STATION ,.

Edited by H GO GERNS

www.americanradiohistory.com PILOT JUMBO DOUBLE CHOKE UNIT PILOT COIL WORLD'S LARGEST RADIO PARTS PLANT

PILOT 'ILLUMINATED DRUMS DOUBLE AND SINGLE DIALS PILOT ILLUMINATED DIAL VERNIER TYPE PILOT WORLD'S LARGEST RADIO PARTS PLANT

PILOTOHM III I METAL PILOT IO-/ GRID PERFECTED CONDENSERS LEAKS WITH BUILT -IN COM PENSATORS TRIPLE. DOUBLE PILOT ADJUSTOGRAD AND SINGLE LOOK PILOT MOISTURE -PRUF TRADE PILOT MICROGRAD TYPES FOR TRANSFORMERS MARK THE PILOT ALL TYPES REGISTERED

FREQUENT TESTS AND IN- ELECTRIC (MFG P I L O T ENGINEERS ARE SPECTIONS CONSTANTLY DEVELOPING A NEW SERIES MAINTAIN THE PRECISION OF RECEIVERS IN KIT FORM W H I C H CHARACTERIZES PILOT323 BERRY ST BROOKLYN,NY. EMPLOYING TRIED A N D ALL PILOT RADIO PARTS. ti TESTED CIRCUITS. TRADE MARK i THE PILOT PILOT LEADS PROTECTS PILOTONE THE YOU ALL-ELECTRICAL WAY

O u ïi<:`c PILOTONE PILOTONE FRONT PANEL ONE OF THE NEWLY DEVELOP- 'B" ELIMINATOR SIMPLE - BEAUTIFUL ED PILOT KITS. AN A -C DESIGNED ESPECIALLY SIMPLY BEAUTIFUL! JOB WITH PUSH-PULL FOR THE PILOTONE AMPLIFICATION AND A -C RECEIVER BUILT -IN "A" POWER

www.americanradiohistory.com Radio News for March, 1929 801,

easy ays to Make /3°Oan hour in Your.fpare ¡nItAOlOTime Each of these plans, developed by the Radio Association of America, is a big money -maker. Set owners everywhere want to get rid of static, to have their sets operate from the electric light socket, the tone improved, and the volume increased, and trans- formed into single-dial controls. Phonograph owners want their machines electrified and radiofied. If you learn to render these ser- vices, you can easily make $3.00 an hour for your spare time, to say nothing of the money you can make installing, servicing, repairing, building radio sets, and selling supplies. Over $600,000,000 is being spent yearly for sets, supplies, service. You can get your share of this business and, at the same time, fit your- self for the big-pay opportunities in Radio by joining the Association.

Join the Radio Association Earned $500.00 Spare Time Frank J. Deutsch, Penn.: "I have made over$500out ofRadio in my spare time." of America Radio Engineer In One Year Claude De Grave, Canada: "I knew A membership in the Association offers yott A membership need not cost you a cent! nothing about Radio when I joined a the easiest way into Radio. It will enable The Association will give you a com- year ago. I am now a member of a you to earn $3.00 an hour upwards in your prehensive, practical, and theoretical very exclusive organization of Radio spare time -train you to install, repair training and the benefit of its Employ- Engineers, and my income is 225% and build all kinds of sets -start you in ment Service. You earn while you learn. greater than it was." business without capital or finance an in- Our cooperative plan will make it possi- vention -train you for the $3,000 to $10,000 ble for you to establish a radio store. Doubles Income In 6 Months big -pay radio positions - help secure e You have the privilege of buying radio W. E. Thon, Chicago: "Six months afterI better position at bigger pay for you. supplies wholesale from very first. enrolled I secured the managership of at the largeRadioStore and doubled myincome. " ACT NOW -If You Wish the r Radio Association of America Dept. RN -t 4513RavenswoodAve.,Cbicago,lIL No -Cost Membership Plan Gentlemen: Please send me by return mail full details of your Special Membership Plan, and also copy of To a limited number of ambitious men, we will give Special Memberships that your Radio Handbook, may not -need not-cost you a cent. To secure one, write today. We will send you details and also our Radio Handbook filled with dollars- and-cents radio ideas. It will open your eyes to the money-making possibilities of Radio. Name Radio Association of America Address

4513 Ravenswood Ave., Dept. RN -3 Chicago, Ill. City State

Please say you saw it in RADIO NEWS

www.americanradiohistory.com Rádio News for tl'cich; .1929

YALE WS Y Volume 10 March, 1929 Number 9

HUGO GERNSBACK, Editor -in -Chief C. P. MASON, Associate Editor BERYL B. BRYANT, Laboratory Director C. WALTER PALMER, Director Information Service

Contents of This Issue Whither Radio? By Hugo Gernsback 809 The "Dry -Cell Four" - An Economical Radio Cannot Be Heard or Felt 810 Set By B. B. Bryant 833 Real "Radio Mysteries" 811 Hearing RADIO NEWS Blueprints -New Terms of Plants Grow by Radio Our Offer to Readers 837 By Ashur van A. Sommers 812 "It Isn't All in the Set -It's in the Lo- The "Candy Box Special" By Joseph Riley 838 i cation" 813 Radio Echo from the Depths of Space? The Screen -Grid R.F. Tube as an Auto- By C. P. Mason 814 matic Signal -Input Regulator "Miniature Music " -A New Point of View By Donald E. Learned 840 By R. Raven -Hart 815 "Harmonics" - the Cause of Phantom The Wings of Death Short -Wave Stations 841 By C. Sterling Gleason 816 Radio Wrinkles 842 What's New in Radio 818 Figuring the Filament-Ballast Resistances 843 The Radio Beginner- On the Short Waves 844 By C. Walter Palmer 820 RADIO NEWS Laboratories 846 Radio Tubes and Their Characteristics Review of Recent Radio Literature (Part II) By H. M. Bayer 822 By H. M. Bayer 847 What Meters Does the Radio Fan Need? List of Broadcast Station Calls 848 By Robert Hertzberg 824 The Radio Constructor's Own Page 850 The "RAnlo NEWS 1929 Hi -Q" Receiver I Want to Know By C. W. Palmer 851 By Herndon Green 826 131 RADIO NEWS Blueprint Coupon 879

In Our Next Number METHODS OF DETECTION: A simple and under- cussion will be a section devoted to hints on actual standable explanation of the two main methods antenna arrangements. used in broadcast receivers: grid -condenser and CONSTRUCTIONAL ARTICLES: Among the re- leak, and plate rectification. The advantages and ceivers to be the subjects of our blueprint articles disadvantages of each will be listed, and some are a fine seven -tube superheterodyne using screen- practical information on how the systems are best grid amplifier tubes, and an unusually compact used will be given. screen -grid short -wave receiver. The "super" is SHORT -WAVE AERIALS AND GROUNDS: What as sensitive and selective a broadcast receiver as every short -wave should know about can be built to -day, and will appeal to constructors enthusiast radio builders who want the the most important part of his installation -the and custom best. pick -up system. Accompanying the theoretical dis- Blueprint Notice -see page 837

' RADIO NEWS is published on the 10th of each preceding month. There are 12 obtained from the publishers. Copyrighted in Germany. Reproduction of articles numbers per year. Subscription price is 22.50 a year In U. S. and possessions. in Germany is reserved for Radio, Berlin 92. Canada and foreign countries, 23.00 per year. U. S. Coin as well as U. S. Stamps RADIO NEWS Is for sale at all newsstands in the United States and Canada, accepted (no foreign coins or stamps). Single copies, 25 cents each. Checks and and at Brentano's, Ave. de L'Opera, Paris, France. European agents: S. J. Wise money orders should be drawn to order of EXPERIMENTER PUBLISHING INC. Et Cie, 90 Place Verte, Antwerp, Belgium. CO.. HOW TO SUBSCRIBE FOR RADIO NEWS. Send your name, address and re- All communications and contributions to this Journal should be addressed to mittance to Experimenter Publishing Co., 230 Fifth Ave., New York. Mention the Editor, RADIO NEWS, 230 Fifth Ave., New York, N. Y. Unaccepted contribu- name of the magazine you are ordering. We stvo publish SCIENCE AND INVEN- tions cannot be returned unless full postage has been included. All accepted con- TION. RADIO LISTENERS' GUIDE and AMAZING STORIES. Write clearly. tributions are paid for on publication. A special rate is paid for novel experi- ments; good accompanying RATES AND TERMS. The subscription rate for RADIO NEWS is $2.50 per photographs them are highly desirable. Publishers are Year. (12 numbers). When remitting do so by check, money order, or registered not responsible for loss of manuscripts, although every precaution is taken with through the mall such manuscripts, upon thereof. letter if cash is enclosed. Avoid sending cash if possible. Sub- receipt scriptions for less than one year are not accepted. Subscription may be made In RADIO NEWS. Monthly. Entered as second -class matter, July 12, 1924, at the combination with SCIENCE & INVENTION, RADIO LISTENERS' GUIDE, Post Office at New York, N. Y.. under the Act of March 3, 1879. Additional entry and AMAZING STORIES. at Dunellen, N. J. and San Francisco, Calif. Title registered U. 8. Patent Office, POSTAGE. We prepay postage In all parts of the United States, Mexico and Copyright, 1929, by The Experimenter Publishing Co., The.. 230 Fifth Ave.. island possessions. For foreign or Canadian subscriptions we require 50 cents in New York. The contents of this magazine are copyrighted and must not be addition to the subscription price for additional postage charge. reproduced in the United States without giving full credit to the publication. CHANGE OF ADDRESS. Notify us as far in advance as possible. It requires Translation into foreign languages must not be made unless permission is several weeks to make an address change on our records. Always write clearly. 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 IRVING S. MANHEIMER, 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 Radio News for March, 1929 803 1

E,qsy Wny là G T INTo . .tele. lat:Q.Q.. '`'` s(,°^ O. Co?iRES-PoN7De Ater. . Nby- ßy CiS `1:3 t, o-.. iU.¢,Q ;,tX.. ,- Vi irr ow COURSE i , od, o - 01.. ' ,1) t.-i.eP ,;;vo a.7 14-8 0-4-4.04:..

aAA-at 0,0a):A/ ...... NEt -., Y..o R GET 11.1.../ Leaanc FREE ad M. IArLe-e 40.4./tte 0. /2,VIL MIN ss. H. C. LEWIS, presidentin Melt- Coyne Electrical School, Dept.39.O2 ?OSA soo S. Pauline St., Chicago, 111. A Dear Mr. Lewis: PVC A/{04,[_ j{[ e , vd thovtoblieatir send meyonr bigfree catalog and ///«V//77 elldetas '1 ao f F ree E mp 1 oymen tSernce, l viation,' ' Radi O and Automotive Courses. and how many "earn while learning." ELECTRICAL SCHOOL Name COYNE Established 1899 H.. C. Lewis, Pres.Pres Address SOO S. Paulina Street, Dept. 39.02 CHICAGO, ILLINOIS Please say you saw it in RADIO NEWS

www.americanradiohistory.com RO4 Radio News for March, 1929

INDEX TO ADVERTISERS i

PAGE PAGE PACE PAGA'. A D L AccustiCone Labs. 865 DeForest Radio Co., The 864 Lentz, Inc., C. R. «...... 883 Radiatt Labs...... 865 Aerial Insulator Co. 865 De Jur -Amsco Corp. 865 Lynch, Inc., Arthur H. . »... ». ». 865 Radio Association of America.... 801 Aero Products, Inc. 862.873 Dresner Radio Mfg. Corp..... 858 Radio Doctors, Inc. 801 Aerovox Wireless Corp. 862 Dubilier Condenser & Radio Mc Radio Equipment Co. 866 879 Allen- Rogers- Madison, Inc. 865 Corp. Radio Institute of America-807-863 McSweeny Electrical Schools ... 886 Radio Specialty Co. 859 Allied Radio Corporation B Raytheon Mfg. Co. 893 856-865.872-877-890-896 Electrad, Inc. 881 881 M Royal Eastern Electric Supply American Sales Company Electric Specialty Co. 883 Transformer Co. 869 Co. _ ».. »..... ».» 854 American Elkon, Inc. 855 M & Il Sporting Goods Co. 872 ..... 890 Arcturus Radio Co. Excello Products Corp. ... 882 Mason, Fenwick & Lawrence 862 Midwest Radio Corp...... Back Cover s F B Modern Antenna Co 806 See Jay Battery .... »... . 872 Ferbend Electric Co...... 865 Co.. Barawik Company Setbuilders Supply Co. 865 -866 854-856-858-860-865-877-883-885-890 Ferranti, Inc...... _...._ ». »...... 866 .. » Ii Shanklin Mfg. Co ...... 866 Benjamin Electric Mfg. Co 854 France, B. H. »._ _ 881 Franklin Institute 875 Silver -Marshall, Inc. . 808 Benson -Allen Co ...... - - 854 National Co., Inc. «. ». « «.... «» 856 Smith, B. Hawley - 858 Freshman Co., Inc., Chas ..... 881 National Radio Institute ...... ,... 805 .... ».... - . - Birnbach Radio Co. 865 Strauss & Schram - ...... »...... » » 871 Braun, W. C.....« 865 G National School of Visual Edu- cation ...... «.... «.... «.... « »..._.» 895 General Radio Co..... « « .... « « 872 T C H o Teleplex Company ...... ».. ».. »» 87X Carborundum Co., The 885 Hammarlund Mfg. Co. 877 Thordarson Electric Mfg. Co. «» 853 Omnigraph Mfg. Co. .... »...... 876 Cardwell, Allen D....._ 873 Hammarlund- Roberts, Inc 865 Townsend Labs. .... » «...... »._ »« 875 Carter Radio Co. .... »...» 856 Harre, F. A...... »...._.... »_ 885 CeCo Mfg. Co...... ».... ».... » 891 Hoodwin Co., Chas. »..» 866 P V Central Radio Labs. .. 876 -Con Mfg. Co. 865 Per Van Nostrand Co., D. «..«.... «».. 889 Chemical Institute of N. Y. Inc 861 I Pilot Electric Mfg. Co. Chicago Radio Apparatus Co 886 Illinois Transformer Co. .«. »...... 854 Inside Front Cover Insuline Corp. of America...... 865 Chicago Salvage Stock Store Polk, J. L. 876 w Inside Back Cover International Correspondence Schools ».... ».... ».. ».. 886 Potter Co., The 860 Walker Co., The Geo. W...... 866 Chicago Stock Gear Works 871 Press Guild, Inc ...._.... « 891 Western Radio Mfg. Co...... 865 -883 Clark, Paul L. 865 J Prexto Mfg. Co. « ...... ».. » 882 Wholesale Radio Service Co...... 886 Clarostat Mfg. Co. 872 J-M -P Mfg. Co. .. »_....» - 854 Cornish Wire Co. 865 Jensen Radio Mfg. Co. 887 %-Y-z Coyne Electrical School 803 R Craftsman Radio Products 860 S R. B. Specialty Co. 856 X -L Radio Laboratories 882 Cunningham, Inc., E. T. 872 Knapp Electric Co. 867 Radial] Company 864 Yaxley Mfg. Co. 885 NoQ/irJiirsp&tcdc leatfscr bitír^`c S. Gernsback's Radio yckpedia

rrHE most valuable of Radio Books -S. Gernsback's a. Encyclopedia -now the most beautiful. This foremost Radio Encyclopedia is now offered in this luxurious new binding to meet the demand for a more handsomely bound volume. The limp suede leather edition sells for $5.00. The Keratol- leather stiff binding still can be had for $2.00. 0® Remember -this is an encyclopedia -not a dictionary! It took over two years of intensive labor to compile it. ERATOL BINDING. It is the first Radio Encyclo- pedia ever published. 0 FeRNse S. Gernsback's Radio I am°otv° 44°k En- ey Yor& cyclopedia contains the 4244.0 y, °ueÿá ooe ot I 47414. meaning of every word and phrase used in the entire p B oe ore f soot D SEND Radio Art. Every circuit, gthe part and apparatus is thor- N rchepg ' DéO Lóppof r°saenCla N 0 oughly explained. A complete cross index is just one of ( eh b p Gteq,. the many features of this remarkable book. ióp.. '°+.1 Waotl MONEY rAoto.e, Simplypaythepo st - There are 1,930 definitions-549 diagrams, photo- S4gs '' . man on delivery. graphs and drawings-all simple and easily understood. `' .. I Over 25.000 copies in the stiff binding already sold. The book is nearly 1 inch thick and measures 9x11 inches. jj S. GERNSBACK, 230 FIFTH AVENUE, NEW YORK CITY Please say yotp saw it in RADIO NEWS www.americanradiohistory.com Radio News for March, 1929

what B16 money these fellows have made 1 iva dhoU! [/SKI- to in the RADIO BUSINE-SS haw to sutra spare 5375 One Month Spare Time "Recently I made $375 in time or full time one month in my spare time installing, servicing, selling Radio sets_ And; Radio Business not so long ago, I earned enough in one week to pay for my course." of Your Own EARLE CUMMINGS, 18 Webster St., Haverhill, Mass. $1597 In Five Months "The N. R. L is the best Radio school in the U. S. A. Radio's amazing growth is making many big jobs. The world. I have made $1597 in five :months. I shall always tell wide use of receiving sets and the lack of trained men to sell, ;my friends that I owe my install and service them has opened many splendid chances j: success to you." for spare time and full time businesses. HENRY J. NICKS, Ja, 302 Safford Ave., Ever so often a new business is started in this country. We have seen how Tarpon Springs, Fla the growth of the automobile industry, electricity and other9 made men rich. $5164 Spare Time Profits Now Radio is doing the same thing. Its growth has already made many.men. "Look at what I have made rich and will make more wealthy in the .future- Surely you are not going to since I enrolled, $1,164 pass up this wonderful chance for success. money I would not have r win ?ea Sppare Time In ?our had otherwise. I am cer- More Trained! Bad* Men Needed Radio tainly glad I took up A famous Radio expert says there are four to you. Hold your with N. R. I. I am more 'I bring my training job. r good jobs for every man trained to hold them. Give me only part of your spare time. You; than satisfied." has grown so fast that it simply HENRX R. HEIKKINEN, Radio has don't have to be a college or high school 123 W. Erie St., Chicago. HL not got the -number of trained' men it needs. graduate.. Many of my graduates now mak- Every year there are hundreds of''fine Over jobs mg big Money Radio didn't even finish the Sleee Is Four Months among itss many branches such as broad- ,grades. Boys 14, 15 yearn old and men up "My opinion of* the N. R. I. casting stations, Radio factories, jobbers, 'to 60 have finished my course successfully. course is that it is the best dealers, on board ship, commercial land sta- ' Mast to be had at any rice. tions, and many others. Many, of the six to Ton 8e Satidíe4

When I enrolled I didn't ten million receiving sets now in use are only I will give you a written . agreement the day. know a condenser from a 25% to 40% efficient. This has made your you enroll to refund your money if you are transformer, but from De- big chance for. a spare time or full time pot satisfied with the lessons and instruction cember to 'April I made business ofyour own selling, installidg, repair service when you complete the course. You well over $1000 and I only ing sets. are the only judge. The resources of the N. R. I. worked in the mornings." Se Many Oppsrponiies You Can Make Pioneer and Largest Home -Study Radio school AL. JOHNSON, Extra Meney'White Learning in the. world stand back of this agreement. 1409 Shelby St., Sandusky, Ohio. Many of our students make $10, $20, $30 a Get My Book week extra while learning. I'll' show you the Find out what Radio offers you. My 64 -page plans and ideas that have proved d book, "Rich Rewards in Radio" successful for them -show you 71sto` points out the money making op- a how to begin making extra money shortly after r _ ortunities the growth of Radio you enroll. G. W. Page, 1807-21st Ave., S., M(M[0 has made for you. Clip the con- Nashville, Term., made $935 in his spare time /,, n. Send it to me. You won't while taking my course. i. Ofrtt lie obligated in the least. I Give You Practical Radio Experience a. With My Course Qee My course is not just theory. My method Address gives you practical Radio experience- \you learn the `how" and "why" j. E. Smith, Pres of practically every type of Radio 1 set made. This gives -you confi- Dept. 9 -PT dence to tackle any Radio problems and shows up inyour pay envelope too. PhrtionaI Radio Institute Washington, D. C. You can build 100 cir- cuits with the Six Big Outfits of Radio parts I give you. The pictures here show only three of VQ them. My book explains my method of giving prao+ J. E. Smith, tical training at home. President, Get your copy I Dept., 9-PT Radio Washington, 1 National Institute, D. C. t .Dear Mr. Smith: Send me your. book. I want to know more about the opportunities .in Radio and your practical method of teaching' at home in spare time. This request does. not obligate me to. enroll and .I understand no agent will call on me.. Nàaie Age

Address . . City State

Please say you saw it in RADIO NEWS

www.americanradiohistory.com 8O6 Radio News for Illtirch, 1929

° NAa4IROU ND , >> %rnóined in one convenient Unit A wonderful thing has happened in radio! Convenience never before dreamed of ! Clearer, sweeter -toned reception! Radio pleasure with less interruption! These things are brought to you by the amazing, tested, approved, EARTHANTENNA. Many set owners have come to realize the importance of using a dependable antenna, also the value of perfect grounding in getting good reception. Now science has gone a step further; it says that the LOCATION of the antenna is an equally important factor in getting best results. Because the radio wave goes right into the earth -where obviously there is less atmospheric disturbance and interference -it is claimed the logical place Reduces Static - for the antenna should be the EARTH, not the air. This important Gets Clearer, Sweeter Tone conclusion allowed Radio Engineers to work out the EARTHANTENNA. Have you ever listened to reception that almost took your breath away with its faultless reproduction, its pure melodious tone? And then gone home and com- Shielded Antenna Gets Better Reception pared its haunting beauty to YOUR receiver's often unsatisfactory, static- ridden performance? Probably The antenna is insulated or "shielded" against electro- static disturb- nine out of ten set owners who formerly thought they were getting "pretty good" reception have had this ances as are the most advanced, expensive receivers and their various experience. They accepted the shrieks, whistles, knocking and parts. Science declares that the earth itself "shorts" the electro-static howls due to atmospheric conditions -the weak capacity before it reaches the Antenna. This acts as another shield. faulty results of sagging, broken, or soot -laden aerial wires-the interference of other aerials or power line The ground element is constructed of copper, noises -the fading often caused by corrosion or im- perfect contact in an unscientiÈc ground-all as undisputed as the most effective material for necessary evils. obtaining a perfect ground connection. This Progressive radio refused to etc there. The new scientific, successful EARTHANTENNA is designed section of the unit is separated from the to give you clearer, better, more dependable reception - and. t costs no more than the old inefficient aerial-in Antenna by the insulation which shields the fact less than many. Antenna. So in the EARTHANTENNA you EARTHANTENNA is so easy to install that soon people will wonder how they ever put up with the old, have a scientific ground and an antenna of dangerous, slow methods. You simply dig a small hole only two feet below the surface of the ground, drop the modern shielded construction combined in one EARTHANTENNA into it and attach the lead-in compact unit. You can test it yourself right wires to your set. Now you are ready to listen to earth - clarified, sweeter -toned ground wave reception. You now at our risk. Hear the wonderful results! never need to touch the EARTHANTENNA again. f\> Test EARTHANTENNA at OUR Risk Let EARTHANTENNA prove its own value without your risking one cent. Don't remove your old aerial and ground until you've compared the old and modern methods and hear the vast improvement with the new. If possible pick a time when static is bad. Then if you are not convinced that EARTHANTENNA is the greatest discovery you've ever found for your radio -if you are not enthused over the improvement -you don't pay us a cent. The thrilling details of this important development - illustrated-will be sent immediately on receipt of this coupon. Mail it NOW !

u I The Modern Antenna Company I THE MODERN ANTENNA {COMPANY Dept. 827CE St. Clair Bldg., cor. St. Clair and Erie Streets Dept. 827CE. St. Clair Bldg., cor. St. Clair and Erie Sta., Chicago, Ill. I CHICAGO, ILL. I Rush literature on EARTHANTENNA and Free Trial Offer.I I No obligation. 1. I /Name

Address I ANTENNA I I THE MODERN ICity A RTHCOMBINED ANTENNA AND GROUND 1 1 state I

Please say you saw it ivi RADIO NEWS

www.americanradiohistory.com Radio News for March, 1929 "I Found the Short Cut to Success in Radio

through this amazing home laboratory method!"

The only radio training spon- sored by RCA ... General Electric, Westinghouse .. . FREE 50 -page book tells all about it. Mail coupon.

By Frank Halloran the very first lesson to the last I was Today, my income is more than doubled 7 GOT hungry to get into Radio when thrilled! Each subject was explained in .. and I've only just started! I'm cer- 1 I learned about the big money it was simple word and picture form . ... and tainly happy that I found this short cut bringing my next door neighbor. written in such an interesting style that to success!" I was carried along like a novel! He was only twenty-eight years old, but I didn't know the first thing about radio Read This Thrilling his income was over four times as much when I started, yet before many months as I was getting. He owned a fine car, were over I was able to solve many of the FREE Book dressed in expensive clothes, took week- problems which now help me command Frank h allorañ s wonderful success h lust another ends off to go hunting and fishing, and big money. The lessons took me step by typical example of the success which the Radio In- was one of the most popular fellows in stitute is bringing to hundreds of men everywhere step through trouble -finding and repair- through its wonderful Home -laboratory training... town. ing.... through ship and shore and broad- the only official radio training based on the inside knowledge of radio developed in the great experi- "Charlie," I asked him one day, "how did casting apparatus operation and construc- mental laboratories of RCA, General Electric and you become a radio expert?" tion .... through photoradiograms, tele- Westinghouse! vision and beam transmission .... through There is an amazing opportunity for you in Radio. "A cinch," he smiled. "I took it up in my radio salesmanship, store operation and Manufacturers, dealers, broadcasting stations, ships spare time at home." executive work. ...all are calling for trained radio experts. The pay is big-the opportunities are limitless -the work is thrilling! Find out all about it. The Institute has "What?" I asked in surprise, "you actu- prepared an interesting, illustrated booklet telling ally took a radio course by mail l" Success Spare Time! you all you want to know about this vast industry -In and about the remarkable home study -course that "No," he shot back. "Not just a mail or- I didn't have to give up my regular job. can fit you for a brilliant radio career. Just mail the coupon der course, but the only technical home- I learned at home during my spare time. below and claim your copy laboratory training conducted under the And I actually learned by doing ! With of this valuable booklet ... it's absolutely free! Radio auspices of RCA, Westinghouse and Gen- the course, I received an outlay of the Institute of America, eral Electric! Believe me, these 'big- league' finest standard apparatus with which I Dept. R. N. 3, 326 organizations not only know what's what was able to build radio circuits and sets Broadway, New York in radio, but they know how to teach it!" of almost every description .... yet this expensive apparatus cost me absolutely nothing Mail this A Great Piece of Luck extra! coupon Even before I had the course Taking Charlie's advice was the luckiest completed Radio Institute of America was thing I've ever done. It's bringing me I able to earn good money doing odd Dept. R. N. 3, 326 Broadway, New York, N.Y. radio jobs. And it wasn't long after that more money in a week than I've often Gentlemen: Please send me your FREE 50-page earned in a month! I was able to give up my regular work book which tells all about the great opportunities fledged in Radio and about your famous home -laboratory and branch out for myself as a full- method of guaranteed radio instruction sponsored I never dreamed that learning radio at expert in work that is fun and extremely by RCA, General Electric and Westinghouse. home was so easy and so fascinating. From profitable ! Name Address Please say you saw it in RADIO NEWS www.americanradiohistory.com r 1929 808 Radio News for March,

On Top of the World SM S s-M Screen Caid Six and Sargent- Rayment Seven

testimonials here quoted were entirely (AU unsolicited) The plain cold facts are "Just to say that I have one of your 720 Screen -Grid Six's with 670B power simple. The Silver -Mar- unit ... Picked up Japan, 1:00 A. M.-came in strong -four stations in Chi- shall 720 is a six -tube t.r.f. cago and everything up and down the coast ... " set using three screen -grid -F. A. Forbes, Oakland, Calif. tubes, a detector, and two "Think of the thrill of getting your dinner concert from KFI on a 6.tnbe stages of S -M Clough audio receiver away up here in Northern Wisconsin ... At the end of the dial amplification. It's an all- twisting session I had 28 stations over 1000 miles away, from 21 states and 3 metal, shielded assembly, provinces of Canada, and WKAQ, Porto Rico ... " just like the finest ready - -Clinton B. DeSoto, Withee, Wis. made sets, with its own "I am writing to tell you about the results I am getting from the 720 Screen' attractive two tone brown Grid Six. I have brought in stations from New York to Japan with good volume metal shielding cabinet,its on the speaker and the tone quality is very natural ... The following are antique brass escutcheon some of the stations I have received: JO1K, Sapporo, Japan, WHAM, Rochester, plate with two dials, vol- N. Y.... I had two other Japanese and some other foreign stations, but I ume knob, and a small haven't the call letters yet. WLW, WGN, KWKH come in good almost every selectivity knob. Yet this night." -Alonzo Henderson, Mossy Rock, Washington. set with its three stages of screen grid r.f. amplifica- "I am having great success with the 720 and 740 sets. Only today. I received tion, and its audio system 3 orders for 720s and one for a 730. In all my experience of building kits for that money can't buy in a fans, I have never had the feeling of really giving value till I took up your line. ready -made set, costs you I think it is the best that money can buy in its class and my long list of satisfied but $7250 for the S-M customers surely is the proof that their sets are wonderful." packed kit, or $102.00 - Howard Brett, New York City. for an SM custom-built "Last night picked up Halifax, Nova Scotia with such volume that I had to wired receiver, complete turn the volume control half off. We then proceeded to pick distance to the with cabinet. satisfaction of the prospect ... I got his order then and there. -L. Frank Miller, Brooklyn, N. Y. "Boss of the Air"-Doubt It? -Read These: The Sargent- Rayment THE MUNICIPAL COURT OF CHICAGO Seven is the first and only Samcal H. Trude, Judge set to offer four stages of "I am very much pleased with the custom-built 710 Sargent.Rayment screen -grid tuned r.f. receiver. . which I have been using in connection with a cone -type amplification, and the loud speaker at the South Shore Country Club, Chicago. unsurpassed tone qual- "This is a remarkably good receiver for all kinds of radio reception. I ity of the S -M Clough have found that distant broadcasting stations can be tuned in on all wave audio system -the first channels over the entire broadcasting band-one and only one at a time and only set to give one- with the single tuning drum." -Samuel H. Trude dial control, yet at the "It may interest you to know that the first station I tuned in was KOA same time individual (1500 miles away) and that last Saturday morning from 3 to 4 A.M. we stage trimmers that mean listened to three stations in Japan-JOAK, JOGK, and JOAH." the last drop of sensi- -Walter A. Reeves, Seattle, Wash. tivity when you want it. And its seven tubes, with "Some time ago I bought a 710 Sargent-Rayment set from Mr. Toolan of 171, 210, or 250 power Lansing, Michigan... It has marvelous tone, volume, sensitiveness, and tube, give fine tone or selectivity. I am right across the street from WTAM and can tune them hair-splitting selectivity, out...in a few points." -J, W. Carvey, Cleveland, Ohio. super- distance or local "I have just finished building one of your 710 Sargent- Rayment kits. I am programs with thrilling delighted with its performance. It is the only set that I know of that will quality. Shipped from bring in stations here in the day time... It does it with good volume. stock. KIT $130.00 -or FACTORY -WIRED -Claude H. Matthews Roswell, N. M. $175.00. Both complete "The most I can say is-it was worth waiting for -the Sargent-Rayment with handsome satin 710. The most wonderful set I ever had anything to do with -goes together aluminum shielding beautifully and makes a handsome job in its silvery-white finish." cabinet. -The Radio Shoppe, H. O. Hornbake, South Brownsville, Pa.

OTHER S-M KITS HIGH POWER AMPLIFICATION NEW PUSH -PULL APPARATUS Besides the 720 Screen -Grid Six and the 710 The new two-stage S-M 678PD Phonograph Built on the Clough system, with curves flat Sargent-Rayment Seven, S-M manufactures two Amplifier provides full 250-tube volume from from below 50 cycles to well above 5,000, these kin. any phonograph receiver. For use with transformers include all necessary types -input, other thoroughly modern receiver The or radio output, and interstage (between two push -pull "Coast -to-Coast Four" (for D.C. or A.C. tubes) any 110 -volt D.C. dynamic speaker; all power stages). employs the popular four -tube circuit (1 screen- comes from 110 -volt A.C. house -lighting mains. The new 690 double push -pull theatre ampli. grid r.f. stage, regenerative detector, 2 stages Price, less tubes, WIRED $73.00, KIT $65.00. fier, with undistorted power output of 15 to 16 Clough system audio). You can install a 250 power tube and adapter watts, employs these new transformers to give The "Round- the-World Four" short -wave kits in your present set with no changes whatever, by power sufficient to cover large theatres, or are highly successful either for code and phone using the S-M 675ABC high -voltage power stadiums, with such tone quality as only the S-M reception or for re- broadcasting. supply. KIT, $54. WIRED, with adapter $58. Clough audio system can produce.

Silver- Marshall. Inc. Are you getting The RADIOBUILDER regularly? No. 9 (Jan. 1929) 848 W .Jackson Blvd., Chicago, U. S. A. describes these new push -pull transformers, and the 690 Amplifier, as well as .Please send me, free, the complete S-M the new (and differenti) S-M Dynamic Speakers. No. 7 (Nov. 1928) described Catalog: also sample copy of The Radiobuilder. in detail, with complete circuits, a 750-volt rectifying system. Sample copies For enclosed in stamps, send me the may be had without charge as long as they last; use the coupon. following: If you build professionally, by all means ask for information on the .5-M .... 50e Next 12 issues of The Radiobuilder I Authorized Service Station proposition; its money-making opportunities . 31.00 Next 25 issues of The Radiobuilder are greater than ever. SM DATA SHEETS as f of lows, a t 2c each: ....No. I . 670B. 670ABC Reservoir Power Units ....No. 2. 685 Public Address Unipac I ....No. 3. 730. 731. 732 Round- the -World" Short Wave Sets ....No. 4. 223, 225, 226, 256, 251 Audio Trans- f ormets SILVER- MARSHALL, Inc. ....No. 5. 720 Screen Grid Six Receiver I ....No. 6. 740" Coast-to-Coast" Screen Grid Four ....No. 7. 675ABC High -Voltage Power Supply and 848 West Jackson Blvd., Chicago, U. S. A. .... No 8. S rgent-RSapyement Seven6er ....No. 9. 678PD Phonograph Amplifier I Name Address Please sal you saw it in RADIO NEWS 6 www.americanradiohistory.com Editorial and General Offices, 230 Fifth Avenue, New York

Vol. 10 MARCH, 1929 No. 9

Whither Radio ? By HUGO GERNSBACK

THE remarkable thing about radio is not this new art itself, The art of broadcasting as we have it today Is yet in its first but rather the human element connected with it. Strange stage. In Europe it is thought necessary to tax listeners with a to say, those who are intimately associated with it seem to be definite fee every month, in order that the stations may derive least certain whither radio is drifting and what is in store sufficient revenue to keep going. In this country, such an idea for it during the years to come. There is nothing new in this seems un- American, and a proposal to tax the public directly would condition, because it has ever been thus with radio since the days excite their violent opposition; therefore the taxation is indirectly of Heinrich Hertz. maintained, through the advertising appropriations for programs Indeed, when Hertz first discovered "wireless waves," no one took put on the air by big corporations who thus seek publicity. the new discovery very seriously; not even the scientists themselves, No one can foretell, at the present time, whether the "advertising who thought of it as only a pretty lot of laboratory experiments, to tie -up" broadcasting scheme of today is the final one, or that some- which there could not be attached any practical future. It took thing entirely new may not be evolved in the future. almost two decades to yank Hertz's experiments out of the labora- The entire broadcasting industry is in constant flux and there is tory and, even after Marconi brought "wireless" out into the open, really nothing very much settled about it today; it is too young there was another long period of development when few took the and too new for that. It is also to be doubted that, ten years from new art seriously, and even the most far -sighted scientists could now, broadcasting will be done in the channels between 200 to 545 not see much of a future for it. meters now used. It is frequently predicted that, sooner or later, When the first book devoted to this subject, one entitled "The there will be a stampede down to the lower wavelengths, where Wireless Telephone," was written by me in 1910, there was no such there are more channels and other advantages, as well as certain thing as practical radio telephony. Though, by that time, it was disadvantages. conceded that "wireless telegraphy," at some time in the future, So far, large radio manufacturers have turned out no radio set, would have an adjunct in the form of radio telephony, no one which can be sold to the public, capable of being tuned as readily dreamt of such a thing as radio broadcasting. Indeed, even at on the short waves as it can be on the high waves. But it is safe to that time, in the preface to that book, I ventured the opinion that say, that most of the large manufacturers are keeping a weather eye within ten years everyone (particularly farmers) would have a on the short -wave situation and, if one or more break the ice and a "wireless" telephone whereby they could communicate with each good set that makes tuning on the short waves easy is developed, other, instead of using the wire telephone. The prophecy was to we will have another silent revolution in radio. Then the old pre- some extent fulfilled in time, but not at all in the way I had imag- vailing sets will be scrapped in favor of new models, just as the ined. Everyone now has his "wireless telephone"; but it is not battery sets are now being scrapped for A.C. electric sets. used to talk to the neighbors. It is only a one -way instrument, The good thing about all of these radio revolutions is that they whereby we now receive what is put out by the broadcast stations; are orderly and that they do not come over night. Indeed, it has but we do not use it to talk with our friends. been found that sets built even as far back as 1923 still give good In view of the past history of the radio art, he would be a rash service in 1928. The same will probably be found the case with the prophet who undertook to foretell just what is in store for radio present -day alternating- current sets, when the broadcast stations itself. take to lower wavelengths. Most probably, in that case, attach- Thus, for instance, we are now talking glibly about radio televis- ments for present-day sets will be available to make possible tuning ion, radiovision and the like; but, at this time, most of us imagine them to the short-wave bands. that television will parallel broadcasting. It is freely predicted by The objection has been frequently raised, what will happen when everyone who is seemingly "in the know," that the large broadcast all the stations abandon the present wave channels and move stations will sooner or later put on television broadcasts; so that downwards? It is well known that, because of the "skip- distance" anyone who has a set can see what is going on in the distant effect, a local short-wave station will, in most cases, become almost studio or at a remote point where the television program would be inaudible at a short distance; in other words, it will be found that picked up-at the night club, or on the Metropolitan Opera stage, a broadcast station located in New York or Chicago cannot be heard or at a baseball game, or a prize fight, or any other scene of at all or, at best, poorly in the very city where the broadcasting is visual broadcasting. Other wiseacres say that nothing of the kind done; though strong enough further away. will happen and that what we really will get will be "radio movies" This, however, will not frighten the broadcast engineers, and it broadcast from some studio; in other words, the latest Hollywood will be found that this will work out to the advantage of the chain production will be run through a projecting machine at the trans- stations. Suppose that all of the stations were to move tomorrow to mitting station and the result will appear on the screen in your the lower waveband; and suppose that you live in Chicago and find own home. yourself unable to tune in your local station. The easy thing to do But it is quite possible that both these schools of prophets are will then be to tune in the same program from a New York station wrong, and that television will play an entirely different part, which, it will probably be found, though 800 miles away, comes in which we do not even dimly discern today. One thing is sure; just as a local station does today. Thus- unless some new scheme that the young art of television will take on a most surprising is developed whereby it will be possible to get short-wave stations form, once it becomes established. How television and "aural" just as well locally as you get the high -wave stations now -we will broadcasting will finally be amalgamated, even the most daring then listen, not to our local stations at all, but to DX stations prophet does not venture to say. exclusively in their stead.

Mr. Hugo Gernsback speaks every Tuesday at 9.30 P. M. from Stations WRNY (297 meters) and W2XAL (30.91 meters) on various radio and scientific subjects. 809

www.americanradiohistory.com Radio News for March, 1929 aclicananat Heard, ito Fell If ñas no Pgysical c s

-. 5t). C)©O.q _ - rs -

- migu

Beneath the aerial of a 50- kilowatt station which is transmitting, a piece of insulated metal (like an automobile body) quickly gathers an electric charge out of the magnetic field. But a human body does not; nor can the man in the midst of this field tell when it is turned off. ss OMMON SENSE" is a much - There are differences of opinion as to the DISCOVERY OR DELUSION a bused term; its original meaning aesthetic values or pleasure produced by When, therefore, a startling discovery is is an appeal to the basis of all certain impulses on our senses; there are made by anyone, the practical test of its science, as well as of all human slight variations in the sensibility of indi- truth is his ability to show the same thing to actions. It is the "common sense," or unani- viduals. Some men cannot distinguish the others, or to account satisfactorily for their mous agreement of mankind, that iron is color red, others cannot hear certain inability to perceive it. If a person claims heavier than wood, that the sky appears sounds, and some are poisoned by other to see the invisible, he must at least be pre- blue, that ice is cold, that the rose smells men's meat. But, speaking generally, the pared to show to the skeptical that the sweet, that vinegar tastes sour, that the person whose judgments of the outside "something" invisible to them is really there. notes of a fife are shrill; in other words, world differ too widely from the rest of the It is, therefore, in the original meaning of that the same things produce similar results human race is held to be lacking in "com- the words, that we confidently assert that on the senses of any human being. mon sense." "common sense" shows us that radio waves cannot be seen, heard, felt, "hefted," smelt or tasted by human beings. It is only by indirect means, and the interposition of ma- terials which radio perceptibly affects, that its presence can be discovered. Yet, with considerable frequency, RADIO NEWS receives letters such as that repro- duced here. This letter is somewhat differ- ent from the usual run; the writing shows that it is from the pen of an educated man, even though his use of radio terms is a bit uncertain. We have received a letter from one unfortunate who had issued a handbill, "Murdered by Radio," to proclaim that he was being persecuted by unknown enemies, and who implored instructions how to shield himself against radio waves. These are delusions! If any man feels sensations for which he cannot account-mysterious sights, sounds, "hot flashes"-which are not shared by those about him, let him consult a capable physi- cian. The faults are in his eyes, ears, "sen- sory" nerves, or over -strong imagination. Such "hallucinations" were known thousands of years before radio was thought of. They do not necessarily mean insanity in the sense of mental derangement or lack of reasoning power; but they do usually mean a state of ill-health that imperatively commands atten- tion. YEARS' EXPOSURE PRODUCES NO SIGNS Operators of a 50kilowatt station like WRAF, exposed to magnetic radiation of high intensity And, to physicians as well as to the laity, day in and the only thing about a trans- and day out, feel no physical effects from this source; be timely to say that radio as radio mitter that is dangerous is a live wire or port, as in any power plant. it may

e

www.americanradiohistory.com Radio News for March, 1929 811,

does not produce effects of sight and sound. far as his own bodily organs are concerned, We know that people occasionally hear there will never be any way by which he strange sounds coming from unexpected A Recent Letter can tell that there are radio waves around sources and recognize bits of a radio pro- Editor, RADIO NEWS: him -any more than he can see the ultra- gram, as in the cases described in the ar- Reading the January number, I note violet and the infra -red rays of which he ticle below. But, whenever this has hap- that you have published an article on has been told. pened, there has been metal nearby to pick human radio reflectors and also on If we could conceive of intelligent beings up and carry radio. A man does not walk "mysteries" of radio. I believe that composed of a magnetic substance, such as through the woods and hear the branches of I am in possession of a real mystery iron (as in a recent piece of very striking the trees reproducing radio music. Nor, that will startle you and also seem at scientifiction, "The Metal Emperor," which even though he stands within arm's reach of first impossible until you give the mat- appeared as a serial recently in the pages of a high -power transmitter, does he hear, see ter consideration. SCIENCE AND INvExxioN) they would be able The fact is that some criminals have to feel the action of radio waves, as we do set up in this city and nearby two those of heat and light; and to receive from powerful stations operating on human them, no doubt, sensations of pleasure and frequency. I myself have experienced pain proportioned to their intensity. We an oscillator fever from same. They cannot, of course, imagine what such a sen- apparently do not care one iota for sation would be like; for, while ability to human life or property. I have even feel the presence of a magnetic field might difficulty in driving my machine, due be a boon to mankind -and it might be a to the fact that they are evidently curse -it has not been bestowed upon them. using an etherical (sic) form of trans- A man can put his hand, without feeling mission on a powered beam and I be- lieve is brought about by the use of photo cell lamps and a television sys- tem. They are also capable of estab- lishing vocal communication on same and I have heard them talk and know for a fact that they are our first real air criminals, and believe that they are really insane. So severe has been their activity, power and directional Do not be alarmed if the stove starts to sing, as it did in Santa Barbara. (See page 854.) capability that I was able to plot on Call the neighbors to hear it. a map and trace the definite location of one of these stations to the exact or feel in any way radio waves. If it were block (location described). so--if it were possible that even the most The aerial he was using was of the intense concentration of radio could in one -pole form, tripod style, a series of course of time break down the system like very short wires about 10 feet from X -rays or burn like sunlight -the operators insulator to insulator, of the counter- at the big stations such as that pictured poise system; that is, a wire under here would years ago have felt the effects. each system of direction. I suspect But, neither for sickness nor for health, that the article you published on the does radio affect the system. use of tuning on human frequency as If your radiator starts playing the piano, used at the University of California quietly investigate, like Dr. Summy (Page 858). SHORT -WAVE SYSTEMS is where they procured their idea, and We now touch on the point which our cor- that one or more men are from the anything different about the air or the space, respondent misinterprets, that of ultra- short- east. I will appreciate your help on into a magnetic field in which iron would wave stations. It is true that around a five - this matter and will furnish any in- melt. or six-meter wavelength, and perhaps below, formation possible. I have also taken Therefore, not only to those who believe with very high power, a transmitter will the matter up with the detec- they are hearing radio or feeling it, but to cause a slight heating of bodies very close tives. You know absolutely that this those in authority and in the medical, legal to it. That effect is manifested only by the is new and they may be skeptical in and clerical professions to whom such suffer- conversion of this electrical energy into the matter and work slow, and the re- ers come with their stories, we have only to heat; and a very much smaller amount of sult, this bunch of criminals get away say that the belief has no foundation in electricity in a reflecting heater would pro- and operate again. So please give me fact; and that, if it had, the matter could duce sensible effects on those around it much every possible assistance. and would be demonstrated openly to all quicker. Furthermore, for only a few feet (Signed) - - - within hearing. We have further to say away from a very powerful (and expensive) that, while delusions of persecution caused transmitter can this effect be detected by a by imaginary, invisible voices drove many to human being. madness before the days of radio, in this The experiments described in the article, the waves of a moderate -powered transmit- age of better understanding a correct diag- "Everyone His Own Aerial," do not produce ter. A man may touch the aerial post of nosis should in every possible case be given, the slightest sensation in the participants his set and serve as an antenna to bring in to guard the sanity and to promote the phys- while they are vibrating with and reflecting a broadcast signal out of the ether; but, so ical healing of the sufferers, if possible. Real Radio Mysteries Reported by Our Readers WIIY radio music and speech bursts set down the telegrapher's climbing spurs One thing, however, is generally to be forth in the most unexpected and his hundred -mile reach alike as "medi- noticed; they occur in close connection with places, without the intervention of cine!" (magic) and dismissed all further some system of piping, wiring, or other any apparent means of picking up, inquiry into the methods used. metallic assembly of large extent. The detecting or reproducing the signals, is still The radio experimenter, however, who analyses of the phenomena contained in among the "'Mysteries' of Radio" described has to work hard for his results, feels a press reports are often those of laymen. in the leading editorial on page 619 of the greater interest in the matter. Many odd For instance, the Associated Press carried January issue of RAmo Nxws. But the fact things have been noted from time to time, some weeks ago the dispatch reproduced in is a source of scientific curiosity, rather than but uncertainty as to the exact conditions facsimile in the continuation of this article; of awe. A public which has become used to prevailing (electrically) at any given instant and, of course, the same story appeared in the miracle of radio is not impressed with have prevented an attempt to reproduce the the same words in many papers; many any impossibilities in the matter of its ex- demonstrations; particularly when they of whose readers, on that day, accordingly* emplification-like the prairie Indians who seem to be structural freaks. (Continued on page 854)

www.americanradiohistory.com

S12 Radio News for March, 1929 Hearing Plants Grow by Radio Imperceptible Movements of Plants Affect Sensitive Oscillators and Produce "Beat" Notes, Which are Broadcast by Austrian Scientist, Prof. Richtera

By Ashur van A. Sommers

IN their efforts to present radio programs scription of them may be of Interest. No BROADCASTING A PLANT'S PULSE of a "different" kind, broadcast stations constructional data or constants are given, here and abroad have taken their micro- as the apparatus can be duplicated only by The beat note is then led directly to the phones into strange places and have an engineer having laboratory equipment at modulator circuit of the broadcast trans- will go the air as a peculiar picked up with them many strange and un- his disposal. The original apparatus used for mitter, and over usual sounds. Deep -sea divers have dragged the Vienna broadcasts was designed by Prof. squeal. Another possible arrangement is to "'mikes" down into the green waters of the Richtera, director of the "Ravag" station in reproduce the noise first through a loud sea; aviators have taken them aloft in the that city. speaker, and to pick up the sound waves clouds; surgeons have admitted them to their with the usual studio microphone. This scheme allows the to listen the operating rooms. In New York the sound operators to directly and to determine whether of goldfish swimming in a bowl was success- apparatus is working properly. fully broadcast in a most interesting manner it the actual oscillators used in the experi- from Station WRNY; in Iowa the sounds of In ments the human nerve currents, and in Japan the by Vienna broadcast station, heartbeats of a maternity patient have been "Ravag," which are pictured on this page, "put upon the air" for the edification of the circuits were adjusted to a frequency of local listeners. The explosions of shattered 1,ô00,000 cycles (200 meters). The plates of atoms have crackled in the ears of a distant A simple form of electric nkra- micrometer, the condenser whose capacity is affected by consisting merely of two metal plates fastened the growth of the plant are very thin alum- audience. to adjusting rods. It has remained for an Austrian scientist, inum discs about two inches in diameter. gifted with a sense of publicity values, to go The top plate is attached to one arm of the own lever, while the bottom one is fastened to an even closer to Nature and to reveal her HOW IT WORKS voice over a radio broadcast station. He upright rod. The position of the latter is took a pot of flowers from his living -room Briefly, the idea is to arrange a delicate adjustable, and is determined by experiment window, placed it in the company of a lot of system of levers in such a manner that the with the particular plant being used. complicated electrical apparatus, and then upward movement of the plant as it grows The growth of mushrooms has been ob- actually broadcast the sounds made by the moves one plate of a tiny condenser. This served with the aid of this apparatus. One blossoms as they grew imperceptibly before condenser is connected across the tuning

his eyes ! Needless to say, the radio listen- condenser of a high-frequency oscillator, ers who were permitted to eavesdrop on the which is tuned to exactly the same frequency novel experiment obtained quite a thrill out as a second oscillator of identical construc- of it. tion. While the lever remains stationary, As the instruments which made the stunt the two locally- generated currents do not possible may easily be obtained and put into produce any "beats" because they are tuned operation by any capable radio engineer, we alike. However, the very slightest movement may now expect that ringside descriptions of of the lever, which will be caused by even A more advanced form of electric micrometer, championship prize fights will be enhanced an infinitesimal growth of the plant or flower, with which distances of a fraction of a mil. by noises indicating the growth of bumps on alters the capacity of the midget condenser lionth of an inch can be measured. the protagonists' heads; so that grandmoth- and throws one oscillator off tune. Since er's appreciation of the gory battle will be the oscillations generated by this unit are end of the the except for the odor of the blood on now slightly different from those of the lever is simply rested on top complete of the canvas. Many other uses for the ap- other, they will heterodyne or "beat," a the mushroom; as the latter rises, it and down- will themselves to enterpris- third frequency will be generated, equal pushes the other end of the lever paratus suggest the ing station managers. numerically to the difference between the ward, increasing the capacity of midget condenser and, consequently, decreasing the The principles of operation of the electric two original oscillations. If the values are frequency of the oscillator in whose circuit ultra- nacrometer, which is the name given to properly selected, the beat signal can be to know this remarkable instrument, will be under- made to fall in the audible band, between it is connected. It is interesting that the movements of plant growth are not stood readily by the radio fan, and a de- 16 and about 10,000 cycles. steady, but pulsating-like the strokes of a pump. Left: Inside view of the two oscillators, showing the complete shielding between the parts. Below: Front panel view of the oscillator unit, completely enclosed. The dial at the right adjusts one of the oscillator circuits.

ma views,

www.americanradiohistory.com Radio News for March, 1929 813

MEASURING INVISIBLE DISTANCES As may be seen from the accompanying The electric ultra -micrometer has a prac- illustrations, the oscillators are built into two tical use in the measurement of extremely adjacent metal cans which shield them core small distances, since variations in the length pletely from each other. Each can contains of an object to an extent as small as an oscillator coil, a vacuum tube, and the 1/250,000,000th of an inch can be detected. usual filament resistors and radio -frequency This movement is so much smaller than a chokes. The "A" and `B" batteries for eacln wavelength of light that it is necessarily for- circuit are contained in the same cans, but ever invisible. Very slight changes of tem- separated from the radio - frequency com- perature, which affect the length of pieces of ponents by metal partitions. metal, can be measured with precision to The front panel of the instrument looks, 1/5500th of a degree, Fahrenheit. In fact, like a large one -dial receiving set. It holds when a person enters the room in which the two meters, a. dial to adjust the tuning con- electric ultra -micrometer is located, the rise denser of one of the oscillators (the other in its temperature occasioned by the heat of being fixed), and two auxiliary knobs for a loud The actual apparatus used in the experiments a human body is enough to cause at the Vienna broadcast station. The left end filament control. Once adjusted, the ap- squeal to issue from the loud speaker. of the lever merely rests on the flowers. paratus is left alone. "It Isn't All in the Set It's in the Location!"

N editor's mail contains few surprises, readers, both on long and short waves, and THE GOOD OLD DAYS but, on the contrary, a great deal of wonder why I cannot duplicate their recep- Won't some learned individual or progres. matter which can be expected daily tion with sets that should be many times sive manufacturer come forward with a in proportions determined by the law of more powerful. By the word powerful I really powerful and efficient receiver than averages. If he is a radio editor, he will mean their ability to get distance stations. will reach out and get a few of the station:. know that the quest for "DX" is an un- At the moment I am using a set having that are now on the extreme edge of our dying flame, by the number of inquiries like five R.F. 222 tubes. It has a range, either present reception; which edge is about than this, from a Virginian, "How far can KFI on detector using phones, or speaker vol- same distance away as it was in the old be received in the daytime ? " -or this, from ume using four stages of audio, of about days of the one -tube set? The cost of sus* a Californian, "Is there any set made that 1,200 to 1,500 miles at the outside on a very a set should not prevent a number being can reach out practically any time and pick good night -no greater range than that ob- sold, as $600.00 to $1,800.00 (in Canada) Is up New York from here ?" tained with a duplicate receiver using five being paid for very indifferent sets buried The power of the transmitter and the 201As, or a three -tube Peridyne. On all away in very ornate cabinets, the owners o& signal-amplification factor of the receiver three sets, using the same aerial at about which quickly become dissatisfied when they are the only two terms of the problem that the same time, a number of stations can be realize that they have paid a great deal of occur to the average inquirer. If a receiver heard murmuring away off in the distance; money for a receiver which will do little or gets a 1,000 -watt station 1,600 miles away, but no amount of experimenting with tubes, no better than a set costing ten times lesss. for Smith in Ohio, why should it not get ground, aerial, etc., will make the slightest Quality of tone from nearby stations is any 1,000 -watt station at the same distance difference. This applies to both my town a good argument; but the majority of lis- for Jones in Nevada, or Robinson in New and country location, the latter being by teners would be more than willing to pay York City? Why this discrimination? in- the side of a large lake, where reception more for a receiver that will occasionally quires many an indignant set owner, who should be good. (This is not necessarily get a different station further afield. has been spending money freely in order to true.- Enrroa.) (Continued on page 862) have on his log just as good and far-off stations as anybody. The letter which follows puts the case just as thousands see it, but in so clear a manner that we leave Mr. Timberlake to state the position of the set owner who is disap- pointed of the distance reception for which he is willing to pay, and oftentimes has paid, good money.

WANTED, A REAL DISTANCE-GETTER

Editor, RADIO NEWS: I have been a constant reader of your most excellent paper since the first few is- sues, and I assure you that I have more than appreciated the great interest it has af- forded me over a period of years. I should like to enter a plea, one that will no doubt be echoed by thousands of your readers, a plea for a real distance -getting receiver, if necessary, regardless of cost. I have purchased and built up practically every powerful (so-called) receiver adver- tised in your paper during the last four or five years. I have also built up from the best of parts the majority of sets described by the contributors to your magazine; but they have all fallen short, very far short, of the results claimed by designers or manu- facturers. It may be my own fault, but I cannot see where I have slipped up. I have used patience, the best of parts, and ex- treme care over details. From time to time I read of the very won- Communication companies, to whom certain reception is their bread and butter, cannot depend o,S the best receivers alone. They spend thousands to find a good location, and thousands more derful results obtained by some of your for an aerial system like that shown -a short-wave R.C..4. antenna at Riverhead, N. Y.

www.americanradiohistory.com

814 Radio Nezws fbr March, 1929 Radio Echo from the Depths of Space?

Are Short -Wave Signals, Escaping from the Heaviside Layer, Turned Back by Magnetic Field a Million Miles Away? By C. P. Mason

N astounding, and yet unexplained, a radio wave has, presumably, time to travel must be surrounded by a huge, though in- phenomenon has been observed by twenty -two and one -half times around the visible, electric belt not unlike the well - European scientists and engineers, earth, or out to the moon and back. Re- known rings of Saturn in its arrangement and brings to mind at once all ideas peated observations confirmed the presence (Fig. 2C). At the magnetic equator, this that have been proposed with more or less of the delayed echo; but Mr. Hals, unable to region would be farthest from the earth, practical plans, for communication with give any explanation which seemed logical, while the captured electrons and other elec- other worlds than ours. It is nothing else kept his discovery to himself for several trified particles would come down closest to than the echo of radio signals, observed after months. He then enlisted the services of the earth in the polar regions; thus pro- a period when no possible circuit of the Professor Stürmer, a well-known authority ducing the well-known effect of the aurora, wave round and round the earth's circum- on terrestrial magnetism. The latter made which manifests itself, whenever the sun is ference could leave it with sufficient ampli- arrangements with Dr. van der PoI, technical in a state of electrical and magnetic erup- tude to be recognized. The first hypothesis director of PCJJ; and a series of 31.4 -meter tion. forth, with a plausible argument in its transmissions, with undamped waves, were set Other observers contributed suggestions. waves reflected back effected for the special purpose of testing support, is that the are They point famous the conditions under which this echo was out that audio-frequency disturb- from an electrified region-not the ances of a natural nature (in addition to Heaviside layer, at its supposed height of produced. For some time the results were radio-frequency "static") may be picked up sixty to three hundred miles, but one far out- negative; but, on October 11 last, echoes out of the ether. A distinct dick will be fol- side the orbit of the moon -one which is per- were noted plainly. lowed by whistles at intervals of some sec- haps 1,250,000 miles away. An idea has undoubtedly occurred at once onds; and it is suggested that these are due for some re- to our readers; that radio reflections It has been known time, and from to disturbances, very the moon have been received. Well, perhaps at a great corded by delicate automatic machinery, that plausi- height, whose reflections from enormous dis- ble though that supposition may seem, the the signal from a very powerful short-wave tances over varying paths draw them out is received, only once at the time new observations added even more startling station not from sharp tones to whistles. phenomena to be accounted for. The radio protracted of its arrival over the shortest great -circle Be this as it may, very profound reflec- on arrival echoes were heard after the lapse of from path of reception and again its tions are caused by the reported phenomena, in the direc- three up to fifteen seconds, corresponding to over the longer route opposite no matter what the cause. It has long been it has again around the time of travelling nearly three billion tion, but even after gone known that the sun carries with it (in addi- miles, or to a point five times as away the world. The fact is indicated by a dupli- far tion to its visible satellites, the planets) in the record of as the moon, back again. at- cation or shadowing effect and A race of tendant masses of invisible matter, very 110 laps around the globe, certainly, would the signal on the sheet of the recording in- finely divided, yet of considerable mass in strument. But less than one -seventh of a leave a radio wave rather too exhausted to their total. The phenomenon of the "zodi- second is for a radio wave to go wiggle even the most sensitive aerial circuit. required acal light has not fully analyzed; around the world through the atmosphere. "" been OUR ELECTRON GIRDLE but it is enough to say that, under favorable A SURPRISING DISCOVERY Presenting a purely temporary hypothesis conditions, a broad luminous area may be de- tected in the night sky, centered Late in 1927 a Norwegian engineer, Jilr- in a letter to Nature (London) Professor evidentlf gen Hals, detected a similar effect in re- Stürmer suggests that the wave is reflected around the position of the sun below the ception from the short-wave station PCJJ, from the electrified region in space where horizon (Fig. 2B). This area obviously ex- in in at Eindhoven, Holland, on 30.20 meters. He electrons emitted by the sun are captured by tends past the earth the zodiacal region could hardly believe the fact, for the interval the earth's magnetic field (See Fig. 1). Many which the planets move; for in the place in between the main signal and its "shadow" years ago he published a mathematical sur- the sky exactly opposite the sun may be seen was no less than three seconds. In this time vey of this field, concluding that the earth (Continued on page 881)

DENSE PORTION OF EARTHS F16:1 'MELD OF MAGNETIC FORCE

/ yam' . :- AY": \\ i/ r-s -^ \1//// \ .F! \\II//// \ ----t- ¡/ /AORTR MAGNETIC

POLE ; 1 1

SUPPOSED PATH OF I I / SHORTWAVE FROM I I // l'1\ ELECTRON LAYER I 1 I----- I1 SO /// 250.000TO i 000 I I 1 \\ 01/jl1\\\ MILES FROM E \ ` /%/ \\\\ 1 / /h. \. /// \\\ / .11-- '/ / / / . , . ZODIACAL /: \\ s` - flat) \\ \. OF ELECTRONS -"*.-.- \ \. COMING FROM SUN

T le echo heard, occasionally only, when conditions are right, The reflection of faint light in the night sky indicates that space beyond the indicates that the radio wave is reflected from an electrical layer earth is filled with microscopic particles forced out from the sun. In this region at a distance of more than a million miles. It is calculated that the earth revolves with its magnetic field. The well-known "rings" of the this forms a "toroid" almost empty of electrons. planet Saturn are a more spectacular illustration of a like condition.

www.americanradiohistory.com Radio News for March, 1929 815 "Miniature Music " - - -A New Point of View Since Radio Has Brought Music Into the Listener's Home, Out of the Auditorium for Which It Was Orches- trated, Shall We Revise Our Notions of Quality ?

