RADIO MOVIES and TELEVISION for the HOME (See Page 116)

RADIO'S G ATEST MAGAZINE RAvInvIsION

RADIO MOVIES and TELEVISION FOR THE HOME (See Page 116)

www.americanradiohistory.com RADIOy TUBES

CX 350

The Nerve Center of Your Radio Because Cunningham Radio Tubes carry the true tone and reproduce pure harmony, they are rightly called the nerve center of your radio. Tubes that have had long, constant use should be replaced with new, correct Cunningham. Tubes to enable you to enjoy modern broadcast reception. Never use old tubes with new, ones -use new tubes throughout E. T. CUNNINGHAM, Inc. New York Chicago San; Francisco Manufactured and sold under rights. patents and inventions owned and ur controlled by Radio Corporation of America NNÑINGH4Ë CX`374j; fttl

www.americanradiohistory.com Radio News for August, 1928 97

EARNED $500 SPARE TIME WITH RADIO

Coplay, Pa., June 4 -(RA)- During the few r ionths that Frank J. Deutsch has been a member of the Radio Association of An erica, he has made over $500 out of Radio in his spare time. "Four super -hetrodyne sets of my own constriction brought me a profit of $60.00 each, and the other profit was from sales LEACH of these plans, developed by the Radio i' Association of America, is a big money- maker. of supplies purchased through the Whole- Set owners everywhere want to get rid of static, to sale Department of the Association," he have their sets operate from the electric light socket, said. "The Association certainly has a the tone improved, and the volume increased, and great plan for ambitious men." transformed into single -dial controls. Phonograph owners want their machines electrified and radiofied. In :i neighboring state, Werner Eichler, If you learn to render these services, you can easily Roche+:ter, N. Y., another member of the make $3.00 an hour for your spare time, to say nothing Association, has been making $50 a week of the money you can make installing, servicing, during his spare time. repairing, and building radio sets, and selling supplies. The are only two of the hundreds of Over $600,000,000 is being spent yearly for sets, Radio Association members who are making supplies, service. You can get your share of this money out of Radio in their spare time. business and, at the same time, fit yourself for the big -pay opportunities in Radio by joining the Association. BECOMES RADIO ENGINEER IN Join the ONE YEAR Radio Association Toronto, Canada, May 20 -(RA) -One of the newly admitted associate members of America of the Institute of Radio Engineers is A membership in the Association offers you the Claude DeGrave, a member of the engi- easiest way into Radio. It will enable you to earn $3.00 an hour neering staff of the DeForest Company of upwards in your spare time -train you to install, repair, and build all kinds of sets - this city. "I knew nothing about Radio start you in business without capital or finance an and st trted from the ground up," Mr. invention -train you for the $3,000 to $10,000 big - DeGrave stated, "when I enrolled a year pay radio positions -help secure a better position at ago in the Radio Association. bigger pay for you. A membership need not cost you Its easy a cent! lessons and superb training made it possible for me to become a Radio Expert in less The Association will give you a comprehensive, practical, and than a year's time. My income is now theoretical training and the benefit about of our Employment Service. You earn while you 225% more than at the time I joined learn. Our cooperative plan will make it possible for the Association." you to establish á radio store. You have the privilege The Institute of Radio Engineers is a very of buying radio supplies at wholesale from the very exclusive organization, and its membership first. requirements are very rigid, so that Mr DeGrav has reason to be proud of his ACT NOW -If you wish election. No -Cost Membership Plan Clerh To a limited number of ambitious men, we will give Doubles Income In Special Memberships that may not -need not -cost Six Months Through you a cent. To secure one, write today. We will Radio MODERNIZE OLD SETS send you details and also our book, "Your Opportunity DIAL CONTROL Chicago, Ill., May 9 -Even though his WITH ONE in the Radio Industry." It will open your eyes to the money- making possibilities member: hip in the Radio Association has of Radio. resulted in W. E. Thon securing the manager- ship of a Radio Department in a large COUPON Chicago store, his ambition was not satisfied. RADIO ASSOCIATION Ì Six monr.hs later, he OF AMERICA started his own store. Dept. RN -8, 4513 Ravenswood Ave., "The Radio Association has an excellent Chicago, Ill. plan for the man who wants to get out of Gentlemen: the rut Please send me by return mail full details of your and succeed," says this man who Special Membership Plan, and also copy of your quickly rose from clerkdom to the pro- book, "Your Opportunity in .the Radio Industry." prietorship of a profitable radio store. "I Name attribute my success entirely to the Radio Association of America. Six months after Address I had er rolled, I had doubled my income City State through i :s help." L la

www.americanradiohistory.com 98 Radio News for August, 1928 'NEWS AUGUST, 1928 Number 2

Contents of This Issue

What to Expect of Television Some Inside Facts About "B" Batteries By Hugo Gernsback 103 By William F. Crosby 134 A Visit to Radio Central The Radio Beginner -A Two -Tube Reflex; By Robert Hertzberg 104 Receiver of Simple Construction 136

Getting the Vote by Radio A Booster Unit for the Browning -Drake By Marshall D. Beuick 108 By C. A. Oldroyd 139 Radio Advertising -Does It Pay? A Screen -Grid Short -Wave Receiver By Orrin E. Dunlap, Jr. 110 By Fred H. Canfield - 142 Rain, Rays and Radio Better Direct -Coupled A.F. Amplifiers 146 By C. Sterling Gleason 112 The 'Capacity of a Condenser Combination The Listener Speaks By Himself 114 Arrangement By Leslie R. Jones 149

Broadeastatics 115 Radio Wrinkles 150 Television -Radio Movies and Television The Zero-Reactance Plate Circuit for the Home 116 By Sylvan Harris 152 Why the Weather Affects Radio Recep- Learning the Code Multiplies Radio ;Pleas -

tion - By B. Francis Dashiell 119 ures By 'C. Walter Palmer 154

What's New in Radio 122 Letters from Home Radio Constructors 156

Some Odd Uses for Vacuum Tubes Radiotics 158 By J. E. Smith 126 RADIO NEWS LABORATORIES 159 Radio Novelties from Abroad and Home 128 I Want to Know By, G. `V. Palmer 160- List of Broadcast Station Calls 129 Ún the Short Waves 162 What Is a Good Loud Speaker? By Fred H. Canfield 130 Circuit Changes on the Neutroheterodyne 181

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 $2.50 a year in U. S. and possessions. in Germany is reserved for Radio, Berlin 42. Canada and foreign countries, $3.00 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 40 money orders should be drawn - to order of EXPERIMENTER PUBLISHING Et Cie, Place Verte, Antwerp, Belgium. CO., INC. HOW TO .SUBSCRIBE FOR RADIO NEWS. Send your name, address and re- to mittance to Experimenter Publishing Co., 230 Fifth Ave., New York. Mention the ..411 communications and contributions to this journal should be addressed name of the magazine you are ordering. We also publish SCIENCE AND INVEN- Editor, RADIO NEWS, 230 Fifth Ave., New York, N. Y. Unaccepted contribu- TION, RADIO LISTENERS' GUIDE, AMAZING STORIES and TIDBITS. tions cannot be returned unless full postage has been included. All accepted con- Write clearly. tributions are paid for on publication. A special rate Is paid for novel experi- RATES AND TERMS. The subscription rate for ments; good photographs accompanying them are highly desirable. Publishers are RADIO NEWS is $2.50 per year. (12 numbers). -- When remitting do so check, money not responsible for loss of manuscripts, although every precaution is taken with by order, or registered thereof. letter if cash is enclosed. Avoid sending cash through the mail if possible. Sub- such manuscripts, upon 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, l879. Additional entry AMAZING STORIES and TIDBITS. at Dunellen, N. J. and San Francisco, Calif. Title registered U. S. Patent Office, POSTAGE. We prepay postage in all parts of the United States, Mexico and Copyright, 1928, by The Experimenter Publishing Co., Inc., 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 as 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 C. E. ROSENFELT, Secretary Member: Audit Bureau of Circulations Radio Magazine Publishers Association Editorial and General Offices 230 Fifth Avenue, New York City Advertising Representatives: RHODES & LEISENRING New York Offices: 624 Graybar Building - Chicago Offices: 307 North Michigan Ave.

www.americanradiohistory.com Radio News for August, 1928 99 announcing AGI?EAT, NEW RECEIVER SCOTT CHALLENGES THE WHOLE WORLD OF RADIO TO ANY KIND OF- COMPETITIVE TEST 3 Stage SHIELD GRID AMPLIFIER Cart- gives Be Built TREMENDOUS SELEGTONE SHIELD GRID nhTr GAIN' ByAnyone scoli äASSIoIDweam.® ln4iiollrr/

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www.americanradiohistory.com 100 Radio News for August, 1928

INDEX TO ADVERTISERS

Page Page Page Page A D g S Abox Company, The Back Cover Raven Radio Corp., The 172 Iiimley Electric Co. 182 Scott Transformer Co. 99 Accusti -Cone 171 Deutschmann Co., Tobe 178 See Jay Battery Co. 181 Acme Wire Co., The 179 Smith, B. Hawley 180 Aero Products, Inc. 183 E L Spiegal Radio Co. 182 Aerovox Wireless Corp 181 Starrett Mfg. Co. 186 Electrad, Inc. 171 Lacault, R. E. 188 All Radio Co. 183 Electric Specialty Co. 183 Lacey &.Lacey 189 American Mechanical Labs., Inc 171 Electro Chemical Co. of America 183 Leutz, Inc., C. R 165 American Sales Co. 173 T Excello Products Corp. 181 American Transformer Co. 166 Telephone Maintenance Co. 171 Amrad Corporation, The 181 Teleplex Co. F M 181 Televocal Corp. 191 Fairspeaker Radio Co. 175 M. & H. Sporting Goods Co 172 Thordarson Electric Mfg. Co 163 B Fansteel Products Co., Inc 175 Midwest Radio Corp'n 191 Townsend Laboratories 175 Formica Insulation Co. 183 Muter Co., Leslie F. 175 Transformer Corporation of Barawik Company, The....177 -183 -186 Freshman Co., Inc., Chas. 186 America 176 Tyrman Electric Corp. 171 N C G National Radio Institute 101 General Antenna Co. 187 U-v C. E. Mfg. Company, Inc. 181 Norden- Hauck, Inc. 180 General Radio Co. 182 Carborundum Co., The 186 Underground Aerial Systems 177 Gernsback, S. 172 Carls, M. J. 177 Underground Antenna Company Carter Radio Co. 172 P Inside Back Cover Central Radio Labs. 176 H Pilot Electric Mfg. Co., Inc 100 Chemical Institute of New York, Hammarlund Mfg. Co. 173 Press Guild, Inc. 185 w Inc. 169 Hamilton -Carr Radio Corp. 176 Chicago Radio Apparatus Co 184 Walker Co., The Geo, W 177 Cloverleaf Mfg. Co. 178 Western Radio Mfg. Co. 175 I Wirt Co. 188 Consrad Co., Inc. 164 -168 -170- 180 -185 Independent Electric Works 184 Radiali Company 191 World Battery Co. 166 Consumers Radio Co. 172 Illinois Transformer Co. 183 Radio Association of America 97 Craftsman Radio Products 183 Radio Equipment Co. 182 -Y-Z Cunningham, Inc., E. T. Radio Institute of America 189 x Inside Front Cover J Radio Specialty Co. 167 X-L Radio Laboratories 176 Curtan Mfg. Co. 102 J -M -P Mfg. Co., Inc 180 Raytheon -Mfg. Co. 178 Yaxley Mfg. Co. 188 V4107 EnaltdEERiNG eapredalosats r s tared a rd This iol "Moisture-Pruf" Transformer was removed from the receiver and immersed i iLOT for one entire week as shown. When re-' for (ad w rinstalled in the set, 'it functioned perfectly. e parts "NiASTldiií' -- PRWF" Tit AiVSF i?;MEd3S; EVERY Pilot instrument must be approved by our Board of Engineers. Beauty of appearance is never allowed -.1);PILQTAIRALA1r,.` ROO IRB to supersede beauty of performance. You are sure of the electrical efficiency of every instrument that bears the Pilot name, whether it be a simple little socket, a variable condenser, plug- 'PILOTS "FLYING LAO" in coils, filter, choke, transformer, or complete kit. The Pilot Airplane Radio La- boratory is the Pilot Com- ' SEND 4c. STAMP FOR CATALOG pany's contribution to the development of a radio communication system between 'MOT RADIO FARTS ARE SOLO dill EVERY amateur ground and air stations, enabling pilots to receive directions and weather -- OMIwEO COUNTRY warning while aloft. RHoIOgS, 131 CIGEST rn TrmE wow! 25f VALUE! "RADIO DESIGN," a Quarterly Magazine edited by M. B. Sleeper, national radio authority, is brimming 'LO1 ELECTRIC MFA I over with the newest and latest Short Wave, A. C. Data, Power Amplification, latest Television Development, etc. Send 25c. stamps or coin for four meaty quarterly I issues. 323 BERRY ST. _BROOKLYN,N.Y_, Name ...... TRADE MARK -/ REGISTERED áAddress ...... "WORLD'S LARGEST RADIS PARTS PLANT'

www.americanradiohistory.com Radio News for August, 1928 101

kecutwhat BIG money these fellows have made J wdt 41wW qecc 60 in the RADIO BUSINESS how to sutra spar $375 One Month Spare Time " Recently I made $375 in thne 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 without "The N. R. I. is the best Radio school in the U. S. A. Radio's amazing growth is making many big jobs. The world- in five I have made $1597 wide use of receiving sets and the lack of trained men to sell, months. I shall always tell many splendid chances my friends that I owe my install and service them has opened success to you." for spare time and full time businesses. HENRY J. NICKS, Ja., how 302 Safford Ave., Ever so often a new business is started in this country. We have seen Tarpon Springs, Fla. the growth of the automobile industry, electricity and others made men rich. SI164 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, $1,161 - pass up this wonderful chance for success. money I would not have I Will Train You At Home In Your had otherwise. I am cer- More Trained Radio Men Needed Spare Time tainly glad I took up Radio A famous Radio expert says there are four bring my training to you. Hold your job. with N. R. I. I am more good jobs for every man trained to hold them. Give me only part of your spare time. You satisfied." school than Radio has grown . so fast that it simply has don't have to be a college or high HENRY R. HE1KKINEN, -number of trained men it needs. of my graduates now mak- Erie St., Chicago, Ill. not got the graduate.. 123 W. Every year there are hundreds of fine jobs ing big Moneyoney in Radio didn't even finish the SIROO and men up Over In Four Months among its many branches such as .broad- . grades. Boys 14, 15 years old "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- You Must Be Satisfied to be had at any price. tions, and many others. Many of the six to ten million receiving sets now in use are only I will give you a written agreement the day When I enrolled I didn't money if you are know a condenser from a 25% to 40% efficient. This has made your you enroll to refund your the lessons and instruction De- big chance for . á spare time or full time not satisfied with transformer, but from complete the course. You cember to ,April I made business of ;your own selling, installing, repair- service when you I only ing sets. are the only judge. The resources of the N. R.I. well over $1000 and -Study Radio school -worked in the mornings." So Many Opportunities You Can Make Pioneer and Largest Home AL. JOHNSON, Extra Money-While Learning in the. world stand back of this agreement. 1409 St., Sandusky, Ohio. Shelby 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 61 -page plans and ideas that have proved ` book, Rich Rewards in Radio' successful for them -show you .74i4 aooR+ points out the money making op- how to begin making extra money shortly after " / L portunities the growth of Radio you enroll. G. W. Page, 1807 -21st Ave., S., O vast, What has made. for you. Clip the cou- Nashville, Tenn., made $935 in his spare time Raja pon. Send it to me. You won t while taking my course. be obligated in the least. I Give You Practical Radio Experience iItemgo, With My Course Address My course is not just theory. My method givès you practical Radio experience- E. Pres. 'you learn the "how" and "why" .1. Smith, of practically every type of Radio Dept. SS set made. This gives you confidence to tackle any Radio problems and shows up in your pay envelope too. National Radio Institute Washington, D. C. You can build 100 cir- çuits with the Six. Big Outfits of Radio parts if coupon is good fo I give you. The pictures :FREE here show only three of a copy of m them. My book explains my method of giving prac- l J. E. Smith, WaGualrCe tical training at home. President, Mail it MOW Get your copy I Dept.:SS National Radio Institute, Washington, D. C. 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.. Nanie Age

Address . City State.....,

www.americanradiohistory.com Radio News for August, 1928 102 manng Ground I Antenna Ve6 "aeriezeigion in Intoner

yA 0 1g26 q,4 "1-x1GO 9s Z t>O Ye'' ooag+ 2+ G so4 t,

C,0* y. ; vcy+ tao ÉSSe 9 t 511, ag G SGo f ea C. 1.b 9 a 00 ones 19k,9").9tall ç e a ra et 4So ae // ara `O4 el e vet ea lltpí. yre St a 9 9 y C ci ,p9 ae 1`l mp ro ves Music WonderfùJ4 Q yt` a° i o It is no longer necessary to say "Good -Bye Radio" for the summer. r o91° Science says that clear. pure ground waves remain just the same during Tit8v9 the summer months. They are unaffected by Atmospheric conditions. Aer-O- Liminator is the proved, scientific successful means of bringing these ground waves to your set loud and clear, while others are giving up summer reception in despair because of maddening, music - destroying static. Proof Comes from the Semi -Tropics The letter from Mexico reproduced above speaks volumes. The Spanish are great music -lovers and are trained to judge. When AER -O- LIMINATOR improves music wonderfully in Mexico-a semi -tropical climate -you know it literally gets "Winter reception in summer." Distant stations formerly drowned out by the static interference of noisy air -waves now come in clear and with the melodious tone of a bell. Winter or Summer, there is no comparison in reception with Aer -O- Liminator and without it. Engineer Recommends Aer -O- Liminator to Every Radio Owner Reception on any type receiver is improved with the use of Aer -O- Liminator. This has been proved countless times on both D.C. and A.C. Sets. John E. Christensen, Chicago Radio Engineer, says, "I have tested and thoroughly approve the'Aero-O- Liminator.' I find it increases selectivity and volume without distortion. eliminates static, gives good. clear tones. both on LOCAL and DISTANT stations. I would recommend the use of Aer -O- Liminator to every radio owner to get the best reception from his Set. Send Coupon for Free Trial Install an Aer -O- Liminator (Ground Antenna). Leave your old overhead aerial up. Try out on a night when static is bad. If you do not get a wonderful improvement in freedom from static, greater selectivity and clear, sweet tone without interfering noises, if you can't get good reception on stations that are drowned out by static on your roof aerial, you need not pay us a red cent for this test! Send coupon at once for scientific explanation of Aer-O- Liminator (Ground Antenna), proof of performance. and our conclusive iron -bound guarantee and remarkable Free Trial wo4`cc Offer -Mail Coupon TODAY! 5t{.O I CURTAN MFG. COMPANY e` I Dept. 827 -L.A. 159 E. Erie St., Chicago, Ill. . .m tcÇ,° I P+.° e`, 1 Gr tr4 °c ' 1 o ,.,,e / s1 y4. ct: 1 G AerO-Limìnatir e 4 F` a4'4-s.G I (Ground Antenna) ' e` ` I USE THIS CONVENIENT COUPON TODAY imummmiammumisme®nm.a

www.americanradiohistory.com Editorial and General Offices, 230 Fifth Avenue, New York

Vola 10 AUGUST, 1928 No. 2

What to Expect of Television By HUGO GERNSBACK

that television has actually arrived, it may be well to The aluminum disc is rotated by means of a motor, and your tele- take stock of the new art, and to look into the future. vision receiver will have a rheostat in series with the field of the N OWThe word "Television" was first coined by myself in an machine. By adjusting this rheostat, you will he able to keep the article entitled "Television and the Telephot," which appeared rotation of your disc in step with that of the transmitter at the dis- in the December, 1909, issue of MODERN ELECTRics, the pioneer tant station. Through the holes, a "virtual" picture is built up, and radio publication, which I published. I believe that these were the thus you see what is shown at the broadcast studio. first articles on the art of television published in the United States. This, at best, is a more or less crude way of doing things, and will may use Before going much further, I must sound a precautionary note, not prevail in the future. It be stated that the of the present revolving discs at both the transmitter and receiver corre- and is : do not expect too much of television for some time to that to the and -spark -gap of the old days of come. At the present time, there is feverish activity by many firms, sponds coherer- stage "wire- large and small, to put television receivers on the market. less." The ideal television receiver of the future will have no moving Station WGY of Schenectady may be called the pioneer television parts at all. There will be no motor, or if there is one, there cer- broadcaster, as it started to broadcast television some time in May tainly won't be a large disc such as we have now. What we prob- of this year. Station WRNY began broadcasting television in June. ably will have is some sort of a cathode tube, in which a weightless electron beam will rotate in an induced magnetic field. It will be "What will we be able to see ? " is the question that is most fre- much easier to keep such a device as this in synchronism, there it and quently asked. Frankly, not a great deal. We shall be satisfied if is no doubt that the built -up picture thus produced at the receiving is possible to clearly see silhouettes, letters, designs, diagrams, large end will be far superior to what we have today. print and so forth ; that is, with television broadcast over the usual broadcast channels. Here, for the present, we must be satisfied with The question that is asked frequently about present -day devices is, rather coarse and indistinct details at the receiving side ; although a "How big is the received picture that you see ?" As a rule, it is not number of broadcasters will probably broadcast television on short large. This depends upon the diameter of the disc and the size of waves, where the details will have greater clearness, due to the the plates of the neon tube. Usually, the picture is about two to wider frequency channels available. three inches high, and from one and one -half to two inches wide. It is possible to enlarge this picture by means of a lens, and thus get Like all arts, television must first pass through a preliminary a larger image ; but so far experiments along these lines have not stage, and from the experience we gain during the first few months, been very fruitful, because the picture becomes coarse and loses its better and better transmission may be expected. luminosity as well.

We all remember the time when "wireless" first arrived, and when, As for televising the artists in the studio (that is, showing the radio prior to 1920, all we could get in our head receivers was dots and audience what the artists look like), it seems quite a few months in the dashes -and these not always clear -rather than actual voices and future ; or, if they are shown at the present time, it will be most music, now known as broadcasting. It will he so with television ; so difficult to distinguish a man from a woman. These remarks are don't expect too much, and you won't be disappointed. In my opin- meant to apply only when the impulses are broadcast over the pres- ion, it,will be quite marvelous if, on your television receiver, you will ent broadcast band of wavelengths, that is, between 200 and 550 be able to see good silhouettes, and can read large letters, broadcast meters, and kept within the 5,000 -cycle limit under which broad- from the studio. casters operate. On the short -wave channels, as I said before, details are usually much clearer. And don't expect simultaneous transmission of voice and television. That, at the present stage of the art, is not possible. The From the above, it should be understood that such a thing as tele- procedure will run somewhat like this : vising in detail a moving object in the studio (.for instance, a pianist playing) will not he possible for quite awhile to come. Any- The studio announcer will say, "Now we shall televise such and thing in motion will be extremely difficult to receive and see well, such an object." It will take one or two minutes to show the object, with any kind of detail. and then the voice or sounds from the studio will again be heard in your receiver. In between announcements, you will be able to pick But the important point is that a start has been made, and that the up television on your television receiver ; but you can't get both to- public is interested. That is what counts. If enough people work on gether until an entirely new invention is made, which, to my knowl- the new art, progress will no doubt be made quickly. I predict that, edge, is not as yet in sight. It may, however, come along any time. within one year, such tremendous strides will have been made in television that it will be possible actually to see what is going on in a At the receiving end, we have a revolving disc, which is usually distant studio. made of aluminum, about 14 to 24 inches in diameter, and through it a number of holes. Directly behind the holes is a neon lamp, which But the broadcasting of such events as a ball game or a boxing is attached to your ordinary radio receiver. If necessary, the impulses match would seem, at the present time, to he distant anywhere from coming through your radio broadcast receiver may he amplified in two to five years ; at least, until such time as an entirely new tele- order to make the light of the neon lamp bright enough for receiving vision device will have been invented. That is, as I said before, purposes. not as yet in sight.

Mr. Hugo Gernsba^-k speaks every Tuesday at 9.30 P. M. from Stations WRNY (326 meters) and 2XAL (30.91 meters) on various radio and scientific subjects. 103

www.americanradiohistory.com 104 Radio News for August, 1928

;hat the Radio Fan May See at Rocky oint, Long siandy the Jiu b: of aWorid - Wide Communication System

The scene above includes the main transmitter house at "Radio City), and the lead -ins from the two great aerials; the nearest ..Central," Rocky Point, Long Island (75 miles east of New Pork towers of one aerial are seen at the left. They are 410 feet high.

THE largest and probably the most projection of radio waves, the R.C.A. engi- the whole system of towers, poles and sus- interesting radio installation in neers chose a of the stretch land at Rocky Point pended wires, honeycombing the sky in a - world is the one known as "Radio because the terrain here is very flat and free dizzy manner, presents a picture nit unlike - Central," located at Rocky Point, of metallic obstructions that might affect those highly- imaginative drawings represent- Long Island, at a distance of about 75 miles radio transmission. Some six thousand ing life on- Mars that "Paul" used to paint from. New York City. It bears this name acres of land are included in the property- for some of the old- numbers of The Elec- because of its massed facilities for radio- sufficient to take care of the growing radio trical Experimenter; On a slightly foggy telegraph and radio- telephone communica- plant for several years. day, when the tops of the -aerials- are clouded tion between the United States and the On a clear day a motorist approaching with mist, the towers appear to be miles countries of Europe and South America, on Radio Central can see the outlines of the high. wavelengths ranging from 14 meters all the twelve main towers many miles away. The way up to 16,000 meters. It is owned and sight of the huge steel skeletons lined up in THE MAIN POWER HOUSE operated by the Radio Corporation of a row three miles long is a most thrilling A short ride over a private road leading America, and is the hub one, the height size of that company's and of the structures be- off one of the main Long - Island highways world -wide radio system. - ing emphasized by the bareness of the sur- brings the visitor to the main power house, Radio Central was opened six years ago. rounding countryside. Adding to the gen- or transmitting building. When this was At that time two powerful Alexanderson eral effect is a series of four smaller towers, first erected it was a plain brick affair, with alternators, huge machines capable of gen- each about 200 feet high, recently erected unfinished sides of sheet metal. Today, how- erating the high- frequency current necessary for directive transmission on short wave- ever, it presents the Spanish Mission type for the prod-action of radio waves,.were in- lengths. When viewed from certain ängles of architecture, having cream- colored walls, stalled in a temporary building. These attractive brick trim, and a red -tiled roof. worked with two aerials supported by It is located between the two sets of towers, twelve huge steel masts, each 410 feet high. Which extend away fróm it. a mile and a The original plan was to build 72 such half in two directions. In front of the house towers, arranged like the spokes of a wheel, is a large cement basin, in which jets of with six towers to a spoke, and with an in- water are constantly spouting. These are dividual Alexanderson alternator for each not merely ornamental, but serve as a means unit. ' of cooling the water which is fed to the al- However, the progress of American radio ternators and vacuum tubes for cooling technique, particularly in the line of short- purposes. wave work, made a change in the plan ad- Entering the main entrance of the power visable. In place of the projected addi- hóuse, the visitor finds himself in a large tional towers and giant - alternators, the reception: hall of Spanish atmosphere; large Radio Corporation has erected short, simple tiles underfoot, rough stucco walls, massive aerials supported by wooden poles; and has mission doors with wrought -iron fittings, installed silent-vacuum-tube-transmitters of marble benches and railings leading to compact construction. a balcony. A door connects this room with AN IMPRESSIVE VIEW One of the coils which tunejhe sections of the the machinery hall, the atmosphere of which "multiple- tuned" aerials. Compare it is strictly business. The unceasing whirr of In selecting a location favorable for the with the height of the man beside it. the huge Alexanderson generators and of

www.americanradiohistory.com Radio News for August, 1928 105 dozens of different kinds of pumps and in- series of test letters, usually ABC or XYZ, idental generators and the constant slap- merely to let the receiving operators thou- ping of the big relay keys which tap out the sands of miles 'away - know that the ma- messages makes conversation here a bit dif- chinery is working, properly. The other big is used for transatlantic " telephony i eult. The staggering amount of radio aerial'. a wavelength of about 5,000 meters. be- equipment in this hall, which' is about half on ing- employed in conjunction with a 200 -kilo- tt block square, leaves the visitor helplessly This latter outfit is op- confused until after he has gone around two watt transmitter. the American Telegraph and or three times and identified each machine. erated by Telephone Company; and ties in with the THE INVISIBLE OPERATORS entire American telephone system. Radio Central is a transmitting station or, Although great progress has been made rather, it is eight or nine stations rolled in in long- distance communication on short one, yet the number of people staffing it is waves with-low power, the Alexanderson al- surprisingly small. On the occasion of the ternators, operating on wavelengths above writer's visit only half a dozen or so men 16;000 meters with an output of 200 kilo- were in sight, and these were attendants watts each, represent the backbone of trans- and mechanics who had nothing to do with oceanic message service. The long waves the flow of dots and dashes pàssing through are required for uninterrupted communica- the equipment. It was explained that the tion from daylight to darkness, for uniform actual operators are located in a central of- and reliable transmission 24 hours a day fice at 66 Broad Street, New York, to which regardless of weather. A single short -wave messages from all parts of the country in- transmitter working on one fixed wavelength tended for transoceanic transmission are cannot supply the same class of service; en- routed for handling. However, practically gineers arc now conceding the necessity for all the members of the Rocky Point staff are a group of different transmitters which can experienced radio operators and capable of be shifted at will to meet the peculiar ef- handling messages in an emergency. Spe- fects of daylight and darkness on the car- cial wire lines between Broad Street and rying powers of their respective wave- Rocky Point enable the operators in New lengths. Marked economies are effected York to control the "keying" of the various many times with the use of short waves in- transmitters at will. stead of the longer ones, for less power is At least one of the two Alexanderson al- required and the transmitting speeds can ternators is always operating into one of be greatly increased. At Radio Central short- the big aerials. The various short -wave wave transmitters are handling more and This circular bank of fifteen 20- kilowatt power - Latin America units are likewise kept in continuous serv- amplifier tubes is used in the transatlantic more traffic to Europe and ice, if there is a lull in the message traffic radio -telephone transmitter. It stands about and are being used experimentally , for di- seven feet kink. The coils of hose carries the rective transmission to selected countries. an automatic "kever" is started and sends a water required to cool the plates of the tubes.

One of the two 200-kilowatt Alexanderson alternators used to sup- its driving motor is in the right foreground. The various control ply current for the long -wave transmissions at "Radio Central." switchboards supply the background. These big machines furnish The alternator, proper, is the generator at the extreme left, while current for stations TVQK and 1VSS, from 1875 cycles clown. -

www.americanradiohistory.com 106 Radio News for August, 1928

ADVANTAGES OF THE BEAM S$STEM Although the aerials of the "beano" transmitters produce waves that eventually spread over a considerable distance, the directive system offers the advantage of dou- bling the usefulness of each wavelength. For instance, two separate short -wave beam transmitters directed toward England and South America, respectively, may operate on the same wavelength, because the receivers in England will not pick up the waves directed at South America, and the receivers in South America will be free of serious interference from the waves directed toward England. Secrecy of transmission is not the primary object of the beam system, as many radio fans seem to think. From even the best beam stations, enough energy leaks out through the backs of the reflectors and splashes off through the sides to make the signals- readable in unexpected parts of the world. Surrounding the two Alexanderson long - wave alternators' at Rocky Point are six short-wave transmitters, which may be listed as follows: WTT-40 kilowatts; 16.1 meters. Operat- A series of short -wave transmitters at "Radio Central "; the third utit from the right is ing to South America, daytime only. that of WTT, which operates on 16.1 meters, sending messages to South America. Com- 2XT-40 kilowatts; 16.18 meters. Oper- pare the compactness of these vacuum -tube outfits with the size of the Alexanderson ating to Europe, daytime only. generator on page 105. WBU -20 kilowatts; 14.1 meters. Operat- ing to South America. light work only, because of the peculiarities selves consisting for the most part of short 21.75 WIP-20 kilowatts; meters. Op- of these short waves. In some instances, a vertical lengths of wire or copper rod. - A erating to Central America, Porto Ricci and transmitter working with Europe in day- few of the aerials are merely thirty-foot Europe, 24 hours. light becomes highly efficient for communica- lengths of wire hanging from the guy cables WQQ -20 kilowatts; 14.8 meters. Operat- tion with South America at night, and vice of the big steel masts; yet with them 're- ing to South and Central Americas, from versa. liable high -speed communication with Eu- 5.00 a. m. to 11.00 p. m. While the high -power alternators work rope is maintained day after day. WLL-20 kilowatts; 16.01 meters. Oper- with lofty and widespread aerials, the short- ating to South America and Central Amer- wave transmitters use lower and less con- THE "MULTIPLE- TUNED" AERIALS ica, from 5.00 a. m. to 11.00 p. m. spicuous antenna systems. The latter are The lead -ins from the two aerials, sup- It will be noted that the transmitters op- supported by plain wooden poles, usually ported by the 410 -foot steel towers, drop erating below 17 meters are used for day- not over sixty feet high, the aerials them- to the ground a short distance from the transmitter house, and are connected to the generators and to the telephone transmitter by radio- frequency transmission lines. These big aerials are of the "multiple- tuned" type. Separate lead -ins drop from the overhead wires, where they pass under each of the twelve towers, and connect to huge exposed tuning coils. These tune each of the sections of wire between masts to the wavelength on which the transmitter is working. Thus it may be seen that each of the two big aerials really consists of six separate aerials forming a continuous stretch of wire. The short -wave aérials are removed a considerable distance from the actual transmitters; as far away as a mile. The energy from the transmitters is carried to them over radio- frequency transmission lines, which are merely pairs of thin wires strung on poles about eight feet above the ground. The beam aerials erected for directive transmission are rather unusual in appearance. At Rocky Point there are two types in use: the British and the American. The British system employs four 200 -foot steel towers arranged in a straight line. A series of rigid messenger cables, suspended across their tops, supports a double row of vertical wires, running parallel to each other and separated about twenty feet. One set of these hanging wires acts as the aerial from which the radio waves are radiated; the other as a reflecting wall which throws back the waves and makes them travel only in the direction in which the first set face. This is a section of the receiving house of "Radio Central," located at Riverhead, west The American system is similar, but of the transmitters. The operator is adjusting one -of 'the short-wave receivers, which makes use of short, heavy wooden poles to will be left tuned to the proper wavelength. Behind him, at the left, are four long -wave support the rows of vertical wires which act receivers in their rack. as radiators and reflectors, respectively.

www.americanradiohistory.com Radio News for August, 1928 10z

This unique aerial of vertical wires is designed for the reception of great concave mirror. The energy collected by this system is very signals from an English "beam transmitter," and is located at River- much greater than that picked up by an ordinary antenna; and it is head. One row of wires acts as a multiple aerial; the back row as a therefore possible to get a dependable signal with much smaller reflector which concentrates the radio waves upon the aerial, like a power in the transmitting station.

RECEIVERS AT RIVERHEAD been termed "Radio Central" because of the Radiating from New York are direct concentration of communication facilities at radio communication channels to England, The receiving end of Radio Central is a these points, the Radio Corporation of France, Belgium, Germany, Italy, Holland, few miles west at Riverhead, Long Island. America maintains other stations for serv- Norway, Sweden, Poland, Argentina, Brazil, The grounds surrounding the small build- ice to overseas countries. The central traffic Colombia, Venezuela and Dutch Guiana. On ing housing the receiving apparatus are cov- office at 66 Broad Street in New York han- the Pacific Coast an office in San Francisco ered with aerials of every imaginable type. dles messages, not only through Radio Cen- handles traffic to Hawaii, the Philippines, The most outstanding one is a beam receiv- tral, but also through two Alexanderson- Japan, China, French Indo- China, and the ing aerial of the British type, the construc- alternator stations at New Brunswick and Dutch East Indies. tion of which duplicates the transmitting at Tuckerton, both in New Jersey, and Such have been the developments of a aerial described in the preceding para- through still another station at Marion, on very few years; six since the inauguration graphs. the south shore of Massachusetts. In addi- of Radio Central, and twenty since the first The receiving house, naturally, is not as tion, another receiving station is maintained commercial radio service was put in effect spectacular in appearance as the transmit- at Belfast, Maine, which, likewise, connects across the Atlantic between Clifden, Ire- ter house, but it contains some interesting directly with Broad Street. land, and Glace Bay, Nova Scotia. equipment. 'l'here are 17 separate long - wave receivers, each containing 13 tubes and tuned to a single wavelength. These outfits are arranged in racks, each rack be- The aerial at the right, which differs considerably ing about twenty -five feet long. In a newly - in design from that shown constructed wing of the room a bank of at the top of the page, is a part of the American twenty-four individual short -wave receivers beam system; its method is being installed, about a dozen being in of functioning, however, operation is similar in principle to at this time. Each receiver con- that of the "English" tains a total of thirteen tubes and, like the beam aerial shown above. long -wave instruments, each is tuned to one This, however, is a transmitting aerial, and is so wavelength and left alone. Standard screen - aligned that its emission grid tubes of the 222 type are in use in the is concentrated in the most favorable directions. IL.F. stages, three in number. The radio beam is not sharp, like that of a AN INTERNATIONAL SWITCHBOARD searchlight, but signal strength decreases pro - gressively away from the The outputs of all the receivers are led line of greatest radiation. to a switchboard resembling a telephone As in the picture above, one set of vertical wires board. This is connected by land lines to (those on the left) forms 66 Broad Street, where the messages from the aerial, and the other the reflector. The length the various foreign countries are copied and and the spacing of the routed to their destinations. The radio op- wires is very carefully calculated, as it must be erators at Riverhead think no more of properly proportioned to switching into London or Berlin than a tele- the wavelength used, to secure best results. The phone operator in New York thinks of rout- wires are very rigidly ing a call to Brooklyn, across the river. secured to the wooden masts which support them, While Rocky Point and Riverhead have and kept taut by weights.

www.americanradiohistory.com 108 Radio News for August, 1928 Getting: the Vote by Radio How the Political Parties Lost Their Hold on Public Interest, and How Radio Presents the Only Method of Restoring Contact with the Voters

By Marshall D. Beuick

A get- out -and -vote campaign by radio Secretary Hoover has broadcast stations could do a lot to prod been associated with radio the 40,000,000 voters in the United States since the birth of broad- who to vote 1926. casting, and is a veteran failed in Those millions of the microphone. He represent nearly two -thirds of the qualified has an effective manner voters; for in 1926 and delivery which many there were about 62,000,- a man in public life may 000 persons who could have gone to the envy. polls to declare their choices of candidates for elective offices. The National Civic Federation has been working for several years to arouse the in- ILL broadcasting bring This the apa- thing as broadcasting. analysis shows different voter who prefers to chop wood thetic voter to the polls this year that the most emotionally- active interest rather than go to the voting booth. This when there is a likelihood of two found in politics was apparent in 1876, in organization, in a statement, suggests a job W of the most appealing candidates, the presidential campaign of that year, when for the broadcaster when it says: Alfred E. Smith and Herbert Hoover, meet- about 85 per cent of the qualified electorate `If the deplorable record of 1926 is to be ing in the political arena to contest votes. for the cast At the crisis of the Civil War expunged in 1928, there should be waged an highest office in the land? Radio has as (1864) was not there another indication of entirely different campaign one yet had a real -not of opportunity to show its pull- voter interest, when the percentage was platform oratory and publicity stunts ing power in the alone, stirring interest of voters. close to 85 per cent. but one of real, intensive, individual In the last presidential election in 1924, service." broadcasting was young; THE VOTER DESERTS it was just four What, then, could be more effective than years old. This year, for instance, KDKA From 1876 the votes sloughed off gradu- an intensive campaign over the air that will will celebrate its eighth broadcasting anni- ally until 1904, when they dropped rather reach all the 40,000,000 lazy voters in their versary; for it was in November, 1920, that pronouncedly to about 75 per cent. This homes? it first broadcast election returns for the decline continued up to 1912, when the per- RADIO AROUSES INTEREST few fans who existed in the country. centage became only a a little more than The listlessness of the voter has been in- 60. In 1916 there was a very slight revival The Honest Ballot Association in New creasing. An analysis of the number of bal- of political interest, which may be explained York took the initiative in this movement lots cast in elections since 1865 gives an in- by the introduction of woman suffrage; and one year, by enlisting the aid of broad- teresting interpretation of the political in- in the campaign of 1920 the vote dropped to casters in giving information to voters terest, at least, that which is expressed its lowest ebb, which was just a trifle above about registration and election. The in- through the vote, over a period of nearly a 50 per cent of the qualified voting popu- quiries received after this campaign was half century during which there was no such lation. started showed clearly that the broadcast

The old -time politician wore himself to a frazzle "swinging round the circle" to reach scattered hundreds-

www.americanradiohistory.com Radio News for August, 1928 109 station is a highly effective means of arous- Governor Smith's inf or- mal bat convincing style ing the interest of the voter and of convinc- has been felt over the ing him that there is no mystery or com- radio in many New York state campaigns which he plexity in taking advantage of his right to carried to the voters in vote. this manner. The broadcasting of the proceedings of the conventions of the two parties will be 3111111111111111111111111111111111111111111111111111111111111111111 in itself an influential affair in catching the voter's interest. Many of us have remem- This poor showing re- bered for years the voice which repeated, sulted in the face of clay after day, during the 1924 Democratic the co-operation of a convention in New York: string of important "Alabama, twenty -four votes for Under- organizations, such as wood !" the National Civic Recall the bands that played. Ybu can Federation, the Amer- almost hear the wild applause of the dele- ican Legion, the Na- gates now, when you stop to remember. tional League of Whose blood didn't tingle during those Women Voters, the scorching days of that convention, whether American Federation he was a Democrat or not? That was a of Labor, the Cham- I presidential nomination that was being made her of Commerce of -a great emotional affair if not one of the United States, vital significance to every citizen of the and several national country for the four years to follow. organizations of business men. thousands of miles, and made hundreds of in end of trains, he 1928 A RADIO YEAR Literature of all sorts was available speeches from the rear this work, as well as the opportunity at can now reach millions through one mike. Radio has figured somewhat in previous public meetings and the cooperation of some What he may write will never have in it the campaigns; but there are indications that newspapers. Now we have the new situa- personality that his speech over the air will this year will give the first full opportunity tion arising wherein campaign literature have. The written words of a candidate to show what can be accomplished through will be largely_ supplanted by broadcasting. can be insincere; but it is difficult to cover broadcasting as the medium of reaching the "Who reads campaign literature anyway ?" up bunk when you are talking "mike -to- citizen in his own home. In New York City is the question, of many practical politicians. speaker," which is so much like talking face- the radio was used to some extent during There is so much printed matter mailed or to -face. the campaign which resulted in the election distributed today that the ordinary citizen Someone once said, "Now is the time for of James J. Walker as mayor. At that can only shake his weary head and throw it all good men to come to the aid of their time Governor Smith showed what he could away. With broadcasting, however, the party." This year it will be the time for all do over the air in reaching the citizens; situation is different. Such an overwhelm- good men to come to the aid of their fami- his informal manner of speaking was en- ing majority of the public listens in fre- lies and get set for the political broadcast- tirely suitable to the element of intimacy quently in home surroundings where they ing. If they all do, we shall probably see that broadcasting possesses. are more receptive to ideas, that broad- much more balloting than formerly. Many All previous methods of getting out the casting appears to be the most effective po- of those 4,000,000 voters may get so voter have failed. It is true that the tedious litical instrument. It may very well reduce pepped up through the convention con- method of calling for the voter at his home the campaign rallies to occasional pow- tests and other political -radio activities that is an effective one; but it takes a whole wows which, after all, will be broadcast. you can't keep them from the polls in army to do the job even partially. In November. forty -one states, in 1926, the vote fell off AUDIENCES OF MILLIONS Broadcasting will have its chance this despite the intense non- partisan campaign The advantage to the candidate is tre- year to show its stride as the modern soap- that was put on throughout the country. mendous. Whereas he formerly traveled box for the political speaker.

-While the modern candidate addresses millions in a night, through the broadcast chains, with ease.

www.americanradiohistory.com 110 Radio News far August, 1928 Radio Advertising Does It Pay? Merchant Prince of the Air Says "Be Yourself" is Secret of Success in Direct Selling Through Microphone By Orrin E. Dunlap, Jr.

