcasting, instrumentality we will be using for television one or two years the car is not as sensitive hence, no one:knows; to slight disturbances and variations as the eye. Static but that does not matter. Every art has to ances, battery disturb- go through its stages of development, during trouble, loose connections, faulty synchronization of which a great deal the disc, all tend to make for of information - must be gathered, and the keenest a poor picture and, for some time, minds in the it will be the general rule art concentrated on the problems; but from such beginnings the that the received images are, and must art will slowly evolve into greater and broader accomplishments. be, rather poor, except when you are very close to the transmitter. As in the early days of broadcasting, hundreds For that reason, television, wonderful as it is, even at present, and thousands should of concerns will rush into the production of all sorts of television not be glibly talked to the public; and the public should not be led material, and a good start has already been made while this is to believe that, next month, they will be able to purchase written. A great deal of good material and probably much more perfect television sets through which they can witness a ball game poor material will be turned out by fhese concerns in the scramble u thousand miles away, down to its most perfect details. That for supremacy; but, just as in all other endeavors of this kind, accomplishment, as yet, is in the indefinite future. it may be freely predicted that those with the best technical talent, Let us go sleiwly, methodically, and the television art will grow and those who serve the public best, in an economic sense, will into a tremendous thing: -Letet us keep our heads and not expect probably remain in evidence after all the others have been left the impossible. Evolution in any by the wayside. art is a slow and orderly process. I.et us bear with the necessary delays in perfecting television.

Mr. Hugo Gernsback speaks every Tuesday at 9.30 P. M. from Stations WRNY (326 meters) and 2XAL (30.91 meters) on various radio and scientific subjects. 299

www.americanradiohistory.com Radio 1Vezus for October, 1928 300

Above: The crate at the feet of Above: How a fixed aerial is the three men holds an expert, stretched across the .rings of a nwntal receiver hung on springs, monoplane. The wire is sup- the object of which is to pro- ported by short steel tubes set tect the apparatus from the in special sockets in the wing strong vibration of the plane's tips. This type of aerial is in- engine. The elimination of mi- tended to replace the trailing crophonic noises in the receiver wire usually used for airplane is one of the main problems with radio work, :chich hangs be- which airplane radio engineers neath the body of the plane dur- are faced. Left: Milton B. ing flight and is a real source Sleeper, research engineer of the of danger; in that it may tangle Pilot Electric Mfg. Co., of New in the control wires of the plane York, testing the aforementioned or catch on a tree or other ob- receiver in the cabin of a six- struction if the radio operator or passenger Stinson-Detroiter mono- observer should fail to reel it in plane used by this company ex- before a landing is made. This clusively for experimental radio fixed aerial has the further ad- :cork. The plane is licensed un- vantage that it allows uninter- der the call letters 2XBQ, and rupted communication if the may frequently be heard trans- thane should make a forced land- mitting on 40 meters, in code. ing in a deserted spot.

The Radio Laboratory 'fakes Wings How the United States Army and Commercial Radio Companies Do Their Experimenting with New Airplane Radio Apparatus in the Sky. By S. R. Winters

com- is in flight. Commercial radio signs: those approved for aircraft THE floating radio laboratory found airplane in companies, imbued with a like belief after munication as well as new designs, now on ships and other ocean -going ves- awaiting seeing Uncle Sani's "flying radio labora- the stage of development and sels; the field radio laboratory which as flight on a tory," are planning duplications of the future approval or disapproval, is carried from point to point the approved radio facilities whereby new radio apparatus may tests may determine. Among motor truck; and even the portable 116, developed back, are be subjected to complete tests in the air. outfits are types BC-115 and equipment transported on a man's of the War Depart- of their wide- 'flic Air Corps flying radio laboratory in- by the Signal Corps no longer novelties because ment, which were used in early radio -tele- But the Air Corps of the cludes at least two complete transmitting spread usage. designs of re- phone broadcast reception between a broad- War Department, in keeping with the spirit stations and five different One of the transmitters, iden- cast station in Chicago and an airplane, as of this age of aviation, lias introduced the ceiving sets. air- as type SCR -123, derives its power well as in communication tests between "flying radio laboratory," a new contribu- tified the supply from a double- voltage generator, craft and ground radio stations. Of tion to the facilities of radio research; on (1,000 volts ampere, 15 volts -20 am- experimental receivers, this laboratory withal, complete transmitting, receiving and -0.5 air- peres), connected to the right outboard en -. wings carries one model each of two testing equipment on "wings." of devel- give; also from the standard power installa- plane receivers now in the process An airplane, a Fokker C-2, has been con- Company -. generator opment by the General Electric verted into a workshop for radio research; tion consisting of a '50 .ampere engine, battery and and the ;-Westinghouse. Electric and Manu- the cabin of this plane being specially out- on the left outboard dynamotor Type Bi) -41. The other trans- facturing Company. In addition, the equip- fitted for the accommodation of sending and as mitting set incliìded in this laboratory on ment includes ii type of receiver known receiving equipment and for the carrying super- regenera- the course of wings is a short -wave outfit, operating on BC -137, and a on of experiments during' set;''also a new design of the is an adage a band of wavelengths from` 75:to 100 tive- receiving flight. We learn best by doing, Electric Company. and radio'training, meters. The source of energy for this short- General applicable tö_both'flying maiden journey of this radio labora- this truism gives wave transmitter is a 2,000 -volt, 0.4- ampere The and a modification of on wings Dayton, Ohio, to Buf- that knowledge of French wind -driver generator, mounted on tory -from virtue to the contention falo, New York, and return to Dayton by radio is best obtained under actual the left side of the fuselage. aircraft equipment in this way of Schenectady, New York, Mitchel service conditions, with the radio sending 'lime radio receiving a variety of de Field, New York, and Bolling Field, Wash- and receiving outfits studied while the flying laboratory includes

www.americanradiohistory.com Radio News for October, 1928 301 ington, D. C., is described interestingly by Captain Paul S. Edwards, a radio engineer of the Signal Corps, in a letter to the Chief Signal Officer of the U. S. Army, Major - General William S. Gibbs. STORY OF THE FLIGHT "The radio beacon at Dayton was laici on the course for Buffalo," reports Captain Edwards. "The keying system of the beacon utilized the new interlocking systems where dots are sent on one loop and dashes on the other loop with continuous full -power 1,000 -cycle note. The beacon was heard throughout the entire trip to Buffalo, a distance of 349 miles. Two -way telephone communication was maintained between the airplane and the ground station at Wright Field for a distance of over 262 miles. "Just before reaching Dunkirk, New York, both stations switched to interrupted- continuous-wave telegraph transmission and exchanged messages Until landing at Buffalo. Upon departing one hour later from Buffalo, both stations worked for about twenty minutes, but the noise level was so increased that, while the signals were audible, they were not readable. We arrived at Schen- ectady 5:30 P.M. same date. The weather throughout the flight was clear, with the exception of Buffalo, which was slightly The cabin of the Army airplane, showing part of the extensive radio equipment -ehich is tested overcast with light fog. under actual flying conditions. Electrical and mechanical deficiencies in any piece of apparatus are "During our stay at Schenectady several quickly discovered during a flift/,t. flights were made with engineers of the General Electric Company as passengers, Bolling Field, who observed the operation of the equip- on interrupted-continuous- rangements were macle to work the wave was maintained Bom- ment in the airplane and tested a new type throughout the flight. bardment Squadron SCR -132 (DO 1), Due to delay and of super- regenerative receiver between Al- in delivering the message of Bolling Field was also advised of take -off, communication our de- bany and Schenectady, where the ground did not commence parture. Throughout the trip, communica- until we had reached station utilized an output as low as one Trenton, N. ,1., but tion was maintained with both ground sta- watt. This receiver, in operating condition, signals at that distance were of such tions and the airplane. strength Congressmen James worked very well, but at the present stage that it could have been easily pos- and Chapplin and Judge Clay were passen- of development is not considered suitable sible to have secured two -way communica- gers on the return trip. tion from both for military use; as there is no standby ad- fields. Due to the fact that "Arrangements were made for a the Bolling flight justment and the critical tuning necessary Field transmitter was not in over Washington, carrying seven people: commission for to obtain signals renders it unfit for air- telephone transmission, all Assistant Secretary of War Davison, Mr. craft use. The G. E. engineers also demon- messages Nvere sent and received by inter- Adamson, Major Blair, rupted- Signal Corps, Major strated a new type of short -wave receiver, continuous-wave. Davison, Air Corps, Mr. Knott, "A flight was Captain using one stage of UK -222 radio - frequency made from Bolling Field to Edwards and Lieutenant Wolfe. The As- amplification, detector and two stages of Baltimore, and return, using voice and in- sistant Secretary of War was terrupted- given a dem- audio-frequency amplification. The results continuous -wave throughout the onstration of broadcast telephone reception were so remarkable on this receiver that one entire trip between the airplane and Bolling while in the air. He also transmitted Field. The tele- was purchased for the Signal Corps Air- airplane took off from Bolling phone messages to Mrs. Davison who lis- Field, en craft Radio Laboratory, with a view of route to Langley Field, for the tened in at their homme. Radio- maneuvers, telephone using it as a standard of performance for carrying Lieutenant Wolfe as communication was established with Bolling pilot, Captain aircraft short -wave receiver development. Edwards, Mr. Knott, and Field, and messages were exchanged be- Congressmen James and Hoffman. Mes- FROM NEW YORK TO WASHINGTON tween the Assistant Secretary and the oper- sages were exchanged throughout the trip ator at the ground station. "Departing from Mitchel Field, en route until just before binding at Langley Field. "'Flue airplane departed from Bolling Field to Bolling Field, a schedule with \CFJ3, On the return trip from Langley Field, ar- (Continued on page 370)

The huge tri- motored monoplane which the U. S. Army has out- the behavior of radio apparatus under flying conditions fitted as a flying radio laboratory. Mitch valuable information has been on obtaiimed by arum engineers daring flights in this big ship.

www.americanradiohistory.com Radio News for October, 1928 302 "Wired Wireless " - -What It Is and Why of Four Telephone How Radio Principles are Applied to the Transmission -Wire Circuit Conversations or Ten Telegraph Messages Over a Single By J. E. Smith* Without stringing up more of others. Then, later on, we may include this means! HAT a title! And yet some poles, or laying them in conduits the DeForest for his wonderful contribution, wires on Wthe old- timers who "pounded the street, it is possible to multiply of the the vacuum tube, G. A. Campbell for his under brass" back in the days the number of channels of communication to appre- electrical filters, and many more. spark -gaps will be able by five, ten, twenty -who knows how much. "wireless." Telephone systems in use at the present ciate it. For radio was then as The general principles involved in carrier- we have al- time furnish simultaneously as many From that time to the present over current communication are fairly well un- to mean wire -less, four two -way telephone conversations ways understood the word the telephone and derstood by many of our radio readers. this self -same idea of each line in addition to and have extended normally afforded by We encounter it every day, in operating term "radio." But where telegraph facilities are "hams," late years to the Other systems are arranged our radio receivers or, if we of such a title? the circuit. we start at the is the sense as many as ten duplex- carrier our transmitters. Suppose fact of the natter is that to furnish we have an Well, the whole circuits over each line, in addi- transmitting station. First, is becoming less wireless nowa- telegraph the radio -fre- "wireless" tion to the usual facilities. '1'Itink what oscillator, which generates days. For quite some time we have been currents. Next, we have a micro- through quency transmitting messages and concerts phone into which the performer sings or "space" without intervening wires -hence The speech (audio) frequencies are speaks. wire -less. But it now happens thait we are amplified by the speech amplifier and wires, and not doing likewise through The coil at the right pass On into the modulator tube, into which vacuous space. is a tuning inductor is the radio - through connected in the oscil- at the same time passing Some of you know what is in the wind; lator circuit. frequency current from the oscillator; so others are guessing; and still others haven't the modulator is really a "mixing" is that the slightest inkling of what this article tube. Next, from the modulator, the mixed about. But to drag the dusky gentleman currents may pass on through an amplifier from behind the foliage, let it be known and thence to the transmitting antenna and that at the present time great developments off into space. (See Fig. 1.) are going on in connection with the trans- intelligence over metallic circuits mission of MODULATION AND SIDEBANDS of wire 'at radio frequencies. Therein lies with the secret; we are all well acquainted The most interesting point of the system the transmission of speech in the ordinary is the frequency. The oscillator may he manner over the telephone. Such speech is generating power at a frequency of a mil- transmitted at its own frequencies, namely, lion cycles a second; the speech frequencies tones varying from about 200 cycles per sec- range from perhaps 30 cycles to 10,000 ond to about 2,000 cycles, in commercial cycles. After hieing mixed in the modulator practice. It has been found very practical, these frequencies are considerably changed, for reasons which shall be unfolded as the and instead of two frequencies we have proceed, to transmit speech over wires at many. The most important of these are radio frequencies, in much the same manner known as the "carrier" frequency and the that today we are transmitting through two "sideband" frequencies. empty space, programs from the broad In order to make this clear, let us suppose cast studios. that instead of singing or talking we play on a flute in front of the microphone a of USING WIRES TO THE LIMIT single sustained note with a frequency 1,000 cycles (per second). Also, suppose 'l'Iris matter of utilizing a carrier wave frequency is 1,000,000 r.:;:> , ,, , n: that the "carrier" is not new. 1 vacuum -tube for the transmission of speech for either dupicr t'' or 'wired cycles. 'l'he two side frequencies are then dattes way back It is practically identical The beginning of the work wireless. trans- 1,001,000 and 999,000 cycles, representing Wren as in construction with a broadcast in the nineties, and is due to such mitter; only the values of the circuit the sum and the difference, respectively, of l'upin, Leblanc, Hitin, Slider, Stone and components bring different. the carrier and the modulating frequencies. The wore rule- holds when there are a number of frequencies cooling from the a RECEIVER and in general, we will have TRANSMITTER microphone, situation somewhat as represented in Fig. 2. We have the carrier at 1,000,000 cycles; ti:e upper sideband, ranging from 1,000,030 RADIO - DETECTOR 07: the lower sideband, FREQUENCY to 1,010,000 cycles, and DEMODULATOR SPEAKER OSCILLATOR ranging from 999,970 to 990,000 cycles. (R. F.) This mixture of frequencies passes out N through space to the radio receiver. Here MODULATOR in the R.F. ampli- (R. F.) they are first amplified fier; next they pass into a "demodulator," as a detector. In the AMPLIFIER more generally known SPEECH AMPLIFIER AMPLIFIER (R. F.) A. F.) detector or demodulator the complex radio - 1 AMPLIFIER (R. F.) (A F.) frequency currents again suffer a change FIG.1 MICRO- of frequency, and we finally have left only PHONE the original audio frequencies, amplified by the A.F. aniíilifier and changed into sound waves by the loud speaker. shows the fundamental units employed in a radio -broadcast transmit- This diagram All of these phenomena can be very read- respectively!. A sound mule before the microphone, out the left, ter and a receiver, ily adapted to the transmission at radio is reproduced by the toad speaker, at the right. President, National Radio Institute

www.americanradiohistory.com Radio News for October, 1928 303 frequencies over wires, instead of through space. It would be a very simple mutter to simply string up a pair of long wires where the dotted lines are shown in Fig. 1, and thus connect the transmitting and receiving stations by a complete metallic circuit. MULTIPLE TRANSMISSION The main advantage attached to such a system would be privacy; but unfortunately, it would be a very expensive proposition, and certainly not a profitable one for the telephone company, if they wished to supply service in a manner similar to the service they now supply us, and at the present rates. It is extremely expensive to construct telephone lines, so that the main advantage of such a system lies in the ability to adapt it to the existing lines, and by means of the selective circuits, car- This instrument, which greatly re- Her-currents modulated by speech can be sembles a radio set, is a portable telephone box by means of which work- tuned to resonance in exactly the same way men on a long power line can com- as we tune in one station or another on our municate with a central office. They simply tap on to the line and talk by receiving sets. "wired wireless." For example, it is easy to imagine that a number of oscillators, each one oscillating telephony, and others besides. There is hand cuts down to one-half the necessary at a different radio frequency, being modu- the usual trouble of interference, the trouble width of channel and, by eliminating the lated simultaneously by a different micro- of cross -talk, that of "singing," and so on. carrier also, it is cult down still More. This phone, are connected to the sauce pair of makes it possible to obtain more channels wires. Then, at the other end of the line, SINOI.E- SIDEBAND TRANSMISSION in a single circuit of wire or, for the sante we can imagine a number of radio receivers, As another means of conserving the number of channels, spreads them farther each one tuned to a different frequency. channels, it has been found possible to apart, and thereby reduces interference and is clear It that each current wave could eliminate not only one of the sidebands, but other troubles. be tuned in without experiencing interfer- the carrier frequency as Weil, in certain And now we can go another step farther; ence from the other, in exactly the same special cases. For instance, in Figure 2, we have a system whereby several telephone way as we tune in WJZ and tune out WOR, notre of the speech frequencies are included conversations, and a few telegraph messages or vice versa. Not only that, but it is not in the carrier; they are included can be transmitted on the same circuit necessary only in for all of them to be modulated the sidchands. Furthermore, since the simultaneously. Why not transmit power by side- speech; some of the "channels" may over the same lines at the same time? carry speech, some may carry music, others To tell the truth, this is exactly what is may carry telegraph code, another may being clone today; but we should put it the control tickers, and what not. CYCLES other way around. The 1,010,000 telephone or tele- The number of such "channels" which are graph wires are not being used for power possible in a single circuit of wire is UPPER SIDEBAND very 1,000,030 transmission, for they are too small; but great, and depends CARRIER FRE UENCY mainly on the width 1,000,000 the power lines are being used for the trans- of the sidebands. For example, in the case 999,970 mission of speech and code. Quite illustrated a lot by Fig. 2, in which we are LOWER SIDESAND of work is being done along this line for, supposing music to be transmitted, the 990,000 in addition (PER to its affording a means of sidebands are 10,000 cycles FIG. 2 wide, making SECOND) communication for the public at large, it it necessary to have a channel 20,000 cycles is exceedingly important that the different wide. This is a very wide channel. Gen- II'hen music is transmitted over a "carrier - power plants of the same company, or the erally, intelligible speech requires a hand current" system. the sidebands are quite wide, central power plant and the sub -stations, as .drown above. only about 4,000 cycles wide, and music a keep in very dose touch with each other. hand -width of about 10,000 cycles. hands arc identical in range, why not elimi- LOW CARRIER FREQUENCIES nate one of theme? This has actually been POWER -LINE PROBLEMS However, before going much farther, it done, by applying the Campbell filters at It is clear how this may be done in the may be well to state that such frequencies the transmitter, so that they eliminate one case of alternating -current power; for this band as a million per second are not used in and the carrier, and permit the other can be transmitted at a certain particular band to pass through. carrier telephony or telegraphy; for the A'Iuen this is done. frequency, say GO cycles, and occupy its losses in the wires and in the associated it is necessary to "supply" it carrier fre- own channel (with no sidebands in this quency apparatus at these frequencies would be too at the receiver, si that amplification simple case) just as each band of speech great. Therefore, commercial carrier and detection can be carried out in the frequencies or telegraph code occupies its fre- usual manner. quencies generally lie between 10,000 cycles This is admirably accom- own channel. And, going still a step far- plished by and 50,000 cycles. This then permits only the superheterodyne type of ther, it is clear that constant or direct cur- five bands 10,000 cycles wide, theoretically; receiver, in which the oscillator of the rent can he just as easily transmitted along "super" furnishes practically, it is possible to squeeze in five the carrier frequency. with the communication channels; for di- It is clear off a such hands only by employing special Means that cutting single sidc- rect current has a frequency- zero -and oc- for doing so. The Campbell filter makes it possible to cut these hands off sharply, so that they do not interfere with adjacent hands. Such a filter consists of a series of sections, as shown in Fig. 3, consisting of coils and condensers, and so tuned that An arrangement of coils the'' "cut-off" is very sharp; it and condensers such as can be so that shown at the right designed as to pass any desired band of constitutes a "6/ter" frequencies. The filters are connected be- which can be adjusted to pass only a definite tween the line and the receiver, so that the band of frequencies, to receiver can receive energy only at the fre- the exclusion of all quencies determined by the filter. others. Of course, there are many difficulties to be overcome in such systems; there are the FY- same problems that are found in ordinary FIG. 3

www.americanradiohistory.com Radio News for October, 1928 304 the scheme, nothing has yet come of zero frequency. back of cupies its own channel reasons are not difficult to under- we come to the matter of it. The However, when stand. over power lines POWER LINES of transmitting intelligence In the first place, the number of available operating at high voltages other problems being the programs is limited; so that if a person arise, the most important of these three or four be- and the should not like any of the manner in which the transmitter simply have to currents arc con- ing transmitted, he would receivers of the carrier 1 off. This shortcoming is There are two turn the receiver nected to the power lines. comparison with the great these is shown emphasized by methods of doing this; one of T which the owner of a or receiver freedom of choice in Fig. 4, where the transmitter receiver has. Then again, a lines by high- voltage naa regular radio is coupled to the power receiving instrument is necessary. It of small capacity, these two special condensers has been evidently the plan of the power con- TO TRANSMITTER being connected to a protective ground instruments on a method, OR RECEIVER companies to rent the nection. Fig. 5 shows the other and to make the system so of stringing a pair monthly basis, which consists merely that it would be difficult, if not with the power lines for complicated of wires parallel Two methods of coupling a "carrier-current' impossible, for the home constructor or cus- distance of a thousand feet or more. These communication system to a high -voltage power line a Above, condensers arc used, with a grounded pro tom radio builder to make a receiver of his exactly like antennas. In addition is wires act tective device. Below, on inductive connection own. The income derived from the rental of insulating the made by antennas strung near the power wires. to the difficulties properly of the machines was to be used for the pay- high- voltage power lines, system in these ment of the entertainers. Milers are encountered. For instance, where P "sectionalizing" switches in the lines are WIiY IT FAILED it is necessary to erect what might opened, COWER Possibly the whole plan would have been -pass antennas" in order that ANTENNAS LINES be termed "by very successful if radio broadcasting, as we may pass over the gap. the carrier currents know it today, had not flourished so well. losses, to he sure, but at least This incurs so many good broadcast stations on is necessary only With the gap is bridged, and it all hours of the day and night, of the transmitter the air, at to increase the power and with good radio receivers available at sufficiently to overcome the loss. FIG. 5 TO TRANSMITTER low prices, it is doubtful if many people occurs RECEIVER Another difficulty encountered OR would care to buy or rent an apparatus on the power when great loads are thrown would furnish only limited entertain- mills are running, or that lines, as when large ment during limited periods. However, since at night when the lighting load becomes the tops of the cens, parallel with the tele- have not definitely produced the power companies great. The short -circuiting effect phone wires along the road. (See page stated that they have dropped the scheme, of so many feeder lines Nrws 1926.) by the turning-on 1936, RAmo for June, it may be realized some day. in the characteristics of causes changes, Similar in principle is an application of the lines, Which make it necessary to employ BROADCASTING OVER WIRES "wired wireless" reported from Austria. in the transmitter at such times. more power of "carrier- current" trans- Programs from a studio in Vienna are car- the carrier- current system is The principles And, finally mission have been successfully applied also ried by telephone wires part of the way to as a means of com- being used successfully to the "broadcasting" of voice and music the but for over a hundred from moving trains. In this transmitter; municating over electric power lines and the reception miles high- voltage lines are used for the case, the antenna wires are strung along of the programs in the home via the lamp circuit. socket. A large power company. has been experimenting in this direction for the past live years, and has furnished regular enter- tainment, on a limited scale, to a number of communities. The scenes of these experiments have been Staten Island (part of the city of New York), a section of Washing- ton, D. C., and a small town in Illinois. The entertainers appear in a regular broadcast studio and perform in front of the usual microphone. The program is then put on the power wires instead of being broadcast through the air. Three or four nl... programs of different nature can be transmitted simultaneously, on different fre- .'.' quencies. ,,ts The receiver is a very simple affair, containing only a few tubes and a switch to select any one of the several available programs. It is plugged into any hunp socket, from which it derives, not only the music, but also the power to operate the tubes.

FIXED -TUNE RECEIVERS Electrically, the receiver consists merely of three or four circuits permanently tuned to the frequencies on which the separate programs are transmitted. A switch is provided to enable the user to select whichever program he wants. There is no extensive tuning to be clone, as the reception is entirely limited to what the power lines carry. A loud speaker of standard construction is employed for reproducing the programs as The back of the receiver. The six The front panel of a receiver actual sound. round instruments near the top are used for duplex telephony over regular variable condensers, which wire lines. This apparatus is From time to time, during the past few tune separate circuits. (Photographs virtually a series of radio re- years, newspapers have carried announce- for this article courtesy Westing- ceivers, each tuned to a differ house Electric Mfg. Co.) ent wavelength. ments that this system is "about to he inaugurated on a national scale "; but in spite of the size and wealth of the companies in

www.americanradiohistory.com Radio News for October, 1928 305

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A close-up of a 14-inch photoelectric cell of the type used in television transmitters. (Photograph courtesy Bell Telcpl;onc Lahoratorir;) The Photoelectric Cell - Radio's "Eve" An Elementary Description of the Device That Translates Light into Electrical Current and Makes Television and "Talkies" Possible By Dr. Lewis R. Koller Research Laboratory, General Electric Co.

pHOTOELECTRICITY treats of the interesting property. The selenium cell is relationship between light and elec- still in use for spine purposes, although it tricity. The photoelectric cell is a About This Article - has many undesirable properties. vacuum -tube device by means of. AS the heart of practically all present - DISCOVERY OF THE EFFECT which light can be made to control an elec- Cl day television systems is the photo- tric current. It bas a great many uses in electric cell, every radio fan who ex- The action of the type of photoelectric purely scientific work; and its applica- pects shortly to build a television ma- cell that I am going to describe, however, tions include television, talking moving pic- chine should know something about the is radically different. The underlying prin- cell's characteristics and about photo- tures, photometry, cigar sorting, control ciple was first made clear by the German of paper quality, electricity in general. Here is a good control of sign and street non -technical article which explains in physicist, Hallwachs, in 1888. The first lighting, and many more. understandable language the fundamen- observations of photoelectric phenomena The modern photoelectric cell is a com- tal principles of the device; read it and were made by the pioneer in the field of paratively recent development. Its fore- keep abreast of the times. -EDITOR. radio, Heinrich Herz. He was conducting runner was the selenium cell. The element his famous experiments on electromagnetic selenium was discovered by the Swedish waves, and did not pause to investigate chemist, Berzelius, in 1817. In 1873 the subject further. an covered that this was due to the fact that He merely mentioned Englishman, Willoughby Smith, attempted it in one of his the electrical resistance of selenium de- papers, and it remained to use selenium in making high resistors for Hallwachs to study pends upon the amount of light falling upon the phenomena in for use in transatlantic telegraph work. detail. Hallwachs found He its surface; the brighter the light, the lower that if he charged found that these resistances were a zinc plate to a negative very the resistance of the metal. He was able potential (by con - erratic and changeable, and necting it to eventually dis- to get around his difficulties by the negative terminal of a enclosing battery) and then his resistors in a light -tight box. Follow- exposed it to ultra -violet * From a paper presented before the Radio Di- light, it gradually ing this discovery, cells were constructed lost its charge. When vision, National Electrical Manufacturers Asso- he exposed the plate in the same way, ciation Convention, at Chicago, June 7, 1928. of many different forms to make use of this after first raising it to a positive potential, it did not lose its charge. This phenomenon has been thoroughly investigated and it has been found that practically all substnces exhibit it to a greater or lesser degree. This is the fundamental phenomenon of photoelectricity. Hallwachs used a polished disc of zinc, 3/ inches in diameter. In front of this e as a large shielding plate of zinc (24 x 28 inches) with an opening in which could be placed windows of various materials. The zinc disc was illuminated by the light of the arc lamp in front of the windows. The gold -leaf electroscope connected to the disc told what was happening to the charge on the plate (Fig. 1.) When it was charged with electricity, the leaves stood out away from each other and, as the charge leaked off, the leaves gradually collapsed. Hall - wachs found that, when the plate was negatively charged, the electroscope's leaves remained stationary until light from the arc fell upon the plate. They then began to How the German scientist Hellwache studied the effect of light on the electrical droop, showing that the charge was leaking properties of a zinc plate. lVith the aid of this simple apparatus he made clear the off the plate. No such change was observed fundamental principles of photoelectricity. When the plate was positively charged.

www.americanradiohistory.com Radio News for October, 1928 306 to wander through -day atom) which are free The explanation in terms of present in with the impressed is ab- the metal accordance physics is simple: The light which is the actual motion of sur- electric forces. It sorbed by the photo- (light -) sensitive these electrons that constitutes an electric electrons or face causes the emission of current. An electric current is nothing plate is nega- negative charges. If the other than a flow of electrons. with, these elec- tively charged to begin To return to the photoelectric cell, it can and so the plate trons are able to escape be represented diagrammatically as shown while, if it is positively loses its charge; 2. Light falls upon the surface because in Fig. charged, they are unable to escape metal plate p and causes "photo the plate and of the of the positive potential of electrons" to be emitted from it. The plate the plate remains charged. is connected to the negative terminal of a WHAT ARE ELECTRONS? battery and the wire a is connected to the positive terminal. The positive charge on Perhaps before going further into the a draws the electrons across the space and subject it would be well to say a little about Diagrammatic representation of a photoelectric The cathode, which emits electrons, is a current flows through the circuit. and modern views of the con- cell. so the electron 1'; the other electrode, shown by the small The electrode (P) which emits the electrons of The earliest concep- circle, is the anode. stitution matter. be connected to the negative atom was simply the smallest must always tion of the battery terminal and is called the cathode, particle of matter that could exist. If The force of attraction between the positive to- The positive electrode (corresponding in one took a small piece of matter and cut and negative charges holds the system hold this to the plate of a vacuum tube) is in two; took one of the halves and cut gether, just as the gravitational forces it called the anode. in two, and so on, eventually one our solar system together. Thus the atoms that This is purely a diagrammatical repre- would reach a very tiny piece of matter of all substances are made up of the same sentation of a photoelectric cell. A more could not be any further subdivided. ultimate units, protons and electrons. The that usual form is shown in the illustrations 'I his was the atom. Now, through the work differences between different kinds of mat- in this article. The inside of the glass of Thomson, Rutherford, Bohr and many ter are due to the different arrangements is silvered and contact is made with we have a picture of a vastly- differ- of these two kinds of building material. bulb others, the silver surface by means of a platinum ent structure which leas much evidence to This theory has met with great success in predicting the spectra produced by the flush seal. This silver surface is coated confirm it. such believed to be small different elements. All matter then is made with a thin layer of some material Atoms are now metals (lithium, sodium, systems with a massive nucleus up of atoms like these. Some kinds of as one of the alkali planetary potassium, rubidium, caesium) which are in the center like our sun, and rotating matter, notably the metals, have the power of electrons of readily conducting n current of elec- particularly photo- sensitive. This takes the about this center a number experi- The nucleus, which car- tricity. We believe that in material of place of the zinc plate of Hallwach's like the planets. electrode is in the cen- charge, is made up of this type, that is in conductors, there are ments. The other ries the positive opening serves for the ad- hydrogen, or "protons" packed a large number of free electrons; that is, ter. A circular atoms of of the light. Details of construction together. The electrons are nothing electrons (in addition to the rotating elec- mission closely vary, but the essentials remain the other than negative charges of electricity. trons which are attached to each individual may same. ACTION OF THE CELL The photoelectric cell, as we have said before, allows a current to flow through it when light falls upon it. Its particular value lies in the fact that the current passing through it is directly proportional to the quantity of light falling upon it. Dou- bling the light doubles the current, etc. For this reason the cell can easily be used for measuring light intensity or changes in intensity. Of course, these photo- currents are small, so in order to avoid the necessity for using high -sensitivity instruments, amplification is resorted to. This is done by means of vacuum tubes as in radio work; but there is also a method of amplification within the photo cell itself which is of great value. This method makes use of the ionization of gases. For this purpose, after the cell has been ex- hausted a very low pressure of gas is introduced. This pressure ranges from 1/37,500th of an atmosphere in some of the larger types of cells to fifty times as much in the very smallest cells. The gas used must not react with the sensitive cell surface and it must also not "clean up" during the life of the tube. The gases which satisfy these requirements are the rare gases of the atmosphere and, of these, argon, neon and helium are the most frequently used. The mechanism of the process is as follows. When light falls upon the sensitive surface of the cell, 'electrons are emitted and are drawn toward the anode by its positive potential. Some of these electrons, naturally, will chance to collide with gas molecules. As a matter of fact, at the lowest pressure mentioned there are forty -two thousand million million gas molecules in each cubic inch. Calculations show that an electron travel- Dr. Herbert Ives (left), television expert of the Bell Telephone Laboratories, exam- ing through a gas at this pressure will make ining of the large photoelectric cells used for television transmission. A one two collisions in each two -fifths of an inch close-up of this cell is shown at the top of the preceding page.

www.americanradiohistory.com Radio News for October, 1928 307 of its path on the average. It is the con- the intensity sequence of these collisions that is of of the light falling upon it. inter- However,. this est. The collision may be of the same type statement requires a little modification. It is as when two rubber balls come together; true, provided the color of the light is they will fly apart again, perhaps moving not changed; but it is not true in that equal intensities different directions and at different speeds t of blue and red light, for example, will produce than before, but otherwise unchanged. Such the same response in the cell. In a collision is of no use in producing ampli- this respect the cell resembles fication. the human eye, in that it is not equally sensitive to all colors. The maximum sensi- IONIZATION tivity of the average person's eyes occurs in the yellow -green portion On the other hand, of the spectrum. a collision may take The maximum sensitivity for potassium place with disastrous consequences to the cells occurs near the ultra -violet part of the gas molecule. When a collision of this kind spectrum. takes place the photo electron actually This means that knocks one of a potassium cell does not the electrons in the outermost see colors the same orbit completely cut way that we do; it is of the gas molecule, or far more sensitive to ionizes it. The result blue and less sensi- is that now, instead tive to red light. Caesium photoelectric of the original electron and a neutral mole- cells are the most red -sensitive of all, and cule we have two electrons moving over to consequently are the positive the most desirable for any electrode; and the remainder of work involving color. the gas molecule, which is now positively charged and is called a positive NOVEL USES ion, moves New applications toward the cathode. We have thus multi- of the photoelectric cell W. K. Zworykin, physicist of the Westing- are arising every day. Two of the plied the original charge threefold. There house Company, comparing a photoelectric cell most of his spectacular ones ore is still the possibility of the two electrons design with a radio tube of the 199 -type. television and the talking movies. There are a number of systems making even more collisions before they tion voltage, is exceeded some gas molecules of television, all of then fairly complicated; reach their destination. This is no violation become ionized. As the voltage is increased, but the essential feature in all of them of the law of the "conservation of energy," still more ions are produced so that, is instead the photoelectric cell. A beam of because the energy required is drawn from of being flat, as in the case of the 'vacuum light travels acróss the object to be viewed the battery across the cell terminals. ' cell, the curve and is of current against voltage then reflected back The result of this process is continues to into a photoelectric cell. that, for each rise. Eventually this curve be- The amount of light electron which the action of the comes quite steep falling upon the cell will light liber- and the cell breaks into a depend upon the ates at the surface of the cathode, glow. object; the white parts, let we may us say, sending have several arriving at the anode. a strong beam of light into Since HOW IT "SEES" COLORS the cell and the dark the flow of electrons constitutes the parts a weaker beam. current, I have stated that the current through a These will produce, the gas may be said to amplify respectively, large and the photo photoelectric cell is directly proportional to (Continued current internally. The amount of amplifi- on page 372) cation obtainable in this fashion depends on the nature of the gas, the intensity of the light source,' the construction of the tube, and the voltage applied across the tube.

CHARACTERISTICS OF A CELL The relation between the voltage applied to the tube and the current through it is called "the volt- ampere characteristic," curves of which can be obtained for different conditions of illumination by moving the light nearer to, or farther away from the cell. At low voltages the current rises rapidly with the voltage. The current, of course, is simply a measure of the number of electrons which reach the anode. At first sight, this variable current would seem to be in- consistent with the fact that the number of electrons set free from the cathode depends only upon the intensity of the incident light. The apparent inconsistency is due to the fact that, at low voltages, all of the emitted electrons do not reach the anode. As the voltage is increased, a larger proportion of them reach their goal, and at one point the voltage is high enough to draw over all the emitted electrons. That is why further increases in voltage do not produce any further change in current and the curve continues as a 'straight horizontal line. The voltage which is necessary to draw over all the electrons is called the saturation voltage. In order that the current may be a real measure of the light intensity, the voltage must always be above the saturation voltage. If the light intensity is now increased, a curve is obtained of the sanie shape as he- fore, but the saturation value is higher to correspond to the new value of light intensity. In the case of gas -filled cells the charac- Dr. Roller is shown here with an automatic teristics are radically different daylight recorder later installed on the in form. As ill -fated arctic dirigible "Italia." The soon as a definite voltage, photoelectric cell which operates the mecha- called the ioniza- nism is on the top of the cabinet. (Photo courtesy of General Electric Co.)

www.americanradiohistory.com Radio News for October, 1928 SOS

in of the year, with all Australian and New More on Lightning Conditions Australia Zealand stations. Editor, RADIO NEWS: With regard to daylight work, I have Editor, RADIO NEWS: mid- In the rural centers in the eastern part repeatedly logged 4QG, Brisbane, at I note in your interesting editorial in the Australia, the average listener demands day in summer time, at 950 miles airline, strik- of eastern June issue that instances of lightning his five -tube neutrodyne, T.K.F., etc., also on the loop, as well as all other I agree that ing a radio aerial are very rare. not only cover 250 miles in daylight, Australian stations above 1,500 watts. The every- shall appear- with you in this, but also say that do so at satisfactory speaker strength. New Zealand stations make their but summer thing happens once. This town is situated about 250 miles from ance at from 5:30 p. m. onwards, the aerial 500 New Two years ago, lightning struck Melbourne (5 kilowatts) and 350 miles or winter. Oddly enough, a -watt the street 3LO, than of a broadcast fan directly across (also 5 kw.) and if you Zealand station has more punch here an from 2FC, Sydney from my home. At the time I had enough to offer the radio - its 5,000 -watt brother. erected in were foolhardy for amateur's antenna, 45 feet high, public a five -tube outfit which In conclusion, I wish to thank you feet from where buying was pub- my yard not more than 200 would not give satisfactory volume from an excellent journal. I wish it this altitude, destruc- I the bolt struck. In these stations without fuss, and miles lished weekly. If I were American, of may leap to earth goods." tive bolts lightning above noise level, you would find it impos- would say "you sure have got the so 4[nall as to be hardly notice- publication from clouds sible to make a sale. As an Australian, I say your from such a cloud while able; this bolt came Quite a large number of American re- is "Gbod, oh !" The bolt struck the the sun was shining. are in use here and, if I may be E. MARTYN- JONES, and melted the aerial wire ceivers aerial directly permitted to name a high -grade one-the Box 93, Wagga Wagga, and lead -in completely out of existence, New South Wales, Australia. down to the arrestor; and from the arrestor (Australia, comparable in size with the to earth the wire was not damaged. The ar- United States, and isolated by thousands of restor had done its work, but died doing HIS page belongs to the readers miles from any other country except New the job of grounding the bolt. The aerial 7 of RADIO News. It is theirs for Zealand, has about thirty broadcast sta- was supported on two one-inch pipe poles the purpose of discussing fairly and tions, several quite small. This perhaps has at each end of the ridge of the house, and frankly the needs of broadcasting from something to do with the excellent DX re- about five feet above the ridge. At the base the standpoint of the great public who ception in the antipodal continent.- EDrroa.) of each pole a hole was torn through the listen in. The letters represent, not roof, but otherwise no damage resulted. necessarily the editorial opinion, but My idea is that when a bolt of lightning that of the writers; who are, in the edi- Five -Kilocycle Separation is going to strike at a certain place, the torial belief, fairly typical of groups of Editor, RAmo NEWS: small aerial will not dissipate the earth opinion among the radio public. Make charge and "scare" the bolt to other places your letters concise and offer construc- Previous to December 1, 1927, we here were able to -or it would have struck my larger and tive criticism when you can; remem- in Los Angeles and vicinity higher aerial across the street. But I will bering always that there is something play clearly three stations within a ten - and also say that, had it not been for the aerial to be said for the other fellow's side. kilocycle band, namely: KSB, WLIB on that housetop, which received the shock, Address The Editor, RADIO NEWS, KOMO. As nearly as we could tell, there the house would have been seriously dam- 230 Fifth Avenue, New York City. were no more than ten kc. between KOMO aged. I have had aerials erected all over and KSL for WLIB to get through, and my place of abode since the beginning of we checked this point very thoroughly from amateur days more than fifteen years ago; here. WLIB was not coming through ex- and this was my first sight of lightning Stromberg- Carlson Model 501 -I would like actly in the center -they were about four actually striking one. I always feel safe to give some idea of how it performs under kc. below KOMO and still we (and hun- under a properly -grounded aerial in any our conditions. Also, if any owner of dreds of others) played WLIB easily and kind of electrical storm. such a set in the United States would like clearly. This would indicate that it is pos- A picture of the house, taken at the time, to write me about its performance, I would sible to split up the allocated channels into shows a black streak down the side, where be grateful. (I do not own one.) Here channels of say six or seven kilocycles with- tiny bits of the melted lead -in wire were its performance is equal to almost any dis- out interference from heterodyning car- shot into the weather -boarding of the house. tance under 2,000 miles with a good an- riers; possibly even five kc. if the stations The radio set that was connected to it was tenna system. These sets have frequently were separated sufficiently geographically. only slightly damaged and was easily re- picked up stations in Japan and the Phil- Then, the listeners situated equal distances paired. I thought this instance might be of ippines under favorable conditions. Other from all stations on the same channel would interest to you. high -grade American sets show it similar be able to play any of them; while those near one of them would be no worse NORMAN R. HooD, performance. located Mr. Woodruff and Mr. Staves have some- off than before. We have an example of 1022 So. Ash Street, Casper, Wyoming. thing to say about supers. I cannot help that, with KFSD at San Diego, and WJR at (Two other letters, not dissimilar in na- thinking that some supers are not all they Detroit, supposed to be on the same channel ture, have been received from. our wide- might be; especially Mr. Staves' set, which and yet actually separated sufficient for spread army of readers on the subject; so uses the same (Victoreen) I.F. system as listeners here with a very selective receiver it is evident that the number of cases of any my own. I hold that the air-core super, to separate these two stations enough to damage by lightning to a house with a radio with high -grade A.F. systems, takes some identify them, and with very little or no receiver .in it have been few. In each case, beating for quality reproduction. With my heterodyning. the lightning arrestor functioned as it set, which has high -mu tubes in the I.F., a Now that WLIB has been replaced with should. Lightning falls, seemingly, where it regenerative first detector, power and super- WIBO-WHT, we find that these stations will, and plays queer pranks; but a prop- power audio stages, and a two -foot loop, have moved so close to KOMO that we can- erly- installed radio aerial reduces, rather I have logged such American stations as not play either Chicago or Seattle clear than increases, the probability of o stroke, WEAF, WJZ, WGY, KDKA and KGO in enough to identify them, to say nothing of and conducts away practically the whole of the winter months. The Japanese and Phil-, enjoying the program! When it comes to its force if it does fall.- EmToa.) ippine stations can be logged at any time (Continued on page 375)

www.americanradiohistory.com Radio News for October, 1928 309

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A (RADIO) WAVE CRIME AN INGENIOUS A TUNED -IN ALIBI VERN1ERE: "Did you An oft -asked ques- WIFE (hearing hear about the daring tion is: "Is there any hubby fiddling with robbery down below use for used "B" bat- door -knob at 3 A.M.): last night ?" teries?" "You old owl, what in COYLE: "No, what They are always the world are you do- was it ?" handy when your ing down there at this t ERNIERE: "W h y, neighbor wants to bor- time of night ?" the two Brackets held row o n e. - Popular H ono Y: "Pshh, up the Panel!" Radio Weekly (Aus- (hic) I'm trying (hic) -Efty Kyprie. tralia. to tune out (hic) WOW for WOO." -James Gibson. A HOOSIER BARGAINER DEALER (to thrifty A SCENE IN EVERY FAN'S LIFE TALL MAN : "Congratulate me, Bill, the customer) : " N o w , A TRAGEDY event since I married!" OF 1929 these are the accessor- happiest FIRST OFFICE BOY: or girl ?" ies of the set. These SHORT MAN: "Boy "How'd you lose your PCJJ on one tube!" are the batteries, TALL MAN: "No. ,job, Jimmy ?" -Popular Wireless. these are the tubes -" SECOND OFFICE BOY: CUsroME:R (a thor- "Aw, I told the boss I oughgoing *shopper): page is devoted to humor of purely wanted the afternoon "Are they the kind THISradio interest; and our readers are in- off to go to me grand- you can roll up when vited to contribute pointed and snappy jokes-no long- winded compositions-of an mother's funeral and they get empty and squeeze it all out of original nature. For each one of this na- he saw me at the ball them ?" ture accepted and printed, $1.00 will be paid. Each must deal with radio in some game over the tele- (Dealer faints.) -R. L. Wilson. of its phases. Actual humorous occur- vision "-11'm. G. Mortimer. rences, preferably in broadcasting, will be preferred. Address Broadcastatics, care A FUTURE M. I. R. E. RADIO NEWS, 230 Fifth Avenue, New Harry, aged four, York City. OR A SHORT -WAVE PAN ...,,.,,,,,,,,,,,.,.. turned up the regen- .,,,,, , I,',,,,,,,,,,,,,,, I,, ...... "Is he an optimist ?" eration on our radio "Is he? IT SOUNDED PROMISING Why say, until the usual results he took a course in FATHER (to old -maid daughter): "We've occurred. foreign be- tuned in almost every city of importance languages After working on it fore he bought his tonight, so where will we go next ?" a while, he said: one : "Oh, dad, -tube radio set, so "Daddy, you better DAUGHTER (enthusiastically) Isle of Man !" that he would be able oil the radio. It let's try to get the -E. H. Foley. to understand the for- squeaks." eign announcers!" Dave Nilsen. -Mrs. R. I. P.

AT THE STUDIO DOOR A FAN D.: "Jones looks SPORT STUDIO MANAGER: "What's the matter? MOTHER: "What's your brother Jimmy You look all in." rather sad." doing with the soldering iron and screw- BEDTIME STORY TELLER: "I had to hurry Y.: "Yes, I heard driver?" down without anything to eat; I slept in BOBBIE: "He's going to put another stage he buried his today." hire say of ossified frequency in the radio set, so he STUDIO MANAGER: "Well, make it snappy, Aunt Enna yester- can get the six -day race on 500 kilocycles." and get on the air with your bedtime story." day!" -George Lieberman.