By R. Raven -Hart

N practically all cases, the reproduction all published technique. On the contrary, I paratus of the future will probably be able of an orchestra in a normal home must would suggest that we abandon all attempts to give full-power reproduction, and that, I be at a very considerably lower level of to reproduce the illusion of being present therefore, fidelity can be obtained only if volume than that which would be heard by at a concert, and boldly make for a new the balance is perfect. Admittedly, if it a person having a good seat at the concert. standard in music, suited to radio condi- is a case of reproduction in a hall approxi- For not only is the expense of reproducing tions, and which one might call "miniature mating in size that of the concert hall an orchestra at full power prohibitive in music." By this I mean that radio sets itself; but such volume is utterly undesir- most casés, but also there are "the neigh- should be so designed that the ear receives able in a normal home, and any steps taken bors" to be considered, to say nothing of balanced music; not that the loud speaker to reduce it (e. g., by a volume control in those members of the household itself who should put out a balanced reproduction, but the set, or by putting the loud speaker in wish to study or read or talk. that the parts of the musical scale which another room), at once re- introduce the We may safely assume, then, that in the ear hears as weaker than the rest should defective balance clue to the ear, unless this nearly all cases we shall reproduce the music be over -amplified, taking into consideration defective balance is corrected by an unbal- at a reduced volume. Now it is well known the over -all volume which the set is intended ance of the reproduction. (see page 216 of RADIO NEWS for Septem- to give. (Thus, for example, in a set de- There is one interesting technical devel- ber 1928) that, if the volume of music is signed to give a loud -speaker reproduction opment possible, however, and that is a dis- reduced, the reduction is chiefly noticeable of the unobtrusive sort that can be ignored criminatory volume control, such that, as the on the lower notes; that is to say, if we if one wishes, the bass would be over- volume is reduced, the portions of the scale listen to a well- balanced orchestra from a amplified, and to a less extent the extreme which the ear then hears as over -weakened distance, we shall notice a lack of bass notes. upper frequencies.) are automatically not cut down to the sanie Equally, if our reproduction is perfect as extent as the rest -in other words, a volume regards the balance between high and low NO REAR -SEAT REPRODUCTION control such that the equilibrium, as deter- notes, but reduced in volume (as we can It seems to me, in fact, that it is time mined by the ear, is preserved at all levels assume will be the case), we shall miss the for radio engineers to realize that the lis- of volume that the set will produce. Noth- lower notes; and we shall thus have the tener of the future, and even the listener of ing of the sort seems to have been designed illusion of listening to the orchestra from a the present to a far greater extent than is as yet; a resistance shunt of considerable distance -from the last gallery, or even the realized, will base his musical education on self -capacity, across the loud speaker, would vestibule, let us say. the music as heard by radio, and will very act in this way to a certain extent, as re- rarely attend a concert. Why, then, con- gards the lower notes at any rate, but A NEW STANDARD tinue to strive after the illusion of being something more exact is required. All attempts of radio engineers at present present at a concert (and in a bad seat appear to be in the direction of equalizing at that!) just because the listeners of the WHAT DID BEETHOVEN MEAN? the reproduction through the audible scale, past were more accustomed to hear directly The second objection is that the composers and thus giving us this illusion, thanks to than by radio and thus found it more pleas- did not intend such unbalanced reproduc- the perfect balance of the sounds emitted ant to revive memories of concerts by means tion; that we should strive after the effect by the loud speaker. of a faulty reproduction than to hear all the that would have been produced by their In view of the reduced volume almost in- orchestra, properly balanced but in minia- original performance on persons sufficiently evitably associated with this reproduction, I ture? far away from the orchestra to hear the would reply, emphatically, no; although in Two objections may be raised. One is music at the reduced level suitable for our so doing I may run counter to practically that the average and inexpensive radio ap- (Continued on page 866)

Why strive after the illu- sion of being present at a concert (and in a bad scat at that!) just because the listeners of the past were accustomed to hear di- rectly?' The composers would have liked to have everyone enjoy good seats.

www.americanradiohistory.com "016 Radio News for March, 1929

1

. . G. ...:`'. te111r Íea,sp./

ON the broad piazza of his magnifi- the other end lay a mass of papers-records Mr. Dare, just in the nick of time, glimpses cent laboratories building, Harold gleaned by long hours of intense study, the winged death hurtling through the air, Dare, the great impelling power of watching, and application -piles of prints steps' over to the radio transmitter in the Flicker Films, lounged in a com- and data sheets gathered through long chiefs office, starts up the rotary gap and fortable chair at the dose of a long day of vigils of ceaseless research and deduction. sends out the signal that deflects the tor- strenuous endeavor and accomplishment. The And about this table, the cream of the pedo into the bay? And now, gentlemen, full moon, glowing in the heavens like a soft world's engineering talent sat spellbound, history repeats itself: Diavolo has endea- amber spotlight, threw into bold relief the listening with intense concentration to their vored to duplicate the tragedy that very distinguished features of Harold Dare's chief, as he unfolded a story of dark and narrowly overtook his hated arch -enemy. classic face -the high, broad forehead, the devious doings, of criminal activities against He has failed once; dare we hope that he straight line of his sensitive, artistic nose, one who had ever stood upon the highest will fail a second time? No l! We must and the firmly-chiseled chin. It was for pedestal of honor and rectitude-a story act 1 Let us devise a means of foiling the him a time of quiet meditation upon the which was within the hour to set the whole fiend, as did Mr. Dare in his great celluloid weighty problem of the morrow. world aghast with horror at the diabolical drama! To your places, men l" Suddenly a muffled explosion, followed deeds of a fiend who would stop at nothing Silently that great organization set about by another, and yet another; a flash of to accomplish his fell designs. Beautiful its tremendous task, to pit its combined blinding flame, and great billows of black Dorothy Golden, Harold Dare's private intellectual powers against the terrible cun- smoke belched from the windows across the secretary, recorded for posterity the words ning of a fiend; while outside, the public, street; an instant's deathly silence, and a of this historic conference. warned by swift radio bulletins from the terrific explosion shattered the very founda- "Gentlemen," said Scott, Dare's famous Dare station WROT, suddenly awoke to tions of the night. chief engineer, "let us summarize our find- the perilous situation. The Chief of Police Harold Dare sprang from his chair and ings in this despicable, depraved plot offered his full cooperation, and all the strode rapidly into the laboratory where against the man who has done more than resources of the great city of Los Angeles the technicians were working at their instru- any other man in history, not only to further were placed at the star's disposal. Whole ments. "Come, staff P' he cried: "A terrible the advancement of science, art, and the carloads of detectives armed to the teeth menace threatens the public safety! We movies, but to uplift the masses and raise were sent whizzing through the city in all must avert it! To the rescue! Run hose lines! them constantly to higher and ever higher directions. A cordon of policemen was Man the pumps!" Seizing a carboy of car- realms of happiness, health, and harmony. thrown about each of the city's public bon tetrachloride and a fire extinguisher, "We have found that the terrible explo- institutions, for it was generally conceded he dashed from the room. sion which destroyed the building across that a fiend who would adopt such terrible Fire engines were already arriving, their the way was caused by an incendiary bomb means of accomplishing his private ends roaring exhausts and shrieking sirens mak- -a miniature airplane which dropped out of would as likely as not direct his next attack ing a bedlam of the night; department after the sky, laden with explosives and incendi- upon orphan asylums and hospitals. As department was responding to the summons ary material; while miles away, a cruel, quickly as the keen mind of Scott had to pit its puny strength against the red coldly-calculating fiend sat at a radio trans- formed an opinion, the public likewise demon that was ravishing the beautiful mitter, directing by radio control the flight drew swift conclusions regarding the proba- building. In the light of the red flames, the of the plane with its cargo of death. What bility of Diavolo's implication in the out- . struggling firemen frantically dashed into could be the motive? Would anyone go to rage; yet, although every movement of the the swirling, stifling smoke, only to come the expense and trouble of so complicated villain was shadowed, no clue could be stumbling back, blinded and choking, gasp- and difficult an undertaking as this, merely found to link him with the explosion. The ing for breath, while higher and higher for the purpose of setting fire to an empty aeronautical industry was at a standstill, rose the flames. office building-when a dozen ways would for every airplane, balloon, and glider was Then Harold Dare and his men apppeared have been safer and easier? No! But across looked upon with intense suspicion by every

on the scene. A great cheer went up from the , street, gentlemen, was an immense right-minded citizen. And when the posi- the assembled crowd. Through the smoke- laboratory, wherein an organization of tives of the Dare picture, "The Clutch of filled doorway he led his men, who dragged highly- trained experts work night and day the Corsican," were brought from the vaults with them the heavy armored hose from toward the execution of the plans of a great and exhibited at motion -picture theatres, the laboratory. Dare himself shouted the man for the betterment and benefaction of the rush to see them was so tremendous signal that sent a powerful current of car- his public. And much as I regret to say that scores were trampled to death and the bon tetrachloride pulsing under tremendous it, there is a person-nay, fiend -who would gross box -office receipts were the greatest pressure through the hose. stoop to such a dastardly deed as this. recorded in the history of the industry. The rest was merely a matter of moments. Dandy Diavolo, who, as the world's great- A strange structure appeared upon the Before the heroic efforts of Harold and est villain, has pursued Harold Dare roofs of the Dare studios. At the sugges- his men, the flames quickly gave way. And through countless reels of the Flicker Films, tion of a Dare engineer, a huge steel net when the great film star stood in a window alone would resort to such tactics to ruin - was stretched over the entire group of of the wrecked top -story and faced the and probably blot out of existence-the one studio buildings. Although not a great newsreel cameras that were clicking away whom he has ever hated and persecuted. deal of confidence was placed in this device, a record of the terrific struggle, the crowd "Do you remember," he continued, with still it was hoped that it might lighten the burst into a demonstration which lasted for growing earnestness, "how, in that great effects of an explosion. A captive balloon many moments. As decisively, as dramatic- film drama, 'The Clutch of the Corsican,' was anchored above the studios, and from ally, as gloriously as in one of his own Diavolo, as chief of the ring of opium it observers watched constantly; by day super-productions, Harold Dare had saved smugglers, attempts by means of a radio- through powerful prism binoculars, by the day! controlled aerial torpedo to blow up the night through a super -sensitive sound * « * * * Federal secret service building, where detector. Upon one end of a long table in the Harold Dare, as a U. S. secret service As soon as possible the great Dare or- Dare laboratories, lay a pile of junk: agent, and Ruth Roguish, his co- operative, ganization resumed its regular activities. In twisted scraps of metal, fragments of wire, are on the point of giving to their chief order to safeguard the lives of star and bits of steel, all rusty and smoke -stained, information which will result in the arrest staff, production was concentrated upon all methodically arranged and ticketed. At and imprisonment of the ring; and how outdoor scenes for the time being, and work

www.americanradiohistory.com Radio News for March, 1929 817 upon the indoor stages practically ceased. paralyzed. The handwriting on the wall! Instantly that great organization sprang But, conscious of their responsibility to the A miracle! What was its meaning? into swift action. Engineers seized their public to carry on the plans of their chief "Let us see it again," weakly murmured slide rules, integraphs, transits, levels, ano. for everything that was bigger and better, an engineer. The film was rewound, and plumb bobs, and set to work with tremen- the devoted members of the Dare engineer-. again it clicked through the machine. Three dous energy upon their appointed tasks; ing staff remained faithfully at their posts. minutes passed; the strange pattern of dots while Harold Dare, summoned from his In the laboratories building, where the flickered and disappeared; then again rose executive offices, personally supervised their danger was greatest, the various groups that dreadful spectre, its ghastly grin work. worked calmly at their research, heedless striking many a cold chill to the hearts They had barely begun when the tele- of the terrible hazard, thinking only of their of that dauntless staff. phone rang furiously. The great Scott duty, and of the bonus promised them by The great Scott rose and addressed his seized the receiver. The voice of the look- the thoughtful Dare. unnerved engineers. "Staff, there is one out in the captive balloon came shrilly to The great Scott, with his group of asso- possible cause for the terrible spectre we his ears. "A high -speed airplane motor can ciates, was personally proceeding with an have just witnessed. Some outside station be heard in the sonophone. It is coming investigation which he had been conducting was operating upon our exclusive channel, this way." when interrupted by the terrible explosion. emitting a wave modulated by some peculiar At that moment the door flew open. A The purpose of the test was to determine combination of frequencies. For each cycle laboratory assistant burst into the room. the television transmission -characteristic of of the current, a bright spot was produced "Help !" he gasped. "The death plane -it the Dare broadcast station, when operating on our television screen. The wave must is coming!" by remote control over a short telephone have been keyed in such a way that the The engineers turned white; Dorothy line leading from the laboratories building bright spots formed first the pattern of Golden screamed; but dauntless Harold to the broadcast studio. A test chart con- dots, and then the terrible death's head. Dare had already rushed from the room, sisting of a number of converging fan - Who was operating upon our channel? Miss Scott close behind. shaped, pointed segments of solid black Golden kindly take this note: To the Super- In the radio laboratory, the screen of the against a white background was being tele- visor of Radio, 999th district: `Sir: This televisor showed the same pattern of dots vised. Its television equivalent was carried is to report the reception of interfering which had appeared upon the film. "Quick- to the studio by the telephone line, broad- signals from an unknown station operating ly!" shouted Scott, "Reload the film!" cast, and the received version photographed upon our exclusive short-wave channel. The The table bearing the projection machine upon the motion -picture film, later to be signals were heard from three minutes, be- was wheeled over to the radio tame, and compared with the original. The sharpness ginning at 7:42 p.m. and lasting until 7:45 while the operator loaded the machine with with which the converging points were de- the reel of film which bore the record of fined constituted a measure of the quality "Great Scott!" exclaimed one of the en- the crucial experiment, Scott trained the of transmission. And now, in a darkened gineers, in a queer, choked voice. "7:46! lens upon the bank of photoelectric cells projection room, the engineers were trac- That was when the explosion occurred r constituting the pick -up apparatus of the ing, point by point, the effect of certain Pandemonium broke loose. On all sides television transmitter. He made a few quick adjustments upon the operation of the dr- engineers rose from their chairs, wildly connections. An excited chorus told him cuits. tearing their hair, shouting at one another, that the engineers at the window could see "Cut!" suddenly spoke Scott to the opera- while Scott rapped frantically for order. the plane through their night glasses. tion of the projection machine: "What has "Men," he said, " we must act. We have "Quickly!" cried Scott. "The power!" happened to the Mm?" found the wavelength of the control station Harold Dare flew across to the switch- Across the center of the screen ran a which directed the radio torpedo; for only board and gave the signal which set the series of white dots, like minute punctures a signal such as that used for controlling huge short -wave transmitter of WROT os- of the tiny film of the camera. a tuned -reed relay and other radiodynamic cillating at full power. Scott clicked shut The lights blazed on; the operator stopped equipment would cause the pattern we have the transfer switch which connected the his machine, opened the cover, and extracted observed. We must deduce from the record television transmitter through the remote- the reel of film. the combination of signals which operates control line, to the studio. "See!" he exclaimed, holding the film in the controls, and devise means to deflect "Harold! Harold! Fly! Fly! Your life the powerful light of the projector. "The the plane if it should approach again. To must not be jeopardized!" screamed Doro- dots are printed into the film. Some stray work, men! Duty calls!' (Continued on page 866) current must have interfered." "Nonsense!" snapped Scott: "A burst of static, or battery noise, would have marked perhaps a dozen frames-not more. Per- haps something has gone wrong with the camera shutter. This pattern of dots runs right along for a dozen feet. See! This was no mere stray current." "Perhaps," suggested another engineer, 'another station was operating upon the same wave. A wave modulated by a single audio frequency would force such a pat- tern." "You forget," replied Scott, "that we have an exclusive channel. No station has the right to use the same wavelength. Let us see if the dots continue throughout the film." The film was replaced and projection re- sumed. For several minutes the dots wove a zig -zag pattern across the screen. Then suddenly they ceased and the pattern of the chart stood out in sharp contrast. "See!' said Scott. "It was an exterior signal! It came from - He gasped. Like those at the feast of Belshazzar, all the staff sat petrified with amazement and fear; for across the very blackest of the chart shone forth a gleaming death's head -glistening, threatening, ter- rifying. For a moment it regarded them with a baleful stare; then it was gone. The last of the film clattered through "Scott trained the lens upon the bank of cells constituting the the machine; but that grave group sat pick -up of the television transmitter."

www.americanradiohistory.com 818 Radió News for March, 1929

ak's r II apparatus described in this department has been tested in the RADIO NEWS Laboratories and found of high quality in design and construction.

Scanning Disc Is Adjustable To New Variable is Designed for to 21/2 amperes and can be used with good satisfaction in trickle chargers, as well as Four Transmissions Short -Wave Work those with a faster charging rate. THE usual difficulty encountered by ex- ANOVEL and very handy condenser de- The rectifier is equipped with a regular perimenters with television receivers is signed for short -wave receivers and Edison base, to be screwed into the socket inability to synchronize the signals from transmitters, which can be utilized as either provided for tungar and similar types of more than one or two stations, due to the a single individual tuning condenser or a tubes. The terminal formerly connected to difference in the number of holes in the "vernier" adjustment, has recently been the top or side of the original rectifier tube scanning discs. This has necessitated the placed on the market. One novel feature is connected to the prong on the top of the use of a different disc for every station of this condenser is a screw adjustment metal tube. A very long life is claimed for picked up. The speed can easily be con- which allows the maximum capacity to be the rectifier, which can be refilled with new trolled by either friction or resistance de- metallic elements at little expense. vices, but the discs cannot be changed so Manufacturer: Interstate Electric Co., St. easily. Louis, Missouri. These difficulties can be overcome by using one of the devices illustrated on this page. It is 24 inches in diameter and contains two discs of aluminum, one behind the other. Compact Coil Provides Its Tube One of these discs is fitted with a bushing with Socket for the motor shaft, while the other is cut THE present demand for compact con- out in the center and mounted on the first struction in home -built receivers has led disc by several machine screws. The main to the development of a lever device in is drilled with several lines of holes, in the which the R.F. coil fits snugly about the is usual spirals, and the second also pierced tube socket Essentially, the apparatus is by similar spirals; but they are so arranged a combination of an interstage transformer that the holes of only one spiral coincide in and a tube socket which is mounted within the two discs at the same time. The second the coil form, so that the same sub -panel disc is mounted with slotted holes and a key space is occupied by both the tube and the is provided so that any of the spirals can coil. The transformer consists of a molded - be used by merely sliding the discs with the bakelite form, one end of which is dosed, key until the holes match. An indicator except for four small holes to receive the Fig. B shows which set of holes is in line. screw connections on the tube socket which The disc is provided with four sets of The two brass plates of this condenser are is mounted on the closed end of - the form has 24 holes is suitable mounted on an aluminum frame. Their spac- holes. The first and ing is adjustable, varying the maximum The latter measures 1% inches in height, for use when receiving WGY, W2XAD, capacity. and the same in diameter. No. 30 enameled W2XAF, Schenectady, or W4XA, Memphis, wire is used for winding the primary and Tenn. The second has 36 holes for W6XC varied, in order to adapt the condenser to secondary, the leads of which terminate at 45 on the at Los Angeles. The third has for different uses. A bushing, placed four soldering lugs at the bottom of the WCFL and WIBO, Chicago; and the fourth shaft of the rotor plates, and two nuts with form. moved closer has 48, the recommended standard, used by a spring, allow the rotor to be To mount this R.F. transformer, it is nec- other transmitters such as WRNY and to or further from the stator plate. essary to drill eight holes in the sub -panel W2XAL, New York and W3XK, Wash- With the plates exactly / -inch apart, ington. the condenser has a maximum capacity of Manufacturer: Pohl Brothers, Detroit, 17 mm£; while, by placing them doser to- Fig. D Mich. gether, this capacity can be increased to (below) almost double this value. The condenser is Tke neat base shown on this mounted on a sturdy cast frame, with the tube is actually an R.F. trans- former whose terminals are the insulation at the corners; the least possible lugs at the bottom. The tube it- amount of the latter material is employed, self is connected through screw in order to keep the losses low. This con- terminals which run through denser should find a great many uses with the sub- panel. The assembly of an R.F. stage is thus mode ex- the short -wave enthusiast, in both receiving tremely compact for shielding. and transmitting work. A cross-section of the coil- Manufacturer: Radio Engineering Lab- socket appears on page 819. oratories, Long Island City, N. Y.

Metallic Rectifier for "A" Supply Has Lamp Base AMETALLIC rectifier, which can be used to replace the rectifier bulb in the 2- ampere chargers using this method of rectification, has been placed on the market by a St. Louis manufacturer. The advan- tages claimed for the new rectifier are longer life, ruggedness, and an economical replacement of the rectifying elements when Fig. C the rectifier shows signs of deterioration. (above) The rectifier is of the "dry" type, using This half -wave dry metallic Fig. A rectifier fits the Edison base metallic discs for the rectifying action. The used by vacuum tubes of simi- The key shown below turns the 24 -inch disc up to present a 24 -, 36 -, 45 -, or 48 -hole spiral. unit is adaptable to all battery chargers lar duty -rating.

www.americanradiohistory.com Radio News for March; 1929 819

(four for the socket terminals; four for the the end, so that the most effective pressure off, there is enough resistance in the line coil lugs), using a drilling template which can be obtained; this feature allows it to to match that of the speaker. This allows accompanies each set of coils. The compact- be adjusted to the particular circuit re- signals to be heard from the other speakers ness of the components makes their external quirements of the set. A lock nut also is in the circuit at the same volume as before field comparatively small; it is thus possible provided, so that the setting can be kept in- the first speaker was cut out. Thus, the to place them close together and yet obtain tact after the crystal has been adjusted. maximum number of speakers any amplify- a fair degree of stability of operation. It is Unlike the usual galena and similar crys- ing system will carry can be connected in recommended that a shield of copper or tals which were used so extensively some series or parallel; and the volume of each aluminum enclose each unit to insure maxi- years ago, the Carborundum crystal requires speaker will be smoothly adjusted to fit in- 1 mum results. a heavy pressure in order to give the great- dividual requirements, without interfering These units are available for the 201A- est sensitivity. The pressure is rather criti- with the others in the circuit type tube, for which UX sockets are sup- cal and much better results can be obtained The constant-input resistor is of a size plied, as well as for A.C. tube operation, with one of these crystals if it is properly easily assembled in standard outlet boxes; adjusted. The method employed in the new it is housed in a molded -bakelite case with method of mounting effectively overcomes the difficulties often encountered in the past. The new crystal functions in exactly the same manner as the older type and should have a bias of about 11/2 volts, to give the SECONDARY best detecting action. The usual method of using a potentiometer and dry cell can be SOCKET employed to obtain this. Manufacturer: The Carborundum Co., PRIMARY Niagara Falls, N. Y.

eCi 9Ci Sc 9 COIL SOLDERING Loud -Speaker Control Does Not al LUGS Affect Others in Use Fig. 3 SPECIAL panel- mounting resistor to With this -hook-up of the dual volume control A control the volume of one speaker one resistance increaser as the other decreases; without affecting the volume of others con- so that the load on the set is the same. Fig. 1 When a tube is plugged into the socket in this nected to the same amplifier has been made R.F. coil, contacts arc made through the base. available by a Mid- Western manufacturer. air -tight metal cover, 1% inches in diameter. The resistance element is divided into two These units are made up to match the im- which requires one coil mounted with a UY pedances of the speakers with which they (five- prong) socket. are to be used; the manufacturer recom- Manufacturer: Gainey's Radio Shop, Dan- mends that these be measured in ohms at ville, Ill. 1,000 cycles when computing the needs of a speaker circuit Crystal Detector Adjustable Manufacturer: Central Radio Labora- by Screw Pressure tories, Milwaukee, Wis.

THE use of fixed crystals in the Inter - flex and Peridyne receivers and others Small Plug -In Short -Wave for detection purposes, has brought about Coils Rugged renewed demand for a crystal which will Are HAVING in mind the present interest in Fig. E short -wave reception, a New York radio The dual- resistance volume control, mounted on manufacturer has designed a new group of the frame of a cone- speaker, with knob to the front. It is suitable also for use on the panel coils, to facilitate the construction of short- of a radio receiver. wave sets. The coils are 2 inches in diam- eter and equipped with plugs which allow a special tapers, one of which will maintain in quick change from one waveband to another.' the line a constant resistance equal to the The coils are wound with a definite spacing impedance of the speaker used; the other is between the turns and supported on a thin tapered to give a smooth and gradual con- but strong layer of transparent dielectric' trol of volume. The first resistance is in material, in which the wires are partially series with the line and the second is shunted embedded. This prevents them from coming across the speaker; both are regulated by loose and affecting the characteristics of the one knob. Turning the knob to reduce vol- coils. ume by shunting the speaker will add to the The primary winding, which is used for output load enough of the other resistance all the coils, is mounted on the base, which to maintain it at a constant impedance; so also contains the jacks into which the coils that, when the speaker is completely turned (Continued on page 867)

Fig. F These coils, constructed on a well -known prin- ciple, are very compact and for use below 50 meters.

Fig. 2 Cut -away view of new Carborundum detector; A, adjusting screw; C, Carborundum crystal; P, plungers, S, springs and T, terminals.

be equally adaptable to all circuits. In an- swer to this demand, a well-known manufac- turer has introduced a crystal mounted in a cartridge from which it can be readily re- moved to facilitate replacement. The crys- tal is equipped with an adjusting screw at

www.americanradiohistory.com 820 Radio News for March, 1929

IIIIII;1' ` I IpI Begume IdIIOi, ;`

Radio "Filters" and Their Many Forms and Uses By C. Walter Palmer

r-i-"%HE advent of "B" power units and denser will pass high- frequency currents in this case; this is just opposite to the op- electric sets has caused a large in- more readily than one of lower frequency, eration of the band -pass type. crease in the use of filters in radio while it stops or "blocks" the flow of direct sets. When battery- operated receiv- current; and third, that tuned circuits will LOW -PASS FILTERS ers were used exclusively, the electric filter permit the passage of alternating currents As explained above, the "low- pass" filter was very little known and its use was con- in a narrow band of frequencies and will is used to allow all frequencies below a cer- fined almost entirely to telephone engineer- oppose the flow of currents at other frequen- tain value to pass. An inductance coil in ing and other similar highly specialized fields. cies, or vice versa. By a proper arrange- series with the line, as shown in Fig. 1, will However, because of the wide use of these ment of condensers and coils, any desired allow low- frequency currents to pass with filters in power packs, almost every radio filtering action can be obtained. little "impedance," while it will oppose enthusiast can now tell what sizes of chokes higher- frequency currents to a much greater and condensers are used in the filter cir- TYPES OF FILTERS extent. In order to return the high -fre- cuit of a power unit and how they are Besides the special filters, which are used quency currents to the source, a condenser connected. Of course, the filter used in the only for special purposes and will be de- is often connected across the line. By choos- "B" power unit is only one of a number of scribed later, there are four general dasses. ing the correct values, high- frequency cur- types and, even in this case, most fans can- The first is the "low- pass" filter, which pre- rents are by- passed; while the impedance to not tell how the filter operates or why cer- vents currents of a frequency higher than a low- frequency currents is high enough to tain values are chosen for the coils and con- certain predetermined value from passing. prevent them from being by- passed with the densers. This type of filter will pass direct current others. At the right of the diagram the The purpose of an electric filter is not and all alternating currents of a frequency combination of coil and condenser is shown. very different from that of any other filter; lower than the critical value mentioned Since the "cut -off points" of the coils and it is simply a device for separating several above. condensers in such a filter are not sharp, a things which are mixed together. In this series of such sections is often used to im- comes the "high filter, which case they deal with electric currents of dif- Next -pass" prove the operation of the filter. A prac- will all currents of a frequency higher i.e., direct and alter- pass tical application of the low -pass filter is the ferent characteristics; value. filter nating currents, or alternating currents of than a certain In most cases a "B" power unit. In this case, the "recti- of this type will stop the flow of direct cur- different frequencies. The electric filter fied" direct current is passed through the rent as well as that of low -frequency alter- acts just as a sieve does, in separating ob- choke coils with little trouble and, since di- currents. jects of different sizes. nating rect current cannot pass through a con- Although the design of filters involves the The third is the "band -pass" filter, which denser, the direct current is kept in the cor- use of intricate mathematical calculations, is designed to let through any current which rect path. The high- capacity condensers in the general nature of these units and how has a frequency between the upper and this filter are so designed that alternating they operate will be of interest to most ra- lower limits of the band covered by the currents of both high and very low frequen- dio beginners. Their action depends on sev- filter. In this case, currents of either higher cies are by- passed, which leaves the output eral well -known facts: first, that an inductor or lower frequencies are stopped. free of all alternating currents which would ( "inductance ") permits the passage of di- The fourth and last of the general types otherwise cause "hum." rect currents and low- frequency currents is the "band- elimination" or "band- exclu- In most "B" power units a two-section with much less resistance than it offers to sion" filter. The frequencies between the filter is employed, comprising two choke high -frequency currents; second, that a con- limits covered by the filter are suppressed coils and two or three filter condensers.

LINE UNIT FILTER LINE UNIT BY PASS UNITT i BY-PASS A B C UNIT LOW -PASS FILTER FIG. I A B FIG.3 BAND-PASS FILTER

LINE UNIT BY- PASS FILTER UNIT

LINE UNIT FILTER A B c HIGH- PASS FILTER A e - c Fl G.2. FIG -4. BAND- SUPPRESSION FILTER The "filter" arrangements above shown, though not commonly so called, The "tuned R.F." stages of the ordinary radio receiver sound much simpler will be found throughout every schematic radio diagram. It will be seen than "band-pass" filters; but the latter is a description that may be applied that the only difference between the "low- pass" and the "high- pass" filters to them with perfect accuracy. The "wavetrap" too is a "band- pass" or is their arrangement and the way they turn "traffic." "band- suppression" filter -as you choose to view the signal.

www.americanradiohistory.com Radio News for March, 1929 821

When using 30-henry chokes and 2- micro- denser in parallel (as shown in the cc. er of in series; these units are shown at the left farad condensers, the filter will pass cur- the diagram) connected across the line- ar- and center of Fig. 4, while the complete fil- rents of afrequency lower than 20 cycles, rying the current, will offer the great.--t ter is indicated on the right. The applica- which excludes the 60 -cycle hum which it is opposition to currents of the frequency to tion of the band- exclusion filter is limited desired to eliminate. Most of the "line which it is tuned. By combining the two mostly to telephone work; although a filter noises" and all the "harmonics" of the 60- circuits, which are adjusted to the same fre- this variety might be required in a radio cyde hum arc also included in the scope of quency, a fairly sharp cut -off on either side re, fiver of special design. the filter, so that it is almost ideal for this of the required frequency will be obtained. Tnc general types of filters described purpose. By increasing the number of filter units, the above are often varied, so that the correct IIIGH-PASS FILTER band can be made more sharply defined. filtering action may be obtained at the re- The combination of the two filters is shown quired frequency. For instance, in the band- The operation and construction of the at the right side of Fig. 3. pass filter, either the condenser or the coil high -pass filter is just the reverse to that The application of this type of filter will may be removed from the series or shunt of the low -pass filter; a combination of this be found in wavetraps using "acceptor" and position; in order to increase or decrease type is shown in Fig. 2. The high -pass filter "rejector" coils. Every tuned circuit in a the frequency; since the limits of the fre- is designed so that all frequencies below a radio set is really a single -section filter, de- quencies which may be covered by a tuned certain value are by- passed back to the signed to pass currents of one particular circuit of the type shown are limited. source (through the inductor); while the small band of frequencies to which it is Resistors cannot be considered as filters, them frequencies higher than this value are al- tuned, and block all others or by -pass since they impede currents equally at all be. the tuned Iowed to pass. An inductor will allow a to ground, as the case may If frequencies. They do, however, have a dif- is in at the comparatively free flow of currents of low circuit arranged series (as left ferent effect on filter circuits. They do not change the frequency at which the filter op- erates; but they do affect the sharpness of the band. In other words, they may be used when it is desired to broaden the tuning of the filter and, if the filter is to be tuned very sharply, care must be taken to keep the resistance of the circuit as low as pos- sible. A similar effect may be obtained by increasing the number of units in the filter, but as a general practice it is less advisable.

SPECIAL TYPES Besides the general types of filters de- scribed above, there are a number of others which cannot be brought under these classi- fications; although they follow the same rules as these four general types in the mat- FIGS VREELAND FULL-BAND TUNER. ter of the use of condensers and inductances for specific purposes. One of these is the The two tuned circuits LI -Cl and L2 -C2 have in common L3, which causes them to tune sharply, Vreeland "full- band" filter, which was de- not to their exact natural frequency, but to a band on each side of it; while excluding everything scribed in the March, 1928, issue of RADIO in "RADIO NEWS on 826. else. The principle it used the Hi -Q" described page NEWS. The data for building a filter of this type were published in the December, 1928, frequency, while a high - frequency current of Fig. 3), the filter passes the required fre- issue, so that it is not necessary to give them is hindered much more. A condenser in quency; while if it is in shunt (as at B) here; but we reprint the diagram in order series with the line will prevent the flow it blocks the required frequency and passes to illustrate the operation. (See Fig. 5.) of direct current and, if the correct value all others. The selected frequency is then This unit is really a band -pass filter of is chosen, the low- frequency currents up to carried on to the other apparatus, usually special design and has the advantage that the required value will also be blocked. In the grid of the vacuum tube. currents within the band are amplified to this case, also, the number of units may be an almost, if not quite, equal ratio. This -EXCLUSION TYPE increased to make the cut -off frequency BAND provides the necessary selectivity (10-kilo- more sharply defined. The band -exclusion filter is used for a cycle coverage) without reducing the qual- The actual application of this type of fil- purpose just opposite to that of the band- ity, and without making the tuning too ter is not as common as that of the low - pass type; to prevent the passage of the broad. As explained in the original article, pass type; but it will be found that most current in the band, a tuned circuit of a the Vreeland system employs two "reactive applications of radio -frequency choke coils coil and a condenser in parallel are con- couples" LI -Cl and L2 -C2, preferably alike, in a receiver actually make up a single -sec- nected in series with the line. The by -pass each having a capacity and inductance that tion high -pass filter. For instance, in the unit then consists of a coil and condenser (Continued on page 869) detector plate lead, a radio -frequency choke is placed in series with the line, while a by- pass condenser is connected from the plate to the filament. The low- frequency currents (the audio -frequency "signal") and the di- e,1-3MEOOHMS g from the rect currents "B+Det" lead pass TI T2 a ze.r.f. a choke while r: though the the high- frequency z . fá (radio -frequency "component") currents are carried back directly to the filament cir- cuit through the condenser. ao R BAND-PASS FILTERS The purpose of the band -pass filter is to 11111111)11 allow the passage into a circuit of currents 4I 1 11 ¡Mno A- of a narrow band of frequencies, excluding .11111111'111111 A+ all others, whether higher or lower than the B- limits of this band. Fig. 3 shows the make- B+. ET. up of this filter. The combination of a coil and a condenser in series (as shown at the SOMERSALO FREQUENCY- FILTER B+R.F left of the diagram) will "resonate" on a certain frequency and the circuit will have The three tuned circuits ahead of the first tube here compose a filter which is followed by an untuned least "reactance" to currents of. this fre- amplifier. In this manner, there is no source of feed -back through the system. It will be noticed quency. On the other hand, a coil and con- that the primaries of the coils L2 and L3 are each open at one end.

www.americanradiohistory.com r822 Radio News for March, 1929 Radio Tubes and Their Characteristics [PART II.[

With e Explanation of the Alternating- Current Tube and dust Where the Alternating Current Is Used By H. M. Bayer

THE question has often been asked, tube to be used in radio circuits. This tube unknown. This resulted from the grid's ac- How can alternating current be ap- was a crude affair containing a filament tion in responding to the feeble flow of en- plied to the filament of a tube with- which, when heated by a battery, served as ergy collected by the antenna and so af- out the accompanying 60 -cycle hum the electron- emitter, and a plate which was fecting the current of electrons from fila- becoming a pronounced factor in the out- kept positive by connecting it to the "-i-" ment to plate. The introduction of the grid put?" It can readily be seen that this prob- side of a high- potential generator (the "B" made possible also audio -frequency ampli- lem becomes somewhat hazy to the uniniti- battery). When the filament was heated it fication, radio - frequency amplification and ated, when they know that raw alternating emitted a constant stream of electrons which the adaptation of the vacuum tube to radio- current is used to light the filament of the were directed toward the plate, by its at- telephone and telegraph transmission, where 226 -type tube, and, to all appearances, the traction for the electrons, which are nega- it is employed as a generator of high fre- 227-type tube as well. tive. (The half -wave rectifiers described in quency currents. There is no doubt that, this article are actually "Fleming Valves" without the triode or three- element vacuum THE "DIODE" in operation, though greatly improved dec- tube, radio telephony could never have even In order to gain a dearer understanding trically and mechanically.) neared the perfection it enjoys today. of the functions of an A.C.- operated tube, As long as the filament remained Mean - While the battery- operated three -element it is first necessary to review the electronic descent there was an electrified region be- vacuum tubes gave excellent results, and for action which adapts a vacuum tube for use tween filament and plate, providing what that matter still do, the public's demand for in radio reception and transmission. With- is known as "a path of unilateral conduc- increased simplicity of operation brought out entering too lengthy a discussion of tivity"; that is, permitting a current in one forth A.C. tubes, designed for operation this subject, it may be stated briefly that direction only. This "one-way" characteris- from the light socket. Incidentally, it may the electrical characteristics of the vacuum tic provided a sensitive rectifier (or what be mentioned here that (contrary to a gen- tube depend on the electron -emitting prop- was then considered sensitive) necessary to eral belief) there is a theoretical difference erty of a heated metal; this action was first "detect" radio waves and reduce them to only in efficiency between the two classes of discovered by Thomas A. Edison and is audio frequencies. vacuum tubes; the practical differences are known as the "Edison Effect." Edison found merely in the convenience of main- THE "TRIODE" found that, by heating a piece of metal to a tenance and operation. Where the 201A- high temperature, he obtained conditions This development was the forerunner of type requires a storage battery or an "A" permitting the flow of electricity in a vac- the modern three -element vacuum tube, power unit with rectifier and filter, the 226 - uum; now known to be due to the emission which was invented by Dr. Lee de Forest and 227 -type tubes require for filament ex- of electrons. and by him styled the "audion." He found citation only a step -down transformer; Some time after Marconi had obtained that, on inserting a third element (the grid) which in turn is connected to the house - his first patents, J. A. Fleming made use of between the filament and the plate, he ob- lighting line, thus doing away with the this effect and constructed the first vacuum tained a sensitivity of detection heretofore routine of charging and watering a battery.

BASIC STORAGE-BATTERY- RAW -A.C- INDIRECT- THEORY OF HEATED FILAMENT HEATED CATHODE THE HEATED 20I -A TYPE DIRECT EMITTER RAW A.C. HEATER. EMITTER 2.6 -TYPE 27 -TYPE

w

110 VOL 110 VOLTS A.0 STEP-DOWN A.00 FIG.1 TRANSFORMERS

The filament or "A" current takes no part in the operation of a unit) has only direct current in its filament; so has the No. 27 -type rube, except as it is used incidentally to give bias. A tube may tube at the right, in which the alternating current does not enter theoretically be operated with a gas flame to heat its filament, as the cathode, which acts as a filament. The 26 -type, however, has at the left. A storage -battery tube (even if operated from an "A" slight A.C. coupling in its filament circuit.

www.americanradiohistory.com Radio News for March, 1929 823

However, for the benefit of those who lack 1.5 and 2.5, in addition to a separate supply a source of alternating current it should be for an accompanying power tube. repeated that, other things being equal, they are equalling the results of the A.C. tube 15 -Volt 26 -Type (A.C.) users except in the previously mentioned Use, detector; socket, UX -type; matter of convenience. Filament voltage 1S raw A.C.; current 0.35 -am pere; WHAT THE A.C. TUBE DOES Plate voltage 2236 to 45; current 1 to 2.5 Ella. Grid bias 4% to 9 volts positive. In the first diagram (Fig. 1) a three-ele- ment vacuum tube, the filament of which is 28 -Type brought to incandescence through the me- Use, amplifier (not power); socket, UX -type; Filament voltage 15 raw A.C.; current 0.35-atm dium of a flame, is shown at the left. This, pere; of course, is merely to illustrate the "Edi- Plate voltage 90: current 7.5 mla.; son Effect" in its basic form and has no Grid bias 1.5 volts; A.C. plate resistance 9,000 ohms; practical counterpart in the commercial or Amplification factor 10.5. present -day experimental field; though Dr. de Forest is said to have used a flame in 30 -Type his early experiments in order to obtain Left, a photoelectric cell; center, a neon tele- Use, power amplifier; socket, UX -type; vision lamp. Right, an "overhead -filament" Filament voltage 15 raw A.C.; current 0.35am electronic emission from a filament. It will 3 -volt A.C. tube, with three prongs. pere; be noticed that the plate current, carrying Plate voltage 180; current 22 mla.; the signal heard in the loud speaker, travels allow as little "ripple-voltage" or hum as Grid bias, 27 volts; A.C. plate resistance 3,500 from filament to plate and "return" and is ohms; possible. Such a resistor must be connected Amplification factor 3.8. entirely independent of the heating method as shown in Fig. I, where it is balancing used on the filament. the filament of the 226 -type tube; as the al- 32 -Type (High -mn) The second sketch in the same illustration ternating current flows back and forth in Use, amplifier (not power); socket, UX -type; Filament voltage 15 raw A.C.; current 0.35 -asst shows the conventional direct- current tube the filament, voltage at its center is prac- with filament. course, pere; its battery-heated Of tically uniform. This resistor is absolutely Plate voltage 135; current 1.5 mla.; this may as well represent any of the dry - essential when using 226 -, 171 -, 210- or 250 - Grid bias 3 volts; A.C. plate resistance, 32,000 cell tubes; the principle is the same with type tubes in A.C. circuits. ohms; the exception of the voltage and current de- Amplification factor 30. mands the respective filaments. Here, as of 15-VOLT A.C. TUBES 40 -Type in the first sketch, the filament -plate current Use, power amplifier; socket, UX -type; follows the same path. The first part of this article, in last Filament voltage 15 raw A.C.; current 0.4-am- Before proceeding with a description of month's ItAmo NEws, described the 1%- and pere; Plate voltage 180; current 21 mla.; the A.C. tube, it should be emphasized that 2%-volt alternating current tubes, which in- Grid bias 4034 volts; the only difference between the latter and clude the 226 -, 227 -, Hi -Mu 26- and A.C. 22- A.C. plate resistance 2,000 ohms; the D.C.-filament types lies in the construc- types. Amplification factor 3. Another class of current tion of the filament This is, of necessity, alternating- tubes 48 -Type (A.C.) makes use much heavier in construction in the A.C. of the separate heater -filament Use, amplifier; socket, UX -type; tubes. Necessarily, there is a difference be- for all types, instead of A.C. current led Filament voltage 15 raw A.C.; current 0.35 -an- tween the filament circuits of both types; directly to the filaments as in some of the pere; the grid and plate circuits, however, are A.C. tubes listed above. These tubes re- Plate voltage 90; current 4.5 Ella.; Grid bias 4% volts; similar and require no, changes in the event quire a step -down transformer with a single A.C. plate resistance 9,200 ohms; that a D.C. receiver is rewired to use A.C. fifteen -volt secondary; whereas the others Amplification factor 11. tubes; except that the return is made to the require transformer secondary voltages of (Continued on page 872) "midpoint" of the filament circuit. This re- fers to the 226 -type tubes, which can be used only in radio -frequency and audio -frequency amplification circuits, and not as a detector. THREE - HALF -WAVE THREE - ELIMINATING A.C. HUM ELEMENT RECTIFIER. ELEMENT The schematic structure of the 227 -type VACUUM TUBE FILAMENT VOLTAGE Fig. 1; TYPE REGULATOR A.C. detector is illustrated in this TUBE tube employs a "heater" which is entirely independent of the grid, plate and filament- return circuits and, for this reason, produces less hum than the 226 -type. Many com- mercial receivers employ these tubes throughout the amplifying stages to guard THREE-ELEMENT FULL -WAVE PHOTO- possibility rA TUBE A.C.HEATEO RECTIFIER. ELECTRIC against any of hum. Unlike the CATHODE TYPE FILAMENT CELL 226, this tube employs for its electron -emit- (221) TYPE. ter a fourth element known as the "cathode" (this accounts for the fifth prong on the UY socket), which is nothing but a cylinder built about the filament or "heater." It is the sole function of this heater to heat the SCREEN -GRID FULL-WAVE NEON -GAS cathode until it has reached the tempera- TUBE(222) - RECTIFIER. GLOW -TUBE ture where it will emit electrons. (See the FILAMENTLESS (TELEVISION sketch at the right of Fig. 1.) This ex- TYPE LAMP) plains the slight delay which takes place between the switching -on of an A.C. receiver and the moment its detector begins to func- tion; this interval averages about 30 seconds and has always been somewhat of a mystery SCREEN -GRID TWO -ELEMENT to the layman. A C TUBE VOLTAGE - Another hazy subject, to the beginner, is REGULATOR TUBE the center- tapped resistor which is placed across the secondary of the step -down 11/2 - FIG. 2 volt filament transformer used in lighting the filament of the 226 -type tubes. Briefly, 0 the reason for the use of this component The symbols used in schematic diagrams to indicate the types of tubes here is the necessity of providing an electrical described. The first, and commonest, symbol is the same for a direct- current tube balance in the filament circuit, in order to or for one working with raw alternating current on its filament.

www.americanradiohistory.com Fr-7-._

' 824 Radio News for March, 1929

A typical group of mheters, as found on the work -table of an active experimenter. Left to right: 0 -100 milliammeter; 0 -6 D.C. voltmeter; 0.600 A.L.-D.C.. voltmeter; 0-50, 0-250 D.G. high -resistance voltmeter; 0.250 milliammeter. What Meters Does the Radio Fan Need? By Robert Hertzberg

IT is a fact, though an unfortunate one, tubes, requiring power supplies widely dif- overcoat pocket and drove to his friend's that most radio experimenters and ferent. The man who contemplates any house. In five minutes he learned that the many custom radio builders do not serious experimental work, or who has oc- detector tube was being supplied with 102 properly appreciate the value of volt- casion to do even casual testing of power - volts, the R.F. tubes with 16 volts, and the meters and ammeters. They regard these units, will be as helpless without meters as A.F. tubes with 49 volts, instead of their re- instruments, usually, as desirable luxuries; an automobilist driving in the dark without quired 200. The grid circuit of the audio whereas they should consider them as impor- headlights. power tube-a 171A -was practically open, tant necessities. Some men will spend hun- The writer wishes to reassure the reader a condition which accounted for the scratchy dreds of dollars on radio parts and acces- that this article is not inspired by manufac- signals. In another five minutes the knobs sories without even thinking of meters until turers of meters who desire to increase the were adjusted to give 67 volts to the R.F. some time when they encounter puzzling sales of their products. It is the result tubes, 20 to the detector, 200 to the resis- problems; and then they suddenly realize rather of considerable observation of home tance- coupled audios, and 180 to the 171A, that a good set of measuring instruments radio experimenters, custom builders and with the proper 40 -volt grid bias. The re- would help to find the trouble in a few min- service men, and of their methods of work- ceiver then resumed its normal condition of utes. ing. The incident that led directly to its stability and gave forth music that was a A few years ago the home experimenter preparation for RAnIO NEWS was an inter- pleasure to the ear. A single, simple volt- or service man could get along fairly well esting and illuminating one, and serves to meter did the whole trick. with a 98 -cent combination meter that looked emphasize the points the writer brings out. The writer is not going to recommend a like an overgrown pocket watch. With this A man owning a tuned R.F. receiver of list of necessary meters a yard long but, he could test the six -volt storage battery a good commercial grade, equipped with an rather, will tell how to get along with the and the 90-volt `B" battery that formed external resistance-coupled audio amplifier fewest number. The ambitious experimenter the power -supply equipment of practically and "B" power supply, found one night that or builder can start at the top of the list all broadcast receivers of early vintage; if the set squealed badly, was very weak, and and complete his collection as his finances the readings satisfied him, his use for the produced scratchy music when it produced allow or his business requires. meter was ended. Today, however, there any at all. He learned that his 11- year -old The first, and by far the most important are actually dozens of different types of son had innocently twisted the knobs on the meter for present -day work, is a high- resis- power unit; thereby upsetting the output tance voltmeter, for measuring the output voltages and throwing the receiver alto- of "B power units of all kinds. The most gether out of kilter. He telephoned for a popular and useful instrument of this classi- local service man -so called-who arrived fication has a double scale, one reading from with his pockets jammed with tools, tubes 0 to 50 volts and the other from 0 to 250. and wire, but no meters, and twisted the Either scale may be used if the connection knobs for a hour without helping matters is made to the right one of two "plus" posts much. The variable resistors used in the on the base of themeter. A third post, al- power unit happened to be of the compres- ways connected to the negative side of the sion type, with an adjustment range of three circuit, is also on the base. The meter must full turns. He finally left, saying he'd be be of the "high- resistance" type, so that only back with some more tubes and remarking a very small current is consumed by it. The that the unit was well adjusted. usual medium -priced instruments have a re- sistance of between 750 and 1,000 ohms per THE RESCUE TO volt of scale reading. The owner of the set called the There are many small voltmeters with writer, explained the trouble, and scale readings which take in the usual volt- asked what could be ages developed in radio power units; but - done about it. Being these are not suitable because they take al- idle at the moment, the most as much current as a complete radio latter put a high- resis- receiver. A small voltmeter of the low- tance voltmeter in his resistance type may draw as much as 20 mil- liamperes, which is as much current as a 171A power tube takes. This drain seri- .,1111,,,,,111 1,,,,1,,.,,.,t. 1., u,1 i,,,,,,,,, 11111 lll 11.1, l,,,. ously affects the output of the power pack, and makes the meter readings false. Worth its weight in gold- the Weston A.C. -D.C. test INCREASING THE SCALE RANGES set. This is equipped with a rotary switch which A voltmeter with a 250 -volt scale can be makes the two meters read power units designed every current and voltage used as it stands, for value in a receiver. for sets employing R.F. and A.F. tubes of

www.americanradiohistory.com Radio News for March, 1929 825 the standard 201A, 226 or 227 types, and a such devices, which are very effective in re- units, but he usually doesn't know their power audio tube of the 171A type; for lieving some of the objectionable features of resistance in ohms because the labels have these tubes work on a maximum plate volt- A.C. operation. come off, or they are so dirty that the age of 180. When it is desired to measure A word of advice in regard to the proper numbers cannot be distinguished. Every voltages in excess of 250, this range can handling of the meters is in order. Remem- now and then he wants a resistor very badly, be extended by simply inserting a resistor ber that, when you are playing with a "B" and then he has to take a chance with any in series with either the positive or the nega- power unit, you are likely to encounter volt- one he picks up. tive side. A simple and reliable method of ages as high as 1,000 in 210 and 250 power The method of measuring the resistance determining the value of this multiplying re- packs and as much as 300 even in small 171 value is very simple. Simply connect the sistor was described in detail on page 742 of units. Don't hold the two wires from the milliammeter in series with the resistor to RADIO News for February, 1929. meter in your fingers while you are measur- be tested, and connect the combination Briefly, the idea is to use either a fixed ing the voltage across any particular sec- across the lowest -value output posts of a or a variable resistor, the latter of the "uni- tion of the circuit. Put a clip on one of "B" power unit. Clip the voltmeter across versal" range type. Before connecting it, the wires, snap it in place, and keep only these same posts. Turn the unit on and ob- clip the meter across any available power one wire in your hand at a time. If you serve the meter readings. If the milliam- unit so that you obtain a reading of exactly make a habit of this one -hand method you meter does not read at all, or if the needle ninety volts on the 0 -250 scale. Leaving the will never be shocked, as you are not part moves only a fraction of a degree, increase adjustment of the power unit unchanged, of a complete circuit. the "B" voltage until you obtain a reading now connect the variable resistor in the The 110 -volt line will not sting much but, that you can note accurately. The resistance meter circuit, and adjust it until the meter as a matter of safety, keep your fingers of the resistor in ohms is then equal simply reads exactly thirty volts. This means that away from live connections. to the voltage divided by the current. For the scale reading is to be multiplied three With these two voltmeters, the experi- instance, if the voltage is 96 and the current times. The meter can thus be used for menter, custom builder or service man can 10 milliamperes (.01- ampere), the resistance values up to 750 volts. diagnose about 90 per cent of all the is 96 divided by .01, or 9,600 ohms. This The writer found that an ordinary 250; trouble usually developed in either home- figure is exact, and not merely approximate. 000 -ohm grid leak was just right as a three - made or factory -built receivers, defective time multiplier for his 0- 250 -volt meter. If tubes excepted. In the absence of an ex- This method can be used only with resis- a variable resistor is used, its adjustment pensive tube -tester, the easiest thing to do is tors of the type employed for power units, should not be disturbed, once it has been to replace the suspected tubes by good ones, and other applications where they normally determined; and it should not be used for and to note the difference in results, if any. carry more than a few milliamperes. It will work out easily for resistors under 25,000 any other purposes, unless you are willing AMMETERS AND MILLIAMMETERS to re- calibrate it every time you want it for ohms or so; because most resistors of this voltmeter service. Ammeters and milliammeters are very comparatively low value are intended for On the 0-50 scale, this same voltmeter may useful for experimental work of all kinds, power use. Grid leaks and similar high - be used quite successfully for measuring but are not indispensable to the service man. value resistors will not pass more than a storage batteries or "A" power units de- About the most useful meter of this class small fraction of a milliampere without signed for the 201A and similar tubes, which is a direct- current milliammeter, reading burning up. work on six volts. from 0 to 100 milliamperes. This can be As a further check on the operation of used for measuring the current load im- A.C. INSTRUMENTS alternating- current tubes, an A.C. ammeter posed on "B" power units by the tubes of reading up to 5 amperes is useful; this meter The next meter, in the order of impor- receivers of all kinds. The average five-. or is more or less of a luxury, and makes a tance, is one for measuring alternating-cur - six -tube set with a 171A power tube draws nice addition to the experimenter's or cus- rent potentials up to 150 volts. There are perhaps 35 milliamperes, and larger sets with tom builder's instrument case if he can af- on the market a number of very convenient 210 or 250 tubes 65 or 75 milliamperes. Cur- ford its cost. meters for this work which have three scale rent drains of this order are easily and ac- readings: 0 to 4 volts; 0 to 8 volts, and 0 to curately measured. LOW-RANGE D.C. METERS 150 volts. The first takes in the filament The main value of a milliammeter in meas- As stated before, a high -resistance D.C. voltages required by A.C. tubes of the pop- uring the "B" circuit load is that it allows voltmeter can be used for measuring six ular 226 and 227 types; the second the fila- the owner of the set to determine whether volts, as furnished by storage batteries or ments of power -amplifier and rectifier tubes or not the rectifier tubes are being operated "A" power units to sets using direct- current like the 210, 250, 280 and 281 types; and the properly. There is a definite safe operating tubes. If you have occasion to do extensive third allows the measurement of line- voltage value, for every type of rectifier, at which testing or trouble -shooting on receivers of on the house line. Either scale may be se- the tube will work efficiently for a long time( this type (and there are many thousands lected at will by connection to the proper without developing an excessive amount of (Continued on page 879) post on the base of the instrument. heat. If current in excess of the figure An A.C. voltmeter of this kind is nowa- given by the tube manufacturer is passed days considered by most service men fully through the tube, its life will be shortened as important as the high- resistance D.C. considerably and it will overheat badly, per- meter previously described. As many radio haps injuring neighboring apparatus as a experimenters have learned to their finan- result. Rectifier tubes are by no means as cial distress, A.C. tubes are sensitive to volt- cheap as smaller receiving tubes like the age changes, and blow out on the least pro- 201A, so it pays to watch them closely. If vocation, apparently. A few minutes' trial the filament voltage as measured by the with a three -range voltmeter will quickly A.C. voltmeter is normal (or preferably tell whether the so-called "110-volt" house slightly below normal) and if the current current line gives really 110 volts or 126, through it is within the safe maximum fig- and whether or not the individual tubes are ure, the tube will last a long time. A life being underloaded or overloaded. Most peo- of three years or more for slightly- under- ple are prone to blame the tubes themselves loaded rectifiers is not unusual. when they blow out but, in many cases, the The combination of a milliammeter and trouble is actually caused by overloading. a voltmeter may be used for the measure- When a transformer that is designed to ment of resistors of unknown values. work on 110 volts is used on a 115- or 120 - Every experimenter has a fistful of volt line (as many are), trouble is bound odd resistors, taken from old power to develop. An A.C. voltmeter left connected across the house line will also indicate to some ex- tent whether annoying set noises are caused 'Another high -grade a11- purpose in- by line fluctuations. By watching the needle strument, the Jewell. The meters an hour or so are thrown in and out of the cir- for you will discover that the cuit by meows of small push- buttons. voltage changes considerably. If the fluc- With the plugs, readings are taken tuations are very bad, the only remedy is an at the sockets. automatic regulator. There are a number of

www.americanradiohistory.com 826 `Radio News for Marth, 1929 The Radio News 1929 H1 -Q

A Six -Tube Receiver Combining the Highest Quality with DX- Getting Ability

By Herndon Green

THE "1929 Hi -Q" is probably the Fig. A finest all -round broadcast receiver The "1929 Hi-Q" built into a con- which It i io Naves has yet been able sole cabinet of very attractive de- sign; many styles are available to present to its readers. It is de- Nowadays. signed specifically to operate under the pres- ent difficult conditions of broadcast recep- tion, and possesses all the necessary require- and reproduce only what is fed into it by ments of quality, selectivity, sensitivity and the detector tube, which in turn receives the from the -frequency amplifier. set owner to receive programs from very ease of control. Its main feature is the use signal radio it is evident even a distant stations when he feels so inclined, a circuit, comparatively new in broadcast- Hence, that perfect of provide high -quality and also because it makes possible quite sat- receiver construction if not entirely new in audio system cannot output from the loud speaker, if distortion isfactory reception from local and moder- principle, which is of the band- pass -filter ately distant stations on a small indoor an- type and ideally suited for the reception of tenna, even in unfavorable locations. How- broadcast stations without interference. The ever, selectivity and sensitivity are also in- arrangement also makes possible a degree This receiver, one of compatible. of tone quality hitherto not obtainable with the finest ever made TRUE AND FALSE SELECTIVITY ordinary forms of radio-frequency ampli- available to home and fiers. custom radio builders, in- One of the reasons for this condition is understood, Briefly, the tuning system in the "RAmo corporates two "flat top" not generally and is even more seldom NEWS 1929 Hi-Q" provides even greater se- band -pass filters, de- taken into consideration. The aver- lectivity than the old- fashioned "razor - No. 76 scribed in previous issues age receiver owner or experimenter bases his almost on edge" regenerative set expertly operated, of Rena NEWS. These transformers, judgment entirely the appar- and sensitivity equal to that of most super - which must be laboratory- matched, ent selectivity; this is quite natural, in view heterodynes: In addition, the output from make it possible to give both selectiv- of the fact that the actual selectivity of a the loud speaker will satisfy the most criti- ity and very high amplification. Full receiver can be determined only by a series of very careful measurements. The cal music lover. Since the receiver in gen- constructional blueprints will be fur- appar- ent selectivity radio set de- eral is distinctly new and different, the de- nished for 25 cents; coupon which ap- of the ordinary creases as its sensitivity increases. There- tails will be given. pears on page 879 should be used to expedite the order. fore, of two receivers having exactly sim- THE "SIDE-BAND" PROBLEM ilar "actual" selectivity while one has, say, To start at the beginning, the layman will three times the sensitivity of the other, the selectivity is readily agree that good a highly set having the higher sensitivity (or amplifi- desirable of any radio set. Good attribute is introduced in the R.F. amplifier; clue, let cation) will invariably seem broader or less been selectivity, however, has hitherto un- us say, to excessively sharp tuning, techni- selective. derstood to mean sharpness of tuning, which cally known as "side-band cutting." This This principle is very clearly shown in is not conducive to quality of reproduction. illustrates the opposite nature of two desir- Fig. 1. Line A is the response -curve of For example, the high -quality audio-fre- able characteristics, quality and selectivity. the less -sensitive receiver when tuned to 600 quency coupling devices now available make Also, high the attainment of a degree of kilocycles (500 meters). Assuming that no 600 -kc. station is on the air at the time, no sound will be heard from the loud speaker, as the sensitivity of the set is not great enough to bring a 580 -ke. station (which is assumed to be on the air at the time) above audibility. Line B represents the response -characteristic of the more sen- sitive receiver and, under conditions de- scribed, the 580 -ke. station will now be heard; since the increased amplification of the more sensitive receiver is sufficient to r bring the signals above audibility. Thus, it is quite easy to understand why the more sensitive of the two sets will "appear" to be less selective; although in reality one is Fig. B equally as selective as the other. This fact need The center knob VC is the volume control; the tuning control Cl governs the antenna condenser, illustrates the for specially-designed and the right knob the four condensers tuning the band -pass filter circuits. tuning circuits in a receiver having a very high degree of radio - frequency amplifica- possible the construction of a practically- radio-frequency amplification (sensitivity) tion, if it is to have an unusual degree of perfect audio amplifying system. If a is a distinct asset, if it can be attained with- selectivity. power tube is used in the last stage of such out instability (tendency toward self-oscil- SCREEN -GRID TUBE PROBLEMS an amplifier, and its output fed into a lation of one or more tubes), which impairs The enormous amplification and extremely speaker of the best type, the system leaves the quality of reproduction. High amplifi- low plate -to-grid capacity of the screen -grid little to be desired; it can, however, amplify cation is desirable because it enables the tube would at first glance seem to make this

n RADIO NEWS Blueprint Article No. 76. www.americanradiohistory.com Radio' Ns321s for March, 1929 827

One constitutes the primary of the trans- 6 100 former and is connected in the plate circuit FIG. 2 of the preceding tube; the other coil acts 90 as a secondary and is connected to the grid 11 Each coil is tuned 1 1 i- of the following tube. 1 1 Z to resonance with the desired signal by 80 u.t d I 1 means of a .00035 -mf. variable condenser I 1 C12). Because of the rather 1 70 (C4, C5, C10, 1 1 w

unusual arrangement, the mutual inductance 1 1 the and the or coupling between primary I t 60 secondary is much smaller than in ordinary I 1 circuits. Z However, this floes not mean that the en- So Fw.. ergy transfer from primary to secondary is z inefficient In the case of the coupling coils 4o tu used in the receiver under discussion, the > o voltage is with maximum secondary obtained 3o 570 580 590 600 610 620 630 a coupling co- efficient in the order of one áJ Lal While B is the curve of a more sharply -tuned per cent. The physical arrangement of the set than A, the additional amplification of B coils as shown in the various accompany- 20 into audibility signals in channels beyond f0 brings ing photographs of the completed receiver those heard with A. The result is an effect of "broader tuning" in B. was chosen, because it seemed the simplest to way to secure such loose coupling while coils still close to each other; ideal amplifier; but yet it has ac- keeping the o an thus conserving space. quired the reputation of causing "broad 970 980 990 1000 1010 1020 1030 tuning," for the reason explained above. R.F. "BAND -PASS" COUPLING KILOCYCLES The natural advantages of the screen - Due to the inherent characteristics of The sharply -defined peak of A here is that of grid tube were carefully considered by the circuit. It will perceptibly "cut various loosely- coupled tuned circuits, each of these a resonant designers of the "1929 Hi -Q," and double-tuned radio-frequency transformers sidebands." That of B represents the combina- the apparent disad- tion of two loosely -coupled circuits, as em- methods of overcoming really constitutes a "band- pass" filter. This investigated. Two stages of ployed in the R.F. transformers of the "Hi -Q ". vantages were is quite clearly shown in Fig. 2, illustrating radio-frequency amplification were decided these reasonably the tuning characteristics of one of on actual measurements of one of the new upon as sufficient, .,as they could double -tuned, loose -coupled transformers. over -all voltage radio-frequency transformers used in the be expected to produce an The clotted line represents the response thousand. In order "1929 Hi -Q." gain of more than one curve of one tuned circuit alone, and the degree of selectivity with While the use of one of these double-tuned to achieve a high solid line that of both circuits properly an amplification, some special radio-frequency transformers produces this amount of coupled. will be noticed that the former two The combina- It unusual degree of selectivity, the use of form of tuning is necessary. is a typical "resonance-curve very sharp in vast im- antenna coupler and "; such stages in cascade results a tion of a conventional on the top at exact resonance and sloping provement As an illustration, note that the two interstage tuned- radio- frequency trans- gradually toward zero as the frequency is response of an interfering signal 20 kilo- is wholly inadequate in the matter formers increased or decreased. On the other hand, cycles below resonance on the solid curve selectivity, although the amplification is of the solid curve of the double circuit is quite of Fig. 2 is 9% or about one -eleventh of The tuned- plate- impedance, coupling- but good. broad and almost flat on the top, but slopes at the frequency for which the and grid -leak arrangement speci- the response condenser more steeply on the sides and the response is tuned. This is for one stage only. the manufacturers of the tube was set fied by approaches zero much more rapidly above After going through the second stage, how- passed up for the same reason. Calculation and below the resonant frequency. showed that it was quite feasible to tune The curves shown in Fig. 2 are based both the grid and the plate circuits of these screen -grid tubes. This is one of the marked advantages of this type of tube; since an attempt to tune both the grid and plate cir- Fig. C cuits of an ordinary amplifier tube invari- ably results in uncontrollable oscillation. The phonograph -radio combination shown opposite; the receiver has been slid ont, MULTIPLE -TUNING SYSTEM showing flic fop of its assembly. When both grid and plate circuits are tuned, a two -stage radio- frequency amplifier has a total of five tuned circuits, including the grid circuit of the first tube. This in- creased number of tuned circuits would, naturally, produce a marked increase in se- lectivity. In fact, the scheme looked so good on paper that an experimental receiver embodying these ideas was constructed. On test, this model performed in a truly re- markable manner, greatly exceeding expec- tations. The radio-frequency gain was very high; enough to bring in many distant stations, including one on the Pacific coast The se- lectivity was such that more than a dozen of these distant stations were received while the locals were operating. (This test was made last May, using a 75 -foot antenna, lo- cated in mid -town New York -a location, be it said, full of interference and not con- ducive to making DX records.) The remarkable performance of this re- ceiver can best be understood by a consid- eration of the principles involved in its de- _!iwdve_ smo.má.w.+néew. w.-z:a+Ffx*ét,.-_'' sign. The inter -stage radio-frequency trans- formers (L2, L3) are quite unique in that they consist of two exactly similar coils.

www.americanradiohistory.com 828 Radio : News for March, 1929 ever, the intensity of this interfering signal will have been reduced to 0.8%, less than PLUG IN '8 ELIM.' RECEPTACLE one one -hundredth. At the same time, the ON 'A' ELIMINATOR. addition of the second stage does not ma- terially affect the shape of the top of the

response curve. The top of the curve re- 1 mains substantially as shown in Fig. 2; while the sides become much steeper and the response approaches the zero line at a C20 I I much more rapid rate. 2 3 The width and flatness of the top of the - PC hIÌIIIIIIIII)IIIIIIIIIIIIIIII IIIIIII I IIII I solid curve shown in Fig. 2 has an important I c,,;;,;, ,,,,,, bearing on the quality of the received speech and music. This is due to the fact that broadcast stations do not transmit a single 111111111111111111111111111111 111111111 frequency, but rather a band of frequencies. .I II. 11-11.1.111 The width of the side -bands varies some- what, depending on the transmitter adjust- ments and also on the type of program being broadcast; they are, however, generally con- ceded to require about five kilocycles for high -quality transmission. It is therefore apparent that the receiver should be capable of amplifying a ten -kilocycle band of fre- WOOD quencies, with substantial uniformity, if the BASEBOARD 8^ X 12" program Is to be.received faithfully. Hence l_5 V_-! + B- + C- the desirability of the wide flat top on the A. C. 90 V 45V 135V. C+ 180 V. 4.5 V over-all response curve of a high -grade re- vcu.ow BLUE GRAY BROWN GREEN ceiver. Fig. 3 When the top of the response curve is The compact layout of the power unit; compare with illustration and schematic diagram on page sharp instead of flat, all the frequencies in 829. A .filamentless rectifier tube is used, and a voltage- dividing resistor of special design, the band are not amplified equally. Conse- quently, certain of these frequencies reach making the output from the loud speaker One variable condenser, .00035-mf. (C1); the detector dull and muffled. Two two -gang variable condensers, .00035 -mf. 'each much stronger than others; section (C4- C5- C10 -C12); with the result that even the most perfect RECEIVER COMPONENTS Two drum dials, illuminated; audio -frequency amplifier and loud speaker Four adjustable compensating condensers, 35 -mid. will be unable to reproduce The following parts are required for the (C3- C6C9 -C13) ; the program -matching transformer for phono. Construction of "RADIO NEWS 1929 One impedance with its original quality. This is the type the graph pick -up (T1); of distortion referred to previously as Hi-Q ": One audio-frequency transformer, standard type "side -band cutting" and results in the loss One antenna coil, tapped (LI); (T2); or weakening the high Two R.F. transformers, specially made, screen -grid Two push -pull audio -frequency transformers (T3. of audio frequencies, type (L2-L3); T4);

Fig. E

The completed "Hi-Q" without . its shield topa; note the clip on Ll which adjusts the primary to the aerial weed.

www.americanradiohistory.com Radio News for March, 1929 829

C21 ¡"r PHONOGRAPH LOUD PICKUP SPEAKER r C4 i CS I C10 j C12 M AERP C3-i ;C6 C9y T4 V1 o F V2 V3 V5

E

METAL BASE

M- YELLOW BLUE GRAY BROWN CREEN TO 'B ELIM.' RECEPTACLE REO BLACK. B+ B+ B+ B - B+ C- ON 'A" ELIMINATOR. 90V 45V. I35V. C+ 180V 4.5V. o

Fig. 5 This receiver with its "B" unit may seem complex, but is really tically all the work. The volume control C21 -R14 is mounted ow simple to assemble, because more difficult connections are included the phonograph's turntable board; and the -magnetic pick -up is in the components, and with the proper chassis, the wiring is prat- connected to two binding posts on a bakelite strip above TL

Six tube sockets, UX -type; One S.P.S.T. toggle switch for motor control; rate shaft and has a separate drum dial; Three R.F. choke coils, 85 millihenries (RFC1- One potentiometer volume control, 0- 20,000 -ohm thus enabling this circuit to be tuned to RFC2-RFC3) ; (RI4); exact resonance with the received signal, Three shield cans, 8x6x53 inches, aluminum; One by -pass condenser, 0.25 -mf. (C21); One potentiometer, incorporating filament switch, One motor board; regardless of the type of antenna used. 0- 100,000 -ohm (VC -SWI); Two needle receptacles. The volume control is quite out of the Two filament resistors, 10 -ohm (R1-R4); ordinary and possible only through the char- Two filament resistors, 15 -ohm (R2 -R5); MECHANICAL CONSTRUCTION of the screen tubes. Two resistors, wire -wound, 5,000 -ohm (R3 -R6); acteristics -grid It con- Two filament ballasts, %- ampere (R8 -R10); The two double -tuned radio - frequency sists of a 100,000 -ohm potentiometer VC con- One grid condenser, .00025 -mf. (C14); transformers used in the "RADIO NEWS 1929 nected across the 45 -volt "B" st ply. The One grid leak, 2- megohm (R7); Hi -Q" necessitate the use of four variable movable arm of this potentiometer provides One resistor, metallic type, 50,000 -ohm (R9); each Two resistors, wire -wound, 50,000 -ohm (R11 -R12); condensers -one to tune of the four a variable voltage which is impressed on the Four by -pass condensers, 0.5 -m£. (C2- C7- C8-C11); coils. Since all four of the tuned circuits screen -grids of the two R.F. amplifier tubes, One by -pass condenser, ,001 -mf. (C15); are identical, these four variable condensers The amplification obtainable from the latter Two phone -tip jacks (J); are rotated by a common shaft actuated by varies within wide limits as the voltage on Four binding posts; One seven -wire plug -in cable and cable connector; a drum dial which has a smooth positive the screen -grids is varied; being at maxi- One front panel, 7x24x34 inches, drilled and en- drive without back -lash. The tuned input mum around 45 volts and dropping rapidly graved; circuit connected to the grid of the first as the screen -grid potential is reduced. This One steel chassis, 23%x12 inches (inverted -dish shield -grid tube V1, and often type, 1 -inch deep) already drilled; (13-C) Two screen -grid tubes, 222-type (V1 -V2); referred to as the antenna One detector tube, 200A -type (V3); coupler, is of the conventional One general- purpose tube, 201A -type (V4); type, having a tapped primary Ciè Two power tubes, 171A -type (V5 -V6). L1 adaptable to different length "R" POWER COMPONENTS antennas. The variable con- denser Cl, which tunes this One power compact with built-in chokes and buffer condensers (PC); antenna coupler, is on a sepa- One filter condenser, 2 -mf., 400 -volt rating (C16); One filter condenser, 2 -mf., 200 -volt rating (C17); One filter condenser, 4 -mf., 200 -volt rating (CIS); One condenser bank containing three 1.0 -mf. by- pass condensers brought to terminals 0- 1- 1 -1 -mf. C19) ; Fig. F One filter condenser, 1.0 -mf., 200 -volt rating (C20); This power unit sup- Two resistors (special design), (R); plies all "13" current, One tube socket, UX -type (V7); but filament current for One filamentless gaseous- rectifier tube, 125 -mia. the push -pull stage only. (V7); The resistor R is pro- Eight spring -clip binding pests; vided with proper taps One wooden baseboard, 12x8x% inches. for this receiver and needs no adjustment. 5 VOtrA.c, PHONOGRAPH EQUIPMENT FILAMENT One motor and turntable; One phonograph pick -up with arm; One S.P.D.T. toggle switch, mounted on phonograph board (SW2); +18

www.americanradiohistory.com 83Ó .1 idtio 'News for. March, 1929 provides a smooth control of volume within themselves to cause self -oscillation, this ad- negative leg of each screen -grid tube fila- aide limits without affecting quality or tun- vantage is nullified if feed-back occurs in ment. Since the screen -grids of both these ing in the slightest degree. other parts of the receiver. Taking this tubes are biased by the 10,000 -ohm poten- into consideration, every effort has been tiometer, 5,000-ohm isolating resistors R3, ISOLATING CIRCUITS made to isolate all circuits in which coupling R6 are inserted in the leads to the screen- While the screen -grid tubes have an ex- might result in instability. The negative grids, which are in turn by- passed by means tremely low value of capacity between plate bias for the control grids of the R.F. tubes of separate 0.5 -mf. by-pass condensers C2, and grid, thus almost entirely obviating the is secured by the drop across individual ten - C8. The plate circuits of these tubes are tendency of feed -back through the tubes ohm resistors (Rl, 114) in series with the likewise isolated by individual filters con-

1141.7`Ñ `.I--III''U 11

ASV-0 N3389 'AM +9 AVae +3 9 NM089 nsv+e am9 -- +V 038 A06+9 M0113A +0-8-V >IJVIB

N01103 N N00 A o81 iio1V1S +8

www.americanradiohistory.com Radio News for March, 1929 831 sisting of separate radio- frequency choke screen -grid tubes V1, V2 are so located of the circuit. This arrangement produces coils and by -pass condensers RFCI, C7 and that the leads to the control grids are as the minimum of coupling between output RFC2, Cll. short as possible and farthest away from the and input circuits, which is extremely im- In addition to these precautions, the en- plate leads, which are also short. By placing portant. tire R.F. end of the receiver is thoroughly these tubes between the cans, the side walls shielded. Each stage is entirely enclosed in of the latter are used also as electrostatic TIIE AUDIO END a snug- fitting aluminum box which is se- tube shields, effectively preventing coupling curely fastened to the metal chassis. The between the tube elements and other parts The audio -frequency amplifier is of the conventional type, consisting of two stages of transformer- coupled amplification. The A.F. transformers used have a flat fre- quency- characteristic over the usual range. A radio- frequency choke coil RFC3 is placed between the plate of the detector tube and the first A.F. transformer to pre . vent any stray R.F. voltages from getting into the A.F. amplifier. i In addition to the three regular A.F. transformers, the set is equipped with an impedance- matching transformer TI which couples an external phonograph pick -up unit to the A.F. amplifier itself. The use of this transformer provides high -quality reproduc- tion of voice and music from phonograph records. It is thrown in and out of the cir- cuit by means of a single -pole, double - throw toggle switch SW2, mounted on the board which supports the phonograph motor and turntable. When this switch is thrown to "Radio," it cuts out the phonograph pick -up and the transformer T1, and con- nects the plate circuit of the detector V3 to the primary of the first audio transformer T2. This is a very simple arrangement and in no way complicates the operation of the radio receiver and amplifier.

