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L lcrusll't NEWS ex, I .I:I:i I4 JI% S HUGO GERNSBACK, Editor formerly

LADY TELEVISION ENGINEER SEE TELEVISION NEWS =1949= NOV _IS= 1949

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U. S. una CANADA LATES IN RADIO - ELECTRONICS - TELEVISION www.americanradiohistory.com 4

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YOUR TELEVISION WILL BE IMPROVED WITH A D OUTDOOR AERIAL

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The modern miracle of pictures by air can be a most satisfying means of entertainment. But be satisfied only with a picture comparable to a class "A" motion picture-on every station in your area. It is unnecessary to compromise! HERE'S WHY: Television waves are like light beams - solid objects reflect and refract them, making it impractical to pick up all stations from an indoor aerial. That is why you get double images on some stations. In addition, indoor aerials have poor signal pickup making it difficult to get good pictures on all stations. FURTHERMORE: Your indoor may have a high level which increases the amount of interference as you ad- vance the contrast control to bring up a weak picture. All of these technical difficulties are eliminated by a WARD out- door aerial installed by a competent radio serviceman. In every case, a Ward outdoor antenna will improve reception over an indoor aerial. Also, Ward aerials are so well de- signed, they are attractive on a house. It is unnecessary to compromise!

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www.americanradiohistory.com Hugo Gernsback, Editor -in -Chief

RADIO Fred Shunaman, Managing Editor 1:1.1:1:iR11\ I/:S M. Harvey Gernsback, Consulting Editor formerly RADIO -CRAFT Robert F. Scott, W2PWG, Technical Editor lemroeratlee elAYg ISION NEwS R. H. Dorf, W2QMI, Associate Editor RADIO e ISION Tr.dem.rk registered U. S. eu,rna UmeS I. Queen, W2OUX, Editorial Associate John J. Lamson Angie Pascale, Production Manager Sales Manager Wm. Lyon McLaughlin, Lee Robinson Technical Illustration Director General Manager G. Aliquo Circuiullon manager Contents_ November. 1949 Editorial To the Service Technicien by Hugo Gernsbock 19 FM (Pages 20 -22) Limiter -Discriminator versus Ratio Detector by H. K. Milward and R. W. Hollows 20 Television News (Pages 23 -30) S SECOND HEATING Lady Television Engineer by Tex Borborite 23 no waiting, saves power Indoor and Built -In Antennas -Their Strong and Weak Points..by Ira Kamen 25 Television Station List 27 RIGID-TIP Tv Custom Instollations by David T. Armstrong 28 latest in tip engineering Theory and Engineering (Pages 31 -32) Microwaves, Part VII. by C. W. Polmer 31 LONGER REACH Amateur (Pages 33 -34) full 51/4 inches How to Become o Ham, Part II- Learning the Code by George Shuart 33 SOLDERLITE Code Practice Stations 34 - spotlights the work Broadcasting and Communications (Pages 35 -36) Case of the Elusive Blip.. by James W. Essex 35 STREAMLINED Sideband Suppression by I. Queen 36 perfectly Test Instruments (Page 37) balanced Tracer Uses Tube as Probe by Alva R. and Kenneth W. Wilson 37 DUAL HEAT Electronics (Pages 38 -39) single heat Cameros Are Tested with Simple Setup .by Fred C. Gabriel 38 200 watts, Construction (Pages 40-41) dual heat Miniature -Tube Receiver Hos Permeability Tuner...'by John E. Hozelrigg 40 200/250 Push -Pull Crystal Receivers by Rufus P. Turner 41 watts; Audio (Pages 42 -43) 115 volts, Design of Class -B Drivers by W. H. Anderson, VE3AAZ 42 60 cycles Servicing (Pages 44 -60) Service Technicians Hold Convention (see The Radio Month, page 9) You can do every kind of soldering Service Data, Technicians, and Money by John T. Frye 44 with this new 250 watt Weller Gun. Curing I.F. Oscillations by John A. Dewar 46 Power -packed, it handles heavy Home Study Courses Useful to Radiomen by Samuel Freedman 47 work with ease -yet the compact, Radio Set and Service Review (Eicor Model 1000 Tape Recorder) 50 lightweight design makes it equally Fundamentals of Servicing, Port IX -The Diode Vacuum Tube..by John T. Frye 56 suited for delicate soldering and Foreign News (Pages 62 -66) getting into tight spots. European Report by Major Ralph W. Hollows 62 Pull the trigger switch and you Departments solder. Release the trigger, and off goes the heat -automatically. No The Radio Month 8 Association News 84 wasted time. No wasted current. No Radio Business 10 Technotes 85 need to unplug the gun between New Patents 68 Miscellany 86 jobs. `Over and under' position of New Devices 70 terminals People providesgreater visibility Radio -Electronic Circuits 74 89 with built -in spotlight. Extra 5'/4" The Question Box 80 Communications 91 length and new RIGID-TIP mean Try This One 83 Book Reviews 95 real soldering efficiency. ON THE COVER: Tex (Mrs. Rose Ann) Borborite, television engineer, do- Chisel -shape RIGID-TIP offers ing maintenance work on the equipment at RCA's Exhibi- more soldering area for faster heat tion Hall, Radio City, New York, N. Y. Kodochrome by transfer, and new design gives brac- Avery Slack. ing action for heavy jobs. Here you get features not found in any other RADIO. ELECTRONICS, November. 1949. Volume XXI, No. 1. Published monthly. Publication Office, Erle Ave. soldering tool ... advantages that I. to l; Sheets. Philadelphia 32, l'a. Entered n second ieaa dit o, September 27. ln,Inn. t the post office t save hours and dollars. Your Weller Philadelphia, Pa.. under the Act of March 3. I87n. SUBSCRIPTION RATES: In U. S. and Panade, In U. S. possessions. Mexico. South and Ventral American countrlea. $3.50; $6.00 for two ; $8.00 for three ream; Gun pays for itself in a few months. innate coplee Stc. All other foreign countries $4.50 a year, $8.00 for two years. $11.00 for three years. Allow une Order from your distributor or write month for change of address. When ordering change please furnish an address stencil Impremion from a ecent wrapper. NADCRAFT PUBLICATIONS, INC. Hugo Gernsback. Pres.: 51. H Gemsbsck. Vice -Pros.; G. , Aligne, Seer. for bulletin direct. Contents Copyright, 1949, by Radcraft Publications, Inc. Tert and Illustrations must not be reproduced without of copyright owners. prrmluslon SOLDERING TIPS EDITORIAL and ADVERTISING OFFICES, 25 West Broadway, New York 7, N. Y. Tel. REctor 5 -9890. BRANCH -get your copy of ADVERTISING OFFICES: Ching.: 308 W. Washington Rtreet. Telephone RAndolph 6 -7383. Los Angeles: Helps W. the new Weller guide to easier, faster Wilshire , 1 Harker, 1127 Blvd.. Tel. MA 8 -1271. San Franelseo: Ralph W. H 582 Market St. Tel. Oarneld -2481. soldering -20 pages fully illustrated. FOREIGN AGENTS: Great Britain: Ails, furnishing and Distrinuting l'o., Ltd., 18 Bride Lane. Fleet St., Loo don E.C.4 Australlc McGill' Agency. 1711 Elisabeth Street. Melbourne. F lBrentano's. 37 Avenue de l'Oper.. Price 10c at your distributor, or or- Pais 2e. Holland: Trilectron, Heemateedsrhe, Dreef 124 Heemstede. Greece: International Honk A News Agency. 17 der direct. Amerlkls Street, Athens. 8a. Atrita; Central News Agency. Ltd.. Cor. Itlssik S l'ommúWmer Sta.. Johannesburg; 112 lung Street. Capetown; Min Smith Street. Durban. Natal. Universal Book Agency, 70 Hrrlon Street, Johannes- burg. Middle East Strltnateky Middle Fact Agency. Jana Road, Jerusalem. India: 8ua11 Gupta IUmtrlbutursl Co., Arrolla Basar Patrika Lt.. 14 Ananda Chalterlee lane, Calcutta. Broadway News Centre, Poet Hag #5557. Hadar, Bombay #14. K. L. Kannappa Mndall, 30 General Patters Road. Mount Road. Madras 2. Pakistan: Paradise Hook Stall. ODD. Regal Cinema. Preedy St.. Karaehl S. Editorial and Executive Offices: ELLER MEMSER AUDIT BUREAU OF CIRCULATION WMANUFACTURING COMPANY 25 West Broadway, New York 7, N. Y. \ 828 PACKER STREET EASTON, PA. RADIO -ELECTRONICS for

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Get Complete Training. You Receive and Keep All Equipment, Parts and Lessons. No Extra Charges. You will find all lessons easy to under- w GOOD PAY stand because they are illustrated and Unlimited Opportunities throughout with clear diagrams and step -by -step examples that you work in JOBS LIKE THESE: out yourself. Every piece of the eqiup- ment and complete lesson material we Business of Your Own send you is yours to keep and enjoy, Radio Manufacturing, Sales, Service including the multifester, experimental Broadcasting, Telecasting equipment, all parts of the Superhetero- Television Manufacturing, Sales, Serv- manual, radio dictionary. ice dyne, tube Laboratories: Installation, Maintenance and complete, modern Television texts. You receive complete standard equip- of Electronic Equipment, All parts are standard equipment. ment, including latest type High -Mu Electrolysis, Call Systems Tubes, for building various experi- Garages: Auto Radio Sales, Service Shop Method Home Training ... mental and test units. You progress Sound Systems and Telephone Com- step by step until you build a com- panies; Oil Well and Drilling Com- Earn While You Learn plete Superheterodyne Receiver. It is panies; engineering Firms With our practical resident Shop yours to use and keep. Theatre Sound Systems. Police Radio Method Home Training. you study in your spare time. You receive Spare And scores of other good jobs Time Work Lessons, which show you in many related fields how to earn while you learn. Service neighbors' radios and TV receivers, ap- YOU CONDUCT MANY pliances, etc., for extra money and ex- EXPERIMENTS LIKE THESE! perience. Many National students pay all or part of their training with spare time Checking action of condensers earnings! Experiments with AF and RF : Experiments with resonance DON'T DELAY! The Radio- Television Producing beat frequencies Industry needs trained men NOW Calibrating oscillators YOU RECEIVE THIS Experiments with diode, grid -bias, grid - For quick oction, PROFESSIONAL MULTITESTER! leak and infinite impedance detectors APPROVED mail coupon Practical experience in receiver trouble FOR You will use this professional instru- shooting today and we'll ment to locate trouble or make VETERANS! home Application of visual tester in check- rush you full in- delicate adjustments -at -on ing parts and circuits Check coupon below I service calls. You will be proud to Experiments with audio oscillators formation. own this valuable equipment. Com- Advanced trouble- shooting plete with test leads. . . . . and many, many others I You construct SIGNAL GENERATOR the Transit roo Free! Signal Genera- Complete Training by Practical tor shown here. demonstrating Est.1905 NEW, ILLUSTRATED Transitron prin- Resident Trade School, OPPORTUNITY ciples in both The same highly trained faculty, in- BOOK AND SAMPLE RI,. and A.F. struction materials and methods used stages. You resident LESSON SHOW YOU study negative here in our large, modern type oscillators school, are adapted to your training HOW WE TRAIN at fìr-thand. in your own home. Shop Method Home FOR Training has been proved by hundreds YOU ... SEND of successful graduates. THEM TODAY! NO Resident and Home Study COST. NO Both OBLIGATION. AUDIO OSCILLATOR: Courses Offered An electronic device, which YOU produces audio - NATIONAL SCHOOLS frequency sig- LEARN BY LOS ANGELES 37, CALIF. EST. 1905 1'frä:lk nals for modu- lating R.F. () carrier DOING FIND OUT NOW ... MAIL COUPON TODAY waves, testing A.F. (audio frequency) You receive Notional Schools, Dept. 11 -RE Mail in envelope amplifiers, speakers, etc. special labora- tory experi- 4000 South Figueroa Street or paste on T.R.F. ment lessons Los Angeles 37, California penny postal. RECEIVER to show you Send me your FREE book "Your Future in Radio" and You build how to build the sample lesson of your course. I understand no sales- several with your own man will call on me. T.R.F. Re- hands various ceivers, one experimental NAME_ AGE. of which, a 4- units such as ADDRESS r tube set, is shown those shown at here. You learn construction, align- left, and how CITY ZONE.___.._. STATE..__ ment, make receiver tests, and do to conduct Check here if Veteran of World War II trouble shooting. many tests. NOVEMBER, 1949

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Fortune post techniques) and take you step -by -step through the more ad- Get in and get ahead in Television . . the field that Magazine says is "the most dynamic single element in the en- vanced subjects of TV and its related fields. tire American economy!" Within a few years, says the magazine, Don't wait another day. Television won't wait for you. In all our TV will be one of the first ten industries in the U.S. 22 years of association with professional radiomen we know that New FCC frequency allocation plans call for 2,245 video stations the man who acts promptly is the man who succeeds. The facts in 1,400 communities. Since a television station requires many more about CREI, our courses, and what we can do for you, are described technicians and engineers than the average AM station, you can in our 32 page booklet. It's worth rending. Send for if today. readily see the great number of good jobs that are needed to be (Veterans: CREI training is available under the G -I, Bill. For filled within the next year or two. most veterans. July 25. 1951 is the deadline -act now!) If you are now in radio, this is the time to prepare for your future SAMPLE Now, see for yourself, how interesting it is in Television. CREI offers the very training you need to go after - to study of home and improve your ability LESSON FREE! the CREI way. and get -a good TV job. CREI courses can be studied in your schedules. They spare time and can be fitted into the most crowded "THE ORTHICON AND IMAGE ORTHICON" -this lesson describes the devel- are designed to give you a thorough grounding in basic principles opment of the small, 3 -inch image orthicon tube; theory and operation of the (remember that all new electronic developments have their roots in orthicon; image orthicon; specific features.

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www.americanradiohistory.com The Radio Month using all -elec- TV SERVICE CONTRACTS may be tronic methods and utilizing only the made by independent service organiza- present 6 -mc channel was demonstrated tions (as well as by manufacturers and .defr to the FCC last month by RCA. Result- dealers) in New York State and may he ing from new and basic technical de- substantially identical to those previ- velopments, the system permits color ously in effect -including renewal pro- transmissions to be sent over existing, visions- provided that new parts are unmodified transmitters and to be re- not furnished without additional charge. ceived in black and white on present This was (effectively) the ruling laid receivers. Receivers built for color re- down in an interpretive bulletin issued ception or equipped with a color con- last month by Alfred J. Bohlinger, verter can receive programs either in Deputy Superintendent of the State In- color or in monochrome so that stations surance Department, to clarify the de- /N1E/%ffiPf need broadcast in color only shows partment's position on the opinion given suited for it. The system is all -elec- earlier by State Attorney -General Na- tronic, with no moving parts. thaniel Goldstein. An additional pro- Dr. E. W. Engstrom, vice -president vision forbids "insuring" the set against in charge of research at RCA Labora- damage from other than normal use, tories, who prepared the engineering such as by fire; but standard service statement for the FCC, said that there contracts have never covered such ex- is no degradation in picture quality, ternally caused damage in any case. whether images are received in color Goldstein's original interpretation of or monochrome, on special receivers or the law (see September issue of RADIO - on standard ones. No receiver adjust- ELECTRONICS, page 9) appeared to in- ments are required when stations dicate that independent contractors switch from color to black- and -white or could not operate at all. vice versa. The new color system is based pri- TV RELAYS owned by private corpora- tions and those marily ql' a time multiplexing system, operated by the Bell by which three camera signals are suc- System should be interconnected, said cessively sampled at high speed. Each the FCC last month in a proposed de- signal carries picture information of cision directing Bell to drop its policy Spark Plugs art minia- one of the three primary colors. The against interconnection. The policy has ture broadcasting sta- heretofore prevented programs relayed tions, send signals that signals are combined and passed to the interfere with radio transmitter after filtering, containing for some distance by Du Mont or Philco reception, distort tele- relay systems from being carried fur- vision. The New Auto - no components of higher frequency than Lite "Resistor" Spark 4 mc. ther by Bell. While stating that tele- Plug reduces this in- vision relaying will eventually be a terference.* At the receiver the r.f., pix and sound i.f., second detector, and sound business exclusively for common car- circuits are standard. The video signals riers, the Commission called the pres- acv are separated into their color com- ent refusal to tie up unjust and un- ponents and fed to three cathode -ray reasonable because of Bell's lack of tubes, one with red phosphor, one with adequate facilities. green, and one with blue. The three "PAY -BACK" TV SERVICE was an- images are projected on a screen in nounced last month by Sylvania Tele- AUTOLITE register so that in the final picture vision as a new plan for reducing both each color shows up in its correct value. set owners' contract cost and the num- NEW INSTRUMENT called the cholel- ber of nuisance service calls. Under ithophone locates gallstones inadver- Sylvania contracts, the buyer receives tently left in a patient's body after a a book of coupons, each good for one removal operation. Some of the stones service call. While the number of calls are as small as grains of sand; they is not limited by the coupons, the owner SPARK PLUG are usually transparent to X -rays. receives a refund for each coupon he The instrument has a thin, flexible holds at the end of the year. Knowing Here's How It probe which the surgeon inserts in nar- that saved service calls mean saved Works to End row ducts. When the probe tip encoun- money, owners will not request them Interference ters a stone, it acts like a phonograph without good reason 'and technicians needle. The relayed will not waste time The "Resistor" acts tiny click is to an unnecessarily. to dampen the spark amplifier and loudspeaker, which emits plug radio signal to a distinctive "ping." CITIZENS RADIO CORP., holder of an acceptable level' the patents on the first transceiver to while still delivering The inventors are Dr. E. A. Walker the full high voltage and E. G. Thurston of Pennsylvania be approved by the FCC for use in the discharge required to citizens band, was sold last month to ignite the fuel. State College and Dr. C. K. Kirby of the University of Pennsylvania Medical Stewart-Warner Corp. Al Gross, inven- Auto-Lite Ignition Engineers, working School. tor of the .transceiver, will continue as with leading automotive manufacturers, chief engineer. Large -scale production have developed the new Auto-Lite "Re- BONDED TELEVISION SERVICE is scheduled to begin soon; the firm has sistor" Spark Plug with this built -in was launched last month in Boston, been flooded with orders. resistor that reduces spark plug inter- Mass., by the Federal Television Co., a ference.* Remember, the "Resistor" also service contractor, as its solution to the THEATRE TELEVISION may require helps deliver smoother idling, improved problem of contractor reliability. The 60 channels, each 50 mc wide, for a com- economy, longer electrode life. Dealers bonded warranty is backed by the plete and competitive nationwide the- are being supplied as rapidly as pos- American Fidelity Co., a Vermont in- atre TV system, according to a state- sible. Write for Booklet M -1186 surance organization. The company says ment made last month by the Society sor full information. its guarantee is unique in that the cus- of Motion Picture Engineers. Picture THE ELECTRIC AUTO -UTE COMPANY tomer is assured of his year's service. quality will eventually have to rival Toronto, Ontario Toledo 1. Ohio Even if the contractor went out of motion pictures, say the engineers, and tinder 35mv /m from 540 k.c to 150 me. at SO ft. business, the contract would still be the 50-mc bandwidth may be essential Tune in "Suspense," Thursday. 9:00 P. M., E. T...dS performed by the insurance company. to provide the extra definition. RADIO -ELECTRONICS for

www.americanradiohistory.com TlcThe IsliRadio Month 9 SERVICE TECHNICIANS HOLD CONVENTION Radio service history was made in by Carl Quirk of Du Mont practically the three -day convention and exhibition filled the stage.) staged in Philadelphia on September John Rider, Al Steinberg, and A. T. 18, 19, and 20 by the Philadelphia Radio Alexander covered the general situa- Service Men's Association (PRSMA). tion. Mr. Steinberg covered especially Held for the purpose of publicizing and the relations among service technicians, promoting Pennsylvania's Preventive distributors, and manufacturers. Mr. Maintenance Month in October, it was Alexander spoke on the problems of the first full -scale professional combined servicing and of service training from convention and show ever held by radio the manufacturers' viewpoint on a na- service technicians. More than 1,700 tional scale. persons registered for the first evening Other papers covered television serv- of the convention, which began at 5 p.m. ing and maintenance from the antenna IIIIIIIIIIIIII on 18th and closed at 4 p.m. on the to the picture tube, with special atten- the Jobbers: Write for Price Information 20th. The evening of the 19th, attend- tion to front ends, alignment, electronic ance so greatly surpassed that of the antennas, multiple reception, and test first evening that it was necessary to equipment. The papers were exception- several hundred -people away. ally well received, and the hall was turn NEW About 500 technicians were in constant crowded during every one of the lec- attendance at the daytime sessions on tures and demonstrations. TELEKITS Monday and Tuesday. The convention was presided over by Fifty -two booths were occupied by Dave Krantz, president of PRSMA, who 10 -B $69,95 interest- lost n opportunity to drive home the companies whose products are 7 -B $49,95 ing to the service technician and by impornce of the Preventive Mainte- radio magazines which deal with serv- nance Month campaign to the service Pointing ice problems. Exhibits ranged through technicians of Pennsylvania. Sparkling new Telekit 10 -B has 52 -inch screen. the whole gamut of radio and television out that the example of Harrisburg last Bland new compact lay -out has video tube mounted such a campaign on chassis. Big illustrated easy -to- follow instruction test equipment and accessories from winter proved that book guides you step by step through easy as- to technical books and could increase repair business as much sembly. No special knowledge of television is antenna towers iron, pliers, ar- 25%, he urged that every set owner required. All you need is a soldering service data. end screw driver. 10 -B Kit can be used with and technical sessions received in the state be given an opportunity to 121/, -inch tubes. Telekit 10 -B, $69.95. 10 -B Telekit Booths in- almost equal attention from the attend- have his set checked over to assure con- cabinet, $15.95 to $24.50. Telekit Guarantee and to avoid cludes free factory service. ing service technicians. The latter in- tinued good performance Write for catalog listing 10 -B and 7 -B Telekits. be 7.11 cab- cluded talks on the technician's techni- possible major repairs which may New 7 -B Telekit for 7 -inch tube, $49.95. cal and business problems and demon- necessary later. inet $15.95 to $24.50. strations of television servicing and Members of PRSMA cooperated to do trouble shooting, backed up by ample the organizational, executive, and me- equipment. (Both the Dynamic Demon- nial labor needed to keep the convention strator operated by John Meagher of running smoothly, and it is to their ef- RCA and the oscilloscope and projec- forts that the great success of the un- tion equipment used to assist the talk dertaking is due.

TELEKIT BOOSTER $12.95 If you live in o fringe area this fine Telekit booster will bring in TV signals bright and clear. There is a 20 to 30 times signal boost on all channels. NOT A KIT. Completely assembled. Works with Telekit or any other TV receiver.

13 CHANNEL TUNER $12.95

NEW 13 CHANNEL TUNER is a small compact unit with stage of R.F. Tunes all TV and ZFM channels. Made to conform with Telekit or any other TV set having video I.F. of 25.75 Mc. Com- plete with tubes, pre -wired pre -aligned; only three connections to make. See your jobber, or write to us for informotion. Your cost, $19.95. Write for catalog of Telekit antennas, boosters, television kits, tuners, television ports and tubes. Above --Dave Krantz opens a ses- sion of the conven- tion. Below -Serv- TELEKfT ice technicians visit the exhibitors' SANDERS ELECTRONICS CO. booths. AVIATION BLDG., 3240 N.W. 27th AVE. MIAMI 42, FLORIDA

N O V E M B E R 1 9 4 9

www.americanradiohistory.com lO Radio Business THE MOST WELCOME Radio Corp. of America, RCA -Victor WILLIAM O. SCHONING, of Lukko Division, has placed on the market a Sales, Chicago, was named chairman CHRISTMAS GIFT new TV receiver to sell for $199.50. The and AARON LIPPMAN, of Aaron Lipp- FOR A RADIO MAN set has a 61- square -inch screen and 22 man Co., Newark, vice chairman. The tubes. The price is $70 lower than any committee will consider the greatest previous RCA set and is the company's interests of the greatest number of dis- first below $200. tributors in advising the educational program committee and other commit- Zenith Radio Corp, reports estimated tees on features to be incorporated in net consolidated profits for itself and the 1950 show, to be held at the Hotel its subsidiaries for the first three Stevens, Chicago, the week of May 22. months ended July 31, 1949, of its cur- rent fiscal year amounting to $170,945 Misleading television after federal income provision ads have gone tax of too far, industry leaders stated last $218,133, depreciation, excise taxes, re- month. serve for Especially bad is the practice of contingencies, and a deduc- advertising screen sizes tion of $251,376 representing amortiza- in square inches; for a 121 -inch tube, for ex- tion of good will incident to acquisition ample, six different manufacturers of a subsidiary. ar- rived at six different "square- inch" fig- Shipments for the quarter were down ures. Criticism was also directed approximately 10% from the same at the practice of advertising little -known re- quarter a year ago, due principally to ceiver models as "nationally the normal summertime seasonal de- famous." BENJAMIN ABRAMS, president cline and a two -week vacation shut- of Em- erson Radio & Phonograph down. Corp., sug- gests that tube -face diameters be used Stewart -Warner Corp. sales for the instead of areas to make advertising VIDEO HAND BOOK first six months of 1949 were $27,875; less confusing to the public. Unless this plan is adopted, he believes the FCC Now in one great hook all the c..ent tat knowledge of 957, a decline of 26.4% from 1948, television for laboratory terhuirian esperintenter or the Better Business Bureau may - JAMES S. KNOWLsoN, chairman and everyone interested ini workingw at tele- step in. Complete, up-to -the -m' teinfr anged president, revealed in a letter sent to for reference Mr. Abrams wrote 15 quick -easy to read . mathematics. stockholders. Sales in the first half of to about major Oser 900 pages more than R00 photograph, dia- producers requesting their views. Most gram- and drawings. Here of the subjects 1948 were $37,868,485. -ue approved of the plan, catered:red: Fundamental,, the TV sta - Net profit for the six months ended many indicating the . antenn,, program- 30 $796,564, they would adopt it themselves. Large ming, in,tallati'n. service. tel equip- June was Profit in the first ment. data. tern.. rir $ 5.00 half of 1948 was $1,874,601. retailers, however, said they could not change unless everyone else did. RADIO DATA BOOK Motorola, Inc., for the six months The only radio handbook of it. period ended July 2, 1949, showed net Sylvania Electric Products Corp. has kind! Cover, everything in Radio earnings of $1,908,255, equal to $2.39 entered the television receiver field with for lab teclnirian experimn,ter- rr a nJ per share. This compares with earn- a line of sets priced between $199 and Over 900 pages. 12 big section,. ings for the corresponding period last $450. Introducing the sets, E.E. LEWIS. wilbn hundred. of drawings and dia- of $1,650,039, $2.06 . Some of the subjects covered year equal to per president of Colonial Radio Corp., the Testing. Measuring nul share. wholly owned subsidiary of Sylvania Alignment . All about Antennas The sales figure totaled $33,822,368, which makes the receivers, stated . that . Sound Systems Recording Complete Test Equipment or nearly $7 million more than the cor- a period of television price stabiliza- Data . Complete Tube Manual responding figure for 1948. which was tion is beginning. Further TV price . . . Charts. Graphs and Curve. . 50 Tested Circuits ... Code.. $26,918,540. reductions could be made only through Symbols and Standards . 150 elimination of important components Rash. Circuits . . . Dictionary of Planet Mfg. Corp., Bloomfield, N. J., Radio Term. . . . etc., etc. $ 5.00 which would create a compromise with has been organized to manufacture quality and performance, Mr. Lewis RADIO & TELEVISION LIBRARY , according to PHILIP GREEN - believes. SPAN, president. Other corporation of- The new television sets feature built - A complete library ficers are GEORGE F. JEPSON, vice presi- in in antennas, special sensitivity, one - covering everything dent in charge of sales, IRvING A. Radio and Television hand tuning, intercarrier sound, and GREENFIELD, JOSEF in over 1800 pages. treasurer and LIN- stabilized sweep oscillators. completely illustrated! GER, secretary, all formerly with Solar Mfg. Two handsomely Corp. Radio Corp. of America bound books (con- has signed a tents described above Admiral Corp. has increased its pro- contract with Fabian Theaters, Inc., for in attractive slip ease duction capabilities to 15,000 receivers installation of instantaneous projection television . . . compact, concise, comp ere! per week, vice president, J. B. HUARISSA equipment in Fabian's Brook- Over 1800 Pages $9.00 stated recently. Increased expansion lyn Fox Theater. The equipment, cost- was made possible by the development ing $25,000 plus installation charges, %nd Don't forget this month', ropy oil at Admiral's Cortland Street plant in is the first of its type to be ordered for Chicago of the longest straight produc- a theater. S. H. Fabian, president of tion line in the industry, and by in- the theater chain, said the Fox would stalling facilities for the manufacture be the proving ground for theater tele- RAM DIIZ! 3III3V4IIo of 500 sets per day at the Harvard, Ill., vision in this country. WILINIV2MM1CMC plant. John F. h'1 Dco uplete trade journal des°tool to .ale, and -rrsice Rider, Publisher, Inc., an- I Radio. \ ideo, Andin. Radio Parts and Electronic Equip- nounces that the forthcoming Rider

. copie. 25,, per year. 2 yew,. nt,le $3.00 55.00 ment Shows, Inc., Chicago, through its Television Manual Volume d will be All produrts of president, JEROME J. KAHN, announces published in a larger size than previous BOLAND & BOYCE INC., Montclair :3, NJ. a distributors' advisory committee, manuals. Page size will be approxi- are available at your made up of 10 of the industry's leading mately 12 x 15 inches, dimensions pre- local distributor's counters. Order now! jobbers, to consult with the directors viously used only for special double- and management of the 1950 Distribu- spread pages. The larger size will re- tors Show on ways and means of mak- duce the number of folds in giant -size ing the show of major interest and serv- pages, adding convenience and extend- ice to jobbers. ing the life of the book. RADIO -ELECTRONICS for

www.americanradiohistory.com r 11 HOW Buil d and Keep Big Screen Top Quality Television Receiver at Home as You Prepare for a Profitable job in

Choice of 10, 12% or 16 inch picture tube Oscilloscope Now you can get this amazingly prac- ceiver. Standardized chassis is adapt- tical aid for learning Television at able for a 10, 121í or 16 inch direct sad home, to help you get started toward view tube that gives big, bright, sharp,

FASCINATING WORK . . . GOOD steady pictures. This is an optional MONEY . . a THRILLING FUTURE - training advantage- designed to pro- in a real job, or your own sales and vide the utmost in practical "learn-by. service business. When you complete doing"home training in Television. Mail our regular home training- described coupon for complete details. See why below -you can build and keep a top you owe it to your "Television Future" quality commercial -type Television Re- to enroll for DeForest's Training, Inc. Multimeter sf You also build See how D. T. l.'s amazingly effective T -V circuit training, (2) and keep this methods help start you toward a double -range R -F SIG- GOOD JOB or your OWN BUSINESS NAL GENERATOR, (3) Professional in one of America's most promising jewel- bearing MULTI - fields- including Television, F.M. Radio, METER, (4) quality 6 -tube Type Equipment Aviation, Train, and Taxi Radio, Broad- SUPERHET RADIO. Then cast Radio, Industrial Electronics. Get build and keep that big R -F Signal modern lessons . . . plus 16 ship- new Television Receiver. Generator ments of Radio- Electronic parts. Work Here's EVERYTHING YOU over 300 experiments and projects - NEED for real laboratory including building of (1) commercial - type training AT type OSCILLOSCOPE for practical HOME!

Modern Chicago Laboratories Employment Service

* If you prefer, you can get ALL * When you complete your train- your preparation in our new, ing, our effective Employment Chicago training laboratories Service helps you get started 6-Tube .. ore of the finest of its kind. Receiver Ample instructors . modern toward a real future in Tele- equipment. Write for details) vision-Radio-Electronics. You oho use HOME MOVIES! MAIL THIS a D. T. I. Exclusivo! COUPON NOW! DeFOREST'S TRAINING, D. T. I. alone includes the modern, visual 2533 INC. training . . . MOVIES . . . to help you North Ashland aid Avenue, Dept. learn faster, easier at home. See electrons on Chicago 14, Illinois RC -F 11 ' the march and other fascinating "hidden Without obligation, action " -a remarkable home training advan- give me complete how I may facts showing tage that speeds your progress. make my start in Television.RadioElectronics. Name...... ' ...... Age...... De FOREST'S St reet...... ,INC. Apt...... CHICAGO 14, ILLINOIS City Zone...... State ...... A DE VRY Institution .