RADIO RHYMES No. 12

THE NEXT' NUM &e-R ,TATION WOOP "TRE 'ROAD To i NULL FROM STATION -- we. SHALL Nov) MANDALA'(" /JOW KoKO WILL .se -- HEAR THE = Se 12ENDE2E0 By " THE TdoATO To FAVORITE SELECTION -fete ORCUESraA d MAN DA LAy THE 120AT) 'To AT S rATN ON MANDALA'( y = WOP

ti a IT sEEr1s WuENE'ER I THI5 VERY SONCr, UPON My yE GODS ON HIGH I-. IT S 6y C,OLL'1 !-- mow Ar LAST TUNE M4 SeT WORD. HERE ONCE MORE - I SEE THE= SAME REFRAIN) 1 AT LEAST A TI-IOUSAND WELL. WOULOÑT 'THAT JUST WHATS MEANT ey ALWAYS GET F TIMES 1 VE tIEARD GET 401.) SORE RADIO FREQUENCY

www.americanradiohistory.com 310 Radio News for October, 1928

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A New Screen -Grid Receiver The person who builds this set has the for providing the desired values of grid option of two different systems of wiring. bias, and by -pass condensers. Using the Roberts Circuit The diagram which accompanies this article From the schematic diagram it may be shows the circuit used when the set is in- seen that the R.F. circuit of the set is much a well -known FROM the laboratory of tended for battery operation. However, the the same as the standard, except for the Chicago has come an inter- manufacturer instructions supplied with the kit show the fact that a screen -grid tube is used in the esting development of the popular Roberts four -tube circuit; namely, a screen -grid ver- sion comprising one stage of tuned radio- C3 frequency amplification, a regenerative detector and two stages of audio- frequency _J AERIAL ..L R- amplification. The new set, which is avail- 'I C2 able in complete kit form, possesses interesting new features. It was tested in the TCI Ti V3 T2 V4 L1 CAP RADIO NEWS Laboratories, and yielded un- usually good results for a simple four -tube affair. It is pictured and described on this page. From the pictures presented herewith it may be seen that the receiver resembles in mechanical construction the modern factory - built receiver. All of the parts inside the set are mounted on a pierced steel chassis, which is housed within an attractive metal finished in two -tone brown moiré, cabinet, R1 with gold high lighting. The tuning of the receiver is accomplished by means of two SW knob -operated drum controls, which are mounted on a bronze escutcheon plate to- o o 0 0 0 cap with the sensitivity knob, volume GROUND +45 A,B -C+ A+ +45 t 135 C -3 +135 C -AMP +180 gether RED- BLACK BLACK BLACK BROWN MAROON GREEN RED knob and battery switch. The chassis is MAROON GREEN RED mounted on a highly -polished mahogany base. TO CABLE The all-metal design of this receiver not only provides the set with a finished com- This diagram shows the complete circuit of the screen -grid Roberts receiver; the mercial appearance, but also with other symbols employed to identify the various parts correspond to those used in the text mechanical and electrical advantages. The and pictures. This diagram shows the set wired for D.C. operation, but an A.C. has been all -metal cabinet, which is of one -piece con- circuit using practically the same parts developed. struction, fits tightly over the chassis, thus providing a low- resistance shield for the set. method for wiring the set when it is de- R.F. stage. This tube provides a voltage When the cabinet is removed all the parts sired to use A.C. tubes and a "B" socket- amplification between 20 and 35 throughout and wiring are readily available for adjust- power unit. 'l'lte essential circuit of the set the entire broadcast waveband, thus making ment or repair. The use of the pierced steel is the same in each case, but there are sev- it possible for this receiver to equal in sen- chassis makes it possible to locate a large eral slight changes in the parts and in the sitivity the usual five- or six -tube receiver part of the wiring under the base; this gives filament wiring. In the electric set the extra using standard tubes. Also, the amplifica- the appearance of neat workmanship. parts include fixed and variable resistors, tion of the circuit is not very great when compared with the not of the tube and, as a result, good selectivity is obtained. The input circuit of the set employs a standard coupler, the secondary winding of which is tuned by a .00035 -mf. double - spaced variable condenser of modified SLF- SLW design. The primary of the coupler is in two sections; half the winding is connected when great selectivity with a long aerial is desired, and the entire winding is employed with a short aerial. Volume is controlled in the receiver by means of a rheostat connected in series with the filament wire from the "A+" battery post this system prevents the distortion which would be caused by overloading of the detector if the volume control were located in the A.F. circuit. A choke coil is also connected in the supply wire to the screen grid, and this overcomes coupling through the plate batteries. An R.F. transformer with a fixed tickler of picture is a front view of the new four -tube, screen -grid Roberts receiver. winding is used to couple the plate circuit This circuit of controls are mounted on a handsome bronze escutcheon plate, and the the screen -grid tube with the grid The tuning winding of this metal cabinet is supported on a highly -polished mahogany base. the detector; the secondary

www.americanradiohistory.com Radio News for October, 1928 311

The ballast shield, which is illustrated in the drawing, accomplishes two very important functions in a radio receiver. When installed it prevents electrostatic pick -up by the tube elements and consequently improves the selectivity and stability of the circuit. Secondly, it increases the mechanical inertia of the tube to such an extent that the elements will no longer respond to audio-frequency impulses and vibrations, and the familiar howling caused by such response is, therefore, prevented. The ballast shields are available in two standard sizes: one for the screen -grid and other standard -size tubes, and the other for the small 199 -type tubes. The large -size ballast shield is made in two sections and consists of a heavy die -cast base into which the bakelite base of the tube fits, and a formed copper shell which fits over the tube proper and screws onto the base. The tube is protected by felt pads, which are placed around it before the ballast shield is fastened in place. The small size ballast shield is a die-cast case finished in copper and lined with felt. It is designed to slipover the 199 type of tube, but it is not supplied with a base. In this chassis view of the new Roberts receiver all parts are shown mounted in Seven different interchangeable inductors, their proper positions. It will be noted that practically all wiring is located of the type shown at A in the picture, have under the metal chassis. also been announced. This series of coils includes radio- frequency transformers for transformer is tuned by a variable con- secondaries; in I.2 the 20 -turn winding is use in circuits functioning at broadcast fre- denser similar to the one used in the R.F. used as the tickler. quencies; a transformer and a tuned im- stage. In this circuit regeneration is con- The operation of the receiver is very sim- pedance unit for use with screen -grid tubes in intermediate- trolled by a .000075 -mf. variable condenser ple. The two drum controls (C1 and C2) an frequency amplifier op- (C3), connected so that the tickler coil is in are the only tuning adjustments of the set. erating at a frequency in the neighborhood series with the condenser between the plate The only additional adjustments are the of 115 kc.; and an oscillator coupler cover- of the detector tube and the "B-" or volume knob and the regeneration control. ing a waveband of 180 to 460 meters and ground. In operating the set it will be found that suitable for use in superheterodyne receivers Probably the most unusual feature of the the two tuning dials have approximately the employing a 115-kc. intermediate- frequency new receiver is the A.F. amplifier, which same settings for any given wavelength. amplifier. Also, in the near future, transformers employs a new type of coupling device. Manufacturer: Silver -Marshall, Inc., Chi- will be available for the reception The amplifier coupling units were designed cago, Ill. of short -wave signals. especially to eliminate the distortion due to The mechanical construction of the inter- hysteresis; they do this by isolating the di- changeable inductors is shown clearly in a rect plate current and preventing it from New Special Components drawing which accompanies this article. The flowing through the winding of the auto - for Set Construction base of each coil form is equipped with four transformer coils. A resistor and a con- prongs which have been designed to fit into SIX radio parts intended denser connected to each winding, as shown, for use in the a standard UX -type tube socket. Also, each accomplish this purpose. season's new kit receivers have recently coil is provided with an easily removable Very uniform amplification is obtained been introduced. They primary coil, and vari- over the entire band of audio frequencies. include: ballast shields ous sizes of primaries vacuum According to actual tests made in the manu- for tubes, shield are available separately, facturer's laboratory, these units provide compartments, tube -base, so that the type of type plug-in coils, inter- practically equal amplification at 65 and at primary winding best 1,000 cycles. The amplifying units in the mediate- frequency trans- suited to the require- formers and balancing two stages are of different design; Ti has ï condensers. an effective transformation ratio of 4.3 to 1, and T2 has a ratio of 3.5 to 1. The overall audio amplification of the receiver, when .1111111111111,,,,,,01111,,,,,,,,,11,1,111,,,111 .11llllll ...... l MOM* using a 112 -type tube in the position V3 and a 171 -type tube in the output stage, Four new parts which have ap- is approximately 500; or more peered on the market recently than twice are shown here. A is a new the amplification obtained from a two -stage 1 tube -base plug -in R.F. coil; B is a plug -.n intermediate trans- amplifier using the same tubes and 3 to 1 ' former; C is a stage shield; ratio A.F. transformers. and D is a neutralising con. With the exception of the audio units and denser. the metal chassis, cabinet and escutcheon plate, the parts employed in the construction of the receiver are of standard design. The R.F. transformers (L1 and L2) are of identical construction and are wound on threaded bakelite tubes 2% inches in diameter. The secondary windings consist of 72 turns of No. 24 enameled wire spaced to a length of 2/ inches. In addition, each coil has two other windings, consisting of 20 and 35 turns, the latter space -wound, of .. Ja No. 34 D.C.C. wire. These coils are .,, I`. wound on 2/ -inch diameter tubes, which are F placed just beneath the filament ends of the

www.americanradiohistory.com Radio News for October, 1928 312 Cap) Below, combination ballast Removable of the individual circuit can be in- -type tube; ]vents and shield for 199 CONTROL GRID FELT r stalled. To remove the primary it is only Center, similar shield for the the top of the bakelite screen -grid 222 -type and other TERMINAL necessary to lift out standard tubes. Right, plug - secondary coil form and to unscrew the two in tube -base inductance coif primary. small terminal prongs in the base. These with interchangeable prongs project through the base of the secondary form and screw into inserts in the form on whidl the primary is wound. Another type of plug -in inductor is shown at B in the picture. These units also use a standard UX -type socket as a terminal hase and they are designed especially for use in the intermediate- frequency amplifier of a superheterodyne. Their most interesting fea- CASE ture is that they may be tuned to exactly the desired frequency by adjusting the small screw at the top of the case. This screw changes the capacity of a small condenser which is continuously variable over a limited range. Inductors of this model are available in two different types; the first is a transformer for use with standard tubes, second is an impedance unit for use and the Primary with screen -grid tubes. Both types arc tuned to a frequency of 115 kilocycles. Secondary compartment illustrated at C 'l'he shield television is sup- is of copper, sufficiently heavy est problem in transmitting in the picture of Television In- cell with sufficient be rigid. It is 3 inches wide by 51/2 Efficiency plying the photoelectric to for its operation, and the solution to inches deep by 51/2 inches high. The top Disc light creased by New is greatly simplified by the use and bottom of the shield are removable, so the problem improved de- boles in the disc. that mounting of the parts and wiring may METAL television disc of of square The shield is in- sign, with square scanning holes, has Manufacturer: The National Company, be accomplished easily. by a to accommodate two been placed on the market recently Malden, Mass. tended primarily is tube sockets (in one of New England manufacturer. The disc standard UX -type reception is mounted and in the other suitable either for transmission or which a tube It is -in coil), and the necessary by-pass and is of very rugged construction. Motor a plug has forty- Special Television but it is not limited to this ap- twenty-four inches in diameter, condensers, with a large plication. The base of the shield is drilled eight holes, and is equipped V ery Accurate the disc to a motor for the parts mentioned above, and a bushing for attaching When it is used for An alternating- current motor which has bracket is supplied for supporting the with a / -inch shaft. television 11/2 by 11/2 inches. been designed especially for socket for the coil away from the bottom of receiving the image is the compartment. In previous issues A small balancing condenser is shown at of this magazine the discs 1) in the picture. This instrument has a use of scanning capacity range of 5 to 70 inmf., and may be for the transmission adjusted with a screw -driver by turning the and reception of tele- de- small adjustment screw. It is ideal for bal- vision has been ancing two or more condensers for one - scribed so f requently control operation; when used for this pur- that little need be said How- pose, one balancing condenser should be in this article. connected in shunt with each section of the ever, the construction multiple condensers. The balancing con- of the disc has never is also useful for increasing the maxi- received much consid- denser of mum capacity of a variable condenser. eration. In most Manufacturer: Gray and Danielson Mfg. the discs on the mar- holes Co. (Remler), San Francisco, Cal. ket the scanning are circular, as this construction is much simpler from the mechanical viewpoint. The square holes in this disc are much more This television motor is very responsive to regu- which are used lation, while steady in its speed. The large con- difficult to cut, but they are highly to be denser in the case at the left acts on the desired. A square motor's rotation like the airchamber of a pump. hole will allow 27% more light to pass reception and transmission is illustrated through the disc than herewith. It is a condenser -type, single - a round hole of equal phase, ball -bearing motor and the speed width, and this greatly may be varied very easily with a series improves results. rheostat. It is quiet in operation and does The additional light not cause radio interference. which is provided by In a television receiver or transmitter the square scanning boles motor which turns the scanning disc is in a television disc probably the most important piece of ap- is very valuable at a paratus. At the receiving end the speed transmitting station of the motor must be synchronized exactly and is helpful also in with the speed of the motor at the trans- receiving. The great- mitter, and if the motor is not easily adjustable or if it does not hold a constant .0..11111,11,,,1,.,...... 1.,..,,11 speed, successful television reception is im- The square holes through this disc possible. Also,_ the motor should not be are in the center of the white dots type, as the tiny and are, of course. too small to show of the usual commutator in reduction. The workmanship on (Continued on page 382) the disc is excellent throughout.

www.americanradiohistory.com Radio News for October, 1928 313 Interesting New European Screen -Grid Tubes

One Model Designed for A. F. Use Has Three Grids; the Auxiliary Electrode Neutralizes the Effect of Electron Emission from the Plate By R. Raven -Hart (PARIS, FRANCE)

ONE of the most interesting recent This European is perhaps the first tube in which it productions is a screen - has been necessary grid tube to take steps against the adapted to the last stage effects of secondary of audio- frequency amplification. emission -the emission of electrons by the plate under The internal arrangement will be seen the bom- bardment to which it is subjected by from the picture, Fig. A, and the drawing, FIG. I the filament. In a normal three -element Fig. 1. It will be noted that there are tube three such electrons are at once grids, an auxiliary grid being placed re- attracted by be- the plate and their charges tween the plate and the screen grid, and reabsorbed. Here, however, the plate is frequently connected to the center of the filament. The at a CONNECTION potential less than that of the function of this grid is to neutralize the screen grid TO THIRD (since an alternating voltage effects of secondary emission from the.plate, is developed (EXTERIOR) GRID across the loud speaker) ; as will be explained later. The four prongs and this, being 2 alternately added in the 4 to and subtracted from base connect to the control grid, the the voltage plate, of the plate battery, makes the and the filament; the screen grid be- plate negative ing connected to the with regard to the screen extra terminal mounted every half oscillation. on the side of the base, Under these circum- and the third grid stances the electrons having no external connection whatever. of the secondary emis- F F G sion would be attracted The constants given by the makers to the screen and are SCREEN give rise to as follows: filament voltage, undesirable effects. The pres- 4 volts; fila- ence of the third ment current, 0.15 GENERAL FILAMENT grid, held at the potential ampere; plate voltage, 50 of the center to IN volts, with the ARRANGEMENT PLAN of the filament, causes them screen grid at the to be repelled same voltage as towards the plate, and they the plate; amplification fac- are there reabsorbed tor, 100; mutual conductance, Above: Cross-section view of the five -electrode during the next (posi- 1.8 millimhos; screen -grid tube. Note that the extra grid, tive) half oscillation. and internal resistance, 55,500 ohms. EG, has no external terminal, being connected Fig. 2 Mows the circuit arrangement, merely to the center of the filament. which is quite normal. will It be observed Below: Hotu the tube is connected in an A.F. A DIFFERENT R.F. TUBE that this tube can be substituted for an or- circuit. dinary (three-element tube) triode with very It may be added that the same makers little change, by merely connecting the ter- produce a screen -grid tube for radio -fre- minal on the base to plus "B." quency amplification, which is in general Owing to the high internal resistance, the very similar to the American tube. How- dynamic characteristic tends to approxi- ever, it possesses the interesting variation mate closely the static curves (as in the case that the terminal mounted on top of the of all screen -grid tubes); and thus a high tube is not that of the screen -grid, but that dynamic amplification factor and mutual of the plate; the screen being connected to conductance are retained. Further, as the the pin in the base which would normally go static curves are rectilinear between their to the plate. The internal arrangement can working limits, the dynamic characteristic (Continued on page 360) is substantially straight, even with an external impedance (loud speaker, etc.) very much lower than the internal resistance. In fact, instead of the condition aimed at with a normal three -element tube for a straight dynamic characteristic -that the external impedance shall be at least twice the in-. ternal resistance -the condition here is that the external resistance shall not exceed one - half the internal resistance. Otherwise, the plate may become negative with regard to the filament, the alternating voltage developed across the loud speaker exceeding that of the plate battery under these cir- cumstances. Fortunately, this condition is exceedingly easy to realize.

FREQUENCY DISTORTION REDUCED Thanks to the high internal resistance of the tube, frequency distortion (suppression of the high notes) is greatly reduced. With an ordinary tube, the impedance of the loud speaker is by far the greater proportion of the total impedance of the circuit, but here the internal resistance predominates. Hence the increase in the impedance of the loud Fig. A: The five -electrode speaker for the higher audio frequencies screen-grid tube. Fig. B: does not so greatly affect the total im- the new four -element tube. The glass has been broken pedance, and there is less tendency for these away in each case to notes to be weakened. show the elements.

www.americanradiohistory.com Radio News for October, 1928 314

Under this heading, RADIO NEWS publishes each month descriptions of the latest developments in the extremely interesting field of television. "Seeing" Music with a Television Receiver ordinary voice and music TELEVISION has arrived, but as yet at random in the RADIO NEWS Laboratories. to show how stations are An electric fan, which was about to be "looks" in a television receiver. The geo- only a few scattered formations built up television images. While packed away, was instead dusted off and the metric patterns and transmitting extremely interesting preparing for regular television pro- blades and wire guard removed from it. by the apparatus are More will be said about the grams, however, the radio fan can perform As the fan was of the "oscillating" type, to behold. it swing later. some highly interesting experiments with the worm mechanism which makes operation he can back and forth was unhooked, so that the a simple television apparatus that A CHEAP, USABLE DISC ma- motor would remain 'stationary while in construct himself at little cost. This lay it aside gen- operation. (These operations did not ruin After taking the fan apart, chine has all the parts of what is now the scanning disc. standard television the fan, as the blades, guard and worin for a while and make erally considered the discs which are now being sold disc pierced by mechanism can he reattached in a few min- All the receiver: namely, a scanning commercially for television purposes are a motor to drive it, a utes.) It was decided to use a fan instead a spiral of holes, made of aluminum and are accurately a means of controlling of a special television motor because fans neon glow tube, and with round or square holes, not motor. By assembling are very widely used, and because the sum- drilled the speed of the one sixteenth of an inch across. a good in- mer will be well over by the time the con- more than it, the experimenter will obtain -made contraption, an ordi- theory and practice of structor builds this machine. Few people For this home troduction to the nary flat piece of cardboard is perfectly television without having to spend a great would care to spend $25 or $30 for a special After motor just for an experiment, but they can satisfactory. It should be not less than a deal of money on complex apparatus. and cut into of the fun- easily make use of an idle electric fan. sixteenth of an inch thick, acquainting himself with some diameter. principles and practi- 'l'he general appearance of the complete a disc 12 inches in damental theoretical With the aid of a pencil, a ruler and a difficulties, he will be better machine, as assembled in the RADIO NEws cal operating compass (which you can borrow from your to make and use a real television re- laboratories in about two hours, is shown able page, son's or little brother's school bag), now ceiver when regular television service is in the pictures on this and the facing and in uncompleted form on the front mark off 24 radii (lines running from the available. center of the disc out to the edge). These The parts composing the crude machine cover. It was built, not for the purpose should he 15 degrees apart. As a circle has in these pages were picked up of receiving television images, but merely illustrated 360 degrees, the lines will radiate outward evenly. If you have forgotten how to subdivide angles with a compass, simply draw one diameter first through the center of the disc. Then draw another one exactly at right angles to it. These gives you four lines. Now spot the middle of each of the four sections a's closely as you can, and draw four more lines from the center. If you now subdivide each of the resulting sections into three equal parts, you will have the twenty -four lines. Take the ruler and measure a distance of 51/4 inches along the vertical center line. Make a mark at this point. Proceeding on the next line to the left, measure a distance of 5 3/16 inches. Proceed along, measuring off the distances as indicated in Fig. 1 on page 315; you will have a total of 24 points. Through each one, drill a hole slightly less than / -inch in diameter; then, with a piece of stiff wire or a narrow strip of brass, ream out the holes so that they will be square in shape. Their edges are bound to be a little fuzzy, but do not worry about this. For those who want to save themselves the trouble of marking out the individual lines, RADIO NEWS has prepared full -size blueprints which can be used as drilling templates. To use one of these blueprints, you simply lay it over the piece of card-

board and punch through the - center points marked on it. (These templates are free; simply write to RADIO NEWS, 230 Fifth Avenue,: New York, N. Y., and ask for the Television Disc Blueprint.) If you haven't a piece of cardboard of the right size at home, go to the nearest stationery or draftsmen's supplies store receiver in the RADIO NEWS Laboratories. The only adjust- and ask for a piece of heavy bristol board. Fig. A. The experimental television music are observed meut is the knob regulating the motors speed. The patterns created by the This will cost only a few cents. through the square hole cut in the cloth, opposite the neon lamp.

www.americanradiohistory.com Radio News for October, 1928 315

reproduces the changes as variations of NOTE: 15° BETWEEN CENTER LINES light. When a regular television receiver ALL HOLES 8"- SQUARE, is being operated with television impulses, DIMENSIONS GIVEN ARE a picture is built up on the plates of the FROM CENTER OF DISC tube with the aid of the scanning disc. TO CENTER OF On the other hand, if voice or music im- SQUARES pulses are led to the tube while the disc is rotating, endless varieties of patterns will be observed. After watching them for a while you will be able to distinguish a low note from a high one by merely watching the picture it makes; and you will be able to tell the difference between voice and 15° I5° music. The neon tube is suspended just behind the scanning disc. It may be either fastened to the underside of the bread board that holds the radio receiver as shown in the pictures (Figs. B and C) or supported on an arm such as that shown on the front cover. In the laboratory machine, four corner pieces (old broom sticks) were used to allow a cloth cover to be tacked around the fan. A hole was cut in the front of the cloth, so that the upper section of the disc between the farthermost -iN and innermost holes could be observed. The neon tube should be so placed that the hole which is 5% inches from the center of the disc passes just across the top of the plate, and the hole which is 3 13/16 inches from the center just across the bottom edge. THE CIRCUIT A double -impedance unit, such as are used in audio amplifiers, is mounted anywhere along the breadboard on which the motor rests. A 60 -ohm rheostat for controlling the speed of the motor is mounted on the After drilling Fig. 1. Details of the scanning disc used in the scanning disc, the next the setup. The holes overlap; but very inter- front edge, so that it can be adjusted easily. problem is to mount it to the shaft of esting images are obtained. (Continued on page 385) the fan motor. Obtain from a hardware store a pulley that will fit the shaft of your particular motor. This will have a set screw which allows it to be tightened against the shaft. To fasten the cardboard disc to the face of the pulley, first drill and tap the latter for four 8 -32 screws, then clamp the disc between two 5 -cent phonograph records and pass the 'screws through into the pulley, as shown in Fig. 2 (page 385). This was the arrangement used in the original model of the machine; but any other that suggests itself may be employed. The important thing is to make the disc run as smoothly and as evenly as possible. After mounting it, give it a coat of black paint. Liquid shoe polish will serve just as well; the idea is merely to darken the cardboard.

THE FLASH LAMP The main item, of expense involved in this "television" receiver is the neon glow tube. This costs about $12, but is a good investment because you will be able to use it later in any real television instrument you build. This tube is about six inches long and two and a half inches in diameter, and is fitted with a standard UX -type base, which fits in a standard tube socket. It contains two flat metal plates, placed about a sixteenth of an inch apart and parallel to each other. When an electric current of the proper value- is passed through it, the entire surface of one of the plates lights up with a pinkish -red glow, characteristic of the gas neon. The eye- catching red signs now being used so extensively for advertising purposes contain this same gas. The neon glow tube responds to changes Figs. B and C. The apparatus with the cloth cover in electrical current just removed; N, neon lamp; D, as a loud speaker scanning disc; P, phonograph records used for clamp does but, instead of producing (see Fig. 2) ; F, fan base; sound, it R, motor rheostat; L, double -impedance unit (see Fig. 3).

www.americanradiohistory.com Radio News for October, 1928 316 Radio- Picture Equipment for Police German System Transmits Illustrated Circulars to All Large Cities Simultaneously Within Three Minutes By Dr. F. Noack (BERLIN, GERMANY) operating at high trans- ment suspending the galvanometer mirror, effect this in systems THE pioneer of radio -picture speed. Professor Korn's apparatus func- who has and the width of the slit are so propor- mission, Professor Korn, u moderate speed; although in the tioned that a very slight deviation of the tions at devoted over twenty years to experiments it was operated at a new mirror will not cut off the light beam; early task, has lately developed a one, transmitting about 10,000 Prussian but that resulting from a strong signal very high system, with the cooperation of the at- dots per second (a practical television and of the police. will do so. Thus slight disturbances, ministry of the interior not sufficient to pro- speed), this was found to require the use designed for use in the mospherics, etc., are The equipment a visible spot on the picture. This of a galvanometer which was too sensitive of pictures and facsimile mes- duce The transmitter transmission freedom from interference, essential for to electrical interference. police headquarters in various of 2,400 sages between the important purposes of the police and now in actual use sends at the rate cities, and illustrated here, has been constructed by the C. Lorenz Company of Berlin. The transmitting apparatus employed is somewhat similar to that of the Telefunken- Karolus system, now in extensive use in Germany and Austria (see Ranio NEws for November, 1926, page 466), but there are numerous differences in the receivers. In the latter, the light impulses are converted into electrical variations by the ring -shaped Karolus photoelectric cell, which is very costly. In the Lorenz-Korn system a small tube -shaped photoelectric cell of the ordinary type is used; with 120 volts across it, its response to light is in the order of .01- microampere to each lax (slightly less than a foot -candle.)

NOT TOO SENSITIVE The Korn system transmits impulses only as black or white, being therefore much less sensitive to interference, static and other disturbances than the Karolus method, which is designed to transmit and reproduce half- 4, tone shadings. 1, galvanometer; 2, casing of picture cylinder; 3, motor; synchroniz- The radio -picture receiver: motor rheostat. The Korn receiver is of the usual vacuum - discs; 6, switches; 8, hole for adjustment; 11, synchronizing -note filter; 47, ing opposite, Figs. 2 and 3. tube type; the detected signals, which cor- Other parts are shown in the diagrams respond to the impulses impressed by the other government agencies, is obtained only dots, each 1 /100 -inch square, per second; image on the photoelectric cell at the trans- found to be to by abandoning the attempt to transmit in- and reception at this speed is mitter, are passed after amplification free from interference. sensitive mirror termediate depths of shading. practically the windings of a highly- In order to synchronize the transmitter 1 Fig. B and galvanometer (shown as in SYNCHRONIZING MODULATION the following ingenious beam, cast and receivers, 20 in Fig. 2). This reflects the used; a commutator -disc (10 in source of light, One of the requisites of successful picture method is upon it from a suitable on the shaft of the driv- covering of the transmission is the synchronization of the Fig. 1) is mounted through a small slit in the of the transmitter. By this which is covered with revolving mechanism at the transmitter and ing motor receiving cylinder, means an 1,100 -cycle alternation is im- The thickness of the fila- at the receivers; it is extremely difficult to sensitized paper. pressed on the grid circuit of the amplifier, and modulates the signals which are broadcast. At the receiver, this doubly-modulated signal is detected and amplified, as we have said; the 1,100 -cycle modulating note is passed through a special amplifier and filter, and passed to the synchronizing motor which drives the mechanism. At the same time, an 1,100 -cycle current is carried to a glow lamp which illuminates a clise mounted on the motor's driving shaft. By means of the "stroboscopic" effect (explained in RAmo NEWS for August, 1927) it is easily possible to determine when the synchronizing impulses have brought the motor at the receiver into step with that at the transmitter. A steady illumination will then be seen on looking at the disc. Any needed correction is made by simply adjusting the resistor regulating the motor's speed. The synchronizing signal, however, is not of sufficient strength to disturb the of the Lorenz -Korn radio -picture system: 1, picture cylinder in its mounting; comparatively insensitive galvanometer and Transmitter lens. Other 3, photoelectric cell, and 4, its lens; 5, source of light and 2, its condensing affect the picture. apparatus is indicated in pig. 1.

www.americanradiohistory.com Radio News for October, 1928 317

second necessitates only two and a half minutes to receive a picture about 5 x 7 inches. The adaptability of radio -picture service to many purposes is apparent; such as the transmission of news events, fac- similes of public and commercial documents, manuscript, etc. The appearance of the transmitter is shown in Fig. A, and its schematic circuit is diagrammed in Fig. 1. The receiver is pictured in Fig. B; its schematic circuit is shown as Fig. 2, and a pictorial diagram is Fig. 3. The parts can be identified readily from the captions of these illustrations. While this system differs only in details from other radio- picture methods, it marks a distanct advance in the practical applica- Y,ri4:inalF,., :. tion of el Berlin 1-7er1323., +;®r_ 18, Janauar 1925 the system to broadcast, rather than point -to-point transmission. F e a t n a hm e wegenì Aiordea Karl Trauer, Mechaniker, 17, 3.78 1,05 gross, hraune Auzen,Schunsverletzun,,er-; Berlin geh., ar*: linken Unterarm. Fig. C. Typical German police broadcast of Grenzutertritt verrct.tFt. Im Erfolti:fa11e aofort Fun'rlaehrìct the picture and fingerprints of a man who is wanted. Kripo $r1i7a rrim-l.nspeltiotr A zu 170 IV., V Though in black- and -white, the pic- Ir. C. ture received has a photographic latrv`xv.,taa.+t:T <.:,: `t`:t,..äiïR"3cïx.-x ..A.-saz.-.n:-. effect.

The right moment for the commencement of rotation of the picture -cylinder is sig- nalled by an impulse from the transmitter, which is received by a polarized relay at the transmitter. This closes a circuit which Fig. 1, the transmitter: magnetically operates a 6, amplifier; 7, transmit- coupling clutch, ter; 8, driving motor, and connecting the worm -gear of the motor to 9, gearing; 10, synchro- the shaft of the cylinder. niz :ng disc. Figs. 2 and 3, receiver: 5, gear; 7, slot for galvanometer ADVANTAGES OF THE SYSTEM light -beam: 9, magnetic coupler; 10, synchroniz- The ing -note amplifier; 12, nature of the modulation is so even radio receiver; 14, relay; that the transmitted wave is very sharp; 15, case for film; 16, 19, the 20, lamp, lens and gal- carrier-wave, at this low speed of trans- vanometer; 21, strobo- mission, is modulated by only 1,200 cycles s c o p i c" synchronizing lamp. See Figs. and the side bands are very narrow, so A and B. that there is no jamming of the channels ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, of communication. Transmission at the rate of 2,400 dots a The "Fultograph" Radio Picture -Broadcast System BROADCASTS of pictures have been chromate of potash; when a negative print depth of color with demonstrated, and will the value of the current. be, in increas- is taken upon it, the glue exposed to light The transmitted, ing numbers, it is and consequently the re- believed, a feature becomes insoluble. That representing the ceived picture, of European programs. The system of is divided by a screen into Capt. white areas (black in a negative) is dis- dots like a halftone illustration. Otho Fulton has been designed for the pur- solved. The black surfaces in the original The Fulton apparatus is driven pose of home reception with a minimum of by clock- picture appear as bare metal. work instead of motors; for purposes apparatus. The photoelectric cell is not em- When of the prepared foil is wrapped synchronization, a metallic conducting strip ployed; the receiver, in particular, looks around a metal cylinder and a metal con- is left on the transmitting cylinder. When- back to the principle of Morse's original tact caused to move over it, each spot of ever the contact reaches this, an impulse telegraph apparatus discoloration of hare metal is - passes an electric impulse which sent which operates a magnetic relay at the chemically- prepared paper by current flow. is amplified and broadcast in the usual man- To prepare receiver and lifts the printing contact, thus a picture for broadcasting, it ner. When it is received and detected (a synchronizing is transferred the two cylinders at each photographically to a thin two -tube amplifier is said to be sufficient) revolution. sheet of copper, by a process somewhat simi- each flow of signal current passes through It requires some time-about 45 minutes lar to that of making halftone "cuts" for a contact into a sheet of paper which has -to make up the copper foil picture for printing. This copper plate has been cov- been wrapped around a similar cylinder, and transmission. A picture 3% x 4% inches is ered with a film of glue treated with bi- causes a brown discoloration varying in sent in 3% minutes, says Amateur Wireless.

www.americanradiohistory.com Radio News for October, 1928 318 The Radio Bean Sorter A Novelty Unique Machine Which Automatically Separates Colored Beans Uses Photoelectric Cell and Radio Amplifier ; Can Be Built Easily

By Herbert W. Augustadt

was punched, making a hole the size of the the photoelectric accomplish this purpose, one should use, THE applications of beans it was desired to sort; a bakelite to many operations, industrial for the first three stages, "high mu" tubes, cell high disc, with the saine size of hole, was fitted commercial, are scarcely limited. whose distinguishing feature is their and into the solder box. The disc was attached only take the place amplification factor. The last tube should This cell can not to a crank, which brought the hole in the in many ways, but in pass a large amount of current to actuate of the human eye box and the hole in the disc in line functions that the the relay; and hence a power tube should solder others it can perform with each other every revolution, allowing a human eye cannot. Because of its wide be used. may be obtained bean to pass through. A small arm was field of application, and because of its new- The bias for the tubes from old "B" battery cells, that were long fastened to the crank in the bottom of the ness, the photoelectric cell should be very and ago unfit to supply plate current, but still hopper, to scrape and stir the beans interesting to the experimenter; new appli- The beans have voltage. A high bias is necessary to make them fall into the hole. cations for experimental purposes suggest means of a keep the plate current low in the first tubes. were then led to the belt by themselves all the time. spout, and guided into the middle of the The machine with which this article is The potentiometer around the bias battery for the purpose of will make it easy to adjust this voltage for belt. concerned was built The kicker, which threw the colored beans of all colors from different conditions, and hence is suggested. separating colored beans from the belt, is the contrivance shown at an automatic seeming in- 'l'he bias can be obtained direct from the white ones. As B, in Fig. 2, and is made from an ordinary it not only makes a striking ex- battery without the potentiometers; but in telligence, to make buzzer; soldering a brass strip to the arma- hibit, but also a very interesting machine that case the adjustments are hard taps every 1% ture of the buzzer and increasing the length for the average experimenter to work up. without a battery that has volts. of travel by bending back the armature. CONSTRUCTION The first relay, A, in Fig. 1, is the more The kicker was controlled by relay C. variation of light is of the machine is sim- sensitive of the two. The experimenter can Since the niaximuni The cónstruction desired at the time of the passage of the ple, for anyone who has done the least bit use telegraph relays, if he has nothing else; dark bean under the focus of the photo- work in radio. It is well known that a they were tried and worked very satisfac- of electric cell, a lamp, L (Fig. 2), was used to photoelectric cell passes more current when torily. The relay is set to act on the least obtain a bright spot of light on the belt falls on it, than when in the dark. current possible and still have positive ac- light over which the beans must travel. The lamp is used in this machine by tion. Its contacts close on the second relay, This principle was obtained from an old automobile the beans to pass under a light that in series with a 1% -volt cell. These contacts used causing and adjusted to have its focus about a foot is reflected on a photoelectric cell. The then close on the buzzer, which is used as the 'front the lamp. Inside the lens a card- beans reflect less light than the "kicker" to throw the colored beans off the colored board was then inserted, with only a small white ones; hence, the current through the belt. It was found better to use two re- hole in its center. Over this hole, and on the changes. This change in current is am- lays, to prevent burning of contacts and cell outside of the lens, a watchmaker's eyepiece plified and caused to actuate a relay which inductive kicks passing through the machine. was placed. By this means, it was possible removes the colored bean from the belt. MECHANICAL DESIGN to obtain a bright spot of light not much Since direct current is used in this ma- is larger than the beans to be sorted. the amplifier must be built to amplify The construction of the machine proper chine, of The photoelectric cell was then placed so direct current. The frequency of the vari- shown in Fig. 2. The belt was made wide, and passed that it would face the small spot of light, ations is so low that it would be impossible white canvas about an inch M, was and fitted with a hood that allowed light to to use an amplifier of any other kind than a around two spools. A small motor, the come in only from a small opening directed resistance -coupled one. The diagram of used as the driver. The hopper, H, fed drop only on the spot of light. Unless a hood of this such an amplifier hook -up is shown in Fig. 1. beans to the belt and was built to kind is used, variations in the light of the The variations in current are very small; one bean at a time on the belt. from an old room, or shadows from observers, will af- of a single bean under the The hopper was constructed for the passing the working of the cell and may cause the cell does not cause a great funnel, the bottom of which was removed fect focus of relays to chatter. in the light and, hence a large to make an opening about the size of a the variation The time -lag, of the effect of the varia- amount of amplification is necessary. To solder box. Then an ordinary solder box

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135V.

A a 171A or a 210. Old "B" batteries may be used to btas the grids Fig. 1. The electrical circuit of the sorter. P, photoelectric cell; amplifiers. the parts of the amplifiers are shielded, the C, relays; B, "Kicker," made from buzzer. The first three tubes of the If and than if left unshielded. should be of the high "mu" type, like the 240 and 340 tubes; the last circuits will be more stable

www.americanradiohistory.com Radio News for October, 1928 319 tion of the light, on the cell and the action of the relays is very small, in fact it is almost zero; and so the light -spot should be focused directly ahead of the arm that kicks off the colored beans. will It be found easier Fig. 2 to focus the light and cell, if they are mounted so that they can be moved in two planes. ADJUSTMENT The values of bias given are approximate, and so it is desirable to adjust the machine to the best working conditions. This is accomplished in the following manner: All the tubes are removed except the first and second. A milliammeter is then inserted in the plate circuit of the second tube, and on this tube is placed a bias that will keep the normal value of the plate current under 4 milliamperes. After this is accomplished, a colored bean is placed on the belt and run back and forth through the light -spot. The grid bias is adjusted until the variation in plate current is the greatest. If no variation is recorded, it is more A general view of the bean sorter. than likely that the, cell is not directed M, motor which turns the belt; H, hopper; P photoelectric cell; L. toward the light spot. This can be deter- source of fight; B, "kicker." With mined by shutting off all of the light. Such the aid of this sketch an ingenious constructor can readily assemble a action should produce a difference in plate working machine. current. If it does not, the cell should be moved around until the plate current does vary and should he fixed in the spot will cause the kicker to kick all the time. cause a decrease in plate where the plate current is at minimum. current, rather This trouble can be remedied by adjust- than an increase, in The plate current will drop to a minimum the second tube. ing the plaie current to a lower value, and It is well to place the machine at the time that the maximum light is fall- in a room by placing a 1 -mf. condenser across the which has an even distribution ing on the cell; because the two tubes in of light; so contacts of the first relay. It is not well that the passing of a the amplifier are connected so that plate person in front of to draw current from the "A" battery of the machine will not current through the first causes an in- cause a shadow to the amplifier for the relays, as this may fall on the belt or affect the amount of crease in negative bias on the second. The cause trouble. opposite effect light on the belt. These changes in the takes place when no light A second trouble that will cause the relays amount falls on the photoelectric of light may be so small that they cell. to chatter is difference in the color or are not noticeable The adjustments for the third tube are with the naked eye, and light- reflecting qualities of the belt. Hence hence one must guess made in a similar manner. A plate- current at this source of it is necessary to color the belt with some trouble. Of course this effect variation of 5 milliamperes is to be can again be ex- finish that has about the same reflecting noticed in the pected in this tube, when change of the plate current the black bean qualities as the surface of the white bean. of the passes through the light last tube when someone steps near -spot. 'l'his varia- In many cases, white ink will be found the instrument. tion in plate current If the change is not great of the third tube will very satisfactory for the work. enough cause a change to cause an appreciable difference in grid bias on the fourth A third possible source of trouble is in tube, large the plate current, the machine will work enough to give an increase of kicker. This part of the apparatus should satisfactorily. at least 50 milliamperes plate current. be colored the same as the belt and the The experimenter will Hence the tube can be biased to pass no no doubt think white bean. One can determine whether of other methods of making current when a white bean is under the up a photo- it is the source of the chattering of the electric machine. These light spot; and yet, when a black bean goes can easily be relays or not, by inserting the milliammeter worked up once one under the focus of the cell, it will has the idea and a pass in the plate circuit of the last tube, and method of approach. enough current to cause the relays to act. The construction of pushing the kicker across the surface of the machine is not as complicated as it The machine is now adjusted and ready to the belt. If the travel of this kicker work. across may sound and it makes a very interesting the belt causes an increase in plate current, exhibit, when POSSIBLE TROUBLES it is built. That described the trouble lies in it. This may be remedied here was shown on Engineer's Day The only at the serious trouble that may be ex- by sloping the kicker so that, on closing, University of North Dakota, Grand Forks, perienced is chattering of the relays; this it will throw light into the cell and hence North Dakota. Radio News Free Blueprints Available for the Asking DURING the past six months RADIO May, 1928 number: This set was designed NEWS has prepared a number of specifically for the beginner in radio blueprints WRITE PLAINLY -the showing the construction man or boy who is interested in making of several different types of broad- writing for the RADIO his own radio receiver and who wants cast receivers, to short -wave receivers, audio - WHENNews free blueprints, please start with something that is cheap and frequency amplifiers easy and power packs. typewrite or print your full name and to build. It is a "sure-fire" outfit that will These blueprints include full -size panel and address clearly. Many requests which work without trouble the first time it is sub -panel drilling layouts, pictorial and we receive cannot be filled because hooked up. If you know some youngster schematic wiring diagrams, details of coils the handwriting is illegible or the who likes to make things with tools, send and special components, and complete lists address incomplete or missing alto- us his name and address and we will mail of the parts actually used in the outfits. gether. him a set of these blueprints. They are absolutely free to the readers of SEND NO MONEY. Just give the No. 55, "An Amplifier for the Simple RADIO NEws; to obtain any of them all you number or numbers of the blueprints Two -Tube Receiver," June, 1928 number: need do is write in and ask for them. you want and they will be sent to you The two -tube set mentioned in the previous The following blueprints are available. free of COSt.- EDITOR. paragraph is designed to work with head- Simply order them by number. phones. After you get it operating satis- No. 53, "A Simple Two -Tube Receiver," (Continued on page 367)

www.americanradiohistory.com News for October, 1928 320 Radio Television in Natural Colors Demonstrated Application of Three -Color Separation Process Used in Photography and Printing Makes Possible Transmission and Reproduction of Brightly- Colored Daylight Scenes By Ronald F. Tiltman (LONDON, ENGLAND) THE last few months have witnessed 3rd for the first time to the press and to image and a green image, and if the source two spectacular strides. in the art of a party of scientists. of red consists only of red, as does the television. The first was the trans- By kind permission of the British In- ordinary neon tube, it will be impossible for mission of images, using ordinary ventor, I am allowed to publish full details the receiving apparatus to produce blues daylight, and this has removed television of this most remarkable achievement. and greens. The problem was to find a of a single lamp which would give red, blue, from the laboratory to the open air. . Any At the transmitter, in place and green, light now sufficient for an ordinary photo- exploring spiral, three spirals are used, graph to be taken is sufficient for television arranged consecutively round one disc, each purposes. spiral being covered with a daylight filter. This step was demonstrated by Mr. J. The first spiral is covered with a green filter, L. Baird in London on June 11th before which allows only the green rays to pass representatives of the press, and subse- through. The second spiral is covered with quently before several eminent scientists, a red filter which passes only the red light. including Dr. J. A. Fleming, 1!'.H.S., The third spiral is covered with a blue world -famous as the inventor of the ther- filter which allows only the blue light to mionic valve, who described it as "a very pass through. (See diagram.) striking advance" and "a great step for- As the clise revolves, the face is scanned ward." (See also description of American first by the red spot of light, then by the experiments, page 258, September RADIO blue spot of light, and then by the green NEws- Editor.) Writing in a technical spot of light, and the cells react to these paper after his visit to the Baird Labora- lights, 'sending out first an image composed tories, Dr. Fleming referred to television of the red parts of the -picture, then an im- as "a quite genuine and veritable scientific age composed only of the blue parts of the invention" and concluded with the words: picture, then an image composed of the "the writer left the laboratory with the green parts of the picture. strong conviction that it was the birthplace At the receiving station a similar disc re- step with the disc at the transmit- Arrangement of the spirals on the Baird of new, interesting, and very important volves in multiple- colored television disc. inventions." ting station, and this disc has behind it, in neon tube, two sepa- place of the ordinary colors which TELEVISION IN COLOR for, as it is well known, all rate glow discharge lamps. red, blue and This demonstration was almost immedi- we see are made up from afterwards followed by a demonstra- SUPPLYING THE COLORS green; purple for example, is only a mix- ately mix- of even more striking character. The It was at the receiver that a problem im- ture of red and blue, yellow only a tion fashion, problem of color television has at least been mediately arose. It is obvious that the re- ture of green and blue. In similar up by com- solved, and it was demonstrated on July ceiving disc must give a red image, a blue any other color can be made bining three primaries, or two of them, in the requisite proportions. wimp r° ''"' irr di+r,naa. saMr bt re Thus it will be seen that it was essential aEistr.,eaud to have three primary colors, and the neon a ESOP r.ce, au red. r.. ,ws sws wr mwc ., arw ut rias tube contains only ...srrs. -+r.s.tr ss The problem was solved by using two nlR,i t+erA On% r1iM' rat ali/.10111 M2. WAS R" ' a.sx,r;

Sonie Advice to the Set Constructor who is Getting Beyond the Beginner Stage and Wishes to Experiment By Fred H. Canfield

N the first installment of this article, sizes of the various parts which he is to use. two very different functions in a radio re- which appeared in last month's issue When a power tube is employed the plate ceiver. A choke coil is connected in a cir- of RADIO NEWS, the principle of the current is often so heavy that it would clam - cuit where it is desired to arrest the flow of schematic diagram was explained and age the winding of the loud speaker and, a current of a given frequency and at the three important parts of a radio receiver therefore, a protective device should be same time allow direct current and current were analyzed, viz.: the antenna circuit, employed in the plate circuit of the last of a different frequency to pass. On the inter -stage R.F. coupling circuits and the tube. Two different types of units are other hand, a by -pass condenser is employed detector circuit. This concluding install- used for this purpose; the first is known to arrest The flow of direct current and ment of the article will analyze other im- a.s an output transformer and the second permit alternating current to pass. portant parts of a radio circuit, and it will as an output filter. The output transformer Both choke coils and by-pass condensers also show how it is possible to build a re- is a 1:1 -ratio audio transformer, connected are made in different sizes for use in ceiver entirely from the information con- as shown at E in Fig. 1. The output filter various parts of a circuit. For example, tained in a schematic diagram. consists of a 30 -henry A.F. choke coil and in a radio- frequency circuit, small R.F. Following the detector in a radio receiver a l -nif. A.F. by -pass condenser, connected choke coils having an inductance in the comes the audio- frequency amplifier and, as shown at F. order of 60 to 8.5 millihenries and low -ca- therefore, this is the next logical part of the CHOKES AND CONDENSERS pacity by -pass condensers of approximately circuit to consider. Often the A.F. ampli- In all modern radio circuits it will be .001- to .01 -mf. are used, whereas in power fier is the most expensive part of the set noticed that choke coils and by -pass con- and audio- frequency circuits the choke coil but, fortunately, it is one of the simplest to densers arc connected in various positions. will have an inductance from 1 henry up, understand. Usually there are no adjust- Frequently, these parts are not essential to and the by -pass condensers a capacity of able controls in this part of the set. The the operation of the receiver, and many ex- 0.5 -inf. or more. signal is passed from one tube to the next perimenters make the mistake of omitting The diagrams in Fig. 2 show several ways and amplified by theta, additional amplifi- them from the circuit. However, both by- in which choke coils and by-pass condensers cation being furnished by the step -up ratio pass condensers and choke coils are very may be used to advantage in a radio re- of the coupling device in the case of a important considerations, and when they ceiver. Diagram A shows how a choke coil transformer- coupled amplifier. The inter- are used intelligently greatly improve the (L) may be employed as an antenna coup- esting thing in all amplifiers is the coupling performance of a receiver. ling inductor where it is not desired to device, which allows the signal to pass from Choke coils and by -pass condensers are time the grid circuit of the first tube. In ene stage to the next, and which insulates used frequently together, but they perform this circuit the R.F. voltage drop across the the grid circuit of each tube from the plate circuit of the preceding tube. A large majority of receivers now have standard transformer-coupled amplifiers (see A in Fig. 1), and the others use either resistance -coupled, impedance coupled or double-impedance-coupled circuits (see dia - grams B, C and D, respectively). These circuits require practically no explanation. Iii the case of the transformer- coupled circuit, the primary winding of each transformer is connected in the plate circuit of a detector, or A.F. tithe, and the secondary winding in the grid circuit of the following tube. A 201A -type tube is generally used in the first stage and a power tube in the last stage. In the case of resistance, impedance, and double-impedance- coupled amplifiers three

. stages are usually required in order to obtain sufficient amplification; and 240 -type SI ( "Iii-mu" tubes) may be used in the first two stages and a power tube in the last 0+ stage. The resistance -coupled amplifier has an .01 -mf. condenser coupling the plate and r- grid of the tubes and resistors connected, in a the plate circuit of the first tube and in the r- grid circuit of the second tube, respectively. 0 'Chen 240 -type tubes are used, these two resistors each have a value of 250,000 ohms. The impedance- coupled circuit is the sanie as the resistance -coupled circuit, except that a plate impedance (choke coil) is substituted for the resistor in the plate circuit. 'This impedance is not critical in value and may be 30 henries or larger. The double - impedance circuit is also similar, except 1:.;.:;. These diagrams show four methods of wiring the rectifier circuit of a `B' that an impedance is used in both the plate socket -power unit. Diagram.A shows the circuit used with a full -ware gaseous - and grin circuits. Double -impedance units t7,pe rectifier; B is the circuit for use with a half-wave filament -type rectifier; C are manufactured for this purpose and the shows the wiring for a full-wave filament-type rectifier. and D shows how two builder does not have to worry about the half -wave filament -type rectifiers may be used in a full -ware circuit.

www.americanradiohistory.com 322 Radio News for October, 1928

AERIAL I

R,^A

LI 1f IJI C

0 AFC2

GROUND

O b O A- A+ C-RF B+DET. B+R.F. B+A.F. C-PWR.

Fig. 4. This schematic diagram of a modern six -tube tuned R.F. receiver provides sufficient information to enable a well- informed experimenter to build a receiver employing the circuit. Experience would supply suitable values for each of the parts used. choke coil produces a potential in the input ling through the batteries in R.F. circuits. and condensers perform the function in circuit of the tube (V) and permits the re- In this circuit a radio- frequency choke coil this circuit as in other parts of the set with ception of signals. Of course, the efficiency (L) is connected in series with the plate- the result that the A.C. component is re- of a circuit of this type is not as high as supply wire to prevent the R.F. energy tarded and bypassed until practically pure that of a tuned circuit, but it has the ad- from entering the battery or power circuits, D.C. is available at the output. The choke vantage of eliminating one tuning control. and two by -pass condensers (C) are em- coils (L.1 and L2) should have an induct - This circuit is used frequently in multi- ployed to provide a low -resistance return unce of at least 30 henries each and the filter stage, one- control tuned -R.F. receivers to the filament for the R.F. current. One condensers (Cl and C2 and C3) should have where it is not desired to use a separate by -pass condenser is connected between the a capacity of approximately 4-inf. each. condenser for tuning the antenna circuit. filament end of the grid inductor and the A voltage- divider circuit is also shown in filament, thus by- passing the current diagram E of Fig. 2. This consists of the USES OF CHOKES around the "C" battery, and the other by- three fixed resistors (R1, R2 and R3) con- Diagram B of Fig. 2 shows how an R.F. pass condenser is connected in the same nected in series across the output of the choke coil (L) and by -pass condenser (C) relative position in the plate circuit. Both filter. The resistors of the voltage divider are connected in the plate circuit of a de- by -pass condensers should have capacities cause drops in voltage and make it possible tector tube. The choke coil is connected in of 1 -tuf. In diagram D the same arrange- to obtain any desired potential for the series with the plate wire to the A.F. trans- ment is shown for use in audio and detector operation of the various tubes of the re- former (T) and prevents R.F. currents circuits. The only difference is that an ceiver. The exact resistance for each sec- from entering the audio amplifier, and the A.F. choke coil is used in place of the R.F. tion of the voltage divider cannot be stated by -pass condenser is connected between the choke coil. The A.F. choke coil which is without knowing the output voltage of the plate of the detector tube (V) and the fila- used for this purpose need not be very power unit and the number of tubes to be ment, to provide a low -impedance path for large, as any choke having inductance of operated in the receiver. However, an ar- the R.F. energy to return to the filament. In 3 henries or more will be found satisfactory. ticle entitled "Applying Ohm's Law to Radio Apparatus" which appeared on page this case, the by-pass condenser (C) should THE FILTER CIRCUIT have a comparatively low capacity so that 1348 of RADIO Nt:ws for June, 1928, gives the A.F. current will be forced to pass Diagram E of Fig. 2 shows another way complete details for designing various types through the primary winding of the trans- in which choke coils and condensers are of voltage dividers, and readers are re- former rather than go through the con- used, but in this circuit they are called filter ferred to this for further information on denser. A condenser having a capacity of choke coils and filter condensers. This dia- the subject. It should also be noted that .002 -mf. usually is used for this purpose. gram shows a filter circuit such as is used each section of the voltage divider is In diagram C of Fig. 2 a method is shown in a "B" power unit for eliminating the bypassed by a condenser to the "B -" wire. for utilizing by -pass condensers and R.F. .A.C. hum in the pulsating direct current These condensers (C4 and C5) are needed choke coils for preventing inter-stage coup- supplied by the rectifier tube. The choke to prevent coupling in the resistor circuit;

V5 C3, TO C= cx RIO LOU) sPEA0.E4 RFC3 V2 Tí. CIO V3

L3 ® CS

AFCI AFC2 GROUND

RFC1 RFC2 o o C RF B.RF 8.011 B+AF C-PWR. B+PWR.