LAYOUT OF SET

The general arrangement of the RADIO NEWS 1929 Hi -Q is clearly shown in the various accompanying illustrations. The components of the receiver proper are mounted on a pressed -steel chassis to which is fastened an upright front panel. It is possible to buy both panel and chassis com- pletely drilled and engraved for the various parts. These two units are very cheap and save the constructor an enormous amount of work; with the panel and chassis on hand, the assembly of the set is then merely a mat- ter of screwing down the various coils, con- densers, sockets and transformers. The coil Ll and condenser Cl, comprising the tuning elements of the grid circuit of the first screen -grid tube VI, are enclosed in an aluminum shielding can; this occupies the left front corner of the chassis and sub - panel, and the tuning is controlled by its own drum dial. The components of the first band -pass fil- ter stage occupy a second can which is placed in the center of the chassis, against the front panel. The parts enclosed are as follows: the double tuning condenser C4 and C5; the first interstage radio- frequency transformer L2; the two midget compensat- ing condensers C3 and CG; the volume con- trol VC; and the by -pass condenser C7. If the reader will refer to the photographic il- lustration on page 828, showing the top view of the assembled receiver, he will no- tice that the shaft of this double condenser extends through the wall of the middle can and terminates at the drum dial to which the shaft of the other double condenser (which M3LIOS `JNI1f1OW 13)43Vä9 likewise extends through the wall of its can) 210103NNOO 3.19VO is fastened. The dial thus controls both double condensers at once. The parts in the third can include, besides the double con- denser C10 and C12, the matching con-

www.americanradiohistory.com 832 Radio News for March, 1929 dessers C9 and C13; by-pass condensers C11 and C15, and the second interstage radio- Fig. D C8 R5 frequency transformer L3. ( '6 The detector and audio system is ar- Here we have the bottom of the "Hi-Q" chassis, il- ranged along the back edge of the chassis. lustrating the various leads The socket for the detector V3 is located and the proper method of 1 directly behind the third can; together with wiring, actually used in the grid leak R7, grid condenser C14, R.F. the set; whereas the dia- grams on the preceding choke RFC3, and the receptacle for the bat- pages show the connec- tery cable. Following in line are the im- tions at right angles, for pedance- matching transformer Tl; the first - the sake of clearness. T2; socket for the The "shortest distance be- stage A.F. transformer tween two points" is good first A.F. tube V4; the push -pull input practice in radio construc- transformer T3; sockets for the power tubes tion. The "Aerial" and V5 and V6; and, finally, the push -pull out- "Ground" posts are mounted on a bakelite put transformer T4. The filament -ballast strip which insulates the and other fixed resistors R8, 9, 10, 11 and former from the chassis. 12, are mounted directly along the back edge of the chassis. This arrangement makes '4:121A1) °ROU9 the wiring very short and very easy to in- stall. A DESIRABLE COMBINATION cabinet, directly above the rear compart- The "Aerial" and "Ground" binding posts ment, is hinged and, when opened, reveals are located in the extreme rear left corner The receiver as it stands is a complete a phonograph turntable and an electric of the chassis. Slightly to the left of them is unit, except, of course, for the necessary pick -up mounted on a square board set be- a pair of tip jacks, insulated from the metal "A" and "B" supply units. It can be in- low the level of the top. The turntable is chassis and connected directly to the sec- stalled in any suitable cabinet of either the revolved by a small electric motor. Also ondary of the output transformer T4, to re- table or console type. The particular re mounted on the phonograph board are two ceive the loud -speaker cord tips. ceiver illustrated on pages 826, 827 and 832 switches: one to turn the electric motor on The underside of the chassis holds merely is an exceptionally-complete, high -grade in- and off, and the other (SW2) to switch from a few fixed resistors and by -pass condensers. strument. The set itself occupies the lower phonograph to radio. The phonograph board Another picture (at right) shows these and portion of the cabinet. The upper -right sec- is provided also with two small receptacles the directness of the wiring. tion (as viewed from the rear) contains, for used and unused phonograph needles. All of the connections should be made first, a loud speaker of the dynamic type with insulated wire, as the metal chassis and also an "A" power unit; the `B" supply This complete phonograph and radio com- forms part of the circuit. The point-to- unit and the phonograph components are at bination is as fine an instrument as any point system of wiring may be used. the upper left. A section of the top of the music lover would care to possess. The custom -radio builder who boasts of a fairly well-to-do patronage can undoubtedly sell several such instruments in the course of a year. Of course, he can also incorporate the receiver into simpler and less pretentious cabinets, of which many are available. The "B" power unit is of perfectly stand- ard and straightforward design. It consists of a power compact which includes a step - up transformer and choke coils; five fixed condensers; rectifier tube and a resistor bank; these parts are mounted on a simple wooden baseboard. The various binding posts and connections are plainly indicated and need no explanation. The rectifier tube V7 is of the filamentless type; a filament - type rectifier tube may easily be substituted in this position, if the constructor so desires. POWER SUPPLY Many readers will express surprise on learning that the "129- Hi -11" receiver is not an A.C.-operated set; that is, it does not use A.C. tubes, although they were tried in early experimental models. It is believed preferable to substitute tubes of the D.C. type and to use an "A" supply unit which works off the 110-volt A.C. line. This ar- rangement is fully as satisfactory in every regard as straight A.C. operation with A.C. tubes working off an A.C. transformer; if anything, even better. There are numerous "A" power units on the market which work quietly and efficiently and which require practically no attention. The constructor who has a storage battery or a storage -battery-and -charger combina- tion may, of course, use this with the "Hi-Q." The switch to turn the whole set on and off must necessarily control the current of both the "A" and "B" units. Most "A" Fig. G power units are equipped with a long flex- In this rear view of the opened console, A is the ible cord to which is attached a switch of "A" power unit (at the constructor's option) B the pear type. Also most of them have a the "B" unit and M the motor driving receptacle into which the plug from the "B" the phonograph. unit may be connected.

www.americanradiohistory.com Radio News for March, 1929 833

The "Dry-Cell Four" completely set up and ready for operation. Behind the set are the dry "A" and 'B" batteries, and at the right a cone -type loud speaker. The compactness of the receiver is obvious.

"The Dry -Cell Four " - -An Economical Set* By B. B. Bryant

THE receiver described in this article this a rather easy method and a highly con- is what may be termed an "advanced THE "DRY - CELL venient one at that. With the assumption is its beginner's" receiver, so simple FOUR" has been that a battery cable or a set of battery re- construction; and yet it offers produced in response to leads must be used, there is no reason why sults desired by the fan who has built his an insistent demand from the cable cannot be incorporated into the simple one- or two-tube outfit and is now readers, which shows that construction of the set, thus bringing down will looking about for something which offer is still need for a flock of birds with the proverbial pebble. to there him quality reproduction, ability bring No. 77 compact, economical sets Four binding -posts are used; one for the withal, sim- in that distant station and, from batteries. While no aerial connection, one for the ground, and initial cost and operated plicity of construction, low attempt is made to offer this set as a two for the loud -speaker cord. The ground low upkeep cost. "portable," it more nearly deserves post is secured to and makes electrical con- Primarily, this receiver has been designed this name than any other of like tact with the shield. The aerial post also of his location for the listener who, because power. It may be taken anywhere, is secured to the rear shield, but is insu- or other circumstances, finds it inconvenient and operated from dry batteries. Its lated from the latter by means of a hard - to operate an A.C. receiver, (or other device con- or impossible filament consumption is but three - rubber bushing any while he has no facilities for the charging eighths of an ampere at three volts; venient to the constructor) which will pre- This condition com- of storage batteries. the fact that the screen -grid tube vent the post from making a short circuit of dry -cell batteries for fila- pels the use uses the same voltage as the 199- with the shield. In the event that the for plate current. ment lighting as well as type permits the inclusion of an R.F. builder finds difficulty in arranging this, This is not meant to imply that dry -cell the aerial post may be mounted on the base- "; stage of high amplification which, operation is a matter of "Hobson's Choice with the regenerative detector, snakes board and the coil lead to it brought out really excellent results and reproduction of this the equal as a distance- getter through the can. The same procedure may use of set goon quality are obtainable with the of any set except the very largest. be followed in mounting the ground post, 199 other 3-volt tubes, pro- it the -type and It is probable that, in any ordinary though will hardly be necessary because of viding they are intelligently handled. location, this set Will give reception the simplicity of the suggested method. a The receiver described bere employs as distant as any receirsr can afford. The two binding posts for the speaker sensitive 222 -type screen -grid tube in on highly- In addition to this, n, '.withstanding terminals are mounted a strip of hard amplifica- is a stage of tuned -radio-frequency its low filament voltage, the 120 -type rubber and the latter, in turn, mounted tion before the detector. The regenerative tube used in the final stage is a true on two terminals of the last socket, V4, is 199 two the detector a -type tube followed by power amplifier, practically equal to facing rear of the baseboard; these ter- -coupled stages of transformer audio-fre- the 112A, and suitable for operating minals are the plate post and one of the quency amplification; the first of which com- any speaker at room volume. filament posts of the socket. It should be prises a 199 -type tube and the last a 120 - Those who desire the large blue- carefully noted that, although the speaker- type power amplifier. One metal can, which prints (with list of parts used) for terminal strip is mounted directly to two is divided into two compartments by the the "Dry -Cell Fonr"'must fill out and socket binding- posts, only one speaker post insertion of an extra partition, furnishes send in the coupon provided for that is connected to one socket post. The plate necessary when post of the the shielding which is so purpose on page 879, with the re- socket is connected to the -grid tube. speaker post directly with using a screen quired 25 cents. No more blueprints in line it, while the filament post MECHANICAL DETAILS will be sent free. of the socket and the re- maining post on the speaker strip may be A 7 x 18 -inch hard -rubber panel mounts said to go about their business in standard two tuning dials of the vernier type, a baseboard is necessary to allow for the fashion. That is to say, the filament post high -resistance control for regeneration, and wiring, which is to go underneath and thus of the socket is led to the filament circuit a 20-ohm midget rheostat. The baseboard run directly into the six -lead cable, thus and the second speaker post to the 135 -volt is of wood, 15 x 1/2 x 7 inches, and has un- obviating the need of binding posts. The lead of the cable. The foregoing should der each end a strip of wood, measuring small number of terminals and the sim- be watched carefully as, with the suggested 6 x % x 1/2 inches. This raising of the plicity of the wiring in this receiver make mounting of the speaker posts, the con-

* RADIO NEWS Blueprint Article No. 77.

www.americanradiohistory.com 834 Radio News for March, 1929

AERIAL Ti V3 T2 1 L1 2

3

GROUND

R4 CABLE LOUD SPEAKER 1 Q B +45 VOLT A+ A-B -C+ B +I35 VOLT 8+90 VOLT (BROWN) (YELLOW) (BLACK) (PINK) 8 E)

The various "A," "B" and "C" wires are bunched together to form all the tubes. This is the best arrangement when dry cells are a cable. If desired, binding posts may be mounted along the back used as a source of "A" supply. A storage battery may, of course,. of the set instead. Note that rheostat R4 controls the current to be used with sufficient resistance in series with the tubes. structor is apt to yield to temptation and hardly pay to go to the trouble of scouting construction of this receiver seems to be connect the second speaker post to the about for the proper materials, and build- about the simplest. Two small blocks of filament post of the socket; which, of course, ing the can, when a neatly -finished product wood, a trifle larger than the inside diam- would bring undesirable results. can be obtained for considerably less than eter of the coil form, are screwed to the READY -MADE VS. HOME -MADE the total cost of the material and the value bottom shield of the can, and each coil is Perhaps the most awesome part of the of time spent in constructing the shield. forced over one of these blocks; this wilt receiver in the eyes of the beginner who may The shield used in this receiver required hold the form in a firm, upright positions build this receiver is the matter of shielding. nothing more than the addition of the di- and also facilitate its being removed from The can used in this set is composed of viding section as mentioned above. and replaced in the set, should the occasion arise. aluminum and measures 8 x 6 x 5% inches. The two coils, L1 -L2, are the only other An additional section of the same metal, components to be constructed; these are PARTS REQUIRED 514 x 6 inches, is inserted so that it divides wound on one -inch cardboard, fiber or hard - The components herewith listed are those, the shield into two compartments of equal rubber tubing with No. 30 enameled wire. which were used in the original model, Kerr dimensions and thus provides for the two As the illustrations offer complete data on illustrated; and, while substitutions may be tuning circuits. Those who desire to con- the winding of these coils, little need be made, it is suggested that, if so, the alter- struct this shield can easily do so with a said regarding their construction with the native parts be chosen with an eye for quantity of thin sheet aluminum, copper or exception of the age -old warning that wind- similarity of size and wiring positions of brass and a pa,- of tinsmith's shears. ings on the same form must turn in the their terminals. The reason for this is However, the .manufacturer's price of same direction; which should be strictly obvious; an oversized component will neces- this can is so little that it may be recom- heeded. A right-angle bracket may be em sitate a new layout and different measure -, mended that this item be purchased, if it ployed to secure the coils to the floor of ments for the front panel and baseboard. can be done conveniently; as it would the shield can; but the method used in the Two variable condensers, .00035-mf. (Cl- C4); Two fixed condensers, .006 -mf. (C2 -C3) ; One fixed condenser, .00025 -mf. (C5); One fixed condenser, .0005 -mf. (C6) ; One resistor strip, 10 -ohm (R1); One grid leak, 5- megohm (112); One variable resistor, 0 -2000 -ohm (R3) ; One rheostat, 20 -ohm midget type (R4); Four tube sockets, UX -type (V1- 2 -3 -4); Two audio- frequency transformers (T1 -T2); One shield can (as per text) and partition; Two vernier dials; One screen -grid vacuum tube, 222-type (V1); Two vacuum tubes, 199 -type (V2 -V3); One vacuum tube, 120 -type (V4) ; One hard-rubber panel, 7 x 18 x 3/16 inch; One wooden baseboard, 15 x 7 x i/2 -inch; One battery cable, 6 -wire; Four binding -posts; Three coil forms, 1 -inch diameter, 3 inches long. RADIO -FREQUENCY CIRCUITS Rai The first compartment of the shield can The half- completed set, as it appears from the front, with the panel and tuning condensers removed. houses the stage of tuned -radio -frequency The symbols on the parts correspond with those in the schematic diagram above. amplification with its screen -grid (222-type)

www.americanradiohistory.com Radio News for March, 1929 835

tube. The other components which go to The connecting leads from the first to make up this circuit are the inductor Ll, 1-0.{ the second audio stage are run under the consisting of a primary and a secondary baseboard to the left of the receiver where 40 TURN5s30 winding; the .00038 -mf. variable condenser ENAMELLED WIRE the second audio-frequency transformer Cl, which tunes the secondary of Ll; the T2 and its tube socket V4 are mounted to vacuum-tube socket VI, which is of the SECONDARIES the left of the shield can. Here, as in the 150 TURNS * 30 UX type; the fixed condenser C2, which is ENAMELLED WIRE case of the first audio stage, provision soldered directly to the "G" post of the 25 TURNS should be made for mounting the rheostat *30 ENAMELLED socket; and the resistor strip Iì1, one ter- WIRE R4; this component is of the midget type minal of which is soldered to the "F -" post 60 TURNS and bas a resistance of 20 ohms. Mounting *30 ENAMELLED of the socket. The lead connecting the WIRE the loud-speaker terminal strip on the rear stator plates C1 with the control -grid posts of L1 L2 of the socket V4 has been dealt with cap on top of the screen -grid tube should in a previous paragraph of this article and be a piece of flexible wire about five inches so requires no further mention. in length, to the tube end of which has been Details of the coils. Ll, antenna coupler, L2. No view of the baseboard is shown, the soldered a clip designed to slip over this interstage transformer. The top winding of few wires being there hardly requiring that the latter is the tickler, the center one the terminal of the control -grid of V1. This secondary, and the bottom the primary. elaboration. Under the baseboard are clip may be constructed of any springy placed also the by -pass condenser C6, which metal, and shaped by wrapping it about a returns the R.F. component to filament; lead pencil or any other suitable object of and grid leak R2, which is connected from and the terminals of the battery cable, which similar size. the grid of the detector tube to the "A+" is secured to the under side of the base- The second compartment houses the de- line, instead of across the grid condenser board at the extreme rear by means of a tector circuit and its tuning components. as usually the practice; and the grid con- U- shaped bracket. It is then a simple matter As a matter of interest, it may be men- denser C8, which is rated at .00025 -mf. In to wire the leads of the cable to their vari- tioned that, although the detector is re- the same compartment is found the by -pass ous circuits. condenser C3, which is part of the screen - generative, the oscillations it sets up do not WIRING HINTS enter the antenna because they are blocked grid tube's plate circuit, and is secured to by the previous stage of tuned- radio-fre- the shield. Here, as in the first compart- The most convenient manner of wiring this quency amplification. For this reason the ment, leads between terminals of compon- receiver is by stages. First screw the front operator of this receiver need have no fears ents are made as short as possible; which, panel to the baseboard, after having drilled of annoying his neighbors with a "blooper." for that matter, is not difficult considering the necessary holes for the variable con- The advantage of this particular circuit is the size of the allotted space and the close densers, the regeneration control and the that all the advantages of regeneration (as proximity of the various parts. rheostat; then mount the front and bottom regards DX) may be enjoyed without any shields of the can, mount the apparatus pre- THE AUDIO END danger of creating a source of radio inter- viously described, and wire as much as pos- ference. The screen -grid R.F. stage before To the right of the detector compartment sible. By taking note of the "A -" lead in the detector not only prevents this annoy- is the first audio-frequency transformer Ti, the circuit diagram, those terminals which ance, but adds greatly to the sensitivity and with its accompanying tube socket V3 are soldered to this circuit may be connected selectivity of the receiver. mounted directly behind it. Care should be to any part of the shield; thus simplifying The components in the detector compart- exercised in mounting this transformer; as the wiring job to some extent. For example, ment are very much like those in the radio- the regeneration control R3 must be it is unnecessary to run any leads from the frequency stage. They comprise the .00035- mounted on the panel, somewhat in front of rotors of the variable condensers Cl -C4 to mf. variable condenser C4, which tunes the the transformer. This control has a high re- the "A -" circuit; because, when these secondary of the inductor L2; a vacuum sistance value (0 -2,000 ohms) and is components are mounted, they make firm socket of the UX type; the grid -leak holder shunted across the tickler winding of L2. contact with the front shield of the can and

Top view of the "Dry -Cell Four" receiver, with the panel and cover Ti, V3, first audio; T2, V4, second audio; R4, filament rheostat; of the shield can removed. Ll, Cl, VI, Rl, components of the R3, regeneration control. The shield compartments afford ample R.F. stage. C4, L2, V2, R2, CS, components of the detector stage. room for the components without crowding; the coils are very small,

www.americanradiohistory.com 836 Radio News for March, 1929

so provide a "ground" circuit without the necessity of extra wiring. The operation of this receiver is much like that of any similar type; if the con- structor desires, he may install a jack ar- rangement at the output so that phones may be used for distance work. It will be no- ticed that a "C" battery of 221/, volts is specified for biasing the last audio - frequency amplifier tube; this is highly important and must be used, as the 120 -type power tube used in this stage requires this much "C" voltage ap- t. bias for proper operation. Any 4MOLES preciably lower than that specified will bring Z MOLES WAV -171A.4 cou taR51nK about distortion and, in general, cause un- satisfactory reproduction, as well as waste 18' plate current. Drilling details of the front panel. This may be of bakelite, hard rubber; formica, or other standard pond material, 3/16- or '''4.inch thick. Various arrangements for wiring the dry cells are optional with the constructor; three cells wired in series makes a basic "A" power supply. No fewer than three should with the best standards of radio engineering around aerial combination for the broadcast be used to operate the filaments of 199 -type that circumstances will allow. For this fan measures about 100 feet in length, and tubes. The constructor who desires to for- reason a little rehash on the old subject of is made up of No. 12 or 14 single- strand get about his "A" supply for as long a time antenna installation will not be amiss. An- enameled copper wire for the aerial, and as possible, may wire six cells in series -par- tenna systems (meaning everything con- No. 14 rubber -covered single strand copper allel as illustrated in the diagram. This ar- nected to the "aerial" and "ground" posts wire for the lead -in. The latter gauge of rangement gives the same voltage as three and outside the receiver) may be classified wire is used also for the ground lead. cells wired in series, but lasts approximately as having four distinct members: the aerial, If it so happens that the required space twice as long. which is the horizontal overhead wire; the for an aerial of this length is not available, lead -in, which is all the wire between the may make use of an The choice of plate batteries is, of course, the constructor aerial the the proper; "flat so called entirely up to the builder; however, he must aerial and set; "ground" of the -top" type, because of and the wire connecting the ground to the its appearance. Such an aerial is made up remember that 135 volts with taps at 45 receiver, which is known as the ground of two more wires two volts and 90 volts arc required to obtain lead. or stretched between When considering the length of an aerial, "spreaders," for which purpose broom han- proper results. For this purpose three 45- lead -in the all- volt blocks will do; these are obtainable in the must be taken into consideration; dles serve admirably. Perhaps best for this reason, when the length of various sizes, and it is this choice which is an aerial around aerial of this type comprises four is discussed, lead -in and aerial open to the constructor, depending on his both proper wires, each wire spaced at least two feet purchasing facilities. Obviously, the largest are covered by that appellation. Therefore, from the next, and insulated from the the desires to have an aerial while sizes (generally termed "heavy-duty ") last if constructor spreaders, the spreaders are insulated much longer than their smaller brothers and, 100 feet in length, and his lead -in measures from the rope holding the aerial aloft. Four 20 feet, his should down for this reason, are recommended as a mat- overhead span, or aerial, leads are brought from the aerial ter of ultimate economy. be 80 feet. Many fans, when informed that wires to a converging point, where they are their antenna is the cause of broad tuning, soldered together, and from thence a lead -in ANTENNA SYSTEM will say that this is impossible, as the length wire which is brought down to the receiver. of their aerial is but 75 feet. However, in- Careful installation of the lead -in is just As this receiver has been designed with vestigation, as a rule, discloses a lead -in as essential as in the aerial. In all cases an eye to DX, the aerial and ground must some 75 feet or thereabouts in length. keep it as far from the wall of the building of a necessity be constructed to conform Experience has proved that the best all- as possible and, where contact is inevitable,

A-B-C+ (BLACK) C-22.'- yours (MO A+(YELLOW B+45 VOLTS (BROW N) B+13S V OLTS(pINiQ B+gOVOLTS(GREEN)

,.4. c , lfl. - , 22.- , ai 1 15. r_ S, f OINKr¡';, LREEN

J4 I _t_L\.i--_c-_,z, i L---_YELLOW (LC, `J -- - - , 9 I SLACK J -` - 1 F - BLUE L 1

I I I O. -- _

` 1 I3. I L - - , - _T ' - - V n 19. ¡I (31C -1 I --111

C6 I rI - DQ I R3 i 18. 01 R4 - -, 24 UNDERVIEW OF BASEBOARD 16. 17 -

Under view of the baseboard of the "Dry -Cell Four," showing the page; each hole is marked with the same number 'n bo h diagrams. connections to the battery cable. Wherever a wire is shown coming The . wiring above is shown in straight lines; actually, the wires out of a numbered hole, it can be traced to the top side of the may be run directly from . point to point, in order to keep them baseboard by reference to the picture diagram on the following as short as possible.

www.americanradiohistory.com Radio News for March, 1929 837 OMI rWFMIL a I Aa111 P 24

C4 C

T1

p.` IIP C3I c- *44.00ÌIpg, 4.1011= a_

r. F

GROUND ®SCREWED TO SHIELD AERIAL Above: Layout of the "Dry -Cell Four." Compare with view of the wiring under the baseboard, on page 836; the holes are numbered alike. It is a good idea to cross out each wire in the diagram as the corresponding lead is soldered. Below: How the power supply of the set is made up, by wiring together six dry cells for the "A" current, three "B" and one "C" batteries as shown. use some form of "stand -off" insulator. are or are not the acme of efficiency; either Many constructors, in order to avoid solder- they employ one or more of them or use no ing in the aerial assembly, run a single GABLE FROM SET ground at al. strand horizontally for a suitable distance, However, those in suburban or rural com- continue it on through the hole of the in- munities may avail themselves of a fairly + A sulator, make a few securing turns and con- B+ good ground if they will go to the trouble of tinue the same wire down to the window. 0 0 0 11114.11_ 244351- digging a sizeable hole for the burial of a The matter of a suitable ground is one number of copper, brass or galvanized-iron that stumps many a constructor. City fans plates. These are soldered to a suitable wire have the problem solved for them without and the ground lead connected to the latter. Ae. nATTERIES choice; they must use one of the piping sys- DRY -CELLS W WIRED IN It is suggested, also, that this particular tems available, such as the water pipe or WIRED IN BATTERY SERIES spot be watered at times, so that the con- SERIES - 221 VOLTS. radiator pipe; do not use the gas pipe. It PARALLEL ductivity of the ground may be bettered. matters little to then, whether these grounds This usually is worth the trouble.

RADIO NEWS BLUEPRINTS New Terms of Our Offer to Readers (Read This Before You Write) BEGINNING with the publication of this issue of RADIO NEWS, we announce a new policy with respect to the distribution of blueprints to our readers. A charge of 25 cents for each set furnished will be made; the filling of this order will be expedited by using the coupon printed on page 879 of this issue. This will apply to all blueprints (from No. 52 up) issued by RADIO News, except those called for by the Free Blueprint Coupons printed in our December, 1928, January and February, 1929, issues; these will be sent free, in exchange for these coupons, until our present stock on hand is exhausted. All other- blueprints which we have issued in our free distribution series will be charged for at the rate of 25 cents a set. (Those made up prior to April, 1928, were produced by a more costly individual process and cannot be furnished at the above price.) We believe that our readers are entitled to a frank explanation. During the past year we have distributed to them more than 68,000 blueprints -over 12,000 of the well -known "Junk -Box" alone. This has necessitated frequent reprints of the blueprints, and the maintenance of a large staff whose time is given up to this alone. The postage bill has been very large, as may be imagined. As RADIO NEWS has no apparatus for sale, it cannot recoup the outlay in this manner, like a manufacturer who sells kits at from $20 to $200. The price which we have established, 25 cents, is our average cost of a set of blueprints -a low figure obtained only by quantity production. The free distribution has entailed a huge expense, which has increased from month to month; and there is no doubt that thousands who are not regular readers have been taking advantage of it. We have therefore decided to charge a uniform price of 25 cents for each set of blueprints; not with the expectation of making any profit from them, but with the intention of breaking somewhere near even. Those desiring previously -issued blue- prints, not specified in any of the three "Free" coupons we have mentioned, must send this sum with their orders; which will be filled more promptly if the form printed on page 879 is used, as we have said. Other requests will not be supplied; nor will our "I Want to Know" department send any longer free hook -ups, diagrams, or other circuit information by mail. We have said many times before that we have no blueprints of commercially -manufactured apparatus for sale at any price; nevertheless, ten or fifteen letters asking for them are received every day. Neither can we furnish bluprints to use the particular set of parts the constructor has in mind; it costs several hundred dollars to prepare a set of blueprints; and we cannot undertake to do this to order for a nominal sum. We shall, however, continue to issue blueprints of sets of our own design that will, we think, appeal to our readers; and to publish full circuit and wiring diagrams in the pages of RADIO News, as we have done. Those of our readers who wish, in addition, full sized blueprints of these sets may obtain them by sending in a Blueprint Coupon with 25 cents for each set requested. This applies to Blueprints Nos. 76 and 77, the "RAmo NEWS 1929 Hi -Q" and the "Dry-Cell Four," published in this issue, and to all later sets for which blueprints will be prepared..

www.americanradiohistory.com Q3S Radio News for March. 1929 The "Candy -Box Special"

A Novel Little Short -Wave Receiver That Produces Real Results

By Joseph Riley

RADIO receivers have been built into many odd objects like fountain pens, vanity cases, sea shells, pipes and The completed "Candy - umbrella handles, but for the most Box" Special receiver set up for operation, part these instruments have been mere nov- with a plug -in coil and elties possessing no practical value. They the two tubes in place. are intended to be shown as examples of Two of the other coils are shown at the left mechanical ingenuity, and not to be used of the box itself. for regular reception of radio signals. How- ever, it is possible to make a novel and un- usual set that at the same time is more use- ful than for mere purposes of display. The writer constructed such an outfit out of midget variable condensers, each .0001 -mf. enough room and because an external rheo- parts that were gathering dust under his maximum capacity; three DX-type tube stat allows the use of either 199 -type tubes table, assembling them in a tin candy box sockets (one for the plug-in coils and the on dry cells, or 210A -type tubes on a stor- that was once full of better things. When other two for the detector and amplifier age battery. Three ordinary 43/2 -volt "C" the completed receiver was shown to the tubes); one audio -frequency transformer; batteries connected in parallel, and a single person who the original the was recipient of grid condenser and grid leak (separate 223/2 -volt "B" battery block will work the box, she remarked, appropriately enough, units, not a combination) ; and two tip jacks set very nicely. These batteries may be put "Isn't that sweet ?" for the phone connections. The coil and in another box, and connected by three flex- Electrically, the set is a short-wave affair ible wires to the set itself. One wire is for patterned after the famous RADIO NEWS "A" minus and "B" minus, the second for "Junk -Box" receiver, and uses the same con- "A" plus, and the third for `B" plus. A venient system of midget tuning condensers THE construction of the novel 10-ohm rheostat mounted on this second and tube base plug -in coils. The circuit is box and wired in the "A" minus lead will be exactly the same except for the elimination little receiver described in this article very useful. All the resistance will be needed of the filament switch and the R.F. choke is so simple and obvious that no constructional blueprints when the set is first turned on, but as the coil. By keeping the Junk-Box idea in mind, battery voltage starts to drop the knob must the constructor who has a small box or case for it have been prepared. The accompanying be turned down. of any kind on hand can make a very un- illustrations show all the usual- looking little receiver that will arouse details of the assembly and A HANDY PORTABLE wiring clearly and plainly, and a lot of comment from visitors and also pro- An outfit consisting of two such little duce real radio signals. Any small box every reader will be able to fol- low them without trouble. boxes makes a fine portable set for the radio about six inches long will serve the purpose: fan who travels frequently and who likes to an old cigarette tin, a small cigar box, a listen in when he gets to a hotel in a strange jewelry case, a camera case, etc. town. The set works perfectly well on no MUSIC FROM A CANDY BOX aerial at all; with a 20 -foot length of flex- tubes stand upright when the set is in op- ible wire stretched on the floor or thrown The particular box used by the writer was eration, the cover being swung back. With out of the window it will bring in practically s.one -pound candy tin tastefully decorated the coil and tubes removed the box closes everything in the short-wave channels. in light lavender. It is six inches long, four in its normal manner. For permanent use in the home this wide, and three deep, and is fitted with a No provisions for filament control are "Candy -Box Special" makes a good set for binged cover. Into this space were put two made in the box itself, because there is not the man who has a complete broadcast re- ceiver that he does not want to disturb and who wants to try his luck on the short waves. It represents very little of an in- vestment; even if he has to go out and buy all the parts he won't have to spend more than five dollars. For such indoor service the best source of "A" current is three No. 6 dry cells -the good old- fashioned doorbell variety. When used with two 199 -type tubes these batteries will last at least a month. The length of service depends, of course, on how often the set is used. The operation of this short -wave re- ceiver -or any short -wave receiver, for that matter -will not affect a broadcast receiver in another room in any way. The construc- tor may dabble with it in the kitchen or bedroom without causing the rest of the family to lose their evening's radio program The writer selected a tin box for his set because the metal itself forms a common "ground" and thus saves much wiring. For instance, when the tuning and regeneration condensers (C1 and C2) are mounted, the rotor plates are automatically connected to- The parts before assembly: below, left to right, grid leak, grid condenser, rheostat, pin jacks, gether and to one side of the filament cir- knobs; center, tube sockets, transformer, condensers; rear, coils, candy box. cuit. There will then be only one wire from

www.americanradiohistory.com Radio News for March, 1929 839 each of these instruments, instead of two. box, near the top edge and above the socket MOUNTING THE COIL SOCKET Similarly, one of each pair of filament posts for V2. These jacks must be carefully on each tube socket (including also the insulated from the metal box, as neither The third tube socket, which accommo- socket for the plug -in coil) may be is to be grounded. The easiest way to in- dates the plug -in coils, is mounted just "grounded" directly to the box. A soldering sulate them is to drill the mounting holes below the level of the top of the box, in lug bridged from the terminal to one of the about a sixteenth of an inch oversize, and the rear right corner. It is supported in screws holding the socket itself down will to put thin fiber, heavy cardboard, Bake- this position by means of two simple L- do the trick. lite or hard rubber washers over the holes. shaped brass brackets, the size of which It may be necessary to loosen and remount will depend on the particular socket. The LAYING OUT THE PARTS the jacks several times in order to center socket is mounted this way, and not on the Before drilling any holes in the box, it the mounting studs in their holes, but this bottom of the box, in order to make room is a good idea to lay out all the parts to operation takes only a few minutes. Test for the grid condenser CB, which is of .0001 - make sure there is room for everything. In the jacks against short circuit with the mf. capacity. One end of this grid con- the set shown on these pages the tuning con- phones and a battery. If either jack is denser should be connected by a short piece denser Cl was mounted first, on the front grounded the set will not work, because of wire to the G post on the socket for side of the box, with the rotor plates open- the "B" battery will be short -circuited to Vl, and a three -inch length of wire soldered ing oút to the left. The regeneration con- the filament either directly or through the to the other end before the socket for the coils is mounted permanently. The free wire from the condenser is soldered to the stator terminal of condenser Cl, and an- L PLUG -IN COIL wire 1 other run from here to the G post on ¡ O the coil socket. The coil socket, by the i F (RIGHT) ^ way, should be turned so that the two x I I filament posts face the back side of the box. P TRANSFORMER Another piece of wire should be soldered sEc. V2 to the P post of the socket for VI, also before the coil socket is mounted, as this C terminal will not be accessible later. The G and P posts of the socket for V2 should also have wires soldered to them before the socket is mounted, as they arc rather close to the sicle of the box. With all the parts installed, the wiring may now be completed in accordance with the accompanying schematic diagram. The 0 wires five -foot lengths of lamp *. ' TIP JACKS FOR PHONE battery are A cord, twisted together to form a cable. One R2 Bt wire, which forms the "A" minus "B" minus. TWISTED WIRES connection, is soldered to the free filament Cl C2 =.0001 mf."MIDGETi posts on the tube sockets, and runs to the R'. 10 OHM RHEOSTAT minus side of the "A" battery, preferably C4 = "POSTAGE STAMP` through a rheostat (R2). The second wire. CONDENSER is soldered directly to the metal box at 224 VOLTB BATTERY any convenient point, and runs to the plus GROUND TO WATER OR STEAM PIPE of the "A" battery and to the ground. The latter may be any nearby steam or water - the. pipe. The third and last wire runs to The circuit of the "Candy -Box" Special is a straightforward regenerative one, with a stage of transformer- coupled audio. It works very nicely with 199 -type tubes and dry cells. B post on the audio transformer and tc one of the tip jacks. The other tip jack (Continued on page 876) denser C2 was placed in the right front phone windings, depend- corner, with its rotor plates opening toward ing on which jack is the front side of the box. touching the metal of the The audio transformer was pushed into box. the left rear corner, with its primary posts The clip mounting for facing the back. If the terminals of the the grid leak Rl is transformer you happen to have on hand screwed to the back of are at the bottom of the instrument, solder the box, on the inside, five -inch lengths of wire to them before above the socket for the screwing the transformer down; otherwise tube VI. It should be you will have difficulty in soldering later. placed so that the leak, Use short machine screws for the actual when in position, will be fastening, with the nuts oli the under side parallel to the bottom of of the box. Twist the wire from the F the box. The dip on the post on the transformer under the head of left is grounded to the one of the fastening screws, to ground it box by means of a solder- to filament. ing lug bridged to the The smaller the transformer you can find, mounting screw. the better. It need not be one of high quality, as you will be listening with ear- phones and the distortion in only one stage of amplification is not bad. Small trans- formers which are perfectly suitable for the purpose can be picked up for as little as 89 cents on "Radio Row," in large cities. The socket for the detector tube VI is Inside view of the set: placed against and to the right of the trans- Rl, grid -leak mounting; former. The socket for the amplifier tube VI, detector -tube socket; corner, in front L, coil socket; C2, re- V2 goes in the left front generation condenser; Cl, of the transformer and to the left of the tuning condenser; V2, am- tuning condenser Cl. plifier socket; AP, trans- The two tip jacks for the phone connec- former. tions are mounted on the left side of the

www.americanradiohistory.com 840 Radio News for March, 1929 The Screen -Grid R. F. Tube as an Automatic Signal -Input Regulator

A Circuit Which Overcomes Swinging and Fading by Varying the Voltage on the Screen Grid By Donald E. Learned

Now that the screen -grid tube has and pianissimo portions of a selection would of the set, diminishing and increasing in been on the market long enough for be rendered with almost equal volume, and sympathy with the - received signal, if the most of the newness to wear off, the loud- voiced villain of the play might pos- set is tuned to the carrier -wave. and the "dyed -in- the -wool" fans sess a milder voice than the very dainty Suppose a set tuned in to the carrier of have all tried their favorite theories on it, heroine. a station. If the set has two or more radio- the author would like to add to the many However, the carrier- frequency amplitude frequency stages, or their equivalent, there uses developed for this versatile tube his is affected very little by the efforts of the will be a sizable reproduction of the carrier - bit -a scheme to control signal fading, performers; the volume delivered to the mi- frequency current in the plate circuit of the within certain limits. crophone is expended chiefly on the side - detector stage. If, now, this amplified car- A little study with a milliammeter of the bands. Consequently, if there were no fad- rier current be tapped, and used to react on screen -grid tube will show that the plate ing, the strength of the received carrier the input stage of the set in such a manner current is under very direct control of the would remain approximately constant, and as to diminish the amplification constant of "screen- grid "; i.e., variations of the poten- the volume at the loud speaker would be a the input tube in exact ratio to the signal tial supplied to this element will cause vari- faithful copy of the original performance, increase, signals varying greatly in strength ations of current in the plate circuit of the at least as regards volume- shading. of carrier wave will be handed on to the tube, due to variation of the space charge. second tube with approximately the same DISTANCE -EFFECTS Therefore, the output of the screen -grid signal strength. Stations large and small, tube may be easily controlled by varying the Unfortunately, fading intervenes, some- near and far, will tune in with the same potential on the screen -grid. times giving effects exactly contrary to those signal strength to the second tube; provid- The subject of volume control by means of produced by the performers. Or a signal ing always that the received carrier does not the carrier -frequency impulses has already fades at the critical moment, losing an an- fall below a certain critical value. Fading, been discussed in this magazine (See RADIO nouncement, or the vital part of a speech. so far as the speaker is concerned, would be NEWS for April, 1928, page 1131); but a If, to offset this fading, we now adjust the absent. little review will doubtless do no harm. set to give satisfactory volume while the Such an ideal is hard to obtain in prac- While it is evident that the final (audio) signal is at a minimum, it may "raise the tice; the author has, however, set up such output of a radio set might be employed to roof" when the signal returns to normal. conditions that the reproduced signals of regulate the input of the set, and thus even (This is very offensive at 2 a. in. after ev- nearby stations have actually been weakest up the volume of reproduction, a little con- eryone is soundly asleep except the DX from the speaker when strongest at the an- sideration will show that this method is not hound.) tenna, and vice versa. This demonstration entirely suitable; because it would not take Now, all these fluctuations of received sig- is especially good when performed on into account the volume -shading of the per- nal due to fading are more or less faithfully KDKA, the "fadingest" station known in formers before the microphone. Fortissimo reproduced in the radio -frequency circuits his locality (Columbus, Ohio).

This peculiar circuit will furnish many hours of interesting experi- teur. A similar scheme is used in a very expensive commercial ment. It is the first practicable arrangement for automatic volume receiver. The special coupler R.F.T. should be purchased; it is an control that has been made available for construction by the ama- iron -cored coil which the experimenter cannot well match.

www.americanradiohistory.com Radio News for March, 1929 841

A SPECIAL CIRCUIT course, determined by the coils used; C4 and R are varied inversely as the input of the C5 are 1 -mf. fixed condensers; C6 is 2-mf. carrier. A circuit suggestion is shown in the ac- volume It is desirable to place the -control When using this set, all controls should companying diagram. Note the link stage L tube VC near the link stage L to shorten be set to secure maximum results from some which, while providing a first audio stage, radio-frequency leads; VC is preferably of nearby, strong station, with tube VC turned also amplifies the carrier -frequency com- will be the 240 type. A milliammeter very off. The milliammeter will probably show ponent; this gives the equivalent of three useful in non -oscillating sets, when tuning from 1 to 2 milliamperes through tube R. stages to amplify the latter to a value R.F. in; this should preferably have a total range Turn on tube VC; then cut down volume to which will be useful. An additional at it of 5 milliamperes and should be located at a reasonable amount by means of resistor stage may be added to the circuit, if audio MA in the input stage. The circuit, of R7, watching the milliammeter meanwhile. carefully. Additional radio-fre- handled course, should be tried only by experienced If necessary, adjust the rheostat and the po- quency stages may be added between the constructors. tentiometer on tube VC, and retune, until a input and the detector stage D, or stage R The operation of such a circuit is as fol- marked reduction in the plate current. of the regeneration may be introduced. The vari- lows: the carrier-frequency current is am- input tube is shown by the milliammeter. condenser C3, about .0001 -mf. maxi- able plified by the first three stages and is passed With all controls set correctly, the meter mum, may be added as a regeneration con- to the grid of the volume -control tube VC. will show a decided drop as the set is tuned trol. current of this Here it acts on the plate to a carrier. Fluctuations in the carrier - The other elements are as follows: RI is tube, modulating it at carrier- frequency; wave may be readily followed by observing megohm fixed or variable; a 0.3- grid leak, this plate current thus becomes proportional the milliammeter. When everything is ap- variable; R2, 2,500- to 25,000 -ohms, R3, 12; to the amplitude of the received carrier -fre- parently functioning correctly, make a final 000-ohm, fixed or variable; R4, 200 -ohm (or quency signal; but (since R.F. plate current adjustment of resistor R7 for comfortable R5, 24,000 -ohm fixed higher) potentiometer; is derived from capacity C4, which is also volume. Observe, also, that this resistor af- noiseless resistor; RG, 25-ohm rheostat; R7, supplying potential to the screen -grid ele- fects the milliammeter reading. 0- to 50,000-ohm variable. RFT is an aperi- ment) the potential on the screen -grid is odic radio -frequency transformer (untuned, thus made to become less as the amplitude Once the above adjustments are completed covering the entire frequency range of the of the carrier - frequency signal becomes correctly, the potentiometer and the resistor set. The old Radio Corporation UV -1714 greater, and vice versa. Consequently, the R7 will take care of any ordinary volume re- is very good here.) Cl and C2 are, of plate current and the amplification of stage quirements.

"Harmonics " -the Cause of Phantom Short -Wave Stations HE subject of harmonics in radio is the wire, it will vibrate and cause a "twang- tone of just twice the frequency or pitch, is probably one which causes more per- ing" noise to be heard. On further exam- the second harmonic; but there is possible plexity to the average fan, especially ination we will find that the motion of the an indefinitely long series of harmonics, T the short -wave fan, than any other. wires is between the limits of two curves, third, fourth, fifth and so forth-correspond- We have received innumerable letters from as in Fig. 1. Now, if we touch the wire ing to frequencies three, four, or five times short -wave enthusiasts who have picked up lightly half -way between the two supporting that of the fundamental. This is because with their short -wave receivers stations op- blocks, and again pluck it, a higher tone will the frequency of the tone caused by the vi- erating on the broadcast band. In many be heard; and the wire will be found to be bration of a section of the string doubles as cases the set is blamed and the fan wishes vibrating in two distinct sections, as though its length is divided by two, and so forth. to know how to fix his set so that these sta- a solid support had been placed at the This we may compare to the radio rule that tions will not be picked up. One, in par- middle. This effect is shown in Fig. 2. By the frequency multiplied by the wavelength ticular, received a station a number of times touching the wire at distances from its sup- gives always the same number; we may and was sure that he had heard short -wave port, equal to one -third, one - fourth, or one- therefore picture a radio aerial "vibrating" transmissions from London, England. When fifth of its length, it may be made to vibrate electrically with currents which flow from he finally heard the call letters, he was dis- in even shorter sections. one end to the other, and also with currents appointed to find that he had been listening which flow only back and forth in sections A MUSICAL COMPARISON to London, Canada, broadcasting on the one -half its length, etc. using more complicated apparatus, it wavelength of 329 meters. By RADIO HARMONICS is found that the wire can be caused to vi- Probably the best way why to explain brate in several different series of sections A radio transmitter, therefore, may send these signals are picked up is to give a me- at the same time. For instance, it might be out waves on frequencies higher than those chanical comparison, describing a similar vibrating as a whole and also in three, five of its fundamental, or carrier -wave fre- action which can be more easily understood. and seven sections. This is rather hard to quency; though the lowest radio frequencies Suppose we take a piece of piano wire and are higher than the highest audio frequen- stretch it picture, but it can be readily found by using tightly between two blocks of the correct instruments. Photographs which (Continued on page 882) wood about three feet apart. we pluck If illustrate this very well have been made by Prof. D. C. Miller, and will be found repro- duced in Elementary Principles of Physics

WIRE VIBRATING AS A WHOLE GIVES A FUNDAMENTAL TONE, by Fuller, Brownlee and Baker. FUNDAMENTAL OR The "quality," "timbre," "tone -color," or FIRST HARMONIC characteristic combination of sounds in a musical instrument is note produced by a SECOND HARMONIC determined by the ability of the string or other sound -producing element to vibrate at several simultaneous frequencies. A differ- THIRD HARMON ence will be observed when "A" is sounded on a violin and on a piano, or even on two NODAL POINT NO VIBRATION violins; in the latter case, of course, the dif- ference is slight and may escape any but highly trained ears. The characteristic qual- WIRE MAY VIBRATE IN TWO SECTIONS. GIVES SECOND HARMONIC ity is dependent on the presence and respec- tive strengths of the higher-pitched tones produced at the same time as the principal .. which and loudest tone, the "fundamental" FIRST AND FOURTH is due to the vibration of the string as a HARMONICS WIRE MAY VIBRATE BOTH WAYS whole; these higher notes are the "harmon- F16.2 GIVING A COMPOSITE TONE ics" and "overtones." F16.3 we consider the lowest tone, or funda- Transmitting -circuit oscillations may give a If Harmonics are theoretically separate; in fact composite wave, as do vibrations of a string. mental, as the first harmonic, its octave, a only "components' of curves like G and H.

www.americanradiohistory.com I 842 Kadin News for March, 1929

A Connector Which Makes a house which may be blown. So we have some distance from an electrical -appliance still a fuse worth a nickel and a glass base store. While it Is true that all constructors Positive Contact which has cost nothing but a little labor. living near the larger merchandising centers EXPERIMENTERS who have found dif- The next operation is to put a screw - can obtain these switches cheap enough, ficulty in making a neat binding -post hole through the bottom of the glass base their suburban cousins may find themselves connection, when using stranded hook-up and, for the benefit of the amateur who does in need of a switch of this type, but minus wire, will find this odd wrinkle a cheap not know how to accomplish this, here is method of making positive contact. how it is done. Take a three -cornered file A number of eyelets, (obtainable at any and have it ground so that it is sharp on stationery store), and a pair of pliers com- all three edges, with the end pointed at prise the necessary equipment. First, twist a blunt angle. This makes a very good drill the strands of the end of the wire to be for glass. Put a few drops of turpentine connected, and loop this terminal about into the cup-shaped end of the fuse base and, with the file in a suitable brace, start drilling in the center of the base. A fairly heavy pressure may be maintained until the v UNPRESSED EYELET. drill is about halfway through; then turn the base over, apply a few more drops of WIRE ABOUT EYELET. turpentine, and start from that side. A smooth hole will be the result and, as the Cg4.,,,, READY FOR THE POST. glass is quite soft, it takes little time. The illustration (Fig. 2) shows two models which Fig. 4 The simple materials shown make a practical switch Fig. 1 may be of use in +special cases. -Contributed which will come in handy in a pinch. A metallic eyelet of the type shown holds the by Clarence C. Waldrip. strands of hook -up wire tightly in place. the shopping conveniences of the city ex- perimenter. one of the eyelets; damp the eyelet firmly The switch illustrated herewith (Fig. 4) in the pliers, and it will be found that the is built from a block of wood 31/e x 2 x s/s end of the wire is being gripped between inches, and the three spring -dip binding the two sides of the eyelet. The latter can posts mounted thereon. Under the center then be slipped on and off the binding -post spring clip is placed the knife of the switch, rapidly, and without danger of the wire which may be a strip of brass, aluminum being forced from under the head of the or copper about 2% inches long and 1/2- post, as often occurs when using stranded inch wide. A rubber or wooden knob placed hook -up wire. -Contributed by John R. at the end of the knife completes the as- Mullaney. sembly.-Contributed by Cecil Kuhn.

A High- Resistance Insulator An Adjustable Tickler for for a Nickel Home -Made Coils is wrinkle for the amateur who ALTHOUGH as a rule take HERE a Fig. 3 ticklers now desires a cheap and easily made stand- The common or garden variety of ground clamp the form of fixed windings on the off insulator; this one can be had for the may be fastened upon a battery terminal to give same coil form which holds the secondary, cost of one screw, three nuts, two washers a good low- resistance contact. there are occasions when an adjustable tick- and a small piece of brass strip. The basis ler is advantageous in a circuit. The wrin- of its assembly is the common plug fuse Battery Terminal Replacements kle presented herewith makes use of a with glass base, selling for five cents in Quickly Made (Continued on page 885) nearly all "5 & 10" stores. Buy one for each insulator wanted; unsolder the fuse ONE contributor has found that a wire where it is connected to the brass small ground -damp, of the type shell, and take off the shell. The porcelain equipped with a spring -dip binding post, tip with the fuse wire may then be removed makes an excellent substitute for the vari- and the fuse saved to replace any in the ous components which make up the post of a storage battery. These parts, as a rule, suffer badly from corrosion and finally break off or wear off, leaving nothing but a short, rounded shank to which a ground-clamp may be fastened. It must be remembered that the clamp has a tendency to corrode rapidly unless liberal coats of heavy oil or vaseline are applied. -Contributed by Glenn W. Woodroffe.