"In the Sweet Bye and Bye," "Onward, ,11,,,11,1111,,,,,,,,,,,1.11111,1111111111111111111111111 Christian Soldiers," and so forth. But the ace of the "The. Friendly Farmer" air is Mr. Field in person! doing his stuff for his huge, appreciative and SUITING THE PUBLIC TASTE responsive Mid - Western radio audience. If direct selling ever spreads to other stations, the advertising agencies will prob- 1,,,,,,,,,,,,,,1,111111,,,,,,1,,,,,,,,,,,1,,,,.,:,,,,,,,1,,,,,, ably strive to write the broadcast copy for tooth paste, airplanes, automobiles, ginger ale and everything under the sun. The best IS radio's destiny to be direct selling? in his shirt -sleeves before the microphone copywriters will be put to work and the Is the emptiness of space to become a and tell the millions all about his seeds, announcer with the trained voice will go

world -wide billboard upon which elec- bacons, auto tires, pig meal, fresh . hams, on the air to act as the salesman to put tric waves etch invisible lettering that radio batteries, prunes, paint, tea, coffee, the message across! receiving sets and televisors will reveal as shirts, shoes, socks, sparrow traps, over- "That's what you New York fellers will blazing signs that everyone "who runs may read?" These are the questions that are puzzling the broadcasters. Congress is pon- dering over direct advertising on the radio while formulating laws for the future; and national advertisers, ever alert for new and SOME years ago, when the wonders and possibilities of radio burst into the con- novel methods of introducing and keeping sciousness of the business world, its first thought was "At last-the universal their products before the public, are won- advertising medium." Staid leaders of the advertising profession immediately re- dering if they can buked the audible thinkers; first, said they, for an unethical idea, which would invite sell through the micro- public condemnation, and phone secondly, for the folly of spending money where there could without loss of good -will. So far, be no possible return. the broadcasts are softened by such phrases as "sponsored by -" or "by courtesy of-." Nevertheless, those who were unawed by these arguments went ahead and created The announcer does not say "paid for by-." the enormous and unrivalled broadcast organizations which are entertaining the But the great question today is, will direct American listener tonight -all in the belief that the advertising value of radio will selling be allowed Mid tolerated on the justify an investment of many millions. radio? In the first place, does direct selling on Surely, some of them were too optimistic and some too unskillful; money, was spent ze'ithout.. proper planning, as in all other forms of advertising. the radio reap as bountifully as it is To create the sowed technique of a new art, as much money had to be spent as to develop the apparatus to the four winds of heaven? To answer which has made broadcasting and its reception possible. this one must turn to Henry Field, "the friendly farmer," "seller of seeds," "go- But the American public has not resented radio advertising so much as its self. getter" and owner of station KFNF in appointed guardians predicted. The radio advertisers who used the necessary effort - Iowa, out where the corn grows tallest. and brains -to please their audience and patrons have enriched themselves in many He is the past master at selling on the cases -none more striking than the subject of this article. radio. Let's see what the owner of The answer to the question at the top of this page is "Yes!" Radio advertising another sta- pays you if you know how to do it. The people tion in Iowa who are most concerned with says about the pioneer mer- whether advertising is good or bad (from the listeners' standpoint) are those who chant of the air. patronize the advertiser if his program is goad and who tune him out and buy else- FRIENDS AND FOES where if it does not suit. The answer to the radio advertising question is automatic. "He goes over big," said the manager The only complication is "stray" circulation- distant listeners who hear a station of a station which might be considered a outside the area within which its advertising is acceptable to its service audience. competitor as far as entertainment is con- And that is a problem, not of advertising, but of all broadcasting -that the "inter- cerned: "A listener is either dead against ference" area of a station is so very much larger than its service area.- Enrroa. Field or he turns on the loud speaker and lets Henry come right up to his fireside with direct sales -talk and bargains. The majority in the Corn Belt consider him a friend but, should his waves reach New alls, chicken feed, Bibles, ladies' and gents' do if it comes to selling on the radio," said York, they would probably be given a cold hosiery and what not. His waves spread a westerner: "That's where you'll make shoulder and. be tuned out. Henry is a over Iowa, Nebraska, the Dakotas, Minne -. your mistake. But you'll wonder why you showman as well as a salesman. He knows sota, Missouri, Kansas, but they strike with can't sell a carload of hams or thousands what the public want. He gives them the the greatest force in Iowa and Nebraska." of bottles of ginger ale. The trouble is old fiddlers, devotional exercises, the sweet One secret of Henry's success is that he that you'll talk over the heads of the public. twitter of the seedhouse canary and the old appeals to the farmers. He is one of them. You want to remember that the radio audi- classics that touch the heart with their He knows what they most desire. There ence belongs to the masses, and you know melodies. He broadcasts a news digest are no Metropolitan Opera stars to grace they say that the average mind is that of and then confides with his listeners for an KFNF's studio. Home talent entertains the fourteen- year -old child. So why not hour regarding the mail he has received. and actuates the microphone with "Swanee learn your lesson now and be one of the He becomes a friend, who can sit down River," "Silver Threads Among the Gold," crowd just like Mr. Field? He never writes

www.americanradiohistory.com Radio News for August, 1928 111 his speeches or sales talk. It's all inspira- Judge Sykes replied, "There is no author- in time be withdrawn by the force of an tional and informal. That's what makes ity under the law for the commission to adverse public opinion. friends. This high -brow stuff on the radio regulate direct advertising (i. e., where the Contending that the present law is ade- doesn't count. 'That's why Henry has ex- price is mentioned), but I understand that quate to suppress direct advertising by tended his mail -order business. He knows it has been suggested that such advertis- radio if the commission should elect to his public and he knows his stuff. He tells ing be limited to daylight hours." follow such a course, Representative Wal- the farmers in the Corn Belt that his so- The Radio Act of 1927 stipulates (Section lace White of Maine said: may pre- pranos sing as God intended, free of the 19) : "All matter broadcast by any radio "The commission, generally, screeching caused by long training. They station for which service, money, or any scribe the nature of the service which a par- sing like the common people. The KFNF other valuable consideration is directly or ticular station is to render. I am inclined artists sing the hymns as they ought to be indirectly paid, or promised to or charged to believe that the language of the law is sung, just as anyone in the farm house or accepted by, the station so broadcasting, broad enough to say that, on this particular sings them in church on Sunday." from any person, firm, company, or cor- station, you may or you may not put out Mr. Field began broadcasting in Shen- poration, shall, at the time the same is so advertising, direct or indirect. I have felt andoah in 1925, when his gross sales were broadcast, be announced as paid for or that there were doubts as to the soundness $900,000 for seeds and nursery products. furnished, as the case may be, by such of that construction, and for that reason I In 1927 the gross sales are said to have person, firm, company, or corporation." have brought the question forward for the leaped up to $2,500,000, of which $1,500,000 Some consider direct advertising on the committee's consideration." was for general merchandise. In less than radio an evil. Others contend that it falls Most of the broadcasters contend that eight months he sold $340,000 worth of in with the provision of the law that broad- they are not making a profit. Is that be- automobile tires. In six months he dis- casters should have as their slogan, "public cause they are not radiating direct adver- posed of $50,000 worth of shoes over the interest, convenience and necessity." tising? Will-necessity force them to change air, without the bother of having the cus- Radio Commissioner Orestes H. Caldwell,: from indirect and good -will programs to tomers come to the store and try them on. of New York, calls attention to the fact direct selling and quotations of prices That's salesmanship! that the commission has no power of cen- through the microphone, in order to sur- It is reported that he has disposed of sorship under the law; and he has testified vive? 'rime will tell whether or not the as much as a carload of coffee a day, some that, in his opinion, direct advertising in "impresarios" in the lavishly-decorated stu- of which warmed up pilgrims at the studio, many instances provides a distinct service dios with their tapestries, statues and trim- where he gives each visitor a cup of coffee. to the listener. mings of gold will come down off their During a flower show he staged, more than "It is my belief," said Mr. Caldwell, "that "hifalutin" perch and just be "one of the 31,000 visitors came to the KFNF studio nearly every program that goes on the air common people." to catch their first glimpse of the elusive has a background for some form of pub- However, radio is a big field, the ether radio and of their friend Henry Field. The licity. It would be hard to draw a line is vast, the audience is countless, the tastes population of the town is only 5,000. Hams between those stations which advertise di- are many; so some may broadcast from and bacons he has sold at the rate of half rectly or indirectly and those that profess studios of gold while others entertain from a carload a week. Henry is the Merchant to furnish programs of cultural value." the old- fashioned farmhouse parlor. But, Prince of the Air. He is the Roxy of the Mr. Caldwell said that he thought it to be successful in advertising, in selling great open spaces! would be unwise to attempt to censor by and in making friends, they must learn the law. Programs, lie asserted, that are in simple formula of Henry Field-"Be Your- HIS SECRET any way objectionable to the listener will self." At aluncheon of the advertisers at Des Moines, Mr. Field told those who seek fame and fortune by selling to invisible customers that the secret of success is "Be Your- self :" When talking over the air he dis- penses with his coat, just to be one of the common people. Then he chats with his "folks," with such phrases as "we was" and

"we ain't got." He has - cast aside all "hifalutin" ways. Henry Field has voice personality and sincerity in his nasal twang. When he begins to sell this is what he says, "Howdy, folks. This is Henry, Henry Field talking, folks. Henry himself." 'l'hen perhaps his voice weakens a trifle as he turns from the microphone to ask Sally, "What's your next number goin' to be ?" How different from the prim voice of a New York announcer's "Good evening, ladies and gentlemen of the radio audience." Henry Field's broadcasting studio is a modern version of the old -fashioned farmhouse parlor and he appropriately calls KFNF the "Friendly Fanner station." On one birthday celebration on the air Henry received 226,000 telegrams, to say nothing of the sacks of congratulatory wail. So much for the sage of Shenandoah, who strives to he one of his audience, "just a friendly, neighborly bunch of folks" who care little for the "hifalutin" things in life. THE FIGHT ON ADVERTISING But what does the radio law say about making a marketing place of the ether? At a congressional hearing, Federal Radio Commissioner E. O. Sykes was asked regarding the policy to he pursued toward a station "spending most of its time in ad- Henry Field of Shenandoah, Iowa, whose station, KFNF, broadcasts his personality vertising." --anti his mail -order business -to millions of listeners daily.

www.americanradiohistory.com 112 Radio News for August, 1928

BATTLING with hardships, dark dis- When scientific research had shown that viewing with alarm the situation, seeing in couragement and terrible trials, and this spot was indeed the long -sought health it a menace to the public weal, hinting that urged on by the adamant will, the paradise, Harold Dare's millions worked Harold Dare had betrayed the public con- calni confidence, and tender sym- wonders. Soon many cottages nestled on fidence. To these accusations, Harold Dare pathy radiated from the powerful person- the hillsides, and mingled with the shouts could make no reply. Puzzled, perplexed, ality of Harold Dare, certain members of of happy children echoed the blows of the with his best experts baffled, in his great the staff of the Dare studios carne at last hammer, as on the floor of the valley a new soul he blamed himself for this error of to a little valley high up in the dry, rarefied studio for the Dare films neared completion. judgment. Was his engineering staff's in- atmosphere of the Sierras. They came not No longer did the workman return, tired terpretation of the results of their research for personal glory, nor with mercenary in- and discouraged, to a bedraggled wife and at fault? Or had a fickle Fate frowned tent, but to gratify the life dream of the pale, wan children; for with the wonderful upon his long- cherished plan for uplifting great and benevolent Harold Dare. atmosphere and ideal sunshiny climate, his public? For years the great screen star had been Mother Nature wrought miraculous cures. A new plaint swelled the chorus of criti- saddened by the trials and tribulations of So was the great dream of the illustrious cism. Radio listeners began to complain the poor, downtrodden working class. His and beloved Harold Dare being encom- that radio reception was impossible during heart went out to the helpless, struggling passed. the rains. For some time previous to each parents, endeavoring to rear and educate Suddenly the heavens opened their flood- storm, broadcast signals began to weaken. the rising generation, trying to catch a few gates. Rains of unprecedented violence fell, At the same time, a continuous barrage of crumbs from the table of the more for- materials to the valué of thousands of dol- static settled down over the whole radio tunate. His heart bled for the children of lars vanished in the swirling waters. Con- spectrum. With the fall of rain, signals the sordid city, imprisoned by environment struction work of all kinds was halted. entirely disappeared and Health Valley with temptation and evil, filth and disease. Murmurs of discontent began to be heard was totally cut off from radio communica- Here, in this wonderful valley, would he among dwellers of the valley, as pneumonia tion with the outside world. build a model city. Here the air, dry and and influenza stalked in the wake of the The local radio listeners' club held a clear, was pure and filled with life -giving dampness and cold. stormy session. Tired fathers, their faces oxygen and ozone. Here not a drop of rain . Keen -nosed newspaper reporters, scent- drawn and haggard and their eyes encir- had fallen for years, yet the fertile valley ing profitable scandal, seized upon the situ- cled with dark rings, testified that they had abounded in springs of clear, cold water rich ation. Headlines shouted: been forced to walk the floor all night, for in vitamines and nuxated iron. Here the their radio- raised infants strenuously re- sun, shining unremittingly at least 365 days Dare Health Haven Hoax, Charge Hurled -Probe Dare Poor People's Paradise fused to go to sleep without their accus- each year, filled the air with health- building tomed bedtime story. Brides were forced ultra- violet rays, infra -red rays, and X -rays. The public's confidence in their great to resort to delicatessen fare, since radio The place had long been inhabited by a race benefactor began to waver. Unprincipled recipes were not forthcoming. Tired busi- of powerful -muscled Indians of great demagogues appealed to the jealousy of the ness men, their muscles grown flabby and strength and huge chest expansion. They misguided masses; calculating editors of soft without the stimulus of radio setting- called it "Urn -pah," meaning "land of clear the predatory press played upon the preju- up exercises, forsook the golf links to play sky and eternal sunshine." dices and the passions of the plain people; checkers or tiddlewinks. Wives and serv- ants alike threatened to leave at once if radio entertainment was to cease. As to the cause of the trouble, many theories were current. Some contended that sunspots were responsible; others that the earth had slipped in its orbit. One of the club's experts maintained that in coming through the rain -drenched upper atmosphere, radio waves became so highly damped that they lost their carrying power and were unable to reach the valley. The meeting finally resulted in a petition to the Radio Commission that radio service be resumed without delay. From the executive offices of Harold Dare came the command to the Dare laboratory staff to make a comprehensive survey of the situation. Forthwith the valley became alive with scientific experts. Putteed sur- veyors in broad- brimmed hats peered in all directions through their transits. Avi- ators circled ceaselessly above the valley region, photographing and testing with various radio stations. Geologists went about with their hammers, knocking everything. Me- teorologists sent up thousands of balloons to explore the- upper atmosphere; astrono- mers and mathematicians collaborated to "A sudden Patter of raindrops caused him to look out of the window. Absent -mindedly he raised the fluoroscope to his eyes. `Himmel!' he gasped. This is strange!'" determine if any conjunction of planets or

www.americanradiohistory.com Radio News for August, 1928 113

other celestial aberration lay behind the storm clouds seemed to have massed at this Wynn, in charge fór the time being of climatic cataclysm. Linguists harangued point and discharged their entire burden operations in Health Valley, stepped into the stoic Indians, archaeologists squatted of moisture upon Health Valley. The de- the Dare radio-telegraph office to summon for hours over tribal records on rugs, pot- tectives had no comment to make other Scott, who had returned to Hollywood on tery, and stone, in an effort to discover some than that the integrity of the two hikers business, he found a group of experts parallel occurrence in the history of Health was above all question. gloomily inspecting the radio transmitter. Valley. Then Harold Dare suddenly rose to his "It's no use," said the operator in charge. When, a week later, the Dare engineers feet. "Men," he said, "from the first I have "About an hour ago, the static shut down met in conference to report their findings, liad a feeling that something more than a and we have not since been able to break the atmosphere was one of intense gloom freak of Nature lay behind this mystery, through on any wave. Our only connection and discouragement. The results of the that a human hand somehow was directing with the outside world is by long- distance investigation were highly inconclusive. The the sinister turn taken by this cataclysm, telephone." archaeologists had found one clue, a picture threatening as it does to undermine the At the sanie moment, in a room of the scratched on stone; but because of its crud- very foundations of our civilization in huge Dare hospital across the valley, Dr. ity, it was impossible to decide whether it Health Valley. von Stück, fluoroscope in hand, was con- was a tribal record of a heavy rainstorm "There is one person who would move ducting an X -ray examination. A sudden or a portrait of a man taking a shower heaven and earth to work me harm. That patter of raindrops caused him to look out bath. One expert contended that these In- person is Dandy Diavolo, my arch -enemy of the window. Absent -mindedly he raised dians had never seen a shower bath; where- of the Flicker Films, who pursues his role the fluoroscope to his eyes. upon a colleague tartly called attention to even more relentlessly in real life than be- "Himmel!" he gasped. "This is strange!'' the fact that apparently none of them had fore the camera. He alone would stoop In the fluoroscope appeared a cluster of ever been out in the rain, either. The to strike at me in such a way. It is my wavering, striped streamers radiating from grizzled Chief Standing Pat assured the theory that he is beneath this demonstra- a bright spot in the sky where the clouds linguists that in all the many moons within tion of storm and strife. If so, he will were heaviest. For a moment he studied the memory of his people, no water had soon endeavor to make his triumph com- the phenomenon, and then stepped into the fallen from the skies. His son, young Run- plete. We may therefore look for another adjacent office and picked up the telephone. ning Bluff, contradicted the statement, rain in the near future; and this time we loudly boasting that he bad often seen water must discover the means used by the mon- * fall from the heavens at the command of ster. 'Carry on !' must be our motto. Carry Across a hundred miles of mountain and the tribal medicine man, and that he, him- on! until in the very last episode, right canyon, river, plain, and desert, guided only self, could command it to do likewise, if shall triumph, and villainy receive its just by a pair of tiny twisted wires, thrilled he chose. However, he dill not choose, and reward !" tiny quivers of electricity -now through the so the linguists were left in doubt. * * * dark tunnel of a lead -sheathed underground The sensation of the evening was the re- It was with a strange thrill of fulfilled cable, now across the intricacies of a huge port of the Intelligence division. According prophecy that the Dare engineers looked telephone exchange, to a room where a man to their report, two hikers had made the up one morning to see that the sky was sat before the control panel of a radio ascent of Peril Peak just before one of the becoming overcast and that huge dark clouds transmitter and shaped the meaning of the rains. They had just reached the summit were massing themselves overhead. From tiny impulses into the clicking of a key. when the storm broke. Rain fell in such Peril Peak, where a lookout station liad been Out from a slender web of wires swung torrents that only with the greatest diffi- established, crime the word that the air between tall towers, waves rippled the culty were they able to maintain their foot- was warm and humid, and that clouds were ether; and high up above a panorama of ing. But, although the whole valley was moving in from all directions and converg- peaks and valleys, the radio operator of being deluged, on all sides the surrounding ing upon a spot directly above Health Harold Dare's private air transport handed mountains were in bright sunshine. The Valley. And when Assistant Engineer (Continued on age 175)

"The rest of the story belongs to history: hoa. the Dare courageous forces, under the rounded and captured Dandy Diavolo and his henchmen: and how they fount leadership of Harold Dare himself, went out into the hills, sur- cleverly concealed in the underbrush a dozen huge, mercury-vapor arcs."

www.americanradiohistory.com 114 Radio News for August, 1928

More About Gyps over the country. Station interference can can walk. An attempt like this, to form by one or more of the follow- a national organization from the top, would Editor, RADIO NEWS: be eliminated over a larger be a gigantic undertaking. A federation of The article on the "Radio Gyp" in the ing ways: Spreading stations division of time, placing chain clubs formed of local listeners, as they June issue of RADIO NEWS is a step in the waveband, is would be natural method of evo- right direction, but why confine it to Phila- programs on the same wavelength if this grew, the delphia? It might well be spread from one possible, improving broadcast and receiv- lution.-EDITOR.) end of Cortlandt Street to the other in at ing apparatus, and as a last resort, by least some of its phases. eliminating some of the stations. Inter- The practice of trying to substitute tubes ference produced =.,y. defective electrical by the neces- Troubles We Make Ourselves for those advertised is prevalent in all of appliances can be eliminated Editor, RADIO NEWS: -class ones. sary state legislation. the stores, even the so called high As I read "The Listener Speaks," I see it sounds The radio listeners of America can be They all have the same story; some good suggestions; but they seem to a course; "The Cun- like correspondence be all for station managers. I will gamble cheap tube, let ningham (or RCA) is a that some who have complained about re- only 50e me show you the "Gypatron" for THIS page belongs to the readers ception have different home appliances more which is absolutely guaranteed" -(try of RADIO NEWS. It is theirs for causing interference. and realize on the guarantee.) the purpose of discussing fairly and The first step toward good reception is O. C. Moos, frankly the needs of broadcasting from to have the listening public as a whole FRED J. DEESEN, the standpoint of the great public who unit, instead of its being divided into deci- R. E. LocKE, represent, not listen in. The letters mal fractions. Regardless of what type of E. V. INOLET, but necessarily the editorial opinion, program is preferred, the first step is to J. P. DuFFY. that of the writers; who are, in the edi- clear the air of 60% of the interference Company, Southern Pacific torial belief, fairly typical of groups of due to household appliances. As I write, 165 Broadway, N. Y. C. radio public. Make opinion among the at 3:00 p. m., some of my kind neighbors your letters concise and offer construc- have gone out, and their vibratory charger when remem- tive criticism you can; is on, and will stay on until their return Editor, RADIO NEWS: bering always that there is something - on your usually about 10:00 or 11:00 p. m. Usu- Allow us to congratulate you to be said for the other fellow's side. in your ally, when one vibratory charger stops, expose of the "Gyp" store June Address The Editor, RADIO NEWS, NEWS. the another starts in retaliation; and the ma- issue of RADIO Keep up good 230 Fifth Avenue, New York City. work. jority suffers as a result. Modern Electrics started us in 1908, and When one has over 80% amplification at we're still at it. The retail business is rot- 50 cycles, and a speaker that will reproduce ten for the small dealer, and your article organized if our radio publications will de- that frequency, the 60 -cycle vibrator gives on the Parker gang in Philadelphia gives vote space to explaining the merits of such a roar that can be amplified enough to us a slight ray of hope that the fakers will an organization and at the same time call- saturate the last audio tube. all be in a class with the spark sets of by- ing on their readers to become members. A We had a "Clean the Air" movement gone days. membership fee of 25c per month will be here, but as soon as it was found out that HARRY FREUND, required and each applicant should be re- it would cost a couple of dollars, it was Pioneer Radio Service, quested to pay for as many months in dropped. Let the majority of listeners de- 1686 George St., Brooklyn, N. Y. advance as his pocketbook will permit, in mand of their respective city councils or- order that heavy advertising be carried on dinances forbidding the use of such articles in the different radio publications and over without suitable filters in the line. 'l'he Who Will "Bell the Cat ?" the air. That is, we must pay as we grow power companies will tell where they are; Editor, RADIO NEWS: and, of course, the more we pay, the faster and the public will be surprised to find that I believe that, if the radio listeners of we will grow and the sooner we will reach "the transformer on that pole" has sud- America were organized, they could compel the stage at which we can enforce our denly become quiet without being fixed. the enactment of legislation that would give demands. The next step will be to demand that an them the greatest benefit from radio. These Each applicant from an unorganized dis- engineer be put in charge of the Federal listeners are now standing by, patiently trict should state at the time if he will Radio Commission- someone with backbone waiting for some one to say "Let us or- donate hiS services as a local secretary or enough to make the different stations bring ganize"; and this "someone" should be the organizer. From this information, the na- their apparatus up to standard and keep radio publications of America, because their tional office will appoint temporary local station distortion down to a minimum. I prosperity depends upon the broadcast situ- secretaries and organizers for each district. had a good laugh when I saw a picture ation being cleared up to the entire satisfac- When the membership is large enough, the of a very expensive station using an R.C.A. tion of the radio listeners. national office will establish state and city 20 to check their programs with. The gen- The object of the organization will be to branches which will be financed by receiv- eral trend of receiver design seemed to be make conditions such that every radio lis- ing a part of the membership fees. 'l'he competition in quality of reproduction until tener in the country will be able to get just required state and national legislation will the advent of the A.C. tubes; and then what he desires over the air and with the then be drawn up in proper form and something had to suffer in order to keep clearest possible reception. (Hitching turned over to the local organizers to cir- the hum at a minimum. Squeals we had the wagon to a star. -EDITOR.) culate for the required number of signa- all become used to. As to clearing up reception; we will have tures. These petitions will then be put Engineers published charts showing re- to eliminate man -made interference, such through the proper channels by the secre- sponse curves of different amplifiers and as station interference and that produced taries of the districts to which they pertain. speakers, told us what was going right over by defective electrical appliances. Static EDWIN H. WHITE, our heads, unless we had similar apparatus. will be counteracted by increasing the power Dos Cabezos, Arizona. We bought it. Now we get a station hum and by a more even distribution of stations (All organizations must creep before they (Continued on page 179)

www.americanradiohistory.com Radio News for August, 1928 115

OUR COUNTRY'S HERO CORRECT! GO TO THE HEAD A HAPPY THOUGHT JONES: "What's all OF THE CLASS HOUSEHOLDER (sud- TH5 IS SrATION TEACHER (who is N\ the crowd for? And denly awakened by --, I.O.U. - who is that fellow working up to a lec- noise in night, from they're cheering so ?" ture on the wonders head of stairs):. : . i 7 SMITH: "Haven't of radio) "Can any "Who's there ?" to me ç (1 Vie_ {% you heard? That's the of you name (Clicks gun.) l' [ man who has just in- something that talks, RESOURCEFUL BURG -L-- sings, that was vented a radio set plays, LAR (hoarsely): "This. that will always work not in existence is station IOU, Walla . when you have company in to hear it!" twenty years ago ?" Walla, Washington, signing off. Good night, -Leiland Seay. HANDY ANDY : "Yes'm, oh, -yes, ma'am!" ladies and gentlemen!" TEACHER: "What is it ?" -Albert A. Snyder. IT WAS TICKLISH ANDY: "Me!" -J. Leo Ubry. A radio dealer was waiting on a flapper HE KNEW THE KIND customer in my presence, and she explained, A SCIENTIFIC BLUNDER Evidence that the "razzing" sometimes "My father wants a new radio tube; some- Al PROFESSOR OF Psr- given stations by the press comes home was thing's wrong with our radio." CIIOLOGY: "Jones, I given by an unconscious (or sub -conscious) "How does he know it's the tube ?" asked have come to the con - slip on the part Of an announcer at station the dealer. c=.( elusion that you have WGN a few days ago. He was describing as "Because it hollers when he pokes at it what is known an a, sport of cricket fighting which is some- with his finger," explained the young `Inferiority Com- times practiced in Japan, and opened his woman. -Mrs. R. A. Hill. plex.'" heart to the radio audience. °\( t ; ST uDENT (a radio "These critics sometimes are a very blood- ANOTHER CRUEL SLAM i fan `That's where thirsty and murderous lot!" : D SALESMAN "This is you're wrong, Professor Floyd; mine is an -Alvin Carlson. the most selective set eight -tube superhet." H. N. Webster. we have. You can ab- ,11,,,,,1 11111111 0111111111,,,,,,,,,,1111 111111111111111111111111111111 "THE EASIEST WAY" solutely tune out THIS page is devoted to humor of purely BILL: "I say, old every station except radio interest; and our readers are in- to 4 t vited to contribute pointed and snappy man, are you going the one you want." jokes-no long- winded compositions-of an take in the flower SANDY: "Aweel, it original nature. For each one of this na- show this evening ?" ture accepted and printed, $1.00 will be seems tae me 'twoulcl paid. Each must deal with radio in some Jim: "No. I think be better, gin. ye could of its phases. Actual humorous occur- I'll go to bed early rences, preferably in broadcasting, will be get hair than ane. 'Tis nae use wasting preferred. Address Broadcastatics, care tonight and get it quid music when ye ha' paid oot siller tae RADIO NEWS. over the radio." hear it." -J. Thomas Scott. -E. W. Trebilcock, Australia. PRIDE GOES BEFORE A SERVICE THEIR FUTURE STATE MOTHER: "Hurry MOTHER (reprov- IN THE NEAR FUTURE? now, Pa, and get into ingly) : "Oh fie, Min- "AND 50 DEAR orn. FONE FlAIr: "Say, I jyour Sunday clothes." nie! Do you know CHiLO2EN, THE POOR just heard a haul in LITTLE RARRT FATTIER : "What for, what becomes of lit - ATE THE E G Australia drop a pin! ask you. you that? I We're not tle girls who tell 'BEM ! Can beat going anywhere to- stories ?" r?K TELEVISION HAIr: A w! day." ROMANTIC MIN - RATS. "Huh, that's nothing. ll MOTHER: "Don't NIE : "Yes, Mamma; I had that fellow argue, I tell you. I'm they grow up and get tuned in, too, and saw going to tune in the services up at the to be lady story- tellers the pin drop!" cathedral." -E. H. Foley. over the radio." -J. Leo Ubry. -J. Thomas Scott.

RADIO RHYMES No. 10

(N. LEMIc, J-, 4P1 RADIOS EARLY (NFANT THE ART 'PROGRESSED-- THEM CAME THE ULTRA - ß0T HERe5 A riREe -rage, DAIS AND taNE AND 8'4E 1,LOOAEQ- Dkf.'JE 5ET T(-IATS STRANGE -- A ONE- oia.e 5EY WAS OUR -t-Oees BEGAN TO THAC 80AST5 EIGHT T08E5 1 SERVES A Moe AND ALL THE C7QP E MULTIPL`l - -- OR MA`113E NINE! VARIED RANG.e !

www.americanradiohistory.com 116 Radio News for August, 1928

Under this heading, RADIO NEWS publishes each month descriptions of the latest developments in the extremely interesting field of television. Radio Movies and Television for the Home

EARLY in May of this year, C. Fran- about six inches square, and remarkably stand in front of the televisor in the studio. cis Jenkins, the noted radio inventor, clean cut. In most of the systems of tele- THE JENKINS TRANSMITTER demonstrated in Washington, D. C., vision and picture -transmission shown up his latest system of radio photogra- to this time, it has been usually difficult for The Jenkins system is quite different from phy, or rather "radio movies," as he prefers the observer to determine whether he is see- others which have been described in RADIO to describe it. Using a wavelength of 300 ing the image of a rolled newspaper or that NEWS. The general layouts of the trans- meters, in the regular broadcast band, he of a man scratching his nose; but with the mitter and receiver are shown in Figs. 1 transmitted a number of reels of specially - Jenkins apparatus the definition is so good and 2, respectively. Unfortunately, no pho- prepared standard-size motion- picture film, that the images are instantly recognizable. tographs of the transmitting equipment are while members of the Federal Radio Com- The illusion of motion is excellent; al- available, but a number of views of the mission and a number of other nationally most as good, in fact, as that produced by actual receiver are shown here. prominent individuals looked on. The sig- a regular motion picture thrown on a screen. In Fig. 1, the essential parts of the trans- nals were picked up in the homes of Com- The received radio images appear with a mitting apparatus are shown in approxi- missioner Sam Pickard, W. P. MacCracken, frequency of 15 a second; whereas regular mately the positions they occupy in rela- Jr., of the Department of Commerce, Cap- motion pictures are projected at a rate tion to each other. The film reels are tain S. C. Hooper, U. S. N., and William only one per second faster. arranged on a simple framework, one above Gibbs McAdoo, where they were converted It is the present plan of the inventor to the other, in such a manner that the film into light impulses and viewed by the on- produce the complete radio- movies instru- is pulled vertically downward by a set of lookers through a large magnifying glass. nient on a commercial basis and to sell it as sprockets which are, in turn, driven by an A private demonstration was arranged an accessory to the regular broadcast re- electric motor. One end of the shaft which later for a member of the staff of RADIO ceiver, as a device for home amusement. drives the sprockets is fitted with a gear NEWS, who was very favorably impressed Whether or not a suitable broadcast service meshing with another of only half its size. by what he saw. 'lie original film showed, will be available is another question, which The small gear is attached directly to the in black and white silhouette, a little girl cannot be answered at this early date be- shaft of the motor, which is a synchronous bouncing a ball, dancing and kicking into cause of the unsettled state of broadcast alternating -current machine developing 1,800 the air. It was reeled off in front of the affairs. However, the apparatus does work revolutions per minute. Because of the radio -movie transmitter at the rate of 15 well, and its possibilities are numerous. reducing action of the gears, the pictures pictures per second, the pictures at the There is no reason why it cannot be ex- are pulled past the sprockets, or past any receiving end being reproduced at the sanie tended eventually to operate as a true tele- fixed point next to the film, at the rate of rate. The images seen through the observ- vision machine; that is, to transmit (and 900 per minute, or 15 per second. ing lens at the receiver were, apparently, receive) the images of people as the latter At the other end of the sprocket -driving

REEL OF FILM CONCENTRATED "PINHEAD OF LIGHT, PIERCING FILM

ARC LIGHT AMPLIFIER

TO BROADCAST TRANSMITTER

<-1:2 GEAR 1800 R. P. M. TO D. C. SYNCHRONOUS SOURCE A. C. MOTOR SPROCKETS DRIVING FILM DISC STUDDED WITH 48 SEPARATE LENSES (REVOLVES AT 900 R. P. M.)

RECEIVING REEL FIG.f

General layout of the radio -movie transmitter, showing the essential "to broadcast transmitter" run to the regular input amplifier of parts without the supporting frameworks, etc. The leads marked the broadcast station through which the pictures are being sent out.

www.americanradiohistory.com 117 Radio News for August, 1928

Above: A six- target -neon tube and drum, used in experimental work. Right: This illustration shows dhe neon tube inside the drum, ready for operation. This drum is a four -hole model.

48 shaft is a heavy metal disc, about 1.5 inches SCANNING THE PICTURE into position and another series of light in diameter and about one inch thick; its beams starts to pierce it. All this is ob- edge is studded with 48 separate little A close study of the apparatus will make vious, as both disc and film are moving at lenses, each having an "optical speed" of its operation clear. The disc is revolving the same rate; one complete revolution of f. 3.5. Each lens is designed to .concen- at the rate of 900 revolutions per minute, or the disc consumes one fifteenth of a second, trate the light from a powerful arc lamp 1.5 per second. The separation between the and the downward movement of one com- into an intensely -brilliant "pinhead" bean, centers of the lenses is just equal to the plete picture through the light beams con- which is caused to pierce the film as the width of the film. The film moves steadily sumes the same amount of time. latter travels down past the back of the down at the rate of 15 pictures per second While this movement is taking place, the disc. This disc is a very carefully -con- (its action is not jerky, as in a moving - light beams fall with varying intensity into structed unit; according to a member of picture projector). Now let us start with the photoelectric cell, which produces an Mr. Jenkins' laboratory staff, it cost about a pinhead of light from one lens piercing electric current that varies with the trans- $9,000. The principal part of this expense through the lower right -hand corner of the parency of the film. This varying current is represented by the lenses, which are all first picture on the film. As the disc re- modulates the output of a broadcast trans- matched to each other. volves, the pinhead of light travels hori- mitter in the same manner that voice and Directly behind the film is fixed a sen- zontally across the film; the instant it runs music impulses do in ordinary broadcast. sitive photoelectric cell, so placed that it off the left edge, the beam of the next lens Forty -eight lines of alternate black -and- receives the "pinhead" beam of light pro- starts at the right again, but at a point a white areas per picture are "written" into jected through the film by each lens. The trifle above where the first one started. The the cell, and by it sent out to the receivers. cell is connected to a three -stage resistance - darting print is higher on the picture be- THE RECEIVING END coupled amplifier, and that in turn to an cause the film is moving down at the some eight -stage amplifier of similar design. To time while the disk is turning. Just as the The Jenkins receiver is altogether differ- prevent the amplifiers from picking up ex- second beam runs off the left edge of the ent from any of the other television and ternal disturbances of various kinds, which film a third one starts on the right at a picture machines now in existence. It con- would be registered as part of the pictures. still higher point on the picture. This move- sists of six essential parts, arranged as Mr. Jenkins has buried them under double ment is continuous during the operation of shown in Fig. 2. The heaviest unit is a copper shields. The photoelectric cell itself the device. 3,600- r.p.m. synchronous A.C. motor, to the is also completely sheathed in copper, ex- Forty -eight separate beams of light shaft of which is attached a hollow metal cept, of course, for a small aperture which travel across each individual picture on the drum about seven inches in diameter and is left to admit the light beams. The eight - film, this operation consuming one fifteenth about five inches wide. The center of this stage- amplifier shield is fully' the size of an of a second. At the start of the second drum is a hollow spindle with a thin wall. ordinary business desk. fifteenth of the second, a new picture slides In corresponding places on the drum and

MAGNIFYING LENS I MIRROR SET ANLE OF AT CONTACT BRUSHES 45 DEGREES TURNED BY SHAFT 4 REVOLVING FOUR- 3600 R. P. M. DRUM SEGMENT SYNCHRONOUS '_l A. C. MOTOR . QUAR \ I RODS

HOLLOW 1:4 GEAR '' ; SPINDLE ei A- ¡ COMMON ELEMENT

i\7SOLID$ _ RING \4`' / FOUR- "TARGET" NEON TUBE ;; __ t (FIXED INSIDE SPINDLE WITH ..Ji/ I TAR GETS FACING UPWARD) V -1

INPUT (TO "OUTPUT" POSTS HOLES (FOUR OF RADIO RECEIVER) OF I R SETS FIG . 2

General layout of the picture receiver. The whole lower as.oembly- the mirror and the magnifying lens. The images are viewed line is enclosed in a wooden box, on the top of which are mounted through the latter, as illustrated on the cover of this magazine.

www.americanradiohistory.com 118 Radio News for August, 1928 the spindle (both outer and inner surfaces) are four spiral rows of tiny holes, twelve holes to a row. A short piece of quartz rod between the outside and inside connects each pair of corresponding holes. The purpose of the 48 little rods is to conduct light from the inner spindle to the holes in the outer drum with as little loss as possible. Fixed inside the hollow spindle, with the flat little plates facing directly upward, is a special four -"target" neon tube. This tube is similar in general operation to the standard flat -plate neon tubes now sold generally for television purposes, but is in reality a quadruple tube. It is about four inches long and one inch in diameter, the little plates or "targets" being about %- inch square. A straight wire running near the edges of the plates acts as a common element. In Fig. 2 this lamp is shown out of the spindle; in actual use it fits inside the latter without touching it. The other end of the motor shaft is fitted with a 1:4 reducing gear which drives a revolving switch. The revolving element C. Francis Jenkins (second from the left), showing his apparatus to Commander C. C. Hooper, is simply a pair of contact brushes con- extreme left; Brig. General George O. Squier; Carl H. Butman, Secretary Federal Radio Com- nected together; one effects mission; Capt. C. H. Hill, U. S. Signal Corps; and Federal Radio Commissioners Harold brush continu- La Fount, Ira E. Robinson and Sam Pickard. ous electrical connection to a solid brass ring imbedded in an insulating disc, while standing upright, is a magnifying glass contact brushes have just made contact with the other makes a wiping contact over the about ten inches in diameter. four the upper right ring, as shown in Fig. 2, and sections of a split ring. The four The input posts of the picture receiver that segments connect with the one of the quartz rods in the first four targets of unit are connected to the last audio ampli- (outermost circle) the neon tube, while the solid ring goes to is pointing straight up. fier tube of a regular receiver. For his This condition corresponds with the start of one of the input posts of the machine. The demonstrations Mr. Jenkins used common a popular a picture in the transmitter, just when the element of the neon tube goes to one -dial receiver with an additional power pinhead the other of light is starting to sweep across input post. amplifier stage. the All the apparatus film. described so far is As the contact contained in a wooden REPRODUCING THE PICTURE brushes have just closed box about two feet the circuit to long and a foot the neon -tube plate at the square at the end. Directly Now let us follow through the operation extreme right, above the top this "target" lights up imme- of the revolving drum is a of the receiver: the modulated signal of diately and fluctuates square opening in the top of the cabinet; in accordance with the transmitter is picked up by the aerial, the modulation of the signal. over this opening an ordinary mirror is The fluctua- amplified, detected and again amplified by tions of light are carried up the mounted at an angle of 45 degrees to the the receiver, quartz and then led to the "radio - rods and projected through the holes top. About a foot in front of the mirror, movie" in the projector. Let us assume that the (Continued on page 173)

Television Experiments in Boston Create Great Interest GREAT interest among radio fans in and created by a series of experimental tele- Post, and carried on through around the city of Boston has the short -wave been vision broadcasts sponsored by the Boston transmitter of Station WLEX, located at Lexington, Mass., a suburb of Boston. The broadcasts were first attempted during the late part of April, and were continued during May. A number of New England radio manufacturers built the transmitting apparatus and offered for sale the essential receiving components, such , as neon tubes and scanning discs. It is reported that over 2,000 neon tubes were sold within two weeks of the initial experiment. Great quantities of sheet alminum, for the scanning discs, were also purchased by local radio fans. However, the general results so far are said to have been negligible, practically no individual experimenters having reported successful reception of the broadcast images. The "tele- vised" objects were rolled newspapers and the hand of a man. RADIO NEWS has been informed by D. E. Replogle, of the Raytheon Mfg. Co., makers of the neon tubes, that toward the end of May the results had been greatly improved, the image of a man's face being plainly discernible. At the time this issue of RAnto NEWS went to press, no further information was available. More detailed reports of the experiments will be published in forthcom- An experimental television receiver set up in the laboratory of James Millen, Malden, Mass. ing numbers.

www.americanradiohistory.com Radio News for August, 1928 119 Why the Weather Affects Radio Reception Some Facts and Some Unsolved Problems about the Atmos- phere and the Pranks It Plays on Transient Radio Waves

By B. Francis Dashiell

IF Mark Twain had been a "wireless" manifestations lias been found, except at a many explanations for the causes of fad- operator or a radio fan, he would have considerable loss of signal strength. If ing, some apparently quite accurate, but no been fully justified in making his fa- static is to be entirely eliminated, we must one has suggested a real cure. A cure for mous remark that, while everybody al- cease using space and the atmosphere for a fading, except for that caused by certain ways talked about the weather, nobody did transmitting medium, and electromagnetic inherent faults in the apparatus, is hardly anything about it. waves must be replaced with some other likely. In the early days of "wireless" a very form of non -electrical energy. Another matter that greatly concerns disgusted operator threw down his headset Besides the annoyance of static, the radio radio engineers and meteorologists is the and turned to me with the remark, "I hope fan and operator has become familiar with phenomenon of variations in signal intensity that some time someone will do something from day to day. This is a subject upon about this weather and climate mixing up which many investigators cannot agree. The with wireless signals." This remark, made theories advanced have not held good in all on a night when static was bad and distant cases, and the proportion of favorable re- stations failed to respond to the most allur- sults about balances the number of failures. ing adjustments of his detector, expressed This fact leaves the situation open for much for all time the universal and hopeless ap- discussion and future research, and the pro- peal of all operators and the millions of pounders of these tentative theories are left radio fans yet to come. Even in the first in a rather temporizing position. days of wireless telegraphy, there were defi- This has brought us to three great basic nite conclusions that the weather and cli- kinds of natural radio interference: static, mate had their effect on wireless communi- fading and daily variations in distant -sta- cation. tion reception. Each is entirely separate; Since that night many years have passed. there is no conclusive evidence that the But the conclusions that weather affects things affecting one will also affect the radio are firmly- intrenched in the minds of others. Therefore, in order properly to radio people everywhere. And still nothing discuss the effects of the weather on each, has been done about it in a remedial way. it is necessary to deal with them sepa- While more data have been gathered and rately. the correlations have become. more and STATIC AND ATMOSPHERIC ELECRICITY more obvious, we still have no sound theories which will stand scientific analysis by the We all know what static is, as far as its radio engineer and the meteorologist. How- effects in our radio receiver are manifest, ever, conclusive investigations show that but it would be quite difficult to attempt to some of these theories must be generally show what static actually is. In fact, the accepted, since they appear quite sound and keenest minds of science cannot entirely ex- reasonable. Each of these eight strokes caught by the cam- plain all its ramifications and the reasons era is a transmitter of "static" waves, caught for its presence in the atmosphere. That it STATIC, FADING & CO. at great distances. by radio receivers is a form of stray electric charge, wave or Of all the natural phenomena which af- current, is agreed to by all. fect radio operations, static is the most im- the rapid variations in signal strength, or One should not confuse static electricity portant for consideration. Static has taken fading. There has been less observed obvi- with the atmospheric electricity that is up the attention of radio engineers from the ous relationship between signal fading and known to exist between the surface of the time the first "wireless" apparatus was set the weather than in the case of static. earth and some point beyond. Atmospheric up, over 30 years ago. Static will always Fading signals from a broadcast station are electricity exists above the earth and has a .interfere with radio, at least until some en- not at all regular; for on one night the very definite "potential gradient," increas- tirely new communication system is in- fading will be bad, while on the following ing normally to some' point of .elevation vented. No real cure for its persistent night none will be noticed. Scientists give where it becomes constant. It is not bé-

Here is a thunderstorm, as seen from a neighboring mountain. The air is These clouds are highly changed, and as they drift along, their movement charged to a high voltage, discharges are frequent, and resulting "static" is changes the distribution of their electricity incessantly, causing thousands severe. (Photos by U. S. Weather Bureau.) of short -range static impulses. *.Member, American Meteorological Society.

www.americanradiohistory.com 120 Radio News for August, 1928 lieved that this normal potential is changed to any extent by changes in the weather or storms. This electrical potential gradient above the surface of the earth does not, so far as investigation can disclose, cause the stray or foreign static effects. Just what part it takes in radio activities is not known and, for the present, we might as well leave it out of this discussion. Static seems to be entirely free from atmospheric electricity, and of a different kind. COMPOSITION OF THE ATMOSPHERE The earth is surrounded by two great belts of atmospheric distribution. The lower one is known to meteorologists as the troposphere. The outer one is called the stratosphere. Between the two there is a region known as the tropopause. (See Fig. 1.) For instance, a study of recorded temperatures during an ascent throughout the two regions shows definitely:that - the temperature falls off rather sharply as the distance from the surface of the earth in: creases toward the tropopause. From that region temperatures ..remain constant .arid even are known to increase slightly out into

space. . It is in the lower belt, the troposphere, that our familiar changes in the weather The stratosphere is a region above the weather; it does toot change in temperature, but its radio occur. It is believed that this region is "ceiling," the Heaviside Layer, moves up and down under the electrical influence of the sun's rays. the breeding place of atmospheric static and that little or none originates above the over the polar or temperate regions, and not the rule; rather, it is the exception. tropopause. This latter region, and the belt that passing storms, cold waves, and other The fact that underground antennas elimi- immediately above, the stratosphere, while weather changes cause it to fluctuate in ele- nate static pulsations to a great extent not breeding static, affect transmission by vation. When the tropopause is relatively shows the fallacy of this line of reasoning. the development of much ionization by day higher it means that the depth of the tropo- On the other hand, aviators and balloon- beneath the outer boundary, the Kennelly - sphere is greater and more static -producing ists carrying radio sets while on flights have Heaviside Layer. atmosphere is present; and when the tropo- experienced intense static reception while Static is not evenly distributed over the pause is lower, there is less static bearing in the clouds, and often when in clear sky. surface of the earth. At times it may cover area beneath. In fact, aerial receivers, while many hun- a relatively small area, while a nearby region Some believe that considerable static is dreds or thousands of feet above the earth's may be quite free from its interference. The produced through conflicting and neutraliz- surface, have become so charged with elec- tropics abound with static, while the polar ing earth -currents due to irregularities in tricity that the antennas had to be dis- regions probably never experience static as the flow of normal atmospheric electricity to connected, an operation accompanied by we know it. During summer static is much different portions of the earth, or due to severe sparking and shocks to the aero- stronger and more persistent than in winter. uneven distribution of the replenishment of nauts. It is, therefore, perfectly reason- If we now reconsider the tropopause ions to the air from the earth. While it able to believe that practically- all known region, we find that in summer it will rise is quite plausible that some earth currents static is of atmospheric origin. to higher elevations than in winter, that will flow in sudden pulsations up the No one has been able to determine how over the tropics it is always higher than grounding wires into the radio sets, such is atmospheric static is actually produced, except to state that certain meteorological events cause intense ionization in the atmosphere. If there is any static produced by causes other than weather, those causes have not been fully determined. Of course, -4- Charged Clouds- this is exclusive of "static" produced by modern electrical and mechanical apparatus. IONIZATION OF THE AIR We know that the atmosphere is constantly in a state of agitation. There are warm and cold winds, ascending and de- {` scending air currents, dry and humid re- f l D t rE'ctl 011 Of 1 gions of atmosphere, and underlying land `\\ \ Qìscharges, and water areas that influence the condi- ¡_ tion of the air above. These conditions affect the ionization of the atmosphere. Whenever the moisture- content of the air is great, or when dust is excessive, ionization may be quite heavy; since ionization depends upon the presence of electrically-. charged atoms and electrons and ions in the atmosphere.: The natural gases of the atmosphere may become ionized, but when additional matter is present, in the form of much water vapor or dust, the ionization is much denser. Atmospheric ionization is believed to be caused by impact and friction between atoms and electrons, the electrical charging -We may consider electricity as flowing from the ground to the clouds; attracted by the charge of the small globules of moisture deposited above, as well as :n the opposite direction. A very slight discharge of electricity from the aerial upon minute dust particles, and the break- into the atmosphere may cause a terrific noise in the speaker.

www.americanradiohistory.com Radio News for August, 1928 121

ing -of raindrops, snowflakes or ice particles. flash, travels as a sound wave, while the method of forecasting weather. When a Falling rain may produce great ionization lightning flash travels as a light and elec- night of static freedom is followed imme- due to the impact between drops, and their trical wave. One may see a lightning flash diately by increasing static noises it is safe constant breaking and recombining. The and hear it as static simultaneously, while to assume that a change to unsettled or drops themselves bring down to earth con- the thunder will be heard many seconds bad weather will result within twelve hours siderable positive electricity; while the fine later. or more. With the use of a directional loop spray from breaking drops, when thrown antenna, an expert might be able to locate off into the atmosphere, gives a negative TYPES OF STATIC approaching storm centers a day or so ionization. in advance with some fair degree of reli- From this we see that the atmosphere be- When a charged cloud or other area is ability. However, this is merely an experi- comes filled with many millions of small passing overhead it attracts or induces aft mental matter which cannot be relied upon patches or areas of Atmospheric gas which opposite charge in the ground area be- as accurate. is ionized to some degree. Each area, there- neath. As the attracted charge flows along fore, has its individual electric charge. This the earth's surface at the same rate as the WHAT IS FADING? cloud's travel, some of it flows up the ground charge is sufficient, when it comes into con- that peculiar phenomenon to discharge through wires of radio receivers and discharges into Signal fading, tact with an antenna, which causes radio signals to rise and fall radio set with a loud static crash. Even the air through the antennas. (See Fig. the in intensity, at times with remarkable regu- oppositely- 2A.) These momentary surges of the earth a discharge in the air between larity, but mostly with an uncertain and some little distance away charge give rise to severe static crashes charged areas at irregular periodicity, seems to be not of will up a minute electromagnetic wave in the receiver. Induced currents in the set meteorological origin. Without doubt, fad- that will be heard by all sensitive receivers antenna also produce similar symptoms as ing eventually will be found to be directly within range. In severe conditions, when they flow down into the earth. (See Fig. related to changing conditions in the con- the highly charged, per- 2B). atmosphere is very ductivity of the total atmosphere, especially a more areas of Static noises have been classified into a haps thousand or drifting outer ionized portion of the strato- charged atmospheric gas might drift past few different types, such as "grinders," the sphere, variations in the height or level of an antenna within a minute, each giving "clicks," "hisses," etc. It is obvious that the Heaviside Layer, or perhaps to some off its excessive electricity in the form of each classification is produced by an en- extent in counter earth- currents which may a static discharge. tirely different source. The static crash of lightning is different in sound from the affect the uniformity of the transmitted earth wave to some slight degree. STORMS little clicks and hisses caused by patches or areas of drifting electrified atmospheric gas, However, it is likely that a certain amount When this charged atmospheric condition such as may be noticed on clear, hot and of fading is due to atmospheric conditions. becomes greatly excessive a thunderstorm dry days in summer. This is an assumption only, although years will develop. Whenever we have a hot and Intense static may be produced by hot of meteorological and radio correlations humid ascending air current which comes dry winds, such as are experienced over seem to indicate that such may be the case. into contact with low- running cooler air some of the Middle Western states. These It appears that this form of fading results currents from above, dense clouds are built winds carry a great deal of dust -and there from large movements of ionized atmos- up as this rising air condenses into heavy, are cases on record when the air has been phere drifting past transmitting or receiv- Clark and wet fog. When there is violent so highly charged that ignition systems of ing stations, mostly the former. It is quite cloud activity the electrical ionization is automobiles have been seriously interfered likely that the conductivity of the mass of heavy, and soon the clouds become charged with; and fences, windmills and other metal ionized air is of sufficient importance to with a potential of millions of volts. When objects have become charged to such a high affect the transmission of the electromag- this potential between clouds having oppo- potential that severe shocks were experi- netic waves being broadcast out from the site charges, or the clouds and the earth enced by those touching the objects. Dur- antenna of the transmitting station directly beneath, becomes too great, the strain and ing such occasions radio sets produced a below. The action is that of an absorbing stresses in the intervening air space cause constant static roar and much greater inter- and deflecting blanket spread over the a breakdown in the natural insulation and ference than during a thunderstorm. transmitter, which effectively prevents all a lightning flash occurs. Powerful elec- The fact that atmospheric static is proof the power of the emitted wave from tromagnetic waves are sent out for great duced while the air is undergoing changes passing on and up toward the Heaviside distances, and affect all radio receivers that precede and accompany rainy or gen- Layer. (See Fig. 3.) Thus, the variations within the area. erally bad weather has been used as a (Continued on page 177) The electrical discharges in a thunderstorm are many and varied. Some are very short and occur between fragmentary portions of one cloud, others between the earth and clouds, and still others between clouds Heaviside Layer entirely separated. Some lightning flashes are often more than a mile in length. It has been believed that a lightning flash is oscil- latory in action, and perhaps some actually are; but recent discoveries have given good indications that it is a one -way current flow creating an electrical rather than an surge Drifting Area o onized Atmospher oscillation. In any case, whether oscilla- tory or surging, the current has its powerful electrical field which induces current surges with a static crash in all radio receivers within range. When we consider the vast amount of electrical energy liberated by a lightning flash, and that it has been estimated that about 1,500 flashes are occurring each minute throughout the world, it is no small wonder that a little static may be heard in sensitive receivers at nearly any time. Some parts of the country have more thunder- Radio Waves storms than in other parts; Florida ex- periencing the most and the coast of Cali- fornia the least. Thunderstorms are prac- Transmitting tically unknown in northern latitudes, but 5tation Fig:3 are of common occurrence in the tropics and in the summer in high mountain regions. Thunder, which is the sound of air expansion due to the heat liberated by the lightning The natural boundary of the waves is the Heaviside Layer; but they may be stopped or turned aside by electrified masses of air, very muci, lower.

www.americanradiohistory.com 122 Radio News for August, 1928

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New Short -Wave Coils Fit used on all the tickler windings and colored silk -covered "Litzendraht" wire on the grid Into Standard Tube Socket windings of the two small coils. Solid wire is used on the grid windings of the two A receiver kit, consisting of four short- larger coils. -.The coil form is so wired that wave coils wound on plug -in type forms the grid and F minus terminals of the tube which fit into a standard Uri -type tube socket the grid socket, has recently been placed on the mar- provide the connections for ket to satisfy the increasing demand for coil and the plate and F plus posts of the short -wave receiving apparatus. The same socket the tickler connections. manufacturer has also developed an R.F. Manufacturer: Dres- sier choke coil for use in short -wave receivers. Radio Manufac- A booklet which contains complete direc- turing Corp., 11- e w tions for building a short-wave receiver and York. a short -wave converter unit for a broadcast .,,,,,,,,,,,,"",,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, receiver is supplied with the parts. This hand microphone The set of four short -wave coils and the (right) has been designed for use with receivers short -wave R.F. choke coil (A) will be using A.C. tubes. It is found pictured on this page. Each coil has provided with a cord and UY -type plug for inser- two windings, grid and tickler. When em- tion in the detector ployed in the manner recommended by the socket. manufacturer the set of coils will cover the wave band of 16 to 210 meters. be concealed in another room; then the hid- The molded bakelite forms on which the Hand Microphone Has 5- den person may insert humorous passages coils are wound are 2' inches long by in a radio program or make comments on 13/16 inches in diameter. Each form is Of Prong Plug for A. C. Sets his friends in the other room. The stunt is A hand microphone, which, when con- sure to mystify everyone. nected with a radio receiver, makes it pos- Most of the microphones now on the mar- sible to announce through the loud speaker, ket are equipped with a standard UX-type provides a constant source of amusement in tube -base plug and they may be used with the home. In addition, it may be employed any battery- operated receiver. However, for many useful purposes. These micro- because of the increasing popularity of the phones usually are provided with a tube - A.C. electric receiver, a demand for a micro- 8 base plug, and are connected with the re- phone with a UY -type five -prong plug now exists. The microphone 8 ceiver by removing the socket of the de- illustrated above is O .00015 made in this manner. o mf. tector tube and inserting the tube -base plug in its place. The wire from the microphone A special feature of this A.C. type micro- to the set may be as long as desired, so it is phone is that, after the plug has been in- possible to talk in any part of the house and serted in the detector socket of the receiver, have the voice reproduced by the loud the detector tube may be inserted in the top speaker, wherever the latter is located. The of the plug. This arrangement avoids the audio amplifier of the receiver amplifies the necessity of incapacitating the radio re- Detector -circuit diagram of standard short- ceiver wave receiver using tube -base plug -in coils. voice currents developed by the microphone, during the time the microphone is and as much volume is obtained from the connected. Also, it makes it possible to leave the microphone a different colored bakelite, in order to per- loud speaker as with radio signals. The connected at all times. The microphone mit easy identification. When used in a microphone is an "electromagnetic" device, is provided with a small push switch mounted circuit employing two .00015 -mf. variable and is operated without a battery of any on the case; when the instrument is in use condensers (one in shunt with the grid coil kind. it is necessary to hold a finger and the other in series with the tickler) the It is not difficult to think of a number of on this button. With the switch in its normal position the microphone black coil will tune from 16 to 32 meters, ways in which the microphone may be used is disconnected and the radio the brown coil will tune from 29 to -58 for both practical and amusement purposes. set operates in the usual way. 54 is ideal for inter -room communication, meters, the blue coil will tune from to It Manufacturer: 110 meters and the red coil will tune from both in the home and in :an office, as it Brooklyn Metal Stamping Conzpanp, New York. 103 to 210 meters. The coils are of low- avoids the necessity of calling. When the

loss construction, the turns of the windings instrument is -being used to _ .muse guests being spaced. Enameled copper wire is the announcer and the microphone should New A. C. Screen -Grid Tube Has 15 -volt Filament ANS who are interested in both A.C. operation and screen -grid amplification will be gratified to learn of the development of a new screen -grid tube which may be operated from an A.C. supply. This tube is of the heated- cathode type, but otherwise has characteristics similar to the standard 222 type. It is equipped with a standard

UX base, the cathode being . connected to plug-in coils make possible operation on four different short -wave bands and one terminal of the heater, which is a thin These four tube -base coil designed for enable continuous reception between 16 and 210 meters. A is an R.F. choke carbon filament. use in short-wave receiving sets.

www.americanradiohistory.com Radio News for August, 1928 123

The accompanying cutaway view shows a variable inductor, or "variometer," its in- GRID CONTACT the mechanical construction of the new tube; ductance value being adjustable within a OUTER INNER this, it will be noticed, is very similar to narrow band. The adjustment is provided SCREEN SCREEN the D.C. type, but two important changes by knob V, which turns a rotor wound with GRID III' GRID have been made. First, the filament con- a few turns of wire; the rotor coil is in struction had to be changed in order to per- series with the fixed winding on the cylin- mit the use of a carbon heater and cathode; drical tube. This arrangement obviates the and second, a wire mesh has been substituted for the spiral coil used as the outside section of the screen grid. The terminals of the new tube are arranged in exactly the same order as those of the D.C. type, and the cathode is connected to the "A--" terminal, thereby eliminating the necessity of a UY -type (five -prong) base. Mann facturer: Arcturus Radio Company, Newark, N. J.