NOVEMBER 1949

www.americanradiohistory.com 12

114STRYMENTS THAT STAY ACCURATE

the

MODEL 303

VACUUM TUBE VOLT- OHMMETER

. A Worthy Companion of the 260

SPECIFICATIONS DC Voltage Rages -1.2, 12, 60, 300, 1200 (30,000 with Accessory High Voltage Probe) Input Resistance -10 megobms for all ranges DC Probe-with one megohm isolatingvesstor Polarity reversing switch Ohms Ranges -1000 (10 ohms center) 100,000 (1000 ohms center) 1 megohm (10,000 ohms center) 10 megohms (100,000 ohms center) 1000 megohms (10 megobms center) Smaller and Handier AC Voltage for Greater Portability Ranges -1,2, 12, 60, 300, 1200 A worthy companion of the world- famous Model 260 is this brand Impedance (with cable) approx. 200 mmf shunted by 275,000 ohms new addition to the Simpson line -the Model 303! AF Voltage Skilled Simpson engineers spent months of painstaking research Ranges-1.2, 12, 60 Frequency Response -Flat to 100,000 cycles in the laboratory to produce the Model 303, which is one of the Decibels most versatile instruments ever made for TV servicing. This rug - Ranges --20 to +3, -10 to +23. +4 to +37, gedly constructed instrument offers the maximum in portability +18 to +51, +30 to +63 Zero Power Level -1 M. W., 600 obms because it is approximately 60% smaller than other vacuum tube Galvanometer volt- ohmmeters. However, no sacrifice has been made in read - Zero center for FM discriminator alignment and other galvanometer applications ability. The 303 has a large 41/2" meter, despite its handy com- R. F. Voltage pactness. (Si8,,al tracing with Accessory High Frequency Crystal Probe) One of the many features of the 303 is its low current consump- Range-20 volts maximum tion. The AC voltage range is wider than on any other similar Frequency-Flat 20 KC to 100 M.C. 1.2 volts 1,200 105-125 V. 60 cycles instrument -from minimum to maximum. Like all Size 51/4 "x7 "x311/s" (bakelite case). Weight: 4 lbs. other instruments bearing the Simpson name, the Model 303 is Shipping Wt.: 61/2 lbs. an instrument of highest quality at an amazingly low price. Dealer's Net Price Model 303, including DCV Probe, ACV-Ohms probe and Ground Lead - S $58.75; Accessory High Frequency Probe, $7.50 I M P S O N E L E C T R I C C O M P A N Y Accessory High Voltage Probe, $14.85 5200 -5218 West Kinzie Street, Chicago 44, Illinois Also available with roll top rose, Model 303RT- $64.75 In Canada: BachSimpson, Ltd., London, Ontario

RADIO -ELECTRONICS for

www.americanradiohistory.com 13

te(44 /950 s'eat`ckir PUSH -PULL EXTENDED RANGE 5" OSCILLOSCOPE KIT ecitu,te4-

The flrst truly television oscilloscope. Ectended sweep range 15 cycles to Tremendous sensitivity .06 Volt RMS 70,000 cycles' per inch deflection. New television type mullivibrater generator. Push -pull verticalandhoricontolomplifers. sweep New magnetic alloy shield included. Useful frequency range to Yh Mega- 'y'1... Still the amusing price of $39.50 The new 1950 Push -Pull 5" Oscilloscope has features that seem impossible in a $39.50 oscilloscope. Think of it- push -pull vertical and horizontal amplifiers with tremendous sensitivity only six one hundredths of a volt required for full inch of deflection. The weak impulses of television can be boosted to full size on the five inch screen. Traces you couldn't see before. Amazing frequency range clear useful response at 212 Megacycles made possible by improved push -pull amplifiers. Only Heathkit Oscilloscopes have the frequency range required for television. New type multi -vibrator sweep generator with more than twice the frequency range. 15 cycles to 70,000 cycles will actually synchronize with 250,000 cycle signal. Dual positioning controls will move trace over any section of the screen for observation of any part. New magnetic alloy CR tube shield protects the instrument from outside fields. -All the same high quality parts. cased electrostatically shielded power transformer, aluminum cabinet, all tubes and parts. New instruction manual now has complete step by step pictorials for easiest assembly. Shipping Weight 30 lbs. Order now for this winter's use. CONVERSION FOR OTHER MODEL NEATNKIT OSCILLOSCOPES A conversion for all 03 and 04 scopes is available changing them to the new push -pull ampli- fiers (does not change the sweep generator). Complete kit includes new chassis, tubes and all parts. For a small investment. add the latest improvements to your present oscilloscope (Except C.R. Tube Shield). Shipping weight 10 lbs. Order 05 Conversion Kit No. 31 5 ;1Zr50

THE NEW 'W Weir HANDITESTER KIT MORE 7eaaiei1 THAN EVER BEFORE Beautiful streamline Bakelite cose. Quality Bradley AC rectifier. AC and OC ranges to 5,000 Volts. Multiplying type ohms ranges. 1% Precision ceramic resistors. All the convenient ranges 10-3 Volts. Convenient thumb type adjust control. 300-1,000 -5,000 400 Microampere meter movement. Large quality 3' built -in meter. The instrument for all -the ranges you need- beauty you'll enjoy for years and you can assemble it in matter of minutes -an instrument for everyone. The handiest quality voltohmeter of all. Small enough to put in your pocket yet a full 3' meter. Easy pictorial wiring diagrams eliminate all assembly problems. Uses only 196 precision ceramic divider resistors and wire wound shunts. Twelve different ranges. AC and DC ranges of 10 -30- 300 -1,000 -5.000 Volts. Ohms ranges of 0-3,000 ohms and 0- 300.000 ohms. Milliampere ranges of 10MA and 100MA. Hearing aid type ohms adjust control fits conveniently under thumb for one hand adjustment Banana type jacks for positive low resistance connections. Quality test leads included. The high quality Bradley instru- s ment rectifier was especially chosen for linear scales on AC. The modern case was styled by Harrah Engineering for this instrument. The 400 microampere meter movement comes already mounted in the case protected from dust during assembly. An ideal classroom assembly instrument useful for a lifetime. Perfect for radio service calls, electricians, garage mechanics, students, amateurs and beginners in radio. The Itate only quality voltohmeter under $20.00. An hour of assembly saves you one half the cost and quality parts give you a better HANDY instrument. Order today. Shipping weight 2 lbs. OHMS ADJUST

.:.:...... ^.-ve,:n>....woo...:«:::»a,oio-:.o>:.:x:.:;.:>oo.ax::a:>;r:>.::

EXPORT DEPT. 13 East 40th St. 7tie HEATH COMPANY NEW YORK CITY (16) CABLE: ARLAB -N.Y. ... BENTON HARBOR 20, NOVEMCER 1949

www.americanradiohistory.com II %IF

Beauty Quality Economy

te eaitZez4- IMPEDANCE BRIDGE KIT A LABORATORY INSTRUMENT NOW WITHIN THE PRICE RANGE OF ALL

Measures Inductance from 10 microhenries to 100 henries capac- itance from .00001 MFD to 1000 MFD. Resistance from .01 ohms to 10 megohms. Dissipation factor from .001 to 1. "Q" from I to 1000.

Ideal for schools, laboratories, service shops, serious experimentors. An impcd. n.: bridge for everyone - the mr st useful instrument of all. which heretofore has been out of the price range of serious experi- mentors and service shops. Nuw at the lowest price possible. All highest quality parts. General Radio main calibrated control. General Radio 111(1(1 cycle hummer. Mallory ceramic switches with 60 degree indexing - 2110 micro -amp zero center galvanometer - 1 . of I c; ceramic non - inductive decade resistors. Professional type binding posts with standard VI" centers. Beautiful birch cabinet Directly calibrated ' Q' and dissipation factor scales. Ready calibrated capacity and inductance starsd.srds of .Sr/rrr Mica, accurate to 12 of 1,6 and with dissipation factors of less than 30 parts in one million. Provisions on panel for external generator and detector Measure all your unknowns the way laboratories do - with a bridge for accuracy and speed. Internal 6 volt battery for resistance and hummer operation. Circuit utilizes Wheatstone. ItodeNyt Hay and Maxwell circuits for different measurements. Supplied complete with every quality ELSE TO BUY part - all calibrations completed and instruction manual for assembly and use. Deliveries are limited. Shipping weight, approximately 15 lbs.

10,000V. H.V. TEST PROBE KIT

No. 310. GxrcnJs range of any 11 mcgohm VTVAI to 3.000 and ?tea, qieeidleer- 10,000 Volt ranges. A necessity for television. T E L E V I S I O N 1116611111ftweew-_ Shipping Wt., 1 pound. $4.50 ¡ A L I G N M E N T

...:..::::...... Re. :::.:...... ::. . . .-. GENERATOR R.F. CRYSTAL TEST PROBE KIT KIT

No. 309 kit to assemble. Everything you want a R.F. probe extends VTVM in tele- vision alignment generator. A range to 100 Mc. Corn - wide hand sweep generator cover- plete with 1N34 crystal. ing all FM and TV frequencies Ship. Wt., 1 ib.... $6.50 0 - 110 and 165 to 220 Mega- cycles,a marker indicator covering 19 to 43 Megacycles, AM modu- lation for RF alignment va- - ELSE TO BUY riable calibrated sweep width 'lag 0 - 30 Mc. - mechanical driven /4 V/c.Rl/(4 inductive sweep. Husky I 10V. 60 cycle power transformer operated - step type output attenuator with 10.1100 to I range - high output on all ranges - band switching for each TOOL KIT range - vernier driven main calibrated dial with over 45 inches of calibration - vernier driven calibrated indicator Now a complete tool kit marker tuning. Large grey crackle cabinet 1618" x UM" to assemble your Heathkit. 7 -3/l6" Phase control for single trace adjustment. Uses four high frequency triodes plus Consists of Kramer diagon- 5Y3 rectifier - split stator tuning condensers for greater efficiency and accuracy at high al cutters and pointed nose frequencies - this Heathkit is complete and adequate for every alignment need and is assembly pliers. Xcelire supplied with every part - cabinet - calibrated panel - all coils and condensers wound, screwdriver. 60 Watt 110V. calibrated and adjusted. Tubes, transformer, test leads every part with instruction soldering iron and supply - manual for assembly and use. Actually three instruments in one TV sweep generator of solder. Shipping 5X't , 2 - - lbs. Complete kit ... $5 95 TV AM generator and TV marker indicator. Also covers FM band.

EXPORT DEPT. 13 East 40th St. e NEW YORK CITY (16) 7 HEATH E: mis riAL CABLE: ARLAB -N. Y. ... BENTON HARBOR 7.0, MICHIGAN RADIO -ELECTRONICS for

www.americanradiohistory.com li all in HEATHKITS...

TUBE CHECKER KIT 7eatu/red.

1. Measures each element individually 5. Checks every tube element 2. Has gear driven roller chart 6. Uses latest type lever switches 3. Has lever switching for speed 7. Uses beautiful shatterproof full view meter 4. Complete range of filament voltages 8. Large size 11' x 14' x 4' complete 9. Checks new 9 pin piniatures Check the features and you will realize that this Heathkit has all the features you want. Speed - simplicity - beauty - protection against absolescence. The most modern type of tester - measures each element - beautiful Bad -Good scale, high quality meter - the best of parts - rugged oversize 110V. 60 cycle power transformer - finest of Mallory switches - Centralab controls - quality wood cabinet - complete set of sockets for all type tubes including blank spare for future types- fast action gear driven roller chart uses brass gears to quickly locate and set up any type tube. Simplified switching cuts necessary time to minimum and saves valuable service time. Short and open element check. No matter what arrangement of tube elements, the Heathkit flexible switching ar- rangement easily handles it. Order your Heathkit Tube Checker today. See for yourself that Heath again saves you 2/3 and yet retains all the quality - this tube checker will pay for itself in a few weeks - better build it now. with detail instructions all parts cabinet roller Complete - - - ELSE TO BUY chart - ready to wire up and operate. Shipping Wt., 15 lbs.

Wealr.lie- Heat qeadleee NEW rai e tild¢cc SINE AND SQUARE WAVE BATTERY SIGNAL TRACER AND AUDIO GENERATOR KIT ELIMINATOR KIT UNIVERSAL TEST SPEAKER KIT

ELSE TO BUY $2Z5ó Experimenters and servicemen working with a square wave for the first time invariably wonder why in was not introduced before. The charac- teristics of an amplifier can be determined in seconds compared to several hours of tedious tracer has now Now a bench 6 Volt power supply kit The popular Heathkit signal plotting using older methods. Stage by stage, test speaker at for all auto radio testing. Supplies 5 - been combined with a universal amplifier testing is as easy as signal tracing. no increase in price. The same high quality than 1%) and linear 7%2 Volts at 10 Amperes continuous The low (less antenna to speaker db.) make this Heathkit equal S 15 Amperes intermittent. A well fil- tracer follows signal from output (± one or quick- or superior to factory built equipment selling tered rugged power supply uses heavy -locates intermittents -defective parts greater for three or four times its price. The circuit is duty selenium rectifier, choke input filter er -saves valuable service time -gives the popular RC tuning circuit using a four gang with 4.000 MFD of electrolytic filter. income per service hour. Works equally well variable condenser. Three ranges 20 -200, 200. on broadcast FM or TV receivers. The test 0 15 Volt meter indicates output. Out- - 2.000. 2.000- 20.000 cycles are provided by ranges to put variable in eight steps. Excellent for speaker has assortment of switching selector switch. Either sine or square waves pull or single output impedance. instantly available at slide switch. All compo- demonstrating aufo radios. Ideal for match push pickups PA systems nents are of highest quality, cased 110V. 60 servicing can be lowered to find Also test microphones, - - 110V. 60 cycle power transformer. Mallory F.P. filter con- sticky vibrators or stepped up to equiva- - comes complete - cabinet - tubes, test probe, densers, 5 tubes, calibrated 2 color panel, grey lent of generator overload - easily cycle power transformer - crackle aluminum cabinet. The detailed instruc- two hours. all parts and detailed instructions for assembly interesting and in- constructed in less than tions make assembly an Shipping and use. Shipping Wt., 8 lbs. structive few hours. Shipping Wt., 13 lbs. Complete in every respect. \Vt., 18 lbs.

EXPORT DEPT. 13 East 40th St. NEW YORK CITY (16) CABLE. ARLAB -N. Y. ... BENTON HARBOR 20, MICHIGAN NOVEMBER, 1949

www.americanradiohistory.com 16

74 N E W 1 9 5 0 i e,cte &Z` VACUUM TUBE VOLTMETER KIT eaexerze.t

New 200 microampere meter. Accessory probes (extra) extend ranges to 10.000 Volts and 100 Megacycles. Uses I °ó precision ceramic divider resistors. Burn-out proof meter circuit. Modern push -pull electronic voltmeter circuit. 24 complete ranges. Electronic AC circuit. No current drawing Isolated probe for dynamic testing. rectifiers. Most beautiful VTVM in America. Shatterproof plastic meter face.

A new Model V -2 Heathkit VTVM with new 200 microampere meter' four additional ranges -full scale linear ranges on both AC and DC of 0 -3 V., 30 V , 30 V., 100 V., 300 V., and 1,000 V. Accessory probe listed elsewhere in ad extends voltage range to 3,000 and 10.000 volts D.0 New model has greater sensitivity, stability and accuracy -still the highest quality features-shatterproof plastic 6111 view meter face -automatic meter protection, push -pull electronic voltmeter circuit. linear scales -db scale -ohmmeter measures 1/10 ohm to 1 billion ohms with internal battery -isolated DC test prod for dynamic measurements -11 megohm input resist ance on DC -AC uses electronic rectification with 6H6 tube. All these features and still the amazing price of only $24 50. Comes complete with cabinet -panel -three tubes new Mallory switches -test prods and leads, 1% ceramic divider resistors and all other- parts. Complete instruction manual for assembly and use. Better start your laboratory with this precision instrument. Shipping weight 8 lbs. Model V -2

Zeal 1950 VERNIER TUNING R.F. ee,atitiecr SIGNAL GENERATOR KIT 7eareete4.

New 5 to 1 ratio vernier tuning Cathode follower output for greatest for ease and accuracy. stability. New external modulation switch- 400 cycle audio available for audio testing. use it for fidelity testing. Most modern type R.F. oscillator. New precision coils for greater Covers 1SOKc. to 34Mc. on fundamentals output. and calibrated strong harmonics to 102 Mc.

The most popular signal generator kit has been vastly improved -the experience of thousands combined to give you the best. Check the features in this fine generator and consider the low price $19.50. A best buy for any shop, yet inexpensive enough for hobbyists. Everyone can have an accurate controlled source of R.F. signal voltage. The new features double the value -think of being able to make fidelity checks on receivers by inserting a variable audio signal. Internal 400 cycle saw -tooth audio oscil- lator modulates R.F. signal and is available externally for audio testing. The new 5 to 1 ratio vernier drive gives hairline tuning for maximum accuracy in scale settings. The coils are already precision wound and calibrated. Uses turret type coil and switch e assembly for ease of construction. The generator is 110 V. 60 cycle transformer operated and comes complete in every detail- cabinet -tubes -- coils -beautiful two color cali- brated panel and all small parts -new step- bstep pictorial diagrams and complete instruction manual make assembly a cinch even for novices. Why try to get along with- out a signal generator when you can have the best for less than a twenty dollar bill. Better order it now. Shipping weight 7 lbs 19.50 CONVERSION KIT FOR G-1 GENERATORS Conversion kit for G -1 generators for vernier tuning and external modulation includes new high band coil for greater output. Gives all the features of new G -5 listed above. Order G -5 Conversion Kit No. 316 $4.50 .....««x«cawwaa+:

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elatlt ifew 'qeeatiaiZ`' ELECTRONIC SWITCH KIT F M T U N E R K I T THE UTILITY OF ANY SCOPE DOUBLES A truly fine Fist Tuner with the coils ready f ìi, j wound, all alignment completed -all that is necessary is wiring and it's ready to play - uses super regenerative circuit - 110V. 60 cycle transformer operated - two gang tuning condenser -slide rule calibrated dial - two tubes - complete instructions including pictorial enable even beginners to build successfully. Shipping \\'t., -í lbs. Beautiful mahogany cabinet for FS( CABINET Tuner (shown above) cxn. $3.75 r_ t EXTRA $1475 ELSE TO BUY

An electronic switch used with any oscilloscope provides two separately controllable traces on the screen. Each trace is controlled KIT independently and the position of the traces may be varied. The CONDENSER CHECKER input and output traces of an amplifier may be observed one beside the other or one directly over the other illustrating perfectly any change occurring in the amplifier. Distortion - phase shift and other defects show up instantly, 110V. 60. cycle transformer oper- ated. Uses 5 tubes (I 6X5, 2 6SN7's, 2 6SJ7's). Has individual gain controls, positioning control and coarse and fine sweeping rate . controls. The cabinet and panel match all other Heathkits. Every part supplied including detailed instructions for assembly and use. '7eCtta,te4. Shipping Wt., 11 lbs. Power factor scale Bridge type circuit Measures resistance Magic eye indicator 'e44 Measures leakage 1io V. transformer 3 -TUBE ALL WAVE RADIO KIT Checks paper -mica- operated electrolytics All scales on panel Checks all types of condensers. paper -mint- electrolytic- ceramic over An ideal way to learn radio. This kit is corn. a range of .0001)1 MFD to 1000 MFD. All on readable scales that piece ready to assemble. with tubes and all other arc read direct from the panel. NO CHARTS OR MULTIPLIERS parts. Operates from 110V AC. Simple, clear can read without a detailed instructions make this a good radio NECESSARY. A condenser checker anyone training course. Covers regular broadcasts and college education. A leakage test and polarizing voltage for 20 to short wave bands. Plug-in coils. Regenerative 500 volts provided. Measures power factor of electrolytics between circuit. Operates loud speaker. Shipping Wt., 05 and 505. 1.10V. 60 cycle transformer operated complete with 3 lbs. rectifier and magic eye tubes, cabinet, calibrated panel, test leads 11530 Headphones per set $1.00 and all other parts. Clear detailed instructions for assembly and use. $875 2!'t" Permanent Magnet Loudspeaker 1.95 Why guess at the quality and capacity of a condenser when you Mahogany Cabinet 2.95 can know for less than a twenty dollar bill. Shipping Wt., 7 lbs. CABINET EXTRA Ìe4tssit` R D E R B L A N K H I G H F I D E L I T Y O

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EXPORT DEPT. 13 East 40th St. NEW YORK CITY (16) CABLE: ARLAB -N Y. ... BENTON HARBOR 20, MICHIGAN

NOVEMBER. 1949

www.americanradiohistory.com 18 H ow to Pass Commercial Radio Operator I can train you to pass your FCC Lircose Exams in a few short weeks FC if you've had any practical radio expericuce -- antaleur, Army. Naiv. radio servicing, or other. My time- DOE, on ihr t.. 444.44,70).,,,0 Let me send you FREE ktit the entire story tx4MSCENst

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www.americanradiohistory.com Editorial 19 I

To the Service TecI,niciái.

. . . How many service techni-

emus are there in the U.S.A.? . . .

By Hugo Gernsback

HIS particular article is addressed exclu- ber of times, even if you are in a locality not served to learn all sively to the radio servicing trade. The reason : by a television station, now is the time Ever since the inception of this magazine, in you can on the subject, because the moment a tele- 1929, a large percentage of its reading matter vision transmitter begins functioning in your re- has been addressed to the service technician. gion it will be too late and time will be too short over 21 as our old readers well remem- to get practical experience. For years, keep all ber, this policy has never The editors these points in mind in changed. of their From time to time we the formulation have made various sur- editorial policy, particu- ex- larly from the long - veys to ascertain the They tent of service -technician range viewpoint. readership of the maga- also know that today á. service tech- zine and have been able there are ìwì.yu who service only to draw certain conclu- nicians from this. Yet, the editors in planning the radios, but do not touch television. Some confine sions do magazine over a long -range term must have certain themselves to television receivers, while others vital information as to its readers. No one can give both. that information to us better than YOU. To give you the magazine you want at the pres- Several years ago we made a mail survey and ent time, when the whole servicing industry-due impact of television in a state of flux, = we found that 53% of our readers were connected to the -is with radio servicing. it is of utmost importance to the editors to have in one way or another which only With the advent of television, revolutionary certain information on radio servicing changes have taken place within the servicing in- you can supply. The editor therefore, urges you to do us a great = dustry. To find out what the prevailing trends are, required. service and fill out the short blank which you will a new survey is urgently to us as quickly of during the find on page 52 and mail this back The sensational advance television will give us the information neces- leaves no doubt whatsoever that the as possible. It past two years you in the future the articles and will soon be blanketed completely sary to bring to entire country which you want and need most. with television stations. information This is the first time in 21 years of publishing Yet, speaking populationwise, 40% of the coun- has asked for your as this is written. It is your magazine that the editor try does not have television cooperation in this manner. certain, however, that by 1953 nearly all of this you be good enough to comply with this of a Won't country's inhabitants will be within range simple request and return this short questionnaire . as soon as possible? Service technicians who have read RADIO -ELEC- If you know others in the servicing industry, TRONICS have no doubt observed that not all of our please tell them about this too. The information is readers see eye to eye with us on our television vital and most important to them and to you, as policy. Those readers who are not now in an area well as to us. served by television stations particularly criticize For our part we will, as soon as the returns are us for carrying television articles at all. The reason complete, publish a comprehensive resumé of this is that to them, for practical purposes, television questionnaire. This will appear probably in our articles are only of theoretical interest at present. March issue -sooner if feasible. Yet, as we have pointed out editorially a num- Thank you for your cooperation! NOVEMBER. 1949

www.americanradiohistory.com 20 I- ---RM _

48V. T113 ÇOVNO OISCR. rRArAS_ c C5`2 1 81T 3 4

X 33 C159 5C

IF C200 L 1.5a9 0.1I5 roK 9/1T 15' so .. y,:/" O,eC02

V'Ib

...... :¡.. A v010 TUN INC. By H. K. MILWARD 3 4

and R. I `2, W. HALLOWS r N 1 J I L

IN Britain there is jection as yet no regular ts'"n e t , parison of the two FM broadcasting, circuits, however, it and there has been with one limiter is a slightly better per- is immaterial whether peak or no propaganda blitz r.m.s. over the re- former than the ratio detector; values are used so long as the same spective merits 2. of the limiter -dis- The discriminator with two lim- measure is used for both. criminator and ratio iters is -detector systems decidedly superior to the ratio A block diagram of the complete test as noise rejectors. An inquiry into detector; this circuits is shown in Fig. 1. The r.f. and question can thus be 3. The undertaken with superiority of the discrimina- first i.f. stages were part of a receiver a completely impartial approach and tor is most marked when the noise level designed with for FM. The i.f. and oscillator no background of "political" bias. is high. stages were modified to give an That is why In output the Editor asked us some the measurements made, peak val- at 10.7 mc. Two small coils of one months ago ues turn to make a series of com- of both signal and noise were used. each were wound on the parative Actually, output trans- tests and to report the results the annoyance effect of im- former of this i.f. stage and the output which we obtained. pulse noise is Standard compon- proportional to peak val- fed via two short co -axial leads ents made by ues to the leading firms in the only when the recurrence of pulses test circuits. This insured that the United States were is slow. As sent us in England the recurrence frequency test circuits were fed with similar sig- and these were used in circuits made up increases, the annoyance level becomes nals so for that comparative tests could the tests, which were conducted in proportional to r.m.s. valuesl. For com- be made simply by switching. one of the best equipped radio labora- The noise generator was made up tories in the country I BBC Research Department. Report 0.036. from a 6 -volt vibrator, a car ignition The ratio detector is simpler than the discriminator with its necessary limiter or limiters; it requires fewer compon- ents, and, although a little more difficult to adjust in the first place, it is likely NOISE GEN. RF 1. IST IF STAGES VARIABLE -GAIN to be considerably cheaper to - DB METER produce AF AMPLIFIER than the other. It is therefore important to know how its inherent noise rejection -+1 2 LIM,STAGES DISCRIM. -one of the great advantages of FM I over AM- compares with that of the FM SIGNAL GEN. 1---c7b-I 400NOSC.I limiter- discriminator. The conclusions we reached as the result of measure- OUTSIDE CAGE INSIDE CAGE ments and a series of aural tests are: 1 1. Though the difference in noise re- Fig. 1- Equipment used to compare ratio detector with limiter- discriminator. RADIO- ELECTRONICS for

www.americanradiohistory.com RM 121

band- controlled by varying the feedback path coil, a spark plug, and a 6 -volt storage lined up at 10.7 me with a 160 -kc battery. These were mounted in a width with the aid of an oscilloscope in fixed steps of 4 db. was a v.t.v.m. with double metal box as shown in Fig. 2. and sweep oscillator. Response curves The output meter was intended to vary the for the two test circuits were made as two inputs, one for r.f. and one for a.f.; Originally it in signal by altering the coupling of similar as possible. The curves showed and the meter itself was calibrated noise The a response which was level to within decibels (reference 1 milliwatt). approxi- 3 db 70 kc each side of 10.7 me and meter input impedance was was 6 db down at ± 80 -kc deviation. mately 6,000 ohms, and the amplifier to The loss beyond these limits was about output impedance was adjusted 0.4 db per kc. match. Thus readings of relative signal When the i.f. stages were satisfac- strengths could be made directly. The torily lined up, the demodulators were scale readings for a.f. signals were tackled. The discriminator gave the checked and found to be accurate. For curve of Fig. 6 -a without adjustment, both a.f. and r.f. inputs the meter above OUTER BOX INNER BOX and the ratio detector gave that in Fig. measured peak volts for anything /INNER BOX INNER BOX 6 -b after adjustment of the tuning 30 cycles or 30 pulses per second. I/ -AX LEAD the CO-AX LEAD fD slugs in the transformer. The ratio de- After this preliminary work tector was then adjusted for maximum main test readings were taken. First b C AM rejection by injecting a 400 -cycle the output meter (r.f. input) was con- POUTER BOX signal into the suppressor grid of the nected to the output of the two i.f. Fig. 2-Details of noise generator. stages of the ratio -detector circuit, and off. The noise the coil feeding the receiver, but this the a.v.c. was switched on, a reading was found unsatisfactory, for the noise generator was switched switched off signal stubbornly refused to be atten- taken, and the generator To assure complete impartial- level of noise with uated by more than a few db. The diffi- again. This gave the generator was culty was overcome finally by feeding no signal. The signal comparative test of 400 -cycle FM the first r.f. coil as shown in Fig. 3, and ity, this then switched on (with ± about varying noise strength at its source. deviation 22.5 kc, representing and read- Three levels of noise were obtained by ratio and phase detectors was 30',1, of maximum deviation) each of several gen- 1. Connecting the inner conductor of ings were taken for control settings. This the co -axial to the outer box in a very erator output arranged in England, where -to -noise ratios for small loop (Fig. 2 -b). gave a set of signal 2. Connecting it to the inner box in the r.f. side. has the output meter was a small loop (Fig. 2 -c) . regular FM broadcasting Following this side and a.v.c. 3. Connecting as in Fig. 2 -a with a connected to the a.f. detector. large loop. switched on for the ratio not as yet been established. the sig- For the tests the noise generator was Readings were then taken with shielded cage in nal generator operating the whole time, placed outside the For which the rest of the work was done, its output being varied as required. each previously charted output level, and the co -axial led through the mesh produced a sig- fiat r.f. stage, which a.f. readings for both detector circuits of the cage. was amplitude-modulated. nal which were taken of noise output with modu- The presence of output containing a CO -AX FROM lation off and modulation output with NOISE GEN. was shown by the 400 -cycle component noise off. These readings gave output values were oscilloscope2. The circuit signal -to -noise ratios for each circut. OVERSIZE adjusted until this component was a IF SHIELD CAN The actual signal -to -noise improve- minimum. ment, a.f. ratio r.f. ratio, depends on a of the two demodulators The outputs number of factors including percentage via a changeover switch were connected modulation (in the case about 30, 1), to the a.f. amplifier and meter. No de- accuracy of the output would and also the emphasis circuit was used as it radio frequencies. Thus the relative merits of meter at not have affected the improvement ratio shown by these re- LfCNASS 5 The a.f. amplifier was a the circuits. sults is not necessarily accurate, but 1 1 simple, two -stage, negative feedback the comparative output figures are. The MC RF COIL with an input impedance combination, results are shown in Figs. 7 -a and 7 -b. Fig. Method of injecting the noise. about 20,000 ohms. The gain was 3- of The ratio detector was then altered Some attenuation of noise level was This procedure is described in full in "The Ratio to the form shown in Fig. 8 and a by leaving a long cable be- Detector." by Seeley and Avina. /IC'a h rL , test made. The results (Fig. obtained June. 1947. further tween the cage and the generator. The lowest level provided gave output sig- nal -to -noise ratios of around 1 for sig- nals which were just above threshold 8H6 for limiter or a.v.c. action. The gen- 8+ erator produced 50 -70 noise pulses per second. The signal generator was a simple r- FM oscillator which had been cali- i ÌCO-AX brated for the tests. The deviation it produced was not linear; but as the tests required only a signal to be com- TO LIMITERS pared with the noise, this was no dis- advantage. The circuits tested are shown in Figs. 4 and 5. (The schematics have been simplified by leaving out screen and suppressor connections.) They were Fig. 4 Simplified circuit of the ratio 'elector used in the experiments. NOVEMBER, 1949

www.americanradiohistory.com 22 FM

e+

1. RELATIVE OUTPUT 0 VOLTS

251 Ȓ FROM -150 -100 -50 0 +SO +100 +150 FRED DEV ATION IN KC PHASE DISCRIMINATOR

Fig. 5-The limiter -discriminator parallel of the circuit shown in Fig. 5.