A Home -Made Knife Switch A SIMPLE method of improving either Fig. 2 Ll a single -pole double -throw or a single - The insulating base of an ordinary electric -light pole single -throw knife switch is Fig. 5 fuse makes a handy device for the experimenter presented For an adjustable tickler (or primary) the arrange. who deals with high voltages. by a wrinkle fan who, obviously, resides ment shown is simple and effective.

www.americanradiohistory.com Radio News. for March, 1929. 843 Figuring the Filament-Ballast Resistances How the "A" Supply Is Tempered to the Needs of Tubes When Different Types Are Used In One Receiver, as in Many Circuits Now Popular, and What Resistors May Be Used

WITH the introduction of receivers em- that of the 5 standard -volt tube (201A, FIGURING RESISTANCES ploying several specialized types of 112A, 171A types) ; the former is 25 ohms tubes in their successive stages, the problem and the latter 20. But if the 222 were put A very easy way to calculate the value of regulating the filament voltages becomes of the filament resistor required to reduce more complicated than it was in sets of the the voltage of a given current source to older design in which general- purpose tubes that required for one or more tubes is sim- were used throughout. ply to take the difference in voltage between In the A.C. electric sets, this situation the supplied voltage and the required volt- is met by the provision of a step -down age and divide that by the current drain of transformer with several low -voltage sec- the tubes with which it is tu be used. For ondaries, each calculated to furnish the instance, the difference between the 6 volts voltage required for one type of tube. In supplied by a storage battery and the 5 this case, proper regulation of the input volts required by quarter- ampere tubes such voltage on the primary (110-volt) winding as the 201A -type, etc., is one volt. If only of the transformer will insure a satisfactory one tube is to be used, the current drain "A" supply. is 0.25 -ampere and the resistance required On the other hand, if direct-current tubes will be 1.00 divided by 0.25, or 4 ohms. If are used, either the 3 -volt ( "dry- cell") or three tubes are to be used, the total current the new 3.3 -volt ( "screen -grid ") filaments drain will be 0.75- ampere and in this case will require special protection if they draw 1.00 divided by 0.75 equals 1 1/3, the num- their current from the saine source as the ber of ohms required. 5 -volt ( "storage- battery") tubes. For this If several tubes of the same type of fila- purpose, resistors, commonly called "bal- Four types of filament resistors in common use. A is a self- adjusting resistor, which should not ment are connected in parallel, their com- lasts," are used; either of a self -adjusting be used in series with a "mavuai". (hand -) bined resistance is equal to that of any type, which automatically change their re- operated rheostat like C; B, a wire -wound re- one of them, divided by the number used; sistance with their temperature, and con- sistor; and D, a metallised-glass fixed resistor and a single resistor in series with them hermetically sealed in the capsule shown. sequently permit the flow of a certain must be divided in similar proportion to across the "A" leads, even after the rheo- stat had cut the voltage down to 5, it EACH TUBE 200HMS -5V.DROP -AMP. -.25 would draw one -fifth of an ampere, or 200 25 OHMS-3.3V. DROP- O.132-AMP. 20 OHMS DROP 201A 200A 201A 171 A milliamperes, instead of the 132 for which -5V. - O.25-AMP. it is designed. Consequently, an additional 222 , 200A 222 171 A resistance of about 13 ohms in series with 1V 1V the filament of the 222 will be required. In dV all cases, it will be found better to use a resistor reducing the voltage of the tubes slightly below their rating, rather than one LL.'_.1 which will permit an excess of current. The 120 -type semi-power tube operates similarly !OHM to the 222. 40HMS I V. DROP 2IOHMS 4OHMS IuDROP I AMP. The filament resistance of the 199 -type 2.7V.DROP IV. DROP II 0.132 -AMP. .25-AMR tube, we find, is much higher than that of w Q25*MP =1III1 the foregoing-50 ohms -but its current - carrying capacity is much less. very With 6 VOLTS 6 VOLTS the 199 -type tube across a 5 -volt supply, 21OHMS fIG.1 27V DROP about 33 1/3 ohms in series will be required RHEOSTAT 0.132-AMP. Above is a simple care; the filaments of the to safeguard its filament; and 50 ohms if tubes require the same supply. One fixed re- it is exposed to the full 6 volts of a storage This possible hook -up is more complicated. sistor is sufficient, though the voltage falls as battery. Each tube has its own ballast, adding just the battery discharges itself. enough resistance to regulate the amount of heating current from the battery. The rheo- stat here is turned "up," out of the circuit. only, or fixed amount of current resistors 2.77 V DROP which properly divide the voltage existing 3 V. DROP .055-AMP. .06 -AMP. EACH the value required to protect single within the circuit and leave only the cor- 199 199 199 199 a one of them. rect amount across the tube filaments. Such resistors are commonly inserted in the For instance, two 222 -type tubes in paral- "A -" return leads from the "F -" socket /J111 lel have only half the resistance of one- w e 12y ohms instead of 25. Consequently, terminals of amplifier tubes, in order to se- the resistor which ballasts cure a negative bias on the grids of the 500HM S them, and passes twice tubes. (Properly, this is a positive bias on the current, should have one half the the filament, but it amounts to the same 1 resistance of that used with one tube, or 61/e ohms, to maintain the proper voltage thing; the filament is kept above ground 250HMS across their filaments. potential by the amount of the drop through 39V.DROP its series resistor.) 0.055-AMP In the case of a filament -ballast resistor designed especially for a given tube or The most method, satisfactory perhaps, tubes, whether it is of the fixed or the self- is to connect to each tube, or group of + 25OHMS 6OHMSÌ adjusting type, the manufacturer's instruc- similar tubes, its own resistor; then a master 'ku1.5 V. DROP 033V.DROP tions should be read carefully, Q6-AMP.. EACH and the user rheostat between all the tubes and the 0.55-AMP. 4 5 VOLTS should make certain that he has the correct battery permits all voltages to be varied type for the tube or tubes which it is to proportionately, if it is so desired. Here we have tubes requiring much greater protect, before inserting the resistor in the The filament resistance of the screen - voltage drop. When the rheostat is turned "down," as shown, it reduces the voltage circuit. A resistor designed for two grid (222 -type) tube is a more across or trifle than the first tube, and current, too. (Continued on page 883)

www.americanradiohistory.com 844 Radio News for March, 1929 the hort e s ENGLAND'S SHORT -WAVE PIONEER therefore chose the 130 -meter wavelength for the realize the trouble and expense my assistant and crystal; this frequency was doubled and redoubled, I have gone to, to make these experiments success- The most famous amateur phone station of the then amplified. The input to the final amplifier ful, and they can readily imagine that we had very world, undoubtedly, is G2NM, Caterham, England, was 1200 watts, and the two special modulators little spare time available after attending to the located a few miles to the south of London. Two handled also 1200 watts. This gave me a 60% maintenance of the station. I would like my views of its transmitting equipment appear on modulation, free from distortion, which was sub- readers to understand, however, that this was these pages. It is owned and operated by Mr. controlled by two 75 -watt tubes in parallel. purely an amateur effort and the only reasons for Gerald Marcuse, who is vice-president of the In- "These were connected by a private telephone attempting these broadcasts were the same as exist ternational Amateur Radio Union and acting vice - line to the house of my assistant, Mr. Percy in other amateur stations; namely, to try and find president of the Radio Society of Great Britain. Valentine, about a mile away, where the control out something which has not been discovered be- Mr. Marcuse has been for many years well known room and studio were situated. We were for- fore and also to prove that short-wave broadcasts among the "ham" fraternity of the world; although tunate in having the use of a music room, com- are a really reliable proposition. After all, the to broadcast listeners, of course, short -wave work plete with organ and piano, etc., for a studio; British Empire is a large one, and I consider that was an unknown quantity until very recently. and inter -communication telephones were used it is England's duty to provide her scattered sub- The continuing demands for "overseas broad- throughout. The control room housed the note jects with Empire programs." casts" which rolled into Great Britain from the oscillators, early A.F. amplifiers, and broadcast When this was written, no subsequent informa- Dominions and Colonies in 1927 were met by the receivers, used in rebroadcasting various programs. tion about schedules for the coming year was avait- British Broadcasting Company with the uniform "My wavelength throughout these experiments able; but it may be hoped that Mr. Marcuse's reply that short-wave technique bad not advanced was 32.5 meters; the aerial a full -wave I-Iertzian, patriotic efforts will receive the same encourage- sufficiently to justify the necessary expense. This with Zeppelin feed, both feeders being tuned to ment from official sources that they have been may be set down to conservatism, and the fear give identical readings. One end of the aerial was given by the British press, and that overseas lis that listeners in other parts of the earth would attached to a mast 90 feet high, and the other toners will continue to enjoy reception of G2NM. expect local quality and certainty of reception; to a mast on the house, about 60 feet high. The but it was evident that a need existed. Mr. Mar - filaments of the tubes were fed from storage bat- ease stepped forward and offered to undertake at teries of large capacity, separately housed. The FROM SENOR CESPEDES his own expense a short -wave Empire broadcast plate power supply was available from either 50- Editor, RADIO NEWS: service. This generous offer overcame official in- cycle 240 -volt alternating current, stepped up by I thank you for the insertion the of my call letters ertia; Mr. Marcuse started on this work, and a transformer and rectified by tubes, or from a among the short -wave broadcast stations successful demonstration forced the hand of the motor of the -generator. Two separate voltages were avail- world; an honor gained by the constancy of B. B. C., which then undertook its short-wave able; 2000 for the crystal drive and amplifiers, my regular amateur broadcasting. The work is well transmissions from 5SW. and 4000 for the modulators and output amplifier. repaid every week when I receive letters many years of experimenting on the from all "After The total power used by the transmitter was America. This mail brought me four short waves," says Mr. Marcuse, describ- from the various 3500 watts. United States to show the DX my little ing his system in a letter to RADIO NEWS, "and station "This station worked during the authorized six is giving. Mr. Charles J, in that these were being received with week, Schroeder another finding signals hours per with a few extra programmes letter repeats my words, in Spanish such remarkable regularity and consistency in vari- thrown in, continuously for twelve months without and English, and reports reception R -8 (Very good -almost loud- ous parts of the world, I thought it would be an a breakdown, except for an unfortunate accident speaker strength) of a special program to periods of I gave him interesting experiment attempt short at the first opening broadcast. The transmissions on Nov. 3. He says it was "the night broadcasting. Unfortunately, private enterprise of have been rebroadcast in Australia and of nights," Ceylon; because of the marvelous clearness of my trans- this description in this country is not very favor- one of my most interesting experiments was when missions. ably received by the various government depart- I received a program from Australia Sydney, on I am doing all I can, and hope will ments concerned; but they realized that there was 28 meters which rebroadcast on 32.5. was that I have I This soon a 75 -watt amplifier in order to get more DX room for experimentation of this kind, and they received back in Sydney satisfactorily and with throughout the United States. granted me certain which practically I am glad to repay accordingly facilities no time -lag. Many artists have come thus the education I have received in Uncle enabled me to carry tests on a fairly extensive have Sam's out forward and greatly assisted in these ex- schools. I am on the air every night scale. periments by giving their services freely. from 10:30 to I1:30, E.S.T., on 30.5 meters. I use 500 volts "I realized at the time that, in order to put out "My present license expires on Nov. 30 and, on the plate of a Ceco in to L -10 tube, modulated by a stable signal free from 'frequency pull' order owing the international regulations coming into two others of the same type. to give the distant listeners the best possible force on January 1, I am not able to say what Cordially. AMANDO CESPEDES MARIN, signal, it was necessary to use crystal control. I the future of G2NM will be. My readers will Stations NRH, NR4AC, Apartado 40, Heredia, Costa Rica, Central America. w NO FREE VERIFICATIONS Editor, RADIO NEWS: The enclosed letter speaks for itself, for I wrote to 5SW for verification and got it and this let- ter. I use a Bremer -Tully short -wave set and find by mounting condensers on sheet copper and grounding it to "A+" it works fine. I have also a piece of tin between transformers to prevent coup- ling, also grounded to "A -f-." TERENCE BUCXLE-t, Taftsville, Connecticut. (The enclosure was a form stating that the Brit- ish Broadcasting Co. has received so many requests for verifications from overseas listeners that it has decided to charge for making them by mail; though answers would be made free only in a publication issued by that company, and which has considerable circulation in Great Britain. In the early days, when short -wave broadcasting was snore highly experimental and the only listen- ers were amateurs trained in short-wave work, all short -wave stations were glad to get letters and acknowledge them, in order to learn the definite lim- its within which transmissions at a given wave- length from a given point might be heard. In fact, by this means almost entirely, short -wave work has been made of such high commercial value that most of the high frequencies have been taken away from the broadcasters and the amateurs and allo- cated to public utility and other companies. Now, since it has been found that, over large areas of the earth's surface, a high -power short- wave station "comes in like a local" almost any. where at times (though it does not give room adjoining the studio of G2NM, about a mile from the consis- Mr. Marcuse in the control the transmitter. tent "blanketing" that a commercial service are shown, and the monitor receiver and speaker. Lower right, a area The shielded amplifiers short-wave must have) and the number of broadcast listeners receiver; English and foreign broadcasts have been picked up here and relayed over G2NM. A tele- with short -wave sets is increasing phone instrument of the English type is at the lower left. enormously, it is undoubtedly onerous to suck stations to answer all

www.americanradiohistory.com r-- 1Pnd;n AI tropic fnr kÑnrcln 1979 845

merely to exhibit cards to frequencies used and power output. Hitherto no to the Byrd Expedition, whose present address in thrill-seekers who wish this their awe -stricken friends. Much, therefore, of the official record has been available as to what is actu- Antartica, however, is not reached by the mails short -wave DX listening must now be its own re- ally going on over the short waves in this country; summer (...... ). Mr. F. E. Meinholtz, who trans- ward. Very low -powered stations, of course, still let alone foreign transmitters. mitted the message, is manager of the Times station in with Com- welcome distant -reception reports; and the ultra - and has been, at times, closer touch a recent front - skort transmissions (below 13.0 meters) are still $0 SHORT WAVES FROM AFRICA mander Byrd than with the Times, as page article in that paper revealed. Mr. Meinholtz far in the condition of uncertainty that reports by short -wave listen- An opportunity is available to was sitting in his home in Queens Borough, New skilled observers are valuable to the experimenters. -metre telephony transmissions from -EDITOR.) ers to hear 30 York City, listening to a dispatch from the City of wildest Africa. We understand that, until further New York, then in Antarctic seas, when he.heard his on this notice, Major Court Trcatt is transmitting own name mentioned: "Meiaholtc, the Times wants -Arab, Sudan, be- FOR DEAR, OLD SHORT -WAVES wavelength from Bahr -el Southern you to hang up your telephone receiver so it can call tween 6 and 8:30 p. m. G. M. T., using the call - Editor, RADIO NEws: you on the phone." The operator at the Times sta- sign FXCT.- Popular Wireless. Your short -wave department in RADIO NEWS has, tion in New York, unable to call his chief by phone, I am sure, attracted much attention throughout the had requested that the message be relayed from the world. (Right!) Personally, I am deeply interested BROADCASTS IN SUMATRA Byrd ship ten thousand miles away-and it was done in the development of short -wave broadcasting; in A nautical correspondent, after a trip across the successfully! See "SCIENCE & INVENTION" Maga- fact, so much that I seldom, if ever, listen in any Indian Ocean, writes that, in addition to other rine for Mardi for full story.) more between 200 and 600 meters. It may interest stations we have previously listed, one at Medan, on some of your readers, especially here in the southern the island of Sumatra, is sending out a 37.50 - states, to know that I have received the following meter program on Mondays, Tuesdays, Thursdays, EASTERN CANADIAN BROADCASTS foreign stations all with loud -speaker volume: EAM, and Fridays, between the hours of 8 and 10 p. m. Station VAS (Louisburg, on Cape Breton, Nova 2NM, 5SW, CJRX, PCJJ, PCLL, RFN, 9RH, 2ME While it is not so stated, we presume this to be its Scotia), which is regularly operated in commercial and 3LO, the latter station coming in from 5 to local time, about 11% hours later than Eastern work, is now transmitting on both the broadcast 7 A. M. with excellent volume and little fading. Standard, or 6% hours later than GMT. band and on short waves for the benefit of the Canadian Maritime and of fishermen at sea. The 28 -meter transmission, carrying weather fore- Mr, Quimby used casts, storm warnings, press dispatches, etc., begins RFC "Scotch" (tube-base) at 11:18 p, m., Eastern Standard Time. Atlantis r- coils with 15 -mmf. con- Time, used at the station, is an hour later. b 1 densers. L2 has 37 turns of No. 28, 16 IÌL2 AFT RI of 22, and 7 of 22 SHORT -WAVE TIME SIGNALS 1 for 80 -, 40- and 20- In addition to the numerous long -wave time sig- I T3 meter bands; L3 25, nals, such as those from the Eiffel Tower, Paris, and R4 20 and 10 respectively NAA, Arlington, Virginia, there are short -wave sig. óíL3 CI of No. 30 raire. The nais which may be picked up and used for the cor- 1/ 11 fan may use specifi- rection of timepieces, determination of longitude, etc. LI g cations on page 876 Chelmsford, England, sends out on 24 meters, (ö4 ¡ 1 C2 0 for condenser sizes daily except Saturday and Sunday two signals, at C5 there given. Ll is 1300 and 2100 GMT -8 a. m. and 4 p. m. Eastern R2 two turns of bell wire Standard -of six dots at one-second intervals. The on the tube base, R2 last begins the hour. is 0- 50,000 -ohm; C4 Arlington gives signals from the naval observa- (.0005 -mf.) and A+ B+ 45V. R4 tory at Washington; on 74.7 meters at noon and 10 A- (1 /10 -meg.) are to fil- p. m.; on 37.4 meters at noon, 10 p. m. and 3 a. m. ter out noises. every day. Elgin (Illinois) sends out a larger num- ber on 33.5 meters from WNBT. These are at 1, 9 and I1 a. m., 1, 3, 5 and 7 p. m. except Saturday I am using a hook -up as by P. H. prescribed "RADIO NEWS" TO THE ANTARCTIC afternoon and Sunday. The 1 a. m. signal, which is Quimby in Q.S.T. of March, 1928, using detector RADIOGRAM -The New York Times given on Sunday also, is heard regularly in the and one stage of audio amplification in a cabinet Radio Station, Times Square, New York. Antipodes. These signals, like Arlington's, consist 8 x 9t/, inches; top on of this cabinet I use an D 132 WFAT SS. Eleanor Bolling, Nov. 22, 1928 of dots sent out at intervals of one second, the 29th two Atwater -Kent -stage audio amplifier which gives RADIO NEWS, New York City: and the 55th to 59th being omitted from the series. me of audio with three stages perfect control from Please mail to catch SS. Makura leaving San They begin five minettes before the hour. 15 to 90 meters. This may account for the loud- Francisco November 28, October and November is- speaker reception the foregoing stations. of foreign sues RADIO NEWS. Address Byrd Antarctic Expe- (Not necessarily; a signal must be received before dition, care Tapley, Dunedin, New Zealand. We are SHORT -WAVE CLUB IN ARGENTINA it can be amplified.) not leaving Dunedin until arrival this mail about Editor, RADIO NEWS: I trust this may help -wave to further the short December 20. MALCOLM HANSON I am enclosing copy of the Buenos Aires Herald art, and will be glad to hear from my fellow- listen- Mr. Ifuco GERNSBACK: announcing the organization of the English- Speaking ers, especially in foreign countries. With every Please airmail these to Frisco. Radio Club. Part of the aims of this organiza- good wish for your short -wave department, I am, MEIN HOLTZ, Times. tion includes broadcasting in English and we ask RALP II E. HOWARD, (The requested issues were airmailed accordingly (Continued ois page 886) 167 East Lake Terrace, Decatur, Ga. CODE INTERFERENCE ON SHORT WAVES Editor, RADIO NEws: I take the liberty to make some comments regard- ing short -wave transmissions. KDKA's 25.4 -meter transmitter is practically on the same wavelength as some powerful foreign code station which causes their signals to be distorted. You cannot tune out this station, and its signals are always present when KDKA is tuned in. WGY's short-wave transmissions are also rendered distorted as a re- sult of code stations surrounding their wavelengths. Fading is the principal bugbear of short -wave transmission; but when you have to put up with code, it is almost hopeless to listen in. The time has come when some international agreement should be made whereby code should not be per- mitted to use wavelengths which interfere with the principal short -wave broadcast stations. The ultimate success of such transmissions is worth while, as a good overseas radio market could be established and manufacturers could extend their sales to tropical markets. L. R. BOURNE, The Palms, Cheapside, Barbados, B. W. I. (According to the international radio convention, effective Ian. 1, 1929, the bands from 50 to 48.8 meters, 31.6 to 31.2, 25.6 to 25.2, 19.85 to 19.55, 16.9 to 16.85, and 14.0 to 119, are reserved ex- clusively for broadcasting. On these waves there should be no commercial interference.- EnaTosj

RECORDS TO BE KEPT Announcing that a 509 -watt experimental license had been granted to the Bell Laboratories, 463 West St., New York, to operate between 50 and 200 The transmitter of G2NM, located at Coombe Dingle, Caterham, Surrey, England, a feu, miles meters, the Federal Radio Commission took the op- to the south and west of London. This 1,200 -watt station has been heard in all parts of the portunity to announce that it will require monthly world. Its call was familiar to all amateurs long before Mr. Marcuse undertook short -wave broad- reports from all experimental transmitters as to casting for the benefit of listeners throughout the British Empire -and incidentally others.

www.americanradiohistory.com 846 Radio News for Marcia, 1929 acho News praforïe5 RADIO manufacturers are invited to send to RADIO NEWS LABORATORIES menrs. 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 or they advertise in RADIO NEWS, the RADIO NEWS LABORATORIES being an inde- good mechanical and electrical construction is given a certificate. As the sera- pendent organisation, 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 hour "What's New in Radio" department, as its news value and general interestnterest 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

A.F. TRANSFORMER DYNAMIC SPEAKER SHIELDED HOOK -UP WIRE The "type A -100" A.F. transformer manufactured The "Peerless Model 19- AR -60," submitted by The shielded hook -up wire submitted for test by by the National Company, Inc., Abbott Street, the United Reproducers Corp., Peerless Division, the Belden Mfg Co., 2300 S. Western Ave., Chi- Malden, Mass., is of modern design, incorporating Rochester, N. Y., is an electrodynamic speaker of cago, Ill., is of "Colorubber" stranded hook -up a nickel -steel core of high permeability; the sec- the single -turn moving -coil wire, over which has been placed a braided tinned- ondary windings are split, resulting in more efficient type. The input from the copper sheath. It has been designed especially for transformation. The turns -ratio of this transformer receiver is connected to a use in screen -grid R.F. sets in order to prevent is 4 to 1; its amplification maintains almost constant step -down transformer with feed -back through wiring. Normally, the stranded its value from 32 to 5,000 cycles when used with but one secondary turn, wire is used for connections, while the sheath is a 201A tube. The transformer's metal case is 234 which is connected by heavy grounded and serves as a shield. It is supplied inches long, 3 inches high and 2/ inches wide, and copper strips to a single - in rolls of 50 and 150 feet. of a black crystalline finish. turn coil on the apex of the AWARDED THE RADIO NEWS LABORA- AWARDED THE RADIO NEWS LABORA- cone. The cone, 9 inches TORIES CERTIFICATE OF MERIT NO. 2516. TORIES CERTIFICATE OF MERIT NO. 2503. in diameter, is anchored to a die -stamped supporting frame by thin chamois TELEVISION MOTOR R.F. CHOKE COIL strips. The field winding is The "Type K113" television motor submitted by The "Type 90" R.F. choke coil, submitted by of the low-voltage type, supplied with current by the Electric Specialty Co., Stamford, Conn., is of the same manufacturer, bas an approximate in- a special step-down transformer and dry -rectifier the induction type and operates directly from the ductance value of 90 millihenries, and is designed element. The complete chassis assembly is very 110 -volt, 60 -cycle power supply circuit It is rated for use in radio-frequency circuits rugged, and of such construction that repairs or at a -h.p. and runs at 1,800 r.p.m. The motor is 6 operating on wavelengths up to 600 adjustments may be easily made. The chassis is inches high, 5; inches wide and 8% inches long; meters. Its D.C. resistance value, housed in a Gothic mantel -type walnut cabinet its rotor is of the "squirrel -cage" type. The motor as measured, is 360 ohms. It is which serves as a baffle for the low -frequencies. is provided with a "starting" and a "running" wind- very compact, designed for mount- The cabinet is 14% inches long, 16% inches high ing; the formbr being cut out of the circuit auto. ing in the standard grid -leak and 10% inches wide. This speaker will handle matically after a proper speed has been reached. mounting; its over -all length is 2 inches and it is tremendous power with remarkable fidelity in re- AWARDED THE RADIO NEWS LABORA- jfi -inch in diameter. production of music and speech. TORIES CERTIFICATE OF MERIT NO. 2517. AWARDED THE RADIO NEWS LABORA- AWARDED THE RADIO NEWS LABORA- TORIES CERTIFICATE OF MERIT NO. 2504. TORIES CERTIFICATE OF MERIT NO. 2507. ELECTRIC- SWITCH CLOCK The electric- switch clock submitted by the Nova TUNING CONDENSER Electric Corporation, 40 W. 17th Street, DUPLEX CONE SPEAKER New York The "type ET" tuning condenser shown, sub- mitted by the same company, is of low -loss con- The "Helios" duplex -cone speaker, submitted by struction, with plates shaped to give a straight -line Peter Grassman, Berlin SW68, Charlottenstr, 6, frequency tuning Germany, employs two individual floating cones curve. The conden- which are driven by two reproducing units of the ser has a maximum balanced- armature direct -drive type; they are en- capacity of 500 mmf. closed in a cylindrical housing placed between the with a minimum of skeleton -frame cone supports. A rod extends from 1.5 mmf. The rotor, the units to allow adjustment of sensitivity. The which is supported small cone is 12 inches in diameter, and the large by a die -cast alumi- cone 16; the over -all height is 17'/s inches, width num frame of girder 16% inches and depth 6%o. inches. type, is of the float- AWARDED THE RADIO NEWS LABORA- City, has been designed to close an electrical cir- ing type, allowing TORIES CERTIFICATE OF MERIT NO. 2508. cuit at any predetermined time. It consists of a interchange of shafts clock movement, provided with a switch of 750 or ganging of two or more condensers; the stator MILLIAMMETER watts (250 -volt A.C. or D.C. rating) which is oper- accurately spaced and are supported from ated by the alarm mechanism of the clock. The plates are 200" shown, girder frame by strips of hard rubber, which The "type milliammeter submitted clock movement and the electric switch are en- the by Inc., 120 W. 42nd Street, New York are placed out of the electrostatic field. This con- Ferranti, closed in a metallic housing of Gothic design, fin- City, N. Y., is of very rugged construction and denser requires back -of -panel space '/a inches high, ished in foliage -green polychrome. A 10 -foot exten- designed to give a scale 3 inches wide and 3i/y inches long; it is provided sion cord with a special adapter is provided for the reading 0 a rotor stop at maximum and minimum po- between and light socket or receptacle, with a socket provided with 200 milliamperes of cur- sitions. for the device or appliance to be controlled. When LABORA- rent. The meter is of the desired, the circuit may be closed or AWARDED THE RADIO NEWS D'Arsonval opened manu- TORIES CERTIFICATE OF MERIT NO. 2505. type, the coil ally by an independent control on the clock. having a -point suspen- Its two dimensions are 6 inches high, 5r/s inches long and sion; the permanent mag- TONE FILTER 2/s inches wide. net is of the annular ring AWARDED THE RADIO NEWS LABORA- The tone filter manufactured by the same com- type. In shunt with the TORIES CERTIFICATE OF MERIT NO. 2519. pany is designed for use in coupling a lbud speaker moving coil is a wire - to a final audio stage, in which may be used a wound resistor. The in- power tube of the UX -112, UX -171 or UX -210 dicator is of girder con- A.C. RADIO RECEIVER type. The direct current for the plate supply flows struction, rigidly -fastened The "Model 34" 7 -tube A.C. receiver shown, through -a choke which is designed to carry as to the moving coil, and properly counterbalanced, submitted by the Browning-Drake Corporation, much as 35 milliamperes without saturation; the The scale has a satin- silver finish accurately en- 353 Washington Street, Brighton, Mass., is of the A.C. component which it blocks is coupled to the graved. A -fuse for protection of the meter is all -electric type and op- loud speaker through a 2 -mf. Tobe filter con- provided and may be removed by unscrewing a erates directly from 110- denser. The latter prevents the passage of direct screw on the face of the meter; another screw is volt 60 -cycle house cur- current through the windings of the speaker, guard- provided for setting the indicator at zero. The rent. Four tuned cir- ing against overloading and saturation. The filter entire mechanism is enclosed within a black molded cuits are employed, with is 2% inches wide, 4 inches deep, and 3% inches bakelite case; the diameter of the face is Sys inches, three stages of radio fre- high. A five -foot phone cord is supplied for attach- and that of the case 2N inches. The depth of the quency using 226 -type ment to any set. meter is 1% inches. A.C. tubes, and the con- AWARDED THE RADIO NEWS LABORA- AWARDED THE RADIO NEWS LABORA- ventional 227 heater -type detector. The audio sec- TORIES CERTIFICATE OF MERIT NO. 2506: TORIES CERTIFICATE OF MERIT NO. 2510. tion consists of three stages, with two 226 tubes

www.americanradiohistory.com Radio News for March, 1929 847 and one 171 power tube. A power transformer, been designed for television use; it operates di- ing; a base with extension arm is supplied as a employing a full -wave rectifier of the 280 type in rectly from 110 -volt 60 -cycle A.C. circuit, and de- part of the mechanism. A volume control and conjunction with a well -designed filter system, fur- livers 1 /10 -h.p. at 1,725 r.p.m. The motor is sup- adapters for either electric or battery receivers are nishes humless "B" power. The filaments of all plied with a starting and stopping switch, and with also provided. The pick -up, arm, base and volume tubes are supplied from low- voltage secondaries on a condenser bank to suppress sparking; its speed is control housings are finished in gold. The instru- the power transformer. A single tuning control controlled by a heavy -duty carbon type rheostat ment gave excellent reproduction in connection with operates four condensers, which are ganged on a an ordinary two -stage audio -frequency amplifier. single shaft; the scale is of the illuminated -drum AWARDED THE RADIO NEWS LABORA. type, with its knob directly under the scale. That TORIES CERTIFICATE OF MERIT NO. 2526. of the oscillation and volume control is found on the right side of the panel, and the power switch on The electric phonograph motor submitted by the the left. The receiver and power unit are as- some company is of the A.C. induction type and sembled on a die -stamped aluminum chassis en- operates directly on the 110 -volt 60 -cycle alternat- closed within a polished walnut cabinet of pleasing ing current. The motor is suspended from a cast design, 22 inches long, 12 inches wide and 10 inches base frame and belted to a speed governor and a high. Cord -tip jacks are provided for the loud worm -gear which drives the turn -table shaft. A speaker, while binding posts are terminals for the starting switch operated by a lever is fastened under antenna and ground; a 10 -foot extension cord pro- of rugged construction. The motor is 5% inches vides for connection to the light receptacle. Ample high, 6 inches wide and 7% inches long. sensitivity, without sacrifice of selectivity, was dem- AWARDED THE RADIO NEWS LABORA- onstrated with fidelity of reproduction. TORIES CERTIFICATE OF MERIT NO. 2523. AWARDED THE RADIO NEWS LABORA- TORIES CERTIFICATE OF MERIT NO. 2520. DRUM DIAL PHOTOELECTRIC CELL The "SDW -1" drum dial shown here, submitted 'The "G -M Visitron Model 21," submitted by the by the Hammarlund Mfg. Co., 424 W. 33rd St., G -M Laboratories, Inc., Grace and Ravenswood New York City, is of the indirect -drive type, and Ave., Chicago, is alkali metal- Ill., of the hydride consists of two parts, the drum the base, and an additional lever which type, and designed for use with a small support scale and the rotating mechanism, operates through a cam controls the rotating speed of where low electrostatic beam light The driving mechanism consists governor disc. Lugs on The the by placing friction on the capacity is desired. bulb of of a frame support, through the base are supplied for fastening to the motor is enclosed in a standard UX -type cell which extends a 4-inch shaft board. A velvet-covered die -stamped turn table, 10 tube base; the "G" prong is the posi- with special wind -up bushings. inches 10 extension cord for terminal, the filament prong in diameter, and a -foot tive and To the latter are fastened the connection to the 110 -volt circuit, are supplied. diagonally opposite the negative ter- ends of a cord that passes around AWARDED THE RADIO NEWS LABORA- minal. This photoelectric cell was a small cast drum, through which TORIES CERTIFICATE OF MERIT NO. 2527, found very sensitive. passes the gang shaft, and which is supplied with AWARDED THE RADIO NEWS LABORA- set screws for fastening to the gang shaft. The TORIES CERTIFICATE OF MERIT NO. 2521. drum scale is 4 -7/16 inches in diameter, and con- VOLTAGE REGULATOR sists of an aluminum disc, to which is fastened the The "Antennavolt Type 98" and the "Resistovolt An escutcheon plate of PHONOGRAPH PICK -UP translucent celluloid scale. Type 99," submitted by the Insuline Corporation of and socket for the minia- The "Truphonic No. 502" phonograph pick -up, pleasing design, a bracket America, 78 Cortlandt St., New York City, have submitted by the Alden Mfg. Co., Brockton, Mass., ture lamp, and a mahogany molded -bakelite knob been designed for use in the is of the electromagnetic type, designed to be placed are supplied with the necessary additional hardware, reduction of house -lighting on the tone arm of a template and instructions. voltages to the values recom- AWARDED TIIE RADIO NEWS LABORA- phonograph, for electric mended by tube and radio - reproduction of speech and TORIES CERTIFICATE OF MERIT NO. 2524. receiver manufacturers. Each music from ordinary consists of a resistance ele- phonographic records, and ment enclosed by a perforated used in connection with PHONOGRAPH PICK -UP AND MOTOR metal housing which prevents an audio-frequency am- The "Type B -4" phonograph pick -up, submitted excess heating. One end is plifier. It is of the bal- by the L. S. Gordon Company, 1800 Montrose Ave., provided with prongs for in- anced- armature type, ad- sertion into the light- circuit justed in the factory. The mechanism is contained receptacles, and the other with in a molded black bakelite case, designed with a a receptacle for the insertion of the extension cord flange, to fit over the phonograph's tone arm; it is from the radio receiver. The measured resistance 2 inches in diameter and 1), inches thick. It is was 10 ohms when operated under a load of 75 supplied with an adapter and extension cord for watts. The only difference is that the Antennavolt connection to the radio receiver. has a binding post, as illustrated, for connection AWARDED THE RADIO NEWS LABORA- to the aerial post of a receiver; the antenna of TORIES CERTIFICATE OF MERIT NO. 2522. Chicago, Ill., is of the electromagnetic type, and which is then formed by the lighting system. in connection with an audio -frequency amplifier AWARDED THE RADIO NEWS LABORA- TELEVISION MOTOR %IT makes it possible to reproduce music and speech TORIES CERTIFICATES OF MERIT NOS. The television motor kit shown, submitted by from ordinary phonograph records. It is of the 2528 AND 2529. the Master Electric Company,- Dayton, Ohio, has balanced-armature type, enclosed in a metallic bous- (Continued on page 893) J Reviews of Recent Radio Literature By H. M. BAYER FILTERETTES -A NEW DEVELOPMENT, BY THE ELECTRIC WORD: THE RISE which accompanied the rise of radio, and due, also, TOBE DEUTSCHMANN. Published by 'l'obe OF RADIO, by Paul Schubert. Pub- in no small measure, to the excellent technique of his pen. Deutschmann Company, Canton, Mass. lished by the Macmillan Company, New Pamphlet, 11x81/a inches. Photographs. York City. 81/x5% inches, 311 pages; Perhaps it is in the first chapter that the author supplies "food" for the radio professional, and again Free distribution. line drawings. Price $2.50. brings up the question, "What are Marconies?" Whines, whirls, clicks, clacks, and other sundry To Mr. Schubert belongs the credit of jogging the With Schubert's attempt (if we may consider it as bits of man -made static which are illegitimate by- radio industry into a pleasant awakening. That is, such) to answer the "problem" we find a detailed products of the very essential wheels and motors of not exactly an awakening; for those connected with narration of the actual work done by Marconi progress, can be donc away with, according to the the industry and its allied enterprises bave always which led to the filing of his patent claims. It is author of the above pamphlet. And, what is more, realized that the science with which they are con- interesting also to note the obvious attempts by the not only does he assure the reader that disturbances nected has another story beside those told with the author to justify Marconi's priority claims. The emanating from near -by motors can be suppressed, aid of tables and equations. However, it remained fact that the data which makes up this book were but invites those afflicted to write their troubles to for the author, a Naval Academy graduate who obtained by the author through interviewing authori- him and he will do his best to offer a solution. resigned a commission in the navy to enter the ties in the industry casts a significant reflection on From the technical reputation of the above pub- journalistic field, to find in the field of radio com- the first chapter; in fact, one would believe that lishers, the inquirer may rest assured that, if they munication a story of scientific achievements, com- Schubert was the recipient of conflicting views of can be of no assistance to him, his problem is mercial attainments, political machinations and legal the Marconi matter in the course of his researches. certainly a very difficult one. manipulations such as rarely has been found in the Or perhaps his notation in describing Marconi's use To their credit it must be said that they were growth of other industries. of the "coherer" was meant to air one side of the the first to produce, as a catalogued item, an inter- Paul Schubert has given us an excellently written, matter. "It," he writes, "was his 'detector' and it, ference filter. Ever since therm they have devoted detailed history of the radio industry; starting with too, had been the discovery of other men." (Hughes a good deal of effort toward the development of elec- the promotion difficulties of the youthful apparatus - 1879 - Branly, 1892-Popoff, 1893.- EDtroR.) noise filters until, as evidenced by their collector, Marconi, and leading up to and including trical However, The Electric Word should be read pamphlet, they have succeeded in producing a line the part played by radio in the recent presidential by is everyone interested in radio; it is very well writ- to meet as many emergencies as possible, elec- campaign. He has written the biography of a ten, possesses the historical accuracy science and in doing so has as essential for trically. avoided, much as a work of type most service not only possible, this and proves convincingly Furthermore, their free problem the technicalities of radio which would have is a more is magnanimous, that radio great deal than just an ins- sounds alluring, but also rather robbed the book of its romantic appeal. As it is, mense "I square R" loss. and incidentally is the answer to a radio editor's Schubert's work borders on the romantic; due, of prayer. course, to the political and commercial intrigues (Continued on page 893)

www.americanradiohistory.com J r- Radio News for March, 1929 List of Broadcast Stations in the United States

Radio > á `D Radio w Radio Radio Call BROADCAST STA. é By q Call BROADCAST STA. 3q Call BROADCAST STA. li, z IN Call BROADCAST STA. áßj Letters Location 3 n.,3 Lattera Location Letten Location tf i°; Letten Location ;f 6;

KDKA East Pittsburgh. Pa.. 306 25000 ROY Lacey, Washington 250 10 WBAL Baltimore, Md...... 283 10000 WGH Newport News, Va.. 229 100 KDLR Devils Lake, N. D 248 100 KHJ Los Angeles. Califf 333 1000 W B A P Fort Worth. Texas.-, . 375 25000 WGHP Mt. Clemens Mich 242 750 KD Y L Salt Lake City. Utah 232 1000 KH Q Spokane, Wash 508 1000 W BA W Nashville, Tenn 201 5000 WGL Fort Wayne, Ind 244 500 KEJK Los Angela., Calif 240 500 KICK Red Oak. Iowa 211 100 W B A X Wilkes-Barre, Pa..... 248 100 WG MS See WLB KELW Burbans, Calif 384 500 KIDO Boise, Idaho 240 1000 WBBC Brooklyn, N. Y. City.. 214 250 W G N Chicago, IS 416 25000 KEX Portland, Oregon 254 5000 KJBS San Franoiaúo,Cal(day) 273 100 WBBL Richmond. Va...... 219 100 MICR Buffalo, N. Y 545 1000 K FAB Lincoln, Nebraska 389 5000 KJR Seattle, Wash. 309 5000 WBBM Chicago, Ill. 380 25000 WGST Atlanta, Ga 337 250 KFAD Phoenix, Arions 484 500 KKP Seattle, Wash 219 15 WBBR Itosavdle, N. Y.Ctty., 231 1000 WG Y Schenectady N. Y 380 50000 KFBB Havre, Montana 220 250 KLCN Blytheville, Ark. (day) 232 60 Ve8BW Norfolk, Va 250 100 WHA Madison, Wis 526 750 KFBK Sacramento, Calif 229 100 KLOS Independence.Mo.(Ltd)316 500 W BB Y Charleston, B. O 250 75 w HA D Milwaukee, Wis. (day) 268 250 KFBL Everett, Washing}ton 219 50 KLRA Little Rock, Ark 216 1000 WBBZ Ponca City, Okla.... 250 100 WHAM Mc eater, N. Y 261 5000 KFBU Laramie. Wyoming 500 500 KLS Oakland, Calif. (day) 208 250 W B C M Bay City Mich 213 500 W HAP New York City 231 1000 KFCB Phoenix, Ariaona 229 100 KLX Oakland, Calif...... 341 500 WBCN See WE1iR W HAS Louisville, Ky 366 5000 KFCR Santa Barbara, Calif 200 100 KLZ Denver, Colo 535 1000 WBET Boston, Mass 220 500 W HAZ Troy, N.Y . 231 500 KFDM Beaumont. Texas 535 500 KMA Shenandoah, Iowa.... 322 500 Wit IS Boston. Mass 244 500 WHB Kansas City, Mo 316 500 KFDY Brookings 5. D 545 500 KMBC See KLDS WBMH Detroit. Mich 229 100 W H B C Canton, Ohio.. 250 10 KFEC Portland, Oregon 219 100 KMED Medford. Oregon 229 50 WBMS Fort Lee, N. J 207 250 W HBD Bellefontalne, Ohio 219 100 KFEL Denver, Colorado 319 250 KM IC Inglewood. Calif 268 500 W B N Y New York City 222 250 HF Rock Island. IU 248 100 KFEQ St. Joseph. Mo. (day) 535 2500 KMJ Fresno, Calif.... 250 100 WBOQ See WABC Ww HBS L Sheb oygan. W b 213 500 KFEY Kellogg, Idaho 248 10 KMMJ ClayCenter, Neb. (day) 405 1000 W BO W Terre Haute. Ind 229 100 WHBP Johnstown, Pa 229 100 KFGQ Boone. Iowa 229 100 KMO Tacoma, Wash...... 224 500 WBRC Birmingham. Ala 322 500 W HB Q Memphis, Tenn 219 100 KFH Wichita, Kansas 231 1000 KMOX St. Louis. Mo. 275 25000 WARE Wilkes-Barre, Pa 229 100 W H BU Anderson Indiana 248 100 KFHA Gunnison Colorado 250 50 KMTR Hollywood, Calif 526 1000 WBRL Tilton. N. H 210 500 w H B W Philadelphia, Pa 200 100 KFI LOB Angeles, Calif 468 5000 KNX Los Angeles. Calif..... 288 5000 WBSO Wellesley Hills, Masa. WHBY West De Pere, Wis.. 250 100 KFIF Portland, Oregon 211 50 KOA Denver. Colo 361 12500 (Time limited) 384 250 WHDF Calumet, Mich 219 100 KFIO Spokane, Wash. (day). 244 100 KOAC Corvallis, Oregon 535 1000 WBT Charlotte, N. C 278 100.13 W HD! Minneapolis, Minn 216 500 KFIU Juneau. Alaska 229 10 KOB State College, N. Mex. 254 10000 WBZ Springfield. Mass...., 303 1500) WHDL Tupper Lake, N. Y, 211 10 KFIZ Fond du Lac. WIS 211 100 KOCW Chickasha. Okla 211 100 WBZA Boston, Mass 303 500 WHEC See WABO KFJB Marshalltown. Iowa 250 100 KOH Reno, Nevada 219 100 WC AC Storrs, Conn...... 500 250 WHFC Chicago, Ill 229 100 KFJF Oklahoma City. Okla. 204 6000 KO IL Council Bluffs. Iowa 238 1000 WCAD Canton. N. Y. (day) .. 246 500 W H K Cleveland. Ohio 216 1000 KFJI Astoria, Oregon 219 50 KOIN Portland, Oregon 319 1000 W CAE Pittsburgh, Pa 246 590 W H N New York City 297 250 KFJM Grand Forks. N. D 545 500 KOL Seattle. Wash 236 1000 WCAH Columbus, Ohlo 210 250 WHO Des Moines. Iowa 300 5000 KFJR Portland. Oregon 231 500 KOMO Seattle. Wash. 326 1000 WC Al Lincoln, Neb 503 500 WHOH Glouceeter,Maae.(day) 219 1000 KFJ Y Fort Dodge, Iowa 229 100 KOOS Marshfield. Oregon.... 219 50 W C A L Northfield, Minn.. , , . 240 1000 WHPP New York City 21k 10 KFJZ Fort Worth. Texas 219 100 KORE Eugene, Oregon 211 100 .WCAM Camden, N. J. 234 500 W HT Chicago, III 203 5000 KFKA Greeley. Colorado 341 600 KOW Denver. Colo 216 500 WCAO Baltimore, Md. 500 250 W IAS Ottumwa, Iowa (day). 211 100 KFKB Milford, Kansas (day) 265 5000 KPCB Seattle. Wash 248 100 WCAP Asbury Park. N. J.... 234 500 W IBA Madison, Wis 248 100 KFKU Lawrence, Kansas 246 1000 KPFW Westminster. CAL 201.25000 WCAT RaDId City, S. D..... 250 100 W IBG Elkins Park. Pa. (Sum ) 3228 50 KFKX Chicago. Illinois 294 5000 KPJM Prescott, Arizona 200 100 WCAU Philadelphia Pa 258 5000 W IBM Jackson, Mich. 219 100 KF KZ Kirksville, Missouri , 250 50 KPLA Los Angeles, Calif 526 1000 W C A X Burlington. Vt. 250 100 W IBO Chicago, IU 526 5000 KFLV Rockford, Illinois 213 500 KPO San Francisco, Calif... 441 5000 WC AZ Carthage, Ill. (day) 280 100 W I R R Steubenv,W e, Ohio 211 50 KFLX Galveston, Texas 219 100 KPOF Denver, Colo 341 500 WCBA Allentown, Pa 208 250 W IBS Elizabeth, N. J 207 250 K F M X Northfield, Minn 240 1000 W IBU Poynette. Wie 229 100 KFNF Shenandoah, Iowa 337 500 W IB W Topeka, Hans 231 1000 KFOR Lincoln. Nebraska 248 100 W IS X Utica, N. Y 250 100 KFOX Long Beach. Calif 240 1000 W IBZ Montgomery. Ala 200 15 KFPL Dublin, Texas 229 15 THIS list of stations in the United States operating under W ICC Bridgeport, Conn 252 500 KFPM Greenville. Texas 229 15 licenses issued by the Federal Radio Commission is corrected W IL St. Louis. Mo. 211 100 KFPW Siloam Springs, Ark. W ILL Urbana, Ill 337 250 224 50 to January 11, 1929. Powers shown are the night strength, or W IN R Bay Shore, N. Y 248 100 KFPY Spokane, Wash 216 500 minimum. W WO Miami Beach. Fla 242 1000 KFQD Anchorage. Alaska 244 100 WIP Philadelphia. Pa 492 500 KFQU Holy City, Calif 211 100 W ISN Milwaukee, Wis 268 250 .wwi.,wwnnn.uum.nwn9,unn,wnnenw.wnunuenew,wnnnuw wu,wwwi,,,w,.nwiwmwwne.,«w.wwmnnnnnwn.wxnuu, WJAD Waco. Texas 242 1000 KFQZ Hollylwood. Cal. (Ltd ) 353 1000 WJAG Norfolk, Neb, (day) 283 1000 KFRC San Francisco, Calif 492 1000 KPPC Pasadena. Calif. 250 50 WCBD Zion Illlnols"Ydsy) 278 5000 WJAK Kokomo, Ind ... 229 50 KFRU Columbia. Missouri 476 500 KPQ Seattle, Wash 248 100 W C B M Baltimore, Mdd. 219 100 WJAR Providence, R. I 337 250 KFSD San Diego. Calif 500 500 KPRC Houston, Texas 328 1000 WC BS Springfield IU 248 100 WJAS Pittsburgh, Pa 232 1000 KFSG Loe Angeles, Calif 268 500 KPSN Pasadena, Calif 316 1000 WCCO Minneapolis Mimi.. , 370 15000 WJAX Jacksonville, Fla 238 1000 KFUL Galveston. Texas 232 500 KQV Pittsburgh. Pa 217 500 WCDA New York Gllty 222 250 WJAY Cleveland. Ohio 207 500 KFUM Colorado Springs. Colo 236 1000 KQW San Jose, alit. 297 5 00 WCFL Chicago, Ill. (Ltd.)..., 309 25000 WJAZ Chicago. Ill 203 5000 KFUO St. Louis. Mo. 545 500 KRE Berkeley, Calif 219 100 WC GU Brooklyn, N. Y. City. 214 500 WJBC LaSalle. 111 250 100 KFUP Denver, Colorado 229 100 KRGV Harlingen. Texan 238 500 WC LB Brooklyn. N. Y. City. 200 100 WiR) Red Bank. N. J...... 248 100 KFUR Ogden. Utah 219 50 KRLD Dallas, Texas 288 10000 WC LO Kenosha Wis. 250 100 WJBK Ypsilanti, Mich. 219 50 KFVD Venice, Calif. (Ltd.) 428 250 KRMD Shreveport, La. 229 50 WC LS Joliet, Ill 229 100 W J B L Decatur. Ili. 250 100 KFVS Cape Girardeau. Mo 248 100 KRSC Seattle. Wash. (day) . . 288 50 WCMA Culver. Ind 214 500 WJBO New Orleans, La 219 100 KFWB Loe Angeles, Calif 316 1000 KSAC Manhattan, Kane..... 517 600 WCOA Pensacola, Fla 268 500 WJBT See WBBM KFWC San Bernardino. Calif 250 100 KSBA Shreveport, La 207 1000 WC OC Columbus Mles. 341 500 W J B U Lewisburg, Pa. 248 100 KFWF St. Louis, Missouri 250 100 KSCJ Sioux Clty, Iowa 225 1000 WCOH Greenville. N. Y 248 100 WJBW New Orleans, La 250 30 600 KF W 1 San Francisco. Calif 322 500 1(50 St. Louis, Mo. 645 WCRW Chicago, Ill 248 100 WJBY Gadsden, Ala 248 50 KFWM Oakland. Calif 322 500 KSEI Pocatello, Idaho 333 250 WCSH Portland Maine 319 500 WJJD Mooseheart, Ill. (Ltd ) 254 20000 KFXD Jerome, Idaho 211 50 KSL Salt Lake City Utah 265 5000 WCSO Springfield, Ohio 217 500 WJKS Gary. and...... 220 500 KFXF Denver, Colorado 319 250 KSMR Santa Marla. Calif 250 100 WCX See WJR WJR Detroit. Mich 400 5000 KFXJ Edgewater. Colo. 229 50 1150 Clarinda Iowa 217 1000 WDAE Tampa. Fla. 484 1000 WJSV Washington. D. C 205 10000 KFXR Oklahoma City, Okla.: 229 100 1(500 Sioux Falls. S. D. (day) 270 1000 WDAF Kansas MY, Mo 492 1000 WJZ New York City 395 25000 KFXY Flagstaff. Arizona 211 100 KSTP St. Paul, Minn 205 10000 WDAG Amarillo. Texas 213 1000 WKAQ Sastn JuLanan, Porto Ricoch 337 500 KFYO Abilene, Texan 211 100 KTAB Oakland, Calif 545 500 WDAH El Paso, Taxas 229 100 WKAR Ea sing , Mi KFYR Bismarck, N. D 545 500 KTAP San Antonio, Texas , 211 100 W DA Y Fargo. N. D 234 1000 KGA Spokane. Wash 204 5000 KTAT j Fort Worth, Texas 242 1000 WDBJ Roanoke, Va 822 250 WKAV Laconia, N. H 222898 7.00 KGAR Tucson. Arizona 219 100 KTBI Los Angeles. Calif 231 1000 W DBO Orlando. Fla. 484 1000 WKBB Joliet, BI 229 100 KGB San Diego, Calif 220 250 KTBR Portland, Oregon 231 500 WDEL Wilmington, Del 288 250 W KBC Birmingham. Ala 229 10 KGB Ketchikan, Alaska 333 500 /(THS Hot Springs, Ark 375 10000 WOGY Minneapolis. Minn 218 500 W KBE Webster. Mass 250 100 KGBX St. Joseph, Mo 219 100 KIM Santa Monica, Calif 428 500 WOOD Chattanooga, Tenn 234 1000 WKBF Indianapolis. Ind 214 500 KGBZ York, Nebraska 322 500 KTNT Muscatine. Iowa (day) 256 5000 WDRC New Haven, Conn 225 500 WKBH La Crosse. Wis 217 1000 KGCA Decorah. Iowa (day) 238 0 KTSA San Antonio, Texas 232 1000 WOSU New Orleans, La 236 1000 W KB' Chicago. Ill. 229 50 KGCB Enid, Okla 219 50 KTUE Houston. Texas 211 W O W F Cranston. R. I 248 100 W K B N Youngstown. Ohio 526 500 KGC I San Antonio. Texas 219 100 KTW Seattle. Wash 236 1000 WDZ Tuscola Illinois 280 100 WKBO Jersey City, N. J 207 250 KGCN Concordia, Kansas 211 50 KUJ Seattle, Wash. 200 10 WEAF New York City 454 25000 W KBP Battle Creek. Mich 211 50 KGCR Brookings, S. D 248 100 KUOA Fayetteville, Ark 216 1000 WEAR Ithaca, N. Y. (day) 236 1000 WKBQ New York City 222 250 KGCU Mandan, N. D 250 100 KUOM Missoula. Mont 526 500 W-OM Plnlnleld. N. J 219 100 WKBS Galesburg, ll 229 100 KGCX Vida, Montana 211 10 KUSD Vermillion, S. D 337 500 w- RN Providence. R. I. (day) 545 540 WKBV Brookville. Ind 200 100 KG DA Dell Rapids, S. D 219 15 KUT Austin. Texas 268 500 warn Columbus. Ohio 545 750 W K B W Buffalo. N. Y 204 5000 KGDE Fergus Falls, Minn 250 50 KVI Tacoma. Wash 224 1000 W. AR See WTAM WKBZ Ludington. Mich 200 50 KGDM Stockton, Calif. (day) 261 50 KVL Seattle. Wash. 219 100 w.,4 Rouanne. Wis ... 234 1000 WKEN . Buffalo. N.Y. (Ltd.) 288 1000 KG DP Pueblo, Colorado 248 10 KVOO Tulsa, Okla 263 5000 Wc.ar Cambridge. Ohio..... 24R 10 WKJC Lancaster. Pa. 250 100 KGDR San Antonio, Texas 200 100 KVOS Bellingham, Wash 250 100 w .l et Hnrriebunr. Ill 245 50 WKRC Cincinnati. Ohio 545 500 KGDY Oldham, S. D. 250 15 KWBS Portland. Oregon 200 15 w.eR4 Buffalo. N. Y 229 100 W K Y Oklahoma City. Okla 333 1000 KGEF Loe Angeles, Call/ 231 1000 KWCR Cedar Ranids, Iowa 229 100 wwsW Beloit. W14 (day) 500 250 WLAC Nashville, Tenn 201 5000 KGEK Yuma. Colo 250 10 KWEA Shreveport, La. 248 100 W)4 Ohl'aeo, 10. 248 109 WLAP Louisville. Ky 250 30 KGER Long Beach. Calif 219 100 KWG Stockton. Calif 250 100 30 WLB Minneapolis, Minn 240 1000 wens Ede. Pa 211 229 KGEW Fort Morgan, Colo 250 100 KWJJ Portland. Ore. (Ltd.) 283 500 wc51 Mana .. 50R 500 WLBC Muncie. Ind 50 Boston. 211 100 KGEZ Kalispell, Montana 229 100 KWK St. Louis. Mo. 222 1000 W -.4c P.oanatnu. Tll. 229 1041 WLBF Kansas City, Mo 211 100 100 Va 250 100 KGFF Alva. Oklahoma KWKC Kansas City. Mo 21.9 WaIK PhIla,lnlnhla. Pa -210 JI O WLBG Petersburg, KGFG Oklahoma City, Okla 219 100 KWKH Shreveport, La. 353 200!70 Weal.; )4.wrten Sarine, Mich. 508 10r0 WLRH Farmingdale. N. Y 211 30 KGFH 250 60 Glendale. Calif. 300 KWLC Decorah Taws (day) 238 w-. et (711e10n. 111 345 25000 WLBL Stevens Point. Wis. KGF! San Angelo. Texan 229 100 KWSC Pullman, W'P0 216 500 w-oc GInllreacer, Mass 210 140 KG FJ Los Angeles. Calif 211 100 HWTC Santa Ann. Cn1U 200 100 Ww0 New York City 231 M W t,R O Ga esburg. Ill. 229 2100 KGFK Hallock. Minnesota 250 50 KWWG Brownsville. Texas 238 500 w -ev st. ronde. Mo. (day) 945 iron WIBV Mansfield. Ohio 248 KGFL Raton, New Mexico 219 50 W 5111000 1("4 Seattle. Wash. 5241 W -nA T1.111 a. Te'AS 2R4 259 ^0 LB W Oil City, Pa. KGFW Ravenna. Neb 211 0 KXL Portland. Oregon 240 500 We44 PhilvIosnhin. Ra 402 540 WLBX Tenn Bland City N.Y. 200 100 KGFX Pierre. S. D. (day) 511 200 K`Cn Et (r ^ntrn, (BM 100 wen,: Trnorville. Tenn 250 59 WLBZ Dover- Foxcroft, Me 484 250 G 248 50 KG F Ficher. Oklahoma 297 500 KXRO Abera4 -n. Wash 211 75 2541 149 WLCI Tthnra. N. Y KGGH Cinelnnxtl. Ohio 211 100 Cedar Grove. La 229 50 Kg R Ran 1".ancin4x.. rn1H,,, 244 1000 we.1a5 hantas. Pa 239 141 WLEX Taxlneton. Mass KGGM Albuquerque. N. M 219 100 K gulf and KYWA See KFKX toe's t Cnikwitine Minn 210 Inn W41111 SP. WON KG HB Honolulu, Hawaii 227 250 (..,. -`e 104 WLIT Philadelphia, Pa 53.4 500 KG HD KZ NI ^4 Calif 210 WFBL Rvm^pa.. N. V 333 750 Missoula. Mont 211 50 gin R, Asaln.nnn VP. 414 1001 O E esa... .. KGHF pueblo, Colo 250 (te`nnnro.no 241 me- 345 5000 227 wean Cinelnnatt. Ohio 211 95 tara, 1(W) watta) .L CChhleeelseaWD. KG HG McGehee. Ark 229 50 WwW WM1F wear Ohleavn, m. (day) . . . 328 500 Tn41nw.4nna r44,(rdd) 244 500 l Raw MC H I WFBM Little Rock. Ark 200 100 w a stern, 7040 wiry P.nnrlva. N. Y 214 500 KG H L y M Newark. T. 240 250 (a1í9 : aR 428 25000 Billings. Mont 011 500 ` A at T;1.1= (day) 290 860 us w (inefnnatl, Ohio KGHX Richmond. 50 C07, N.J. *.d. (em 273 5000 Texas 200 a AW Omaha, WON. (day) 454 M wester e.1Hmn cn (temp.) 2 94 900 vow YOrt (`ily KG 10 Idaho Fails, Idaho. 297 2a. W it not vnrk 700 tonss.,I, n. (rnaonn.da. N. Y. 526 500 KG IQ City 340 5000 run. an.womn Tan Twin Falls, Idaho 227 250 soon se Trim..nn na PAS ... -. Dw11 w. 5a. s>n, 19.rtmO0t11. Mme: KG1R ..r w 7500 Butte. Montana 220 250 car 'Ann._. *qnM 900 1M .. an....u..(Thin 1îy 217 1590 . K moron. N. Y KGIW Trinidn4. (loto ..,Ann 1w.,.hinatnn. T...... r-1 260 KGJF 211 100 17..11..0.1. N. Y 4x14 b5 -w. dr.u.w '-"In 2a. $50 0.... Little Ronk. Ark 807 950 !ARV R1.nadelnl.ta. .4o_..rA lawn.d,a..wln, Pa. 229 50 tous eN OMnmbus, Ohio K GK B , . WA IRV Brownwnnd. Texas. 240 )nn yr... (lrl.ns. La San A Ces. Wt.1Y w: A Chime.. Tri 447 5000 KG Kt. San Angelo Terra 210 15 inn 1)00M0 Wwet.!ar l.nnna.4ter. on. 950 v a., T 'lia. Mo 250 100 KG KO Wichita Falla. Texas 528 warn corgis. 250 nweleh. 1 7 .leg 1,eomn.. N 955 4100 n T a n Ga KG Tdaho A . KX Ran4nMnt 911 15 w n 114 Rnve1 Oak. *sleh 200 W._R.! wrwnw111 TanlL 416 Sf10 n 200 2500 KGO Oakland. ('elfe 100 .u..o ru R. I 10x0 waill C^htmbon. Ohio (Ltd) ¡OR 5 06n W(1 va.nna.dns and 541 500 Toteo.It. 211 100 KG RC San Antonin. Texas... 210 1a. we 1.1( Wilton, Grove. W.1R1 m 541 250 Mich Pa 900 Da wisee Panda. Tip 208 500 KGRS Amerinn, Teuee. . 213 Bon WART ..on Ailhp.n Ala...... , 241 b9nno wows sw vnrk (ri!Y (Ltd.) 250 100 695 500 KG TT San Francis.", tfalif.. 211 5M) Wags (WW1 RAn1AR. 100 w..R. Miami Beach. PIS KG Honolulu. Hawaii Mini¿ 20R 5R woo. r..i.erk. 4'h 940 Richmond. Va 246 100 319 540 WRAA West 'Lafayette. , Newark. car. .. 240 250 w..Rq W 7ncl 214 (WI woe. J 211 100 KG Portland, Oregon 484 1000 WBAK Harrisburg, Pa. (day). 210 500 WOES Chicago. EL. 220 500 WMBH Joplin. Mo.

www.americanradiohistory.com Radio News for March, 1929 849

Radio Radio Z Radio r ¡Z Radie ¡ % Call BROADCAST STA. S 31 Call BROADCAST STA. q 3q Call BROADCAST STA. at 34 Call BROADCAST STA. a: 3n L Location q' ÿ; L Location q a°,; Latter . Location ;i ÿ3 Latter Location ;i ÿ;

WMBI Chicago. Ill. (day) .... 278 5000 WOAN Lawrenceburg, Tenn.. 500 500 WQBZ Weirton, W. Va. 211 60 WS IS Sarasota. Fla 297 250 W MBJ WUkinsburg Penna... 200 100 WOAX Trenton, N.J 234 500 WRAF LaPorte, Ind 250 100 WSIX Springfield, 'Penn 298 100 WMBL Lakeland. l'In. 229 100 WOBT Union City. Tenn..... 229 15 WRAK Erle, Pa 219 50 WSM Nashville. Tenn 461 5000 WMBM Memphis. Tenn 200 10 WOBU Charleston. W. Va.. ,. 517 250 WRAW Reading. Pa 229 100 WSMB New Orleans, La...,, 227 750 WMBO Auburn, N. Y 219 100 WOC Davenport. Iowa 300 5000 WRAX Philadelphia. Pa.(day) 246 250 WS MD Salisbury Md 229 100 WMBQ Brooklyn. N. Y 200 100 WOCL Jamestown, N. Y 248 25 WRBC Valparaiso. Ind.(day) 242 500 WSMK Dayton. Ohio 526 200 w MBR Tampa. Fla 248 100 WODA Paterson. N. J 240 1000 WRBI Tifton, Ga. 229 20 WSPD Toledo. Ohio 224 500 WMBS Ilarriaburg, Pa 210 500 WOI Ames, Iowa (day) 535 3500 WRBJ Hattiesburg Miss ... 200 10 WSRO Middletown, Ohio 211 100 WMC Memphis. Teno 384 500 WOKO Peekskill, N. Y 208 500 WRBC Columbus, GaO 250 50 WSSH Boston. Mass..... 211 100 W MCA New York City 526 500 WOL Washington,D.C.(day) 229 100 WRBQ Greenville. Mise 248 100 WSUI Iowa City. Iowa 517 500 W MES Boston, Maas 200 50 WOMT Manitowoc, \lis 298 100 WRBT Wilmington. N. C 219 50 WSUN St. Petersburg, Fla 333 1000 WMMN Fairmont. W. Va 337 250 WOO Philadelphia, Pa 200 100 WRBU Gastonia, N. C 248 100 WSVS Buffalo. N. Y...... 219 50 W MPC Lapeer. Mich 200 30 WOOD Grand Rapids Mich 236 500 WNSW Columbia, S. C 229 15 WSYR Syracuse, N. Y 526 250 WMRJ Jamaica, N. Y. City., 211 10 WOQ Kansas City. Mo 492 1000 WRC Washington, D.C 316 500 WTAD Quincy. Is 208 500 WMSG New York City 222 250 WOR Newark. N. J. 422 5000 WREC Memphis. Tenn 500 500 WTAG Worcester. Mass 5170 250 WMT Waterloo. Iowa 250 100 WORD Chicago, Ili. 203 5000 WREN Lawrence, Kansas 246 1000 WTAM Cleveland, Ohio 280 3500 WNAC Bee WBIS WOS Jefferson City. Mo 470 500 WRHM Minneapolis. Minn,.. 240 1000 WTAQ Washington.. WIa 225 1000 WNAD Norman. Oki 297 500 WOV New York City (day) 265 1000 WRJN Racine, Wls. 219 100 WTAR Norfolk, Va 384 500 WNAT Philadelphia. Pa 229 100 WOW Omaha, 508 1000 WRK Ohio 229 100 WTAW College Station, Tes 268 500 WNAX Yankton. S. D . 526 1000 WOWO Fort Wayne, Ind 258 10000 WRNY New York City 287 250 WTAR Streator III. 248 50 W NBF Binghamton, N. Y.... 200 50 WPAP New York City 097 250 W RR Dallas. Texas 284 5000 WTAZ Richmond. Va 248 15 WNBH New Bedford, Mawr... 229 100 WPAW Pnwtuoket, R. I. 248 100 WRUF Gainesville, Fla. 204 5000 WTBO Cumberland, Md. ,. , 201 50 WNBJ Knoxville, Tenn...... 220 50 WPCC Chicago, III. 526 500 WRVA Richmond. Va. 270 5000 WTBQ Wilmington, Dei 200 100 WNBO Washington. l'a. 50 15 WPCH New York City (day). 370 500 WSAI Cfncennati.Ohfo(L1d.) 375 5000 WTFI Toccoa Falls. Ga 207 500 WNBQ N. Y 200 15 WPG Atlantic City, N. J 273 5000 WSAJ Grove City, Pa 229 200 WTHS Atlanta, Ga 229 100 WNBR Memphis, Tena 210 500 WPOR See WTAR WSAN Allentown, Pa 208 250 WT IC Hartford. Conn .. 500 250 WNBW Carbondale, Pa 250 5 WPRC StateColrg, Pa 250 100 WSAR Portsmouth, R. I 207 250u Permit 283 meters. 50.000 watts. WNW( Spr(nac 250 10 WPSC tuteCollCollege. e. Pu.(day) 244 500 WSAZ Huntington.(q. W. Va 17 250 WTMJ Milwaukee, \Yls 484 1100 WNBZ Saranac Lake.Lake, N. Y. WPSW Raleigelphia, 440 50 WSB Atlanta. Ga 405 10000 WWAE Detroit, Ili. 250 100 (day) 202 10 WPTF N. C. 441 10000 WSBT 248 100 W Wl New ansh :353 1000 W Chicago, Id WNJ Newark. , 537 250 QAN ScantMiami, 'FloridaFa.l 242 750 WSBT South IIend, Ind 244 500 WWL New Orleans, La 353 5000 WNRC Knoxville. 535 1000 WQAN Scranton. Pa. 341 250 NYC New York N. C 208 500 W QBC See WPAP ., WSDA Brooklyn.y, 214 500 WWNC Asheville, N. C 200 1000 WNAC New York City 250 500 WQBC Cuira, burg, 220 300 WSEA Norfolk, Va 384 500 WWRL Woodside. N. Y... 200 100 W0A1 ban Antonio. Texas 252 5000 WQBJ CWrk96u[g, W. Va.., 250 65 WSGH See WSDA WWVA Wheeling, W. Va 258 5000 LIST OF CANADIAN BROADCAST CALLS CFAC Calgary. Alm...... 434 500 CHCT See CKLC CJRM Moose Jaw. Sask 297 CKPC Preston. Ont. 248 25 CFBO St. John. N. B 337 50 CHGS Summende, P. E. I 268 25 CJRW Fleming. Sask. 297 500 CKPR Midland, Ont 268 50 CFCA Toronto. Ont 357 500 CHLS Ste CKCD CJSC See CKCL CKSH St. Hyacinthe, Que 297 50 CFCF Montreal. Que 411 1650 CHMA Edmonton. Alta 517 250 CKAC Montreal, Que 411 1200 CKUA Edmonton, Alta 517 500 CFCH Iroquois Ont 500 250 CHML Mount Hamilton, Ont. 341 50 CKCD Vancouver, B. C. 411 CKWX Vancouver, B. C 411 100 CFCL CLalO, CHNC See CKNC CKC1 Quebec, Que 341 CKX Brandon, Man 556 500 CFCN Calgary. Alm 434 1800 CHNS Halifax, N. S 322 500 CKCK Regina, Bask 312 500 C K Y Winnipeg, Man. 384 5000 CFCO Chatham, Ont. 248 25 CHRC Quebec Quebec 341 CKCL Toronto, Ont 517 500 CNRA Moncton, N. B 476 500 egina, CFCT Victoria, B. C. 476 500 CHWC Sack 155 CKCD Ottawa. Ont 434 100 CNRC See CFAC CFCY Charlottetown, P. E. I. 312 100 CHWK Chliliwack, B. C. 248 CKCK Brantford, Ont 297 50 CNRE See CJCA CFJC Kamloops, B. C.... 268 15 CJBC (Uses several Toronto 341 50 See or CFCF stations)..517, 357 or 312 CKCV Quebec, Que CNRM CHYC, CRAC, CFLC Prescott, Ontario 297 50 B. 411 50 CNRO . 434 500 20 CJBR See CKCK CKFC Vancouver. C. Ottawa, Ont. CF MC Kingston, Ont. 268 CROW Bowmanville, Ont 312 5000 CNRQ See CKCV CFNB Fredericton. N. B 248 50 CJCA Edmonton, Alta 517 500 1000 CNRR See CKCK CFQC Saskatoon. Bask 329 500 CJCJ Calgary, Alta 434 250 CKLC Red Deer. Alberta 357 CFRB Toronto, Ont 312 1000 CJGC London. Ont. ... 329 500 C K MC Cobalt, Ont 248 15 CNRS See CFQC CFRC Kingston, Ont. 268 500 CJGX Yorkton, Bask. 476 500 CKMO Vancouver. B.C. 411 50 CNRT See CFCA CHCA See CJCJ CJHS Saskatoon, Sask...... 329 250 CKNC Toronto, Ont, 517 500 CNRV Vancouver, B. C 291 500 P. E. L 312 30 CJGC Lethbridge, Alm...... 268 50 CKOC Hamilton. Out. 341 100 CNRW See CKY CHCK Charlottetown. VAS Louisburg, 434 CHCS Hamilton, Ont...... , 341 10 CJOR Sea Island, B. C 291 50 CROW See CFCA NovaScotia LIST OF SHORT -WAVE STATIONS OF THE WORLD (Some ca is may have been altered under new international. regulations.)