This diagram shows the circuit which is used in connection with. tite special screen -grid tuning unit described on this page.

1: 1. 111::: 1: 1:: 1:: 1:::::::::: 1 1::::::::1 :::::::::::: 1 :::::::::::::: 1:::::::::::::::.:.:111::

necessity for an external "trimmer" con- New Dials Accompany denser to keep the grid circuit of the screen - grid tube (V1 in the diagram) sharply in 222 -Type R. F. Unit tune with the grid circuit of the detector NEW H.F. tuning unit designed espe- tube (V2). A cially for use with the 222 -type screen - The knob T on the end of coil L2 controls grid tube, and two new dials for use with a tickler coil which turns inside the extreme standard variable condensers, have been right end of the fixed (secondary) winding. brought out by a New England manufac- This tickler provides the means whereby re- turer. These items are pictured on this generation is obtained in the detector cir- page. cuit. The tuning unit will appeal to the home The circuit for which this tuning unit is This A.C. screen -grid tube differs from the radio builder because of its neat construc- intended is very similar to the hook -up most battery type only in the construction of the may be Browning -Drake, filament and of the outer grid, winch is a mesh tion and of the ease with which it commonly known as the of wire instead of a spiral coil. built into a complete receiver. It consists which comprises one stage of tuned radio - of two variable condensers (Cl, C2), frequency amplification with a regenerative The essential electrical characteristics of mounted on a long, rigid metal frame, which detector. However, it is designed to take the tube follow: also supports, at its left and right ends, re- advantage of the superior H.F. amplifying tube, Amplification constant, 400 ( "mu "). spectively, an antenna coupler (L1) and an characteristics of the screen -grid Mutual conductance, 445 micromhos. interstage transformer (L2). The two con- which is used in the position indicated at Plate -to- control -grid capacity, .04 mmf. densers are operated as one by an illumi- Vl in the accompanying wiring diagram. Filament potential, 15 volts. nated drum dial, the position of which may Stable operation of the receiver, without Heater current, 0.35 ampere. be observed in the accompanying illustra- trouble due to oscillation, is readily obtain- Plate potential, 135 volts. tion. able without recourse to neutralizing meth- Screen -grid potential, 30 volts. The unit fits on a regular 7 x 18 -inch ods or the use of shields. Although shield- is held to be im- Control -grid bias, 1 wilt. panel, in which only seven holes need be ing of screen -grid tubes Plate impedance, 900,000 ohms. drilled. Additional support for the frame- perative for best operation, the usual aluminum or copper cans may be dispensed with From the above it will be seen that the work must be provided by a sub -panel, on in receivers incorporating this tuner, be- filament requires a potential of 15 volts A.C. which the tube sockets and other com- cause of the simplicity of the hook -up. This voltage may be obtained easily from a ponents necessary for a complete receiver standard step -down transformer of the type may be conveniently placed. The accompanying diagram shows the de- used for the operation of toy electric trains. The antenna tuning coil Ll is in reality tailed connections of the circuit recomi-

This unit contains the essential parts of a screen -grid receiver comprising one R.F. stage and a regenerative detector; around this a receiver may be constructed with a minimum effort.

www.americanradiohistory.com 124 Radio News for August, 1928 mended for the tuning unit. The aerial is coupled to the grid coil Li through a fixed condenser of .0001 -mf. capacity. The plate of the screen -grid tube runs directly through the primary P of coil L2, the battery circuit being shunted by a heavy by -pass condenser (1 -mf.). The screen element of the tube (to which connection is made via the "G" post on the tube socket) runs to the "B" battery through a radio- frequency choke, RFC. Another heavy by -pass condenser is used in this portion of the set. The purpose of the by- passes and the choke is to keep radio- frequency energy out of the battery circuit, which, being common to both amplifier and detector tubes and to the plate and screen elements of the screen -grid tube alone, might cause considerable oscillation troubles. The detector portion of the set is of standard design. The leads marked "to A. F." may be continued to any audio amplifier of the usual models. Except for scale markings, these two dials are identical wizen viewed from the front. The dial at the left is for condensers with shafts at right angles, to the panel, and the drum dial for those The two new dials have silvered panel parallel to. it. A front view of the dial is shown in the picture of the tuner on page 123. plates of identical appearance; but one model is of the "drum" type, while the other is of the straight -mounting variety. They ceptacle and the transformer. Therefore, Scanning Disc Made for are of sturdy construction, and turn without with this arrangement it is necessary only backlash. They may be used with prac- to plug the "B" power unit into the re- Television tically any variable condensers. ceptacle, in order to have it controlled by FOR both the reception and transmis- Manufacturer: The National Co., Inc., the switch which governs the filament trans- sion of television, "scanning discs" are .Malden, Mass. former. required. Such discs are usually of metal, The transformer has been designed to and are drilled with a number of holes lo- provide ample filament current for the aver- cated in a spiral path near the outer edge. In both transmitting and receiving the discs , are rotated at the same definite rate of TO 110 -V. speed. In the transmitter, one such disc is Filament Transformer For SOCKET 41. placed between the object and the photo- A. C. Sets electric cell; and in the receiver it is placed spectator and the neon tube. THE filament- heating transformer pic- between the is the object of the discs to analyze tured on this page has been designed to H0 -V It the images which are tele- facilitate the construction of electric radio RECEPTACLE and reconstruct 2.5V. vised; and, unless the discs of the trans- receivers using A.C. tubes. It will simplify 4. mitter and receiver correspond exactly in the wiring of any radio installation in which every way, including speed of rotation, tele- it is used, regardless of whether the re- TOSWITCH vision is impossible. Many ceiver is a new model or a battery- operated ON PANEL OF SET }5V have endeavored to construct their televis- set which has been converted for A.C: c ion discs, but: have found-it Very difficult eration. The new features of the' trans- L to obtain satisfactory results.'" Every hole former are the wires which haYe been pro- must be of just the required diameter and vided for connecting an external switch, -The connections of the new filament - internal in exactly the proper position, and it is and the 110-volt receptacle heating transformer described Herewith.. mounted on the difficult to accomplish this with the neces- case for plugging in the "B" socket -power t employing a combination of sary precision with ordinary tools. unit. These make it possible to-turn on the ge receiver and it may The television disc pictured on this page receiver at one switch without the neces- 226 -, 227- and 171 -type tubes, many as seven. has just been placed on the market to aid sity of a complicated circuit arrangement. be used for -operating: as winding for the 226 -type tubes experimenters in their work. It is avail- The wiring of the transformer is shown The, 1%-volt is capable .of delivering a current of 4 able in several sizes for the different sys- in an accompanying diagram;` it . will be is for four tems of television which will soon be regu- noticed that its primary winding and thè amperes, which sufficient heating 2% -volt winding has a maximum larly broadcast. The arrangement shown receptacle for the "B" power Unit are con- tubes; the and will provide is for receiving the pictures which are being nected in parallel, and the wires for the output of 1.75 amperes for one 227 -type tube; and the 5- power switch are so arranged current that they supply of control the power going to both the re- volt winding with an available 0.5 ampere provides current for two 171A- type tubes. The picture shows the external appearance of the transformer, which is housed in a compact metal case measuring 3 by 3 by 51 inches. The wire with plug (P) attached for connection to the 110 -volt socket, the wires (SW) for the power switch and the receptacle (R) for the "B" power unit are mounted on one end. At the other end, the eight binding posts for the filament voltages are mounted on a bakelite panel. Two binding posts are sufficient for the 1% -volt winding, and three each are required for the 2- and 5 -volt windings, which are provided with center -tap connections. The transformer is mounted on small metal feet which have been drilled to facilitate mount- la this filament- heating transformer provision has been made for connecting a switch to con- ing. These television scanning discs have been de- trol the operation of the entire receiver. SW, Manùfacturer: Dongan Electric Mfg. Co., signed to receive the broadcasts from WGY wires for switch; R, receptacle for "B" power and WRNY. They are 12 and 13 inches in unit; P, plug for light socket. Detroit, Mich. diameter, and have 24 and 36 holes, respectively.

www.americanradiohistory.com Radio News for August, 1928 125

broadcast by station WGY. It is 12 inches In fact, if a lamp of the type used for this method of modernization which may be ap- in diameter and has 24 holes; and is de- purpose were connected to the loud- speaker plied to his circuit. signed for use in reproducing a picture 1.5 binding posts of a broadcast receiver, it Recently, a number of R.F. booster units inches square. An 18-inch disc with 36 would convert the electrical energy into have been placed on the market, to satisfy holes is designed for WRNY television light vibrations instead of sound vibrations. the demand for a device which will bring broadcasts. At this writing (a month be- It may be seen, therefore, that the familiar up-to -date these old receivers. These units, fore publication) experimental tests are still type of heated -filament (incandescent) lamp usually, are designed for use ahead of the being made with this novel development. would be entirely unsatisfactory, as a change R.F. amplifier of the receiver and, when afnnufactnrer: Doren Radio Corporation, in time intensity of its light requires too connected in this manner, they provide the Newark, 1V. J. great a length of time for the instantaneous advantage of an additional stage of R.F. impulses of television. amplification. A booster unit uses one tube A gas -discharge tube of the neon type and adds an extra tuning control to the re- provides the only known, practical, solution ceiver. It may be operated from the same to time problem of obtaining sufficiently batteries or socket -power units which are Large Neon Tube Now Made rapid light variations. The tube is of very used for the receiver. simple construction, as may be seen from Two pictures, and a diagram on page 170, for Television the illustration. It consists of two large give details of a R.F. booster unit of recent A\IATEUIIS who are experimenting with plate elements, parallel to each other and design. This device employs one of time radio television apparatus have found separated a fraction of an inch. 'l'he tube new 222 -type screen -grid tubes which pro- that their circuits require a larger neon is filled with neon gas, and is mounted on vide an enormous amplification when used (glow) lamp than is generally available a standard UX -type base. The circuits in in R.F. circuits. As a result, when a which it is used are very simple; a diagram booster unit of this type is connected ahead on this page shows one of the possible ar- of a receiver, the effect is greater than it rangements. V1 is the last -stage amplifier would be possible to obtain with an addi- and V2 is the neon tube: The "B" battery tional R.F. stage of standard design. 'l'he which supplies plate current for the ampli- device when properly operated will increase fier tumbe also provides the necessary poten- the sensitivity, selectivity and volunie of the tial for the neon tube. receiver, or in other words, provide the According to the manufacturer's specifi- extra "pep" which is needed. Also, the cations, the tube has a dynamic resistance booster unit permits more satisfactory re- of 1,200 ohms. The current passed through ception during summer static by making the tumbe should never exceed 20 milliam- possible the use of a shorter aerial. peres I).C., which corresponds roughly to The wiring diagram shows the exact cir- a terminal potential of 200 volts D.C. In cuit of the booster unit; the grid circuit operation, either terminal may be connected of the tumbe is directly coupled to the aerial to the negative terminal of the battery. circuit, and a variable condenser (Cl) con- However, when the tube is operated with nected in shunt with a coil (Ll) is the D.C., a current-limiting resistor should be tuning control. Two binding posts are connected in series with the circuit at all provided for aerials of different length; times, in order to prevent overloading. post S provides maximum coupling for a Manufacturer: Raytheon Manufacturing short aerial, and post L gives greatly re- Co., Cambridge, Mass. duced coupling for a long one. Inductive - capacitive coupling is employed to connect the plate circuit of the booster with the receiver; the R.F. choke coil (I2) and (Cont. on page 170)

Two vines of new neon tube, showing construction of parallel plates. These tubes arc used Left, the screen -grid R.F. in television receiving circuits. booster unit with the cover of its shield removed. Be- low, appearance of booster in metal cast. B is time battery today. In answer to this demand, the tube cable, and the other symbols shown in the above illustration has been correspond to similarly-designated parts in the test and placed on the market. This tube is much diagram. larger in size, and will pass approximately ,,,,,,,,,,,,,,,,,,,,,,.,,..,,...... ,,,.,,,,,,,,,,,,,"."11,,"",,,,,. twice as much current. as the tubes pre - viously used. In order to receive television pictures, there is required a source of light which is capable of changing its intensity almost instantly. This light reproduces the picture which is being transmitted, and its Screen -Grid Booster Unit position in the circuit is comparable to that of a loud speaker in a broadcast receiver. Improves Receiver

Pr HERE are thousands of old -style re- VI V2 ceivers in operation today which fall just short of the mark set by the modern INPUT o broadcast listener for satisfactory reception conditions. In a majority of NEON under present TUBE cases one of three complaints is made; the set lacks sufficient volume, it is not sensitive U , enough to receive distant stations, or it does not provide the selectivity required to 11111111111111111111 separate local stations. Usually, the owner hesitates about discarding the receiver, as The circuit customarily used when connecting the results are otherwise quite satisfactory; a aeon tu be to the output of a vanrnm -ta be amplifier. and he is looking constantly for some

www.americanradiohistory.com 126 Radio News for August, 192' Some Odd Uses for Vacuum Tubes Their Best -Known Work is in the Parlor Radio Set; but Science and Industry Find Many Unusual, though Valuable, Applications for Them

By J. E. Smith

A4ANY are the eulogies that have AUXILIARY TUBES electrical measurements are very numerous. Many radio fans know something been sung about the wonderful Next, we may look into our power- supply or .other we all use in about the way in which the vacuum tube is vacuum tube that apparatus, if we have a set that operates many used as a voltmeter or as an ammeter. our radio receivers; many, from house current. First, there is re- been spoken Fig. 1 illustrates the use of the vacuum tube t mes has its great versatility quired a rectifier tube, which so alters the as a voltmeter. of. But unless you happen to be making alternating current supplied by your elec- Suppose we have a generator supplying radio your business; it is improbable that tric company that direct or constant cur- current to a load of some any of kind; we -can connect you will get to know at first hand rent becomes available for operating the an ordinary vacuum may be tube across the this the thousand uses to which a tube plate circuits of the tubes. But it often terminals of load, as at your radio put, excepting its applications in happens that the voltage supply in your receiver. house is not very constant; sometimes the to ac- It is the- purpose of this article voltage is high and sometimes it is low, so a the quaint you, more or less, with few of that the voltage applied to your radio re- hope to uses of vacuum tubes. We cannot ceiver may vary considerably. In order to include all of the uses, for there are far too correct this difficulty, which will cause poor many of them for the space available in this operation of the set when the variations are magazine. There are many more, perhaps, great enough, there may be used in your radio than you imagine. Just think, in your power supply what is known as a regulator dif- set alone, there may be as many as six tube. If the power supply is constant ferent applications of the vacuum tube. enough, this regulator tube is not necessary, You are acquainted with these applications, although it is often used. so we will take time only to mention them. These are the six main types of tubes Frst, we have the radio -frequency ampli- used in radio receivers, but there are many fier tubes, which amplify the radio -fm- variations of them. For instance, there are quency impulses which the antenna collects. tubes operated by direct current, tubes op- we have the detector tube, which so The vacuum -tube voltmeter is a device employ - Next, erated by alternating current, gaseous ing an ordinary tube. It affords a very exact changes the form of these radio- frequency comparison of voltages in the range of its tubes, tubes having very high vacua, two - "characteristics." impulses that they now become audible, or electrode tubes, three- electrode tubes, half - capable of being heard, providing they are wave rectifiers, full -wave rectifiers, and so strong enough. If these are not sufficiently on. These things are much written about ab, and a current -indicating device A (such powerful to operate the loud speaker they in the press, so we will not discuss them as a milliammeter) will tell us how much are amplified by the audio- frequent'- ampli- here; you have no doubt read much about current is flowing in the plate circuit of this fier tubes. It often happens, however, that them in RADIO NEWS from time to time: tube. Then all we have to do is to discon- the ordinary audio -frequency, amplifier From now on this article will be devoted to nect the tube from the load, and connect it tubes become overloaded; that is, they are some interesting but not well known appli- to some other source of voltage which we called upon to do more work than they are cations of the vacuum tube. can control. By varying this until we ob- designed for. Therefore, in many receivers tain the same current indication at A, we there is employed a more powerful tube, TUBES AS MEASURING DEVICES knów the second voltage tó be equal to the which is called a power-amplifier. The applications of the radio tubes to former, or line- voltage. .In other words, the line- voltage produces a certain effect on the tube, causing a certain plate current to flow. Any other source of potential that produces the same plate current must have the same voltage as the line. Next, suppose we want to find the cierrent flowing in the main line. We could insert á resistance R, or use any resistance which may happen to be in the line already, whose value we know, and connect the vacuum tube across its terminal, as at cd, Fig. 1. The voltage across this resistance is measured by the same method used to measure the voltage across ab. Then, knowing the voltage drop in the resistance, and the value of the resistance, the current flowing through the latter is obtained by simply dividing the voltage by the resistance. There is an interesting application of this method to the measurement of very high voltages, such as we have in power packs. The tube as used in Fig. 1 amplifies, and is well adapted to the measurement of small voltages. The higher this voltage the higher will be the reading of the milliammeter A. Very high voltages, for instance, say 500 volts, would cause the tube to be saturated, or considerably overloaded. For this reason, we must use special tubes for measur- The Verigraph, a device which determines the thickness of a continuous sheet of material as it is ing high voltages, or else find some special being made. The capacity caused by the dielectric web is recorded continuously through its effect on a vacuum -tube circuit. Left, A. Allen, one of the designers; right, W. A. Ready. way in which to use the ordinary tubes. x President, National Redio Institute

www.americanradiohistory.com Radio News for August, 1928 127

at the saine value, regardless of how the generated voltage is affected. In the arrangement of Fig. 4, a constant line -current is obtained by placing in series with the line a small resistor It. Across the terminals of this unit is connected a vacuum tube, the plate circuit of which completes the circuit of a shunt field winding. Now suppose some of the load is taken off the line. The current momentarily decreases; the generator voltage then goes up and the generator momentarily supplies more current to the line. But this momentary increase of line -current causes a momentary increase of the voltage drop across the resistance, so the grid voltage on the tube is ht Fig. 2 an ordinary tube is "hooked up backwards to measure higher voltages. In Fig. 3 we - have a circuit employing a special tube to regulate a dynamo's output voltage. increased. This causes an increase of plate to- filament resistance within the tube, so that the current flowing through the shunt - WORKING BACKWARD malee the increases pretty nearly equal the field winding is decreased, the generated decreases; so that we should have very con- voltage is lowered and the line -current de- Fig. 2 illustrates one of these special ap- voltage supplied at the terminals of livered is restored to its original value. Of plications of the ordinary tube. The tube is stant the generator, as at ab, in Fig. 3. Such an course, these changes take place auto - so connected that it does not amplify, but arrangement is made possible by the fact matically, each one as fast as the other. If rather de- amplifies, so to speak. The tube that shunt field windings of such machines the circuits are properly proportioned, a circuit is inverted, the plate being used for very constant line -current can be main- the grid for the plate. To the grid, and tained. explain: suppose the tube which we are SERIES FIELD considering has an amplification factor of REMARKABLE SENSITIVITY seven; this means that one volt applied to 1111, 0 the grid in Fig. 1 will have the same effect w There are certain other applications of as a voltage of ,seven applied directly in the ARMATURE the vacuum tube which are very interesting of / on account of the fact that they permit plate circuit of that tube. In the case R Fig. 2, however, a voltage of seven applied measurements of extremely small distances to the plate will have only the same effect and, by virtue of this faculty, also permit as one volt applied directly in the grid of measurement of extremely small weights. circuit. Used as such, the name ultra- micrometer is FIG. 4 The current in the circuit of Fig. 2 also given to these arrangements. They were varies differently. In Fig. 1, we have said first introduced by Professor Whiddington that increasing the voltage at ab causes the If we require from a generator a constant cur- of the University of Leeds, England, and rent, instead of a constant voltage, as in Fig. 3, plate current in A to increase. Contrari- we may utilize the circuit shown above. depend upon the properties of an oscillat- wise, in Fig. 2, an increase of voltage at ab ing vacuum tube. There are two classes of causes the "plate" current in A to decrease. ultra- micrometers, one class called hetero- This does not cause any difficulty, however, have rather high resistance in comparison dyne -beat ultra -micrometers, and the other for we do not care much what value the with the field windings, and consequently called zero -shunt ultra -micrometers. "B" current may happen to have; all that carry a fairly low current, which is within Fig. 5 illustrates the principle of the zero - we want to know is its value, so that we the range of the operating plate current of beat ultra- micrometer. On the left, we have can duplicate it when applying our known the tube. an ordinary Hartley oscillator. On the voltage in order to find our unknown quan- Another and somewhat similar arrange- right, we have an oscillating detector, which tity. ment is shown in Fig. 4. There are some may be of the type shown or of the three - cases, where instead A REGULATOR TUBE of a constant voltage circuit -tuner type. In the output circuit of output of the generator, there is required a this oscillating detector, we have a split A specially -designed vacuum tube, one de- constant current output. For instance, in primary transformer. An ordinary "push - -signed to carry more plate current than our certain electroplating systems, or in certain pull" circuit transformer may be used ef- tubes, has been used to regulate the volt- arc- lighting systems, when part of the load fectively for this purpose. Now suppose we age of direct- current generators. Such an is taken off the line, or if some of the lamps set the oscillator on the left oscillating at application is pictured schematically in are extinguished, the current must be kept (Continued on pa ye 171) Fig. 3. Here we have represented a com- pound- wound, direct- current generator. The shunt field has in series with it the plate circuit of the vacuum tube, and the input circuit of the tube (that is, the grid and filament) is connected to the armature of the generator, as shown. Now suppose, for some reason or other, the engine driving the generator should increase its speed momentarily or, perhaps, if our generator is being driven by a motor which is operated on power supplied by the electric company and the line -voltage should drop, the speed of the driving motor would decrease. At the same time, the generator speed would decrease and the generated voltage would become less. This means, then, that the negative voltage applied to the grid of the tube would become less, and consequently the resistance in the tube between the plate and filament would decrease, thereby allowing more current to flow through the shunt field winding. This increase of field current would increase the generated voltage, and if the cir- The "zero- beat" ultra- micrometer is one of the most sensitive measuring devices which has yet been invented. Two oscillating circuits are-brought to a perfect balance; then the slightest alteration in cuits are arranged properly, it is possible to either of the circuits becomes audible.

www.americanradiohistory.com 128 Radio News for August, 1928 Radio Novelties from Abroad and Home Camera Sketches of Late Developments in Radio, on the Largest and the Smallest Scales

A SKIP- DISTANCE REGULATOR The aerial system shówn, in the two views at the left has just been constructed at Nauen, Germany, for work with short waves. By regulating the angle at which they are sent against the reflecting layers in the upper atmosphere, it is believed that the waves can be projected so accurately as to be receivable with full force only at the desired station. The size of the reflecting system can be judged by comparison with the figure of the man. Photos. SENDING A RADIO BEAM HEAVENWARD © Wide World The cover of RADIO NEWS for February, 1927, bore a somewhat sensational illustration of a vertical reflecting system for sending a radio beam at any angle. Many readers undoubtedly considered it fiction -but if so, it has been turned into reality, as the pictures above show. The frames above are erected to carry a short -wave aerial at their center (focal axis).

NOT A BURGLAR'S DARK LANTERN As you would think at first glimpse: the curious apparatus at the left is the newest type of studio microphone.

RADIO IN THE HOME That's just it: lì'illiam H. Reumann (left) has his broadcast station in h i s residence. The transmitter was built by Mr. Re: menu, a well- formerk n o w n amateur.

REVERSING THE USUAL THE CONDENSER MIKE IN USE PROCEDURE Above, the new microphone as it is The housewife who puts the speaker in placed to pick up the program; lhishart the kitchen while preparing a meal is Campbell at the keyboard in station no longer news; but here is Mrs. William CKGW, Toronto, Canada. The micro- H. Reumann at the mike of WWRL, phone comprises two metal plates, the Woodside (-New York City) broadcasting capacity between which is altered by household hints from her own kitchen. their vibrations in accordance with the The Reumann met in a studio, were sound received; the upright cylinder con- married -iii one, and now they are living tains also a stage of A.F. amplification. in a home which is also a studio. The device is exceedingly faithful and © Herbert Photos, Inc. delicate, and may replace the present familiar "birdcage."

www.americanradiohistory.com Radio News for August, 1928 129 List of Broadcast Stations in the United States

Radio of úr I Radio m o Radio Radio Call BROADCAST STA. á« VA Call BROADCAST STA. mÿ ám Call BROADCAST STA. mÿ -m Call BROADCAST STA. and óñ Letter Location Letter Location Letter Location Letter Location d3

KD KA East Pittsburgh, Pa * *316 50000 KGEW Fort Morgan, Colo 219 *100 KWG Stockton, Calif 345 100 WDWF -WLSI Cranston, R. I.. 248 250 (Also 62.5, 42.95, and 27 meters and other KGEZ Kalispell, Montana 294 100 KWJJ Portland, Ore 250 50 WDZ - Tuscola, Ill. (daytime) 278 100 short -wave transmissions on varying KGFB Iowa City, Iowa 224 10 (Also 53. 54 meters, 100 watts) WEAF tBellmore, N. Y.....**492 50,000 power.) KG FF Alva, Oklahoma 205 25 KWK St. Louis, Mo 234 *1000 WEAM North Plainfield, N. J. 263 250 KDLR Devils Lake, N. D 231 15 KG FG Oklahoma City, Okla 216 50 KW KC Kansas City, Mo 222 100 WEAN Providence, R. I. 275 500 KD Y L Salt Lake City. Utah 234 500 KGFH Glendale, Calif 263 250 K W KH Kennonwood, La 395 3500 WEAO Columbus, Ohio 283 750 KEJK Los Angeles, Cal 252 250 KGFI San Angelo, Texas 220 15 KWLC Decorah, Iowa 248 50 (Also 54.02 meters, 250 watts)w (6XAN, 105.9 meters, 250 watts) KGFJ Los Angeles, Calif 213 100 KWSC Pullman, Wash 395 500 W EAR Cleve and p i 442 1000 KELW Burbank, Calif 229 500 KGFK Hallock, Minn 224 50 KWTC Santa Ana, Calif 273 100 WEBC Superior, Wis 242 1000 KEX Portland, Ore 278 2500 KGFL Raton, N. M 222 50 KWUC LeMars, Iowa (day) * *244 1500 WEBE Cambridge, Ohio 248 10 KFAB Lincoln, Neb 319 5000 KGFW Ravenna, Neb 297 10 K W W G Brownsville, Texas 278 500 WEBH Chicago, Ill 366 *500 KFAD Phoenix, Ariz 322 500 KGFX Pierre, S. D. (day) . 254 200 KXA Seattle, Wash 535 500 WEBQ Harrisburg, Ill 224 15 KFAU Boise, Idaho 286 *2000 KGGF Picher, Oka 207 100 KXL Portland, Ore 220 250 WEBR Buffalo, N. Y ... 242 200 KFBB Havre, Mont 275 50 KGGH Cedar Grove, La 213 50 KYA San Francisco, Calif 361 1000 WEBW Beloit, Wis...... 258 500 KFB K Sacramento, Calif 275 100 KG HA Pueblo, Colo 210 500 KYW Chicago, Ill 534 *2500 WEDC Chicago, Ill 242 500 KFBL Everett, Wash. 224 50 KGHB Honolulu, Hawaii 227 250 KZM Oakland, Calif 231 100 WED Erie, Pa 219 30 KFBU Laramie, Wyo. 484 500 KG HC Slayton, Minn 210 15 NAA Arlington, Virginia *5434 1000 WEEI Boston, Mass 508 500 KFCB Phoenix, Ariz *244 125 KG HF Pueblo, Colo 210 250 WAAD Cincinnati, O 231 25 WEHS Evanston, Ill 216 100 KFC R Santa Barbara, Calif 211 100 KGHG McGehee, Ark ... 50 WAAF Chicago, Ill 389 500 WEMC Berrien Spgs., Mich 484 1000 KFDM Beaumont, Texas 484 500 KGHI Little Rock, Ark 15 WAAM Newark, N. J 268 250 WENR see WBCN KFDX Shreveport, La 236 250 KG HL Billings, Mont 222 250 (Also 65.18 meters, 50 watts) WEPS Gloucester, Mass 297 100 KFDY Brookings, S. D 545 500 KG H O Fort Stockton, Texas ... 50 WAAT Jersey City, N. J 246 300 WEVD Woodhaven, N. Y 246 500 KFDZ Minneapolis, Minn 216 10 KGHX Richmond, Texas...... WAAW Omaha, Neb. (daytime)441 500 WEW St. Louis, Mo. (day) 353 1000 KFEC Portion!, Ore 214 50 KGHP Hardin, Mont 23 50 WABC Richmond Hill, N. Y 309 *2500 WFAA Dallas, Texas 545 500 KFEL Denver, Colo 227 250 KGJF Little Rock, Ark ... 250 (Also 64.0 meters, 500 watts) WFAM St. Cloud, Minn 252 10 KFEQ St. Joseph, Mo. 231 *1000 KG KO Wichita Falls, Texas 250 WA BF Kingston, Pa 205 250 WFAN Philadelphia, Pa 224 500 KFEY Kellogg, Idaho.. 232 10 KGO Oakland, Calif * *384 5000 WABI Bangor, Me. (Sundays) 389 100 WFBC Knoxville, Tenn 234 50 KFGQ Boone, Iowa 210 10 (Short -wave transmitter, 10 to 40 WABO See WHEC WFBE Cincinnati, Ohio. 246 250 KFH Wichita, Kan 246 500 meters, 10,000 watts) WABW Wooster, Ohio 248 50 WFBG Altoona, Pa 268 100 KFHA Gunnison, Colo 250 b0 KG RC San Antonio, Texas... 220 250 WABY Philadelphia, Pa 248 50 WFBJ Collegeville, Minn 273 100 KFHL Oskaloosa, Iowa 213 10 KG RS Amarillo, Texas 244 *250 WABZ New Orleans, La 238 50 WFBL Syracuse, N. Y. 258 750 KFI Los Angeles, Calif 468 5000 KGTT San Francisco, Calif 220 50 WA DC Akron, Ohio 238 1000 WFBM Indianapolis, Ind 275 1000 KFIF Portland, Ore 229 50 KGU Honolulu, Hawaii 270 500 WA FD Detroit, Mich....: 231 100 WFBR Baltimore, Md 244 *250 KFlO Spokane, Wash 246 100 KG W Portland, Oregon 492 1000 WAGM Royal Oak, Mich 225 50 WFBZ Galesburg, 111 248 50 225 10 10 WFCI Pawtucket, 1.. KFIU Juneau. Alaska KGY Lacey, Wash - 246 50 WAIT Taunton, Mass 214 R. 242 100 KFIZ Fond du Lac, was :* *268 100 KHl Los Angeles, Calif 400 1000 WAIU (Columbus, Ohio 283 5000 WFDF Flint, Mich 273 100 KFJB Marshalltown, Iowa... 248 *100 (Also 104.1 meters; 50 watts) WAIZ Appleton, Wis 227 100 W F I Philadelphia, Pa 405 500 - Hopkinsville, 273 ' KFJF Oklahoma City, Okla.. 5000 KHMC Harlingen, Tex 236 100 WALK Willow Grove, Pa 201 50 WFIW Ken 201 1000 KFJ I Astoria, Ore...... 250 50 WAPI Auburn, Ala 341 1000 WFJC Akron, Ohio 227 500 KFJ NI Grand Forks, N. D.... 333 100 KU Spokane, Wash 370 1000 WASH Grand Rapids, Mich 256 280 WFKB Chicago, Ill 224 500 KFJR Portland, Ore 240 500 KICK Red Oak, Iowa (day) 322 100 WBA A West Lafayette, Ind * *273 500 WFKD Philadelphia, Pa 248 50 KFJ Y Fort Dodge, Iowa 232 100 WFLA Clearwater, Fla 517 750 KFIZ Fort Worth, Texas 250 50 W GA L Lancaster, Pa 252 15 KF KA Greeley, Colo 250 *500 WGBB Freeport, N. Y 246 150 KFKB Milford, Kansas 242 -1500 WGBC Memphis, Tenn 229 15 KF KU Lawrence, Kansas 254 500 HE list of stations here corresponds to the latest list of WGBF Evansville, Ind 236 250 KFKX Chicago, Ill ... 526 2500 T licenses issued by the Radio Commission at the time of W G B I Scranton, Pa 231 250 KF KZ Kirksville, Missouri.... 225 15 WGBS tNew York, N. Y 349 500 KFLV Rockford, Ill _268 100 going to press ; and is subject to changes ordered by the WGCM Gulfport, Miss 222 15 KFLX Galveston, Texas 270 100 regulating authority after June 10, 1928. WGCP Newark, N. J 268 250 KFMR Sioux City, Iowa. 232 100 WGES tChicago, Ill 242 500 KFMX Northfield, Minn 236 500 WGHP (Fraser, Mich 278 750 KFNF Shenandoah,Iowa(day) 4(31 2000 WGL tSecaucus, N. J .. 294 1000 KFOA Seattle, Wash 447 1000 W G M Jeannette, Pa 208 50 KFON Long Beach, Calif 242 1000 KJ BS San Francisco, Calif 245 100 WBA K Harrisburg, Pa. (day). 300 500 WGMS Minneapolis, Minn 246 500 KFOR Lincoln, Neb .... 217 100 (6XAR, 62 meters; 50 watts) WEAL tBaltimore, Md * *286 .5000 WGN -WLIB Chicago & Elgin I1141615,000 KFOX Omaha, Neb 258 100 KJ R Seattle, Wash 349 2500 WBAO Decatur, Ill 208 100 WGOP Flushing, N. Y 200 100 KFPL Dublin, Texas 275 15 (Also 105.2 meters; 5 to 250 watts) W BAP Fort Worth, Texas 500 5000 WGR Buffalo, N. Y 303 750 KFPM Greenville, Texas 231 15 KKP Seattle, Wash 203 15 W BA W Nashville, Tenn 240 5000 WGST Atlanta, Ga 270 500 KFPR Los Angeles, Calif 232 250 KLCN Blytheville, Ark. (day) 286 50 WBAX Wilkes Barre, Pa 25(1 100 WGWB Milwaukee, Wis 270 250 KFPW Carterville, Mo 263 50 KLDS Independence, Mo 270 1500 WBBC Brooklyn, N. Y 227 500 WG Y Schenectady. N. * *380 KLS Oakl d, Calif 246 250 Y... 50,000 KFPY Spokane, Wash 246 250 WBBL Richmond, Va 234 100 L (Also on 31.4, 21.96, and sometimes (7XAB. 105.9 meters, 100 watts) KLX Oakland, Calif 508 500 WBBM tGlenview, Ill * *380 5100 5 meter KFQA St. Louis, Mo .. 234 50 KLZ tDupont, Colo 353 1000 WBBP Petoskey, Mich 240 100 ison, Wise 333 750 KFQB Fort Worth, Texas.... 333 1000 KMA Shenandoah, Iowa 395 1000 WBBR Rossville, N. Y 256 1000 WHAD Milwaukee, Wisc 270 500 KFQD Anchorage, Alaska.... 345 100 KMBC see KLDS WBBW Norfolk, Va 236 100 WHAM Rochester, N. Y *280 5000 KFQU Holy City, Calif...... 220 100 KM ED Medford, Oregop 270 50 W B B Y Charleston, So. Car 250 75 (Has short-wave transmitter) (Also 31, 53, 63, 106 meters, 50 watts) KM IC Inglewood, Calif 224 250 WBCN Chicago, Ill 288 *000 WHAPtCarlstadt,N. J236 1000 Wash.. 217 100 KMJ Fresno, Calif ... 366 50 WBES Takoma Park, Md 205 1 WHAS Louisville, KY KFQW Seattle, ..... 286 100 322 500 KFQZ Hollywood, CaliI 232 250 KMMJ Clay Center, Neb..... *250 WBET Medford, Mass 288 500 WHAZ Troy, N. Y. (Monday) 306 500 (Also 108.2 meters, 50 watts) KMO Tacoma, Wash,. 254 500 WBIS See WRAC KMOX Louis, Mo 300 5000 WHB Kansas City, Mo 341 500 KFRC San Francisco, CaSI 454 1000 tSt. WBMH Detroit, Mich 211 100 WHBC Canton, KFRU Columbia, Missouri 250 500 (Also 49 meters, 15 watts) WBMS Union City, N. J 200 100 Ohio 236 10 KFSD San Diego, Calif 441 500 KMTR Los Angeles, Calif 516 500 W B N Y New York, N. Y 236 .500 WHBD Bellefontadne, O 222 100 KFSG Los Angeles, Calif 252 500 (Also 108.2 meters; 250 watts) W BO Q Richmond Hill, N. Y 309 500 WHBF Rock Island, Ill 222 100 (Has short -wave transmitter) KNRC Santa Monica, Calif :375 500 WBOW Terre Haute, Ind.... 208 100 WHBL Sheboygan, Wis 204 *250 Galveston, Texas 253 500 (Also 108.2 meters; 100 watts) WBRC Birmingham, Ala 303 KFUL KNX Los Angeles, Calif .. 337 500 250 WHBP Johnstown, Pa 229 *250 KFUM Colorado Sags., Colo 486 1000 WBRE Wilkes Barre, Pa 250 100 WHBQ 0rs; Memphis, Tenn KFUO tClayton, Mo 545 *1000 (Also 107.1 100 watts) WBRL Tilton, N. H 232 500 232 100 KFUP Denver, Colo 227 100 KOA Den Colo 50006 (1XY. 105, 109 meters, 250 watts) WHBU Anderson, Ind 220 15 22.° 50 KOAC Corvallis Oregon (day) 270 7000 WBRS Greenville, N. Y 211 W H B W Philadelphia, Pa 220 100 KFUR Ogden, Utah KOB :395 *5000 250 KFUS Oakland, Calif 208 50 State College,New Mes WBSO Wellesley Hills, Mass 384 100 WHBY West De Pere, Wis 250 50- Lake City, Utah 250 50 KOCH Omaha, Neb 258 250 WBT Charlotte, No. KFUT Salt KOCW Chickasha, Okla 252 250 Car 258 1000 WHDI Minneapolis, Minn 246 500 KFVD Venice, Call( 216 250 WBZ tSpringfield, Mass *333 15,000 WHEC -WABO (Also 105 meters. 50 watts) KO IL Council Bluffs, Iowa. . 319 5000 (Has short-wave transmitter) Rochester, N. Y. 254 *250 Ktn 225 50 (9XU, 61.06 meters, 500 watts) WBZA Boston, Mass WHFC Chicago, Ill 216 200 KFVG Independence, 319 1000 *333 500 I Texas 233 50 KO IN (Portland, Oregon WCAC Mansfield, I WHK Cleveland, Ohio KFV Houston, 309 1000 Conn 535 500 .....**265 *500 KFVS Cape Girardeau, Mo * *221 50 KOMO Seattle, Wash WCAD Canton, N. Y 244 *500 (Also 66.04 meters, 500 watts) Calif 353 1000 KOOS Eugene, Ore 207 50 WCAE Pittsburgh, KFWB Los Angeles, KORE Eugene, Ore 200 50 Pa 461 500 WHN New York, N. Y 395 500 (Also 105 and 40 meters, 50 watts) WCAH Columbus, Ohio 234 250 WHO Des Moines, Iowa 535 KF WC Ontario, Calif 248 100 KOW Denver, Colo 219 250 WCAJ Lincoln, Neb. (day) 380 500 5000 214 250 KPCB Seattle, Wash 231 100 WCAL W H P P Englewood, N. J 205 10 KFWF St. Louis, Mo 214 Northfield, Minn 286 500 KF W I San Francisco, Cal 268 500 KPJM Prescott, Ariz 15 WCAM Camden, N J 224 500 ,W HT tChicago, Ill 306 5000 KFWM Oakland, Calif 236 *500 KPLA Los Angeles, Calif 288 500 WCAO Baltimore, Md 244 250 WIAD Philadelphia, Pa 288 100 KFWO Avalon. 300 250 KPNP Muscatine, Iowa 211 100 WCAP Asbury W IAS Calif..... KPO San Francisco, Calif 422 1000 Park, N.J 240 500 Ottumwa, Iowa (day) 322 100 (Also 53.07 meters, 100 watts) WCAT Rapid City, So. Dak 248 100 W IBA Madison, Wis 240 100 KPOF I Denver, Colo 201 500 KFXD Jerome, Idaho 201 *15 WCAU Byberry, Pa 261 1000 WIBG Elkins Pk.,Pa.(Sund'ys)441 KFXF Denver, Colo 283 250 KPPC Pasadena. Calif 316 50 WCAX Burlington, Vermont 254 100 50 210 50 KPRC Houston, Texas 294 1000 WCAZ WIBO tChicago, Ill 306 5000 KFXI tldgewate',Colo.(near) KPSN Pasadena. Calif 316 1000 Carthage, Ill 250 50 KFXR Oklahoma City, Okla 224 50 WC BA Allentown, Pa 222 100 WIBR Steubenville, Ohio 250 - 50 KFXY Flagstaff, Ariz. 205 25 KQV Pittsburgh, Pa. 270 500 WCBD Zion, Ill 345 5000 WIBS Elizabeth, N. J 204 100 K Q W San Jose, Calif .. 257 500 250 KFYO Breckenridge, Tex 211. WCBE New Orleans, La 227 250 WIBU Poynette, Wis 217 20 KFYR Bismarck, No. Dak 250 50 KRAC Shreveport, La. 220 50 WCBM Baltimore, 225 231 100 Md 100 W I B W Topeka, Kan KGA Spokane, Wash 261 2000 KRE Berkeley, Calif. WC BS Springfield, Ill 210 250 204 250 Diego. Catif 248 100 K R L D Dallas. Texas 461 500 WIBX Utica, N. Y 238 *150 KGB San KRSC 273 50 WCCO tMinneapolis, Minn * *405 *5000 (Also 65.18 meters) Seattle, Wash WCDA Cliffslde, N. J 213 250 W I BZ r- Iontgomery, Ala 231 15 Ariz 234 100 KSAC Manhattan, Kansas 333 500 KGAR Tucson, La 268 1000 WCFL Chicago, Ill 484 1500 WICC Easton, Conn 265 500 KGBU Ketchikan, Alaska 400 500 KSBA tShreveport, WCGU Brooklyn, N. Y 219 500 WIL KGBX Joseph, Mo 288 100 KSCJ Sioux City, Iowa 244 *500 St. Louis, Mo 258 250 St. KSD St. Louis, 545 500 Also 54 meters, 150 watts) WINR Bay Shore, N. Y KGBY Columbus, Nebraska 222 50 Mo WC LB Long Island City, N. Y. 200 100 211 500 KGBZ York, Nebraska 213 100 KSEI Pocatello, Idaho 333 250 WC LO Kenosha, WIOD Miami Beach, Fla 248 1000 10 KSL Salt Lake City, Utah 303 5000 Wise 227 100 KGCA Decorah, Iowa. 248 WC LS Joliet, Ill .. 216 501) WIP Philadelphia, Pa 349 500 KGCB City. Okla 216 50 KSMR Santa Maria, Calif 273 100 Oklahoma KSO Clarinda, Iowa 227 500 WCMA Culver, Ind 261 500 WISN Milwaukee, Wis 270 250 KGCH Wayne, Nebraska 201 250 WCOA Pensacola, Fla 250 500 W IVA Norfolk, Va KGCI San Antonio, Texas 229 250 KSOO Sioux Falls, So. Dab 210 *250 WCOC ....210 100 KSTP Westcott, Minn 220 3500 Columbus, Miss 231 500 - WJAD Waco, Tex 333 KGCL Seattle, Wash 241 100 WCON Danbury, Conn 265 100 500 KGCN Kansas 204 50 KTAR Oakland, Calif 280 500 'WJ AG Norfolk, Neb 286 *25o Concordia, KTAP San Antonios, Texas 229 250 WCOT Providence, R. I. 225 100 KGCR Brookings. So. Dais 208 15 WCRW Chicago, Ill 224 500 WJAK Kokomo, Ind 234 50 KGCU 240 100 KTB I Los Angele, Calif 275 1000 Mandan. No. Dak , KTBR Portland, Oregon 229 500 WCSH Portland, Maine 3fí6 5000 WJAM Cedar Rapids, Iowa 240 250 KGCX Vida, Montana 244 10 (Also 63.79 meters, 250 watts) WJAR Providence, R. KGDA Dell Rapids. So. Dak. KTHS Hot Springs, Ark 500 *1000 I 484 500 KTNT Muscatine, Iowa 256 2000 WCSO Springfield, Ohio 250 500 WJAS Pittsburgh, Pa 970 (daytime) 254 15 WCWK Fort Wayne, Ind 214 250 500 KGDE Barrett, Minn 205 50 KTSA San Antonio, Texas 265 2000 WJAX Jacksonville, Fla 341 1000 KTUE Houston, Texas 213 5 WCX See WJR 1>4 Also 40 meters. 50 watts) WDAE Tampa, Fla 258 500 WJAY Cleveland, Ohio 227 500 KGDM Stockton. Calif. 2)7 10 KT W Seattle, Wash 395 1000 KUJ Seattle, Wash 200 10 WDAF Kansas City, Mo 370 1000 WJAZ. tMt Prospect, Ill 263 5000 KGDP Pueblo, Colo... 224 10 WDAG Amarillo, Texas 263 1000 WJ BA Joliet, Ill 248 KGDR San Antonio, Texas 207 15 KU OA Fayetteville, Ark 297 1000 50 KUOM Missoula, Mont 461 500 W DA H El Paso, Texas 234 100 WJBB Sarasota, Fla 238 250 KGDW Humboldt, Neb . 294 100 WDAY Fargo, KGDY Oldham. So. Dak 207 15 KUSD Vermillion, So. Dak. 484 250 No. Dakota 545 *250 W J BC LaSalle, Ill 227 100 KGEF Los Angeles, Calif 263 1000 KUT Austin, Texas 232 500 WDBJ Roanoke, Va.... 231 250 W1131 Red Bank, N. J 263 250 KV I 283 KGEK Ynma, Colo. (day) 263 10 Tacoma, Wash 250 WDBO Orlando, Fla 288 *500 W J B K Ypsilanti, Mich.. 220 15 ICGEN El Centro, Calif 225 100 KVL Seattle. Wadi 273 100 (4XE, variable, 250 watts) KVOO Tulsa, Okla. 349 5000 WJBL Decatur, Ill 213 250 KGEO Grand Island, Neb 205 100 WDEL Wilmington, Del 297 100 WJBO KVOS Bellingham, Wash 210 250 WDGY New Orleans, La 263 100 KGEQ Minneapolis, Minn 204 50 KWBS Portland, Oregon 200 50 Minneapolis, Minn... 286 500 WJBT Chicago, Ili 389 500 KGER Long Beach, Calif 216 100 KWCR Cedar Rapids, Iowa 240 250 WDOD Chattanooga, Tenn... 244 500 KGES Central City, Neb 204 10 KWEA Shreveport, La...... 213 100 WDRC New Haven, Conn.... 283 500 (Continued 015 page 157) *Allowed higher daylight power * *Standard or constant-frequency transmission. t Remote Control.

www.americanradiohistory.com 130 Radio News for August, 1928

Five speakers of popular types, all free -edge except the double -fixed -edge cone in the center.

T has been stated in radio periodicals it is not. Practically all speakers which looked over back copies of this magazine provide reproduction nearing the point of and several other radio publications, in or- gineers have not kept abreast of the perfection are of enormous size and for this der to recall to his memory all of the vari- times in the design of loud -speaking reason are not practical for home use. ous types of speakers which have been used sound reproducers. The articles in which However, there are many excellent small - since broadcasting became popular. The ar- this statement has appeared have pointed sized loud speakers available on the market ticles in these magazines proved very inter- to the rapid strides made in the develop- today; but the problem still remains for en- esting, and show clearly the steady and ment of all other pieces of radio apparatus, gineers to develop a new principle which rapid progress which has been made in many of which are now said to approach speaker design in the past few years. On perfection. In comparison with this, they the average of, at least, once every six have explained, little is known about sound months a new design of loud speaker was at- reproduction today that was not general tracting public attention, and in a surpris- knowledge in engineering circles five or ten ingly large number of cases the new designs years ago. represented an actual improvement over In the writer's opinion, the above state- previous types. ments are not entirely correct. It is true In order that the reader may understand that considerable theoretical information better the present loud- speaker situation relative to sound reproduction has been and appreciate the desirable characteristics available for a number of years; but most of speakers to be made in the future, this of these data have not been applied prac- article will endeavor to explain the prin- tically until recently. And any engineer ciples upon which loud speakers operate, will not hesitate a moment in confirming trace the development of radio loud speak-. the fact that a vast amount of work is re- ers up to the present time, and point out the quired between the date of conceiving an principal features of present designs. idea and the date on which that idea has been developed to the point where it is HOW SPEAKERS OPERATE Fig. D. A typical electrodynamic unit and commercially practical. free-edge cone, built into an amplifier and `B" It should not be necessary to explain that In the case of loud speakers, although few power unit. a loud speaker is a device for converting new principles have been discovered since electrical energy into sound waves. How- the era of broadcasting, it cannot be de- permits the construction of a moderate - ever, the way in which this is accomplished nied that there has been a great amount of size speaker capable of delivering undis- is a mystery to a large number of radio practical development. With the average torted reproduction. fans. In the case of a radio receiver, the speaker of five years ago, the radio repro- While preparing this article the writer electrical energy which is used for the pur- duction of the human voice was hardly understandable; whereas, with the best speak- 111111:111111111111/11111111111tttlItttlIt,,,11111111111,111111111111111111111111111111111111. ers available today, it is difficult to detect a difference between the reproduction and Fig. A. Five horn speakers of older models, once the best available. Their the original. short tone chambers caused, not only In the above paragraphs it was not in- a high "cut-off frequency," but also tended to give the impression that the resonance points, which impaired the reproduction especially of voice and modern loud speaker is distortionless, for lower musical tones.