+12 7-a ) are substantially the same as those noisy. The ratio detector with a.v.c. for the original circuit. The results and discriminator with one limiter were +6 taken for two limiters with the dis- tried first. When the noise level was so criminator and one limiter with the high that all but loud passages were RELATIVE OUTPUT 0 ratio detector are interesting in that masked, the judgment averaged about VOLTS they suggest a connection between noise 3 to 1 in favor of the discriminator, 6 rejection and AM rejection. This is not each observer listening to about 10 surprising, for noise pulse a effectively changeovers. When noise was low 12 consists of two parts: that which af- enough to be noticeable only during soft O.TMC fects only an FM system, and that passages, the results were about even -150 -100 -50 0 +50 +100 +150 which FRED DEVIATION IN KC affects an AM system. There for the two circuits if the switching RATIO DETECTOR would be a certain minimum noise re- was done during loud signal passages Figs. 6 -a, 6-b--Curves of phase sponse from the most perfect FM sys- and 3 to 2 discrim- about for the discriminator inator and ratio detector, no tem, and any practical system would if done during the soft passages. noise. be worse in proportion to its AM re- When the discriminator was used +32 9 sponse. with two limiters, the ratio detector Finally, the two circuits were tested remaining as it was, the results were +24 aurally. The receiver was coupled to 100% for the discriminator on the loud a short rod antenna and tuned to the noise test and about 7 to 1 on the low OUTPUT +16 BBC experimental SIGNAL /NOISE FM transmissions. noise. These results confirmed the meas- RATIO (PEAK) The noise generator was placed outside urements generally, although the dif- WITH 30%M00,48 the building with a short length of wire ference appeared to be more noticeable -16-12 -8 -4 protruding as an antenna. A variable aurally than was to be expected from 0+4 attenuator was inserted in the output the actual figures. o.D(SCRIM.WITH LIMITER PRAT)) DETECTOR of the ratio- detector circuit and ad- During the e tests both circuits stayed K.ALTERNATIVE RATIO justed so that the output from a loud- in adjustment and no difficulty was ex- DETECTOR speaker was the same for both circuits. "-16 perienced in lining up and adjusting CO.,.. AA.lO -36 -32 Flicking the made 2e 2+ -20 switch it possible to either. The ratio detector was some- WRIT SIGNAL /NOISE RATIO (RF PEAK) compare noise levels. what more tedious to adjust, and the Fig. 7 -a-Comparison of the two types. In the tests four observers were component values appeared to be a asked to judge which circuit was least little more critical. +32 Thought, Memory, Produce New Brain Waves +24 I1)ENTIFICATION of OUTPUT +16 a hitherto un- as the reader concentrated on a new SIGNAL /NOISE known brain wave, which seems to paragraph. Similar RATIO (PEAK) graphs made while WITH 30%M0+6 be associated with thought, is reported the subject was performing mental mul- by a research team of the a.DISCRIM.W TH 2 Institute tiplications and other tasks requiring LIMITERS for Applied Experimental Psychology, thought show a remarkable correlation e. RATIO DET WITH Tufts College, Medford, Mass. Readers of kappa bursts I LIM.INSTEAD OF to periods of thought. e AVC familiar with electroencephalography The kappa waves are detected by vill remember that previously recog- electrodes placed just back of the ex- X16 nized brain waves not only appear best ternal canthi of the eyes (the corners DB,,- 4-40-36-32-28-24 -20 .hen the mind is at rest, but are ac- of each eye where the upper and lower INPUT SIGNAL /NOISE RATIO IRE PEAR. tually inhibited by thought processes. eyelids meet). Fig. 7- b-Limiter helps ratio detector. Later research, reported by the same workers to the recent meeting of the American Psychological Association at s s s Denver, indicates that the kappa waves are particularly Dips show drop in "tl glut output" as active when the brain subject finishes reading line of type. is attempting to remember something. They reported that when a student was The four researchers, John L. Ken- learning new material, kappa -wave ac- nedy, Robert M. Gottsdanker, John C. tivity was moderate. When the student Armstrong, and Florence Gray, have was trying to recall imperfectly- learned named the new manifestation "kappa material the kappa waves reached a waves." The figure shows how the maximum, and when reciting perfectly waves appear when the subject reads. memorized matter they again sunk to a The irregular waves are produced as new low, the scientists reported. the reader scans each line of type, and Further research is being carried out the retrace results in the drops at S. on these waves, which appear to rep- Fig. 8 alternate ratio detector. The third and longer wave was recorded resent a new advance in brain study. -An RADIO -ELECTRONICS for

www.americanradiohistory.com Cover Feature Television News 123

O

by TEX BARBARITE

The author repairs a camera

MAINTAINING an electronic exhibit like the Radio Corp- oration of America's Exhi- bition Hall in the heart of Radio City, New York, means a great deal more than replacing knobs and pilot lights removed by souvenir hunt- ers. It includes turning a bushing on a lathe as well as answering the queried of John Q. Public on AM, FM, and television. My engineering bent was formed in my early childhood. My hobby through- out my younger days, until I was en- rolled in a girl's private school, fol- lowed radio lines. My three brothers sets. ., KT - - and I constructed our own crystal :..'_ When crystal sets were outgrown, we graduated to vacuum -tube circuits. When I entered the girls school, I found myself very unhappy because the administration felt that science and mathematics were unnecessary subjects elec- for a girl. Finishing secondary school, The most important exhibit here is If nonuniformity exists in either field, the result is what I decided to go to the Texas College of the television field camera mounted in tric or magnetic Mines in El Paso to study for a degree a "See Yourself" display. This camera is commonly known as S distortion. I a (see cover), used in conjunction with As a well- focused beam of low- veloc- in mathematics. There received (see scholarship to study electrical engi- the field power supply, sync generator, ity electrons strikes the target At Pur- and camera control, utilizes an image drawing), enough electrons are depos- neering at Purdue University. it negative due my interest was spurred by the orthicon tube. Highly sensitive, it is ited on the target to make most useful where low light levels are to the remaining electrons in the beam the fact that the field of engineering, any hitherto dominated by men, was being available. When the camera is in use, and repel them. The potential that by the wartime short- the cover can be removed and the view- point on the target will reach is termed opened to women The beam age of men. finder attached on top of the camera. the "equilibrium potential." in Cam- A plug receptacle provides all the con- is kept constant, and the electrons From school I went to RCA are attracted to the rear den, N. J., and worked in the Tele- nections between the two units. The turned back Design viewfinder is a monitor using a 5FP4A end of the tube which is at the highest vision Terminal Equipment final function of Laboratories. This division handled de- kinescope. The sides of the camera are positive potential. The hinged to give access to the unit for the tube is to amplify the "picture in- sign for the microwave transmitter, electron distribution amplifiers, video amplifiers, maintenance and servicing. Selection formation" ih the returning orthi- of any one of four lenses is made pos- beam. Several multiplier dynodes are synchronizing generators, image potential than con and iconoscope cameras, and all sible by a rotating turret controlled by used, each at a higher a handle at the rear of the camera. the previous one. From the last dynode associated equipment. electrons are at- Having little knowledge of television, (there are five) the the com- Orthicon Ingenious tracted toward the collector mesh (sig- I took advantage of courses to an external pany offered in night school. In the I consider the image orthicon one nal plate), connected laboratory we operated our own experi- of the most interesting and ingenious load resistor. I have ever worked mental transmitter, W3XEP, for which pieces of equipment Exhibit Projects phone license. with. By means of the lens system, the New I got my commercial making here in the This provided all- around experience- optical image is focused on the semi- Projects in the students served as announcers, projec- transparent photocathode, which is at Showroom include a monoscope camera engineers, a high negative potential with respect and a master monitor, both to be in- tionists, cameramen, station racks. The in other essential positions. At to ground. stalled in the control -room and camera is a camera with the that time I was also teaching basic The radial electric field produced by monoscope the accelerator grid between photo- test pattern on the mosaic of the icono- theory and code to Civil Air Patrol of This background was the basis cathode and target, and the axial mag- scope. The pattern is composed cadets. on an aluminum plate. for my transfer to the RCA Exhibition netic field produced by the focus coil carbon deposited around the tube, assures proper focus- The carbon and aluminum have differ- Hall when it opened in New York in Electrons April, 1947. ing of the photoelectrons on the target. ent emission characteristics. NOVEMBER, 949

www.americanradiohistory.com 241 Television News

emitted by the scanning of the pattern entertained the mayor and his wife set owners complain because the A- are collected on the wall of the mono - from my home town in Texas. It's all batteries of their portable receivers scope tube. This coating is at a posi- in a day's work. have gone dead before the end of the tive potential with respect to the Reaction of the public to a female guarantee of the radio, or that the pattern, but is a.c.- coupled to ground. technician is varied and amusing. I portables won't play in a steel -con- Therefore, the picture signal appears seldom talk to visitors; but, in the two structed building. Then there are our between plate and ground. The master years and more that I have been at the friends of the would -be- technician monitor uses a 10 -inch kinescope and Exhibition Hall, just about every con- type who are at leisure and want to use a 5 -inch oscilloscope and is adaptable ceivable reaction has come to me. I'm all of ours picking up what they didn't to the supervision of composite picture not siding with my sex, but women, learn in school. signals at any stage of our transmis- by far, are easier to talk to than men. Recently, I spent two weeks in Cam- sion. A switching arrangement on the The women know nothing about radio den, N. J., at RCA's home office, learn- monitor allows it to be used as a con- and don't pretend to, whereas too many ing the latest television circuits and techniques. Most important to me was FOCUS COIL the antenna information. Service and installation men will be glad to hear of A7CAL MAGNETIC FIELD the Woodward antenna which receives signals from only one direction at a MULTIPLIER DYNODES 11000., time. Not an answer to any and all ELECTRON GUN-. romoll reception difficulties, it is most effective in cutting down co- channel interfer- 11DDD ence when the receiver is located in a fringe area between AXA. MAGNETIC FIELD two transmitters. Consisting of an array of four 8 -foot

FOCUS COIL dipoles in the form of a square, with the opposite members 8 feet apart, the A partial cross section of the image orthicon, showing path of the electrons. antenna can be made to receive from one direction or the other by flipping a switch trol unit for the film camera chain. men are out to "stump the experts." at the receiver. Interconnec- Both master monitor and monoscope Men tion of the dipoles through a diplexing also seem reluctant to talk to network makes must be wired for power and for our women about a medium that used to this one -way reception type of switching system, and adjusted be exclusively theirs. possible. Efficient reception on high for optimum operation. bands is achieved by "shortening" the Working as a maintenance engineer Public pours out troubles dipole with V's fastened to each leg. Of special interest to the radio ama- for the Promotion Department is not Many people come here to complain all repair work -not for a girl anyway. teur is the TV interference suppressor about the operation of their radios. recently developed by Captain John Once I was called on to don my best The majority of these cases do not dress and attend a champagne cock- L. Reinartz of RCA's tube department require a technician, but some instruc- in Harrison, N. J. This device, con- tail party fashion show at the Ritz. I tion and a little public relations. A had to forego the champagne, however, nected into the ham transmitter, traps full recitation of the circumstances harmonics before they can reach as my job was to set up and operate a usually paints an entirely new picture. the PA system for playing records. Another antenna. But service technicians do know of Hams are forever being blamed for time I purchased and installed an in- instances where Junior has dropped the verter for Mrs. John McCormack, wid- many of the ills in television reception. new radio in the brook while the 90- I have seen ow of the famous Irish tenor. I even at least one case where this day guarantee was still effective. Other was not true. In a small town just west of Philadelphia, there are only two ama- CONVERTERS FOR THE ULTRA -HIGHS teurs in the entire area. Even though Stanford Research Institute in Stan- operated by John H. Poole, sponsor of their logbooks showed they were off the ford, Calif., recently reassured the na- the project. Another is variable from air, they were blamed for a peculiar tion's present and future TV- viewers 475 -675 me, and a third tunes from 475- type of disturbance. The noise appeared about the coming advent of u.h.f. pic- 890 mc. in the form of a flash of maggots (similar to ignition noise). Just for a second it would disrupt the scene; oc- casionally it would travel downward in a bar effect. Service engineers from Philco, RCA, and Stromberg- Carlson traced the trouble to power lines and the power company remedied the dif- ficulties. My ambition -one that comes natur- ally to most radiomen and women - is to have my own well equipped shop. However, I am now involved in a pro- ject that has top priority; I am in the throes of building a shop in the base- ment of my home, not for radio, but for woodworking. It is my idea to gain some experience in the art of cabinet ture transmission. The Institute's De- The tuners used are shown in the construction and finishing. I would partment of Electrical Engineering has photo. At left is a cylinder oscillator. like eventually to be able to design, developed three new u.h.f: to- v.h.f. con- A modified "semibutterfly" oscillator is construct, and finish custom cabinets verters which are both simple and in- in the center, and a 475 -890 -mc crystal for radios, television receivers, phono- expensive. With such a converter, a mixer at right. With the usual TV re- graphs, and combinations. In the final standard receiver will need no internal ceiver, noise figure of the converters analysis, I suppose that I have a differ- modifications to receive u.h.f. programs. is about 11 db, sensitivity 200 µv. Os- ent outlook on my ambition than a One of the laboratory models is fixed - cillator radiation at the converter's man would have. I prefer to make it tuned at 530 mc to pick up transmis- antenna terminals is 56 mv. Image sup- a hobby rather than a money- making sions from an experimental station pression is 42 db. vocation. RADIO -ELECTRONICS for

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ndoor and Built -In Antennas Their Strong and Weak Points

The indoor TV antenna yields only a compromise performance By IRA KAMEN

JOHN STUART MILL said, "In Fig. 1. The Oscillator Interference though it may operate satisfactorily times of crisis we must avoid both Chart shows that when a television re- for channels now in use. Nearly every ignorant change and ignorant op- ceiver is tuned to channel 2, 3, 7, 8 or indoor installation is a costly, time - position to change." This statement 9, its oscillator radiates interference consuming experiment, and the set user is wise counsel today both to those on either channel 5, 6, 11, 12, or 13. is almost never fully satisfied. There receiv- are call -backs and a resultant financial selling and installing television The final solution ers and to landlords of multiple dwell- loss every time a new station goes on ings. The permanent solution to the mul- the air. The urban television dealer has not tiple- dwelling problem is a vacuum -tube- There is no such thing as a high - been able to realize full sales possi- type master antenna system such as gain indoor antenna. Even an adjust- bilities because many building owners approved by the engineering commit- able unit barely approaches the per- have refused to permit tenants to erect tee of Television Broadcasters Asso- formance of a simple outdoor dipole rooftop antennas. Often, to make his ciation and conforming to RMA speci- on the channel to which it is adjusted. sale, the dealer has installed in apart- fications. To date, two systems have Careful comparative tests should be ments TV receivers with indoor an- been tested and approved, one made by made on all new "sensational" indoor tennas, the poor performance of which RCA and the other by the Intra -Video antennas before embarking on a whole- increased the tenant's resentment sale indoor -antenna program. against his landlord. The indoor antenna is not practical The latter is often justified in refus- as a final solution to the problem. TV ing his permission, or, as shown in the signals do not pass readily through photo, the roof becomes cluttered with steel structures and are attenuated by a maze of disfiguring antenna rods, the materials of which houses are built. and the landlord becomes liable for pub- Such antennas are always a nuisance, lic, personal, and property damage. whether installed under a rug, in a In addition, random installations of closet, on a table or simply on top of rooftop antennas may result in pen- the receiver. alties for violation of local fire, build- Indoor antennas usable ing, and electrical ordinances. There are two main reasons why so many There are, however, many locations buildings have roofs like the one in the where indoor antennas can provide a photograph: either the landlord did satisfactory compromise signal from not to offend or he used must, how- . want tenants, Fig. Interference from another set. most stations. The set owner the permission as a way of persuading 1- ever, overlook faults. There is a reduced them to agree to a rent increase. Corp. of America. Both these systems signal -to-noise ratio and contrast will Some landlords are neither cringing suppress oscillator radiation enough to depend not only on the control, but nor greedy, but allow the antennas so prevent its marring the pictures of that tenants can enjoy television, feel- other RMA standard receivers connect- STEEL TAPE -7 _e/....LEAD ing that the appearance of the roof - ed to the system. Any type of TV re- never exactly artistic in any case, with ceiver may be connected to the system. clqtheslines, water towers, and so on- Neither system is in common use. and the rather remote possibility of Many a dealer is temporarily con- /1212-L) damage are subordinate to peaceful re- vinced (against his better judgment) TAPE FEED MECHANISM lations between landlord and tenant. that this or that indoor antenna is the Fig. 2- Slide -Rule is a folded dipole. On all rooftops overloaded with an- answer, for he knows that a successful tennas interference between television indoor antenna would mean greatly in- on the positions of people and furniture receivers may be so bad that on many creased sales. in the room. With an "under- the-rug" evenings only two or three of a pos- Installation companies guaranteeing antenna, every time someone walks sible six or seven channels can be used in the original contract reception for across the room the contrast changes. by most tenants. All other channels stations not yet on the air should be- The signal quality varies, too, with show r.f. interference as pictured in ware of the indoor antenna even the season. Window screens and foliage NOVEMBER, 1949

www.americanradiohistory.com 26 Television News

signal which has a different angle of customer who will accept and pay for polarization from the original. By set- such an installation. ting the V at the correct angle the two It is conceded that a built -in TV in- (direct and reflected) signals of differ- door antenna (Fig. 4) would be a ent polarization can be combined in great stride toward full realization of phase and the signal increased. customer acceptance of television. Cap- Many receivers with only average italizing on this fact, several manufac- sensitivity may be installed with an turers have made judiciously worded indoor antenna yielding a weak signal, claims to having solved this problem. if a booster amplifier with a minimum However, as one of these manufacturers gain of 20 db is connected between an- stated: "gold is where you find it" In- tenna and receiver. The booster should door antennas -whether built -in or not oscillate and should pass the full portable -will pick up television signals 6 -mc bandwidth required for good re- only if they are present in the vicinity ception. Many boosters have such nar- of the indoor antenna, and the quality row bandwidths that they do not per- of the reception cannot be improved mit the TV receiver to "track" on pic- over the quality of the signals received. ture and sound simultaneously. Many Actual tests of built -in antennas indi- oscillate on some channels, mismatch cate early enthusiastic customer reac- the antenna input, and are unstable. tion in some areas (Brooklyn, Queens, Kings, and Westchester County in New 7 he Tele -Tone has rotatable V antenna. Another practical indoor antenna is the Radio Craftsmen slide -rule. The York) where strong TV signals from affect it during the summer, and during length of a folded dipole is adjusted a majority of nearby TV stations have the winter, when the indoor antenna like a steel measuring tape. While the an unobstructed path to the indoor an- is picking up a reflected signal from length of this antenna is adjustable, tenna from one general direction. As a building or a mountain, ice formation it cannot offer a perfect 300 -ohm match on those surfaces may change picture except at one adjustment (if at all) ISOLATING SUPPORT INSULATING SUPPORT quality and strength. for the distance between elements can- BAND e f The only time, in fact, when an in- not be varied. This distance should door antenna works excellently is when vary from 0.54 to 0.145 inch for op- it is near a window from which it is timum results from channels 2 to 13. possible to see the TV transmitting This antenna's shape is not like that of antenna. a conventional folded dipole, either, as HI BAND in Fig. 2. illustrated 300, LINE TO TV RECEIVER Practical indoor antennas Fig. 3 shows a typical under -the -rug For portable receivers, the indoor antenna with high- and low -band folded antenna is of course a must. The most dipoles made of ribbon line. Occasion- practical is the rotating adjustable V ally three or four of these must be which can be turned and the length of installed and a switch provided at the Fig. 3-Under -rug unit of ribbon line. which can be adjusted. A typical one receiver to select the one adjusted for is used with the Tele -tone receiver in the desired station. In other installa- expected, in Manhattan, dealer and the photo. While the V antenna was tions pairs of dipole rods are installed multiple -dwelling reception with built - originally a means of minimizing the in different sections of an apartment in antennas has been generally poor. space needed for a dipole, it definitely and co -axial cables circuited to a co -ax The following disadvantages have been has an important advantage. Although switch at the receiver. While several noted by TV dealers: TV transmitters send out horizontally indoor antennas and a switch may pro- On stations where signals are weak, polarized waves, reflections produce a vide satisfactory reception, it is a rare the tuning adjustments become complex to the layman. The customer must keep his hands off the top of the cabinet as he tunes the antenna or else he affects the tuning. Metal trays or other large appurtenances cannot be placed on top of the cabinet by the customer. In first -floor dealer establishments the built -in antenna will work on only one or two stations in one or two loca- tions in the store, which reduces the flexibility of the dealer's sales opera- tion. In many cases the dealer's service- man must sell the customer on accept- ing the reception of the built -in antenna or rapidly install an outdoor antenna before the customer rejects the mer- chandise. The service technician who has the responsibility of asking the "lady of the house" to relocate the TV receiver with built -in antenna in another sec- tion of the room or a different room where the TV receiver will pick up more channels, must have an outstand- ing sales personality. Many amusing situations have arisen where the re- ceivers with built -in antennas work best in the middle of the living room, in Forest of antennas on apartment roof. n... proximity can cause interference. front of a window, and in other loca- RADIO- ELECTRONICS for

www.americanradiohistory.com Television \mi 1,27

Lions which the customer usually rejects. The idea of installing a TV antenna Tv STATION LIST on the power line cord or as a perma- WE receive occasional reports of MASSACHUSETTS in rear of console TV nent unit the a television Boston WBZ-TV 4 built stations 1,000 or more set as though it were a -in radio miles away being received clearly on Boston W NAC -TV 7 antenna is impractical. Several manu- ordinary receivers. Reports of such tele- MICHIGAN facturers have spent considerable vision reception Detroit W J B K -TV 2 dx are both valuable Detroit W WJ -TV 4 money and time to prove it. Certainly and interesting because they indicate for apartment -house installations, it is Detroit WXYZ -TV 7 the extent of this undesirable long - Grand Rapids W LAV -TV 7 impossible except when the TV receiver distance propagation. MINNESOTA ix against a favorably placed wall or Beginning with the next issue, Minneapolis KSTP -TV 5 in front of a window. RADIO -ELECTRONICS will publish Minneapolis WTCN -TV 4 The increasing number of TV sta- reports of long -distance TV recept' . MISSOURI tions will start the indoor antenna on Readers are insited to noii1v' us of their St. Louis KSD -TV 5 TV dx experiences in detail, giving the NEBRASKA date, time, name, location, and distance Omaha KMTV of the stations. quality of reception, tv pe Omaha WOW -TV 6 of receiver and antenna in use, as well NEW JERSEY as any other pertinent data. Newark WATV 13 'l'o aid tlx'ers, the following e plete NEW MEXICO list of stations gives all necessary log- Albuquerque KOB -TV 4 ging infornsaiion. NEW YORK Buffalo WBEN -TV 4 New York City WABD 5 City Call Channel New York City WCBS -TV 2 ALABAMA New York City WJZ -TV 7 Birmingham WAFM -TV 13 New York City WNBT 4 Birmingham WBRC -TV 4 New York City WOR -TV 9 CALIFORNIA New York City WPIX II Los Angeles KECA -TV 7 Rochester WHAM -TV 6 Los Angeles K FI-TV 9 Schenectady WRGB 4 Los Angeles KLAC -TV 13 Syracuse WHEN 8 Los Angeles KNBH 4 NORTH CAROLINA Los Angeles KTLA 5 Charlotte WBTV Fig. I -Phi Ieui s built -in TV antenna. Los Angeles KTSL 2 OHIO the road out except for portable re- Los Angeles KTTV 11 Cincinnati W C PO -TV 6 Cincinnati W K RC -TV II for those people willing to Son Diego KFMB -TV 8 ceivers and San Francisco KGO -TV 7 Cincinnati WLWT 4 accept compromise reception. San Francis, KPIX 5 Cleveland WEWS 5 CONNECTICUT Cleveland WNBK 4 OSCILLATOR INTERFERENCE CHART* New Haven WNHC -TV 6 Columbus WLWC 3 Receiver tuned Osc. freq. Interference DELAWARE Columbus WTVN 6 with channel to channel (mc) Wilmington WDEL -TV 7 Dayton WHIO -TV 13 5 (76-82 mc) 2 (54-60 mc) 81.25 DISTRICT OF COLUMBIA Dayton WLWD 5 3 (60-66 mc) 87.25 6 (82-88 mc) -TV 13 7 (174 -180 mc) 201.25 11 (198 -204 mc) Washington W MAL -TV 7 Toledo WSPD 8 (180-186 mc) 207.25 12 (204 -210 mc) Washington WNBW 4 OKLAHOMA 9 (186 -192 mc) 213.25 13 (210-216 mc) Washington WOIC 9 Oklahoma City W KY -TV 4 for receivers with 21.25- 27.5 -mc i.f. Washington WTTG 5 PENNSYLVANIE The plight of viewers living in mul- FLORIDA Erie WICU 12 tiple dwellings will be finally relieved Miami WTV1 4 Lancaster WGAL -TV 4 Philadelphia WCAU -TV 10 when the landlord again faces a buy- GEORGIA Atlanta WAGA -TV 5 Philadelphia WFIL -TV 6 ers' market and realizes that he must Atlanta WSB-TV 8 Philadelphia WPTZ 3 give his tenants television outlets just ILLINOIS Pittsburgh WDTV 3 as he provides heating, plumbing, venti- Chicago WBKB 4 RHODE ISLAND lation, and other fundamental services. Chicago WENR -TV 7 Providence WJAR -TV II Chicago WGN -TV 9 TENNESSEE Many of our readers will not agree with Mr. Chicago WNBO 5 Memphis WMCT 4 Ka men .m this controversial subject. For a dif- INDIANA TEXAS ferent view, sue Nell and Mandl in bast month's Indianapolis WFBM -TV 6 Fort Worth WBAP -TV 5 i .na 1 ear,. 291 Editor. KENTUCKY Houston KLEE -TV 3 TELEOGLERS GET TELESQUAT Louisville WAVE -TV 5 UTAH LOUISIANA Solt Lake City KDYL -TV 4 TV fans may be getting "telesquat" New Orleans WDSU -TV 6 Salt Lake City KSL -TV 5 and "telecrane" spinal ailments, Dr. MARYLAND VI RGINIA Martin R. Stone, president of the Chi- Baltimore WAAM 13 Richmond WTVR 6 cago Chiropractic Society, said in an Baltimore WMAR -TV 2 WASHINGTON interview with a reporter of the Chi- Baltimore WBAL -TV I I Seattle KRSC -TV 5 cago Daily .yews. WISCONSIN WTMJ -TV 3 Persons who perch themselves pre- Milwaukee cariously on the edge of their spines Television Channel Frequencies by sitting in a slumped position are Chan r H Frequency The following stations, not on the air asking for trouble. They are doing the Numb ( mc) when the above list was made up, are " telesquat." 2 54 -60 expected to open on the dates indicated 3 60-66 on the bottom of spine below. "They sit their 4 66 -72 and not on their bottom like nature 76-82 5 Probable intended. The ` telesquat' can cause a 6 82 -88 starting low backache and other physical dis- 7 174 -180 City Call Channel date turbances," he said. 8 180-186 Kansas City, Mo. WDAF -T.V 4 10/16/49 Sitting in a forward bent position 9 186 -192 Greensboro. N. C. WFMY -TV 2 9/22/49 10 1 92-1 98 puts a strain on the vertebrae of the Columbus, Ohio WBNS -TV 10 10/I/49 neck. This is what Dr. Stone calls "tele- 11 198-204 12 204 -210 Johnstown, Pa. WJAC -TV 13 9/15/49 crane." This practice can cause severe 13 210 -216 Dallas, Tex. KBTV 8 9/17/49 neckache, headache, and eyestrain. Jacksonville, Flo. WM BR -TV 4 10/16/49 NOVEMBER, 1949

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By DAVID T. ARMSTRONG

INSTALLATIONS

The author explains techniques of success- ful custom -built television installations

THERE is a great deal of custom suggestive selling using high- class, service business is made for two rea- building to be done in all sections direct -mail techniques to reach those sons: first, not enough of it is likely of the country, but few people people who have the means to finance, to come your way to warrant going know where or to whom to go to and the interest in TV to desire, a into it full time at the start; and, sec - get the information they need. The custom installation. ond-at the beginning anyway -you service technician who wants his share The author's recommendation that can hardly handle more than one job of this business should go in for subtle, custom building be an adjunct to a a month satisfactorily. The rewards are enticing enough to make one good custom installation per month suffi- ciently profitable to keep you going. Take it easy and build your business slowly, surely, and successfully. Last month we had an over -all view of custom installations. In this issue we are going to follow a single installa- tion step -by -step to give you some idea of the problems you are likely to meet. The drawing of Fig. 1 sold this job. The room was small, 8 x 10, and was used as a den. There was a door on the extreme right and one on the ex- treme left. The door on the left led to the basement; the stairwell was be- hind the TV installation. That meant leaving that wall alone but it did solve the ventilation problem nicely. As you can see from the sketch, the TV installation is relatively simple, but the cabinet work is extensive and ex- pensive. During the first call on Mr. Prospect, he decided where the TV would be and what he would like done with the remainder of the blank wall. He indicated he wanted a desk with some pigeonholes for letters and some drawers on either side of the desk, plus some shelving for books. To be a good salesman, you must swallow your own preferences. Per- sonally, I think the pigeonholes for letters and knick- knacks a little corny, but that was one of the most appealing features of the sketch for Mr. Prospect. Fig. 1- Drawings like this one help to sell the installation to your prospect. We gave him drawers on the left side RADIO -ELECTRONICS for

www.americanradiohistory.com Television News 29 and a cabinet on the right. In making dimensions shown are absolutely essen- the drawing we made an additional tial for installing the parts- chassis, sketch of three drawers for the right power supply, speaker, and picture side similar to the three on the left and tube. The audio amplifier as the heav- pinned them over the storage cabinet iest component belongs at the bottom shown. The monotony of the design at of the assembly, resting on the floor once convinced the family that it was for best support. The record player is better as we had it originally. just above the amplifier, built on a Here is another point. The depth of trolley arrangement so that it may be the shelves for hooks is 20 inches, mak- slid out for operation. This means that ing it possible to use the back part of the cabling must be of very flexible the shelves for dead storage of infre- wire that will not break. quently used books and the front part Note the thimble through the wall for the currently consulted ones. How- at the back of the audio amplifier. ever, the possibilities of such shelving This amplifier generates a large amount are infinite. We asked if he had much of heat and so does the power supply. liquor storage space, suggesting we You will recall that the wall behind the make false partitions just behind a row TV location was a stairwell, making it of books and put in removable panels convenient to cut through for a venti- behind which liquor could be stored. lation hole. The stairwell side of the But he wasn't much of a drinking man, thimble is covered with a perforated and that was out. A little safe could metal grill. be put back there and few people would suspect it. Other possibilities will oc- Ventilation is necessary cur to fertile minds; have the courage Ventilation of TV custom installa- to use them. tion is extremely important, so much so that RCA will not approve or per- Drawings are important mit an installation until the specifica- it is hard to overemphasize the sell- tions show that proper venting is pro- ing effect of good drawings. Fig. 1 vided. They usually figure that a 40' required about one hour to complete. C or a 72° F rise above ambient temper- Of course it was done by an expert ature is the maximum for safe receiver draftsman. Drafting is a profitable skill operation. Assuming that 70' F is the for those who intend to make some normal room temperature, an addi- money in this game. It is perhaps the tional 72° rise would bring the temper- chief stumbling block to many. There ature to 142 ", the temperature of do- are so many separate and different lit- mestic hot water, which is more than tle skills needed to sell and install TV most hands care to stand. Actual tests Photo courtesy nuan uu 07071! Laos., INC. that many little men give up. Perhaps have shown that, with proper ventila- A receiver this is easy the calls for tion, operating temperatures are usu- like to install and it's just as well; industry finish to the customer's specifications. men who can and will take the time ally around 90° to 100'. to learn what they need to know. Note another thimble cut into the to permit hot air to flow easily out of The choice of a wood finish is im- wall behind the picture tube and the the upper thimble. In other types of portant. This room was plaster and 9 -inch open spaces along the rear wall installations some provision is made paint, but we sold the idea of a knotty t pine finish for the entire room including 10E1111 3. the doors. Here the cabinetmaker got I- ' SPAR MOUNTING PANEL - out of the job than we did; FROM FRONT more work ,4 REMOVABLE but since he was working for us, the -c_-1 S01 R COMPARTMENT LINED WITH I SPNR major portion of the profit on the job PANEL IB/2I EINCH 0217E BLANKET was ours. I / by 3/4 We used to hire a cabinetmaker 1 ...... AR WALL the job, but we have since found it :4 profitable to have one permanently on 79 1/2 20.1/4 / our staff. He is paid a base sum per SCREEN l VENT IN REAR WALL week whether he works or not and a EI higher flat rate during the time he is ó 3/4 actually working for us. He has his own 0 O,1l' I I shop and makes his services, skills, and -. 4" IN REAR FOR VENTILATION RADIO TUNER I tools available to us at all times. Some- 70 times he is busy on a private job of I I 4 3/4 his own and we have to wait a week 0 0 0 0 0 0 I for his services, but that is not a seri- I ous problem. People who are quality - C RECORD CHANGER DRAWER I 14 minded and who pay quality prices RECORD PLAYER I II I 3.4 realize you can't hurry a good crafts- ` lj man. That is part of why it requires I a month to do a job. IN REAR WALL AUDIOMPL \l/%22-1/2 ENT I 12 ,I I \ REMOVABLE PINE I C Construction procedure I i j VENEER PANEL The series of sketches in Figs. 2 II-1/4 .1 19-1/2 and 3 break Fig. 1 down into dimen- 22-1/2 DIMENSIONS IN INCNES sional detail. Let's consider first the front elevation and the cross- section FRONT VIEW CROSS SECTION ON E views of the front elevation. The basic Fig. 2 -A front -panel view and cross -section of the installation in Fig. 1. NOVEMBER, 1949

www.americanradiohistory.com Teievisioll News

precisely with the shafts on the chassis. ^`1 The reinforcing corners in the /CORNER REENFORQMENT C41 speaker assembly are necessary to pre- vent the panel from sagging under the 19-1/4 weight of the speaker. They are wooden 18-1/2 pieces, and all cabinetmakers know how to install them. Cover the sides and back of the speaker compartment with a I -inch Ozite blanket for sound deaden- CROSS SECTION IN AM L COMPARTMENT ing. Try covering the bottoni and top and let the customer decide which sound ALL FRONT PANELS TO BE REMOVABLE he finds most pleasing. FROM FRONT - FASTEN WITH CATCH OR DECORATIVE SCREWS WITH CLEAT The details of the record player in 24 -1/2 Fig. 3 will vary with the player se- 2S -I /2 lected. RCA will supply the installer