Radio Radio Radio Call BROADCAST STA. Call BROADCAST STA. Call BROADCAST STA. Letters on Lotion Location Letters Location

AFRICA HOLLAND SWEDEN A IN Casablanca, Morocco 51.00 SKR Constantine. l'unis 42.80 PCJJ Eindhoven 31.4 30.000 SAS Marlsbrg 52.50 IB Jolumneuburg, U.S. Afrka 32.00 PCKK Kootwijk 18.00 SAA Karlskrona 44.40 PC LL 7L0 Nairobi. Kenya - 33 50 2.000 Kootwilk 18.00 32.000 Wotala 41.45 1,000 PCMM Ymulden 96.50 SAJ Karlsuorg 47.00 AUSTRALIA PCPP Kootwllk 18.50 SMHA Stockholm 41.00 2BL Sydney 32.50 PCRR Kootwik 37.00 2FC PCTT Kootwijk 21.00 SWITZERLAND 2ME Sytdney 28.50 PCUU The llague 37.00 3AR Melbourne.. 55.00 H9OC Berne 32.00 ILO Melbourne 32.00 ITALY H9XD Zurich. 85.00 and 32.00 GAG Perth, West Australia 32.90 11AX Rome 2000, 40.00 350 GWF Perth 104.50 1AY Piacenza 20.00, 45.00 UNITED STATES KDKA_(W6X1() East Pittsburgh, Pa. 62.50 40,000 AUSTRIA (1VBXS, W8XP- portable) 42.75 OHK2 Vienna 70.00 25.40 OATH Vienna 37.00 KEJ K"(W6XAN) Los Angeles, Calif 105.90 Vienna 22.20 250 HIS list of the short -wave broadcast KEWE Bourns, Calif ... 14.10 KFPY (W7XAB) Spokane, Washington 105.90 100 BELGIUM 1 stations throughout the world is not KFQU (W6XBH) Holy City. Cast 31.00 50 E6442 Brussels 42.00 300 complete, although we have endeavored to KFQZ (W6XAU Hollywood, Calif 108.20 50 list every statioq of whom we have heard KFVD (W6XBX)) Culver City, Calif 105.00 50 CANADA KFWB (006X810 Los Angeles. CF Drummondville, Quebec 32.00 reports ; since in many cases reliable in- Calif 105.00 50 cJRX Winnipeg, Man 25.60 2.000 formation about the programs, wavelength KFWO (W6XAD) Avalon, Calif 53.07 100 VAS Louisburg, N S. 28.00 and power of the stations cannot even be KGER-(WSXBV) Long Beach. Calif 48.86 obtained from stations themselves. KGB the Diego, 40 COSTA RICA (See page 844.) Barr inn. 40.00 5 SRN Heredia 30.30 714 KGO (W6XAX, W6XN) San Francisco. Calif 10 to 40 10,000 KHJ (W6XAU) Los Angeles, Calif 104.10 50 DANTZIG KJBS (W6XAR) San Francisco, Calif 61.00 50 EK4ZZZ Dantzig 40.00 KJR(W7XC, W7XO) Seattle, Washington 105.20 250 DENMARK JAPAN JFAB Taipeh, KMTR Los Angeles. Call, 108.20 250 D7MK Copenhagen Formosa 39.50 KNRC (W6XAF) Santa Monica. Calif 108.20 100 O7RL 42.12 and 8424 JHBB Ibarakiken (Hiraslo).,, 37.50 2,000 JIPP Tokio 20.00 KNX (W6XA) Lee Angeles. Calif 107.10 100 ENGLAND JKZB Tokio 20.00 KOIL (W9XU) Council Bluffs, Iowa 61.06 500 SSW Chelmsford 24.30 KWE -KEWE Bonnat, Calif 14.10 15,000 Tokio 60.00, 35.00, 500 KWJJ 2NM CKterham 32.50 l A K I ..30.00. 40.00 (W7XAO) Portland, Oregon 53.54 100 GBS Rugby 29.40 WAAM (W2XBA) Newark. N. J 65.18 50 WABC (W2XE) Richmond Hill. N. Y 58.50 500 FINLAND JAVA WAJ Rocky Point, N. Y 22.48 Helsingfora (Helsinki) 31.50 ARE Bandoeng 15.93 WBRL (W1XY) Tilton, N. H 109.00 250 FRANCE WBZ Springfield Mom 70.00 F8GC ( WCFL Chicago Ill 3724 Paris "Radio IA,") 61.00 500 MEXICO WCGU (W2XBH) FBAV Nogent 80.00 500 Brooklyn, N. Y 54.00 150 Radio Vitus Paris 37.00 1,500 XC51 Mexico City 44.00 WCSH (W1XAB) Portland, Maine 63.79 250 Eiffel WCX Pontiac, Michigan 32.00 75 Tower Paris (time signals) 32.50 WEAJ YR Lyons ("Radio Lyon ") 4020 250 MOROCCO Rocky Point N. Y 22.48 Agen WEAO (W*XJ) Columbus, Ohio 54.02 25 30.755 AIN Casablanca 51.00 WGY (W2XAF) Schenectady, N. Y.,,.. 31.40 YN Lyons 55.00 8.000 (W2XAD) Nancy 15.50 500 Schenectady, N. Y 21.96 FW4 Ste. ARise 24.50 NORWAY WHK (W6XF) Cleveland, Ohio 66.Ó 500 GERMANY LCHO Oslo 33.00 WJR -WCX (WSXAO) Pontiac. Michigan 32.00 AFl Kohkswusterhausen 14.00 LON Bergen 31.25. 30.00 W IZ Vow Brunswick. NN. J 43.45 AFL Hamburg 70.00 and 52.00 WJZ (W3XL) New York, N. Y 59.96 30,000 AFT Konigswusterhausen 14.00 U. S. S. R. (RUSSIA) WLW (W6XAU Cincinnati, Ohio 52.02 250 AFU Konigswustertmusen 14.00 RDRL Leningrad 28.50 WNAL (W9XAB) Omaha, Neb 105.00 50 AFK Berlin (Doberita) 37.56 75.36 RDW Moscow 83.00 WNBT Elgin, Ill. (Time Sures) 35.50 500 HEA Nauen WND Ocean Township, 1' . 11.00 Khabarovsk (Sibcrin) 5500000 12,000 J 46.48 AGC Berlin 17.20 RFFN N Mo WOR (W2XAQ) Kearny, N. J 65.40 50 AGJ Nauen 56.70 RA39 Tomsk (Siberia) 37.00 WOWO Fort Wayne Ind 22.80 1,000 AGM Nauen 11.00 WRNY (W2XAL) New York, N. Y 30.91 500 LA Langenberg 43.90 WSM (AXIS) Nashville, Tenn 31.43 iPOF Nauen 11.00 SPAIN WTFF Mt. Vernon, Va 56.00 POZ Nauen 1.10 RAM Madrid 30.70 (Several short waves are used for transatlantic tel- Stuttgart 41.00 EAR55 Barcelona ephony. This is private business, not broadcasting.)

www.americanradiohistory.com 850 Radio News for March, 1929 The Radio Constructor's Own Page Wherein Custom and Home Set Builders and Experimenters All Over the World Swap Experiences and Suggestions About Hookups and Accessories

A DIRECT -COUPLED A.C. SET lieve this circuit will be interesting to the advanced I found that this made a better ground than experimenter. the water pipe and greatly strengthened the sig- Editor, RADIO NEWS: W. M. JACOBS, nals. Then, connecting to the water pipe as a The enclosed diagram is that of a direct -coupled 3225 Franklin Boulevard, Sacramento, Calif. ground, I used the buried can as an "aerial" and radio receiver using A.C. 22 -type tubes and satis- brought in distant stations throughout the sum-, fying, I believe, Mr. Sydney O'Rourke's definition (This direct -coupling method has found seme favor in England as a method of operating a re- mer without static. This can is buried in moist of a direct- coupled radio receiver. Any method of earth never have to pour water around or touch indicated by ceiver on 220 -volt D.C. house lighting mains; it -I volume control may be used; but that it -and is nearly fifty feet away from the set. arrows varies the grid bias and, if the filament is, we believe, the device of Mr. J. F. Johnston. The special merit claimed for it is that the ripple W. A. DENT, voltage on the R.F. tubes is adjusted correctly, 826 West Grace St., Richmond, works very well. Also, plate rectification is used in the voltage supply tends to balance out in each Virginia. on the detector, which requires some adjusting of tube; the apparatus used is simple. For a receiver using the customary American number of - plate and grid voltages for best results. Still, high THE "MILK SHAKER" CURDLED the conventional grid leak and condenser can be voltage tubes, however, 220 volts is inadequate. used, and will allow a reduction of 50 volts "B" Mr. Jacobs' hook -up, while it will probably not be Editor, RADIO NEWS: supply; as the plate tap can be dropped to the same Imitated by many, will appeal to enterprising con- I built your "Milk- Shaker Special" which I found point as the last R.F. plate, since the detector grid structors by its ingenuity.- EDIroa.) unsatisfactory from a selectivity standpoint; the may be isolated from the latter. volume was fair, and tone qual- It is needless to say that all R.F. circuits must ity very fine, however. By re- be well shielded and (while the diagram does not arranging the circuit as shown show this) the resistor strip used in a power unit herewith I increased the selec- must be well by- passed by condensers at each volt- tivity and volume about double age tap. Over -all voltage is obtained from a 281 that offered by the original rectifier; it is necessary to by -pass considerable model. Following the original current to keep the resistor stable. diagram, LI and L2 are wound The first tuning unit is a modified band -pass on 2 -inch forms, 90 turns of 26 filter, the R.F. energy is passed through a tuned D.C.C. wire; L3 is the tickler circuit inductively coupled to the second tuned circuit, and this in turn to a third tuned circuit, at the filament end. The choke RFC, of 200 turns, is inserted at the lower end of the grid coil, to Mr. Lowther finds this an effi- bias the grid and keep the R.F. energy from leak- cient rearrangement of the ing to ground. The first two tuned circuits con- "Milk- Shaker Special." sist of two standard solenoid coils, mounted side by side, one -half inch from each other. The third 33333 111,111111111111111111,11111111 11111 111111111111111111111,11111111, coil is of the same construction and, if not shielded, should be mounted at right angles to the first and which is wound with the same second and about three inches away. Each coil wire on a similar form, adjusted and its associated condenser is contained in an once and left fixed; RFC are aluminum can. the radio-frequency chokes; R1 In the plate circuit of the detector and first is a 500,000 -ohm variable resis- audio, I am using two Thordarson autoformers. tor for volume and oscillation I am contemplating substituting two "Z" couplers control; C3 is a 1 -mf. by -pass between these two stages. The power resistor is condenser; C4 a '''4-nil. by -pass the standard one supplied with an Amertran 210 A NOVEL ANTENNA condenser, and C6 a .002 -mf. fixed condenser. I power pack. The volume control is composed of Editor, RADIO News: found no advantage in shielding the second coil. two sliding contact arms connected by an insulat- Your magazine has saved me money from time R. P. LOWTHER, ing strip so that they slide together, altering the to time in finding the proper accessories and equip- 1025 Riverside Drive, South Bend, Ind. plate and grid bias together on the first two R.F. ment, as well as in suggestions from readers. I (The circuit described by Mr. Lowther is a very tubes. All plate taps are by- passed with 1 -mf. feel that I am greatly indebted to you for much close adaptation of our old friend, the Browning - condensers to "B- ". From the detector on, high - valuable information and better radio reception. Drake circuit and as such, is still an excellent cir- voltage condensers should be used; as the voltage Perhaps my combination ground and antenna will cuit for the constructor. As a rule, if there is local and current keeps increasing toward "B+350." be of interest. I used for a core form a plain, interference, it is preferable to shield the second While most of the tapped voltages are not critical, smooth half -gallon bottle wrapped with paper, coil.) the approximate values are indicated. around which I wound a hundred feet of No. 14 All the condensers in the tuning circuits, of cotton -covered armature wire; the end of which I DISCOUNTS AND THE SET BUILDER course, must be insulated from each other, both soldered to 36 inches of lead -covered cable. I Editor, RADIO NEWS: rotors and stators. I use individual condensers then enclosed the coil in an air -and- watertight In the December Constructor's Page, Mr. Albert connected together by bakelite condensers and bell can, about 14 inches long, made of sheet copper E. Gleason says that the practice by parts supply cranks. The selectivity is very good, and I be- about the thickness of ordinary stovepipe. (Continued on page 887)

I II SINGLE- CONTROL - - - -T - - - -

C i C3r C41 .AC-22 L4 AC -22 L5 Y -27 AT 1 AC-22 AT2 -A i I á o T' oq G o C2T TT C5 ° C6 9 o ó Li L2 L3 tt I RFC áa B- Bi- 550 V. qi qlp Qip ip 0---110 II II 11110100 11111111111 1111111 iUliUIil- I12V145V45V IZVt 45V 45V 41 45V. ' IZV. 222V 672V 45V. 180V. TO 9V

The first impression of the reader will be "what's wrong with this diagrams' a bias on each cathode, more positive than on the grid; and a positive voting However, the apparent high positive biases on the grids are not such; the on each plate, compared with the cathode. Mr. Jacobs does not state how the progressive tapping of the battery supply (as built, a power -unit resistor) puts heaters are connected; though each should be positive compared with its cathode.

www.americanradiohistory.com Radio News for March, 1929 851

ilil,qu, - ;. d .,_píitdif0l111fiGd Conducted by C. W. Palmer Important Notice to Correspondents BECAUSE of the large influx of mail, RADIO NEWS now finds it (2) We cannot give blueprints or layouts for commercial ap- necessary to discontinue answering free of charge, all inquiries paratus, or data which the manufacturers have kept secret. to this department. With several hundred letters received daily by (3) We cannot advise, even confidentially, on the respective mer- this department, the editors have been taxed so severely in answer- its of trade -marked apparatus or "what make to buy." ing the present mail that the magazine has begun to suffer. Here- after, therefore, only letters accompanied by our standard fee (4) We cannot send dither replies, blueprints, books or maga- (which, by the way, covers only the actual writing of letters and zines C.O.D. stenographic help) can be considered. Kindly note these simple (5) When in doubt, please inquire as to the cost for our services, rules, now in effect: before remitting. (1) Correspondents asking answers by mail must enclose 25c for each separate question. Simple radio problems will be answered, (6) Be brief. Typewrite or write legibly in ink, on one but for this nominal charge we cannot make long calculations or side of the sheet only. No attention can be paid to pencilled thorough investigations. matter.

Alsomonmenummeniummuneunnuiiiiii 1111111 iiiii iiiiiii iiiiiiiiiiiiiiiiiiiiiiiii iiiiiii Mum.. iiiiii .Iu iiiiiiiiiii 4.11.1111111W111.1111111 iiiii .11111111111111111.111.11410111.

A.C. MILK- SHAKER SPECIAL (Q.) "Will you supply me with the diagram One 3 -volt "C" battery (or two flashlight cells in of a receiver using a stage of reflexed amplifica- series; (2329) Mr. B. G. Till, Toronto, Ont., writes: tion and a regenerative detector? I have a one- One neutralizing condenser (about 20 -mmf. ca- (Q.) "I am desirous of building the "Milk - tube set using a capacity-controlled regenerative pacity) NC; Shaker Special" receiver, described in your October, detector and I would like to improve it. I believe One dry -cell tube VI, and socket; 1928 issue, but using A.C. tubes and an audio - that the rAfiex system would be the most suitable, One .005 -mf. fixed condenser C6; frequency amplifier. I will appreciate it, if you as it is not practical to use many tubes here on One .00025 -mf. fixed condenser CS; advise me of the necessary changes in the circuit." account of the necessity of using dry batteries. One .0001 -mf. fixed condenser C4; (A.) We have received a great number of re- I am an old reader of RADIO NEWS, and I am One 30-ohm rheostat RI; quests for information about this set, and many certainly pleased with the "new" magazine. It One radio -frequency choke (about 85 ntillihenries) fans would like to build it, substituting an A.C. is a great improvement over the old system." RFC; screen -grid tube for the D.C. type specified. A (A.) We are printing, as Fig. Q2330, the dia- Binding posts, wire, etc. few changes will be necessary in the apparatus and gram of a set of the type that you desire. In Place the two coils at right angles and as far wiring; but these are very easy to make, and we order to obtain the best service, the radio -frequency apart as possible to prevent any interaction, and believe that no one will encounter serious trouble amplifier must be neutralized or stabilized and, keep all the grid and plate wires away from each in effecting these alterations. for this reason, a double primary coil is employed. other. If the set does not operate correctly when to Q. 2329) By referring the diagram (Fig. The coil L2 which you are using in your present first tried, reverse the connections to the primary you will see that the grid -return leads must be set will be satisfactory as a R.F. coupler if you of the A.F. transformer to obtain the correct re- changed and that it is necessary to use five -prong remove the primary winding and replace it with lation between the various circuits. The neutraliz- (UY) sockets in place of the usual four -prong type. a double winding. This is done by taking two ing condenser is adjusted until the amplifier does A 227 -type tube is employed as the detector and, pieces of wire of the same length and gauge and not oscillate; first connecting a pair of phones in since the filament voltage required for this tube winding them together on the coil; the correct the plate lead of the detector tube and turning off is the same as for the screen -grid tube, the two length in this case is the same that is used in the the rheostat in the radio -frequency amplifier. Then, filaments can be heated from the same transformer primary at present. adjust the neutralizing condenser until the signals winding. The other parts for the set should be The aerial coil Ll is wound on a tube of the fade out or are at minimum volume. The regenera- arranged in the same manner as for the original same size as the detector coupler and similar to tion in the detector should be suppressed, so that circuit. All the parts shielded in the original it, with the same size of wire, etc. The primary the detector will not oscillate while adjusting the should be shielded in the A.C. model also. is placed on the same tube, about 4-inch away amplifier. Then remove the phones from the de- The grid bias for the radio-frequency amplifier from the secondary, and contains 8 to 10 turns tector plate lead and the set is ready for opera- must be obtained in a different manner from that of wire. tion. During the neutralizing of the amplifier, the it is used in the D.C. model, as not possible to The other apparatus, needed for the double-pur- two phone or loud -speaker binding posts should be use the voltage drop across the filament resistor. pose amplifier, is as follows: connected together, so that the plate circuit will By connecting a resistor of correct value in the One .0005 -mt variable condenser Cl; be complete; or the loud speaker should be left lead from the cathode to the "B -" post, the cath- One audio -frequency transformer (about 3:1 or connected to these binding posts. ode will be given a positive bias with relation to 4:1 ratio) Tl; Diagram appears on the following page. the grid, which is connected directly to the nega- tive terminal of the "B" battery. The resistor required for this purpose should have a value of 1000 ohms, to give the required voltage drop of 14 volts at 14 milliamperes, which is the plate current consumed by the tube. In order to pro- vide a low- resistance path for the radio -frequency currents, a half- microfarad by -pass condenser (C7) is connected across the resistor. The connections to the detector also are changed, to use a five -prong socket for the 227 -type tube in the detector circuit. The cathodes and the by- pass condensers in all of the circuits are connected to the common terminal which serves as a ground connection and "B -" lead, óut is not connected to the filaments. Twist all the filament wires, to prevent the hum from being excessive; and keep all of the grid and plate wires as far as possible from these filament wires, to further reduce this possibility. Any good audio-frequency system can be em- ployed with the set. A suitable amplifier using one stage of transformer coupling and one of push -pull, which is designed to operate from an A.C. supply with a "B" power unit, was described in the "I Want to Know" columns of the June, 1928, issue of RADIO NEWS,

REFLEX WITH REGENERATIVE DETECTOR (2330) Mr. M. Gayman, Beamsville, Ontario, Here is the circuit of a "Milk- Shaker Special," using an A.C. screen -grid tube in the first stage. Sev- Can., asks: eral changes in the circuit will be necessary, however, from the battery model.

www.americanradiohistory.com 852 Radio News for March, 1929

the transformer should be designed to take, under load, 1.7 amperes at 65 volts, the remaining 50 volts being dropped in the tube. If the line - N.C. C2 R3 2 MEG. voltage drops or rises 10 volts, the voltage across 0005 Mr NVN the tube will correspondingly change, but the trans- Vt former primary voltage will remain constant at 650. O The "ballast" tube requires about ten minutes to o heat up fully, and the voltage drop increases rapidly 1 C1 for the first few minutes, after which it increases 00 0005 MF up to the final temperature; the "glow" tube men -. C4 tioned previously functions instantaneously, as soon -° as the glow is seen. The "ballast" tube is equipped -_ MF L2 I. with a special screw base; while the voltage- regu- lator tube uses the standard four -prong UX base 3V .005 MF. R1 of the type used for receiving tubes. } GQor F ¡ Tt FILAMENT TRANSFORMER B P (2332) Mr. Arthur F. Clark, San Antonio, Y Texas, writes: (Q.) "I am a constant reader of your magazine and I have been looking for some time for in- SW. , J structions for making a transformer for lighting O a b b the filaments of A.C. tubes. I have been dis- B+45V. A- A+ LOUD B+ appointed, however, since I have never seen the details for making a transformer of this type. I SPEAKER 90 V. Q-2330 OR PHONES have also looked in your latest edition of "1001 RADIO QUESTIONS AND ANSWERS" but I do not find the instructions in this book, either. Will you give me these ?" two -tube receiver shown here (see preceding page for description) adds one tube to a single The reflex (A.) The diagram (Fig. Q2332) shows the circuit regenerator and makes a "bloopless" circuit with R.F. and A.F. stages. core of a suitable transformer for 60 -cycle current. The core is made of strips of silicon steel .014 - inch thick and 1''4 inches wide, which are cut to VOLTAGE -REGULATOR TUBES Tube Operation two lengths; the longer are 4'4 inches, and the shorter pieces 2g inches long. The strips are There is drawback in (2331) Mr. N. B. Johnson, Cleveland, Ohio, one the use of "glow" cut from sheet metal and the corners are filed to tube; that is, in order to have the tube operate Writes: prevent any rough edges from protruding; after (Q.) "I have a "B" power unit in which I the laminations have been cut they are shellacked would like to use a voltage -regulator tube. The or varnished on at least one side to insulate them. unit has two variable output taps and a maximum About 170 of each size will he required; the in- tap for the power tube; the last gives about 180 sulating coat should be thin and evenly spread. volts, and the variable taps supply voltages between B+ The coils are made by preparing a block of wood 20 and 150 volts. I understand that a tube of MAX. 1 5/16 inches square and about 5 inches long; this type can be incorporated without changing the this is wrapped with several layers of heavy paper internal wiring of the power unit. Can you help B+ and a piece of fiber 2;5 inches wide over the paper. me to solve my problem ?" AMP Two pieces of fiber 34 inches square are also pre- (A.) The use of voltage -regulator tubes in pared and a hole 1 5/16 inches square is cut in be of interest to a number the center of each; the two washers thus formed "B" power units should B+ of fans, as it is of great assistance in cases of are placed over the ends of the fiber strip which variation in the voltage in the unit; whether they DET. has been wound on the wooden block. This will are due to line -voltage changes or to current changes provide a spool made of the pieces of fiber, into in the load which cause corresponding changes in which the transformer windings are to be placed; the voltage. Such tubes operate by absorbing from the washers are glued firmly in place to make it the power unit all output current which is not secure. The spool is 244 inches wide and may being used by the receiver at any instant. Thus readily be slipped over one of the long segments the output voltage is maintained at a constant of the core. value; the receiver, or load, receives exactly the 8+ Next, the primary winding is placed in the power that it requires and the regulator tube takes MAX. spool; it contains 528 turns of No. 22 D.C.C. wire, the remainder. layer -wound. (The easiest way to wind this is B+ to fasten the block in some manner to the chuck The tubes are designed in such a way that their 135V. of a hand drill, or of a lathe if one is available.) is automatically decreased with any in- resistance A layer of varnisher) cambric, or several layers in the applied voltage. If, on the other crease B+ of heavy paper, is placed over this winding, after hand, the voltage decreases, the resistance increases; V. the two ends of the wire have been brought out whether more or less current is passed 90 so that through holes in the end of the spool; and the regulator tube depends on the voltage through the first of the secondary windings is over the of current consumed by the B+ placed input and the amount primary. Between each successive pair of the set. The commercially -available tubes are made H DET. windings, a layer of varnished cambric or paper voltage is at 90; in a so that their output kept must the watts, be placed, to insulate windings more power unit supplying a constant output in B thoroughly. the voltage- regulator tube will take sufficient cur- A winding to give 15 volts across its ends will rent to keep the output voltage practically constant need 72 turns, and one for 74 volts 36 turns, of within the limits of the tube. Of course, if its Q-2331 No. 14 D.C.C. wire. A 5 -volt winding contains 24 input voltage is increased over the rated maximum - turns of the same wire; a 3 -volt winding contains 15 value of the tube, since it will take only current The voltage-regulator tube across a power -unit tap turns and a VA -volt winding 12 turns. For a its maximum amount of current the terminal volt- maintains its output at 90 volts. 14 -volt winding, 8 turns of wire are sufficient, accordingly increased. age will be (Continued on page 890) A voltage -regulator tube may be inserted between and the 90 -volt tap of a the negative terminal correctly, it must be supplied with about 125 power unit of almost any type, without disturbing volts for an instant, in order to make it glow. neces- the unit in any way. Fig. Q2331A shows the This can be done by turning on the power unit be- sary hook -up for such a tube in a unit with two fore switching on the receiver; as soon as the set variable taps, as used in a number of commercial is switched on, the voltage drops to 90 volts, which units. If the tap is provided with a by -pass con- is the correct value. It is also necessary to con- denser, the only additional connections are those nect the tube correctly; if the polarity is right, from the tube to the "11+ Amp" tap and the nega- the glow will be noticed around the large circuit tive terminal. Fig. Q2331B shows connections plate. If the tube is incorrectly connected, the for a unit using the potentiometer, or series, output glow will be around the small terminal; no dam- arrangement. The voltage at the terminal should age will result from a temporary reversal of the be somewhat over 90 volts without the tubes; so connections, but the tube should not be left in this that some current will flow through the tube and condition for any length of time. In some cases, enable it to operate correctly. it is advisable to connect a 1000 -ohm resistor in Two voltage -regulator tubes may be connected series between the 90 -volt tap and the tube, to in series for the output of a 180 -volt supply, as prevent an excess of current from flowing through shown in Fig. Q2331C. Inn this case, the output the tube. voltage will be maintained at 180, even though the Another tube, called a "ballast" tube, is often input from the rectifier and filter is increased above used to keep the receiver's power supply constant; this value. By connecting the tubes in this way, being connected in series with the primary of the the output of the complete unit will be maintained power transformer. Its operation controls the at a practically constant voltage. The maximum - current supplied to the power unit. After this variation voltage range also will be higher than tube it is necessary to use a special transformer with a single tube, so that greater voltage- varia- with a primary designed for 65 volts, instead of Two voltage- regulator tubes in series, as above, 6s tions can be accommodated. 110 to 115. If the line -voltage averages 115 volts, the "B+Amp" value at 180 volts.

www.americanradiohistory.com Fadto News for Marclt, 1YLY ÓJJ

7i)

cthordarson 'Equipped. a GThrillirvo' GTorte Purity \N a di o's tichest6-Voice i

We have now been using Thordarsoe transformers for some four yéars, which should be proof conclusive that THE manufacturers of the world's we think them capable of maintain- calls; and in Thordarson Audio ing the high quality of Sparton Radio finest receivers realize the im- Receivers, which we so jealously Transformers a fidelity of repro- portant relationship between the guard. duction that renders their receiv- choice of transformers (power sup- rs musical instruments of the ply and audio) and the perform- highest caliber. ance of their instruments. Almost President -General Manager The purchaser and builder of universally they have turned to The Sparks- Withington Company radio receivers who seeks the ulti- Thordarson as the source of their transformers. mate in performance will insist on Thordarson In Thordarson Power Supply Transformers Radio Transformers. they have found an efficiency of design, an abund- THORDARSON ELECTRIC MFG. CO. ance of power and a constancy of performance Transformer Specialists Since I895 that makes their power unit free from service Huron, Kingsbury and Larrabee Streets, Chicago, Illinois THORDARSON TRAN 5 FORMERS SUPREME IN MUSICAL PERFORMANCE ye,

'tease sa.v _volt saw it in RADIO NEWS

www.americanradiohistory.com 854 Radio News for March, 1929

TUNE IN ON THE SHORT WAVES Real "Radio Mysteries" Get distance- escape static on the long wave broadcast ÌBL'NyTPACE MAPa N (Continued from page 811) band. See Call Book for short wave stations. SUB- MARINER wave band in- at once dipped and mailed the item to this cludes all powerful stations /! that broadcast programs on office. It relates that a Santa Barbara short waves- thousands of Cle -Ra -Tone voice SUBMARINERS now in (Calif.) housewife heard the of a radio use -short wares are the announcer and the strains of music coming new adventure - a new thrill awaits you. from a pot of vegetables cooking on an dec- Short Waves Popular Radio The SUBMMARINER has trie range. Whether or not the sound em- taken the country by storm. Nothing made like anated from the range, the metal of the it. Many users hare been pan, or the boiling water, we cannot be posi- getting London, England: Sockets many get Holland, even tive; although one of our readers con- in summer. Short waves are great distance carriers, with less static. Best of All Your present radio receiver, whether battery operated or an electric, will bring in short wave broadcasting when used with THE SUBMARINER It le easy to connect a SUBMARINER. Simply remove a tube from receiving set and place in SUBMARINER MUSIC BURST FORTH socket; then Insert SUBMARINER plug in place of tube. Attach regular aerial and ground to clips on SUB- MARINER. That's all. No changes in wiring of set FROM ELECTRIC RANGE necessary. No additional tubes or batteries required. If set operates a loud speaker. It will do so with SUB- MARINER. We guarantee that the SUBMARINER will Santa Barbara Woman, Stirring operate within the ware band covered equal to any short wave receiving system known when attached to your re- ceiver. Completely shielded metal cabinet. Fine tuning 'Mans, Is Astonished by Melody dial. ratio 32 to 1. Get the short wave musical programs and other activities, including television signals. Never -Experts Puzzled. before has so much In radio been offered for ao Bttle money) Order a SUBMARINER novel FOUR MODELS SANTA BARBARA, Cal., Dec. 16 20 to 65 meter range -tor battery operated radios, $15.00. For all electric radios, $17.50. 10 to 160 meter range- (.5 . -There may be sermons In atones for battery operated radios, $22.50. For all electric radios, and books In the running brooks, but $22.50. 10 to 160 meter range modela have three inter- changeable coils. A fourth coil: 160 to 340 meter range It was left for a Santa Barbara wo- will be supplied when specified as extra equipment- man to reveal today that there is a price $2.00. Schubert melody in a pan of belling, If your dealer does not cans, order direct from factory. Specially Designed vegetables. Sent anylchere In the U. S. postpaid upon receipt of price. As the hoarse velce of a radio an- Canada and Foreign. Boa additional Money order only. for nouncer burst through the kitchen Also sent C.O.D. plus postage in U. S. if $1.00 accom- steam of home here and the panies order to Insure carrying charges. In ordering be a.9ulet sure to name net and tubes sued. such as UY199, 11E196, A. C. Detector Tubes strains of "Ave Maria" filtered from 201A. 11E226, or ÚY227. See dealer or order direct today. a pan of beans simmering on the 1M -P MANUFACTURING CO., Inc. electric range, the housewife might Fond du Lac Ave. Milwaukee, Wis.. U. S. A. have been excused had she exhibited 3409 Spring supported, shock absorb - 'a touch of nervousness, because ing. The tube -holding element there was not a radio set anywhere ,in the house. But she did. "floats" on perfectly balanced She approached the range and stirred the beans vigorously. In an- springs. Reduces microphonic swer a whole chorus burst Into a hunting song, followed by a crooning disturbances, tends to lengthen plantation melody. life of tube, and lessens the possi- Radio experts admitted they Were baffled by the phenomenon. but bility of short- circuiting closely - pointed nut that radio music had peen heard in hot air shafts con- spaced tube elements. nected with electric furnaces. The bottom òt the pan might have acted as a diaphragm and reproduced a Y -Type, Green Top, for S Prong radio program. picked up Inductively A. C. Tubes: for mounting on by the electric power line, they added. Dealers top Of panel, $1.00; for direct Set Builders- attachment to panel, 75c. Make BIG 4. PROFITS- with Benson -A I 1 e n Red Top, for Standard UX Radio and Tele- Type Tubes: For mounting on A netos dispatch which thousands of our vision. Nationally readers have already seen. advertised lines. top of panel, 75c.; for direct Many "special buys." attachment to panel, SOc. 2,000 ITEMS B 1 g Bargain Book is 64 tributed a discussion of the possible action crannied with over 2,000 money -saving radio values. AGES At all Radio and Electrical of the salts to produce an electrolytic recti- Shows complete lines of Radio Sets. Chassises (both A. C. and Dealers and Jobbers fier in a suitable magnetic field. Battery), Cabinets, Dynamic and Magnetic Speakers, Tubes, A and IN CITIES OF STEEL B Eliminators. Benjamin Electric Mfg. Co. TELEVISION SECTION However, this fact has been ascertained- Includes television receivers, 120 -128 S. Sangamon high outfits, tubes, and parts. Get Street that an imperfect metallic contact of in on ground floor of this Chicago resistance may have "unilateral conductive gigantic new industry. properties," and consequently act as a de- WRITE TODAY New York San Francisco for this big FREE tector. (This was explained in RADIO NEWS Radio Catalog 247 W. 17th St. 448 Bryant St. for September, 1927, in an article by Pro- BENSON- ALLEN, Inc. who 456 S. State St. fessor H. Pelabon, of Lille, France, Dept. 33, Chicago, I1L AUDIO TRANSFORMERS showed that the effect is obtained with steel Think of It! A 24.00 audio transformer- 97C a genuine IUiools "aU frequency" unit of the fin- more readily than with metals of better con- est musical capability, offered direct from the factory for only 97c each. A real bargain oppor- ductivity.) In addition to this, in steel tunity. Thousands have bought them. Sold with construction a multiplicity of res- poeltive guarantee of satisfaction or money back. building Supplied in ratios of 144 to 1, 3 to 1. and 5 to 1. onant circuits must occur, as well as in pipe Order now. ILLINOIS TRANSFORMER CO, Dept. 113 223 W. Elm St. Chicago, Ill. systems, wiring systems, etc. The flow of FREE TO SET BUILDERS 0 a slight, perhaps not measurable R.F. cur- AND DEALERS To rent in any of these circuits would escape A101'eP!'OftS Set Builders observation under ordinary conditions; but NEW 100 PAGE CATALOG HAMMARLUND OFFICIAL DISTRIBUTORS One good radio idea may be worth - it is sufficient to prevent the use of certain millions. Barawik has thousands of ideas SILVER - MARSHALL KIT HEADQUARTERS for radio set builders to make more money. costly antenna systems in large cities for NATIONAL COMPANY AUTHORIZED JOBBERS Berawike Big Radio Book will help you of wave- AERO SHORT -WAVE AND DAVEN TELEVISION while elections are on and big national broadcast transmitters certain events stir the world. lengths. Not only that, but when a group We are ready to ship all kits or parts produced Send for your copy today - NOW. by the above manufacturers as well as any others tae t of buildings absorbs, partially or entirely, specified in any radio publication. BA RAW IK CO. calticAaó.S,u..nä'a the signals broadcast in their direction from 31 Years of Service to the Trade Mail This Coupon Now For Free Copy a nearby powerful transmitter, it is evident ROYAL -EASTERN PAYS THE FREIGHT Name that in their metal parts there must be cer- Lowest Wholesale Prices currents" capable of be- tain minute "eddy Send for your copy of our catalog Address ing detected. A systematic survey of a ROYAL - EASTERN ELECTRICAL SUPPLY CO. modern steel building with a delicate wave - 20 West 22nd Street, New York City, N. Y. Please say you saw it in RADIO, NEWS

www.americanradiohistory.com Radio News for March, 1929 855

tube recti_ e in Á1a ieinn 1, H tyre fra gle cgCea 1000 óour cid TrrcWo horgcrs. Mills new Elkon all - dry metallic rectifier Type U -P -8 is so designed that it replaces the wet jar rectifiers designated as Philca- tron A and Philcatron AA used in Philco Trickle Chargers, Philco "A" Powers and Philco A and B combinations. Very simple to attach, two wires to con- nect. May be done in a minute by any- one. No liquids to bother with -no attention -just satisfaction. Do not be surprised at its small size - for in its sturdy couples are packed thousands of hours of perfect service. Its compactness is one of the reasons for its efficiency. The U -P -8 is a fitting member of the Elkon family of dry - metallic rectifiers. Visit your dealer today. ELKON, Inc. Division of P. R. Mallory & Co. 350 Madison Ave., N. Y. C.

of Not a music lesson but one of the T9v°V_4 9nrópmakee many accurate processes of testing rectifiers. TncklercLargers. Elkon

Please say you saw it in RADIO NEWS

www.americanradiohistory.com 8S6 Radio News for March, 1929

meter might produce some interesting re- sults. So, also, when we find that power Adapt your Set lines, steel rails, etc., are absorbing a large HUM part of a station's power in one direction ADJUSTER (see RADIO NEWS for July, 1927, page 12) Over es million built in 1928 for -V V fives we know they are carrying the signals. by CARTER the Short We find, also, that metallic objects not in- tended for the purpose may serve as audio- frequency reproducers. One of our corre- A. P. Type A. Type spondents heard sounds from his tuning (Pot.) 75c (Rheo.) 50c condenser when at resonance with a high - power station a few hundred feet away-in- Small in size. Diameter 1t/z "; dicating the effect utilized in the electro- mounting depth '/4 ". Sturdy static speakers which we described last construction. Rheostat and month. Potentiometer In addition to the above news dispatch, Types, with or sent to us from so many sources, we publish without slotted shaft. Mounts the letters describing "mysteries" which have on sub panel. In stock in 6- reached us immediately after publication of 10 - 15 - 20 and 40 ohms. the January editorial above mentioned: and Special resistances for set The National Thrill Box will give our readers others as they are re- manufacturers. (This ceived. magazine is made up some Ask your dealer. he radio owners four to six weeks If cannot More and more satisfied in advance of publica- supply, write are pulling in stations half way 'round tion, to allow time for printing and distribu- the world with the NATIONAL tion, and therefore correspondents can never THRILL BOX short -wave receiver- see a letter in "the next" issue.) Carter Radio Co., Chicago listening to broadcasts,-yes -music and Carter Radio Co., Ltd., Toronto Australia, Java, speech, -from Europe A CHIMNEY TALKS England. Editor, RADIO NEWS: They are using the NATIONAL I was employed for several years in the ,r THRILL BOX to adapt their present Cottage Bakery at Springfield, Ohio, and THE NAME GUARANTEES set to the short -waves-it's easily looked after a boiler. One morning THE PRODUCT arranged. in the year 1922 or 1923 (I cannot be exact as to They are using the THRILL BOX for the date) as I was cleaning the flues, I Television and code reception. heard a band playing. I thought at first it Made in two types -without audio, ',BATTERY (2 tubes), and with one stage of audio, (3 tubes). ELIMINATOR Write us for particulars and prices

N AT 11 0 NAIL MONEY BACK GUARANTEE No more worry with "A" batteries or trickle chargers. 10 Hook up an R.B. TH DRY sox "A" Eliminator and forget "A" Battery troubles forever. This marvelous Invention meant better reception and more real pleasure from your set. The Short- Completely Equipped -No Extras to Buy Wave Set Write for Operates perfectly on any alternating current house wiring. Short -Wave Gives constant voltage and steady power to any set up to that brings air tubes. Completely assembled. Only two connections; Bulletin plug into light socket and connect to set. Costs no more in stations than a good storage battery-lasts forever. No upkeep cost. half way No. RN -132. Write for Absolutely Dry-No Tubes-No Acids 'round the Full wave DRY rectifier eliminates costly rectifying world. it today. tubes Beautifully finished metal case. Send No Money -Mail Name and Address

Rush name and address today for details of NATIONAL CO. INC. special bargain offer to readers of this mega. MALDEN, MASS. sine. No obligation. R. B. SPECIALTY CO. 100,00,r:M0.0C3t6:-tK-00K-o:'sC41J Dept. J -313 Cincinnati, Ohio

A boiler that not only turns itself into a horn speaker, but picks up more than local distance is This Wholesale a good "mystery," we must agree with Mr. Woolfe. Catalog SET BUILDERS was outside, but almost instantly, to my Will Save You Money amazement, I heard a voice say, "This is Write today for our large illus- GetmisBoo/Z KDKA, Pittsburgh, Pennsylvania" very trated new Catalog "B -5," show- ing how this organization of men Berswik, the first and oldest radio plain and clear. This continued for fifteen specialty house, offers you unusual with years of experience in Radio service this year. Bigger stocks, minutes or more; the music, though low, was quicker shipments lower prices. can give you personal service. Deal with an old established, reliable as dear as a bell, not muffled or periodic. house. Get honest goods, honest service, honest prices. Bsrewik service makes you There were a few times when it would cease, more money. Send now for big new Catalogehow- but when it did so, it did not fade away. ing lowest wholesale prices. AIIRed7Radio BARAWIK It would stop all at once, then come on and CO. eliCAGO u S.A. remain with full volume for five minutes or 111 W. LAKE Moil This Coupon Now STREET, CHICAGO for Free Radio Guide more. It appeared to come out of the boiler Name stack. Address The boiler was so constructed that the Insure your copy reaching you each month. Sub- fire went back under the scribe to RADIO NEWS -$2.50 a year. Experi- shell and returned menter Publishing Co., 230 Fifth Ave., N. Y. C. Please say you saw it in RADIO NEWS

www.americanradiohistory.com Radio News for March, 1929 857

I Make Sure That My Entire Family Reads "YOUR BODY " - -- There's a Reason "INVARIABLY, every time I bring home BODY. They know that it is a medium devoted I the new issue of YOUR BODY, my to the welfare of the human body and that it is makes to their advantage to read carefully every page. daughter a rush to capture it. I don't Sex, psychology, treatment of all maladies, the stand a chance of getting it back until she senses, our instincts, all are fully explained in the has digested its entire contents. Of course plainest of untechnical language. In YOUR I have to be reasonable. I realize that, much BODY there is a section for every member of the as I want to read it, the contents of YOUR family, mother, father, brother and sister. Go to BODY is of great in the newsstand today and get your copy of this value teaching her the valuable magazine. Over 112 pages -fully illus- real truths of life. I know that each issue trated-large magazine size. is practically an endless source of informa- tion on sex, prevention and care of diseases, the senses and the normal functions of na- ture as related to our bodies. All of this CONTENTS worth -while knowledge is of great impor- tance in forming a basicly firm character in WINTER ISSUE adolescent children. That is the reason I Sex Customs of Primitive Races willingly share my newspaper with my wife Is Medical Cure of Tuberculosis In Sight? and wait patiently until Madeline, having Reproduction in Men and Animals read every page, grudgingly hands it back. Control of Diabetes However, in the future, I have a little Frigidity and Impotence scheme that will make it possible for both How and Why We Get Hungry of us to read YOUR BODY at the same Sex Education time. I am going to buy two copies; then, Psychoanalysis I won't have to wait." Before the Baby Comes * * * How the Catarrh Originates This is the story that just one of our readers The Truth About Rejuvenation tells. We know that there are many more homes throughout the country where the same condi- 50c. per copy tion prevails. Our readers have found a world of valuable knowledge in each page of YOUR AT ALL NEWSSTANDS OR WRITE DIRECT

EXPERIMENTER PUBLISHING COMPANY, INC. . 230 FIFTH AVENUE, NEW YORK, N. Y. Please say you saw it in RADIO NEWS

www.americanradiohistory.com 858 Radio News for March, -1929

to the stack through the tubes. So, when I opened the door to clean the flues, the open- illU+,p i.v/. NE W! 90 Volt li ing to the stack was in front and above my r head. The stack was probably thirty feet a;N high and when I opened the doors there was L'iiii il í Power Unit more or less upward draft. \\` : I mustered up courage enough to tell some of the boys what I had heard; I knew they would "kid" me, because I was a radio fan. On this particular morning, there was no i one I could call to hear it. But, in a few days the same thing took place; I then called some of the boys and they, too, heard it, but thought it nothing unusual, as they had often heard "cross-talk" on a telephone. -in all ils phases! I tried to explain that this could not be the Complete instruction course in three case here, but that in some unaccountable volumes. Every point of aviation effic- Positively Eliminates way something was converting R.F. into iently and thoroughly treated. Subjects Hums, Line Noises, etc. $ 12. 7 5 audio waves. covered in these volumes- Greater Volume and This happened twice more, not on succes- Clarity Guaranteed sive mornings, but during probably two MODERN Non-acid and noiseless. All detector and intermediate weeks. There was no radio in the bakery, voltages plainly marked. Simpler to book up than dry nor a private residence near it where a AIR CRAFT cells Operates 1 to 12 tubes. If not thoroughly satis- fied return atter using 30 days for complete refund. radio could have been playing so that it Guaranteed further 2 years. For 110-120 volta A.C. 25 to 60 cycle current. 90 volts. $12.75: 1125§, 615.25; could be heard. Soon after, the boiler was 700 Pages 135, 617.50: 15754, 819.50; 180, 624.00; 202M, 626.00. Also built for D.C. current 110 and 32 volts at only repaired and the stack replaced, so that I 500 Illustrations 63.00 additional, any size above. Ample stocks -same day shipments. Simply say-ship C.O.D. or write for never heard it after that. my interesting literature, testimonials, etc. CARL R. WOOLFE, Contenta of each chapter - Oregonia, Ohio. I. Aircraft Types. II. B. HAWLEY SMITH lighter- than -Air Craft. 334 Washington Ave., Danbury, Conn., U.S.A. A STEAM PIANISTE 11I. Early Airplane De- signs. General Design Editor, RADIO NEws: Considerations. IV. De- sign and Construction of I had the pleasure of visiting New York Aerofoils. V. Arrange- City the week before Christmas and, know- ment, Fabrication and Bracin g of Airplane Wings. VI. Airplane Fuselage and Lauding Gear Construction, DRESIVFR Shielded ing that I would have some time to spare, VII. Airplane Power Plant Types and Installation. purchased the January RADIO NEWS at a VIII. Aviation Engine Design and Construction. Air- Cooled Engines. IX. Aviation Engine Design SHORT WAVE stand on the evening of December 20. My and Construction. Water -Cooled Engines. X. Avia- companion and I were occupying room 521 tion Engine Auxiliaries. XI. Aircraft Propeller COWER ER Construction and Action. XII. Airplane Equilib- in the Hotel York, on Seventh Avenue at rium and Control Principles. XIII. Uncrating, Set- Thirty -Sixth Street. I sat down in this ting Up and Aligning Airplane. XIV. Inspection and Maintenance of Airplanes and Engines. XV. De- 1650 room, by the steam radiator, and started to tails of Modern Airships and Airplanes. XVI. Sea- complete read your article on the " 'Mysteries' of planes, Flying Boats, Amphibians and Other Air- craft. XVII. Some Aspects of Commercial Aviation. Radio "; the time was 5:50 p. m. I had just XVIII. Aircraft Instruments and Aerial Navigation. about finished the article and was musing on XIX. Standard Nomenclature for Aeronautics COILS Report No. 240, Part I. the wonders of radio, when my dreams were This book is _- written in simple, understandable arrested by the music of a piano. language. Only Set Ordinarily, I would have paid no atten- PRICE $5.00 with a Wave- length Ranee tion to it; but, thinking that possibly it was AVIATION 15 to 550 Meters something unusual, I listened more closely ENGINES First time offered! New 1929 model -completely as- sembled; can be used on any set; built in beautiful for the music -which seemed to come from mahogany finished metal cabinet. Highest efficiency This treatise, written by a at amazingly the radiator. My peculiar action arrested recognized authority on all low price. Gets programs broadcast on of the practical aspects of abort waves by many powerful stations throughout the attention of my companion, for he in- internal combustion engine America and Europe. construction, maintenance, If your dealer cannot supply you, send money or- quired the reason. I asked him if he heard and repair. e)la the need der direct and we will ship at once. Guaranteed. as no other book does. (When ordering unit, be sure to specify whether any music, and he replied that he heard a The matter is logically it is to be used on AC or DC set.) piano. I got up and opened the window, arranged; mat- DRESNER RADIO CORP. ter expressede and MANUFACTURING only to hear the noise that comes from Sev- illustrated, so that 640 Southern Blvd.. Dept. R -3, New York, N. Y. anyone can understand air- enth Avenue at the rush hour; listened at plane engine operation and repair even if without pre- the door communicating with the next room; vious mechanical training. This work is Invaluable or went into the hall, finding nothing. I re- anyone desiring to become Don't Miss an aviator or aviator median- turned to the room and listened again to the Wan. strains evidently coming from the radiator. AMAZING STORIES 274 PACES (PRICE $1.25 I asked the clerk at the desk in the office "The magasine of scientific adventure, if there were a piano in the hotel, or a A. B. C. OF excitement and romance" radio; he replied in the negative and did AVIATION not take my account seriously. I returned At All Newsstands This book describes the basic to the room, but the music had ceased. We principles of aviation, tells how a balloon, or dirigible is heard it no more that evening and retired made, and why it floats in the I0:30, tired day. Mr, Describes how an airplane about from a strenuous I Hies. It shows in detail the fell asleep immediately; my companion at different parts of an airplane. what they are, and what they SET BUILDERS 11 o'clock woke me to say that the radio do. Describes all types of air- planes and how they differ In was going again. It continued for about construction, as well as de- tailing the advantages and GetthisBook five minutes. disadvantages of different 6:00 o'clock types of aircraft. It includes a Darawik, the first and oldest radio At next morning (the 21st) complete dictionary of avia- specialty house, offers you unusual nothing could be heard. Our train left at tion terms and clear drawings service this year. Bigger stocks, of leading airplanes. quicker shipments, lower prices. FREE 8:35 and at 7:30 we had called a taxi and Deal with an old established, reliable house. Get honest goods, honest service, put on our coats, ready to leave, when our PRICE $1.25 honest prices. Barawik service makes you more money. Send now for big new Catalog show- piano again started and again lasted for ing lowest wholesale prices. about five minutes. We will give a sworn Remit by cash, stampe, cheek; or money order No C.O.D.'. B A R AVV I K CO. CHICAGO. g s: A. statement as to these facts, and would be Mail This Coupon Now for Free Radio Guide pleased to hear if you find out any more We Pay Postage On All Books Name about this. C. E. SoMMr, D.D.S., Add CONSRAD COMPANY, Inc. Primghar, Iowa 302 FIFTH AVENUE NEW YOBS Please say you saw it in RADIO NEWS

www.americanradiohistory.com Radio News for March, 1929 859 WHO LE SIL fort/ealers, Communilq SetBuilders, General Repairmen / NEW ISSUE! and Jgenfs! JUST OFF THE PRESS! Our new, HUGE 260 PAGE WHOLESALE CATALOG No. 19 enjoys the enviable dis- tinction of being universally accepted by the RADIO TRADE in the same manner that a school treasures the Dictionary and En- cyclopedia Brittannica -or the home the Bible and Almanac!!

The preparation and distribution of this MAMMOTH Catalog COSTS A TRE- MENDOUS SUM -the huge volume of business derived from it warrants this cost I as well as the genuine pleasure it gives us to know that those "in the know" regard our G catalog AS THE OFFICIAL ORGAN OF THE 1929 RADIO SEASON!!!

P This FREE CATALOG is literally a most valuable ENCYCLOPEDIA -YOU cannot R well afford to be without one -and, you do not have to. Your request for one is all I that is needed! A day or two later, it is in your possession. Surely, a TEST 01? OUR PROMPTNESS PLEDGE!

E And we are right on the job, ready to supply television apparatus, toot We list more such parts than appear in any other Radio U Catalog. Those having No. T 18 Catalog should immediately send S for No. 19. ALL THIS PRICES HAVE BEEN REDUCED 260 PAGE TREMEN- ?75 DOUSLY! "`+'HOO KU PS RADIO 1500 We can supply any CATALOGUE parts and kits de- I LLU STRATI ONS scribed in this issue. Send for prices FREE at once I ßttfiom kadios Oldesi Orden/oase! In these many years we have been in the Radio Mail Order Business, we bave learned from EXPERIENCE bow such an organization must be efficiently run in order to GAIN AND RETAIN THE GOOD WILL OF OUR CUSTOMERS. In this, our DETERMINED GOAL, RADIO SPECIALTY COMPANY OFFERS TO SHIP ALL ORDERS IN FROM 6 TO 24 HOURS-OFFERS YOU 100% QUALITY MERCHANDISE ON A STRICT MONEY -BACK BASIS IF NOT THOROUGHLY SATISFIED -AND O FFERS YOU ALL MERCHANDISE AT ABSOLUTE ROCK BOTTOM NET PRICES! Our employees -our executives, are all pledged to handle your ever y order and inquiry in an intelligent mariner. Our 24 -HOUR SIIIPMENT SCI -IEDULE MUST BE UNRE- SERVEDLY MAINTAINED! And to this pledge, we owe our daily increasing patronage. It will pay YOU to be numbered among our many thousands of customers! A trial is all we ask! OUR CATALOGUE CONTAINS THE LARGEST ASSORTMENT OF RADIO MERCHANDISE IN THE COUNTRY. Only the most successful manufacturers' products are lisled -such fines as PILOT- SILVER -MARSHALL- CARTER-AFRO- YAXLEY- TOBE- HAMMARLUND- AMERTRAN- CUNNINGHAM- DONGAN- THORDARSON- MUTER. etc. etc. THE LATEST IM- VpSiilO`"ficW PROVEMENTS IN I:ADIO ARE LISTED AND THOROUGHLY DESCRIBED IN THIS GREAT CATALOG: A.C. ALL ELECTRIC Sets with self- cnntatned ARC power supply -Public Address Ampli- And, if we do not list in our cata- fier systems-A.C. Set Converters -A and B eliminators-Dynamic Speakers and Units- Magnetic Speaker Cheeses - 250 Tube Amplifiers - Airplane Cloth Speakers Push -Pull log your Radio requirements, WE Power Amplifiers- Electric Phonograph Turn -Tables- Combination -Radio and Electric Phonograph Consoles -Speaker Tables-Short Wave Sets and Adapters- WILL OBTAIN SUCH PARTS, Shield Tube Kits-Television Parts. BILLING YOU AT THE USUAL AFFORDTO 11E 'WITHOUT OUR CATALOG -SEND YOE O E NOW! TRADE DISCOUNTS!

98W PARK PLACE, NEW YORK

Please say you saw it in RADIO NEWS

www.americanradiohistory.com 860 Radio News for March, 1929

(The sounds heard by Dr. Sumnny seem to bear some relation, in the manner of their conduction, to others which have been heard SAVE YOUR MONEY f Potter in odd places. In this case, however, there is nothing to indicate from what broadcast BE YOUR OWN SERVICE MAN station, if any, they came. There are, how- THE RADIO Condensers ever, several transmitters comparatively TROUBLE On close to the location indicated.) FINDER THE LAMP LISTENS IN Even the highest- Watch Editor, RAmo Nzws: priced radio set Day and The effect described here is one not men- occasionally de- tioned in the article on " 'Mysteries' of Ra- velops a fault and Night dio," and perhaps not described before. One that at a time night this winter I was in the attic, using when you least GUARDING the expect it -maybe operation of the finest a three -tube regenerative set, and speaker. A kerosene lamp furnishing light was sitting right in the mid- radio receivers to in- dle of an interest- sure perfect opera- on the same table about a foot from my ing program. But, tion, making it a real musical instrument. audio end. I placed a fixed condenser across a handy copy of the "P" and "F terminals on my first The Radio is Potter T -2900 Condenser Block -" Trouble Finder the sim- ampli- audio transformer. To my surprise, the ple means for tracing every defect and for the single 250 type tube remedying manner fier- $20.00. lamp burned brighter; the flame rose about it in the easiest a quarter of an inch. I tried it several possible. There is no mishap that could Potter T -2950 Condenser Block times with same my com- befall a radio, but what is fully covered the result, and in this for the push -pull 250 type tube panion, Harold Vanzant, and I laughed valuable book. amplifier- $22.50. The Radio Trouble Finder is edited about it. The set had to be oscillating. 1 by men fully versed in the subject Potter T -2098 Condenser Block tuned in a number of stations, and then covered-men with years of actual ex- for the single 210 type tube ampli- picked up the condenser again and placed it perience behind them -and who have fier- $20.00. across the same terminals. Do you think grown to prominence since the infancy Potter T -280 -171 Condenser Block that light would do it again? And all that of radio. for a power - pack with 280 type had been moved was the dials. I was using Don't wait till your set goes bad -get tube rectifier for a 171 type tube a 6:1 Erla and a 3:1 Thordarson. Music your copy of this remarkable guide to power tube -$18.00. creeps out of my transformer without a radio trouble now. Fill in the coupon speaker. and we will send you by return mail a Potter SM -673 Condenser Block G. D. BET-minx, copy of The Radio Trouble Finder, for Silver- Marshall Power Amplifier a money -saving investment. You can and Power Supply Units- $20.00. R. F. D. 1, Dayton, Ohio. be your own service man. (It is difficult to tell here whether an R.F. or an A.F. vibration was pt3datcing Potter Interference the effect upon the lamp, from the descrip- The Copy Eliminator tion. An oscillating tube might generate 25C R.F. current which would find some reso- Your radio broadcast circuit in the of the lamp; though programs need no longer nant parts be spoiled by interference it is difficult to see how.) BUILD YOUR OWN from oil burners, ice ma- NOT 80 MYSTERIOUS RADIO SET chine motors, vacuum Editor, RADIO NEWS: cleaners, violet rays, etc. The circuit to which 150 RADIO The remedy is to con - I am introducing you nect a Potter Interference is startling, amazing and mystifying; it HOOK -UPS al- Eliminator to the inter- needs nothing but a set of headphones, This is the latest fering device. though I assure you that an aerial and issue of this re- ground will decidedly increase the volume. markable book. A. C. Supply Whenever I want to receive the same station Absolutely new Code Size Line Volts Price that my neighbor is receiving, I have but to and up - to - date. 103-03 1 x2' z4ÿ¢' 110 82.25 stick one phone tip in my mouth and hold All the best cir- 104-04 1ÿÿ:23('x4ÿ4' 110 3.00 cuits of the day. 105-05 1 %'x2'//4 'z4ÿ s 110 3.75 the other tip in my hand; and I get 'em 303-03 1' x2' x4ÿ¢ 220 3.00 distant, Full instructions 304-04 1% x2y'x4 %. 220 3.50 quite a few miles too. But the vol- on how to build. 305-05 2' x25('x43,ÿ 220 6.50 ume is increased to a marked degree when Make your own the phone tips are connected to the aerial set from the dia- and ground. I Would be glad to hear from grams shown in a fellow fan who has tried the "Parasitic 150 Radio Hook - The Potter Co. Pauper," more properly termed "Saddler's Ups. Write today -pick the set North Chicago, Illinois you want to build and make it. Then 4 NdNe.at Orseei.m ¡on at row *rate Super Simpledyne." OWEN L. SADDLER, you are sure to be satisfied with the results you get. 548 Taylor Street, Wilmington, Del. (Unfortunately, we Mr. Saddler can- 150 Radio Hook -Ups was prepared by fear the staff of Radio News. An accurate SAVES YOUR SPEAKER not raise much gooseflesh with this radio guide to better set construction for the We guarantee our Dollar Speaker Filter to re- ghost, or patent his new circuit. As Chris- lieve speaker of plate D.C.. 180 -250 volts. Give radio "fans." yours a chance. $1.00 postpaid. topher Columbus remarked, apropos of the Craftsman Radio Products, 351 Halsey St., Newark, N. J. egg he had just stood on end, "It's no mys- tery when you know how it's done." The The Copy same effect was described in an article, 25C "Wireless Radio Dancing," in RADIO NEWS MAIL THIS COUPON NOW for February, 1926 (page 1120), in which One good radio idea may be worth millions. Barnwik has thousands of ideas the editor of this magazine suggested a CONSRAD CO., INC. for radio set builders to make more money. 230 FIFTH AVENUE NEW YORK, N. Y. Berawiks Big Radio Book will help you means for employing it as parlor entertain- while elections are on and big national ment. To call it "parasitic," as Mr. events stir the world. Saddler CONSRAD COMPANY, INC. Send for your copy today - NOW does, is quite correct. The phones pick up 230 Fifth Avenue, New York. N. Y. Gentlemen: BARAWIK CO. 3ÑCcc. A. the audio field of the neighboring set. This Kindly send me a copy of 150 RADIO HOOK- úrs UPS. .. THE RADIO TROUBLE FINDER... Mail This Coupon Now! For Free Copy effect, however, cannot be detected at any (check which or both). Name great distance, owing to the low frequency, Enclosed did cents in full payment. as.explained on page 640 of RADIO NEWS for Name Address January, 1929. Nor can the phones detect Address radio waves, from either a transmitter or a City State reradiating set.- EDITOR.) Please say you saw it in RADIO NEWS

www.americanradiohistory.com Radio News for March, 1929 861 What These Have Done a YOU CAN DO! "Since I have been studying with your school 1 have been appointed chemist for the Scranton Coal Co., testing all the coal and ash by proximate analysis." F you are dissatisfied -Morlais Couzens. with your present work, if you wish to earn more money, if "I also have some news for you. I have been made you want to get into a profession where the assistant chemist for the concern I am working for. "' -A. G. Delwarte. demand for trained men is increasing as the Chemist plays a more and more important role "I am now cleaner and dyer for the above named company. My salary is almost double what it in the industrial life of this country, let us was when I started the course." teach you Chemistry. -E. H. Lasater.

" Your training has opened things to me that other- wise I would probably be years in acquiring. I now enjoy comforts that before I had to do without. It enabled me to have a wonderful little home, a You, Too, Can Learn fine laboratory of my own, and gave me a respected position in one of the foremost textile concerns in the country." -J. J. Kelly. CHEMISTRY "If it weren't jor your course I wouldn't have the iob I've got now." -George Daynes. AT HOME "Since beginning your course of study / have To qualify for this remarkable calling requires elaborate received an increa a in my pay c'eck. and as I specialized training. Formerly it was necessary to attend a progress my work becomes lighter through a university for several years to acquire that training, but better understanding." thanks to our highly perfected and thorough system of in- -M. G. Cole. struction, you can now stay at home, keep your position, and let us educate you in Chemistry during your spare time. "I am mi'hty glad I took this course. My salary Even with only common schooling you can take our course different in- has been increased several times, and and equip yourself for immediate practical work in a to me for a little advice dustrial plants are coming chemical laboratory. Dr. Sloane gives every one of his a side income." on different things, netting me fair students the same careful, personal supervision E. Van Sickle. that made -M. him celebrated throughout his long career as a college professor. Your instruction from the very beginning is made interesting and practical, and we supply you with apparatus and chemicals for performing the fascinating analyses and experimental work that play such a large part in our method of teaching, and you are awarded the Institute's official diploma after you have satisfactorily J completed the course. FORTUNES HAVE BEEN MADE EASY MONTHLY DIPLOMA AWARDED TO THROUGH CHEMISTRY PAYMENTS EACH GRADUATE Alfred Nobel, the Swedish chemist who invented dyna- You do not have to have even the small Upon graduation each student is mite, made so many millions that the income alone from price of the course to start. You can pay awarded our Diploma in Chemistry, certifying that his bequests provides five $40,000 prizes every year for for it in small monthly amounts or earn it he has successfully doing. is very completed his studies. the advancement of science and peace. C. M. Hall, the as many others are The cost Your name on chemist low, and includes even the Chemistry this certificate will be a who discovered how to manufacture aluminum, source of pride to you all your made millions through this discovery. F. G. Cottrell, outfit-there are no extras to buy with life, as well as an aid to obtaining a position in who devised a valuable process for recovering the waste our course. Write is and let us explain Chemistry. from flue gases; James Gayley, who showed how to save how you can qualify for a trained tech- enormous losses in steel manufacture; L. H. Baekeland, nical position without even giving up who invented Bakelite -these are only a few of the men your present employment. MAIL THE COUPON FOR to whom fortunes have come through their chemical FREE BOOK achievements. COMPLETE LABORATORY Clip the coupon below and mail it at EQUIPMENT once. Your name and address on the NOW IS THE TIME TO STUDY coupon will bring you by return We give to every student, without addi- CHEMISTRY mail our interesting free hook tional charge, his chemical equipment, "OPPORTUNITIES FOR Never before has the world seen such splendid oppor- including fifty -two pieces of laboratory CHEMISTS" and full tunities for chemists as exist today. In factories, mills, apparatus and supp.ies, and fifty -two dif- particulars about the laboratories, electrical shops, industrial plants of all ferent chemicals and reagents. The fitted course and what it V RN -3 -29 kinds, chemistry plays a vital part in the continuation heavy wooden box serves not only as a will do for you. ' and expansion of the business. In every branch of human case for the outfit, bait alao as a laboratory for performing countless experi- endeavor the need for chemists has arisen. Those who accessory CHEMICAL INSTITUTE now Full particulars about this special have the foresight and ambition to learn chemistry ments. OF NEW YORK, Inc. will have the added advantages and greater opportunities feature of our course are contained in our , Home Extension Division afforded while the chemical field is growing and expanding. free book, "Opportunities for Chemists." 3 16 -18-R -East 30th St., New York,N.Y 1 Please scud me, without any obligation on my part, your free book "Opportunities for Chem- NOW ! lets." and full particulars about the Experimental Don't Wait -Mail the Coupon Ala Equipment given to every student. Also please tell me about your plan of payment CHEMICAL Inc. NAME INSTITUTE of NEW YORK, ,ADDRESS N. Y. 16 -18-R -EAST 30th ST. Home Extension Division 3 NEW YORK, crry STATl'. .4 4.