Fig. 5. The above is a pictorial diagram of a receiver using the but it does not indicate the electrical circuit of the set. 1VithovS circuit shown schematically in Fig. 4. This diagram shows the a description of the apparatus pictured it would be difficult to build method of connecting wires to the parts specified for the receiver, from this diagram, unless the builder were able to use a schematic also.

www.americanradiohistory.com Radio News for October, 1928 323 they should have a capacity of 1 -mf. each. THE RECTIFIER The rectifier circuit of a plate ( "B ") socket -power unit is practically the only part of a radio installation which has not been considered in this article. In this circuit a step -up power transformer and a rectifier tube are used to raise the house current to the proper potential and to change it to direct current. There are four different circuits of this type which are commonly used and these are shown in Fig. 3. Here we have at A the method used in connecting a full -wave gaseous -type rectifier tube to a power transformer. T is the TI power transformer with a primary winding + (P) and a secondary winding (S). The secondary winding of the transformer is B+M center -tapped and the two outside termi- RI nals are connected to the cathode terminals B+90 The of the tube. center -tap of the second- R2 ary is the negative high -voltage wire and the anode of the tube is the positive high- B+45 voltage wire. The condensers Cl and C2 R3 are 0.1 -mf. buffer condensers, which pro- 8- tect the tube from line -voltage surges. Diagrams B, C and D show the method of connecting filament -type rectifier tubes to a power transformer. In each of these Fig. 2. By -pass condensers and choke coils may be used in numerous ways in a diagrams it will be noticed that the trans- radio receiver, and the above diagrams show a few of the places where they may be former is provided with two secondary used to advantage in a circuit. windings: Si, the high -voltage winding for the plate supply, and S2, a low-voltage former- coupled amplification, with "push - detector, with an R.F. by-pass condenser winding for heating the filament of the rec- pull" in the last stage. All tubes are oper- (C14) which should have a capacity of tifier tube. Diagram B shows the connec- ated with a grid bias, and A.F. and R.F. .002 -mf. C10 and 113 are the standard tions for a circuit using a two -element chokes as well as by-pass condensers are detector grid condenser and leak. (half -wave) rectifier tube of the 281 type, employed to prevent coupling. The audio circuit is also more or less diagram C gives the connections for a cir- A glance at the diagram will show that standard. The first stage is a standard cuit using a three -element (full -wave) recti- the R.F. and detector circuits are standard; transformer-coupled circuit and the second fier tube of the 280 type, and diagram D except that the R.F. tubes are biased and stage employs a push -pull transformer (T2) shows the connections for a full -wave recti- therefore extra by -pass condensers are and also a push -pull output transformer fier circuit using two two-element (half - needed. The coils LI, L2 and L3 are similar (i'3.) wave) rectifier tubes of the 281 type. R.F. transformers, and the condensers Cl, The by -pass condensers C4, C5, CG, C7, C2 and C3 are variable condensers of iden- C8, C9, C11, C12 and C13 are A.F. by-pass HOW TO WORK tical design. Oscillation is prevented by the condensers to prevent coupling through the In the preceding paragraphs the essential resistors R1 and R2 in the grid circuits batteries or power unit. These condensers parts of a radio circuit have been explained of the H.F. tubes. The condensers Cl and are not absolutely necessary, but they are and the reader should now be ready to C2 are linked for one-control operation, and refinements which greatly improve the gen- study a radio diagram. A two -stage tuned - the small adjustable condenser (Cx) is em- eral operation of the receiver. The con- R.F. receiver with all modern improvements ployed to compensate for any difference densers should have a capacity of 1 mf. each. is shown in Fig. 4. This is a six -tube set between the capacity of the two tuning con- The two R.F. choke coils (RFC]. and RFC2) comprising two stages of tuned R.F., a re- densers. Another refinement is an R.F. choke and the A.F. choke coils (AFC1 and AFC2) generative detector, and two stages of trans- coil (RFC3) in the plate circuit of the also help to prevent coupling through the batteries. The R.F. choke coils are of the standard 85- millihenry type, and the A.F. choke coils have an inductance of 3 henries. The resistors R4, R5, R6, R7, R8 and R9 are automatic filament ballasts regulating the supply of current to the vacuum tubes, and are of the proper size for the tubes used. R10 is a volume- control rheostat having a resistance of 75 ohms. By comparing the schematic diagram in Fig. 4 with the picture diagram in Fig. 5 it may be seen how much more informative the former type of diagram is to the builder of a receiver, after the principle has once been explained to him. The experienced constructor, with a schematic diagram in his hand, is ready to substitute freely any part to suit the material at hand, when trying a new hook-up. If his tuning condensers are larger or smaller than the size specified, he uses with them coils which he knows will cover the waveband. If he wishes to use a special tube in any position, he wires his set with the proper resistors and battery voltages; Fig. 1. popular A.F. amplifier systems are shown schematically above: A, For the in this regard. transformer -coupled; B, resistance- coupled; C, impedance- coupled, and D, dual - freely modifying circuit the published information impedance- coupled. Diagrams E and F show two types of output circuits used in He preserves with A.F. amplifiers. (Continued on page 373)

www.americanradiohistory.com 324 Radio News for October, 1928

The "Milk-Shaker Special" Receiver* By the Staff of RADIO NEWS Laboratories

GETTING started in any new field THE CIRCUIT of endeavor is a most difficult prob- A glance at the pictures, which accom- lem, fact that this and this observation applies to THE receiver is called pany this article, will show that the "Milk - radio -1 the "Milk- Shaker as much as to any other Special" does not Shaker Special" receiver is of very compact activity. After the beginner has built his indicate that it is a new -model radio design; but this does not indicate that first receiver he does not hesitate to add to cold -drink dispensary, or anything of efficiency has been sacrificed. The set com- it, as a rule, nor is he slow to provide him- that nature. On the contrary, it is an prises one stage of tuned radio- frequency self with a new set when the old one be- inexpensive, two -tube set using a screen - amplification followed by a tuned detector comes antiquated. However, more often grid R.F. amplifier, thus equalling the circuit; the R.F. stage employs one of the than not, the newcomer in radio who con- ordinary two stages of R.F.; but it is new 222-type, screen -grid tubes and the templates the purchase or construction of easy to construct, being designed espe- detector circuit is regenerative. This com- a receiver considers the matter seriously cially for the beginner. Its title is de- bination is very simple, but it is also very for several months before he is able to derived from the unusual character of the sensitive and selective. With a pair of cide to take the initial step. This state of shields which are used in the R.F. cir- headphones connected in the detector cir- mind may likened be to a man learning to cuits; they are simply converted bev- cuit of this set it is possible to receive just swim; he is afraid of the water until he be- erage shakers of the variety sold in 5- as many distant stations as with the average comes accustomed to it, and then he thor- and -l0 -cent stores. The use of these five -tube receiver, and the set will also oughly enjoys diving in head -first. common household items in the con- have the ability to separate powerful local The "Milk- Shaker Special" receiver, destruction of the set is one of the factors stations. in this article, has scribed been designed responsible for the low cost of the re- At this point it should be explained that especially to answer the requirement of ceiver. It may be used with any good this receiver is not intended to operate a the average radio beginner. was It built A.F. amplifier; the "Extension" ampli- loud speaker. It employs only two tubes in the RADIO NEWS Laboratories, and these fier (described in the June issue of and at least two extra (audio- frequency three aims were constantly in the mind of RADIO News -Free Blueprint No. 5S) amplifier) tubes would be required in order the engineer in charge of its development: with a 171A -type tube will be found to provide sufficient power to operate a First, the construction of the receiver especially well suited for this purpose. speaker. However, it requires but an in- must be as simple as possible. -EDITOR.) stant to connect any standard A.F. am- the cost of Second, building the set must plifier unit externally to this receiver and be reduced to a minimum. under these conditions the volume and qual- And, third, the set must be highly efficient ity of reproduction obtainable from the set and of modern design. description is being presented in "The Ra- will equal that of any other using a similar When the completed receiver was tested, dio Beginner" department, as it is con- amplifier. It should also be explained that, it was found that it satisfies the given considered an ideal set for the man just start- though this receiver was designed for very op- ditions satisfactorily. Therefore, its ing in radio. eration from batteries, it may be operated from a socket -power unit if it is so preferred. From the date presented in the above paragraphs, it may be seen that the "Milk- Shaker Special" is not a complete receiver, but merely the tuner unit. By following this plan, the designer was able to simplify the construction and reduce the cost to a very low figure. It should not, therefore be considered an undesirable feature. The tuner unit will do everything the average receiver will do, except provide volume for the operation of a loud speaker; while it may be added to at any time. It provides a modest start for the beginner and provides a future way for him to enlarge his radio installation at any time without discarding any of its parts.

SIMPLICITY OF DESIGN Proof tht the set is a beginner's receiver is found in the construction; it may be built by any individual of average intelligence, regardless of his mechanical skill or previous experience. Also, only tools of the simplest type are required. Less than S3 a dozen small holes in the front panel are needed; and these may be drilled either Fig. A. This rear view of the receiver shows the milk- shaker shields in place. SI with the usual hand drill or with a standard and S3 shield the antenna and R.F. coils, respectively, and S2 shields the screen- grid tube Vl. brace and machine drill. Practically all of the parts are mounted on a wooden base- RADIO NEWS Free Blueprint Article No. 64.

www.americanradiohistory.com Radio News fur October, 1928 325 board, and fastened in place with wood - Two by -pass condensers, paper-type, 1 -mf. L2; and the three R.F. choke coils, L3, LA screws. There is no need for great mechani- C3 and C4) ; and L5. Also, the shields, Si, 52 and S3, cal precision in assembling the set, for One grid condenser, mica -type, .00025 -mf. must be made from three beverage shakers slight deviations from the specifications will (C5) ; which may be readily purchased for a few not affect the efficiency of the receiver. In One mica fixed condenser, .001 -mf. (C6) ; cents each. All of these parts are easy wiring the set, flexible. insulated connection One antenna coupler, home -made (Ll) ; to make, and the builder is able to save wire is used; so that the builder does not One R.F. transformer, home -made (L2); considerable expense by employing his en- have to worry about short circuits if the 'l'hree R.F. choke coils, home -made (L3, LA ergy in this direction. wires are not separated properly. Of and 1.5) ; course, all connections should be soldered; One fixed resistor, 10-ohm (R1); MAKING THE COILS but this is really a very simple job if di- One filament rheostat, 30 -ohni (R2); rections are followed carefully. One grid leak, 2- megohui (114); Winding the antenna coupler, Li, and A second indication that a set is suitable One lìlament- ballast resistor, 5 -volt, 0.25 the R.F. transformer, L2, is a very simple coils very for a beginner is found in its adjustment ampere (113) ; task. Both are of similar con- and operation. Many receivers, after their One variable high resistor, 0- 2,000 -ohm struction and on forms of Yidentical size; each has two windings, which wound in construction has been completed, require (115) ; are numerous adjustments before they may be Three shields- beverage shakers, bought at the same direction with No. 28 D.S.C. wire. used and, oftentimes, these adjustments are "5 and 10" store (Si, S2 and S3) ; The coil forms are bakelite tubes, 1/ inches very delicate. In the case of the "Milk - One screen -grid tube, 222 -type (V1); in diameter and 3 inches in length. The Shaker Special," however, as soon as the One standard vacuum tube, 201A -type (V2) antenna coupler consists of a primary coil wiring has been completed and found to One battery switch, (SW) ; (p) of 20 turns of wire and a secondary be correct, the receiver is ready for opera- One telephone ,jack, single -circuit, dosed - coil (s) of 98 turns of wire, with a space tion. The only parts of the set which may type (J): of / inch between the windings. The R.F. be adjusted are the panel controls, and One grid -leak mounting, vertical type; transformer has a grid coil (g) of 98 turns even these are very easy to operate. The 'Iwo tube sockets, UX -type; and a tickler coil (t) of 40 turns, also with two large dials Cl and C2, on the front Two tuning dials, 3/ -inch; a space of / inch between the windings. panel, are the wavelength tuning controls, Nine binding posts; Further data on winding the coils will be 2. and these both have approximately the saine One terminal strip, 3/16 x 3/4 x 10-inch; found in the drawing, Fig. setting for any wavelength to which they One front panel, bakelite, 3/16 x 7 x 18- After winding the coils, L1 and L2, it are tuned: The knob R2, at the left of the inch; is wise to protect their windings with a coat of insulating varnish. Collodion, which may be purchased at any drug store, is R2 CI SW t2 R5 ideal for this purpose; as not only does it hold the windings in place, but it is water- 1 proof and prevents the absorption of moisture. A small brush of the type used for Fig. B. The two dials work be used, one on the front panel o the water -color may and "Milk- Shaker Specia " re- coat should be sufficient. ceiver arc the wavelength tuning controls. The Before the coil is completed it is neces- knob R2 at the left is sary to provide terminals for the windings. the volume control. and A accomplish this is to drill the knob RS at the right simple way to is a regeneration control. a bole at the end of each winding and four other holes at the base of the coil form 13,1,.,,111111,1,,,,,.,,1,,,,,,,,,,,,,,,,,,,,,,,,,,,1,,,,,.,,,,,, about ?/a -inch from the edge. When winding the coil three or four inches 'of wire should be left over at the ends of each winding, and panel is a rheostat, connected in series One baseboard, wooden, / x 8 x 17 -inch; this wire should be threaded through the with the filament of the screen -grid R.F. Connection wire, flexible, with push -back nearest hole in the tube and brought to tube, and serves as a volume control for insulation; the base of the form. Then, it should be the receiver. The knob R5 at the right Copper sheet (for base of shields). looped several times around the edge of of the panel controls a variable high re- By looking over the above list it may be the coil form and through one of the holes sistor which is the regeneration adjustment seen that live parts used in the receiver provided for the purpose. When you con- for the receiver. The small knob SW, in the must be home -constructed; these are the nect the coils in the receiver, the hook -up center, is the battery switch which turns the antenna coupler, 1.1; the R.F. transformer, wire may be soldered directly to the wire set on and off. In constructing the set, provision is also made for connecting it easily in any desired way. The phones may be plugged into the jack .1 in the lower right corner of the front panel or, if a separate amplifier is used, it may be connected to the binding posts marked "output" on the terminal strip at the rear of the baseboard. 'l'he circuit is so arranged that, when the phone plug is inserted in the jack, the external amplifier is disconnecter) automatically. To connect the set with the batteries binding posts on the terminal strip have been provided in place of the usual battery cable. This plan was considered advisable in the design of this receiver, as it tends to make the set more flexible. COMPONENTS NEEDED Before continuing further with the description of the receiver the parts required for its construction will be listed. The symbols printed in connection with the various pieces of apparatus correspond to the symbols used in the text and illustrations when referring to the parts. The list follows: Fig. C. The exact arrangement of all apparatus on the baseboard of this receiver Two variable condensers, .00035 -mf. (Cl is shown in the top view of the set; the parts are fastened on the wooden base with and C2); wood -screws, and all wiring is in plain view. Compare with Fig. 4.

www.americanradiohistory.com 326 Radio News for October, 1928

of the coil at the point where it is looped at the base of the coil form. The winding of the R.F. choke coils, I.3, S3 ó3l I.5, is even than the coils CAP oT! L4 and simpler SI TERMINAL S2 R5 just described but the job is more tedious; P2 wvvvvti .1 for there are several times as many turns 1I VI LI I \!\ of wire. Each R.F. choke coil is a single P V2 winding on a bobbin of the dimensions AER O 4qq given in Fig. 2. No. 36 D.S.C. wire is used P o/ (6) and the number of turns required on the I d Gsi '_Cl G i7 L5 coils is as follows: L3, 1,000; 1.4, 1,100, and GND - 12; L5, 900. No attempt should be made to 112 ' wind the wire in layers, because the choice RI J coil will have a higher efficiency if it is fl C3 C6 "jumble" wound. It should also be ex- R2 a C4 IPHONES the number of turns on the G plained that L3 4 R3 choke coils need not be exactly the number specified, nor is it necessary to use a bobbin of exactly the size shown; however, the specifications should be followed as closely as possible. SW THE SHIELDS O O o O A- the beverage shakers into ra- A+ 8+ OUTPUT Converting B- 45 V 135V. óéT dio shields is not at all difficult, and the only tools needed are a hammer and a heavy pair of scissors. The cover of the shaker is Fig. 1. Schematic diagram of "Milk-Shaker Special" Receiver.

R5 R2

TO STATOR PLATESi

OUTPUT A- A+ B+ B+ 8+ AER GND 8- DET 135V 45V Fig. 4. All connections.in the set are clearly shown in this pictorial wiring may be reduced greatly. The diagram shows all parts on wiring diagram- When making connections, each .tire should be the front panel and baseboard in their proper position, but slightly crossed out on the diagram with a colored pencil after it has been reduced in size in order to make the drawing more legible. The installed in the receiver and in this way the possibility of error in flexible lead from LI to T'1 passes through holes in S1 and S2.

www.americanradiohistory.com Radio News for October, 1928 327

mounted. Also, a hole y2-inch in diameter in the top of the shield S2 is required for I8' making contact to the control -grid terminal of the screen -grid tube; and a hole in the 316 4g 3116 3' side of the shield cover of Si is required for the wire which connects the coil Ll with the grid of V'2. When the construction of all the homemade parts has been completed the various 13/32 DRILL BASEBOARD pieces of 6 HOLES 216 apparatus may be mounted on i á 2' - the baseboard. First, the shield bases are 2' fastened in place as described. Si is lo- DRILL I 5/3p - 3HOLES cated at the extreme left of the baseboard I f and 1% inches from the rear edge. The shields S2 and S3 are located 1% inches from the rear edge of the baseboard, and 2. 2 '4-7 there is a distance of 1 inch between Si ¡ 8'8 8 8 ° i 8 8 .-gINDING and S2 and between S2 and S3. After the -e- POST STRIP- shield bases have been fastened in place, the }imo coil Li is mounted in the base of Si, the Fig. 3 tube socket for in the of ,'3/16 GRILL. II HOLES `1 base S2, and 16 Drilling layout for front the coil 1,2 in the base of S3. The two coils panel end terminal strip. are held in position by angle brackets, as shown in Fig. 2. used as a hase for the shield. First the position of these is best determined when cover is cut as indicated in the drawing, wiring the set, after the shields have been LAYOUT OF THE OTHER PARTS Fig. 2, and then it is hammered flat. Next, The next step in assembling the set is to a piece of sheet copper is cut to the inside mount the binding posts on the terminal diameter of the cover. To mount the strip and then fasten the terminal strip in shields in place on the baseboard, the base No. 64 the center of the baseboard on the rear is placed in the desired position, the copper A set of large blue- edge. The two by -pass condensers, C3 and disc is placed inside the base, and nails are prints and a list of the C4, are mounted between the shield bases driven through the copper to hold the en- parts used in the con- with wood screws in the position shown in tire shield base in place. The top of the struction of the "Al ilk- the pictorial diagram and pictures. The shield fits into the base and is held in Shaker Special" receiver rear edges of these condensers are on a line position by friction. shown here will be sent postpaid to with the center of the three shield bases. After the shields have been made, it will any applicant. See that your name The two choke coils, L3 and 1.4, are mounted he necessary to drill a number of holes for and address are written or printed in the rear of condensers C3 and C4, re- the wiring to pass through. Four holes are legibly. Ask for blueprint No. 64. spectively. needed in the base of each shield, but the (Continued on page 386)

N2.0 -32 x BRASS BAKELITE '18' L'G ROUND MOUNTING TUBING \ HEAD MACH BRACKET - II/2" DIA SCREW

BRASS ALL 3 CHOKES MOUNTING ___- WOUND WITH BRACKET N2 36 D.S.C. SECONDARY WIRE 98 TURNS OF N2 28 D.S.0 WIRE

Cf) PRIMARY li u) 20 TURNS OF N2. 28 O.S.0 WIRE FLANGES AND CORE TO BE MADE OF BAKELITE OR HARD RUBBER DETAIL OF CHOKES 3 L3 - 1000 TURNS DETAIL OF COIL L4 1100 " LI L5- 900

BAKELITE TUBING BASEBOARD SMALL NAILS ; I1/2" DIA.

GRID COIL 98 TURNS OF III NMI N9. 28 D.S.C.WIRE

12 SLOTS. TICKLER CUTOER I EQUALLY -40 TURNS - OF SPACED Ná.28 I D.S.C. WIRE SHEET COPPER ALUMINUM SECTIONS BENT IN OR TO CENTER MOUNTING DISC. BRACKET DIMENSIONS GIVEN ABOVE ARE THOSE OF DETAIL OF COIL L2 AN ALUMINUM BEVERAGE SHAKER WHICH CAN BE PURCHASED

Fig. 2. The above drawing gives complete directions for construct- tion; and a pair of scissors may be used to convert the aluminum ing the homemade parts used in the "3111k- Shaker Special" receiver. beverage shakers into shields. The locations of the holes in these The two coils and the R.F. choke coils are of very simple construe- should be determined by the constructor.

www.americanradiohistory.com 328 Radio News for October, 1928 The "Combine" Receiver -a $100 Prize Winner

A Double Set Which Makes Both Standard and Short - Wave Broadcasting Available on the Loud Speaker at Will

By W. H. Scheppele

FROM the viewpoint of circuit de- tubes, but the expense of building a second sign the "Combine" receiver is highly THE "Combine" receiver described audio amplifier is also avoided. efficient, but not in the least unusual; here has the following features is, the electrical system is more SIMULTANEOUS that which will at RECEPTION BETTER conventional and freak combinations once attract the enterpris- or less ing radio constructor: Many interesting experiments are pos- have not been employed. However, the set (1) Wavelength range from 15 to sible with the "Combine" receiver, as it is possesses one outstanding feature which is 550 meters. possible to use the short -wave and long - both practical and novel may be oper- -it (2) Quick and easy to change from wave sets at the same time. In this connec- ated at maximum efficiency on all wave- long to short waves -operates on both tion the writer has tried tuning in the pro- 15 and 550 meters with lengths between only at once, if desired. gram of WGY with the long -wave set and, one wavelength tuning control. (3) Broadcast circuit employs three at the same time, having the short -wave set There is nothing mysterious regarding the tuned tuned to 2XAF, one of the short -wave sta- wavelength range stages of R.F. with non- regenera- great of this receiver, for, tive detector. tions which transmit WGY's regular pro- in reality, it consists of two sets long- -one (4) Short -wave circuit employs tickler gram. With the receiver adjusted in this wave and one short-wave -built into one regeneration and tube -base plug -in coils. manner, the signals may be received with cabinet. It is, nevertheless, interesting to (5) Set is very compact and excellent volume and without added distor- note the compactness and simplicity of the employs only six tubes altogether. tion or interference of any kind:. Also, it design. The front panel measures only 7 by (6) Single- control tuning on both long may be noted, oftentimes a station will fade 18 inches, and all the parts are mounted on and short waves. on the long waves and not on the short a baseboard 10 inches deep. These dimen- waves; but with the double receiving system sions are less than those of the average ,just described interruption to reception re- broadcast receiver using an equal number sulting from this cause is reduced greatly. of tubes, and the number of controls on the on another rheostat and throwing a switch In addition to WGY and 2XAF, there are does not exceed which front panel that of most connects the aerial with the proper many other stations with which the same sets. section of the set. stunt may be tried. The National Broad- Most combination sets are very compli- In addition to compactness, other advan- casting Company programs are transmitted cated to operate, and have an elaborate tages arc obtained by combining two sets in by the short -wave transmitter of Kl)K.1, switching system for changing from short the manner followed in the "Combine" re- and these may be received and combined long waves. In this set, however, to both ceiver, and chief among these is economy. with any one of a dozen stations through- change -over have the tuning and the been If the two sets were housed in separate out the country which are transmitting the made as simple as possible. A large double cabinets, five tubes would be required for sanie program. WRNY, WLW and WABC is only wavelength broadcast drum dial the tuning the receiver and three tubes for are also among those sending the same pro- one is used for tuning the control; section the short-wave set, making a total of eight gram on both short and long waves, on regu- long -wave set and the other for the short- tubes. However, since the two sets are lar schedules. wave set. Thus, it will be seen, the receiver mounted in one cabinet, it is entirely prac- is single- control whether it is operated on tical to employ the same audio amplifier LAYOUT OF SETS the long or the short wavelengths. The for the two receivers, and in this way the The accompanying pictures clearly show change from long to short waves is accom- same efficiency is obtained with six tubes. the appearance of the receiver. Fig. plished by turning off one rheostat, turning Not only does this result in a saving A is in a view of the front panel of the set. In the center 4 V6 4 L3 V ç ,vs, (E-2) wi CI of the panel is the drum -dial control; the left side (CI, C2 and C3) is used for tuning when broadcast stations are being received, and the right section (C4) is employed for short -wave reception. The knob (111) at the extreme left of the panel is the rheostat used to turn on the broadcast set, and this serves also as a volume control. The knob, SW, to the right of this rheostat, controls the switch turning on the receiver. On the right side of the set, the knob R7 is used to adjust a universal -range variable resistor, which is an oscillation control for the short -wave section of the set; and the knob ß3 operates the rheostat turning on and controlling the volume of the short - wave set. Apparatus on the baseboard of the set is shown in Fig. B. The four tuning condensers are mounted directly to the sub -base panel, near the front, with their shafts run- movstakIt». ning parallel to the front edge. The condensers, Cl, C2 and C3, on the front edge, P2 T2 L2 are a triple unit, employed for tuning the circuits of the broadcast set. Each section Fig. C of this condenser has a maximum This rear capacity view of the "Combine" receiver shows the set ready for use, with the of .00035 -mf., and three compensators are tubes and coil in their respective sockets. Cl, C2 and C3 is the triple condenser provided for adjusting the various sections used for tuning the broadcast circuit of the set, and C4 the tuning condenser for to exactly the same capacity at any given the short -wave section. L4 is the plug-in short -wave coil. setting. The condenser, C4, at the right of * RADIO NEWS Free Blueprint Article No. 65. (See page 383 for rules of prise entries.)

www.americanradiohistory.com Radio News for October, 1928 329

the drum dial, is for tuning the short-wave ing in this part of the circuit. To control ticed that the grid leak, R5, is connected, circuit; it has a maximum capacity of the set a filament switch, SW, is connected not in shunt with the grid condenser, C5, in .00014 -mf. in the negative "A" battery wire and when the usual manner, but between the grid of Directly behind the variable condensers turned on this lights the tubes in the A.F. the tube and the \-I-" battery- wire. This are the coils and tube sockets of the R.F. amplifier. Ilowever, in order to turn on plan is followed because the detector tube circuits. This arrangement of the parts has the tubes in the R.F. circuits it is neces- works best with a positive bias, and the been found most satisfactory, as it makes sary to turn the rheostat R1 for the broad- filament cidc of the R.F. transformer, L3, possible very direct wiring and high effi- cast set or the rheostat R3 for the short- leads to the " -A" wire because the triple ciency. The small coils Ll, L2 and L:3, and wave detector tube. The battery switch, condenser is connected in this way. It will the three tube sockets \'1, V2 and V3, at the SW, may be used for turning oft' all tubes also be noticed that a filament- ballast re- left of the sub -base, are in the R.F. cir- of the receiver. sistor, 112, is connected in series with the cuit of the broadcast set. The tube socket The broadcast receiver comprises a more tubes in addition to the rheostat, RI. Con- \'4, at the right of the panel, is the detector or less standard two -stage R.F. amplifier, necting the resistor in this manner pre- tube of the short -wave set, and the five - followed by a non -regenerative detector. vent; overloading the tubes by turning the prong, UY -type tube socket, L4, is a re- LI, the antenna coupler, and L2 and L3, the rheostat too far. ceptacle for the plug -in coils of the short- R.F. transformers, are home -made coils,

wave circuit; I.5 is a R.F. choke coil which having the saule - number of turns on their SHORT-WAVE COILS is common to the plate circuits of the de- secondary windings, so that they may be -wave circuit the most inter- tector tubes of the two sets, and is em- tuned simultaneously by the triple con- In the short is the plug-in coil, LA. The ployed to prevent the R.F. energy from denser, Cl, C2 and C3. 1.2 and L3 have esting feature of receiver is from entering the A.F. amplifier. The units Pl the same number of turns on the primary wavelength range this 15 200 meters and it is impractical to and P2 are oscillation- suppressing devices, windings, but L1 has fewer in order to im- to cover this with a single coil. Therefore, connected in the plate circuits of the R.F. prove the selectivity of the circuit. Oscil- the is to tubes of the broadcast receiver. 'l'he ap- lation in the circuit is prevented by "Phasa- the simplest solution to problem use coils of the plug -in type, which may be paratus in the A.F. amplifier is mounted trols," Pl and l'2, which are shown en- changed easily when it is desired to operate at the rear of the sub -base panel. Ti and closed within dotted lines. on .waveband. The coils in this set T2 are the two A.F. transformers, and \ -5 In connecting the output circuit of the another have three windings-primary, secondary .,,,,1,,.1,11..11,.,11111,,,,,,,,,,,,,,,,,,,,,,11,..,1....11ll.11lll.l..,. and tickler -and are wound on Bakelite forms fitted with prongs similar to those on Fig. A a vacuum tube. As one wire from tine primary- winding is connected to one end of The arrangement of controls on the front pane!. of the secondary winding, only five prongs are the "Combine" receiver is required, even though the coil has three shown in this front view of the sct. The left sec - windings; and these prongs are arranged twn of the drum dial, C 1 -3, in the same manner as those of the base of tunes the broadcast circuits and the right section. C4, a t'Y -type tube. Therefore, a standard the short -wave roil. 7'hese i'T -type tube socket is used as a receptacle are the only sarcle,: nth tuning Controls. for tine coils. llll.11..,l 11,,,,1,,,.,,.l. 1,.1,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, The circuit in the short -wave section of the receiver is regenerative and of tine tickler feed -back type. Tuning is accomplished by a variable condenser, C4, con- and \'G the sockets for the two tubes; VG broadcast set to the audio amplifier, it will nected in shunt with the secondary wind- is for the power tube. LG is the output be noticed, the R.F. choke coil 1,5 is con- ings; and regeneration is controlled by a choke coil, and Cl the output condenser. nected in series with the wire from the variable resistor, Rî, in shunt with the Fig. C shows the appearance of the re- plate of the detector tube, V:3, and the first tickler winding '1'. The circuit has the usual ceiver when seen from the rear. In this A.F. transformer, 'l'1. This choke coil keeps grid condenser, CG, with a grid leak RG in picture the tubes are shown in the sockets the R.F. energy out of the amplifier, and shunt, in the grid circuit; and tine filament - and also one of the set of short -wave coils the fixed condenser, C8, serves to by-pass ballast resistor RI, is connected in series is in its socket. An interesting feature of this current to the filament. It will be no- with the rheostat R3 in order to prevent the receiver, which is illustrated in this picture, as well as in Fig. 13, is that very little of the wiring of the set is visible above the sub -base panel. In constructing the set, holes are drilled adjacent to the binding posts on the various parts, and the wiring is passed through these and completed under the base. In this way the appearance of the set is improved greatly. Another thing which will be noticed is that the usual binding -post strip has been omitted and in its stead a battery cable is employed for making connection to the batteries. Ilow- ever, four binding posts are provided for connecting the wires from the loud speaker, aerial and ground.

THE TWO CIRCUITS The complete schematic wiring diagram of the receiver is given in Fig. 1. Here it will be noticed that the receiver is divided two distinct parts; the upper half of s-, into the diagram is the short -wave circuit followed by the audio amplifier, and the lower half gives the wiring in the broadcast receiving circuit. The aerial connects directly with a single -pole double -throw switch, S \t'1, making it possible to connect it easily with either of the two circuits. Fig. B The output circuits of the broadcast and The exact location of all pmts on the base panel is shown in this top view of the knob controls short -wave sets are connected with the in- receiver. The only parts mounted on the front panel are the four put circuit of the audio amplifier at all ante the drum dial; the renyaininy pieces of apparatus, including the variable are made. times, thus avoiding the necessity of switch- condensers, are fastened to the base panel, under which most connections

www.americanradiohistory.com Radio \Tcws for October, 1928

AERIAL R7 C6 V4-7 V5 12 1 6Ò00Pa QG P 0 °o R4

R3 A+ YELLOW R8 o A- B- C+ BLACK o B+ DET. BLUE o B+ 90 WHITE B+ 180 RED o C 4Z ORANGE a C POWER GREEN

Fig. 1 The schematic diagram clearly shows the electrical circuit of in the pictorial diagrams, below and on the opposite page. The the "Combine" set. This corresponds exactly with the wiring long and short -wave tuning units the same A.F. amplifier.

BLUE 8¢ DET. YELLOW C -42 C -POWER GREEN

C 13 47 66 11

SCREWS FOR CONDENSER FRAM

28 26

15 ç30 19 ig 31

Fig. 6 Pictorial diagram of the wiring under the base panel. This drawings may be marked off with a colored pencil. These diagram, together with Fig. 5, opposite, should be used by the diagrams show all of the parts in their correct relation to beginner as a guide when wiring the "Combine" receiver and, each other and indicate how the wires are connected to the as each connection is completed, the corresponding line in these various terminals of the apparatus and battery cable.

www.americanradiohistory.com Radio News for October, 1928 331

overloading the filament of the detector tube One variable condenser, .00014 -mf. (C4) ; Two grid leaks, 2- megohm (R5 and R6); V4. The output circuit is connected to the One mica grid condenser, fixed, .00025-mf. One variable resistor, universal range (R7); audio amplifier in the saule manner as the C5); One filament -ballast unit, 5 -volt, 0.5- ampere broadcast circuit; that is with the R.F. One mica grid condenser, fixed, .0001 -mf. (RS); choke coil L5 in series with the plate wire, with clips (C6); One battery switch (SW); and the by -pass condenser C8 connected be- One by -pass condenser, paper type, 1 -mf. One aerial switch, single -pole, double - tween the plate and the filament. (C7); throw (SW1); The audio amplifier of the receiver is a One mica fixed condenser, .001 -tuf. (C8) ; Five vacuum tubes, 201A -type (VI, V2, V3, standard transformer- coupled circuit having One antenna coupler, home -made (L1); V4 and V5) ; two stages. Ti and T2 are standard 2:1- Two R.F. transformers, home -made (L2 and One vacuum tube, 171A -type (V6); ratio A.F. transformers, and Di and C7 L3) ; Two Phasatrols (PI and P2) ; are the output choke and condenser, re- One set of short -wave coils, tube -base plug - One battery cable, 7 -wire type; spectively. Both tubes of theaniplifier are in type for five -prong UY -type socket, One front panel, bakelite, 18 x 7 x 3/16 - biased properly, and a power tube may be four coils in set (L4) ; inch; used in the last stage if desired. R8 is a One R.F. choke coil, 60- millihenry (L5) ; One sub -base panel, bakelite, 17 x 10 x 3/16- filament- ballast resistor to regulate the cur- One output choke (30- henry) L6; inch; rent for the two tubes. Two A.F. transformers, 2 -to -1 ratio (T1 Four binding posts, push -type; and T2); One drum dial, double type; LIST OF PARTS One rheostat, 10 -ohm (R1); One dial light, five -volt (DL) ; The following is a complete list of the One filament -ballast unit, 5 -volt, 0.75 -am- Six tube sockets, UX type; apparatus required for the construction of pere (R2) ; One tube socket, UY type (for L4); the "Combine" receiver: One rheostat, 20 -ohm (R3) ; One grid -leak mounting for R5. One triple condenser with compensators, One filament -ballast unit, 5 -volt, 25- ampere Three pieces of angle brass, 1 x 7/16-inch .00035 -ref. per section (C1, C2 and C3) ; (R4); (to support front panel);

R7 R1

C4 .I

o 19 'C '1'YII'II;4 . IPPPamm-mlici...i. 12 ,,ii aaar.iii,giwr- - 1m tim y= Jm iir

B C SW1

12 R6 C6 / 9 A lo O G cs V4

C7 B+ G

Fig. 5 Pictorial diagram of wiring above the base panel. This shows the various parts by passing through holes drilled in the base panel. exact method followed in the original model of the "Combine" Each hole through which a wire passes is numbered and the num- receiver. As much es possible of the wiring is concealed under the bers correspond in both diagrams. Each piece of apparatus is marked base, and most of the wires make contact with the terminals of the with the same symbol in the text, list of parts and all illustrations.

www.americanradiohistory.com 332 Radio News for October, 1928

Three brass brackets, / x 1/ -inch (to sup- 18 port R.F. coils) ; r Three brass legs, 716 -inch (base -panel sup- 9- ports) ; r Connecting wire, screws, solder, etc. I r! i WINDING THE COILS III In constructing the "Combine" receiver L f -14- the first problem which confronts the con- rn" - r- structor is securing the necessary coils. The _ L_ coils for the short -wave circuits may he M- 2=----f°--I;---- purchased already wound; or they may be 71-'s I homemade, if desired. However, the coils I I d.-+; °---z#-- --- 1- 7-J-4:1-1. I Q , for the broadcast circuits must be con- _^ structed by the set builder; as manufac- ,r _----- tured coils answering the exact specifica- Lf- r O,\ 4,., 4 4 tions are not available. Fig. 3 Data on the construction of the three coils in the for the broadcast set is given in Fig. 2. This drawing shows the exact locations and sizes of all required holes front Directions the large hole required The drawing shows the mechanical construc- panel of the "Combine" receiver. for cutting tion, and the chart gives data on the num- for the drum. dial are given in the text. ber of turns of wire required. The coils are throughout. The primary coil is located ntents for drilling holes in this panel are wound on bakelite or other composition forms near the base of the form, the secondary is not given here, as the builder might wish to 11/ inches in diameter and 1% inches long, wound at the top and the tickler is placed make substitutions in the parts; but a com- and each coil has two windings. The antenna in the center. All are wound in the same plete sub -base drilling layout will be sup- coupler Ll has a primary of 15 turns and a direction, and a distance of ?}- to r/, -inch plied with the free set of blueprints for this winding of 80 turns. Both windings are is left between each pair of windings. After set. The latter shows the exact location of wound in the same direction with No. 32 the coils have been completed, they may be every hole required for mounting the ap- D.S.C. wire. A splice of / -inch is left be- identified easily by painting each coil form paratus specified in the list of parts; it may tween the windings. a different color. The chart gives the num- be used as a template, as it is printed full If it is decided to make the coils for the ber of turns required on each winding and size. Also, the size of each hole is specified short -wave circuit at home, their construc- also the wavelength range of each coil. on the blueprint. tion will be found slightly more difficult. - The next step in the construction of the When the drilling of the sub -base panel is The drawing in Fig. 2 illustrates the exact receiver is drilling the front and sub -base complete, all of the parts, including the mechanical construction of the factory -made panels. In preparing the front panel the variable condensers, may be mounted in coils, and the experimenter who is gifted with most difficult thing is to cut the hole for place. When screwing parts to the sub- a little mechanical ingenuity should be able the drum dial, but it may be clone accurately base, it is important to make sure that they to build duplicates from this data. Coil with the template supplied with the dial. are fastened in the proper positions, and forms fitted with a five -prong tube base are Small holes are drilled close together around is true particularly of the tube sockets available on the market; but if these are the edge of the large hole, then the large and transformers. However, a careful ex- not at hand the base of a UY-type tube, hole is knocked out with a hammer. The amination of the baseboard layout (Fig. 4) with a bakelite tube fitted over it, may be edges of the large hole may be macle smooth will show that all identifying features of used for the purpose. The coil form should with a small file. All of the other small each piece of apparatus have been indi- be I % inches in diameter and 21/, in holes required in the panel may be drilled °ated, so that the builder should have no length. The coil form of the manufactured with standard drills; the exact locations, as difficulty in this particular. coils is ribbed to reduce the area of con- well as the sizes of these holes, are indi- The method of mounting one or two of tact between the wire and the dielectric, cated in the drilling layout (Fig. 3). the parts may seem somewhat puzzling. For but this is not an essential feature, although example, the three coils of the broadcast set, AND WIRING it does increase slightly the efficiency of the MOUNTING Ll, L2 and L3, are supported 12 inches coil. Preparing the baseboard for mounting above the sub -base panel with brass angle For tuning between 15 and 200 meters a the parts is next in order. Fig. 4 indicates brackets, and the grid leak 115 (for the set of four coils is required. Each coil has the exact location of all parts on the sub- broadcast set) is mounted under the coil three windings- primary, secondary and base panel and this arrangement of parts L3, as indicated by the clotted lines in Fig. 4. tickler -and No. 24 D.S.C. wire is used should be followed, if possible. Measure- The three mica fixed condensers C5, C6 and C8 are not mounted to the sub -base with screws, but held in place the wiring. a by SECONDARY--.1 The wiring may be started as soon as the DETAIL mounting of parts has been completed. OF L4 Flexible insulated wire should be used and, ^'" DETAIL OF COILS wherever possible, it should be run under Lb 1.2 AND L3 the sub -base panel. Therefore, a number I of extra holes must be drilled in the sub - panel for the wiring; the positions of these holes are shown in the set of blueprints as well as in the two pictorial wiring diagrams, WAVE LENGTH SECOND PRIMARY TICKLER SIZE Figs. 5 and 6. In wiring the the ART SYMBOL set builder COIL TURNS TURNS WIRE MIN MAX TURNS may follow either the schematic diagram,

2 3# 5 L4 Fig. 1, or the pictorial wiring diagrams, of A 17 30 D. S.C. which Fig. 5 shows the wiring above the 24 FIVE- PRONG 52 2 L4 B 30 7 9 D. S. C. baseboard and Fig. 6 shows the wiring under UYTYPE BASE 24 the base. Wherever the wiring passes 3 18 10 L4 C 48 105 D.S.C. through the sub -base in the diagrams it is 24 D 93 203 44 17 L4 indicated by the wire terminating at a cir- 4 D. S.C. cle, and the number placed next to this cir- 6 2 E 200 550 15 80 NONE LI D. S. cle is employed to designate the continua- 32 tion of the wire in the other diagram. It F & G 200 550 22 80 NONE L2 613 D.S C. is unnecessary to give complete data for SAME SIZE WIRE USED ON ALL WINDINGS connecting each wire, as all details may be found in the diagrams. Fig. 2 The front and sub -base panels are not fastened together until after the wiring has The and table in the above illustration give complete directions for constructing drawings completed. The drilling of the front various coils required in the "Combine" receiver. The plug -in coils may be made by been the been arranged so that the drum using a UP -type tube base with a bakelite tube fitted over it for each coil form. panel has

www.americanradiohistory.com Radio News for October, 1928 333 dial will meet the shafts of the variable con- space of a fraction of an inch between the densers when the sub -base panel is sup- arm B and terminal C. With the switch ported 716 -inch above the bottom of the No. 65 arranged in this manner, a small capacity front panel, and this provides ample space A set of large blue- is placed in series with the aerial, the effec- under the sub -base for the wiring. The two prints and a list of the tive length of which is reduced greatly. panels are held in this position with brass parts used in the con- Opening the aerial switch may cause too angle brackets, and the rear of the sub -base struction of the "Com- much reduction in signal strength on the panel is supported by three small brass feet bine" receiver shown here short -wave set and if this is the case, a located at each side and in the middle of will be sent postpaid to any applicant. small fixed condenser should be connected the base on the rear edge. See that your name and address are in series with the aerial wire. This con- As soon as the set lias been wired and as- written legibly. Ask for Blueprint denser should have a capacity of approxi- sembled it should be checked carefully against No. 65. mately .0001 -mf., and may be short -circuited the diagrams and tested. In testing the set, when receiving on broadcast wavelengths. connect the "A" battery to the "A" leads The ground for the receiver may be the of the battery cable and insert a tube in standard water -pipe connection. each of the six tube sockets. First turn on to the battery, the set must not be con- It has been explained that the receiver is the battery switch, SW, and make sure that nected to the batteries before locating and equipped with a two -stage audio amplifier the two amplifier tubes 1'5 and V6 light. correcting the cause of the trouble. and, therefore, is capable of providing suf- Next, with the switch turned on, advance the ficient ACCESSORIES AND OPERATION signal strength for the operation of rheostat Rl and see that it controls the a loud speaker in connection with either filaments of the three tubes V1, V2 and V3 Operating the receiver requires very little the short -wave or long -wave circuits. How- in the R.F. circuits of the broadcast set, instruction, but there are several points ever, on short wavelengths, the signals from and then advance the rheostat 1t3 and make which should be remembered. In the first some distant stations are weak, and it is sure that it controls the filament of V4. place, inasmuch as the set is a combination often advisable to use headphones for After this has been clone, all tubes of the long -wave and short -wave tuner it is ad- tuning-in. When it is desired to use phones visable set are lighted and, to complete the test of to use "A" and "B" batteries for its the builder may do so by connecting the the filament circuit, turn off the battery operation. "A" and "B" socket -power units cords to the two primary terminals, "B +" switch and make sure that it turns off all of could be used when operating on broadcast and "P," of the second A.F. transformer T2, the tube filaments. wavelengths, but on short waves consider- but the phones should never be connected To test the "B "circuits before connecting able inteference results from their use. For to the speaker binding posts; as accidentally the plate batteries, the "A -" binding post the "B" circuits three 45 -volt heavy-duty tuning in a strong signal might cause injury should be connected with the "A -" wire dry batteries will give best results, and a to the ear of the listener as well as the of the cable. Now, with the battery switch six -volt storage battery should be used for phones. and rheostats of the set turned on and the the "A" supply. tubes in their sockets, touch each wire of The selection of an aerial for this receiver After the receiver has been connected the long-wave the cable to the " +" terminal of the "A" is another important consideration. With properly, set may be adjusted for best efficiency. tune in a battery. The tubes of the set will light the average aerial of 100 to 150 feet excel- First, station operating on wavelength when the "A +" wire touches the binding lent results will be secured from the broad- a of approximately post of the battery but, if the set is cor- cast circuit; but such an aerial may prove 300 meters; i.e., in the middle of the broadcast waveband, rectly wired, the tubes will not light when to be too long for the short -wave set. it and set the dial at the point If where the "C" or "B" wires of the cable are is found that the aerial is too large when maximum signal strength is obtained. touched to the battery. If a tube should operating on short waves first try opening Now adjust the three compensator knobs light when a "B" or "C" wire is touched the aerial switch (SW1) so that there is a (Continued on page 382)

III 111.11111=1M1 III II I nmllI

111111111

ifl11lll l

Fig. 4 This drawing shows the location of all parts on the base constructor should remember that they must be in the correct panel of the "Combine" set. The apparatus is shown full positions, as well as in the proper locations. This applies size, in proportion to the base. When mounting the parts the particularly to the tube sockets and transformers.

www.americanradiohistory.com 334 Radio News for October, 1928 A Completely Shielded Short -Wave Receiver

Features of Set Are a Stage of Tuned R. F. Amplification and Wavelength Range of 10 -230 Meters; Attractive Brass Cabinet Acts as Effective Shield

By Herndon Green

TWO features of interest in the day equipment it is not practical to at- length, the greater is the loss in efficiency. short -wave receiver described in this tempt to use single -dial control on a set article The regeneration control found best are the use of a stage of designed to operate much below 50 meters, adapted for use in radio -frequency this set is a variable amplification, with due to the extremely accurate tuning re- resistor in the plate circuit of the detector a screen -grid tube, and the plug -in coils, quired to bring in short -wave stations. It tube. This (R5) with the by -pass which permit the reception con- of extremely is, of course, possible to use an untuned denser C6, shown in the diagram, gives short wavelengths. The set was originally stage of radio - frequency amplification; how- smooth and even control of the regenera- designed by Charles Atwater, owner of ever, this results in broad tuning and lack tion which makes it possible amateur station 2JN, Montclair, to receive N. J., for of signal strength, and the lower the wave- both code and short -wave phone stations the purpose of conducting tests on the ten - meter band, which was recently assigned for amateur use by the Department of Com- merce. A duplicate of Mr. Atwater's set con- FREE structed in the RADIO NEWS laboratory was found to give excellent results. A few slight changes have been made in this model Blueprints to simplify the construction as much as possible for the honte set -builder. How- ever, these changes have not altered the op- No. 66 eration of the set in any way. A c o m - In order to get the greatest possible am- plete set of plification from the screen -grid tube on the blueprints short wavelengths, the designer found it showing the desirable to completely shield the entire construction of this fine set. This is an important receiver will be sent free point, and the to any reader builder writing in should follow very closely the for it. A list of the ac- method of construction and assembly out- tual parts used in the lined in this article. original model is included. A glance at the front of the set shows Write your name and that there are three adjustments or tuning address clearly. Send no controls. The large dial at the left is for money. Be sure to ask the variable condenser used to tune the for Blueprints No. 66. stage of screen -grid R.F. amplification; the one at the right tunes the grid circuit of the detector tube. The small center knob Right: A view of the detector -A.F. is the regeneration section with the right end of the control. With present- brass cabinet removed.

without the annoying squeals and howls which are usually found in regenerative sets. CABINET ENTIRELY OF BRASS The cabinet is constructed entirely of sheet brass one-sixteenth of an inch thick and measures 15 inches long, 8 inches wide and 8 inches high. The constructional details are shown in Fig. 1. Brass angle strips one -half inch wide are used to hold the corners of the cabinet together and a hinged cover is provided to allow easy access to the inside. The cabinet is divided into two compartments by a brass partition. The left -hand section of the cabinet contains the stage of screen:grid amplification, which is completely shielded from the detector and audio - frequency amplifier. In the screen -grid compartment are mounted the socket for the screen -grid tube and another for the plug -in coil, 1.1, together with the variable condenser Cl, radio- frequency choke coil L3, by -pass condensers, and the fixed filament resistor for the screen -grid tube. The compartment at the right -hand side of the partition contains the detector tube, Looking into the top of the set. The R.F. stage occupies the left compartment, the the mounting for the plug -in coil L2, the detector and A.F. stages the right. Note how the two sections are separated by a detector tuning condenser C9, the regenera- brass partition; they are completely shielded from each other. tion control resistor, grid condenser and

www.americanradiohistory.com Radio News for October, 1928 335

FIG.1

1"BRASS HINGE RIVETTEDTO LID AND SIDE )4r

I C.

. O ° *". \.,, - f-- FDR R; ,WIRING. i"\ ¡i n I I

N I\, 0 ANGLE 1 I .e1 FOR ; PARTITIO

CUT 3 PIECES OF SHEET('/;) BRASS -8 "X8 ",AND FOUR USE FOUR BINDING 8"X15:' ASSEMBLE BY POSTS, CENTERED 3/4" DRILLING AND TAPPING FROM EACH EDGE,FOR FOR SCREWS. l'ANGLE LEGS. JOIN WITH STRIP.

The details of the brass cabinet. The best thing to do is to have the a few rents and will sore you much time and trouble. A brass beets cut to the proper size by a tinsmith or machinist, who can do cabinet is something unusual and not only has decided electrical the work in a few minutes with a cutting press. This will cost only advantages, but presents a rather spectacular appearance. grid leak, audio- frequency- transformer and Two radio -frequency choke coils, (L3 and One variable resistor, 0 to 200,000 ohms, audio- amplifier tube, together with the L4); (R5); radio- frequency choke coils and by -pass One tapped resistance unit for filament of One audio- frequency transformer, (T1); condensers. 222 -type tube, 25 ohms, (H1); Three UX -type tube sockets; Another interesting feature of this re- Two fixed filament resistors for use with Two UX -type sockets, for the plug -in ceiver is that by means of the five sets of 199 tubes on six volts, (R2 and 113) ; coils; plug -in coils (ten coils in all) a wavelength One grid leak, 1- megohm, (RI); Two vernier dials; range of 10 to 230 meters may be covered. If desired, an additional set of coils may be constructed to cover the broadcast band FIG3 from 230 to 500 meters. The tuning coils, two. to a set for each wavelength range, are used in positions L1 and L2 shown in Fig. 2A and 213, each consists of two windings. The windings of Ll are used as the antenna coil and the grid tuning coil of the screen -grid tube; V3 while the windings of 1.2 serve as the grid coil and the tickler coil for the detector. 'l'he number of turns in the grid coil of L1 corresponds to the number of turns in the grid coil of L2, but the tickler coil on L2 has a little more than twice the number of turns used on the antenna coil on Ll.

THE PARTS REQUIRED A complete list of the apparatus required for the construction of the receiver is as follows: Two variable condensers, double -spaced, ? .000125 -mf. (Cl and C9) ; L- Seven by -pass condensers, 0.5 -mf. (C2, C3, C6, CS, C10, C11 and C12) ; AERIAL GROUND A -B- A+ B +4SV. One fixed mica condenser, .001 -mf. (CT); One fixed mica condenser, .00025 -mf. The complete schematic diagram of the receiver. The dptted lines indicate the (C5); brass cabinet, to which the tuning condensers Cl and 09 are "grounded." I71 is One fixed mica condenser, .006 -mf. (C4); the screen -grid tube.

www.americanradiohistory.com 336 Radio News for October, 1928

The start of the winding, Pl, is connected to the prong in the tube base which was FIG. 2 originally connected to the grid of the tube. DETAILS FOR The end of this winding is connected to the LI AND L2 corresponding filament prong, F -. The ABOVE 20 METERS upper end of Si is connected to the plate prong, while the other end of this winding `. fi, I 1 goes to the remaining filament prong, F+. ' All eight coils are wound in exactly the P same manner and all are connected alike, '' i 1' 1 p : the only difference between them being in 11' i \`\., the number of turns of wire on them. r I i , .s I , t The two coils comprising set No. 2, have i I , I i Si a wavelength range of 60 to 130 meters. iP `; !) tT FI Due to the fewer number of turns required, if S a slightly larger size of wire may be used ; -1i .`Iw(fr, r- ` i to advantage for these windings. The coils I 1 1 1 in the set shown here were wound with No. II if 1 , ,,., I I 1 1 26 D.C.C. 1 1 The coil Pl on Ll consists of 28 turns, with six turns in Si. On L2, G` a ; . I l1 1 1 1 I FU i' I© 28 turns are used for P2 with 19 turns in F the tickler coil. I I I LIL No. 3 is wound with No. 26 D.C.C. wire DETAIL OF i F+i r and No. 4 with No. 20 D.C.C. wire. Pl on LI AND L2 FIBRE TUBE FITTED F- G P Ll in set No. 3 consists of 14 turns, with 4 turns in Si, while the P2 on L2 consists of BELOW 20 OVER OLD TUBE BASE 14 turns with nine turns for S2. This set METERS AND FASTENED. covers the wave band from approximately 32 to 65 meters. The upper winding Pl on METERS COIL P1 51 COIL P2 52 SIZEOFWIRE L1 in coil set No. 4 consists of 7 turns with 10 -2.0 L 1 4 4 I-2 4 3 16. 4 turns in the antenna coil; while the two 20 -35 L1 7 4 L 2. 7 6 2.0. windings on L2 consist of 7 and 6 turns, respectively. 32-G5 L1 L2 14 9 2.(0. 'These two coils are used for 14 4 stations operating in the band between 20 60-130 L1 28 6 L.2 28 19 2G. and 35 meters. 120-7-3o L1 55 10 L2 55 ZS 30. THE 10- METER COILS The coils 1.1 and I2 used in set No. 5 7' co plug -in roils are used for each wavelength range of the set: LI for the antenna are designed to cover the band between 10 and screen -grid input circuit, and L2 for the detector circuit. Their dimensions and 20 meters. They are self- supporting, are given above. being wound with No. 16 bare copper wire. Details of the construction of coil Ll are One grid -leak mounting; over the tube bases with small machine shown at Fig. 2A. It is first wound on a One vacuum tube, 222 type, (V1); screws and nuts. The winding is started form one inch in diameter, with the turns Two vacuum tubes, 199 type, (V2 and about one- eighth of an inch from the top spaced about one -sixteenth of an inch apart. used and a tap is taken V3) ; of the tube. Each of the eight coils has Seven turns are One battery switch, SW; two separate windings. from the mid -point on the winding and con- Four binding posts; The two largest coils have a wavelength nected to the two filament prongs on the One four -wire battery cable; range of 120 to 230 meters. In order to get tube base. The start of the winding is con- Two tip- jacks; the desired number of turns on these coils it nected to the G prong, while the last turn Five sets of plug-in coils, home- macle, will be necessary to use No. 30 D.C.C. wire. connects with P. Coil I.2 consists of two (for Ll and L2); The winding is started at the top of the separate windings, space -wound and self - Twenty-five inches of bakelite tubing, form and 55 turns are used for coils Pl supporting, following the same method of used for L1. Coil PI has four 14/6 inches in diameter, for the home- on L1 and P2 on L2, for the first set of construction made coils Ll and 1.2; coils. A space of one- eighth of an inch turns, while S2 has 3 turns. Ten UX -type tube bases; is then left and ten turns are wound on 1.1 Two radio -frequency choke coils are required, L3 1.4, in the diagram, Four brass panels, 15 x 8 x 1 /1G inches, for the coil Si. This serves as the antenna and shown (for top and bottom and front and back coil. The second coil, S2 on I2, is wound Fig. 3. The ones used in the receiver shown of cabinet); in the same manner but in this case the in the illustration were factory -made. How- home -made ones will give just as good Three brass panels 8 x 8 x 1 /1G inches, winding consists of 28 turns, and is used ever, (for ends of cabinet and partition); for the tickler coil. Nine feet of % inch brass angle strip, to hold edges of cabinet together. All of the parts mentioned in this list are standard, with the exception of the plug-in coils. Factory-made forms may be used for these, if desired, but the winding should be done at home.