DETAIL OF SPAR FRAME X. FASTEN GRILLE CLOTH ON-BACK OF FRAME with a template for the component used. Here the front panel is securely fixed to the record player drawer, and the handle is the slot cut into it near the top. The installation discussed is only one 18-/2 of many possible types using equip- ment made by any of a number of man- ufacturers. It shows the kind of plan- T ning needed, the precision and care with which you must work, and the type of selling job involved. Many custom installations use pro- 1 II-I/4 jection viewing systems. A typical one is made by General 22-1/2 Electric. Fig. 4 shows how the optical system works, DETAIL OF REMOVABLE SPAR MOUNTING PANEL - 3/4''F10. PLYWOOD and, roughly, how the components must 3/4 TEMPLATE OF CUTOUT SUPPLIED BY MANUFACTURER be placed. Obviously it requires a some-

DETAIL OF TELEVISION PANEL -3/8 *KNOTTY PINE PLYWOOD what different layout from the direct - view installation. One of the easiest installation jobs 8 1/8 is the Du Mont unit shown in the photo- - is 8-1/e n graph. It shipped in the plywood case just as you see it, 2 2.7/8 ready to work. I/2"DIA(61 All you have to do is make a place for it and finish off the front with paneling. While the installation is simplified, it 20 takes a good bit of space ' A 7 d and lacks `2Ie5/8 ( v2-I/4 2-5/0 22 -1/2 the distinctiveness of an individually II-1/4 DETAIL OF RECORD PLAYER DRAWER planned job for a specific location. I 22.1/2 FRONT PANEL KNOTTY PINE VENEER \'hile I have no special preference DRAWER MOUNTS ON EXTENSION SLIDES for any one manufacturer, I DETAIL OF RADIO TUNER PANEL - 3/8- KNOTTY PINE PLYWOOD DIMENSIONS IN INCHES have re- ceived much help and advice from the Fig. 3- Details of the panels on the individual compartments. The over -all di- Consumer Custom Products Depart- mensions and the positions of the holes will vary with different chassis sizes. ment of RCA in New York. If you make for openings in the paneling the an RCA installation, you will have to at amplifier, and speaker are removed have them base of the unit; the grill work around only for OK your plans anyway be- servicing; they may be held fore they will sell you the equipment. the speaker provides the upper open- in place with decorative screws, or just ing. So great is the chimney effect that pushed into place and held there with a thin paper streamer held against the spring- loaded catches. The record upper opening will blow out like a flag. player front panel may be a slide which When that happens, you are getting a fits into a niche on the right or left REFLECTING MIRROR good draft and you will have no trouble side or at the bottom of the reproducer; with overheating. The minimum open- or it may be the front of a drawer in IMAGE ing area permissible for ventilation of which the reproducer is located, slid- the entire unit is 64 square inches. ing out on ball -bearing runners. What The importance of dissipating heat is done depends on the desires of the from the TV installation and chassis is prospect and the skill and experience seldom understood. The capacitors and of the cabinetmaker. Spring -loaded VIEWING SCREEN resistors in the front end of a tuner catches are wonderful because they are heat -sensitive, and the stability of make a little mystery of removing the the oscillator depends to some extent on panels, but they require a degree of CORRECTOR LENS dissipating the heat generated in the precision to install that not every cab- oscillator and mixer sections. inetmaker possesses. PIX TUBE

The enlarged views of the MIRROR tuner and SPHERICAL PROJECTION .i Installations are flexible the television screen panels indicate Many variations are possible with the hole layout for the cabinetmaker. NONREFLECTING SURFACE the removable panels for the audio holes The are large enough for the con- OPTICAL AXIS amplifier, record player, and speaker. trol knobs and shafts and permit some The panels for the tuner, picture tube, tolerance in case they do not line up Fig. 4 -A typical TV projection system. RADIO -ELECTRONICS for

www.americanradiohistory.com Theory and Engineering MICROWAVEs

l'art / / -.1 tiou of below- rut attrnnatorx. and of TEl ani! anti -TR 8witehem

By C. W. PALMER

Court,' Sglrania Electric Products Inc A TR assembly for waveguide insertion

WE discussed waveguide at- of attenuation. Since the relationship The space between exciting and pick- tenuators in a general way is linear, a scale on the movable loop up loops is adjusted by one of several in an earlier part of this or disc can be calibrated directly in mechanical methods, the simplest of series and showed how a decibels. Attenuators of this type usu- which consists of two telescoping metal resistance strip could be inserted into a ally have an insertion loss of about tubes, each of which contains a loop waveguide to introduce an adjustable 10 to 20 db at the position of maximum and is terminated in the co -axial lines amount of attenuation. coupling and more as the coupling is or waveguides. A rack -and -gear drive Another type of attenuator used ex- reduced. controls the amount of telescoping and, tensively in microwave work is called When co -axial line is coupled into a consequently, the spacing between loops, the "waveguide- below- cutoff" attenua- cutoff attenuator with loops, a serious which varies the attenuation. tor or sometimes simply mismatch co the cutoff at- to the line results, a -axial TR and ATR units tenuator. line terminating in a loop being prac- A wave propagates through a wave- tically short- circuited. Three methods In radar and microwave communica- guide with very little loss, provided the of reducing the bad effects of such tion systems in which the same antenna is used for and re- diameter or width of the guide is mismatch may be used. The most com- both transmitting necessary - greater than the cutoff point. If these mon is to pad the input and output ends ceiving, it is to use a fast dimensions are operating transmit -receive switch to below cutoff, then there of the cutoff attenuator with lengths of prevent transmitter power from reach- is no longer any real wave propaga- high -loss co -axial cable. These add tion; instead ing the sensitive crystals and vacuum the magnetic and static about 10 db of attenuation, and their tubes of the receiver and also to pre- fields of the r.f. waves are attenuated resistance damps out the effects of very vent the received signal from being rapidly down the length of the reflection from the mismatched co -axial absorbed in the transmitter. guide. line termination. A transmit -receive (TR) box is an Another way is to use resistor discs, electronic switch which operates in a XPP little circles of graphite or carbon, fraction of a microsecond. It must pro- ExLOOPIr LOOP made to fit the co -axial cable, with a vide an excellent short- circuit for the hole in the center AV!.GUIDE BELOW CUTOFF to contact the inner receiver, since even a small part of the a wire. The resistance of these discs transmitter power would burn out a should be equal to the characteristic silicon or germanium crystal. EXCITINGO '1 PICKUP impedance of the line so that the line WAVEGUIDE DISC DISC is 0 terminated correctly. SIGNAL PICKUP PROBE

WAVEGUIDE BELOW CUTOFF A third method is to make the loops b of a resistance material and adjust the Fig. 1- Couplings are loops or discs. resistance of the loop to equal the char- WAVEGUIDE BELOW CUTOFF EXCITING LOOP acteristic impedance of the line. PICKUP LOOP t MOVABLE I Cutoff If the guide diameter is made small attenuators are also made to work in waveguide at the higher fre- compared to the free -space wavelength, PROBE quencies where co -axial COUPLING LOAD the attenuation is independent of fre- line is not desir- TO able because of high losses. Fig. 2 WAVEGUIDE quency over a very wide shows range. The how this is Fig. Attenua) ar between waveguides. modes done. A rectangular or cir- 2- generally used for such attenu- cular guide is joined ators the to the small are TEt,t and the TM0,1. The "below- cutoff" section with a pickup Some form of methods gas discharge device of exciting waveguides in these probe near the termination of the large is generally used for this purpose. Note two modes are shown in Fig. 1. Here a guide. This probe ends in a fixed loop Fig. 3. Here the transmitter power co-axial line is terminated in either a for exciting the small guide. A second builds up a voltage across the gap, coupling loop or disc and the reduced (movable) loop used as the pickup which then arcs over so that most of power is picked up in another co -axial point ends in a probe extending into the transmitter power goes out to the line. The distance between the exciting another section of large guide to con- antenna. This simple scheme could be and pickup loops controls the amount tinue the waveguide circuit. employed in either a co -axial line or a NOVEMBER, 1949

www.americanradiohistory.com J21 Theory s>lud hufiiueeriug waveguide, but unfortunately it doesn't loops inserted into the cavity. The step - not change impedance enough to pre- offer enough protection to the receiver. up ratio of the transformer is controlled vent an excessive loss of received signal. The simplest way to improve it is to by the size of the coupling windows or In these instances, an anti -TR box is insert a voltage step -up transformer loops, the. ratio increasing as the win- used. before the gap and a step -down trans- dow or loop size is decreased. former after it. And this is just what When weak microwave currents pass i.; done, in the form of a resonant cavity through the waveguide or co -axial in which the gap is placed. cable, the TR tube permits power to This resonant cavity may take the pass through. But if a strong wave - form of a cylindrical box with perfectly such as would be set up by applying conducting walls and with two posts in power to the magnetron transmitter of the axis of the cylinder, separated by Fig. 5- passes down the guide, the tube a b a gap, as shown in Fig. 4. In the low- breaks down and becomes a short Fig. 4- Voltage is highest across gap. est mode that will function in such a circuit. The shorting of the TR gap cylinder, the electrical field is parallel applies a "solid The anti -TR box is very similar to wall" at the junction of the to the axis of the cylinder and increases the T side arm of the waveguide, and TR box except that it has only one toward the center. The magnetic field sets up a strong standing wave in the coupling window instead of two. It is side arm which prevents the transmitted placed in a T side arm between the TR and the magnetron. On transmit, it SPARI( GAP ERNA YMITTER TO ANTENNA signal from reaching the receiver. In receiving, the magnetron is not fires just as the TR box does and re- fired, and since most magnetrons have flects a solid wall at the junction of the a considerable change in impedance be- T side arm, thus allowing maximum tween hot and cold conditions, it is pos- power to reach the antenna. sible to tune waveguide On receive, however, being situated TO the to provide RECEIVER a matched impedance condition when a quarter- wavelength from the TR box Fig. 3 -The principle of the TR switch. the magnetron is fired, thus introducing and tuned in length so that when it is lines are circles perpendicular to the a gross mismatch when the magnetron not fired it reflects signals coming from axis of the cylinder and currents tend is not fired. This sets up a standing the direction of the antenna, it thus to flow radially and up and down the wave in the line between the TR tube prevents loss of signal in the magne- tron. the distance from anti -TR center posts, as shown in the cross - and the magnetron so that most of the If the section drawing. received power goes through the cold to the TR is correctly chosen, a maxi- Energy may be fed into and out of TR box to the receiver. mum received signal will pass through such a cavity either through windows Some magnetrons, particularly those the unfired TR to the receiver. in the cylinder walls or by coupling on 3 cm and shorter wavelengths, do ANT

ACT TER

A DETECTOR- FILTER CIRCUIT TR SWITCH II CAVITY

is Heterodynes, caused by beating be- of the tuned circuit equal to the TO REU VER tween adjacent- channel signals, are cathode resistance at resonance, the Fig. 5 -TR switch in ant nna circuit. often annoying to users of high- fidelity audio voltage will be divided equally receivers and tuners. A heterodyne filter between the plate and cathode circuits. A TR switch may not fire in the first is combined with an infinite- impedance Since these voltages are 180 degrees few cycles of the transmit signal and detector in a circuit described in Elec- out of phase -as in a kangaroo phase the high- voltage pulse may damage the tronic Engineering (London). inverter -the audio voltage will be zero receiver. To prevent this a "keep- alive" A parallel- resonant circuit L -C2 is in- at the junction of Rl and R2. electrode is often built into the TR serted in series with the detector plate Rl and R2 may be replaced by a po- tube. An auxiliary electrode or gap and B-plus in the circuit shown. The tentiometer to permit balancing the near the main gap of the TR tube, it cathode bypass being small, system for best performance. The cath- is connected to a source of voltage suf- the cathode voltage will follow the mod- ode capacitor is chosen to have a re- oient to keep a small arc always fired ulation envelope. Audio output is taken actance much smaller than the cathode in the TR to supply the necessary ions 8 +200V resistor at the lowest signal frequency to cause the main gap to fire on the -usually 550 kc -and much larger first pulse from the transmitter. This C2 .01 than the resistor at the resonant fre- causes a small loss of received signal,

CI .02 quency of L-C2 (approximately 9,000 but prevents damage to the delicate re- 6J5 cycles). Cl is selected for a reactance ceiver parts and is thus a worth -while SEC OF RF OR 250K equal to the resistance of R1 plus R2 compromise. IF TRANS .01 at the lowest audio frequency to be The use of TR and anti -TR switches 5001t VOL CONT passed by the audio system. If its re- in a microwave communication system actance is too high, bass boost will be permits duplex operation. Transmitter 0..1T PUT introduced. Feedback will occur at low power can be applied momentarily to when it is to 22K 100yuf frequencies if the reactance is too low. the antenna desired talk, L is a 30 -mh shielded r.f. choke. One but reception is possible at all times with a powdered -iron core is preferable. that the transmitter is not active. It from a bridge composed of the internal C2 should be a high -quality mica unit. also permits a single antenna and re- resistance of the tube, Cl, R1, and R2. L -C2 may be replaced with a commer- flector system to be used for transmit At frequencies above and below the cial heterodyne filter if it is considered and receive. This reduces cost and al- resonant frequency of L -C2, the plate - desirable. lows focusing on point -to -point trans- circuit impedance is low and most of If the receiver has a separate detec- missions to be simplified greatly. An the audio voltage is developed in the tor, the filter may be incorporated in an even more important advantage is in cathode circuit. If Rl and R2 are equal a.f. amplifier stage. In such cases, the radar, where the rotating antenna and the reactance of Cl is low, the out- cathode bypass capacitor is omitted and makes it extremely convenient to use put voltage will be half that developed the cathode resistor adjusted for nor- one antenna for transmission and re- in the cathode circuit. If the impedance mal amplifier operation. ception. RADIO -ELECTRONICS for

www.americanradiohistory.com Amateur How to Become a Hain

Learning the I'ni/i

By GEORGE SHUART HE International Morse code was the first and -for a time -the only way of conveying intelligence by T radio. More important to the would -he amateur, the Federal Com- munications Commission requires you to be able to send and receive it at a rate of 13 words per minute before you can get a license. That being the case, the thing to do is to get to work and I(a.e a friend send the code chile you copy it down. learn it. The code is used to transmit intelli- gence in exactly the same way as the the letters to you -even if just until at the pencil; that will get you nothing. spoken word. In speech, sound is varied you can recognize the 26 letters and Each letter should he formed carefully to form words: in code, the duration 10 numerals. The rest you can do your- and slowly. It will then be more legible, and spacing of a single type of sound is self. and you will find it less difficult to copy varied. In either case the effect is the behind the sender. same. It is the complete sound that gets If you can get help A great many code students believe the idea across, not the individual vari- that fast writing allows greater time ations. For example, should a person You'll need a code- practice oscillator for concentration on what is being say "fishing rod," you would visualize or buzzer, which can be built following sent. That is wrong! Write slowly and a fishing rod, not think of the letters instructions in any of the articles listed keep yourself relaxed. If a letter is that make up the words, nor of the at the end of this story. missed or improperly formed, go right words themselves. So it is with code - Don't look at any tables showing the ahead to the next as though nothing one does not listen to the component code in print -not even at the one given had happened. If you stop for one let- parts of letters. but visualizes complete in this article. Sit down at a table with ter, you will lose a dozen before you letters or words. a good supply of paper and pencils. Let get going again. If I were walking gown the street your "instructor" send you the letter and heard a voice Gehind me say, A. The first few times, he should tell "Shuart!" my head would turn almost you what it is. Then let him send it If you have no help instantly whether I wanted it to or not. over and over again, perhaps 30 times. If there is no one to help you, use the Having been called Shuart for a num- And each tinte he sends it, write it table printed with this article. Notice ber of years, I know that when some- down. Then do the same with the letter that there are no dots and dashes, only body says "Shuart" he usually means B. Next, try it with alternate A's and (lits and dahs. A dit (short sound or me. I don't have to think about it. I B's until you can copy them straight dot) in print looks very much like a answer to the name just as quickly and in any order, identifying each correctly. dah (long sound or dash) so your fu- unthinkingly as my leg jumps when the Each letter should be sent at a good ture progress is not so likely to be im- doctor hits my knee with his little rub - clip, with long enough spaces between peded by a mental picture. ber hammer. them for you to identify and write Don't learn the code by eye. Put the A good code man operates on the them down. table before you and rest your hand same basis. When he hears a long and Now try C. Then D. Then A. B, C, on the key. To learn the letter A, just a short sound. his hand writes "N" and D. And so on through the alphabet let your hand follow the instructions automatically. He doesn't think about and numbers. After a while you will to push once briefly (di) and once long it-he hasn't time. The long -short sound not have to think so long for certain (dah). The space between the two combination is directly associated in letters, and you'll know you are learn- should be only as long as necessary to his mind with the letter N. No mental ing. This whole procedure may take get the key up and down again. The pictures of printed dots and dashes a number of sessions, each of which di -dahs, remember, are just instruc- come between the sound and the letter. should be stopped when you feel your tions for your hand, not things for your There's a lesson here for you. It's so mind is getting cluttered and is no mind to learn. Make the sounds indi- important that it is almost all you need longer alert. cated with the key and oscillator and to know: As soon as you have learned a few immediately pause and write each let- The only good way to learn code is by letters, have your instructor send com- ter down. After you've made the sounds ear. plete words, short ones, of course, with for A and B many times, mix them up Never look at, any of the tables that long pauses between them so that you -and write down each one. Then go show dots and clashes (or even dits and can write down the word immediately on to C. Next, mix up A, B, and C. dahs) next to the letters they represent. after it has been sent. Thus you'll avoid And so on through the list. From the very start of your training the pitfall of attempting to write down To send correctly, hold the key light- learn by having someone send letters each letter as sent. The beginner will, ly, palm parallel with the operating to you and then tell you what each one of necessity, he copying slowly. Try to desk, and with the elbow and the fore- is. That isn't practical if you can find remain at least two letters behind the arm muscle resting on the desk in a no one to help you. But it is worth sender. Do your early copying at a direct line with the key. Bounce the while to move heaven and earth to find very slow rate of speed ... stop if you wrist. When the wrist is lifted, the key someone who will sit down and send find that you are hurrying. Don't strain will go up. As the wrist is lowered.

NOVEMBER. 1 9 4 9

www.americanradiohistory.com Amateur 34 I

the key will go down with it. Rapid machines on the market. Those who CODE -PRACTICE STATIONS bouncing makes the dots, while slow have to learn alone should certainly bouncing will make the dashes. Be have one. Investigate the various types One of the best ways to increase your proud of your "fist." Good sending is to find the one most suited to your code speed is to copy government and immediately recognized. You'll receive needs and pocketbook. Phonograph rec- commercial radiotelegraph transmis- many more replies to your calls if your ords -sold by most radio mail -order sions with the aid of your receiver. The signals are easily understood. If your houses-are especially useful to the table below lists stations of Mackay characters are slurred and your send- lone student. In any event a practice Radio, Radiomarine Corp. of America, ing wobbly, the other fellow will pass outfit will be needed. This can be built and the U. S. Coast Guard which trans- you by and go to someone else who is or purchased. mit useful material for practice at rea- easy to read. Just one final tip: don't get discour- sonably low speeds. Stations whose calls begin with N Working up speed aged. You may get on beautifully for a few weeks, then be unable to improve are Coast Guard. They broadcast Once you've learned the bare letters at all. But if you keep up your practice, weather and marine information. WSL, and numerals by either of the two you will eventually forge ahead. You KFS, and DZM send press, while the methods above, your real training be- may hit another snag a little later. others transmit weather. gins. It is simple; it is also tedious. Again, don't quit, for you will even- Other good sources of practice ma- Progress will be slow for a while, then tually break the tieup. Boosting code terial are ARRL information and code - suddenly speed up. speed is a very peculiar process, but practice transmissions (write ARRL or The procedure can he given in two anyone at all can do it. Nobody gets see QST for schedules) and miscel- laneous commercial and government code stations you may run across. TABLE OF CODE SOUNDS Foreign countries, notably England, broadcast traffic and press in a number A. di dah Y. dah di dah dah of languages. B. dah di di dit Z. dah doh di dit Note that you will require a special C. dah di dah dit 1. di dah dah dah dah receiver for frequencies below 550 kc. D. dah di dit 2. di di dah dah dah This can be constructed by the listener, E. dit 3. di di di dah dah or he can use surplus beacon receivers, F. di di dah dit 4. di di di di dah some of which receive over a range ex- G. (lah dah dit 5. di di di di dit tending from 200 to 500 kc. H. di di di dit 6. dah di di di dit Time Free, Call Station )GMT) (kc) sian Location I. di dit 7. dah dah di di dit 0018 408 KSE Torrance, Calif. 0418 8.457.5 J. di dah dah dah 8. dah dah dah di dit 1618 16.990 K. 21118 dah.di dah 9. dah dah dah dah dit 11330 127 NMR San Juan, P. R. L. 1330 4. ;95 di dalt di dit dah dah dah dah dah 11350 . 425 NMF Boston. Mass. M. flah dah 1550 0400 425 NMC San Francisco. Calif. N. dah dit SPECIAL CHARACTERS 1600 nue 5.555 WSL Amagansett, N. Y. O. dah dah dah AR. End of item. 11,115 0420 425 NMA Miami, Fla. P. di dah dah dit R. Received and understood. I620 0420 480 NMV New York. N. Y. Q. dah dah di dah K. Go ahead. Transmit. 1620 0430 425 NMO Long Beath, Calif. R. di dah dit DN. Slant bar. 1630 S. SK. End of 0450 410 NMN Norfolk, Va. di di di contact. 1650 T. dah I i. Query. Repeat. 0500 126 IMH Bolinas. Calif. 1700 436 U. di di dah AS. Wait a minute. 8.440 1 1.160 V. di di di dah String of dits. Error. 22.325 0500 425 NMW Seattle. Wash. W. di dah dah BT. Break. 1700 0520 425 NMG New Orleans, La. X. dah di di dah AAA. Period. 1720 0530 410 NMI Ketchikan, Alaska Notes Line through zero tO) distinguishes it from 1730 "Dit" indicates a short sound (dot). "Di" is letter O. 0550 464 N M V Jacksonville Beach. Fla. the 1750 same but omitting 'Y" indicates that the In special characters, a line over two or three 0605 6.270 KFS Palo Alto, Calif. next sound comes immediately. letters indicates they are sent as one character 12.550 Only listening to others can give an idea of without spacing. 0900 425 NMO Honolulu. T. H. correct spacing, but the italicized sounds may Instructions for building code-practice oscil- 2100 1700 8.670 01M Manila, P. be very slightly accented mentally to give each lators were given in the following issues of this t. character 1748 418 W PA Port Arthur, Tes. a rhythmic individuality. Each dah magazine, 1:149: Feb., p. 86; 1948: Mar., p. 63, should actually be the same length, as should Apr., p. 44, May, p. 80. Sep., 82, Oct. p. 84. each di or dit. p. Any of these oscillators should be satisfactory. HINTS ON COMMAND SET RIGS A number of amateurs are using the words: Copy code! Have a friend send anywhere without constant practice. Be transmitters from the SCR -274 -N and it to you or listen to it on your receiver. assured that no matter how discourag- ARC -5 command sets. At W2PWG, we Commercial stations send fast but well. ing matters seem, more practice will have found a few interesting points Amateurs may send fast or slowly, well pay off handsomely. that we have not yet seen. or badly; but whatever you listen to, Many people who are interested in If you modulate the plates of the you will learn code as long as you put radio have never learned the code, 1625's, remove the .01 -0 plate bypass down on paper every letter you can rec- simply because they believe it to be a (C66) and replace it with a .002 - or ognize. fantastically difficult undertaking. That .005 -µf 2,500 -volt mica capacitor. This Peculiarly, you will make just as fast is not so! Learning the code is not hard, prevents most of the audio from being progress (though with less sop to your if you give yourself a chance. Just bypassed to ground. ego) listening to 25-words -a- minute follow these four simple rules: The PA stage must be retracked. press as to 15 -word sending from a 1. Relax! Take it easy! Tune to the high end of the band and friend. You may catch only one letter 2. Proceed s-l- o- w -1 -y. adjust the PA padder C67 for minimum a minute at the start, but soon you'll 3. Do not set a deadline. plate current. It should not vary more get more. 4. Take it in small doses. than 6 ma as the rig is tuned to the Above all, never copy for practice With the help of these four rules low end. If it does, adjust the slug for anything you can get "solid" (com- and the simple information contained minimum dip. Return to the high end pletely). It should always be faster in this chapter, you may find learning and check the variation in current. Con- than you can really copy. the code one of your most worth -while tinue the adjustments at high and low There are many fine code -teaching experiences. ends until current is within 6 ma. RADIO -ELECTRONICS for

www.americanradiohistory.com Iiroadc:wlstiogl and Communications

CASE OF THE ELUSIVE BLIP

The proli/em that nearly stymied a liriiiii/iiis1 station

By JAMES W. ESSEX Looking east, west tower in foreground.

SETTING up a directional broad- stallation was such that the transmitter scribed previously, the values obtained cast installation sometimes proves house could not be set directly in line were plotted. to be a greater problem than ob- with the towers, it was built in the po- Soon gasoline consumption reached taining the necessary permission sition shown in Fig. 1. This was to con- large proportions and the transmitter to operate a broadcast station. True, tribute dire complications to the system room was becoming a litter of graph the difficulties of obtaining a license are in due course. paper-each run failing to bring us any tremendous and require a great deal of Having set up the phasing units at closer to the desired result. The blip preparation and planning, but the prob- the base of each tower to obtain the was determined to remain. lem of getting two towers to work as 90- degree displacement, we were now From the end of November to the they were designed is often minimized prepared to make our first check on the middle of December, work carried on. to such a degree that a faulty pattern resulting radiated field. though with increasing difficulty as can hold up an anticipated opening for Using a loop receiver with an output snow began to fall. With the roads be- a long time. circuit driving a meter calibrated in coming difficult to negotiate by car, we Take this station as an example. microvolts per meter, we made a trip abandoned the auto for a jeep.This car- CKBW is located in Bridgewater, Nova by automobile, completely circling the ried us well into the null area by resort- Scotia. Power was planned at 1000 two towers, stopping at each t) degrees ing to the farmers' fields; and with the watts and a license obtained to work on where such radials intersected an acces- aid of skis when any walking had to 1000 kc. The site was chosen, land pur- sible road at a distance greater than be clone, our mobility was complete. chased, equipment ordered, final assem- one mile. Points appear in Fig. 2. It happened that the district experi- bly of studios and transmitter com- Our first complete run having been enced a record snowfall this particular pleted, and all items checked and re- made, all readings obtained in micro- season, and we felt that even the ele- checked for proper adjustment. Finally volts per meter were evaluated into ments were against us. The colder it came the opening day. ratios, resulting in a set of numerical got, the warmer our tempers became. Using a two -tower antenna system values. These figures plotted on a polar We persevered. When phase shifting operating with a 90- degree phase dif- graph gave us a directional pattern did not bring the desired result, it was ference between the two towers, a null similar to that shown in Fig. 3. suggested that some reflecting object area was to be had west of the line of The distortion that appeared was a might be adding a third signal to the towers -the towers running due east clear indication of trouble, the fore- array. producing the blip in the null a fa- TOWER runner of disappointment and delay. area. Thi, became the basis of WEST TOWER EAST on «; E Because of the strict adherence to vorite joke. A large sign the wall Department of Transport (Canadian of the transmitter house stated: "All equivalent of the FCC) regulation., the wearers of watchchains, etc., must %MISSION UNE CONNECTING THE TOWERS distortion or "blip" clearly indicated in cease wearing same forthwith. They the null area could not be accepted. A are blamed for reradiating the signal %MISSION LINE FROM HOUSE TO WEST TOWER long struggle was begun to rid the pat- that causes our Blip." was gone MT TER HOUSE tern of it. The date for going on the The reflecting- object theory air was promptly shelved, and the bat- into thoroughly, even to the point of Fig. 1 -l'la ement of lowers and house. tle of wits began. having the telegraph company tempo- and west. This was laid down in the Tackling the problem on the basis rarily remove copper wires which trav- brief submitted to the licensing author- that incorrect phasing between towers ersed the tower array directly back of ity, on which basis the license had been was causing the distortion, we shifted the east tower. This, however, did not granted. This station was not to con- the phase slightly above and below the remove the distortion in the pattern. tribute any interference on the 1000 - mean of 90 degrees. With each shift in and the search continued. k.c. channel in a westerly direction after phase, a trip by car was taken, running With the approach of milder weather sundown. It would operate non- direc- through the area where the null was spirits were lightened somewhat and a tional by day and directional by night. supposed to appear, west of the towers. final effort was made to solve the riddle. Because the site chosen for the in- At the conclusion of each run. as de- (Continued on bottom., page 3R1 NOVEMBER, 1949

www.americanradiohistory.com :ili liroadcastiu9 and Communications

oscillators are provided, one operating at 405 kc and the other at 505 kc. Either Sideband Suppression one may be switched into the circuit. No matter which one is used, the second i.f. (carrier) will still be 50 kc and the range will be from 46 -54 kc. The second By I. QUEEN i.f. amplifier has a passband from 50 -54 kc, so it transmits only the carrier and one sideband. Single -sideband systems provide a phasing for each new set of conditions. There is an important fact to note. very effective method of reducing inter- To illustrate how single -sideband se- When the 405 -kc oscillator beats against ference. Since the desired signal occu- lection works, assume a conventional 451 -459 kc, it produces a range from pies only half the usual frequency band, receiver i.f. of 455 kc and a bandwidth 46 -54 kc; therefore the lower sideband there is less chance of picking up spuri- of 8 kc. Then the total range is 451 -459 will be suppressed. When the 505 -kc ous radiation, heterodyne whistles, and kc. Before suppressing a sideband, this oscillator is used, the i.f. channel ex- general noise. With conventional double - i.f. is converted to a lower value by tends from 54 -46 kc and the upper side- sideband transmission the same im- beating it with a crystal -controlled os- band is lost. provement can still be had by chopping cillator. A portion of the mixer output is also off one of the sidebands at the receiver. For maximum noise reduction it connected to a sharply tuned 50 -kc am- Patent No. 2,364,863, utilizing this should be possible to suppress either plifier and detector. This controls a res- principle of interference elimination, sideband at will, to determine which onance meter for indicating correct re- was issued to James L. A. McLaughlin gives better results. Therefore two receiver tuning. about four years ago. Although more complicated than systems which rely on I.F. AMPLIFIER MIXER 50-54KC BANDPASS AMPL AUDIO crystal filters, Wien bridges, or highly DETECTOR AUDIO FREO.AMPL.I selective circuits, the results are more I-11f nIn I i OUTPUT effective. This is because an entire side- 455KC 50KC 50KC band is eliminated rather than just a o small portion (notch or rejection slot). TUNING METER XTAL OSC.505KC -0V0. XTAL OSC.405KC DETECTOR METER In addition, operation is easier because AMPL 50KC there is no need for critical retuning or Block diagram shows how receiver selects one Sideband, su tpre -ses other.