4c'

www.americanradiohistory.com Radio News for August, 1928 131 pose is a pure direct current to which has respond to the usual design of electric super -sensitive phones which are capable of been added a pulsating D.C. component. It motors; as the high inertia of a rotating producing considerable vólume. In each unit is the pulsating D.C. component of this cur- machine makes it impractical to consider is a permanent magnet with coils of fine rent alone which is utilized by the loud using it for sound ,reproduction, which re- wire wound over the pole pieces. In the speaker for producing sound, and it is the quires almost instantaneous variations of design illustrated in Fig. 1, the iron dia- frequency. Also, vibrating devices of the phragm is placed over the poles of the mag- type used as loud -speaker driving units net and separated from them by a small make ,the mechanical problem of converting fraction of an inch; while in the other an the mechanical energy into sound waves armature, which is coupled mechanically to much simpler. a large mica diaphragm by a. driving rod, is At this point it should be explained that placed between the pole pieces. practically all loud speakers, and head- Both phone units operate in the same phones as well, operate on exactly the same manner. The coils of the unit are connected electrical principle. In a device of this type in series with the circuit in which the pul- the electric energy produces in the magnetic sating direct current is flowing; and the field variations which correspond to the current varies the flux of the magnet, caus- sound waves which are being reproduced. ing the diaphragm (directly or through the The magnetic energy is employed to cause armature, as the case aimay be) to vibrate. an armature to vibrate, and the armature. It may be seen easily- that.the.vibrations of is coupled mechanically to a diaphragm. the diaphragm must correspond to the fre- which also vibrates. The diaphragm sets quency of the pulsating current, and, there- the air in vibration; thus producing sound. fore, the pitch of the desired music is re- From an electrical viewpoint there is very produced. Also, as the current varies in in- little difference between headphones and tensity with the vohime of the sound, the loud speakers, even though mechanically amplitude of the vibrations will increase in they may be not at all similar. Of course, the same proportion. the driving unit used in headphones is much Most of the loud speakers on the market smaller than that used in a loud speaker, but use driving units of the construction shown in some cases they are of exactly the same in Fig. 2. This is because this type of unit mechanical construction. In the case of may be made larger, so that it will handle large power speakers, however, the driving a greater volume of sound without over- units are necessarily of very different de- loading. However, in power speakers an sign to permit the handling of the enormous entirely different type of unit is sometimes output, which frequently is a thousand times used. This type of unit operates on the as great as plumes are ever required to pro- principle of Magnetic attraction, but em- duce. ploys an electromagnet instead of a permanent magnet. It is needed only when more Fig. C. Cut-away view of double fixed -edge cone; than the average volume is required. showing mechanical construction: --1, apex; C, front cone; R, rear cone; F, metal frame; G, speaker TWO GREAT TYPES unit; D, driving rod. In mechanical operation all loud speakers in general use may be placed in one of two sole purpose of the radio receiver to produce classes; namely, the "horn" and "cone" this current. types. :Although probably hundreds of dif- Pulsating direct current of the type men- ferent kinds of mechanical construction, tioned is of a different character from that which do not appear to resemble each other, used for any purpose other than the trans- are used in loud speakers, a careful analysis mission of sound waves. Current used for will show that there are only two operating lighting, heating or power usually is con- principles. stant at all times; that is, it, is of a uniform In the horn type a small diaphragm sets frequency and of unchanging intensity. On a long column of air into vibration, and in the other hand, current which is used for this way the sound waves are concentrated. sound transmission is of neither a uniform In the cone type a large diaphragm is used, frequency nor amplitude, but it corresponds and this sets vibrating a great amount of exactly with the sound waves. In other air, thus avoiding the necessity of the horn. words, it is interrupted at a frequency which It is interesting to note the various stages is equivalent to the pitch of the sound, and of development through which the radio its magnitude varies with the volume of the Fig. 3 (left). An early speaker which employed a loud speaker passed before it reached its sound. pair of phones as a driving vcnit. Fig. 4 (right). Another early speaker, with phone unit mounted present stage of perfection. The first loud With electrical energy available which in base. speakers offered by radio stores were merely duplicates exactly the desired sound waves, makeshifts, and it is easy to understand -the it may be seen that an electric motor TELEPHONE UNITS reasons. When broadcasting first started it needed to convert the electricity into me- was considered an experiment in home chanical energy of precisely the same- char- Figs. 1 and 2 illustrate the mechanical amusement rather than a necessity for home acteristics as to frequency and the varia- construction of two popular types of phone entertainment; and, as a result, the person tions in volume. The loud- speaker's driving driving units. That shown in Fig. 1 is the who invested as much as twenty -five dollars unit is the motor which has been designed type found in the average pair of phones, in a complete radio installation was con- for this purpose. Of course, it does not cor- and the one shown in Fig. 2 is used in sidered very extravagant. Secondly, the

Fig. B. Four modern "exponential" horns, with tone chambers six to 'ten feet long, designed for building into a cabinet.

www.americanradiohistory.com 132 Radio News for August, 1928

first broadcast receivers did not provide set and obtain greatly amplified signals. most of these speakers would resonate at sufficient volume for satisfactory loud- This announcement almost doubled the pub- some frequency. speaker operation. And thirdly, the quality lic's interest in radio, and it also created As broadcasting improved the horn speak- of music transmitted by the first broad- the first demand for loud speakers. ers of the type illustrated in Fig. A be- casters was so poor that the merits of a came less and less popular because of the good speaker could not be appreciated. EARLY STAGES OF EVOLUTION distortion caused by the resonating of the \VI;cn broadcasting first attracted public One of the first loud speakers to appear horns, and because of their inability to re- on the market is shown in Fig. 3. As may produce low tones. Attempts were made to be seen from the illustration, it is a short metal horn coupled to a pair of headphones. Needless to say, it gave very poor results; but most fans at the time were particularly pleased with the .design, because it was possible to use the same pair of phones for individual receiving and with the loud speaker. Figs. 4, 5 and 6 show three other types of loud speakers which were popular during this period. The speaker illustrated in Fig. 4 probably was made by a manufacturer of automobile horns, as it bore a marked re- semblance to the latter. It was designed so that a standard phone unit could be fastened in the base. The speaker shown in Fig. 5 was a feature of the 5- and-10 -cent stores, and consisted of a small cardboard megaphone with a coupling device which could be used for attaching a phone unit. Fig. 6 shows a coupling unit designed to combine M a phone unit and the tone chamber of a A phonograph as a loud speaker. All of the 1111111111111111 speakers described above gave oloP\NA IIIIlWl poor results as judged by present -day :IIIIII!. I,,,°,,, ,,,,.,a,,a,,,, tt standards; but they seemed quite satisfac- II tory at the time; as the available music was so distorted at the broadcast stations that further distortion by the loud speaker had ilhi scarcely any effect upon the quality. How- //LaII I ' \\\\l'p\\\ Fig. 1. Drawing showing mechanical construc- ever, as the horns were of very short length, tion Fig. 2. Diagram showing mechanical construc- of standard phone unit: Nf, permanent the "cut -off frequency" tion of a magnets; C, coils of wire; P, pole- pieces of was very high; i.e., super -sensitive type of phone unit: magnet; D, diaphragm. only the high-pitched tones were reproduced Al, magnet; C, coil; A, armature; D, driving rod; P, pole -pieces. and the low tones were totally lacking. This attention loud speakers were unknown. caused men's voices, particularly, to sound very peculiar. make horns of non -resonating. material, such Fans would build simple crystal receivers, Secondly, the phone units as wood and were unsatisfactory for the paper-pulp, but the results were costing less than ten dollars, complete with purpose, as not wholly satisfactory. they were easily overloaded and would rat- The first solution aerial and headphones, and would listen to of the problem was tle violently. Thirdly, the tone chambers found in the develop- phonograph music broadcast by a local sta- ment of the cone speaker. tion. Later, some experimenters constructed were inefficiently designed and "resonated" simple regenerative receivers, which enabled at some frequency, thus causing severe dis- THE CONE ARRIVES tortion. them to listen to distant stations with head- In the first part of this article it was ex- phones when using only one tube. Of course, As radio grew more popular the trans- plained that the cone -type speaker operates with both of these arrangements loud- mission of broadcasters was improved and on an entirely different principle; namely, speaker reception was impossible; and there better loud speakers were required. In an- that of vibrating a large diaphragm which were at least fifty installations of this kind swer to this demand horn speakers of the acts on a great volume of air. With this for every more elaborate receiver then in type shown in Fig. A were developed. These type of speaker the tone chamber is elimi- existence. speakers were entirely satisfactory at the nated and this avoided many of the difficul- The first step forward for broadcasting time but they would not begin to measure ties which had been experienced with loud was when the reflex circuit was presented up to present standards. All of these horns speakers in the past. These speakers were, to the public. Radio experts explained that were equipped with larger loud- speaker therefore, very satisfactory; as, when an it was possible to add two inexpensive items units which would not overload as easily efficient unit was used, the reproduction -an A.F. transformer and a crystal de- and the tone chambers were longer, thus would be fairly uniform over a wide band tector-to a simple one -tube regenerative lowering the cut -off frequency. However, of frequencies. Also, it may be said that the

SQUARE WOODEN FRAME FRAME

CROSS BARS PAPER SUPPORTING CONE FELT UNIT INSULATION DRIVING ROD UNIT LOUD -SPEAKER DRIVE UNIT

DRIVING LINEN ROD DIAPHRAGMS APEX

Fig. 9. Two types of free- edge-cone speaker construction; left, the baffle -board Fig. 10. These drawings give details of the ntw linen diaphragm loud type and, right, the box -baffle type. The baffle prevents interference of sound speakers. This type of construction provides a very sensitive reproducer when waves from the two surfaces. suitably balanced and equipped with a high -quality unit.

www.americanradiohistory.com Radio News for August, 1928 133 cone is still considered one of the most These speakers are in most general use to- popular types of speakers. day, and each type will be considered in- After the development of the cone many dividually, as fol- were introduced. A ma- lows: exponential "trick" speakers UNIT TONE CHAMBER jority of these did not provide any improve- horns; fixed- and ment in sound reproduction, but some pre- free -edge cone s; sented a more attractive appearance. All tense- (linen) dia- speakers of this class, whether they are of phragm types; and conical shape or not, operate on the prin- the electrodynamic- drive cones. The first step taken during this trend Fig. 7. The coiled exponential horns shown in Fig. B of development in loud speakers proved to would look like this if PAPER DRIVING be a great surprise to everyone interested straightened. in radio. This is because the improved type, and it was CONE ROD speakers were of the horn tion of all audio frequencies. Such a horn radio horns had been popularly thought that would even be too large for use in a theater, before because they discarded several years as for a 16 -cycle cut -off the horn would be of sound. However, are poor reproducers over 65 feet long and feet in diameter UNIT the 17' the new horns are very different from at the bell. However, by coiling the tone been used speakers of this type which had chamber, it is possible to reduce the size in the past. They were first called "ortho- so that a horn may be made for home use known phonic" horns but later they became which will reproduce well frequencies below horns. They by the naine of "exponential" _100 cycles; and such horns answer prac- are much larger, of a different shape, and tically all requirements. to were designed mathematically according In Fig. B pictures of five different com- APEX a definite scientific principle. mercial exponential horns are shown. These The first exponential horns were designed horns are of the coiled type and have air especially for use in modern phonographs, chambers from six to ten feet in length. and these attracted the attention of radio engineers. It was found that exponential designed to radiate uni- horns could be DRIVING formly all audible tones, and also that the undesired resonance of the horn could be ROD FRAME reduced to practically zero by correct con- BALSA-WOOD struction. Therefore, with a horn of this DIAPHRAGM type, the only thing to prevent distortionless ' reproduction is the characteristics of the loud- speaker unit. However, the size of the horn is another factor which .limits its util- ity, but this will be considered in another UNIT paragraph. kic(01 Fig. S. The usual double-fixed -edge come is constructed as pictured above, whatever its An exponential horn may be described as external appearance. a tone chamber whose area of cross section is multiplied by a constant figure for each tiple of vibrating a large diaphragm; and, unit of length, and this "rate of expansion" determines the "cut -off frequency" of the therefore, may be considered members of the Í!' is, the frequency down to which cone family. They have been presented in horn; that jÍ! the horn provides uniform concentration of many odd forms, including pictures for the FRAME wall which concealed a large sounding board all tones. Of course, the horn will repro- of paper or balsa wood, table lamps with a duce tones below this frequency, but they do not pass with equal facility. The second vibrating shade, ship models with vibrating Fig. 12. A wood-diaphragm speaker is a highly sails, Lindbergh planes with vibrating important factor which must be considered efficient reproducer, and may also be quite in the design of exponential horns is the di- decorative. Frequently one is- employed as the wings, etc. backing of a tapestry or painting. After the development of the cone, the ameter of the cross section at the bell. This design of speakers was rather standardized diameter should be equal to one -quarter the wavelength of the cut -off frequency, in order until power amplifiers came into general use, Any of these horns, when equipped with to avoid resonance. The shape of a truc an and these called for a further improvement efficient loud- speaker unit, makes an excel- exponential horn is illustrated in Fig. 7. in loud speakers. With a power amplifier it lent reproducer of sound. They are not of was found that, although the low bass notes In this article space does not permit a attractive appearance, complete explanation of the design of horns but have been de- were amplified by the tubes, the small -sized signed only for use inside a radio cabinet. cone -type loud speakers were unable to re- of this type; but it may be said that the produce these tones at their full volume. two factors mentioned in the above para- MODERN CONES graph make necessary a horn of great Therefore, engineers started work on sev- length The for the reproduction of low tones. Because second improvement in loud speakers eral new designs of speakers which would was in the of this fact it is entirely impractical to con- development of the fixed -edge provide practically uniform reproduction cone type. It was found that the low -note over the entire band of audio frequencies. sider constructing a horn for home use which would provide undistorted reproduc- (Continued on, page 179)

FRAME

CONE MOVING COIL

FIELD WINDING

FIELD MAGNET

MAGNETIC PATH

FELT Fig. 6. A speaker z -tit and adapter convert a phonograph tone chamber into a loud speaker. Fig. 5. An early "5- and -10 store" design of 'Fig. 11. Constructional details of the stan- With an exponcntia horn good results may loud speaker. The horn is an ordinary paper dard electrodynamic- be obtained. speaker unit; it requires megaphone, to which a unit is attached. current to keep its field windings excited.

www.americanradiohistory.com 134 Radio News for August, 1928

DESPITE the fact that socket -power carefully of the best possible materials, in space of time, and a shipment of such bat- units and A.C. tubes have achieved order that they may stand up for a consid- teries might be the direct cause of a con- great popularity, the old- fashioned erable period of time and be able to deliver siderable loss of business. The average `B" dry cell for "A," "B" and "C" volt- their maximum voltage over a period of battery used on the average set under ordi- ages is still extremely popular; not alone in manv months. This is particularly true of nary operating conditions should last any- rural communities, but also in many cities the dry "B" battery, which the average set where from nine months to a full year; and and suburban towns' where owners of radio owner is not anxious to keep changing all there are many cases where such batteries sets desire to use their old sets and refuse the time. For this purpose it is interesting have lasted over periods considerably longer.. to be led into changes which might involve a to look into the manufacturing processes in- great outlay of money. If a man has a volved and the care with which these bat- WHAT IS A BATTERY? radio set which is working properly, giving teries are put together by manufacturers. A "B" battery is composed of a number of him all that he can desire in the way of Each manufacturer has his pet formula small 1y,-volt units; each a miniature dry quality and distance, he may rightfully and his rigid specifications. More than half cell such as used for doorbell- ringing pur- enough reason that any additions or changes the secret of long life is absolute uniformity poses, but of course much smaller. See might involve a change in his set's perform- throughout the cells which make up the in- Fig. 1. In a 45 -volt block of more or less ance; hence, he is loath to take a chance. dividual `B" battery. One weak or defec- standard design there are 30 of these cells; Dry cells for radio use must be made tive cell will make trouble within a short each cell consisting of a seamless zinc can in the center of which is placed a carbon stick, the remaining space being packed with a mixture of manganese, graphite and sal -ammoniac. It is essential that the can CONNECTION END OF be seamless for, with the older type of con- POSTS struction, where the zinc was soldered, an CARBON ( +) electro- chemical action would soon set in TOP OF ELECTRODE; between the unlike metals at the soldered SEALING WAX joints. The result was that this joint would BRASS CAPPED soon corrode and render the battery useless. Strictly, there is no such thing as a really CELL dry battery; for the mixture just mentioned is moist and must remain moist as long as WRAPPER the battery is to last. One really dry cell in the series of 30 in such a battery would make the whole block useless, regardless of the condition of the other twenty -nine. It is therefore apparent that care must be exer- cised to keep air out of the cells. This is also one of the reasons why most manufacturers request that their batteries be kept away from heat.

MANUFACTURE The mixture of manganese, graphite and sal- ammoniac is packed around the carbon stick, wrapped by hand in a special material, and then tied tightly to keep it from breaking and causing an internal short- circuit. This unit is called the "bobbin" and comprises the positive element of the OUTER cell. It is placed in the seamless zinc can WAXED CARTON and the electrolyte (in this case a solution ACTIVE of sal- ammoniac or ammonium chloride) is poured around it. A washer of non-con- SOLDERED CONNECTION MIXTURE ducting material is placed on top of this and the can is then hermetically sealed with SEALING WAX AROUND/ SEPARATOR a prepared wax. This performs the function INDIVIDUAL CELL of keeping the air out of the cell and prevents rapid drying up. CARBON ROD The individual cells are carefully assem- SEALING WAX' bled in a box with waterproof separators between them. Then the electrical connec- SEAMLESS ZINC CELL Fig.! tions are made with more than 60 soldered joints. Throughout the entire assembly, the unit is inspected occasionally and double - This drawing shows the internal construction of a typical "R" battery of the indi- checked to insure uniformity. depends upon vidual -cell type. The unit contains 15 cells and develops 221 volts. The life of a "B" battery

www.americanradiohistory.com Radio News for Augitst, 1928 135 the depolarizing agent used in its construe - .-Corbon(+). complex to be worth mentioning in this tion, than on any. _other single factor. Porous separator article. more containing electrolyte. In most of the factories the exact formula rDepolarizer mixture. "Internal shorts" nmaa; be found in a -Carbon(+). "B" battery; but due to the rigid inspec- for this agent is a carefully -guarded secret. ZInC( -). depolarizer is to pre - Porous separator tions made in factories where good batter- 'l'he purpose of the containing lectrolyte. vent the formation of a film of hydrogen Depolarizzr mixture. ies are put together, these are extremely gas, which naturally accumulates about the Fig.3 rare. In the case of an internal short, a carbon, or positive, pole of the cell when The elements of the `B" battery of the layer - single cell, or probably a few, will show a constructed tope. The carbon is painted as a the current is flowing. -Since hydrogen is a thick layer directly opon the surface of the low voltage and the balance will show their non -conductor of electricity, the active sur- zinc plates. normal voltage of 1.5 or 1.6 volts. face of the positive pole in contact with the It is also possible to short -circuit one electrolyte gradually decreases in area, SHORT CIRCUITS half of a 45 -volt battery and not the other causing the internal resistance of the cell The useful life of a `B" battery is often half; that is, from the negative to the center to rise until a point is reached where it is prematurely ended by a short -circuit, with- 22 / -volt tap or from this tap to the 45- no longer possible for current to flow. Part out the owner's knowing when or how it volt terminal at the other end. This is of this reduction in current is.caused by the happened. The cells of a short -circuited explained by the fact that batteries of this fact that the hydrogen (which causes the battery will be all, or in part, corroded, the type are usually composed of two separate cell to become polarized) also sets up . a electrolyte will generally leak out and the blocks of 22/ -volts each, connected to- flow of current within the cell itself, in op- pressure of a fingernail against the zinc gether by a wire. position to the normal flow. When the ex- shell will often be sufficient to break through Sometimes, certain tap wires are taken to ternal circuit is opened, the flow of current it, especially near the top. (This part of the set from one of the intermediate taps within the cell itself should cease, theoreti- the shell is where the upper part of the on a battery, such as the detector tap where cally; and the more complete the actual ces- bobbin ends and corrosion there is more a "soft" tube is used. This particular sec- sation, the longer the cell will last when on pronounced than anywhere else.) tion of the battery will have a greater rate the shelf. However, in the case of batteries which of discharge than the others, and will there- have become shorted after having delivered fore be exhausted sooner. A short occur- LENGTH OF LIFE a great part of their energy through nor- ring in any of these tapped sections would All the time current is flowing, the zinc mal use, a subsequent short- circuit is gen- exclude that part from the circuit in very container, or negative pole, in contact with erally not sufficient to cause any change short order. the electrolyte, is slowly disintegrating. in the appearance of the zinc. This disintegration, comparable with the There are other methods of determining TILE PIONEER IDEA REVIVED horning of fuel, liberates the energy con- in the laboratory whether or not a battery One manufacturer of "13" batteries has tained in the battery. If a short-lived bat- has been subjected to a short circuit or brought out a source of voltage which goes tery. (one which has not been short -cir- an extraordinary drain; but these are too (Continued_ on page 164) cuited or subjected to abnormal drain) is opened, the zinc cartridge or can will be found in almost perfect condition, with no evidence of corrosion. On the other .CONNECTION POSTS hand, if a long -lived battery is opened, SEALING WAX the zinc shell may he found to be badly corroded. In the first case, because of either polarization or the drying up of the electrolyte, the positive pole had virtually become insulated from the negative; consequently the cell became useless in short order. In the second case, the depolarizing agent and the electrolyte maintained their efficiency to the end. It should be remembered that it is the disintegration of the zinc that causes the current to flow and naturally enough, the area, thickness and purity of the metal will have a large bearing on the useful life of the cell. "B" batteries, to he satisfactory, must have the following characteristics: long shelf life, long service life, freedom from noise, and uniform quality. A battery which can render long service after long periods of idleness is said to have a "long shelf life." The word service or service life, when used in connection with batteries, is usually taken to paean the ampere -hours or milliampere -hours delivered by the battery before the voltage falls to a fixed value. A -45 -volt battery, for example, has reached the end of its useful life when the voltage has dropped to about 34. At this voltage the internal resistance of the battery becomes fairly high and, although it may still appear serviceable, it is far better to replace it with a newer battery. Batteries used for a "C" supply, or "negative bias" on the grids of vacuum tubes, have a service life practically equal to their shelf life; for the reason that they CARTON are called upon to deliver but a very small amount of current. The service life of a battery is dependent upon the way it is used as much as upon the quality of the POROUS DIAPHRAGM DEPOLARIZER materials entering into its construction. CONTAINING ELECTROLYTE MIXTURE Any battery, no matter how well made it is, if called upon to deliver too heavy a What a layer- constructed `B" battery would look like if one corner of the outer load, will necessarily have but a short life. carton were cut away. This model develops 45 volts.

www.americanradiohistory.com 136 Radio News for August, 1928

A Two -Tube Reflex Receiver of Simple Construction HUNDREDS of different types of as R.F. amplifiers, then the energy is recti- duced by the receiver would be much more receivers have been described in fied by the detector, and returned to the be- satisfactory. radio periodicals and newspapers ginning of the circuit, thus causing the tubes The reflex receiver which is described in during the last few years, and to operate a second time as A.F. ampli- this article is a two -tube set, but it does not many of these have attracted considerable fiers. In this way, with three tubes, it is provide five -tube results. In building the attention from constructors. However, al- theoretically possible to obtain results which receiver, the designer endeavored to secure most without exception, the description of a compare with those delivered by a six- or the maximum from each stage, but was good reflex circuit excites ardent enthusiasm seven-tube receiver. careful not to overload any circuit or tube. on the part of many readers. Probably this At this point of the explanation the ques- As a result the receiver gives excellent per- is because everyone considers the reflex the tion asked most frequently is: "Why are not formance, but the results more nearly cor- ideal circuit from the viewpoint of economy, reflex circuits used more generally if they respond to those obtained from the usual and hopes that some day a perfect receiver possess exclusively of this type will be developed. this economical lea- In some ways the reflex circuit may be corn- ture ?" The answer is, pared with a perpetual- motion machine, that a large number for there is an attempt on the part of the of designers of reflex designer to obtain something for nothing. circuits have become Of course, this is impossible; but there is no question about the fact that with circuits of this type greater volume is obtained from a Fig. A. The simplicity given number tubes is of the Two -Tube Reflex of than possible with is apparent on its panel. other methods. Therefore, the cost of parts, While there are two tun- and the cost of operating set; is - ing controls, they should the a mini keep in step over the mum, considering the results obtained. waveband. Rl -controls volume. WHAT IS "REFLEXING.?"

a11.11131331311131111 1 1 1 1 1311111 111 1111 1 1111 111 1 111111111111111 1111., Before continuing further with this article, the principle upon which all reflex re- too miserly in their ceivers operate will be explained. In all cir- attempt to obtain cuits of this type the reflexed tubes are maximum output from called upon to do double duty; that is, they each tube, and, as a operate as both audio- and radio -frequency result, have_ impaired the quality of perform- three -tube receiver. In the case ance. However, if builders amplifiers. of a three -tube re- were satisfied In circuit design the receiver employs a flex receiver, for example, slightly less than double the circuit would with performance stage of reflexed R.F. amplification, a so the three from their tubes, the over-all be arranged that tubes act first results pro- crystal detector, a stage of reflexed transformer-coupled A.F. amplification, and a straight stage of transformer -coupled A.F. amplification. Semi-power tubes are used in each stage to prevent overloading, and no attempt was made to combine a second R.F. stage with the second A.F. stage; as this would have an undesirable effect on the performance of the receiver.

SIMPLE AND COMPACT The receiver is very simple in operation. There are only two tuning controls, one volume control and a battery switch mounted on the:: front panel. The two tuning dials control the variable condensers connected in the R.F. and detector circuits. The volume control is a variable high resistor in the grid return circuit of the first tube. In tuning it will be found that react- ings of the two dials closely approximate each other for all wavelengths in the broadcast band. The small size of the set is another important feature of the design. The front panel is only X13% x 7 inches, and all the parts are mounted on a wooden baseboard 63 inches deep. The total weight of the set is only 6' poúnds, but this figure does pot include a cabinet. These facts make Fig. B. A rear view of the Two -Tube Reflex Receive.. this set ideal for semi -portable use, as a

www.americanradiohistory.com Radio News for August, 1928 137

but a cardboard tube may be used if nothing better is available. However, if a card- AERIAL A C PT2G board forni is used it should be painted with 11 collodion before it is wound with wire. Cl, C3 Ç4 L3 For winding the coils No. 28 D.S.C. wire is used throughout. In making the antenna B A L2 o coil (L1) start the secondary winding about / -inch from the end of the tube and wind 76 turns of wire. A space of -inch should D R1 C2 / V1 be left between the end of the secondary and rILI the beginning of the primary winding, which 4. 1111 4. consists of 15 turns of the same size wire. 0000 Also, it is important to make sure that the P B primary and secondary are both wound in GROUND T1 11R2 c D R3 the same direction. .1M OM The RI?. transformer (L2) is very similar in construction to the antenna coil, but SW the windings have a different number of turns of wire, and the secondary winding is tapped at one point. The secondary coil is b started / -inch from the edge of the tube; C- B+ C-POWER A-B-C+ B+POWER it consists of 56 turns of wire and it is tapped at the 24th turn from the beginning Fig. 1. This circuit diagram shows the characteristic appearance of a reflex cir- of the winding (32 turns from the end near- cuit. Parts are lettered as in the List below and in the illustrations. est the primary winding). The primary winding has 22 turns of wire and is wound in the saine direction as the secondary. set of this type, complete with batteries, Two phone -tip jacks; After winding the coils they should be could be transported to a summer home or Flexible insulated connecting wire, screws, painted with collodion to protect them from camp without difficulty. Since only two solder, coil mounting brackets, etc. moisture. Then, four holes should be drilled tubes are used, it would not be expensive in the tube I/ -inch apart and / -inch from to operate both the filament and plate cir- the edge at the primary end of the coil. cuits with dry batteries for short periods No. 60 These holes are for the various wires of the of time. coil to pass through and they should be The construction of the receiver is very A complete set of large marked "A," "B," "C" and "E," respec- simple, and a novice should have no diffi- working blueprints, with tively. The wire from the outer end of the culty in building a duplicate of the set the list of parts used in primary winding passes through hole "A," shown in the illustrations. In fact, it was the original Two -Tube and the wire from the inside of the primary designed esjiecially to provide an inexpen- Reflex Receiver de- winding through hole "B." The wire from sive set for the beginner to start with. All scribed here, will be given the inner terminal of the secondary plisses parts are mounted on a wooden baseboard, free to anyone writing in or calling through hole "C,"' and hole "E" is for the with the exception of the instruments on the at this office for them. wire from the tap in the secondary wind- frontpanel,_and all the wiring is above the Ask for Blueprint No. 60. ing of the R.F. transformer. The wire from base. Therefore, practically the only tools the outside end of the secondary winding is required when building the set are pliers, not brought to the base but passes through screwdriver and soldering iron. Of course, MAKING THE COILS a hole marked "D" at the other end of the a few holes are required in the front panel, As the coils are home -made, these must tubing. It is highly important that the which is of bakelite, but the store where the be wound befóre starting the construction various wires be correctly marked, as these panel is purchased will drill these, if re- of the receiver. Both coils are wound on markings are followed in wiring the requested to do so. tubing 1s inches in diameter, and a length ceiver. PARTS REQUIRED of 21/4 inches is required for each coil. The MOUNTING AND ASSEMBLY tubing should be bakelite or hard rubber; After winding the coils the next step is The first step in building the set is to secure the necessary parts: The following is a complete list of the apparatus required: Two variable condensers, .00035 -mf. (Cl and C2); One adjustable condenser, 2 to 25 neuf. C3); One fixed condenser, .00025 -mf. (C4) ; One antenna coil, homemade (Ll) ; - One R.F. transformer, home -made (L2) ; Two A.F. transformers, 3/:1 ratio (T1 and T2); One R.F. choke coil, 85- millihenry (L3) ; One crystal detector, carborundum type (D); One volume -control resistor, 0- 500,000 -ohm (R1); Two filament- ballast units, 5-volt, 1- ampere type (R2 and R3); One battery switch (SW) ; Two tube sockets, UX type; Two vacuum tubes, 112A type, or one 112A type and one 171A type (`'1 and V2); Two tuning dials, vernier type; Eight binding posts; One baseboard, 63 x 123 x 3 inches; One bakelite front panel 7 x 13T x 3/16 inches; One binding -post panel, 2 x 123 x 3/16 inches; 4 One detector panel, 3 x 13 x 3/16 inches; Fig. C. This top view shows the actual size and position of all parts.

www.americanradiohistory.com 138 Radio News for August, 1928 drilling the panels. In the front panel four binding -post panel and the crystal -detector type, but three mounting screws are needed large holes, 7/16-inch in diameter, are re- panel. to prevent the frame of the vernier dial quired for the shafts of the instruments With the panels drilled and the coils from turning. Both the resistor .011) and mounted on the panel, and eight small holes wound, the assembly of parts may he the battery switch (Stir) are of the single - for mounting screws. The panel layout started. First, mount the parts on the front hole mounting type. shows the exact position of these holes. The panel. Both of the variable condensers The parts on the baseboard are all fast - other layouts give details for drilling the (Cl and C2) are of the one -hole ntountin.g (Continued on page 168)

SW 0

L1 SECONDARY

iiiiñi nmummMnnu - 1111111111n11m111e1111m1 11111 unmmmm1111nlxummxnnl mimiimiúriiiiwiim ÌIiÌI

V1 C3

OUTPUT B+ C- A+ CND. AER. B+ POWER C-POWER A-B-C±

Fig. 2. Pictorial wiring diagram, .showing front panel and base- small panel for the detector D is held by the binding posts 13 and board of the Two-Tube Reflex. All wiring is in plain view. The P of the A.P. transformers.

www.americanradiohistory.com Radio News for August, 1928 139 A Booster Unit for the Browning -Drake Details of a Home -Made Device Incorporating One Stage of R. F. Amplification Which Will Add to the DX of this Excellent Receiver By C. A. Oldroyd

FEli' sets and circuits have enjoyed and miles from the writer's location, and EASY TO ATTACH the Browning - its reception was a good omen foi the pos- the great popularity of The circuit diagram of the complete Drake or Roberts type of receiver; sibilities of the booster unit. booster unit is shown in Fig. 1, and from and it looks as if sets of this design will win even more friends in years to come. this drawing it may be seen how easily the A well -made receiver using one stage of device may be connected in front of the R.F. and a regenerative detector, with two Browning -Drake, Roberts, or, in fact, any stages of audio, is a remarkable distance - other type of tuned R.F. receiver. One getter; and the DX fan whose purse is "A" voltage and one "B" voltage are re- -tube "super - not long enough for an eight quired for the operation of the unit, and het" will find this set, which uses only half these are obtained from the supply devices the number of tubes, an excellent substitute. Precision -made units make construction employed by the receiver, which may be easy and certain for the beginner; the com- either batteries or socket -power units. In pleted set need not fear comparison with addition to the three "A" and "B" wires, high -grade factory -made receivers. On the there are only two binding posts which must other hand, the experienced radio con- be connected in order to install the unit; structor may build many of the parts easily. the aerial post which connects with the The writer has been a Browning -Drake lead -in, and the output binding post which enthusiast for some time, since he is par- connects to the aerial binding post of the ticularly interested in DX work and trans- receiver. The complete apparatus may be atlantic teception (from the European side connected and placed in operation in five of the "pond ") he finds the circuit hard to minutes' time. beat for this class of work. During the Another interesting feature of this booster winter, even on nights when static was unit is that it may be disconnected easily severe and code interference from ships and quickly. It will be noticed that the most annoying, his "four- tuber" located in switch (SW1), which is shown in dotted Barrow - on - Furness, England, regularly lines between the aerial and output binding brought in American stations, usually at posts of the unit, connects the aerial di- loud- speaker strength. Fig. A. The booster unit, cased in a home- rectly to the receiver without affecting any some unresolved made shield, which prevents interaction with But, there were still the set itself. of the circuits of the receiver in any way. whistles which defied the operator and, to It is a single -pole, single -throw switch which get still greater range, an experimental Many other American stations were may be connected externally to the booster "booster" was rigged up. This consisted brought in during the following nights, some unit. Therefore, when this switch (SW1) of one additional stage of R.F. amplifica- of them with magnificent loud- speaker vol- is open and the battery switch (SW) of tion ahead of the receiver proper; it adds ume, especially WPG. The aerial used for the booster unit is closed, the booster is a tuning control, certainly, but tuning is these receptions was about twenty-five feet ready for operation. Then, to remove the not more difficult than with a standard long and just under thirty feet high. (A unit from service (SW1) is closed and the three -dial neutrodyne, for instance. Also, word to skeptical fans; this is not stretch- battery switch is opened. Under these con- it may be disconnected easily when not ing the truth, we have seen. confirmations ditions the booster tube is turned off and the needed for DX work. of reception from WIOD, WPG, WGY, receiver performs exactly as it would if A DX- BRINGER IfDKA, etc.- EniTox.) the booster were not connected, i.e., only up his mind the dials in the receiver cabinet require The addition of the booster extended the On one point the writer made be al- for tuning. The ease with which range of the already very- sensitive set con- from the very start; nothing must adjustment de- the booster may be connected not only per- siderably, and DX work became a much tered in the original Browning -Drake be mits a saving of current when the unit is more comfortable indoor sport than be- sign, so that the booster unit can added circuit not required but simplifies tuning. The fore. Without the booster, some weak sig- or removed without any internal desired may be located on the dials nals had to be wrestled with for half-an- changes. station hour or more, before clear reception was possible; with the booster on the job such signals could be pulled in fairly easily. The booster improves selectivity as well, and-last, but not least-it is easy to build and its cost is very moderate. To give one or two examples of the sensitivity of the new set; on a roughly -made loop, stations over 300 miles away came in with good volume on the speaker. With an outdoor aerial, the set has, of course, a much greater range. The original booster unit was completed late one night, and duly connected up. All English broadcast stations had by this time shut down, and even the Spanish stations with their late operatic programs were off the air. A healthy whistle showed that somewhere a radio station was busy; a few adjustments -and dance music came in with good volume on the speaker. At last the announcer-"Station WIOD, Miami, Flor- ida." This Fig. B. Top view of booster unit with sh<<.la 'removed, showing posit 'ror, of parts s i ssb -base. The station is well over four thous- tuning ..ou i:; -t home -made.

www.americanradiohistory.com 140 Radio News for August, 1928

.0005 -mf. variable condenser (Cl) connected in shunt. Also, the antenna coil (L1) is tapped at the midpoint for connection to the neutralizing condenser (C3) which is connected between the center -tap of the antenna coil and the plate of the booster tube (V1). The plate circuit of the booster unit is of the shunt -feed type; a system in which an R.F. choke coil (L2) is connected between the plate of the tube and the positive terminal of the "B" battery, and the plate circuit is coupled to the next stage through a fixed condenser (C4) having a capacity of .006 -mf. With this circuit the plate current reaches the tube by passing through the R.F. choke coil (L2) and the R.F. energy passes through the blocking condenser (C4) in order to go to the grid of the next tube. In addition to the features of the booster unit already mentioned the only additional point of consideration is the filament control, which is taken care of automatically by a self -adjusting filament- ballast unit. This simplifies the construction of the unit considerably and reduces the number of required controls to one tuning dial and a battery switch. Fig. C. The method of mounting parts is shown clearly in this view of the booster unit. The condensers C2 and C4 are held in place by the wiring. REDESIGNING THE UNIT The author's model of the booster unit is of the set with the booster unit out of the the results in all cases are not entirely sat- identical in circuit design with the device circuit, and then the booster may be con- isfactory. Without very careful design it pictured in this article. However, as Ameri- nected for greater sensitivity. This method is difficult to build a three -stage R.F. re- can -made apparatus was not available to avoids the necessity of simultaneous adjust- ceiver which is entirely stable in operation him, he used parts of British manufacture. ment of the three dials when receiving DX. and, because of this fact, the addition of As a description of the original booster a booster unit to a receiver employing would be of little value to most of its CIRCUIT USED two or more stages of tuned radio- frequency readers, RADIO NEWS decided to duplicate In circuit design the booster unit is the amplification would be apt to cause the the unit as nearly as possible with standard equivalent of a one -stage R.F. amplifier R.F. amplifier to oscillate, thus ruining parts. The following paragraphs tell how to which is connected ahead of a Browning - reception. This is not true in all cases, construct the device built in RADIO NEWS Drake type' receiver; thus converting the but it frequently happens. Laboratories. set into a two -stage tuned R.F. receiver In the schematic wiring diagram (Fig. 1) A complete list of the parts needed for with a regenerative detector. The booster it will be seen that the antenna circuit is the construction of the booster unit is as circuit is neutralized and, because of this coupled directly with the grid circuit. The follows: fact, the addition of the booster will not aerial is connected with the antenna coil cause unstable operation with a receiver (L1) through a small fixed condenser (C2) One variable condenser, .0005 -mf. (Cl) ; of this type, having a capacity of .0001 -mf., and the One mica fixed condenser, .0001 -mf. (C2) ; a was In previous paragraph it stated ground connection is made through the One neutralizing condenser, 2 to 25 mmf. that the booster could be connected in front "A -" wire, which is grounded in the re- (C3); of any standard tuned R.F. receiver, but ceiver. The antenna coil is tuned with a One mica fixed condenser, .006 -mf. (C4) ;

One aerial coil (homemade) (Ll) ;

One R.F. choke coil (homemade) (L2) ; One filament -ballast unit, 5 -volt, I- ampere (R1) ; C3, RI ,

AERIAL

A+

A- B- GN O B+ 90V.

OUTPUT

Fig. 2. In this pictorial diagram all connections are shown, though the parts have been shifted slightly for clearness.

www.americanradiohistory.com Radio News for August, 1928 141

A-B- A+ 13+ B+ GND 45V 90v.

Fig. 6. The use of a screen -grid tube with the modified circuit shown above increases the amplification. For further details, see page 174.

Fig. 1. This is the circuit of the unit as illustrated, with a 201A type tube. The lettering is that of the pictures and list of parts.

One battery switch (SW) ; may be seen that the first step of construc- winding the aerial coil (Ll) One vacuum tube, 201A type (VI); 61 tion should be One vernier dial; Na. and the R.F. choke coil (L2) ; both of these One tube socket, UX type; Large blueprints with coils may be made easily by the constructor. Five binding posts, push type; full constructional details 'i'he aerial coil is wound on a bakelite or 1 inch in diameter and 3 One front panel, 43 x 7 x 3/16 inches; and the list of parts used cardboard tube One wooden baseboard, 4% x x y4 inches in length. The winding consists of here inches; in the booster unit 125 turns of No. 30 D.C.C. wire, and a tap One binding-post panel, 2 x 41/1. x 3/16 illustrated will be given or mailed free is made at the 62nd turn (midpoint) for

inches; . to anyone asking for them. Write connection to the neutralizing condenser Copper sheet for shielding (See drawings) ; your name and address clearly when (C3). The R.F. choke coil is wound on any etc., etc. convenient wooden, bakelite or hard- rubber Connecting wire, screws, solder, applying by letter. spool with a core y2-inch in diameter; No. COIL DATA Ask for Blueprint No. 61. 36 S.S.C. or enameled wire is used for the After reading the above list of parts it (Continued on page 174)

DRILL FOR SW i ' 16V DRILL 311 X32 <8

- n - 1/S DRILL 3 HOLES BAKELITE, HARD $- o.p RUBBER 5/3n2 DRILL --to OR '7HOLES WOOD Ì -0- M1

In In < < 34 2 13/32 DRILL FOR SHAFT 1500 TURNS OF N2. 36 ENAMELED WIRE. -BINDING POST STRIP- OF C1 S.S.C. OR BAKELITE OR HARD RUBBER CV -DETAIL OF COIL L2-

\, r

5/3p DRILL 2 HOLES 15".. 15" `-16 Ì6}

CENTER TAP 3" 511, 1111110mhou 5/32 1 T 1 " DIA. FRONT END 32 IIII Iq'lI,II'!IIlllM; ! llll!!IlII - BAKELITE 5" OF CAN. t j. TUBE. 4ist 3" illlifil ü i II IIIh 4 1 88 LEFT OPEN. Ì 1/g DRILL 25 TURNS OF OPENING FOR MATERIAL- SHEET. COPPER 2 HOLES. N2. 30 D.C.C. WIRE BINDING POSTS I/64 TO 1/2 THICK - DETAIL OF COIL LI-

Fig. 4. Complete drilling and winding details for coils and panels, and dimensions of the shield for the booster unit.

www.americanradiohistory.com 142 Radio News for August, 1928 A Screen -Grid Short -Wave Receiver A Three -Tube Set Employing the 222 -Type Tube as an R. F. Amplifier at Ultra -High Frequencies

By Fred H. Canfield

THE screen -grid short -wave receiver described in this article is entirely different from the usual short -wave receiver. Most of the short -wave sets which have been described heretofore in RAmo NEWS have been designed primarily for the. experimenter who desires economy and maximum efficiency, rather than ease of control. As a result, the average short- wave set employs only two tubes and is rather complicated in its operation. In this receiver an attempt has been made to simplify the construction and operation as much as possible, nevertheless retaining a high degree of sensitivity and selectivity. In other words, this set represents an endeavor on the part of the designers to build into a short -wave receiver the desirable characteristics of the usual broadcast receiver. Fig. A. This picture, taken in RADIO NEWS Laboratories while testing the Screen -Grid Short-Wave At this point it should be explained that Receiver, clearly shows the neat, unencumbered appearance of the front panel. The roils for other there is a great difference between the effi- wavebands are at the left. ciency of a receiver and the sensitivity of a receiver. Every efficient receiver must R.F. receiver, the set possesses all the de- a regenerative detector followed by a stage necessarily be sensitive; but it does not sirable features of the regenerative set and of A.F. amplification, making a total of follow that a sensitive set must be efficient. in addition becomes much simpler to oper- two tubes. It is seldom that a short -wave

For example, a corrèctly designed - three - ate and the circuits are much more stable. set using more than two tubes is con- tube receiver, employing a regenerative de- structed; as the addition of a tuned R.F. OF THIS SET tector and two audio stages, may be both DESIGN amplifier to a receiver of this type might highly efficient and very sensitive; whereas The principle of design described above complicate the set to such an extent that a carefully planned five -tube set, employing has been applied to this short -wave receiver. the added sensitivity would be of little two R.F. stages, a non -regenerative detector In .building the set, sensitivity and selec- Value. On the other hand, if an untuned and two A.F. stages, may be equally as tivity were given the first consideration, R.F. amplifier using a 201A -type tube were sensitive, but not as efficient- because two stability and ease of operation second con- connected .ahead of the detector, the gain extra tubes are required to do the same sideration and, then, the efficiency was made in amplification would be practically negli- work. as high as possible. Of course, it would gible. Therefore, up to the present time, the From the example in the above paragraph have been possible to increase the efficiency, set employing a regenerative detector with it may be seen that high efficiency is not but this increase would not have been de- a one -stage A.F. amplifier has been con- always a necessary, nor even a desirable sirable; as it is not needed, and it would sidered the. best possible combination for characteristic; as a five -tube tuned R.F. complicate the operation of the set con- short -wave reception. receiver is mach to be preferred over the siderably. However, notwithstanding these The screen -grid short -wave receiver has three -tube regenerative, even though -both facts, this receiver is more sensitive and several advantages over the usual regenera- sets are capable of providing practically produces greater volume than most short- tive type. It employs a total of three tubes the same results. The reason is that, by wave sets of other designs. in a circuit consisting of one stage of R.F., slightly lowering the efficiency of the tuned The average short -wave set consists of a regenerative detector and one stage of A.F. amplification. The R.F. amplifier is of the untuned type and uses the screen - grid (222 -type) tube. Therefore, it does not add a tuning control; but it does provide an appreciable gain in amplification, due to the fact that this to 'e is used. Ac- cording to James Millen, the designer of the receiver, the amplification of the R.F. stage is between 3 and 4, depending upon the wavelength. The addition of the R.F. stage has many other desirable effects upon the operation of the receiver. First, it makes the receiver much more stable in operation. Sec- ondly, it prevents the detector tube from radiating energy into the aerial. Thirdly, it makes it possible to calibrate the tuning dial of the set; as the size of the aerial has no -effect upon the tuning condenser. Fourthly, the dead spots (points on the tuning dial where the set cannot be made to oscillate because of aerial characteristics) of the set are eliminated, by virtue of the fact that the aerial is not connected to the Fig. B. Ample space is available on the baseboard for mounting parts without crowding. This greatly increases the efficiency of the set, esbecially at the ultra -high frequencies. 'detector circuit of the set.

www.americanradiohistory.com Radio News for August, 1928 143

A close examination of the circuit will 6 show that it possesses several unusual features and refinements. Automatic filament - T. C4 L3 c, resistors (R1 and 112) are A '006 ballast used in 5 y J1 place of rheostats for controlling the fila- AER. > L2 ment current of the tubes. 111 regulates C5 V2 VI G V3 the filament current of the screen -grid tube CG P ie and R2 controls that of the detector and

P. A.F. tubes. The volume and regeneration L9 Ci of the receiver is regulated by a variable B+ in R2 resistor the plate circuit of the detector. C2 This resistor (R4) varies the voltage ap- R plied to the detector tube, and it is shunted -C3 R3 R4 C6 by a 1 -mf. by -pass condenser (C6). An i R.F. choke cciil (L3) is connected between the plate terminal of the detector tube and the primary winding of the transformer, DL U and this prevents R.F. current from entering the A.F. amplifier and also improves SW the control of regeneration. PARTS REQUIRED A -B- M- B+ B+ B+ B+ Another feature of the receiver which GND 45V. 67 V. 90V 135 V. YELLOW BLACK BLUE GREEN MAROON RED has not been mentioned previously is that the use of plug -in coils permits a wave- Fig. 1. The symbols used in this complete schematic wiring diagram of the Screen -Grid Short- length range of 15 to 115 meters. Also, Wave receiver correspond to those used in the text, list of parts and other illustrations. another coil may be obtained which permits the reception of stations in the broadcast The picture shown as Fig. A reveals the circuit of the screen -grid tube with the wave band. Four coils are needed to cover simplicity of this receiver as compared grid circuit of the regenerative -detector the band of short waves mentioned with above other short -wave sets. In the center tube. The coupling between the various and these coils are used in the position of of the front panel is there an illuminated windings is fixed; P, the primary winding, L2 in the circuit. They fit into a special vernier dial, and this serves as the only is in the plate circuit of the screen -grid six -contact socket and it is a simple matter tuning control for the entire receiver. The tube, S, the secondary winding, is in the to change from one coil to another. knob in the lower left corner of the panel grid circuit of the detector tube and T, A complete list of the apparatus required controls the battery switch, and that in the tickler winding, is in the plate circuit for the construction of the receiver is as the lower right corner of the panel the of the detector tube. The receiver is tuned follows: volume- control resis- One variable tor. These are the condenser, double- spaced .000 - 125-mf. only controls; as all (Cl); rheostats and coup- Two by -pass condensers, 0.5-Inf. (C2 and ling adjustments were C3); avoided by the de- One fixed mica condenser, .001 -mf. (C4) ; when signer building One fixed mica condenser, .00025 -mf. (C5) ; the receiver. One by -pass condenser, 1-inf. (C6) ; One special R.F. choke mnnnnumnmmunnm111111111111111mi m 1 1 1 1 1 1 11 1 1 111. coil for antenna coupling (L1) ; Fig. D. This bottom view of the baseboard One set of four plug -in coils, with socket shows that the battery - cable leads are attached (L2); directly to the parts. One R.F. choke coil, short -wave type (L3) ; One filament -ballast unit, 222 -type (R1); One grid leak, 6- megohm (112); One The pictures (Figs. B, C and D) show by Cl, the variable condenser connected in filament -ballast unit, 112 type (R3) ; the simplicity of construction behind the shunt with the secondary winding. The One volume- control rheostat, 0- 500,000 -ohm panel and under the baseboard. With the A.F. circuit of the receiver is standard and (R4) ; exception of the three instruments mounted employs the usual audio transformer (T1). One A.F. transformer (Ti); on the front panel, all parts of the set are fastened to the wooden baseboard and, in most cases, wood-screws are used for the purpose. Two wooden strips are fastened along the edges of the base on the under side and these make it possible to conceal most of the wiring under the baseboard. 'l'he compactness of the receiver is another important feature. The front panel is 7 x 18 inches and the baseboard measures x 17 inches. The total weight of the set is less than ten pounds. FEATURES OF THE CIRCUIT Fig. 1 shows the complete circuit of the receiver. VI is the screen -grid R.F. amplifier tube, V2 is the detector tube and V3 is the A.F. amplifier tube. It will be noticed that the aerial circuit is untuned, and that an R.F. choke coil (L1), which is connected between the control -grid and the filament of the screen -grid tube VI, serves to couple the aerial circuit to the receiver without the necessity of a tuning control. l >3 is a special plug -in R.F. transformer with three windings, which couples the plate Fig. C. This top view of the receiver shows the exact arrangement of parts; and that on the upper side of the baseboard the wiring, brought through the holes seen in Fir. T

www.americanradiohistory.com 144 Radio News for August, 1928

111111101111111111111

V 31 32

C6 DL 2 1 c-++ CLIP ON TOP TERMINAL 33 (GRID) OF TUBE VI R3 RI

25 30 29 24 28 Fi G P^21 It i_

27 V3 F B+ 23 v--

Fig. 3. Layout and upper wiring of the Screen-Grid Short -TVave Receiver.