CONSTRUCTING THE COILS The ten short -wave coils are constructed as shown in Fig. 2. The base for each of the coils may be obtained from a burned - out or detective UX -type tube. All of the glass should be removed from the base by heating the sealing compound, while the wires may he removed from the four prongs by means of a hot soldering iron. The tubing on which the wire itself is wound should leave an inside diameter of one and three - eighths inches, which will just fit over the outside of the tube hase. The tubing should This picture cannot (lo justice to the fine appearance which the brass cabinet pre- be cut up into 3 -inch lengths and fastened sents. The constructor will he proud to Show this receiver to his friends.

www.americanradiohistory.com Radio News for October, 1928 337

FIG.4 A+ B +45 V. IIIIIN IIIIII' AERIAL GROUND B +90V B -,A- This drawing shows every, wire in the set. In order to beep them be as short as possible; particularly the grid leads. The wire clear, the draughtsman has separated the leads considerably and nurrkerl X connects to the brass cop oar the screen -grid tube. Study made them turn and cross irregularly. Actually, the wires should this carefully before you start soldering and you will have no trouble. results. If home -made, they should consist necessary to follow this layout exactly, it socket used for the coil mounting Ll. The of approximately 50 spaced turns of No. 30 is important that all leads be kept as short ground binding post is connected directly wire on a form one inch in diameter. and direct as possible if good results are to to the brass cabinet. The mid -tap of the he on WIRING THE SET obtained the very short wavelengths, filament resistor R1 is also grounded to for which this receiving set was designed. the cabinet, as shown in Fig. 1. A second l'he layout of the parts and wiring of Machine screws are used to hold the parts insulating strip mounted at the opposite end the set is shown in Fig. 4. 'l'he only parts in position. of the cabinet holds two pin -jacks for the mounted on the panel are the two variable A four-wire battery cable in place of the phone tips. condensers, Cl and CO, the regeneration con- usual array of binding posts is used to con- Fixed filament resistors are used to re- trol resistor, 115, and the battery switch, nect the batteries with the set. Two bind- duce the number of adjustments on the set SW. Their arrangement and the position ings are mounted on an insulating strip at to a minimum. The model illustrates) was of the mounting holes is shown in Fig. 5A. the back (drilled as in Fig. 51i), for aerial designed to operate direct from the usual The arrangement of the parts within the and ground connections. The aerial binding six -volt storage battery. The resistor con- cabinet is shown in Fig. 4. While it is not post is connected to post P the tube (Continued on (raye 854)

www.americanradiohistory.com 338 Radio News for October, 1928 The Search for the Perfect Amplifier Encouraging Results Obtained by British Experimenter in the Development of Unusual Circuits with Inputs on the Filaments and Outputs on the Grids By Sydney P. O'Rourke

the January issue of RADIO NEWS, Lastly, choke coupling in its modern I under the heading, "The Search for form, usually called double-impedance coup- the Perfect Detector," the writer ling, is rapidly gaining in popularity. It described a novel method of rectifica- may give a frequency curve equal to any tion differing very considerably from the resistance -capacity coupling, with less of usual circuits; the radio -frequency input the latter's bugbear of voltage drop across was applied to the filament, the A.F. out- the plate resistor. put being taken from the grid and the whole For further information on these various tube was regulated by the plate, suitably forms of coupling the interested reader is biased. referred to other articles which have ap- In the present article the writer will give peared in RADIO NEWS from time to time, practical details of a new amplifier circuit and particularly to that on page 1140 of which the above system has made possible. the April, 1928 number. Suffice it to say Firstly, it will be necessary to reiterate that, in nine cases out of ten, it is the any sin - briefly the advantages and utility (or other- coupling itself which introduces wise) of the various conventional forms of controllable distortion, slight though it may audio- frequency inter -tube coupling, ex- be. amine where each one fails, and finally en- HOW ELIMINATE DISTORTION? of the The author's filament -input detector circuit, dc- deavor to define the requirements Chat. therefore, will constitute our ideal scribed in his preceding article. ideal amplifier. amplifier, it salt is at all possible with TYPES OF COUPLING. input grid; which would of course render that tube completely inoperative, except First and foremost in popularity among 11)10 fans can spend an inter- simple under special conditions of operation. all A.F. coupling devices ranks the esting evening experimenting much -used -" Having seen that, at present, direct coup- and efficient transformer. This with the novel audio -amplifier circuit much ling is the only cure for coupling distortion, and abused component has received described in this article. The hook- attention from manufacturers and now there let us go back for a few moments to the up is totally unlike any of the stand - filament input circuit of Fig. 2. are many first -class articles on the market arrangements; the tubes being ard this capable, if properly used, of giving prac- actually connected backwards and Considering the greater efficiency of 100 with grid -input tically perfect reproduction from about coupled directly to each other. circuit compared standard to cycles with a useful amplification detectors, the writer has recently been fol- 5,000 RADIO NEWS would like to hear from 30 to 40 per stage. lowing a very interesting line of experiment of about readers who try this circuit or any 'l'he success of this type of coupling in endeavoring to employ this "input to siamilar hook -ups it might suggest. depends almost entrely upon the quality the filament" principle to work a tube as of the transformer, a cheap instrument bean audio -frequency amplifier. ing practically useless for quality reproduc- That this should be possible is quite evi- tion. existing apparatus? It should be able to dent if one examines the "straight" portion Resistance- capacity coupling next claims amplify reasonably well and equally every of a curve obtained from a Fig. 2 circuit. our attention. cycle from 25 to 10,000; these figures cover A moment's consideration would suggest The popularity of this method has in- all the fundamental notes and harmonics chokes to isolate the filament, as in the decreased by leaps and bounds during the audible to the average ear. tector circuit; these would have to be A.F. past several years, due to the introduction Hence, until some new form of coupling chokes, however, and would obviously be of efficient metallized resistance units and is discovered, we oust rule out all the out of the question for carrying the "A" special "high-mu" tubes. This type of coup- usual circuits and take our detector out- battery current to and from the filament. ling is highly favored for true -purity am- put direct to the input of the first A.F. plification; a straight -line amplification tube. THE FIRST EXPERIMENT curve from about 50 to 5,000 cycles and This cannot be accomplished easily in an over -all voltage amplification of 20 to conventional circuits, since the positive These, then, were definitely excluded from 30 per stage are obtainable if values are "B" potential would be applied not only to the start and the circuit of Fig. 3 devel- properly chosen. the output plate, but also to the following oped as it "possibility."

AUDIO (TO LOUD SPEAKER OR NEXT STAGE) CONDENSER INPUT TRANSFORMER y INPUT CONDENSER r INPUT OUTPUT

SEC.

VI V2 Vi Vi V2

RESISTORS CHOKE COILS FIG. IA FIG. IB FIG. IC

Each of the three well- known methods of A.F. coupling, in order device which favors certain audio frequencies at time expense of ¿ó isolate the grid from the preceding plate voltage, introduces a others. The problem of remedying this is a grave one.

www.americanradiohistory.com Radio News for October, 1928 339

Transformer coupling was selected to THE CONCLUSION it will give any fan who cares to hook it up start with. Notice that the end of the an agreeable surprise. secondary opposite to that connected to Fortunately, this is not so 1 » any means. Finally, a few words upon the operation the filament as input is connected, not to The theoretical diagram of the final circuit and working details of the circuit. Cor- the "A" battery, but to "B -" only. If is shown in Fig. 4. I will say nothing fur - rect values and voltages must lie adhered to "B -" were connected to the "A" battery, ther of what the circuit will do except to throughout for best results, although no the impracticability of the circuit would state that, quite unusual though it appears, adjustment is super -critical in any way. Let us run briefly through the details of Fig. 4. Each of the two parallel coils Ll and 1.2 should he slightly larger than a single coil in the usual circuits. Thus, if at present, to coyer a certain band of wavelengths, you are using a single coil of say 50 to 60 turns, then in this circuit you should use two coils of 70 to 80 turns each, not coupled, to cover the same wavelength band; L3 may consist of a coil of 45 to 75 turns coupled to L2. Regeneration is controlled simply by the potentiometer P wired across the "A" battery. If hì is adjusted correctly with respect to L2, the feed -hack action will be found delightfully smooth and easy. Now we cone to the amplifier tube. Leaving the plate disconnected for the nuo- mcnt from the "B" battery, turn the rheostat full "on "; signals should be fairly good now if everything is all right. Now connect the plate to about 10 volts positive on the "B" battery; then lower the filament rheostat until a point is reached when the volume of signals will increase enormously. Lowering the rheostat any further will result in horrible distortion but, at the correct point as above, volume and quality seem perfect. Finally, for maximum results, the "B" voltage should be increased or decreased in sympathy with the rheostat until the tube is taking its correct filament voltage and current. The voltage is not critical and may vary according to the tube and the A.F. choke This is the author's first application of the filament- input idea to an audio ampli- separating the "A" and "B" batteries; it fier. It inclucles, however, the transformer with tchich he i, enfle «voriny to do this choke were omitted, the input and out- «x«y, though good rent li.s were obtained. (Continued on page 356) at once be apparent; since the transformer secondary would then he directly shorted. Fortunately however, the circuit of Fig. 3 functions very well indeed; far better than had been even remotely expected. We are no nearer yet, however, to our conception Of the perfect amplifier; since our new circuit still retains a coupling medium, in the shape, in this instance, of the A.F. transformer. Though a good transformer may introduce so little distortion that it would remain unnoticeable to even a critical ear, yet it seems a case of "'tis folly to be wise;" for we may not rest content until real direct coupling is achieved. Now it is the peculiarity of a filament - input detector circuit that output impulses are present, not only in the grid circuit, hut also in the plate circuit. This fact may easily he verified by inserting a pair of headphones in the plate circuit, when it will be found that signals are but a little weaker than those obtainable in the grid output circuit. That the signals are slightly weaker may easily be explained by the additional resistance lowering the efficiency of the. rectification tuend; and curves may be drawn to prove this. Hence we are provided with a second output electrode which has no high positive "B" potential. It must, however, have a small biasing potential With respect to the filament of the tube of which it forms This is the circuit which the author has arrived at, and which he suggests as a start- part; and here it would seem that we are ing point for other experimenters who are not afraid to try the unconventional. in a "blind alley" once again. Only approximate data are given.

www.americanradiohistory.com 340 Radio Net's for October, 1928

An Amusing "Talking Doll" holes, twist them together inside the tube, and solder then. When made in this man- For the Children RADIOA News has received frofrom read - R ers so many letters and ballots ner, the splice will be hardly noticeable. AN amusing "talking doll" can be made requesting more "Wrinkles" that it Figs. 3 and 4 present two views of a sim- for the children by concealing a small has been decided to re- establish the ple device for holding the wire taut while telephone receiver or loudspeaker unit in department. A year's subscription to winding a coil. Run a rod through the reel the body of an old doll. RADIO NEWS will be given in compen- on which the wire is wound and support this The body fabric in the back of the doll sation for each accepted item. If the on two Xs formed by driving four nails in a is slit open just enough to admit the phone author of the wrinkle is already a board. Empty thread spools are then fast- unit. Enough excelsior or other body filling subscriber, his subscription will be ex- ened with wood- screws in staggered posi- is removed to allow the unit to fit snugly tended one year or he may accept a tions on the board, as shown in Fig. 3. Now inside. The cord is pushed through the one year's subscription to Science and run the wire past the spools as illustrated. back of the doll and the slit for the unit Invention or Amazing Stories, both Different degrees of tension may be ob- and cord is then sewed up again. published by the Experimenter Pub- A loud -speaker unit of the adjustable lishing Co.

u panel equipped with luminous dials presents a strikingly novel appearance and at the saine time provides a cleans of tuning the set in the Clark. A good gracie of radium luminous com- X-CUT OFF THE OVERLAPPING SURPLUS pound should be procured and applied to FIG.1 the dials and markings on the panel of the set with a wooden or glass stylus. It should be forced into all graduations on the dials and other controls; with special care to wipe off all surplus compoutuy so that the markings will present a neat, clean -cut appearance in the light as well as in the Clark. It should be remembered that there are X -WIRES TWISTED &SOLDERED INSIDE TUBE. two classes of luminous compounds; one FIG 2 grade containing no radium salts is effective only for short periods after which it has to be renewed, while the other does contain radium salts and will retain its brightness for years. The latter is the grade that should he used. -Contributed by Dorothy lDietz.

If the cord running to the speaker unit is concealed and the doll placed ou a chai,-. the eiicct on the children is very amusing. Some Useful Hints On Winding FIG.4 type may be used, but in this case it should Fig. 1: Fitting a primary inside a secondary. Your Own Coils Fig. 2: Making a Joint that won't show. Figs. be properly adjusted before it is placed 3 and 4: Keeping wire taut while winding. in the doll. A phone plug is placed at the NO doubt, many home set builders have end of the speaker cord and the plug is at some time had difficulty in procur- pushed into the loud-speaker jack of the ing a primary tube form of the proper di- Wiled by placing the opposing spools at receiving set. ameter for use inside a secondary tube. Fig. l different distances from each other. This "talking doll" will afford amusement illustrates a simple method of overcoming In winding coils with spaced windings, for the children, as it can be made to talk this problem. A short piece of tubing of when a thread is used to space the turns, a or sing at will by merely tuning in the de- the same diameter as that of the secondary similar tension may be placed on the thread. sired station on the receiver. The speaker tube is cut; and the edges are lapped until However, as there is no insulation to mar unit can also be placed inside of a toy dog, it is of the right diameter to slip inside the on the thread, as there is on the wire, staples cat or other toy animal instead of a doll. - secondary. ' /'hen cut off the overlapping may be used instead of spools.- Arthur L. Contributed by H. R. IVallin. portion, which will run in the neighborhood Iíaser. of three- quarters of an inch. The edges are held together until the primary wire is wound in place, and then the wire will hold the tube firmly to the correct diameter. Luminous Dials Make Tuning Protecting the Work Table There are times when, in order to be with a Window Shade In the Dark Easier economical, it is necessary to make a splice in the wire while winding a coil. The usual MY radio work table is in the corner of RADIO listeners who use their receiving splice always leaves an unsightly lump. To the kitchen, because of lack of space sets during the early evening or late avoid this, drill two small holes at the point elsewhere, so my tools are too convenient at night, and who like to listen to the pro- where the splice is to be made, as in Fig. 2. for other members of the family. Besides, I grams in a darkened roost, will find that Min the ends of the wire through these have frequently been annoyed by finding

www.americanradiohistory.com Radio News for October, 1928 341

A Cheap and Handy "Trouble difin :ra i= - -- Shooter" for the Experimenter AHANDY trouble -shooter that will operate either on the house lighting circuit or on batteries is a useful addition to :unv radio work shop. A tester of this kind for use in tracing broken wires, short circuits, etc., can easily be made at home at tE very reasonable cost. The mounting board should be 5 inches BEND THE wide, S inches long and at least one -half NECESSARY PU?E SACK ,THEN DRvE inch thick. Seven binding posts are re- THEM OUT WITH A quired, and should be mounted as shown in SMALL SCREW-DRIVER the accompanying diagram. The bump socket should be wired in series with posts shown A window shade fixed in the posi ion No. 2 and No. 5. Use a 110 -volt lamp of A good low- capacity condenser can be made by not only protects the table from dust but dis- driving out every other plate of a large -sise courages the other members of the family from not over 25 watts rating in this socket. instrument. playing with your tools. Next, make up two five -foot portable cords and solder two 5 -inch pieces of No. 8 cop- ting down the capacity value of these con- chat my table was a catch -all for every kind per wire to one end of them. Wooden densers to meet the requirements for a of household article. To remedy this situa- handles may be slipped over the soldered small-size condenser. If none. of these large tion I fastened an old window shade to the splices for convenience in handling, and the condensers is on hand, they can usually ire wall above my work bench, and when I mm obtained for a small sum. By purchasing through working I pull down the shade these large condensers and removing some and attach it to a hook on the front of the of the plates or double- spacing them for the table. Across the front of the shade I proper values, a good low- capacity con- have printed in big letters "KEEP OFF." denser can he obtained at small cost. The result is that the family has taken In some condensers the extra plates may the hint. Now I can pull the shade over be removed by bending them back so that the table and know that when I let it up they can he driven out with a small screw again my tools and the things on the table driver, as shown in the illustration. In other will be just as I left them.-Contributed by types, the plates can be removed by using lfalcohn. D. Jones, Jr. a pair of long -nose pliers and bending the plates until they break off at the supports. The rough edges may be smoothed off with a small file. After removing part of the plates in the condenser, it is usually necessary to re- Making Your Own Distilled adjust the lock -nuts on the end plates so Battery that the rotor plates pass in the center of Water For the the stator plates. is sometimes difficult to obtain distilled If desired, the condenser can also be triple ITwater with which to refill storage "A" spaced by removing two plates at a time and "B" batteries. At such times the fol- instead of one. In this case the capacity lowing plan may be used to produce the is decreased considerably. Such condensers of water required to re- cyan be used to advantage in amateur trans- small quantity 7. h i s simple tracing broken fill the batteries of any receiving set. tester I'M/ Save or .chart - cir- mitting sets. -Contributed by Clyde A. cuits in a radio vessel, a kettle, and t h e experi- The A large thin -walled menter much set or power (b) n. a large dinner (or soup) plate comprise the time and trou- - cupply unit. parts required. The cooling vessel should ble when he is have a very thin wall, preferably of aluminum, and should he filled with cold water A Handy Connector Plug For (ice water if possible) and suspended close to the spout of the kettle, the dinner plate the Dynamic Speaker being placed directly beneath the cooler. THE new electrodynamic speakers re- The kettle should be filled with water quire four wires for connections. The and this brought up to the boiling point; ends of the wire filed clown to a sharp point. six -volt type seems to be the favorite then the jet of steam from the spout should These cords are then connected to binding and as I am engaged in radio service be adjusted to strike the outer wall of the posts No. ti and 7. A cord and attachment work I am frequently required to wire the cooling vessel. As the steam strikes the plug should next he made up of sufficient receiving set so that the speaker can be vessel it will he condensed and the distilled length to feed the tester from the light (Continued on page 358) water will drip off into the plate. Despite socket. These feeders connect to posts No. 2 its crudeness the device will be found to tintl 3. When using battery current attach produce plenty of distilled water for re- the feeders to No. 1 and 3 and connect a filling the batteries. -Contributed by C. A. pair of headphones to posts No. 4 and 5. Oldroyd The battery and headphones will he SET found best for testing high -resistance coils, SWITCH audio transformers and similar units in - the set; while 110 volts and the 25 -watt lamp may be used for tracing wiring, short - SOCKET OUTPUT by circuits, etc.-Contributed S. Saunders. A + I TUBE BASE SPEAKER BOTTOM BATTERY VIEW r F Low- Capacity Condenser Made FIELD'CURRENT From Large One SPEAKER CORD G THE radio experimenter frequently has PIN need of a low- capacity variable condenser. As there are often any number of large -size condensers laying around the ra- This diagram .chows how an old tube hase may This simple "condenser" arrangement will sup- be converted into a convenient connector plug ply pure distilled water at little cost. dio work shop, a method was found of cut- for a dynamic speaker.

www.americanradiohistory.com ,4' Radio News for October, 19'8

WHAT AN APPETITE! THIS PEAKS EVERYTHING GOOD MANUAL CONTROL, WOT? Testimonial letter in More useful advice, this Advertisement in the 1nu

.,mni,",,,,,,,, 11111.1111,11111.11,111111,1.11,,,,411,,,.,1111,111111,,., 1 11t,,,1,,,,1.,l,lll,,,,,,,,,,,,I ,,,,.

HORSES, HORSES, HORSES! A SELF -CLEANING SET ON THE PLATE SERVE IT New use for colts re- Al/eti - Rogers' catalog MY, NOW NICE! in the the New York lists "plug iu short wave Tempting offer vealed by I ` Springfield (Mass.) News Sun of July 15: "It is INDUSTORS" for use l. (Y. t' of July 17: "For sale, preferable to make this with .00014 -mf, tuning , motorcycle and r a d i o adjustment with the aid condensers. Many a house Y CHOP at 333 Orange of an A.C. COLTMETER wife would appreciate a Street." As a house- connected across the set of these coils, because keeper f am always look- heater terminals of the they would save her some ing for something new in tube. \ \'ith their place work every morning. Or the eating line. This radio in radio established, its perhaps they [lust off the chop sounds appetizing: trend will undoubtedly be static and make the re- should I fry it on the toward better accommoda- ception nice and clean. "grid?" tions for our barnyard -Peter Smith. -Mrs. S. E. Lofgres. friends. -Charles Christman. NOT WITH PLUG -IN COILS! DEARIE! Under the headline "Ra- IN HOT WEATHER, YES OH, dio Amateurs Hear Dis- wrinkle I'eriuntrd advertisement tress Call From Ship," Practical pub. teS in June QST: "For use -. the Crawfordsville (Ind.) lished b the Cincinnati in amateur transmitters says ama- Enquirer of July 22: "A Review "the us' and medium POW - teurs received the mes- satisfactory yet inexpens i)I:RED commercial in sages on wavelengths vary- ive low -range voltmeter stailations, the regular ing from 800 TO 1,000 may be made with a low - of conden- and ' line Cardwell MILES." Looks as if the reading milliammeter sers has no peer." What old days of the stovepipe a variable RESIDENCE." with television coming, the coils were with us be incon- tubing It would rather P.'L broadcast stations will be We hope the venient to carry such a again. though, hiring cosmeticians to see wavelengths didn't vary meter around , that the make -tip of the too much imagine a poor wouldn't it? studios is OK before the Bucher. operator climbing up a 1,000 -mile inductor and ad- -R. cameras start working. -Lcon B. Stroik. justing its turns! -J. C. Markin.

OF IT AN HONEST MAN AT LAST! NOT ALL HOT STUFF! Explanation of these Startling headline in the wise-cracking lectures that eri; U5E Grand Rapids Press of Classified advertisement we get an occasional ear- ANNOOtCY E TION ! I in the McKeesport (Pa.) June 29: ' He Resides in ro RIsE as Did ful of. in the New York T Netvs of July 21: `For a TUBE, Just Herald Tribune of July sale, TEN TUBE Radiant 1)iogenes." To unscram- 22: "The Quantum theory fire reliable gas range. ble this piece of history, the " is that energy is white kitchen cabinet." we might say that radiated in DISCREET What a boon this woull Greek cynic lived in a particles." Let's tune old ' he to the young bride tub and used an oil lan- Quantum out and see if who follows the radio tern in his search, but ¡hit days we can catch Paul White- cooking lessons every that was before the man on the air. ` morning!-Mike Plutko. of radio off -John Kanalauskas. -S. H. Woods.

www.americanradiohistory.com Radio News for October, 1928 343

JAPANESE PROGRAMS TELEVISION ON 62.5 METERS Editor, RADIO NEws: Editor, RADIO NEws: 2XAL'S The regular broadcasting schedule of station Schedule 1-DU will be interested to know that station JOAK, Japan, on short waves, each month, is as WLEX ALL programs of the RADIO NEWS follows: has been granted a temporary three- months license to broadcast experimental station WRNY are transmitted also Date 15 16 17 18 19 20 21 22 television simultaneously through station 2XAL signals on a wavelength of 62.5 meters to Wavelength (meters) 30 60 35 70 30 60 35 70 and on 30.91 meters (9,700 kilocycles). This make use of a frequency hand 200 kilocycles I hear this station and others often. JO. \R is wide. will apply also to the television broad- This is going to permit this station a large lati- casts, the schedule of which will be defi- quite easily received on the Pacific Coast during tude the fall, winter in experimental work and we are expecting nitely given later. and spring months, when atmos- some excellent results pheric conditions are I from these tests. The signals Outside a radius of about 200 miles, this clear. find, after several of this station have has been heard by years of specializing in long distance, that been received by amateurs in station very clearly the most and around this vicinity with short -wave listeners in most states and in favorable atmospheric condition is when the stars very good success. Canada. Regular reports are received also are shining Just at present the station is handicapped by a the, brightest, it being practically impos- weak power from Europe, the northern part of South sible to bear extreme distance transmitter, but work is being done America, Hawaii, Australia, India and during a haze or to increase the power. South Africa. heavy cloudiness. or particularly a fog, the occa- Station sional exception being immediately before. WM.., using a forty -five hole disc, is welcome and verify reports of during or soon be We shall after a rain, when fair reception is possible. to on the air in Chicago. Their wave- reception from all quarters. The hours length, the last I heard, was to be 195 meters. of operation are as follows: The above information is correct and the station schedule authentic. Fairly successful reception of pictures has been from 7 to 9 a.m., Eastern Daylight Time, or L. J. WRIGHT, possible this station by airplane. 1100 to 1300 G. M. T., every day. 3068 Calador Street, Los Angeles, Calif. D. F. REPLOGLE. 11 a.m. to 1 p.m., E. D. T., or 1500 to 1700 Raytheon Manufacturing Co., G. M. T., daily except Sunday, when Cambridge, Mass. the program ends 30 minutes earlier. 2 to 7 p.m., E. D. T., or 1800 to 2300 G. M. T., Mondays, Wednesdays and Fridays. On Sundays, 1:30 to 6:30 p.m., EUROPEAN TRANSMISSIONS E. D. T., or 1730 to 2230 G. M. T. Editor, RADIO NF_WS: After 7 p.m., E. D. T., or 2300 G. M. T., Just a few short -wave notes from an English on Tuesdays until midnight (0400 G. M. short -wave enthusiast which may be of some use T., Wednesday); on Wednesdays till 9 to you. p.m. (0100 G. M. T., Thursday) ; on Fri- The Eiffel Tower, Paris, is days until 11 p.m. (0300 G. M. T., Satur- conducting various day); on Saturdays until 10 p.m. (0200 short-wave tests on about 32 meters. Call FL. G. M. T., Sunday). No fixed schedule. Very strong signal here. Your On September 30th next, New York local correspondent Alvin Carlson, of Gladstone, Mich., time reverts to Eastern Standard Time, says 5S\V (London) closes with twelve strokes five hours slower than G. M. T., instead of gong, of course, this is the Big lien clock, of four as shown. London. Also, 5SW does not transmit on Satur- days. 1 can clear the point about PCJJ- G. W. Rob- inson of Buffalo says PCJJ is at Eindhoven (Hol- land) and you say it is at Hilversum. The actual COMMERCIAL USE OF SHORT WAVES transmitter is at Hilversum but the control studio Editor, RADIO NEWS: is at Eindhoven, so it is always announced as I congratulate you on your wise decision to Eindhoven. Announcements from PCJJ are gen- set aside a special section in RADIO NEWS for com- erally made in Dutch, English, German and French. ments on short waves. The future of radio is The English wireless magazine "Radio World" skillfully enclosed by Nature within the high - says there is a Spanish station at Madrid on 30.7 frequency waves and it remains for men of sci- meters. Call EAM. Perhaps this will help your ence devoted to this study to open up the way by correspondent, Robert M. Sprague, of Hanover, continued experimentation and study of the high New Hampshire. Bandoeng seems to he pronounced frequencies. When this is done international by the Dutch as "P,ondung "; perhaps this will help brotherhood will be a real tangible fact. F. \V. Fitzpatrick of St. Johns, Mich. As to bis In the meantime, do the various Chambers of word "P,ostol-': PCJJ is sometimes heard calling Commerce in the numerous sections of the United up Java as "Allo, radio Dienst-Bandoeng." States realize the tremendous power behind short I hope that the above information may be of waves to open up the markets for American prod- some use to you, even if it is a bit late (RADIO ucts in Central and South America? Please no- The short-wave transmitter of 2XAL is small NEWS does not arrive here until about the tenth tice what Holland, through PCJJ, is doing in and simple, but carries farther than high -power of each month). 1 think RADIO NEWS is a fine sending direct and indirect advertisements to Cuba, sit iti ,s ou luny cr,,t.'s. (Continued on page 392) Argentine, Brazil, Venezuela and Mexico, to sell what they make on the other side of the Atlantic Ocean. Short -wave transmissions could do more for the good will of North and South America than all of the Pan-American. Conventions, and be just as effective as the great flight of the young American aviator to Mexico as good -will ambassador. I do not make any further comments on this matter, but simply would like to open the eyes of stations other than &I)6: \, \VGY, \VLW, \VRNY and WABC, which are transmitting regularly on the short waves, to go ahead and aid in the building of this great international brotherhood. R. DEL \ ALLE SARRAGA, Vice -President, Radio Club of l'orto Rico, Box 935, San Juan, P. R.

AN OPERATING HINT Editor, RADIO NEWS: Anyone wishing to improve the operation of his short-wave receiving set should install another aerial. I now have two aerials and connect one to the plate coil and the other to the grid coil of my short-wave set. I never use headphones any more and 1 receive KDKA on 66 meters loud enough to be understood all over a seven -room house, in addition to hearing amateur stations from all parts cf the United States and Canada. The transmitter house of WRNY and 2XAL at Villa Richard. Coyfesville, N. J., opposite 181st St., New York City. The tarsier aerial is above the pictured scene: that of 2XAL, a Hertzian CARL W. PEADRO, doublet, and in line with it is the counterpoise, another I--, und the R.T. ¡cads separated by Gaye, 111. insulators, may be .ceci.

www.americanradiohistory.com 344 Radio News for October, 1928 List of Broadcast Stations in the United States

Radio Radio Radio ili Radio it YI Óq Call BROADCAST STA. Óq3 Call BROADCAST STA. ç d ñ Call BROADCAST STA. ;RI Call BROADCAST STA. ó ; Letter Letter Location Letter Location 6; Location - Letter Location 3 y; i C; E f G;

Pa.. +316 50000 KGO Oakland. Calif 184 501.10 WBAK Harrisburg, Pa. (day). 300 500 WGN-WLIB Chicago & Elgin, I11416 15.000 KD KA East Pittsburgh. WEAL tBaltlmorc, 512 +286 W G R Buffalo, N. Y KDLR Devils Lake. N. D 231 15 KGRC San Antonio, Texas... 220 250 5000 303 750 234 500 KGRS Amarillo, Texas 244 250 WBAO Decatur, Ill 268 10) WGST Atlanta, Ga 270 500 KO Y L Salt Lake City. Utah W G wB Cal 252 250 KGTT San Francisco, Calif 220 50 W BA P Fort Worth, Texas 500 6000 Milwaukee, Wis 270 250 KEJK Los Angeles. W BA W Nashville, Tenn 240 uddJ W G Y Schenectady, N. Y...380 KE LW Burbank. Calif 229 500 KGU Honolulu, Hawaii 270 0 5000 278 2500 KGW Portland. Oregon 492 W BAX Wilkes Barre, Pa 250 100 WHA Madison. Wise 333 756 KE X Portland, Ore WEBC Brooklyn, N. Y 500 WHAD Milwaukee, Wise KFAB Lincoln, Neb 319 5000 KGY Lacey. Wash. 246 50 227 270 500 . B B Richmond. 100 WHAM Rochester, KFAD Phoenix. Ariz 322 560 KHl Los Angeles, Calif 400 10 W L Va 234 N. Y 250 5000 KHMC Harlingen. Tex 236 10000 WEB M tOlonvlew, Ill 389 5000 W HA P 1Carlstadt, N..; 236 1000 KF AU Boise. Idaho 288 2000 WHAS KFBa Havre, dont 275 50 KH Q Spokane, Wash 370 1000 W B B R N. Y 250 1000 Louisville, Ky 32002 Ited (day) 322 W B B W Norfolk, Va 236 100 WHAZ Troy, N. Y. (Monday) 306 5500 KFBK Sacramento. Calif 275 - 100 KICK Oak. Iowa KFBL Everett. Wash 224 50 KJ BS San Francisco. Calif 245 W B B Y Charleston, So. Car 250 79 WHB Kansas City, Mo 341 500 484 500 KJ R Seattle. Wash 349 2500 WBCN Chicago, III 288 500 W H BC Canton, Ohio 236 10 KFBU Laramie, Wyo. Salisbury, 100 KFCB Phoenix. Ariz 244 125 KP Seattle, Wash 203 WBES Md 285 WHBD Bellefontaine,O 222 100 Barbara. Calif 211 100 KLCN Blytheville, Ark. (day) 286 5Ó W BET Medford, Mass 288 500 W H BF Rock Island, Ill 222 100 KFCR Santa WB IS See WNAC W H B L Sheboygan. Wis KFD Al Beaumont. Texas 484 500 KLDS Independence, Mo. 270 1500 204 250 KFDX Shreveport, La 236 250 KLRA Little Rock, .Ark.... . 204 50 W B M H Detroit, Mich. 211 100 W H B P Johnstown, Pa 229 S. D 545 500 KLS Oakland. Calif .. . 246 250 WB MS Union City. N. J 200 100 W H B Q Memphis. Tenn 232 254)100 KFD Y Brookings. W B N Y New York. KFEC Portland, Ore 214 50 KLX Oakland. Callf. 508 500 N. Y 236 500 WHBU Anderson, Ind 220 15 227 250 KLZ tlupont. Colo 353 W B O Q Richmond Hill. N. Y 309 500 WHEW Philadelphia. Pa 220 100 KFEL Denver. Colo W BO W Terre 100 KFEQ St. Joseph. Mo 231 *1000 KMA Shenandoah, Iowa 395 1000 Haute, Ind.... 208 WHB Y West De Pere, Wis 250 50 WBRC Birmingham. Ala 303 250 W I Minneapolis, Minn KFE Y Kellogg. Idaho 232 10 KMBC see KLDS HD 246 500 210 10 KMED Medford, Oregon.. 270 . WERE Wilkes Barre. Pa 250 100 WHEC -WABO Rochester, N. Y 264 250 KFG Q Boone, Iowa W BRL Tilton, KFH Wichita, Kan 246 500 KM IC Inglewood, Calif 224 250 N. H 232 500 W H FC Chicago. Ill .,. 216 200 KFHA Gunnison, Colo. 250 50 KMl Fresno. Calif ... 366 50 W BSO Wellesley Hills, Mass 384 100 W H K Cleveland. Ohio 265 500 Angeles, Calif.:,,, 468 5000 KM MJ Clay Center, Neb..... 286 WBT Charlotte, No. Cara 258 1000 W H N New York. N. Y 395 500 KFI Los Tacoma. Wash. 254 * WBZ tspringSeld, Mass *333 15,000 229 50 KMO WHO Des Moines, Iowa..., 535 5000 KF IF Portland. Ore WBZA Boston, KFIO Spokane, Wash 246 100 KMOX 1St. Louis. Mo 300 Mass 333 500 W H PP E lewood, N. J 205 10 KFIU Juneau. Alaska.. 225 10 KMTR Loe Angeles. Calif 516 b5 W C A C Mansfield. Conn 535 500 WHT tChicsgo, III 306 5000 KFIZ Fond du Lac. WIS.... *268 100 KNRC Santa Monica. Calif 375 500 WCAD Canton, N. Y 244 '500 W IAD Philadelphia, Pa 288 100 KFJB Marshalltown, Iowa 248 100 KN X Los Angeles. Calif 337 500 WCAE Pittsburgh, Pa 461 500 W IAS Ottumwa. Iowa (day) 322 loo City. Okla 273 5J00 KO A Denver. Coto 326 5000 W C A H Columbus, Ohio 234 250 W IBA Madison. Wis 240 100 KFJF Oklahoma KOAC Corvallis Oregon (day) 270 7000 WC AD Lincoln, Neb. (day) 380 500 KFJ I Astoria, Ore 250 50 WIBG Elkins Pk.,Pa.(Sund'ys)441 50 KFJM Grand Forks, N. D 333 100 KOB State Coll e,New Mex :395 '5000 WCAL Northfield, Minn 286 500 W IBO [Chicago, ltl 306 5000 KEJR Portland. Ore 240 500 KOCH Omaha. Nob 258 250 WC A M Camden, N..1 224 500 W IBR $teubenvtlle, Ohio 250 50 W Okla . 252 250 WCAO Baltimore. Md 244 250 KFJ Y Fort Dodge. Iowa 232 100 KOC Chickasha W I BS Elizabeth, N. J 204 250 Worth, Texas 250 50 ISO IL Council Bluffs. Iowa.. 319 5000 WCAP Asbury Park, N.J 240 '500 WIBU Poynette,A,ls 217 20 KFJZ Fort 319 1000 WCAT Rapid City, So. Dak 248 100 KF KA Greeley. Colo 250 500 KOIN [Portland. Oregon.... W I B W Toppeeka, Kan 204 250 Kansas 242 *1500 KOMO Seattle, Wash 309 1000 W C A U Byberry, Pa 261 1000 WIBX N. 238 KF KB Milford. WC A X Utica, Y.... 150 Lawrence, Kansas 254 500 KORE Eugene. Ore. 200 50 Burlington. Vermont 254 100 WIBZ Montgomery. Ala 231 15 KF KU W Denver. Colo 219 250 WCAZ Carthage, Ill 250 50 K F K X Chicago. Ill 526 2500 KO W I C C Easton. Conn 265 500 KF KZ Kirksville, Missouri.... 225 15 W IL St. Louis, Mo 258 250 K F LV Rockford, Ill 268 100 WINR Bay Shore. N. Y 211 500 KFLX Galveston, Texas 270 100 WIOD Miami Beach, Fla..., 248 1000 KFMX Northfield. Minn 236 500 H E list of stations here corresponds to the latest list of W IP Philadelphia. Pa 340 500 KFNF Shenandoah.lowa(daY) 461 2000 W ISN Milwaukee, Wig 270 250 . 447 1000 KFOA Seattle, Wash 1 licenses issued by the Radio Commission at the time of w I V A Norfolk, Va. 210 100 Calif..... 242 1000 KFON Long Beach. going to press; and is subject to changes ordered by the W J A D Waco, Texas. . 333 500 KFOR Lincoln. Neb 217 100 W J A G Norfolk, Neb. 286 250 KFPL Dublin. Texas 275 15 regulating authority after August 6, 1928. W J A K Kokomo, Ind 234 50 Greenville, Texas 231 15 W J A M Cedar Rapids, Iowa 240 250 KFPM 50 Springs. Ark 263 W J A R Providence, R. 484 500 KFPW Sulphur 250 ,iiiii1i,i.,,ii i,i,mm..mmmu..,nn1i,i,o....n,nmmnun,mm..wi3 I. KFPY Spokane. Wash 240 W J A S Pittsburgh Pa... 270 500 St. Louis, MO. 234 50 W J A X Jacksonville, Fla. 341 1000 KFQA 333 1000 KPCB Seattle, Wash 231 WCBA Allentown, Pa 222 100 KF QB Fort Worth. Texas Prescott, 214 15 W C B D Zion, W J A Y Cleveland, Ohlo 227 500 Alaska 345 100 KPJM Ariz .. Ill 345 5000 KFQD Anchorage, KPLA Los Angeles, Calif ... .. 288 500 W C B M Baltimore, Md 225 100 WJAZ (Mt. Prospect, Ill 263 5000 KFQU Holy City Calif 220 100 WJBA Joliet, 248 50 217 100 KPo San Francisco, Calif... 422 WCBS Springfield, Ill 210 250 Ill KFQW Seattle. wash KPOF Denver, Colo. 201 Wcco tMnnneapolls. Minn 405 5000 W J B B Sarasota, Fla 238 250 KFQZ Hollywood. Calif 232 250 316 1550 W J BC LaSalle, III 227 100 454 1000 KPPC Pasadena, Calif WC DA Cllffslde, N...1 213 250 KFRC San Francisco. Calif 231 100 W J e I Red Bank, N. J. 263 250 250 500 KPQ Seattle, Wash WCFL Chicago. Iii 984 1500 KFRU Columbia Missouri KPRC Houston, Texas 294 1000 WCGU Brooklyn, N. Y 219 500 W J B K Ypsilanti. Mich 220 15 KFSD San Diego. Calif 441 500 318 1000 W J B L Decatur, 213 250 252 500 KPSN Pasadena. Calif W C LB Long Island City, N. Y 200 100 Ill KFSG Los Angels. Calif . 270 500 W J BO New Orleans. La. 263 100 258 500 K Qv Pittsburgh, Pa WCLO Kenosha. Wise 227 100 KFUL Galveston, Texas San Jose. Calif . 297 500 W J BT Chicago. Ill. 389 500 Colo 488 1000 K Q W WC LS Joliet. Ill 216 500 K F U M Colorado Spas., ORE Berkeley. Calif. 231 100 WC M A Culver, Ind 261 500 WJBU Lewisburg. Pa. 214 100 KFUO tClaYton, MO 545 *1000 461 500 WJBW New Orleans. La 238 30 227 100 KRLD Dallas. Texas WC OA Pensacola, FIa 250 500 KFUP Denver. Colo K R M D Shreveport, La 220 50 WC OC Columbus. Miss 231 500 W J B Y Gadsden, Ala 234 511 . 225 50 KFUR Ogden, Utah. KRSC Seattle, Wash 273 50 W C O H Greenville. N. Y 211 250 WJJD Mooseheart, Ill 366 1000 City, Calif 216 250 W J 232 500 KFVD Culver KSAC Manhattan, Kansas 333 500 WCOT Providence, R. I . 225 100 KS Gary, Ind KFVG Independence. Kan 225 50 La 268 1000 WJR -WCX Mich 441 5000 50 KSBA tShreveppoort, W C R W Chicago, Ill 224 500 /Pontiac, KFVS Cape Girardeau. Mo 224 KSCJ Sioux City', Iowa 244 500 WCSH Portland, Maine 366 5000 W J Z tNew York, N. Y. ... 454 30,000 OF W B Los Angeles, Calif 353 1000 KSD St. Louis. Mo 545 500 W K A Q San Juan, Porto Rico 322 500 Cuff 248 100 WCSO Springfield. Ohio 256 ,du K F W C Ontario. KSE I Pocatello, Idaho 333 250 W C W K Port Wayne, Ind 214 250 w K A R East Lansing, Mich 278 500 KFWF St. Louis. MO 214 250 303 5000 W K AV Laconia, N. H 224 50 268 500 KS L Salt Lake City. Utah WCX See WJR KF W I San Francisco. Cal KS M R Santa Marla, Calif 273 100 WKBB Joliet, Ill 216 150 Calif 236 *500 WDAE Tampa. Fla 268 500 KF W M Oakland, KSO Clarinda lows 227 500 W D A F Kansas City, Mo 370 1000 W K B E Webster. Mass 229 100 KFWO Avalon. Calif.. 300 250 So. Dak 210 2.50 W K B F Indianapolis, Ind 252 250 204 *15 KSOO Sioux Falls. WDAG Amarillo, Texas 263 1000 KF X D Jerome, Idaho KSTP Westeott, Minn 220 3500 W D A H El Paso. Texas 234 100 WKBG Chicago. Ill. (portable) 201 100 KFXF Denver, Colo 2S3 250 Calif 280 500 W K B H La Crosse. Wig 231 500 50 KT AB Oakland, W DA Y Fargo, No. Dakota 595 *250 KF XI fEdgewater,Colo.(near)210 KTAP San Antonio, Texas 229 250 W DBJ Roanoke. Va... 231 250 W K e I Chicago, III 216 50 City. Okla 224 50 B N 214 50 KFXR Oklahoma K T B I Los Angeles, Calif 275 1000 WDBO Orlando, Fla 288 *500 W K Youngstown. Ohio KFXY Flagstaff, Ariz. 205 25 KTBR Portland, Oregon 229 500 WKBO Jersey City, N. J 219 500 Tex 100 WDEL Wilmington. Del 297 250 213 60 KF YO Breckenridge, KT HS Hot Springs, Ark 500 1000 WOG Y Minneapolis, Minn 286 500 WKBP Battle Creek, Mich FYR Bismarck, No. Dak 2,11 100 Muscatine, Iowa 256 2000 W K B Q New York, N. Y 219 500 261 2000 KTNT W DOD Chattanooga. Teon 244 500 KGA Spokane, Wash KTSA San Antonio. Texas 265 2000 WDRC New Haven, Coon 283 500 W KBS Galesburg, Ili 217 100 KGB San Diego, Calif 248 100 KTUE Houston, Texas 213 5 W KBT New Orleans. La 252 50 Ariz 234 100 WDSU New Orleans 227 250 100 KGAR Tucson, KT W Seattle, Wash 395 1000 WDWF -WLSI Cranston, R. I 248 250 WKBV Brookville, Intl 219 KGBU Ketchlkan, Alaska 400 500 Longview. Wash 200 10 W KB W Amherst, N. Y 217 5000 Mo 288 100 KUJ WDZ Tuscola. Ill. (daytime) 278 100 KGB X St. Joseph, KUOA Fayetteville. Ark 297 1000 WEAF )Bellmore. N. Y 49250,000 W KBZ Ludington, Mich 200 15 KGBY Columbus, Nebraska 222 50 KUOM Missoula, Mont 461 500 W KEN Buffalo, N. Y. 207 750 213 100 WEAN Providence, R. I. 275 500 50 K G B Z York. Nebraska KUSD Vermillion, So. Dak 484 250 WEAO Columbus. Ohio 283 750 WKJC Lancaster Pa 252 K G C A Decorah. Iowa. 248 10 KUT Austin. Texas 232 500 W KRC Cincinnati, Ohio 246 500 Okla 216 50 WEAR Cleveland, Ohlo *400 1000 150 KGCB Oklahoma City, KV I Tacoma, Wash 283 250 Wig 242 1000 WK Y Oklahoma City. Okla 288 Wayne, Nebraska 294 250 Wash 273 100 WEBC superior, WLAC Nashville, Tenn 225 5000 KGCH 250 KVL Seattle, WEBE Cambridge Ohio 248 10 KGCI San Antonio, Texas 220 K V O O Tulsa, Okla 349 5000 WLAP Louisville. KY 268 500 Kansas 208 50 WEBH t'htcaeo, Ill 366 500 WLB Minn 246 500 KGCN Concordia, KV OS Bellingham. Wash 210 250 W EB Q Harrisburg, 224 15 Minneapolis, KGCR Brookings. So. Dak 208 15 KWBS Portland, Oregon 200 50 Ill WLBC Muncie, Ind. 210 50 WEBR ituitalo, N. Y - 242 200 No. Dak 240 100 250 W L B F Kansas 210 50 KGCU Mandan, KWCR Cedar Rapids. Iowa 240 WEBW Brloit. Wis.... 258 .500 Kansas City. KGCX Vida, Montana 244 10 K W EA Shreveport. La 213 100 WLBG Petersburg. Va 214 100 SO. Dak. WEDC Chicago, Ill 242 500 30 KGDA Dell Rapids. K W G Stockton. Calif 345 100 WEDH Erie, Pa 219 30 W L B H Farmingdale, N. Y 232 (daytime) 254 15 W 250 50 WLBL Point. Wisc 333 1000 50 K J J Portland. Ore WEE! Boston, Mass 508 500 [Stevens KGDE Barrett. Minn 205 K W K St. Louis Mo .. 234 *1000 W L B O Galesburg. Ill.. 247 100 217 10 WEHS Evanston, Ill 216 100 K G D M Stockton. Calif. KW KC Kansas City. Mo 222 100 Spgs., 484 1000 W L B R Rockford, Ill 248 15 Colo 224 10 395 3501 W E M C Berrien Mich 207 50 K GDP Pueblo. KW K H Kennonwood, La WEHR see WBCN WLBV Mansfield. Ohio KGDR San Antonio, Texas 207 15 KW LC Decorah, Iowa 248 50 W L 6 W Oil City. Pa 294 500 Neb 204 100 WEPS Gloucester. Mass 297 100 KGDW Humboldt: K W SC Pullman. Wash 495 500 WEVO Woodhaven, N. Y 246 500 W LB Long Island City, N.Y. 204 250 KG D Y Oldham, So. Dak 207 15 K W TC Santa Ana, Calif 273 100 Iron Mountain, Mich.. 210 50 263 1000 WE W St. Louis, Mo. (day) 353 1000 WLBY KGEF I.os Angeles, Calif K W U C LeMars, Iowa (day'). - 244 1500 W LBZ Dover- Foxcroft. Me 208 250 263 50 W F A A Dallas, Texas 545 500 KGEK Yuma, Colo. (day) K W W G Brownsville, Texas 278 500 W LC I 'Ithaca, N. Y . 248 50 225 100 WFAN Philadelphia. Pa 224 500 KGEN El Centro. Calif K X A Seattle, Wash 535 500 234 50 WLEX Lexington, Mass 216 50 Neb 205 100 WFBC Knoxville. Tenn KGEO Grand Island. K XL Portland. Ore 220 250 WFBE Cincinnati, Ohlo. ., 246 250 WLIB Sec WGN KGER Long Beach, Calif 216 100 KXRO Aberdeen. Wash 224 50 Pa 268 100 Philadelphia, Pa 405 500 Neb 204 10 361 1000 WFBG Altoona, W L IT KG ES Central City. K Y A San Francisco. Calif WFBJ Collegeville, Minn 273 100 WLOE Chelsea. Mass 211 100 Morgan. Colo 219 000 K Y W 534 '2500 KGEW Fort Chicago. Ill W F B L Syracuse, N. Y. 258 750 WLS Chicago Ill 345 .5000 G E Z Kalispell. Montana 294 100 KZM Oakland, Calif 231 100 K W F13 M Indianapolis, Ind 275 1000 See WDWF - WLSI KGFF Alva. Oklahoma 205 25 NAA Arlington. Virginia...434 1000 WFBR Baltimore, Md 244 250 N Y 256 250 KGFG Oklahoma City, Okla 216 50 W A A D Cincinnati. O 231 25 WLTH Brooklyn WFC I Pawtucket, R. I 242 100 W L $Clnclnnatl Ohio 428 5000 KGFH Glendale. Calif 263 250 WAAF Chicago. Ill ... 389 500 WFDF Flint, Mich 273 100 370 5000 San Angelo, Texas 220 15 W A A M Newark, N. J 288 W L W L tKearny, N. J KGFI W F 1 Philadelphia, Pa 405 500 KGFJ Los Angeles, Calif 213 100 WAAT Jersey City N. J 249 300 W MAC Cazenovia, N. Y 225 500 W F I W Hopkinsvllle, Ken 261 1000 428 500 - Maas KGF K Hallock. Minn ^224 50 WAAW Omaha. Neb . (daytime)441 500 WMAF So. Dartmouth, W F J C Akron, Ohio 227 500 N. Y 545 750 KGFL . Raton, N. AI- 222 50 WA BC Richmond Hill. N. Y 309 *2500 W MA K *Martinsville, 10 250 WF KD Philadelphia, Pa Washington, D. C 242 500 KGFW Ravenna. Neb 297 W A B F Kingston. Pa 205 WFLA Clearwater, Fla 517 750 WMAL S. D. (day) 254 200 WABI Me. (Sundays) 389 100 W M A N Columbus. Ohio 234 50 KGFX Pierre. Bangor. W G A L Lancaster, Pa 252 207 100 WA BO See WHEC W M A Q *Chicago, III 447 2500 KGGF Picker, Okla G BB Freeport, N. Y 155 La 213. 50 WAR Y Philadelphia Pa 248 50 W W MA Y St. Louis. Mo 234 100 KGGH Cedar Grove, G B c Memphis. Tenn 229 10 Colo 210 500 WA BZ New Orleans, La 238 50 W WMAZ Macon. Ga 270 500 KGHA Puebti. _ WGRF Cvanscllle. 238 255 227 250 __ Akron. 238 1000 ind...... 204 100 KGHB HOñolulU.Hawaii Pa 231 250 W MBA - Newport, R. I. 210 250 231 100 WGBI Scranton. 252 5000 KG 14F Pueblo. Colo WAFD Detroit, Mich 349 500 W MBB 1Chicago. III KGHG McGehee, Ark 50 WAGS Royal Oak, Mich 225 50 WG BS tNew York, N. Y..... Detroit. Mich 244 10(1 222 10 WMBC KGHI Little Rock. Ark 261 "15 WA Ill fColnmbus,Ohio 283 5000 WGCM Gulfport, Miss W M B D Peoria Heights. IU, , 205 250 100 50nn K G H L Billings. Mont 222 250 W A I Z Appleton, Wie 227 W G C P Newark, N. J 268 250 W M B F Miami Beach, Fla 364 201 K G H X Richmond. Texas...... So WALK Willow Grove. Pa W G E S t ewark, , Ill 242 500 W MBG Richmond, Va 341 1000 11N1 KGJF Little Rock. Ark ...... 250 WARI Auburn. Ala Mich 2728 750 WMBH Joplin. Mo 24 Texas... 280 WASH Grand Rapids. Mich.. 256 250 WGES [Fraser. 5000 KG KB Goldthwaite. MS Minneapolis, Minn 246 500 W MBi [Addison, Ill 263 KG K O Wichita Falls, Texas .. ... 250 W B A A West Lafayette. Ind.. 273 500 WG 'Allowed higher daylight lamer Sie maid o:- rnn:annt- rregoenry Iransud.+ =ion. t Remote Coat toi.