CASE OF THE ELUSIVE BLIP (Continued from page 35)

A complete re- examination of all past magnetic compass, figures being care- the west tower. The search disclosed an investigations and experiments was fully recorded and compared with our inductance not properly shielded, which made, and one fact made itself appar- previous findings as to the position of contributed a mismatch in the line when ent. This was that the transmission line the blip. Knowing the type of transmis- on directional transmission and formed from the west tower to the transmitter sion line in use (an open -wire system) a standing wave. house was running almost at right we decided that a standing wave existed This was remedied by having the coil angles to the point at which the blip on this line, which, radiating, was caus- shorted out by a relay when not in use occurred in the null. ing the distortion in the null. (it was not used when the system was The angle of the transmission line to Armed with these facts, we investi- directional). The parasitic inductance the west tower was determined with a gated the tuning and phasing unit in effect of this coil, detuning the circuit and causing the line mismatch, was elim- inated, leaving the line properly loaded and eliminating any chance of a stand- 200 MV I M CONTOUR ing wave. ATI MILE Our efforts were rewarded at last. Another run through the null area proved that the troublesome blip had been eliminated. And so we stood by and listened, huddled about the monitor speaker in the transmitter house, to the first crisp words from the speafcer, "This is CKBW in Bridgewater." Another station was on the air!

XMITTER CIT[

I I

/ DISTORT OF

I NULL HERNE

.1 rW

READINGS TAKEN AT POINTS MARKED X LEGENC - 41 «.»«» RAILROAD HIGHWAY CROSSROADS DAYTIME PATTERN IF,DIRECTIONAL NIGHT PATTERN Fig. 2- Inlen,ity reading- were taken at 9- degree intervals around antenna. Fig. 3 -The start of all the trouble. RADIO -ELECTRONICS for

www.americanradiohistory.com Test Instruments 37 Tracer Uses Tu be As Probe

A small, convenient unit good for bench use or outside jobs

By ALVA R. WILSON and W. KENNETH WILSON

SIGNAL TRACERS are standard equipment for rapid trouble shoot- signal tracer shown in ing. The Fig. 1- Tracer is Valuable shop help. Fig. 1 is even more useful than the average one because of its many applications. It has a :3 -inch PM speaker (eliminating headphones), a volume The lead -in cable should contain a signal) can then be traced right from control, and a meter which gives a shielded plate lead, a ground wire (or the antenna coil through each stage to relative reading of incoming signal the shield can be used for this since it wherever it stops. strength. Unlike the speaker, the meter must also be grounded), and one fila- Once you have started using this indicates signals of all frequencies, in- ment lead. signal tracer, you will find a number cluding unmodulated r.f. It enables the The values shown in the meter bridge of applications for it in addition to the tracer to be used for checking a re- circuit should be closely followed. A ones already mentioned, and you will soon it is a most useful ceiver's oscillator, for hunting down I -ma meter is preferred for sensitivity. agree that stray oscillations. and even for trans- Before use, the meter is adjusted to piece of trouble -shooting equipment. mitter trouble shooting. When not zero (while the probe tip is grounded) 6K7 AF IF DE SIRED 6V6 otherwise in use, this signal tracer can with the 2,500 -ohm potentiometer. 3 he used as a local broadcast receiver. Thereafter, any input signal picked up ,45 SEE TEXT ,. Soo,. The unique design of the probe, whose by the probe will be indicated by the H r II simplicity is shown in Figs. 2 and 3, meter. If the signal contains audio gives both high input resistance and high components, they can be heard from the with a 6K7, a 6F5, fi 25 amplification. Start speaker. SEE TENT or almost any other metal tube which The audio stage consists of a volume 5.I MEG has a grid cap on top. Cut a piece of '/4- control, a 6V6 (or any other good out- 0 -I MA inch copper tubing about 's inch long. put tube), and a 3 -inch PM speaker. Solder it directly to the grid cap (Fig. The box was built of hard -pressed 511( 3). Now take a piece of No. 10 copper Masonite and is held together by small SIGNAL TRACER wire approximately l'/2 inches long, file finish nails driven into predrilled ? one end to a point (place it in your drill inch holes. If desired, the joints may be ,001 and hold a file against it), then further strengthened by applying model chuck 50A /IOW wrap the other end with a 1 -inch strip airplane cement to the edges before 60 of waxed paper, allowing the paper to nailing. overhang the end of the wire slightly In Fig. 1 the lower control is the it completely from the cop- meter -zero, and the upper control op- j-4 657 6V6 to insulate POWER SUPPLY 2.T per tubing on the grid. When enough erates both the off -on switch and the 2T paper has been added for a tight fit, volume. An off -on indicator light may force the wrapped end of the wire into be mounted on the front panel. the copper tubing, and you have the For broadcast reception a replace- input capacitor. The grid resistor is ment -type antenna coil is used. TO PROBE even more simple. Using a knife, scrape In receiver trouble shooting, the 36500 the paint from the edge of the metal ground clip on the probe is fastened to ANTENNA COIL FOR BROADCAST tube cover where it is crimped over the the receiver chassis. An input signal piece of bakelite holding the grid con- (such as a local station or an oscillator Fig. 2- Complete construction diagram. nection. Now take a pencil and mark all over the bakelite, covering the entire surface between the grid and the shield. Rub the pencil lead in well with your finger, repeat the process once or twice, and you have formed the grid leak. (Note: This might work better in the authors' state of New Mexico than in higher -humidity areas. -Editor) For convenience in changing tubes the probe tube is simply plugged into an eight -pronged female cable con- nector (or an S -type tube socket with a shield over the soldering lugs) to which the lead -in cable is connected. Fig. 3-Tubing is soldered to grid cap and a %ire tip is slipped into tubing. NOVEMBER, 1949

www.americanradiohistory.com 381 Electronics

Radio test instruments check camera shutters and flash synchronizer

variety works nicely), a calibrated audio oscillator, and a photoelectric cell. The shutter speed of a camera is the elapsed time between the opening and closing of the shutter. This time may vary considerably from the value marked on the camera and many pic- tures may be missed before the cause shows itself. Our method is to record the opening and closing of the shutter as marks on the oscilloscope screen. The space between the "open" and "close" markers can then be filled with sine waves of known frequency, and the time interval determined by count- ing them. Here is the step -by -step procedure: 1. After allowing a warmup period Operator sets dividers to exact width of pulse as she clicks r: ra shutter. for all instruments, set the audio gen- erator to a frequency high enough to permit about five cycles to be included in the shutter interval to be measured. For example, a shutter speed of 1 /100 second would include five cycles of 500 - cycle audio. Cameras Are Tested 2. Connect the audio generator to the scope's vertical input, and also to the external sync terminal. Be sure that the sync selector on the scope is at the EXTERNAL position, and then adjust the With Simple sweep frequency to display about 10 Setup sine waves. Use the SYNC AMPLITUDE control to lock the pattern. Remove the signal from the scope vertical input, but leave the sync lead connected throughout the test. This will insure By FRED C. GABRIEL against sweep oscillator frequency drift. If the sweep oscillator is not syn- chronized to the a.f. oscillator, all sub- sequent measurements will be useless. AUSEFUL experiment for the is far beyond the reach of most ama- 3. Hook a photoelectric cell to the radio man who is also an ama- teurs, and the number of professional vertical input terminals of the oscillo- teur photographer is the ac- photo laboratories supplying this serv- scope. Arrange a light source to shine curate determination of a ice is small. An extension of the method on the photo cell (we use a 25 -watt camera's shutter speeds. The method makes it possible to check the opera- bulb in a table lamp; place the camera described consumes no film or other ma- tion of photoflash synchronizers, a boon between light and cell. Adjust the cam- terials; hence it can be repeated as to the indoor photo enthusiast. era to its widest aperture and click the often as desired at no cost. Expensive, The electronic equipment required in- shutter a few times. A bit of experi- conventional shutter -testing apparatus cludes an oscilloscope (the inexpensive menting with the camera position should result in ample vertical deflec- tion of the scope trace. The vertical gain control on the scope will prob- ably have to be near its maximum set- ting. Our setup gave usable deflection from a type 921 photocell (chosen be- cause one was at hand) with a single vertical amplifier stage in the oscillo- scope. A brighter light source will in- crease the amplitude of the trace. In- cidentally, we experienced virtually no hum from the a.c: operated light source. The instantaneous pattern obtained is a more or less square wave, depend- ing on the shutter speed being meas- RADIO- ELECTRONICS for

www.americanradiohistory.com Electronics ured and on the low -frequency response of the scope amplifier. In any case, the opening and closing points are clearly defined. Since the pattern is of short duration, it is necessary to click the shutter several times to be sure that all of the shutter interval is included on the scope face. Set a pair of drafts- man's dividers to the width of the trace between the opening and closing markers (Fig. 1) . The shutter may be operated as often as necessary to set the dividers accurately. 4. Switch the scope vertical input back to the a.f. oscillator. The sta- tionary pattern of step 2 should be ob- tained immediately. Apply the dividers to the screen, and count the number of sine waves between the points, as in Fig. 2. The number of sine waves di- vided by the oscillator frequency gives the shutter speed in some fractional part of a second.

Checking the synchronizer The photoflash synchronizer should Machinist's dividers are used to compare shutter opening with audio sine waves. close the battery circuit to the flash bulb at a predetermined interval be- frequency can be circuits is grounded to the synchronizer fore the shutter opening. If the syn- The required audio determined by The time body, this side must be connected to chronizer has been properly set, the experiment. measure is that between the the ground terminal on the 'scope in- open period of the shutter will coincide interval to synchronizer pip and the mid -point of put to avoid 60 -cycle body pickup the shutter pulse. The synchronizer whenever the camera and synchronizer AF OUT should be adjusted until this interval are handled. Note that the settings of EVT SYNC corresponds to the ignition time of the the oscillator frequency and oscillo- AF rS flashbulb. The ignition time may be scope sweep, sync, and horizontal gain found in flashbulb data tables, or be must not be disturbed during a test. obtained direct from the manufacturer. Short unshielded leads may be used for Since one side of many synchronizer all connections.

.0001 iLr FOR LIVING CELLS SYNCNRONIZER CONTAC-S PHOTOTUBE ANALYZER

_22.5v (

S- 11 The makeup of a single living cell tirely new field of quantitative chem- detail istry. The device has been simplified so Fig. 4-A setup for synchronizer tests. may be analyzed in much greater than ever before possible with the aid that anyone familiar with a microscope centers are being with the peak of light output from the of a new electronic instrument devel- can use it. Research hospitals and laboratories bulb. The desired interval between oped after seven years of work by mem- established at in many places. closing the circuit and opening the bers of the Columbia University Zool- shutter may be read from the "light ogy Department under the direction of output vs. time" graphs distributed by Prof. Arthur W. Pollister. The device, bulb manufacturers. known as a microspectrophotometer, to measure the light In our test we will display a mark- uses a phototube various components of er from the flash synchronizer side by absorbed by the the cell. side with the shutter pulse described All living cells consist mainly of two above. The audio oscillator can then be ingredients, proteins and nucleic acids. used to measure the time interval be- There are two types of the latter, which flash marker and the mid- tween the are the principal components of the shutter (Fig. 3). point of the pulse chromosomes that determine heredity. The flash marker must be readily dis- Each type of nucleic acid absorbs markers, tinguishable from the shutter light of a different wavelength, the and it must not interfere with them. amount of light absorbed indicating the The synchronizer circuit remains closed quantity of acid present. The phototube, after it has acted, but the vertical am- together with a sensitive current -meas- plifiers must be allowed to recover in uring circuit, indicates how much light time to transmit the shutter pulse is absorbed. From this information which follows. The synchronizer pulse scientists can evaluate with very good is differentiated sharply by capacitor accuracy the composition of any cell CI (Fig. 4) and the input resistance they study. of the 'scope. A 22'Á2 -volt battery in The instrument has already revealed series with the synchronizer provides many significant facts about living a large pip easily distinguished from cells. According to Prof. Pollister (see Wide World photo the shutter markers. photo) the technique has opened an en- Polluer and microspectrophotometer. NOVEMBER, 1949

www.americanradiohistory.com 111 Construction

pared to the two -gang tuning capacitor. The space saved permits mounting standard intermediate-frequency trans- formers. The Model 320 is complete with a dial and pointer, antenna and C plete receiver (left) is shown in oscillator coils, tuning shaft, and a hole its cabinet. Photo below emphasizes the for the volume control shaft. The unit set's small size -it's not much longer is factory- aligned to track perfectly than a couple of standard -size cigarettes. with a 460 -kc intermediate -frequency system. To complete the unit it is neces- sary only to purchase a 9- 180 -wtf trimmer for the antenna section and a 700 -800 -µµf trimmer for the oscillator section. Since building this set, I have noted a number of other permeability tuners on the market. I used good- quality, 456 -kc i.f. trans- formers and found that the tuning unit can be made to track just as well as it does at 460. (No harm in tuning the i.f.'s to 460, if you have a signal genera- Commercial slug tuner tor or can get your service technician to do the job. -Editor) makes construction of The easily mounted tuning unit is held to the chassis by the nuts on the a small receiver easy drive -shaft and volume -control bush- ings. Complete drilling and mounting for the experimenter instructions being furnished, it is not necessary to repeat them here. The speaker and dial extend the whole width of the chassis, dial and speaker each being 3'4 inches wide. Minimum height of the set is 5 inches, because of the dial; if the output trans- former is mounted on the speaker, re- cess the speaker into the chassis to keep Miniature -Tube Receiver its height down to that of the dial. The constructor can get a good idea of the relative position of the com- ponents from the back -panel photo- graph. The chassis will have to be cut away for the tuning unit and -in most cases -the speaker. Place your com- Has Permeability Tuner ponents on a piece of paper and project a layout to suit your individual needs. Do not, however, change the relative positions of parts because this layout provides the shortest possible leads. By JOHN E. HAZELRIGG The two tuning slugs and coils also show up well in the back -panel photo; the larger coil is the oscillator, and the ANY home- construction enthu- The permeability- tuning unit I used smaller one the r.f. section. The oscilla- siasts who would like to build is manufactured by the Aeromotive tor section has two coils. One of them a small broadcast receiver Equipment Corporation of Kansas City, is tapped for the converter tube cathode M with the new miniature tubes Missouri. This unit -their Model 320 - and is mounted underneath the chassis are reluctant to do so because of the takes up only 1% inches of chassis close to that tube. difficulty of working in small spaces. space, a considerable economy corn- Except for the tuning unit, the cir- To have a set that is miniature throughout, midget coils and capacitors 128E8 are also required; but they cannot be expected to give as dependable service as standard -size units. By using a compact permeability - tuning unit, I was able to build a set comparable in dimensions to the very small manufactured sets now so popu- lar. Miniature tubes are used, but all other parts except the speaker are standard size. The cabinet is 7?í x 5 x 6 400-700n inches, and the actual chassis dimen- SFNR FLD sions 7 x 4 x 1% inches. Miniature tubes require very little 20 4111. chassis space; and because their socket 35W4 50B5 4BA6 1213E6 4A76 35 W4 terminals are more closely grouped than 117V AC those of octal tubes, there is more room 5 I 7 under the chassis. Thus, larger and 4 ® better resistors and capacitors can be SW ON VC SI /IW used. The two tuning coils are parts of the commercial sing tuner the author used. RADIO -ELECTRONICS for

www.americanradiohistory.com Construction II Push -Pull Crystal Receiver

By RUFUS P. TURNER

the sensitivity and selectivity and L3 are connected together and to high- powered local broadcast stations of a crystal radio may be im- the rotors of the main tuning capacitor. will operate a high -impedance magnetic proved greatly by using a two - Space coils t:6 inch apart. loudspeaker (but not a permanent -mag- BOTHcrystal push -pull detector circuit The components are mounted on a net dynamic). The double tuning scheme and by tuning the antenna coil as well wooden board 8T1; inches long, 5% allows separation of strong local sta- as both halves of the secondary. The inches wide, and 1.1 inch thick. All parts tions. In tests using the same antenna, circuit is shown in the diagram. This ar- except the crystals are screwed to the rangement has pronounced advantages board. The crystals are connected with ABOVE 850NC CATS over a simple detector and one -coil tun- their own pigtail leads directly between SPST SW 04)1 ing. Louder signals, longer- distance re- the stator lugs of the tuning capacitor BELOW BSOKC ception, and sharper tuning are ob- and one of the headphone tip jacks. The ANT MIMET LI tained with the new hookup, which is crystal polarity indicated in the sche- 3E5a o1 only slightly more complicated than the matic must be observed carefully. GNL usual simple crystal sets. Operation of the receiver is very sim- Two 1N34 germanium crystal diodes ple. Connect an antenna and a good are used. The primary coil LI is wound ground to the antenna and ground ter- The full -wave detector uses two 1N34's. between the two halves L2 and L3 of the minals. The best antenna is a long wire. secondary coil. The main tuning capaci- high in the air and out of doors. Use the this receiver has brought in (listant sta- tor is a dual 365 -p.p.f unit. The primary nearest cold -water pipe for a ground. tions not even heard with the best ordi- coil is tuned separately by means of a Tune in your station by adjusting the nary crystal set. The d.c. output of the single- section, 365 -auf variable capaci- main tuning capacitor, then adjust the set (taken across the headphone tip tor. For all frequencies lower than 850 primary trimmer for maximum volume. jacks with headphones disconnected) is kc, a fixed .001 -1d capacitor is connected If the frequency of your desired station 2.5 ma when picking up a 250 -watt in parallel with the primary trimmer by is 850 kc or higher, leave the switch broadcast station 5 miles away! closing the switch. open. If it is lower than 850 kc, close The builder may consider using a The coil is wound in three sections the switch. The entire broadcast band 1 N:35 duo -diode unit in place of the two with No. 32 enameled wire on a 1 -inch- can thus be covered. 1N34's. The 1N35 consists of a pair of diameter polystyrene or bakelite tube 4 This receiver has amazing headphone mounted germanium diodes which have inches long, the turns of each coil being output, even when receiving low -pow- been matched for use in full -wave de- close- wound. L2 and 3 have 137 turns ered broadcasters. When a long, outside tectors and in FM detectors and dis- and L1 has 43. The inner ends of L2 antenna and a good ground are used, criminators.

MINIATURE TUBE RECEIVER (Continued from page 40) cuit is quite standard. The chassis is a simple U- shaped piece of 16 -gauge sheet iron and is quite rugged. One -hole mounting sockets with retainer ring were used for convenience. Two strands of No. 20 bare, tinned, hookup wire were twisted together and anchored at each end to widely sep- arated points on the chassis near the tubes. All ground connections were sol- dered to this lead. This simplifies con- struction, but does place the a.c. line voltage on the chassis. There should be no danger, however. if the chassis is placed in an insulating cabinet and a fiber panel used to cover the back. Be sure to drill holes in the panel for ven- tilation. After the set reaches full operating temperature it is exceptionally stable, due to the high capacitance- inductance ratio in the oscillator section. There is a slight drift during warm -up unless a temperature compensating capacitor is used, but this refinement is hardly worth the additional cost. There was some difficulty in peaking the i.f. coils because of regeneration in the i.f. system, but it disappeared en- tirely when the 12AT6 tube was shielded. Rear view of the permeabilii. -tuned receiver. Tuner is in upper left corner. NOVEMBER, 1949

www.americanradiohistory.com 12 Audio Design of Class -B Drivers

The design of a transformer - coupled class -B driver is simplified by this author's approach

By W. H. ANDERSON, VE3AAZ

OPERATORS of amateur phone former designed for use with the par- nation is not listed; stations are often confronted ticular combination of driver and mod- 3. Driver -to -line and line -to -grid with the problem of selecting ulator tubes being used. This method transformers are to be used. a suitable driver and driver is not practical when: Consider a typical case where push - transformer for class -B audio ampli- 1. The tubes are operated under con- pull 6B4 -G's are used as fiers drivers for a or modulators. The most common ditions other than those specified by class -B '75TH amplifier or modulator. solution is to select, from a catalog or the transformer manufacturer; Tube data manufacturer's shows that the 6B4 -G's will literature, a trans- 2. The driver -modulator tube combi- deliver 15 watts of power when the ef- 250 fective load impedance (plate -to- plate) I CHARACTERISTICS OF 6B4-G I is 3,000 ohms, the plate voltage is 300, and 68 volts of grid bias is supplied o D from a fixed source. The 75TH's re- 200 quire 3 watts of grid drive when oper-

1E4 =6.3V ated with 90 volts of grid bias and 2,000 0 volts on the plates. The peak grid-to- ... , grid driving voltage is 350. Since there 150 -: is a difference in the power in the pri- mary and PUTE MA secondary of the driver trans- former, transformer ratios cannot be calculated by comparing the primary 00 and secondary voltages. lAl The grid circuit of a class -B stage r,/l! presents a constantly varying load to

50 the plate circuit of the driver stage. 7.M%ÑII/I/'g During one excitation cycle, the im- .,,li..WAWA o pedance of the grid circuit varies from a very low value to almost infinity and a, causes distortion which is intolerable ,-'-100 20 400 500 600 in some instances. Distortion from this PLATE VOL S COURTES RCA source is minimized by reducing the Fig. Curves for this~ and other receiving 1- tubes are in your tube manual. source impedance as much as possible. The driver transformer determines the impedance ratio between the driver s00 0 plates and class-B grids; therefore, the greater its step -down ratio, the smaller B.,..C will be the source impedance as seen 400 iii ppEN7.y4 by the grids. Et=SV We have found at VE3AAZ that dis-

30G o, tortion is minimized when the driver is GRI DT ` designed to deliver just enough power to drive the class -B stage when its 2GG 1`5QiRl__ (the driver's) grids are fully excited - Iÿn2r- 4 1.40 driven to zero volts by the speech am- a 1.20 .., 100 _ - plifier. This condition is met by raising ,.r...... a/-GeCill{e__-_ -.2. the driver plate -to -plate load impedance far above its normal value. This pro- 1 .6JJr G vides ó for a higher than normal step - 400 down ratio between the driver plates and class -B grids. Increasing the driver 010C _ .10 : load impedance decreases the voltage '- 0 developed across the secondary load. It 200 is important to remember that, while the voltage ratio varies directly as the turns ratio, the impedance ratio varies .300 0 250 500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 125f as the square of the turns ratio. Thus PLATE VOLTAGE COURTESY E TEL -MCCULLOUGR when a transformer is selected to de- Fig. 2- Constant-current characteristics of the Eimac 75TH trans hitting triode. liver just enough voltage to drive the RADIO -ELECTRONICS for

www.americanradiohistory.com Audio 143 class -B grids, the source impedance sider the class -B operating data for conventional plate -loaded amplifier op- (driver plate resistance) will he lowest the 75TH: erating with identical loads and plate -a requirement for good regulation. D.c. plate voltage 2,000 and bias voltages. If the regulation of The 75TH's require 3 watts of grid Max. signal d.c. plate current 225 ma an amplifier is perfect, the output volt- drive. Since in this case -as in most D.c. grid voltage (negative) 90 age will vary in direct proportion to others -the grid driving power is stated A.f. grid voltage 350 the input voltage. as an r.m.s. value, peak driving power Each tube is carrying 112.5 nia or Take two amplifiers using triode - will be twice as great or 6 watts. This one -half the total plate current; how- connected 6L6's, one connected as a power is delivered to first one grid, then ever since the stage is operating class conventional plate- loaded amplifier and the other, and is provided by one -half B, the peak instantaneous plate current the other as a cathode -follower. Con- the voltage developed across the entire will be three times as high or approxi- sider what happens in each when the secondary. Knowing the grid power and mately 336 ma. The peak instantaneous signal voltage is halved and the re- voltage, the grid impedance can be cal- grid voltage will be one -half the a.f. flected plate load changes from 2,000 to culated by Ohm's law. Since the peak grid voltage minus the d.c. bias or grid -to -grid voltage is 350, each half of 350/2 -90 = 85 volts. the secondary winding will develop 175 The crest operating point X (Fig. 2) volts and the grid impedance (E2 /\V) is the intercept of the peak grid voltage is 1752/6 or 5,104 ohms. and the peak plate current values. This The next step is to draw trial load point shows the peak grid current to be lines on the characteristic curves of a 35 ma. Knowing that this grid current 6134 -G as shown in Fig. 1. One end of is produced by the voltage across half each load line is the point where the the driver transformer secondary, we plate- voltage line intersects the zero - can compute driving power as the prod- current line and the other end is on the uct of 175 volts and .035 ampere (35 Ec (grid voltage) = 0 curve. The re- ma) or 6.1 watts. Similarly, we com- sistance of a load line is determined by pute the grid impedance as 175/.035 = subtracting the minimum plate voltage 5,000 ohms. Note that these values from the maximum plate voltage and agree with those used in previous cal- dividing the result by the maximum culations, but the grid -drive factor does current. Refer to the 3,000 -ohm load not take into account the power loss in the driver transformer. line on Fig. 1. Note that maximum Fig. 3 -A cathode -coupled driver stage. plate voltage is 300 and minimum 75. As the voltage swings from 300 to 75, Cathode- followers as drivers 5,000 ohms (8,000 to 20,000 ohms plate - the plate current changes from zero to Occasionally, a push -pull cathode -fol- to- plate), as it might when the class -B 75 ma so the resistance of the load line lower stage (Fig. 3) is used as a driver stage stops drawing grid current. The is 300- 75/.075 = :1,000 ohms. for a class -B amplifier. This arrange- change in circuit performance is shown Peak power output from a given load ment does a good job because of the in Fig. 4 (characteristic curves for resistance is determined from the fa- high degree of degenerative feedback triode- connected 6L6's with 2,000- and miliar I2R relationship, where I is the due to coupling between the input and 5,000 -ohm load lines drawn in) and in plate current at the point at which the output circuits. The major disadvantage the table below. load line intercepts the Ec = 0 grid of this circuit is that the input signal Cathode-loaded amplifier bias curve. The 75TH grids require 6 must equal the sum of the bias and Drive Reflected load Output Point watts peak power for full output. How- desired output voltages. (volts) (ohms) (volts) (Fig. 3) ever, since the power loss in the driver Load impedance calculations general- 20 2,000 130 A transformer may run to 20/: the driver ly consist of finding a combination of 10 5,000 115 B must be designed for approximately 7.5 plate voltage and a reasonably low load Plate- loaded amplifier watts peak output. Since the 7,000 -ohm impedance that will provide the re- 150 (20+130) 2,000 130 A load line intercepts the Ec = 0 curve at quired output. The stability or voltage 75 5,000 72 C 32 ma, the power output is (.032)2 x regulation of a cathode -follower is That the cathode- follower provides bet- 7,000 or 7.18 watts. such that the load impedance has little ter voltage regulation is evident when The load resistance for a single tube effect on the output voltage. we realize that the output voltage being 7,000 ohms, the plate -to -plate The excellent voltage regulation of should have dropped to 65 (one -half its load will be four times 7.000 or 28,000 a cathode -follower can be seen when its initial value) in both cases when the ohms for a push -pull stage. The grid performance is compared to that of a drive voltage was halved. impedance is 5,104 ohms, so the trans- former turns ratio (primary to one - 200 half secondary) is CHARACTERISTICS OF 6L6 TRIODE \/28,000 2.3 to 1. 5,104 *A -A o If the speech amplifier- driver com- 150 bination is located at a point remote VENAI °4 20V from the class -B stage, a plate -to -line 1 .y .A PUTE ,Ec and line -to -grid transformer combina- > will he required. Disregarding the IP/ tion "a '''AM power loss in the second transformer, ioo I/V the over -all turns ratio should remain JII.I I4 I ; II ,b the same. Assuming a 500 -ohm trans- I / ., mission line, the plate -to -line trans- man ENNA, 1 /r. former will have a turns ratio of 7 to '°° 50 '/.tfI.N% IIIMOI `'i . -to -grid will I `' and the line transformer I.. / .e' /KIM ; have a ratio of 2.3 to 7 between the MU and one half of the secondary. t1/AM11121WiilIMME%K e1, primary VAN2b.-4-d/MMr\I(l P.IMMIP/ OP Calculating driver requirements i4111Mr o OR'neliorz.rz...-- do list m0 ? 0 300 400 500 600 700 Manufacturers not always PLATE VOLTS COURTESY RCA grid -drive requirements, and this must be calculated from available data. Con- Fig. l -Load lines compare performance of plate- and cathode -loaded amplifier'. NOVEMBER, 1949

www.americanradiohistory.com Servicing

Sèroíce Data ... ..a,. .. ec nicians

and Money

ALIE, some wag has said, a libraries simply because they have not to read an upside -down sketch pasted last resort with men, but with formed the habit of using them prop- in the darkest, most cobwebbed corner women it is a form of first -aid. erly. of the cabinet. This masculine reluctance to Many, when they started servicing, This preliminary survey can tell you a mischievous expedient is commenda- felt that they could not afford to buy a lot. It will reveal whether you are ble; but when a radio technician insists service manuals; the servicing proce- working with an a.c. -d.c. set, a trans- upon applying the same attitude toward dure established necessarily excluded former job, or one of those electronic the use of radio service data, he is being their use. Later, when they were able mules that employ a high -voltage series - short- sighted, money -wasting, and just to obtain service data and did so, their filament winding on an autotrans- plain stupid. Nevertheless, the sad truth servicing routine had become so firmly former. It will show whether you should is that there are many who turn to their set that they could not -or at least did expect superheterodyne selectivity or shelves of service data for help only not -change it to take full advantage of are dealing with a t.r.f. receiver - after they have exhausted every other the great help offered by their books. something that cannot be told with a possibility in their attempt to repair a The publishers of modern radio serv- casual glance in this day of four -tube receiver. ice data spend thousands of dollars try- "supers," subchassis- mounted i.f. trans- This is really puzzling. Any modern ing to make their products of the ut- formers, and padded oscillator tracking shop is certain to have a complete set most assistance in servicing every set circuits. It will also reveal whether the of service information on hand. It can that comes into the shop. The material tubes are where they should be; and if be quickly demonstrated to even the is intended to be used all of the time, you tell an old -timer you have never most stubbornly doubtful that radios and is crammed with information cal- wasted time working on a set in which can be serviced much more quickly, culated to be useful to the novice and the customer had switched a couple of pleasantly, and efficiently through the the old -timer alike, but the only way in tubes, you will make him question either use of such data. Every radio shop which any service technician can ex- your veracity or the amount of time you owner knows that minutes shaved off tract the full amount of benefit from have been in the service game! the time needed to repair a set is just it is to build his service procedure If your preliminary examination like money in the bank. In spite of all around its continuous use. shows that surgery is indicated and this, there are far too many shops in that the chassis must be removed from which the books do not have that well - When to use data the cabinet, take another look at your thumbed look that radio service man- The time to slide a manual from the data. See if instructions for chassis uals should have. shelf is the minute you decide which removal are given. Some manuals give Possibly there are a few rare cases set you are going to tackle next. First, detailed information on this subject where the technician is one of those take a quick glance at the description wherever it is needed -and believe me, boys who bull -headedly waste hours of the receiver and at the diagram or it is needed often in opening up some searching a catalog for an item before picture in the book that shows the tube of these ultra- modern creations with looking it up in the index, merely be- layout. You may be able to locate a hidden chassis bolts, concealed hinges, cause he likes doing things the hard similar diagram in the set, but at any and trick cabinet designs. Without such way; but these, surely, are in the mi- rate it is much more comfortable to "open sesame" instructions, you can nority. It seems likely that the rest do study the picture laid out on the bench waste half an hour fumbling around the not get the maximum benefit from their instead of standing on your head trying outside of one of these sleek -looking, RADIO -ELECTRONICS for