8 +135 V. RED - A- .B -.GND YELLOW 8+ 67 V. GREEN A+ BLACK

8 +90 V. MAROON ----- B+ 45 V BLUE --- FLEXIBLE LEADS TWISTED TOGETHER

18 16

15 I = r 17 - 13 I 12ct i 23 22 14 - _i I I 27

TO FRAME ( ROTOR I - - PLATES) OF VAR. CONDENSER C1

21 28 19 24

29 = 1 c- 1ti 1 30 frtil,._._-i 26W 25

IIIIIIIIIIIIIIIIi

Fig. 4. TViring below the baseboard. Each hole bears the same number here as in Fig. 3 above.

www.americanradiohistory.com Radio News for August, 1928 145

design throughout. Therefore, it is ideally 93" reception, but any 9. suited for short -wave efficient condenser of this capacity may be used. COILS REQUIRED The four short -wave coils illustrated in this receiver are manufactured units; how- 1N ever, home -made coils may be used, if desired. The following directions tell how DRILL T/I¿ 7/16 7/16" DRILL DRILL FOR SW FOR P4 FOR JI to build coils which duplicate electrically Ivg DRILL 3' the ones shown in the illustrations: 3 HOLES ~16 Each of the four coils is wound on a 3 DRILL --. 16-` 2 inches in diam- 8 roico ) piece of bakelite tubing Óq,0 Mb N eter. The smallest coil requires a form t-21 21' r------L-- 110 23 inches long, and this coil has a wave- T .. length range of 15 to 25 meters. The next 21' largest coil, with a wavelength range of 3Z 5/3p DRILL-, 2 HOLES. FOR BASEBOARD MOUNTING SCREWS 24 to 40 meters, requires a form 234 inches in length. The two largest coils, with Fig. 5. This drilling layout shows the exact location of all holes required for mounting the various parts on the front panel of this receiver. wavelength ranges of 37.5 to 65 meters and

One single -circuit jack (J1) ; and has an inductance slightly less than 2 One battery switch (SW) ; millihenries. It is much easier to buy this No. 62 222 piece of than to attempt its NEWS'. One vacuum tube, -type (V1); apparatus RADIO A set of large blue- the fan who wishes FREE Two vacuum tubes, 201A -type (V2 and construction; however, prints and a list of the to do so may find it interesting to experi- BLUE PRINT V3) ; parts used in the con - 1.7X-type; ment with coils of various sizes in this ARTICLE Three tube sockets, struction of the Screen - Two grid -leak clips for L1 and L3; position. Also, a resistor might be sub- Grid Short -Wave receiver dial, illuminated type; stituted for the choke coil, but the results One vernier illustrated here will be sent to any 7 as satisfactory. In One front panel, 18 x x 3/16 inches; would not be quite applicant. See that your name and 19 x 9 x inches; order to determine the size of resistor which One wooden baseboard, I address are written or printed leg - One battery cable, 7 -wire type; will give most satisfactory results, several ibly. Ask for Blueprint 1iTo. 62. One binding post; units of less than 100,000 ohms should be Connecting wire, screws, solder, etc. experimented with. The choke coil which Most of the parts mentioned in the above is used in the L3 position also fits in a 64 to 115 meters, respectively, are wound list are standard. However, the two R.F. grid -leak mounting, but this is a standard on forms 35 inches in length. choke coils require special mention. The unit, and any short -wave R.F. choke coil Each of the four coils has three separate R.F. choke coil L1 was especially designed may be substituted, if desired. windings. S, the secondary, is wound with for antenna coupling on short wavelengths, The tuning condenser specified has a spaced turns of heavy enameled copper and is the only one of its kind which has capacity of .000125 -mf. and is of the double - wire. P, the primary, consists of turns of ever been brought to the attention of the spaced type; this condenser is provided fine enameled wire wound between the turns writer. It fits in a standard grid -leak clip with pigtail connections and is of low -loss (Continued on page 184)-

1111111111111 WAVE PRIMARY SECONDARY TICKLER LENGTH HEIGHT DIAMETER (1 - 2) (3 -4) (5 - G) RANGE (A) (B) SIZE TURNS SIZE TURNS 512E TURNS 115.TO 64. 3Z s/8* 1 26 24 16 24 26 METERS , ENAMEL ENAMEL D.S.0 6S.TO 37.5 3 2." 26 13 14 2G 3 METERS ENAMEL ENAMEL 14 D.S.0 40.T024 z3/4' z° 2G 6 14 7 2.6 CONTACT METERS ENAMEL ENAMEL D.S.C. SCREW 2.5.TO15. 23/8' 2" 26 4 14 26 z -- 1111110111111111 _:EAD METERS ENAMEL ENAMEL 4 O.S.0 PHOSPHOR BRONZE, 1 114111W IMI- OR SPRING. BRASS NOTE: SLOT FITS SLOT CONTACT OVER LOCATING LUG. LUG ®1 CHECK HOLDS COIL UPRIGHT IN SOCKET.

:4100 4m DIMENSIONS FOR CONTACT SPACING REMAIN LUG CONSTANT FOR ALL COILS, AS SHOWN.

CHECK

PRIMARY TERMINALS 3 4 SECOI'IDARY " 53 6 TICK L ER a SLOT CHECK 1. 3.

Fig. 2. This diagram gives details for making the four short -wave 15 to 115 meters with a 125 -mmf. condenser, and also how to make plug -in coils which are required, in order to cover the waveband of the base receptacle, into which the coils are plugged.

www.americanradiohistory.com 146 Radio News for August, 1928 Better Direct -Coupled A. F. Amplifiers

Recent Results Obtained by Loftin and White from Experi- ments Directed to the Elimination of Distortion from Radio Reproduction

FEW radio fans are aware of the fact dio literature this word is used very freely, amplifier practically all the causes of dis- that there is a system of audio -fre- and the term distortionless amplification tortion have been removed. With man -made quency amplification which renders often is applied to the reproduction obtain- apparatus and adjustments, it is question- theoretically distortionless reproduc- able from any high- quality amplifier. How- able whether distortion is ever completely tion. It is true that amplifiers of this type ever, it is probably safe to say that there is eliminated, but, nevertheless, it may be re- are not common in broadcast receivers, but not a broadcast receiver in use today, out- duced to such a low value that it is beyond frequently they are used in laboratories by side a laboratory, which does not cause a detection by the human ear. engineers when making precision measure- measurable amount of distortion. Also, A comparison of the circuit diagrams ments. It is possible to construct such a of the various types of amplifiers in use device with modern apparatus, the prin -, shows clearly why all types of amplifiers, ciples having been known to the radio world with the exception of the direct-coupled for years. type, must cause some distortion, theoretic- The type of apparatus referred to in the ally at least, Fig. 1 shows the essential cir- above paragraph is the direct -coupled am- cuits of three popular types of amplifiers, plifier. In circuit arrangement it is very and Fig. 2 shows the simplified circuit of simple; but in its usual form it has a num- a direct- coupled amplifier. In Fig. 1, A ber of very undesirable features which is the circuit of a standard transformer - make it unsuited for use in the average re- coupled amplifier, B is the circuit of a receiver. It is rather difficult to adjust, and it sistance- capacity- coupled amplifier and C is very large in size, due to the number of is the circuit of an impedance- capacity- batteries which are required for its opera- coupled amplifier. In each case, it will be tion. However, it possesses one feature noticed, some piece of apparatus is used to which is not found in other types of am- isolate the grid of the second tube from plifiers; namely, when operated properly it the plate battery of the first tube; and it . does not cause appreciable distortion, and is this apparatus which introduces the dis- this feature makes it invaluable to en- tortion. In A an audio -frequency trans- gineers. former is used for the purpose; but it is Recently there was announced a very a well-known . fact that transformers do interesting electrical development which may not respond uniformly at all audio fre- be applied to direct-coupled amplifiers. quencies. In B and C a fixed condenser This development is a result of the research (C) is employed; as this performs better work of Edward H. Loftin and S. Young on the high frequencies than on the low, White, well -known for the now famous it may be said to cause uneven amplification. Loftin -White R.F. circuit. Their A.F. am- In Fig. 2 it will be seen that, in the direct- plifier system provides a direct- coupled am- coupled amplifier, a battery is used to plifier with its desirable features retained couple the plate and grid circuits of the and its undesirable characteristics either two tubes. As a battery has practically eliminated or modified so that they no no unfavorable frequency- response charac- longer present a problem. Therefore, it is teristics, this arrangement eliminates the now practical for the broadcast listener Essential circuits of three popular types of main cause of amplifier distortion. to enjoy the performance of a direct - A.F. systems. A, transformer coupling; B, resistance- capacity coupling; C, impedance - A complete theoretical description of the coupled amplifier. capacity coupling. improved direct -coupled amplifier previously mentioned, was presented at a recent meet- WHAT IS "DISTORTION ?" even in the best broadcast stations the trans- ing of the Radio Club of America in a Before continuing further with this dis- mission is distorted to sonie extent before paper read by the inventors, Loftin and cussion, it is necessary to explain the mean- the programs are placed "on the air." White. The following paragraphs contain ing of the word distortion. In modern ra- On the other hand, in the direct- coupled the more pertinent parts of the paper from which they are quoted.

PROBLEMS OF DIRECT COUPLING The discussion embraces some practical considerations in the design of direct -coupled, three -electrode, vacuum -tube systems for audio amplification and detection with amplification to take advantage of the possibilities in such systems for overcoming limitations inherent in the several other systems of audio amplification with and without detection. Audio -amplifying systems other than the direct -coupled type have undesirable frequency- characteristics, due to the react- ances and connections used to isolate each grid from the high potential of the preced-

ing plate circuit. . The -absence of such re- actances in the direct -coupled system, and other advantageous features, would have led to its general adoption long ago, had it not been for certain heretofore -uncured pe- This diagram illustrates the first steps taken by Loftin and 1í'hitc to bring into practical farm culiarities and economical drawbacks, briefly E.recht for the necessity of manual the desirable characteristics of direct -coupled A.F. amplifiers. outlined in connection with Fig. 2. adiustment- of the raid -bias batentiometer the circuit rs very satisfactory.

www.americanradiohistory.com Radio News for August, 1928 147

This figure shows a simple system of two VOLTAGES REQUIRED worked almost exclusively with the 240 - type tubes in these positions, there being tubes, directly coupled through a battery Fig. 3 is used to point out the funda- no higher mu tubes commercially available. BI, having a good frequency- characteristic mental steps by which we proceed to bring of amplification, but a goodly share of the into practical form the good points of the GRID -BIAS REGULATION peculiarities and drawbacks heretofore ex- direct -coupled system. Using, for example, necessity for manual con- perienced with such systems. Prior to our a 171 -type tube at V3 in the output circuit Except for the keep work, rather high voltages were usual; thus of a three -tube system, we find that the trol of the grid -bias potentiometer to of potential of battery B2 must be of such power tube V3 operating at the middle value as to bring the plate current of V3 the linear portion of the plate- current char- with different strengths of to below 5 milliamperes with the normal acteristic curve system of 180 volts of plate potential at B3; which incoming signal carriers, the voltage may be derived from a "B "- socket- Fig. 3 is a practical and satisfactory com- power unit. Therefore, the potential of B2 bined detector -amplifier system. The nor- 45- is about 5O% in excess of the normal grid mal use of the 171 -type tube requires a bias of the tube being used, or about 67 volt grid -biasing battery, and the potential volts for the 171 -type tube, which normally of battery B2 is but slightly in excess of requires 45 volts grid bias. this normal requirement. All of the batteries have extremely small current drain, R2 may be several The resistance of and can therefore be ordinary small dry - megohms to keep at a low value the current cell "B" and "C" batteries. drawn from B2. If the current is not al- I Icre a battery replaces the usual coupling device, which is the greatest cause of distortion lowed to exceed 50 microamperes, the com- The potentiometer permits altering the in most amplifiers. mercial types of dry "B" batteries will have grid bias of the first high -mu tube (VI) substantially "shelf- life" in this use. (See to alter the plate -to- filament resistance un- requiring undesirably large and expensive page 135 of this issue.) til the plate- current biases V2 in the right blocks of batteries for each stage, a draw- The potential of battery BI need not degree to cause in turn the right bias on back from both the economical and the exceed 41/4 volts. The resistance of Rl may the output tube to bring its operation at the correct. point on its current char- weight-and -space standpoints. be of the order of 1 megohm. Both Rl and plate- Tubes of the sanie type and make vary R2 are connected to the positive side of the acteristic curve for any strength of signal considerably in filament -to-plate resistance filament system. A potentiometer across carrier impressed upon the input of VI. and, since Fig. 2 shows clearly that the fila- the "A" battery is shown connected in the A carrier of the order of several volts is ment -to -plate resistance of tube VI deter- grid circuit of tube VI for controlling the sufficient to run the plate current of the mines in large measure the biasing effect negative grid bias for this tube. 'rubes last tube up to saturation. Adding negative of battery B1 on the grid bias to VI will bring this excessive grid of tube V2, we current down to the desired operating re- can state with assur- gion. Also, if tubes in positions VI or V2 ance that an adjust- are exchanged for others having different ment for a given tube filament -to -plate resistances, the potentiom- in the position of VI eter can compensate for any difference in which gives the cor- Vl 4111) V2 ID V3 j the adjustment of the system. n_ While potentiometer regulation is satis- 101111 JJJJJ 11311111111111111111111111111111111111111111111111JJJJJ sr r- factory to the skilled operator or for the Most efficient grid -bias laboratory, it does not constitute a desir- regulation is obtained when the filament current r able arrangement for popular types of com- of the 199 -type tube V4 .. mercial receivers. Here an automatic or (see also Fig. 4) is 34 milliamperes. If the plate i_Jr self -regulating effect is desirable to the , aa_ current of V3 is less than point of being essential, and the + fortunately this value, the potentiom- (1) -'l' result can be had simply eter R1 should be used both and to correct the condition. IL441 effectively. RI

AUTOMATIC . ADJUSTMENT rect operation of tube FIG.S Since the output or power tube is the V2 may be so far sufferer from the carrier -current effect and, wrong with a differ- at the same time, has sufficient energy with ent tube in the position V I as to saturate or VI and V2 should be of the high -mu type which to do considerable work, it is only block tube V2; a peculiarity affecting satis- and the higher the mu, the better. We have reasonable that it should be called upon for factory operation to an undesirable degree. Another difficulty in the system as shown in Fig. 2 is the effect of a high-frequency carrier-current impressed on the grid of tube V1, as must be done when the system is used as a combined detector -amplifier. Because of the normal rectifying properties of the tube, the high- frequency carrier-current changes the filament -to -plate resistance in proportion to the strength of the carrier or incoming signal; so that battery B1 alters the grid bias of V2 in proportion to the strength of the signal, thus altering the point of operation on the plate -current characteristic curve of tube V2; so much so for strong signals that the plate current of V2 may be blocked. This feature re- stricts the system of Fig. 2, if unmodified, for use as an audio amplifier; if employed for radio reception, it must be preceded by the usual detector system and sonic forni of audio- reactive coupling, which arrangement would introduce in the input portion of the system precisely those undesirable frequency effects of other systems which An entirely practical direct -coupled amplifier circuit in which the 199-type tube V4 automatically we have avoided by our modified direct - regulates the grid bias. Vl and V2, 240 -type tubes; V3, 171 -type tube; Rl, G25 meg. ; R2, 2 meg.; R3, 0.75 meg.; R4, 4 meg.; R5, 1 ohm; BI, 4.5 volts; B2, 67 volts; B3, 180 volts; coupled system. B4, 22 volts; and Cl, .002- to .006 -mf.

www.americanradiohistory.com 148 Radio News for August, 1928

aid. Quite a large negative bias on the first tively operates in the system of Fig. 4 at racy in commercial high -value resistors, tube is required to overcome the biasing such low temperature that its thermal in- with the result that the actual values of effect of a strong carrier; but the large ertia is sufficiently high not to follow even purchased resistors may differ as much as plate current of the output tube is ideally the lowest audio frequencies; as a result, 100% from the markings. Also, the actual adapted to aid in bringing about this com- we find no evidences of signal and hum - values of resistance may vary widely with pensating bias. However, this output -tube current feed -back whatsoever. different current values through the de- plate current must not be so used as to The over -all sensitivity of the system is vices. The resistors used should be meas- introduce an undesirable feed -back effect, excellent. The effect commonly known as ured in a way employing only a few micro- either in the matter of desired signal cur- detector overloading is not present even up amperes of measuring current, as they are rents or hum currents if a "B "- socket- so used to 20 volts of radio- frequency input; despite in the system. power unit is used. the fact that the first tube has only four The 199 -type tube operates best for the The arrangement shown in Fig. 4 is a volts of plate potential. Because oft this purpose of regulation with a filament cur- most satisfactory solution of the desirable low plate voltage, microphonic effect's are rent of about 34 milliamperes. If the plate - self -regulating feature, and seems to owe not possible, and therefore acoustical feed- supply current differs from this optimum its success to the filament characteristics of back howling is never encountered. Re- current value, compensation is readily had the 199 -type of tube used in position V4. generative oscillation cannot take place. by an arrangement shown in Fig. 5. The grid and plate electrodes of this tube In this figure a high- resistance poten- are tied together to make it in effect a two - VALUES OF RESISTORS tiometer (R1) is connected across the fila- electrode tube. The filament is connected The types of tubes and values of elec- ment- supply system, with slides with of output the so con- in series the plate circuit trical elements for a practical assembly of nected around the filament that adjustment tube V3, so that the filament is heated by permits of supplying additional heating cur- the plate current. Battery B4 is connected rent from the "A" battery if not enough in series with the filament -to -plate (and plate current is available, and shunting path of V4 in order to bias, with the grid) away a portion of the plate aid of resistances and R2, the of current if it RI grid exceeds the desired amount. 171 negatively. Obviously, the lower the filament -to -plate resistance of V4, the greater will be the negative biasing effect ANOTHER ARRANGEMENT of B4 on VI; and, since this filament -to- Fig. 6 shows an interesting extension of plate resistance decreases with the increase the system, recommended potential and elec- of the temperature of the filament, and trical constant values being as given in the may vary between almost infinite value with caption. In this arrangement the 199 -type a cold filament and a comparatively low tube, V4, is used in the dual capacity of value with a very hot filament, the desired regulator and input (detector) tube, being View of the wiring under the baseboard in lÍr. self -regulation is possible by having the White's direct -coupled amplifier, shown also used as a three -electrode tube in the latter plate current of the output tube control the below. 125 is a 1 -ohm filament- ballast resistor. capacity. This arrangement is capable of heating of the filament of V4. a sensitivity considerably in excess of the ordinary grid -leak detector and two -stage, The lube -space resistance varies inversely the system of Fig. 4 are listed in the cap- as the square of the filament current, and transformer-coupled audio system; probably tion beneath this diagram. In assembling a bit too much amplification for ordinary consequently changes greatly with small this apparatus, great care should be taken changes in plate current of the output tube. uses, but it is an easy matter to reduce the to keep distributed capacities low; because amplification to any desired degree. Therefore, carrier waves, or discrepancies high frequency persists throughout the in tube impedances, can be nicely compen- system and an excess of distributed capacity In the arrangement of Fig. 6, the amount sated for, and the plate current of the out- wili attentuate the energy to an undesirable of plate current flowing through the fila- put tube remains very close to its rated degree. The values of the resistors should ment of V4 determines the bias of battery value. be held within 10% of those given, which B1 on tube V1 as before, and thus regu- Although, for general normal operation, is a feature requiring special attention. The lates the plate current of V3. Carrier - the filament of the 199 -type of tube oper- resistors are of high order. Heretofore currents impressed upon the grid circuit of ates at quite a high temperature, it effec- there has been no need for particular accu- V4 have the previously- discussed tendency to change the initial bias of the system; so that regulation is still desirable. In this arrangement the filament current of the 199 -type tube may range from 36 to 40 milliamperes, the average of 38 being prefer- able. Increasing the potential of battery BI above the 9 volts indicated tends to bring in microphonic effects, which, with the aid of the very large amplification, may give acoustical feed -back howling. Because of the extreme sensitivity of the system, however, it is not necessary to go beyond this potential. In this modified arrangement the values of the resistors are not nearly so critical as in that of Fig. 4, and may differ from those given by as much as 100% or more. If the grid circuit of V4 is connected to one side or the other of the filament sys-

tem, the resistance of the filament acts V as a feed -back element because of the plate current flowing there and, with the high amplification, considerable distortion may result. It is possible to overcome this in large measure by using a choke- and -condenser coupling (LC) to the loud speaker, as shown, to shunt and block out signal currents from the filament of V4. To make the system applicable to all forms of loud- speaker coupling, it is desirable to connect a fixed resistor R4 of about 1,000 ohms across the filament and connect the grid Tins direct- coupled amplifier, constructed by S. Young White, uses the circuit shown in Fig. 4. The parts have the same values as those specified in the caption cf that illustration. circuit to about the center of this resistance.

www.americanradiohistory.com Radio News for August, 1928 149

In this direct- coupled amplifier circuit the 199 -type tube V4 is and R2, t meg.; R3; 4 meg.; R4. 1,000 -ohm potentiometer; R5, ised in the double capacity of grid -bias regulator and input (de- filament rheostat; B1, 9 volts; B2, '22.5 volts; B3, 67 volts; B4, 180 teeter) tube. V1 and V2, 240 -type tubes; V3, 171 -type tube; R1 volts; "A," 6 volts; L and C, output filter. It is very sensitive.

PHONOGRAPH APPLICATIONS limiting arrangement. If an excessive sig- present time, it does not seem opportune to nal is encountered, it will not reproduce go into this phase of operation; though Any of the systems can be used as phono- the signal in proportion to the input it may be remarked that there are features graph pick -up and other audio amplifiers, strength beyond a certain point, but will of the system, co- related to the non- micro- as well as detector -amplifiers for radio. to indicate operation distort sufficiently that phonic feature, which tend lo lessen hum '['he arrangement of Fig. 6 is a bit too of the input volume control is needed. sensitive for phonograph work; though in The systems have been operated most sat- difficulties arising in other systems. Con- a combined radio and phonograph system isfactorily with alternating- current supply sidering the high amplification of the sys- the pick-up can be connected across the throughout, using high -mu heater -type tems at 60 cycles, the small hum encount- input of tube VI. The system of Fig. 6 has tubes.. Since commercial high -mu alternat- ered in work so far carried on has been the further effect of acting as a signal- ing- current tubes are not available at the most gratifying.

The Capacity of a Condenser Combination Arrangement By Leslie R. Jones

EVERY experimenter has around his Where C = equivalent capacity of the arrangement, the capacities of each are workbench an assortment of con- combination, and C1, C C3, C, = the re- simply added together, giving the resultant densers, both fixed and variable, which may spective capacities of each of the series capacity. oftentimes be utilized to advantage. condensers. Obviously, if all the condensers Many times during the process of experi- are of the same capacity, the capacity of C= C1 +C2+C3+C, menting, condensers of odd capacities may one divided by the number used gives the The following table shows the resultant be required and, as a rule, a simple com- effective result in series connection. of two capacities in both series and paral- bination of one or more of these "extras," On the other hand, for each parallel lel arrangements. either in series or in parallel, will save the expense of new ones. Also, as their use is usually but tempo- Condenser capacities Resultant capacity (mf.) Condenser capacities Resultant capacity (mf.) rary, that is, only for an experimental test, in microfarads Series Parallel in micro farads Series Parallel this saving and convenience is worth while. .0001 and .00025 .000071 .00035 .0005 and .001 .00033 .0015 .0001 " .0005 .000083 .0006 0005 .002 .0004 .0025 Condensers having capacities such as .0001 " .001 .000090 .0011 .0005 .005 .00045 .0055 .0001, .00025, .00115, .001, .002, .005, .006 -mi- .0001 .002 .000095 .0021 .0005 .006. .00046 .0065 crofarad, are those used in standard hook- .0001 .005 .000098 .0051 .001 .002 .00066 .003 needed, .0001 .006 .000098 .0061 .001 .005 .00083 .006 ups and, when special values are .00025 .0005 .00016 .00075 .001 .006 .00085 .007 these may easily be "built up" by combin- .00025 .001 .0002 .00125 .002 .005 .0014 .007 ing those on hand according to the reference .00025 .002 .00022 .00225 .002 .006 .0015 .008 table on condenser combinations given here. .00025 .005 .00023 . .00525 .005 .006 .0027 .011 .00025 .006 .00024 .00625 The formulas for working out these combinations are not difficult, but oftentimes our work will not permit enough time to The tables below give the resultant ca- densers of the same capacity, in series and con- in parallel. he used for this calculation. Hence this pacity for one, two, three and four reference table which gives readily, at a glance, the desired combinations needed. 2 condensers in: 3 condensers in: 4 condensers in: For any odd combinations not included Capacity Series Parallel Series Parallel Series Parallel here, this formula will be useful to compute .0001 .00005 .0002 .000033. .0003 .000025 .0004 the resultant capacity of any combination .00025 .000125 .0005 .000083 .00075 .000062 .001 of series condensers: .0005 .00025 .001 .00016 .0015 .00012 .002 .0005 .002 .00033 .003 .00025 .004 1 1 .001 = + + 1 .002 .001 .004 .00066 .006 .0005 .008 .005 .0025 .010 .0016 .015 .00125 .020 /1' 2 .018 C C1 . C C3 C, .006 .003 .012 .002 .0015 .024

www.americanradiohistory.com 150 Radio News for August, 1928

Cutting In or Out the Last nects the primary of the second trans- The illustration shows that a fishing rod Audio Stage former in the plate circuit of the first tube; of standard design is used as a mast for second, it connects the filament of the the aerial, and that the aerial is coiled THE above diagram presents wire a circuit power tube with the battery, and third, it up on a fishing reel when not in use. The for switching from one to two stages disconnects the loud speaker from the first support for the other end of the aerial is (or from two to three) of audio amplifi- tube, and connects it to the output filter. provided by a hook, fastened to the end of cation, which may be applied to any stan- The use of a jack dard receiver. A four-pole, double-throw switch to control the operation of an audio jack switch is employed for the purpose, amplifier has several advantages over the use of jacks, which is AERIAL , INSULAORT and every desired change, including -- that the most common of controlling the filament of the last -stage method. When a switch is used, the loud tube, is accomplished with one movement. speaker may be permanently connected to binding posts, and it ;I `HY RK A glance at the circuit diagram will show WIRE WOORNALDON HOOK TO is not necessary REEL- that the amplifier used to illustrate the to change a plug from one -- THROW OVER jack to the next. Also, with a switch, the LIMB. switching system employs a standard two - wiring is stage, transformer -coupled A.F. circuit with no more complicated, yet the mechanical arrangement is much more com- a power tube and an output filter in the BARE AERIAL pact. Lastly, it is possible to change from E WOUND last stage. Rheostats are employed for ON REEL one to two stages of adjusting the filament current of each tube; amplification, or vice versa, much more easily quickly; but this is not an essential part of the and as it is necessary only to turn a knob mounted on LEAD TO SET. circuit, as filament -ballast units could be the front panel of the receiver. 4- POLE substituted without affecting the results. LASHED TO LEAD TO SET. Coleman, Sutton. TREE, CAR OR When the switch is set in the lower posi- OTHER DRY "UPPORT tion (No. 2), only one stage of amplification is connected. It will be noticed A stout fishing rod, a reel, copper wire and that insulator are the essential parts of a simple the switch disconnects the primary of the A Quickly- Erected portable aerial which is ideal for camping and second transformer, and connects the loud Compact, automobile trips. speaker in the plate circuit of the first tube. Aerial for Tourists Also, the switch opens the filament circuit N excellent aerial for portable use is the wire. When erecting the aerial this of the power tube, thus saving battery cur- illustrated in the accompanying dia- hook may easily be caught over a project- rent when the last stage is not being used. gram. It is very compact to carry, yet it ing limb of a tree. When set in the upper position (No. 1), is an entirely practical arrangement. It The parts required for this portable an- the switch connects the last stage of ampli- may be erected almost anywhere in a very tenna are as follows: fication with the loud speaker. To do this, few minutes' time, and its length may be One wooden, jointed fishing rod of good it performs three operations: first, it con- varied as desired. length; One all -metal fishing reel; One hundred feet of No. 20 bare- copper wire; One aerial insulator; LOUD t o One wire hook; SPEAKER Cord to fasten hook and insulator, and to mount mast. The fishing SOFT rod must be of wooden con, struction because it is used as an insulator 1ST. AUDIO at the lead-in end of the aerial. It should B+ be, preferably, of the type used for salt- -1ST. AUDIO water fishing, as these rods are much o 2ND. AUDIO stronger than the fresh -water type. An C- all -metal fishing reel is specified because o 2ND. AUDIO contact is made to the frame of the reel, INPUT B+ 2mf. by the wire which connects the aerial with 30 HENRIES the receiver. If a wooden reel were used, A.F. CHOKE' it would be more difficult to connect the aerial with the set. In preparing this aerial for use, the first step is to solder one end of the No. 20 bare- copper aerial wire to the spool of the fishing reel. Next, wind approximately 95 feet of the wire on the reel. The five feet of wire which is left over is used for Ai- 6 V. a lead -in; and this is connected to the frame TO FILAMENTS OF of the reel by loosening one of the set PRECEDING TUBES INTO OHMS 10 OHMS screws on the shell of the reel, inserting A- B- the wire under the head and then tighten- SWITCH. ing the screw. A three -foot length of the C-F cord may now be used to connect the aerial insulator with the wire hook. After this has been completed the aerial may be A four -pole, double -throw jack switch is ideal as a stage -control device for an audio amplifier. packed and it is ready to take on a motor In the left position only one A.F. stage is in use; while turning the knob to the right connects the second stage. trip, or to camp.

www.americanradiohistory.com Radio News for August, 1928 151

When it is time to erect the aerial the apex to be realigned so that the driving rod assembly will be found very simple. First, on the unit will not be bent. a nro NEws has received from read- car a distance, equal to the For best operation the linen should be stop the at ers so many - letters and ballots required length of the aerial, from some drawn as tight as possible without splitting requesting more "Wrinkles" that it convenient tree or pole. Next, assemble it. The method illustrated here will pro- has been decided to re- establish the the fishing rod, attach the reel arid thread vide a means of making adjustments with- department. A year's subscription to the wire through the leaders. The insu- out the bother of re- setting the unit. The RADIO NEWS will be given in compen- lator may now be attached to the end of large diaphragm is mounted rigidly on a sation for each accepted item. If the wire and then the hook may be caught strong wooden frame, as shown. The small the author of the wrinkle is already - a in position on the tree. The fishing pole diaphragm is mounted free and is fastened subscriber, his subscription will be ex- may now be strapped to some part of the to the supporting frame by four long bolts. tended one year or he may accept a automobile, and the lead -in wire connected Wing nuts are provided on the back, or a one year's subscription to Science and with the aerial post of the receiver. -L. B. screw driver is used to make adjustments. Invention or Amazing Stories, both Robbins. Each of the bolts should be turned the same published by the Experimenter Pub- distance, in order to keep the frames paral- lishing Co. lel. The unit is mounted on the frame supporting the small diaphragm. In this A Good Screen -Grid Clip way, the relative positions of the unit and kept the the tight diaphragm tends to vibrate MAKING a connection to the control - the apex of the small cone are since its surface, rather than at the grid terminal of a screen -grid tube same, even though the position of the apex over entire apex. 'l'his naturally displaces more of the often presents a problem to the home con- of the cone is changed. of this air in the room and, since the larger vibrat- structor. This terminal is a cap mounted When you make a speaker type, it is advisable to "dope" the linen on both ing surface tends to reproduce the lower sides. The linen is not equally absorbent notes better, a general improvement is at all points over its surface, and the use noticed. C. W. Palmer. DRILL HOLE of "dope" on both sides tends to keep the _---- entire coat even. This prevents, to a certain extent, the formation of ridges and bumps which mar the appearance of the A Phone Cord Reel for DX Fans FILE SLOTS CUT OFF HERE speaker and also affect its operation. The washers used to clamp the apexes of THERE are still a great many radio the two cones together often cut the linen fans who use headphones for receiving at the point where the strain is greatest. short -wave programs as well as DX broad- This can be prevented, very often, by cor- casts, and a majority of these listeners still continue to register the old complaint regarding the use of phones; namely, that SHELL -TYPE CLIP WITH in II; WASHERS the phone cords are either twisted or ATTACHED BINDING POST FILED SO THAT the way. The writer has been troubled -type and, as a result, he for 222 I by this many times An excellent termú,al clip a SMALL THEY WILL NOT (screen -grid) tube may be made from an empty built a device which keeps the phone cord cartridge shell, with the aid of a file and pliers. DIAPHRAGM CUT LINEN at minimum length at all times. The draw- ì3 construc- must ing on this page gives complete on the top of the tube, and connection tional details; and from these it may he with a clip. With many of be made to it seen that the window-shade roller which the clips which used for the purpose IIIIIII( are is located under the radio table reels up enough to insure the tension is not great the cord when it is not in use, or provides good contact at all times, and often the set UNIT exactly the length of cord required when becomes noisy for this reason. receiving. The accompanying drawing shows a sim- \ BOLTS When constructing a phone -cord reel of ple way to make a good clip for screen -grid LARGE this type, the first step is to remove the tubes from an empty cartridge shell. Any DIAPHRAGM II' copper peg and washer from the solid end shell between 30 and 45 calibre may be used of the roller. Now cut the roller so that for the purpose; but the cartridge should be LINEN it is short enough to fit lengthwise under fired before any attempt is made to use the These drawings show two simple kinks for building the radio table. In order to make contact shell. First, saw or file off the shell about a. linen- diaphragm loud DIAPHRAGMS speaker. with the phone cord when it is wound on three- quarters of an inch from the primer the roller, a swivel bearing with a double file (closed) end or base; and then four contact is required; and for this purpose slots at right angles, making four prongs. rectly shaping the washers. The accom- a radio jack and plug may be used. The Next, with a pair of round -nose pliers, bend panying illustration shows how these wash- plug selected for the purpose should have the tips of the prongs outward a slight dis- ers should be filed; the rounded a large, hollow rubber cap, and the jack will tance. Slightly below this bend the pròngs surfaces prevent the linen from being cut, and the be of the single- circuit type. In fastening should be bent inward sufficiently to fit the shape tends to enlarge the circle of strain, the plug to the end of the roller, the copper terminal snugly. To complete the clip, en- peg and washer is used as illustrated. How- large the hole through the base to take the so that a greater amount of linen holds the weight. ever, it is first necessary to drill a V4-inch machine screw of a binding post.Joseph The suggestions outlined above will often on 178) 1V. Wild. (Continued page increase the volume and quality of a speaker of this kind to a remarkable degree; BLOCK TO WHICH Hints on Linen -Diaphragm JACK IS FASTENED Speaker Building 4 HOLE MUST of the linen used for the new linen -diaphragm loud speakers will stretch considerably after it has been "doped" and tightened on the frame. For this reason it is advisable to arrange some END OF ROLLER LEADS FROM JACK way of tightening it again without the WITH SPRING TO OUTPUT OF SET necessity of rebalancing it, with relation to the driving rod of the unit. Most of the speakers are equipped with a bolt- and -nut arrangement which allows the two dia- TABLE TOP phragms to be separated in order to tighten them; but this method usually requires the A window-shade' roller, fastened under the radio table he the manner indicated above, will keep phone cords out of the way when not in use, yet they are easily pulled out when needed.

www.americanradiohistory.com Radio News for August, 1928 The Zero- Reactance Plate Circuit Discussion of a System for Obtaining Maximum Efficiency of Energy Transfer in a R. F. Amplifier over the Whole Wave - Band by the Use of Variable Condensers in the Primary Circuits By Sylvan Harris

LTHOUGH hardly anything has been of such a load is, not merely that it does the transformer, and the capacitive react- written, at least in the popular ra- not add to the amplification, but that it ance is furnished by the condenser. When dio journals, concerning the "zero - actually causes the circuits to absorb power. the capacitive reactance is less than the inductive reactance, the net reactance is reactance plate circuit," thoughts REDUCING INDUCTIVE REACTANCE on the subject have been in the minds of inductive; when the capacitive reactance is many radio engineers for a long time; and In the circuit to be described, a variable equal to the inductive reactance, the net re- many of these engineers have tried again condenser is connected in series with the actance is zero; and-when the capacitive re- and again to find some means utilizing this primary of the R.F. transformer and the sistance is greater than the inductive re- principle in the radio- frequency amplifier. plate of the R.F. amplifier tube, as shown actance, the net reactance is capacitive. The reason for the desire to employ in in Fig. 1; and this condenser is controlled the R.F. amplifier a system such that the simultaneously with the tuning condenser R.F. TRANSFORMER DESIGN reactance in the plate circuits of the tubes of the succeeding stage. ' (In the figure There are several reasons for desiring to is zero is quite evident to those who have the batteries and battery wiring have been avoid regeneration which we will not dis- any knowledge of the behavior of electron omitted for simplicity.) The reason for the cuss here, as they have lieen discussed quite tubes. For technical information on the insertion of the condenser in the plate cir- lengthily at other times. (See page 1234 of subject of the effect of plate load on the cuit has to do with the first case mentioned May RAnfo Nzws, "Regeneration "). But operation of the tube readers are referred there is one reason which has not been here- to a paper by J. M. Miller (Scientific Paper tofore brought out with any degree of No. 351, of the Bureau of Standards.) For emphasis, and this is that, on account of the those who do not wish to go into the theory tendency of the tube to oscillate, it was not of regeneration, it will be sufficient to state thought possible to use very efficient R.F. that there are three types of load which we transformers between stages. might have in the plate circuits; and the It is well known that the amount of power action of each of these is different. which can be transferred from the primary The first case is that of an inductive load to the secondary of an R.F. transformer -exactly the kind of load we always have becomes greater as we add to the primary in radio- frequency amplifiers. The primary turns. But, as we add to them, we also of the radio -frequency transformer, aided increase the primary inductance; and before the secondary via the soup- The fundamental circuit shown above controls by the effect of the net reactance of the plate circuit simul- long we have the circuits oscillating, which ing, furnishes an inductance in the plate taneously with that of the grid circuit. of course does not help out in our design. circuit. As a result the tube is caused to The interesting part of the matter is that regenerate, by virtue of this inductive plate above. When the inductive load in the experimenters did not add enough turns, load; the tube furnishes power to the cir- plate circuit is great enough, there will not as we shall see. Let us see first what hap- cuits and a feed -back current is established be merely regeneration, but oscillations will pens to the primary inductance of an R.F. which aids in the amplification of the signals be established in the tube circuits. But transformer as we increase the primary being received. (The reader must remem- by adding a capacitive reactance (in series) turns. ber we are not considering circuits wherein to an inductive reactance the net inductive Suppose we start with a certain number a neutralizing scheme is employed.) reactance is reduced. So, by properly ad- of secondary turns on our transformer- The second case is that in which there is justing the constants of the plate circuit, just the right number to enable us to tune no reactance at all in the plate circuits of the net inductive reactance can be kept over the broadcasting range with a certain the tubes. In this case there is no regen- slightly below the value required for oscil- tuning condenser. Then let us wind turns eration -the tube circuits neither furnish lations to occur; and consequently great on the primary. At first the self- inductance vor absorlJ power, and consequently the amplification can be obtained throughout of the primary is small, and likewise the plate- circuit load produces no effect on the the whole range of broadcasting . fre- mutual inductance between the primary and amplification, except so far as the voltage quencies. secondary windings is also small; the pri- step -up in the R.F. transformer is con- In order to make this clearer-for we mary will have little effect on the second- cerned. This case is the subject of this shall be very much concerned about it in all ary, and rice versa. But, as we keep on article, só we will leave further details that follows -we may put the idea in the winding turns on the primary coil, we find until later on. form of a formula; viz.: that its self -inductance increases steadily The third case -that in which the load Net reactance - inductive reactance = and likewise the mutual inductance in- in the plate circuit is capacitive -is of no capacitive reactance. creases. What happens to the secondary particular interest at this time; as the effect The inductive reactance is furnished by inductance? The effect of the mutual inductance is to make the secondary act as if its self - inductance were less than it actually is; so that we should soon find, after winding enough turns on the primary, that we could no longer tune over the broadcasting range with our condenser. We would find that we could tune to the short waves well enough, but we would be shy on the longer waves. Then, if we tried to add turns to the secondary to bring us up to the longer waves, we would find that we could not rn-"'r"I I i ri'I tune down to the shorter waves. At any rate, you see that the tuning range would be FIG.3 cut down. This is an old, old story; as we all know that there have been many sets Schematic diagram of the R.F. and detector circuits of a two- control receiver embody - on the market that could not tune over the wavelengths. ing this principle. ' If A is out of tune with B, oscillation may result. complete range of broadcast

www.americanradiohistory.com Radio News for August, 1928 153

Now it must be understood that the the primary circuit is in resonance with the secondary has a similar effect on the pri- incoming signal frequency, its net reactance mary. If we should measure the inductance to that frequency is zero. In order to apply of the primary by itself, and then measure o the principle to an R.F. amplifier, all that ID it when coupled to the secondary, we would LI L2 we have to do is to replace the generator find that its inductance in the second case E by the voltage at the plate of a tube, C1 G2 is less than it is in the first case. In other and to connect the condenser C2 across the input to another tube. We have done this words, the effect of the mutual inductance FIG.2 is to make the "apparent" inductance less in Fig. 3, which shows a three -stage am- than the actual inductance. There will be a maximum of current flow, plifier and detector, with two controls. We at any frequency, when Ll equals L2 and Cl have illustrated a two -control circuit in PROBLEMS ENCOUNTERED equals C2. order to point out a very interesting matter, However, as we add turns to the primary, thereby increasing the coupling, we find transformer which has a coupling of 100 CIRCUIT PECULIARITIES that our transformer becomes more effi- per cent; one resonance frequency occurs It is clear, on comparing Fig. 2 with cient; i.e., it can transfer more power from in the band where we want it to occur; the Fig. 3, that, when a signal of a certai,, the primary to the secondary as we increase other resonance frequency is relegated to frequency excites the antenna, and all or the coupling. It would seem that, if we kept infinity (zero wavelength). the condensers are tuned to resonance, tho reactance in the circuit of each tube on adding turns, we might get to a point DESIGN OF THE CIRCUIT plate where the mutual inductance is equal to is zero. Take for instance the second stage: winding, We have now sufficient information to its plate circuit is always tuned to exactly the self -inductance of the primary react- and the apparent inductance of the primary be able to understand how the zero- the same frequency as its input circuit. works out. In Fig. 2 would become zero, the condition for which ance plate circuit Consequently, the reactance of the plate have a simple A.C. circuit, consisting we are looking. Unfortunately, however, we circuit to the frequency that could excite coupled We the primary self -inductance increases more of two tuned circuits together. the input circuit would be zero. As a re- have inductance Ll equal rapidly than the mutual inductance; so that made the primary sult, there would be no oscillations estab- inductance L2 and, like- this cannot be. However, what remains of to the secondary lished in that stage, nor would there be capacity Cl equal to the the primary inductance can be nullified by wise, the primary any regeneration. capacity C2. Under such con- a series condenser such as we have shown secondary On the other hand, let us consider the ditions, no matter what the frequency of in Fig. 1. first stage, which has its condenser inde- voltage E may be, we shall always have As we keep on adding turns, however, we the pendently controlled. Suppose we start out flowing through the soon begin to encounter another effect a maximum of current with this condenser tuned the same as the - device I, located in the one which is well known to hams-and that current -measuring others. There would be no regeneration in of inductances or is that we are soon able to tune in the secondary. If either the the first stage. However, suppose we tune the same station at two different settings of capacities should be changed, secondary condenser A to a higher frequency (shorter have we the tuning condenser. This is known as current would decrease. What wavelength) than the other condensers. The the "double- resonance effect" of R.F. coup- done? plate circuit B would then be tuned to a ling circuits. At first the humps or reson- We have made the two inductances equal wavelength greater than that of a signal to each other, so that the apparent primary ances are close together, so that the set which could excite the tuned circuit A. In is equal to the apparent second- seems to tune broadly; but later on, as we inductance other words, there would be inductive re- inductance. In other words: increase the coupling, we can clearly dis- ary actance in the circuit B when A is tuned tinguish the humps, and can make them as L1- M =L2-M lower than B; and, as a matter of fact, far apart as we please. In fact, the writer Then the secondary capacity C2 nullifies oscillations will be established when A dif- at one time constructed a receiver with the apparent secondary inductance, and the fers but slightly from B. such close coupling in the R.F. transform- primary capacity nullifies the apparent pri- It is clear then, and this is very inter- ers that the receiver became automatically mary inductance. The secondary circuit esting, that when all the circuits are exactly a double -range receiver, dividing the broad- is therefore in resonance and the primary is in tune with each other, there is neither casting band into two almost equal bands; also in resonance, simultaneously. The two regeneration nor oscillation; but when any so that a station of 250 meters wavelength capacities have to be always equal, so we one of the circuits is out of tune we can would tune in at almost the same setting must have two identical condensers rotating have both regeneration and oscillation, de- of the condenser as one of 500 meters. on the same shaft. pending on how far out of tune the circuit (Ramo NEWS for March, 1926, "An Auto- The mutual inductance is made as large is. As was said before, the input circuit matic Double-Range Receiver. ") as possible, so that one of the resonance need not be out of tune with the output However, it is possible to make the coup- humps will be as far as possible below very much; as it has been found that the ling so close that one of these resonances the range to be covered. By employing such influence of the antenna circuit, through is outside of the range of broadcast wave- close coupling we are making our trans- the loose coupling M, is sufficient to throw lengths. This is what happens in an autoformer a very efficient one. Moreover, since (Continued on page 164)

Diagram of a receiver designed by the author, in which the zero- by the use of a seven -gang condenser. The primaries have the same reactance principle was employed in the three R.F. plate circuits, number of turns as the secondaries, which are smaller than usual.

www.americanradiohistory.com 154 Radio News for August, 1928 Learning the Code Multiplies Radio Pleasures Enjoyment of Short -Wave Reception is Increased a Hundredfold by a Few Lessons which Enable the Listener to Understand the Secrets of the Air By C. Walter Palmer

want to have more fun with code in order to know which station is be- more than one dollar. Obtain a telegraph that short -wave receiver? Has ing received. It must be remembered that key, buzzer, a 4% -volt you "C" battery and a °some of the thrill of listening to any change in the aerial, coils and other .001 -mf. fixed condenser. Obtain a key with D short -wave broadcast stations worn apparatus in the set will change the cali- rather heavy contacts and a good solid off? DX music on the short wavelengths bration and necessitate recalibrating. lever. One of the regular telegraph keys, ic, only a small part of the enjoyment that which can be HOW TO BEGIN obtained for a very small you should get with your set. In order to amount, will be ideal for this purpose. A appreciate it fully, you must listen to every- The apparent difficulty in learning the key of this type will help you to send evenly. thing that can be heard. Why not learn the code usually discourages fans; but those Buy a buzzer with a high -pitched note if code? It is not very difficult. In fact, you who "brave the storm" are usually sur- possible; since this will more nearly match will be surprised how much progress you prised at the progress that can be attained the tones produced by continuous -wave can make in a short time. by a few hours' concentration in memorizing transmitters than does the ordinary low - Everyone who has operated a short -wave the code letters and learning the sounds pitched buzzer. The only other apparatus set has heard the amateur and commercial of the letters. There are several methods necessary is a pair of headphones, which code stations -and may have been annoyed which may be followed in learning the code, you probably already own. by them. These signals, however, have an although the easiest is probably that in If it is at all possible, get some amateur attraction that can be realized only by those which two or more persons practice in the neighborhood to send to you at first; who have listened to, and communicated together. with the operators of these stations. There First you must memorize the code letters. are over 20,000 amateurs in the world at Do this by pronouncing. the symbols as present and many of them can be heard at "dit" and "darr" rather than "dot" and any time on the various short -wave bands "dash," so that you will learn the sound of BUZZER PHONES allotted to them. It is true that a small the signals rather than the way they look percentage of these amateurs have equipped in print. Do not visualize the letters as their transmitters with modulating systems "dash, dot, dot, dot" for "b," etc. ; but asso- so that they can transmit voice; but they ciate the sound of the complete signal with °---1ili are comparatively rare. The reason for this the letter. Master a few of the letters every KEY BATTERY is that phone transmitters cannot be heard day by repeating the sound of the symbols as far as continuous waves and the attrac- until the complete alphabet is known. A simple circuit for code practice, which may tion is not nearly as great. Then get a friend to "review" you until be used as shown in the picture below. In order to get the greatest enjoyment you can give the correct symbol without from radio it is necessary to understand hesitating. Practice until you know the so that you will get acquainted with the all that is going on. Broadcast reception sounds as letters without thinking of the "swing" that is used in sending. However, covers only a very small part of this; since dots and clashes. Do not expect to learn there is another method equally effective the thrill of hearing far -distant broadcasting the complete code thoroughly in one day. if you do not know anyone who can send soon gives way to a search for better qual- Take your time and learn a few letters each for you; this will be explained later. When ity, and it is usually only a matter of a day so that you will know every one. It sending slowly, make the letters clear-cut few months or a year before the novelty is a good plan to review the signals you and use wide spacing between the letters to wears off. learned the previous day before continuing attain the slow rate. When practicing, do Another advantage of learning the code on new ones. As soon as you have memo- not try to send too fast, since this will cause is that there are a number of stations which rized the code, you should put it to practical the signals to be choppy and uneven. are controlled by quartz crystals and other use. Make a buzzer practice set as shown HOW TO SEND devices, so that an absolutely constant fre- on this page. quency is maintained. This is of particular PRACTICING When using a key, place it about eighteen service in calibrating wavemeters and re- inches from the edge of the table in a line ceivers; but it is necessary to know the The complete outfit will not cost much with your arm. Adjust the spring on the key, so that there is a slight tension when it is pressed down. Leave a gap of about one -sixteenth of an inch to give a free swinging motion. Use rather heavy spring tension at first, so that the spacing will be kept

steady. Hold the . key lightly with the thumb resting on one side of the knob and the first and second fingers on the top. Bend these two fingers slightly and keep a light grip on the knob. Do not let the other two fingers touch the key. You will see the correct manner in the illustration reproduced here from a photograph. Use a steady wrist motion, so that your wrist and fingers will not become tired. The main thing to remember is to keep your fingers relaxed and not to squeeze the knob too tightly. Leave a spacing equal to about one dot between parts of the same letter and use a spacing equal to three dots between letters and five dots between words. Make a dash about three times the length of a dot. Of course; the exact spacing between Tite best way to learn the code is to rig up the simple circuit shown above, and have a friend letters depends upon the rate of sending, send to you. After a few lessons, short -wave reception will be far more interesting.