www.americanradiohistory.com Radio News for October, 1928 345

L? Radio Radio Radio m Radio e l: ú `« Call BROADCAST STA. or pq Call BROADCAST STA. ow Call BROADCAST STA. A 3o ñ Call BROADCAST STA. 8 Letter Location Letter Location Letter Location ig 63 Letters Location Ai 6;

WSGH WMBJ McKeesport. Penna... 232 50 WOAX Treatcn, N. J 240 5011 WRAW Reading, Pa 238 100 Brooklyn, N. Y 227 500 WRAX Pa W S 1 X Springfield, Tenn 150 W M B L Lakeland. Fla 229 100 W O B T Union City. Tenn..... 205 15 Philadelphia. 250 250 Charleston w. Va.... 268 250 WRBC Valparaiso, Ind 238 250 WSKC Bay City, Mich 273 250 WMBM Memphis. Teno .. 210 10 WOBU WRBH WS M Nashville, WMBO Auburn, N. Y 220 100 W OC Davenport. Iowa 375 5000 Manchester, N. H...., 500 Tenn 337 5000 W R B I Fitton. rial 222 W S M R New Orleans, La. 297 751) w M B Q Brooklyn. N. Y 204 100 W O S L Jamestown. N. Y 224 25 W RB J 10 W 5 M K Dayton. 207 200 W M B R Tampa, Fla .. 252 100 Wu DA Paterson. N. J 294 1000 Hattiesburg. Miss 250 Ohio... Ames. Iowa .. 265 *1000 W RBI Columblla, Ga 2513 50 wspD Toledo. Ohlo 240 250 W M BS Lemoyne, Pa 234 250 WO) W R 214 WOK See W MBB WRBQ CreenVille, MISS 275 100 S o Middletown, Ohlo 236 100 W M B W Youngstown. Ohio.... 50 WRBT Wilmington, 50 WSSH Boston. Mass 288 100 W MC 517 5G0+ W O KO Beacon, N. Y 216 500 N. C 227 Memphis, Tenn w s U I 476 W Manitowoc, Wis 222 100 WRBU Gastonia, N. C 50 Iowa City. Ia. (day) 500 MCA tNew York, N. Y..... 370 :;00 WOMT S. 15 W S U N St. Petersburg. Fla 517 750 WMES Boston, Mass 211 30 WOOD tGraod Rapids. Mich. 261 500 W RB w Columbia. C wSVS Y 204 511 Lapeer, 234 30 WOO Kansas City. Mo 341 5)10 W RB X Richmond, Va 250 Buffalo, N. WMPC Mich W S Y R Syracuse. N. Y .. 294 500 W M R.1 Jamaica, N. 2:17 10 W O R tKearny. N. J 422 5000 WRC Washington: D. C 1.488 5 Y...... W R E C tMemphis, Tenn . 250 W T A D Quincy. Ill 236 '150 WMSG New York, N. Y '36 500 WORD tlSataviS.Ill . 252 5000 500 WTAG C(tW_. 01.3.... 422 500 WREN Lawrence. Kan 254 750 Worcester, Mass. 517 250 WNAC -WBIS Boston, Maas 461 500 WOS Jefferson WTAM l'leveiand, Ohio .....400 *3500 WNAD Norman, Okla.... 240 500 WOV New York, N. Y . ... 294 1000 WRHF Washington.D.C.(day) 322 150 Nebr 508 1000 WRHM tMlnneappoolls, Minn.., 261 1050 WTA Q I ;au Claire, Wis 254 500 W N A L Omaha. Neb. 258 250 WOW Omaha. WTAR -WPOR Norfolk, Va 236 500 WNAT Philadelphia. Pa...... 285 100 WOWO Fort Wayne, Ind 229 2500 WRJN Racine. Wis 248 224 500 WRM Urbana, I11 273 500 WTAS Elgin, Ill 275 500 WNAX Yankton, S. D. (day).. 303 1000 WPCC Chicago, III WTA W 208 tNew York. N. Y..... 328 500 WRK Hamilton. Ohio 205 100 College Station, Tex 484 500 WNBA Forest Park, III 200 WPCH W T A X Streator. III 248 50 WNBF Endicott N. Y... 207 50 WPEP Waukegan. Ill...... 216 250 WRN Y ¡New York, N. Y 320 500 N. 273 5000 W RR Dallas. Tep 461 500 WTAZ Richmond, Va 220 15 WNBH New Bedford, Mass 261 250 WP G Atlantic City. J.... WTFF Mt. Vernon Hills, Va 20310,000 WNBJ Knoxville, Tenn 207 50 WPRC Harrisburg, Pa 210 100 WRUF Gainesville, Fla 20.1 5000 300 500 W RV A Richmond, Va 254 WTFI Toccoa, Ga.. 210 500 WNBO Washington Pa 211 15 WPSC StateCollege,Pa.(day) 227 200 Pa 207 50 WSA I tClocinnatl. Ohio 361 5000 WTHS Atlanta. Ga WNBQ Rochester, N. Y 205 15 WPSW Philadelphia, Conn WNBR Memphis. Tenn 229. 100 WPTF Raleigh. N. C...... 545 1000 WSAJ Grove City, Pa 224 250 WT IC Hartford. 535 500 WNBW Carbondale, Pa 200 5 WQAM Miami. Fla. 384 750 WSAN Allentown, Pa 222 100 WT MI Milwaukee. Wis 294 1000 WNBX Springfield, Vt 242 10 WQAN Scranton, Pa 231 250 WSAR Fall River, Mass 213 W T R L Midland Park, N. J 207 15 Saranac Lake, N. Y... 232 10 WQAO -WPAP tCllffside, N. J 395 500 WSAZ Huntington. W. Va., 250 100 W W A E Chicago, 227 500 WNBZ WSB Atlanta. Ga 476 1000 Ill WNJ Newark, N. J 268 250 WQBC Utica. Mises. (day).... 216 WWI Detroit, Mich 353 1000 WNOX Knoxville, Tenn 265 1000 WQBJ Clarksburg, W. Va.... 240 65 WSBC Chicago, III 232 W. Va 250 60 WSBF St. Louis. Mo. .. , 258 250 W W L New Orleans. La 246 500 WNRC Greensboro, N. C 224 500 - WQBZ Weirton, WQJ See WMAQ. WSBT South Bend, Ind 400 500 W W N C Asheville. N. C 297 1000 WN YC New York, N. Y 526 500 WSDA See WSGH W WRL tWoodslde. N. Y 200 100 San Tex 280 5000 WRAF Laporte. Ind 208 100 WOAI Antonio, WSE A Portsmouth. Va . _263 W W V A Wheeling. W. Va 250 WOAN Lawrenceburg, Tenu.. 240 500 WRAK Erle. Pa 219 30 500 517 'Allowed higher daylight power. Standard or constant -frequency transmission. tRemote Control .

LIST OF CANADIAN BROADCAST CALLS

500 CHGS Summeralde, P. E. I 268 25 CJRW Fleming. Sask ...... 297 500 CKOW Toronto. Ont...... 357 500 CFAC Calgary. Alta 435 Ont 517 500 CKPC Preston Ont 248 8 CFBO St. Jolla. N. B 337 50 CHLS Vancouver. B. C 411 50 CJSC Toronto. CHMA Edmonton. Alta 517 250 CJ WC Saskatoon, Soak 330 250 CKPR Midland. Ont. 268 50 C F C A Toronto. Ont 357 500 1200 CKSH 297 50 411 1650 CH ML Mt. Hamilton, Ont 341 50 CKAC Montreal. Que. 41l St. Hyacinthe Que CFCF Montreal. Que 517 500 CKCO Vancouver, B. C 411 50 CKUA Edmonton, Alta 517 500 C FC H F8ls, Ont 500 250 CHNC Toronto. Ont Iroquois 322 100 CKCI Qiehec, Que.. 341 23 CKWX Vancouver, B. C....., 411 100 Toronto.Ont.(Sunday) 517 500 CHNS Halifax, N. S CFCL 1800 CHRC Quebec. Que 341 5 C KC K Regina, Sunk 312 500 C K Y Winnipeg, Man 384 500 C FCN Calgary. Alta 435 CKCL Toronto, Ont.. 357 500 CNRA Moncton. N. B 476 Victoria. B. C...... 476 500 CHWC Regina, Sask 312 15 CFCT B. C. 248 5 CKCO Ottawa, Ont 435 100 CN RC Calgary, Alta 435 500 CFCY Charlottetown, P.E.I 312 100 CHWK Chllllwack, CKCR Brantford. Ont 297 50 CN RE Edmonton, Alta 517 500 B. C 268 15 CHYC Montreal. Que 411 750 CFJC Kamloops, -517-357 500 CKCV Quebec. Que 341 50 CNRM Montreal. Que 411 1 Ont . 297 50 CJBC Toronto. Ont.. 435 CFLC Prescott. Regina, Sask 500 CKFC Vancouver. B. C 50 CNRO Ottawa, Ont. 500 CF MC Kingston. Ont...... 268 20 CJBR CNRQ Quebec, Que 341 50 N. 248 25 CJCA Edmonton. Alta 517 C KG W Bowmanville, Ont..... 312 5000 C F N B Fredericton. B..... Alta 435 1000 CNRS Regina, Sask... 312 500 CF QC Saskatoon. Sask 330 500 CJCJ Calgary. CKLC Red Deer. Alta 357 312 1000 CJ GC London. Ont 248 CNRS Saskatoon, Sask . 330 500 CFRB Toronto. Ont Sack 476 500 CKMC Cobalt. Ont .5 500 C Ont..... 268 500 CJGX Yorkton, B. C 411 50 CNRT Toronto, Ont. 357 C F R Kingston. OC Lethbridge Alta 268 50 C K MO Vancouver, CHCA Calgary. Alta 435 250 CJ Ont 517 500 CNRV Vancouver, B. C...... 291 500 441 10 CJOR Sea Island, B. C 291 50 CKNC Toronto. CHCS Hamilton. Ont 297 500 CKOC Hamilton. Ont ... 341 100 CNRW Winnipeg, Man 384 500 CHCT Red Deer, Alta 357 1000 CJRM Moose Jaw. Sash

LIST OF SHORT -WAVE STATIONS OF THE WORLD

Radio Radio Radio Call BROADCAST STA. Call BROADCAST STA. Call BROADCAST STA. Location Letters Location Letters Location Letters

S. S. R. (RUSSIA) AFRICA HOLLAND U. 31.40 30.000 ROW Moscow 83.00 U. S. :vtra 32.110 PCJJ Eindhoven 113 Johannesburg...... 1 6 0 0 70.00 4.000 PC K K 16.00 7L0 Nairobi, Kenya...... PC LL Ktletwijk...... 18.10 32.0)0 U. S. S. R. FAR EAST (SIBERIA) PC M M The Hague...... 46.50 RFM Khabarovsk 70.20 12,00(1 AUSTRALIA PCPP 1 ootwl)k 16.50 RA19 Tomsk 37.00 32.50 PC RR Kootwiik 37.00 2BL Sydney PCTT Koniwllk 21.00 SWEDEN 2FC Sydney 32.00 37.00 2ME Sydney 28.50 PC UU The Hague :ALKarlshorg 47.X100 3AR Melbourne 55.00 S M HA Stockholm 41.1 3AR Melbourne 55.00 310 Melbourne...... 32.00 SWITZERLAND West Australia. 32.90 GAG Perth, THIS list of the short -wave broadcast EH98C Berne .. 32.00 stations throughout the world is not EH9XD Zurich 32.00 CANADA complete, although we have endeavored to UNITED STATES CF Drummondville. Quebec 32.00 list every station of whom we have heard CKY Winnipeg, Man.. 2:1.00 2.000 since in many cases reliable in- KDKA (8X K) 1:ast Pittsburgh, Pa 62.50 40.000 reports; (11XS, IMP-portable) ' DENMARK formation about the programs, wavelength 27 and power of the stations cannot even be KEJ K (6XAN) LOa Angeles, Calif 105.90 250 7MK Copenhagen. 32.91) . 10 250 obtained from the stations themselves. KEWE Bolinas, Calif 7RL Copenhagen 84.24 the cooperation of our KFPY (7XAB) Spokane. Washington 10145.90 100 However, with KFQU (6XBH) Holy City, Chilli 31.00 50 ENGLAND short -wave enthusiasts, we hope that we 53.00 will soon be able to make this list com- 63.00 IS W Chelmsford. . 24.30 15.000 32.50 plete in every detail and keep it in an 108.00 2N M Caterlam giving defi- KFQZ (6XAL) Hollywood, Calif, 108.20 50 GBS Rugby ... 25.00 up -to -date condition. Letters 50 about the short -wave KFVD (6XBX) Culver City, Calif . 105.011 nite information KFWB (6XBR, auto) Los Angeles, Calif 105.00 50 FRANCE broadcast stations will be very much 40.00 53.07 100 FSAV Nogent appreciated. KFWO (6XAD) Avalon, Calif 37.00 1.500 KGB San Diego, Calif 65.18 Radio Vitus Puns Minn 50 Lyons 411.00 250 .,. -.:,,,l,,,,,,,,,,,,,,,,,,,,,,,,,,,,,I,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,.,.,,... KGDE Barrett, YN Lyons 58.00 3.000 KGO (6XAX, 6XN) 10t040 10,01X1 15.50 500 RH) (6XAD) Los Angeles, Calif 104.10 50 Nancy ITALY San Francisco, Calif 62.00 50 F W Ste. Assise 24.50 KJBS (6XARi IA Y Rome 43.18) KJR (7XC, 7X0) Seattle, Washington. .. 105.20 250 1M1 45.00 K M O X St. I.001s, Mo .... 49.X1 15 GERMANY K M T R Los Angeles, Calif. .... 108.20 250 14.00 KNRC (6XAF) Santa Monica, Calif ... 108.20 A F I Konigswusterhausen. JAPAN 100 A F r Konig swusterhausen 14.00 KNX (6XA) Los Angeles, Calif 107.10 AFU Kontgswusterhausen 14.00 JFAV Taipeh. Formosa 30.50 KO IL (9XU) Council Bluffs, Iowa 61.06 500 Berlin. 26.50 JHBB Jbarakikcu .. 37.50 2.11111 KWE -KEWE Bolinas, Calif .. 14.10 HEA Nauen 11.00 JIPP Tokie 20.011 KWJJ (7XAO) Portland, Oregon...... 53.54 100 Nauen 13.50 J KZB Tokio ...... 20.00 WAAM (2XBA) Newark, N. J.... 65.18 AGC Berlin 17.20 IAA Iwatsukl 40.011 WABC (2XE) Richmond Hill, N. Y...... 58.50 500 A GJ Narren 56.70 (Yacht MU -I. 2XAO) AG IS Nauen. 11.00 JAVA WAJ Rocky Point, N. Y...... 22.48 43.90 100.00 250 LA Langenberg 33.0)) WBRL (1)(111 Tilton, N. H Nauen 11.00 Malahv WCGU (2XBH) Bmoklyf, N. Y . 54.00 POF ANE Bandoenz 15.9:i 63.79 250 Nauen 14.90 56.00 WCSH (1XAB) Portland, Maine Poz Nauen 15.10 ANF Malabar WC X Pontiac. Michigan.... 33.00 75 Konigswusterhsusen 52.00 ANH Randoeng 17.013 (Continued on page 391) Stuttgart Batavia 46.50

www.americanradiohistory.com 346 Radio ...Vows for October, 1928 The Radio Constructor's Own Pages Wherein Custom and Home Set Builders and Experimenters All Over the World Swap Experiences and Suggestions About Hookups and Accessories

IN DEFENCE OF THE 4 -TUBER wonder your readers like the change. I don't BLUEPRINTS ARE POPULAR think the other radio magazines will have the cour- Editor, RADIO NEWS: Edtor, RADIO NEWS: Eut you have run over the magazine for this age to follow your example. then, Please mail set of blueprints for the "Neutro- I have just always out along original lines, and that I can hardly wait till they come out. I struck heterodyne, published in the June issue of RADIO month; is the feature which makes your publications so have played with radio for five years, and have NEWS. built many good sets from your articles, for in- attractive. I like your home construction articles very much, and the Regenerative Interflex, The manufacturers will perhaps object to a on account of the fact that I enjoy making the stance the Interflex devoted the interest Though I do not favor one -dial "clean" magazine entirely to coils, etc.; also because of the fact that many of also the Peridyne. experimenter, and devoid of sets, this comes nearest to the mark of any I have of the enthusiastic us have quite a number of old parts on hand with. disguised publicity; but the time will come when which can be used in connection with a circuit had experience admit your change was all for the better. On account 6f illness, in the last three years they will of this kind, whereas, there have been so many nothing but build sets for my friends; After all, a radio magazine must first of all stimu- articles of late regarding A.C. tubes, circuits, etc., I have done is done, are several of them I have rebuilt to late the interest in radio. If this skillfully which require the purchase of entirely new parts, and there will soon feel effect. More power models, to include the nice big audio trans- the producers the that it leaves us with some very good old parts later elbow! formers now on the market, power tubes, S.L.F. to your on hand for which we can find no use. and M.L.F. condensers and smaller coils. In this C. A. OLDROYD, W. B. HUNKINS, Barrow -in- Furness, England. length of time I have built not less than 75 sets; Box 655, Hollywood, Calif. all with good parts or I do not build then. which I think Editor, RADIO NEWS: In regard to your newer policy, SUGGESTED NEW TUBE is a good one, the Neutroheterodyne described in Please send me your Blueprint No. 56 as de- the May and June issues will hit many a fan Edtor, RADIO NEWS: scribed in the June issue. just right. I am especially interested in this hook- I wish to call your attention to an idea for a I have been a reader of RADIO News for about up. I wound the intermediate coils for the L2 new tube, though I have no way of making one two and a half years and have derived much Ultradyne described in your May and June 1926 at present. It would be built to displace the space. pleasure and real knowledge from its pages. I issues and, although the transformers were not charge by repulsion, rather than attraction; as is think your recent policy has much to commend it, matched, I could pull any station in the United the case with the screen -grid tube when used this since I believe most of the readers look for in- States with this hook-up, which I still think is hard way. It would have one grid, one filament and formation which will be of value to them in to beat. I also built the Strobodync; some kick two plates; the center element hieing a small, narrow pursuing the elusive radio "bugs." in this set! I listened to Japanese stations such plate with the filament extending up one side and 'thanking you for the blueprint articles and wish- us JOAN and JOCK, also Cuban stations. (No, down the other, as close to it as possible without ing you every success, danger of a short circuit. The rest of the tube 1 did not get Australia.) LEO DEWSEN, In this June issue, I ran across Mr. Maxwell is arranged as in a 301A. The small plate in the 11 IS lane .Street, Wilkinsburg, Penna Hamilton's little speech; now let me add mitre. Mr. center is charged negatively, say 45 'volts, and (Over ten thousand free blueprints have been Hamilton, residing over 100 miles from a super - will repulse the electrons of the space charge from mailed to inquirers to date, and the requests are station; says he tied the can on his Browning -Drake the center of the tube. Being out of the path of increasing. These cannot be sent with the maga- and is using a 5 -tube Neutrody-ne. In defence of the electronic flow, it would do away with any zines, as numerous subscribers request, because of the 4 -tube variety, nothing short of a 7- or 8 -tube absorption or feeding back from through the bat- U. S. postal regulations.) shielded neutrodyne or superheterodyne could be teries. While not as good as the screen grid at considered in my location, three miles from KFI radio frequency, I think this would be much better and ten miles from about fifteen or twenty other as a space -charge displacer in audio and other FAR FROM THE FACTORY lesser stations. The 4 -tube set, such as that men- places where a tube of this kind can be used to Edtor, RADIO NEWS: tioned, and many others of similar power come advantage. If you think this a good idea and I feel I must write to let you know the opinion nearer separating the high -frequency stations than should make a tube like this, please let me know of one of your overseas subscribers. If reverting what any sets 1 have had experience with, and, as for results you have with it. to the old policy means the reintroduction of giving quality: I have one of these four -tubers for local WILLIAM J. IlowARD, data of coilage. then I think it is more than justi- purposes, with two good audio transformers and a 703 Chamberlain St., Corpus Christi, Texas. fed. We in Australia are not in a position to pur- 210 tube using 350 to 425 volts on the plate, a (The idea is ingenious: but the mechanical dif- chase kits until at least twelve months after the well -known cone speaker and an overstuffed chair ficulty of constructing a filament with a plate in- circuit appears ill RADIO NEWS, and in some caser with an amber light; and I am listening at 10:00 side of it is rather too great, as the filament would not at all. So you can see that in R.F. circuits, p. m. to the dance orchestra at the Cocoanut Grove, screen the plate physically and electrically. Many we cannot try out the various coils owing to the Ambassador Hotel. It does not sound bad, either; of our readers suggest the construction of new ap- lack of information. The same trouble exists in I have heard worse. paratus on a purely theoretical basis; we arc unable relation to oscillator couplers; having an inter- Back to Mr. Hamilton: I have rebuilt these so- to undertake development work of this kind, but we mediate and transformer kit, but no coupler, I can- called five -tubers (not ancient ones either) into and our readers are always glad to learn what has not try out the various circuits unless the number four -tubers. With these five -tubers, when you get been done. The inventor echo has conceived a ueco of turns, gauge of wire, etc., are given. I have down below 275 meters, you would think they were idea and publishes it is protected for a period of made several oscillator couplers for various circuits, holding a convection. two years in getting out a United States patent; it but cannot just strike the right thing. FRANK E. EKSTROM, is necessary, of course, that he stall thereafter use When you first published the Infradyne circuit, 636 !Vest 79th St., Los Angeles, California. due diligence in perfecting its details. -EDITOR.) I imported the Remler amplifier and condenser, etc.; but it was over twelve months before the amplifier was on sale here and then, unless you possessed ALL FOR THE BETTER USE AND ORNAMENT a copy of RAnt° NEWS or the Infradyne manual, Editor, RADIO NEWS: Editor, RADIO NEWS: the thing was useless; as no special oscillator was Let me congratulate you on the improvement The speaker illustrated here is of the balanced brought out with it. And the price asked for the in RADIO NEWS since the change of policy! Now diaphragm type on a frame 36 inches square, cov- amplifier alone! Sixty dollars. one really enjoys sitting down reading the maga- Bred with tracing cloth treated with collodion. The The kit system is O. K. for the man who wants zine. ` Every article has a story to tell and adver- rear diaphragm is 9 inches square. It is covered to make a set and leave it; but for one who is con- tising has been forced into'.the background. No with a hand -painted sunset scene in colors which, tinually experimenting with each new circuit it is of course, do not show. useless, unless of course he has money laid on. This serves as a screen One firm out here is making up the Peridyne coils; for the fireplace as well they retail at about $13. as an excellent repro- Tube prices have dropped this last week, the ducer. The frame, legs, following giving you some idea of the now pre- and carrying vailing retail prices: UX -199, $2.40; Ux -201A, bundle are $1.92; finished in walnut with L'X.171, $5.04. The first shipment of screen - an edging grid tubes has been put on the market. being the of tinsel fringe English around the painting. Osram 6-volt 625, retailing at $7.23. The prices are mentioned only WM. I. VAN ARNUM, for comparative pur- Youngstown, Ohio. poses and to show the difficulties under which we suffer in regard to kits. The local "B" class station 2GB announced re- 141 ,,,,,,,,,,,,,,,M III I,,,,,,,,,,, cently that they will be on the air on the short waveband soon, probably on dual wavelengths. The Commonwealth Goverment collects .11r. Van Arnum's solu- our listen- tion of tire three -foot er's license fee, $4.97 per annum, and as the en- speaker problem is shown closed clipping shows, is at last doing something at the left. Of course, to co- ordinate the programs. sómc artistic ability is re- Assuring you of my continued support to RADIO quired for this. NEWS. AI.DERT ]HARRIS.

,,,,,nmrv,vvvv,vnvv,,,,,u,v,v,v.R 14 Ranger Road, Croydon, New South If'ales, .-fns.

www.americanradiohistory.com Radio News for October, 1928 347

A STROBODYNE CONVERT Sgt. Purdin's dia- Editor. RADIO NEWS: P G P G gram w o u l d be When l.acault came out with the translation of even more clearly LUD reproduced if the Lucien Chrétien's Strobodyne method of reception, °SPEAKER I react and reread the articles; but under no cir- C artist had turned the R.F. and de- cumstance could I get the desired kick from the G P tector sockets up- claims as made for the circuit or method used in 3.41...L. side down detection, I want to say that I went so far as to build the oscillator unit, but never could raise GNOD. AEOR 1s= A.F.T. 2'A.F. T. OUTPUT courage enough to rig it up and try the scheme; TRANSFORMER but for the love of "static" don't call having tried so many autodyne methods in my experience and finding them wanting in some set noises by that FILAMENT BALLAST name when they respect. can be eliminated Two or three days ago I didn't have anything to I j by a logical and do and was rummaging through the junk box and simple change of found the coil as I left it six months ago. A happy direction in set thought came to me that I might find out something ( OO if I would try the circuit out. I rigged it up building. If by . 2'R.F.T. i,2RFT building from from memory and hooked it onto the big super - and I want you to know that I have never found 2' TUNING COND. TUNING COND. right to left (and thereby bringing anything to give me the surprise of my life, during grid leads close my experience in radio, that this one tube did to the panel) you (excepting of course to the Armstrong super -re- generator.) This tube, acting as it did, gave me PRINCIPLES OF SET LAYOUT introduce body capacity for Heaven's sake either sonie shields. the impression that it was really some kind of RADIO NEws: reduce or buy Editor, W. II. F. PURDIN, a super- regenerative combination rigged up to het- it, This is a plea for simplicity. In presenting Staff Sergeant, U. S. .4rniy, erodyne through the intermediate branch of the follow I have in mind my own first attempt to Sixth Corps Area, Chicago. circuit, a pictorial wiring diagram -and the howls and Well, further to back up the statement, I have doped out "echoing silence" which ensued until I NEW POLICY A WOW five intermediates in the set. I was using the the schematic. That set was of the "super-blooper- old standard super as it was found to be better than variety and unquestionably was a "howling Editor, RADIO NEWS: the autodyne methods which I have tried, and on dyne' on the verge of writing success." Many times I have been many of the stations I could get them, but not regenerators and the un- and have even gone so far a few times as to start satisfactorily. Now, since the change, I get all Gone are the old -time never sent it. And now grounded rotor and the lead- pencil vernier. Gone, and once finished one but those stations with plenty of power and plenty of and the variom- here it is along with a request for a blueprint. margin; and stations I could not separate at all, too. are the two -pound condensers stack about half way across mother's bis- 1 have been reading RADIO NEWS for a I now get with very good decency in selectivity. eters which reached Have at times been in sympathy has made his "\Curse - three feet high. I am using a center -tapped loop at first trial and cuit board. Every Tom "Dempsey Admirers" out of the old ones; every Dick and other times in a state of am figuring on using the tuned radio stage; but Wurld" circuit argumentative. has juggled the parts for it; and every Bank has can't figure out from further doping on the cir- But still we Think the new policy will be a wow (Not cuit just what the winding ratio is for the three put its old gadgets in new cases. application for the the other "its" from left to Omaha). For instance; the windings; as this is a better method than using build IT and all accompanying. I have built many, same right, leave the most important leads as long as blueprint, a tapped input coil. across type at times and all have acted differently. Think For those wanting a kick I would suggest that convenient and place by -pass condensers calculation, down. a blueprint with the results of scientific they try it out and they will be more than sur- audio stages to quiet them assistance; though of course filament supply has come into etc., should be of big prised with results, provided they use a bit of Now that A.C. we all will, like the musician who improvises, try we add insults to our injuries to "Dame care in parts used. vogue, and improve on the composer. insert a "twisted pair" and heap epi- Yours truly, Electra," I have found that most of the time, under the opprobrium upon the more or less reput- S. W. NEWLAN, thets of old policy, we started a set and naturally being able tube -maker who promised little or no 60 -cycle Chief 7-crtboard Mot, A. T. & T. Co., short of jack had to substitute in lots of cases Long Lines Dept., Key West, Florida. hum! and a good lot of the time it took a lot of trying, Instead of having another parts -juggling spasm of guessing and cussing before we made the bloomin' like that which accompanied the first wave quit oscillating, which- receivers. why not look contraption either oscillate or enthusiasm or T.R.F. not want it to do. Under this new DUAL AERIAL WIRES from "Hamtown" to "Musi- ever we did for a different route we to substitute with a working Editor, RADto NEws: it, try to find one arrangement ought cale," and, while we are about what do when the thing acts Some months ago I wrote concerning distance re- substantial than the old. knowledge as to to both shorter and more up and our correspondence with other bugs will ception and the number of stations that I had My own receiver layout is shown in the accom- from logged. May I say that, to date, I have logged and an aver- let up considerably. Have had lots of letters panying diagram. It roughly illustrates men ou different hook -ups and the trouble have verifications from no less than 469 stations. set, capable of running different age layout for an average usually comes from insufficient directions, mainly The longest distance received on this continent by circles around similar average left -to-right layouts, to me is 3,030 miles, station KEW. 100 watts, at sufficient in constructional data, and usually my queries all -around performance considered. Only when Holy City, Calif. I have picked up about forty involved them were of the same sort, the trouble detail is shown to illustrate the principle down to bedrock. amateur stations, and 31.0, Melbourne, Australia, are included; but it had simmered and none but essential parts Would like to hear from some guy who has 32 meters, on a Sunday evening, about 5 p. m., on room is allowed for the will be noted that ample had some experience with double -grid tubes, par- which I am awaiting verification. The receivers I latter. ticularly being used as an R.F. tube with a have used are a C.G.E. Radiola 193 and a three - Briefly, the following features will he noted: regenerative detector. Can't help but think the tube set built by my sou, a lad of 17. He has in circuits carrying R.F. (a) Short leads all aloe (two stages with one audio of about a 171 built a number of sets which are giving good satis- current, especially oscillating portions thereof; to work right nicely. Some- faction in the district. leads (yes, it power tube) ought (b) Short A.F. grid and plate body please try it and let me know, as the kids I think that one of the reasons for this success helps) : need shoes and I am afraid the Mrs. won't let is the antenna that I have: my aerial. or aerials, is (c) \Vide separation of successive stages and nie eat if I invest and it don't work. 100 feet long, with twin wires 30 inches apart; one portions thereof; R.F. entirely removed from A.F. E. L. Rocou, cut at 60 feet has a separate lead -in; the longer grid and plate leads: Waco, Nebr. can be (Continued on page 388) (d) Filament leads well removed from sensitive portions of circuit; (e) Well- adapted for cable wiring; One truism which has been much overworked in the past is, "Grid leads should be ultra- short, plate leads as short as convenient, and the two well -separated, but battery leads are immaterial." The net result has been that the uninitiated consider a connection a battery lead from the point it leaves the inductor and frequently place it parallel to another similar lead or even a grid or plate connection. Then. without looking the "job" over, we call it "battery coupling" and advise better by- passing, which may help and may not. Would it not be simpler to advise separation of such leads and by- passing direct from inductor to tube? The right -to -left layout allows plenty of room. This letter is in no way a criticism of RADIO NEWS circuits, (barring the now defunct manufacturers' outfits which have already received enough lambasting). Neither is it something new- although it is far more up -to -date than many much- touted "dud -dynes" of recent years -and the writer cer- a tainly has nothing to sell in the way of advice or circuits. ... He always has too little time for experimentation and is still able. to learn, which seems true of the entire radio fraternity with the exception of those who design the latest hits in setdom. The layout as illustrated is but average and necessarily typical of a four -tube outfit. Add stages lfr. Stephens and his DX- getting "portable" at Hobart. Tasmania. The loud speaker in his hand if you wish, either before or after the detector; is especially portably.

www.americanradiohistory.com 348 Radio -Vcz'.r for Octobcr, 1928 ad fo News ora orie RADIO manufacturers are invited to send to RADIO NEWS LABORATORIES meats. No "write -ups" sent by manufacturers are published in these pages, "samples of their -products for test. It does not matter whether or not and only apparatus which has been tested in the Laboratories and found of they advertise in RADIO NEWS, the RADIO NEWS LABORATORIES being an inde- good mechanical and electrical construction is given a certificate. As the secv- pendent organization, with the improvement of radio apparatus as its aim. vice of the RADIO NEWS LABORATORIES is free to all manufacturers, whether If, after being tested, the instruments submitted prove to be built according they are advertisers or not, it is necessary that all goods to be tested be for- to modern radio engineering practice, they will each be awarded a certificate warded prepaid, otherwise they cannot be accepted. Apparatus ready for, or of merit; and that apparatus which embodies novel, as well as meritorious already on, the market will be tested for manufacturers free of charge. Appa- features in design and operation, will be described in this department, or in ratus in process of development will be tested at a charge of $2.00 per Four the "What New in Radio" department, as Its news value and general interest required to do the work. Address all communications and all parcels to RADIO for our readers shall deserve. If the apparatus does not pass the Laboratory NEWS LABORATORIES, 230 Fifth Avenue, New York City. Readers will be in- tests, it will be returned to the manufacturer with suggestions for improve- formed on request if any article has been issued a Certificate of Merit.

-WAVE SHORT COIL KIT T..\BOR.\TORIES CERTIFICATI: mounting; the plates are of hard - The short -wave coil kit shown, OE MERITNO. 2397. rolled brass. The capacity range of submitted by the Air -King Products the 5 -plate midget submitted for test Company, 222-226 Grand Street, SUB -PANEL BRACKET was from 3 to 20 mmf., although Brooklyn, N. Y., enables the ama- The sub -panel bracket shown, sub- other capacities are available. The teur and short -wave hands of from mitted by the Pilot Electric Mfg. condenser is provided also with a 15 to 133 meters to he received by Co., 323 Berry Street, Brooklyn, black bakelite knob. the use of three interchangeable coils N. Y., is molded of bakelite, and is AWARDED THE RADIO NEWS (No. 1, 15 to 33 meters; No. 2, x/ inches long, 1 inch high, and LABORATORIES CERTIFICATE 31 to 68 meters; No. 3, 57 to 133 34-inch thick. Two holes are pro- OF MERIT NO. 2400. meters approximately) when tuned vided at the end for fastening it by a variable condenser of .00014 -mf. to the panel, while five holes in vari- ANTENNA TUNING UNIT Each coil has the (7- plate) capacity. New ous positions are arranged along the The antenna tuning unit (type wavelength range engraved on its Haven, Conn., is two -color FD -1E and top for any width of sub -panel. The shown), submitted by the frame. The coil forms, of skeleton (red black) stranded Celatsite National Company, Inc., Malden, with non- burning bracket, being of insulating material, low -loss construction, are very sturdy insulation. The Mass., is of the Browning-Drake two colors eliminate difficulty and rugged. The primary coil is in ob- auto -transformer type. It consists variable and mounted by a hinged taining the correct polarity when wir- of ing A.C. filament a 60 -turn, center-tapped space - joint to the plug -in base mounting. circuits. Each wound coil lead consists of modern design, shunted of 16 strands of tinned by a .0005 -mf. (25- No. 30 wire. The wire will not introduce stray capacity plate) tuning is available condenser of the in coils 25 feet in length. effects or absorb energy. Its height girder -frame type made by this AWARDED TITE R.\DIO NEWS and length will meet the needs of manufacturer. The coil LABORATORIES the radio set builder who requires is mounted in a vertical position, on CERTIFICATE the rear supporting post OF MERIT Nt). 2395. a wide and low sub -panel. of the con- AWARDED TFiE RADIO NEWS denser frame, by a special bracket. ;Il WIRING CABLE LABORATORIES CERTIFICATE OF MERIT NO. 2398. AWARDED THE RADiO NEWS The ''R -112 Universal Cable" LABORATORIES CERTIFICATE shown, submittal by the some com- VARIABLE GRID RESISTOR OF MERIT NO. 2393. pany, is of the 12 -wire type, and composed of stranded colored Celat- The "Adjustograd," a variable ELECTRODYNAMIC SPEAKER site. There are four pairs of twisted grid stabilizer, submitted by the The speaker (type 1)- 44 -A.C. same company, is of the wire -wound shown) submitted by the Jensen type. Variation of the resistance is Radio Manufacturing Company, Oak- obtained by adjustment of the screw, land, Calif., is of the electrodynamic on top of the housing, which applies moving -coil type. Its field winding pressure to a curved strip of spring is of the low -voltage type, and has Grass which is made to flatten out a resistance of 15 ohms; the neces- against the resistance strip. The sary direct current is obtained from Adjustograd occupies a space on the A "type B" dial (flush-panel type) the A.C. line through a step -down sub -base or sub -panel 2 13/16 inches is provided for turning the variable transformer and a rectifier of the long by 9/16 inches wide; the over- condenser. The unit is arranged for dry metallic type. The cone, ap- all height at minimum resistance is sub -panel mounting and, when assem- proximately 8 diameter, is I inch. The samples submitted for bled inches in wire: on the sub -panel with its dial anchored to the speaker frame by red and black (41 strands test were found to have a maximum set into the panel, has a very neat No. 30 thin kidskin strips, approximately- wire), red and maroon, red resistance within 10% of their rated and pleasing appearance. It occu- and yellow, and red blue ;;4 -inch in width, cemented around and (16 values, and a minimum resistance pies a space 7 inches long, 4 inches strands No. 30 the edge of the paper cone. The wire), provided for of approximately 20 ohms. They wide, and 6 inches high. With A.C. filaments. the complete speaker is housed in a Four single wires will safely dissipate S watts of en- recommended aerial and series tun- (white, slate, brown and green) are ergy, although designed for use as ing condenser, the wavelength range available for "B" and "C" voltage grid stabilizers. The housing of was found to be from 200 to 550 supply. The wires are formed into molded black Bakelite has a pleasing meters. a cable encased by a neat braided appearance. AWARDED THE RADIO NEWS covering of strong material, and may LABORATORIES be obtained in CERTIFICATE any desired length. OF MERIT NO. 2401. AWARDED THE R. \D1O NEWS LABORATORIES CERTIFICATE DETECTOR TUNING UNIT OF MERIT NO. 2396. The detector tuning unit . (type BD -2E_), submitted HOOK -UP WIRE AWARDED THE RADIO NEWS by the same com- LABORATORIES pany, is of the three -circuit -coupler The "Pushbak" hook -up CERTIFICATE wire, sub- OF MERIT NO. 2399. type; it consists of a 110 -turn sec- mitted by the same company, has ondary winding tapped for neutrali- cabinet of pleasing design, which a single strand of No. 20 tinned MIDGET CONDENSER zation 20 turns from the filament end. serves also as a baffle for the low - wire. There are two insulating lay- The primary winding is wound in Midget" con- frequency cut -off. Dimensions of ers; the inner one, single cotton, over The "Neutrograd a slot on a smaller tube which is cabinet are 14 inches in length, 13% which is braided covering; they are denser shown, submitted by the same placed inside at the filament end of of the air -dielectric type, inches high and 11 inches wide. impregnated with paraffin to pre- company, is the secondary; this winding has suffi- This speaker handles tremendous vent loosening of the braided cover- cient inductance to give maximum- power with excellent reproduction ing. This wire is convenient for energy transfer when sited in the of music and speech. connections, as it may be cut to plate circuit of the R.F. tube rec- AWARDED THE RADIO NEWS length and the insulation pushed ommended. The movable tickler, at LABORATORIES CERTIFICATE hack for soldering; after which the the grid end of the secondary, is OF MERIT NO. 2394. insulation may be pushed back to provided with a long extension shaft the joint. This produces a neat and for panel control. The coil is TWISTED A.C. FILAMENT WIRE efficient wiring job. The wire is mounted in a horizontal position, The "Twisted A.C.- filament Cclat- available in red or black in 25 -foot with its filament end attached to the site" hook-up wire shown, submit- rolls. with a Bakelite end plate into which rear post of the tuning condenser by ted by the Acme \Vire Company, AWARDED THE RADIO NEWS is molded a bushing for single -hole it special bracket; the secondary wind-

www.americanradiohistory.com Radio News for October, 1928 349

ing is shunted by a condenser of and 3/16 -inch thick. Cap grips the line socket or receptacle. Special AWARDED THE RADIO NEWS approximately .0003 -mf. capacity (15- ( "trryp- connectors ") are also obtain. four -strand wire cable is used for LABORATORIES CERTIFICATE plate) of the girder -frame type. This able; these may be slipped over the leads to the remote jacks. The relay, OF MERIT NO, 241L unit also is provided with a "type ends of the fuses, connected into the B" dial for panel control; the space circuit by inserting the wires into R.F. CHOKE COILS required is 7 inches long, 5 inches the holes provided, and fastened by The "Magnum Standard" R.P. tightening the thumb nuts. 'These choke coil shown, submitted by fuses may be recommended to the Barns -Jones and Co., Ltd., Magnum careful experimenter as instrument House, 288 Borough High Street, and tube insurance. London, England, has an inductance AWARDED T11E RADIO NE\\'S within 10% of the rated value of LABORATORIES CERTIFICATE 160 millihenries (measured at OF MERIT NO. 2404. 1,000 cycles) and a distributed capacity less than 8 mmf.; its D.C. re- A.C. TUBE PROTECTOR which should be mounted in close sistance is samewhat less than 400 The "Protector" (Model 6 shown) proximity to the radio receiver, re- ohms. It is wound in six grooves submitted by the Protecto 'Mfg. Com- quires a space 9% inches long by approximately !'f -inch in width; the pany, Brooklyn, N. V., is designed 3V4 inches wide. The overall height diameter of the grooves and the for the protection of the A.C. tubes is 3 inches. The insulating parts number of turns in each slot decrease of an receiver. is essen- (base and housing) are of black from the base to the top. The di- wide and 6 inches high. It is ar- electric It fixed is ameter of the base is 1;ßt inches ranged also for sub -panel mounting tially a resistor, which moided bakelite. placed in series in one leg of the AWARDED THE RADIO NEWS and that of the top 'A inch. The and, when used with the antenna base is provided with two screw above, enables A.C. line between the light socket LABORATORIES CERTIFICATE tuning unit described NO. terminals; that for connection to the the construction of a simple and and the radio set; the resistance of OF MERIT 2408. efficient radio receiver, of attractive the unit submitted for test was 7 modern design. The tuning range is ohms at Yi ampere. It is arranged SPECIAL WALL JACK AND from 200 to 550 meters. PLUG AWARDED THE RADIO NEWS The "Lotus" special wall jack LABORA'TORIF.S CERTIFICATE shown, submitted by the same manu- OF MERIT NO. 2402. facturer, is of special design and is used in connection with the "Lotus" VERNIER DIAL relay, for control as well as to allow The "Laboratory Type" vernier in such manner that the user has the speaker to be connected to a dis- dial shown. submitted by the same tant radio receiver. It is of the only to plug it into a lighting re- vacuum tube is marked company, is of the friction -movement open -circuit filament- control type; plate of the ceptacle, and then insert the line "A" (anode). A black molded type. it was designed for use on cord of the receiver in the receptacle although the filament control is used precision instruments, although it bakelite housing fits over the cone- side of the device; this automatically shaped form and is secured in -place may be used on radio receivers or places the resistance in series with wherever a smooth and positure ver- by a flat -head screw at the top. The the line. The device is 1 ;ft inches mounting space required is 1% nier adjustment is desired. The in diameter and has an over -all dial has accurate graduations from inches by 2% inches. length, to end of receptacle prongs, AWARDED THE RADIO NEWS 0 to 100 over half a circle; out the of 354 inches. top portion of the frame is a gradu- LABORATORIES CERTIFICATE AWARDED THE RADIO NEWS OF MERIT NO. 2412. ated scale for vernier readings. In LABORATORIES CER'fIL tCATE mounting, the dial's collar (which OF MERIT NO. 2406. is 7/16 -inch in diameter and extends The "Magnum Short- Wave" R.P. in this case to operate the relay choke coils submitted by the same MICA BALANCING CONDENSER field winding, by opening or clos- maker, has the general appearance The small adjustable balancing ing the circuit in which is a 3 -volt as the "Standard H.F." choke coil, condenser shown, submitted by the battery-. The jack is mounted in a but has been especially designed Remler Division of Gray and Daniel- black molded bakelite housing, whose for use in short -wave receivers. It son Mfg. Co., 260 First Street, San overall dimensions are 2.4 inches has less than 0.5 -ohm (D.C.) re- Francisco, Calif., is of the mica - long, 2% inches wide and 2 inches sistance, and is wound with the dielectric type and designed for bql- high. equivalent of No. 34 D.S.C. wire, ancing or compensating radio-fre- AWARDED TIIE RADIO NEWS in six slots; each slot with a dif- quency circuits; it has a capacity LABORATORIES CERTIFICATE ferent number of turns, to eliminate range between approximately 5 and OF MERIT NO. 2409. self -resonant points. The distributed 85 mmf. The condenser proper is capacity was found of negligible approximately 54-inch from the back very small, being but .54 -inch in di- The special plug shown, submitted valve; the measured inductance is of the dial) is passed through the ameter by % -inch thick, over all. as an accessory for the special jack approximately 0.3 millihenry. panel; the collar has a set screw It is provided with a mounting AWARDED THE RADIO NEWS for tightening it upon the shaft of bracket. connected to the stationary LABORATORIES CERTIFICATE the instrument. The dial is 4 inches condenser plate. approximately 1 OF MERIT NO. 2413. in diameter and the frame is 5 inches in length and 7/16 -inch wide, inches long over all; the knob of CUSHION SOCKET black molded bakelite is 2 inches The "Magnum Vibro Valve in diameter. The dial and frame described above, is longer than the Holder" or tube socket shown, sub- are of nickeled metal with satin usual plug but has the same gen- mitted by the same company, is of finish and neat in appearance. eral construction. The plug grip is the spring -cushion "X" type, and AWARDED THE RADIO NEWS approximately 1 -3/16 inches in dia- LABORATORIES CERTIFICATE meter and of black molded bakelite; OF MERIT NO. 2403. it is provided with two screws, by which may be bent at any angle for which the speaker -cord tips may be INSTRUMENT FUSES mounting: the adjustable locked into position. The over -all The shown, submit- convenient "Littelfuses" plate has a pigtail connection pro. length of the plug is approximately ted by the Littelfuse Laboratories, vided for soldering to the stator of 3 %y inches. Avenue, Illi- of 1772 Wilson Chicago, the condenser to be compensated. A\W. \RDED THE RADIO NEWS designed for the European type low is made nois. are quick- acting fuses of The adjustment is obtained by turn- LABOTt:\TORIES CERTIFICATE "valve" or tube base. It current ratings; the sizes submit- ing the screw near the edge; which 01: MERIT NO. 2410. in two parts; the base is fastened were 1/32, 1/16, ted for test applies pressure to the movable plate, to the socket by spring -brass strips, %, %, 1 and 2 amperes. They were as the socket causing it to flatten against the mica which in turn serve found on test to fuse at a current DRY BATTERY electrodes. It and thereby increasing the capacity. terminals for the tube value very close to the figure given 'l'he "No. 665," 3 -volt dry battery is approximately 154 inches in di- AWARDED THE RADIO NEV shown, submitted by Simons by the manufacturer. 'l'o protect LABORATORIES CERTIFICATE ameter and molded of black bakelite. the tubes of a radio receiver, one of Brothers and Company. Ltd., Wool- NEWS MERIT NO. 2407. AWARDED THE RADIO suitable current rating should he OF wich Works, London, England, has LABORATORIES CERTIFICATE selected; the fuse is inserted in the been found to have a life curve of OF MERIT NO. 2414. voltage supply; when REMOTE- CONTROL RECEIVER approximately 10 ampere hours negative "B" RELAY it is used with instruments the fuse when used with a small current FIXED CONDENSER is placed in series with one lead of The "I.otus" remote -control relay drain. This battery is approximately The "Magnum" fixed condenser shown, submitted by Garnett, White- the same size as the standard No. shown, submitted by the same com- Lotus ley and Company, Ltd., 6 dry cell; it is 6 -Y inches long pany, is of the compressed -mica type; Works, Broadgreen Rd., Liverpool, over all and approximately 2% England. provides remote control for inches in diameter. Such a battery any receiver operating from either a would prove useful in a portable D.C. or an A.C. line; it is so ar- radio receiver or for other purposes ranged that the receiver can be oper- where a greater voltage supply is ated from any number of points by desired in the same space that the use of additional wall jacks. The relay is designed to operate front a 3 -volt battery. and the 110 -volt con- the sample was found within 5% the instrument. The fuse is 1 inch tact points are sufficiently heavy to of its rated capacity of .0003 -mf. in length and lias an over -all diam- carry the load that might be imposed The condenser is sealed with insu- eter of % -inch; mounting blocks are by any receiver. A socket is pro- lating composition in a molded red obtainable, the dimensions of which vided for connection to the receiver, would be normally occupied by a bakelite housing which measures are 134 inches long, %-inch wide, and an exteusio" cord with plug for No. 6 dry cell. (Continued on pale 397)

www.americanradiohistory.com ,î5Ù Radio News for October, 1928

_ . diltliutiltirnGu

Conducted by C. W. Palmer

RADIO NEWS readers send in every month an average of 5000 letters those asking for sketches, diagrams, data, etc.. should send TWENTY - asking information on every phase of radio theory, construction and FIVE CENTS FOR EACH QUESTION : failure to enclose this will cause delay. operation. We can only print the five or six replies which are of iVe cannot answer for this sum questions requiring original research, widest general interest. intricate calculation, or patent investigation; we cannot compare the Other letters will be answered by mail, if inquirers observe these rules: merits of trademarked apparatus, or give constructional data on apparatus RE BRIEF: TYPEWRITE OR WRITE LEGIBLY IN INK ON ONE SIDE OF THE whose makers withhold it. We cannot undertake to answer snore than SHEET ONLY ENCLOSE A STAMPED ENVELOPE ADDRESSED TO YOURSELF. THREE QUESTIONS in each letter. If you inquire concerning a circuit Many letters are not readable. Simple questions will be answered free; which is not a standard, published one, enclose a diagram to save delay.