www.americanradiohistory.com Servicing Jzii

seamless armchair models like a monkey trying to get into a plastic coconut. When the set has been extracted from the cabinet and is resting on the bench in front of you, your service data stands ready to lend a hand, no matter what method of trouble -shooting you prefer. If you use a signal- tracer, the diagram will tell you exactly where to touch your probe, and the stage gain of each section is plainly indicated. Any deviation from the normal can be de- tected at once, and the exact point at which this deviation begins can be pinned down. On the other hand, if you prefer re- sistance measurement, the correct re- sistance from every tube socket con- nection to the common ground is given; and if voltage measurement is more to your liking, the proper operating volt- age at nearly every point of the circuit is indicated. The diagram is right there in front of you. Only a service technician who has wasted time checking and recheck- ing a puzzling low- resistance condition by the leads of every ca- unsoldering Courtesy of Howard W. Sa ma á Co. pacitor that might be involved -only to Fig. 1- Under- chassis view of receiver. Call -outs show location of all parts. find the trouble caused by a shorted by- pass hidden away inside an i.f. shield - capacitor has shorted, causing both the can appreciate the value of working filter resistor R12 and the ballast re- with a diagram. The intelligent use of sistor R14 to char. Cutting loose the printed data removes the wasteful lost output filter capacitor lead and check- motion from radio servicing. ing it with an ohmmeter quickly proved The service data publishers are keen- this deduction correct. ly aware that time is money in serv- A glance at the parts list was all that icing, and they have worked out many was needed to find the correct replace- time- saving features. Take, for ex- ment values for Cl, R12, and R14. It ample, an all -wave set in which only was not necessary to locate the parts one band is out of order. Obviously the by tracing out the circuit diagram. fault lies in one of the components used Only seconds were needed to determine exclusively on this band. But if you exactly what parts were required. Had have ever watched a poor technician the circuit diagram been needed, it was mumbling to himself and making cir- available; but it is surprising how cles in the air with his finger like a many times, when there are visual man trying to describe a circular stair- symptoms of trouble, you can work di- CHARRED case, while he attempts to thread his rectly from the pictures. The beginning RESISTORS way through the maze of a multibank radio technician who has some difficulty t ou rtes,/ of Howard W. Sams á Co. band- change switch, you can realize in "seeing" a receiver in diagram form Fig 2- Charred parts are easy to spot. how he should appreciate a data sheet is especially grateful for this feature. showing an entirely separate circuit What is more, the constant use of diagram for every position of the Data helps beginners service data is the best possible way switch. Speaking of beginners, it is an un- for the newcomer to become familiar happy fact that many fellows try to with radio circuits and manufacturing The value of photos start into servicing without purchasing practices. As he continues to study Another set of sheets gives photo- service data. If anyone needs such help, the diagrams of the sets upon which he graphs of every set taken from dif- these beginners do. The veteran tech- is working day after day, he absorbs, ferent points of view and with the nician has a wealth of practical experi- with out any conscious effort, a knowl- various parts identified by numbered ence to fall back on when he runs into edge of what constitutes standard cir- or lettered "call- outs" right on the unusual problems, but the novice feels cuits and normal values for components picture. Fig. 1 shows a bottom-chassis utterly at sea. The small successes he used in those circuits. Almost before he view of this nature. To show how it has had in locating open filaments and realizes it, he finds himself knowing helps, notice Fig. 2, which is a picture shorted bypasses in AC -DC receivers what to expect when he makes a meas- of the same receiver shown in Fig. 1. stand him in poor stead when he runs urement, and is alert to any abnor- If you will look closely you will notice into a really tough set. He simply does mality that may be encountered. The -as (lid the technician -that the resis- not know where to begin. What he needs constant use of service data is about tors numbered R12 and R14 in Fig. 1 more than anything else is the wealth as quick a way to learn practical radio are badly charred in Fig. 2. Inasmuch of data on normal operation that a as there is. as the positive filter capacitor leads manual presents. A methodical com- It is paradoxical that the beginner's attach to the opposite ends of R12, and parison between the resistances, volt- need for this material is indicated by R14 connects between one side of the ages, and stage gain of the defective the fact that successful veteran tech- line and the plate of the rectifier tube, receiver and the normal values of these nicians invariably have them. These it is not hard to diagnose the trouble items as presented in the service data fellows could repair any receiver, using here: the output section of the filter is almost certain to uncover the trouble. only their knowledge of radio theory NOVEMBER, 1949

www.americanradiohistory.com 16 Servicing Curing I. F. Oscillations

FOR years I have had trouble when Fig. 1. A 1- megohm grid resistor R1 re- ary of one i.f. transformer as shown in building receivers with two stages of places the secondary. The grid is coupled Fig. 2. One coil can be left in the shield 465 -kc i.f. amplification. They invariably to the primary by Cl, a small variable can, the other mounted below the chassis broke into oscillation when peaked to condenser such as a 100 -µpfd trimmer. with a separate trimmer condenser. resonance. Detuning one stage to pre- The trick is to reduce the capacitance of Usually stray wiring capacitance sup- vent this led to lower sensitivity and Cl until the i.f.'s can be peaked without plies sufficient coupling; however, it poor selectivity. I have tried all sorts of the set's breaking into oscillation. (In would be wise to try additional capaci- tricks to stabilize them -isolating re- one instance a "gimmick," two pieces of tive coupling such as the twisted -wire sistors or chokes and bypass condensers hookup wire twisted together, provided "gimmick." Reduce the coupling until in plate and screen supply leads, shield- sufficient coupling.) the amplifier is stable. ing plate and grid leads, lower plate po- It was found that this system gave tentials and higher bias, loading resis- much more gain than the amplifier with GIMMICK MAY NOT BE tors across the i.f. coils, switching i.f. one stage removed, had better selectivity NEEDED leads to change the feedback phasing - than two detuned stages and provided all with indifferent results. better tone. It proved a very satisfac- I finally hit upon a system that works tory arrangement. very well: Alter one transformer to an An even better method is to separate impedance -coupled stage as shown in and shield the primary from the second- Fig. 2- Another cure for oscillation.

CONYI 1571F 2ND IF DET This method gives better gain than impedance coupling and the selectivity o obtained is amazing. On one receiver in SEC.NOT USED which it was tried it was possible to pull in a distant station 10 kc away from a 8+ SRI strong local. The set has to be aligned Ayc very carefully to attain this degree of Fig. 1- Impedance coupling in the first i.f. stabilizes sets with two stages. selectivity. John A. Dewar

SERVICE DATA, TECHNICIANS AND MONEY 1Continued from Page 45) and their practical experience; but they The man who blindly aligns all i.f.'s at nician to make a quick choice from are fully aware that they can do the 456 kc is not much better than the one available stock. same job in a fraction of the time when who maintains you do not really need If there remains any lingering douht a signal generator they have the books to help. to do radio servicing! in your mind as to just how helpful will But when you go Moreover, they know that they into FM and TV service data can be, a bout with a de- be able to do better work. Take, for ex- alignment, service information becomes fective record changer should remove ample, the matter of alignment. Even an absolute necessity. it. Without servicing information, you with AM sets it is essential to know Another feature technicians new and have to trace out the sequence of events the correct i.f.; the position, use, and old can appreciate is the listings of that should take place during the change order of adjustment of the trimmers; manufacturing changes. The service cycle by observation -and observing and certain special information regard- technician can frequently improve the the action of a record changer is about ing such matters as triple-tuned trans- operation of a set over what it was as difficult and nerve -wracking as try- when new. makes formers and a.f.c. circuits, all of which That a decided hit ing to read a long- winded title on a are plainly set forth in step -by -step with his customer! whirling phonograph record. fashion. Receivers can be aligned, after Equally helpful is the practice of a fashion, without knowing these giving the replacement part numbers How different all this is when you things, but the resulting performance of several different manufacturers for have service data! You are shown an will often he short of what it should be. each component. This enables the tech- exploded view of the entire mechanism that reveals the exact shape and posi- tion of every single part. The change cycle is described in detail. For every possible fault in the operation of the changer, several possible causes and cures are listed. The author has no connection with any radio service data publisher, but he is deeply interested in the future of radio servicing, and he feels that an increase in the use of service literature is a most important factor in improving both the quality of, and the profit ffom radio servicing. He has no recommendations as to which of the leading service-data pub- lishers you should patronize. The pro- ducts of each have some distinctive fea- tures not found elsewhere. The impor- Courtesy John F. Rider, Publisher tant thing is to own and use at least The set of service manuals on the shelf is as important as the instruments below. one of them. RADIO -ELECTRONICS for

www.americanradiohistory.com 4 Servicing

Home Study Courses Useful to Radiomen

Correspondence schools can be beacons on the path to success

By SAMUEL FREEDMAN Mr. Samuel Freedman

AM a firm believer in home -study or dicate that home -study training courses more formal schools carrying on class- "correspondence-school" training. Of are most necessary. room instruction in the old, time - the many schools and colleges at Home -study schools are tried and honored manner. which I have trained since 1920, I proven. More than 1,500,000 students, The history of home study begins in don't believe any did me as much good as mostly adults, were enrolled in them 1891 when Thomas J. Foster, an editor the home -study radio course I took in in 1948. More than $50,000,000 was in a coal- mining city, received a letter 1929 -31. That was my turning point from spent on tuition for courses in every from a reader requesting information a dull routine in an unpromising job to sphere of employment. There is hardly on how one of the dangers incident to an opportunity eight years later in be- a field of specialization today which coal mining might be minimized. He ing chosen to head the Maine radio pro- would not collapse if it lost its leading answered the inquiry in his newspaper. gram, and head the prewar NYA radio figures who received some or all of Other readers sent in similar letters, program and become a leader in mobile their training by way of home -study which were also answered. So the editor radio development. That in turn led to methods. began to compile simply worded articles The home field which has the my commissioning as a naval officer -study on the safety hazards of coal- mining greatest record of success during the and finally to my present position in the and on self -protection against them. DeMornay past 20 years is that of radio-elec- microwave field working for From this beginning was conceived a tronics. It has been improved tremen- Budd. plan to furnish practical and reliable As I discovered later, after a thorough dously, and the student gets the benefit by mail. Thus was investigation of home -study schools, of visual aids and extensive laboratory technical education my history is by no means unique. practice in addition to complete printed born the International Correspondence But some people still look askance at reference material for study and for Schools whose headquarters remain in "correspondence courses," and large his future use. The quantity and quality the coal-mining city of Scranton, Penn- numbers of men are unaware of the of instruction may even exceed that of sylvania. (Continued on page 48) good a course of home training can do them. The radio, communications, and elec- tronic fields require a tremendous amount of additional manpower with suitable qualifications. Additional qual- ifications are also needed by the tens of thousands of men already in these fields, who still are wholly or partially unfamiliar with microwaves, television, radio aids to aviation and navigation, nucleonics, FM, mobile radio, and other postwar developments. For national de- fense, the nation also requires as a re- serve pool of technical manpower, over 1,000,000 persons who will qualify themselves in these fields either as a hobby or as a secondary vocational oc- cupation. Most people who need training can- not afford to take the time or incur the expense and loss of income required for formal schooling. (A limited exception is veterans' training under the GI Bill

of Rights.) The requirements of both 7'. :. :tom, individuals and industry definitely in- One of over 20 Army laboratory plants built for electronics and nucleonics NOVEMBER, 1949

www.americanradiohistory.com 48( Servicing

When correspondence schools were malty for a master course covering sev- first introduced, the new idea had to eral subfields of employment within the face prejudice and ridicule. Educating over -all field of radio and electronics. via the mails was pronounced foolish, For this sum, the enrollee receives the and the classroom was declared to be :ollowing. the only suitable place for such a func- 1. A series of lessons ranging from tion and experience the only way to about 30 to over 100, depending on the learn a trade or business. The record size of the lessons adopted by a par- has proven otherwise, and today many ticular school and the type of course of the nation's leading universities op- selected. erate extension (a more refined word 2. Various additional printed fea- for correspondence) services patterned tures such as reference textbooks, radio after the commercial home -study dictionary, books on starting one's own schools. It has made training possible radio business, texts on prerequisite for anyone, regardless of location and material such as mathematics, ques- economic status. It has encouraged in- tions and answers for passing FCC ex- dividuals to enter fields in which they aminations, and so on. have become outstanding, when other- 3. Kits of parts with which to make wise they might have deprived them- experiments. With the parts much use- selves and the world of their talents ful equipment can be constructed -test and leadership. instruments, receivers, transmitters, various Movies showing electron action are a Many noted educators admit the AM or FM modulators, and study aid. The projector is furnished. weaknesses of classroom teaching. other electronic devices. It belongs to only the size, number, and manner of inductors, capacitors, re- OPPORTUNITIES connection of NEW RADIO -ELECTRONIC sistors, and tubes which result in the This list of fields developed since the end of II. Placement of radar on all merchant ves- items into the cate- the war shows only a few of the many opportu sels. thousands of falling nities for employment and advancement open to 12. Airborne radar. gory of radio and electronics. These can the ambitious, well- trained men. 13. The tremendous expansion of useful be mastered by home -study I. V.h.f. FM broadcasting. radio spectrum into microwaves. definitely 2. Large -scale FM receiver manufacture. 14. Television broadcasting. printed material implemented by train- 3. Two -way, mobile radio for taxicabs, rail- 15. Television receiver manufacture, design, components such roads, trucks, automobiles, etc. and service. ing kits of basic radio electronics. 4. The new citizens band. 16. Food sterilization through as are offered by reputable schools ad- 17. New methods of communication involving 5. Aircraft omniranges, which replace the in leading radio- electronics older four -le$ range stations. pulse transmission. vertising 6. V.h.f. aircraft communication. 18. Supersonics. journals. 7. Ground -controlled approach (GCA) sys- 19. R.f. heating. Home -study schools offer the greatest tems for aircraft. 20. Radioactivity detectors. 8. The expanded military radar program. 21. Upper atmosphere research and weather opportunity for the maximum number 9. The tremendously expanded research car- forecasting. to get a foothold in the radio-television- ried on by the Armed Forces, government bu- 22. Radio -control and guided -missile develop- reaus, and industry. ment. electronics field. The future depends on 23. Radio spectroscopy. 10. The radar fence around the U.S., which how many of the rank and file will will cost about a billion dollars and require o 24. Magnetic sound recording. staff of at least 25,000. 25. Electronics in medicine. emerge as creators and leaders to give industry and science new impetus. Such men can emerge via the home -study Oftentimes, lectures prepared by the the student permanently, and the retai route just as surely as they can from few real authorities in a field are avail- value of the parts is appreciable with the classrooms of the nation's schools able only in a few scattered classrooms. respect to course cost. of higher learning. Every home -study student, on the other 4. Consultation service, which con- hand, may receive instruction prepared tinues for the life of the enrollee. I CUT -PRICE CONTRACTORS by a master. In a classroom, if atten- have personally verified and utilized service over a number of years The Television Installation and Serv- tion fails and part of a lecture is missed this Association of Chicago has warned on a course which was started in 1929 ice it remains lost. Those who learn by television dealers against hooking up and completed in 1931. with -price service contractors who service. cut 5. Free lifetime employment may jeopardize the dealer's future by This has great value. The total cost of giving unsatisfactory service (or, as tuition is normally no more than a past experience has proved, no service legitimate employment agency charges at all). for a single placement. The service is Dealers are reminded that their li- available indefinitely, and during the ability does not cease when the con- lifetime of a student may repay many tract has been turned over to a service times the price of the course. Schools company, and that the customer will have full -time placement experts whose continue to associate the dealer with sole job is to discover or develop job the service he receives on his televiser. opportunities. Many employers recog- The wise dealer, says the Association, nize these schools as sources of de- will check the repute, financial stand- sirable employees. In view of the great ing, distributor acceptance, and length Courtesy De.Monm y -H, dd technical developments now under way, of time a service company has been in Orders for this new microwave calori- only some of which are enumerated in busines before associating himself with meter now total more than $250 million. the box on this page, no intelligent per- it. Above all, he will deal with actual or educa- home study can refer to their printed son, regardless of experience service companies, not with sales -and- much and as often as neces- tion can help but benefit from a home - service outfits which may have an in- material as brand of sary. It is always available for re- study course of some kind. The course terest in pushing a competing fresher or reference purposes since it may be for refresher purposes or it may television receiver. property of the acquaint one with new developments. "A slight saving in the cost of a pol- remains the permanent a customer student. Basically, radio and electronics have icy at the expense of losing average home -study school may never been nor are likely to be more and the future business of his friends The is no saving at all," the charge a tuition between $100 and than inductance, capacitance, resist- and relatives is release concludes. about $400. The latter figure is nor- ance, and electron -tube circuits. It RADIO -ELECTRONICS for

www.americanradiohistory.com FREE ALLIED'S 1950 RADIO & TV CATALOG

196 VALUE- PACKED PAGES Seed pot it twcu!

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www.americanradiohistory.com 501 Servicing Radio Set and Service Review Eicor Model 1000 Tape Recorder

or backward, or stops it. The knob at ohm speaker and for signal feeds from the right switches the circuit to ERASE - an external source such as an AM ra- RECORD or LISTEN. dio, FM tuner, program line, PA system, To rewind the tape, it is lifted off the etc. The built -in speaker is 6 inches in capstan and passed across the head diameter -a bit larger than usual in only. It is not always necessary to re- this type of equipment. wind, however, as the unit has a "twin - No tone controls are provided for EI COR'S model 1000 tape recorder track" feature. Recordings are made the operator. A typical response curve (Eicor, Inc., Chicago), one of the on the top half of the tape. When a supplied by the manufacturer shows lowest- priced sound recorders of reel is fully recorded, the full reel can that the output on playback, with a any kind, performs at least as be removed from the right post, in- constant- level, varied- frequency tone well and is as easy to handle as any verted, and placed on the left post; a home -type unit offered today in its new recording can be made on the un- FRED IN 011I5 ERSECON0 price range. All of which indicates that used half. The metal roller shown just the service technician may soon find below the capstan in the photo was ap- the Eicor in the hands of many of his parently added in later production; it customers. is not shown or discussed in the instruc- The appearance of the recorder is tion book. If, in rewinding, the tape is unusually neat. The black leatherette passed from the right reel, directly case is 14% inches wide, 8% inches across the bottom of the magnetic head, E INPUT: CONSTANT VOLTAGE TO RA010 JAO( high (with the lid and 11% E OUTPUT= MEASURED AT EXT SPKR JACK down), to the left reel, no sound will be heard. TAPE -3M BLACK OXIDE. SPEED 7-1/2"/SEC inches from back to front. Three pock- If, however, it is looped over this metal ets are provided in the cover for the roller before reaching the head, the Frequency -response curves for recorder microphone and the cables. The whole high -pitched "Donald Duck" sound of unit weighs 27 pounds. the recording will be heard on rewind, input while recording, stays within Operation is extremely simple. A reel a valuable feature if the tape is to be ± 3 db between about 50 and 5,500 of tape is placed on the left post; the rolled back only to the beginning of a cycles. Above the machine -run curve tape is brought around the bottom of certain selection. Rewind time for a appears the result of a response check the head, over the top of the rubber - full 15- minute reel is 2 minutes; a half - made in our own laboratory at a some- rimmed capstan, and threaded onto an hour reel requires 4 minutes. what higher signal level. Wow and empty reel on the right post. The cen- The audio quality of this recorder flutter in this recorder were extremely ter knob is the ON -OFF- VOLUME control. was judged on test to be acceptable. low. The left control sends the tape forward Jacks are provided for an external 3.2- The tape -pulling assembly consists RADI .001 560K 245V00001 OUT TRANS 32.5V (50) A 6SJ7 6SJ7 6K6-GT o EXT SPKR$ -0 470K 3.2a 3 470K R 14.5Vf501 5 4 255V 9. MIKEoO: SI-b 6 I SI-4 22MEG IMEG (1000) INT SPKRO VC 500K p4 O IMEG 5 28V(5O) .05 1A5 BI 16VI100) .7V(25) J. 2.7K 1100/25V .5K A5 70 25/25V

SI -c ---) RECORD COIL R ÇA5SI -4 R ; IOÓK -_r- GROUNDED PLAYBACK O I C R ONLY PONT 20/350V 47K I o TO CHASSIS 4 o COIL I +p 4L L 3 - NEON NF-SI .01 820 6J5 -GT l VOL INI IC r I BIAS COIL 15K 3 I oL I R C 220K SW ON VC 6x5 -GT Ro óI I ERASE COIL SI-11 2.2MEG oa--o C q SI-8 04 0 a--- FILTER CH o- H I SI -f - 5 8 +255V S2 ° I.00 L--- b e 4 1000) OSC CO. s RECORD 300V ERASE .LISTEN PIN2 11000) 30 20 INTERLOCK RECEPTACLE omDi poGi3D000 MOTOR .3V ALL FILS 350V 47K.05 i/ii PINT T i i//', ii agi 0:(11-11:T Rccon o c NU f t MEASURED PER VOLT METER SET TO RANGES INDICATED IN PARENTHISES THUS - VOLTAGES ON 20,000a (1000) SI: a -h SWITCH SECTIONS NU-NOT USED X- TIE POINTS R- RECORD C-COMMON L- LISTEN Complete amplifier schematic. Apparently the single -point ground is largely responsible for the complete absence of hum. RADIO -ELECTRONICS for

www.americanradiohistory.com 51

Now, For the First Time GUARANTEED TEST INSTRUMENT KITS * READ DETAILS OF UNPRECEDENTED GUARANTEE IN BOX AT BOTTOM OF THIS PAGE

THE NEW MODEL KT -40 VACUUM TUBE VOLTMETER FEATURES SPECIFICATIONS megohms input resistance> 0 to 3 30 - accurate D'Arsnnvai type Meter with high D.C. VOLTS: (At II Uses 4'z - -2 °ó 1.500 Volts. torque movement and Alnico V slug. 130 750 1.000 ohms Volt) 0 te 3'30 150'- Meter against burn -out on ALL electronic ranges. A.C. VOLTS: (At per guaranteed 1.500 Volts. Meter will not be damaged even when improperly switched 750 to higher range. RESISTANCE: 0 to 1.000 10.000 100.000 ohms. 0 to 10 Stabilized degenerative circuit results in linear D.C. scale. megohms 1.000 megohms. equals .006 watts (6 milliwatts) into a test. prod for all D.C. Voltage ranges. D.B. Based on 00b Isolating 500 ohm line. Megohm input resis'ance on all D.C. ranges. 4 +. 10 db to 4- 38 db - 24 db 10 - db measures from 1 10th ohm to I bil- Ohmmeter accurately 58 db + 30 db to lion ohms. - 4 db to 24 db -

Model NT 40 Kit comes complete with MODEL KT -40 COMPLETELY WIRED all parts including test leads. V.T.V.M. S gO READY TO OPERATE 529.50 rod. c,rcgit. operating instructions. etc. I NET

THE NEW MODEL 247 TUBE TESTER thyrat-ans, the Check octals, loctals, bantam Jr. peanuts, television miniatures, magic eye, hearing aids, new type H. F. miniatures, etc. FEATURES we believe. Newly designed element selectors itch reduces the pos- One of the most important improvements. 4. fast action snap switches sibility of obsolescence to an absolute minimum. is the fact that the position are all numbered in enact accordance with the standard When checking Diode. Triode and Pentode ections of R.M.A. numbering system. Thus. il the element sections can be tested individually. multi.purpose tubes. minating in Pin No. 7 of a tube is under test. button allows each section to be A special isolating circuit No. 7 is used for that test. tested as if it were in a separate envelope. The Model 247 provides a supersensitive method of check- and leakages up to 5 Megohms between ing tor shorts 1t,t tomes with all any and all of the terminals. Model 247 parts. new speed-read cara. handsome hand-rubbed o a $9190 MODEL 247 COMPLETELY WIRED net sloped for bench use. A alle- $29.90 n hinged r ver . included for READY TO OPERATE outside use. NET

THE VII-450 SIGNAL MOD EL GENERATOR SPECIFICATIONS Frequency Range: 150 Kilocycles to 50 Megacycles. The R.F. Signal Frequency Is kept completely constant is accomplished by use of as well as A.M. receivers can be speedily aligned at all output levels. This F.M. which provides a constant load with the aid of the Model B -450. Modulation in the special grid loaded circuit on the oscillatory circuit. A grounded plate oscillator B -450 is accomplished by Grid blocking action which has stability. be equally effective mplitude is used for additional frequency provenwllo to Direct reading calibrations are etched on the iront as r frqeniutreceivers. -all R.F. is obtainable separately or modulated by Audro Panel. Frequency. Attenuatcr effective output con- Positive action provides complete trol at all times. Model 4.450 Kit comes with all test leads. etc.tc Noth inu'tog else FMODEL I -450 COMPLETELY WIRED buy, READY TO OPERATE 524.50 1$8" *UNPRECEDENTED GUARANTEE! to All kits advertised on this page are offered subject to the following guarantee: If, after completion, the instrument does not operate your fullest satisfaction, you may return it and we will ship you a brand new factory wired and tested model for only the difference between the price of the Kit and the price of the complete Instrument. Full credit will be given no matter what stage of completion has been reached in wiring the Kit.

20 °e DEPOSIT REQUIRED ON ALL C.O.D. ORDERS NPTRK PLACE GENERAL ELECTRONIC DISTRIBUTING CO. NEW YORK

NOVEMBER, 1949

www.americanradiohistory.com Servicing e,

hum -reducing device apparent in the circuit, these peculiar ground connec- tions are probably responsible for the phenomenally low hum in the loud- speaker. On both recording and play- back, the volume control can be opened wide; with the ear right up against the speaker, the only hum to be heard is the slight whine of the motor. The RECORD- LISTEN switch S1 (our numbering) is a multiple- contact slide unit attached to the chassis and actu- ated by a rod topped with a knob on the motorboard. It has been broken down in the drawing into separate s.p.d.t. sections for simplicity; the sec- tions are lettered and identified on the inset drawing of the actual switch. The four magnetic coils are all in the one head. Either playback coil or microphone is switched to the grid of the 6SJ7. The RADIO input is paralleled with the plate of this tube across the volume control. The 6K6 -GT is the power amplifier, feeding either speakers or the record coil (the latter through an equalizer network). Note the provi- sions for attaching external 3.2- or 500 - ohm speakers or lines. A 6J5 -GT oscil- lator provides erase and bias signals. This upside -down view of the motorboard shows the amplifier chassis. There are four frequency- compensa- tion networks in the amplifier. The ser- screws ies 560,000 -ohm resistor and .001 -µf of a synchronous motor and a simple holding the magnetic head to capacitor between the plate of the 6K6- combination belt and friction drive, the motorboard, too. CT and the of The shown was cathode the previous tube mounted solidly to the heavy metal schematic redrawn feed back (and therefore roll off) highs, from given in 24 -page instruc- motorboard. The motor runs at all times that the beginning at about 250 cycles. The ap- ( when the switch on the volume control tion book supplied with the recorder. parent effect is a bass boost from 250 is ; and In the in the book the turned on) the reels are started drawing com- down. The 50 -µµf capacitor across the stopped by a mechanical clutch arrange- ponents are so arranged as to duplicate 560,000 -ohm resistor increases the ment operated by the FORWARD- OFF -RE- their physical placement on the chassis. treble cut, beginning at approximately WIND knob on the left. Since most technicians try to diagnose 7,000 cycles, beyond the useful range The chassis is screwed upside down trouble in terms of the symptoms, the of the recorder. to motorboard. Plugs connect the functional drawing shown here is likely the The .05 -pf capacitor across the 1,500 - internal speaker and the motor to it. to be much more useful. ohm cathode resistor of the second 6SJ7 The magnetic head is wired directly to The manufacturer's drawing has one reduces degeneration of highs beginning the chassis and mechanically connected very interesting feature, however. Cir- at about 2,000 cycles. This is, of course, by a bonding strip. cuit grounds are shown to be made at semirigid, copper a high -boost circuit. The parallel 820 - and is Four screws atop the motorboard hold unexpected points contact made ohm resistor and .05 -µf capacitor in the chassis, but in disassembling for to the chassis at only one place -pin 2 series with the record coil boost highs is servicing remember to remove the two of the first 6SJ7. Since there no other beginning at about 4,000 cycles. This has very little effect and is the only one of the compensators not in the circuit Service Technician's Information Blank at all times. The functions of the switch sections See Editorial on page 19 for vital information to you. are obvious, with the exception of S2. 1. Are you a full -time or part -time service technician? With the cathode of the 6J5-GT 2. Are you an "independent' service technician or employed by some- grounded only through its cathode re- one else? sistor and capacitor, the bias prevents 3. Do you service radio receivers only, television receivers only, or both 7 oscillation. S2 is a leaf -type interlock 4. In your servicing activities are you commonly asked by customers to switch, which closes only when the recommend or endorse different makes of television receivers? mechanical clutch arrangement is in the 5. Are you in favor of our publishing a greater number of television serv- FORWARD position. This prevents erasure icing articles? when the tape is being rewound, even 6. What other radio magazines do you read regularly in addition to though Si may be on ERASE -RECORD. ours? When S2 is closed and Si on ERASE - 7. Would you like see articles on some phase of television not now to RECORD, the 6J5 -GT cathode is grounded covered by the magazine, or more (or less) of any of the types now printed? directly and the oscillator operates. S1 is, not a stock unit, but a special slide switch built for the purpose. The YOU need not sign your name to this blank. Please poste it on a It post card or technician should take great care, in mail by letter to Radio -Electronics, 25 West Broadway, New York 7, N. Y. Thank of contacts. not to you. adjusting any the misalign them. The operation has been Name carefully timed- certain sections break quickly, others slowly, and some are of Address the shorting type. The sequence of con- City & State tacts is also worked out in a specific order. So beware of tampering. RADIO -ELECTRONICS for

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PLUGS AND CONNECTORS

AN3102.24.3P OVAL 30 NV CHOKES SET. $KCN425 CD 001 -A CORD L PLUG SK-C1423- L043 HI Vollase Installation at 20 MA DC. Used with BC 004 between PENS AN41043413 % ACAN aa2Y03 4Ve Ibe .4e Dynamotor and Transmitter. MSSSA AN310434150 - AN3100324P AN31052525 AZEROVOC $195 10HS25 PL077 5 AN4057.24 AN-3104-244S MICA BUILD TOUR AN3102145.1P AN310415.2 PL147 AN305714 CONDENSER OWN AN10432101S AN30574 .O1 UFO AN31021405 UG21/U GEIGER COUNTER AN3057.10-% 2 PL017110HH14 $000V U/S/U AN310514$25 14.20 Amps PL112 AN3102141-25 PL110 AN3105401a K.C. AN410220-27P PL142 10H/2S1141 1000.1000 MC13$ AN41042217P ARCSSSS AN3104.24.1SP $495 AN31024214P AN31042211 Detects both Beta and Gamma Rays. Search probe AN.2103-14$73 AN31024845 AN310414125 225514 included with 1B85 Geiger Tube. Chassis and Case AN-3104-15$ 1 P batteries, diagrams, and AN-30574 PL115 comes all drilled. All parts, AN3102344P AN31041aS3 instructions included. Exact duplicate of the famous 4 9 e r Geiger Counter 45eeach publicized in the Septem- ber issue of Radio Elec- tronics. $4950 HERSHEL RADIO Mg CO M I C H I G A N 5 2 4 9 GRAND RIVER D E T R O I T

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All orders F.O.B. Detroit- Minimum Order 12.00- Michigan customer* 890 4 FOR add 3°, sale. -20% payment must accompany orders. to all 350 $1.00 PAPER OIL SPRAGUE CONDENSERS METER