www.americanradiohistory.com Radio News for August, 1928 155 since you must make the letters clear and learning the code is a matter of practice easy to copy "behind" the incoming signals, sharp cut when sending slow. It is not ad- and, although they may produce quicker and the results will be gratifying. visable to lengthen the dots and dashes, iesults, it is still necessary to practice con- even though you are sending very slowly, tinually until you completely master the FOREIGN STATIONS since this tends to slur the transmission and code. Automatic senders are of some assist- Besides the American stations which will makes it more difficult to receive. ance, especially since such instruments are be picked up on short waves, there are a TAKING DOWN CODE used by the radio inspector when giving the number of amateurs transmitting in foreign operator's license tests. countries. Because of the remarkable dis- If you cannot enlist an experienced oper- When using the "listening" method you tances that can be covered on short waves, ator, it is better to depend on slow signals should try to pick out stations which are especially with continuous -wave transmit- received from the short -wave or long -wave transmitting just a little faster than you ters, it is not by any means unusual to re- stations. There are a number of commer- can receive. In this way, you will always ceive these foreign stations with consider- cial stations operating on short waves and try to get the few letters which you miss able volume and clarity. These can be some of then transmit quite slowly. Many and you will increase your reception speed. identified by the "intermediate signals," of these stations use tape transmission and When writing down the message, try to which were arranged by the International their signals are quite regular. The speed make the separation between the words Amateur Radio Union, and are'used through- which they use depends upon the reception definite. It is a good plan to receive the out the- world. Several years ago the let- conditions and it is usually an easy matter complete word before starting to write it ters "de" were used before signing the call to find one at about the desired speed for down; write the wordwhile listening to the letters of the station. Now the intermediate code practice. beginning of the succeeding word. A little signal is used in place of this introduction. At first you will be able to pick out only practice in this matter will soon make it (Continued on page 183) one or two letters, but do not let this dis- courage you. In a short time you will find that you can distinguish more of the letters. Use a paper and pencil and mark the letters down as they are received. Do not International Morse Code write the dots and dashes, as this will not help you to increase your speed and it will To be used for all general public-service radio communication. prevent you from reading letters instead of (1) A dash is-equal to three dots ; (2) the space between parts of dots and clashes. Repeat this practice as the same letter is equal to one dot; (3) the space between two often as possible for periods of about a letters is equal to three dots; (4) the space between two words is half hour. equal to five dots.] Learning the code by this method will probably seem more difficult than the use A . - Period of a buzzer system. However, when listen- B -... ing with a radio set, you encounter the C - Semicolon -. - -. D -.. actual operating conditions, including in- E. Comma - -.- terference and static, which are encountered I' whenever you are copying code signals. In - Colon - - - G --. this way, you become used to these inter- H Interrogation .. - -. fering noises from the beginning and natur- I .. Exclamation ally you will encounter no difficulty with J .-- 41091 point - -.. -- getting used to these noises and the irregu- Apostrophe larities of hand transmission. L - - - -, M -- Hyphen SOME ABBREVIATIONS N -. -....- You will soon find that operators do not i) - --. Bar indicating - fraction -.. -. always spell out the complete words but P Parenthesis - - abbreviate a number of then in order to R . Inverted commas . save time. Thus instead of sending the -. -. -. word working, it will be sent wkg. You will T_' Underline - -, be able to interpret most of the other ab- U ..- Double dash -...- breviations in the same manner. A of V list Distress call some of them is given below. - -- -X Attention call to precede every ART -All right Nit -No more y -..- transmission CANS-Phones TT ------That Z CP- Counterpoise WK -Work, weak, week, -- General inquiry call ES-And well -known Ell-Fine business, very W X-Weatlaer Ä (German) good XMTR -Transmitter FR -For YL -Young lady A or A From (de) (i II-Good-by 73 -Best regards (Spanish- Scandinavian) GM -Good morning 88 -Love and kisses Invitation to transmit (go ahead) . III -Laughter, high 99 -Keep out ND- Nothing doing 2DA -Today CH (German -Spanish) Warning -high power NIL-Nothing t (French) Question (please repeat after )- There are also several lists of official interrupting long messages signals used by commercial and government Sr (Spanish)_ Wait . stations and also employed to some extent by amateurs. Among these are the "Q" O (German) Break (Bk.) (double dash) signals, employed primarily by ships at sea but used by amateurs; although the Ü (German) Unierstand .- common usage by amateurs sometimes differs slightly from the official meaning. The . "Z" are used by the U. S. Naval Commu- - - -- Error nication Service; these signals have some- 3 -- Received (O. Ii.) -. what kindred meanings to the "Q" signals. 4 ..- These abbreviations are very seldom heard 5 Position report (to precede all position in amateur circles. g -,,,, messages) - .- SHORT CUTS $ _ -_ :. End of each message (cross) -, -. 9 From time to time, a number of short - - - Transmission finished (end of 0 - (conclusion of correspondence)pondence) cuts to ;earning the code have been intro------duced. Some of these methods have good The "dots and dashes" of the code, which. however, are never heard points but, when you get down to facts, as sac! by the practical lis. tener, to whom each letter and character has its highly- iiidividua sound.

www.americanradiohistory.com 156 Radio News for August, 1928 Letters from Home Radio Constructors

HIGH- VOLTAGE INTERFERENCE 5 -wire cage 20 feet long, all enameled. My aerial The grill in the wall at the right covers an 84- Editor, RADIO NEws: is within 100 yards of a 60,000 -volt line; so I had inch Racon air -column horn. On the panel is a I am writing to you for the blueprint of the some trouble until I got two aluminum rings, double-throw jack switch which enables the oper- Short-Wave receiver. (Sorry, but you will have 6 inches larger than the aerial, and hung one at ator to use either speaker at will. All leads are to come again with your street address. Los the top and one near the bottom and grounded through receptacles in the wall. Angeles has grown in the past forty years. - them. This improved matters so that I get good A single power supply operates either the short- EDITOR.) I intend to build it. Can this be put reception in the daytime. I got this idea from wave or the broadcast set; either may be con- in boxes, so as to shield it? (There is no par- power engineers, who use this idea near their nected in an instant by the double -throw switches. ticular value in doing so, unless close to inter- transmission lines, and it might be of some help to The former is an Aero -Dyne with Erla transform- ference; very large cans would be needed.) I those who live close to high- tension lines. ers, the latter a Bremer -Tully Counterphase with think it would help to clear up distance reception. HARRY MORGAN, three autoformer stages. In both the first and Please tell what kind of aerial is best suited for Los Angeles, Calif. second A.F. stages 112 tubes are used, and a 210 it. (There is very little difference, so long as the in the last. A Bakelite "A" unit and Thordarson -up antenna system is a good energy collector. Short - NO REASON TO DOUBT IT 210 compact are used. The phonograph pick wave aerials have nowhere near the period of the Edtor, RADIO NEws: is provided with a double- circuit filament jack on signals they are receiving, and except for point - Just a few words to let you know how good my the back of the cabinet to plug it in. This dis- to -point reception, there would be no use in at- Peridyne is. connects the R.F. and detector filaments at the tempting to make one directional. 'Sunday morning, March 4, between 1.30 A. M. same time. and 3.15 A. M., Eastern Standard Time, I tuned in JOE BENNETT, 3' the following Pacific Coast stations: KGO, Oak- 527 North Lincoln St., Bloomington, Ind. land; KPO, San Francisco; KFSD, San Diego; KFRC, San Francisco; KFI, Los Angeles; KGW, 4-ROPE Portland, Oregon. A DYNAMIC SPEAKER I tuned in KGW just before 3.00 o'clock, Eastern Editor, RADIO NEWS: Standard Time. At the end of the program he Thinking that some other readers may be con- announced it was 12.01, Pacific Time, announced templating the construction of a dynamic speaker the program for the next day, and signed off. from an old R3 Magnavox unit, as described by My Peridyne has three separate Amoco Con- Mr. Nichols in your May number, I enclose here- densers, using Marco Dials, because I had no with photograph of such a speaker which I re- gang condensers. I am also using three audio cently completed, together with a few suggestions. and one stages, using two National Impedaformers 011111111111111111111111111111111111111111111111111111111111111111111111111MIUMI1111111111111111111111111111011110111111111Mq Thordarson transformer. WEAF comes in on the dials at 95-95-96%; for this page should be as WGY on the dials at 78 -78 -811. Monday eve- LETTERSshort as possible, for so many are re- ning, March 5, between 7 and 8 P. M., at 10 -5 and ceived that all cannot be printed. Unless 13 on the dials, I was listening to amateurs a set is made from a published descrip- talking. Michigan calling CQ came in very loud tion, a schematic sketch should be sent; and clear. I wonder if all Peridyne sets can photos can be used only to illustrate a in amateur stations. (Depends upon the coils novelty, and then only if large and very tune clear. Inquiries for information not given used.-EDITOR.) here should be sent to the constructor Wednesday morning, March 7, between 1.30 direct; but he should NOT be asked to a. m. and 3.05., E.S.T., I tuned in the following furnish data already published, here or Pacific Coast stations: KFRC, San Francisco (not elsewhere. very loud); KPO, San Francisco; KFI, Los An- This department is for free discussion geles; KGW, Portland, Oregon; KHQ, Spokane, to the extent that space permits; but Washington. I had KHQ from 2.25 a. m. to RADIO NEWS accepts no responsibility 3.05 á. m., when it signed off. Am sending pro- for the opinions of readers as to the rela- gram to KHQ to have it verified. tive merits of apparatus and circuits. You may not believe this statement, but I received KFI eleven times in succession between 1.:, 3111111.1111111111321111111111.111111111111.1111.1111.11111.1;1,1. 1111111111111111111131111111.11.11.111111111111111111111111111111,.` Feb. 15 and Feb. 26. Some nights I could just For a cone support, instead of long brace rods hear it, and other nights it came in loud. to a baffle board, I secured a Ford headlight re -. MARSHALL FOWLER, flector, which is just about the right size and shape. 88 Main Street, Williamstown, Mass. This is made of soft brass, easily worked, and will not affect the field of your electromagnet. By A COMPLETE COMBINATION the to prevent the RADIO cutting suitable holes in sides Editor, RADIO NEWS: air "binding" at the back of the cone. and in the GROUND I enclose pictures of a special radio combination bottom to fit the part of the bridge which formerly Mr. Morgan suspends two gr,nanded rings out- built by myself that includes everything, and may supported the diaphragm, and soldering the two side his vertical cage aerial, to conduct away hit close enough to he called an ideal combination, parts together, you have a very strong, rigid unit induced high voltages. complete in one cabinet. in which the cone is well protected. the I am always glad to get your paper, which is not As the top view shows, in addition to a broad- Making this change necessitated supporting end cone by some method other than a catalog. I like Dr. Chase's letters and also cast receiver, it contains a phonograph with elec- rear of the Hamilton, of Porterville; I once tric pick-up and a short -wave set; the latter is that used by Mr. Nichols. This was done by that from Max of the electromagnet ran a shop in Porterville. But a paper can't get controlled by the top dials on the panel. The soldering to the center pole from an old rheostat) V4.-inch on without advertisements. Good firms that pro- regular broadcast set is operated by the lower a small piece (taken are O. K., but your way of testing dials; the round hole at the right, as will be seen in diameter and 4 -inch long. A disc -bridge ar- duce real stuff as the it out is best. Honesty is a nice thing to depend from the inside view, is backed by a cone speaker. rangement, made from the same paper cone, and can be se- on when you read an "ad." The clock at the right is wound by a dry-cell cone, was glued behind the I have an aerial 60 feet high, with a vertical battery. cured in any position through a hole in the center

Mr. Bennett's combination covers everything ; short and long waves at d The short-wave coils are visible, in this view looking down into the cabinet, phonograph, with a choice of exponential horn (built into the wall) or on an upper baseboard; the phonograph motorboard at the upper right. The cone speaker. broadcast receiver can be seen at the upper left.

www.americanradiohistory.com Radio News for August, 1928 157

with a 6 -32 screw. This makes possible adjust- gives to the cone a more direct action with less ume than any ordinary speaker will carry. It is ment of the rear end of the cone while it is in weight and less opportunity for twisting or getting simply wonderful. operation. out of action. I find really flexible chamois skin I have read RADIO NEWS for a number of years The little tripod arrangement also was abandoned about as good a support for the outer end of the and this is my first letter to you. However, I cone as any material that can be easily secured. have constructed many of your circuits and can To make this unit easy to handle, and give it say: "If it is good, you will find it in RADIO a firm base to sit upon, the complete magnet and NEWS." T. C. SHELBY, cone was removed from its base and turned upon 565 Madeline Ave., Memphis, Tenn. its side and again secured to the base by small brackets. These were attached to the electromagnet by putting longer screws in Editor, RADIO NEws: the two holes I have built the on each side, and using one of the tapped holes dynamic loud speaker described in the rear -formerly the bottom. The other ends (Continued on page 187) of the brackets were secured to the base with small wood- screws. This avoided any change in the wiring, and the unit can now be easily set in the cabinet against., a suitable baffle, or removed Mr. Dickensheets' mount- IRON PLATE ing arrangement facilitates adjustment of the coils. BRASS ROD S S Q, BRIDGE SUPPORTING for inspection at any time. DIAPHRAGM. Mr. Shelby uses a headlight re- NO 30 D.C.0 flector as a support for his electro- To appreciate one of TO STEP - dynamic cone. these cones, it must be DOWN COIL heard. Every little de- and the armature attached directly to the cone with tail and overtone in the ic ¢p.ea sewing thread and glue through the little holes music or speech is brought w111111P* which formerly were used for the tripod. This out and with more vol ----a all List of Broadcast Stations in the United States (Continued front gnage 129)

Radio ¿, ¡, o Radio ú `m Radio ú `wÿ Radio m: dw Call BROADCAST STA, m« m 3o 3.. Call BROADCAST STA. m Call BROADCAST STA. 03. m Call BROADCAST STA. á« 3 Letter I S m Location 3 a Letter Location 3i a3 Letter Location 3i 11; 3 Letters Location 3i a3

WJBU Lewisburg, Pa 214 100 WLS }Chicago Ill * *345 5000 WNYC New York, N. Y 526 500 WREN WJBW New Lawrence, Kan 254 75( Orleans, La 238 30 WLSI See WDWF WOAI San Antonio, Tex 280 5000 WRES Quincy, Mass 217 5( WJBY Gadsden, Ala .. 234 50 WLTH Brooklyn N Y 256 250 WOAN Lawrenceburg, Tenn.. 240 500 WRHF WJBZ Chicago Heights, Washington.D.C.(day) 322 15( Ill... 208 100 WLTS Chicago Ill 484 100 WOAX Trenton, N. J 240 500 WRHM }Minneapolis, Minn... 261 100( WJJD Mooseheart, Ill * *366 1000 WLW }Cincinnati Ohio 428 5000 WOBT Union City, Tenn..... 205 15 WRJN WJ KS Racine, Wis 248 5( Gary. Ind 232 500 (Also 52.02 -49.96 meters 250 watts) WOBU Charleston V. Va.... 268 250 WRM Urbana, Ill... 273 50 WJR -WCX tPontlac, Mich 441 5000 WLWL tKearny N. J.. 370 5000 WOC Davenport, Iowa 375 5000 WRK Hamilton. (Also 32 Ohio 205 10 meters, 75 watts) WMAC Cazenovia, N. Y 225 500 WOCL Jamestown, N. Y 224 25 WRNY tNew York, N. Y..... 326 50 WJZ tNew York, N. Y....* *45430,000 WMAF So. Dartmouth, Mass 428 500 WODA Paterson, N. J 294 1000 (Also 30.91 meters, 500 watts) (3XL, 59.96 meters, 30 k.w.) WMAK *Martinsville, N. Y... 545 750 WOI Ames, Iowa 265 *1000 WRR Dallas, Tex 461. 50 WKAQ San Juan, Porto Rico.. 322 500 WMAL Washington, D. C .... 242 500 WOK See WMBB WRUF Gainesville, Fla 203 500 WKAR East Lansing, Mich.... 278 *505 WMAN Columbus, Ohio 234 50 WO KO Beacon, N. Y 216 500 WRVA Richmond, Va 254 100 WKAV' Laconia, N. H...... 224 50 WMAQ *Chicago, Ill * *447 *2500 WOKT Rochester, N. Y 210 500 WSAI tCincinnati, Ohio 361 500 WKBB Joliet, Ill 216 150 WMAY St. Louis, Mo 234 100 WO MT Manitowoc, Wis 222 100 WSAJ Grove City, Pa 224 25 WKBE Webster, Mass 229 100 WMAZ Macon, Ga 270 500 WOOD }Grand Rapids, Mich. 261 500 WSAN Allentown, Pa 222 10 WKBF Indianapolis, Ind 252 250 WMBA Newport, R. I 204 100 WOQ Kansas City, Mo 341 500 WSAR Fall River; Mass. 213 25 WKBG Chicago, Ill. (portable) 201 100 WMBB tChicago, Ill 252 5000 WOR tKearny, N. J 422 5000 WSAX Chicago, Ill. (port.)... 204 10 WKBH La Crosse, Wis 231 500 WMBC Detroit, Mich 244 100 (Also 65.4 meters, 50 watts) WSAZ Huntington, W. Va... 250 10 WKBI Chicago, Ill 216 50 WMBD Peoria Heights, Ill.... 205 250 WORD tBatavia, Ill 252 5000 W5B Atlanta, Ga 476 100 W KIM Monroe, Mich 205 15 WMBE WhiteBearLake,Minn. 208 10 WOS Jefferson City, Mo.... 422 500 WSBC Chicago, Ill 232 50 WKBN Youngstown, Ohio.... 214 50 WMBF Miami Beach, Fla..... 384 500 WOW Omaha, Nebr 508 1000 WSBF St. Louis, Mo 258 25 WKBO Jersey City, N. J 219 500 WMBG Richmond, Va 220 50 WOWO Fort Wayne, Ind 229 *2500 WSBT South Bend, Ind 400 50 WKBP Battle Creek, Mich... 213 50 WMBH Joplin, Mo 204 100 (Also 22.8 meters, 1000 watts) WSDA See WSGH WKBQ New York, N. Y 219 * 500 WMBI tAddison, Ill *263 5000 WPAP See WQAO WSEA Portsmouth, Va . 263 50 WKBS Galesburg, Ill 217 100 WMBJ McKeesport, Penna... 232 50 WPCC Chicago, Ill 224 500 WSGH Brooklyn, N. Y 227 50 WKBT New Orleans, La 252 50 WMBL Lakeland, Fla 229 100 WPCH tNew York, N. Y..... 326 500 WSIX Springfeld, Tenn 250 15 WKBV Brookville, Ind.. 219 100 WMBM Memphis, Tenn .. 210 10 WPEP Waukegan, Ill .. 216 250 WS KC Bay City, Mich 273 25 WKBW Amherst, N. Y 217 5000 WMBO Auburn, N. Y 220 100 WPG Atlantic City, N. J... . 273 5000 WSM Nashville, Tenn 337 500 WKBZ Ludington, Mich 200 15 WMBQ Brooklyn, N. Y 204 100 WPRC Harrisburg, Pa 210 100 WSMB New Orleans, La. .. 297 75 WKDR tKenosha, Wis . 248 15 WMBR Tampa, Fla .. 252 100 WPSC State College, Pa. (day) 300 500 WS MK Dayton, Ohio.. 297 20 WKEN }Buffalo, N. Y 207 750 WMBS Lemoyne, Pa 234 250 WPSW Philadelphia, Pa 207 50 WSPD Toledo, Ohio 240 25 WKJC Lancaster, Pa 252 50 WMBW Youngstown, Ohio.... 214 50 WPTF Raleigh, N. C 545 1000 WSRO WKRC Middletown, Ohio 236 10 Cincinnati, Ohio 246 500 WMC Memphis, Tenn 517 5000 WQAM Miami, Fla 384 750 WSSH Boston, Mass 288 10 WKY Oklahoma City, Okla.. 288 150 WMCA tNew York, N. Y..... 370 500 WQAN Scranton, Pa .. 231 250 WSUI WLAC Iowa City, Ia. (day) .. 476 50 Nashville, Tenn 225 5000 WMES Boston, Mass 211 50 WQAO -WPAP tCliffside, N. J.. 395 500 WSUN St. Petersburg, Fla.... 517 75 WLAP Louisville, Ky 268 500 WMPC Lapeer, Mich 234 30 WQBA Tampa, Fla 238 250 WSVS WLB Buffalo, N. Y 204 5 Minneapolis, Minn.... 246 500 WMRJ Jamaica, N. Y 207 10 WQBC' Utica, Miss. (day).... 216 225 WSYR Syracuse, N. Y.. 294 50 WLBC Muncie, Ind . 210 50 WMSG New York, N. Y .. 236 500 WQBJ Clarksburg, W. Va.... 240 65 WTAD WLBF Quincy, Ill 236 525 Kansas City, Mo 210 50 WNAC -WBIS Boston, Mass.... 461 500 WQBZ Weirton, W. Va 250 60 WTAG Worcester, Mass. 517 25 WLBG Petersburg, Va 214 100 WNAD Norman, Okla 240 500 WQJ See WMAQ. WTAM Cleveland, Ohio *5400 *350 WLBH Farmingdale, N. Y.... 232 30 WNAL Omaha, Neb...... 258 250 WRAF Laporte, Ind 208 100 WTAQ Eau Claire, Wis 254 WLSI East Wenona. III 238 250 (Also 105 meters, 50 watts) WRAH Providence, R. I 200 250 WTAR 50 WLBL -WPOR Norfolk, Va 236 50 tStevens Point, Wise.. 333 *1000 WNATI Philadelphia, Pa 288 100 (Has short -wave transmitter) WTAS Elgin, Ill 275 50 WLBM Cambridge, Mass 231 50 WNAX Yankton, S. D. (day) 303 1000 WRAK Erie, Pa 219 30 WTAW College WLBN Little Rock, 204 50 Station, Tex 484 50 Ark WNBA Forest Park, Ill 208 200 WRAM Galesburg, Ill 248 50 WTAX Streator, Ill 248 5 WLBO Galesburg. Ill 217 100 WNBF Endicott, N. Y 207 50 WRAW Reading, Pa ... 238 100 WTAZ Richmond, Va 220 WLBQ Atwood, Ill 219 25 WNBH New Bedford, Mass... 261 250 WRAX Philadelphia, Pa 213 250 WTFF 1; WNBJ Mt. Vernon Hills, Va.. 203 10.00e WLBR Rockford, Ill 248 15 Knoxville, Tenn 207 50 WRBC Valparaiso, Ind. 238 250 WTFI Toccoa, Ga 210 50( WLBT Crown Point, WNBO Washington, Pa 211 15 WRBH Manchester, N. H..... 500 WTHS Ind..... 248 50 Atlanta, Ga ... . 227 200 WLBV Mansfield, Ohio 207 50 WNBQ Rochester, N. Y 205 15 WRBI Tifton, Ga 50 WNBR Memphis, Tenn 229 100 WRBJ Hattiesburg, Miss 250 10 WTIC Hartford, Conn 535 500 WLBW Oil City, Pa 294 500 WNBT Milwaukee, WLBX Long Island City; N.Y. 204 250 Elgin, Ill. (time siga.).. 35.5 500 WRBL Columbus, Ga 50 WTMJ Wis 294 1000 WLBY Iron Mountain, Mich.. 210 50 WNBW Carbondale, Pa 200 5 WRBQ Greenville, Ga 100 WTRL Midland Park, N. J... 207 15 WLBZ Dover-Foxcroft, Me... 208 250 WNBXj Springfield, Vt 242 10 WRBT Wilmington, N. C..... 50 WWAE Chicago, Ill 227 500 Gastonia, N. C 50 WWJ WLCI Ithaca, N. Y . 248 50 WNBZ Saranac Lake, N. Y... 232 10 WRBU Detroit, Mich 353 1000 WLEX Lexington, Mass 216 50 WNJ Newark, N. J 268 250 WRBW. Columbia S. C 15 WWL New Orleans, La 246 500 WLIB See WGN (Has short -wave transmitter) WRBX Richmond, Va 250 WWNC Asheville, N. C 297 1000 WLIT Philadelphia, Pa 405 500 WNOX Knoxville, Tenn 265 1000 WRC Washington, D. C...* *468 500 WWRL tWoodside, N. Y 200 100 WLOE Chelsea, Mass 211 100 WNRC Greensboro, N. C..... 224 250 WREC }Memphis, Tenn 250 500 WWVA Wheeling, W. Va 517 250 *Allowed higher daylight power. * *Standard or constant -frequency transmission. tRemote Control.

LIST OF CANADIAN BROADCAST CALLS

CFAC Calgary, Alta 435 500 CHCY Edmonton, Alta 517 250 CJOC Lethbridge Alta 268 50 CKOC Hamilton, Ont . 341 100 CFBO St. John, N. B 337 50 CHGS Summerside, P. E. I 268 25 CJ OR Sea Island, B. C 291 500 C KO W Toronto, Ont. 517 .500 CFCA Toronto, Ont 357 500 CHIC Toronto, Ont 357 500 CJRM Moose Jaw, Sask 297 0 CKPC Preston, Ont...... 248 8 CFCF Montreal, Que 411 1650 CH MA Edmonton, Alta. 517 250 CJSC Toronto, Ont 357 500 CKPR Midland, Ont 268 50 CFCH Iroquois Falls, Ont 500 250 CH ML Mt. Hamilton, Ont 341 50 CJ WC Saskatoon, Sask 330 250 CKSH St. Hyacinthe, Que 297 50 CFCN Calgary, Alta 435 1800 CHNC Toronto, Ont 357 500 CJYC Toronto, Ont. 517 500 CKSM Toronto, Ont 517 1000 CFCQ Vancouver, B. C 411 10 CHNS Halifax, N. S. 322 100 CKAC Montreal, Que 411 1200 CKUA, Edmonton, Alta 517 500 CFCT Victoria, B. C 476 500 CHPC Vancouver, B. C 411 1000 C KCD Vancouver, B. C 411 1023 C K W X Vancouver, B. C 411 50 C FC Y Charlottetown, P.E.I 312 100 CHRC Quebec, Que 341 5 C KC I Q Lebec, Que.. 341 C K Y Winnipeg, Man 384 500 CFGC Brantford, Ont 297 50 CHSC Unity, Sask 268 50 CKCK Regina, Sask 312 CNRA Moncton, N. B 476 500 CFJC Kamloops, B. C 268 15 CHUC Saskatoon, Sask 330 500 CKCI Toronto, Ont 357 500 CNRC Calgary, Alta 435 500 CFLC Prescott, Ont 297 50 CH WC Regina, Sask 312 15 CKCO Ottawa, Ont 435 100 CNRE Edmonton, Alta 517 500 CFMC Kingston, Ont. 268 20 CH W K Chilliwack, B. C. 248 5 CKCR St. George, Ont 258 25 CNRM Montreal, Que 411 1650 CFNB Fredericton, N. B 248 25 CHYC Montreal, Que 411 750 CKCV Quebec, Que 341 CNRO Ottawa, Ont 435 500 CF QC Saskatoon, Sask. 330 500 CJBC Toronto, Ont...... 517 -357 500 CKCX Toronto, Ont 517 500 IINRQ Quebec, Que 341 50 CFRB Toronto, Ont 517 1000 CJBR Regina, Sask 312 500 CKFC Vancouver, B. C. 411 50 CNRR Regina, Sask - 312 500 CFRC Kingston, Ont..... 268 500 CJCA Edmonton, Alta 517 500 CFYC Burnaby, B. C 411 500 CJCJ Calgary, Alta 435 250 CKGW Bowmanville, Ont 312 5000 CNRS Saskatoon, Sask 330 500 CHCA Calgary, Alta 435 250 CJCR Red Deer, Alta .. 357 1000 CKLC Red Deer, Alta 357 1000 CNRT Toronto, Ont 357 500 CHCS Hamilton, Ont, 341 10 CJGC London, Ont 330 500 CKMC Cobalt, Ont 248 5 CNRV Vancouver, B. C 291 500 CHCT Red Deer, Alta 357 1000 CJGX Yorkton, Sask 476 500 CKNC Toronto, Ont. 357 500 CNRW Winnipeg, Man 384 500

www.americanradiohistory.com 158 Radio .News for August, 1928

HERE'S TO GOOD OLD ALE - DIPLOMACY DE LUXE WHAT QUAINT BOOSTING ZEAL A of our for- Civic pride, than which Television discovery in large part THEM NEW \ÖRF will STATIONS AFE PIKEI there is no whicher, re- PRO$IT %FOR TELEVI51 Popular Radio for May: eign representation soon be obtained by the OUR STATION HAS vealed in a Weirton, W (fry},; ll "In this sort of scanning GOT MORE METEI ac- ETC Va., dispatch to th the holes are ar- efficient use of, radio, ETC. device, cording to this announce- Steubenville Herald -Sta i}f ranged on a belt which 2: "The loca passes over two wheels, ment in the Regina of May e' _ station WOBZ broadcast one of supplies the (Sask.) Morning Leader which of May 3: "Radio, CON- with 2449.9 meters an, DRINKING FORCE." !-r SUL model, 5 tube, com- 200 kilowatts." And, per This affords possibilities plete." In that case, as haps, 12,000 kilocycles, i4 of making new discoveries before, fidelity, harmony, the inspired reporter had ° 1`. in the coming radio art; that. To avoid- sensitivity, quality, polish come down to cps but the problem of and non- radiation should get this station, you just ing the well -known double- govern an appointment-Wilfred J. Burns. wind 1492 more turns of wire on each coil and plug image effect may become serious. E. Gibbs. in the loud speaker ahead of the detector.-Theo- WE'VE GOT A BASEBOARD ALREADY dore J. Sohn. Neglect of opportunities THAT'S REAL INSULATION on the part of set owners, t MARVELOUS !] DIT- DIT -DIT, WENT THE HAMMER Thoroughness of the - explained by the N. Z. ON THE ANVIL immobile East revealed by Radio Record of March Praise of a fellow - the price list of Messrs. 2: "6WF is usually townsman in the Wor- Deva Dutte Saraogi & passed over as a har- cester (Mass.) Telegram Son, Calcutta: "Insulat- r NO SA NIB, THIS monic, and this is prob- of April 22- "Through ing materials, leatheroid IS NOT THE ably the reason why the his work as an 'IRON 10 MILES and 20 CHINESE WALL TRANSFORMERS MERELY A are POUNDER,' Bates has MILES thick at Rs I -5 -6 SMALL INSULATOR received here by so few caused the name of Wor- per lb." The users of 2 short -wave listeners." If cester to sound from this stuff must be going we had the right sets of coast to coast" -will, we in for safety first at any plug -in coils, could we re- know, cause other "hams" price; possibly have been ceive our condensers and sockets too ? -A. E. Ire- to call right away for the reading about those 6 land (New Zealand). dope from 1GY as to how trillion volts of lightning. -C. M. Sweet (India). he gets that loud clear ,,,,,,,,,,,,,,,,,,, mmm,,,,,,,,,,,,,,,,,,,,,, ,,,,,,,,,,,,,,,,,,,,,,,,I,:m,i mm,,,,,,,,,,,,,,,,,,,,1, note.- Luther W. Eldridge. REVENGE IS SWEET! F you happen to see any humorous mis- prints in the press we shall be glad to AINT THEY CUNNING? (ONLY SIX) Interesting possibility in have you clip them out and send to us. Note from the capital an ad in the Detroit No RADIOTIC will be accepted unless the I ASK YOU VERY of the movie world, en- News of April 22: "West- printed original giving the name of the CONFIDENTIALLY ---j closing cover of Radio on Radio set, PESTER, newspaper or magazine is submitted, with Doings for April 8 with $50 cash." At first we date and page on which it appeared. We announcement of a "Six - hoped no one in our will pay $1.00 for each RADIOTIC ac- tube, self- contained, single vicinity would get hold cepted and printed here. A few humorous station selector, using the of it; there are too many from each correspondent should ac- AC * I lines new CUNNING radio pests around. Then company each RADIOTIC. The most hu- tubes," inquires earnestly we felt a fiendish tempta- morous ones will be printed. Address all "If they are cunning rt74 tion to acquire this in- RADIOTICS to now, what will they he strument of retaliation RADIOTIC DEPARTMENT, when they grow tip? and square up accounts Editor, (You tell 'em, Frank: with them.-Wm. G. Mortimer. c/o Radio News. we've got our girl friend along. Frank S. Scott.

BUT THEY MARRY TALL ONES MR. PUMPKIN EATER OUTDONE Matrimonial tendencies NEIGH! NEIGH!! Housing problems are Influence of Spring in in the Antipodes, in the Dominion revealed THIS IS s0 solved SUDDEN! the Golden State upon ob- according to New Zealand in the Rochester Times - and typographers, L'aion of March 13: servers Radio of March 31: "The noted in the Stockton Hawkes Bay Radio So- "Canada demands increase Record in wave channels; ask in- --(AH -H L, (Calif.) Evening ciety were royally enter- L April 20: "Wild - -- crease of eight WIVE MADEMOISELLE, of tained by the Rev. R. B. - - I LONG Horse RADIO to be Waugh, a keen radio en- LENGTHS." This comes FOR Z E staged this week- end." as a surprise to us, who thusiast who has bis set LONG WIFE(j Oh, gee, gosh! We have in a glass cabinet and his had always pictured the heard radios that squealed WIFE AND DAUGH- gallant Canuck snuggling like dogs and pigs, but is up to some petite, brun- TER." Undoubtedly, ette beauty the north- this to be worse? Or is however, in separate com- of it one of those sets that partments of the console. J. A. Lynn, (New ern wilds. John C. Heberger, 8AEC. you need wild horses to drag a peep out of ?- Zealand). Stiles Martin. RELIEF EXPEDITION ADVISED WE WANT OURS BUTTERED AN ALL -FIRED SIMPLE OUTFIT Perilous state of the Welcome to the crew New engineering practice explained in Allen - OH DEERODEER I'M LOST. "hams" revealed by the of the Bremen as char- NOTHING BUT DX Portland Oregon Journal acterized by the Detroit Rogers - Madison's 1928 April 29: catalog, listing a short- of "It has al- News of April 29: "The wave kit: "The main ways been the LOST of BREADCAST will begin is the amateur to explore at 9:15 a. m. McNamee unit, including socket and develop new terri- will assume the task." FIRED, insuring uni- tory." Here is a great This solves one important formity of range and field for social workers question; it was Graham greatly simplifying con- and home missionaries bread thus cast upon the struction." Also bringing A. among these poor souls, ether. But what we about red -hot reception on - ° whose condition must fill would like to ask Mac is, long - distance programs, any sympathetic soul with how many of the loaves though sometimes burning out tubes in that fired socket. W. Myers. alarm. B. A. Oscarson, 7ADT, 7LD, have returned again ? -Clarence W. Schneider. J. THERE WERE GIANTS IN THOSE DAYS REMOTE CONTROL RECOMMENDED NO CLOSED SEASON Out into the Great New wrinkle from the Sporting tip given by West, where men are Chi -Rad 1928 spring cata- a well- the New Orleans Times - Men and the ladies too log. describing Picayune of May 13: are husky, Montgomery known vernier dial which "Improvement in t h e Ward & Co., sent their I "is still one of the best sharpness of a superhet- winter catalog offering - \ , // and is now microphonic." erodyne may be had by "Bus Bar Wire 10 FT. We have been taught by HUNTING a .0005 vari- Square." Johnny Ink -, 'l.J hard- earned experience to able condenser across the slinger writes us that keep the speaker off- the bought some '. cabinet, and now we will secondary of the filter Paul Bunyan :oil transformer." A well - and wired up his set- - 4 have to put the dials on I side of trained pack of condenser losses were so low he got I j the other the hounds, used to the tricks Uranus on it, but the room from . the panel. and only way to move it was to hitch Babe the Blue Something's always making more work on the set. of the wily variables, H. Balderston. a good 20 -gauge may be used. H. A. PCreD. Ox to the baseboard. Donald Cooney. -W.

www.americanradiohistory.com Radio News for August, 1928 159

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9 Iluiiup ",1IIP,. o m C "'414 °IpliJd6 MI ui!hl i= 1J1>v; W mllw u uDpm, \a.0 to ¡News nllh p raor 1£ RADIO manufacturers are invited to send to RADIO NEWS LABORATORIES meats. No "write-ups" sent by manufacturers are published in these pages, samples of their products for test. It does not matter whether or not and only apparatus which has been tested in the Laboratories and found of they advertise Zn RADIO NEWS, the RADIO NEWS LABORATORIES being an inde- good mechanical and electrical construction is given a certificate. As the serv- pendent organization, with the improvement of radio apparatus as its aim. vice of the RADIO NEWS LABORATORIES is free to all manufacturers, whether If, after being tested, the instruments submitted prove to be built according they are advertisers or not, it is necessary that all goods to be tested be for- to modern radio engineering practice, they will each be awarded a certificate warded prepaid, otherwise they cannot be accepted. Apparatus ready for, or of merit; and that apparatus which embodies novel, as well as meritorious already on, the market will be tested for manufacturers free of charge. Appa. features in design and operation, will be described in this department, or in ratus in process of development will be tested at a charge of $2.00 per hour the "What New in Radio" department, as its news value and general interest required to do the work. Address all communications and all parcels to RADIO for our readers shall deserve. If the apparatus does not pass the Laboratory NEWS LABORATORIES, 230 Fifth Avenue, New York City. Readers will be in- tests, it will be returned to the manufacturer with suggestions for improve- formed on request if any article has been issued a Certificate of Merit. Y1,o,11 ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,

PHONOGRAPH PICK -UP cago, Illinois, contains four coils of The "Port" type vernier dial, sub- The "phone link shown, submit- flexible rubber insulated wire, suf- mitted by the Kurz -Pasch Company, ted by The Phone Link Company, ficient for the wiring of the average Dayton, Ohio, consists of two sepa- 490 Broome Street, New York City, A.C. -operated radio receiver. There rate parts; the dial proper and the is a phonograph pick -up of the vari- are 12 feet of black No. 14 twisted housing, with the vernier arrange- able air -gap type. The vibrating ar- pair for the 11/4-volt amplifier cir- ment. The dial proper is 2% inches mature which carries the phonograph cuit; 6 feet of yellow No. 18 twisted in diameter, made of a white trans- needle is hinged to one of the pole pair for the 21/4-volt detector circuit; lucent substance similar to galalith, pieces and is held in position by 6 feet of red of the same gauge for and is calibrated 0 -100 -0 around its pressure between a flat "U "- shaped the 5 -volt power -tube circuit, and 25 entire circumference. The housing, spring, covered with soft rubber, feet of green No. 18 hook -up wire which is of black molded bakelite, has and a thicker rubber strip. The air - for the rest of the connections. a very pleasing appearance; it is fast- gap between the vibrating armature AWARDED THE RADIO NEWS ened to the panel with three screws LABORATORIES CERTIFICATE after the dial proper has been and the pole pieces carrying the eago, Ill., operates on a 110 -volt 50- pick -up coil may be varied by means OF MERIT NO. 2363. mounted on the corresponding shaft. 60-cycle house -lighting line, and is The vernier ratio is approximately of a special screw, which presses on designed to supply the "B" power the rubber strip; a very exact vol- 1:5. The translucency of the dial FIXED CONDENSER necessary for satisfactory operation makes possible the use of a panel ume control thus is obtained. This of a radio receiver employing a sin- unit is housed in a light aluminum The "Tipon" vacuum mica con- light behind it. denser, submitted by the Tobe gle power tube of the UX -250 type AWARDED THE RADIO NEWS casing which is attached to a hinged in the last stage. This transformer arm pivoting upon a conical support, Deutschmann Company, 11 Windsor LABORATORIES CERTIFICATE operates in conjunction with two half - OF MERIT NO. 2368. ordinarily placed on the motor -board wave rectifiers of the UX -281 type, of the phonograph. Two adapters, a and has three center -tapped windings. UX and a UY type, make possible Two low- voltage windings, rated at the connection of this instrument AUDIO AMPLIFIER to 71/4 volts, provide the heating current The AP -10 power a receiver with either a 4- or a 5- Street, Cambridge, Mass., has its ca- for the filaments of the rectifiers and amplifier sub- prong detector. Each adapter con- pacity elements sealed into an the power tube. The high -voltage mitted by the American Transformer sists of a small bakelite plate with evacuated glass tube, and is thus pro- winding, for the plate supply, has Company, 141 Emmet St., Newark, tected from atmospheric influences. been found to deliver approximately This condenser is the size a stand- of 2 x 670 volts under full load. The ard grid -leak and, being equipped apparatus is well built, sturdy and with two contact caps, fits in any compact, and easy to install. standard grid -leak mounting. It is AWARDED THE RADIO NEWS available in the most used capacity LABORATORIES CERTIFICATE values; the tested units differ from OF MERIT NO. 2366. "Il!ll;u;ly@d4.;4U14ti1, the rated values less than 10 %. unulii'hdCii uvtilb3 AWARDED THE RADIO NEWS The type T -2950 "B" power trans- 4 or 5 holes into which fit the prongs LABORATORIES CERTIFICATE former, submitted by the same com- of the corresponding detector tube; OF MERIT NO. 2364. pany, is similar in construction to two flat springs, partly engaged in the holes for the grid and cathode CENTER -TAPPED RESISTORS (or "A+ ") prongs are connected to The resistor shown, submitted by two pin jacks mounted on the same N. J., is a two -stage transformer - 25 plate, and into which are plugged the General Coil Company, Ster- coupled audio amplifier, which is de- the tips of the connecting cord. This ling Street, Weymouth, Mass., is signed for connection to the detector pick -up is thus connected ahead of stage of a radio receiver; it may be the detector tube, which is replaced operated either from batteries or in its socket. The device is very 3 from an A.C. power supply system. light and does not wear out the The first stage is equipped with two phonograph records as the heavier sockets; one a standard UX four - types do. The reproduction of speech prong type and the other a UY five - and music is of very good quality, prong type; it is so wired up that and large volume may be obtained either a 201A -, a 226- or a 227 -type with radio receivers having a good tube may type T -2900 described above. It he used. The last stage audio amplifier. their employs two tubes of the UX -210 has a higher output, and is intended AWARDED TIIE RADIO NEWS type operating in a push -pull for the "B" power supply of an corn. LABORATORIES CERTIFICATE bination. There are 15 flexible amplifier using two leads OF MERIT NO. 2362. center -tapped and made for use across power tubes of which into two -250 are braided cables; the filaments of vacuum tubes op- the UX type (small public -ad- one contains two leads for dress system). The high-voltage the cur- A.C. erating on raw A.C. The two sec- rent supply of the first audio stage, WIRE KIT winding at full load has a potential tions of this resistor are wound in when the four -prong socket is used The `Colorubber" A.C. wire kit, opposite directions on a fiber tube of approximately 2 x 750 volts. submitted by the Belden Mfg. Com- AWARDED THE RADIO NEWS and two input leads for the detec- 1% inches long and 1/4-inch in tor. The other cable contains eleven pany, 2300 S. Western Ave., Chi- diameter. The resistance value of LABORATORIES CERTIFICATE OF MERIT NO. 2367. leads, of which the seven supplying this unit is approximately 65 ohms the "B" and "C" power are con- and the taps are so precisely located nected to a Yaxley pin plug. The that the difference in resistance be- VERNIER DIAL four remaining leads supply filament tween the two halves has been found current to the power tubes and to the to be less than 0.3 %. first stage when a UY- 227 -type tube AWARDED THE RADIO NEWS is used. The characteristics of this LABORATORIES CERTIFICATE amplifier with regard to quality and OF MERIT NO. 2365. volume of reproduction show a very high degree of perfection. POWER TRANSFORMERS AWARDED THE RADIO NEWS The type T -2900 "B" power LABORATORIES CERTIFICATE transformer, submitted by the Thor - OF MERIT NO. 2369. darson Elec. Mfg. Company, Chi- (Continued on page 185)

www.americanradiohistory.com 160 Radio News for August, 1928 fORBOA, ' çI ï- %°-.--i r /ii % WIAll'1 _ i , , c mRttsrrt d eí6 i j/j VI - ` - 1 .--Oí(<ülltliRll (lil. ti/:" 'O -> r_/ % 1It ..r.mi,,.,,,u lolllrt Conducted by C. W. Palmer

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

anuunnninwuu..unnu,,,,,,wpumwuuuuiwmumnu i 1

R.F. BOOSTER UNIT FOR A.C. in obtaining a five -prong socket which will fit into piece (2291) Mr. R. A. Middleton, Seattle, Washing- the tube base, it may be necessary to take a of bakelite or hand rubber and drill holes at suit- ton, writes: from an (O.) "In the article on the Booster Unit in able points. Prongs should be taken SIZE OF ordinary socket and fitted into the tube base to the May issue of RADIO NEWS, you specify a plug VACUUM -TUBE make contact with the prongs on the tube. to be connected to the socket of the detector tube the SOCKET WHICH It may be advisable, in some cases, to use a in the set. In the Radiola 17, the detector tube FITSIN TUBE BASE of four. For this reason, separate twisted lead for the A.C. filament con- has five prongs instead filament the plug that you specify cannot be used. How nections; since the capacity between the can this Booster Unit be connected to this set without rewiring the set, or how can a plug for the five-prong detector tube be made ?" (A.) We have received a great number of letters in reference to the Grimes R.F. Booster Unit. FIVE-PRONG A number of fans desire to use this unit with VACUUM TUBE receivers, and others with alter- superheterodyne BASE SAWED sets. Naturally, since the Booster nating- current THIS Unit is used either with the fundamental or on OFF TO SIZE the "half- wave" or second harmonic of a signal, this Booster Unit cannot be used with the inter- Detail of the 5 -prong plug required to connect mediate- frequency amplifier of a superheterodyne. the Booster Unit with a UY socket. The only way in which the unit can be used with a superheterodyne receiver is to connect it in the should be twisted together and kept some distance first -detector circuit. This method will work quite away from the other twisted cable. satisfactorily, especially if one or more stages of We would not suggest the use of the R.F. radio frequency amplification are employed before Booster Unit in A.C. -operated superheterodyne re- the first detector; although with a set of this type, ceivers; since the radio -frequency amplification in which a number of radio -frequency amplifier gained by using this unit with a set of this type tubes are used, the gain is not very great. will not improve the operation to any great extent, When employing the Booster Unit with alter- and some trouble may be encountered in keeping nating- current sets of the tuned -radio -frequency the A.C. hum at a minimum. In tuned- radio- type, it is necessary to use a heater -type (227) frequency receivers employing the 227- or a sim- tube in the detector and Booster circuits. Fig. ilar heater -type tube in the detector, or heater tubes Q. 2291 shows the necessary changes in the dia- throughout, it is entirely practical to use this unit gram for employing this type of tube. As you will if care is taken to keep the filament wires away notice, the lettering and specifications of the appa- from the grid and plate leads. The specification ratus employed are all the same as in the original of all of the parts employed in this unit and the unit, except for the tube sockets, tube, filament Connections of the Grimes R.F. Booster Unit instructions for using it in a radio set will be supply and grid return. The grid return is con- when used with a 227 -type detector tube. found on page 1236 of our May, 1928, issue. nected to the heater terminal instead of the filament. It will also be necessary to use five connecting wires and terminals because of the extra and grid wires may cause A.C. hum. In this UNDERGROUND AND UNDERWATER element in this type of tube. case, the three wires marked "P," "B+" and "H" AERIALS The method of making the required plug is should be twisted together as described in the (2292) Mr. C. Williams, Union, N. J. writes: shown in Fig. Q. 2291A. If you have difficulty original article, and the two wires for the filaments (Q.) "I would like to obtain information in

NEUTRALIZING CONDENSER

2MEGOHMS NC "*.0001 ,ir .000Imf p ra TAERIAL 0 NJWJV TAERIAL 4LC SWITCH -oP Q5mf. TO SWITCH AUDIO 05 mf. 00007mí. P FREQUENCY 2 -o b V2 AMPLIFIER R.FC7. TO AUDIO 00007 FREQUENCY g+ LI R.F. co, ó_emf. Q5mf AMPLIFIER HOKE q O GÁ <_+c B+ T0035 .001 LI o .001 mf. mf. mf. 0 30 OHMS 0 OHMS

BALLAST o O RESISTOR o o o A+ B- B+DET. A+ 11+45V. B+90V. B- B+DET 2294 -AA- 42294 -B The Browning -Drake tuning unit, as designed for use with ordinary tubes The screen-grid Browning -Drake must be shielded as indicated by the dotted To use a screen -grid tube in the R.F. stage, it is rebuilt as shown at the riles above. (See page 189). The neutralizing condenser is eliminated, and right. the primary of the R.F. coupler unused.

www.americanradiohistory.com Radio News for August, 1928 161

necessary to use a more sensitive receiver in order Types of Receivers TO SET-.-- to obtain equally satisfactory results. One of the most important points to remember 75' 0" is that you will not reap the full benefits of static Underwater Aerials reduction with an aerial of this type, unless yosa r.r In constructing underwater aerials, the same are using a shielded set. If your receiving set /i have shielded condensers and coils, /&/%4 specifications should be followed for the type of does not already wire, insulation of the end, and length. When the the set can be shielded by placing aluminum or the cabinet LEAD wire is placed in fresh water, it has been found copper plates all around the inside of COVERED ' X18 TO 24'. that it can be submerged as deep as 60 feet with- and then grounding the metal lining. It is impor- WIRE DEEP out an appreciable decrease in signal strength, In tant to remember that the lead- sheathed cable must Q2292-A salt water, however, it has been found that the extend up to the set, and also that the ground wire signal strength drops off very rapidly when the must be a piece of lead -sheathed wire. It will be The most efficient form of underground aerial, wire is submerged to any great depth. In snaking of advantage, in some cases, also to place the a straight length, is directional. an underwater aerial for operation in salt water, filament añd plate supply in a metal -lined box buoys should be fastened to the wire at intervals with the lining well grounded. The wires between in order to keep it close to the surface. The the power supply and the set, unless they are very reference to the operation and construction of under- all "aerials." I have seen a underwater aerial is quite satisfactory for portable short, should be lead- covered and, in any case, ground and underwater lead sheathing on the wires must be connected to number of advertisements in recent issues of the antenna devices of ground. In order to obtain the greatest ratio radio periodicals advertising of signal strength to static, it is best to use bat- to reduce static and increase the selec- this type TO AERIAL BINDING teries to supply the current to the filaments and There have been so many LEAD COVERED tivity of a receiving set. POST ON RECEIVER plates, and to place them in a metal -lined box and exploited from CABLE "static eliminators" advertised as mentioned before. (See Fig. Q2292C.) to all of which were failures, that I am time time, a from the 110 - results obtained with an If "B" power unit -operating rather skeptical about the volt linens used, there is liable to be a feed -back aerial of this type: is es- known in of "strays" .through the power unit. This (A.) The underground aerial is well pecially true in country districts where elevated radio circles and its advantages were proved quite during the war by the electric-light feed wires branch off from the poles conclusively by tests made 6"T08 "BETWEEN --- and then proceed to the house. In the city, where U. S. Navy Department and several individual ex- SPIRALS ' Harris Rogers, whose most of the electric -light wires are shielded and perimenters, led by Dr. James buried in the street, this effect is much less notice- laboratory is located at Hyattsville, Maryland. The the able, and the "B" power unit can be used quite tests made by these experimenters showed that successfully. ratio of static and noise to the signal strength was much less than with the ordinary elevated type of aerial. Dr. Rogers arranged aerials of various F- 3'-p" in all directions around his INSULATED lengths and depths Q 2292-B systems END. laboratory, so that by means of switching Q2292-C combinations or individual aerials could be used Where room is limited, the underground aerial at will. It was found that the underground aerial, may be wound in "pancake" layers separated by when buried in a straight line, is more or less di- layers of earth, as shown above. rectional, in the plane of its length. It was found , that the best wire for use with underground aerial experiments is one with heavy rubber insulation use, since camps are usually located near a sake covered by a coating of lead. Seventy -five feet or other water supply. If desired, a number of SHIELDED is usually considered about the correct length for wires may be sunk in a fan -shaped area, and con- RECEIVER -in, in to increase / \O/ \o/ an aerial to be used on wavelengths between 150 nected together at the lead order ó , and 500 meters. Under average conditions, stranded the pick -up. In underwater aerials, it is extremely CURRENT SUPPLY important that the end of the wire be made water- LEAD COVERED UNITS ENCLOSED or solid copper wire, about No. 14 gauge, with a ÌÌ1 good rubber insulation and coated with lead, will tight; since, if, water enters through the insula- WIRES IN GROUNDED tion, the wire will be grounded and results ob- METAL CASE be found most suitable for this purpose. The wire WATER PIPE OR tained will be very poor. Should be buried in a shallow trench between 12 PIPES DRIVEN and 24 inches below the surface of the ground. An The amount of signal energy received by the INTO GROUND aerial of this type is shown in Fig. Q2292A. ground system is less than that obtained with the P Another type of underground aerial which has average elevated aerial, depending upon the type been used extensively is one consisting of a num- used, and for this reason it is necessary to use ber of spirals of lead -sheathed wire buried in a a set with several R.F. amplifier tubes in order to satisfactory volume. The use an aerial A fully shielded receiver with high amplifica- pit about four feet deep and three feet in diameter. obtain of tion should be used, and the lead-in shielded An aerial of this type is shown in Fig. Q2292B. buried in a large circle or semi -circle will overcome all the way into the set. The end of the wire should be insulated very care- the directional effects to some extent; while it has fully by pcuring melted paraffin or sealing wax been found that the use of the ground aerial in over it and then winding upon it rubber or friction combination with a "coil" (loop) aerial is of assist- tape to prevent the wax from breaking away. In ance in eliminating interference and strays, since SELECTIVITY this way, the end of the wire is made completely under proper conditions, this combination forms (2293) Mr. W. M. Butler, Cedar Rapids, Iowa, waterproof and there is no chance of moisture a unidirectional aerial. writes: short- circuiting the wire to the sheath. The spirals The official naval tests from time to time during (Q.) "In reading articles on the subject of should be made with the turns of wire 3 to 4 inches the war showed some very interesting comparisons selectivity in radio sets, I have noticed that various apart, and the smallest diameter should be about between the degree of signal strength as compared authors have different ideas on the subject and 6 inches. The lowest spiral should be placed to the static when using underground aerials. At very often they are conflicting. For instance, I about 3 feet below the surface of the ground, and ;X ew Orleans, for example, it was found possible noticed some time ago, a reference to the use of a space of 6 to S inches should be left between to carry on steady radio reception from a distant large condensers and small inductance coils to each of the spirals. station, with the underground aerial, while a heavy give the greatest selectivity. Recently, I noticed a The advantages of such an aerial over the first electric storm was directly overhead. It is prac- statement which said that a large inductance coil type mentioned are that it is not directional and tically impossible to accomplish anything like this and small capacity gave the greatest selectivity. is much easier to lay. The disadvantages are that when using a regular elevated aerial, and it would Which is correct ?" the pick -up is much smaller and naturally it is be sometimes rather dangerous to attemf"; it. (Continued on page 189)

2 MEGOHMS 00025mf. VI V2 V3 b. V4 V5 V6 2 mf O 035 mf., OÓ .001 mf. (cD

VOLUME CONTROL

O DL

Imf:_ POWER SWITCH I O O Q2295 1.5V. A.0 GND. C-10V. 25V.A.C. B+45V. 8+135V. C- WR. SV. AC. B+PWR.