PERIDYNE DATA find that the signals with one coil are stronger Broadness, of tuning might also be caused by when the variable condenser is turned higher (with too close coupling between the primary and the (2304) Mr. Chas. Krayner, St. Louis, Mo. the plates further in mesh), remove a small amount secondary coils. When constructing the coils for writes: of wire from the secondary until the signal comes this set, keep the spacing between the turns, of (Q.) "\Vill you kindly help me with my Peri- in strongest with the condenser set at the exact wire on the secondary coil very accurate. If the dyne Five, which I constructed according to the position required for the other coils. Add wire spacing between the turns of wire on the different design and instructions in your December issue? to the secondary if the condenser setting is lower coils is not exactly the same, the capacity between J used the specified parts except for the audio than that required for the other coils. the turns of wire will be different, and this will transformers, sockets and oscillation control. 'I After the set is assembled, you should match be sufficient to change the tuning characteristics have been reading the letters of Peridyne builders the tuned circuits again. This time, remove the of the coils. When building them, follow the in- and the results they have obtained with their sets, first radio- frequency. tube from its socket and structions given in the December issue of RADIO and I am sure that my receiver is not working bridge the crystal circuit across the secondary NEWS, both for winding the secondary coils and correctly. My desire is to correct it as follows: winding of the first R.N. transformer. The shields for placing the primaries in the correct position in First, when the local stations are on the air, I should be in place with the adjustable plates at reference to the secondaries. cannot separate them. Each station requires 10 the highest point, when balancing in this case. Note Improper wiring might also cause broad tuning, to 15 degrees on the dial. Secondly, there are a the exact position of the gang condenser for a since it might introduce interactions between the number of whistles indicating distant stations, but local station. Then remove the aerial and ground circuits, which should be kept entirely separate. it is impossible to clear them up so that the wires from their binding posts and connect them Follow the exact layout specified and wire the stations can he heard. I am using a storage "li" (temporarily, by means of clips) to the primary apparatus according to the instructions given in battery for the plate supply and an outside aerial of the second radio- frequency transformer, and re- the constructional article and in the picture dia- about 75 feet in length. I constructed the coils peat the foregoing test with the crystal across the grams. The final cause of broad tuning is im- and shields exactly to your specifications and 1 second transformer, of course. Repeat with the proper adjustment of the shield plates. If the am sure that they are satisfactory." third transformer. If the condenser readings do plates are too close to the coils, losses will be in- (A.) Because some Peridyne constructors are not match exactly, add or. remove wire from the troduced which will be sufficient to "damp" the having trouble with their sets, we are giving a secondary windings, as advised in the previous circuits. list of suggestions to overcome all of the diffi- paragraph. If the dial reading for one of the coils is lower culties which might be encountered with this popu- Use a triple condenser in which each sections than the other two, this coil can be brought to lar receiver. \Ve are sure that you will be able to has exactly the same capacity as the other sections resonance by moving it a little to one side of the clear your own trouble with the aid of these on each part of the scale. The specified condenser center of the shield. This will increase the capacity suggestions. was equipped with small condensers to adjust each between the wire in the coil and the wall of the sections of the condenser individually. If one of shield and will increase the tuning range of the Broad Tuning the tuned circuits has a higher reacting than the coil. Fig. Q2304A indicates this effect. Notice others for a local station, separate the wiring that a capacity exists between the side of the coil This may be caused by the use of too long an further or reduce the number of turns on the sec- and the shield, and when the coil is moved closer aerial or one which is not insulated very care- ondary coil slightly until the signal is loudest to the wall of the shield, this capacity is increased. fully. Use an aerial between 75 and 100 feet when the condenser is tuned to exactly the same This also shows why the coils must be centered in length. This will give the correct amount of point required for the other coils. When the very carefully in the shields after they have been selectivity and sufficient signal pick -up so that you circuits are all in resonance, a very slight fraction matched previously. can receive both local and distant stations. Also, of a tuns on the Peridyne plates will change the make sure that the ground connection is a good operation of the circuit. You will notice this to Volume and Sensitivity The one; the use of a poor ground will greatly reduce some extent by broadening of the tuning. If the set does not have the is ex- will "pep" that the volume and selectivity of any set. radio -frequency circuits oscillate violently when pected from it, the trouble is due to poor tubes, The main cause of broad tuning in the Peridyne perfect resonance is reached, although this action too high a "B" voltage on the plates of some or resistor 123 receiver is lack of circuit resonance. You must is under perfect control by varying all of the tubes, incorrect "C" bias, lack of cir- match the radio- frequency stages within five per- in tine set. This resistor must have the correct cuit resonance, defective parts or the incorrect cent, so that the Peridyne plates can then bring value, 0-100,000 ohms. placement of the crystal detector. If the tubes the set into exact resonance. To do this you must are suspected, the only thing to do is to try new have the coils matched very closely -within about ones. However, first check the plate and grid three percent- before they are placed inside the voltages on the in to be that these --1 tubes order sure shields. You can match the coils by using therm values are correct. The lack of circuit resonance with a crystal detector as a small crystal receiver. can be overcome as explained previously. Connect the small winding or primary of the first coil to the aerial and ground. If your local sta- Distortion tions are very close by, place a small fixed condenser of about .00025 -mf. its series with the aerial This is usually due to the first (detector coupled) wire. This will reduce the volume slightly aucl audio -frequency tube being overloaded. If a 201A increase the sharpness of tuning considerably. Then tube is used in this socket, the plate voltage should connect the carborundum detector or other crystal never exceed 2214 volts. The results can often he detector to one of the wires from the larger or SHI[:LD improved by reducing this value. secondary coil. The other terminal on the crystal is A 112A tube can be used in this position with connected to a pair of phones and the phones are slightly better results and the "B" voltage may be in turn connected to the other side of the second- increased. In this case, however, it may be neces- ary. You may have to connect a .001 -mf. fixed sary to insert a "C" battery between the negative condenser across the two wires to the head phones filament side of the last radio -frequency trans- in order to hear the radio signals. Une section of former and the negative "A" battery terminal. the gang condenser should be connected across the The value of this "C" battery depends upon the secondary coil, to tune it. plate voltage, but a value of 11/2 to 3 volts will Tune in a local station to the maximum volume. usually be sufficient. The negative terminal of is not very sharp, use the small the battery should be connected to tine secondary If the tuning Q. 2304A fixed condenser in the aerial wire, as explained terminal of the coil and the positive terminal of the if one is being used already, try a i.attery should be connected to the negative filament above; or, The centering of the coils in the shields is very smaller one. After you tune in a stations sharply, terminal. Connect a by -pass condenser of about important. The change in the capacity between .05 -mf. capacity across the "C" battery. disconnect the first coil and try the other two in the coil and the shield aven the former is off turn. If they are matched correctly you will not center is shown by C2. Cl is the normal You must also adjust the filament rheostats very have to readjust the variable condenser. If you capacity. carefully. This point was explained thoroughly in

www.americanradiohistory.com Radio News for October, 192S 351

(Q.) '-Can I take an eight-tithe Ultradyne receiver, remove the antenna coil and oscillator coil, and replace them with plug -in coils for short waves? Will the oscillator work correctly with these few PERIDYNE PLATE turns and could the tickler coil in the modulator circuit be wound to cover all of the short -wave hands.? Jf the Ultradyne circuit will not work t^ correctly in this matter, will you give me the 2 constructional details for a suitable short -wave 1- superheterodyne, specifying the correct intermediate - frequency amplifier and giving the values of all the parts used ?" (A.) We do not believe that the model L -2 Ultradyne would be satisfactory for receiving short waves, since the values of the tuning condensers, both in the aerial and oscillator circuits, would have to be changed; and we doubt if the oscillator would operate correctly on the very short wavelengths. The .0005 -mf. tuning condensers employed in this set have too great a minimum capacity to be used successfully with a short-wave set, and this would necessitate removing them and replacing CORRECT INCORRECT them with .00015- or .00025 -mf. condensers. On the broadcast band, the set would not operate satis- B C factorily with these smaller condensers. Q. 2304 We are printing the diagram and specifications for a short -wave superheterodyne which will work To get the greatest efficiency from the Peridyne 5, the adjustable plates Hurst be in the correct relation to the coils. If they are closer titan 1 -inch, the results rail/ be poor. very efficiently on wavelengths up to about 150 meters. The set was constructed by the writer with a second oscillator coupled as shown to the last T.F. transformer. This was used to receive can is very close to the top. the constructional article. Distortion may arise shield plate in the continuous wave code signals. The set employs more 4 complete revolutions of from overloaded audio -frequency tubes in the other usually not than four tubes in the radio -frequency section, which when the No. 32 screw is used. stages, or from poorly designed audio -frequency the adjusting knob would make a total of six tubes in the complete a of transformers. The choke coil and the by-pass con- When the set is completely balanced, quarter receiver. Three or four stages of intermediate fre- a knob will be sufficient to denser in the plate circuit of the first audio -fre- turn of the adjusting quency amplification may he used instead of the and out resonance. quency tube, if they are of the wrong value, will throw the coil in of two specified, thereby increasing the radio- frequency also cause distortion. Use the specified parts in amplification and also the sensitivity. these positions. This short -wave superheterodyne consists of a VOLUME CONTROL IN A.C. SETS short -wave regenerative detector circuit of the usual Detector Interfiex type, coupled to an intermediate- frequency ampli- (2305) 1\Ir. W. O. Pearce, Bayonne, N. J. do fier operating on a rather low frequency. When The Carborundum crystals used for detection writes: most of them will dealing with waves below 125 or 150 meters, the not all work equally well, and (Q.) "In constructing an A.C. set, I am en- position detuving to an incoming signal offered by an oscil- only work in one way. By reversing the countering difficulty in knowing just how to control volume and can often be lating detector is not sufficiently great to cause any of the crystal, the clarity the volume. The usual filament control method is, order to obtain clear appreciable loss in signal strength. For this reason, increased considerably. In of course, out of the question because of the slug- you may have to place the can make the first detector self -heterodyning. reception, in some cases, gish operation of the filaments in A.C. receivers. condenser between the crystal and In this way, it can be made to furnish the inter- a small by -pass Can yott help me out in this matter ?" battery terminal on the tube mediate frequency, by beating on the incoming the negative "A" (.\.) The tube manufacturers suggest a system should be connected to the signal. This arrangement is similar to that used socket. This condenser which is a very convenient and satisfactory one. which is connected to the grid in the usual superheterodyne, except that with the side of the crystal Tt consists of a potentiometer connected in the socket. _\ small semi-variable latter a separate oscillator is used. terminal on the tube aerial circuit, according to Fig. Q. 2305:\ or B. 20 -mmf. and 500 -mmf., can be In Fig. Q. 2306A, the coils L, LI and L2 are condenser, between In the first case, a potentiometer of about 3,000 purpose. By adjusting this con- the primary, secondary and tickler respectively of employed for this or 4,000 ohms resistance, with the 'slider connected capacity can easily be obtained. the input circuit; they can be almost any form denser thc required to the circuit and the two outer terminals grid of coil designed for short -wave work. (The coils aerial and ground, is employed. This method to the specified for the five -tube, short-wave and broad- Wiring used when a new set is being constructed. is usually- cast receiver described in the April, 1928 issue of It eliminates one of the tuning controls. The other The wiring in the Peridyne set is extremely im- RADIO NEWS will be ideal for this purpose.) The method makes use of a potentiometer with a re- portant and you must do it very carefully. Con- tuning condenser C1 has a capacity of .00015 -mf., sistance of about 25,000 ohms. The slider in this siderable interaction can be prevented by separating and the regeneration control C2 a value of .00025 - is the primary of the antenna the grid and plate leads as far as possible. The case connected to mf. The radio -frequency choke coil in the detector coupling coil, while the two outer terminals are plate and "13" plus leads can he bunched together plate lead is extremely important, and a very good connected to the aerial and ground. This method if desired. At the points where the grid and plate one should be used. to 90 degrees as is more suitable for equipping an existing receiver. leads cross, ais angle as close . \s you will notice, the grid return of the de- There are several other methods which are satis- possible should he used. All of the grid and plate tector is placed on the negative "A" battery ter- factory for controlling the volume of sets of this leads should be as short as possible. minal. It was found that this method gave more the use of a 50,000 -ohm variable type, including stable operation than the usual positive return, resistor connected across the secondary of one Coils and Condensers although loth methods should be tried and the better of the radio-frequency transformers, and the use between the bottom of the R.F. one used. If you desire to make the radio-fre- The distance a high resistor in series with the positive "B" of quency choke coil, it can be wound on a one -half transformers and the bottoms of the shields can battery terminal supplying current to the radio. no inch tube with approximately 150 turns of No. 30 vary between 1 inch and 1% inches with great frequency tubes. The last mentioned method, how- all of the coils to 36 double cotton covered wire. change in the efficiency, providing ever, may cause trouble with hum. are exactly the same distance from the bottoms. You must place the coils in the exact center of Intermediate- Frequency Amplifier the shields (when looking from the top), so that The intermediate- frequency amplifier in this re- the capacity between the coils and shields will be A SHORTWAVE SUPERHETERODYNE ceiver is of the usual type, with two broadly tuned the same in each case. This position can be changed (2306) Mr. C. O. Lorenz, San Antonio, Texas. transformers and a rather sharply tuned filter. A slightly if necessary, as explained under "Broad writes: potentiometer is used for controlling oscillation. Tuning." If the circuits do not match within five percent, you will not be able to get the correct balance. and the Peridyne plates will apparently have no effect on the operation of the set. This is due to AERIAL the fact that the capacity between the Peridyne plate and the top of the coil has a very small value. It was found on test in the RADIO NEWS ANTENNA laboratories that the maximum capacity was ap- COUPLER proximately .000013 -mf. when the Peridyne plate was touching the top of the coil, and the minimum capacity .00000775 -mf. when the shield plate was R1 R1 as far away from the coil as possible. Peridyne Shield Plate

The constructional article ont the Peridyne re- R2 R2 ceiver explained that when the Peridyne shields OIL B were used in other circuits, the shield plate should also never be closer than one inch. The article A. C. method of stabiliz- explained that because of the FILAMENT SUPPLY A C ing used in the Peridyne, this value can he de- GROUND creased to within one -half or three -quarters of B an inch. (See Fig. Q. 23041'. and C.) Less than A Q. 2305 one -half of an inch will result in a considerable absorption of the current from coil, and as the dis- TWO methods of coupling the aerial of an A.C. receiver to the first tube are shoran here. In A, the tance is decreased, the efficiency of the circuit resistor, RI, has a trapue of 3,000 ohms: is A, the resistor. Rl. is about 25,000 ohms. R2 in both will fall off greatly. The notmal position for the cases i..- the icuter- tapprd filament resizior.

www.americanradiohistory.com 35' Radio News for October, 1923

R1 R. F. CH01( EXTERNAL . ÿ_ % 201A OSCILLATOR 0060 L- ''r' a R2 p C3 T2 T3 TL TO AUDIO R5 AMPLIFIER ° LL A + ( lJ

11111

'I(.2 B

i L2

SHORTWAVE UNIT B +90 VOLTS B +45 VOLTS

Q. 2306A

lu onüuory .Jiurt :ea.'e rege/terulirc reacher cou i+c made info a .chartevate superheterodyne, by eoupliny it to u 30- kilocycle intermediate- frequency amplifier. A separate "B" battery is used for the first tube.

The filaments are controlled either by a rheostat last intermediate- frequency- transformer. This os- is as follows: the actuating voltage from a "C" or by automatic filament ballasts. The potentiometer cillator was used for the purpose of receiving con- battery causes the crystal to get thinner and to should have a resistance of about 400 ohms; an tinuous -wave code signals. The audible beat note become longer between the metal plates. Because ordinary 10 -ohm rheostat will be satisfactory for is produced by the signal in the intermediate - of the strained position of the crystal, it starts to controlling the filament current. The detector is frequency amplifier, mixing with the current of release or get thicker and this starts a pendulum- coupled to the last I.P. transformer through a grid the oscillator. In the usual regenerative receiver, like action which is maintained by the exciting condenser and grid leak, C6, 1t2. The condenser of course, the oscillations produced by the feed- voltage and the alternating current in the grid C6 has a value of about .00025 -mf.; the value of back coil is used to produce this audible frequency. circuit of the tube. The expansions and contrac- the grid leak depends upon the characteristics of The oscillator was of the standard Hartley type, tion of the crystal produces an alternating cur- the detector tube. A resistance of about 2 meg- with two 600 -turn honeycomb coils for the in- rent, as explained above. ohms will be suitable for most tubes. ductors. A tuning condenser of .001-inf. maximum In making the crystals, they are cut very care- The primary and secondary of the filter coupler capacity was used to obtain the exact frequency fully on planes determined by measurements with are shunted by .0005 -mf. fixed condensers. These desired. This frequency should be between 600 and optical instruments and they are then ground down condensers must be matched closely in order to 1,000 cycles higher or lower than the intermediate with the opposite sides perfectly smooth and paral- produce satisfactory results; it may be advisable frequency used in the amplifier; the best adjust- lel. The thickness of the crystal is generally used to use semi -variable condensers so that the two ment is found by trial. to determine the frequency, and manufactured circuits can be adjusted correctly. The filter coupler The audio- frequency amplifier has been omitted, crystals are finished either round, square or oblong. is wound on two separate spools, as shown in Fig. since any good type of amplifier may be employed. The crystal mounting consists of two plates of a Q. 2306B. Wooden discs two inches in diameter It is advisable to use separate batteries for the good conducting metal, such as copper or brass. and three -quarters of an inch wide are used for the detector -oscillator and the intermediate- frequency The surfaces of the metal between which the cores; the sides are fibre discs four inches in amplifier. If desired, the "A" battery can be crystal is held are ground smooth, and the crystal diameter. The two spools are fastened together common, Inn much better results arc noticed when is usually held in place by the pressure of a spring with a long brass screw and several nuts, as shown. a separate "B" battery is used for the first tube. on one of the plates. By adjusting the distance between the two coils, This battery should have a value between 22 and In testing the crystals, a vacuum -tube circuit the tuning can be made sharper or broader, as 45 volts, the correct voltage, of course, depending with a receiving tube is used. The grid circuit desired. Both the primary and secondary are wound upon the tube used in this circuit. The condenser of the tube contains the crystal shunted by the with No. 32 D.C.C. wire and each contains 950 C3 in the grid circuit of the short-wave unit should "C" battery, which has a radio- frequency choke turns. The wire should be wound jumble fashion have a capacity of .0001 mf.; the grid -leak value coil in series with it. The plate circuit contains and not in layers. will have to be found by experiment. an inductance coil of suitable size, shunted by a The broadly tuned intermediate -frequency trans- variable condenser in series with a hot -wire millianr. formers are constructed with iron cores. A piece meter. As the condenser and coil are tuned ap- of three- quarter inch fiber tubing about h inch proximately to the fundamental frequency of the long is used to hold the core. Soft iron wire of PIEZO- ELECTRIC CRYSTALS crystal, the hot -wire milliammeter starts to reg- about 24 gauge is packed into this tube until sto ister. When the two circuits are exactly in res- more can be forced in. It is advisable to use enam- (Q!. 2) What is the piezo -electric effect and onance, the tube stops oscillating because the eled wire or to insulate the wires with shellac how is it used in radio? I have often heard of tuned choke circuit in the plate has an extremely before placing them in the tube. The spools are quartz crystals and piezo- electric crystals being high impedance at the working frequency. For a loss made by forcing fibre discs 2 inches in diameter used in transmitters but I am at to know this reason, in a transmitter, this circuit is always over the ga inch tube, as shown in diagram Fig. where to find information on this subject. tuned to a slightly different wavelength than the Q. 2306C. The primary is wound with 2,500 turns (A. 2) When a piece of quartz of correct shape is crystal. of No. 36 enameled wire and the secondary with placed between two metal plates, a condenser is Quartz crystals are being used more and more. 2,600 turns of the same wire. formed with the quartz as the dielectric and the Practically all of the large broadcast stations em- The intermediate -frequency transformers should metal pieces as the plates. When the plates are ploy them now to keep their waves constant. be spaced about 2 inches apart and the cores should connected to a source of alternating current, the be at right angles. In the original receiver, an quartz is found to expand and contract; as the external oscillator was coupled inductively to the emerges on the plates increase and decrease, clue to the changes of polarity. It is also found that _3_ 3_ an alternating potential is generated by the crystal PRIMARY SECONDARY itself; this can be detected a sensitive galvanom- if i 950 TURNS OF NO. 32 D. C. C. WIRE eter is connected to it. From this explanation it 2500 TURNS 2600 TURNS ON EACH COIL will be seen that the action is reversible: alternating OF NO. 36 OF NO. 36 electric currents cause the crystal to expand and ENAMELED ENAMELED contrat, and lengthening and shortening of the WIRE WIRE crystal cause it to produce alternating electric im-

pulses in the plates. SOFT IRON - Although action this takes place to sonic extent WIRE CORE on any frequency, the action is much greater on one frequency, depending on the size and thickness of the crystal. The thinner and shorter the n- crystal, the higher the natural or resonant frequency. When a crystal is placed in the grid cir- FIBRE FIBRE DISCS cuit of a vacuum tube and an exciting voltage is FIBRE impressed on it, it immediately starts to expand TUBE DISCS and contract, which causes the plates to become charged. If the vacuum -tube circuit is tuned to DETAILS WOOD a frequency close to that of the natural frequency OF Ti of the crystal, the crystal will feed currents of CORE DETAILS OF T2_ AND T3 this frequency to the grid of the tube, whose plate circuit will deliver more powerful impulses at the Q. 2306C Q. 2306E1 same frequency. These currents are then amplified and impressed The tuned filter for an intermediate amplifier on the antenna, in the case of Broadly tuned transformers with iron cores for of about 30 kilocycles ran be made as shonnc a transmitter. the amplifier may be constructed around a g. above. Another ex»t.natioo of the action of the crystal inch tube in this manner,

www.americanradiohistory.com Radio News for October, 1928 35

:El 11vl N Cam

Power Supply Transformers These transformers supply full wave rectifiers using two UX -281 tubes, for power amplifiers using either 210 or 250 types power amplifying tubes as follows: T -2098 for two 210 power tubes, $20.00; T -2900 for single 250 power tube, $20.00; T -2950 for two 250 tubes, $29.50. Double Choke Units Consist of two 30 henry chokes in one case. T -2099 for use with power supply transformer T -2098, $14 ; T -3099 for use with transformer T -2900, $16; T -3100 for use with transformer T -2950, $18. Tu0ioN Power Compacts A very efficient and compact form of AUDIO ÑS ORMER, power supply unit. Power transform- R er and filter chokes all in one case. Type R -171 for Raytheon rectifier and UPREME in musical performance, the 171 type power tube, $15.00; Type R -210 for UX -281 rectifier and 210 new Thordarson R -300 Audio Trans- power tube, $20.00; Type R -280 for former brings a greater realism to radio UX -280 rectifier and 171 power tube, reproduction. Introducing a new core mate- $17.00. rial, "DX- Metal" (a product of the Thordar- Speaker Coupling Trans- son Laboratory), the amplification range has formers A complete line of transformers to been extended still further into the lower reg- couple either single or push -pull 171, ister, so that even the deepest tones now may 210 or 250 power tubes into either high impedance or dynamic speakers. be reproduced with amazing fidelity. Prices from $6.00 to $12.00. The amplification curve of this transformer Screen Grid Audio Coupler to is practically a straight line from 30 cycles The Thordarson Z- Coupler T -2909 is 8,000 cycles. A high frequency cut -off is pro- a special impedance unit designed to amplifica- couple a screen grid tube in the audio vided at 8,000 cycles to confine the amplifier into a power tube. Produces tion to useful frequencies only, and to elimi- excellent base note reproduction and that may reach the amplification vastly in excess of ordinate undesirable scratch nary systems. Price, $12.00. audio transformer. r 7 When you hear the R -300 you will appre- THORDARSON ELECTRIC MFG. CO. 500 W. Huron St., Chicago, fl. 35834. ciate the popularity of Thordarson trans - formers among the leading receiving set man- Gentlemen: Please send me your constructional booklets on your power amplifiers. I am especially ufacturers. The R -300 retails for $8.00. interested in amplifiers using tubes. THORDARSON ELECTRIC MANUFACTURING CO Name 1895 `7ransfdrmer Specialists Since No WORLDS OLDEST AND LARGEST EXCLUSIVE TRANSFORMER MAKERS Street and USA. 'tturon and Kingsbury Streets -- Chicago.Ill. Town.. State.

Moore .MV von .caro it in RAnIO gEIVS www.americanradiohistory.com 354 Radio News for October, 1928 A Completely Shielded Short -Wave Receiver (Contiiuted front page 337)

nected in the filament circuit of the 222 tube should not prove difficult, provided the has a total resistance of 25 ohms, with a 10- listener is located within 100 miles of one ohm tap; the 10-ohm portion being con- of the larger cities, and it provides an ex- nected between the filament and the ground cellent check on the operation of the set. connection. By selecting the proper resistors, this set may also be operated from three volts of dry cells, due to the low current drawn by the 222 and 199 tubes. The sockets used for the interchangeable coils are mounted on small wooden blocks one inch in height to reduce the capacity between the terminals on the base of the sockets and the metal cabinet.

OPERATING HINTS The first step after the set has been assembled and connected with the necessary batteries is to make sure that the detector oscillates over the entire range of each set of coils. Ninety volts was found to be about right for the plate voltage on all three tubes; therefore, a single lead is used to supply the plate voltage for all tubes. A 45 -volt tap is taken from the "B" battery for the screen grid of the 222 -type tube. The set, opened at The operator will find that a little experience is required to obtain the best results When the extremely low -wave coils are from this set, and he should not become dis- used the operator will find that very care- couraged if he fails to hear any short -wave ful tuning is required, especially for phone signals the first time the set is used. Per- or broadcast stations. However, there are haps the simplest way of learning to tune a number of high -power stations which are the set is to plug-in the long -wave coils, re- broadcasting on the lower wavelengths on set No. 1, and tune in some of the low - regular schedules, and these will serve as a wave broadcast stations or the harmonics of check on the operation of the receiver on RADIO some of the higher wave stations. This the small coils. TUBE fi'AC Sets The unqualified endorsement of CeCo Radio Tubes by the leading radio engineers, including Cocka- day, Lynch, Hurd, Bernard, and 15" many others, is conclusive evidence of their proven performance. MAKE ALL SCREWS HOLES FIG.SB WITH 5/3z" DRILL AND Their uniformity, extreme clear- COUNTERSINK. ness of reception, and absence of A. C. hum, are largely due to the exclusive CeCo process of evacua- tion. You owe it to your radio to try a set of CeCo tubes to gain the utmost in radio reception. A ALL HOLES THIS Slit CeCo dealer will gladly advise you 9/1e" IN DIAMETER. which types to use.

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CeCo MANUFACTURING Co.,Inc. PROVIDENCE. R.I. Above. drilling layout for panel. Bclote, drilling layout for back of cabinet, on which insulating strips are mounted. Please say yon saw it in RADIO News

www.americanradiohistory.com Radio News for October, 1928 355 Enjoy Any Miraco 30 Days -then decide. Return EVERYTHING, our expense, unless thoroughly delighted.

Latest All- Electric Latest All- Electric Wonderful Selection of Beautiful New Cahinet "AC -9" "AC -8" For AC -9, AC -8 and Battery Super -Shielded AC Chassis Super -Shielded AC Chassis 7's and 6's $83.75 $71.50 30 DAYS' TRIAL -TAKE ''UR PICK Speaker, tubes and cabinet extra Speaker, tubes and cabinet extra Newest Type Richly designed, gen- Newest Type uine walnut console of finest type. Elec- 7 -Tube tro dynamic cone, 6 -Tube magnetic cone or long air column speaker. Battery- Operated \1'onrlcrful value! Battery' -Operated Super- Shielded Super- Shielded Chassis Chassis Equipment extra $49'88 Equipment extra Beautifully graceful . Spinet model, hand- somely designed. Genu- ine walnut electro-dy- Immic, or magnetic cone. (This model for "AC-9" and "AC -S" only. )

The saute charming ARK REGISTERED Spinet model. for battery or AC sets. Elec- t ro- dynamic or magnetic cone or atr col - ti, .n speaker. Cathedral Tone- Super -Selective- Powerful Distance Getters Celebrating its ninth successful year. America's big, Many thousands of Miraco's - bought after 30- old reliable Radio Corporation springs a genuine clay home comparisons -are cutting through locals sensation in high -grade sets. With its latest, super- and getting distance with the tone and power of powered, I -dial Miraco's -the wholly self -contained, costly sets -their delighted users report. Miraco's hum -free, AC -S and are laboratory - built AC9, using AC with finest parts, and tubes, or the new embody nine years' 6- and 7 -tube models actual experience in for batteries or elimi- constructing fine sets. nators -you are guar- Approved by radio'r highest authorities. A most popular walnut anteed values and sav- rcounts to Hi -Boy Console. with ings unsurpassed in drop -leaf desk. For all the fine set field. Miraco Sets. Deal Direct with Choice Compare a Miraco of speakers. Astonish- er-Agents Big Factory ingly priced. with highest - priced radios, for 30 days in Everything reaches you packed and your home. Surprise A Miraco will so delight you and those who hear it splendidly and entertain your that people will ask you to get M iraco's for them. In rigidly tested to in- get their this way our sales grow by leaps and bounds each year. sure your instant en- friends - radio experience needed. You 1005ó No selling necessary -no thusiasm. Enjoy the opinions. Unless your set and make as much extra can easily pay for outfit 30 days -them r^r delighted, return ev- money as you wish, spare or full time, by getting our erything -the complete Amazing Special Offer. decide. Liberal 3-year outfit--at our expense. guarantee on each set. safe, save lots A Lo -Roi- Console that's a Your decision is final Play of gem and very low - priced. -absolutely! money, and insure sat- Walnut finish. For all Only exceptionally fine isfaction by dealing Choice of Miremo sets. radios, of the very latest approved type, at rock - direct with radio's old reliable builders of fine sets speakers. bottom prices, could possibly back up so liberally -ninth successful year. unconditional a guarantee. Send coupon now for Arna:itig Special Factory Offer! UIPORTANT NOTICE! "30 -Day Free Trial" offers usually are money -back Don't Confuse with Cheap Radios guarantees, frequently only ois the "set." Please With its rich, clear cathedral tone, hum -free opera- understand that unless you are thoroughly pleased A new type arm -chair con - tion, tremendous "kick" on distant stations and we pay return charges and refund the FULL pur- ", sole (for AC sets only) con- price on both the "set" and that is very much admired. razor -edge selectivity- -with its costly, sturdy chase ALL equipment Genuine walnut. Electro- struction, latest features, beauty, ease of tuning -tubes, cabinet, speaker, antenna (also on bat- dynamic or magnetic cone. and economy -a Miraco will make you the envy of teries or eliminators with 6- and 7 -tube sets), A splendid value. many whose radios cost 2 to 3 times as much. Could any offer be fairer,' MIDWEST RADIO CORP'N, 404 -AO Miraco Bldg., Cincinnati, Ohio CATALOG, AMAZING A popular. inexpensive com- BEAUTIFULLY ILLUSTRATED SPECIAL FACTORY bination. Table model Miraco Realm-Write'/ OFFER, TESTIMONY OF NEARBY USERS -All the proof you want -of our hon- set on handsome table speak- esty, fairness, size, financial integrity, radio experience and the performance of our er. Table speaker also is sets -including Amazing Factory Offer -sent with catalog. sold separately.

Miraco table model MIDWEST RADIO CORPORATION, THIS COUPON sets may lie had Pioneer Builders of Sets -Ninth Successful Year, IS NOT In tnetal or wood Miraco Building, Cincinnati, Ohio. AN ORDER cabinets. Wood cab- 404 -AO inets in walnut or new shaded silver- WITHOUT OBLIGATION, send free catalog, Amazing Special F-ictory Offer, testimony eh runic finishes. of nearby users, etc. Cathedral electro- 1 dynamic or mag- .... Agent .... Dealer netic speakers to User match. Name Address

Please say you saw it in RADIO NEWS www.americanradiohistory.com 356 Radio News for October, 1928 The Search for the Perfect N Amplifier (Continued from page 339) put impulses would, in effect, be shorted Cle -Ra -Tone across the "B" battery. Tubes of the 199 or 201A types should be found quite suitable in either position. Considering the circuit functionally; pre- Radio sumably the rectified half -wave proceeds from the plato to the filament circuit and there influences the electrons emitted from Sockets the amplifier filament, being received in an amplified form in the grid output circuit. We have achieved a great part of our Whether you want amplifier ideal in dispensing with all electromagnetic and electrostatic couplings and purer tone or clearer a direct low- resistance path be- providing DX, you will get it tween detector output and amplifier input. Any distortion that now occurs is due solely with Quality Tele- to incorrect operating conditions and the remedy is within the scope of any radio fan. vocals. All standard types. Ask for them SECOND STAGE NOT AVAILABLE The only snag lies in the fact that, as yet, at your dealers. I have not found it possible to add a further similar audio stage. Nevertheless, the extra is quite as great W9A volume given by one stage Televocal as that provided by a well- designed trans- Corporation Specially Designed former coupling. How this can he so is a Televocal Building for little perplexing; since it would appear that Dept. A -3 the total amplification obtainable would 588 12th Street A. C. Detector Tubes be limited to the "mu" of the tube in use; West New York, N. J. Spring supported, shock absorb- which in the ease of 199 or 201A types more than about eight. ing. The tube -holding element could not amount to balanced Undoubtedly, however, the extra amplifi- "floats" on perfectly cation is provided by some form of audio springs. Reduces microphonic regeneration or reflex action; also, it should disturbances, tends to lengthen be noted that the unconventional connec- life of tube, and lessens the possi- tions to the tube may alter its amplification i-w eV sä1 bility of short -circuiting closely- factor and impedance very considerably. Quality Tubes spaced tube elements. Whatever happens has no adverse effect

. on the quality and purity of reproduction, Y -Type, Green Top, for 5 Prong as some super-reflex and audio- regenerative A. C. Tubes: for mounting on top of panel, $1.00; for direct circuits unfortunately have. attachment to panel, 75c. Radio- frequency amplifiers may be added Lowest Prices as desired and, to preserve the efficiency Top, for Standard UX Red of the current as a whole, they should be Tremendous stock and sales vol- Type Tubes : For mounting on top of panel, 75c.; for direct properly neutralized. If further amplifi- ume, with rapid turn -over to the attachment to panel, 50c. cation on the audio side is desired, the thousands of radio dealers we writer recommends the addition of a stage serve enables us to make you of double- impedance coupling. worthwhile savings at lowest Shelf Supporting wholesale prices. Write for lat- The resulting over -all efficiency of the est, new illustrated Catalog "B." Brackets complete five- or six -tube receiver should meet the requirements of the most ardent of DX fans and the most fastidious of musi- Allied Radio cal ears. CORP RATI ON 711 W. LAKE STREET, CHICAGO RADIO TERM ILLUSTRATED LEARN CODE At Home with the Teleplea Code Sender. Reproduces actual sendtna of expert operators. A decided advantage for the neat -AND Sends messages. radiograms, etc. -regular code I HAVE trame at any speed. You "listen and learn." and substantial construction of IT FROM RELIAS No experience necessary. Endorsed by SOURCES THAT U S. Navy and leading schools. Complete the set. Used when panel and THEIR SIGNALS W set of Instruction Taper (Wireless or SE Morse) furnished. Remember only subpanel are assembled to make you the 01 teal DX. ETC.,- FTC code brings thrill Write for Booklet NR10. one complete removable unit. The TELEPLEX COMPANY Adjustable Brackets permit panels 76 Cortlandt St., New York, N. Y. to be mounted vertically or at any desired angle. REE RADIO CA ALOG Since t he dawn of Radio. Barawik hue been known the world No. 8629 -Rigid -70c. per pair over as headquarters f radio set builders and fane. Itere under one roof. ev rythtre you need -sets, parts, No. 9029-Adjustable---$1.25 per pr. supplice- thousendsof prod ucts -ready toehip toyou the a.ao your order ar r,res. Barawik priceseave you money. Barawik bervi,.e save, you time. Barawik merchandise al pleases. A Quart er million Satisfied At all Radio and Electrical ustomers T. Barawik is Best." Let us send you she ma Barawik Book free and prove it to Dealers and Jobbers youreett. CANAL STA. BARAWII( CO?cHICAOO, B.S.A: Benjamin Electric Mfg. Co. 120 -128 S. Sangamon Street A -C FILAMENT TRANSFORMER Chicago Supplies stepped down current from ONLY $487 no volt 50.60 cycle lines for six type 226 tubes. two type 227 tubes, and two type 71 New York San Francisco tubes. Guaranteed. Only 64.87. Order today. Money back If not satisfied. 247 W. 17th St. 448 Bryant St. W. "A Grid Leak" Illinois Transformer Co. Dpt c icago Please say you saw it in RADIO NEWS

www.americanradiohistory.com Radio News for October, 1928 357 Safeguard Your Radio Investment With Jewell Instruments

Safeguarding money invested in a Radio Receiver is just as essential as the protection which you accord your other valuable investments. In the new alternating current set you have an expensive investment, especially in the high -priced A.C. tubes, which are commonly burned out by variations in voltage of house Pattern No. 77 lighting circuits. .It is true that most sets carry a compensating arrangement, but which tells nothing of the voltage received by the filaments of the tubes. A portable instrument, moderate in price, but very effective for snak- Right there is where you can safeguard your investment by purchasing a suitable volt- ing the various alternating current meter which will enable you to keep your tube filament voltage in correct adjustment. tests required in the adjustment of Then, too, there is the annoyance that comes with out tubes or when the line filament and line voltages. Ranges burned voltage drops to a point where reception is impossible. of 0 -3 -15 -150 volts are ample to check and adjust all circuits. Cur- Jewell has portable and panel mounting voltmeters that are exactly right for making rent draw is very small. line voltage adjustments. Ask your nearest radio dealer about them or write to us direct. Our Radio Instrument Catalog No. 15 -C, together with Form No. 1145, covers them in detail. Write for a copy of each.

Pattern No. 64 Thermo -Couple Ammeter

A highly efficient instrument for working the short waves. Losses Pattern No. 139 are less than V2. of the minimum High resistance voltmeter of the required by the Navy. D'Arsonval moving coil type. suitable for use by the individual in checking and adjusting B elimini- The JEWELL TRIO nator voltages. Scale range of 0 -300 volts covers all ordinary For Amateurs and Experimenters requirements. It is a thoroughly reliable instrument and can be de- The Jewell Trio of amateur broadcasting instruments, Patterns Nos. 54, 64, and 74 are pended upon. still making radio history. Many of the recent successful pioneering airplane ventures have been guided by Jewell instruments. Where success and life have been trusted to their reliability; they have proven their worth. Every amateur and experimenter should use them. The Pat- tern No. 64 above illustrates their general appearance, as they are uniform in size.

Pattern No. 54 Pattern No. 64 Pattern No. 74 Used for measuring plate A thermo couple type This A.C. instrument is voltage in transmitting sets radio frequency ammeter. It widely used for filament con - as well as for general labora- trot of power tubes. The is extremely accurate and tory work, they are avail- movement is a rugged movable in direct current ranges, has a guaranteed overload ing vane type of prcven running to relatively high capacity of 50 %. The losses voltages, and also in various worth. It perfectly matches ammeter and milliammeter are very low, being less than the appearance of both Pat- Pattern No. 190 ranges. one half the Navy minimum. terns Nos. 54 and 64. type panel mounting A.C. Flush The Jewell Trio is described in detail in our Radio Instrument Catalog No. 15 -C. Write instrument, very valuable for panel for a copy. control of A.C. filament voltage and for line voltage checking. The numerous ranges in which it is available enables a choice to cover "28 Years Making Good Instruments" the requirements of any radio set. Jewell Electrical Instrument Co. 1650 Walnut St., Chicago, Ill.

www.americanradiohistory.com 358 Radio News for October, 1928 Radio Wrinkles fRaythernfl (Continued from page 341) moved from room to room -about the house. I have found that by taking the base KirL.oMLamw from an old or defective UX -type vacuum tube and fastening it to the speaker terminals and putting UX -type sockets on the floor at different points in the house, the speaker can be easily moved from room to room. - Bought Your New The most important thing to watch out Yet? for in making this type of installation is Dynamic Speaker VI ELL, when you do, the voltage drop in the line leading to the for the Elkon field winding. By using No. 14 solid wire, a Rectifier you'll find it on good dynamic- speakers 25 -foot extension can be made without any about in the position noticeable drop in voltage. In my own shown above-no matter whether in sets, cabinets home the speaker installation is about 40 or separate units. You feet from the set and "A" battery, but I can't fail to recognize it, by its solid, husky ap- have a voltage drop of only about one - pearance. eighth of a volt, which does not interfere For your own protection make the dealer show you with the operation of the speaker. I use the Elkon name plate on a 210 -type tube in the last stage of the the end of the rectifier. audio amplifier and, although the 450 volts for the plate of this tube has to travel ELKON through 80 feet of wire before it reaches the tube, this does not seem to affect it RECTIFIERS in the least. Of course, it would be much Standard equipment on the better better and safer to use some kind of out- DYNAMIC SPEAKERS. Q. ELIMINATORS put coupling device between the output of and BATTERY CHARGERS the 210 tube and the speaker. This would keep the high voltage out of the line and TWO PIONEER if a short -circuit occurred, no damage wduld be done. -Contributed by C. H. Jenkins. TELEVISION ACCESSORIES The Raytheon Laborator- Making a Glow Tube for ies invite correspondence Television Experiments both engineers and from AN essential piece of apparatus for a amateurs in regard to these television receiver is a neon tube. Tele- two accessories now in vision experimenters who do not have access ATLANT/C C /7-Y, N . successful operation. to a vacuum pump and who are unable to A new and beautifully furnished Raytheon Kino -Lamp is purchase a neon tube Fire -proof hotel situated on South the first television- recep- North Carolina Ave.. in the Board- of suitable size may walk block near the Steel Pier. tion tube developed to find the following a Where personal service, homelike work on all systems. simple expedient for surroundings and superior food - this purpose. abound. Raytheon Foto -Cell, an Carefully selected clientele and extra sensitive broadcast- friendly prices. Write for Book- let D. ing tube, is supplied in Arthur O. Franklin, Everett L. Cops, A rectifier tube filled with Proprietors either hard vacuum or gas .ei!l flash on the application of suitable volt- gas -filled types. age and may be used in television experiments. RAYTHEON MFG. CO. EVERYTHING IN RADIO Kendall Square Bldg., Cambridge, Mass. secure a QRS First We supply every radio need from 400- milliampere recti- cur mammoth stock of kits, fying tube; these parts and sets of latest design. tubes can be obtained Lowest wholesale prices. Expert very easily and care attention; immediate service. should be taken to Write for big, illustrated Cata- pick out one in which log "B." the glass is quite clear, especially in the middle. Next, apply a Allied Radio thin coating of banana oil over the glass CORPORATION 711 W. LAKE STREET, CHI CAGO and wrap the tube with a smooth piece of tinfoil extending from the base of the tube to a point about three -quarters of the way up on the glass. A square window, about FREE RADIO CATALOG Ai co thuda.n of Radio. Barawik hoe been known the world the size of the image it is desired to receive, over an headquarters for radio set builders and fane. Il ere under ne roof, it, everything you need -act.. earte. should next be cut in the tinfoil with a auooliea- honaandeofproducts -ready to.hi.tayou the some day o r der arrives. Barawilt price.aave you ®n`_ razor blade. This square should fall just money. Barawik service saves you time. Barawik .eRaythe me handiae Iwe A quarter million satisfied pleee. level of the tube ele- cu.tomer. say, Ya.Barawik Is Best." Let ut wad below the horizontal You the Big Barawik Book fr.. and prove it to ._ FotoCell ments. Yeu- 310EE CANAL STA.. BARAWI K CO. cklcaaO. u. s. A. In order to place the tube in operation,

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www.americanradiohistory.com Radio News for October. 1928 359

In the studio of station WEAF, New York, from which some of the most Clearer reception, delightful programs finer tuning, re- are broadcast. duced interference with aluminum equipped receiving sets. Reception as Fine as the Broadcast EVERY DAY millions of families throughout aluminum shielding, aluminum condenser the world are listening to delightful blades and frames, aluminum foil fixed con- broadcast programs with a keener enjoyment densers, chasses, sub -panels and cabinets. because their radio sets are "Aluminum When you see an aluminum equipped set equipped." you will know that its manufacturer has done Reception is made clearer, tuning made finer, everything he can to bring the true enjoyment interference reduced to the minimum by de- of radio to you -to give you reception as fine signers who have found that this wonderful as the broadcast. metal meets the varied needs of radio so Look for aluminum in the set you buy -if admirably. you build a set, by all means, use aluminum. Aluminum is the ideal radio metal because We will be glad to send on request a copy of it combines high electrical conductivity, per- the booklet, tAluminum For Radio," which manence, beauty and extreme lightness. explains in detail the many and varied Leading radio manufacturers recognize its radio uses to which this modern metal is superiority. So, in many receiving sets you find adapted.

ALUMINUM COMPANY OF AMERICA ALUMINUM IN EVERY COMMERCIAL FORM D 2467 Oliver Building Offices in 19 Principal Pittsburgh, Pa. 4 UMIkU American Cities ALUMINUM The mark of Quality in Radio

Please soy you saw it in RADIO NEWS www.americanradiohistory.com 360 Radio News for October, 1928

one lead from the output of the amplifier should be connected to the tinfoil and the other to the plate of the tube. The characteristic neon glow will appear when ap- Outstanding proximately 180 volts is applied across the elements of the tube, increasing in intensity as the applied voltage is increased. Best Reception results will be obtained when a resistance - coupled amplifier is used with a 210- or Equip your Power Am- 250 -type power tube in the last stage, and a high -ratio output transformer.- Contrib- plifier with a POTTER uted by Gilbert Schnlidling, Chicago, Ill. CONDENSER BLOCK and enjoy the pleasure of natural, life- A Compact Aerial like reception. New HOSE whow- live in congested cities and T are unable to erect an outdoor antenna tone brilliancy over will find the following type of indoor aerial convenient for use in small apartments, due the entire receiving to its small size and flexibility. range. Bass tones be- The material needed consists of a window screen with an adjustable frame, four small come full and rich insulators and sixty or seventy feet of insulated wire such as bell wire. The net- in quality. ting of the screen is removed and the in- No. T2900 sulators are mounted in the corners of the where one 250 frame. The aerial wire is then passed type Power Increase through the eyes in the insulators in a loop - Tube is used like manner until twelve turns arc com- $20.00 pleted; this will be found sufficient for most sets. The end of the wire is, of course, No. T2950 your radio connected to the aerial binding post on the where two 250 receiving set. When completed the frame type Power may be placed in any convenient window, Tubes are used enjoyment out of the way- Contributed by Irving $22.50 Schwartz, Brooklyn, N. Y. POTTER BY -PASS CONDENSERS Withstand High Voltages- BY replacing each . Highest Quality tube in your set New European Tubes DC Working with a new Cunning- (Continued from page 313) No. Cap. Test Voltage Price A -1 .1 200V 160 80.60 ham Radio Tube you be seen from Prig. 3 and Fig. B. The dead A -2 .25 200V 160 .70 wire running out from the screen is con- A-3 .5 200V 160 .75 are sure of clear, reso- nected to the magnesium deposit on the A -101 .1 400V 200 .70 nant tone. You are walls of the bulb, thus making this form 4-102 .25 400V 200 .75 A -301 .1 750V 400 .85 virtually giving new part of the screening. POTTER CONDENSERS life and energy to your Have Highest Efficiency- radio, and you thereby Longest Life increase your radio en- The Choice of Leading joyment. Radio Engineers 4 skyour dealerforfull information Don't use old or in- POTTER MFG. CO. ferior tubes with new North Chicago, Illinois ones -use new tubes throughout.

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CUNNINGHAM Every farm, every borne, every man and woman needs radio this year to follow elections, markets. big national events, toothed, sports, music. eta. on the Orange and Baratetk's Big Radio Guide tells you the best sets. methods and supplies tu me and bow to use them Blue carton for best results at lowest tnst. Thousands of clear illustrations and latest valuable information, furnished free. Just send ter Barawik's Big Radio Guide, the guide to radio and real radio selle Want. You can get what you want here a E.T.CUNNINGHAM, Inc. biggest savings. Writ, +.day for free copy. BARAWIK CO. ceicñcóüas:A. New York Chicago San Francisco Mail this Coupon for Free Radio Guido. The four-element tube; PC, plate connection; MP, metal plate covering screen -grid; I. insula- Name tion ; MC, metal cap connected by wire W to Address metallic deposit on bulb, completing shielding.