CAPACITATORS .l MED 7109 VOLTS Type Dot 1. 0.1 MA. nutter sale graduation $295 1 MFD $195 0 4 D.C. Kilo V. and 5000 V. '2.95 0.10 MA D.C. I MFD 6000 V. COLLINS FILTER '4.95 WAFFER SWITCHES CHOKE MFD $IW6 HV, ISO MAO. D.G. ! Vletanc. 100 hma. Teat 6000 V. '8.95 KIT OF V. 2500. 2 MFD 7100 V. '12.50 TEN 5185 SWITCHES AIRCRAFT POWER RHEOSTATS FM RADIO AND TRANSMITTER 25W, 2S ohms 1 amp maximum 090 BC-620-A IGNITION COILS FOR G.E., SYLVANIA. SOW. 30 ohms 1.7 amps maximum 20 MC TO ETC. Photo Flash Tubes 950 279 MC $995 USED VARIABLE CONDENSER Primary: 150V. condenser 5129 discharge. Secondary: 15.000 890 This Xtal controlled FM net has 13 tubes and has dual V. Can also be used on model airplanes. *cal lied Is. It also contain. built -in Fit. and Plate Meter. Tubs used: (411LN5. (1)ILC6. 111 RR 22 K RELAY 1LH4, 12)1291. 101299. (1)1294 Ideal for communlca Used In een)une. 6 Gang silver plated. Sec. 1: 150 MMFD. Secs. 2 3. 4, Ron between trucks. boats. etc. Used. in good Gondi lion with SCR. S: 60 MMFD. Se.. 6: 80 MMFD. 269F. changeover lion. Less power supply. Wt. 38 lbs. Complete with contains 28V. step carrying cage and diagrams. 5295 relay S deck. 6 FULL WAVE METER RECTIFIERS position switch. FOR USE WITH IR(' TYPE HE 12V. OPST. O-1 MA. METER ANTENNA DUPLEXER Originally used on SNIFF equip- 950 100W. Bleeder consisting S (] of sections; ment to allow the u of a m. 750 ohms. 23 ohms. 23 ohms, 7500 mon antenna ohms. 3000 ohms. Total- 11.294 ohms. for receiver and AZIMUTH CONTROL transmitter. 156 to 187 MC- $5.95. MN LF. TRANSFORMER ANTENNA BOTH 52H USED 950 2 meter an UNITS 49, 157.187 MC. Orig.: Mounted in shield 'natty used with ONLY Dial calibrated 360 degree face. SMC with air BNIFF equip. ideal for antenna rationalising in. Impedanu trite. t e $995 pled dicator. 60 to 1 ratio with .witch. DISCRIMINATOR TRANS- fully used ont 144 FORMER TO MATCN___95c MC as a endi notional antenna DETROLA Handles IS CORONA BALLS -$6.9S. 10 - inch rec- Grid and plate co lion. for VT 127. 250 No. M *16 Cross pointer Meter. Two 200 ord% or ten microamp movements. Brand $2.95 RECORD CHANGER TH tc. Ball Type. IOc EA. 12 -inch rec- Heat dissipating $100 500ohmto grid matching Iran.for me. No. 51745._ SSc Slated. Deb. Ceramic Silver Paddere Dual 3 to 12 ords. MMFD or 5 to 20 MMFD 19e TRANSFORMER Ceramic mica Padder single S to 20 MMFD_Wr dl. SIN Automatic 950 Choke -300MA 2014V. Insulated for 5000V. Heavy Audio osculating transform Porcelain Insulator.. Very conservatively Changer er with output and feedback Idle for KW rig 56.95 winding. Only REMOTE POSITION INDICATOR $495 VOLTAGE REGULATOR 6.12V. 60 Cr. 9" Indi 950 with 0.360 Degree Dial $9.95 Carbon pue, magnetic A -3 AUTOMATIC PILOT type, coil e rent. 105 MA. Load nue. S amps Serve) -100 foot lb.. at 18.25V. a BUTTERFLY CONDENSERS st erino ° oar '495 pail dev`te.troll on Oscillator assemblysembly 76 to 300 MC ships. DONT MISS THESE SPECIAL SAVINGS! with tube socket mounted on cond....r $3.95 Powdered Iron. 0, lug 10c PORCELAIN SOCKET Jacks for PLSS. or PL 63 toc Type B Frequency 300.1000 megacycle. . -.. 52.95 Ase't mica condensers 100 (ACORN) 15$ -per 9 1.95 Pin .traiohtener for miniature tubes BC4 Antenna condenser 105.330 91.30 .Doz. 25c MC ..53.95 EACH Ear phones. 2000 ohms, 95c SCR62S Mine detector. used 935.50 MICA CAPACITATOR 75.000 -ohm 200 watt BI Res.__ 9Sc 690 SILVER CERAMIC CONDENSERS 002. MFD.-3000 W.V.D.C. 500 W.V.D.C. 14; ea. 12 tor $1.10 FILAMENT TRANSFORMER Available capacity (MFFDe). 2. 3. 4. S. 7. O. V/, 10. 110V.. SO Cy. See. 1: 4V. 11, 12. 15. 24, 25. 30, 40, 45. 50. SI. dual 60. 70. 72. at M amps. See. 2; 2.5V. at 1.75 71. 10. 61, 95, 100. 120, 12S, 140. 232, 350, 375, 400, '195 amps. insulated for 470. 500. 1000 and 5000. 5000V. Ideal for 2112 and 826 tubes. Her. With 3 RF . (One re.readiation .uppreeser R F.) metically sealed. 12 tube.. Motor and manual tuning. S- meter. Mlee. Si.: 63'..,41<.L. Uvlty control. Crystal Filter. AVG. passing control. NEW BC 223 AX TRANSMITTER ANL. etc. Also furnishes video output for scope. and SOI Oscillator. and 601 power amplifiers. modulators panoramic for scanning. 2.46 Complete with tubes and and 1 -44 speech amplifier xtal frequencies and master *tat, but without power Supply. Power requirement.. oecillator on selector switch. 10 to 30 Watts output. 270V. at 135 MA. New. In sealed case.. Tone voice or C.W. Mod. Ideal for 80 meter ban,. Comes with 3 coil. TU 17A 2000.3000 Kc. TU 25 3500. ARR7 AIRBORNE VERSION 5250 Kc. Black cackle case. Includes two separate in to extra coils. Frequencies chart and tubes OF HALLICRAFTER COAXIAL FITTINGS cluded. packed in original case.. less crystal. at this low price. SX 2*A Sc 25c 35c 20c ANGLE. HOOD SOCKET PLUG ADAPTER $3995 :I2900 50.219 PL -209 M359 81-IR 81ISP 83 -IA,

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www.americanradiohistory.com 561 Servicing Fundamentals of Radio Servicing

Part IX-The diode racoon, tube By JOHN T. FRYE aVING spied on the busy elec- resistor R2 bridged across it so that circuit? Surely the current cannot pass tron while it skipped through any positive voltage from zero (at the through the space between the filament conductors, resistors, coils, ca- extreme left -hand position) to the full and the plate inside the glass sphere, pacitors, and transformers, you battery voltage (at the extreme right - for we have always thought of a vac- may feel that you are an authority on hand position) may be selected by the uum as being a perfect insulator; yet, the behavior of the little cuss; but until moving slider. A voltmeter is arranged there is no other logical explanation you have observed one doing its stuff to read this voltage. The slider con- of what that milliammeter pointer is inside a vacuum tube, you really have nects through a milliammeter to the saying. The current must be bridging little idea of the power and versatility plate of our "vacuum tube." the gap inside the bulb, but how? packed into one of these tiny charges With the slider of R2 set at zero Remember that back in Chapte. I of negative electricity. positive voltage (extreme left), let us we found there are always a number Take look at the experimental setup slowly decrease the resistance of R1. of free electrons wandering aimlessly diagrammed in Fig. 1. The circle rep- permitting more and more current to resents a hollow glass sphere in which flow from the battery through the fila- (LAMENT are contained a couple of loops of re- ment. The passage of this current pro- INSULATING sistance wire and a small metal plate duces heat in the filament wire; and BUSHING mounted near to, but not touching, this when enough current flows, the wire be- wire. Leads are brought out from the comes red hot. Our ammeter reveals 41-400,1 plate and from both ends of the "fila- how much current is flowing through ment" wire, and all the air possible has the filament, but our milliammeter still been pumped from the glass bulb be- zero. we move FIL stands at However, if the NEATR.,i fore sealing it slider of R2 to the positive end of the A-BATT A low- voltage battery, an ammeter, battery, the milliammeter indicates variable resistor Rl, and the filament pronto that current is passing through au*r SURRLy are connected in series. Another, it! B-BATT higher-voltage does battery, with its nega- Where this current come from? TRANS tive terminal connected to the negative It must be flowing from the high -volt- terminal of the filament battery, has age battery, but where is the complete IITVAC q

Fig. 1 (left) -Test setup illustrates diode action. Fig. 2 (right) - Cathode is cylinder surrounding the filament. around through any conducting ma- terial? By applying voltage, we can control the direction and speed of this movement of electrons to a certain de- gree; but even with no e.m.f. applied, the restless little jiggers are constantly hopping around from one atom to an- other. When they come to the surface of the conductor, however, they bump into a force, somewhat resembling the sur- face tension of water, that keeps them from passing through. While they pos- sess some kinetic energy (kinetic en- ergy is power acquired through motion; it is the reason a soft hand can slap so hard), they do not have enough to shoot through this surface barrier. They must have help if they are to es- cape into "the wild blue yonder." Providing heat is the easiest way to supply this help. When the temperature of a body is raised, free electrons begin to feel freer and friskier by the second. They start to accelerate and to shoot ....`"),a madly about like a bunch of water bugs These are a few of the coron diodes -all ..ires and ratings are manufactured. playing tag, and sooner or later one RADIO- ELECTRONICS for

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of them takes a long running jump and pops right through the surface of the 7244A . . . 0 04 M O T IE .tC'ct,tee Vecle& body into the air or vacuum surround- ing it. As the temperature goes still higher, more and more of these heat - IN 1/s WATT OR 1 -WATT ASSORTMENT propelled electrons make the grade un- til finally the heated object is sur- rounded by a veritable cloud of fugi- tive particles that it has emitted. Please note that it makes no differ- ence how the emitting body is heated. It could be done with a blowtorch, a gas flame, the focused rays of the sun, etc., but inasmuch as the emitting material must be heated inside a vacuum in our radio tubes, the heating effect of an electric current has proved to be the most practical. Sometimes the filament itself is the emitting body (or cathode), as is the case in Fig. i; but in other instances the emission is from an indirectly heated cathode, as is shown in Fig. 2. Here the filament is heated by current from an alternating-current transform- er, and this heat passes through a bush- ing made of electrically insulating but heat -conducting material and raises the temperature of the sleevelike cathode to the proper temperature for emission. 1/2-WATT ASSORTMENT Tubes are therefore loosely divided into "filament" and (indirectly heated) $12.50 "cathode" types. When an electron is emitted, its neg- 1 -WATT ASSORTMENT ative charge is subtracted from the $18.75 total charge of the emitting body; therefore the body becomes unbalanced Each assortment, either 12 -watt or 1 -watt, in a positive direction, tending to at- is packed in its own rugged cabinet ... and tract the negative electron back into you pay only the regular price of the resis- itself if some other stronger force is tors, nothing extra for the cabinet! not exerted on that negative particle. Factory packed in each cabinet's 40 separ- That is where the plate in our vacuum ate compartments are 125 carefully selected tube enters the picture. If the plate is "Little Devils" (tol. ± 10%) ... in the -t0 positively charged with respect LITTLE DEVIL COMPOSITION RESISTORS to the values from 10 ohms to 10 megohms most fre- emitting filament, it tends to attract to quently Guesswork's gone ... when you used by servicemen. It's no trouble itself the electrons that have escaped use individually marked Ohmite to find the resistor you need ... fast! into the vacuum; and when there is a "Little Devils." These tiny but Molded of strong, lustrous plastic, and constant parade of electrons from extremely the rugged resistors are available in compact -only 9' x -1 % x 5W- filament or cathode of a vacuum tube to standard 1, Ohmite cabinets protect RMA values, t/, and your resistors, too, the plate, we have a plate current. 2 -watt sizes . 10 22 and help you ohms to check inventory at a glance. These megohms. Tol. ± 10% and ± 5%. You'll want to order both assortments, today. electrons pass from the plate Values to 2.7 ohms available in to the positive terminal of the battery 1 -watt size, ± 10% toI. through the milliammeter, causing it to SEE YOUR DISTRIBUTOR deflect. Incidentally, when only 10 ma is flowing, 6.28 times 1018 electrons are being emitted by the filament and at- tracted to the plate every second (not 6.28 times 1018, as the printer errone- ously reported in Part I of this series). However, the electrons flow from the negative terminal of the battery into the filament at the same rate at which they return to the positive terminal BROWN DEVIL RESISTORS MOLDED COMPOSITION POTENTIOMETER via the plate; so no electrons are really A favorite whit servicemen. these de- Built to last, this Type All Potentiom- lost or gained. pendable, wire -wound, vitreous -enameled eter has a heat -treated, solid -molded re- Now that the mystery of how cur- resistors are easily mounted by their sistance element -not just a film -and rent can flow through a vacuum has tinned wire leads. ToL ± 10 %. In 5, 10, provides unu -wally quiet operation. It been up, us do a little more and 20 -watt sizes. has a 2.watt rating. cleared let experimenting with the apparatus OHMITE MANUFACTURING CO., 4896 FLOURNOY ST., CHICAGO 44 shown in Fig. 1. Suppose Rl is adjusted until our filament just begins to glow a dull red and that R2 is then manipu- lated so that the voltage applied to the se Ríglit with HMIIT plate starts at zero and advances in Rep. U. S. Pot. Off. 10 -volt steps. At each step, let us care- fully note the values of the plate volt- RHEOSTATS RESISTORS TAP SWITCHES age and the plate current. RADIO -ELECTRONICS for

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Next, let us increase the current were heated red -hot in the open air, it WHERE TO BUY IT ... through the filament until the filament would oxidize quickly and be destroyed. is a bright cherry red, and then let us In the second place, if the space be- WHOLESALE RADIO repeat our step -by -step increasing of tween the filament and the plate were of Baltimore the plate voltage, again carefully noting not emptied, the poor little electron the changes in the readings of the volt- would have a tough time trying to meter and the milliammeter. Finally, shoulder its way through the bulky let us combine the results of these two atoms of air and gas which have a mass ill New Low Price! PHILMORE'S observations in one graph, Fig. 3. some 1,800 time that of its own. From this graph we can see that as The two -element tube that we have the plate voltage increases, the plate been studying is a fundamental type, 16" T. V. KIT current for the low -filament -current as we shall note in the next chapter, condition also increases, rapidly at first yet this diode, as it is called, is used 31 TUBE CHASSIS and then leveling off until a further in some form or other in nearly every With Voltage Doubler Pack increase in plate voltage produces prac- radio and television set on the market 1 4 MC BAND WIDTH tically no increase in plate current. The today. Moreover, it is subject to prac- same thing is true after we have in- tically all the ills suffered by its more creased the filament current, but now complicated brethern. the leveling-off point occurs at a higher If the filament breaks, we have no (119.95 value of plate current. For low plate way of raising the temperature to the t,>1 Less Picture Tube voltages, the plate current is practic- emitting point; and "open" filaments :11-1 Stith IO" brackets. ally the same for high or low values of are one of the most common causes of rese inF only Ik1tkit ulth TrNEIt, \ Il. Eli and SOI'NU IF l'HANNELF filament current. tube failure. It is equally obvious that nnplrtrly wired and precisely pre -aligned. Circuits The if , nnilar In ILUITS ami s7UTS. Order Model KP -311.1). total number of electrons emitted any two elements. such as the fila- from the filament depends upon its ment and plate, actually touch each temperature, which in turn depends other, the tube cannot function nor- Save Money! Get Top Quality upon the current passing through it. mally. This "shorted element" route is Sheldon Custom -Made "Telegenic" The total number of electrons attracted one by which many tubes reach the junk T.V. PICTURE TUBES to the plate depends upon, first, how pile. Flat Face, Magnetic Focus and Deflection many are emitted by the filament and, Natural Image! Soft Glow! second, what percentage of these the 108P4 -10" S23.95 attraction of the plate voltage can 12LP4 531.00 win -12" xl FIL 16HP4 -16" S48.50 over from the attraction of the filament CURRENT 13 MONTH GUARANTEE itself. The higher the plate voltage, the higher is this percentage. When our filament glowed a dull red, Save Money On Your a limited amount of were re- electrons PLATE CURRENT Test Equipment leased. When the plate voltage was low, LO FIL CURRENT

QUICK . . . EASY TO ASSEMBLE only a small number of these could be KITS attracted to the plate instead of return- 1 EICO ing 5" to the filament; but as the voltage, SCOPE and consequently attraction, of Model the the $39.95 plate went up, more and more of the available electrons succumbed to its Siren call until finally it was getting () all of them. Beyond this point, an in- -- PLATE VOLTAGE vertical rns,neq,-y Fig. Hotter cathode emits more. cycles to crease in plate voltage obviously could 3- In I m, Ì' 701 lllll not increase the plate current. As was pointed out before, the opera- Provision ' fr , ,fn `;.,r ,,,t,I, When we increased the filament cur- tion of the tube depends upon the ele- rent and raised the temparture of the ments being housed in a good vacuum, filament, we increased the number of and anything that impairs this vacuum electrons emitted. Under these condi- will ruin the operation of the tube. Oc- NEW' SIGNAL GENERATOR KIT tions, it was necessary to raise the casionally minute amounts of gas re- FICO MODEL 320 K plate voltage still higher before it was main in the tube or escape from some signal gen- ..- servicing attracting the total increased output the .rs, nr FM. of the elements after sealing; then un and to pro. of the filament. is videüirc! TV marker Irequen- It apparent that for tube becomes "gassy." Gassy tubes Range lnn ke. to ' r in n hands. wich every value of filament current there cause many headaches in the radio re- ,danmenhlls to 34 qe 400 eerie audio D ñ is a certain value of plate voltage which business, they not always ,uts h,m oKril. pair for are . will attract all the emitted electrons as easy to detect as other defective 6 and beyond which no further increase types. $19.95 will result in more plate current. This Even under normal conditions, the FICO VACUUM TUBE VOLTMETER maximum current is called the satura- electron emission of a filament or cath- tion current of the tube, and it is im- 4 l::, . b i..li ode will fall off after a while, and this 'K. 523.95 portant that the tube be so designed deterioration will be speeded up if the NEW! FICO MULTI- SIGNAL TRACER that this saturation condition is never tube is subjected to overloads. Such re- l,. reached with the normal values of fila- duced emission results in the "weak" $18.95 ment current and plate voltage that are tubes indicated by a tube tester. applied. Poor connections between the leads Wr,te for Free "FYI" aulletin and the tube elements can result in Address Orders to Dept. as -93 or Can Mulberry 2134 "noisy" tubes that make a rasping. Why the vacuum? staticlike sound in the speaker; and if Perhaps you are wondering why the various elements are not held rigid- WHOLESALE there is a "vacuum" in vacuum tubes. ly in place, the tube will often make a MI RADIO PARTS CO., Inc. Emission Tain take place in the open ringing sound come from the speaker 311 W. Baltimore SP. air, but there are two good reasons for when the tube is touched or bumped. BALTIMORE 1, MD. placing our tube elements inside a vac- Such tubes, because they behave like uum. In the first place, if the filament a microphone, are called "microphonic." RADIO- ELECTRONICS for

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Dept. RE-119, MURRAY HILL BOOKS. Inc., 3-RADIO TROUBLESHOOTER'S HANDBOOK 232 Madison Ave., New York 16. N. Y. Enclosed find $ for books checked; or send C.O.D. (in Cuts Service Time in Half on 4 u. S. A. only) and I will pay postman this amount plus a few cents post- age. In either event, it is understood I may return books after 10 days Jobs Out of 5 and you guarantee to refund the purchase price. SPECIAL OFFER: All three of these big This is the most recent of the 3 big Ghirardi books -and the Ghlrardl boots only S14 ($15.50 outside U.S.A.) handiest of all for the man who knows his way around in radio Ghirardi's RADIO PHYSICS COURSE, SS ($5.50 outside U.S.A.) servicing. Just refer to RADIO TROUBLESHOOTER'S HAND- Ghirardi's MODERN RADIO BOOK for specific data on the radio you want to repair. It SERVICING $5 ($5.50 outside U.S.A.) covers common troubles, their symptoms and complete repair Ghirardi's RAb1O TROUBLESHOOTER'S methods for over 4,800 receivers by 202 leading set manufac- HANDBOOK, $5 ($5.50 outside U.S.A.) turers. It eliminates useless testing, saves time on literally hundreds of Address jobs. Over 300 additional pages contain tube data, charts, etc. to help you work faster, better, more profitably on any radio ever made. Contains 744 Name manual -size pages. Weighs almost 4 lbs. Only $5. Use coupon. See money City, Zone, State saving offer on all 3 Ghirardi books! NOVEMBER. 1949

www.americanradiohistory.com Foreign News 412

PRESENTS European Report OUTSTANDING PRECISION By Major Ralph W. Hallows , INSTRUMENT KITS RADIO- ELECTRONICS LONDON CORRESPONDENT

221 -K show was open I was otherwise engaged MODEL in looking anti- guns in VTVM KIT after aircraft 1110 the wide marshes near the mouth of Build this Vacu- Precision the River Thames. I attended my first Tube Volt- um il Tri meter. 15 radio show as a youngster, thrilled by ranges! AC ant rang'°: the marvels of what was then called Oand/í/1Il 0 /1110 /5011 I go now a dyed -in- the -wool /1000 Volte. Ohm- wireless. as meter range: old- timer. I'm pretty well stunt -proof ohms tot tor Zero Center by now, but I get as big a thrill as ever TV alignment. Rig I did out of the genuine advances in burn meter rouble burn met. Double radio, radar, and television techniques triode stahlr, guaranteedg circuiteireuh assures -6p $23.9$ that one is sure of finding at every bridge po-130 V, performance. 6- z 5'... Radiolympia. 9 7 /16' z cycle. Size VTVM w ed The scope of Radiolympia has been FACTORYWIREDbut completely 1.95 Model 221. Same. SAIc_ and tested ...... very much enlarged. This year it cov- calibrated, ered not only broadcasting, but every You Build 'Em In One Evening - form of telecommunications, besides THEY LAST A LIFETIME! HE first Brit- television and land, sea and air radar. ish Radio Ex- A word about TV first. Two important NEW! Sensational TV -FM hibition, in the tendencies were noticeable here. Num- is SWEEP SIGNAL far -away days ber one the virtual disappearance of when broadcasting the small -image receiver using a 5 -, 6 -, GENERATOR KIT was a new thing, or 7 -inch tube and designed to attract Model 360 -K. .t., l marker oscillator with va- wasn't held at Olympia. The number of the purchaser by its low price. Time riable amplitude. Covers all TV and FM alignment receivers in use away back then in 1922 has shown that the smallest image frequencies between 500 '23 kc and 228 mc. Sweep- or (I forget which), cannot have been which folks will accept is one of about width variable from 0 -30 much over 30,000. Nor were there many 45 square inches. The 8 -inch tube is me. with mechanical inductive sweep. All TV and FM Channels marked directly on panel for instan- radio manufacturers. The organizers therefore almost the minimum size in taneous reference. Provides for injection with external signal generator marker. Phasing control Included. felt that a hall of modest size would televisers nowadays, and even that is Vernier driven. tuning dial for master oscillator needs of both public and not overpopular. Many people to directly calibrated in frequencies. 3 -color etched answer the prefer panel, and durable steel cabinet. Complete with all manufacturers. Actually, the show was put off purchasing until they can afford tubes: 6X5GT. 12A1t7, two 6C4'a. Crystal not In- cluded. Sire: Ion x 8. x 6%n. !99.95 almost overwhelmed by the flood of a set giving at least a 63- square -inch Complete Kit. mite 77 visitors. was staged the following picture. And I imagine, is FACTORYBUILT AND TESTED$39.95 It that, rather MODEL 360. Ready to use year in the great London building going to be the standard for mass - known as Olympia, and there it has produced, popular -priced British TV re- 5" SCOPE KIT been held ever since, except during the ceivers. Model 400 -K. Laboratory war 1948. is precision scope, for FM, years and in I can claim an In this connection there an inter- AM & TV servicing. De- unbroken attendance record from the esting advance in C -R tube construction flection sensitivity: .65 volts per inch full gain. very first pre -Olympia show to the by the British General Electric Co. The Horizontal sweep circuit. 15 to 30.000 cycles. Fre- present time, except for 1939. The ex- maximum size of the image that a tube quency response of hoc!. hibition was held that year, but in of given size can show depends largely aontal and vertical amps is from 50 to 50,000 cy- September, 1939, the war began for us; upon how much of its screen is wasted cle.. Graph screen. Op- erates on 110 to 130 volts hence during the few days that the because of the curvature of the glass AC, 50 -60 cycles. 3 -color etched, rub -proof panel. is Sire: S% r 17n z 13n high. 3 -color etched KEYESV11.Lf3 panel $39.95 RADIO SERVICE FACTORY -BUILT OSCILLOSCOPE tang 'Aims, fa+. Modal 400. Fully wired, assembled. and tested$49.9S SIGNAL GENERATOR KIT Model 320 - K. F. r service, lab, and Sdmol use In FM- AM alignment and to pro- vide TV marker frequencies. Ceramic insulated variable condensers. Highly Stable Ilartley oscillator has range of 150 kc to 100 mc with fundamentals to 34 mc. Cnl- plus audio oscillator sppt les pure 400 cycle sine ware voltage for modulation. Large V dial. Easy-to -read calibrations. Easily aligned. Complete with tube.. Ion z ran z 4%n. 3 -color etched panel. $19.95 FACTORY WIRED AND ALIGNED Modal 320. Ready to use $29.95 SEE THESE INSTRUMENTS AT YOUR LOCAL JOBBER Complete simplified instructions and Illustrations come with every EICO Instrument Kit, Making it pure en107- ment to build your own equipment. Nothing more to buy. Anyone can build it. Write for catalog C.

ELECTRONIC INSTRUMENT CO.. INC. 276 NEWPORT STREET Suggested by: Herbert C. Tayb,r, KeyarOle, Va. c BROOKLYN 12, N.Y. "It took me quite a while to train him. lie's worth three servicemen." RADIO -ELECTRONICS for

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A recent intensive survey discloses that among the major television set manufacturers, more than 75% use Sylvania cathode ray tubes! This impressive showing is a tribute to the research and quality production techniques employed by Sylvania. You can take advantage of this ready acceptance by having a complete stock of the various types of these television picture tubes so widely used by set makers -who in turn, of course, sell to your regular customers. See your Sylvania Distributor about the

complete line ! For complete data write Sylvania Electric Products Inc., Dept R -1711, Emporium, Pa.

These leading television set manufacturers use Sylvania Television Picture Tubes Admiral Air King Andrea Ansley Automatic Bendix Crosley DeWold Emerson Fada Farnsworth Garod Hallicrafters Hoffman SYL\N IA Magnavox Midwest Motorola National Olympic Packard -Bell Philco Pilot Raytheon -Belmont Regal Scott Sentinel Silvertone Spartan ELECTRIC Stromberg- Carlson Tele -King Tele -tone Temple Trav -ler Westinghouse Zenith

CATHODE RAY TUBES; RADIO TUBES: ELECTRONIC DEVICES; FLUORESCENT LAMPS, FIXTURES, WIRING DEVICES, SIGN TUBING: LIGHT BULBS; PHOTOLAMPS NOVEMBER. 1944

www.americanradiohistory.com Foreign News

near its rim. To be acceptable to the eye, the image must be nearly flat, and this definitely limits the screen area that can be usefully employed. G -E has developed a new way of making the INVENTORY CLEARANCE glass envelopes of tubes which allows the whole screen to be very nearly flat to within a short distance of the rim. The secondary tendency is toward a WHILE QUANTITIES LAST!! brighter image. People are no longer content to have to draw blinds and cur- tains when they want to use the tele- METERS New, or removed from new equipment, Viser by day, or to switch off most of 0.50 D.C. Ammeter (A) 7 Round. (R.S.1 Ampo. the lights after dark. The aluminized Relay. Stand -oR type. Less Shunt. $6.95 ±500 screen is playing an important part (B) 5" Round (Weston) Zero center Mieroamps. D.C. Blank Seale. Luminous Pointer $3.25 here. Tubes fitted with it are not nec- (C) 314' Fan (Weston) 0 -50 V,D C $3.25 essarily more expensive than others, ID) 3' Round (Trip.) 2 Scale. 0 -15 -300 SI.A D.0 and the process definitely insures a $2.45 l %Ith 15 M.A. Shunt) much brighter picture without the use Sher. Seale. (E) 3' Round (Trip.) 1 M.A. D.C. of anything beyond normal high -volt- (With 30 V. Multiplier) $2.85 age. (F) 3" Round ISimp.) 0.2.5 Amps. R.F. (With Thermocouple) Many a housewife has told me in the (G) 3' Round Stand -off type (G.)1.) 0 -15 past that the thing she would most like 11.0 $2.50 to have was a radio receiver of tri- 0 -:.O Volt, (H) 3' Round Stand -off OTw 1(:.1:.( DC 9w c4 y.c. t( angular cross section, which would fit into a corner of room, 1J) 2" Round !Weston) .507 1ogr. Seale 0 -10 oul 01. anpin . t,a°,nernr and Rm... AI lot 75 80 mom C.W., ,n. a standing on a D.C., Wood Case $2.35 1 -0its (Rash F.S. 1.2 51a. orporahny Mn. I.e?.rn -3 row mukpufpor. ?ab.-Cryrwl wall bracket if a table model, or on cormetIont IrWM -Impro.ed r°p.nereo.. tea. vow -WIrn (K) 2" Round (Simp.) 0.8 Amps. 11.F $1.65 yd.DC V. the floor if a console. Some years ago 110 pew gr dy -a "ed la rton., beaSue."+ (L) 2' hound (Gruen) 0-150 Tolls 1).1' 51.50

www.americanradiohistory.com Sound Advice From One Serviceman To Another!

MACS A dí. REPAIR Chow.% Montana

Inc. Publisher. Rider good F. that John Street effect are Canal circles to the themselves I 480 N. Y. {or since York 13, business such rumors New aroundd into such have Bone cell si e running L can am Just Bradstreet, Rumors radiomen a halt I I think Dun k the .L ayear and pool. Since many starving that red ink take after line customer to to part could a tips ám anfrot deepas cashblycash-on-the-line e, on som radio as a aped ass the easy it 115 t ma are pr0bablYtmen1a still ors department a entering wood itlsor contemplateontemP above-mentionedbove- your a good a of now in capital. advantage who are GOOD some working and a too ex haohave c stressed business. must test equipment, be are repair re cannot Jebs radioreal adequate lib tough man o{ radio, the entering dBe ood ratebs and A B. the J R That mean and the LIBRARY. Jobs. operating' REFERENCE right is because library crackers radios in much, on radio changes setting ors made all dependent are tawf cr cases there found In most according that havee If the manufacturers Unfortunately key in Rider's. haes5embled cot letede manuals included re-assembled only Rider'sR1 are the use °{ and those changes discardeddiscs do with the set. should much t0 changes has end Rider's' mind other is completed schematic. work on f`NIWYHI" the Information with which of speedy repaidodone o you the give This is not a code. is SPEED the interestLt. with manuals seal customers. in It The In PLEASED manuals Plea tea money income. is It. Rider's mean extra ory You simply an abbreviation of a who rice used means satisfactoryac A customer P and if advertisingill proves very important condition in Paying 8 Hood radio that every word-of-mouthcord work the operating life of a serv- and good advartwslnB that is nearly BUSINESS doing conscientiousonscieáña ice shop. HIWYNI means and hat many of REPEAT business manuals. HAVE IT WHEN YOU NEED IT. rOPOS Rider sure Rider's your t am set of get without In It applies to many things, will operating the business a comp shops and failure but especially to RIDER are newcomers investmentsBass matrue an Make There between rho MANUALS. sure that especially smeBnwillrill thedifference the boys you have a complete library newcomers some of also the will help and of RIDER MANUALS on hand manuals it will their their business. that leftLett in improve at all times. their with th a hair is of this little help written chat Q` /'¡eZ(, L have log out corvo our business. iJ busy will to // 0 G are hopea that a better name the give truly, YcCOARLE with thus Yours A. E. work

These RIDER books are the result of twenty years of specialized publishing for the Radio Servicing Industry Television Manual, Volume 2 (Plus Automatic Frequency Control Systems. Inside the Vacuum Tube, 424 paces. "How It Works" and Index) .$18.00 144 pages $1.75 Illustrated $4.50 Television Manual, Volume I (Plus Servicing Superheterodyne.. 288 pages, CathodeRay Tube At Work, 338 Pages, "How It Works" and Index)..$18.00 illustrated 92.00 illustrated $4.00 PA Equipment Manual, 1 Volume $18.00 An- Hour -A Day with Rider S : Servicing by Signal Treeing Volume 19.80 360 XIX "Alternating Currents in Radio Re Pages, illustrated $4.00 NOTE: Are yep your copy Volume XVIII 'D.C. Voltage Distribu- Volume Servicing by Signal Treeing. (Span- I "Sueeessfulreceiving eivingn "7 It's XVII 16.50 tien "Resonance and Alignment" ish 404 page.. Volume 8.40 "... Edition), Illustrated Rider's own publicetìon of Interest XVI . "Automatic Volume Control" 96 Volume XV 19.80 $4.00 to every serviceman In it you will pages each each $1.21 Understanding Vectors and Phase, 160 Volumes XIV te VII (each rolumel nl1 of the circuit changes 1In Servicing Reeei By Means el Re pages, paper binding, 99c cloth.6 I.89 etc... as soon they are re 16.50 sistance 203 s Volume VI $12.50 Measurements, pages Vacuum Tube Voltmeters, 180 napes. leased. It's FREE: $2.00 Illustrated Abridged Manuals I to V (one volume) $2.50 $19.8 Aligning Philce Receiver., Two Vol- Understanding Mlerowaves. 385 Record Changers and Recorders. umes. Vol. 1, 1929 to 1 936. 176 Illustrated $6.00 . 11, 1937 NOTE: The Mallory padlo servl ee Master Index, Covering Manuals. Vols. Vol. to 1941. 200 A. C. Calculation Charts, 160 pay a h I to XV $1.50 pages. Each Volume $2.00 9V," 12" $7.50 referodienceet aonlytone source Of radio TV, How It Works. 203 pales 02.70 Radar - What It It 72 pages 61.00 High Frequency Measuring Techniques receiver schematics -Rider Man TV Picture Projection and Enlarge FM Transmission and Reception, by Using Transmission Lines. 64 paga. ate. ANOTHER NOTE: The c Di ment John F. Rider and Seymour D. Us illustrated $1.50 Capacitor Manual for Radio Servit. Installation and Servicing of Leg. tan, 416 pages, illustrated $3.60 The Meter at Work. 152 pages, lllus rey, 1948 edition No. 4, makes Power PA System.. 208 pages $1.89 Broadcast Operator's Handbook, by trated $2.00 refer. n to only one source of re The Oscillator At Work. 256 gapes. Harold E. Ennes, 288 pages, illus. The Radio Amateur's Beam Pointer ceivernschematics-Rider Manuals. illustrated $2.50 tested $3.30 Guide. $1.00 JOHN F. RIDER PUBLISHER, INC. 480 Canal Street, New York 13, N. Y. Export Agent : Rock. International Corp., 13 East 40th Street. Neer York City Cbles A RLAB

RIDER MANUALS mean Successful Servicing!