-I he schematic diagram of the All- American 6 -tube electric receiver, showing its special balancing method.

www.americanradiohistory.com 162 Radio News for August, 1928

SHORT -WAVE PHONE STATIONS CHANGE BY PCJJ wire (12- gauge) aerial. Not being able to put (Reported to the Department of Commerce) Editor, RADIO News: a counterpoise the full length of the aerial, I have Here is something may put in a 50 -foot 12 -wire one; and in the room where Meters Call that interest some short- wave fans. In a letter dated May 17, 1928, re- the set is, I have put in a double loop; the upper 11.00 Nauen, Germany AGA, AGI{, POF, ceived from PCJJ, Eindhoven, Holland, the fol- one 24 inches from the ceiling and 14 inches from (Also 58 meters) AGB, AGC the wall, composed of twelve 14 -gauge wires spaced 14.00 Konigswusterhausen, Germany, lowing facts are given out. Our transmissions take place at present 4 inches, and in a horizontal position. The lower (Also 36 meters) AFI, AFJ, AFU one has guides in each corner, so that I can raise 17.40 Bandoeng and Malabar, Java ANE, ANH every Tuesday from 16 -20 GMT, (11 it close to the upper one or lower it. There is (Saturday, 7:00 a. m. to noon, and as an- to 3, E.S.T.) every Thursday from 16 -20 GMT, 450 feet of wire in each one, and in the counter- nounced-Times, reduced to E.S.T.) - (11 to 3, E.S.T.) poise out in the yard there is .600 feet of wire. 16.00 Kootwijk, Netherlands, PCPK, PCLL, I have a ground also of two copper cables of PCMM, PCPP, PCRR, PCTT every Friday from 23 -2 GMT, (6 to 9, E.S.T.) 350,000 mils each, down nine feet, and three cop- (Wednesday, 9:00 to 11:00 a. m., 40 kw.) per tapes E x 1/32 -inch down five feet. Each of (Also 60 meters and other wavelengths) every Saturday from 15 -18 GMT, (10 1, these grounds has its own hole, and all connec- 24.00 Chelmsford, England G5 SW to E.S.T.) "It would be very helpful for us, if you could tions are soldered and come to a common lead -in, (8:30, 9:30 a. m., 2:30 p. m. on) 45/i feet from set to ground. 28.50 Sydney, Australia A2ME, send us a report now and then, in which kindly 2FC state I have tried combinations of every possible (2ME. Sunday, 1:30 to 3:00 p. m.; 2FC the following: "1. Is there any difference in reception since hook -up of antenna system. Using the inside loops week days, 1:30 to 3:30 p. m.) I get fine, clear, static -free reception, but not so 29.80 Melbourne, Australia A3LO the station's transfer from Eindhoven? "2. Is fading experienced and if so, at what much volume. Using the outside antenna, I can get (Sunday, 1:30 to 3:30 p. m.) reception on the RCA 100A loud speaker, but it 30.00 Norwegian SS. `Norwegia" ARFS time? "3. What are the signal strength and general does not fill the room with music by 6a long ways. 30.20 Hilversum, Netherlands PCJJ Sitting three to five feet away, one can hear and 32.00 Sydney, Australia A2FC qualities of the transmissions? "4. Is the wavelength constant and state gen- understand very well. 32.00 Johannesburg, So. Africa JB Now, after all this, tell me why I can get only 32.00 Berne, Switzerland H90C eral reception conditions? "5. At what time are WGY on the short waves? There are several other (Mon., Thu., Sat., 3:00 to 4:00 p. m.) strongest signals received? "Owing to the interference caused by telegraphy broadcast stations, but all I get is the carrier 32.50 Caterham, England G2NM waves. I am not kicking, but just asking if you (Tues., Thu., Sat., Sun., 1:00 to 2:40 a. transmitters working on about the same wavelength as our station, we have altered our wave- know why. Sun., 11:00 a. m. to 1:00 p. m.) PARKER P. BALDWIN, 37.00 Paris, France "Radio Vitus" length to 31.4 meters." No doubt Castilla 115, Tocopilla, Chile. (Wed., Fri., Sun., 4:00 to 5:45 p. m.) PCJJ will be hard to get now, as 2XAF transmits on 31.4 meters. (More favorably -situated fans will admire the 39.68 Norddeich, Germany I{AV determination and resourcefulness which led Mr. 45.00 Rome, Italy I1XAX RAY C. PAYETTE, 27 Broadway, Haverhill, Mass. Baldwin, at the foot of the Asides Mountains, in 53.16 Riga, Latvia KCZ a location evidently none too favorable, to go to 60.00 Paris, France LL such lengths in the endeavor to secure good radio 61.00 Paris, France LL reception. We believe that he will yet succeed, A number of vessels are using phone on 150 to AN ELABORATE SYSTEM especially since short-wave broadcasts are increas- 280 meters: Danish ships on 150, German on 160 Editor, RADIO NEWS: ing; and a location impenetrable from some direc- and 180, Canadian West Coast ships on 198.60, I am enclosing some pictures of a set that I tions may be reached from others by the right and numerous others on 200 and somewhat longer don't think you ever saw before. I mounted the waves.-EDITOR.) waves. RADIO NEWS Short -Wave Special that way -each The above list varies somewhat from other de- part on a hollow mica tube 8 inches long, to iso- tailed reports which have been received; and, of late them from each other. course,' changes in their transmissions are fre- This is how I have rigged up the primary of STATION HARMONICS quently made by such stations. the antenna coil. On the baseboard I have a Editor, RADIO NEWS: We are glad to receive reports of any short -wave quadrant (from a steam gauge) to which the coil Tonight at about 8:15" o'clock I received WGY stations received, especially when the wave is de- is connected by a celluloid rod; from the quadrant on my short -wave set. As this is the first time termined, by announcement or by wavemeter; or I have another celluloid rod to the front panel, that I have ever received a station over such a when the locality and call letters are announced. with a button to move the coil nearer to or further distance I am naturally a bit enthused. There is, however, no possible way to answer a away from the secondary. This gives a fine tuning. I am using a home -constructed set of two tubes, reader who writes in and asks what and where a combination, as I do not have to put my hand one of them an audio amplifier. The circuit is station is, without being able to give the wave- near the set. regenerative, and uses a fixed tickler and condenser length, nationality or location -as some have done. I have put up a 50 -foot pole and a 150 -foot 4- (variable) for oscillation control. This circuit appeared in THE EXPERIMENTER, but I got it out of the October issue of RADIO REVIEW for 1925, Fading was very noticeable. At times the signal faded out entirely, but it always came back again. The volume was very good, considering that I am using 199 tubes with 45 volts of "B" battery. At first I thought I had a local station. Although the day was warm, there was no static at all. Static has been bothering me a little, but there was no trace of it tonight. I also received KSL at Salt Lake City on the same set. This station was not listed as having a short -wave broadcast outfit but they came in at about 33 meters on my set. I have written to the station but have not received a reply as yet. I shall be glad to give you any further data on short -wave stations that I receive. Mr. Baldwin's anti -hand -ca LEWIS RAINS, pacity tuning gear and his R. R. 9, Seattle, Wash. skyscraping assembly of. the (In addition to the short -wave broadcasts de- Short -Wave Special. liberately planned, broadcast stations emit harmonics, though with energy comparatively feeble, which may be heard in short -wave receivers. Twelfth, thirteenth, and even higher harmonics may be heard at short distances; and the lower harmonics over a wide area, even when the fundamental carrier is not detectable. Mr. Rains may have heard the ninth harmonic of KSL at this distance. -EDITOR.)

UNDER THE MIDNIGHT SUN Editor, RADIO NEWS: rua I wish to say a few things about short -wave or intercontinental broadcasting. I live in central Mr. Raldzoin's mast carries both a vertical asid a horizontal aerial Each wire is fully insulated Yukon Territory in Canada, next to Alaska, at 64 from its supports; "I have gone to extremes," he writes, 'so soldering and insulating." (Continued on page 188)

www.americanradiohistory.com Radio News for August, 1928 163

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Watch dogs of tone quality safeguarding the musical reproduction of broadcast programs, Thordarson Audio Transformers do their part in making real musical instruments of hundreds of thousands of receiving sets annually. Among leading set manufacturers, Thordarson transformers have long been recognized for their fidelity of reproduction. Today their use is so universal that it is difficult to find a dealer who does not sell at least one make of receiver so equipped. Try this simple experiment. Ask your dealer for a demonstration of his receivers. Pick out the instrument with the most natural reproduction, and then look inside the cabinet. You will find, in the majority new! of cases, Thordarson amplifying and power supply transformers. THORDARSON 8-300 You will realize that it is wise to specify Thordarson amplification when buying your receiver, for the AUDIO TRANSFORMER manufacturer who is far -seeing enough to equip his A superior audio transformer that will satisfy the most critical musical ear. The sets with Thordarson transformers, may be depended high impedance windings of the R - 300 upon to have the balance of his instrument in keeping are wound on a core of D -X Metal, a re- with this high standard. cent development of the Thordarson laboratory. This new core material has an exceedingly high A.C. permeability, and an inductance that is 50% greater than that of the highest grade silicon steel In performance, this transformer re- HORDAR S sponds exceptionally well to the lower frequencies and provides the same de- RADIO TRANSFORMERS gree amplification to the diapason of the grand organ as to the note of the flute. Ratio 3:1. Dimensions, 21/2" x 21/2" x 3" upremñ high. Weight, 2 lbs. Price, $8.00. mus ícaZ perormance

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www.americanradiohistory.com 164 Radio News for August, 1928 Some Inside Facts About "B" Batteries 1' (Continued from page 135) l . \\\`;, e s a back to the days of the "voltaic pile," the tween the two piles and the connections to . original form Of battery, which was com- the binding -post terminals on the outside. posed of strips of alternating metals, sepa- The difficulty, of course, lies in the pos- rated by cloth wet with salt water. It is sibility of leakage from one cell to the next interesting to note that the radio adapta- and of a resulting internal short circuit; F[FIOIiiUI 1N tion of this battery is its first commercial but this has been taken care of satisfac- use since its advent about 150 years ago! torily by the adoption of a dam along the This particular battery, instead of using edges of the plates. This is also treated to the cylindrical cells usual in the others, prevent seepage. has its elements arranged in tiers forming In this type of cell, it is apparent that two cubes which, when housed within a every particle of space is used and, since

to`B -"on set tö B +DET' to"B+APIP" to"B+PWR° 45 volts ,90volts ;135volt

45-VOLT BLOCKS

, to "B+DE T

;45vo{ts ; 90volts - -.,

Fig.5 22--VOLT BLOCKS As you like it Batteries, whether in 22r/z- or in 45 -volt blocks, are tapped in 2254-volt units of 15 cells each, cardboard container, form a battery of the zinc no longer acts as a container, the standard size. See Figs. 2 and 3. The battery will continue to render service even BUILD YOUR OWN elements are of practically the same ma- after the zinc is eaten to the appearance terials used in the ordinary battery, but of old lace. The fact that interconnections LOUD SPEAKER are of different shape. The carbon element, are also eliminated adds to the reliability "How --to Build MODERN LOUD for example, is painted in a thick layer and length of life of such a cell. SPEAKERS." by Clyde J. Fitch, is a complete upon the zinc. below comes a history of Radio acoustics. Every phase of Next porous With ordinary care, it will be found that Loud Speaker design and construction is fully separator containing the electrolyte, and good dry "B" batteries will stand up and and accurately explained. The many and various methods of attaining true tone repro- then the mixing block which comprises the last for a considerable length of time. The man- duction are treated in a clear and concise manganese dioxide and other materials fact that all kinds of so- called "eliminators" ner. All types of Loud Speakers, the Exponen- usually used this Below this con- tial Horn. the Cone, the Piezo Electric Speakers, at point. are now available does not, necessarily, Roll Type Speakers. in fact, every method that tinues a series of similar carbon and zinc has been used to produce clear, audible signals mean that radio batteries will pass out of is most thoroughly covered. elements, until the entire assembly of the required number of plates is in place. This the picture. In fact where first cost is the The good and bad points of each development are honestly and unbiasedly treated. This is method of construction does away with all primary consideration, it is apparent that unquestionably one of the most comprehensive internal connections except three be- the humble dry battery is still supreme. treatises on the subject ever written. -that BUILD YOUR OWN LOUD SPEAKER This valuable book contains full constructional data and diagrams for the building of the Loud Speaker best fitted to give you The Zero -Reactance Plate Circuit maximum satisfaction with the particular receiving circuit that you employ. (Continued from page 153) 52 pages -fully illustrated-6' x 9' the circuits out of balance and produce cases ordinary bakelite tubing was used. In oscillations. Locking all the condensers to- the one case we had a single -layer double - gether, making a single- control set out of wound coil. The primary and secondary 25c it, helped matters considerably, but did not were wound at the same time, the first THE COPY entirely cure them. The slight tendency to turn being a primary turn, the second a ON ALL NEWSSTANDS oscillate that still remained could be damped secondary turn, the third a primary turn, OR WRITE DIRECT out very easily by placing a few ohms of re- and so on. The main disadvantage of this sistance in the antenna circuit. The trouble style was the length of the coil. In the CO., INC. THE CONSRAD could also be cured very nicely by employ- second case, the primary was first wound 230 Ave. New York, N. Y. Fifth ing a neutralizing scheme in the first stage; on the tubing, and then. the secondary was CONSRAO COMPANY, INC. but this, of course detracted from the sim- wound directly on top of the primàry. Io 230 Fifth Ave., New York, N. Y., plicity of the arrangement. each case, both the primary and secondary Gentlemen: Enclosed find 25c. Kindly send m.: a copy of HOW TO BUILD MODERN LOUD windings had the same number of turns; SPEAKERS and it was interesting how much smaller DESIGN OF COILS Name. the secondary was in comparison with the Before closing this article, it will be of usual secondary employed in the ordinary Address interest to explain how the coils were made. circuits. This is because of the large mu- Therd two out; in both inductance. Clty State ...... were styles tried tüál

www.americanradiohistory.com Radio Nca's for August, 1928 165 The Radio Book You Warnt "MODERN RADIO DECEPTION" By CHARLES R. LEUTZ A Complete Ready Reference Educator

MODERN RADIO RECEPTION 250 384 Pages -250 Illustrations 384 $3.00 Fully Bound -6 x 9 inches ILLUSTRATIONS Three Dollars Complete PAGES PRACTICAL HELPS IN HANDY FORM Diagrams, charts, graphs, illustrations, tables, easily read to be a practical daily help to both the student and professional text make:difficult problems easy. worker, as well as the broadcast listener. "Modern Radio Reception" is a good book, explaining all Professional and Student Radio Engineers find "Modern important subjects on radio reception and radio receivers, Radio Reception" a Time and Money Saver. The book that written in a clear manner easily understood by anyone. It is every Broadcast Listener should own. not too technical, and the mathematical examples are confined Here is an up -to -date, quick ready reference and text book to simple problems. on radio reception. It is the only up-to-date book exclusively Considerable information is given on the operation and care on radio reception. Such late improvements as A.C. Tubes, of radio receivers and accessories. The most powerful receiver Shielded Grid Tubes, "A" Eliminators, Push Pull Power for broadcast reception in the world, the Transoceanic Silver Amplifiers, 400 -volt "B" Eliminators, etc., are covered in detail. Ghost," is described in detail. Short Wave Reception is also All the different important subjects relating to radio recep- covered, as this is one of the coming things in world -wide tion are covered in an interesting and clear manner. By reading broadcast reception. this book you can probably save the price of the book many As this handy book covers the entire field of broadcast times, the suggestions will save you money and enable you to reception in such a clear and complete manner, it will prove secure the best results in your radio receiving work. A RADIO EDUCATOR This single volume contains all the practical up -to -date radio receiving information that the professional radio worker, broadcast listener, student, or amateur needs. "Modern Radio Reception" is fully bound, size 6 x 9 inches, 384 pages, over 250 illustrations, including many graphs and circuit diagrams. It is nicely bound, a book that will look well on your library table, furnishing the means of a thorough knowledge of radio reception by spare time reading and study. Some of the Subjects Covered Antennae Meters Tungar Chargers List Short Wave Stations Counterpoise Oscillators Coupling Methods Universal Transoceanic Ground Audibility Meter "A" Eliminators Super- Heterodynes Condenser Plate Shapes Capacity Bridges "B -C" Eliminators Consoles Acoustic Chart Mechanical Oscillators Power Amplifiers Universal Silver Ghost Transmission Units Ammeter Western Electric Super-Heterodyne Super-8 Dynamic Loud Speakers Beat Oscillator Grebe Synchrophase Universal Plio -6 Cone Loud Speakers Amplifier Test Set Norden Hauck Super-10 Wave Antenna Dynamotors Push Pull Amplifiers Frequency Changers Radio Servicing Inductances Vacuum Tube Bridge ' Vacuum Tubes Tube Characteristics Condensers String Oscillograph Ballast Tubes World Time Chart Shielding Piezo Electric Oscillator A.C. Tubes Overloading Tubes

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www.americanradiohistory.com 166 Radio News for August, 1928

It is hardly necessary to state the results v...... ,1iS:;r'.:i11=.:a. l' obtained with this receiver, except that it WHAT SHOULD was very sensitive and tuned very sharply. It was possible to use "C" battery bias on all the R.F. amplifier tubes (all of which A RADIO DEALER were 201A's) and, when using a "C"-battery detector, the interesting diagram of Fig. 4 READ? resulted. The same bias was used for the R.F. amplifiers and the detector. Each stage was individually shielded and the WHAT should a radio dealer read in shielding or order to keep informed of the growth ground was made 3 volts negative with inside the industry? Where can he respect to one leg of the filament by con- obtain this information in a clear and concise necting this side of the filament to "C-}-" manner that will answer authentically just and the shield (or ground) to "C -3." The what he desires to know and not cause him "B -" "A -" and "C+" were connected to waste his valuable time in wading through together, with 90 volts on the R.F. ampli- seemingly endless pages of inconsequential trade notices fier plates and 45 volts on the detector. The and announcements? first audio stage was.also worked on 90 volts In plain words, where can a radio dealer find a plate. The leg of the filaments which trade paper that is a trade paper and was not just a medium for FREE publicity. A only made "C+" was joined to ground through cold analysis shows the following to be un- Guarantee o o a 001 -mf. by -pass condenser, as shown in deniably a fact. An absolutely unequaled Fig. 4. The plate voltages of the R.F. am- value! We want you to test RADIO NEWS DEALERS PERSONAL the World "A" Socket Power 1 plifier tubes were fed through R.F. choke Unit and compare it with W./ coils -the familiar shunt -feed arrangement. EDITION covers the radio trade like a any other of two or three C.O.ta blanket. It goes to over twenty -seven times the price. Try for ten No by -pass condensers were necessary in days at our risk. Then if you are not convinced thousand hand -picked radio dealers located that it is unsurpassed as to quality and wonder- the plate circuits, as all of the tuned cir- throughout the entire country. ful results, purchase price will be refunded in full. Operates on 50 or 60 cycles at 110 volts cuits were connected directly to ground. A. C. Highest quality Westinghouse electrical As regards the selectivity of this re- RADIO NEWS DEALERS PERSONAL equipment. No hum or noise. Approved by Radio EDITION is bound News Laboratories and other leading Authorities. ceiver, it may be pointed out that there under one cover with Just write were seven the foremost magazine of radio -RADIO Send Order Today yourname and tuned circuits; viz., four input NEWS. Thus the dealer obtains the leading address on a slip of paper -pin a one dollar bill circuits and three to it and mail today. We will ship same day output circuits. Naturally; consumer magazine at no cost, absolutely order is received for $12.75 C. O. D. 5% discount the output circuits tuned broadly on account FREE. for cash with order. Remember you are the judge and are fully protected -so send order of the large plate -to-filament resistances in NOW. series with the primary coil and condenser; RADIO NEWS DEALERS PERSONAL but, nevertheless, EDITION is edited-by the entire radio-trade. this tuning contributed Every important'. trend is reviewed by those somewhat to the selectivity. The power 1241 S. Michigan Avenue out- actively engaged in some phase of the in- Dept. GO Chicago, Illinois put, as well as sharpness and sensitivity, dustry, not by professional writers who must r Station W. S. B. C., owned and operated by was all that could be desired. The drain on depend more on "a play on words" than . i. World Battery Company the "B" supply was very small, not exceed - actual experience in order to write with any ing 20 milliamperes for the entire set. This degree of intelligence. was clue to the bias on the R.F. tubes, as RADIO" NEWS DEALERS PERSONAL well as on the other tubes. EDITION carries no trade notices to the effect that "John Jones, formerly of Smith AMMTLAN PF -250 BIG EUROPEAN STATIONS Radio, is now with the John Doe Co." Ours The super -power station at Lahti, Fin- is a magazine for the whole trade and not for the individual. Power Transformer land, recently illustrated in these pages, is for operating on 1525 meters. Czechoslovakia RADIO NEWS DEALERS PERSONAL is about to erect a new 50- kilowatt station EDITION naturally inherits the background UX 250 Power Tubes near Progue. of RADIO NEWS, that of the leader. A husky transformer built for Where else can a dealer find another paper doing the that has all of these attributes? Speaking job, not for looks. The PF -250 is rated at IN OUR from the standpoint of experience and in full 1200 -600 volts plate, 7iiz volts power tube, AUGUST ISSUE: cognizance of the subject in question, we can 7Y2 volts rectifier tube filament. Center The Skylark of Space, by Ed- honestly state- nowhere. taps are provided on each of ward Elmer Smith, in collabo- the filament ration with Lee Hawkins Garby. Wise dealers all over the country are filling windings. Continuous rated capacity of (A Serial in Three Parts) Part in this coupon and returning it to us. Why plate windings, 160 MA., continuous I, Much conjecturing has been not do likewise? By mailing in rated done on the far -reaching effects this coupon capacity of each 7% volt winding, and possibilities of the energy contained now you will obtain RADIO NEWS 3 Amperes. D C plate output in an atom, if it ever could be released. DEALERS PERSONAL EDITION, together with The discovery a method, two UX 281's of very probably, with a free copy of RADIO NEWS, at the full wave, up to will be accidental. The first instalment special 450 volts with sufficient ex- is chock -full of intense moments and subscription rate of $1.50 for the thrilling detail. year. (Regular rate $2.50.) Mail this coupa t cess for "C" Bias. NOW. Armageddon -2419 A.D., by Philip Francis Ask for Bulletin No. 1033 describing Nowlan. While enormous strides were fully the PF -250. made during the World War. both in the EXPERIMENTER PUBLISHING CO. Inc. type of mechanical warfare and in the 230 FIFTH AVE., NEW YORK, Y. uses of poisonous gases, the limit has not N. Price, each-$30.00 been reached, In this story, the author Slightly higher West of Rocky Mountains tells some amazing things, which are sci- ATTACH YOUR LETTERHEAD entifically correct. It contains a number of interesting prophecies, many of which THIS IS IMPORTANT American Transformer Co. arc sure to cone true. Transformer Builders for more than 28 Years The Perambulating Home, by Henry Hugh EXPERIMENTER PUBLISHING CO., 260 Emmet St., Newark, N.J. Simmons. This is the fourth of the series Inc. of "Hicks' inventions with a Kick." It 230 Fifth Avenue, New York, N. Y. is funnier and more thrilling than the preceding stories and gives us sonie very Gentlemen: startling new ideas. I desire to take advantage of your special subscription offer and am enclosing $1.50. Kindly send me RADIO NEWS DEALERS PERSONAL The Head, by Joe Kleier. Recent experi- EDITION for one year, beginning with the current ments in Germany have proved that it is issue possible to decapitate insects and trans- plant the heads from one to another, with no obvious harm to the insects, after the Name wounds are healed. If it can be done with insects, why not with animals, and perhaps with human beings, sometime in Address the future ?. And Others. City State

www.americanradiohistory.com Radio Ncws for August, 1928 167 WHOLESALE PRICE S fórDeczlers,CommunikSeEBuilclers,General Repairmen and iqeth!

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www.americanradiohistory.com 168 Radio News for August, 1928

. 7Avo, . o. o, ,01.0 oA o, . . . , ,o . The Radio Beginner - --A Two -Tube Reflex (C'ontinned from page 1:38)

ened in place with wood -screws. The coils place by the binding posts of the A.F. trans- are mounted on opposite sides of the base- formers (Ti and '1'2), as shown. board, 2 inches from the front and A -inch from the edge. Ll is mounted in a hori- WIRING INSTRUCTIONS zontal position on the left side of the baseboard and L2 is placed in a vertical posi- The wiring of the receiver is very sim- tion on the right side. One tube socket is ple. All wires are above the base, and mounted in the rear of each coil. They are flexible insulated wire is used for the pur- STFk.OBODYNE located one inch from the nearest edge and pose. If the builder is not proficient at TA-inch from the rear of the board. The soldering, the connections may be made with two A.F. transformers (Ti and T2) are the binding posts on the various parts; but mounted 134, inches apart and 1 -inch from it is always more satisfactory to solder the the rear of the base. When located in this wire direct to the soldering lug wherever position, each is adjacent to one of the tube possible. sockets. The R.F. choke coil (L3) is It is always best to start with the filament mounted in the center of the base 2/ inches wiring. First, one terminal of the battery from the front edge, and the filament -bal- switch (SW) should be connected by a wire last resistors (Rl and R2) are mounted on to the binding post marked "A -B--C+" each side. The last part to mount on the and the other terminal of the switch with baseboard is the adjustable condenser (C3), one terminal of each of the filament -ballast which is placed on the left rear edge of the units (Rl and R2). The other terminal of base. The pictorial wiring diagram shows ballast unit R2 should be connected with 'The Greatest Super the approximate position of the various the "A -" terminal (one of those marked pieces of apparatus, but their size has been "F ") of the tube socket V1, and the free ter- reduced in some cases to show the wiring minal of unit R3 with the "A -" terminal tleterocl yne more clearly. of the tube socket V2. To complete the fila- After the parts have been mounted on ment wiring, the "A-1-". terminals of the the baseboard, the front panel and binding - tube sockets (Vl and V2) should be con- post panels may be screwed in place. Two nected with the "A+" binding post. This revolutionary principle is em- and now be by in- ANEWbodied in the Strobodyne. This new wood- screws are used for the front panel, part of the circuit may tested principle is based on what is known as the and three screws for the binding-post panel. serting tubes in the two sockets and con- "Stroboscopic Phenomenon." It is the appli- The panel for the crystal detector (D) may necting a 6 -volt "A" battery to the two "A" cation of this phenomenon to the basic prin- also be mounted at this time. It is held in binding posts. The tubes should light when ciples of Super- Heterodyne construction that has placed the STROBODYNE so far ahead of all other Super-Heterodynes. The STRO- BODYNE employs eight tubes and is a marvel from the standpoint of selectivity, accurate tone reproduction and as a DX set.

Of course CONSRAD, the oldest and original radio pattern publishers, were given the task of publishing complete instructions for the building of an efficient STROBODYNE RECEIVER. In designing the best and most comprehensive instruction material, they have excelled. The STROBODYNE PATTERN BY CONSRAD contains four full size blueprints and a special 16-page instruction book- 32 32 ` 32, let that answers fully every question on STROBODYNE construction.

Write today -Get a full set of STROBODYNE patterns from CONSRAD- You will he ALL SCREW HOLES 5/32 -DIA. more than satisfied with the results that a ALL OTHER HOLES Vi6 " -DIA STROBODYNE RECEIVER assures you. Full constructional data only 50c Ip 5 -14" 4 I" 4 THE CONSRAD CO., Inc. 230 FIFTH AVE., NEW YORK, N. Y. 3/9" DRILL. qy 12 ry DETAILS OF L1 & L2 THE CONSRAD CO., INC., Y TAP 230 Fifth Ave., New York, N. Y. /^\ LI : PRIMARY Gentlemen: Kindly send me full set of blueprints 15 TURNS and all data required for building the efficient STRO- BODYNE RECEIVER. Enclosed find 50e. to cover. SECONDARY o 76 TURNS L2: PRIMARY Name 22.TURNS SECONDARY. PRIMARY 56 TURNS . z- > Address 4 TAPPED 32 ^-4 TVRN WOUND ON SAME SIZE TUBE, Li & L2.it City State WITH RS D.S.C. WIRE ON BOTH WINDINGS, Fig. 3. Panel and coil details for the Two- Tube _Reflex Receiver. 1111111IIIIIlIII1III11IIII111111IIIIll11111111IIIIIIIl.lIi.IIiIIIIIIIlI!ll111111111111

www.americanradiohistory.com Radio News for August, 1928 169 BURIED TREASURE can still be found in CHEMISTRY Good Chemists Command High Salaries You can make yourself indepen- What Some of Our dent for life by unearthing one Students Say of This Course! I have not written since I received the big of chemistry's yet undiscovered set. I can still say that it far exceeded my anticipations. Since I have been studying with your school I have been appointed chemist for secrets. the Scranton Coal Co., testing all the coal and ash by proximate analysis. The lessons are helping me wonderfully, and the interesting you remember how tales of pirate gold fire way in which they are written makes me wait Do the used to patietly for each lesson.- MORLAIS COUZ- your imagination and make you want to sail the uncharted ENS. seas in search of treasure and adventure? And then you I wish to express my appreciation of your prompt reply to my letter and to the recom- would regret that such things were no longer done. But that mendation to the General Electric Co. I in- is a mistake. They are done and everyday on tend to start the student engineering course at -today -not the works. This is somewhat along electrical desert islands, but in the chemical laboratories throughout lines, but the fact that I had a recommendation from a reliable school no doubt had con- your own country. Quietly, systematically, the chemist works. siderable influence in helping me to secure the His work is difficult, but more adventurous than the blood- job. H. VAN BENTHUYSEN. curdling deeds of the Spanish Main. Instead of meeting an So far I've been more than pleased with your course and am still doing nicely. I hope early and violent death on some forgotten shore, he gathers to be your honor graduate this year.-J. M. wealth and honor through his invaluable contributions to hu- NORKUS, JR. T. O'CONOR SLOANE, Alfred Nobel, the Swedish chemist who I find your course excellent and your Instruc- A.B., A.M., LL.D., Ph.D. manity. invented tion, truthfully, the clearest and best assem- dynamite, made so many millions that the income alone from bled I have ever taken, and yours is the fifth Noted Instructor, Lecturer and one I've studied. -JAMES J KELLY. Author. Formerly Treasurer Ameri- his bequests provides five $40,000 prizes every year for the can Chemical Society and a practical From the time I was having Chemistry it chemist with many well-known advancement of science and peace. C. M. Hall, the chemist has never been thus explained to me as it is achievements to his credit. Not who discovered how to manufacture aluminum, made millions now. I am recommending you highly to my only has Dr Sloane taught chemis- friends, and urging them to become members try for years, but he was for many through this discovery. F. G. Cottrell, who devised a valu- of such an organization.- CHARLES BEN- years engaged in commercial process for recovering the waste from flue gases, JAMIN. chemistry work. able James I shall always recommend your school to my Gayley, who showed how to save enormous losses in steel friends and let them know how simple your les- manufacture, L. H. Baekeland, who invented Bakelite -these sons are. -C. J. AMDAHL. I am more than pleased. You dig right in are only a few of the men to whom fortunes have come from the start. I am going to get somewhere through their chemical achievements. with this course. I am so glad that I found you. -A. A. CAMERON. I use your lessons constantly as I find it more thorough than most text books I can secure. -WM. H. TIBBS. Now Is the Time to Thanking you for your lessons, which I find not only clear and concise, but wonderfully interesting. I am -ROBT. H. TRAYLOR. Study Chemistry I received employment in the Consolidated Gas Co. I appreciate very much the good Not only are there boundless opportunities for amassing service of the school when a recommendation wealth in Chemistry, but the profession affords congenial was asked for. -JOS. DECKER. employment at good salaries to hundreds of thousands who merely follow out its present applications. These applications are innumerable, touching intimately every business and every product in the world. The work of the chemist can hardly be called work at all. It is the keenest and most enjoyable kind of pleasure. The days in a chemical laboratory are filled with thrilling and del ghtful experimentation, with the alluring prospect of a discovery that may spell Fortune always at hand to spur your enthusiasm. You Can Learn at Home To qualify for this remarkable calling requires elaborate specialized training. Formerly it was necessary to attend a university for several years to acquire that training, but thanks to our highly perfected and thorough system of instruction, you can now stay at home, keep your ; position, and let us educate you in Chemistry during your spare time. Even with only common schooling you can take our course and equip yourself for immediate practical work in a chemical laboratory. Dr. Sloane gives every one of -. his students the same careful, personal super- , CHEMICAL vision that made 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 INSTITUTE with apparatus and chemicals for performing. the fascinating analyses and experimental ,OF NEW YORK work that plays such a large part in our method of teaching, and you are awarded the , Experimental Institute's official diploma after you have satisfactorily completed the course. , Home Extension Equipment Division 8 Furnished to Every Student Easy Monthly Payments 16- 18 -R -E. 30th St. ,' NEW YORK, You don't have to have even the small price of the course to start. You can N. Y. 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Write us and let us explain our plan in full -give us the titulars and full par - heavy opportunity about the Experimental Equip - wooden box serves not only as a case for the outfit of showing you how you can qualify for a highly trained a ment given to every student. but also as a useful laboratory accessory for performing technical position without even giving up your present employment. -tell Me Also please countless experiments. O about your plan of payment MAIL COUPON FOR FREE BOOK Your name and address on the coupon will bring you by NAME CHEMICAL return mail our interesting free book, " OPPORTUNI- INSTITUTE TIES FOR CHEMISTS." and full particulars about the course and what it will do for you. You owe it to OF NEW YORK, Inc. yourself to get this book. Send the coupon right ADDRESS now while it is fresh in your mind. Or just write , your name and address on a postal and mail it , Home Extension Division 8 to us. 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www.americanradiohistory.com 170 Radio News for August, 1928

the switch (SW) is closed and should be be a 112A type, and the tube in the V2 po- off when the switch is opened. sition may be either a 112A or a 171A. A Next, the antenna coil (Ll) may be con- six -volt storage battery is used for provid- nected in the circuit. Terminal "A" of this ing filament current, 135 volts of "B" bat- coil connects with the "Aerial" binding post; teries are required for the plate supply, and terminal "B" connects with the "Ground" 22/ volts of "C" batteries are needed for binding post; terminal "C" connects with grid bias. the frame (rotor plates) of the condenser The 135 -volt terminal of the batteries is Cl, and terminal "D" connects with the connected to the post marked "B+ Power" stator plates of Cl. In addition, terminal and the 90 -volt terminal to the "B+" bind- "C" is connected to one terminal of the ad- ing post. The 22/ -volt negative terminal of justable condenser (C3), and terminal "D" the "C" battery is connected to the binding is connected to one terminal of the variable post marked "C- Power," and the 3 -volt resistor Rl, and the "G" terminal of vacuum negative terminal of this battery is con- tube socket VI. nected to the binding post marked "C -." In wiring the R.F. transformer in the The operation of the receiver requires no circuit, terminal "A" is connected with one explanation. After the set has been turned terminal of the fixed condenser (C4). This on at the switch it is necessary only to ad- condenser has not been mounted on the just the. dials (Cl and C2) until signals are baseboard, but is held in place with two heard at maximum strength, and then ad- wires; the other wire being that connecting just the volume control until the desired sig- the free terminal of the condenser with ternal strength is obtained. minal "P" of the tube socket Vl. Terminal "B" of the R.F. transformer connects with the "A -" terminal of VI; terminal "C" Price $1.97 connects with the stator plates of C2 and What's New in Radio the "B" terminal of the first A.F. trans - former (T1); terminal "D" connects with (Continued from page 125) the frame (rotor plates) of C2;. and termi- fixed by nal "E" connects with one terminal of the -pass condenser (C3) are used for A crystal detector. the purpose. Rl and R2 are fixed filament The next step in wiring resistors, but R1 produces also a voltage should be to com- drop plete the connections to the binding posts. which is employed as a negative bias RADIO for the control grid. The "C-" binding post should be connected mechanical by wire to the "F" terminal of transformer In construction, the unit is very compact; it is housed in a metal EDUCATION Ti. The "B+" binding post should be con- cabi- net 4% x 6 x 7% inches which nected to terminal "B" of transformer T2, serves also IN 5 as VOLUMES and the "F" terminal of this transformer a shield, and there are only two controls on the should be connected to the binding post front panel, the tuning condenser "THE RADIO marked Power." The binding post (Cl) and the battery switch (SW). At "C- the rear of the unit marked "B+ Power" should be connected will be found the exit . EDUCATOR" hole for to one of the tip jacks and the other tip a four -wire battery cable (B) and the binding -post jack should be connected to terminal "P" strip on which are mounted Theory, Design, Construction, the two aerial posts and the output Operation and Maintenance of the socket V2. post. Six wires are now required to complete LEARN AT HOME the receiver. First, connect the free terminal of the volume- control resistor Rl with I-o TH E S E five component the "G ". terminal of transformer Ti. Next, TO connect the "G" terminal of T2 with the AERIAL parts of a complete Radio POST Instruction Course are outlined "G" terminal of the tube socket V2. Con- ON SET. in five volumes that contain not nect terminal "P" of Ti with the free ter- merely the essentials as so minal of the crystal detector, and connect P of T2 with one terminal of the R.F. choke many books do, but more, they coil L3. Now connect the free terminal of contain all that any modern up- the choke coil to terminal "P" of the tube to -the- minute textbook on any socket VI, and run another wire from ter- subject would cover. They are minal "P" of the tube socket to the free in themselves a COMPLETE terminal of the adjustable condenser. Circuit of the screen -grid booster unit. From 45 to 90 volts is used on the screen -grid, de- radio education teaching every TESTING AND ACCESSORIES pending on the "B+" voltage of the amplifiers. possible portion of Radio science. With the wiring of the receiver completed, It is a very simple matter to connect the the circuits should be carefully tested. To booster unit to any receiver. Usually the Size of each 6 9 inches, book by do this, insert tubes in the two sockets, con- unit is placed at the left of the receiver so handsomely bound and illus- nect one terminal of the "A" battery with that it is convenient to tune the dial, con- trated with charts, diagrams, the "A+" binding post and close the fila- nect the battery cable to the power supply descriptions of equipment, etc. ment switch. Now connect a wire to the used by the receiver, and run a wire from Each volume 52 pages. free terminal of the "A" battery and touch the unit to the aerial post of the set. All the free end of this wire to each of the free original connections to the receiver are left SEND NO MONEY for these posts on the binding -post books. Just forward your strip. The tubes as they were except the aerial lead -in, which name should light when the wire is connected with is connected to the proper post of the and address. We send you the the "A -" post; but they should not light booster unit; then a wire is run from the books at once. On receipt of when contact is made to the other posts. If output post of the latter to the aerial post same you pay the postman the test does not prove that the circuits are of the receiver. After this has been accom- $1.9 7 plus a few cents postage correct, the wiring must be carefully tested plished, a 222 -type (screen -grid) tube is and then they are yours. until the error in wiring has been dis- placed in the socket of the booster unit and covered. the installation is ready for operation. Distributed by After the set has been completed and However, it must be remembered that, in tested it is ready for operation. It should order to operate the set, it is necessary to The Consrad be connected with an outside aerial approxi- turn on the switch in the booster unit as Co. mately 100 feet in length, and the ground well Incorporated as that on the front panel of the re- connection may be a wire firmly connected ceiver. 230 Fifth Ave., New York, N. Y. to a well- scraped -spot on the nearest cold- Manufacturer: Sterling Manufacturing water pipe. The tube in socket VI should Co., Cleveland, Ohio.

www.americanradiohistory.com 171 Radio News for August, 1928 Odd Uses for Tubes

(Continued from page 127) any convenient frequency, says 1,000,000 Solve Your Radio Problems with cycles (300 meters). Then, if the oscillator detector is tuned near 1,000,000 cycles, a beat note will be heard in the telephone receivers. If we tune it exactly to 1,000,500 Electrad Radio Controls hear a beat of 500 cycles. cycles, we shall These resistances are backed by the highest reputation of Or, if we tune the two oscillating circuits to must uphold that reputation. Therefore, if quality. We any wavelength or frequency we please, only the most scientific designs and finest materials are we make the difference between them equal used in their construction. To assure the highest order of to 1,000 cycles, we shall hear a 1,000 -cycle performance and satisfaction, insist on Electrad Controls. note in the phones. Electrad specializes in a full line of Now suppose we set our 1,000 -cycle Controls for all Radio Purposes buzzer going. The 1,000 -cycle current from this buzzer mixes with the beat note of the PHASATROL oscillators, and if the beat note of the oscil- Reg. U. S. Pat. Off. lators is made exactly 1,000 cycles, we shall A TRUE BALANCING DEVICE hear only one tone, since both tones are the FOR RADIO FREQUENCY AMPLIFIERS saine. But, if tlïe beat note of the oscil- You can solve the problem of R. F. oscillation noises by inserting a Phasatrol for each stage of R. F. ampli- lators differs by even so little as a half a fication. After installation of Phasatrol, it is possible second from the 1,000-cycle buzzer, to adjust its variable resistance to a permanent value cycle per for an amplifying tube so that no further chance of then we shall hear this beat in the phones. oscillations breaking out is experienced. Very easy We shall still not be able to distinguish the to install in the circuit. Price $2.75 each. two separate tones, for they differ too little to cause any perceptible change of musical TONATROL pitch; but the beat note will be there, and Trade -mark is recognized as a rhythmic waxing and A COMPLETE LINE OF VOLUME CONTROLS waning of .the tone heard in the phones. Smooth, gradual control of intensity under all conditions and a will be your reward if you incorporate the Tonatrol If it is desired, a crystal detector Volume Control in your receiver. Tonatrols are variable microammeter may be placed in series with resistors of the famous Royalty type, especially designed be I with the requirements of different circuits in mind. the phones, and these beat notes can Furnished in standard types or with battery switch or seen, as the needle of the meter climbs up power switch attached. From $1.50 to $3.00. S slowly and falls slowly, accompanying the waxing and waning of the note. These are we ROYALTY secondary beats, and the phenomenon ' be termed "beating of the beats." °niIIIIIIIIIIIIU'' VARIABLE HIGH RESISTANCES Electra - have may inc., course we may make these secondary A standard resistance widely recom- / Of mended for its accuracy and depend- / Dept. N -8, beats anything we please, and may vary ability wherever variable high re- beats per second up sistances are required in high fre- New York, N. Y. them from perhaps two quency circuits. There is a type please send me de- to the audible limit, which is somewhere for every radio purpose -11 1scriptive circulars on in all, designated Type A to /the following products about 10,000 per second. Type L. Potentiometer / and put me on your mail - / mg list for similar literatue types, $2.00. All others, / General Circular; ...Tons- $1.50. trol Volume Controls;_...Phasa- ULTRA- DELICATE MEASUREMENTS /trola; ...Royalty Variable Re- ./ sistois; ..Truvolt Divider Manual . (enclose Vic. for mailing);...Electrad) if any of the constants of either / Control Manual (enclose 10c. for mail- Now, Mall GOUpOn / What B Eliminator Shall I oscillating circuit are changed, even in the for full Build." (enclose 10e. for mailing). I am ,particularly interested in minutest degree, the secondary beat note Informs- / will change. So, if we want to measure a thin/ very small capacity, we may connect it Name across the terminals ab, of Fig. 5. Then / Address we adjust the variable condenser C by a City State micrometer dial or screw so that the secondary beat is as near zero as possible. Next, disconnect the unknown condenser from the terminals ab. Secondary beat notes will be heard in the phones, or seen order to make on the microammeter. In I n the secondary beat again zero, condenser C ELECTRA must be decreased slightly; and the amount we have to decrease it is equal to the capacity we are trying to measure. Great A handy manual of 36 I EAS I yrintvi &7oí must in making such measure- D pages and cover-88 Shielded Grid Awplimax care be taken illustrations-over 20,000 words - ments, for the apparatus is extremely sensi- practical- concise -understandable- USING SHIELOPLATE TUBES TYPE SP132 '`. prepared by Austin C. Lescarboura and Absolutely New and Different tive. The capacity of a two -inch piece of our engineering staff. That's "The The fastest selling kit on the market. Has been acclaimed Gateway to Better Radio " -yours for America's Geatest Receiving Set" by Radio Engineers, bus -bar is easily and accurately measured, 25e., from your dealer or direct from us. Designers, Editors, and Jobbers. Set Builders have if condenser C is accurately calibrated. American Mechanical Labs., Inc. been astounded by the revolutionary performance of this Specialists in Variable Resistors, receiver. Write for details or ask your dealer today. To illustrate how the apparatus may be 285 -7 N. Sixth St., Brooklyn, N. Y. TYRMAN ELECTRIC CORPORATION 314 W. Superior Street Chicago, Ill. used to measure extremely small weights, the terminal a can be connected to the pan of a sensitive chemical balance and terminal AIRPLANE CLOTH SPEAKERS FOR b to a plate beneath the pan. The slight Send for Free Catalog fiN motion of the pan when a small weight is It contains many bargains in all types From Chicago's Oldest of Cone Speakers, Units, complete parts -7, Radio Jobbers. The most valu- placed upon it is detected as a change of to build all types of cone speakers. Also able Radio for your capacity (in the condenser formed by the the latest parts of the New AIRPLANE Catalog. Write Cone Speaker. Accessories. copy today-IT'S FREE! pan and the plate beneath), which is meas- ACCUSTI -CONE, 1 No. 7th St., Phila., Pa. TELEPHONE MAINTENANCE CO. ured exactly as described in the preceding 123 -5 S. WelisSt., Dept.87 Chicago, Ill. paragraph. By special arrangements of apparatus, it Insure your copy reaching you each month. Subscribe to Radio News -$2.50 a year. has been possible to measure a weight as I Experimenter Publishing Co., 230 Fifth Avenue, New York City.

www.americanradiohistory.com 172 Radio News for August, 1928

small as one thirty -thousandth of an ounce, and a change of distance between two plates BUILD A DAVEN of only one three -millionth of an inch has TELEVISION RECEIVER been detected by this method! COMPLETE ESSENTIAL KIT -$45.00 The zero -shunt ultra -micrometer is used S. GERNSBACK'S in a similar manner. is shown in Fig. 6 The first complete Kit enabling anyone to build It `RADIO ENCYCLOPEDIA his own Television Receiver -and sponsored by and is seen to consist of a simple oscillator. Daven! The Kit consists of a Daven 21- aperture scanning disc for receiving WGY, Daven Motor, In the plate circuit of the oscillator is Bushing, Daven Television Tube, Three com- placed a resistor, and across this are con- plete stages of Daven Television Amplification JVew limp ! and Instructions for Building. nected in series a battery, a microammeter Suede f or galvanometer, and another variable re- Editio ' DAVEN 2 -STAGE POWER sistor. The purpose of this latter shunt cir- ESSENTIAL KIT -510.00 cuit is to enable us to use the most sensi- For use with 210 tubes -2 stages of Daven Power tive electrical measuring instrument known Television Amplification complete with Daven to science, the galvanometer; hence the Super Davohms and Instructions for Building. name of the system. DAVEN TELEVISION APPARATUS Each Daven Television Scanning Disc, 24 apertures for WGY S5.00 Daven Television Scanning Disc, 36 apertures for WRNY 6.00 Daven Television Scanning S. GERNSBACK'S RADIO ENCYCLO- Disc, 48 apertures 7.00 first Daven Special Television Am- PEDIA is the radio encyclopedia ever plifier (3-T) 12.50 compiled. The many -sided labor of research Daven Television Tubes, 20 to involved in collecting the vast amount of in- 80 milliamperes, striking formation required to make this work a com- voltage 150. Plate 1' -4 x1 i, in. 12.50 plete, dependable, and accurate guide, can Doyen Television Motor 15.00 best be realized from the fact that it took over Daven Bushing to fit ;' %a two and one -half years to gather the material and ?ë -in. motor shafts + 1.00 Daven Television Photo Elec- that it contains. Dávee nTeletision Resisto- Every known circuit, each and every hook. Couplers (stages 1. 2 and 3) 1.25 up, every modem development in radio and for stages 4 and 5 4.65 DAVEN electricity, every person of renown in the radio Doyen Mu -20 Tubes for Am- world, every word used in radio practice 9 - plifier Stages 25 this is what you will find S. GERNS- Daven AC-71 Tubes for out- in put tube in serles with Tele- BACK'S RADIO ENCYCLOPEDIA. vision Lamp 3.50 Daven AC-10 Tubes for out- The "zero- shunt" ultra -micrometer circuit is But you will find it much more than just a put tube in serles with Tele- sensitive to the smallest capacity changes. dictionary of these terms. This pioneer radio vision Lamp 9.00 encyclopedia is a manual of applied information, a working guide and instructor and an Daven Te:evlsion Write for Television Booklet Tube endlessly useful reference aid. There are The polarity of the batteries is arranged 1,930 detailed definitions, 549 photographs, THE DAVEN diagrams of circuits and drawings. A com- CORPORATION so that, whereas the "B" battery tends to plete cross -index is just one of the many Amplification Specialists Newark, N. J. send current around the shunt circuit features of this remarkable book. through the galvanometer in the direction S. GERNSBACK'S RADIOTEN- of the arrow a, the other battery opposes CYCLOPEDIA can be had in either of two beautiful bindings. this, trying to send current through the galvanometer in the direction of the arrow The luxurious limp suede edition ($5.00 a AR.T]EIE? was made for a copy) to meet the demand b. By properly adjusting the resistor R, more handsomely bound volume, after the the two may be made equal; so that we have usefulness of the book had been demonstrated New Outlet Plate by its extraordinary popular success in its a net zero current flowing through the gal- plain first dress. This edition, designed for FOR AERIAL- GROUND AND vanometer circuit. Hence the name "zero those connoisseurs who admits only, choicely covered volumes to their libraries, is a master- POWER RECEP- shunt." piece of de luxe binding. TACLE FOR The plate current of an oscillator is very The keratol -bound edition of this master A. C. SETS Radio Encyclopedia can still be had for the sensitive to changes of inductance or ca- original price of $2.00. This is a neat, sturdy, pacity. Consequently, suppose we start our workman-like book, offering precisely the Finished in same text, on equally attractive type pages. Satin Brass oscillator going and add a very small ca- $1.00 in the Both editions are of the large 9' z 12' size, pacity to the terminals cd. A change printed in clear, legible, large type. Both are Brown Bake- value of the plate current will take place. adorned with gold -embossed cover titles. lite 1.25 If, before we add the capacity to the termi- More than 25,000 copies of the keratol- Etched nals cd, we adjust the resistor R so that cover edition have already been sold, and are now being used, day in and day out, by that Bronze 2.25 the galvanometer reads zero, then on adding number of actual workers and students of the unknown capacity to cd, the change of radio, in colleges, schools, and public libraries, Folder on complete wiring of house and special radio and other scientific institu- plate current will produce a deflection of state in the country. furnished on request tions in every the galvanometer. This system is almost as Mail this coupon now. No radio sensitive as that previously described. enthusiast can afford to be without rCarter Radio Co, this authentic guide, convenient C H I c A G 0 Before closing this article, it will be well and attractive in form, unfailingly by no serviceable in content -S. GERNS- %MO( to remind the reader that we have BACK'S RADIO ENCYCLOPEDIA. means exhausted the list of applications of the vacuum tube. We have not touched upon S. GERNSBACK'S RADIO ENCYCLOPEDIA the multi -grid tubes, which have a number Limp Suede Bound Edition $5.00 of applications. We have not mentioned Keratol Leather Stiff Binding 2.00 the application of vacuum tubes to systems employing photoelectric cells. Indeed, it was S. GERNSBACK the vacuum tube that made it possible to 230 FIFTH AVE.. NEW YORK, N. Y. use the photoelectric cell effectively, on ac- 4.=1 count of the amplifying properties of the S. GERNSBACK, 230 Fifth Ave., New York, N. Y. InESTABLISHED 30 YEARS former. We have not touched upon the Kindly send me one copy of THE RADIO various relays and remote control systems ENCYCLOPEDIA. I will pay postman. We Have Complete Kits For All Circuits Limp suede leather binding -S5.00 plus postage. Now appearing or which have appeared made possible through the use of the Keratol leather binding-32.00 plus postage. in "Radio News" and other publications. vacuum tube as a detector and amplifier of (check which binding you want) Send for Circuit Booklet % Catalog very weak impulses. Radiodynamics, or M. & H. Sporting Goods Co. control at a distance by means of radiations Name 512 Market St. Phila , Pa. of various kinds, has profited greatly by the Address 6 -TUBE RADIO COMPLETE vacuum tube. And last, but by no means S34.75 to $66.66 Licensed R.C.A. Circuits. Shielded. One Dial the least, we have the oscillators, speech City State Write for catalog. Bic discounts to agents amplifiers, modulators, regulators, in broad- ConsumersRadioCo., Dep.148.4721LincolnAv.Chicago cast stations.

www.americanradiohistory.com Radio News for August, 1928 17. Movies Radio eJ C9 (Continued from surge 118) HAMMARLUNDPresenIs outer drum upon the mirror. '['he light thus produced on the mirror follows the shading 1 of the images on the original film, so that ct< a picture is built up in the mirror. This ../. / may be observed through the magnifying `., / mirror. Knob-Con trol A complete picture of 48 lines (corresponding to the rate of transmission) is built up on the mirror with every four DRUM DIAL revolutions of the drum. At the beginning of the second revolution, the contact brushes turn to the next segment of the switching ring (because of the gearing) and the second target of the neon tube is illuminated. 'l'he third and fourth quarters of the picture are similarly built up from targets :3 and 4, Ind the cycle then begins again with NO. 1 and the first spiral of holes. During one second the drum turns (ill times; since four A richly em bossed oxi- dized bronze escutch- revolutions eremite one picture, 50 revolutions eon of exclusive de- create 13 pictures. This gives us the speed sign and graceful proportions. Figures of 15 pictures per second mentioned jn the and graduations are early of this article. illuminated from the part hack. Of course, it is necessary to maintain perfect synchronism between the transmitting as in all and receiving motors, systems of HAMMARLUND now offers a new illum- Back View inated drum dial of unusual beauty, rugged design, and distinctive Note position of the mechan- Control Knob. By us- ical features. ing a Condenser Shaft of suitable length, the It is controlled by a knob, cleverly planned to Control Knbb may be be placed in any position on the panel, desir- placed at any desired able for attractive balance. distance from the dual, thus giving a pleasing The driving mechanism utilizes an exception- balance to the front of ally strong silk and linen cord, gripping a of the panel. drum, snubber fashion. It cannot slip - absolutely no back -lash or lost motion. Thoroughly tested for wear under actual working conditions, this cord withstood 36,600 full -range movements of a large multiple condenser without stretching, fraying or breaking. It will never receive similar treat- ment in average use. The original Hammarlund two- finger -control Drum Dial, introduced last season, will be supplied for those preferring that type.