Insure your copy reaching you each month. Sub. Although this a rrangement of the contacts scribe to RADIO NEWS -$2.50 a year. Experi- makes menter Publishing Co., Inc., 230 Fifth Avenue, it more difficult to use the tube in a New York City. Please say you saw it in RADIO News

www.americanradiohistory.com Radio News for October, 1928 361 If you are really looking for a future -if you are really out for SUCCESS Learn RADIO -the most fascinating of all professions

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socket designed for ordinary tubes, it presents the advantage that the physical separation of the plate circuit from those of the Centralab Radio screen and (especially) of the control grid is Box rendered very much easier than in the case Control Protects of the American tube. "AC "Tubes from High One of the most interesting of the recent developments in French tube production Line Voltages Radio Sets using "AC" tubes are is the so-called "plateless" tube. Needless ELECTRICdesigned to operate on a line pressure of 110 L U volts. Any high voltage overloads the tubes and to say, the plate exists electrically, being greatly shortens their life. In many cities the normal line pressure runs from 120 to 135 volts. In nearly all cities the voltage fluctuates with the lighting load, and at SPEAK FL some period during the day Is high enough to damage the delicate tube filaments. That is why tubes lose their pep after short service and why the new Centralab Radio Control Box is an essential and economical accessory for most "AC" set owners. PERPER4, ION The Centralab Control Box is a manual line o be voltage control for "AC" sets. It can adjusted for any set and for any local condition. It will protect radio tubes from high line voltage that would otherwise soon paralyze or burn them out. It from a insures longer tube hie and better radio reception. The Centralab Control Box Is easily mounted within the cabinet. Adjustment is made by means of a knob, and when once set to obtain the average workable voltage need not be adjusted again. Connected as easily as placing a lamp into a wall socket" Furnished complete with receptacle and cord. No other wiring necessary. NO "TUBES " -NO "B" BAT- Price $3.00 TERIES - NO COSTLY At your dealer's, or write us. "ELIMINATORS" CENTRAL RADIO LABORATORIES 19 Keefe Avenue Milwaukee, Wisconsin WITH THE SKINDERVIKEN

TRANSMITTER UNIT Fig. C. This is a picture of the new "plate - Simple microphone unit provides a most effec- less" tube now available to French experi- tive and inexpensive way to satisfactory speaker menters. operation. Easy to build and operate circuit. Everybody can do this now with formed by a metallic deposit (chiefly mer- a Skinderviken Transmitter Unit. The unit is fastened to the dia- cury) on the inside of the glass wall of the phragm of the speaker unit. It will tube, to which contact is made. act as a "mierophonic relay." Every time an incoming signal actuates The filament takes 0.06- ampere at 3.5 volts the diaphragm. the electrical resist- (the standard French filament voltage), ance of the microphone unit will be varied correspondingly and the cur- and works with plate voltages about half rent from the battery, in series those of the ordinary tubes. An internal with it and the loud speaker, will fluctuate accordingly. Thus the problem of securing sufficient power resistance of from 25,000 to 40,000 ohms loud speaker is simply and adequately (( to actuate the (according to type, the tube being pro- solved. The results from this very novel and simple unit duced in three types, for use as radio -fre- will astound you. quency amplifier, detector, and audio -fre- The expense of this hook -up is trifling compared to the elaborate tube circuita that give no greater quency amplifier, respectively) and an am- actuation of the speaker. plification 12 15 values Besides this there are many other valuable uses in constant of to are Radio Circuits for this marvelous little unit. Every given by the makers. The most striking builder of Radio sets should have a few on hand. feature is the practically complete absence Model LISTENING THROUGH WALLS of microphonic effects. XL This Unit makes a highly sensitive detectaphone, Less the real thing-you listen through walls with ease. Static Plenty of fun and real detective work too. Bring Your Set to SharperP Tuningg Maximum Sharpness SOUND THROUGH In Our CONDUCTING October Issue: IN EVERY HIGH GRADE CIRCUIT TODAY WATER The Menace of Mars, by Clare MODEL "N' VARIO-DENSER -Micrometer ad- Make yourself a miniature submarine signaling Winger Most lustment easily made, assures exact oscillation control. apparatus like those used during the war. Simple Harris. of our Quick, easy tun- with this microphone unit gives splendid resuks. readers will note with pleasure ing, more volume, circuit this announcement of a new clearness and sta- story by Mrs. Harris. In this bihtr. Capacity 12 -PAGE INSTRUCTION BOOKLET range 1.S to 20 containing suggestions and diagrams for innumerable tale, the structure of the atom micro-micro- uses, furnished with each unit. and the analogy of the planetary systems /wads. Price 81.00. of the universe thereto, and cosmic changes affecting the earth disastrously, Model(' P. G. MICROPHONE TRANSFORMER are all treated in a most instructive Made in 3 sanable capacity ranges: price, each, $1.50. manner. FREE wiring diagrams A Modulation Trans- olaeagwt ldin`ri . Wtetoday %oy. former specially de- The Voyage to Kemptonia, by E. M. Scott. signed for use with Certain Irregularities of our moon's motion the Skinderviken Trans- have led some Unit. of our astronomers to be- mitter Has many lieve that there is another body -small, to XLRadio Laboratories other uses. Primary be sure -between the earth and the moon. resistance, Around the idea of Dept. A. 1224 Belmont Ave., Chicago. Ill. 14 ohmhmsec- this extra -terrestrial body is woven an absorbing tale of un- ondary, 55 usual ohms. interest. The Skylark of Space. In the concluding FOR SALE AT LEADING DEALERS chapters of this story, our author confines the travels of the Skylark to their newly Or Order Direct, Using Coupon Below discovered planet, the inhabitants of which seem to have made marvelous New Hook -ups. This book SEND NO MONEY strides in mechanical science, but fall shows how to make Short -Wave When the postman delivers your order you pay him for short of the advances in atomic theories Receivers, and Short - Wave whatever you 'ave ordered, plus a few cents postage. and chemistry made by the Earth people. Adapters. How to use the new screen - grid tube in D.C. and A.C. PRESS GUILD. INC. R-10-28 To the Moon by Proxy, by J. Schlossel. circuits. 16 -18 -R -East 30th St., New York, N. Y. The mechanical man, to most of us. seemed How to build Power Ampli- Please mail me at once as many of the following items nothing more than a far -fetched dream fiers, and ABC Eliminators. Up- as I have indicated. only a short time ago. Yet today we have lo- the -minute information on 'rite not only "the silent salesman" and all new radio developments. . Skinderviken Transmitter Units at 95c. for 1; $1.75 "auto- Set Builders, Fana, Heaters, for itl fG. 2; 3T53n.2o matic change maker," but we actually send for it today! .. P. M i8c2ro50h onre roe4 at 82. have a mechanical man When -a product of the delivered I will pay the postman the cost of the Westinghouse Electric KARAS ELECTRIC COMPANY items specified plus postage. Company -who will start your vacuum carpet cleaner, answer 4038 -K N. Rockwell St.. Chicago, Illinois your telephone, and do various other Please send me your Free Book! Name things, in response to the proper stimulus. The author conceives a creature of vastly Naine more Address extraordinary abilities, and so gives Address us a most absorbing story. City State City State 4010 -K

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THE NEW LEUTZ UNIVERSAL TRANSOCEANIC 9 TUBES

o WITH FOUR UX222's AND 2- UX210's OR 2- UX250's NEW IMPROVEMENTS UNIVERSAL TRANSOCEANIC push - pull system. The push - pull THEhas now been completely redesigned power amplifier will take either two 210 to use the new 222 Screened Grid Tubes or two 250 power tubes, the most power- in the four stages of radio frequency ful audio amplifier one could desire. The radio fre- The undistorted output available for amplification. total the loud speaker is approximately five quency amplification is now approx- times greater than a receiver using imately 810,000 compared with only only one 210 or 250 power tube. 10,000 obtained with the 201A tubes. This allows increased receiving range, The 400; 500 Volt BC Current Supply greater volume on distant signals, and has been changed to the full wave without any loss in selectivity. The type, using two 281 rectifier tubes for to increased output. Provision has been detector circuit has been altered made to use a Dynamic speaker if use the new 200A type detector. desired. The addition of the Leutz The audio amplifier has been further "A" Current Supply having a capacity improved, a total of four stages being of 3 amperes at 6 volts makes the set employed, two of these stages in a available for all electric operation. PRICE - COMPLETELY CONSTRUCTED AND LABORATORY TESTED $250 NO ACCESSORIES) Complete Constructional Blueprints -3 Large Sheets -$2.00 Postpaid A NEW RADIO BOOK for Custom Set Builders, Broadcast Listeners, Experimenters and Radio Engineers : "MODERN RADIO RECEPTION" by Charles R. Leutz PRICE $3.00 POSTPAID

384 PAGES-OVER 250 ILLUSTRATIONS FULLY BOUND-6 x 9 INCHES Subject to refund if returned as unsatisfactory within 7 days C. R. LEUTZ, INC. 195 PARK PLACE, LONG ISLAND CITY, NEW YORK

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www.americanradiohistory.com 364 Radio News for October, 1928 RADIO DIRECTORY

RADIO - AMERICAN BAKELITE PANELS BUILD THE NEW MAHOGANY or BLACK Screen -Grid Hi -Q 29 LITE - 1/8 3/16 Cardwell 7 z 18 51.00 $1.50 7 z 21 1.20 1.75 Balancer TENNA 7 24 1.40 2.00 rammarlund 7 z 26 1.50 2.15 e Roberts An efficient USTOM -BUILT Write fw details All Odd Sizes Cut to Order, condenser Sub -Panel Brackets I1/2e Per Sq. In. Radio for neutra- Sub -panel brackets in various Mail Orders Filled Same Day A.C. and D.C. Models lizing. bal- sizes ranging from 1" to 21/1" Send Stoney Order, Plus 15e ancing, ver- in height and from 7" to 11" for Postage Send 25c for nier, etc. It is also manufactured in dual mo- in length. Cut illustrates No. CENTURY RADIO PANEL Construction Book 11. Write for del having two sets of stator plates literature. CORP. which In operation give an increase Now located at Hammarlund- Roberts, American Radio Hardware Co. on one side and corresponding de 67P Cortlandt St., New York Inc. crease on other. Write for catalog. AERIAL INS. CO. Dept. 108. 135 Grand St. Telephone New York, N. Y. Rector 7468 1182 B'way, Dept. C, N. Y. GREEN BAY, WIS. Allen O. Cardwell Mtg. Corp. 81 Prospect St., Brooklyn, N.Y. VALLEY POWER UNITS CABINETS Dependable, Silent "B" For Those Who Power Supply Buy the Best Distinctive. to Operates from say the least. 1 to 12 tubes. are these ex- Designed f or ouisitely operation with w or k ed all radio re- radio cabinets. The Standard Resistances ceivers. Toggle Each ono of USE YOUR RADIO MORE! of Radio switch on the m a n y Thousands of homes get more El Meneo radio products have be- panel controls styles. a mas- use of their radio because of come standards of quality and lighting cir- terpiece of the performance sheer cuit. Ampli- KLOBER SOCKETS, type 125, 60e. the exceptional economy and by merit alone. and de- crafts- dependability of our "li" and Resistances of accurate and un- fier Genuine bakeltte throughout. Abso- man's a r t . changing values. 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Just plug the - There is a Harfield Resistor for Horne Broadcaster Into detector clamps, bus bar strier, --In fact Silencer Socket. Universal. and every place that resistances are dynamic units. Beautiful two-tone everything to make set con- Na -aid Deluxe one of these Is walnut finish to match the popular socket of your radio and you can sure to meet your called for in radio. Write us broadcast your voice Just like struction better and easier requirements. seta. Write for literature. the Write for literature on this and and let us tell you about them. announcer. Write today for data. Write for literature ether Na -aid achievements. O'NEIL MFG. CORP. Brooklyn Metal Stamping Corp. F. R. Zierick Machine Works HARDWICK-FIELD, INC. West New York New Jersey 715 Atlantic Ave., Brooklyn, N.Y. 6 Howard St., New York, N.Y. ALDEN MANUFACTURING CO. 122 Greenwich St, New York Springfield, Mass. LINCOLN REVOLUTIONARY A. F. Transformers Sandar FAMOUS Designed by Speakers FAHNESTOCK Kendall Leaders by Clough. Give Popular CONNECTION S05ó more Choice CLIPS undistorted Sandar low - KROBLAK aniplif i- tone quality PRESS n. CUM ce tie reproduction BAKELITE and RESISTORS Fahnestoch Heavy bass hasplaced this BERE frequency line of speak - For A, B, and C Eliminators clips meet every HARD RUBBER demand of register. erslrstin pop. ENGRAVING KROBLAK resistors never the Marvelous DRILLING - regardless radio public. ular demand. PUNCHING - STAMPING change their values, Use them for appearance, positive tone quality. e0ow recep- Latest Circuit Panels in Stock of operating conditions. Write contact, Specified in famous Lincoln 8 -60 ion over the as well for literature, or ask your. and durability. Write for receiver. Write for information We enter to retail catalog or pick them out at your on entire musical scale. Write to us. as manufacturing trade. dealer to show this line to you. nearest dealers. Lincoln No. 105 first. and Lincoln No. 106 second Audio Transformers. SANDAR CORPORATION Cortlandt Panel Engraving Co. C. E. MOUNTFORD FAHNESTOCK ELECTRIC CO. Long Island City - New York 165 Greenwich St., N. Y. C. 30 Sullivan St., New York Long Island City, New York LINCOLN RADIO CORP. DiViSion of Farrand Mfq. Co., Inc. 329 S. Wood St.. Chicago, III. ROLLER - SMITH PRECISION NOPHONIC INSTRUMENTS FOR RADIO TUBE PYREX CAPS Pacent Radio's Stop That LJ_ STANDARD Howl! PHONOVOX - To get the Sis Insulating best from raT Material your set.be THE ELECTRIC sure that If Its Insulation -be all tubes PICK- UP sure it's PYREX. employ WESTON INSTRUMENTS Nophonle Tube Caps. Stops WESTON INSTRUMENTS are Write for descriptive all vibration of the filament. precision instruments. boot 25e Pacent Electric Co. We manufacture an instrument for List Price every Ask your dealer or turtle direct WESTON ELECTRICAL Inc. need in radio. Send for bulletin. Coming Glass Works INSTRUMENT CORP.. Corning, Now York MERTZ SPECIALTY CO. 91 1306 Stockton Street 589 Freiinghuvsen Ave.. Newark. 7th Ave. New York ROLLER -SMITH COMPANY Wilmintton, Del. N. J. 2134 Woolworth Bldg., New York VITALITONE Lifeliktone SAVE YOURSELF MONEY SPEAKER RED LION SEND SET BUILDERS Cabinets Ask for! DEALERS! litcrattue FOR Save money. time Authorized and bother by furniture for BRAIDITE OUR purchasing kits all Atwater Hook -Up Wire Carborundum and parts from Rents. Each THE LOGICAL DETECTOR us. Maximum die- design a work "The Braid Slides Back" MONEY moats to dealers. of art. Walnut Slake your connection. solder Bell -clear. Noiseless, Sensitive Latest kits and finished; two- it and the insulation slides The Detector alone is suited for SAVING parts always in toned panels. right back into place. use In any set wired for a per- stock. Send NOW Write for de- SOLD 11Y ALL DEALERS Reception so perfect that you will manent crystal detector. CATALOG tattsendprices If yours can't supply you, to the studio with for catalog. Model Illus- believe you are Write for literature. order direct the artists. Take no substitute. Wholesale Radio trated. Sí5.00 25 Ft...15e 25 Ft...30c INSIST on Vitalitone CARBORUNDUM COMPANY Service Co. RED LION CABINET COMPANY CORNISH WIRE CO. VITALITONE RADIO CORP. Niagara Falls, N. Y. flow 6R Church St. Red Lion - - Pennsylvania 32 Church St., New York 88 University PI., New York, N. Y. New York

The RADIO DIRECTORY is your buying guide. Space permits display of only one product at a time.www.americanradiohistory.com Write advertisers for complete catalogue. Radio News for October, 1928 365 -RADIO DIIZECTOIZY L? MAJESTIC CONE Natural RAMCO Tone If you want B -L List more hours of $1rice Designed Line of RECTIFIERS 2.50 for use service per tube, Bone -dry with or insist upon Radio Noiseless. Durable YOUR Without Compact PRICES power PERRYMAN tubes Moisture -Proof Extension Cords Cabinets B-L Rectifiers em- $2.25 RADIO TUBES body a new prin- Itirnbaeh Poslpai J Extension Cords permit "The tubes with Beautiful cabin- ciple. They are the Loud Speaker to be mined to the patented shock- ets made by adaptable to all any room In the house. Attaches proof bridge." craftsmen to suit types of electrical Instantly. Install a Jtirnbarh Cord the tasteof every- equipment requir- AMPLIFLEX LOOPS and put an end to distortion so A tube fur every radio pur- one. Model illus- ing low voltage Collapsible, Folding - Built -in often due to badly lnsutated cords. pose. All the A.C. types. trated lis known rectifiers. Write Compass. List price, $32.50: our Your neighborhood denier has these Write for literature. as our for further infor- price. $2.79, postpaid. Write for sizes in stock: 10- 211.30.40 -5o -100 Perryman Electric Co., Inc, imported overlays. Pricen 536.50. mation. Special Bargains nor. foot lengths. Send for Catalog. 33 West 60th Street Write for literature THE BENWOOD -LINZE CO. New 1132 Washington SPIEGEL RADIO COMPANY BIRNBACH RADIO CO. York City RADIO Avenue 254 W. 31st St.. York ALLIED MFRS. CORP. St. Louis, Mo. I35 Liberty St., New York City New 1340 S. Michigan Av., Chicago, III. GAVITT

TILE B.B. L. MOTOR AIR -KING The Ultimate in Precision EXTENSION CORDS BACO VOLTAGE REDUCER WEBSTER Short-Wave, Plug-In Coils An improved motor for loud speaker A One. durable cord. Rubber In- Equalizes A.C. voltages on the re- AU TO- POTENTIALATOR Write f.,r complete details sulated, ceiver. Saves the tubes from over- operation. Power without saturation. A Webster twisted, and covered over Eddy currents reduced to minimum. product that instantly and and free instructions for build- all with high -grade mercerized braid. strain. Prolongs lite. Install them Permanent adjustment automatically regulates local A.C. ing an efficient short-wave for absolute protection. assures the voltage, producing even supply of receiver. iVrUe for literature. highest quality tone reproduction. current best suited for operatics of Write for details AIR -KING PRODUCTS CO. Write for literature A.C. seta. Send for OUT car dog. GAVITT MFG. CO. BEST MANUFACTURING CO. THE WEBSTER COMPANY 222 -226 Grand Street 154 Chicago. III. Brooklyn, N. Y. Brookfield - - Massachusetts BACO ENGINEERING CO. 1200 Grove St. Irvington, N. J. Blackhawk St.. 1341 Flatbush Av., Brooklyn, N.Y. VICTOREEN RADIO PRODUCTS RADIO PARTS OF EXCELLENCE 200,000 RADIO NE \N S readers T b e carefulb sran the RAD7O heart DIRECTORY every month. of the VOUR product here. at Super the lowest cost. in the Hetero- world's largest and most d y n e widely read radio maga- R. F. zine. Trans- RATE CARD: BODINE H. A. STILES formers. A complete line of quality radio Per Issue ELECTRIC TURNTABLE Virtor- parts and tools. Sockets to acmn- Three time rate 125.00 Beautiful Cabinets e e n mrntate all tubes. Beautifully Six time rate 20.75 Designed by experts for radio-phono- matrhed graph combinations. Positively no Be sure and see our line of cab- designed dials and hnnhs. Bind- Twelve time rate 22.50 before Iron. precision assures maximum re- ing posts, extension connectors: No order for less than interference in the loudspeaker. inets you Beautifully sults. Send for our catalog and many other radio parts. three insertions accepted. Write today for full information on designed -beautifully made aml hill data on the Victoreen cir- Write for inform at inn. this big new development. beautifully finished. All standard cuit. HOOSICK FALLS RADIO AND sizes. Write for literature. ELECTRICAL PARTS MFG. Radio News. 230 5th Ave. BODINE ELECTRIC CO. THE GEO. W. WALKER CO.. H. A. STILES & CO.. CO.. INC.. 2242 West Ohio St., Chicago, I. 174 2825 Chester Ava. Cleveland. O. Hoosick Falls. N. Y. Portland St.. Boston. Mass. SMITHCRAFT WROUGHT IRON RADIO TABLES Arcturus Ferranti HERALD Leads Transformers Gothic Again and Chokes Mantel for Speaker The ARCTURUS Every type 22 was the Purpose For Electric first shielded-grid and tube on the. market. Battery ARCTURUS not The uniform Sets UTAH Exponential Horn only leads In devel- high quality Illustration shows Serifs 1000--A opment, It leads in quality. also. of the FER - very Handsome, compact, wonderful pur- Popular number for Phonograph Send for our catalog of .4 serums tubes RANTI line oI radio products has ity of tone. Cabinets. Send for complete catalog of -leaders. first, last, and always. made them the standard for compari- Equipped with new tone the various horns of this type filter. Never rattles, regardless of the that son throughout the radio world. power behind It. Send for particulars we manufacture. ARCTURUS RADIO COMPANY Write Jur complete literature Newark UTAH RADIO PRODUCTS CO. B. H. SMITH SALES CO.. - - New Jersey HERALD ELECTRIC CO. 1615 S.Michigan A ve.,Ch icago, III. FERRANTI, INC. 755 Boylston St.. Boston. Mass. 130 W. 42nd St., New York,N.Y. 29 East End Ave., New York, N.Y.

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The RADIO DIRECTORY is your buying guide. Space permits display of only one product at a time. Write advertisers for complete catalogue. www.americanradiohistory.com Radio News for October, 1928 WHOLESALE PRICE S forYlealerc ,(ommunifyfet$uilders,Generaf Repairmen and iqenis!

Be sure to get this great 144 -page book with net prices to the radio trade. Radio Specialty Company is radio's oldest radio parts mail order house in the country, and the new confidential prices on standard radio merchandise are the lowest of any radio house. We are ready now to appoint additional agents in all parts of the country. If you are contemplating making big money in radio merchandise, be sure to get in touch with us at once. daiSiOn is here! Radio Specialty, as usual, is first with all new things. Send at once for free booklet for lowest prices on all television parts which have been put on the market so far. (If you have Catalog No. 18, just ask for the Television Supplement.) I6:75 '64HOO KU PS 500 LLU STRATI ONS

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98W PARK PLACE, NEW YORK

Please say you saw it in RADIO NEWS www.americanradiohistory.com Radio News for October, 1928 367 Radio Free Blueprints Available (Continued from page 319)

factorily in this manner, you can make it work a loud speaker by adding this simple two -tube amplifier to it. This amplifier will (4 also work perfectly with any tuning system if it is connected after the first detector our tube. No. 5G, "The Neutroheterodyne," June, 1928 number: This is a seven -tube superheterodyne of advanced construction and design. Although we do not recommend it to the beginner, the man who has made one or two small sets and who is ready for Prese something more ambitious will find this outfit very interesting. It is considerably cheaper and easier to make than most super - heterodynes, as the intermediate transformers can be wound at home and matched without trouble. Unlike most "supers," this receiver tunes with only single sets of dial readings, and not with double readings. eí No. 59, "A Sturdy and Dependable Power Unit," July, 1928, number: This is a husky "B" socket -power unit, designed especially for the Neutroheterodyne, but which can be made an Electric will work equally well with practically any other receiver. It provides a maximum of A.C. Set without changer in :350 volts for the operation of a 210 -type power tube and has enough capacity for a ten -tube receiver. wiring or even the cost of new tubes No. 57, "A Crystal Set," July, 1928 number: This is the very simplest possible radio receiver that can be made for the actual reception of signals from broadcast stations. COC7°HERE'SHERE'S no necessity for discarding a good The whole thing is only six inches square operated receiver to get the conven- and three inches deep and can be assem- ience of A. C. operation. The Kuprox A. C. Power bled at a cost of less than $2.00. It uses Pack converts any good set into an electric A. C. neither tubes nor batteries, but will bring set, without changes of any kind in wiring, within stations up to 25 or 30 miles away. It out the use of harnesses or adapters. by any in- can be assembled in an evening Kuprox A.C. Power Pack. telligent 12- year -old boy. Makes any battery set an electric A. C. receiver. Kuprox equipped, your present set, using your No. 58, "A `Junk Box' Short -Nave Re- $32.50 up. present tubes will give you super -fine A. C. op- ceiver," July, 1928 number: This is one of eration. Everything your radio did before, it will the most popular receivers RADIO NEWS has to bother two -tube do even better. And there's nothing ever described. It is a simple set on and off at your affair assembled on a small board, and uses about ... the entire turns parts that practically every experimenter light socket. The Kuprox A. C. Power Pack is can find in his junk box. With four plug-in a permanent addition to your set that will double coils wound on tube bases, it covers the your radio enjoyment. short -wave channels from 20 to 100 meters. Hundreds of people who have built this Several models are offered. One that supplies all have heard short -wave broadcast sta- set Kuprox Multi.rate Recti- radio power for any size set. Or separate fila- tions in many parts of the world. fier, for trickle charging, models desire this dynamic speaker opera- ment and plate for those who No. 60, "A Two-Tube Reflex Set of Sim- tion, etc. $11.50 form. And an efficient "A" model that supplies ple Design," August, 1928 number: Another filament current and will operate in conjunction good set for the beginner. It uses two with any good "B" eliminator. Priced from $32.50 tubes, but gives the results that about 31/2 up. See the various models at your radio dealer's. give in an ordinary circuit. tubes would Or, if you first desire more information, we'll be No. 61, "A Booster Unit for the Brown- glad to send it if you will write. ing Drake," August, 1928 number: 'l'he original Browning Drake uses only one stage radio- frequency amplification. If of tuned THE KODEL ELECTRIC & MFG. CO. you own one of these receivers and want to Kuprox Replacement Unit Formerly The Kodel Radio Corp. increase its sensitivity and selectivity, make eliminates acids. liquids, up this simple booster and hear more DX. bulbs from trickle char- 501 E. Pearl St. . . Cincinnati, Ohio gers $5.00 Yo. 62, "A Screen -Grid Short -Nave Re- ceiver," August, 1928 number: Most short- wave receivers use a simple regenerative ° circuit. This one has an additional radio - frequency amplifying stage which makes the reception of distant short -wave broadcast stations more reliable. It has only one tun- -3 ing control and does not require complicated shielding. It is an inexpensive, easily - UPROX constructed set that will work without trouble. Yo. 63, "The Screen -Grid Strobodyne," POWER PACK September, 1928 number: This fine set has

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www.americanradiohistory.com 368 Radio News for October, 192'

been acclaimed the most sensitive one of the year. It is an improvement over the original Strobodync, which was described in RAnlo NEWS last summer and which has MASTER achieved world -wide fame. The large blueprints show every detail of the interesting VOLTAGE construction. The three latest blueprints are listed else- CONTROL where in this number of ltauto NEWS. They show the construction of a completely This voltage regulator (patent pending) is a -wave receiver, a simple necessity on all A-C seta. It protects A-C shielded short tubes from burning out by reducing excessive screen -grid set for the beginner, and a com- line voltage to the proper value. Anyone can ood install it. Requires no guesswork in setting broadcast and short -wave outfit. bination for the proper voltage.1 Has no moving parts, Antenna System Please remember to write your name and therefore nothing to wear out or get out of address clearly, and to state specifically adjustment. will improve' what blueprints you want. NO TOOLS NECESSARY Your Radio Sete Simply call up the power company m your Few set owners realize Reception in a Draped Room district and ascertain how important it is to have the maximum line vol- is More Pleasant tage. Plug your A-C a good antenna system. An set into the marked out- old, corroded antenna picks AROOM which is generously furnished let of the MASTER with rugs, stuffed furniture and cur- VOLTAGE CONTROL up very little energy from to correspond to that tains or other draperies usually has better line voltage. These var- broadcasting stations, and which is ious line voltages are acoustical properties than one clearly indicated so that the receiver cannot work comparatively bare; and it, therefore, can the proper setting may properly. A Bel den amel be had. No voltmeters, be expected to make the radio reproduction no tools or a service Aerial Kit assures an an- sound better to the listener's ears. In a man's time is required for installation. Once tenna system of high effi- hare room the sound produced by the loud installed it requires no ciency. Furthermore, it is speaker tends to develop echoes, which further attention. To get proper life out permanent, because a Bel - sometimes completely spoil the performance of A-C tubes and keep of the set. them from burning out denamel Aerial cannot use a MASTER VOLTAGE CONTROL. corrode. Beldenamel Aerial PRICE $2.50 Bare Copper Wire is protected of a Baseboard Aerial Wire against Treatment At your dealers or write us. Corrodes con n IF you plan to use a wooden baseboard . Rapidly . as a permanent part of a radio receiver, MASTER ENGINEERING CO. it is a good idea to give it two or three Dept. 827 -N 124 South Michigan Ave., Chicago, U. S. A. ®®ó# coats of shellac or varnish before mount- - (a`d'd ing any instruments on it. It will then be less susceptible to warping than if it were left uncoated.

Other Belden Radio Products PENETRATING RADIATION When Dr. Brown's X-ray machine ARTE Indoor Aerial Kits, Colorubber Hookup Wire, Aerial Accessor- Made static in our block A New Principle in ies, Battery Cords, Extension The neighbors lost their patience and Cords and many other items are The patients lost their Doc. RESISTORS included in the Belden Line. -Helmers Huebner Steel Tube -- - Vitreous Ask your dealer to show you the New Belden Loudspeaker Enamel Extension Cord that is flat and lies under the rug. No unsightly wiring around the room. Does 40 Non -Technical not wear the rug. Belden Manufacturing Co. Radio Articles New steel construction makes 2314A S. Western Ave. Chicago them unbreakable. Dissipate every month for the beginner, the layman more heat. Lighter in weight. and those who like radio from the non- Terminals will not become technical side. loose. Carter again leads SCIENCE AND INVENTION, which can with this new product. be bought at any newsstand, contains the largest and most interesting section of 'Carter Radio Co. radio articles of any non -radio magazine MEneC CHICAGO in existence.

Plenty of "How to Make It" radio articles and plenty of simplified hook -ups for the layman and experimenter. The radio section of SCIENCE AND INVENTION is so good that many RADIO NEWS readers buy it solely for this feature. Ket9eiiIllfu!ll/#h/i21 Radio Articles Appearing TO SET BUILDERS

in October Science and Elections, footba 1 games, big National events will boost radio Invention Magazine business this year. Set builders will - reap a rich harvest. Barawik service will make you money. Everything in A-C sets, AUTOMATIC TUNING FOR THE RE- parts, supplies. World's largest radio stocks on hand. Orders shipped same day. Lowest rock -bottom CEIVER wholesale prices. BUILDING A PARROT LOUD SPEAKER Mail coupon for free Radio Catalog stow NEW RADIO DEVICES BARAW1KCO. céICAGO,ús:i. RADIO WRINKLES Mail tills coupon for Free Radio Guide RADIO ORACLE LATEST PATENTS Name Addree

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Three stages of Loftin -White constant coupled tuned radio frequency amplification, giving practically a straight -line amplification factor over the entire broadcast wave band. Giving 10,000 cycle separation, and due to new design of coupling in each stage it has an unusual sensi. tivity factor. True single dial operation with tuned antenna input and fu!1 range volume control. Automatically adjusted below the point of oscillation. Non -regenerative detector feeding the audio amplifier that has an amplification factor of over 750, which is from three to five times greater than any commercial types that are now on the market. Two stages of Jewell Dual Impedance audio amplification, assuring straight line amplification over the entire band of audible frequencies, feeding into a 250 -power tube that has an undistorted output of over 500 milli watts. This amount of power is capable of overloading any of the commercial loud speakers now on the market. In other words, nothing has been left out in the engineering of the receiver that could be desired by the most discriminating radio critic, and also due to the fact that the JEWELL DUAL IMPEDANCE Miessner system of A.C. operation is employed the A.C. hum is reduced to an absolute minimum. POWER AMPLIFIER Mr. Radio Fan and Professional Set Builder! Distributors for Loftin -White Tuner R. F. Amplifier, Jewell Audio Why not capitalize the prestige and distinction that goes with being our local representative in Amplifier, CeCo Tubes, Airchrome, your territory by selling the most remarkable radio receiver that has ever been offered to the and Jensen Loud Speakers American public? This receiver was designed and engineered by the most prominent radio engineers in the world today. Write us NOW for our EXCLUSIVE REPRESENTATIVE PLAN.

FIELD REPRESENTATIVES WANTED Unconditional Guarantee -- -You Being the Judge RADIO PRODUCTS LABORATORY We unconditionally guarantee this receiver to be the best radio broadcast receiver that can be 1931 Broadway, New York, N. Y. built under the present known theories of the science and if, for any reason, it does not come your every expectation, it may be returned to us, in good condition, any time within Gentlemen: Kindly send me, without obligation' up to your Field Representative Plan. thirty days and your money will be refunded in full.

Name RADIO PRODUCTS LABORATORY F. A. JEWELL- GENERAL MANAGER Address 1931 BROADWAY - - NEW YORK, N. Y. City State Please soy you saw it in RADIO News www.americanradiohistory.com 370 Radio News for October, 1928 Laboratory Takes Wings (Continued fruta page 301) at 2:00 P.M., en route for Dayton. Coln - munication was maintained between Bolling Field and the airplane until Burgess Field was reached, where we landed. The last one-half hour schedule was interrupted due to a "short" in the keying circuit in the airplane transmitter, but signals from the Bolling Field station were as audible at Uniontown as throughout the trip. Upon D00 taking off at Burgess Field a short sched- ui. 47 ue.ww ule was worked with WTI at that station by telephone. As the beacon from Dayton was laid on the Uniontown -Dayton course, WTI was asked to stand by while the airplane worked Dayton by phone. Telephone communication was established before reaching Wheeling and maintained until landing at 6:45. ARMY SETS SUCCESSFUL "This trip has amply demonstrated that the SCR -134 can -work far in excess of its conservative rating. The experimental double- voltage engine -driven generator func- TONATROL tioned perfectly throughout the 22 -hour Trade mark flight. This type of generator used some- Exclusively Licensed by Treh- what in excess of the power requirement for. nidyne Corporation under ti A Complete Line of Volume Controls Patent Nos. 1593654, 1034 Urt. the SCR -134, and will be used for the long- 1034104 Concerts, sporting events, speeches, jazz -how much better they come in if your volume is just right! range bomber sets now under development. Tonatrol enables you to control volume smoothly and The adoption of this generator will lighten adapt it to each occasion. There are types designed expressly for your circuit, whether it's battery or A.C. the power load on the bomber, over the Can be had with filament switch or power switch SCR-135 power installation, approximately attached-$1.50 to $3.00. 190 pounds and will displace power equipment and other apparatus at a saving of approximately $600.00 per bomber. A sim- TRUVOLT ilar type generator for observation planes U. S. Pat. Ott. Reg. will reduce the observation load approxi- ALL -WIRE RESISTANCES mately 50 pounds, and displace equipment $100.00. A The ideal variable, fixed, and tapped voltage controls. costing approximately similar Truvolt Variables simplify B- Eliminator construction generator will eliminate the need for bat- by eliminating difficult calculation and making all will the adjustments easy. 22 Stock Types -$3.50 each. teries on pursuit planes and lighten Truvolt Fixed Resistances are adjustable to different pursuit load considerably by the displace- set values by the use of sliding clip taps -an exclusive ment of dynamotor and battery. Truvolt feature! Made in all desirable resistance and Patents Pei values and current ratings. "With the facilities for directly compar- Electrad specializes in a full line of ing various types of apparatus in the air- ® Controls for all Radio Purposes plane during flight, and for making repairs SCUT HERE and changes on apparatus during flight, the ELECTRAD, INC.. Dept. N -10. 175 Varlck St., New York. N. Y. has more than paid for itself, Please send me descriptive circulars on the following products and put me C -2 airplane on your mailing list for similar literature. even in the limited time that it has been ....General Circular: Tonatrol Volume Controls:....Phasatrols: ..Royalty Variable Resistors: ....Truvolt Divider' . .Electrad in commission as a flying radio laboratory. Control Manual" (enclose 10e. for mailbag: ...."What Eliminator Shall I Build ?" (enclose 10e. for mailing). Considerable data have been obtained on I am particularly Interested In short -wave propagation during the day, and this type of airplane, due to its navigation Name Address and power equipment, will make it possible to safely and economically conduct long-- range night radio and navigation experiments." PRIVATE EXPERIMENT Radio airplane experiments of extensive RAQ. nature are now also being conducted by the Pilot Electric Mfg. Company, of Brooklyn, New York, under the supervision of its research engineer, Milton B. Sleeper. For this work a specially- constructed six- passen- DEPENDABLE "B" BATTERY POWER KOOK -UP BOOK FREE ger Stinson -Detroiter monoplane is being Improve your reception with used, the various experimental transmitters CARBORUNDUM of the plane operating under the call letters Stabilizing Detector Units, 2XBQ. A portable ground station with the Grid Leaks and Resistors call letters 2XBP, erected at Curtiss Field, THE CARBORUNDUM COMPANY Long Island, is also on the air frequently. DEPT. D 1. NIAGARA FALLS. N. Y. Pictures of this plane appear on page 301. The metal "fuselage" of the plane is bonded together to forum a low- resistance M01`pP1r1tSloSet Builders electrical path, to be used as a "counter- One good radio idea may be worth poise," or artificial ground. The ignition 100 Volt Edison Element. millions. Barawik has thousands of ideas to prevent Non Destructive, Rechargeable "B" Flattery with for radio set builders to make more money. system is thoroughly grounded charger. Shipped dry with solution, 812. 140 Volt with Barawik's BIB Radio Book will help you interference. Details of the interest- charger. $17. 180 Volt Power Unit with Trickle while elections are on and big national spark Charger, 824.00. Free sample cell. See how it events stir the world. ing work being done with this plane will be operates. Send for your copy today - NOW. EXPRESSMAN in a forthcoming number of SEND NO MONEY -PAY 210 C,ne15'°,ion . published Write for our Free Illu ed 24-page Booklet BARAWIK CO CHICAGO, U. S. A. SEEJAY BATTERY CO., 915 Brook Ave., New York R lino Nrws.

.cav yola saw it in RADIO NEWS www.americanradiohistory.com Radio News for October, 1925 3, 1

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Please sny yun su.v it in RADIO NEWS

www.americanradiohistory.com 372 Radio News for October, .1928 The Photoelectric Cell - _4 Radio's "Eye" (Continued front page 307) small currents in the cell. 'Thus the shading of the object is translated into an electric current of varying magnitude. TELEVISION 'l'he application to the talking movies is Amplifier Kit extremely simple in principle. Sound, as you know, consists of vibrations of the air. Edell pitch has a definite frequency that is a definite number of vibrations per second. Sounds are recorded on a strip of film, along one side of which little wavy lines represent individual sound vibrations. When this film is run at the customary speed, a certain number of these lines pass a given point in each second. Where they are closely spaced, Mozart-Radioceive of course, more pass than where the spacing is greater. A narrow beaus of light is passed Speakers and Speaker Units through this film into a small photoelectric cell in back of it. Where there are no wavy FOR SEASON 1928 -9 lines, the intensity of the light bears remains ITH this precision -built kit you can assemble W at minimum trouble and expense an efficient 1 ERIT, and merit alone, will constant and, consequently, the current amplifier for securing quality reproduction in NI sell and keep sold a loud through the cell stays constant. When the your television reception apparatus. speaker unit in a discriminating little lines move across the light beam, how- The audio amplifier is an extremely important the craze part of television receivers. Where the signal to market where continual ever, they cut off the light a definite num- be received contains frequencies of from 18 to is for better and better perform- ber of times per second. This means that 20,000 cycles, the audio amplifier must be able to ance. Hence the only reason for amplify all frequencies within these limits. Such time photoelectric -cell current decreases and an amplifier is available at your dealer in the the Radioceive Twin Armature coupled amplifier kit. (double motor) speaker unit increases again the same number of times Lynch resistance per second. If this current is passed Your dealer has a Lynch precision - again far outselling all others in its built resistor for every resis- class during the past summer through a telephone receiver a note will re- tance need. Send for free book. season to New York City fans. sult, having its pitch corresponding to that of vibrations per second, and in this ARTHUR H. LYNCH, INC. is still last word number Here indeed the speech eau be re- General Motors Building in a Super -Sensitive unit for oper- way musical sounds or ating almost any type of dia- produced. 1775 Broadway, at 57th Street phragm with minimum current New York, N. Y. consumption and at voltages all AUTOMATIC INSPECTORS the way from 90 to 400. + Another application of the photoelectric Or where a complete Speaker is cell has been to the sorting of cigars. After Your Set Can required our Mozart Wall -Cones cigars must be sorted into Now Get manufacture, Waves or Drum type fitted with this unit various grades, depending upon their rela- Short are still guaranteed on a money - Sent anywhere In the U. S. II tive degree of lightness or darkness. For- post paid upon receipt of back basis, to excel in appearance price. Canada and Foreign, merly this was clone by eye. Now the cigars 65e additional. Money or- and performance all others in the der only. Also sent market at anything approaching pass on a conveyor before a photoelectric C. O. D. plus postage in U. S. if 51.00 accompanies their prices. cell, and a beam of light directed on the order to insure carrying cigar is reflected into the cell. The lighter charges. In ordering be Armature (double motor) sure to name set and tubes Twin the cigar, the more light is reflected into the used, such as ÚV199, Speaker Unit complete with UX199, WD11, 201A, UX226 will be the in or U Y227. Price 515.00 or Cord s 6.00 cell, and the larger current separated into a $17.50 for A. C. Sets. complete the cell circuit. Cigars are 26" Wall Cone Speaker number of different groups, according to The SUBMARINER with Twin Unit 8.00 will convert your regular set luto a abort-wave receiver by simply their shades, by the action of selective re- Inserting a plug in place of one of the tubes. This takes but a few 36" Wall Cone Speaker complete Seconds. With "submariner" It will enable you to tune between lays operated by the photoelectric currents 26 and 68 meters. with Twin Unit 10.00 This device operates with all sets, such as T.R.F., Neutrodyne, which cause the cigars to be dropped into Super-Heterodyne and others A C or D C operated. No addi- Drum Type Speaker complete tional tubes. batteries, or coils required. If set operates a with Twin Unit 12.00 the proper bin. (See the article, "A Photo- speaker it will do so with "Submariner" attached. Operates 318 of this is- as a wave changer with Super -Heterodyne and as detector electric Bean Sorter, on page unit with others. THE FERGUS CO. dU e.- Enrroa. ) SHORT -WAVE RECEPTION is macle use of Is practical, and especially In summer, as they penetrate better 239 ELIZABETH AVENUE A rather similar principle and there Is leas static. The "Submariner" waveband includes cell device for testing practically All Powerful Stations Which Broad Pro- NEWARK, N. J. in a photoelectric grams. You may also listen to amateurs from all parts of the breakfast foods. The corn flakes come out world who transmit code messages. You will have one of the most efficient short -wave receivers when the "Submariner' Is of the oven on a conveyor and pass beneath attached to your set. Get a "Submariner" so you may have command of the short -wave activities as well as the broadcast a photo cell. If they are overdone, they are band. It your Dealer does not carry dark in color and little light is reflected into ORDER TODAY DIRECT the cell; while if they are underdone, more TM.? device has been nationally advertised. and sold to all parts of This Catalog Will the world for the past two years light passes into the cell. In the first case J-M-P MANUFACTURING CO., INC. Save You Time the cell current is comparatively small and Department 53 Milwaukee, Wis., U. S. A and Money in the second large. 'l'he cell current is used furnace Write today for our large illus- to operate relays which control the trated new Catalog "B," showing temperature. $ 1 SAVES YOUR how this organization of men interesting application is the au- in Radio Another with years of experience recording of daylight. The cell is can give you personal service. tomatic SPEAKER exposed to diffuseti daylight and the cell current is passed through a recording meter. The CRAFTSMAN Dollar The meter records on a strip of paper the Speaker Filter is guaranteed Allied 'Radio variations in current which tare, of course, to relieve speaker of plate CORP RATION in in- D.C. (180 to 250 volts). Com- III W. LAKE STREET, CHICAGO proportional to the variations daylight tensity. plete Protection. One Dollar 6 TUBE SUPERPHONIC RADIO-S16.95 Postpaid. FREE-Sir tubes. tested and matched is to the control of An amazing value that can't be beast Latest 6 -tube tuned Another application CRAFTSMAN RADIO radio frequency circuit. Metal chassis. shielded. Extremely street or sign lighting. When the light in- selective. Long- distance reception. Send for complete de- PRODUCTS scriptive circular. Value $60. our price 416.95. Write today. tensity drops below a definite value, the 9 Orchard St., Newark, N. j. Radio Equipment Co., D. 1211, 549 S. Wells St., Chicago. III. Please say you saw it in RADIO Saws

www.americanradiohistory.com Radio News for October, 1928 373

current through the cell also drops propor- tionately; and it can be made to operate a relay which will switch on the lights. These are a few of the applications of the photoelectric cell. It has great possibilities for any work in which light plays r a part, and I believe that, once its characteristics are understood by engineers, it will find as many uses as has that other member of the vacuum tube family, the radio tube.

How to Build from the Schematic (Continued front page 323) available to him in the pages of RADIO NEWS, to be consulted when necessary. He knows the precautions tq be taken in running his leads and in the use of shielding, when he introduces it into his construction. He reads the schematic circuit as a plan which allows him considerable latitude in his selection of FREE RADIO BOOK as electrical effects - material, so long its are properly proportioned. In other words, describes many opportunities the schematic diagram is his servant; while for the neophyte the pictorial diagram is a HUNDREDS OF MEN HAVE to make big money master who must be obeyed literally. WON SUCCESS THIS WAY The National Radio Institute la the oldest and largest Radio in home -study school in the world. It has prepared hundreds of men the Radio field. for the Radio profession -some Here's a book that's shown man after man the way to Wire Useful of them now holding leading po- Lengths of Flexible sitions In this industry. You'll "cash in" on the big opportunities in Radio. I'm not and N.R.I.-trained men in prac- in Experimenting tically every Radio organization asking $5 or $6 for this book -it's FREE. If you're of any importance throughout earning a penny less than $50 a week clip the coupon ORl)IN.1RY flexible lamp cord, which the world. The same practical tested training that enabled these below and get a copy of this free Radio book for yourself. is the equivalent of No. 18 wire, is men to get ahead is now open to you. And this training has been Salaries of $50 All the Way Up to $250 Weekly very convenient for temporary connections Improved, enlarged greatly te keep up with the constant ex- Not Unusual in experimental work. It is a good idea pansion of Radio opportunitiee. Radio -the NEW, speedy, growing, live -a ire profession-needs trained Executive with Big asen for its good jobs. Television trans -Atlantic Radio telephony, n any to cut up a dozen or so pieces of different Corporation "Am other wonderful inventions and developments are being made constantly lengths (one foot to three feet) and equip now Secre- in this field! Each one means more big -money opportunities for a !rained tary and Treasurer Radio man. My book gives facts about these Radio opportunities. their ends with clips. Quick connections of big Hammer. the lund-Roberta or- And more -it tells how you can get all the training in Radio you need, can then be made with these wires without ganization. My quickly and easily in your spare hours at home, by my new and practical or for use success here and in r methods. In a short time you, too, as have hundreds of others, can be the necessity for soldering the myformerposition prepared to take advantage of these big -money Radio opportunities- pliers. as Editor of Radio of lily Free of Home due to the salaries $50 all the way up to $250 a week not unusual. splendid training I Book will give you all the Facts and Proof. got from you." Leslie G. Biles, 1182 Broadway,- New York City. Extra Dollars for You Almost At Once Earns $1000 by Spare Time Think of making $15, $20, $30 extra each week "on the aide," aitbcut The Humorists Begin Worrying for Us Work interfering with your regular job! I'll show you how to do that, too, by m spare time In using spare time that you're wasting now. I'll show you how to turn the evening I have you almost when and get made about $1000 what I'm teaching into cash at once, you I since starting your started together. My Free Book tells you all about it. if you send for course. I sin going the book today, and if you have the average man's ability, it's possible t with for you to be making extra money thirty days from now. And you'll be theh lessons and ready for a good full -time Radio position after eight to twelve months' work hard, for Ra- of spare -time training. - diosure isafleldof, unlimited oppm` I'll Send You this Big 64 -Page tunity."- Dekoss Brown, South St., Foxboro, Mass. Book FREE From Miner to Over MOO Yearly My book is filled with photos and facts -the pay - "Two years ago I raising facts you want to read. If you're interested in enrolled for your Radio, or if you're interested in making more money, training-a coal you owe it to yourself to read this book. The book miner by trade. absolutely won't cost you a cent, and you place Now I'm manager <. for the entire state + w yourself under no obligation by sending for it. ofMlchigan tor the No previous. Radio experience needed to take NationalLeadBat- advantage of this offer. No special schooling re- tery salary Co.. J. E. Smith - quired. Send-coupon today. 53480, bonus WO, and commission on sales that Address E. SMITH, President boosts It over $5000. Your train- J. ing gets all the credit. "-Wm. National Radio Institute, Dept. 22SS,Washington, D. C. "When the latest television invention is attached H. W 1420 S. Michigan Ave.. Cilsonhicago, It!, . to our telephones, zee shall be able to sec the m dma IMO .1=1. r person we are speaking to- l to J. E. SMITH, President, Y s National Radio Institute, Dept. 22SS, Washington, D. C. Dear Mr. Smith: Kindly send me your free 64 -page Radio book, with all information about learning Radio for bigger J pay. I understand this places we under no obligation.

Name

Address

State --but no invention has yet been discovered that Town e_ntircly eliminates the possibility of being suddenly switched on to a wrong number!" -"London Opinion." !lease say you sow it in RADIO Naws www.americanradiohistory.com 374 Radio News for October, 1928 Television in Colors (Continued front page 320)

placed in front of the transmitter, and ap- Now- - peared on the receiving screen in a most vivid blue. This was replaced by reef car- nations, and the red blossoms appeared TELEVISION very clearly. the A human face was then transmitted, and -and when the tongue was put out, the pink accepted motor for ít: color showed clearly, the face appearing in a different shade of pink. A policeman's Television requires a motor which will not N JUNE FOURTH through Station spark; sparking distorts thereceived picture. helmet was then placed before the trans- O WLEX, Lexington, Mass., before The Baldor VariableSpeed Motor has mitter, and the blue shone up most strik- a gathering of business and engineer- no brushes, commutator or automat- ingly. By far ing leaders of the radio industry, a ic switch, or any device that can the most impressive part of very successful demonstration of spark. the demonstration was a basket of ripe Television requires a motor with little fric- strawberries, the red fruit showing in Television was held. The images tion, so as to be able to follow the moving an were sent over the air and accu- picture accurately. amazingly vivid fashion against the white The Baldor Motor is ball bearing, basket. I also clearly saw the living rately received without the noise that which means minimum friction, and mov- had previously accompanied earlier is easy to keep accurate. ing images of a man tying a red and blue experiments. The Baldor Motor il- Television requires a very quiet receiver, so handkerchief alternately around his head. lustrated above was responsible for the as not to transmitnoises to thereceivingset. Ba ldor Motorisquieta At present there is great activity in pre- success of the Television demonstra- The nd humless. paring tion. Many motors were tested but Get the factson this improved motor. for the commencement of a broadcast the Baldor Single Phase Motor with Send for Bulletin No. 11. television service in Great Britain. Tele- constant or adjustable varying speed vision will be publicly demonstrated by Mr. gave, by far, the best results. It is the INTERSTATE ELECTRIC CO. Baird at the Radio Exhibition, to be held only approved motor. 4355 Duncan Menue, St. Louis, Mo. in London between September 22nd and Distributors for the Baldor Variable Speed Motor 29th, and it is hoped to have the first re- Television requires at the receiving end a motor which can be varied to suit. ceiving sets available at that time. The Baldor Motor is designed and A popular type of "Televisor" will be built expressly for variable speed work. It is possible to vary the speed from marketed, this being a self -contained com- 50 to 1100 r. p. m. in the 6 pole motor bined radio and television receiver, with a and 100 to 1700 r. p. m. in the 4 polo motor in gradual steps. screen about nine inches square on the right and a dynamic type loud speaker mounted behind a grill on the left. It can be used as a normal radio set, and when television is being broadcast, it will merely be necessary to tune to the special station and then turn a switch to wake the television screen to life. There will probably be but two controls, and the current needed for operation of the television apparatus will be taken from a twelve -volt storage battery. At the couunenceuuent the programs will he transmitted for one or two hours each evening and will consist of sole items such as entertainers, lecturers, cartoonists, com- edians, etc. One of the first stations to he put into operation will be 2TV, London, Baird's station, which uses a wavelength of 200 meters 1929 Cataio$ and a power of 4 kilowatts. Other stations DEALERS AND SETBUILDERS will be opened in the leading provincial HE NEW 1929 Catalog is crammed CZSr Bli centres later. T of the FINEST, NEWEST, na- Although the first tionally-known A.C. sets, consoles, cabin- programs will naturally ets, dynamic speakers, kits, he of a rather restricted nature, the experi- and accessories at LOWESTeliminators, PRICES. ence in the operation of public television Largest stock of Radio Parts. Prompt ' services in Britain and the U. S. A. must delivery. Write for our FREE catalog. quickly lead to improvements. WESTERN RADIO MFG. CO. 128 WEST LAKE ST. Dept. RN-10 CHICAGO, ILL. f' FROM DOWN BELOW íeBgFtendlyRadsoHous Hades, our radio authority, says that he winds his own cigarettes.-Popular Radio lreeklil (:ustrnlin.)