Please sa.-t :voll saw it in RADIO .YEWS www.americanradiohistory.com Radio News for March, 1929

It's in the Location ! " CARE SHOULD BE (Continued from page 813) BUILT BETTER CONDENSERS AND RESISTORS I have heard rumors that large corpora- TAKEN tions holding patents will not permit the Without a Doubt more rapid development of long -range re- IN CHOOSING The Most Complete Lane of ceivers; also that manufacturers are far too Condensers E3 Resistors busy on production of low- priced jobs to LOUD SPEAKER bother about the minority who are inter- No matter what your requirements may be ested in DX. in the fixed condenser or resistor field, you Acoustic Engineers Recommend are sure to find an AEROVOX unit exactly Perhaps a word from you in your maga- suited to your needs. zine will bring forth suggestions that will Use of Book by Well -known prove of very great interest There must be Authority for Instruction Filter Blocks Pyrohm Heavy Duty Units thousands of people who, like myself, are Buffer Blocks Edison Base Pyrohms anxious to get away from the general run Socket Power Tapped Pyrohm Resistors for loud High Voltage & Universal Tapped Resistor of receivers and try out something --even "The necessity care in choosing a Transmitting "Adjustable" Units though it may prove a little costly-that will speaker cannot be over-estimated," say Condensers Wire Wound Units bridge the gap between the stations we have acoustic engineers. A radio is but the vehicle Bypass Units Center Tapped A.C. Units been listening to for years, and the stations used to bring in broadcast entertainment, the "A Power" Units Grid Suppressors we have hoped to get with every new re- true reproduction of sound depends almost Bakelite Case Non -Inductive Lavites ceiver built.-R. B. TinrBERLeKE, 1636 St. entirely on the speaker. It follows, if the Moulded Mica Grid Leaks & Resistors P. Q., Catherine Street West, Montreal, loud speaker does not meet the requirements Interference Resistoformer Kits Canada. Filters Resistor Mountings of the receiver, reception will not be at with illustra- THE CRITICAL POINT maximum. Consequently the entertainment lei COMPLETE CATALOG tions of the listener -in is often unwittingly spoiled and da- is true that commercial considerations tailed descriptions may be obtained free of It by failure to recognize the importance of a charge on request. bring about the production of more receiv- ers designed especially for local reception, good speaker in getting maximum results T h e Aerovox than of those intended for great distance; from his set. Research nevertheless there are available to the con- Education of the public in speaker con- Worker is a structor who builds his own, as to the set struction and design is necessary according to monthly pub- owner who is willing to commission a cus- these experts. They recommend "HOW TO lication that tom builder to construct a set to his liking, BUILD MODERN LOUD SPEAKERS," will keep you abreast of the latest radio de- receivers with power sufficient to bring up on written by Clyde J. Fitch, as being the most velopments. Your name coil be put the to auditorium volume any signal that can mailing list free of charge on request. efficient source from which this information be received. And it is not necessary to put may be obtained. The book is written in a up $1,800 for the purpose. style that is not only tremendously interesting 'AEROVOX WIRELESS CORD But note that a signal avast be received but also decidedly easy to read. "HOW TO Y. O--iF 78 Washington St., Bklyn., N. before it can be amplified. That is to say, BUILD MODERN LOUD SPEAKERS" is the impulse picked up by the antenna must PRODUCTS THAT ENDURE O) of kind avail- give a distinct radio -frequency voltage, sep- the most complete treatise its arate from all the other million-and -one elec- able. It thoroughly explains every known trical components which are chasing back type of speaker and gives full instructions for and forth in the antenna system, to modify building. It is well to remember that if the (through the grid -bias fluctuations) the proper speaker is not used the enthusiast plate current flowing in the first radio-fre- leaves himself open to all manner of distorted quency tube. There is a great deal said, in reception. Crackling noises, fryings, whistles every issue of every radio publication, about and squeals -these disturbances, often laid the necessary sensitivity of the detector to the set, can in reality usually be traced to TóeBigGreenBeoltgivee tube. But no signal that does not impress the speaker. Also the fact that a speaker itself unmistakably on the first R.F. stage the very lac .st detailsonAero works well one set and not with another Coils and Kits, Short Wave Radio, will ever get to the detector, or issue from with newest broadcast radio receivers. short is no reason to lay faulty reception to the set. waveconverters, telephone transmitte_s,coil kits, the loud speaker. adapters and a host of new wrinkles for 1929. "So," the experts point out, "you must under- Theoretically, we can calculate the field 24 Different New Kits strength of any broadcast station anywhere stand the speaker if you are to receive the Shown for 1929 in the world. And, theoretically, any of the maximum results from your receiver." The kits everyone is talking about are fully high could any- "HOW TO BUILD MODERN LOUD described in the new 1929 Aero Green Book - -power stations be heard Aero 7 -29 Aerodyne6-29. Chronophase, Metro- where in the world -with a set of high sen- SPEAKERS," by Clyde J. Fitch, is not only politan, Trio, International. Standard. Radio - phone-in ShieldGrid,A.C. and D.C. models. sitivity and amplification, of any of several the best source from which to obtain this Be sure to send for your copy of this 25c Big types available today -if its waves did not essential information, but also probably the Green Book- worthC5.00to aayoaewhowants with elec- to keep up with thelatest radio wrinkles. encounter an atmosphere charged cheapest. Complete, dependable data on Mail canton for your copy today -NOW! tricity and an earth full of metals and min- every speaker known in radio -full instruc- erals which absorb and reflect waves. The tions for building. All this for only twenty - 1110 PRIODUCTS1 conditions of the atmosphere are at present Z INCORPORATED five cents, the price per copy of "HOW TO unpredictable, except that we know unusual WAIL E. Ravenswood Ave., Dept. 143 BUILD MODERN LOUD SPEAKERS," CHICAGO, ILL. electrical disturbances make reception un- MAIL THIS COUPON NOW usually difficult. The radio reactances of by Clyde J. Fitch. Mail this coupon to AERO PRODUCTS, INC. Dept. 143 4611 E. Ravenswood Ave., Chicago, III. the earth will undoubtedly be some day Consrad Company, Inc. 230 Fifth Avenue, Send me your Big Aero Green Book, 25e, giving the latestinformationon What's New in radio,short wave, thoroughly surveyed, and much more New York, N. Y. etc. Nome learned about its mineral resources, as the demands on them increase. CONSRAD COMPANY, INC., We have seen, in last month's RADIO NEws, 230 Fifth Avenue, New York, N. Y. that surveying of mineral deposits is pos- Gentlemen: Enclosed find twenty-five cents, for which please send sible because each bed of conductive miner- me a copy of "How to Build Modern Loud Speakers," MASON, FENWICK & LAWRENCE als sets up a counter -force when a radio by Clyde J. Fitch. PATENT LAWYERS wave encounters it. This is measured at 600 F. ST. N. W., WASHINGTON, D. C. short range; but when the waves of a pow- Name ESTABLISHED OVER SIXTY YEARS-SEND SKETCHES Electrical and Chemical Inventions Carefully erful broadcast station are passing through Handled. Practice before the II. S. a or two thousand miles of miner- Courts and the Patent Office. thousand Address alized earth -even if they penetrate com- vtáesewegTrade -Marks Registered c paratively but a few feet -they must be City State Please say you saw it in RADIO NEWS

www.americanradiohistory.com Radio News for March, 1929 863 subject to strange deflections. There are places where the radio waves seem to con- verge, and reception is good, from many di- rections; there are others in the shadow, as it were, of the earth's radio shields, where few if any stations can be heard. WHAT RADIO ENGINEERS DO Some years ago, when WEAF's 5,000 - Yours FREE watt transmitter was located in downtown New York City, there were "dead spots" This fascinating 50 -page in this city where that station could not be book about radio's world picked up with a sensitive receiver. Two or wide opportunities. three miles away the tall steel structures of midtown New York and the rocks of Cen- tral Park formed a barrier to waves that could be received -at times -in Australia. In every large city today we have freaks of reception. The disturbing element in this case is comparatively obvious; we know its nature, at least, if we cannot pick out the particular pile of steel that is causing trouble in a single case. But the effect of the subsurface minerals is still an open field for investigation, and would well repay the establishment of a radio survey. It is rather notorious that an island in the sea, for instance, is a better place for reception, from stations on the other shores, than is a valley in the mountains for re- ception, from the other sides of the peaks. (Of course, there may be some "freak" lo- cations that will turn this rule upside down.) Reception across the ocean, other THIS QUICK WAY things being equal, is more favorable than reception overland; but a small lake is not necessarily reason for good reception. But to the point; if distant reception were to LEARN RADIO simply a question of receiver design, why should the Radio Corporation and others en- gaged in radio communication as a business Has the official approval of spend large sums on receiving stations? They must be able to pick up distant sig- the biggest Radio and Electrical nals regularly, regardless of weather, of time of day; it is a matter of dollars and Industries in the World . . . cents. They spend thousands of dollars in test work, sending engineers from point to YOUR chances for success and shore operating, broadcasting, point along the seacoast, determining what in Radio are ever so much photoradiograms and television. A places are most favored for radio reception. magnificent outlay of apparatus sup- They acquire huge tracts of land and erect greater when you complete the plied with the course gives not only aerial systems, costing many thousands of dollars, for reception purposes. If it were course of instruction given by theoretical but also expert practical possible to receive as satisfactorily by add- the Radio Institute of America. training. ing to a receiver, say four screen -grid stages, at a cost of less than a hundred dol- It's America's oldest and fore- Your success in Radio depends up- lars, would it not be madness to go to the most Radio School! It's the on the training you get. And the RIA expense which these companies incur to find only is spon- training is regarded by the entire locations and put up suitable antennas? radio school that Radio industry as the finest, most ANTENNA PROBLEMS sored by RCA, General Electric, complete obtainable. That is why Some of our readers are- of the opinion Westinghouse and National bankers, lawyers, merchants, execu- that the antenna makes little difference; "a Broadcasting Company. tives in Radio corporations are good outdoor aerial and a good water -pipe among the students of the RIA. ground," and the rest is left to the eight - or ten -tube receiver. Some can even bring Naturally, RIA graduates find it Send for the big RIA book about Ra- in (with phones, it is true) all that any easier to get good jobs. They have dio. It will be a revelation to you. It's DX listener can possibly obtain, and on two, been posted right up to the minute Free. Mail the coupon at once. Radio three or four tubes! They have "good lo- cation." in everything in Radio. Being close to Institute of America., Dept. WS-3, The ten -tube set of modern design has an the s ource ofRadio's greatest achieve- 326 Broadway, New York City. enormous reserve of power; in a good loca- ments, RIA students get first-hand tion it is impossible to use the whole of its knowledge and get it complete! 1 amplification on a signal. If the number RADIO INSTITUTE OF AMERICA, were doubled to twenty tubes, there would No matter how little you may know Dept. WS-3, 326 Broadway, New York, N.Y. Please send me your big free 50 -page book be no added gain in reception. A signal about Radio at the beginning, when which tells all about the great opportuni- must be received at the aerial in sufficient ties in Radio and about the home laboratory you finish the RIA course you may course sponsored by Radio Corporation of strength to be heard above its natural and America, General Electric, Westinghouse, artificial interference. If it is not above the consider yourself a full -fledged and the National Broadcasting Company. "noise level," nothing can be done with it; Radio expert. You will have learned because the noise amplifies with the signal. all there is to know about servicing, Name There is, however, a possibility of obtaining selling, repairing, set -building, ship Address. dearer signals by limiting directional inter- ference; as with the loop. The trouble is Please say you saw it in RADIO NEWS

www.americanradiohistory.com r OA Radio News for Match, 1929

that, to be practicable, the loop is now made small, and the signal voltage across it thereby lessened. If set owners could use loops of, say, twenty to forty feet on an edge, made of a single copper tube with low - loss construction, they might considerably improve reception; but, as we commented last month, such loops are not well adapted to kitchenette apartments. The tuned aerial, resonant to signals, has a considerably greater pick -up, especially on feeble distant signals, than the ordinary "semi- aperiodic" type. A set, however, using such an aerial, requires care and skill in operation. It cannot be snapped on like the parlor lights and left to function by itself during the entire evening's entertainment. for installing AMPERITE in -Q your radio, any one of which `V You cannot buy "location" at the radio is enough. But the one big store; you must have it on the premises. reason is that Amperite is the only self djmting fle. You can't buy distance and have it installed mentcontrot the only rests. tance tSatautomaticallystalw in quartered oak; you have to work for it- iliaes the ebb and Bow of "A" even though, if you are favored with loca- current to your tubes. Its pat- will come ented principle cannot even tion, it a good deal more easily be imitated. Don't let out- and at more frequent hours. But it may be ward resemblances mislead you. remembered, also, that some men have found rich mines in their back yards, while others, Price $1.97 less favored by good luck, have not been Order AMPERITE by name and insure the able to raise even a good dish of radishes by fine quality of performance your tubes were is designed gis their sweat. It a partial and prejudiced we live on, and nothing proves it A type for every tube, A. C. or D. C., $1.10 old planet A with mounting (in It. S. A.) at all dealers. more fully than the inequitable manner in which she parcels out sites for radio re- q rGM[LIN Sr. Nry Ynv ception. RADIO This la a gram {triteDept. RN3for ¡diagram 1788B --Amperite Blue means of modern circuits and valuable construction data -. Soil Materials Affect Lightning EDUCATION THE old proverb, that there is no telling IN 5 VOLUMES PERITE where lightning will strike next, lost dis- "SELF-ADJUSTING" Rhcartirf something of its application with the "THE RADIO covery of the lightning rod. It has been further limited by the discovery, according EDUCATOR" to a correspondent of Wireless Age (Lon- Theory, Design, Construction, don), that French tests have shown that Operation and Maintenance limestone soils are less visited than rocky or mineralized areas. This is attributed to LEARN AT HOME the fact that the air over the latter is more highly ionized; and this may also have its HESE five component effect on vagaries of radio reception at dif- T parts of a complete Radio ferent locations. Instruction Course are outlined in five volumes that contain not A RADIO PHILOSOPHER merely the essentials as so many books do, but more, they contain all that any modern up- The name "De Forest," to- the -minute textbook on any embedded in the black subject would cover. They are bakelite bases of the new in themselves a COMPLETE perfected De Forest Audions is the hall-mark radio education teaching every of recognized vacuum tube possible portion of quality. It is your assurance of Radio matchless performance in clarity, science. volume, sensitivity, and in more Size of each book 6 by 9 inches, entertainment hours. handsomely bound and illus- trated with charts, diagrams, Made in all popular types, both descriptions of equipment, etc. for A. C. and D. C. Sold by dealers Each 52 everywhere. volume pages. SEND NO MONEY for these ON THE AIR every Sunday be- books. Just forward your name tween 10:00 and 10:30 P. M. (E. S. T.) and address. We send you the -The "De Forest.Audions" -over the books at once. On receipt of nation -wide Columbia Broadcasting same you pay postman System. the $1.9 7 plus a few cents postage and then they are yours. DE FOREST RADIO CO. Distributed by Jersey City, N. J. The Consrad Co. Incorporated 1E IFOIFt IE S lr "A hook -u¢ is just like a woman. When you 230 Fifth Ave., New York, know everything's all right -it isn't!" N. Y. AqJa1aoRiS -Der Deutsche Rundfunk, Berlin. Please say you saw it in RADIO NEWS

www.americanradiohistory.com y Radio News for March, 1929 865,

RADIO - M -POWER

LITE- E VI ' u SP IO-INOOV NG SE48N0 UT. DM= TENNA ,PLEr wan CAUBR:T , TALte,alEa fi' í`./''J50j Moisture-Proof Extension Cords Write for details F/ /ltsOfORy,¡,la Birnbach Extension Cords r3 permit PER -CON RADIOCOLLAPSIBLE a- ¡sÉgr the Loud Speaker to be moved to GROUND auto Canes BAL- A perfect efficient and noiseless tao+.+.lt9uE 900 Caa any room in the house. Attaches ground Consists of three sec- instantly. Install Rimbach , a Cord tions. Drive one at a time. Easy p SI ACCUSTI -CONE and put an end to distortion so to drive. Any length required. (Double Diaphragm) often due to badly insulated cords. Contact point copper, to which is SYNCHRONIE -IN. ID-SECS Aeroplane Cloth Speaker Your neighborhood dealer has these soldered lead -ln wire. Drive in sizes in stock: 10- 20- 30 -40 -50 -100 PAUL L. CLARK, Truly a revolutionary step in ra- basement or in close places. AERIAL INS. CO. dio reproduction! Sensi for catalog. foot lengths. Send for Catalog. PER -CON MFG. CO. 590 E.ZIiST.,&toDCrR. N.Y. GREEN BAY. WIS. Accosti -Ceno Laboratories BIRNBACH RADIO CO. Richmond Indiana One No. Seventh St., Phila., Pa. 254 W. 31st St., New York

LOWEST WHOLESALE PRICES! FREE Sot Builders and Dealers! LYNCH Let the largest Radio Mail Wholesale Order House In the East Hello China: Hello TUBADAPTA serve you! You'll get better Australia; Hello service and better merchan- CATALOG New Zealand: Hello Beor dise at the lowest wholesale Send for the most com- tter Ireland; Hello Danzig, 9,0Úu prices obtainable anywhere . plete book of nationally miles away ; Hello Iceland NEW 1929 BUYING GUIDE known Parts. Kits, Cabi- 10,000 miles away. All con- TONE Your copy is ready for you. nets, Consoles. Speakers, It lists all the latest Radio Power Sets, etc firmed Reception. Most amaz- A simple Units, ing performance of any Radio Parts, Accessories, Sets and All at lowest wholesale device for Kits. Catalog K also lists prices. Quick service on Receiver ever designed U. S. using two HEAVY DUTY Stations all locals on the Electrical Supplies, House- all your needs. Write tubes hold Appliances, Golf and now, it is FREE-- Magnaformer 9 -8. Write today In parallel. For radio frequency "B" POWER- 518.50 for FREE X -RAY Wiring Complete with Tube. Delivers up Tennis Equipment, Cameras. or last audio stage. Prolongs to 180 volts on any set. Dry Traveling Bags, etc. Send Setbuilders Supply Co. D i a g r a m and Instruction Ute of tubes. - Romberg. Bldg., Chicago Sheet. no liquids. Write for literature. for your cony now. It's free. Radiart Laboratories Co. ARTHUR H. LYNCH, INC. FERBEND ELECTRIC CO. Allen - Rogers- Madison, Inc. 1012C Assn. Bldq., Chicano. 111. 1775 Broadway New York 425 W. Superior St, Chicago, Ill. 35 W. 31st St.. New York

SEND FOR NEW HERE IT IS! 200,000 RADIO NEWS readers RADIO BOOK SILVER MARSHALL carefully scan the RADIO 630 SHIELDED DIRECTORY every month. All the new hook -ups. GRID SIX YOUR product here, ab b Parts, supplies, A.C. the lowest coat in the The Radio Set with Dis- world's largest n3 most HOOK -UP WIREh sets, television, short tance and Tone to spare. widely read radio maga- THE BRAID SLIDES BACK '' zine. wave, etc. List $99.00. Write for free copy AT ALL DEALERS Your Cost while they RATE PER ISSUE 25 ft. Stranded 350 flow. last, $36.95. $25.00 25 ft. Solid 300 Red Green Yellow RAWNER RADIO & No order for less than Blue Black three insertions accepted Send 10e for sample TELEVISION CO. Write for information 142 Liberty Street CORNISH WIRE CO. Dealers. write for catalog. 11C Canal Sta., Chicago Radio News. 230 5íh Ave. 24 Church St, New York New York City W. C. BRAUN CO. 5520 Monroe St., Chicago SEND NOW This RADIO'S HALLMARK Send for for BUILD THE NEW TELEVISION We have a new illus- OF QUALITY trated catalog showing New 1929 Screen -Grid Hi -Q 29 Kits and Parts our up - to - the - minute WESTERN RADIO'S Complete re- stock of kits, parts and CATALOG celeen assem- sets everything you WORLDS LARGEST Jramma Llund bled in 15 - MANUFACTURER OF minutes.5 want in radio -- all at LATEST and FINEST, -B HIGH GRADE RADIO PARTS nationally k:town A.C. cor sToM trrrn models fro m dealers' wholesale prices. sets. consoles. cabinets. Radio 537.50 up. Write today for Catalog DISCS USED BY LEADING speakers and accessories A.C. "B -5: SET at LOWEST PRICES. and D.C. Models MOTORS MANUFACTURERS AND SPEC- Catalog sent FREE on Send 25e for NEON TUBES ALLIED RADIO IFIED IN ALL THE BEST CIRCUITS request. Construction Book AMPLIFIERS CORPORATION WRITE FOR CATALOG and other parts 711 W. Lake St. WESTERN RADIO Hammarlund- Roberts, DEDUR AMSCO CORP CO. Write for Catalog MFG. Inc. Insuline Corp. of America Dept. "B -5," Chicago, Ill, 8900 NM AOJO LAFAYETTE STS 128 W. Lake St. NEW 1182 B'way, Dept. 78 -80 Cortlandt St., N. Y. C. Kr Dept. RNC3 Chicago C, N. Y.

The RADIO DIRECTORY is your buying guide. Space permits display of only one product at a time. Write advertisers for complete catalogue More Duplicate Broadcasts an hour or so for the stations to resume af- All the Comforts of Jail area ter, presumably, an SOS? If there were op HE endeavor to increase the field only one broadcast GOVERNMENT utilities sometimes work two station in the state, the l of a powerful station by operating question would with a fair degree of co- operation in wave- be even more pertinent. The synchronized transmitters on the sanie Wellington, New Zealand, foreig countries. Where railways, tele- the "dead Radio Society re- length and program, to cover cently took up the question of asking their graph and telephone systems, post -offices and which reception in any modern spots" attend local, 2YA, to hoist a red light on an broadcast stations are operated under the of a sup- aerial city area, has led to the licensing mast whenever the transmitter unexpectedly same auspices, there is opportunity for this. five -kilowatt transmitter plemental three- to shuts down; but one humorist suggested, in- In Hungary, for instance, railway passen- Chicago. This is owned by the for KYW, stead, that a cannon be fired for the benefit gers find attached to each seat a pair of Westinghouse Company, which has operated of the listeners out of sight of the headphones which have been sealed in a and WBZA at towers WBZ at Springfield, Mass., (2YA is a five- kilowatter). sanitary wrapper. A rental of 12 cents an Boston for three years on this plan; and hour obtains the radio programs from Buda- is evidently satisfied with the general re- pest to while away the monotony of the trip. sults obtained. WGN has also been author- Mineral -Water Static to ized to use a one -kilowatt transmitter OTHER forms of static having exhausted 15 -kw. station near supplement its present their possibilities, seemingly, it is re- Elgin, Ill., covering the Chicago territory. ported from Wiesbaden, Germany, that If Kerry Doesn't Mind crackling noises and rumblings in radio re- HONGKONG'S new broadcast station, it ception are due to the action, electrical or is reported, is to work on 300 meters, "[Stand -By" Announcements radioactive, of the mineral waters under that using the call GOW, as Hongkong is a Brit- DID you ever find the set quite dead, and city which have made it famous as a health ish colony. In addition to local programs, wonder whether to start "fault -find- resort; and that such disturbances are es- the plan is to relay London programs trans- ing," as our British cousins say, or to wait pecially strong after sunset. mitted by 5SW, Chelmsford, England. Please say you saw it in RADIO NE WS

www.americanradiohistory.com f-_ 866 Radio News for March, 1929

Almost as good as a 66 Miniature Music" TUBE (Continued from page 815) 5 SETS 14'° homes. This argument may at first sight appear unanswerable, but in reality has no In beautiful walnut cabinets The Greatest Compliment that Can Be Paid weight whatever. First of all, it seems ob- Any Radio Receiver vious that the masters would have liked to THE MOST have everyone enjoy good seats (and cer- ASTOUNDING OFFER The selectivity, sensitivity, tone quality tainly not to listen from the vestibule, un- and refability of a Victoreen is positively Ever made in radio unequalled by any "production" receiver on less as a penalty for late arrival!). Sec- T.R.F. Circuit the market. ondly, it is rather futile to argue that they GUARANTEED for Tone Quality and Selectivity would not have used something new had it If after trying. out one of these sets you do nos been available to them, merely because they feel that this is the MOST WONDERFUL BUY YOU EVER SAW IN A RADIO SET, we will did not know of it. I personally would bet cheerfully refund your money in full. These pretty heavily that most of them (and the sets were taken in trade by dealers for all - electric sets. The dealers having been loaded greatest were all innovators in their day, with these battery operated sets liquidated. We remember!) would have jumped at the idea purchased them for spot cash at a tremendous the home their min- sacrifice, therefore, the reason for the ridicu- of bringing to music "in lously low price we quote. All sets tested before iature" rather than an illusion of being in we ship and guaranteed perfect. Orders will the vestibule at a concert hall. be filled in the order that we receive them. ACT Victoreen Parts Are the Standard of Quality AT ONCE. Send money order with order. It would be interesting to have the com- There is no real substitute for them, and made before body musicians, Complete equipment for 5 -tube sets $14.75 more. for what they do. Victoreen developments parison a of This includes tubes, speakers, batteries and are continually in advance of the times, yet between "miniature music" and the "vesti- aerial kit. they never are offered to the public until the bule illusion," but only on the condition that most exhaustive tests have proven their merit. Attention Dealers and Set Builders: Write for they divest themselves of all ideas as to our price sheet of bankrupt stocks of radio parta and accessories. Blue Prints and Assembly in- the so- called "naturalness" of the reproduc- structions are FREE. State tion and listen with unprejudiced minds to CHAS. HOODWIN CO. whether you wish A. C. or D. C. the "miniature music." Dept. M The heart of the new circuit is the Vic - toreen Super Transformer, vastly improved 4240 Lincoln Avenue Chicago, Ill for 1929, tuned and matched to a precision of 1/3 of one per cent. In addition, the Dealers in Bankrupt Stocks Victoreen Circuit itself contains improve- ments far ahead of its time. The Wings of Death Complete Kits Available (Continued from page 817) A. C. or D. C. Either thy Golden; but her cry was unheeded in FERRANTI The George W. Walker Company that tense moment of activity. Radio Products Merchandisers of Victoreen Radio Products The plane became suddenly visible in the 2825 Chester Ave., Cleveland, Ohio beam of the huge searchlight. It was but for Real Reception a few hundred feet away. Even as it Highest quality heavy duty audio and output transformers for power and gen- swooped downward in a long swift glide, eral purpose amplifiers. Scott snapped the switch that started the Technical data and prices sent on request. projection machine. Dorothy uttered a piercing shriek and collapsed in a dead FERRANTI, INC. faint. Courageous Harold Dare caught her 130 W. 42nd St., New York, N. Y. in his arms. FERRANTI, Ltd. FERRANTI Hollinwood - ELECTRIC, Ltd. The plane's nose dipped -downward, still England Toronto, Canada downward, directly toward the window where Harold Dare awaited it, coolly, un- flinchingly, fearlessly. In the glass of the photoelectric cells was ShancO ,sr BatteyyClip Suporphonlc7lsa world beater! An exeoptionally high reflected a score of tiny images of the grade receiver that is amingtheaz Radio World. Latest 7 tube tuned radio frequency circuit, using radio frequency dreaded death's head which had sped the amplifiers. detector and 2 stagesofaudio. Power tube can be used in last audio stage. Extremely selective,selective marvelous sen- Dare organization to its utmost endeavors. 11E Shanco Battery Clip design assures free sitivity. Single drum dial control. Straight length a roar, the speed. 1 and uninterrupted flow of electrical current. condensers permit accurate. equally spaced tuning over en - With plane picked up No springs to heat up, burn or drop out. Made of tire wave band. AU sockets spring cushioned to eliminate shot ahead; its nose lifted) and microphonic noises. Bakelite subpanel f 8'h' deep 1 insures It it powerful tension, tempered spring steel solidly minimum dielectric losses. Clear and realistic reception guar. swooped upward -clearing by a few scant riveted together. All parts electroplated before anteed. An exceptionally beautiful walnut finish, metal assembly (not galvanized or tinned), acid- resist- panel chassis. yfront feet the top of the magnificent laboratories ing. Jaws open wide and are easily applied. The mounted ready to special toolsnteeded. All hook -up wire and colored battery cable included. Value building. It turned in a slow spiral, climbed Griptite bulldog teeth "stay put" and bite right $60.00: our price $16.05. through corroded bars and terminals. Clip cannot TESTED AND APPROVED -and beautiful Dorothy Golden opened fall over and "short" your battery. Severe laboratory tests have proved the remarkable efficiency her eyes to see the dread 74 literature and prices. of this set. Owners everywhere are sending us letters praising bird of ill omen Write Dept. for free Its wonderful receptive qualities. disappear whence it had come, over the dis- SNANKLIN MANUFACTURING CO. SIMPLE WIRING DIRECTIONS Dept. 76, Springfield, Illinois Very easy to wire this set with the instructions we furnish. tant housetops. Just connect a few wires. All you have to do is to follow numbers. Simple as adding 2 and 2. Can be wired In In a few fleeting moments came a faint a few minutes by anyone. No radio knowledge needed. Make money by wiring these seta In your spare time and trembling in the air, and a dull, sullen roar selling them to your friends. was heard from the direction of the de- COMPLETELY WIRED It you would rather receive Superphomo 7 completely wired parted plane. Throbbing motors and dis- This handy book should we will be glad to have It wired for you at an additional charge of only $2.00. Please indicate on your order whether tant sirens were heard far off, hurtling go with every Radio ! or not you want Superphoulc 7 wired. toward a faint red glow which grew mo- SEND NO MONEY It is concerned with radio We ship away. mentarily larger and brighter. parts -their functions - right Upon arrival Par only $16.95 plus where they are- and a small delivery charge. (Foreign countries send $19.50 their names. It gives the with order. We pay shipping charges.) A soft, sibilant sigh broke the tension in symbols used in radio RADIO EQUIPMENT CO. the little group of watchers, and Dorothy hook -ups. so that you Dept. 12 -C, 549 S. Wells Bt., Chicago, Ill. will be able to read any Golden, from the safe haven of Harold's diagram and understand lt. It discusses air waves arms, cried triumphantly, "The fiend is -the aerial -then takes You through every radio FREEWholesale Radio CataIo finally foiled; the wings of death are part-and finally the clipped!" actual reproduction of Set Builders -Dealers! Bound. Save Money! s a a Send for the most complete book of nationally known e a a This Is a book that Parta, Kits, abinets, Consoles, Speakers, Power Unite,. will give you a full under- Sete. etc. All at lowest wholesale pprices. Quick service The morning's papers told how Dandy Standing of your set. mall your needs. Write now, it is FREE- Diavolo, while waiting ALL ABOUT RADIO PARTS SETBUILDERS to hear the explosion SUPPLY CO. which was to signify the end of his 534 a 744 Inches, fully illustrated Sept.1312 Romberg Bldg. Madison and Market Sts CHICAGO, ILL. hated On it from any newest 'rid or direct rival's triumphant career, was caught THE . CONSRAD COMPANY, INC. in the 230 Filth Avenlle New York City Please say you saw it in RADIO NEWS

www.americanradiohistory.com Radio News for March, 1929 867

explosion ensuing when his radio-controlled aerial torpedo proved a boomerang. He .4or6V'ojts was taken to a specially guarded room in the general' hospital, where he was kept ie pending the preparation of criminal charges against him by Federal authorities. "A great deal of the credit," said Harold i Dare, in a personal statement, "belongs to Scott and his men. We realized that quick action was imperative. Since the signal controlling the plane was upon the same wavelength as our short-wave transmitter, we sent out a signal which, being more Knapp powerful, overrode Diavolo's signals. The death's head was the televisor's version of the signal causing the plane to head down- A POWER ward. Naturally the opposite signal would cause the plane to rise, and this was given by reversing the film, which contained a record of. the signal, and projecting it back into a television transmitter. The reversed signal caused the plane to take a course opposite to that which brought it, and nat- urally brought retribution upon the heads of Diavolo and his henchmen. Thus (as Dor- I.Tjmproveto othy Golden phrased it) the wings of death were clipped, and right triumphed over etj°Q ps f°r °ej2 f wrong. May this be a lesson to Diavolo, volte oPer. and to all of my great public as well!" filter 3' CoEIIrut.Threere srate of4,1)d:0.011,7. brv 5 °edcf °stead What's New in Radio :.;;dent s oke Co. witch (Continued from page 819) Operates on 105 to 6' ó1a1 sek°we CoE R umlAas are plugged, as shown at the left of Fig. F. 120 volts, 50 to 60 >. ele,° cycles. p egoS V°Iraa4 Like the interchangeable windings, it is sup- 8.8a¡ to°tp 9, edPlnrs ¡Wet, ported by an insulating film and a hinge is Dé vier used to allow a variation in the coupling, 10. which is particularly helpful in overcoming wOpd t PL. Cover. the "dead spots" often encountered. These The only "A" Power Fuetead dead spots are often caused by the receiver being tuned to either the fundamental fre- Suitable for all Sets quency of the aerial or one of its harmonics. At these frequencies, the coupling is greatly tubes increased, resulting in absorption of consid- - Irrespective of number of - including erable energy; this effect can be reduced SuperHets, Short Wave and Television receivers by loosening the coupling between the pri- mary and secondary. The kit of three coils is designed to cover THE newKnapp "A" Power is designed for the most with a 125 -mmf. condenser, approximately exacting service -- super.hets, short wave and 15 -30; 27 -59; 52-.107 meters; while other coils are available extending the range down television receivers included. I knew that if it would to 8 and up to 215 meters. The exact range perform satisfactorily with these receivers that there of each coil, of course, depends on the maxi- could be no question as to its efficiency on ordinary mum and minimum capacity of the tuning condenser, and the stray capacities between broadcast signals. The three Elkon dry condensers, the apparatus and wiring. the improved choke coils and the special Elkon dry Manufacturer: Hammarlund Manufactur- ing Co., Inc., New York City. rectifier make the difference between ordinary and Knapp performance. BAR DU SNUS? LARS: "Aye tank aye bane got Los An- No Change in Price yeles last night." Even with these wonderful and costly OLE (pulling out snuff box) : "Hoh, dat improvements, there has been no ad- not bane so mooch. Aye yoost tap das fal- ler, an' aye get Copenhagen !"-John Stre- vance in price -due to the tremendous jeck (Alaska). volume going thru my plant. Remem- ber that the Knapp is the fastest selling "VOICES ARE SO DECEPTIVE" "A" Power on the market. IMAGINATION ^ - PACT KNAPP ELECTRIC, Inc. David W. Knapp, Pres. I. -Division of P. R. Mallory t9 Co., Inc.- 350 Madison Ave., New York City .p eteb.. See your dealer today st,ScQ Go to your dealer today. Most of the good ones carry the Knapp in stock. 1LpQ atgp° Atete 1PtO r Do not accept a substitute - because 3ge° ecOP - only in the Knapp will you get full Seáy0at . satisfaction as typified by the famous Knapp "A" Power. If your dealer .Amateur Wireless, London. cannot supply you send the coupon. Please say you saw it in RADIO N E IV S

www.americanradiohistory.com AMC MECLIA% ICJ'-THE BOOK OF THE AGE The greatest book on modern aviation ever published. The many ramifications of the aeronautical field that it covers can be better appreciated by a glance at a synopsis of its contents. CONTENTS IN BRIEF: Theory and Fundamental Principles of Flight. Stability -How an Aeroplane Flies. Complete Design, Construction and Assembly. Scale Drawings -Names of Parts. Flying Instructions -How to Become a Flyer. Motors-Latest Inventions-Instruments, Use and Function. Radio Installations. Gliders. Airports and Lighting. Glossary of Aeronautical Terms. The Aeroplane Mechanic. Model Making. AERO MECHANICS, written by Augustus Post, is the most complete MR. AUGUSTUS POST treatise of its kind ever published. It deals with every phase of Editor of AERO MECHANICS aeronautical construction and operation, and its entire contents is passed upon by Mr. Post, who is one of the best known pioneers Mr. Augustus Post, editor of AERO ME- CHANICS, has been prominent in aeronautical of aviation. Learn all about this kw= circles throughout the country for over great new field. Obtain your copy twenty years, his experience and adventures EXPERIMENTER PUBLISHING CO., INC. made him have aviation history and placed in Of AERO MECHANICS today. Over 230 York City, N. Y. a position to pass on to the readers of AFRO Fifth Ave., New MECHANICS honest, accurate and entirely 112 pages. Fully illustrated. dependable information on every phase of 9" x 12" size. Gentlemen: Aviation. Says the North American Re- Large Enclosed find 50e, for which please send view of Mr. Post: "No man in America me a copy of your remarkable new book, has been more continuously at the centre of AERO MECHANICS. aeronautic activities in this country, and in THE e COPY touch with more history -making airmen 5 here and abroad, than has Augustus Post Ij At All Newsstands, or Write Direct Name who besides having the "history of the air" in his head, has personally participated in some of the most thrilling adventures of Experimenter Publishing Co., Inc. Address aviation." 230 Fifth Avenue, New York City City State

Please say you saw it in RADIO NEWS

www.americanradiohistory.com r w Radio News for March, 1929 869

The Radio Beginner - -- Filters (Continued from pago 821) cancel or balance each other at the same frequency; while a third element L3 is com- mon to both circuits. 'l'he third element (which may be a coil as shown, or a con- denser) has a reactance small in comparison with that of the two reactive couples. The functioning of the circuit may be ex- plained somewhat as follows: At some par- ticular frequency Fl (at which the reac- tances are balanced) the overall reactance of the circuit including LI -CI, L2 -C2, will be zero; current will circulate through that circuit without going through L3, and the system will have zero reactance at this fre- quency. At any other frequency, the reac- tive couples LI -Cl, L2 -C2 will not be bal- anced within themselves and there will be a voltage across (difference of potential be- tween) the ends of L3. If the given fre- quency is lower than FI, the reactances of LI -CI and L2 -C2 will be "capacitive" or "Let's due to their condensers. L3 will then tend to neutralize the unbalanced capacities, pro- vided that their combined reactance is not greater than that of L3. The width of the go over to band frequencies passed depends on the re- lation of the value of L3 to the other two reactances of the circuit. If L3 is a coil, Bill's house the width of the band depends on the ratio of its inductance to the inductances L1 and L2. If it is a condenser, the band's width -his set hasn't adenoids' depends on the ratio of its capacity to those of CI and C2. is discouraging to realize In designing the coils, the coils and con- It mighty densers LI -CI and L2 -C2 are so selected that your set doesn't command the that they will cover the wavelength range same enthusiasm and respect as that required; and L3, whether a coil or a con- denser, is then designed to regulate the re- of one of your friends. quired frequency band. The coils L1 and L2 may be changed if desired, but it will be But it can be easily corrected. All it necessary to follow the specifications exactly needs is an "adenoid" operation. Sim- for L3. The coils should be shielded very ply take out the trouble-causing in- carefully in order to get the best satisfac- tion, so that LI and L2 will not be coupled ferior transformers and replace them except through L3. with one of the AmerTran audio AmerTran Push-Pull Power Stage (illustrated above) systems. completely wired with input- A MULTIPLE FREQUENCY-FILTER transformer and a choice of 4 output transformers de- Another very interesting application of With any of the AmerTran audio pending on speaker and the band -pass filter is the Somersalo tuned power tubes. Price, east of systems you will get music from your Rockies -less tubes- $36.00. filter, which was described in our February, 1928, issue. Here a different method of pro- old set that you never thought possi- cedure is used to approach the ideal tuning ble before -and it doesn't make any characteristics. By referring to Fig. 6 it how old or out of date it is will be seen that the filter is coupled, as in difference the Vreeland system, in front of a broadly either. With the AmerTran Power tuned or untuned radio- frequency amplifier, Amplifier (Push -Pull for 210 tubes) whose output is detected and amplified at audio frequencies in the usual manner. The and the ABC Hi -Power Box you can filter consists of three tuned coils LI, L2, make your old set as modern as any and L3; the coupling from the aerial coil have the AmerTran DeLuxe Audio LI to L2 is made solely through the capacity set regardless of price -and Transformer, (illustrated the above,) Standard of Excel. between primary and secondary of L2 finest toned set possible commercially. fence, 1st Stage; Turn Ratio, since the primary of that coil is open at one 3: 2nd Stage; Turn Ratio, 4. end. In actual construction, this capacity is See your dealer or write to us. Price, each $10.00. made very high by using a very large pri- mary coil. AMERICAN TRANSFORMER COMPANY The explanation given of the operation of Manufacturers for more than 29 years this filter is as follows: The capacity be- Transformer tween the primary and secondary of each 32 Emmet St. Newark, N. J. coil forms a condenser which is charged by the current circulating in the preceding tuned circuit; and the charge is directly proportional to the current. There is con- sequently a current continually flowing in the open coil, which is transferred to the next circuit (secondary) through the com- paratively large capacity between these ME&TKAN coils. The advantages claimed for this Please say you saw it in RADIO NEWS

www.americanradiohistory.com 870 Radio News for March, 1929 WILBUR C.WNITEHEAUSI IZCZV"Pjcture peaches MethodD E Drawing for partners. easilyantiy. for2coLoRsquicklPOO

WILBUR C. WHITEHEAD, the world re- nowned bridge expert, has written this interest- ing instruction course for you. BRIDGE by Whitehead is unique in that it teaches the entire game of bridge by a new and original form of illustration known as Whitehead's "PICTURE METHOD." Every hand is illustrated, each card in its proper color, red or black as the case may be. Thus the beginner, or even the most An example of the way in which each seasoned player, has an actual illustration of the hand is illustrated. manner in which the play is made always be- fore him.

Whitehead, whose reputation as the foremost authority, national or international, on the game of bridge, is one whose advice cannot be taken lightly; he knows the game as few others know it. In this book he passes on to his readers, in an easily understandable fashion, his picture method -that made him a success. Get your copy of BRIDGE by Whitehead today -100 pages -9" x 12" size. Beautiful colored cover. Each point illustrated. 50c THE COPY

At All Newsstands or write direct EXPERIMENTER PUBLISHING CO. 230 Fifth Ave., New York, N. Y.

MAIL THIS COUPON OW

r EXPERIMENTER PUBLISHING CO. 230 Fifth Avenue j Nor York, N. Y. -

Gentlemen: Enclosed find 50c, for which please send mea copy of BRIDGE by Whitehead.

Name a Illustration Address of how the play is made. City State

Please say you saw it in RADIO NEWS

www.americanradiohistory.com î?adio News for March, 1929 871 method of tuning are that the tuning de- vices are entirely separate from the ampli- fying circuits so that both may be made as Portable Phonograph efficient as possible. Because of the num- ber of individual sections of the filter, the _-- Folds band characteristic is sharply defined, as sent for explained under band -pass filters. Like a The construction of the coils for the Som- only Suitcase ersalo filter may be as follows: The primary and secondary may be wound on a single tube, with about 1/16 -inch between. The primary should contain about 200 turns of No. 30 enameled wire closely wound, and the secondary about 100 turns of the same wire, spaced at 60 turns per inch. The tubing in this case is 11,4 inches in diameter and about 41/2 inches long. Each coil is placed in a copper or other suitable shield, large enough so that a space of about an inch is left be- tween the coil and the shield. The coils S are made alike except that the primary of the first (Ll) is grounded to the shield. The The NEW tuning condensers for these coils should be Portable ganged together and a midget condenser suitcase é p oc ancryi g should be shunted across each section. handle.alk So light and con- venient-easily carried The radio-frequency amplifier is either wherevveryouwantit.

untuned, or each stage should be tun'd 'P.id costandardi onn- down derful tone and volume rather broadly, so that the advantage of se- records Covereda i m AÏAlligator togenie genuine o eíFabicod (absolutely waterproof.) lectivity with sensitivity gained by the use with Hinged new. u.i features Includedá col- of the filter will not be lost. It is desirable umn ornofIa the newest etrs Ì finestorco reproducer on the t,pe.the shield the complete in a cab- m ordulnceted hardw.prouelf a throughout, self to set metal carry without breakingor rattling. Weight 7 ..1Ootntin- inet or by using individual shields for each Records stage, to prevent a pick -up in the coils or up- -330 selecttiions.n Shpa.wat. packed comb ete about lbs. a feed -back between the various stages; the to-date coupon, $250 monthly. Tootalpricce, $24.95 coils of the filter proper must be shielded individually, even though the rest of the set is unshielded. Although this article does not cover the Selections actual design of filters of the various types, Yes, only$1.00 with coupon below. brings this portable phono- it may give a good general idea of what graph with a special assortment of 15 latest double face 75c new electric process records -30 selections in all-to your home on type must be used for a given purpose, and asyondeorfa. also help the beginner to understand just able as your own. See why coil condenser is used 30 Days Trial what a wonderful con- how and a or a venience it is to have a phonograph that you can carry from to filter mixed currents in a radio set. The room to room, place to place, wherever and whenever you rules for figuring the values of inductance want it. And the tone and volume - That you get everything in this phono- and capacity necessary are beyond the scope We Guarantee: repro- duction that a 3260 phonograph ç ngive, also theaexact reproducer, of this discussion. The various formulas the exact style of tone arm and the same grade of records. That's why you get, on this wonderful offer, absolutely the best in munie that and equations can be obtained from Circular ever days trial and and, you are not No. 74 of the Bureau of or from satisfied in send Itback at r expense and we'll refund Standards, your dollar plus all transportation charges you i an electrical engineer's handbook. But you decide to keepkee the outfit, pay only 32.50 a tie until you have paid that a The Records $25O a Month sational price on this special $11.25 worth of high sale -only $24.95. Think of it, a first class, high grade phonograph grade 75e records in- and 15 latest double face Recorda (30 selection.) s complete outfit, ready cluded in this offer. to play. only $24.95 -std easy monthly terms. besides I 30 selections -15 don. ble face records. Made by the new electric Send Coupon NOW! 40 Non -Technical process; more lifelike, Seize this opportunity while it lasts. Our supply for this more volume, less sur- special sale is limited. Send only face noise. Play long. Free Catalogg $1.00 with coupon now. Remem- Radio Articles er. Very latest popu- of home furniahingesent ber you don't risk a penny - lar songs, dance mu- on request with or with - your money back if not satisfied. sic, band and instru- out order. See coupon. every month for the beginner, the layman mental pieces. Read Send the coupon now. and those who like radio from the non- our wonderful offer. JA technical side. Straus B Schram, Dept. $osa. Chígago, Ill. Enclosed find M. Ship special advertised Puritone Portable Phonograph SCIENCE AND INVENTION, which can with 16 Double Face 75e New Electric Process recorde -30 selections. be bought at any newsstand, contains the I am to have 30 days free trial. if I keep the outfit, I will pay you $2.60 largest and most interesting section of monthly. If not satisfied, I am to return the phonograph and records radio articles of any non -radio magazine within 30 days and you are to refund my dollar and express charges I paid. Punitone Portable Phonos/mph and 15 Double in existence. Face Records, W3136WA, $24.95 Plenty of "How to Make It" radio arti- cles and plenty of simplified hook -ups for Name the layman and experimenter. The radio Street, B. F. D. section of SCIENCE AND INVENTION or Boa No is so good that many RADIO NEWS Shipping readers buy it solely for this feature. Point Post Office State -- Radio Articles Appearing in Straus B Schram brasglee o aCóter SCIENCE AND March 1063, : Dept. Chicago, W. If you want only our FREE catalog of home furnishings, mark X bere ti INVENTION Magazine

RADIOS 20,000 MILES TO TALK TEN MILES CODE LESSONS FREE DYNAMIC SPEAKERS OF LATEST ,Alts inn ls- with each DESIGN -By Paul L. Welker GEARS... In Your Home. Teleplox Code The m st accurate nade and prices Instructor wo furnish complete code In- A STATIC RECORDER structions. Lessons recorded on waxed-tape reasonable. We Cory a complete clear. NEW RADIO DEVICES line of gears in stok for immediate records make everything simple and shipment. Can also quote on special Teleplox reproduces actual sending of ex- RADIO ORACLE gears kinds. Send pert operators. Sends you messages, of all us your radiograms, etc., just like an operator WRINKLES Inquiries. Navy and RADIO Write for Catalog 40 would. Endorsed by V. S. LATEST PATENTS leading schools. Write for booklet NR. Chicago Stock Gear Works TELEPLEX CO. 11$ Se. Jeaerson 5., Chicago 76 Cartlandt St., Now York, N. Y. se,romaeuwa,,,,,ne,,,,,,,,,,,,,.,,1.,.1,,,.,,,,,.,,,,,,nn.ae,m,m,,.eawee,,,,,.,,,,.,,-,,.,,,,.,...c

Please saY .. òu saw it st RADIO NEWS

www.americanradiohistory.com 872 R..,T,., ATarr,e f.,,- AA . l, 10711 Tube Characteristics (Continued from page 823)

22-type (15 -volt A.C.) Use, voltage amplifier (not power); Socket, UX -type; Since Filament voltage 15 raw A.C.; current 0.35 -am-, pere; any radio, Plate voltage 135; current 1 mla.; old or new, Grid bias, control -grid 1 volt, screen -grid 30; A.C. plate resistance 700,000 ohms; is only just Amplification factor 400 (theoretical). The difference between ex- as good as cellent radio and medi- "OVERHEAD-FILAMENT" A.C. TUBES ocre radio is a matter of the tubes in precision - the proper bal- its sockets, Still another type of A.C. tube is familiar ance between all values concerned. to many because of its distinctive "over- And resistance, accurately arrived it is clear head" construction; the terminals of its at by test, is the most precise how cathode heater are brought out from the balancing means. All of which spells vital a tube through a bakelite top; while, though point perfectly bal- four prongs are in the base of the tube, only three of these are employed electric- anced tubes are. the precision variable resistance The brand of radio ally. One is connected to the grid, a second available in many types, ranges to the plate, and the third, which provides and capacities for every radio use. tube is just as import- the grid return for the circuit, to the heater - Ask your dealer about Clara- ant as the "make" of filament. These tubes differ from the others stets. Or write the set. which have been described in that they re- us for literature. quire a three -volt A.C. supply for the fila- Better still, ment. send 25e in Insist on stamps or coin e 401 -Type (Overhead Filament) for this book- 20,000 words, Use, detector- amplifier (not power amplifier); 88 illustrations, Socket, UX -type (filament connection through of radio dope! RADIO / TUBES special cable); Filament voltage 3 raw A.C.; current 1 ampere; CLAROSTAT MFG. Plate voltage 150; Co., INC. for Clear Grid bias 4 4 to 9 volts. Specialists in Radio Aids 403-Type (Overhead Filament) 281 N. 6th St. Brooklyn, N.Y. Use, power amplifier; Reception Socket, UX -type (filament connection through cable) ; Filament voltage 3 raw A.C.; current 1.5 am- peres; Plate voltage 180; Grid bias 40 volts.

DEPENDABLE "B" BATTERY POWER RECTIFIER TUBES Rectifier tubes are divided into three classes; the first, gas -filled, filamentless, full-wave rectifiers; the second, high -vacu- "Radio's largest-- um, electron - emitting - filament rectifiers, comprising two half -wave and two full -wave hit supply house rectifiers. With the latter, it is necessary to provide a supply of current (usually ,ESTABLISHED3OYEARS from a low- voltage secondary on the power transformer) to heat the filaments; this is We Have Complete Kits FOR ALL CIRCUITS unnecessary with the first type. The third Now appearing or which have appeared 100 Volt Edison Element. comprises gas-filled tubes with filaments. in "Radio News" and other publications. Non -Destructive, Rechargeable "B" Battery with charger. Shipped dry, with solution. $12. 140 Volt Three types are offered in the first Dealers and professionals with charger, $17. 180 Volt Power Unit, with Trickle Charger. $24.00. (gaseous) classification, all using UX Set Builders, write for our SEND NO MONEY -PAY EXPRESSMAN sockets; the first is a moderate -power full - Write for our Free Literature NEW WHOLESALE CATALOG SEEJAY BATTERY CO., 915 Brook Ave., New York wave filamentless, rectifier designed to sup- ply plate voltage for a standard radio re- Hi -Q 29 Kits in Stock ceiver using no tube of heavier duty than the 112A -type. This is known as the "B" Silver Marshall Kits type and has an output rating of 60 milliam- Wholesale peres at 150 volts, with a maximum allow- National and Aero able input A.C. voltage of 275 per "anode" Short Wave Kits Prices (positive electrode). Convert your present set to the low -wave bands. Tremendous stock and sales vol- The next in this class is the "BH" type, ume, with rapid turn -over to the a heavy -duty full -wave rectifier having an Amertran thousands of radio dealers we Power Equipment serve enables us to make you output of 125 milliamperes at 300 volts. worthwhile savings at lowest This tube will rectify sufficient current to Write for FREE BLUE PRINT wholesale prices. Write for lat- supply the plate requirements of a standard for the new 250 push -pull power amplifier. est, new illustrated Catalog "B -S" receiver using the 171A -type amplifier in M. & H. Sporting Goods Co. the last audio stage. The transformer-sec - Am 512 ondary A.C. voltage may be as high as 325 Market St., Phila., Pa. per anode. The rectifier in this series was de- 711 W. LAKE STREET, CHICAGO third signed to supply "A," "B" and "C" voltages Don't Miss to series -filament receivers using quarter- AMAZING STORIES Quality Apparatus ampere tubes; its rating is 350 milliamperes Our latest bulletin No. 929 describing our com- "The magazine of scientific adventure, plete line of quality apparatus is yours for the at 200 volts. Known as type "BA," this asking. Write for it today, tube has a maximum allowable input A.C. excitement and romance" GENERAL RADIO CO. voltage of 350 per anode. 30 State St., Cambridge, Mass. At All Newsstands Please say rau saw it in. RADIO NEWS

www.americanradiohistory.com Radio News for March, 1929 873

FILAMENT-TYPE VACUUM RECTIFIERS In this class, the high -vacuum, filament rectifiers, are found four types, the 280 - type, a full-wave rectifier, the 281- type, a half -wave rectifier; the 213-type, a full -wave SHORT WAVE HEADQUARTERS rectifier for a full -wave circuit; and the 216B -type, a half-wave rectifier for a half - Aero International Short or a full-wave circuit. Wave Receiver 213 -Type (Full-Wave Rectifier) This Is the first short wave receiver Socket, UX -type; designed exclusively for the reception waves. Broad- ú 5 ' Filament voltage 5, current 2 amperes; of broadcast on low (I ü short waves is re- Plate voltage 220 A.C. maximum (per plate); cast reception on If you wish to purchase only the Aero markably clear and free from static. Coils for the Aero International. order D.C. output (both plates) 65 milliamperes maxi. Programs come in from greater dis- the L. W. T. 10 Kit. The price is mum; 170 volts at maximum current, as ap- tances with the utmost simplicity Of $10.50. These coils are designed to be plied to average filter. control. Complete kit includes every- used with our foundation unit. thing necessary to assemble the set. 216B -Type (Half -Wave Rectifier) Aero Kit No. 8-Price $55.30 Socket, UX -type; Filament voltage 7.5; current 1.25 amperes; Plate voltage 550 A.C. (maximum); Aero International Short Wave Converter D.C. output 65 milliamperes (maximum); D.C. Will add thousands of miles to your receiving range. Broadcast reception on output 470 volts at maximum current as applied short waves Is remarkably clear and Ina from static. Programs are brought in with utmost ease. Build the Aero and receive short- to average filter. from greater distances If you prefer to furnish your own founda- wave programs on your present set. Nc changes in wiring necessary. Just plug tion unit for the Aero International. 280 -Type (Full-Wave Rectifier) into detector socket. order the L. W. T. 11 Kit. The coils UX -type; are the same sa in the L. W. T. 10 Kit. Socket, Kit No. 9 -Price $38.90 but a mounting strip is provided. The Filament voltage 5; current 2 amperes; price is $11.50. Plate voltage 300 A.C. maximum (per plate); D.C. output 125 milliamperes maximum (both Aero Standard Short Wave New 1929 Receiving Coils plates); 260 volts at maximum current, as ap- Receiver Designed f o r plied to average filter. the new ama- A three -tube short -wave receiver of the tour 20, 40 and 281 -Type (Half-Wave Rectifier) standard time -proven regenerative type, -..; e - meter Q' bands, for use Socket, UX -type; brought to its greatest perfection. New with .00003 Filament voltage 7.5; filament current 1.25 improved Aero Interchangeable Coils condenser, in- am- cluding Plug- peres; assure maximum selectivity and sensi- in base with Plate voltage 700 A.C. (maximum); tivity. Either for A. C. or D. C. new design ad- Tubes. justable space- D.C. output, 65 milliamperes recommended; 85 wound primary. milliamperes maximum; voltage maximum 620, Kit No. 10 for A. C. Tubas, $49.95; Complete Kit, as applied to filter of average circuit. L. W. T. 13, No. 11 for D. C. -Price $49.95 3 coils, $12.50. Single rolls FILAMENT GASEOUS RECTIFIER TUBES 8.2 to 12.6- Aero Standard Short Wave Converter meters; 19.1 to These are of the hot-cathode gas -filled rec- 27.6 meters; 34.4 to 48.6 meters: 61.6 tifier type containing, at low pressure, the No extra tube is needed. Plug into detector socket of your receiver and insert to 90.2 meters, $4.00 each. L. W. T. the tube which you removed from set Into the Converter. Kit is complete with Plug -in base, $3.00; .00003 Con- denser., $1.50, inert gas argon (found in small quantities all parts. Can be assembled in a few minutes. in which is ionized the atmosphere) by the Kit No 12 for D. C. Tubes, $32.00; Kit No. 14 for A. C. Tubes....$32.00 New 1929 Transmitting Coils emitted electrons from the incandescent In accord with filament. This ionized gas acts as the prin- Aero Short Wave Radiophone Transmitters 1 9 2 9 practice. Por either the man who wishes to build his first low -power transmitter and First use of cipal current-carrier, with the result that become initiated in the mysteries of round the world" communication. or for plug-in the bulb operates with very low voltage - the dyed -in- the -wool amateur who waists to purchase all the parts for a high highh power a powered installation from one source. Aero Transmitter Kits offer a means of to 15 amperes. drop (3 to 8 volts) and is capable of pass- obtaining reliable parta in a circuit in which all Heavy aluminum constants are properly coordinated. carries 500 watts ing a current of several amperes; the cur- Aero Complete Kit No. 55. as illustrated-4185.00 safely. New ma- For those who want a Code Transmitter only, for terial space bar rent limit depending on the design and size battery .operation, another kit is supplied con- superior to glass. taining tre oscillator only. Many new fea- of the tube. Two elements make up the in- tures. For use ternal construction Aero Kit No. 56 -Price $95.00 with 440-mmfd. of the tube; the cathode AERO I.IT No 52-A high -powered unit for condenser. Kit (lower electrode) consists of a filament of C. W. operation using 852 tubes or in connection of 2 coils with with Kb. No. 55 constitutes a 200 -watt phone plug-in mounts, small tungsten wire coiled into a closely transmitter. When used in this way, two UX -860 16.5 to 45 me- tubes are employed. Price on application for above ters, $15.00; 39-88 meters, $15.00. wound spiral, and the anode (upper elec- and other- high -powered transmitters. Single coils, less mounts. $5.50. trode) is graphite of relatively large cross - section. Get the Big Green Book-Mail Coupon Aare Products, Inc., 4611 E. Ravenswood Ave. The tube rectifies because, on the half - Dept. 139, Chicago, Ill. Please send me a copy of your 25c Aero Green Book cycle when the graphite anode is positive, moot showing 64 pages of newest modem circuits for short wave the emitted electrons from the heated fila- opt)INCORPORATED and broadcast receivers, transmitters, coils and kits. ment are being pulled toward the anode by 4611 East Ravenswood Avenue Name the voltage across the tube. They collide St. á No with the gas molecules ionize Dept. 139, Chicago, Ill. and them; City State that is, make them conductive in the direc- M SMBa tion from anode to cathode. During the other half of the cycle, when the anode is negative, any electrons that are emitted are driven back to the filament; so that the gas "The 'Best is The Cheapest" in the bulb is non -conductive during that -Benjamin Franklin half- cycle. =URA pennies invested in the best obtainable These tubes have been designed primarily condensers pay handsome dividends and using for heavy-duty work such as storage- battery second rate condensers is poor economy. chargers, rectifiers for "A" power units and Cardwell Taper Plate Condensers are sturdy,vib- commercial needs. They are available in rationless, hold their calibration indefinitely and the both half -wave and full -wave types; the for- purchase price includes satisfaction insurance. mer, which has been described above, is in Good enough for the biggest of the big boys -fel- most lows like the G. B., R. C. A., and Uncle Sam, and if common use and is produced in three they don't know who does? Gold plates and funny current ratings; the smallest is a 0.6- ampere jim- cracks may look impressive, but they don't type designed for trickle chargers using a TAPER PLATE -Type 151E influence the fellows who know their condensers. o r v e Recwóere half -wave rectifier circuit. It requires a Idead f Short W a W R I T E F O R L I T E R A T U R E filament current of 6 amperes, and a trans- THE ALLEN D. CARDWELL MFG. CORP. former- secondary "pick -lip," or "starting" 81 PROSPECT STREE'C BROOKLYN, N Y. voltage of 8 to 12; it requires a transformer the secondary of which must deliver at least 25 volts for a 6 -volt storage- battery load. Insure your copy reaching you each month. Subscribe to Radio News-$2.50 a year. The 2- ampere type requires a filament Experimenter Publishing Co., 230 Fifth Avenue, N. Y. C. Please say you saw it iss RADIO NEWS

www.americanradiohistory.com 874 Radio News for March, 1929 Prices Slashed! Order Today! OFFER MAY BE WITHDRAWN IN THIRTY DAYS

ZIour Favorife MagazinesIk'a at . No. 30 ecordMahn .Deductions. THE GRADE A" SPECIAL, YOUR CHOICE OF ANY ONE OF THE FOLLOWING:

RADIO NEWS 1 Year AMAZING STORIES ALL 3 OR . . RADIO NEWS . ONLY SCIENCE & INVENTION 1 Year SCIENCE & OR AMAZING STORIES 1 Year INVENTION $5 75 AND ANY ONE OF THE OFFERS LISTED BELOW:

1 . ( ALL Both for OFFER 3 Offer No. only YOUTH'S COMPANION 1 yr. ONLY 8- AMERICAN BOY 1 yr. 51.00 PICTORIAL REVIEW 1 yr. $5.25 9- AMERICAN MAGAZINE 1 yr. 4.50 10- BETTER HOMES & GARDENS 1 yr. 2.85 OFFER 2 ALL 11 -CHILD LIFE 1 yr. 5.60 12- COLLEGE HUMOR 1 yr. 4.00 GOOD HOUSEKEEPING 1 yr.3 ONLY 13- COLLIER'S WEEKLY 1 yr. 3.75 14- COSMOPOLITAN 1 yr. 4.75 MODERN PRISCILLA 1 yr. I. $6.25 15- DELINEATOR 1 yr. 3.00 16 -ETUDE (for music lovers) 1 yr. 4.00 3 ( ALL OFFER 17 -EVERY CHILD'S MAGAZINE 1 yr. 3.50 COSMOPOLITAN 1 yr.iON3LY 18- FOREST & STREAM 1 yr. 4.00 19 -GOOD HOUSEKEEPING 1 yr. 5.50 1 yr. . $6.25 MODERN PRISCILLA 20- LITERARY DIGEST 1 yr. 6.50 ALL 21- McCALL'S MAGAZINE 1 yr. 3.00 OFFER 4 ( 22- McCLURE'S MAGAZINE 1 yr. 4.75 23- MODERN PRISCILLA 1 yr. 3.50 REVIEW 1 yr.) ONLY PICTORIAL 24- PATHFINDER 1 yr. 3.00 McCALL'S MAGAZINE 1 yr. $4.00 25- POPULAR SCIENCE MONTHLY 1 yr. 4.50 26- PICTORIAL REVIEW 1 yr. 3.00 OFFER 5 ( ALL 27 -SMART SET 1 yr. 5.25 28- YOUTH'S COMPANION 1 yr. 4.2$ PATHFINDER 1 yr. {orrLY MODERN PRISCILLA 1 yr. $4.40 EXPERIMENTER PUBLISHING CO., Date 230 Fifth Ave., New York City. 6 ( ALL OFFER Gentlemen: I am returning this coupon with $ AMERICAN MAGAZINE 1 yr.j yNLY for which I am to receive your OFFER NO. and McCALL'S MAGAZINE 1 yr. l $5.50 PUT X IN BOX D RADIO NEWS 1 yr. OFFER 7 r ALL OPPOSITE YOUR D SCIENCE & INVENTION 1 yr. CHOICE. D AMAZING STORIES 1 yr. DELINEATOR 1 yr.ioNLY MODERN PRISCILLA 1 yr. , $4.50 NAME BIG FAMILY BARGAIN No. 29 ADDRESS MOTHERS HOME LIFE 1 yr. ALL ILLUSTRATED MECHANICS 1 yr. CITY STATE TODAY'S WOMAN & HOME 1 yr, 7