If your Dealer can't supply you, write direct to us. Ask for Hammarlund literature. HAMMARLUND MANUFACTURING COMPANY 424 -438 W. 33rd Street New York

11115111111011111011110111P

ANOTHER SPECIAL OFFER! Left: A four -target neon tube. used in the radio -movies receiver. Xioht: an experimental six-plate lamp. UNI- RECTRON POWER AMPLIFIERS Model AP -935 television and radio photography. In the The UX -210 super power As the Uni- Rectron stands amplifying tube and the Washington demonstrations the transmitter it is a super power ampli- -216B fier. UX or 281 rectifying and the receivers were on the sanie power which can be used in tube are used with this am- connection with any radio plifier, which cannot over- line, so little difficulty was experienced in set and loud speaker. Bind- load. From the faintest keeping the pictures steady. ing posts are provided for whisper to the loudest crash input to the Uni - Rectron of sound -R. C. A. Uni- 'l'he pictures, as they appear through the and output to the speaker. Rectron each note Requires no batteries for its amplifies magnifying lens at a distance of about ten at its true value. High and operation. It obtains its List Price 588.50 low notes are all treated feet, are clean -cut black silhouettes against power from the 110 volt, (Without tubes) alike. The volume 60 cycle alternating deliv- the characteristic reddish glow of the neon current lighting cir- and quantity ered will be a revela- tube. They possess no fine shading; as cuit of your house. Special $19. 75 ea. tion. such refinement is not possible without the Every one new and packed in original factory carton use of a very wide band of frequencies at AMERICAN SALES CO., 19 -21 WARREN ST., NEW YORK CITY the transmitting end.

www.americanradiohistory.com 174 Radio News for August, 1928 A Booster Unit for the Browning -Drake mie (Continued from page 141) RADIO NEWS AMATEURS winding and approximately 1,500 turns are and tested, a shield should be made before needed. The drawing (Fig. 4) gives full the unit is permanently installed. This details of the coils used in this unit. shield may be constructed from sheet cop- HANDIBOOK Fans who do not wish to wind their coils per 1/64- to 1/32 -inch thick. The shield is may use standard apparatus. As a choke We inches high, 8/ inches deep and 4 5/16 coil, a standard 85- millihenry choke is en- inches wide. The front end of the shield is tirely satisfactory, and the secondary of left open for the front panel, and a hole an R.F. transformer may be used for the 2% inches high is cut in the rear of the aerial coil after the primary winding has shield at the base for the binding -post been removed. However, it is important to panel. In making the shield, solder is used make sure that the transformer has been to hold the edges together. designed for use with a .0005-mf. tuning condenser. USE A SCREEN-GRID TUBE ASSEMBLY In the letters received after the publication of a constructional article in this mag- The construction of the unit is so simple azine, many requests are always found for that little need be said regarding the method data telling how to adapt the receiver to to be followed. The panels are drilled the new screen -grid tubes. In anticipation

EL :I) :_= SW COPPER SHIELD J?IYJ'TECHNICAL e! RAI) 10 FANS VI BRASS f BRACKETS, EVERY WORTHWHILE LI DEVELOPMENT Ci NEW CIRCUITS AMPLIFIERS wQI® i _ iiiiiii SHORT -WAVE SETS IIIÌIIIII! TRANSMITTERS THEORIES & 4. PRACTICES Every worthwhile development of radio can be found reflected somewhere I within the pages of this great collection of circuits. The latest and approved methods of amplification, new and tried \ WOODEN receiving circuits, transmitters -every- BASEBOARD thing of interest to the experimenting 8'4" LONG X 4%4°WIDE X3/4'THICK fan is accurately and unbiasedly treated Fig. 5. This cross -sectional view of the Booster Unit shows the placement the in this amazing Handibook. The of RADIO NEWS AMATEURS' assembled parts, and the position of the shielding when it is placed over the unit. HANDIBOOK might be truly said to contain authentic data on every important event that has taken place according to the layout given in the ac- of this demand the circuit diagram of this since the beginning of radio as an companying diagrams. Five binding posts booster unit wired for operation with a industry. are mounted on the small panel and this 222 -type tube has been prepared and will may then fastened For the fan who loves to tinker with be to the rear of the be found in Fig. 6. From this diagram it radio, the "Handibook" should prove baseboard with wood screws. The variable may be seen that very few changes have a great help. Get your copy now. Fill condenser (Cl) is mounted in the center of to be made. First, the filament -ballast unit in the coupon. There is a.complete the large panel and the battery switch is is removed and the resistors R2 and R3 radio education in the pages of the mounted above the condenser. After the are substituted. These resistors should have RADIO NEWS AMATEURS' condenser has been mounted the aerial coil a total resistance of 17 ohms and should be HANDIBOOK. (L1) should be fastened in place with divided in such a way as to provide the

Over 116 pages -fully illustrated brackets as shown in the drawing. - grid of the tube with the proper bias. Replete with circuits on every- If worthwhile development. Me Before fastening the front panel to the the voltages suggested by the tube manu- this coupon now baseboard three parts should be mounted facturer are .used, the total resistance may EXPERIMENTER PUBLISHING CO., Inc. on the latter; they are the R.F. choke coil be placed in R2, and then R3 would be 230 Fifth Ave. New York, N. Y. (L2), the filament -ballast unit (R1), and eliminated. However, if lower voltages are the tube socket. The remaining parts in- used, R2 should tom -la be made smaller and R3 ------clude only the fixed condensers which are proportionally larger. An arrangement EXPERIMENTER PUBLISHING CO., INC. held in place by the wiring. which usually gives satisfaction gives R2 a 230 Fifth Ave., New York, N. Y. - Gentlemen: There is nothing of particular importance resistance of 11 ohms when R3 is a 6-ohm Enclosed fmd 50e.. for which please send me a copy to mention with regard to the wiring or resistor. of the RADIO NEWS AMATEURS' HANDIBOOK. testing of the unit, as everything is so sim- The second change is the elimination of ple that it is difficult to make a mistake. the neutralizing condenser (C3), and the Name Flexible insulated wire should be used for third change is the substitution of a shielded and all connections should be socket for Address the purpose the standard UX-type socket. soldered. Also, an extra binding post is required City State After the booster has been constructed for the screen -grid voltage. (See Fig. 6).

www.americanradiohistory.com Radio News for August, 1928 175 Rain, Rays and Radio (Continued front page 113)

a hastily -scribbled message to his chief.

"Return at once to Hollywood to pick up fluoroscope. (Signed) Wynn." a "Right!" nodded Dare. He handed the With Message to the pilot, who nodded, swung his controls, and headed the ship swiftly TOWNSEND about in the opposite direction. "e,, Socket Power From This Month's Mail A.C.-D.C. Frenchtown, N. J. Any Cycle Your Eliminator is working fine. I have not as yet "What do you believe," demanded Harold seen its equal. S. Chester Opdycke, Jr. Dare, as an hour later they were approach- Delivers up to 100 volts Monrovia, Calif. on any set. Full tone, I am well pleased with my Eliminator which I have ing the range of peaks behind which lay Clarity, Volume, Distance. been using for several months. I like it better every day. -George Beebe. Health Valley, "to be the cause of the Lakewood, N. J. strange phenomenon which Dr. von Stück I have had your Eliminator in use for over a year Logs 380 Stations on my five -tube Freshman set and find it O. K. reports?" Geo. C. Datum, Jr. From CUBA to CANADA ! Wichita, Kam. "It could have been but one thing," re- I have used my Eliminator for over a year. It's Never in the history of Radio has there been anything fine. plied the great Scott. "A fluoroscope, as that gets such sensational results at this astounding low -Dr. R. A. Thomas. price. Just read this letter received April 25th, 1925: "Your Monticello, Ill. you know, merely converts light of a fre- Townsend does its work, and more besides. I have it working The Eliminator I bought from you several months quency so high as to be invisible, into light about six or seven hours every day. I have tuned in 380 ago gives perfect satisfaction. -E. O. Michau. Stations all over the country, and Canadian, Cuban, Mexican, Montreal, Que. which can be detected by the human eye. and Haiti Stations -all on a 5 -tube Atwater Kent. And Your Eliminator works line. Reception comes in besides, only a 60 -foot Antenna. Yes sir, it is a dandy! loud and clear. Could not wish for better. Evidently there is in the atmosphere a dis- Nobody can beat it." Hartshorn. (Signed) WM. SCHULTZ, -H. play of some radiation higher in frequency 72 Seventh Ave., N., Tonawanda, N. Y. Lincoln, Nebr.. I have used your Eliminator for a year and it has than the extreme violet. any- Just plug a Townsend "B" Power into light socket and get given perfect satisfaction. F. Dewey. It might be your radio -M. share of these thrills. Columbia, Utah. thing between ultra -violet light and gamma I have used your Eliminator for months and like rays -or even the cosmic ray." it very much. -J. A. Gill. SEND ONLY $1.00 Buffalo, N. Y. Scott raised his fluoroscope to his eyes Simply fill out coupon and slip it into an envelope with only Have had good service from our Eliminator and 51.00 and mail at once. Your Townsend "B" Socket Power are very much pleased with it. -L. A. Beach. and stared steadily toward the dark masses Unit will be sent promptly. Deposit only 55.55 plus postage of cloud on the distant horizon, while Dare with the postman. Try out 10 days -then if not more than pleased return it, and purchase price will be refunded. peered ahead through a pair of binoculars. Only under the black pile of clouds dici TOWNSEND streaks of yellow light show that rain was falling. LABORATORIES Swiftly they 713 Townsend Street drew near, and as beyond Dept. 25 the nearest rho of mountains appeared CHICAGO, ILL. rain -drenched I-Iealth Valley, the earth beneath them was hidden in a low- hanging Money Back Guarantee floor of cloud. A bright flash of light illu- Approved mined the fluoroscope; and to the radio and passed by the rigid operator at his set came a strange shock; laboratory tests of Popular Radio Radio News for in a hissing of static, the signals of and WROT at Hollywood vanished, and instead through the turmoil, sharply shrilled the piping note of WROU at Health Valley! Now. Scott saw that the bright streamers Attach Only $1.00 to this were beams, as of a circle of searchlights Coupon concentrated on a spot in the center of the bank of clouds. He drew out his watch, TOWNSEND LABORATORIES 8-28 713 Townsend St., Dept. 25 Chicago, IIß: removed its crystal, and held it up in front Gentlemen: Attached find $1.00. Kindly of the fluoroscope. A round shadow showed send at once Townsend "B" Socket Power Unit, C.O.D. for $5.85, plus postage, on that the radiation did not penetrate the guaranteed 10.day free trial. glass. "Ultra -violet!" exclaimed Scott. Name 1 - At last the solution of the mystery lay 10Days Address clear in his mind. FREE "Land at Health Valley!" he directed. Se nd for ; City State TRIAL Ltierature "We shall catch the conspirators red - _. handed !" The rest of the story belongs to history: how the Dare forces, under the courageous leadership New DYNAMIC Speaker of Harold Dare himself, went Operates on electro- inductive principle out into the surrounding hills, surrounded Write for parilculars. and captured Dandy Diavolo and his hench- Balkite ALSO men; and how they DYNATONE ELECTROMAGNETIC POWER found cleverly con- SPEAKER UNITS cealed in the underbrush a dozen huge mer- FANSPEAKER RADIO COMPANY cury -vapor arcs for the production of beams Radio 74 Dey Street - - - New York, N. Y. of ultra- violet light. "And yet," demanded Harold Dare, after his prisoners had been safely manacled and hustled back to Hollywood by a convoy of armed guards, "there are a few points which are not clear in my Dependable mind. Just how DEALERS -SET did Diavolo produce Radio rain by the use of BUILDERS- AGENTS MUTEiR ultra- violet radiation ?" Write for this Catalog. New Products . Summer and Fall Book. Save money "Well," replied Scott, "the purpose of on newest hookups, sets, kits, parts, The Complete Quality Popular Priced Line - the ultra -violet searchlights was to accessories at lowest prices. Send for Comprehensive Catalog break The "Big, Friendly Radio House" LESLIE F. MUTER CO. the atoms of the atmosphere into WESTERN RADIO MANUFACTURING CO. 76th and Greenwood Dept. 827 -L Chicago ions- 126 West Lake Street, Dept. 18 Chicago, Illinois

www.americanradiohistory.com 176 Radio News for August, 1928

that is, into free electrons and protons, or nuclei. Rain is often formed by moisture collecting on particles of dust or charged CONSIDER FIRST particles existing as a result of ionization. - Diavolo chose a time when a good deal of moisture was present in the atmosphere. The Volume Control This moisture then settled on the ions Care must be formed by the ultra -violet rays, and gradu- taken to ally grew into drops large enough to fall Cent- =:- choose Vol- ume Controls to earth. t hat give long- "To illustrate the electrical action, think est trouble - free service- - of two spherical drops of moisture, each con- a type that taining a positive charge. When the two KNOW THYSELF will not introduce noise to combined, they would form a larger sphere. interfere with But the charge on a sphere is proportional quality of reception after a to the radius, and the radius of the larger short period of sphere is certainly not twice that of the service. Centralab Volume Controls have a two small ones. Therefore the potential of patented rocking disc contact that the new sphere would rise, and in this man- eliminates all wear on the resistance material. This feature adds to the ner clouds formed by this process would smoothness of operation, because a accumulate a high potential. Other clouds spring pressure arm rides smoothly on the disc and NOT on the resistance. would be negative with respect to these Bushing and shaft are thoroughly in- which were more highly charged, and would sulated from the current -carrying parts. NOT This simplifies mounting on metal panel be attracted, so that the clouds would grow or sub -base and eliminates any hand larger and heavier. By the same process, capacity when the volume control is in A a critical circuit. Full variation of re- the earth, also negative with respect to the sistance is obtained in a single turn highly-charged cloud, would attract the of the knob. Centralab has carefully studied every moisture drops, and a heavy precipitation "HEALTH" volume control circuit and has built-up would result." tapers of resistance that for each application assure a control that smoothly "But how would this affect radio com- MAGAZINE and gradually varies volume from munication?" inquired whisper to maximum. Dare. The specific circuit in which each of "Because any substance containing free these units is used, in outlined in a folder. Write for it. electrons, any substance easily ionized, is a good conductor of electricity. Now these CENTRAL RADIO LABORATORIES beams of ultra -violet light were arranged 19 KEEFE AVE. MILWAUKEE, WIS. in a circle about Health Valley. Any radio wave coming from the outside would meet POPULAR one of these beams and be conducted directly to earth. The same thing would be PRACTICAL true of signals originating in the valley itself. The circle of beams formed a shield, KNOWLEDGE just as a sheet of metal placed about a ABOUT THE radio coil shields the coil from outside influences." MECHANISM "So," mused Harold Dare, "if an acci- OF THE dent had not intervened, if Dr. von Stück had not looked up through his fluoroscope ORGANS just at the right time, our whole plan for OF THE v.,-tee t Used in the development of a great health resort ßODY Every High Grade Circuit and model city would have been ruined, HUMAN and we would have lost the confidence of or Receiver Today! the entire world. The long arm of coinci- X -L NEW BAKELITE INSULATED PUSH POSTS dence has saved us." The perfect binding post at last! Con- "Yes," agreed Scott; "as Dandy Diavolo venient, simple; permanent connec- SEXOLOGY tions. You don't have to remember to should have learned long since that, in real tighten them. Push down the X -L. Insert wire. remove pressure. Connec- life just as truly as in reel life, the long tion Is tight and will STAY tight. No PHYSIOLOGY vibrations can loosen. Release in- arm of coincidence invariably reaches out stantly. Engraved In all standard to markings. Price each, 15 cents. protect the virtuous from the machina- new up-to date book or wiring dlagran,= tions of wrong. If Dandy Diavolo would MEDICINE FREEBigof all leading circuits. Write today for copy. not extend his career of villainy to life beyond the camera, he would not meet with ANAT°MY XLRadio Laboratories disaster and retribution." ON However (he added to himself), then ALL, ,I Dept. A, 1223 Belmont Ave.. Chicago, Ill. there. would have been no story. S 50 Power Tubes Get Hot cOPY RADIO CATALOGUE A RADIO tubes of the 199 and 201A vari- To Dealers -New, illustrated 1928 eties do not develop much heat, even Wholesale Radio Catalog gives lowest prices on accessories, kits, packs. parts and after they llave been in operation for sev- Sets. Features master -built single control radio DEv®ÑD sets for both battery and all -electric operation. eral hours; but power-amplifier bulbs of Full showing of 'A" and "B" Eliminators and E thousands of other great values. Write on bust- the 171 and 210 types get quite hot. ee:, letter -head for this free book today. Therefore, before touching these HAM ILTON -CARR RADIO CORPORAT ION latter 711 Wnst Lake St., Dept. 396. Chicago, III. tubes after they have been in use for more !N )FN BBO-Y than five minutes, turn them off and give Nc MA Amplipack Makes Your Set them a chance to cool, otherwise you may a Modern A.C. Power Receiver acquire a few small but painful blisters. AT ALL LEADING DEALERS The heat generated by these tubes is a CAN BE ASSEMBLED IN ONE EVENING normal part of their operation; it is noth- EXPERIMENTER PUBLISHING CO. The latest word on Power ing to worry about. FREE BOOKLET Amplification and A. C. 230 FIFTH AVE. Conversion. Send for it. The same remarks apply to "B" rectifier TRANSFORMER CORPORATION OF AMERICA tubes, only more so, as these tubes handle NEW YORK CITY 1428 -1432 Orleans Street Chicago, III. considerably more power than amplifiers.

www.americanradiohistory.com Radio News for August, 1928 177 Weather Affects Radio (Continued from page 121) in the transmitted wave are similar to power variations; and the result is that the received signal will vary in intensity. This form of fading is slight compared to that produced through other natural phenomena. Much has been said about the effect of weather on the intensity of radio signals. It seems to be true that this occurs; but the correlation is generally associated with temperature more than with air pressure, except that pressure and temperature always are directly related. In other words, reception is best, and reaches over greater distances, during clear cold weather, and is not so satisfactory, relatively, in warm . and stormy weather. Regardless of the time of year, temperature is higher during cloudy and stormy periods and lower when the weather is clear and the air pressure INSTALLED Ground Out StaCc weather is associated with IN A FEW higher. Clearing MINUTES a fall in temperature, and is decidedly more favorable to the best radio reception and freedom from static. THE WEATHER MAP AND RADIO I-AERIAL Some investigators have found that, when two different weather areas, or centers of Let Ground Waves Bring You Amazing Distance, differing air pressure, are indicated on a weather map, reception will be best along a Crystal Clear Tone Quality, and Greater Volume line drawn connecting the centers of the and Selectivity without Distortion. two pressure areas. Such a line will then cross the "isobars," which are lines connect- SUB- AERIAL has brought a new epoch in Radio, No need longer ing points of equal air pressure. There is to bother with troublesome overhead Aerials. Why risk breaking no sound reason for this theory. Certainly your neck to put up roof aerials only to have the first storm blow troubles. Why use there is nothing known to meteorology to them down? Forget your Aerial not the whole earth as a static and noise filter with Sub -Aerial? justify it, yet on the face it is quite obvious. However, exceptions to the rule are such COSTS NO MORE THAN AN OVERHEAD OR LOOP AERIAL that the theory cannot be accepted as con- and less than many. Hook your set on to the newly discovered clusive. Ground Waves that bring practically static -free reception. Don't stand for the squawks and tin -pan reception you get from Air Waves In this caseb we might best consider tem- lines "isotherms," which are when you can step right out and leave that stuff. perature or If you don't believe us, try it yourself. If you do not find we're lines connecting points of equal temperature, right- absolutely right -you don't pay us a cent for the test. and their relation to air pressure. Isotherms i and isobars are seldom parallel; the former We know so well the surprising results you'll get we'll let you .0... ee mostly at right angles to the latter. that put in a being TRY IT FREE! Sub -Aerial entirely at our Risk, 0# 0 í1 Therefore, if we are to say that reception Don't take down your overhead Aerial. Pick a summer 4 aGxv°teof ° is best along a direction which is across the noise interference on your old 4 night when static and # 5 9e4ts' isobars, it is then best in a direction mostly Aerial are "Just Terrible." If Sub -Aerial doesn't Sell 01 teetti, parallel to the isotherms, or at least through Itself to You Right Then on Performance -you 0 5tßáo 5s needn't pay us a cent. Send for "all the Dope 5,c an area of equal temperature. While the I G>,o e4 continuity of isotherms is often broken, on Sub -Aerial." You'll be surprised. Do it 4A.5iot ga° due to local temperature conditions, eleva- NOW. 11,0%,,,, tion, etc., the writer holds that reception is Underground Aerial Systems 0.. Q.e o °° Bldg., Dept. 9-L. St. Clair G4

www.americanradiohistory.com 178 Radio News for August, 1928

the normal conductivity of the air and pre vent all of the power of the emitted wave from passing on up toward the Heaviside Laver. Fading produced by ionized areas interfering with the deflected portion of the received wave as it comes down from the Heaviside Laver. Fading produced by earth currents and surges up the ground wire in opposition to, or partial neutralization of, the radio wave because of the attraction of passing overhead atmospheric and cloud charges. GOOD RADIO WEATHER AVIATION Good reception will be noted during clear EVERYBODY'S AVIATION and cold weather with little static dis- turbance. GUIDE is a complete discourse List Poor reception, as a rule, during warm on practical aviation, by MAJOR Price VICTOR W. PAGE, one of the $4só and cloudy weather with much static interference. Even when distant reception is leading men in the field. Unlike good, the noise level is too great for good most books of instruction, reception. EVERYBODY'S AVIATION Good reception, as a rule, when the direc- GUIDE is written in a unique tion is through an area of equal tempera- question and answer fashion, ture, parallel to isotherms, or across isobars. which makes the subject far easier to study and a great deal more attractive as an in- Radio Wrinkles struction course. (Continued from page 151) was recently The use of Ionized Helium gives This book published and to the Raytheon "BH" Tube a hole for the phone cord in the is absolutely up -to -date in every way. superior ruggedness, side of the a far longer plug cap. It has had very favorable criticism life and a sustained voltage. Be throughout country -wide aviation cir- sure you get a Raytheon "BH" for After following the directions given in your eliminator when the tube cles and has been highly recommended needs replacing which is generally the above paragraph, attach the cord to by all those in a position to pass every nine to twelve months. the plug and wind the cord on the roller. judgment. The roller may now be mounted under the We list table; the spring end is mounted in the here the contents in order that you may see for yourself how com- same way as when used for a window shade; pletely the field of Aviation is covered. and a radio jack mounted on a wooden block constitutes the bearing for the other Contents: end. The tension is regulated in the same Early Aeronautic History -First Flying way as that of a window shade.- Walter Machines -The Atmosphere Forms of Aircraft -Airplanes and Air - Dean, Jr. shipsC Lighter- Than -Air Craft -Balloons and Dirigibles How An Airplane Flies- Elementary Cuff Buttons Good Clips Aerodynamics THE experimenter who Airplane Parts and Their Functions tries first one cir- Fuselage Forms and Landing Gears cuit, and then another, often finds bind- Wing Arrangement and Construction ing posts Power Requirements, Engine Types and a great inconvenience when mak- Engine Location ing frequent changes of connections. Aircraft Propellers. Design and Applica- tion Siffi Airplane Equilibrium and Control Enjoy Louder, Clearer Official World and American Air Records Better DX at Our Risk Why listen-in on weak, noisy, scratchy, squealy air waves when ground waves are clean, smooth and strong? Why listen to fading, jumbled -up distant reception when you can bring it in loud, sharp, and clear, like local? The New Improved SUBANTENNA -the first and only satisfactory device to pick up ground waves, completely does away with the old style"aerial" and enables any set to get distant stations that it never could get before. STATIC BANISHED Price $2.00 Ground waves are far less affected by static than air waves. Subantenna receives these practically static-free ground waves and transmits every note pure and audible. And with Subantenna you have no roof climbing as with an aerial and no risk from lightning Approved by Thousands of Fans and Leading Engineers John White, of Brooklyn, N.Y., plainly received both Melbourne and Sydney, Australia, on a six -tube set with a SUBANTENNA These snap -on cuff buttons make very con- Over 248 pages -a distance of 10,144 miles, when an "aerial" brought In venient and satisfactory test connections. Beautiful red cloth binding -Title in gold nothing but noise. W . C. F. of Chicago got Havana, Cuba and Buenos Aires, S. A., on a Subantenna. Radio News, Radio Replete with illustrations Age, Radio Digest and other leading laboratories approve and A device of the type illustrated above recommend Subantenna. Easily and quickly installed. Never DIRECT TO needs attention. Write at once for particulars of FREE TRIAL provides a very simple solution to the prob- WRITE GUARANTEE OFFER which permits you to test the New Improved SUBANTENNA on your set entirely at our risk. lem. An old discarded pair of snap -type CONSRAD CO., Inc. Write today. cuff buttons is used for the purpose, and CLOVERLEAF MFG. CO. 230 Fifth Ave. New York , N. Y. 2714X Canal Street Chicago, III. one -half of each button is fastened to the baseboard of the set while the other half connects with a of CONSRAD COMPANY, Inc. wire the battery cable. 230 Fifth Ave., New York, N. Y. By snapping the two halves together a good Gentlemen: Kindly send me one copy of your book, EVERYBODY'S AVIATION GUIDE electrical connection is made, and by pull- Enclosed find S2.00. ing them apart the circuit is broken. For fastening the button to the baseboard the Name head of a screw is soldered to the back. The Address back of the other half of the is TOBE A FILTER with any good two-ampere button charger eliminates the A BATTERY soldered to the desired lead. W. Satter- Send for pamphlet for full details J. City State TOBE DEUTSCHMANN CO., Cambridge, Mass. white.

www.americanradiohistory.com Radio News for August, 1928 179 The Listener Speaks (Continued from page 114) Take the Advice and whine, hums from chargers, leaky mixture is faulty with poor ignition. A of Leading Radio A.C. lines, roars from violet rays, frying good circuit is no good with poor tubes and Service Organizations noises (similar to potatoes being thrown in a poor circuit will work good with good hot fat) from motors of different types and tubes. Play Safe with arcs from trolleys -and yet, the people I enclose a picture of my World's Record who want better reception are the cause of super; I used the loop and tight -coupled PARVOLTS! 60% of the interference. They seem to aerial for this reception. Over 3,000 miles want the penny and the candy too. daylight reception would seem to repay me for an extra outlay in tubes. Let the chains broadcast all they want to ; I know only one spot where it is impossible to get anything else sometimes. That is from

1,1,,,1,,,,, .1.1,1111.111,,,"11,11, t,".11,,,, Mr. Cox will meet with more envy than sympathy in his story of the joys and woes of reception.

I have something, I think, that will cause WEAF, 610 kc., to WCAE, 650 kc. Try a lot of `how- come" letters; it is a verifica- and get rid of local interference; then we Mr. Mc- can have radio. Donell says: tion from 2L0, London (enclosed) for re- Our PAR -

A good many . homes never see a radio VOLT display board ception at 12:44 p. m., E.S.T., and at a time is very useful, for we magazine, and articles under the frequently which does not fall in the schedule of 5SW, printed have occasion to programs in the newspapers would be the show our clients how these To me, is condensers are made." its short -wave rebroadcast. there only possible way of informing such owners no kick in short -wave reception. of the faults of their appliances. Try and If you want the real truth about condensers, go Everybody knows that a good motor is get your newspaper to run such an article. to an organization that builds, services, and repairs every type of radio receiver very poor with poor carburetion, and a good HERBERT Cox, 1936 Ferry St., Easton, Pa. and power supply unit. Mr. Frank McDonell, of Rossiter, Tyler & McDonell, says: "We think so well of ACME PARVOLT Condensers that What Is A Good Loud we have samples constantly on display for all clients to Speaker? see. Those of our customers who know radio also know that PARVOLTS are thoroughly reliable. We like our (Continued from page 133) clients to realize that we use the best .in radio." Should a condenser blow out, many dollars reproduction of these speakers could be inforce each other, and seriously affect the would be lost in ruined tubes, transformers, greatly improved by increasing the diameter sound, if it were not for the baffle. There- chokes, and other parts. The experience of of the paper cone. Speakers of this type 36 fore, as the size of the baffle is increased, the nationally known house of Rossiter, inches in diameter were found- to produce the cut -off frequency is reduced. Tyler & McDonell should be a good guide results; but these were generally From a theoretical viewpoint a for other builders and service men to follow. excellent baffleboard Don't take considered too large for home use. At pres- six feet or more across would be required any chances with condenser breakdown. Play safe with ACME PARVOLTS. ent, a 24 -inch speaker is being presented as in order to reproduce the lowest notes which a compromise between the small 16- and 18- are broadcast. However, for a cut -off fre -' inch sizes and the three -foot size; and it is quency of 100 cycles, a much smaller baffle very satisfactory. In the cone speaker, may be used, and this cut -off frequency is however, there are so many factors to con- entirely satisfactory for home reception. sider that it is difficult to explain the differ- Also, by use of a box -shaped baffle the size ence between a good and a poor instrument. of these speakers may be greatly reduced. The quality of the paper, the design of the From a practical viewpoint, the free -edge driving unit, the length of the driving rod, cone speakers are no larger than a double etc., all have an effect on the reproduction; fixed -edge cone which provides the equiva- and, therefore, the only way to determine lent in quality of reproduction. the quality 'of a cone is by a demonstration. Speakers of the free -edge cone type have ACME PARVOLT FILTER CONDENSERS-. Fig. 8 and Fig. C clearly illustrate the con- several advantages not possessed by the Supplied in all standard mid. capacities for. 200, 400, 600, 1000, and 1500 Volt D. C. requirements. Uni- struction of this type of speaker. fixed -edge type. First, they are ideally form height and width for easy stacking. Supplied The free -edge cone is suited for mounting singly or in complete housed blocks for the important speaker anôther inside a radio cabinet; power supply units such as Thordarson, Samson type which has been greatly improved re- and, secondly, a short driving rod is pos- and others. ACME PARVOLT BY -PASS CONDENSERS are cently. Such a speaker has a single cone sible and this helps to reduce distortion. supplied in all standard mfd. capacities and for all which is attached to a "baffleboard," but not Also, if correctly designed, they provide required working voltages. rigidly, with chamois, and is capable of ex- practically uniform amplification over a very cellent reproduction if correctly designed. wide band of frequencies. Fig. 9 illustrates ACME PARVOLT CONDENSERS Free -edge cone speakers need not have a the construction of two free -edge cones. Made by the Manufacturers of large cone in order to provide good results, ACME CELATSITE but they must be attached to a large baffle; THE TENSE -DIAPHRAGM TYPE as the size of the baffleboard determines The HOOK -UP WIRE linen -diaphragm speaker is one of Celatsite Flexible and Solid, Battery and Power the cut -off frequency. Speakers of this type the latest developments; and this is gaining Supply Cables, Spaghetti Tubing. Stranded and set up air waves simultaneously from the Solid Antenna Wire, A. C. Celatsite Wire, Loop wide popularity, because of the excellent re- Aerial Wire, "Pushbak" Wire, Window front and the back of the cone, Lead -ins. and these production it is capable of providing, and The ACME WIRE CO., New Haven, Conn. waves would alternately neutralize and re- because it is more sensitive to weak signals

www.americanradiohistory.com 180 Radio News for August, 192e

than many other types of reproducers. These speakers resemble a drum more nearly %;1 ; 90 Volt Power than any other instrument. They consist of two square diaphragms of stretched linen 4 on parallel wooden frames, with the centers v_* l of the diaphragms drawn together and connected to a loud- speaker unit at this point. Unit :: $12.75 The frames are usually mounted about eight inches apart and their usual size is twenty - four inches square. The diagram in Fig. 10 clearly illustrates the construction. Speakers of this type possess several important mechanical features. Because the two diaphragms are perfectly balanced, the slightest vibration of the loud -speaker unit -in all ils phases! will produce an audible sound. Also, the Complete instruction course in three fact that the diaphragms are balanced im- volumes. Every point of aviation effic- proves the quality of reproduction; as the iently and thoroughly treated. Subjects load on the driving rod of the speaker unit covered in these volumes- Hums, line noises, etc., positively impossible with is equal in both directions. Another inter- this new advanced unit. Plug in and forget. Non- dia- acid and noiseless. All detector and intermediate esting fact is that the highly -taut voltages plainly marked. Simpler to hook up than phragms make it almost impossible to over- MODERN dry cells. Operates any type set 1 to 12 tubes. AIR CRAFT Greater volume and clearness guaranteed. If not thoroughly load the speaker, even with a large power satisfied return after using 30 days for complete refund. amplifier; and this avoids the rattling which Guaranteed further 2 years. For 110 -120 volts A.C. 25 to 60 cycle current. 90 volts, 512.75; 11234, 115.25; 135. is so frequently experienced with cone -type 700 Pages $17.50; 15734, $19.50; 180, 524.00; 20234, $26.00. Also built for D. C. current 110 and 32 volts at only $3.00 speakers. 500 Illustrations additional, any size above. Ample stocks -same day ship- ments. Simply say-ship C.O.D. or write for_my interesting literature, testimonials, etc. THE ELECTRODYNAMIC SPEAKER Contents of each chapter - The electrodynamic -cone speaker is an- I. Aircraft Types. II. B. HAWLEY SMITH Lighter - than - Air Craft. other type of speaker which is now gaining III. Early Airplane De- 334 Washington Ave. Danbury, Conn., U. S. A signs. General Design rapid popularity. This speaker has been Considerations. IV. De- designed especially to enable fans to realize sign and Construction of the full advantages of power amplification. Aerofoils. V. Arrange- Your Set Can ment, Fabrication and Bracing of Airplane Wings. VI. Fig. 11 and Fig. D show the construction. Airplane Fuselage and Landing Gear Construction. Now Get VII. Airplane Power Plant Types and Installation. Short Waves The difference between the electrodynamic VIII. Aviation Engine Design and Construction. Sent anywhere in the U. 5. and the more familiar free -edge Air-Cooled Engines. IX. Aviation Engine Design post paid upon receipt of speaker and Construction. Water -Cooled Engines. X. Avia- price. Canada and Foreign, cone speaker is not in the construction of tion Engine Auxiliaries. XI. Aircraft Propeller 60c additional. Money order only. Also sent the cone; for these are of identical design, Construction and Action. XII. Airplane Equilib- C. O. D. plus postage in rium and Control Principles. XIII. Uncrating, Set- U. S. if 51.00 accompanies but in the construction of the loud- speaker ting Up and Aligning Airplane. XIV. Inspection and order to insure carrying unit. The electrodynamic loud-speaker unit Maintenance of Airplanes and Engines. XV. De- charges. In ordering be tails of Modern Airships and Airplanes. XVI. Sea- sure to name set and tubes operates on a different principle from the Amphibians Other Air- used, such as UV199 planes, Flying Boats, and UX199, W D11, 201A, UX226t permanent- magnet type which is used in all craft. XVII. Some Aspects of Commercial Aviation. or UY227. Price $15.00 or XVIII. Aircraft Instruments and Aerial Navigation. $17.50 for A. C. Sets. of the other speakers discussed in this ar- XIX. Standard Nomenclature for Aeronautics ticle. These speaker units possess valuable Report No. 240, Part I. The SUBMARINER This book is written in simple, understandable will convert your regular set into a short -wave receiver by simply characteristics found only in this type of inserting a plug in place of one of the tubes. This takes but a few language. seconds. With "Submariner" it will enable you to tune between reproducer, and they avoid many of the PRICE $5.00 26 and 68 meters. This device operates with all sets, such as T.R.F., Neutrodyne, faults of the permanent- magnet type of Super-Heterodyne and others A C or D C operated. No addi- units. AVIATION tional tubes, batteries, or coils required. If set operates a ENGINES speaker it will do so with "Submariner" attached. - Operates a wave changer with Super -Heterodyne and as detector unit In electrodynamic speaker units there is a with others. This treatise, written by a large field coil, which must be excited by an recognized authority on all SHORT -WAVE RECEPTION of the practical aspects of is practical, and especially in summer, as they penetrate better external source of direct current in order internal combustion engine and there is less static. The "Submariner" waveband includes force. construction, --- .maintenance, practically All Powerful Stations Which Broadcast Pro- to produce the necessary magnetic A and repair, fills the need grams. You may also listen to amateurs from all parts of the moving coil is freely suspended in the field as no other book does. world who transmit code messages. You will have one of the The matter is logically most efficient short -wave receivers when the "Submariner" is of this coil and the moving coil is attached arranged; all descriptive mat- attached to your set. Get a "Submariner" so you may have ter is simply expressed and command of the short -wave activities as well as the broadcast directly to ' a small free -edge cone. The copiously illustrated, so that band. If your Dealer does not carry - anyone can understand air- audio -frequency currents pass through this plane engine operation and ORDER TODAY DIRECT coil and cause it to vibrate. This method of repair even if without pre- This device has been nationally advertised, and sold in all parts of vious mechanical traininr. the world for the past two years a number advan- This work is invaluable for construction provides of anyone desiring to become J -M -P MANUFACTURING CO., INC. tages. an aviator or aviator mechan- Department 53 Milwaukee, Wis., U. S. A. ician. place, field in In the first the magnetic 274 PAGES PRICE $1.25 which the moving coil is suspended is of great strength and constancy, and the forces A. B. C. OF acting on the coil, which produce the sound, AVIATION NEW SHIELDED are dependent entirely upon the current in This book describes the basic the' coil and not upon the position of the principles of aviation, tells SUPER -10 how a balloon, or dirigible is coil in the field; also, there is no armature made, and why it floats in the air. Describeshow an airplane 5 Screen Grid R. F. Amplifiers to over -saturate. These features result in flies. It shows in detail the different parts of an airplane. 4 Stage Power A. F. Amplifier almost complete freedom from distortion in- what they are, and what they Illustrated literature gratis troduced by the speaker unit itself. In ad- do. Describes all types of airplanes and how they differ In Complete Constructional Blue Prints, dition, there are other merits: the drive is construction, as well as de- $2.00, postpaid tailing advantages and applied directly to the cone, thus eliminat- disadvantages of different ing the necessity of a driving rod, which is a types of aircraft. It includes a NORDEN- HAUCK, INC. complete dictionary of avia- cause of The tion terms and clear drawings Builders of Highest Class Radio Apparatus in the World frequent distortion. speaker of leading airplanes. Marine Bldg., Philadelphia, Pa. offers almost a pure resistance load on the Cable Address "NORHAUCK" power tube, as the inductance of the moving PRICE $1.25 coil is very low. This results in a high "power- factor" and an impedance which Remit by cash, stamps, check, or money order No C.O.D.'s varies but slightly with the frequency. Also, As one cf the oldest patent the motion of the coil is across the air gap We Pay Postage On All Books firms in America we give in- PATENTS ventors at lowest consistent and, as a result, there is no danger of its charge, a service noted fol results, evidenced by many well known Patents of extra. hitting the pole pieces when loud signals are CONSRAD COMPANY, Inc. 'ordinary value. Book, Patent- Sense, free. Lacey & Lacey, 631 F St., Washington, D. C. Estab. 1869 being received. 230 FIFTH AVENUE NEW YORK

www.americanradiohistory.com Radio News for August, 1928 181 Circuit Changes on the CAL -1 O Neutroheterodyne For Radio Consoles SINCE publishing a series of three ar- A new console designed for ticles describing the theory, construc- 18 after. RADIOLA MODEL tion and operation of the Reich Neutro- or other receivers, either A.C. or D.C. heterodyne receiver and its power unit (in the May, June and July numbers), RADIO NEWS has received a considerable number of Clearer letters from readers who desire further information on the circuit. Many of these contained simple questions about the con- IO struction of the set, but others suggested changes and improvements and requested our opinion on revised arrangements. There- fore, this. article will consider the most popular queries received, for the benefit of firn those who are interested in the set but did not write in. Also, it will describe a circuit improvement perfected by Mr. Reich since the publication of his article.

SCREEN -GRID TUBES NOT ADVISED Probably the question most frequently asked us regarding the Neutroheterodyne receiver is this: "Is it advisable to redesign the set to permit the use of 222 -type (screen -grid) tubes in the intermediate - frequency amplifier stages ?" In this con- Excello Console Model R 43 nection it may be explained that the use of screen -grid tubes in place of 201A -type Receiver compartment is a sliding drawer 29 in. x 91A tubes in the intermediate stages of a re- in. x 12 in. deep. Ample room in speaker compartment for cone speaker and eliminator. Cabinet, walnut ceiver may result in one of two possible ad- with fancy butt doors. throughout, walnut veneer vantages: either an increase of - amplifica- .41 your Dealers, or write for complete catalog offull line. tion, or a decrease in the number of tubes. EXCELLO PRODUCTS CORP. 4832 W. 16th St., Cicero, Ill. (Suburb of Chicago) On the other hand, when used with 201A- Pacific Coast representative- Pacific Sales Corpora- type tubes, the Neutroheterodyne, as now Larkin Street, San .Francisco, Calif. tion, 426 designed, at all times gives more than ample sensitivity and volume. Gaining additional sensitivity per stage, by use of 222 -type BATTERY POWER DEPENDABLE "B" tubes, in order to male possible the elimination of ene intermediate stage without reducing the range of the receiver, is not entirely satisfactory; as the selectivity of the receiver would be impaired to an undesirable point. There would, therefore, be no real advantage in the use of 222 -type tubes, and their use would introduce a number of needless complications. These tubes, also, tend to be very microphonic.

100 Volt Edison Element. on Destructive, Rechargeable "B" Battery with 199 -TYPE OSCILLATOR charger. Shipped dry with solution, $12. 140 Volt with charger, $17. 180 Volt Power Unit with Trickle Charger, $24.00. Free sample cell. See how it The type of the tube used in the oscil- operates. also attracted some attention. SEND NO MONEY -PAY EXPRESSMAN lator stage Write for our Free Illustrated 24 -page Booklet In the text and list of parts in the second SEE JAY BATTERY CO., 915 Brook Ave., New York installment of the article, it was stated that either the 201A- or 199 -type tube may be used satisfactorily in this position; and sev- EARN CODE eral experimenters have found that better Quickly and easily at home with the TELEP LEX C ode results are obtained with the 201A -type. It GAIN CeCo blazes the Instructor. No experience necessary. Simply listen is true the coils of the set were de- to expert operators send mesaoees, radiograms. etc. - that trail in radio engineering regular code -traffic as sent on the air. Provides prac- signed especially for a circuit using a 201A- tice when, where, and how you want it. Endorsed by achievement by introducing U. S. Navy and leading schools. Complete course of in- type tube and, when a 199 -type tube is used structions (Wireless or Morse) for beginners and advanced students furnished. Learn code and enjoy the in the oscillator stage, there is some reduc- the popular Screen GridTube thrill of real DX. Write for booklet NR8. tion in signal strength on long -wave sta- in an A.C. type: -the AC22. TELEPLEX COMPANY tions. Also, the dials do not remain per- I 76 Cortlandt St. New York, N.Y. fectly synchronized on all waves. The CeCo line of A.C. tubes If it is desired to use a tube of the 199 - is most embracing type permanently in the oscillator stage, it complete, will be best to reconstruct the oscillator practically every existing type resistors and coupler. Adding five turns of wire to each condensers that are winding of the coupler will make it possible CeCoTubes are carried in stock Built Better to endure. to obtain the same efficiency with a 199 -type by dealers everywhere. Write Write for The Research Worker. tube as from a 201A -type with the original us for unusual and interesting A free monthly publication. coil. Also, the use of a 199 -type tube in booklet entitled "Getting the AEROVOX WIRELESS CORPORATION this position effects a reduction in the fila- most out of your Radio." 68 Street Brooklyn. N. Y. Washington ment current required for the receiver. When building the power unit for the re- CeCo MANUFACTURING Co. Inc. ceiver, it may be found necessary to reduce P R O V I D E N C E , R 1. MHP4 its size slightly in order to fit it into a con- ON CONDENSERS For full informat on address Department RN, www.americanradiohistory.com 182 Radio News for August, 1928

sole cabinet. It is possible to make the power unit somewhat smaller by removing two of the parts and placing them in the receiver. The first -detector "B" choke may be mounted above the first audio transformer in the receiver, instead of in the power unit, and this arrangement will not affect the efficiency of the circuit in any way. In addition, if preferred, the output choke coil may be mounted in the receiver, over the second audio transformer. Be- cause of the limited space, it will be necessary, however, to use a choke coil having smaller mechanical dimensions. A choke of the type used in the first -detector "B" circuit may be employed for the purpose. In operating the receiver, with the first - detector "B" choke mounted in the power unit, if a fairly loud 60 -cycle hum is heard at all times in the loud speaker, it probably is caused by stray fields from the power transformer, which are picked up by the choke coil. In order to eliminate this hum AMAZING STORIES QUARTERLY, a big, in- the choke coil should be turned about until tensely interesting magazine of truly remarkable best results are secured. If it is found im- tales, is on the newsstands ready for the public to grasp and enjoy. AMAZING STORIES possible to eliminate the hum entirely, it QUARTERLY is a book full of tales of 'inter - may be necessary to place the choke coil planetarian communication-not foolish impossible fiction, but "scientifiction " -fiction with in the receiver as described in the preceding a plausible scientific background. Tales of other paragraph. Also, the power unit should be worlds -of strange people -of weird happenings - of the future -this is what AMAZING STORIES placed at least three feet from the receiver QUARTERLY brings its readers. Only those wherever possible. who have read it can fully appreciate the value of this remarkable magazine. Words fall far short in describing, with the smallest degree of ADJUSTMENT OF I.F. TUNING accuracy, the true nature of AMAZING STORIES QUARTERLY. An important operating kink has to do Stories by some of the best-known authors with the connections to the adjustable con- of the day-gripping narratives well worth reading. You will not want to miss this out- densers which are used to tune the inter- standing quarterly issue of AMAZING STORIES. mediate- frequency transformers of the re- There are many hours of pleasant reading await- ing you. ceiver. One terminal of each condenser makes electrical contact with the adjusting AMAZING STORIES QUARTERLY screw; to prevent detuning during adjust- Over 144 pages -fully illustrated ment, it is essential that this terminal be Large 9 -in. x 12 -in. size connected to the transformer terminal R, AT ALL NEWSSTANDS OR WRITE DIRECT and not to G. Also, it will be noticed that these condensers change slightly in capacity with their temperature. It is, therefore, best to adjust the receiver carefully after Experimenter Publishing Co. the set has been in operation for several 230 FIFTH AVENUE hours, and has warmed up completely. Also, NEW YORK, N. Y. it is well to check this tuning occasionally.