SET BUILDERS` OUR BRITISH COUSINS HAVE 'EM, TOO WHOLESALE GetthisBoofZ, PRICES Barawik, the first and oldest radio Here you will find a new up -to- specialty house, offers you unusual service this year. Bigger stocks, date stock of kits, parts, acces- quicker shipments, lower prices. sories and sets -everything you Deal with an old established, reliable house. Get honest goods, honest service, want in radio. Write for Catalog honest prices. Barawik service mains you more money. Send now for big new Catalogshow- "B," quoting special dealer's log lowest wholesale prices. wholesale prices. BARAof I K CO. CN CAGOU. S. A. Mail This Coupon Now for Free Radio Guide Name Address 711 W. LAKE STREET, CHICAGO - Wireless Constructor (London). Please say you saw it in RADIO NEWS

www.americanradiohistory.com Radio News for October, 1928 3, The Listener Speaks (Continued from page 308) a choice of heterodynes, the writer would rather hear a peanut-whistle than a fog- horn grunt-wouldn't you? t Another beautiful mess in KOIN and KOIL- neither of whom can he heard clearly enough for identification when transmitting simultaneously. Still, we can as a separate WMAQ and WQJ from KFOA Deadly enough to get the announcements and music from either with only a faint whistle; simply because it appears that the Chicago Serpent's stations are up a few kilocycles to let us in. On the other hand, KQW and \VEAF, as well as KFRC and \1'JZ are absolutely Fangs: "the bunk" -the two Pacific Coast stations invariably have a bad grunt mixed up with their transmissions. If these fellows were about five kc. apart, we can see no real reason why the reception would not be clear for all except those actually situated under their aerials, who would be unaffected by Play Safe With the change; inasmuch as they were unable to tune that close in the lirst place, and the local would be so powerful that any overlap would be drowned out. It is a PARVOLTS! cinch that the thousands of listeners be- VOLTAGE Surges in elec- Why take chances tween the stations in question would have with more of a chance of getting either one or tric- powered radio strike at ordinary condensers when the other of two stations on the saine chan- filter condensers with the light- ACME PARVOLTS nel; and they should be able to get both give you of them, and clearly enough to identify ning speed and deadly power of positive protection? and enjoy the program. a venomous snake. The re- allocation would give at least These condensers are made Imperfect condensers, improp- half again as many available channels, and only from highest grade insula- perhaps twice as many; thus solving the erly - rated condensers, non- problem to the last decimal. Very few, if tion papers and special foils. any, stations would be required to cease uniform condensers -all break Every detail of manufacture is operations, while those who wanted could down sooner or later under the make arrangements for splitting time so under the constant supervision no two stations would be using the destructive action of voltage that of experts who have devoted saine channel at the sauce time. overloads. Blown condensers Of course, it all rests upon the possi- many years to the manufacture bility of close adherence to assigned fre- usually mean blown tubes, of condensers for heavy and quencies, as a deviation of a kilocycle would burned out transformers and raise Cain in some instances; but if Mr. continuous industrial duty. Doolittle can regulate to 100 cycles, that is chokes, and even the destruction surely close enough. of speaker units. Every PARVOLT is tested to Now, the theory that a channel must be wide enough to pass 8,000 cycles at least R.M.A. and N.E.M.A. stand- sounds O.K. on paper; but can any one ards and can be relied upon for explain to us why we are able to play half a dozen three -station groups with ten -kc. accuracy and CONTINUOUS bands-and we know they are pretty close DUTY. Sold by leading jobbers to being ten kc.; say within a half -kc. of the assigned frequencies? Isn't it possible and dealers. that the factor of interference does not hold true for stations widely separated geographically? Made by THE ACME WIRE ACME PARVOLT FILTER CONDENSERS- CO., New Haven, Conn., manu- Therefore, we would like to see some- Supplied in all standard mid. capacities for 200. 400, 400, 1000. and 1500 Volt D. C. requirements. Uni- thing done in bringing pressure to bear on form height and width for easy stacking. Supplied facturers of magnet and enam- singly or in complete housed Mocks for the important the Federal Radio Commission, toward the power supply units such as Thordarson, Samson and others. eled wire, varnished insulations, end of adopting this plan or something ACME PARVOLT BY -PASS CONDENSERS are supplied to all standard ntfd. capadHes and for all similar, assuming there are no serious flaws required working voltages. coil windings, insulated tubing in the plan or that something can come of and radio cables. it in which there are no flaws. We are sure of one thing-anything would be better than the present condition, with hetero- ACME PARVOLT CONDENSERS dyning carriers on nine out of ten channels. One authority recently stated that even Made by the Manufacturers of though two 500 -watters were separated by the entire width of the continent, and even ACME CELATSITE WIRE PRODUCTS though their normal voice range was only ENAMELED CELATSITE WIRE, AERIAL WIRE ACME a few hundred miles, if they be transmitting FLEXIBLE and SOLID ACME COILS, SPAGHETTI Enameled copper wire in both MAGNET WIRE, on near the same frequency channel, stranded and solid types. For all types of radio A superior cambric tubing for or miring. High waves would' heterodyne and Also Acme Lead -ins, Bantry insulation & VARNISHED all practical radio and other their carrier Cables, Indoor and Loop value. Non - inflammable. INSULATION electrical requirements. Sup cause such interference that neither of them Aerial Wire. 10 colors. plied in 10 colors. could be understood. It is believed that

Please say you saw it in RADIO NEWS www.americanradiohistory.com 376 Radio News for October, 1928 THESE i

MAGAZINES THE PRICE A year's subscription to these OF Canada and in Europe. This list two popular magazines for the of call letters is carefully checked price of Radio News -alone. If and corrected in each quarterly you were to buy Radio News and edition. Radio Listeners' Guide and Call RADIO NEWS is read each Book individually for one year month by more radio enthusiasts they would cost you $5.00. By our than any other publication in the special combination yearly sub- field. It contains the latest devel- scription rate you can get both of opments and the most modern cir- these foremost radio periodicals cuits of the radio world. Honest, at the tremendous bargain price of unbiased opinions on every sub- $3.00. In order to keep up with ject of interest -this is what the latest developments of Radio, RADIO NEWS gives you. to know the newest sets and how to build Write today- insure your re- them, to find every radio broadcasting ceiving each issue of RADIO station you must read these leading peri- LISTENERS' GUIDE a n d 0 CALL <) at odicals of radio. BOOK and RADIO q-'''',,-.1',..` NEWS. Take advan- rc ro The RADIO LISTENERS' GUIDE AND tage of this special a511ne ',a CALL BOOK is the foremost quarterly subscription offer- to wc;N magazine in the field. A special feature of T w o magazines Q ,ea10 Lt this remrakable magazine is the up- to -the- for the price of ;¿p Q e-Pooa minute a log of every station in this country, one. ' a°acts ot .. o° Special Combination Yearly Subscription Rate i °° 40 'y a4Pvs ivti h a ra $3.00 J4G4 a +`," ,F 4'°c1J`g45 For the Radio Listeners' Guide and Call Book and Radio News *,;<..v4-0,4i e ac9 / o ti i r r9 ° EXPERIMENTER PUBLISHING ; F Qw4w14%`y',e`°o 4a C v<99á 9y COMPANY ° atc 230 5th AVE., NEW YORK CITY, N. Y. 4 ti Pa

Please say you sago it in RADIO NEWS www.americanradiohistory.com 377 Radio News for October, 1928

the carrier wave interference is effective al about four times the normal voice range. Something ought to be done anti mighty 0 quick; or there won't be any umore DX ! 'Phis, for thousands of radio fans, means no more radio for them! Let's see what can be done -we are open for suggestions. Why SCAN THE not move one -half the country's stations up or down 5 kc. as an experiment? V. V. ltoE, ETHER South Gate, Calif. (A problem in radio is caused by the harmonics of broadcast stations, many of which can be heard at several frequencies which are multiples of their carriers. The Radio Commission was led on this account The New to discard proposals to part several stations halfway between the even 10 -1:c. bands originally adopted. One of the troubles "222" attending the broadcast reapportionment is the strength of other considerations be- SHIELD side those of sotind radio engineering cord GRID practical business methods.- EDITOR.)

Likes the Ukulele Combining the proven, hyper -sensitive NEws: STROBODYNE system with the tre- Editor, RADIO mendous amplification obtained through the Haying repaired sets for some time, I use of the new shield grid tubes, in a special into contact with many radio circuit making full use of their extra high have come amplification factor. fans, and they all wonder why the sweetest music is slighted. In short, they would The "222" STROBODYNE all appreciate more, or at least some, Ha- Latest Design by waiian music. R. E. LACAULT, E.E. have written to Many of my friends leaves far behind all other types of sets. Its performance studios, and their efforts were not even bas amazed experienced engineers and it has come through recognized. The hope of getting more hard tests with flying colors. Hawaiian music through the medium of SPECIFICATIONS me incentive to write Itanio NEws gives the 1- QUALITY OF REPRODUCTION this, as I believe the first stations to wake Through the use of high grade audio transformers com- power will become the bined with a push -pull amplifier and the best method of up to its drawing detection, the most remarkable fidelity is obtained. The most popular of all. results will amaze the most critical musicians. Wm. H. PEET /., 2- VOLUME New York. The tremendous amplification of the shield grid tubes 1514 East 94th St., Brooklyn, produce unusual volume which may, however, be regulated to any desired value through a special control. 3- SELECTIVITY The very high impedance of the shield grid tube, com- Modulation Problem bined with the special circuit used makes the tuning The very sharp without affecting the quality. Editor, RADIO NEWS: 4- SF.NSITIVENESS to Speed The sensitiveness of this receiver is so much greater In his article, "Vacuum Cameras than that of any existing set that it is beyond com- Up Television," in the July issue of Ranfo parison. There is NO LIMIT to the range. The noise Mr. Clarkson asks why it is neces- level is the only factor affecting it. NEWS, 5- SHIELDING sary to employ a band of frequencies for Entire R.F. system completely shielded. television transmission, rather than a single 6-EASE OF CONTROL frequency. Only two dials, a volume control and sensitiveness con- fact that elec- trol are used -making the set easy to operate. Surely, it is a well -known 7- STROBODYNE SYSTEM trical communication of any kind, whether The STROBODYNE method of reception -a time -tested voice or television, cannot and proven circuit -is incorporated in the set, causing it be by telegraph, very weak signals to produce a tremendous response. be maintained by means of a single fre- 8- MATERIAL quency. It is necessary in every case to Only the very best of tested parts are used in the entire set, insuring permanent high efficiency. a band of frequencies. Mr. lt. V. L. employ 9- DESIGN Hartley, the noted research engineer, has The new "222" STROBODYNE is designed by R. E. in a fundamental study of the fre- Lacault, E.E., well known creator of several famous shown circuits, whose reputation is a guarantee of the high quency relations in electrical communica- grade radio engineering incorporated in this set. tion, that the width of the frequency band or spectrum used is a direct measure of the build it in the September issue of Radio News speed with which intelligence of any kind Read how to may be transmitted. For 20 -cycle telegraph and Blue Print No. 63 width nec- transmission, the frequency-band We equipped to give you essary for good signal quality is from 60 to are 80 cycles. For voice transmission, a frequency hand 8,000 to 10,000 cycles wide MAIL ORDER SERVICE should be used. :1 well -known laboratory PROMPT for communication research demonstrated All genuine parts carried in stock of at recently that a frequency -band width Special least 0,000 cycles is necessary to obtain EXPORT ORDER DIRECT from reasonably -good resolving power in tele- Department vision apparatus. This wide frequency hand is. of course, rendered necessary by the R. E. LACAULT, INC. speed which "Intelligence units" enormous at 65th Street, Dept. 405, New York City mast be transmitted in television. 116 West Amplitude modulation of a carrier wave Cable Address Long Distance Phone without introducing additional frequencies LACRAD NEW YORK SUSQUEHANNA 2095 Please Say you saw it in RADIO News

www.americanradiohistory.com 375 Radio News for October, 1928

in the process, as suggested by Mr. Clark- son, is manifestly an impossibility; for a A REMARKABLE N Now Receive change in amplitude is invariably accom- i panied by a change in frequency (i.e., a band of frequencies is immediately pro- C Broadcast duced). This fundamental concept is almost as old as the art of electrical com- SUPER on Short Waves munication itself. A clear idea of the nature of complex TRANSFORMER waves can be obtained, by anyone having an elementary grasp of the infinitesimal calculus, through reference to Byerly's "Fourier's Analysis and Spherical Har- monics," a book which has been in print, I believe, for twenty or thirty years. Yours very truly, T. A. JONES, 463 West Street, New York City

(In addition to Mr. Jones' letter, the ad- After long and particularly exacting tests Ilse new Victoreen Super Transformer Is now dress of which alone would indicate that he announced as a radically nest and better product -one that will be as Outstanding In These are the new has some familiarity with his subject, an- Its superiority during the 1929 season as the Acro L. W. T. coils other making similar representations has precious type has been in years past. used in been received from Arnold Lesti, of Los Write for FREE Blueprint of the new and perfected Victoreen A.C. Cir- Angeles, Calif.) cuit, using this marvelous new Transformer. The set is easy to build -of unsurpassed tone quality and reliability. The George W. Walker Company Merchandisers of Victoreen Radio Products 2825 Chester Ave., Cleveland, O. The Good Reception "Down Aero International Under" Broadcast reception on short waves is remarkably clear and free from static. Editor, RADIO NEws: Programs are brought in from greater distances with the utmost simplicity I am situated northwest of and about of control. 400 air miles from Adelaide, about 800 air You can easily assemble the Aero International. miles from Melbourne, 1,000 from Sydney This remarkable set is built around the new Aero L.W.T. Coils -the acknowledged leaders and about 1,100 from Brisbane; and yet 1 in the short -wave field. The foundation unit can log all the Class "A" stations in these for this receiver comes with holes already drilled, assuring ease of construction and cities on ali 8 -tube set at very great proper placement of all parts. As an aid to speaker volume at any time of the Clay, home builders, Aero Kits include both large 7Iiis Book schematics and actual size pictorial wiring and at any time of the year; and I have diagram. them at good speaker strength on a live - BringslDeálers Ask your dealer for a complete Kit of all parts tube neutrodyne. for the Aero International. If he can't supply you, write us, giving his name. Curiously enough, the amateurs, and par- BIGGER PROFITS ticularly those who work on wavelengths Uses Aero Coil Matchless bargains in radios and accessories. Full line of Sleeper under 250 meters (Experimental work on Brown ingD rake, Carter, Utab, Tower Speakers, Temple, Ma)estic, 10 the Kodel, G.E. T Ungar, Burgess, Jewell, Belden. Cunningham tubes, L.W.T. Kit broadcast band is snore freely allowed nationally advertised parts, storage batteries, chargers. etc. Big wish in Australia, where there are comparatively opportunity for live ones who can sell radio. Double sales quick. If you to purchase only the Aero Coils less your letterhead. Exclusive open. for this short-wave receiver. order the L.W.T. few broadcast stations. -Editor.) come in NEW ENGLANDGLAND MILLS COMPANVCOW! 10 Kit. The price is $10.50. These coils are Nationally Advertised Radio Lines designed to be used with our foundation unit. with very much greater strength than the Dept. R200 851 -55 Washington Bird. Chicago. III. If you prefer to furnish your own foundation "B" stations; although they use only from unit, order the L.W.T. 11 Kit, price $11.50. This Kit includes mounting base. 15 to 50 watts, whereas most of the "B" FREE stations use from 100 to 500 watts. SET Builders Elections have brought back Custom On Sunday last, February 19, I logged Set building. Business is booming. The New Aero WOWO at good speaker strength Thousands of old -timers are clean- at 6:30 ing up. Let Barawik show you they 12 p. m. (3:00 a. m. Central Standard Time way to bigger profite, more sales. L. W. T. Coils - Send today for Barawika Big Bar. evidently an experimental transmission) or gain Book - the radio mans bible. Io6B 1tü011WN1A, BARAWIK CO: CHICAGO, U. S. A- vmMV A REAL Here are the newest Aero Coils -the SPECIAL OFFER! L.W.T. 12 Kit. These coils are small in i diameter, providing a much smaller external field, and improved efficiency. Order LIST PRICE this Kit if you want the very maximum results from your short-wave receiver. The New Gould Consists of three Aero Interchangeable $39.50 EA. Coils and base mounting with Primary Kathanode n1 Coil. Price, $12.50. GOULD PRODUCT WITH BUILT -IN RELAY Automatic Radio "A" Power From Lightr Socket Convert Your Present Model the Aero Short -Wave AC-C-K (6 -volt) Kathanode t;niposver is the highest quality "A" Power Build Unit built. Furnishes rich, smooth, unfailing and receive "A" current without any trace of hum Receiver Converter for the largest power tube sets. installed in less than three minutes. makes any set as short -wave programs on your present set. No simple and convenient to operate. as an expensive AC outfit at only a traction extra tubes needed. Just plug into detector of the cost. No rewiring necessary in your set. socket of your set. Ask your dealer for com- Its Kathanode construction Insures longer lite and freedom from service expense plete Kit parts or write us. We have com- and when sold it will take care of itself. is very economical of EXTRA It and will outlast plete Kits for shielded grid, A. C. or D. C. e75 several storage batteries. Its Kathanade construction is an exclusive patented SPECIAL $10 feature now being used by the U. S. Government In their Submarine Batteries which are furnished by Gould. ',FPO Equipped with a new noiseless Balkite Charging Unit which has four graduated ', Brand new, in original charging rates and in addition one booster DUM rate (1i amperes) for an emergency INCORPORATED' L'NO factory cases, complete charge. Operates on 110-120 V., 50 -60 A.C. cycle current. with extra fuse. Dept. 105 4611 Ravenswood Ave. Chicago, III' AMERICAN SALES CO., 19 -21 Warren St., New York City

Please say you saw it in RADIO NEWS www.americanradiohistory.com Radio News for October, 1928 379 about three- quarters of an hour before sunset, while the light was still very strong; and at the salue time last night (the 21st) KFKB came in so loud that it could be The New Knapp "A" Power Kit heard distinctly 60 yards from the speaker, with a good wind blowing at the time. Among other things, it would seem that locality plays a very important part in daylight reception; as in Adelaide, for instance, which is 400 miles nearer to Mel- bourne than we are, it is said to be quite impossible to get 3LO, or any of the other stations in Victoria or New South Wales in the daytime. With best wishes for the future of RADIO NEWS, which is quite on its own as a radio publication, and which is widely read in Australia. K. L. WILLIAMS, Arcoona Station, via l'imba, South Australia. Y.S. -Can you publish a list of the broadcast stations in Manila, as I have heard four besides KZRM, but have not been able to get the call signs on account of static? I think, however, they arc KZRO, KZKZ, KZIB and KPM. (While this reception is remarkable, it will be remembered that, though the receiver was in daylight at the height of an Australian summer, the transmission was in the dead of night in an American winter, and about nine- tenths of the path of This is the °A" power after you have assembled it. A professions job. Operate, on the radio soave was in darkness. 105 ro 120 volts, SO to 60 cycles AC. Supplies official list of stations from Greater rippleless DC current for operating any set The latest using Standard 5 or 6 volt tubes and p.rwer Washington shows only three broadcast tubes. stations at Manila: KZIB, 260 meters, 20 Efficiency- scatts; KZKZ, 270 meters, 100 watts, and KZRQ (succeeding KZRM) 413 meters, 1,000 zoatts. RPM is a commercial station. Improved Design and Appearance -Lower An American short -wave listener reports what seems to be a short -wave broadcast Price- Money- making Plan for Set -Builders station giving its location as Manila. Has it been heard by others?- EDITOR.) You radio fans who made my "A" power the largest sellinge`A" power last spring have made itpossible for me to offer thefinest "A" Power ever developed-in Kit form -even more complete than before. TIME TO RETUNE Study the illustrations -read the improvements -and you will "How do you like the program sponsored wonder how I was able to reduce the price. You are the answer. I Iry the Goodstone Rubber Co." sold 5 times as many "A "Powers as I expected to-and this season "Aw, they tire me to death l " -1V. G. M. I am counting on you to help me again by buying even more. The 8 Improvements THE SET- BUILDER TAKEN RADIO TERMS ILLUSTRATED 1. Larger Filter System -3 Elkon CARE OF Condensers instead of 2. Ideal You set -builders played with me (as for Super Hets and Short Wave the saying goes) and I am going to continue to play with you. My engi- Sets. neers have designed an "A" Power 2. Improved Choke Coils which is well -nigh perfect -my production men, based on tremendously 3. Pendant Switch Controlling "A ", large quantities have cut their cost, "B" Eliminator & Set so that I can keep faith Dial for regulating voltage with you by reducing 4. the cost. And regard- 5. Celeron Front Panel less of what the estab- finish lished trade may think 6. Baked - about i t -I am going to 7. Heavier gauge metal cover continue to give you the maximum discounts. B. Die Cast Base Plate instead of wood The coupon will bring you the full details of both the new "A "Power COMPLETE KIT -EASILY and the special dis- ASSEMBLED counts to set -builders. David W. Knapp, Prey Like my Kit last year, the New Knapp KNAPP ELECTRIC, Inc., Port Chester, N.Y. Kit is a tooled job-the parts seem to Div. P. R. Mallory & Co., Inc. fall into place. Every hole is drilled - r all that it is necessary for you to do is Mr. Dar id W. Knapp, President, to put the screws and nuts in place KNAPP ELECTRIC, Inc., a few wires. Everything 336 Fox Island Road, Port Chester, N. Y. and connect Kindly send me complete information on the is supplied. Nothing for you to buy Knapp "A" Power and your special discounts for extra. The fool -proof instruction Set- Builders. sheet makes it easy for anyone to Name assemble. Address

'Input " -"Output[ Please say you saw it in RADIO NEWS

www.americanradiohistory.com 380 Radio News for October, 1928 Adjusting and Operating the ransmission Of Photo's by Radio Screen -Grid Strobodyne OF PHOTOGRAPHS the electron fiòw constitutes a dis- ANSMISSION By R. E. LACAULT BY RADIO - Various methods have charged circuit, so that the grid be- been devised and are now in use for comes less negative. The first ampli- the transmission of photographs by fying tube is a direct current potential Vi);1tY thorough instructions were given radio. Among these may be mentioned amplifier, and is resistance cßápled. n the September issue of RADIO NEWS the systems of Belin (q.v.), Baird, and The grid and plate connections of the for the construction of the new Screen -Grid Jenkins. The principles underlying amplifier are connected across a con- the Jenkins system are explained denser which becomes discharged with Stroboclyne receiver (Free Blueprint Article under the heading of Television. the fall in the grid to plate resistance No. 63). Some further suggestions, how- Using the system developed by Capt. of the valve brought about by the grid ever, may be welcomed by the constructor R. H. Ranger, photographs were potential fluctuations. A charging cir- as to the operation of this wonderfully sen- transmitted by radio from Honolulu cuit' is connected to the condenser and sitive receiver in order to take fullest ad- to New York, a distance of 5,136 miles. is controlled by a valve, the grid cir- vantage of its possibilities. Recently commercial picture trans- cuit of which operates by variations mission service has been inaugurated of the potential across the condenser. It will be found that the voltages shown 1, 236) between New York and London using The charging current is fed through . in the diagrams (Fig. page are the Ranger apparatus. Two distinct the plate circuit of this valve, in which about correct, as stated previously; but in ethods have been applied for analyz - a relay is connected, which working many cases the signal _intensity may be ing the picture in the process of trans- through other mechanical relays in increased by raising the voltage on the screen -grids of the tubes to some value between 45 and 67. It is also recommended that a separate battery be used to supply the voltage for the screen -grids of the tubes; because this avoids the chance of a feed- back between this grid circuit and the "B" battery circuit; that is, the supply which is connected to the plates of the various tubes. If the "B" batteries used are new and do not have much internal resistance, it is satisfactory to use the same set of batteries; but, when the batteries are beginning to weaken and their internal resistance increases, it is preferable to have a separate battery for the screen -grid circuits. On an efficient "B" power unit, where all the taps are bypassed by the necessary condensers, it is satisfactory to connect the screen -grids A pencil of light traverses the picture which is attached to the glass drums and is analyzed by a slow rotating action as well as a backwards and forwards movement of the carrier. to the 45 -volt tap, or a slightly higher potential if required. mission. One arrangement consists of cascades,' controls the radio trans- roducing an image as a non-conduct- mitter. . Wave trains from the trans- OPERATING THE SET deposit upon a metal foil which is mitting. station after detection and, versed by a stylus, while the other amplification, are applied to the pic - The tuning of the receiver is not diffi- thud makes use of an opaque image ture recorder. The recording mechan- cult and, although the dials do not run ex- osited upon a transparent film ism, in order that it may be sensitive actly alike over the entire scale, they are Lich is traversed by a beam of light, to exceedingly small currents, com- sufficiently close in reading to rind easily to coil, light interruptions being recorded prises, a small moving in a mag- stations between 200 and 550 meters; that y a light sensitive cell. The Ranger netic. field created by three electromag- is, over the entire broadcast band. In istem makes use of this latter method. nets. . The coil of wire, in moving in (1(2) The image is p e to ' rded the field, as the received fluctuations normal operation the rheostat should Ipon a eel not be turned on quite full; that is, its eco,' slider should be placed about a quarter of an inch away from the end. When receiving weak signals, the sensitiveness of the set is somewhat increased by reducing the fila- S.Gernsback's ment current of the Strobodyne tube (V2) and you will notice that on most weak sta- Radio tions the signal will increase in intensity when the tube almost stops operating; that Encyclopedia is, when the rheostat is turned just a little A facsimile of a portion of a page from S. too low. If the tubes stop operating, turn Gernaback's Radio Encyclopedia is reproduced the rheostat on again and reduce it slowly herewith. A glance at the thorough manner in is which each item is treated cannot fail to instill a until the most sensitive point found, true appreciation of the value of the remarkable where the signals are the loudest. This book. S. Gernsback's Radio Encyclopedia is the first ever publishes. It is not a dictionary. amplification is obtained on most stations, It covers every possible phase of radio. Every 14.32 but it seems that the percentage of the circuit, each piece of apparatus, all the leading ' wave has some- characters of the industry. broadcasting, re- I Il_ modulation of the carrier ceiving, television. telephoto, everything con- thing to do with the amplification obtain- nected even in the slightest way with the growth " able by this method. of radio or its kindred sciences, is most authen- tically explained. There are over 1930 separate On most stations, however, some increase definitions. 549 illustrations, a complete cross num,m", , index. and many other special features. is obtained by burning the tube as low as S. Gernsback's Radio Encyclopedia comes in possible without stopping it from operating. 'i two beautiful bindings, large 9 x 12 in. size. The volume- control resistor (R9) is used Cut here COUPON Cut here merely to reduce the volume when signals are too strong, as happens on local stations n Beautiful Limp Suede Edition (de luxe) $5.00 recording mechanism of the receiver. nu and even on some of the distant stations O Stiff Binding which a moving co Keratol- Leather $2.00 which are received like locals. Write your name and address in the margin below, mark which binding you prefer, and applied through its windings, the book +rill be sent to you C. O. D. plus ates a stylus while travelling ADJUSTMENTS postage. ss the surface of the paper. The us traverses the- paper in perfect After the receiver has been placed in S. GERNSBACK chrony with the carriage of the operation, it is necessary to adjust care- 230 FIFTH AVE. NEW YORK, N. Y. nsmitter, the paper being lifted fully the small adjustable condenser (221 in order to obtain maximum efficiency from

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www.americanradiohistory.com Radio News for October, 1928 381

the B.F. circuits. This condenser is em- i ployed to balance the circuits in shields S1 and S2, so that the simultaneous one- dial tuning is as efficient as if two dials were used. The first step in making this HAMMARLUND' S adjustment is to tune in a low -wave station and disconnect the ground wire from the set. With only the aerial connected, it New Contributions probably will be found that stations operating on waves below 300, meters may be received at two points on the left tuning to Better Radio dial (C1 and C2), and this is indicative of the fact that the circuits are not properly balanced. Shield-Grid Coils To correct the condition described above, Exceptionally efficient low- resistance, space- wound, self- supporting inductance, 2 inches the adjustment screw of the condenser C21 in diameter, fur real results with shield -grid is turned in one direction, and then in the tubes. A high -impedance primary with duce taps other, until a point is found where there is for desired pick -up and selectivity. only one setting on the dial for receiving Antenna coupler and R. F. Transformers for any given station. For example, it may be use with either .0005 mfd. or .00035 add. condensers. which a - found that the two points at low Vertical mounting bracket. Convenient SOW/. wave station may be received on the left ing terminals. dial are 5 and 9 degrees. Also, it will be found that turning the adjustment screw one turn to the right causes the dial settings to change to 5 and 11 degrees, and that turning the screw to the left causes the settings to be 5 and 7 degrees. Under these conditions, therefore, it will be necessary to turn the screw further to the left until the highest setting is reduced to 5; Knob -Control Drum Dial or until only one point on the dial remains Unmatched beauty and a mechanism that at which the low -wave station may be would delight a watchmaker. The control knob is uniquely planned to be placrd tuned in. in any position on the pastel desirable for Because of the simplicity of its controls, attractive balance. the set is tuned and operated very easily Numbers and degrees on a translucent drum illuminated from the back. by anyone; and this makes it more practical than the former model, described in !Lido NEws for August, 1927. The original Stro- For the Short -Wave Fan Ito(lvnc had more controls to manipulate Plug -in Coils, covering the short -wave bands and it was somewhat more critical than the from S to 215 meters. Extremely low resistance; widely -spaced plug - new design; in which many things have been in terminals. Adjustable primary, held in any improved and corrected in order to make position by friction. this circuit more efficient all around and better in every particular. 'l'he Screen -Grid Strobodyne is designed for operation only with an aerial; but ang aerial will operate it, and this means any- "Battleship" Multiple thing from a few feet of wire to a regular 100 -foot installation, such as are used for Condenser Leader of the gangs. Built for strength as the majority of sets. If one cannot put well as beauty. Die -cast frame, free - j up an outdoor aerial, the set will operate moving rotor. Sections accurately matched to within of one per cent (plus or minus.) very with any sort of indoor Si satisfactorily Made in 350 mmfd. and 500 mmfd. sizes, energy collector; such as a piece of wire with two, three, and four gangs. fastened around the picture molding, or Recesses in the frame permit direct attachment of new type Hammarlund Equalizing JV t. .paLA1t.tL aQ.C(,lD' even laid under the carpet in the room. Condensers for utmost precision. The ground may be anything from a water Write for literature on these and pipe to a radiator, or any large surface of other ne:v Ilanunarlund developnter.ts. ammarlundREC/5/ON metal which is in electrical contact with the HAMMARLUND MFG. CO. ground. 424 -438 W. 33rd St. New York PRODUCTS It should be pointed out also that there are on the coil LI three terminals to which D 011+s0sssrIWIL In the aerial may be connected. These posts are marked 2, 3 and 4, and the aerial should be connected to the one which pro- BUILD YOUR OWN vides the best results. RESNMA DYNAMIC SPEAKER Because of its design, this set is unsuited ULTIMATE RADIO Complete set of blueprints and instructions for to the reception of short-wave broadcasting Fit., N building your own Dynamic cone speaker. Easy below 100 meters. We do not advise the and inexpensive to build at home with few tools. AT ALL Guaranteed to work; thousands now enjoying builder to try to adapt it to the reception Dynastic reproduction. Mail $1.00 today and you will receive complete set, postpaid. of short waves, because it tunes too sharp AUTHORIZED FANSPEAKER RADIO COMPANY for this purpose and there would be re- 74 Dey Street New York, N. Y. quired several changes in the circuit which DEALERS are not considered advisable. In conclusion, the writer wishes to repeat the fact that he considers the Screen-Grid FREE Strobodyne the most sensitive receiver he FRIEWItelesaleRadiorat SET Builders has ever handled and the most satisfactory Elections have brought back Custom Set Builders -Dealers! Save Money! Set building. Business is booming. all- around receiver for broadcast reception. Send for the most complete book of nationally known Thousands of old. timers are clean- Parts, Kits, Cabinets, Consoles, Speakers, Power Units, ing up. Let Barawlk show you the If carefully built, in exact accordance with Seta eta All at lowest wholesale prices. Quick service way to bigger profits, more sales. the instructions given in this article, the *nail your needs. Write now, it in FREE- Send today for Barawik'a Big Bar- SETBUILDERS SUPPLY CO. gain Book - the radio mans bible. most blasé experimenter will find new thrills Dept 13 -4 Romberg Bldg. Madison and Market Sts. CHICACO, ILL 2106CHICAGO,'U. CO. S. in operating this marvelous receiver. B^RM-'K A.

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www.americanradiohistory.com 382 Radio News for October, 1928 What's New in Radio (Continued from page 312) 8POPULAR' sparks produced by the brushes sliding over the surface are the cause of serious interference. At the transmitting end the motor MODERIN is just as important an item, for the speed must be absolutely constant in order to allow motors at the receiving stations to MOVIE operate at the same speed. A feature of the motor which is shown in the picture is that it is of the induction type and, therefore, does not rely upon a NOVELS commutator either for starting or running. This insures the fact that the motor will not cause interference. Secondly, the motor GREATEST OFFER EVER MADE may be adjusted easily to any speed between 750 and 1,750 revolutions per min- Take Advantage of Titles of This An Addition To ute, and it will hold its speed very constant This Amazing Tremendous Bargain Offer Your Library after it has been adjusted. The motor has a high efficiency, the starting current is Bargain very low and it is cool running, quiet and 1. New York These books will Eight full size books 2. The Campus Flirt clean. It is available in three types, one for one dollar. Never be a worthwhile of which is intended especially for trans- 3. Almost a Lady before has an offer of addition to your mitting stations. A machined flange for this kind been made. 10. Sensation Seekers library, You will the scanning disc and rubber cushioned bases Only quantity produc- 11. The Rambling Rangers for the motors are also available. tion permits us to make find many hours 12. Don't Tell the Wife Manufacturer: Co., this astounding offer of enjoyable Interstate Electric 14. Tracked by the Police truly St. Louis, Mo. now. Take advantage in of it while you have 15. Tell It to the Marines reading each the opportunity. Need- 19. Irresistible Lovers beautiful volume. less to say these mod- 20. The Cohens and Kellys Printed on fine pa- ern up -to -date movie In Paris Receiver hits cannot last long per with large clear The "Combine" - at this tremendous bar- 21. The Divine Woman type. Beautiful $100 Prize Winner gain price. Each book 22. Jazz Mad colored covers of at least (Continued from page 333) contains two 23. The Crimson City flexible durable ma- color "stills" of an 24. You Can't Beat the Law actual scene from the terial. These books at the rear of the triple condenser for still 25. Punctured photoplay. Don't hesi- Tillie's are undoubtédly greater volume. This operation may require tate. Mail this coupon Romance considerable experimenting before the dr- now. Every story 26. Forbidden Hours one of the greatest based on an actual values ever offered cuits are properly adjusted, and it would moving picture tri- be well to tune in a comparatively weak sta- umph. The greatest 8 BOOKS FOR $1.00 at this amazingly tion for the purpose of making the adjust- book bargain of the Your Choice low price. ments. age. The next problem for the set builder is to suppress oscillations in the long -wave set, Write Now ! Don't Wait ! This bargain cannot last long at this price and this is accomplished by adjusting the devices PI and P2. In making these adjustments, best results are obtained when re- CONSRAD COMPANY, INC. ceiving a station operating near the lower 230 FIFTH AVENUE NEW YORK, N. Y. end of the broadcast waveband. This station should be tuned in as loud as possible with the dial, and the rheostat should then CONSRAD COMPANY, INC., 230 Fifth Avenue, New York, N. Y. be turned up until a whistle or squeal is Gentlemen: Enclosed find $1.00. Kindly send me the books listed by number herewith:. heard in the loud speaker. While the set is whistling the units Pl and P2 should he Numbers adjusted with a screw -driver until the Name whistle disappears. If these units are ad- Address justed properly on the low wavelengths the receiver will be stable in performance over City 'tate the entire broadcast waveband; but it may be necessary to repeat this adjustment sev- SPECIAL OFFER! eral tinges before best results are secured. A REAL After the broadcast set has been adjusted properly it is very easy to operate. It is UNI -RECTRON POWER AMPLIFIER necessary only to turn the drum dial until ( Ideal for use with Dynamic Speakers) the desired station is received, and then Model AP -935 adjust the rheostat, RI, for the degree of As the Uni -Rectron stands The UX -210 super power volume needed. it is a super power ampli- amplifying tube and the In the -wave section of fier, which can be used in UX -216B or 281 rectifying operating short connection with any radio tube are used with this am- the receiver the only important thing to re- set and loud speaker. Bind- plifier, which cannot over- ing posts are provided for load. From the faintest member is to use the correct coil for the input to the Uni- Rectron whisper to the loudest crash wavelength which it is desired to receive. and output to the speaker. of sound -R. C. A. Uni - Rectron amplifies each note The wavelength range of the various coils is Requires no batteries for its at its true value. High and approximately as follows: red, 17 to 30 operation. It obtains its low notes are all treated from the 110 volt, List Price $88.50 meters; orange, 30 to 52 meters; yellow, 48 power (without alike. The volume 60 cycle alternating tubes) and quantity deliv- to 105 meters, and green, 93 to 203 meters. Current lighting cir- ered will be a revela- cuit of your house. Special $19.75 ea. tion. With the proper coil in the socket, the oscil- Every one new and Hacked in original factory carton lation- control knob R7 should be advanced, the condenser dial C4 should be ad- AMERICAN SALES CO., 19 -21 and WARREN ST., NEW YORK CITY until the station is located. Then SEND FOR OUR LISTS OF RADIO BARGAINS justed the knob R7 should be readjusted until a

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clear signal is received. The knob 113 may he used to regulate volume, if desired.

Terms of Prize Awards R. SCHEPPELE, the winner of the m $100 prize for his ingenious "Combine" set, is a custom radio builder of Waterloo, Iowa; and his design of this receiver is the result of experiments which he has carried on over a period of several months. It is the desire of RAnlo NEWS to award such a prize every month; but it can be given only when a radio receiver or other apparatus embodying some novelty suitable for general construction is submitted by a home or community radio constructor. It cannot be awarded for an old design, how - ever well built; nor for apparatus, however ingenious, which is too complicated for the average set constructor to put together with the aid of the RAU10 NEWS blueprints. It cannot be given to a manufacturer or his engineer, as it is intended solely to encour- The Mershon Con- age independent experiments and invention. denser gives a very Applications to enter this contest should large capacity in a be addressed to "Editor Monthly Construc- very small space. tion Feature, RADIO NEws, 230 Fifth Is self -healing in N. Y." and be accom- Avenue, New York, case of puncture, panied by photographs showing that actual and is unaffected work has been done and a schematic wiring diagram, showing the circuit used, in order by changes in tern - that its practicability and its novelty may perature, or by be determined. All papers must be of good moisture. quality, with legible writing in ink or type - writing, and each sheet must hear the sender's name. On receipt of these, the constructor will be advised whether or not he is to send in Expert radio amateurs used any apparatus. 11ADlo NEWS reserves the the Mershon Condenser for right to construct another receiver or other more than six years in their device using the prizewinning circuit, but transmitting equipment. To- substituting other components, for its illus- day the Mershon Condenser trations and published blueprint diagrams. is being widely used over For the best entry from a home or custom the whole country in con- radio builder each month which its suitable nection with electrical radio for and published as ca Free Blueprint sets, whether new AC tubes article, One I- hundred Dollars will be paid, as we have stated. are used, or battery sets are In addition to this, if the idea is patent- attached to house current able, RAnlo NEWS will pay the entire cost thru the use of Eliminators. of taking out the patent in the name of the inventor and for the inventor's sole benefit. The publication of the article will protect the inventor for a period of two years. We Zeocd for experience of The AMRAD Corporation believe that the combined Hillside, Mass. our army of readers should produce many Your Medford Free Copy new book ingenious and valuable designs for home unti Please send a copy of your custom builders. MERSHON on the ONDENSER, of showing hook -ups and designs. Thit gook.... Name...... WRNY\ Address 326 METERS - 0OKI1LOCYCLES and 2 %AL, 30.91 METERS FREE RADIO GUIDE is owned and operated by the RADIO SCHOOL ' Radio has been changing sofast ' NEW IArt- I magazine SEND FOR CATALOG lately that it's hard to keep up 'BOOK publishers of this with it. Barawik's Big Radio Guide I is/qlÓilr' of Our Editors will talk to you will keep you posted on the newest MASSACHUSETTS RADIO and wrinkles. Thousands of illustrations several times every week - TELEGRAPH SCHOOL of sets. parts, new ideas. Big chance to save big money. Send for free copy now. See your ACewspaper 18 Boylston St. Boston, Mass. Canal for details BARAWIK CO ., uCHICAGO. U S S. A. IN ON. TUNE E.C.A. "A" Eliminator GO cycle, 105 -120 V. output 2;5 amens 6 V. No Battery-SILENT-516.00; "B" Eliminators. 150 V. ' WRNY 40 millamps , 4 taps, with 280 bulb, $10.00; Model KW. 180 volts. 60 mills. 5 taps 280 bulb. 2-5 volts. 35 amp. tape for Insure your copy reaching you each month. Sub- power tube; "ABC" Eliminator. one unit 2% amps. 6 V. A aide, 180 volts, 5 taps, 60 mills "B," 4.5:9. 40 volts "C," Com- scribe to RADIO NEWS -$2.50 a year. Expert- plete 520.00: 2 ampere "Z" metal charger electrolytic. $6.50 2 ; menter Publishing Co., 230 Fifth Ave., N. Y. Trickier, 53.75; amp. screw base DRI rectifier, 52.25; Speaker C. output filter, protects speaker-51.50. Underground aerials $3.00 Dealers wanted. Catalog. ELECTRO- CHEMICAL COMPANY OF AMERICA. Indianapolis. Ind. Please say you sato it in RADIO Nr.tvs

www.americanradiohistory.com Radio News for October, 1928 SECOND I S S U E J U S T OUT

In This New Issue 20, Complete Instructions For Building a Television Receiver sudden There can be no question but that Television is here to stay. Like radio, its popularity came practically overnight. It has taken a decided grip on public opinion and bids fair to sweep the entire country in a never- before -witnessed blaze of enthusiasm. So, fans! Dig out the old soldering iron, the bus bar and the rest of your paraphernalia and get to work on the latest hobby.- Build yourself a Television Receiver. from perfected. It is still in a most elementary stage. Of course, Television is far made and it There is little use in trying to gloss over the truth. But a start has been in radio, in developing the new art.. remains for the "fans" to do their share, as you ambi- In the latest issue of TELEVISION there are full instructions from which efficient experimental set. With this set you will be able tious enthusiasts, can construct an will con- to receive some of the Television programs now being broadcast. Experimenting of TELEVISION today! Start to work on your tinually improve reception. Get your copy The old Teledisor tonight! Be the first in your neighborhood to have a Television set. "fan days" are here again. Don't miss the fun! Partial List of Contents HOW TO BUILD A TELEVISION RECEIVER Sta- Movies Practical Demonstrations Scheduled for New Jenkins Radio tion WRNY New Berlin Photo Transmitter Campbell Swinton Television System Vacuum Cameras to Speed Up Television Quartz Crystals Synchronize Television Sets Infra -Red "Eye" Sees at Night Baird Optical Lever Increases Speed Valensi Television Recording Pictures with Air Jet Connection of Photo- Electric Cell How to Build a Radio Photo Recorder and many other articles of equal interest THE 25e COPY At all newsstands, or write direct EXPERIMENTER PUBLISHING CO., INC. 230 Fifth Avenue, New York, N. Y.

EXPERIMENTER PUBLISHING COMPANY, Inc. 230 Fifth Avenue, New York, N. Y. Gentlemen: Please forward to me a copy of TELEVISION. Enclosed find 25 cents

Name

:ddress. City ...... state

Please say you saw it in l nuio Nt:ws www.americanradiohistory.com Radio News for October, 1928 385 Television -"Seeing" Music (Continued from page 315)

This rheostat is connected simply in series with the motor. Try any rheostat you happen to have on hand, and see how much New control it gives. Of course, the radio receiver need not be mounted on the top of the framework, as shown. One of the new Stewart -Warner T.C.A. AMPLI-PALK Makes Your Set an Ultra-Modern A. C. Power Receiver A Complete A.C. Power Supply -"A" and "B" and "C "- illakes any D.C. Set For into Modern A.C. Receiver. an Ultra- 1 -250 two 210 type tubes in Push -pull; Uses Type or one of the new 250 type tubes. Power Amplification gives perfect reproduction Tube over the entire musical scale range. PULLEY Lets You Enjoy Real Musical Reception SHAFT Clear, bell -like tone. Powerful volume. Am- plipaCk gives you an advanced radio instrument at less cost than ever before offered. Consumes no more current than an ordinary 50 -watt light. The Cool, quiet, dependable. Quickly Assembled T. C. A. You can assemble an AmplipaCk easily in one evening. A screw driver, a pair of pliers and a High Quality Line soldering iron are all the tools needed. We supply complete layout diagrams. Simple to install. also includes Attached to set in 3 minutes. 171 Push -Pull and Straight AUDIO TRANSFORMERS 210 Power Packs AUDIO OUTPUT CHOKES Complete power supply units for honte con- POWER PACKS and CHOKES structed amplifiers. Compact, scientific design Fig. 2. The method of clamping the scanning disc to the fan shaft. It must be centered together with silent, absolutely dependable op- exactly. eration make these our most popular Power Packs and other Transformers for honte construction. Every coil in our Transformers is vacuum A.C. receivers, which had been submitted At All Leading Dealers impregnated with a special compound. This to RAnIO NEws Laboratories for test, the Ask your dealer for AmplipaCk. He can give prevents noisture disintegration and short cir- so happened to fit nicely in this position, you full details and our simple assembly dia- cuiting. Clean cut laminations make them hum it was used. grams. Don't be satisfied with out -of -date re- proof and banish noise interference. The method of connecting the nèon tube ception -build an AmplipaCk tonight! is shown in Fig. 3. A "B" buttery of 180 Send Coupon for Free Booklet volts is required for the neon tube itself; TRANSFORMER CORPORATION although fairly good results will be obtained Transformer Corporation of America, socket - 1428 -32 Orleans St., if the high -voltage side of a "B" OF AMERICA Chicago, Ill. power unit is used. The resistor marked 1428-32 Orleans St. Please send me Booklet on your coni- R in this diagram is not the motor rheostat plete line of radio products. No obliga- marked R in the picture on page 315, but CHICAGO, ILL. 9 tion or cost. - a universal -range rheostat for adjusting the local current through the neon tube; r Name it should have a resistance of from 200 to B Address

City.... Ctate ee ami m aw m m iest im mi limmi d

NEON TUBE 1r- $ç ,°buys ,firlllllll;,, this _famous cabinet.. All the New Kits The Iradine Sizes range from 7x18x10 to 7x30x12. Mahogany finish, .5.50 to 58.75. Solid Walnut, 86.50 to 510.25. F.O.B. Hickory. L_ Everything in radio -kits, parts, Twelve -hour service. Write for Catalog. SOUTHERN TOY COMPANY, MANF'R. HICKORY,N.C, DOUBLE} accessories, sets. Improved de- IMPEDANCE signs and styles. Big selection at UNIT R worthwhile saving. Immediate service ; personal attention. Send Fig. 3. Schematic diagram of the lamp cir- for complete, illustrated Cata- cuit. This resistor R is not the one pictured log "B." in Figs. A, B and C (which is in the motor Radio has been changing sofast circuit) and it does not require continual lately that it's hard to keep up adjustment. with it. Barawik's Big Radio Guide will keep you posted on the newest Allied Radio wrinkles. Thousands of illustrations of sets, parts, new ideas. Big chance to 500,000 ohms. The procedure is to adjust CORPORATION save big money. Send for free copy now. 711 W. LAKE STREET, CHICAGO neon lights this rheostat until the tube just BARAWIK CO.,uc Ls. S.A. up; then the signal fluctuations will cause

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www.americanradiohistory.com 386 Radio News for October, 192e

the light to vary and the patterns will appea r. To "see" music with this television receiver, tune in a broadcast- station in the LJ usual manner, and then connect the left side of the output impedance unit to where the loud speaker normally attaches to your set.. Start up the motor and look through THE BARAWIK CO. has, all these years, the disc into the neon tube, and you will been famous for its variety of radio supplies. observe the music "pictures" immediately. which it offers at monetv-aaving prices. New- est dynamic speakers, B" eliminators, socket By varying the speed of the motor, you power equipment, A-C harness, fine cabinets can make the patterns move back and forth, and furniture, amplifiers, latest amateur equipment, tubes, batteries; in fact, anything and up and down, and perform many other you can ask for is here, ready to ship, at a interesting antics. By connecting the loud saving in price. Quality merchandise, selected goods by reliable makers - just what you speaker ist series with the double impedance want - at big discounts. unit, both it and the neon tube can be made to operate together; and the different effects Your Savings areTremendous Ask any of the quarter million Barawik customers produced by different notes can readily be why they trade here, and they'll tell you that, quality considered, our prices can't be beat. compared. That's something to think about! Quality comes Easy to build. , unequalled performance first -new, fresh, good reliable merchan- Although this entire machine is a crude dise, but the price always means a .. at a price you will be glad to pay tremendous saving, nevertheless. affair, there is no reason why it cannot Get our catalog and prove this Marvelously Realistic Reproduction be made to reproduce actual television to yourself. Don't spend a nickel until you see our offer- Remler Audio System .... Perfect Control of ings first. Volume from Maximum to a Whisper. images; provided, of course, the listener is You steed this great radio Simple to Operate , .. Expert Results for within range of one of the stations now Every bargain book as never be- Member of the Family. transmitting television impulses. - Station fore - Mail the coupon now TODAY. All the Selectivity that Could be Desired . . . is On - Clean -Cut Separation of Stations on Adjacent \VGY the air every Tuesday, Friday Channels. and Thursday afternoon between 1:30 and j BARAWIK CO.agl¢Aaö,aústs:a. Superheterodyne Sensitivity .... Shield -Grid 2:00 p. in., Eastern Standard Time, trans - Amplification. I Mail Ma Coupon see FREE Bargain Book. mitting on its regular 380 -meter wave. By Stable Operation Completely, Shielded Throughout. .... the time this article appears, other stations Nam. Easy to build .... Can be Assembled. Wired will also probably be on the air with tele- and Put into Operation in One Evening. No Address Special Knowledge or Experience Necessary. vision. If you can. pick up a television Most of the Wiring Completed and the Cir- program, try it on this crude televisor; cuits Balanced at the Factory ... Only a Few you may have good luck and actually see Wires to be Installed by the Builder in Ac- cordance with Color Code. pictures Eliminator or Battery Operated. Combined Power Amplifier and Plate Supply CX 350 (UX 250) Power Tube . Full The Radio Beginner -The DRESNER Wave Rectification .... B Voltage Regula- tion Provided For. Steel Chassis Amplifier Construction . "Milk- Shaker Special" SHORT -WAVE CONVERTER Compact and Rigid. 327) Power Transformer Primary Tapped for Dif- (Continued front page ferentLine Voltages. WAVE- The socket for V2 is located 1 inch from LENGTH COMPLETE the right edge of the baseboard and about RANGE 2/ inches from the rear edge. The (la- 15 to 550 $22.50 ment- ballast resistor 113 is located directly Meters (SPECIAL) in front of the socket, and the vertical mounting for the grid leak III is fixed at May be used with any type of broadcast receiver. the rear of the socket. Next, complete the Easily connected in just a few moments' time. No complicated wiring. Simply plugged into the assembly of parts on the baseboard by detector socket in the set. Covers the entire range REMLER POWER AMPLIFIER mounting the R.F. choke coil LS near the of wave lengths from 15 to 550 meters. Maxi- The story of the "29," what it is and what it front edge of the baseboard slightly to the mum satisfaction from top to bottom. Don't miss does, is complete in Bulletin No. 17. Sign the the excellent programs now being broadcast on coupon for your free copy. left of the filament -ballast resistor. the short waves. Get a Dresner Converter. Five interchangeable coils furnished with each unit. Arranging the parts on the front panel is If your dealer can't supply you, call on us direct. Remler Division, Gray & Danielson Mfg. Co. a very simple matter after the panel hais Write for booklet 260 First Street, San Francisco, California. Gentlemen: Please send me: been drilled. The layout in Fig. 3 shows DRESNER RADIO MANUFACTURING CORP. D All the "dope" on the "29 ". the location of all holes required and also 640 Southern Boulevard New York, N. Y. Bulletin service for professional set builders. the size drill needed for drilling the holes. The hole on the left side of the panel is for Name the rheostat 112, and the bole in the same Addre.r r corresponding position on the right of the MOVIES teachYOU City State panel is for the variable high resistor 113. The battery switch SW is mounted near the ELECTRICITY bottom of the panel in the center, and the AMAZING new film method prepares you at ,jack is located in the hole in the lower home, easily, quickly, for bigger pay lobs in J all branches of electricity: Radio, Automotive. right corner of the panel. The remaining Aviation, Switchboard Work. etc. Actual motion holes are for mounting the two variable pictures make everything simple and clear. and WRITE train you for a better iob and more pay. condensers, Cl and C2. DeVry Motion Picture Projector and thousands of TODAY feet of film supplied at no extra coat. Easy to operate in home. No dry text books. but WIRING SUGGESTIONS live, fascinating instruction. Prac- Send for large, new illus- ticing engineers endorse training as Before starting the wiring of the receiver, sure, quick, practical. trated Catalog "B," showing it is wise to fasten the front panel to the We promise in writing to help get you a better job and more pay, or the latest of everything in baseboard with three wood- screws. This is you need not pay a cent. necessary because there are a number of Three Les sons and New radio at wholesale prices. FREETi ook,' The Film Way two on the panel with Bigger Pay in Electricity." Send wires which connect parts coupon for your copy now. those on the baseboard. When wiring the set it is best to use National School of Visual education Allied 'Radio the pictorial wiring diagram (Fig. 4) as a 537 S. Dearborn St. Dept160Chicago CORPORATION In this dia- Please send free lessons and book, "The Q 711 W. LAKE STREET, CHICAGO guide for making connections. Film Way to Bigger Pay in Electricity." gram each piece of apparatus is shown in Name As one cf the oldest patent its correct position; but the settle of the firms to America we give in- St. or R.F.D ventors at lowest consistent parts in relation to that of the baseboard PATENTS charge, a servire noted tot has been reduced somewhat, in order to al- City results, evidenced by man' well known Patents of erta ordinai value. Book, Patent -Sense. free. low ample space for showing the wiring. State Lacey & Lacey. 631 F St.. Washington, D. C. Estab. 1888 Please :ay you saw it in RADIO NEWS

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