HOUSEHOLD GUEST - 1 yr. ONly POULTRY TRIBUNE 1 yr . IF THE MAGAZINE YOU ARE INTERESTED IN IS NOT AMERICAN FARMING i yr. $3.00 LISTED HERE, WRITE US FOR COMBINATION PRICE. Please say you saw it in RADIO NEWS

www.americanradiohistory.com Radio News .. f or March, 1929 . 875 current of 12 amperes, a "pick -up" voltage of 9.5 to 15, and a transformer-secondary minimum of 30 volts at 6 -volt storage-bat- tery load. The 5- ampere type requires a filament current of 18 amperes, a "pick -up" voltage of 11 to. 16, and a transformer-sec - ondary minimum of 30 volts at 6 -volt stor- age- battery load. Both 2- and 5- ampere tubes are of the half-wave type. The full- wave -rectifier tube differs from the half -wave type only in the addition of another graphite anode; thus giving an in- Townsend 'B' Power units ternal construction consisting of a heavy tungsten -wire filament and two graphite must be anodes. However, this tube is used on rare Now in Use --they good! occasions and so may be difficult to obtain. All the above -mentioned tubes make use of the standard 110 -volt screw -lamp socket for They ARE good! Besides Full tone, clarity and volume, you get the thrill of startlingly clear long - the base through which the filament leads distance reception. Never in radio history has any- are brought out. The anode is brought out thing given such sensational results for such a low through the top of the glass bulb in the price. UNSURPASSED QUALITY built in with form of a projection of heavy wire, to which money saved by unified production methods and low connection is made by means of a spring - merchandizing costs. New thousands of set owners dip binding post, which is in turn connected learning amazing value of this Unit. to a flexible lead. Utmost economy and convenience. Plug into light 100 on any REGULATOR TUBES socket and forget it. Delivers up to volts set on D.C. or A.C.-any cycle. YOU TAKE NO The 874 -type tube is a voltage- regulator RISK. Sold on real GUARANTEE -it must tube designed to maintain constant voltages satisfy or money paid us will be returned. supplied by "B" power units at different APPROVED current drains. The tube has two elements, Fill in coupon and send with SEND an anode and a cathode, contains a low- ONLY $1.00 only $1.00. Prove this marvel- and passed by the and rigid laboratory tests pressure mixture of gas. It maintains a ous value to yourself. Use it t n days. Then if it fails paid us of "Popular Radio" constant potential of 90 volts to the radio to do everything we say, return it and money will be refunded. a REAL receiver of your set. and "Radio News." receiver. (See page 852.) Make The 876- and 886 -type tubes, on the other From n hand, are designed for maintaining con- stant the current to radio sets operated This Month's Mail Eliminator bought from you from A.C. house lighting circuits; the for- about eighteen months ago is still giving first -class service. mer 1.7 amperes and the latter 2.05 am- and I haven't had to touch it since I put it into service. It peres. The useful property of these tubes has given me the best radio is that, within their rated voltage range, Programs I ever experienced on the my five -year -old set and I current through them remains approximately wouldn't swap for the best all - electric set made. constant. Such a tube should be used only Ralph Dunham, Portland, Me. in a circuit especially designed for it, and Words cannot express how well must satisfied I am with your Elim- never be placed in a lamp- socket on inator on my 6 -tube Super- Me house -lighting line. Heterodyne. Minnie Schade. Ashton, Ill. 874 -Type (Voltage -Regulator) Your Eliminator after two years Socket, of service is still going strong. UX; G. Markwick, Hamilton, Ont. D.C. rated voltage, 90; Starting voltage, 125; Your Eliminator sure has been worth the money many tines. Maximum current (direct) 50 milliamperes. H. D. McConnaughey. 3 -29 Black Lick. Pa. 876- and 886 -Types (Current -Regulator) TOWNSEND I Have been Eliminator IABORATORIES' Socket, large ( "Mogul using for Ucer. ") screw type; almost a year and find it most Attach only 25, Operating amperes, 876 -type, 1.7; 886 -type, 2.05; satisfactory. Sure cute the 713 Townsend St., Chicago, 111, Voltage. range, 40 to 60. cost of B" power to very 18. 1 little. W. M. Pearce. to this Gentlemen: Attached and $1.00. Walker. ilia, Mont. Kindly send at once Townsend 11" Socket I TELEVISION LAMPS coupon Power Dlu9 Doetage, Your Eliminator bests any on guaranteed 10-day Free ria4 $30.00 one I have yet seen. rs ` Under this head conte the tubes used in E. M. Barrett, reproducing televised images at the receiver; West Graham, Va. -' Name.. they were formerly known as Have had your Eliminator for Ì Address "neon -gas over a year and get wonderful glow-lamps," but the new designation was results on my Diamond of the Air. James Bleckie, p City State decided upon by the Television Toronto, Ont. I, Committee . tt taa tt a att saat aat a saat sa\ a alt of the Radio Manufacturers Association. t t t These tubes should be used in the plate cir- cuits of 171- or 210 -type tubes, in order to obtain best results; also, they require a series resistor to prevent excessive current Travel on from reaching them, and a minimum direct - "Uncle Sam's" Payroll current voltage of 180, independent of the plate voltage applied to the last tube in the RAILWAY POSTAL CLERKS ammo MS NM MI audio amplifier. Gradual blackening of the COUPON 4r e-- FRANKLIN INSTITUTE bulb indicates an excess of direct current Dept. N181, Rochester, N. Y. MAIL CARIIERS Sire: Rush to me, WITHOUT passing through the lamp. CHARGE. FREE 32 -page book with $1700 to $3000 Year list of U. S. Government positions open Television Lamp to men and women, sample coaching, and full particulars telling how to get Socket, Many U. S. Government Jalo Obtainable them. UX -type; SHOULD Plate 180 volts D.C.; maximum current 20 mia., MEN - WOMEN, 17 UP MAI COUPON Name while 10 is recommended. (Current is gener- Steady Work No Layons Paid Vacations /Address ated by. output of amplifier, not by television lamp.) PHOTOELECTRIC CELLS

These tubes may be considered the "eyes" Insure your copy reachi fg you each month. Subscribe to Radio News -52.50 a year. of the television transmitter; for it is their Experimen ter Publishing Co., 230 Fifth Avenue, N. Y. C. Please say you saw it in RADIO NEWS

www.americanradiohistory.com 876 Radio News for March, 1929

function to convert into electricity the fluc- toelectric cell explains its use in light- tuations of light reflected from the subject recording apparatus, fire -alarm systems and I ndi vidual, Independent being televised and send them on to the other commercial applications where light is transmitter, where they are converted into required to operate a mechanism. These' Spe aker Volume Control radio waves and sent out like voice or mu- cells are manufactured in two types; those, sic. These impulses, by now familiar to of the high -vacuum volt- The Centra- type require a high lab Constant many listeners, when received on the loud age, about 600 volts D.C. for best results. Impedance speaker sound very much like dot-and -dash The proper voltage for the gas-filled type, Volume Con- code signals with very rough notes, except is found by exposing the cell to the maxi- trol is the that they are all dashes. In mechanical mum light to be used and gradually increas- only unit form the cell usually comprises a light -sen- ing the applied voltage until "ionization" that allows a sitive coating on the inside surface of the occurs. This voltage is noted, and a poten- number of glass, and a metal electrode facing this tial about ten lower is selected as the opti- speakers op- coating. While no light is shining on the mum to be applied. One stage of audio- erated from the same am- cell, no current will pass between the coat- frequency amplification is required for ex- plifier to be ing and the metal; but, as soon as the cell perimental operation of the cell; the re- controlled in- is excited by light, an electron- stream, the quirements for commercial application de- dividually intensity of which depends upon that of pend upon the duty of the photoelectric without af- the light, will pass from the coating to the apparatus. As the manufacture of these fecting the metal element, thus dosing the circuit. cells is not yet standardized, characteristics Constant Input other speak- This description of the action of the pho- are not given here. Resistance. ers in the LIST PRICE Circuit. It $3.00 is a dual re- sistance unit with one resistance shunting the The "Candy -Box Special" Short-Wave Receiver speaker for volume control and the other resistance in series with the line. (Continued from. page 839) Adjusting the knob varies both re- goes to the P connection on the socket for Coil 3: Grid and tickler windings, each sistances so that while one short cir- the audio-amplifier tube V2. These three 15 turns; range 85 to 45 meters. 1 cuits the speaker to control volume, a hole in the windings, the other resistance is added to the wires are led out through Coil 4: Grid and tickler eats line, maintaining a constant imped- back of the metal box. 22 turns; range 45 to 64 meters. Tickler ance. Easy to install, smooth and ef- Insulated wire should be used for all the wound double -layer to save space. ficient in operation. Send for inter- connections inside the box, to avoid short Coil 5: Grid and tickler windings, each esting booklet of picture and wiring circuits against the metal. It may be a 40 turns; range 62 to 110 meters. Tickler) diagrams, "Voltage and Volume Con- bit difficult to solder some of the wires, also double layer. The tube base itself ir, 1(1trols -Their Use." because of the cramped arrangement of the too short for this coil, but may be made to parts, but if the wires are held in place serve the purpose if it is wound with a few, with a pair of long -nosed pliers the work layers of thick paper to form á tube about can be accomplished successfully. two inches long. The wire is then wound 20 Keefe Avenue over the paper and will hold it in place. Milwaukee, Wis. THE PLUG -IN COILS The grid coils are all wound with No, In the matter of coils the constructor has 24 wire, and the ticklers with No. 26 or some choice. The writer happened to have 28. It makes no difference whether thd on hand a set of four factory -made coils grid coil is near the prong end of the tube) consisting of two-inch lengths of molded base (as in the coils illustrated on these bakelite tubing 1% inches in diameter and pages) or near the top. If the former ar-i equipped with four prongs to fit a standard rangement is used, the start or bottom UX -type tube socket. Coils of this type the grid winding is soldered to the G ping are widely sold, and are very cheap. If of the tube base, and the end of this same] the reader can obtain blank forms of ap- winding goes to the left F post. The start proximately these dimensions, he can wind of the tickler winding (which is spaced his own coils, using the data contained in about a quarter of an inch from the end a sketch on this page. The coils illustrated of the grid coil) goes to the other F post; herewith are designed to cover the usual and the end of the tickler to the P post. -wave bands with a .0001 -mf. tuning t short ANTENNA COUPLING CONDENSER r POLK condenser. POST If the constructor wants to follow the In the schematic diagram an antenna 15 Cts. r Insulated. No holes to original "Junk Box" idea, which has proved series condenser, C4, is indicated. This Each = fish for. Insert wire in he can use tuning and may be of the "postage stamp" variety, any position. Quick ac- immensely popular, tion and holds tight. regeneration condensers of 32 -mmf. capacity such as used for neutralizing purposes in; Standard markings. and coils wound on the bases of old vacuum sets of the neutrodyne type. It may J. L. POLK tubes. For the benefit of those who missed screwed to the back or right side of the 41 Belle Ave. TROY, N. Y. the articles on the Junk Box or haven't the box, and once adjusted, requires no fur' blueprints on hand, the coil data for ther attention. .000032 -mf. condens- ers are given as fol- BOTTOM OF GRID COIL lows: TOP OF TICKLER Coil 1: Grid and tickler windings, each 7 turns; wavelength range approximately BOTTOM OF TICKLER 19 to 25 meters. TOP OF GRID COIL CODE LEARNED EASILY Coil 2: Grid and AT HOME HAS HELPED THOUSANDS TO BETTER tickler windings, each GRID COILS POSITIONS IN RADIO AND TELEGRAPHY 10 turns; range 28 to COIL 1 - 7 TURNS') The OMNIGRAPH Automatic COIL 2 - 13 J NO.22WIRE Transmitter will teach you the 35 meters. COIL 3 - 25 - Wireless or Morse Codes, easily, COIL 4 -50 - 1,10.2.t. WIRE Quickly and cheaply. Start now. Ideal opportunities for TICSCLERS you as an operator, broadcaster, The coils shown here are experimenter or railroad official, for use with .0001 -mf. COIL I - 7 TURNS etc. U. S. Army. Navy, radio They COIL - 9 N0.26WIRE. schools and scientific institutions throughout the condensers only. COILS - 18 world use the OMNIGRAPH. Dept. of Commerce will not cover the speci- COIL 4 - 30 ° tests all applicants for a Radio license with it. fied bands with midget Ask for Catalog. OMNIGRAPH MFG. CO. condensers. 0 O SIO E. 39th Street Dept. M Brooklyn, N. Y. Please .say you saw it in RADIO NEWS

www.americanradiohistory.com Radio News for March, 1929

Another idea in antenna coupling is to connect the aerial wire to the cover of the box, and to bring the cover toward the plug-in coil. The capacity between the metal and the coil will, in most cases, be Whether You Use the NEW Arrangement sufficient to form an excellent coupling medium. of the "HiQ -29" Receiver, or Follow the The operation of the "Candy Box Special" is exactly like that of any short -wave re- Original, ceiver, and all the detailed directions on short -wave tuning published in the past few issues of RADIO NEWS should be ob- served. The operator should use his left HAMM:ARLUND PARTS hand for turning the tuning condenser and his right for the regeneration condenser. INSURE SUCCESS In the absence of vernier dials, the knobs will require rather careful adjustment, but The New Arrangement of the Master broadcast and code stations can be tuned "HiQ -29" Receiver, which will in without trouble. arpeal to many set builders, The tickler coils specified for the tube- employs the new Hammarlund base coils are rather large, but are made 'Battleship" Multiple Con- so deliberately to insure a good regenerat- denser and Push - pull ive With any action. one coil in place, "Battleship" Audio Amplification. and with the tuning condenser set at maxi- Multiple Condenser mum capacity, the set should fall into oscil- Master "HiQ -29" Coils lation as the regeneration condenser is turned up to maximum capacity. If the set oscillates long before the latter posi- tion is reached, remove a turn at a time This from the tickler until it does work in this Plan your Master wonderful new manner. will receiver, It then regenerate and oscil- "HiQ -29" either way with tuned late smoothly at lower wavelength settings band -pass filters, was without the controls being unduly critical. -using the New Ar- designed for extra- A grid leak of five megohms is shown. rangement or follow- R. F. Choke Coil This is usually the correct value, but of ordinary performance ing the original spe:1- course it is a good idea to try others of and is fications. You will that what it both higher and lower resistance. delivers. be delighted with Unheard of GRAND RECEPTION selectivity, results beyond all amazing RADIO CoNsnwc -ron: "Have any luck with volume and delight- your television set yet? What did it bring former standards. in ?" ful tone. RADIO EXPERIMENTER: "A whole house full of televisitors, the first night."-Morris Cavanah. Illuminated Drum Dial The coils, conc'ensers, chokes, shields, "drum dials and In Our foundation un:.t are of Hammarlund design and manu- March Issue: facture - whir h means QUALITY UNSURPASSED. Into the Green Prism, by A. Hyatt Verrill. (A Serial in 2 parts.) Part I. Imagine a re- HAMM.ARI:,UND MANUFACTURING CO. flection in a mirror suddenly coming to life in its three di- 424 -438 West 33rd St., New York, N. Y. mensions! Yet it is not as foolish as it seems at first. Why, is very well told in this new story by our well - aO't. EQitRIL ÌdTICÚA known author, who collects material for Send 25e for "Hi¢ If Your Dealer his tales first -hand in unexplored lands. 29" Construction Can't Supply You, Manual. h gives ammarlund Write Direct To The Worm, by David H. Keller, M.D. all details. PRECIS/ON Us. Although the versatile author cannot en- a tirely escape using the science of psy- PRODUCTS chology in his stories, this one is pre- dominantly different in theme -and no less interesting. ..R.JLJL rsst=g eMA 0i'i'i'i'i'i' The Airlords of Han, by Philip Francis Nowlan. When "Armageddon- 2419" was published, we received a surprising num- ber of requests for a sequel. Mr. Nowlan has finally given us one which is not only Everything lin 'SET BUILDERS worthy of its predecessor, but surpasses it. We know you will follow, with bated Radio at Wholesale breath, the work of the scientists of both GettRislioo/, factions Hans and We supply every radio seed from -the the Americans - Berawlk, the first while they prepare more - and oldest radio and more effect our mammoth stock of kits, specialty house, offers you unusual tive means for attack and defense. latest design. service this year. Bigger stocks, parts and sets of quicker shipments, lower prices. Lowest wholesale pricer. Expert Deal with an old established, reliable The Face of Isis, by Cyril G. Wates. Most house. Get honest goods, honest service, of our readers will remember that in our attention ; immediate service. honest prices. Ba awik service makes you cover -illustration contest (December, 1926), Write for big, illustrgted Cata- more money. Send now for big new Catalog show- Mr. Wates' story, "The Visitation," was log "B-5." ing lowest wholesale prices. unanimously acclaimed worthy of the prize. BARAVVII In "The Face of Isis," the author bases CO."cc to,u s.". his plot on the discovery of an ancient Mea Thü Coupon Now for Free Radio Guide Egyptian casket and on the science of archaeology. The contention is that the Aztec culture was an offshoot of ancient Egyptian civilization; it is made quite plausible.

And others. Insure your copy reaching you each month. Subscribe to Radio News -$2.50 a year. Experimer ter Publishing Co., 230 Fifth Avenue, N. Y. C. Please say you saw it it RADIO NEWS'

www.americanradiohistory.com 878 Radio News for March, 1929

Books no Home should be without

HOUDINI'S SPIRIT EXPOSES the hair, the eyebrows and lashes adding that extra pound or taking off and excessive weight-all is covered. DUNNINGER'S PSYCHICAL C51 BEAUTY SECRETS should be every woman's constant companion at INVESTIGATIONS the boudoir. Critics the country over By JOSEPH DUNNINGER have claimed that a fair price for a book of this kind would be from three to five In this remarkable new book the voice dollars. However, due to our unique of Houdini has been resurrected, as way of publishing, we are able to give though from the dead, and can be heard this book to you at the phenomenally to echo again in sullen denunciation of low price of- the ever -increasing number of spirit- ualistic mediums who, since his de- cease, have been parasitically bleeding the innocent public of its choicest pos- 50c sessions whilst posing in the sacrilegious Per Copy guise of the living dead. Joseph Dunninger, famous magician, Chairman of the Science and Invention Sold at all newsstands or Investigating Committee for Psychical write direct -112 pages -fully Research and the author of several illustrated -large magazine size notable works on magic, was a close personal friend of the late Harry Hou- dini. All the data appearing in this book was taken from the personal POPULAR CARD TRICKS notes of the dead magician now in the By WALTER B. CIBSON possession of Dunninger. These and the accompanying remarkable conclu- Pleasant Entertainment for All sions drawn from the various success- Walter B. Gibson has written what ful exposés of Houdini, together with is conceded to be the most complete the tremendously interesting revela- book of card tricks ever published. tions contained in Dunninger's Psy- There are literally hundreds of these chical investigations, make this a book clever little tricks. You need not be that all should read. Over 116 pages. a professional in order to work them Large 9x12 -inch size. out. There is no sleight -of -hand re- quired. You can do any of them with Only little or no practice. Simple to per- form- difficult to guess. Complete instructions -. hundreds of illustra- 50c tions. Once you have mastered a few of the Per Copy tricks that this book contains you will At all newsstands become extremely popular-always or write direct entertaining. Imagine the fun you can have at a party. Just nonchalantly pick up a deck of cards and inquire if anyone has "seen this one." Then BEAUTY SECRETS while all attention is focused on you By EVA NAGEL WOLF do these tricks one after another to the admiration and wonderment of all. This book, by Eva Nagel Wolf, prominent editor of the beauty column This big book of entertain - of one of the leading women's magazines ment, fully illustrated -large and internationally known authority, magazine size divulges to seekers of beauty the true secrets of their type -just what is nec- Only essary to make themselves most at- tractive. "BEAUTY," says Miss Wolf, "is not difficult to obtain once 25c you have learned the simple secrets of type." It is the purpose of this book Per Copy to pass on to every woman these se- crets-to show her the quickest and all newsstands easiest way to genuine beauty and at- At tractiveness. or write direct There is nothing left unsaid -every phase of beauty culture is fully treated. The art of make-up, care of the hands, I 4 ,1t'c

SlyCy Og$,c° r 4JpStoL' . s EXPERIMENTER PUBLISHING CO., Inc. et ectetg 1SS3 4 $est9 S na eg 230 Fifth Avenue 'gY ti V> I E1Z Aws c9`oQ tai4ssOjss xYSg.Z30 .'.. New York, N. Y ep: tbebsvs9áovge Csf fi e U o pt ..g 0 áe {Ot;v 4 Citg Sts" AO Ge°S t9 8stse

Please say you saw it in RADIO NEWS

www.americanradiohistory.com Radio News for March, 1929 879 Meters the Fan Needs "You Can Forget the ;ondensers -If They Are DUBILIERS ' (Continued from page 825) Typo PL 1120 especially desist f for D.C. voltmeter read- the Thordarson types R-480 am 1-280 still in use) a separate Power Compacts, used with 11 typo ing from 0 to 8 volts is very desirable. tubes and the 280 type tube R tiller or the Elkon E -80 metallic Re iSer. With this meter you can make more accu- Price $15.50 rate measurements, and determine whether or not individual tubes are receiving their There is AA proper voltages. A voltmeter like this is essential when 199 -type tubes are being han- Sstbstitute dled; as small voltage- differences seriously ! affect the operation of these tubes, which For QultlitJ are rated at three volts and 60 milliamperes NO amount of lurid cl ms of filament current. by nimble- penned 1d- SPECIAL DEVICES vertising writers will lke There are on the market a number of the place of quality in :he special radio set testers and "analyzers" final analysis -the op ra- that are literally worth their weight in gold tion in your power sui ly. to the bona -fide service man who has the gold to pay for them. They consist for the Ever since the adven of most of two or three meters, each of part Radio, Dubilier has 1 en which performs several duties at the turn of the td- a special switch or the pushing of certain manufacturers' st; Dubilier Light Socket Aerial buttons on the case. One meter is usually and -and the set built rs' -"A Moulded Bakelite Product" a three-range A.C. voltmeter, 0-4, 0-8 and stand -by. Built in e ;ry Bring in programs with a minimum 0 -150 volts; the other a combination high - Dubilier Condenser a of interference. Simply attach to resistance D.C. voltmeter and D.C. milliam- factor of safety whit'. is the set and plug into the nearest with two, three or four voltage scales meter, your y and two current scales. In some types of safeguard for trs light socket. Uses no current. Sold testers there are three meters, one A.C. and of service without fail re. by all good dealers. Price $1.50. two D.C. Write 1 Dept. 13 for Practically all these testers are equipped f catalog with test cords and adapters which allow the operator to determine all the operating 5114 conditions of a radio receiver of any kind in Dubilier from ten to twenty minutes. All these tests may be made by using the regular voltages 1fßeSR CONDENSER normally supplied to the set by its batteries Re J.S. Pet.Off, CORPORATION or power units, and without disturbing any of the normal connections. On the more IO E st 43rd Street New York City flexible instruments, any one of the meters provided for its multiple purposes is avail- 76 77 able for external use; as perhaps for experi- RADIO NEW BLUEPRINTS Nos. and work. Connections are made to the mental age the construction of radio apparatus illustrated in proper binding posts the proper "mul- O this maga- after Tlma make it easier for our readers, RADIO NEWS makes up each tipliers" or shunts have been put into the month larg blueprints of the diagrams which accompany the principal con- circuit. These analyzers represent some- RADIO structional ticles; these sets include full -sized drilling templates, coil data, thing of an investment, but they pay for etc., where quired, and in each case a list of the apparatus originally used, NEWS with full cifications. Several thousand of these have been distributed themselves very quickly. each month. BLUE PRINT If you sire a set of blueprints for any or all of the apparatus described in this um] .'s Blueprint articles, fill out the attached coupon as directed and send it with 25 cents for each set requested. The blueprints requested No Patents in Australia will be mai to you postpaid. We cannot send blueprints with magazines. problems in the radio field have PATENT Back -number RADIO NEWS bluepri s can be obtained at the same rate while the stock lasts. caused much disturbance in the indus- See page 837. try outside of the United States. In Great We cannot furnish blueprb ; of commercially-manufactured 'radio apparatus. Britain it appears that more or less success MMMMMMMMMMMM I ------r - - - - I has been shown along the line of collecting royalties directly from set builders -a pro- Blueprint Department, RADIO l ;`S: (D) cedure which would be attended with some 230 Fifth. Avenue, New York; 4". Y. (U. S. A.) difficulties in the United States. In addi- tion to this, it would appear that a patent I enclose 25 cents for each i in checked; for which please send me a set of large cannot be withheld from public use; but a RADIO NEws blueprints. license under it may be demanded, on pay- ment of a royalty deemed adequate by ad- ministrative officers, subject to court review. No. 76. The "Radio News 19 Hi-Q." The Australians, however, seem to have cut No. 77. "The Dry-Cell Four. the patent knot. Practically all patent No...... rights on major radio inventions on that continent were owned by Amalgamated Wireless, Ltd., which operates the principal Name radio stations. After long negotiations, an arrangement was reached between the Street Number company awl the Australian government, whereby all those patents are thrown open freely to public use by dealers, broadcasters Postofficc and listeners. In lieu thereof, the company receives three shillings (75 cents) a year State (Province, etc.) from the proceeds of each listener's license. It is believed that this will result in a con- siderable growth of radio activity in that (Please typewrite your name ace address or print it with a pen -not a pencil-as Commonwealth. many signatures cannot be read. is will avoid errors in addressing the mail.) Please say you saw it in R. DIO NEWS

www.americanradiohistory.com w Radio News for March, 1929

Up-to-the- from all foreign countries, from the most distant climes. England, France, Germany, towns on minute data the African continent, from every conceivable worth- corner of the globe where a station is located - -All programs come in with surprising volume and while circuits- clarity. One would think they were hearing a New York, Chicago or San Francisco station until Prepared by Eminent Short Wave Experts the voice of the announcer, many thousands of Edited by H. M. BAYER, Tech. Editor of RADIO NEWS miles away discloses the true location of station. foremost book on This is unquestionably the In the Short Wave Manual you will find com- short wave receivers and the theory of short wave plete diagrams, full size blueprints pasted into it con- reception ever written. The data which the book. These tell plainly how to construct all tains is a compilation of the knowledge of an the short wave circuits which our tireless eminent board of Short Wave Experts. laboratory researches have shown to be most As practically some every one today knows, of efficient. the finest programs are being broadcast over the short wave bands. There are many The SHORT WAVE MANUAL contains com- reasons for this. Paramount plete information on everything concerning among them all is the fact Short Wave reception. Large size book (same that that entertainment, size as Radio News) with a beautiful colored broadcast in this band, cover. Replete with illustrations, diagrams can be received and with FULL SIZE BLUE PRINTS. over distances This big valuable book will show you how which with to receive all the foreign countries t h e ordinary clearly and easily. Write today for broadcast re- your copy. ceiver would b e impossible! Mail This Coupon Thousands of let- ters, which pour in an unremitting EXPERIMENTER PUBLISHING CO. stream into our offices 230 FIFTH AVENUE. NEW YORK. tell the same tale -it is Gentlemen: Enclosed find 50c for which please send me a copy of THE a common and everyday SHORT WAVE DLANUAL. matter to receive programs Name

EXPERIMENTER Address .... PUBLISHING COMPANY, Inc. Beautiful City Stata 230 Fifth Avenue, New York Colored Cover Please rav Ton saw it in RADIO NEWS

www.americanradiohistory.com Radio News for March, 1929 Radio Echo from Space (Continued from page 814) sometimes a luminous spot, called the rrge- gensehein" and referred to the refraction of the sun's rays by the earth's atmosphere. We may therefore conclude that the sun Puzzle fans attention: J. C. o , Charles Vogtmann, Mrs. J. E. either emits or collects particles of minute Fiel Viola Javins, Alvin Smith Mrs. John \' 1 Giliies, cob Braucher, each won sedans in our last size, yet capable of reflecting light, into an auto puss . Over 800 prizes awarded in one year. Over $11,000.00ií October, Iu hou few area in which the smaller planets at least months will and between 300 and prizes through our pug.. move. He, therefore, has also belts like ales. Here's t one for you. Saturn, but of low visibility. FIN] THE "DIFFERENT" AUTO The care in the o all look exactly alike at first glance. They are not all alike. One is d rent from all the others. There is a real difference. REFLECTION FROM THE LAYER Something is purl), y left off all the other cars but this one. The difference may be in the fenc bumper, nameplate, radiator or top. The one that Consideration of the earth's magnetic field is' different" is tb eal Buick Sedan I am giving away in addition to three other cars in my m :friendship advertising campaign. You may be the one indicates that it also must have attending ho will find it belts, possibly dimly visible from other plan- AND WIN DICK SEDAN OR $1800.00 CASH 4 sedans and 28ot prizes totaling over $5.000.00. 32 prizes and duplicate ets. A field of electrons, however, is quite prizes paid in ca ,f tics. If you can find the "different" auto you may invisible, as they are too small to intercept be the one to ge ds great prize. Certificate it $480.00 to apply on grand prize sent the waves of visible light, though they may immediate as below if you find the "different "car, Immediate snick Ion -no delay -we send certificate for $480.00 to add to refract them. The longer waves of even a you win and direction, Buick NV óDr.. iIce otio.50 h totadvertise ° products, short -wave radio transmission, however, are the Nsa MO RE LYLES TO SOLVE. Nolista of wordam maksor write or other , nee. This is an. rewarded it e eey ted. N, It obligation. Nothing now, later. ever. quite readily acted upon by even a weak Just the number of the "different" auto in magnetic field, if it be of sufficient extent. et or a post card. That's all, send eo money. B. H. France, Dept. it is suggested that even twenty or thirty 500 N. Dearborn St., Chicago, III. million electrons to the cubic inch would be sufficient - though almost an electrical vacuum by earthly standards -if properly 'located in space.

A REA) SPECIAL OFFER!!

UNI -REC RON POWER AMPLIFIER (Idee For use with Dynamic Speakers) Model AP -935 As the Uni -Rectron stands The UX -210 super power It is a super power ampli- amplifying tube and the fier, which can be used in UX -216B or 281 rectifying connection with any radio tube are used with this am- set and loud speaker. Bind- plifier, which cannot over- ing posts are provided for load. From the faintest input to the Uni- Rectron whisper to the loudest crasis and output to the speaker. of sound -R. C. A. Uni- Rectron amplifies each note Requires no batteries for its at its true value. High and operation. It obtains its low notes are all treated power from the 110 volt. List Price $88.50 alike. The volume 60 cycle alternating (without tubes) and quantity deliv- current lighting cir- ered will be a revela- cuit of your house. SpE .ial - $19.75 ea. tion. Every one t t and packed in original factory carton AMERICAN SALES CO 19 -21 WARREN ST., NEW YORK CITY Phis represents a suggested method of sending s radio wave to the ,noon and back; to deter- mine by the reception of the reflected wave the permeability of the Heaviside layer. It eons proposed in Roto NEWS for February, 1929. by H. Gernsback, the editor.

However, if this layer can reflect signals w that they pass back over a path of even Ti you are it rested in radio, the quicker you decide to make radio your 130,000 miles and arrive at a point on earth life work th sooner you will be assured of success and Big Money. arith one -twentieth or more of the strength ear is possible for men connecting at once h our big National Radio Service organi- of the original signal -as heard at 400 miles $5,000 Ion. from the transmitting station -its reflecting I Need 1200 M at Once for Chain Service Stations win properties must be very good; and if, from Don't be a "tinke ;" get in on the ground floor with a big THE :a distance of over a million miles, it can eon - proposition. Iaves late at once. centrate reflected broadcast signals on "Have a licensed 1 dio Doctor &x it" is the slogan where our RADIO the men operate. earth in recognizable form, it would DOCTOR seem Write today for - free booklet, "Why the Radio Doctor" that it must be as sharply defined as the E. W. PAR: R, Pres. RADIO DOCTORS, INC. surface of the mirror in a reflecting tele- Dept. 5 Essex St., Salem, Mass. scope. This is hard to reconcile with the rapid variations in the time of the echoes - from three to twelve seconds, with sometimes two echoes at four -second intervals. Further ,Write for descriptive circula -07 4111 RESH MA experiment, however, will doubtless result in Electrad Specialized Conty s. YOUR ULTIMATE data on which a more complete theory will Dept. RN -3, 175 Verick St.,New York Cil N.Y. RADIO 1 be based. AT ALL However, if the Heaviside laver, so long claimed to be radio -proof, has been pierced AUTHORIZED by radio transmissions, only to have them DEALERS Please say y 0 lt saw it in R. DIO NEWS

www.americanradiohistory.com Radio News for March, 1929

882 turned back a million miles further on, we 7 are still a long ways from being able to get PHONO through that "message to Mars." FROM ABOVE-OE BELOW Radio Consoles It is interesting, however, at this point to consider another possibility. We may refer to an article (which appeared in RADIO NEWS for February, 1927) entitled "Can We Radio the Planets ?" by Hugo Gernsback, editor of this magazine. Two illustrations from it are reproduced here, as Figs. 3 and 4. The proposition was there made that, since longer waves are turned back from the Heaviside layer, thereby increasing reception strength on earth at the expense of that on other planets (fortunately for the sponsors of commercial broadcasts who have no re- tail distribution on the moon), ultra-short waves are desirable for a test of interplan- etary reflection, if not communication. It was suggested that a transmitter with a wave of less than two meters (which could A companion of Fig. 3 suggested that the be directed like a searchlight) should be metallic core of the earth might be outlined by the method illustrated. Query: how long used to send a beam directly at the moon, will it take a wave to pass through the mineral which is presumably a body of considerable layers above the core, and return, reflective power (See Fig. 8). Such a trans- mitter would be particularly useful with magnetic and electrical effects, it loses which to test the effect produced on its strength by the setting up of counter-cur- transmissions by the earth's "space charge," rents in the material. Therefore, a radio im- For Radio or Phono-Radio Combina- compare tion. A beautiful Walnut Cabinet with to our planet to the grid of a tube pulse might take as long to pass through sliding doors of matched Butt Walnut. whose filament is the sun. several hundred or thousand miles of the Ample space for Receiver, Speaker, However, let us consider Fig. 4, also re- earth's crust, if it were strong enough to and Phonograph equipment. produced from the article last quoted; the find its way through, as to leap out a million A descriptive bulletin of new 1929 use of the same transmitter in a downward miles into empty space and return. Is there styles sent free on request. direction might settle very quickly the pos- a possibility that the radio echoes are effects sibility of an alternative solution to the coming up from the magnetic core of the EXCELLO PRODUCTS CORPORATION problem of the radio echo. earth, from which they have been reflected, 4832 West 16th St., Cicero, Illinois A radio wave moving in empty space rather than down from the invisible regions which is non -magnetic moves with "the speed which lie between us and the other planets? of light" -that maximum speed of about The beam transmitter of Fig. 4 would tell, Make Your Set WireLess 186,000 miles a second which figures in all perhaps; if directed, not to one side of the An antenna and ground wire is Just as obsolete rough calculations -but in a magnetic field it core, but against it, to measure, not the time today as batteries. A is more or lesa When conglomeration of wires retarded. it is passing of passage, but the time of descent and re- inside and outside of through material more or less susceptible to flection. X -L the house is unsightly, undesirable, and by the Link use of an X -L LINK totally unnecessary. List Your set can be made really wireless, oper- Harmonics Cause of Phantom -Wave Stations Price ating entirely from a Short single light socket or $5.75 wall plug by simply (Continued from page 811) connecting it through an X -L Link. This cies. The harmonics of broadcast stations, nlonic or fundamental. Some rare cases enables you to obtain an excellent antenna beginning with one having half the wave- have been noted where a signal has been and ground from the shielded light wires. In length (twice the frequency) of the carrier, picked up on a longer wave; but these are addition the LINK must fall in the short-wave band -except, not due to harmonics, but merely to waves provides a positive REGULATORLINE VOLTAGE of course, for the first harmonic of a station produced by some body of metal or other DOUBLE SOCKET on 400 meters or over. They must, there- conductor which has been "shocked into os- OUTLET AND SWITCH FOR POWER UNITS OR DYNAMIC SPEAKER, COMPLETE FUSING TO PRO- fore, be picked up by short-wave receivers cillation," therefore "re- radiating" the sig- TECT THE TUBES AND OTHER PARTS OF THE SET. which are tuned to them, exactly as if they nal at a wavelength equal to its own suft- Unconditionally guaranteed by the manufacturers of the X -L Vario- Denser. if your dealer cannot supply you, Bend were the broadcasts of a short -wave station ural resonant frequency. is his name and the purchase Price direct. of equal power. As with the vibrating wire, COMPLEX FREQUENCIES it will be found that some of the harmonics XLRadio Laboratories are stronger than others in the broadcasts It must not be assumed by the reader from a radio transmitter; and that the odd - that the fundamental tone or wave, either of Dept. A. 1224 Belmont Ave., Chimp, iii. numbered harmonics, such as the third, a violin string or a radio transmitter, and fifth, seventh, etc., are sent out much its harmonics exist entirely separate and stronger than the even- numbered ones such distinct, having individualities like a mother as the second, fourth, sixth, etc. The higher and her children; though this is an idea harmonics, however, continually decrease in which might be conveyed by the usual strength; so that it is rare to pick up fre- method of dealing with the subject. As a. quencies higher than the seventh or ninth at matter of fact, when the fundamental is is- with The PREXTO tube increases Volume and Distance. Bringe any great distance from the transmitter. sued together one or more harmonics, many distant stations in like locals. Its use often results Another question which has been asked is the latter are merely modulations of the as though an additional tube had been added to the re- ceiver. Insert - tube in detector socket. Use in any set whether a station can transmit a signal or fundamental. using 201 -A tubes. Guaranteed for 1 year. Tested by a lower frequency longer Fig. 3 shows the bigger members of a RADIO. NEWS, RADIO . WORLD and the RADIO harmonic at or a DIGEST, and other leading publications. 25.000 users today. Money back guarantee with every tube. ORDER wavelength than that of the fundamental. harmonic family. It will be observed that TODAY and enjoy those DISTANT stations. Price 53.00. By referring again to the vibrating wire, it their "nodes" or neutral points (corre- WHAT USERS SAY "Your tube cannot be beat." Fred Geiger, St. Joseph, Mo. will be seen that the lowest tone which can sponding in radio waves to the ,point where "Pick up stations I could not get before now using your tube. Distance and volume increased 50% and more." be produced is that sounded by the wire the voltage is about to change polarity), Jas. T. Garrison, Duenweg, Mo. I am delighted with Your tube. It sure has the power and kick." George B. vibrating as a whole. For a similar reason, show many coincidences; and so do their May. San Jose. Calif. 'Your tube a MIlItTer for distance, volume and selectivity." R. O. Dorm aMe mour, Conn. a radio transmitter cannot emit a harmonic points of maximum voltage. And hundreds of other letters from us ORDER NOW. at a higher wavelength than the first har- If we create a note or wave whose lowest PREXTO MFG. CO. Dept' , +9eadmont, Texas Pleas e say you saw it in RADIO NEWS.

www.americanradiohistory.com Radio News for March, 1929 component frequency corresponds to, say, Any A. C. Socket Po, er Set can be used on D. C. supplies- that of B in Fig. 3, it is not a harmonic; it is then a fundamental, and D and F then if an "ESCO" Mo r Generator or Dynamotor is used third harmon- correspond to its second and Machines for operating 60-cycle ics. But, as said above, the thing to bear in A. C. Radio Receivers, Loud mind is that a musical note or radio wave Speakers and Phonographs from does not usually have a simple form, such Direct Current Lighting Sockets as the "pure sine waves" shown in the first Without Objectionable Noises of six curves. If a wave contains simply a any Kind. fundamental and its third harmonic, we get The dynamotors and motor generators a complicated wave such as that shown at are suitable for radio receivers and for G, which is the resultant of two components. combination instruments containing If we combine the fundamental and the phonographs and receivers. Filters are fourth harmonic, we get such a shape as we usually required. The dynamotors and find at H; and the combination of a note motor generators with filters give as and several of its harmonics at once will good or better results than are obtained line which be identi- from ordinary 60 -cycle lighting sockets. give a wriggly cannot They are furnished completely assem- fied, at first sight, as having any relation Motor Generator with . !ter bled and connected and are very easily to any one of them. For Radio Receiver installed. But with a wave of this form, a receiving These machines are furnished with wool. apparatus tuned to either the fundamental packed bearings which require v y little attention, and are very quiet running. or any of the harmonics contained in the Write for Bulletin No. 243 -C. curve will be sensitive to its modulations. Suppose that the fundamental wave is a million cycles-300 meters, and carries a ELECTRIC SPECIALTY COMPANY strong third harmonic-100 meters. It is 211 South Street Stamford, Conn., U. S. A. modulated with a 1,000 -cycle note. If we TI sE MARK tune it in with a set whose R.F. circuits are "ESCO" set at 300 meters, we shall get the 1,000 - Manufacturers of 'otors, Generators, Motor - Generators, cycle note. But we shall not be bothered Dynamotors and Rot p Converters for Radio and other purposes with the 3,000,000-cycle note, which is also there, because we can't hear it. On the other hand, if we have a short- wave receiver, tuned to 100 meters, the same signal will also come in, and we shall de- Send for tect and hear, not the 1,000,000 -cycle note which is there, but only the 1,000 -cycle note. It is only in such a complex wave as those caused by the interference of two broadcast stations which are fairly near together - within twenty kilocycles, at *least -that an undesired audio note can be created by their "heterodyning." The harmonics do not set up a heterodyne, in the ordinary sense, with their fundamental, but they do create a wave capable of being received at several frequencies. Also, one harmonic component of a wave may interfere with the wave of another transmission at a frequency from DEALERS AND SEI BILDERS which it does not differ greatly. Thus the THE NEW 1929 Cat lg is crammed second harmonic of a transmission on 670 full of the FINEST, ' EWEST, na- kilocycles might cause a whistle in a re- tionally -known A.C. sets onsoles, cabin- ceiver set to the wave from a 1,335- or eta, dynamic speakers, s, eliminators, 1,345-kilocycle transmitter. It was this con- and accessories at LON CST PRICES. Largest stock of Radio arts. Prompt sideration which caused the Radio Commis- delivery. Write for our 'REE catalog. sion to veto the proposition to split up wave 6- WESTERN RA IO MFG. CO. channels into kilocycle and smaller strips 128 WEST LAKE ST. Dap RN -3 CHICAGO, ILL. to accommodate more broadcast stations. ÍI 9fegigFiieen Radio Housé Figuring Filament Ballasts (Continued from page 843) more tubes in parallel would allow an un- duly high flow of current through one of New Catalog Coveris the same type; and it can be seen why it is undesirable to have any tubes out of their All 1929 Model sockets when the battery switch is turned Every farm. every home, every man and woman on. This risk is reeds radio this vear to renew the news. mutes., eliminated when each tube Now Ready big national events. football, sports, muslo. eta. has own resistor. Barawik's Big Radio Guide tells you the best sets. its methods and supplied to use and how to use them The use of a reliable voltmeter, need for best results at lowest coat. Thousands of clear it illustrations and latest valuable information. fur- not be said, is as desirable in skillful set C. R. nished free. Just send for Barawik's Big Radio LEUTZ, IN Guide, the guide to radio and real radio enjoy- operation as that of a steam gauge in the ment. You can get whet you want here a operation of a steam engine. For this pur- Long Island Cit biggest savings. Write today for tree copy. pose, the higher its resistance, the more re- BARAWIK CO. CHI CAGO,D.á,A. Mail this Coupon liable its readings, as a rule; for a low - New York for Free Radio Guide resistance voltmeter is a load on the cir- Name cuit it is testing and, by drawing additional Address current, makes its readings deceptively low. The figures below indicate the resistances necessary to reduce the "A" supply to the Insure your copy reaching you ch month. Subscribe to Radio News -$2.50 a year. specified working voltages, and consequent Experimenter Pu thing Co., 230 Fifth Avenue, N. Y. C. Please say you saw it in RA 10 NEWS

www.americanradiohistory.com Radio News for March, 1929 FANS: third big edition

Don't Over

Miss COMPILED BY THE STAFF OF 150,000 RADIO This NEWS 111ó'1km Copies y Big ti Already

EiFSi1lN$\\ Q.,.,T. Er Issue Rws A Sold

:.,,FL., At,` EXPERIMENTER PUBLISHING CO. ¡i/'o 1ç1NEW YORK jJl"CITY

Compiled by the Staff of RADIO NEWS Completely Revised- Up -to- the -Minute 1001 RADIO QUESTIONS AND structed. Concise, authentic answers ANSWERS, the most sensational to every question that can possibly be seller in the radio field, is now in its asked concerning the many and varied third new and revised edition. No one branches of radio reception on both interested in radio should be without short -wave and broadcast bands. a copy. The staff of RADIO NEWS, the leading fan magazine, has striven to FANS! Don't hesitate! Get your copy make 1001 RADIO QUESTIONS AND today! Over 112 pages - fully j ANSWERS the foremost work of its illustrated large magazine size kind available. There is a full and complete explanation of every worth- e G54'., while circuit that has appeared since fi tl y 5 50c a4 4`4ÿJ the beginning of radio, not only the THE COPY 4-Qo¢lo toe tisá y9 explanation, but also complete dia- ASK YOUR NEWSDEALER ti5I 44fia iY 4. 4J y¢ 0 .. grams from which the set can be con- OR WRITE DIRECT SQA Çc.> ",i`.' w o4"

¢ P ' EXPERIMENTER PUBLISHING COMPANY, INC. , 44%so N1¢ ill ' e¢ o,í19 yaO ,4 %.0. 230 Fifth Avenue, New York, N. Y. ßa7§

Please say you saw it in RADIO NEWS

www.americanradiohistory.com Radio News for March, 1929 proper flow of current, through tubes of the types given. Type of Tube Series Resistor Ohms 6 -volt "A" supply One 201A (or other % amp., 5 -volt tube) 4 One 199 (or other 60- millianip., 3 -volt tube) 50 One 199 (at 3.3 volts) 43 One 222 (at 3.3 volts) 21 (If the filament circuit of several tubes in parallel returns through one resistor, I divide the above resistance by the number of tubes.) CARBO LgTl®TI)-LTM DETECTOR *One 201A, one 222 2 3/5 e'rwo 201As, one 222 1 3/5 ATURN of the pr sure screw gives you perfect tone balance. 222 1 1/7 *Three 201As, one Then, positiol is fixed by adjusting lock nut, so that pres- *Two 201As, three 22>s 1 1/7 *Three 201As, three 222s 7/8 sure remains per anently sensitive. qJust another improve -. *Four 201As, three 222s 3/4 ment to further in ire the Perfect Tone Quality you always get *One 201A, one 199 3 1/4 with the Carbor idum Detector -and tone quality is every - 'Two 201As, one 199 1 4/5 thing. gRecol mended by noted radio -circuit designers. °Three 201As, one 199 1 1/4 (For purposes of calculating current DEAL: OR DIRECT-$1.50 IN U. S. A. drawn, two 222s equal one 201A, approxi- Send for ree Book "Carborundum in Radio" D -I mately, and two 199s equal one 222. A /- The ,rhorundum Company, Niagara Falls, N. Y. ampere tube, 112 or 171, counts as two Cana< . Carborundum Co., Lad.. Niagara Falls, Ont. Carborundum i, the Registered Tnde dark 201As.) of The C.rbnn,:dum Company for in *As this resistor reduces the "A" voltage Silicon Carbide and te ite moluths pnportS only to 5, additional resistors will be neces- sary in series with the low- voltage tubes. 5 -volt "A" Supply (Behind Resistor) One 222 (at 3.3 volts) 13 One 199 (at 3.3 volts) 27 One 222 (at 3 volts) 15 One 199 (at 3 volts) 30 4/ -volt "A" Supply One 222 (at 3.3 volts)- . -_. -_ .v 10 One 199 (at 3.3 volts) 19 One 222 (at 3 volts) 12/ Here's news r puzzle fans! Alvin Smith, C. F. Meting, C. W. One 199 (at 3 volts) ___. 25 Francis. A. F. I ., won from $1800.00 to $8500.00 each in our last puzsles. Over 800 cash ces awarded in one year. In October, 1928, alone, we paid over $11.00 0 in prizes, and in the nest few months will award be- 4-volt "A" Supply tweet 300 and cash prizes. You can be nest. One 222 (3.3 volts) 6 WE $3500.00 CASH One 199 (3.3 volts) 12 Here are eie en pictures of Charlie Chaplin, the world famous United Artists star. N they're not all alike, even though they look alike. Only One 222 (3 volts) 8 two of these Ct ins are alike in every way. Some are different in the One 199 (3 volts) 17 color of vest, th td coat, some have different hat bands and shirts. Each one is different m the rest except two-find them. Just send the num- bers of the twit hapllns on a postcard or letter-today. The figures above given are minimum re- Find he Twin Chaplins sistances and, though fixed filament voltages 300 prizes at luplitate prizes paid in case of ties. If you and the twin Charlie Chaplin re will send, as soon as correct answer is received, rar- need not be critical, a lesser value should tibcato for $1,00 e to add to the first prize of $2.500.00, if you win, and not be employed -remembering always that directions for at ng largest prize. We spend over $150,000.00 this way each year to adv se our products locally. No cost or obligation. Nothing resistors may be slightly below their rating to buy, now, la or ever. Everybody who takes active part positively rewarded. Just od the numbers of the twin Chapllas in a letter or and that power units, in particular, may de- on a postcard. it's all. Send no money. liver slightly over their rating. The appli- F. A. HARRE. Dept. 505. 510 N. Dearborn St.. Chicane, III. cation of too much voltage across a tube Aftem aae filament, within reason, will not burn it out; but it tends to shorten greatly the effective life of the tube.

Radio Wrinkles (Continued from page 842) simple mounting which can be assembled in little time and with little effort by the constructor. A piece of round bus bar, 1/8 -inch shorter SET BUILDERS than the diameter of the secondary coil YA^Y Radio Convenience Ot ts form, is placed through two holes in the Cable Connector Ph GetthisBoo/Z tickler form drilled diametrically opposite Rheostats Potentio ters Jacks Switches Res: Ince *Units Beranek, the first and oldest radio each other. After drilling and shaping two specialty house, offers you unusual For greater convenience service this year. Bigger stocks, wooden blocks, 1 x 1/, x % -inch, for the in receiver operation and quicker shipments, lower prices. ends of the bus -bar shaft, mount a spring dependability in set con- Deal with an old established, reliable struction house. Get honest goods, honest service, on each bus -bar projection and insert it make up your honest prices. Barawik service makes you list of parts and acces- more money. Send now for big new Catalogshow- into one of the blocks; the entire assembly sories from the New ing lowest wholesale prices. is then Yaxley Catalog. FREE, r3HH slipped into the secondary form Send for it to -day. RARAWI K CO. CHIC GO.0 s °a where it can be rotated, or moved up and Mail Tbts Coupon Noun for Free Rodio Guide down, with the assurance that the tickler YAXLEY MFG. CO. will be held in any desired position. -Con- Dept. N, 9 S. Clinton St. Chicago, Ill. tributed by T. A. Donothan. Please say you saw it in RADIO NEWS www.americanradiohistory.com 886 Radio News for March, 1929 On the Short Waves (Continued from page 845)

that you will kindly publish a note announcing this, G. E. FULLER, Avellaneda 255, Buenos Aires, Argentine Republic. (The newspaper account stated that it was sug- gested that the club be known as a "short- wave" organization; and while this motion was not adopted, the proposed transmissions will undoubtedly be at- tempted on short waves for foreign listeners. We have asked for details as to the programs which will be transmitted.)

Everything You LOCAL INTERFERENCE AVIATION Want Editor, RADIO NEWS: to Know About RADIO The other night we tried, as usual, to tune in on Station WGY and could only hear the program very EVERYBODY'S AVIATION Every branch of radio knowledge is covered in this tom -. pieta 5- volume Radio Library. For everybody in the radio faint. By a mere accident one of us happened to lay GUIDE is a complete discourse Seid- mechanics, operators, inspectors, service men. sales- his hands on the short -wave adapter and to our sur- on practical aviation, by MAJOR men, owners of radio stores. Written by such experts as prise the reception came in very clear. Thus we Harry F. Dart, E.F,., Member, Institute of Radio En- VICTOR gineers: C. H. Vose, B.S. in E.E., of the Radio En- continued with "the laying on of hands" during the W. PAGE, one of the gineering Dept. of the General Electric Co., and other rest of the time that WGY was on the air and with leading men in field. prominent Radio Engineers. Gives you the whole science the Unlike of radio in clear, understandable English. Handsomely very good results. most books of bound. pocket-size volumes, stamped in gold. Includes The next day the adapter was taken apart to see instruction, Picture Transmission and Reception. Send the coupon there was wrong with it. Inside we EVERYBODY'S AVIATION with 87.50 in check or money- order. Your money will be if anything refunded if you are not satisfied found a spider had spun a very beautiful web which GUIDE is written in a unique had caused the entire adapter to be grounded. question and answer fashion, International Correspondence Schools, The tube on top of the adapter must bave been re- Dept. 8283 -H, Scranton, Pa. moved long enough to allow the spider to enter which makes the subject far I am enclosing $7.50. for which please send me your five - through the boles on top. volume RADIO LIBRARY. It is understood that I may easier to study and a great retain the books in five days and you will refund my We are very curious to know if you have heard money It I am not satisfied. from anyone else who has had a similar experience; deal more attractive as an in- Name if not this may be of some benefit to others who use struction course. -wave in Address the short adapter the tropics. ALBERS M. CLAIR, This book was recently published and Chicle Development Co., is absolutely up-to -date in every way. C/o Alvaro Peres, Sucs., It has had very favorable criticism Alvaro Obregon, Tabasco, Mexico. throughout country-wide aviation cir- (A spider's web should not cause an electrical cles and has been highly recommended short- circuit, being akin to silk which is a good in- by all those in a position to pass sulator; but this, and other material a large tropi- cal spider might drag in, could alter the conden- judgment. ser's capacity; which is evidently what happened.) We list here the contents in order that you may see for yourself how com- pletely the field of Aviation is covered. AN AERIAL- CONDENSER LEVER Editor, RADIO NEWS: Contents: Thanks for the "Wonder Box," which is my new name for the "Junk- Box." Here is a pointer: when Early Aeronautic History -First Flying is well Machines-The Atmosphere WIOLESALE PRICES on nationally -known mer- the small aerial condenser C3 insulated from Forms of Aircraft-Airplanes and Air - chandise! Biggest discounts on standard equipment. the baseboard it smoothes out lots of troubles. I shape TREMENDOUS SAVINGS. Everything shown in mounted mine on two Polymet resistor bases. My Lighter- Than -Air Craft -Balloons our newest 1929 Catalog Guide -just out! Nothing and to compare with it. Immediate personal service on panel is attached to the sub -panel with my son's Dirigibles all orders. How An Airplane Flies -Elementary your erector parts; there is a 3% -inch space between the Aerodynamics SPECIAL PROPOSITION FOR DEALERS AND panel and the sub -panel. I used more erector parts AGENTS ON LAFAYETTE ALL -ELECTRIC Airplane Parts and Their Functions RADIO RECEIVERS to make a simple lever, attached to the sub-panel Fuselage Forms and Landing Gears Wing Arrangement Dealers and Agents-Write for this book of money - brace; and I can adjust the aerial condenser with the and Construction easing bargains, showing confidential price lists set in operation. When the tickler coils are just Power Requirements, Engine Types and and special proposition on the famous Lafayette All- Engine Location Electric Radio Receivers. ABSOLUTELY FREE. right, this little condenser can be very critical; but, Aircraft Propellers. Design and Applica- But you must act at once as supply Is limited. after I ran a lead from the soft-iron erector parts to tion Print name and address in coupon. Mail TO -DAYI the ground post of set, body capacity disappeared. I Airplane Equilibrium and Control Mail to WHOLESALE RADIO SERVICE CO., added a stage of audio; last transformer, choke and Official World and American Air Records Dept. 303, 8 Church Street, New York City. grid condenser are under the sub-panel. Name The hams around 80 meters roll, in on this little Address set on the speaker, strong and clear, from all parts Town State of the United States atad Canada, while the hams : themselves are howling "I can't get U, OM, QRM here to-night." This is my first letter after several .;;>\\ years of reading the only real radio paper ever EVERYRODYS ? AVIATION ' Complete Stock of printed. CUIDE JOSEPH MOORE, Silver -Marshall Parts General Delivery, Flint, Michigan. Price ` $2.00 Including No. 730 "Round- the -World" 4 We are authorized jobbers of Silver - CORRESPONDENTS WANTED Marshall apparatus. Complete stock on hand at all times. Special prices on Editor, RADIO News: No. 730 Short Wave Receiver. I would appreciate it if some amateur or short- Over 248 pages 1929 Catalog wave fan could help me in getting a license. Beautiful red cloth binding -Title in gold -FREE PAUL B. LOVEGREN, Replete with illustrations Includes description and complete parts 7846 Euclid Ave., Chicago, Illinois. for Remler 29 Shield -Grid Receiver, WRITE DIRECT TO Madison -Moore "A C," New Thordar- Some of the other readers of RADIO NEWS who son Power Amplifier, World's finest Dynamic Speaker. express a desire to communicate with other short- CONSRAD CO., Inc. wave Fletcher, 173 Avoniel Road, Discounts fans are: James for Set Builders Belfast, Ireland; Kendall B. Wood, 3 Harvard 230 Fifth Ave. New York , N. Y. CHI -RAD a... Place, Ann Arbor, Mich.; Melford C. Kupps, (wishes California correspondence) 537 North Mey- CHICAGO RADIO CONSRAD COMPANY, Inc. ler St., San Pedro, Calif.; Ben F. Locke, Martha- 230 Fifth Ave., New York, N. Y. APPARATUS CO. ville, Louisiana (interested in the "Pilot Wasp "); Gentlemen: Kindly send me one copy of your 415 S. Dearborn St., Dept. RN Larry Lucas, 19928 Canalport Ave., Chicago, IlL book, EVERYBODY'S AVIATION GUIDE CHICAGO (wishes letters from hams); Earl Eugene Martin, Enclosed and $2.00. 114 So. 34th St., East, Cedar Rapids, Iowa; George C. Brown, 96 Eighteenth Boulevard, Rockaway Name Beach, New York; John A. C. Bechtler, 114-11 One Y Hundred and Twenty-Sixth St., South Ozone Park, Address lamaI BODE u fee CALF'C' Work. Write for BIG FREE BOOK and remark. New York (broadcast receivers and accessories as able tuition offer FREE RAILROAD .nelnd.a. FARE- well); William Henderson, Route 2, Thomaston, City State isCZ0.0.7i -Y CLEVELAND. Georgia. Please say you saw it in RADIO NEWS

www.americanradiohistory.com Radio News for March, 1929 887

between WBZ at East Springfield t WBZA at The Constructor's Page Boston, the power of WBZ is 15,00 watts; while (Connued from page 850) that of WBZA is only 500 watts. 'he problem, houses of offer dealers' discounts to individuals however, is complicated by the fact at some in- should be discontinued; as it would soon ruin terefering condition exists at Won, ter or near the parts business. it which blocks reception of WBí from people In my estimation, no such business exists out- very far east of Worcester; and b ks reception side of such houses. Since reading his letter, I of WBZA from people living ven :ar west of bave visited several radio stores (some in Spring- the city. field) trying to buy parts, and failed in buying A. R. As r, even a binding post. They not only tail to carry 125 Chestnut St., I yoke, Mass. with Veranit parts in stock, but will not offer to obtain them on special order. WOMEN'S INTEREST IN ADIO insist on giving a long monologue on They also Editor, RADIO NEws: bow foolish it is for anyone to build a receiver; Mr. 1 aeker voices obtained May I combat the opinion as much better manufactured sets may be in the September issue? He is cons zed women's ,' (those they sell, in particular). sentimental carrying only interest in radio magazines is I do not blame these dealers for not one; leading me to believe that t knows only ft is not enough demand for them; parts, if there the type who prefers her newspape for the pic - not believe a dealer who will not risk but I do tures rather than as food for though I am earn - his money carrying parts and does not want to majority women are Honest estly convinced that the sell them, anyway, is entitled to the profit. earnestly endeavoring to grasp some f the essen- experimenters should not be forced to pay list reception, u tep and an doing tials relative to good prices when they have to take the trouble of insight into the future of radio. While some parts themselves. the dealer's work in sending for might enjoy knowing more intima y the facts If anyone is ruining the parts business, it is if amateur set pertaining to the personalities in lio, they the dealers who try to discourage had the slightest experience in t line, they builders and experimenters. realize that such interest is futile I quote R. NAPOLEON A. YOUNG, W. Service: 15 High Street, Monson, Mass. "Dreams are best- (There were in 1923, in the United States, not But ye must not seek too nr.,, radio parts; it less than 24,000 stores retailing For the shut -in, the isolated won woman is is to be doubted that, at the present time, there her best friend, councillor, and insp :ion. Music endeavor to are snore than 300 snaking a serious is the language of the soul and, e more she dealers complain that mail -order com- do so. The makes it an important of her C, the more of them part petition is killing their business; yet most does her heart, mind and soul expand Real women long discontinued their line of parts, even had desire more than the frosting on ,I cake. the mail -order houses began to offer goods before (Mss.) E. I CORSON, The reason is, of at practically wholesale prices. Manhasset, L. i New York. course, a dealer has to have a complete stock jenéen that Te in order to carry parts at all; and most dealers frankly admit that this is too much work and bother FROM A JUNIOR REA. :R for them, and that is why they have taken to the Editor, RADIO NEws: set business entirely. I am only twelve, but I am very t ch interested AUDITORIUM Our correspondent, in his letter, has stated the in radio. I have been listing all the ations I can case accurately.- Eotron.) get, 33 in the last three months. T only station I got on the dial over 75 was GB; Rugby, Eng- SPEAKER NOISY A.C. DETECTORS land (This was an American rebroad t-GBS is a Editor, RADIO NEWS: short -wave station and cannot be hec on a broad - DYNAMIC. OF COURSEl In the majority of cases, frying or bumming cast receiver without an adapter.) I ave the Jan - noises in an A.C. electric set may be traced di- uary issue of RADIO NEWS and find i, elpful to me. rectly to the 227 -type detector. One can easily I have given two speeches on radio at hool and got Here is a new dynamic speaker by tell by disconnecting the aerial and tapping the 88 and 90 per cent. in oral Englie I will give 227 tube, with the set turned on. Usually the another Thursday. I hope it will I successful. I Peter L. Jensen which again sets tapping will cause the noise to cease temporarily. know I would not have got over 83 cent. before the standard of reproduction, just Now here is the point: it is often impossible to if I had not read the October RADIO :ws. If thiv as his first dynamic 1927. n obtain adjustment on these tubes, as they test letter will do any good, you can pub. it, to show cone didin perfect. What can we do with them? They rep- that boys as well as men can run I take apart It is called the Jensen Audit°. resent $4.00 each; shops accumulate several dozen radios. in a month. J. P. PAPES rium Speaker, and brings to you a Becoming disgusted, we decided to put some of 101 Elmwood Avenue, Ith New York. quality, a brilliance and a volume them out of their misery, by placing the beater (Many of our youngest readers t an exceed - terminals directly across the output of a good, ingly intelligent interest in radio, an nake it their of reproduction never attained healthy storage battery. Result? No, the tube business to learn thoroughly, where any of their before. did not flash out; the heater did heat, though. elders skim over the subject.) Now, is it not a natural conclusion that these For use in auditorium or thea- frying noises produced by the tube are caused by tre this new all- purpose speaker poorly- welded connections and that the excessive DON'T ASK FOR A LOCATION .UEPRIN't voltage produced a high temperature in the heater Editor, RADIO NEws: should be operated from the larg- element which corrected these? We checked the The real test, as Mr. O. R. Aikmt calls it, of a est amplifier. For home use it is tubes for emission in a tube tester and then tried set is to use a wet "A" battery and y "B "s, and them in sets. The noises were gone. disconnect both aerial and ground. I e in a stucco just as efficient when operated If you have a flock of noisy 227 tubes, try this: house, plastered-over metal lath or de, and am from one type 171 amplifier tube. apply S or 6 volts for about 30 seconds. If they able to tune in all local stations, d some out - don't burn out, there is a pretty good chance the siders as far as Denver on a four -tu T. R. F. set Three models are available; one useful life of the tube is extended. without aerial or ground. If Mr. :iman doubts for field from 110 Volt PAUL L. McCovr, W9EHB, this, let him write to any friends b may have in operation 1218 So. 17th St., St. Joseph, Mo. Los Angeles and ask them to call me and be DC; one for 220 Volt DC; one for . (Desperate cases may require desperate remedies. convinced. With the denial and gro, I I bave had 110 Volt AC. The latter type, illus. One method of reducing hum-not contact noises- reception, verified by letter, of 4QG, isbane, Aus- is to put a positive voltage, say 45, on the heater tralia. It's not the set -it's the Joe, m. trated above, requires a full wave of the 227 tube, as compared with the cathode. R. WILLIS, 280 or 380. -EDITOR.) 6332 So. Cottage St., Huntingc Park, Calif. rectifier tube, type Approximately 18 watts are re- TWO STATIONS ON ONE WAVE RECEPTION WITHOUT A: ENNA quired to excite the field. The Editor, RADIO NEws: Editor, RADIO NEWS: 11 diameter. The letter of Albert E. Gleason regarding the I note with interest the letter fr Mr. O. R. cone is inches in fading of signals from WBZ and WBZA causes Aikman of Salem, Illinois, and yo, comment in Write to us, or let your dealer me to write to say that the same thing is observ- regard to readers being able to rec e on power - able here; two years ago the editor of the Rutland unit line alone as an aerial. demonstrate. Herald spoke of it in an editorial. I wrote to I have for some time been puzzled the peculiar MFG. COMPANY the radio editor of the Boston Post and suggested action of a superheterodyne of my m design, with JENSEN RADIO that it might be due to the signals part of the 338 N. Kedzte Ave., CHICAGO, ILL. a one -stage Robert's neutralized lio-frequency CAL. time, but he could not agree with me. However, amplifier ahead of the first detec This set 212 Ninth Street, OAKLAND. I do know that reception from WBZ has not been Jemen Patents Allowed and Pending- Licensed under receives all of the more powerful s Ions without Lektophone and Magnavox Patents as good since WBZA began using the same wave- either ground or aerial connection f any sort. length, as it was before. Ordinarily, I use an indoor aeria If about 25 R. L. HASTINGS, feet with a waterpipe ground. To sconnect the Granville, Vermont. aerial reduces volume about 25 pe ont, and to further disconnect the ground lea reduces the

Editor, RADIO NEWS: n volume about the same. I thus Ave stations v . If it will be of any help in solving synchroniza- with about 50 per cent volume shout either IIcnen tion problems, I will add the information that, ground or aerial leads attached. V n aerial and ><.t UDOTOR/UM SPEAKER.. while Worcester, Mass., is approximately half -way ground are disconnected, the tuning the antenna 'JrZ Please say you saw it in ADIO NEWS

www.americanradiohistory.com Radio News for March, 1929

RADIO NEWS N Everything Worthwhile in Radio! FIVE years ago the first issue of the building a TELEVISOR, cheaply RADIO NEWS AMATEURS' and simply. Television is in its infancy, HANDIBOOK was published. Each build a receiver now and enjoy the ex- year, since that date, a new revised edi- perimenting and constant improvement tion has been issued. Today RADIO which is sure to follow. The RADIO NEWS AMATEURS' HANDI- NEWS AMATEURS' HAND'. BOOK holds an unprecedented record BOOK is replete with the new up -to- for a book of this kind -MORE THAN date circuits for radio receivers, ampli- 200,000 ALREADY SOLD,-NOW! fiers, short -wave sets, eliminators and THE FIFTH BIG REVISED EDI- electric sets, in fact everything worth -. TION, 50,000 MORE COPIES while in the industry. GOING FAST. And the reason? RADIO NEWS AMATEURS' The big new issue contains over 112 HANDIBOOK contains complete in- pages - More than two hundred illus- formation on everything of interest to trations, diagrams the radio enthusiast. All the latest de- and drawings - velopments in both the television and Beautiful colored the radio field- circuits galore. Com- cover - Large plete diagrams and instruction for magazine size.

mo MMMMMMMMM I= ow an ma News- EXPERIMENTER PUBLISHING CO., At All 230 Fifth Avenue, New York City. 1 stands or Gentlemen: I Enclosed find 50c for which please send me a copy of the Direct RADIO NEWS AMATEURS' HANDIBOOX -Vol. 5. 1 1 Only I EXPERIMENTER Name PUBLISHING 50C Address 1 COMPANY I City State 230 Fifth Avenue, New York City . the copy

Please say you saw it in RADIO NEWS

www.americanradiohistory.com in- Radio News for March, 1929 889

circuit changes about one degree on the dial and when it was impossible to secure pa and a requires very fine adjustment. complete receiver was unheard of (tI is, for This set uses an inductively -coupled coil in the broadcast reception) I have since bu for my antenna circuit, wound on a two -inch tube; and own use and experimented with every cuit that neither positive nor negative filament leads are I considered worth while. had the negative Perhaps it would interest to knc my Here's grounded. This set previously you that the filament lead grounded; but, in order to use a present receiver, which I consider to t the peer short -wave converter, I found it necessary to dis- of them all, is none other than the N rohetero- connect this lead in the set. dyne, first described in RADIO News I in my Answer Last night I had good reception from Kansas opinion this receiver has not received to notice City, Mo., and Hot Springs, Ark., using neither that it deserves. Instead of the circui yublished to every question about the aerial or ground, and atmospheric conditions were I am using a stage of tuned R.F. als I of the principles, methods, or appa- not good. When receiving in this manner, I find first detector and three stages of interns ate R.F. ratus of radio transmitting that to place the ground lead within two or three at 850 meters, instead of two at 650 s ers, and inches of the aerial coil produces a noticeable I also use the grid -bias method instt of the and receiving. increase in volume. condenser -leak method on second dete . The I recommend for those superheterodyne fans who A.F. amplification and power pack ar separate, wish really clear, natural reception the use of the using three stages of audio; impedance -, :sistance- Tim: crystal as a second detector. I am using a car - and transformer -coupled, respectively; e trans- borundum unit with flashlight -battery bias and the former feeds into two 71 tubes connecte in paral- tone of this set is as nearly perfect as any set I lel. The output transformer is home -t structed, have ever heard, with almost complete absence feeding into a home -constructed dye do cone RADIO of noise. speaker made from an old Magnavox un F. L. WORCESTER, I do not believe the Neutroheterody has re- Mutual Bldg., Richmond, Virginia. ceived the attention that is due it and, eucour- age its use, I shall be glad to assist one to MANUAL INTERNATIONAL HETERODYNING NEXT? the extent of my ability in constructing nd oper- ating this receiver. The only thing : isk is a A Complete Course in Editor, RADIO News: stamped envelope for reply. Japanese broadcasting has followed the American One of the worthless articles .11 RADIO Radio of appearin Operation lead, and the BCJ chain (Broadcasting Corp. News recently is the Loveless entente I have completed at the beginning of Novem- Japan) was no patience with articles such as this. [t would In a Single Volume We now able to hear everywhere ber, 1928. are be perfectly all right if it were just Cored by degree, originating in Osaka or A Handbook programs of high your readers, although even then it aid take Tokio. American DX hunters around the Pacific up space in your magazine that could b srofitably for coast should be able to hear the same, from 8 p. m. used for something worth while; but it t not ig- (3:00 a. m. the same day, Pacific Students Japanese time cored by a great number of your reade j edging on some of the Japanese wavelengths. standard time) from the number that write you both p sing and Amateurs On Nov. 10 at 3 p. m. all Japanese radio listeners condemning it. Now I am not an ex -t nor a Operators heard over the BCJ chain the "Banal' shouted by "designing engineer" (as some of my ends call Inspectors Premier Tanaka before the "Shishinden," where the themselves) but the aerial question was tatted as enthronement of the Emperor and Empress was far as I am concerned several years go. Up For the first time taking place; also the National Anthem played by until that time I followed every fad an entire course of the navy band and the voices of the people gath- d fancy training in one regarding aerials, loop, underground, i - ered the ceremonies. de, out book the most at side, vertical, horizontal, bare and insu ed wire. - I am experiencing trouble occasioned by a con- complete and up- For everyday t Melbourne, satisfactory reception s as the to -date work on tinual heterodyne whistle between 3L0, majority of us want, the best place radio. Developed Australia, and JOCK, Nagoya, Japan; as well as ani est kind of aerial is the most convenient one; t means simply and clearly between 3L0 and an unidentified station which I from the elemen- - just string it up in any convenient pl , fifteen am sure is 7CA, Calcutta, India, at times. There tary stage right feet or more above the ground and for or more through all phases is one regularly between 2FC, Sydney and COHB, feet long. If and sometimes between 2BL, the receiver is what it ould be, of principles, practice, and ap- Harbin, Manchuria; such an aerial will bring paratus so that a beginner Sydney, Australia, and JOFK, Hiroshima, Japan. is just as mat stations, with just as much volume and select ty, with with no knowledge of elec- This is caused because stations occupy channels so tricity may get all he the same amount of static both natural ad man - needs close together as 370 and 371 meters. I am able made either for amateur operation might in proportion to signal as any er trick or to qualify for a government to find two pairs of stations which cause aerial ever conceived. a heterodyne: KGO, Oakland, California, and The least of wort is your license as operator or inspector. aerial. Needless to have se - JOGK, Kumamoto, Japan; also KPO, San Fran- say I not triec Love less aerial nor do I intend trying it; f: cisco, California, and 2FC, Sydney, Australia. I would Prepared by Official not use such a cumbersome outfit even it per- I hear that in the United States a careful clearing formed as the author k has carried out, and that claimed. You drop Examining Officer of wave channels been this rot. The author, is Radio all the stations are being picked up easily without G. R. Sterling, Inspector V. F. HOLLAND, and Examining Officer, Radio Division, U. S. heterodyne squeals. I am anxious to know if this is Dept. of Commerce. 528 Pinckney Court, Spartantn , S. C. The book has been edited true, and if readers of RADIO NEWS at different in detail by Robert S. Kruse for five years (1Ve must bespeak the kind palien of our Technical Editor of QST the Magazine points throughout the world would drop me a line readers for of the to tell what heterodynes they find, shall be much articles which may seem a ecessary Radio Relay League. Miany other experts as- I to them; but we may point obliged. out that the cost con - sisted them. venient type of aerial differs for residen MINORU NAKAXURA, of New Elementary Electric- York and residents of Nevada, perhaps One of 16 Chapters Cover: ity and Magnetssm Yamate, Oiso, Kanagawaken, Japan, our readers in Canada writes that the i s of dis- Motors and Generators; Storage Batteries and (The troubles of regulating radio in North Amer- tilling water ica and in Europe alike have been many. In the for battery purposes is r culons- Charging Circuits; The Vacuum Tube; Circuits it is necessary only to melt new -fallet snow to Employed in Vacuum Tube Transmitters; Modu- former, with only four countries to consult, inter- lating Systems; Wavemeters; Piezo -Electric Os- obtain an ample supply. And, probably s reader tuitional problems have not been acute; but the com- in Panama cillators; Wave Traps; Marine Vacuum Tube has simply put small stations in the United would have no more patienc, with this Transmitters; Radio Broadcasting Equipment; mission suggestion than Mr. the same waves and let them interfere Holland has with ; pie who Arc Transmitters; Spark Transmitters; Com- States on reside on the with each other to their heart's dissatisfaction, twelfth floor of a twenty fur -story mercial Radio Receivers; Radio Beacons and Di- building, and who have the same oppt snity to rection Finders; Radio Laws and Regulations; while giving cleared channels to highpower sta- put up Handling and Traffic. tions. As a ten -kilocycle whistle is rather above a good outdoor aerial that he s to be ordinary ears audio amplification, little trouble elected president of the United States. may be never before available and further remarked New should be experienced by owners of fairly selective -as it is elsewhere in is issue Information such as a complete de- the importance scription of the Western sets, except in locations so near to a transmitter -that of the antenna s em ccn- Electric 5- Kilowatt not be Broadcasting Transmitter; description that its wave seems unduly broad. In Europe, with overrated, so far as distance r. ption is and cir- concerned.- Eoxrost.) cuit diagram of Western Electric Superhetero- many populous nations in a small area, greater dyne Radio Receiving Outfit type 6004 -C; Navy trouble is experienced in making allocations; and the Standard 2- Kilowatt Spark Transmitter; etc.; first of this year has ushered in wide and sweeping etc. Every detail up to the minute. THE EAST PASSES C changes. However, heterodyning between continents JUDGME is a new proposition; and if it must be taken into Editor, RADIO NEws: I bave been a constant reader Free Examination consideration, all the problems previously facing of you: tagazine "The Radio Manual" has just been published. Nearly radio become insignificant. for several years, as well as of several ter pub- 700 pages. Profusely illustrated. Bound in Flexible administrators will We Fabrikoid. The lications, both British and American, s derive coupon brings the volume for free ex- have learned that reception across the Pacific is amination. If you do not agree that it is the best seemingly better than across the narrower Atlantic; much pleasure and information from the Radio book you have seen, return it and owe nothing. but apparently high DX sensitivity must bring Radio broadcasting over here has not en very If you keep It, send the price of 80.00 within ten days. drawbacks. It would be a terrific surprise to the popular in the past, the fundamental re: n being average DX listener if he found WIZ heterodyned the lack of broadcast stations. Howe there Order on This Coupon by Hamburg, Germany; IVGY by Stuttgart or are some very keen amateurs here who succeed WLW by Frankfurt. Have any of our readers in bringing in far-away stations, especia on the D. 'Van Nostrand Co., Ina, with supersensitive sets been troubled like this?) short waves. However, we are assort by the of a s Warren St., New York government local broadcast static in the Send me THE RADIO near future. MANUAL for examina- WE ARE REBUKED tion. Within ten days after receipt I will either Radio dealers here are very few; but sat return the volume or send you $0.00, the pries they in full. (E.G. 3-29) t Editor, RADIO NEWS: have for sale are good quality parts of both I have been an ardent radio enthusiast since British and American origin, widely vertised Name the opening of the pioneer station KDKA, and in your own and other radio journals; s ve have St. & No. remember well the opening of some of the other a fairly good chance of comparing B ish and old- timers such as WWJ, WJZ and WSB and American parts and ideas. The writer is opinion City and State Beginning with a simple tube others. one set that, providing parts of well -known n kes are Please say you saw it in R, DIO NEWS

www.americanradiohistory.com LtuutV LYr.'WJ It!/ LYL(lrLlb, 17G7

selected, there is very little to choose in general between both countries. You Americans excel I Want to Know and in superheterodyne construction, "A" "B" (Continued from page 852) power units and socket- powered sets, as well as in R.F. amplification. and, in this case, No. 12 D.C.C. wire should be But there is one point in which the writer is used to carry sufficient current for a number of dissatisfied with American apparatus, and that 226 -type tubes. Center-tapping of the windings is in the matter of vacuum tubes. It is his un- which require it should be done as the winding biased opinion that the British tubes are very much progresses, and the ends of the wires should be superior, and I think that the American public brought out through holes in the end of the spool. The newest radio wrinkles-A-C, grid tube, does not realize it. Take, for instance, the 201A One section of the core should be assembled with short wave, television, dynamic speakers is approximately 10,000 and type of tube; the impedance the long laminations, (offsetting every other one, newest tubes and circuits-anything amplification factor 8, filament current 0.2S- everything in radio -are now ready for ohms, 1% inches, so that the core will fit together cor- you at Barawik's. With inaugural, foot- ampere, volts S; the conductance being roughly rectly; see Fig. Q2332) using enough to make a ball, National broadcasting Rosy and 0.7 milliamps per volt. The 199-type has an im- pile 1% inches high; the pieces are then bound other big doings filling the air, thou- pedance of 16,000 ohms, amplification factor 6, firmly together with friction tape. The spool con- newcomers will take to sands of filament volts 3, filament current .06- ampere; the taining the windings is next slipped over the core radio this year as never before. Busi- mutual conductance being roughly 0.3. These art ness will be good -Set builders will and fastened tightly by forcing several wooden make money. You can clean up big representative examples of your general- purpose wedges between the coil and the core. Finally, by Buying from Barawik -the old- tubes, as used for both radio- and audio -frequency the rest of the core is assembled around the coil est, biggest, most reliable radio amplification. and the complete core is firmly bound with friction house in the world. Let as prove it. Against these may be compared the British to prevent the laminations from vibrating. Send now for the Bb Book -all tape ready for you -free. Get the latest "valves" for general purposes, such as the new radio information and lowest prices. Marconi and Osram DEL610, whose characteristics are: filament volts 6; current 0.1- ampere, imped- ance 8,000 ohms, and an amplification factor of BARAWIK CO. 15. The DEL410, with a filament voltage of 4, 13-B CANALSYL, current of 0.1- ampere, has an amplification factor of CHICAGO, U.S.A. 15. And compare the 240 -type with the DEH610; the former has an amplification factor of 30 for This Big Book Sent FREE an approximate impedance of 150,000 ohms; while to You Free BWK the latter has an amplification factor of 40 for an impedance of only 60,000 ohms. And look Name also at the British screen -grid tubes, especially Ediswan; the SG610 with a filament voltage of 6 0.1- amplification Address and current of ampere has an factor of 140 for an impedance of 100,000 ohms; while the 222 has an amplification of 180 for an City impedance of approximately 800,000 ohms. You will see that British tubes.are enormously superior. A simple test can easily be made by the substitu- tion of a British tube in an American circuit de- signed for say, the 201A -type, for which a DEL610 is very suitable. The amplification obtained will be increased very noticeably, In the Browning- Drake circuit, such a test in the radio-frequency amplifier increased amplification enormously; so Four laminations are used for each layer of th you will see that there is a good deal to be done core; they are "staggered" to make it firm. I f in the matter of improvements in American radio should be bound firmly together. upisc tubes. The introduction of the Ceco "Type K" is a step in the right direction; but results as It might be well also to clamp the laminations CLEAR yet do not compare with the British tubes. tightly between wooden blocks, although this is The does not wish to disparage the Ameri- writer not essential. Such blocks are 5 inches long, with can product; but in the craze for sensitivity and boles cut in the ends to carry bolts. Four are volume would it not be more sensible and logical required, and placed at the opposite ends of the for the manufacturers to look into the matter of core; at. each side with a bolt at each corner. vacuum laboratories one tubes? American research To design a transformer for 25 -cycle current, the T have done extremely well in the performance of cross -sectional area of the core should be twice Q4; amplifier coupling devices, both radio- and audio - the given value, or 114 inches square; the same frequency, such as the Loftin -White, the Jewell, number of windings will be used in each case. the Hiler, the Clough and others; let us see some improvements in tubes. There will be a huge market for the sale of radio HIGH -FREQUENCY FILAMENT SUPPLY. in China in the near future, if only the govern (2333) Mr. A. H. Murray, Rochester, N. Y. ment becomes a little more settled and officials writes: do not consider radio sets as contraband of war. (Q.) "Can you give me some data as to bow But literature and catalogs relating to American I may step up a 6 -volt 60 -cycle current of four products are rare here. The writer, as a dealer or five amperes to radio frequency? I believe and constructor, would welcome any which your that the Fansteel Company uses such an arrange- manufacturers may send him. ment in their new radio receiver. If details can- EDWARD CHAN, not be given, I will be satisfied with an idea of P. O. Box 262, Hongkong. how to proceed, so that I will be able to do some (The late Col. Mulberry Sellers, with all his experimenting along this line ?" VITo optimism, never visualized the market which a (A.) Most A.C. receivers produce a small amount modernised Orient offers for radio. 77íe criticism of hum, even though care is taken to prevent this. which our correspondent offers impartially may be The 226 -type tubes cause a considerable amount ARCTURUS of interest to our readers; although American tubes, of hum unless they are carefully balanced, and A -C LONG LIFE TUBES developed for the American trade primarily, are of even the 227's with isolated heater -filaments are the highest quality, they may not be so satisfactory not absolutely free from bum. The "A" power ° ARCTURUS RADIO CO. as the European tubes for consumers bent on strict units used to electrify battery -type sets are prac- NEWARK, N.J. economy. The design of the American tubes has tically hum -free, if properly constructed, but they reached a high degree of standardisation; the short are affected by changes in the supply voltage. list of tabe -types which we are now publishing is Series -filament arrangements have been used with hardly a tenth as lang as the European roll of some success, but radical changes must be made "valves." The American receiver of commercial in the wiring of the set for such a method of manufacture furnishes the principal demand for supply. Other complications, such as audio feed- tubes; and no such economy is sought in their use backs, are also encountered and are often hard as in Europe, where it is important to squeeze the to eliminate in sets of this type. last bit of energy out of each tube. The British One method of overcoming these difficulties has WRITE radio press chronicles with awestruck surprise that been utilized by a radio manufacturer, to change TODAY the average set exhibited at the World's Fair in the rate of alternations in the supply voltage from New York last fall had seven tubes; and wonders 25 cycles or 60 cycles to a frequency above the Send for large, new il- what in the name of Croesus the maximum could audible range. In this way, ordinary battery -type lustrated Catalog "B -5," have been. If the American manufacturer finds tubes can be operated from an alternating -current that a couple of extra tubes which add no ampli- supply without noticeable hum. A frequency is showing the latest of fication will make it easier for the lady of the chosen above the audible band but not high enough everything in radio at house to operate the receiver by the snap of a to cause interference in the radio frequencies. switch alone, he incorporates them in the design, Such high -frequency currents are produced by a wholesale prices. and they are charged to the paying teller of the 250 -type tube, which is supplied with current from family. Nor, since there are light -sockets every- an ordinary high -voltage "B" power unit, using where (almost), does an extra hundred, or two 281 -type rectifiers. hundred, volts of "B" present The 250 , an obstacle. In tube is connected as an oscillator with Allied Radio Europe, as in Asia; such Sybaritic luxury does a suitable coil arrangement, using either very CORPORATION not appeal to the average home thin laminated iron filings even, 711 W. LAKE STREET, CHICAGO constructor iron, or air only, EDITOR.) in the cores. An ordinary oscillator circuit, such Plase say you saw it in RADIO NEWS

www.americanradiohistory.com Radio News for March, 1929

as the Hartley, is used and suitable. cils - are coupled to the oscillator inductor to light the fila- ments of the tubes in the set. The tubes are connected in the usual parallel manner. Offhand, one would not suppose that a 250 tube can supply sufficient current to light the filaments of the tubes used in a radio set; but .it must be remembered that the plate current of this tube is almost 25 watts at maximum value and the current required for the filaments of an average RITY 5- or 6 -tube set, rarely exceeds 12 watts. The L frequency of the current does not affect its ability to light the filaments as long as there is sufficient current, and a suitable oscillator arrangement can SPEAK FL be made to supply this current. The power tube or tubes in the receiver can be operated from the usual 110 -volt -primary, step. down transformer; since very little hum is noticed OPER ION when these tubes are operated on. the 60 -cycle supply, and this lightens the load on the oscillator even more. The transformer must be specially con- fro a structed, as mentioned above, and no information is available as to the construction of a filament transformer of this type. If the system is to be tried out, the experimenter will have to try dif- ferent core arrangements, etc. No one except an wzaCRY-SaRiamsz amateur familiar with transmitting work and R.F. currents of some magnitude should attempt it. NO "TUBES" - NO "B" BAT- Another point which must be considered is the control of the filament supply. This may be accom- TERIES - NO COSTLY plished by controlling either the filament voltage or the plate voltage in the oscillator tube; it might °ELIMINATORS" be varied also by adjusting the value of the grid WITH THE leak on the oscillator. The filament current for the 250 oscillator tube in manufactured power units is supplied from a special filament winding on SKINDERVIKEN the power transformer; which supplies also the plate current for this tube and the other tubes TRANSMITTER UNIT in the receiver. Simple microphone unit provides a most effec- tive and inexpensive way to satisfactory speaker operation. Easy to build and operate circuit. Everybody can do this now with a Skinderviken Transmitter Unit. THEM AIN'T WOLVES, THEY'RE The unit is fastened to the dia- phragm of the speaker unit. It will MOSQUITOES( act as a "microphonie relay." Every Aspersion on New Jersey's suburban residence time an incoming signal actuates belt and on the RADIO Naws station is, we fear, the diaphragm, the electrical msist- in this from the latest ance of the microphone unit will be contained by innuendo listing varied correspondingly and the cur- Citizen's Radio Call Book: "W2XAL -WRNY, COY- rent from the battery, in series OTESVILLE, N. J." Our worthy chief engineer, with it and the loud speaker, will fluctuate accordingly. Thus the problem of securing sufficient power to actuate the loud speaker is simply and adequately solved. The results from this very novel and simple unit will astound you. The expense of this hook -up is trifling compared to the elaborate tube circuits that give no greater Y! actuation of the speaker. R ,M A Besides this there are many other valuable uses in a Radio Circuits for this marvelous little unit. Every builder of Radio sets should have a few on hand. LISTENING THROUGH WALLS This Unit makes a highly sensitive detectaphone, Mr. Maresca, climbed the aerial masts with his Noted for the the real thing -you listen through walls with ease. Plenty of fun and real detective work too. trusty Springfield, and reported not a coyote in sight. -Joseph Riley. CONDUCTING SOUND THROUGH WATER Bell -Like Clarity Make yourself a miniature submarine signaling NO USE-WE TRIED IT apparatus like those used during the war. Simple Volume- control tip from the Providence Journal circuit with this microphone unit gives splendid results. calls for resistor of about 100,000 ohms which of their Tone 12-PAGE INSTRUCTION BOOKLET "should be inserted so as to control the LATE volt- containing suggestions and diagrams for innumerable age on the radio-frequency tubes -all three or four CECO's exquisite tone quality is uses, furnished with each unit. of them." Our "B" batteries have run down until not accidental. It is the result of we can speak of their voltage as the late lamented; deliberate effort in design, a higher P. G. MICROPHONE TRANSFORMER but we don't believe any resistor will get another special and amp. out of them. We'll just have to buy more. quality of materials and A Modulation Trans- -Chester H. Page. exclusive processes which are em- former specially de- ployed in the rugged construction signed for use with theSkinderviken Trans- of these beautifully toned, long - mitter Unit. Has many lasting tubes. Sold everywhere. other uses. Primary resistance,h a e Station Have you heard CeCo's delight- eì4 ohm; sec- s7 ondary. 55 fully entertaining radio program ohms. over the entire Columbia Broad- casting Chain of 20 cities -every FOR SALE AT LEADING DEALERS WRNY Monday evening, 8:30 Eastern Or Order Direct, Using Coupon Below N EW YORK time, 7:30 Central time? 297 METERS -1010 KILOCYCLES SEND NO MONEY and W2XAL, 30.91 METERS CeC° Mfg. Co., Inc. Providence, R.I. When the postman delivers your order you pay him for is oumed and operated by the- whatever you have ordered, plus a few cents postage. publishers of this magazine PRESS GUILD. INC. Our Editors will talkt to you 16 -I8-R -East 30th St.. New York, N. Y. Please mall me at once as many of the following items several times every week- as I have indicated. ,... Skinderviken Transmitter Units at 95c. for 1; $1.75 See your2*(ewspaper for 2: 52.50 for 3: $3.20 for 4. .. P. G. Microphone Transformers for details 0 at 52. When delivered I will pay the postman the cost of the TUNE IN ON r Items specified plus postage. WRNY Name Radio Tubes Address FOR EVERY RADIO NEED

City state Please say you saw it in RADIO NEWS

www.americanradiohistory.com 892 Radio News for March, 1929 AN AMPL/F/FiE' AND.pp¡yF

A.C. RECEov.g2 ORSON

Radio Listeners' Guide and Call Book NEW ISSUE JUST OUT Un -to- the -Minute News and Views

RADIO LISTENERS' GUIDE AND CALL BOOK reflects every thing of pertinent interest to the radio enthusiasts. In the new issue, just off the press, are articles that call forth particular attention. Some of these are building a corner cabinet for the radio set, giving all dimensions, layouts, instructions, etc. A very interesting article by Mr. John Rider, called the qualifi- cations of a radio service man. A new article on the series to sell custom built sets etc. Another feature of note in the new issue is a complete list of the call letters and wavelengths of every short- wave broadcasting station in the world. Still another interesting feature is the section called "THE RADIO SET MARKET." Herein are listed the names of all worthwhile custom set -builders, those indi- viduals whose business it is to build receivers to order. For those who desire to buy a radio set it would be well to consult our geographical list of these builders. In this way you are assured a fine custom built job with none of the flaws that are so prevalent in the manufactured type of receiver. Custom Set- builders are invited to utilize the service of this magazine by inserting their ads at no cost. See RADIO LISTENERS' GUIDE AND CALL BOOK for conditions. OTHER CONTENTS A complete list of all U. S. Broadcast Stations in alphabetical order, by wavelengths and by states. Also Canadian and foreign stations. A series of eleven articles on "How To Build Radio Sets." Full construction information, diagrams and dimensions. RADIO LISTENERS' GUIDE AND CALL BOKK -over 150 pages. Large maga- zine size. Replete with photographs and diagrams. THE 50c COPY On All Newsstands and Radio Stores

230 Fffth Avenue, CONSRAD COMPANY, Inc. , New York, N. Y.

say von saw it in RADIO NEWS Please www.americanradiohistory.com 7 Radio News for March, 1929 893

as follows: "A.C. tubes are the equal of any other Radio Literature type -providing the user has a mental age of more page 847) than 10 years. Every high -priced commercial re- (Continued from ceiver built today -offering tonal quality, ease of such as Raytheon N. AMPLIFIER MANUAL, pub- operation and cleanliness of maintenance f POWER was never dreamt of five years ago -employs A.C. lished by Thordarson Electric Manufac- tubes throughout. In the vernacular- caugh that K1rL9 IgniP turing Company, Chicago, III. Pamphlet, off !" . the book, 7t/2x10 inches, 64 pages, circuit and sche- However, all this does not describe which contains about everything worth-while know- matic diagrams, half- tones. Price 25e. ing about A.C. tubes and their operation. It is Here is a little booklet which should please the chock full of circuit diagrams, curves and sug- radio constructor who finds himself dabbling with gested circuits, and presents its subject matter in power units and power amplifiers. The publishers, customary Rider style. More than that cannot well -known manufacturers of radio apparatus since be said of any book. the days of 200 -meter "spark" amateurs, have pre- sented to the radio fan every type of "B" power unit and power amplifier worth bothering with. And have done so in commendable manner- plenty Radio News Laboratories of schematic diagrams, circuit diagrams and pic- tures for the fan who feels their need. While it is (Continued from page 847) only natural to assume that the publishers have for specified and illustrated their own products through- "A" POWER UNIT Television out -and they have-it should be borne in mind The "No. 600" "A" power unit submitted for that the diagrams they offer apply to standard test by the R. B. Specialty Company of 318 Syca- apparatus produced by any manufacturer of power - more Street, Cincinnati, Ohio, is designed to operate Reception unit components; schematically, a power trans- directly from a 110 -volt 60 -cycle house -lighting cir- former is just a power transformer, and the same cuit. Under actual use, two amperes of current at This lamp is made in numerous may be said of a filter condenser or a resistor. In six volts were obtained without hum or undue heat- types and styles, which provide other words, should the constructor desire to build ing. The rectifier element is of the dry-disc type suitable light sources and light- from this pamphlet with suitable apparatus he has and rated at 2.5 amperes. The entire apparatus, sensitive relays for all systems. on hand, he will have no trouble in doing so. comprising a step -down transformer, choke and filter condenser, is enclosed within a black enameled sheet List Price, $7'50

A RESUME OF THE TUNED- DOUBLE- IMPEDANCE SYSTEM OF AUDIO - á Raytheon FREQUENCY AMPLIFICATION, by John F..Rider. Published by Hider Audio Fotofell Corporation, Irvington, New Jersey. 11t/2x8% inches; 16 pages; pamphlet; dia- grams and curves. Free distribution. Mr. John F. Rider, though he be ever so slightly bald and wears glasses, is a research engineer who metal case, 6 inches by 8 inches by 5 inches. A has done more to make the "characteristic curve" bakelite panel serves as a mounting support for the popular with the experimenter than has any other rectifier element and also for tip jacks which are pioneer in this difficult and worthy endeavor. Fur - used for the adjustment of the device. A ten -foot thermore, the gentleman in question possesses an extension cord leads to the light receptacle, and uncanny knack of emerging from his laboratory two three -foot colored leads are supplied for the (famous for its thorough instrumental equipage) output. and presenting to all who are interested in tech- AWARDED THE RADIO NEWS LABORA- nical radio a compilation, a table or a curve. What- TORIES CERTIFICATE OF MERIT NO. 2532. for ever it may be, the reader may rest assured that it is accurate and worthy of reading -otherwise Television Mr. Rider would not have bothered with it. The CAGE -TYPE ANTENNA KIT pamphlet reviewed herewith is somewhat of a com- The cage -type antenna kit submitted by the Thor - Sending pilation or, better yet, a thesis accompanied by a ola Radio Products Co. of 110 E. 21st Street, Chi- group of enlightening turves which deals with cago, Illinois, is composed of five strands of No. This is an extra -sensitive broad- relative audio -amplification systems and just why 16 enameled wire, separated by four discs which casting tube, supplied in either they are or are not that way. Though the handling taper from a diameter of 4 inches at each end. of the subject is somewhat above the beginner's The length of the cage is approximately 30 feet hard vacuum organ filled types, ken, it should be read by all who are interested without the lead -in; it is supplied with two porce- and in two sizes of each. in this subject; for Mr. Rider promises in the fore- lain insulators and a lightning arrester. The con- Information and prices on application word of his excellent pamphlet to emerge from his struction is very rigid and will withstand hard laboratory every so often with a new pamphlet on usage. the same subject until he has completed a series AWARDED THE RADIO NEWS LABORA- which will cover the subject in his usual thorough TORIES CERTIFICATE OF MERIT NO. 2534. r ]E$a he on BH style. tLONG LIFE RECTIFYING TUBE d While it is not the reviewer's position to ques- tion or affirm the contents of the pamphlet, it must SHIELD CANS be admitted that the cause of the tuned- double- The "Type AS.1" shield can, submitted by the impedance audio amplifier is championed in a most Ilammarlund Mfg. Company, 424 W. 33rd St., New convincing manner. In fact, the mathematically York City, N. Y., has been designed to enclose precise proofs offered by the author and the manner R.F. stages of radio receivers where a shielded in which the entire matter is presented should be compartment 6x7x6 inches is required. The can is enough to sway any experimenter interested in constructed of sheet aluminum 1/32 -inch in thick- audio -amplification systems. ness; its sides are held together by aluminum cor- ner pieces which slide into place, making a rigid and positive contact joint. When completely as- sembled, the can was found a very effective electro- A.C. TUBES -HOW TO USE THEM, by static shield, due to the lap joints of the various for John F. Rider. Published by Radio Trea- sections. The "Type AS -29" shield can is of the same general characteristics but with dimensions of "B" Power tise Company, New York City. 11 %x9 6 inches by 8 inches by 5A inches, and designed inches; line drawings and curves, 75 pages. for use in the Hammarlund- Roberts "HiQ -29 Mas- Eliminators Price $1.00. ter" radio receiver. There AWARDED THE RADIO NEWS LABORA- Over a hundred different makes should be a law compelling every radio NOS. constructor to read TORIES CERTIFICATES OF MERIT of and study the contents of this 2535 AND 2536. "B" Eliminators require this book. It is the best dollar's worth of vacuum -tube tube, and take no other. There literature ever presented to the experimenter. are millions of them in daily, We are very anxious tq have every "expert" who satisfaction- giving use. doubts the efficacy of the A.C. tube read this book; for we are quite sure that, even though it is noth- List Price, $4.50 ing more than a simple treatise, he will stagger through the very comprehensive and intelligent Write for further information on any writings of Mr. Rider. Then we are positive that of this equipment we will be rid of another pest of the know -all type. In his introduction the author says, "A.C. tubes No. 2536 No. 2537 are satisfactory -providing that the tube used is of RAYTHEON MFG. CO. good design and that it is correctly employed." The 'Type HQS" shield can, submitted by the In our estimation that is not strong enough, though same concern, has been designed for use where a CAMBRIDGE, MASS. we admit it was written by a mind a bit more con- double -compartment can is desired. It is con- servative than ours. It should have been worded (Continued on page 895) Please say you saw it in RADIO NEWS

www.americanradiohistory.com 894 Radio News for March, 1929 OPPORTUNITY AD -LETS Follow these advertisements every month. Reliable advisers from all over the country offer their most attractive specials in these columns. Classified advertising rate twenty -six cents a word for each insertion. Names and addresses must be included in the above rate. Cash should accompany all classified advertisements unless placed by an accredited advertising agency. No advertisements for less than 10 words accepted. Objectionable or misleading advertisements not accepted. Advertisements for the May issue must reach us not later than March 2nd. CIRCULATION LARGER THAN THAT OF ANY OTHER RADIO PUBLICATION EXPERIMENTER PUBLISHING CO., INC., 230 Fifth Avenue, New York, N. Y.

Agents Wanted Old Money Wanted Radio (Cont.)

Guaranteed Genuine Gold Leaf Letters anyone can put on Old Money Wanted. Will pay $100.00 for 1894 Dime. Build Your Dynamic. Speaker with our castings and in- atore windows. Large profits, enormous demand. Free 8. Stint., $50.00 for 1913 Liberty Head Nickel (not Buf- tructioha Send M. O. for $8.50 to A. C. Klein Co., 1058 samples. Metallic Letter Co., 922 N. Clark, Chicago. falo). Big premiums paid for all rare coins. Send 4c N. 10th Street, Reading, Pa. for Large Coin Folder. May mean much profit to you. Numismatic Co., Dept. 112, Ft. Worth, Texas. Bargains, used radios. Guaranteed perfect working Agents -$50. Weekly Selling Shirts. No capital or order. Blue Ribbon 5 tube, 2 dial, Console $19.95. in Samples Old Coins. Large Spring selling catalog of coins for Freshman $14.95. Atwater Kent $19.50. Tubes included. experience needed. Commissions advance. famous makes. money Free. Madison Products. 560 Broadway, New York. sale -free to collectors only. Catalog quoting price. paid Many Send order with order. for coins, ten cents. William Hessleln, 101E. Tremont SL, Bargain list on request. Surplus Radio Co., Dept. 2 -C, Boston, Mass. 172 W. Harrison St., Chicago. Agents Cleaning Up with Lenowa Combination: 65c clear . For Salo -New type short-wave coils and receivers. profit every dollar sale: write for free sample. Great $2 to $500 each paid for hundreds of Old or Odd Coins. A. R. Dempster. Ultrichsville, Ohio. Western Industries, 4125K Penn., Kansas City, 510. Keep all old money, it may be very valuable. Send 10c. Powerful, shieldless, loop, antennae circuit, Archer, New Coin Book 4x8. $1. lllll nomu lllllllll 41.111M llllllllllllllllllllll =mount llllllllll 11.10111.01111111111111111111 lllll 11111011111111 for Illustrated Value Guaranteed 617 Decatur St., Brooklyn, N. Y. prices. Get posted. We Cash. Clarke Coin Com- pay , 1e,,,, 1,,,M 1 1M,,,,,M o,,,,,,,.,, 1,.M, 1, o,,,,M,,,,,M, ,MO, e, i .M a .,iewMe,a,e,,,.,M,Ma,eM,M,w pany, 14 Street, LeRoy, N. Y. Business Opportunities Salesmen Wanted Patent Attorneys Screw- holding screw driver! Amazing brand new pat- Free Book. Start little Mail Order business. Hadwil. entee invention! Retails $1.50. Factories, garages. elec- 5A -74 Cortlandt Street, N. Y. tricians. auto. radio owners buy on sight! Exclusive state territory. Genuine opportunity earn big money. Free trial offer. 1058 Winthrop Bldg., Boston. Amateur Cartoonists: Sell Your Cartoons New Plan. Jlgy. Smith's Service L'ä1194, Wenatchee, Wash. Song Writers Inventions Commercialized. Patented or Unpatented Write Adam Fisher Mfg. Co., 278 Enright. St. Louis. Mo. Song -Deem writers. Address, Monarch, 238 West 55th Patents -Time counts In applying for patents. Don't Dept. 322, New York. risk delay in protecting your ideas. Send sketch of model Song- for or for book, "How to Writers:- Communicate with Kendis, Gusman & instructions write free Obtain Samuels, Inc.. Music Publishers, 145 W. 4551: St., New Chemistry a Patent" and "Record of Invention" form. No charge for York. Enclose return information on how to proceed. Communications strictly postage. confidentiaL Prompt, careful, efficient service. Clarence Song Poems Wanted: Write at once. Valuable instruc- Learn Chemistry at Homo. Dr. T. O'Conor Sloane. A. O'Brien, Registered Patent Attorney, 309 Security tion book given Creel (tell Music Co. D -11. St. Louis, Mo. noted educator and scientific authority, will teach you. Our Bank Building (directly arrosa street from Patent Office), home study correspondence course Ms you to take a position Washington. D. C. Stamps as chemist. See our full page ad on page 661 of this issue. Chemical Institute of New York. 16 E. 30th Illustrated U. S. Price List 50e; Large U. S. and Street. New York City. Canadian List Free. Stanley Gibbons, Inc., 38Z Park Row, N. Y. C. Correspondence Courses Telegraphy

Used correspondence school courses sold on repurchase Patents -Free instructions. Former Patent Office Ex- Telegraphy -Both Morse and Wireless taught thoroughly, basis. Also rented and exchanged. Money -back guarantee. aminer. Moderate terms. Booklet. Albert Jacoba. 740 Big salaries. Wonderful opportunities. Expenses low. Catalog free. (Courses bought). Lee Mountain. Pisgah, Barrister Bldg., Washington, D. C. chance to earn part. School established fifty years. Cata- Alabama. log free. Dodge's Institute. Cour St., Valparaiso. Ind. Patents -Write for Free Instruction,. Send Drawing or Model for Examination. Carl Miller, Registered Patent Attorney (former Patent Office Examiner). 262 McGill Detectives Building, Washington, D. C. Detectives Needed Everywhere. TraveL Experience un- Patente -Send for forts "Evidence of Conception" to be The FUTURE necessary. Particulars Free. Write, American Detective signed and witnessed Form. fee schedule. information free. System, 2190 Broadway, N. Lancaster and Aliwine, Registered Patent Attorney. in United States and Canada, 269 Oursy Bldg.. Washington. M sY,,, 1,,,,,,,,,,,,,, ,,,.,,,.,,,,,n.mn,,. D. C. By For Inventors Patents -Bend drawing or model of your invention for examination and instructions. Advice and booklet free. Professor A. M. Low Inventions Commercialized. Patented or Unpatented. Highest references. Best results. Promptness assured. Write Adam Fisher Mfg. Co.. 278 Enright. St. Louis. Mo. Watson E. Coleman, Patent Lawyer, 724 9th Street, N.W., Washington, I). C. "THE FUTURE is one of the most remarkable books of the age. Professor For Sale Inventors- Should write for our Free guide Book, "How Low, the author, is a scientist of interna- To Obtain A Patent" and Record of Invention Blank. Send Model or sketch and description of inventions for Inspection tional reputation, also an experimenter Alfalfa Seeds, hardy common varieties $8.40. $10.20. and Advice Free. Radio. Electrical, Chemical. Mechani- and inventor in the many branches of $12.60 bushel; Grimm variety Alfalfa seed $18. Scarified cal and Trademark Experts. Terms Reansonable. Victor J. sweet clover $3.90, $5.20; Alsike or red clover $15. Evans & Co.. 922 Ninth. Washington, D. C. science. This book written by him has Bags Free., Send for samples and catalogue. Kansas Seed Co., Salina, Kan. aroused wide-spread interest. It deals

1111, with the world of the future, certainly an ,,,,,,,,,,,,,,,,,, M,,,,,,.,,,,,,.,.,,,,,,,,,,,,,,, ,,,,,,,,,,,,,,,,,,, 1,,,,,,,,,,,,,,,,,, 1,,,,, ,,,,,,,, 1M,,,,,, .,,,,, 111111$1. Patents unusually absorbing subject. in Help Wanted-Instructions Written Inventions Cemmereialized. Patented or unpatented. the popular, non-technical fashion, "The Write Adam Fisher Mfg. Co., 278 Enright, St. Louis, 51o. Future" reveals the many advances and Wanted Immediately, names of hard -working men and women. 18 to 55, who want to make more money. Write, changes that are in store for humanity in Instruction Bureau, 251, SL Louis, Mo. Printing, Engraving and Multigraphing a new life to come. This book has received favorable com- Instruction M uItlg rap hing, two dollars thousand. blisrelianeous ment in book reviews the world over. Do Printing. Mayer Rey Corporation, Monmouth, Illinois. not neglect to read this treatise on the Learn Chemistry at Home. Dr. T. O'Conor Sloane, future by Professor A. M. Low. It is a noted educator and scientific authority. will teach you. Finest Bond Letterheads. 84 r 11. $3.955f. Envelopes, literary treat for everyone. Our home study correspondence course ate you to take a $2.95M. Oberman Company, Box 1042, Chicago. Position as chemist. See our full page ad on page 861 of this issue. Chemical Institute of New York. 16 E. 30th Mail your order nowl Don't wait, every- York Street. New City. Printing Outfits and Supplies body is reading this remarkable book.

Male Help Wanted Print Your Own Cards. Stationery. Circulars, Adver- tising. etc. Complete outfits, $8.85; Job Presses. $11, $29: Price -$2.00 Rotary, $149. Print for others; big profit, Easy rules Firemen, Brakemen, Baggagemen (white or colored). furnished. Write for Catalog Presses, Type. Paper, etc. Sleeping Car, Train Porters (colored), $150 -$250 monthly. Kelsey Company, J -13, Meriden, Conn. Experimenter Publishing Co. Experience unnecessary. 237 Railway Bureau, East St. 230 Fifth Are., New York, N. Y. I1L Gentlemen: Enclosed find check or money ,outs,,,,Mmmnum,MO,eu M,,,e,ne,e,e, III,a,aMneeueM, order (cheek which) for $2.00. Kindly send me a Radio copy of Prof. A. M. Low's new book "THE FU- Miscellaneous TURE." Dealers and Set Builders -Write for lowest prices on Forms to Cast Lead Soldiers, Indiane. Marines, Trap - A and B power devices. D. L. G. Mfg. Co., 2937 West Name pers, Animals, 151 kinds. Send 10c for illustrated Cata- Lake, Chicago. logue. H. C. Schiereke. 1034 72nd St.. Brooklyn, N. Y. Address Wanted: Men to wont with National Radio Service Inventions Commercialized. Patented or Unpatented. organization. No selling scheme. Radio Doctors, Inc., City State Write Adam Fisher laite. Co., 278 Enright. St. Louie, Mo. Dept. N. Essex St., Salem, Mass. Please say you saw it in RADIO NEWS

www.americanradiohistory.com Radio News for March, 1929 tos

the spring levers of two '/4 -inch collars with set Radio News Laboratories screws; the latter are placed on opposite sides in (Continued from page 893) such a position to give a universal -joint action. The use of these coupling devices permits a slight mis- structed of 3/32 -inch sheet aluminum, which allows alignment of the condenser shafts and, at the same greater mass conductivity than is obtainable in the time, a positive rotating action without lag, cans above described. The sides and ends slide into AWARDED THE RADIO NEWS LABORA- grooved aluminum posts which are held to the TORIES CERTIFICATE OF MERIT NO. 2542. bottom of the shield by screws. After the apparatus is mounted and wired, the top is screwed down. Each compartment is 3% inches wide by 8% PHONOGRAPH PICK -UPS inches long by 5% inches high. The "Type IiQS -1" The "Type IA" phonograph pick -up submitted shield can, submitted by the same manufacturer, by the Webster Electric Company of Racine, Wis- is identical in construction to the "IiQS" except consin, is of the electromagnetic type and makes it that it has only a single compartment. It is 3% possible to reproduce music and speech from ordi- inches wide, 8% inches long and 5% inches high, nary phonograph records when used in connection inside measurement. with any A.F, amplifier. The pick -up is attached AWARDED THE RADIO NEWS LABORA- to a channeled arm which swings freely from the TORIES CERTIFICATES OF MERIT NOS. bell -shaped base, in which is contained a volume 2537 AND 2538. control actuated by a knob in its top. The arm is in two pieces, hinged two inches from the pick -up unit to allow the insertion of a needle or change DYNAMIC REPRODUCER of records; provision is made for fastening the base The "Type No. 107 -B" speaker, submitted by of the support to the motor board of the phonograph. Wright- DeCoster, Inc., St. Paul, Minn., is of the The pick -up unit consists of a permanent horseshoe electrodynamic moving-coil type. The field winding magnet with a single winding placed in the magnetic is of low voltage and uses field. The armature is of the balanced type and is heavy -gauge wire; the nec- held in position by soft cushion rubber. The pick -up essary current is obtained proper is 234 inches long, 134 inches wide and 1 f rom a step -down A.C. inch thick; the support arm is 6% inches long, transformer, and converted 3= -inch wide; while the base of the support is 3% by a dry metallic rectifier. The cone is 8 inches in di- ameter and anchored to a cast-iron speaker frame by thin kid -skin strips, which are cemented around the edge of the paper diaphragm. The speaker's chas- sis is enclosed in a walnut cabinet, the front and back of which are grilled and screened to allow passage of sound waves; this serves as a baffle for the lower frequencies. The cabinet is 18% inches inches in diameter and 3'/z inches high. A special long, 14 inches high and 11 inches wide. Cords adapter is provided, for either battery- or A.C: for connection to the lighting circuit and the radio receiver adaptation. receiver are provided. The speaker handles tre- AWARDED THE RADIO NEWS LABORA- mendous power with fidelity of reproduction from TORIES CERTIFICATE OF MERIT NO. 2543. 20 to 5,000 cycles. AWARDED THE RADIO NEWS LABORA- The "Type 1B" phonograph pick -up, submitted TORIES CERTIFICATE OF MERIT NO. 2539. by the same manufacturer, comprises a pick -up bead for You in which is identical in construction to that of the Type IA; except that it is provided with a flange FUSE AND MOUNTING designed to fasten over the tone arm of the phono- The %- ampere fuse and mounting shown, sub- graph. A separate volume control of the "Cen- mitted by the Oak Park Mfg. Company, Box 524, tralab" make is provided, in addition to the adapter (Electricity Oak Park, Illinois, has been designed for use to for either a battery or an A.C. receiver. protect one or more '''4- AWARDED THE RADIO NEWS LABORA- You Learn by Seeing It Work ampere coils, TORIES CERTIFICATE radio tubes, OF MERIT NO. 2544. you pay transformers, "B" batter- Now can fit yourself for a big ies, power job in electricity by watching real "B" units or DRUM other devices that could DIAL motion pictures in your own home, Easy be damaged by electrical The dial submitted by the Ormond Eng. Co. ,Ltd and fascinating as seeing a show at the surges. The fuse is in 199 Pentonville Rd., London, N. 1, England, has theater, You see electrical machinery in the shape of a fine wire, placed in a glass tube been designed for use on receivers where a drum operation. Moving diagrams make all the over the ends of which are metal caps. The fuse scale is desired, and can be facts easy to understand. wire is soldered to the caps, the latter also serving used only with tuning con- as contact points. A special mounting block is densers that do not require a Easier, Quicker, Surer mounting space provided to render the replacement of fuses more greater than This industry is constantly for 1% giant calling meq easy. The fuse tube is 3'''% inches long and '''44- inches from center of shaft to fill jobs paying from $70 to $200 and more inch in diameter; the mounting block, 2 inches to the panel, The drum which weekly Practical electrical men, holding down jobs. long, 3á -inch wide and ;finch high, to top of clips, carries the celluloid scale is 3 big praise this new way as the easiest and and provided with screw terminals and a single inches in diameter. A special best way to learn how ro do electrical work hole for fastening to the panel or baseboard. bushing for a 7/32-inch shaft is AWARDED THE RADIO NEWS LABORA- fastened within the drum; it is You Get This Pledge TORIES CERTIFICATE OF MERIT NO. 2540. set into a special molded-bake- We promise in writing to give you the training and lite strip which supports employment service necessary ro get you a better the job milled -edge thumb -control which and more money, or you need not pay a cent. BINDING POST protrudes through the panel. The shaft of the $75 Projector Given thumb-control carries a special friction wheel which post, by The "grid -type" binding submitted J. L. engages a flat disc inside the drum and serves as Every student is given a DeVry Motion Picture Poke, 41 Belle Avenue, Troy, New York, is of projector to keep, at no extra cost So simple any- a drive. A special die -stamped aluminum bracket, one can operate it without experience Used with molded black bakelite, and supplied with any mark- fastened to the panel, serves as an anchor ings desired; its mounting screw of No. of the regular light socket, farm lighting equipment. or drum's position with a special split pin. The es- automobile battery. Thousands of feet of motion 6 size passes through the panel and is cutcheon plate is of black molded picture film are supplied. fastened by a nut and lock- washer. The bakelite 3 inches long, 1% inches wide and 334 inches head of this screw, which passes through thick; the Our Big New Book, "Theíe window opening measures 1 inch by 3 -inch. FREE the body of the binding post, has a AWARDED THE RADIO NEWS Film Way to Bigger Pay" toothed under- portion which grips the LABORA- TORIES CERTIFICATE OF MERIT NO. 2545. Tells how we use moving pictures to train you for wire when the pressure of the spring bigger pay. Get your copy now Send the coupon. contained within the hollow body is re- Representatives with School Experience, Write. leased. In operation, the body is BAKELITE BINDING POST pushed downward, the -wire inserted and The lettered bakelite binding post shown here, 4he NATIONAL SCHOOL of the body then released, making firm contact. The manufactured by the Pilot Electric Mfg. Company, VISUAL(4)EDUCATION maximum diameter of the binding post is % -inch Inc., 323 Berry Street, Brooklyn, New York, is sup- and its length overall I% inches. plied with any markings desired. The - qh< F11m Way to Bigger Pay AWARDED THE RADIO NEWS LABORA- knob is of the non- removable type and 537 S. Dearborn Sr., Chicago, Ill., Dept. 9 -N .1 TORIES CERTIFICATE OF MERIT NO. 2541. screws down upon the broad -faced nut; Send your book, "The Film Way to Bigger Pay." the threaded portion of the binding post with full facts about this new, easier way to . master Electricity. proper (which is IFCONDENSER COUPLING No. 10 size with 32 threads to the inch) is pierced with a Name Age The "Type 12A" insulated condenser coupling, 1/16 -inch bole for the insertion of a St- or A.F.D. -_ submitted by the Pilot Elec. Mfg. Co., 323 Berry phone tip or connecting wire. The por- Street, Brooklyn, N. Y., is designed for use in tion of the screw which passes through City coupling gang condensers where the various rotors the panel is No. 8 size, with 32 threads State 1 of the condensers are to be kept at different poten- to the inch and % -inch long, an- m---- r----- m - -lay tials. It consists of a bakelite disc, 1% inches in AWARDED THE RADIO NEWS LABORA- diameter and 3/16 -inch thick, to which are riveted TORIES CERTIFICATE OF MERIT NO. 2548. Please say you saw it in RADIO NEWS

www.americanradiohistory.com 896 Radio News for March, 1929 A NEW CATALOG JUST OFF THE PRESS

p rECLEAHr O IE.VER!'THORAACSETSp.C, StsN ER :K EAKE fPR TS oT Q AND

r YOU MEN Who Buy RADIO/ By making your problems bur [1.1"' problems, we know the service you nventory Sale require -and to render you such Prel service the entire Allied organiza- APRE- INVENTORY SALE featuring some of the most drastic tion is dedicated -to give you the price reductions of the season. Our tremendous stocks must be you a right to expect. reduced. Prices have been cut to the bone. Everything in our service have large stocks of radio merchandise is included. You will marvel at Tremendous stocks, remarkable the remarkable values. Now is the time to buy. A new large catalog, values and a real desire to serve, featuring these remarkable values is now ready. Every radio enthu- all combine to make Allied your siast -every dealer -every set builder should send for this new cata- ideal source of supply. log- quoting lowest wholesale prices on everything in radio. upeemummummemommw SET BUILDERS! RADIO DEALERS Set Builders, Amateurs and so called "Hams" will delight The live radio dealer-the man who keeps pace with the rapid in the unusual variety -and remarkable values that are advance of radio will find much of real interest in the Allied offered in standard kits and parts. Tremendous stocks - Catalog. New A -C Sets, D -C Sets, Dynamic and Magnetic real organization -prompt shipping service all combine Speakers, television equipment, in fact everything that an im- to make Allied your ideal source of supply. patient radio public is demanding. Lowest Wholesale Prices Allied Service will prove a revelation to you in what radio service can really be. Allied Executives backed by years of training in radio are practical men. They know radio. Their vast experience has built up around them an organization trained to serve. Months of effort have built up here a tremendous reserve of stock that makes for prompt shipments; and this stock is new stock comprising the sea- sons pick of such prominent manufacturers as Silver -Marshall, Tyrman, Aero, Hammerlund- Roberts, etc. You Profit When You Buy Right Buying right is half the battle. From the small set builder to the large dealer, your success depends upon gauging the public pulse of A. C. radio and in buying right. Everything that is new in radio -the items the radio public is now demanding are here, ready for your ELECTRIC SETS call. Write now -the catalog is free for the asking. Allied offers you a new-complete line of A -C Receivers, available in Write for Catalog Now either chassis form or in a wide variety of beautiful console models. Prices range from $32.95 to $199.00. Dollar for dollar they stand out as one of the season's leading receiv- Alliediltadlo- ers. Engineered to unusual perfec- COR PORATI ON tion they offer you features found only in the highest priced sets. 711 W. LAKE ST. Dept. B -5 CHICAGO, ILL.

Please say von saw it in RADIO NEWS

www.americanradiohistory.com Order From Greatest Values This Page Ever Offered On this page are a few of If it's radio, sets, parts or the thousands of typical bar- gains that we offer. Our new equipment of any descrip- 1929 Catalog lists all the new tion, we have it. We carry standard and nationally fa- the most complete line in mous sets and parts. Send America. Our prices are for it now. If you prefer absolutely the lowest. Our that we ship C.O.D. send enormous buying power and only 25% of the value of the volume assures you that. purchase with your order. Every item we sell is brand Add additional postage or new and guaranteed by us express charges. 12 -hour mail order service. and the manufacturer. BIG CHIEF Magnetic SPEAKER The very newest in and ' design Tyrman construction. A stom most laithful re- -Gilt Shielded Grid producer with a lull rich tone quality.

Net price S4 .95

Shll,Piltg weight ,,11» Willard "A" and "B" Combination Power Unit An Amazing Receiver Set Builders and Dealers At An Amazing Price Save Money on Everything For battery or eliminator operation. Especially designed in Radio for Shield Grid tubes. The Tyrman "60" sets a new standard of comparison in performance and value in six. HEADQUARTERS tube receivers. Panel is only 7x18 inches equipped with the Catalog also lists Tyrman Single Vernier Drum Dial. Complete parts, fac- parts and kits for tory packed, ready to as- Tyrman, Carter. The premier of all power units. Convenient. semble. Shipping weight Tobe, Utah, Ores- SM simple. und efficient. It is controlled auto- net.. Hammerlund. matically by the switch of your radio set. 16 lbs. .lust plug in your Aero, Frost, Amer - light socket. Rego- $ Regular List Price $69.50 (ran. Thordarson tar ILst price 577.a0. 95 Shipping weight 82 Our Special Reduced and hundreds of others as race bottom ]b B. Price wholesale prices. WILLARD WILLARD STANDARD BALKITE''J" CHARGER Standard "A" "B" POWER UNIT Riff Reduction Power Unit It develops with ease 150 volts at List Price $17.50 30 milliamperes entirely free from hum. As a "B" supply for sets of average current it $6'95 has no superior. Trickle or List Price $35.00. Heavy Duty Use Our Net Price Noiseless charger for 4 or 0 volt "A" $14.60 batteries. Charging current is supplied through a trickle charge of .7 Shipping weight Shipping weight amp. ouput. A relay switch is 25 lbs. 10 lbs. included as part of the unit ORCHESTRION where this feature is desired. RADIOLA 28 Volt A. C. R'(th Relay. 0O 4 Abox Converter t l'rir0 It provides a steady 4 -wit direct cur- CONE Loops rent for set and with a S $1O your "It" Enclosed in rich two -tone ma- Shipping weight 45 lbs. eliminator it transforms the not to hogany cabinet. Pure reproduc- A. C. electric operation. work. only tion. marvelous tane, and res- when set is ion and full Relay. the in ouerlt does onant. Sensitive to the faintest Without 95c not store up current. impulses. Has a 12 -inch List price $32.50. $9.50 Don't confuse full dia Our Net Price Reinder Pries $27.50 95 phragm actuated by the Orehes- I heu. with the Shinning weln. 15 Ns. $8 trion cone unit. Designed to stand SPECIAL ELECTRIC assent bled the heavy volume of power tubes IRONS NUM type. 6 VOLT ABOX and power amplifiers. SOLDERING List $7.50. Price List Price 3 Our Net Pris nO (List Price 52.50) Shipping 335.0Regular0 Our Net 65 Shire SI 4.95 Shipping weight Net Price wei:bl 4 !ha Shipping weight 2 lbs. 85c Shipping weight 25 lbs. 6 lbs.

Estab- lished Shed 1915 Qiicago Salvage Stock Store 1915 Lo Tone BAKELITE 3 Circuit TUNER Oholargarf Radio Store in America ..d Speaker FILTER Place it between the loud speaker Not only makes your net better and Alun the sneaker itself will Notarent, but perform better. Men- produce much better clarity of tone. Iton for condenser de- Protects the speaker tram burning sired. Shipping seglot. South State Street out. List 52.50. $ I lb. 50 98/e 9WHOLESALE DEPT. A. N. 9 CHICAGO, ILL. lbs. in NET.... 1

www.americanradiohistory.com FACTORY TO YOU'-SAVE 50%- COMPARE WITH COSTLIEST OUTFITS BEFORE YOU BUY set or ^ complete a 9OWCYÍU1 e - Outfit DA5 toil AC Electric or Battery aC g RE E 3 Year Guarantee Get Our Built like, Looksiike, Send No Performs like a $200 set Money Marvelous new 3-year guar - hted 1- d,aleontrol 9th Áteed.11ilt me I Super Shielded calbinet. Fronremoved pho- nograph sickup connectiont, Anniversary and 1l latest features. Built Offer! er section on AC The Latest, Finest and CosuiestConstruction

Wide Selection of Beautiful Cabinets AC or Battery Sets DAYS 30 HOME TRIAL E r Richly designed, gen- TRADE MARK REGISTERED uine walnut console of finest type. Elee- CATHEDRAL TONED, SUPER SELECTIVE, POWERFUL DISTANCE GETTERS tro- dynamic or mag- netic power cone, or Celebrating its 9th successful year, hum -free operation, tremendous long air column America's big, old, reliable Radio "kick" on distant stations and speaker. Marvelous Corporation springs a genuine razor -edge selectivity -with its value. sensation in high -grade sets. With costly sturdy construction, latest its latest, Superpowered, 1 -dial features, including phonograph Miracos -the - pick-up connec- A l l Electric BIG DISCOUNTS tion, ease of tun - wholly self -con- ing, beauty, and tained, hum- Exclusive Territory economy -a free, AC-8 and to User -Agents on Miraco will A popular walnut Hi- AC-9, using AC make you the Boy Console, with drop - BATTERY OR AC leaf desk. Beautiful tubes or the new ELECTRIC OUTFITS envy of many two-tone finish. Rare 8 -tube models whose radios bargain! for batteries or Eliminators -you cost 2 to 3 times as much! are guaranteed values and savings Many thousands of Miracos- AC-S-$71.50 Unbeatable value in a 3- unsurpassed in the fine set field. bought after 30 day home corn - guaranteed Super Beautifully graceful Compare a Miraco with highest- parlsons -are cutting through MtaCl si Spinet console, genuine priced radios, for 30 days in your locals and getting coast to coast two-ton a wale u t. C ho i c e home. of costly of speakers. Also comes Surprise and entertain with the tone and power in Electric Phonograph - your friends -get their opinions. sets, their delighted users report. Radio Combination. Unless 100% delighted, don't buy Miracos are laboratory-built with it! Return everything-the corn- finest parts, and embody 9 years' piece outfit-at our expense. Your actual experience in constructing decision is final -absolutely! fine sets. Approved by Radio's Only exceptionally fine radios, highest authorities. Also New, More of the very latest approved type, at Deal Direct with Big Factory Powerful Battery rock- bottom prices, could possibly Everything reaches you splendidly packed Sets back up so liberally unconditional and rigidly tested to insure your instant The newest and latest in A new -type ar m -chair enthusiasm. Enjoy the outfit 30 days- battery operated sets, de- console. Genuine walnut. a guarantee. Send coupon now for vitir Very then decide. Liberal 3 -year guarantee on signed same ed- pretty. Low priced. -Amazing Special Factory Offer! lots of money, Electro- Dynamic or Mag- each set. Play safe, save elenced seise es u ed idé netic-r Po.ver Speakers. Don't Confuse with Cheap Radios and insure satisfaction by dealing direct choice of cabinets. High with Radio's old, reliable builders of fine estquality,amazinglylow With its rich, clear Cathedral tone, sets -9th successful year. priced! At right, a Lo- Miraco Outperforms 'em All In Chicago light socket. I want to say that your set does outperform On will I got to date the other sets I have. I put it up against a World Record Boy console, the Miraco Unitune, to start with, say: one. I against a finish, 61 stations outside of Chicago, from the Pacific Ocean to the Super 9 and beat that Then put It up walnut Atlantic Ocean, and from Anchorage, Alaska, to the Gulf of (names expensive make), and beat that one. Next I put it thatcostslittle. Mexico. and I tried the set with 3 different antennas. That up against a Neutrodyne and beat that one. HARRY A gemi is an outside aerial 152 feet, an inside aerial 20 feet, and KOPP, 6555 South Peoria Street, Chicago, Illinois. MIDWEST RADIO CORPORATION, 404 -RM Miraco Building, Cincinnati, Ohio Above, popular inexpensive BEAUTIFULLY ILLUSTRATED CATALOG, AMAZING SPECIAL FACTORY OFFER, TESTIMONY OF combination. Set on Table NEARBY USERS -All the proof you want-of our honesty, fairness.size financial integrity. radio Speaker (sold separately) aierSalD experience and the performance of our sets- including Amazing Factory Offer -sent with catalog. Metal orwood compact style cabinets. Wood Te/ cabinets in walnut or MIDWEST RADIO CORPORATION I IS COUPON new shaded silver - Pionee> Bild s of Sets -9th Snccessjuf Year I IS NOT chrome finishes. Cathe- / 404 -RM Miraco Bldg., Cincinnati, Ohio AN ORDER dral Electro -Dynamic or Magnetic -Power ipaet,' WITHOUT OBLIGATION. send free catalog, Amazing Special Factory Offer to match! Speaker \to" MI testimony of nearby users, etc. User Agent Dealer ..,- -1 l Check here If Interested in an EXCLUSIVE TERRITORY PROPOSITION NAME ADDRESS

www.americanradiohistory.com