NOVEMBER, 1949

www.americanradiohistory.com 66 Foreiqn News

choice of three local programs, the Home Program (middle- brow), the Light (low- brow), and the Third (defi- nitely high-brow). There are scores of possible alternatives from the conti- nent of Europe, but fading, static (man -made or natural), heterodyne whistles, and other forms of interfer- ence severely narrow the choice. The number of worthwhile alternatives available to the discriminating listener is thus comparatively small. For these reasons the radiophonograph is very popular and there is great encourage- ment to manufacturers to develop its possibilities in the fullest way. Phonograph record nowadays are ap- pearing in an almost bewildering di- because versity of types. Diameters range from 10 to 18 inches; playing speeds from TELREX CONICAL BEAM ANTENNAS 3313 to 78 revolutions per minute; max- "V" imum audio frequencies from 8,000 to are performance- proved 20,000 cycles; recording systems from the standard to the microgroove; play- Up to 200 miles over land and up to ing times from 2% minutes upward. 300 miles over all -water TV paths The demand here is for instruments that can deal faithfully with records For both remote or high signal areas, Telrex Conical Window of a wide variety of different types. Mounts, Stacked Bi- Directionals and Stacked Arrays are the an- This year's Radiolympia showed that service men can depend upon for consistently the demand is being well met. There tennas dealers and was, in fact, at least one instrument good results. Each type is thoroughly engineered in the laboratory, whose makers claim that it can play service- tested in the field and built for long service life. Using Telrex any type of record now on the market. Conical Antennas on every installation is one sure way to better, The discriminating listener, by the brighter pictures and a minimum of service call backs. Ask your dis- way, was well looked after at Radiolym- tributor for catalog or write direct outlining your antenna problems. pia, for he could try out the radios, the phonographs, or the radiophonographs in sound -proof rooms specially provided TELREX ANTENNAS COVER CHANNELS 2 TO 13 for such purposes. And while he was AND FM -NO HIGH FREQUENCY HEAD NEEDED thinking over his choice he could find diversion by flattening his nose against TELREX TELREX MODEL 2X -BD the glass walls of BBC's television stu- dio or by gazing at the pictures of MODEL 1X-BD Ii- Directional Stacked London "printed" on the PPI tubes of Conical "V" learn sets with the aid of a scanner Vertical Angle radar Bi-Directional Ni -Gain Low revolving above the roof of Olympia. Conical "V" horn Extremely High Signal to Broad land Full Audio Noise Ratio and Video land Pass Constant Center Impedance SUB -MINIATURE Low Vertical Angle Uses 72, 150 or 300 Ohm PRINTED ELECTRONIC CIRCUITS Non -Varying Center Impedance Transmission lines

2 to 1 Front to lack Ratio Universal Mounting Clamp Components and assemblies ovailobte from stock! Circuits printed on ceramic, plastic and paper Uses 72, 150 or 300 Ohm FOR THE ULTIMATE IN BI- Transmission tines bases Designed for miniature rodio and elec- DIRECTIONAL GAIN. USE tronic applications. Universal Mounting Clomp TELREX MODEL 4X BD. Single Stage Circuits Voltage Amplifier PENDING PATENT SAMPLES Power Amplifier .65 s 1.90 s .255 in. TELREX MODEL 4X -TV TELREX High temperature resistors, silver leads and capacitors fired on special vitreous bass. Com- 2 lay Uni -Directional SUPEREX plete amplifier less popular brand subminiature Conical "V" loam tube $2.99 each. Stote amplifier desired. C.O.D. orders. Broad Band -Full Audio and Video With antenna PLASTICS A ELECTRONICS COMPANY Band Pass angle arm adjust- 272 Northland Ave. Buffalo I. New York Low Vertical Angle, able through 180° Minimum Reflections azimuth arc. Maximum Signal Far high signal area. "ALL -SEE" to Noise Ratio Window, wall sr attic mounting, TRANSPARENT

to 1 Front le lock with flexible orientation possible. 2 -piece BOXES! Ratio All Frequencies arm is provided. Short arm is useful for parallel- Safe and Loss -Proof Containers for Non-Varying C Impedance to -wall orientation. Second arm permits ether than Screws Nuts Universal Mounting Clamp parallel orientation. Small Parts Guard those small parte -so easy to lose and very hard to replace -with a set of these "All -See" Plastic COPYRIGHTED 1949 transparent containers and rovers. Assure easy and ALL TELREX ELEMENTS ARE MADE OF LASTING DURAI safe storage. Pay for themselves, AMCKILA a Each set contains: one box. 1 74" sq.: Bee boxes. l':" if 7 s 15 /16': four boxes, 15/16' sq. 10 boxes in all. OUTSTANDING Transparent case. Order a set for yourself aeq and s set for that tinkering of yours. TELEVISION Inexpensive and unusual gift. No ee _4 for each order p.O.D.'... please. Remit $1 BEAM t complete set It for 151. s r send for FRta. Irate! R,'. r CARGILLE, Dept. RC, 116 Liberty St. A S B U R Y P A R K 10, N E W J E R S E Y New York, N. Y. RADIO- ELECTRONICS fo

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NEW CATALOG SO HOT IT NEEDS ASBESTOS COVERS! 5 SPEAKER BARGAINS - Big Values Speak Volumes ! IT'S FREE! 15" PM SPEAKER 12" RCA SPEAKER ll here else can you buy a Renu- Here's Mr. Big among c. brand new RCA 12" speaker speakers. 25 -watt rating .,t this price? 15 watt capacity. guarantees power to spare t; oz. Alnico V magnet. Voice with a minimum of distor- coil impedance + tion. Massive lb. per- ohms. A terrific val.vat- I manent magnet: 6 to 8 ohm ue. Don't pass it up. 54 voice coil: extended bass and No. 99N7023R (weight treble range. Dollars less lbs.) than anything in its class! 6 10" ALNICO PM SPEAKER No. 99147034R '1295 Fine performance at a new low in price. (weight: 9 Ibs.l 10 watt rap. 6.8 oz. Alnico V magnet. J Voice coil impedance of 3.4 ohms. No. 99N7019ß (weight: 5 lbs) 121e ALNICO PM SPEAKER 4" x 6" OVAL SPEAKER Ilandles 14 to 18 watts with excellent sound quality. Alnico V 1.47 na. 3cH" c 47^I," BUMPER CROP OF VALUES 6.8 oz. Alnico V magnet, 6 -8 ohm mounting centers. Dustproof /¡ voice coil. Ideal for use with FM 5 cap. 3 -4 ohms V.C. impedance. S L 9 VV PROVE U -PAY LESS AT receiver or P.A. system. Rated 3 watts. 41 peak. Less transformer. No. 99H7010R (weight, 6 lbs.) No. 99N7012R (weight: 3 bs.) LAFAYETTE!

Whether you're a service man, SAVE ON THESE 2 MOTORS ham, advanced amateur or be- 1414 4 ginner, you'll find this practical EVEN 4 Equip- TQeue encyclopedia of Electronic / ß`t4 / SPEED ment the most useful "tool" in POWER FILTER your kit! All the latest on Tele- PHONO MOTOR vision, High Fidelity Radio and TRANSFORMER CHOKE Phonograph Systems, P. A., Test Equipment, Parts, Tools, Electri- Rim-driven. 9" turntable. .t A teal bargain! Single shell mtg. Excellent quality 25 Henry Filter speed (78 rpm). self-$ w electrostatically shielded. Extruded Choke. 60 M.A.. 200 ohms DC resist- cal Appliances, etc., etc. Starting. 110 V., 69 nuar . for 2 -hole mounting. Primary ance. Unshielded. strap type cycles only. $ L shell ing. Overall dimensions It's the most complete catalog in 117 V. 50/60 cycles. Secondary out- No. 99N8003R (weight: 6 lbt.I 211s" x 2'" x 1% ". Mtg. our 29 years of saving money for put: 600 V. CT at 50 C renter 2% ". Return coupon mil, 6.3 V. at 2A. 5V. No. 991451558 (weight: 8 or .1 men like yourself. HP MOTOR 1/20 CT at 2A. Color -coded 5139 now for free copy - and also to Many uses for this leads. . order popular items shown here fine 1/20 hp motor. No. 99N5156ß (weight: 3 lbs.$ CONDENSER KIT 'uiy! 2900 rpm. 115 v.. (a few of thousands that always 50.60 cycles. AC. cost less at Lafayette.) 2%" x 2%" x 3ttt" NAME BRAND Pick tap high. t/4" top iniallty Shaft co long. tubular SHOP IN PERSON AT ANY OF Y4" 6 -VOLT VIBRATOR denstrs fore song. Wax a 1 , LAFAYETTE'S OUTLETS - Impregnated. G ^t" $389 Popular universal 4- NEW YORK: 100 Sixth Avg. L I nd. Rd. N. 90N7079ß ( weight: 3 Ibo prong vibrator -re- t-IndoeU ! 542 E. Fordham From .002 places the great majority mid. to .5 CHICAGO: 901 W. Jackson Blvd. of vibrators, including dd. Long. B05tA pigtail ATLANTA: 265 Peachtree Street standard,. / lead. fleets RSIA DELCO VOLUME 294. 4 -4. Radiart I Mallory C BOSTON: 1 0 Federal St. 5300. SO -1. Utah NP- Ave. No. 9914278R ( weight: I t/, lbs.) MJ 1 NEWARK: 24 Central CONTROLS - 42. Delco 5.040.000. 5.052.378 and Meissner n ® ® PRICE EOI. Stock up and save! STOCK NO. OHMS EACH No. 99N3950R (weight: 8 or i 98 99N2155R 50.000 24t 99N2157R 100.000 24: 99N2160R 300.000 22C SOLAR TYPE DY LAFAYETTE RADIO, Dept. 1K -9 99N2161R 500.000 27t 901 W. Jackson Blvd., Chicago 7 99N2162R 600.000 27t ; 100 Sixth A , Now York 13 99N2165ß I Metohm 27C ELECTROLYTIC CONDENSERS 99N2167R 2 Metohm 27C Cheek here for FREE Catalog (Please don't check It you have already gotten 99N2168ß 3 Metohm 27C 25c each 10 for $225 your catalog.) 99N2172R tapped at 100.000 29t 500.000 Please 811 attached order. I enclose 3 In postal note. money NO. CAP MFD. VOLTAGE 99N2174ß' 500.000 tapped at 200.000 27e STOCK order or check. I am Including shipping charges based on weight and none 29C 99N2176R I Metohm tapped at 100.000 99N3486R 30!30)15,30 300 50 99N2177ß I Metohm tapped at 200.000 271 99N34455 504 50/40 150,25 NAME 99N2181R SPST Snap -on Switch Be 99N3475R 30+15+15+15 300 99N3452R 10+15/20 350/25 ADDRESS switch Will not take 99N3492R 40+40/5/20 350/250/25 CITY ZONE STATE

NOVEMBER, 1 9 4 9

www.americanradiohistory.com 68 New Patents MODULATION SYSTEM Patent No. 2,463,275 TELEVISION KITS Roy A. Henderson, W. Collingswood, N. J. (Assigned to Radio Corp. of America) \ J O INSTRUMENTS A high percentage of modulation with littlt distortion is produced by this circuit. Thetrans- mitter has a grounded -grid final amplifier and a It screen -grid exciter. Since the final does not re- verse the polarity of a signal applied to it, the r.f. at the final plate is in phase with the r.f. 4.16 at the exciter plate, making it possible to modu- late three elements simultaneously: the excite: Build it screen, the exciter plate, and the final plate. 11= in 1 Day! GIANT 160 Sq,In. PICTURE; Has 16" PICTURE TUBE MODEL W 16RS TV KIT

(All Glass Picture Tube, giving bright, clear, steady picture.) LESS THAN $200! KIT COMES SEMI -WIRED and SAVE UP TO 1/2 on the cost of equiva- ALIGNED. lent picture -size sets. For NEW LOW Can be completed in one day! PRICES, see your Transvision Outlet SAVE by installing the set yourself. listed below.

The Transvision Improves Installations! ! Saves 3/r the Work! ! Has numerous features and advantages. including -11) Measures actual picture signal strength (2) Permits actual picture signal measurements without the use of complete television set. (3) Antenna orientation can be done exactly (4) Measures losses or gain of various antenna and lead in combinations . . (S ) Useful for checking receiver re- radiation (local The modulation transformer has two secon- oscillator) . (6) 12 CHANNEL SELECTOR daries. One modulates the exciter screen ; the (7) Amplitudes of interfering signals can other modulates the plates. The audio voltages be checked . (8) Weighs only 5 lbs. . applied to the exciter elements should be propor- (9) Individually calibrated ... (10) Housed their d.c. potentials for lowest distortion. in attractive metal carrying case 11) Initial tional to ... ( should have cost of this unit is covered after only 3 or 4 The final filament transformer installations . . . (12)Operates on 110V, 60 adequate shielding for low capacitance to ground, Cycles, AC. since the filaments are at an r.f. potential above NEW LOW PRICE ground. Model FSM -1, complete with tubes Nef 579.50 SAWTOOTH GENERATOR 5" OSCILLOSCOPE NEW: Patent No. 2,458,367 WIDE George W. Fyler, Lombard, and BAND, Garth J. Heisig, Chicago, Ill. SERVICE- DEALERS , . HIGH (Assigned to Motorola, Inc.) GAIN A multivibrator instead of a blocking oscilla- Be the TV Sales Center tor is used in this vertical deflection circuit. It provides push -pull output to the electrostatic and Service Center in your community! plates of a kinescope. Relatively small coupling IDEAL capacitors to the deflecting plates of the kine- at a Beat competition profit. FOR scope are possible. multi - Stop being undersold -by anybody! TV Tubes V1 and V2 forms a free -running vibrator at approximately the frequency of the Here's a real opportuni'y to MAKE MONEY in vertical sync signals which trigger VI. There- qualify, you con the Television. If you can become fore is possible to maintain sync in the pres- Transvision Television Center in your community MODEL it - ence a certain amount of noise or with weak and BUY TV and RADIO PARTS ATJOBBER PRICES. 450A of no investment required.This offer is open sync pulses. Capacitor Cl charges while VI is Practically NET only to service -dealen in territories where we do not have on authorized distributor. .005 /exv Contact Transvision Outlets listed below, or write 250V to New Rochelle, for details on Tronsvision's "TV Center Plan." DO IT TODAY! $99 BMEG SYNC VERT,' SEP PLATES wAILTourinnsoti.on pi; tee, OF TRANSVISION, INC., Dept. RE,NEWROCHELLE,N.Y. ic s5% hlanerradst of tM issi snips tht T VI NNE SEOPE For FREE 20 -page TV BOOKLET and CATALOG SHEETS, SEE YOUR TRANSVISION OUTLET! CALIF: 8572 Santa Monica Blvd., Hollywood 167 -01 Hillside Ave., Jamaica 3471 California St.. Son Francisco. 75 Church St., New York City DEL: 4 East 15th St., Wilmington 606 Central Park Ave., Yonkers FLA: 42 Southeast Eighth St., Miami 622 No- Salina St., Syracuse OHIO: 901 Roce St., Cincinnati ILL: 1002 So. Michigan Ave., Chicago 2001 Euclid Ave.. Cleveland MD: 1912 No. Charles St., Baltimore 53 W. Norwich Ave., Columbus MASS: 1306 Boylston St., Boston PENNA: 235 No. Broad St Philadelphia MICH: 23216 Wilson Ave.. Dearborn 620 Grant St., Pittsburgh N. J.: 601 Brood St., Newark 700 N. Y.: 1425 Boscobel Ave., The Bronx TEXAS: Commerce St., Dallas 485 Coney Island Ave., Brooklyn CANADA: Hamilton, Ont. RADIO -ELECTRONICS for

www.americanradiohistory.com New Patents 69 blocked and discharges abruptly svllcu the tube conducts. The sawtooth voltage is amplified by V2 and applied to one of the kinescope deflection plates. V2 and V3 are coupled by a differentiating net- work Ito sharpen the pulses( and a voltage di- vider to reduce the input to V:1, which feeds the THE "ALL PURPOSE" deflecting plate. The voltage outputs from V2 and V3 must he equal and opposite. TELEVISION KIT 10" - 121/2" - 16" BACK GUARANTEE LESS TUBES MONEY FEATURING Latest Type r Circuits ACC-Automatic Gain Control icture and Sound Automatically Locked Sound Cannot Drift N on M is roe nonio Stagger Tuned I.F. for Mac. Cain and Ease of Alignment 12 Channel Tuner Electromagnetic Focus and Deflection Automatic Stabiliaed Synchro-Lock Circuit Nolds Picture Stady Voltage Regulated Circuit for Stability COMPLETE WITH ALL TUBES erne clarified stanrbyetage pletures and schematics b. Insure :... of construction. fuarauteed to work. b soy- fa:u.k e:uarantee -buyo n inspect it. If you don, 10" KIT $134.50 think It's the twit bun the market-return Ono.. it 121'2" KIT $149.50 within 5 days and your money will be refunded. All prices F.0.D. New York. 2fr'e deposit with order. 16" KIT $169.50 IMMEDIATE DELIVERY

SOVEREIGN TELEVISION CO 5SUC New Utrecht Ave. Bklyn 19, N. Y. "Did over $5,000 additional business installing ESPEY Ordinarily, large coupling capacitors are chassis" De Young, Ithaca, N. Y. needed to pass the 60 -cycle sync pulses to the kinescope. Small capacitors distort the wave so THERE ARE THOUSANDS OF OUT -MODED RADIOS IN YOUR "BACK that it looks like b instead of a. A feedback cir- YARD" JUST WAITING TO BE REPLACED -AT YOUR SUGGESTION cuit compensates for the attenuation of the low frequencies slue to small capacitors. A large Here is the custom -built AM -FM chassis that means BIGGER PROFITS for you! resistor (30 megohms) feeds back voltages from V:; to Cl. As Cl approaches the end of its peri- The NEW ESPEY model 511 odic charge, the V3 anode is at maximum posi- FEATURES tive potential and therefore feedback is greatest. beginning of the charge feedback is mini- 1. AC Superheterodyne AM -FM Receiver. At the 2. Improved Frequency Modulation Circuit. Drift mum. The feedback voltage is shown at e. When Compensated. curves h and e are combined, a grsnl sawtooth 3. 12 tubes plus rectifier and electronic Tuning Indicator. tubes. a is 4. 3 dual purpose produced. 5. Treble Tone control. is -pass net ao rk to attenuate the C2 -1t3 a low 6. 6 -gang tuning condenser. horizontal line pulses. RI adjusts vertical picture 7. Full -range bass tone control. size. R2 controls the frequency of the multi - 8. High Fidelity AM -FM Reception. vibrator. 9. Automatic volume control. 10. 13 watt (max.) Push -Pull Audio Output. 11. 12 inch PM speaker with Alnico V Magnet. 25 watts rating. GENERATOR 12. Indirectly illuminated Slide Rule Dial. POLYPHASE SPECIFICATIONS 13. Smooth. 6ywheel tuning. Patent No. 2.460,790 tubes, an- If. Antenna for AM and folded for FM Supplied ready to operate. complete with Reception. Charles W. Jarvis, Washington, D.C. tennas. speaker and all necessary hardware for mounting 15. Provision for external antennas. (Assigned to the United States of America in a table cabinet or console. including escutcheon. 16. Wired for phonograph operation. 17. Multi-tap trans., 4 -8 by the Sec'y of the Navy) Power requirements 105'125 volts AC. 50 60 cycles. output -500 ohms. os represented 18. Licensed by RCA. Power consumption -85 watts. ro. Subject to RMA warranty, registered code symbol polyphase is electronic rather .174. This generator Chassis Dimensions: 13'2' wide a 8 "," high a I0" deep. than mechanical. Its output is weak, but ampli- Carton Dimensions: units) 20 a 14'2 x l0., inches. fying stages may be added to bring it up to 117 (2 Makers of lino radios since 7921. volts if desired. The circuit Mown here generates Net Weight 16'2 pounds each. three phases, each of the tubes contributing one Sold through your favorite parts distributor. of them. Write for Catalogue K -11 Contain- MANUFACTURING COMPANY, INC. B+ ing Complete Specifications on 528 EASL 71nd Si REEL, NEW YORK 11, N Y This and Other Models

EASY TO LEARN CODE SURPLUS EQUIPMENT It is easy te learn er fnrrrase speed TROUBLE SHOOTING MANUALS with an innmemvraph Code Tearhrr. .tti,l, lbe nulrkrst and +t or :,e- (Includes Schematics) ttt tie 9luul 4 to low E'u 1+ glut. :nlvune1 -,11.111 .%% Ill B(.-348 Receiver l,le tape1' frout I Ciunel'. .11,11111e t II1-779 (SuperProI Reeeiter' I" Moo :d I a.. - ' :dl ,Wneet-. td l -..t'm"ttl'N, sbsav., SCR-52'2 Trtulsntitter- rereher

I .nh n, ,tI1V. B(: -6111 Transmitter ENDORSED BY THOUSANDS! ANY BOOK $1.00 EACH r r: r I loo r,,aaseI [4 hut... ' tie : 1 :u,;.df : \ Add for tam , ,tres :"t, ,a Quantity Ditaunt : ,i. ,tï ùï'iur- s hate 30 OUTPUT he u'l u rsn,:a °aï iL , ,..et, FL-8A Filter -51.37 Each stage has our It -C phase shifting net- Write. for catalog work. If each stage is designed to shift the INSTRUCTOGRAPH COMPANY LECTRONIC RESEARCH LABS. is 3611 degrees. voltage by 120 degrees, the litai 1021 -E t 'all nw hill St. Philadelphia 23. Pa. Since the output of the last stage is in phase 4;01 Shea idas Rd. , Dept. RC. Chicago 40. III. with the input to the first. and is fed back to it. oscillation takes place. Y, .,,r name on ,tr Marling List & As in any phase -shift ,seilltor the fre- PEN -OSCIL -LITE ney may be varied by .hanging the grid 9LP1 Cathode Ray TUBE $1.00 Extremely convenient test oscillator for all radio servicing; alignment Small as a pen Self leaks R. For convenience all three may be Magnetic focus -deflection: 7700 V. anode, War powered Range from 700 cycles audio to over ganged. Surplus: JAN; New, guaranteed, wt., 7 Ibs. 600 megacycles u.h.f. Output from zero to 125 Individual phases are taken from potentio- V. Low in coat Used by Signal Corps & LUCITE write tor Information. meters in the plate circuit. Each should be POLYSTYRENE adjusted to give the same amplitude. P controls cut. machined 6 engraved to your specs. GENERAL TEST EQUIPMENT the over -all amplitude by governing feedback GOULD GREEN, 254 Greenwich St., N.Y.C. - 7 38 Argyle Ave. Buffalo 9, N. Y. to the first stage. NOVEMBER, 1949

www.americanradiohistory.com 70 New I cviccs - OP

THREE -SPEED VIBRATOR FOR PHONO MOTOR TRANSFORMERS TELEVISION TESTING Alliance Mfg. Co., Chicago Transformer Division, Alliance, Essex Wire AND SERVICING Ohio Corp., Model 1 is suitable for playing rec- Chicago 18, III. ords at 33-1/3. 78, or 45 r.p.m. The A new line of replacement vibrator Advanced shift lever hos two positions and a transformers for automobile radios has reversible disc allows for the third lust been introduced through jobbers. practical The units are exact duplicates of the originals, allowing installation without engineering extra holes or components. All trans- formers ore sealed in drawn steel coses gives you for shielding and moisture protection. HIGH -GAIN BOOSTER Astatic Corp., Conneaut, Ohio The Channel Chief model AT -I is a four -tube television booster with much higher gain thon ordinary boosters. The is said to be free of speed. motor Gain of all twelve channels is uniform. vibration and wow. E"er a 9- or 10-

inch turntable is fur: - d. SIGNAL TRACER KIT NET PRICE $12750 Electronic Instrument Co., Inc., Combines the two essential instruments Brooklyn, N. Y. needed in television testing-alignment The Eco model 145 permits audible complete oscilloscope and a complete -service. A signal tracing of r.f., i.f., FM, audio, sweep generator that can be used independently. Tee and video circuits up to 200 mc. A test Vee 90 combines two units for compactness and -meticulously portability speaker is built into the case. A high engineered in advanced design and construction. Oscilloscope also has its own variable linear sweep. Sinusoidal sweep with phasing control for use with internal RF sweep generator when testing band pass charocteristics. Synchroni- sation provision for either internal positive, external or line frequency. External jock provided for trace blanking. Requires 10 volts of negative pulse to blank a normal intensity level trace. Independent sweep generator has a center fre- quency range of 1.5 to 45 megacycles giving a choice of any IF frequency desired. The bond width can be varied continuously from 0.5 KC to 7 MC. Attenuation of RF is continuously variable from 0 to 500 millivolts and the output is applied through low loss coaxial cable. Traveling detector probe is included Dual tuning controls ore provided for for observing signal at any point of the RF Circuit under test. 105 -130 volts 50 -60 separate adjustment of sound and pic- cycles. Weight 25 lbs. Size 14 x 18 x 121/4 inches. Finished in attractive hammer - ture signals. The dual tuning is said to tone grey. Supplied complete with tubes, probe, coaxial output cable and improve the over -all selectivity so that operating instructions ready to operate much interference is minimized or lün n .,r 1. sr !. eliminated. Another control varies the booster's gain so that the receiver is not overloaded by strong signals. The RADIO CITY PRODUCTS CO., INC. on -off switch controls the internal freauency probe is provided. The instru- power supply and also removes the ment is isolated from the power line booster from the antenna circuit. transformer. 152 25th 1, ON a WEST ST NEW YORK N. Y. TELEVISION TOWERS TELEVISION Penn Boiler & Burner Mfg. Corp., TRANSFORMERS Lancaster, Pa. e More leading engineers and Merit Coil & Transformer Corp., The teletower is triari .- each sec. tion being formed of three pieces of Chicago 40, Ill. 3A-inch, 18-gouge steel tubing braced A complete line of replacement hori- inch -thick Standard sec- technicians have built oscillator by 1/4- strops. zontal and vertical blocking 10 feet high, from which a receivers tions ore transformers for television is tower of any reasonable height may now available. Units may be hod for Tech -Master for their own use than be constructed. Bases ore available for any receiver. flat mounting or for placing on o sloped roof. any other Television Kit RADIO HYPODERMIC 3 -SPEED CHANGER the best! Walter L. Schott Co., want Beverly Hills, Calif. Cornet Corp., you Chicago, Ill. best ... The Wolsco Confactens Injector is a th e hybrid tool with the hollow needle of o This fully c c changer plat. hypodermic and the rubber bulb of an all records available today, 7 -, 10 eye dropper. It is useful for getting and 12 -inch and 33 1/3, 45 -, and 78 cleaning fluid or lubricant into tight places in a radio receiver. The cover of a volume control need not be opere 1. TECH- MASTER SOLDERING GUN Weller Mfg. Co., deluxe 630 -TK TELEVISION KIT Easton, Pa. RCA The WD -250, o new version of the with the original 630TS Circuit Weller soldering gun, is rated at 250 Supplied complete with genuine RCA pert: 98% assembled. Ultra- simple wiring dia- grams make it a simple matter to finish the r.p.m. All records are changed by the final wiring in a week -end. For all picture edge-push -off method. Two spindles e furnished, one with the standard tubes from 10 to 20 inches. diameter for ordinary records and the other with a diameter of P/z inches for There is one TechMaster RCA 45.r.p.m. discs. A two-stylus crys only ' tat cartridge 'h id j ustment plays . - - accept no substitute! all records .'.. . , force of 6 to B grams. A v. .. rs used. At all leading distributors. Write for name of your nearest distributor. LOW -COST Few choke jobber territories still available TRANSFORMERS Audio Development Co., South Minneapolis, Minn. watts as against the 135 watts of the The Yeoman line of transformers is TECH -MASTER PRODUCTS CO. first model, Especially suited to radio designed to afford economy along with and television work, it heats in five high performance. All have open -frame -1 I C1.3 Broadway, Dept. RC New York 13, N. Y. ,/ seconds, and has a chisel head. The construction and 10 -inch leads, Im- bulk hos not been increased, and little pedance- matching, in pjt output, and weight has been added. power tronsfor --.---s tided. RADIO- ELECTRONICS for

www.americanradiohistory.com 71

Amazing SUPREME Values in

- ( )ffen Seeded f,ffen - .Vesd - New TELEVISION Manuals 1949 1948 t)47 F. N. All three giant Television Manuals shown at the left I"rlevi-i(1, d are available to you for only $8, total cost. nothing else Television Television for you to pay, nothing else to buy, and we will even prepay the f Mane" shipping charges. (Or you can buy these .- manuals separately at only $3, $3. and $2.) Take ad- vantage of this amazing Supreme offering to step into Television at a tremendous saving. For over 16 years, radio servicemen expected and received remarkable values in Supreme Publications service manuals. And now, the three -volume Television and F.M. series beats all previous bargains. Only a publisher who sold over one million of various radio manuals can offer such bargain prices based on stupendous volume -sales. New 1949 TELEVISION 1948 T -V MANUAL 1947 T -V L F.M. FIND -FIX ALL TELEVISION FAULTS Use Ibis new giant hand- In this mammoth vol- " Here is your manual of book of television servit ing ume you have practical Instructions for trouble- Use these timely television manuals as your guide to as your guide to quirk fault factory sen ire data on all shooting, repairing, and quick fault finding and repair of any television set. finding and repair of any popular 1949 T -V sels of alignment of all popular modern T -V set. Eliminates guesswork -tells you just where to look Easy -to- all makes. Let this man- 1947 F.11 and TELE- and what to do. Cuts hour -wasting jobs to pleasant understand description of ual show you how to make VISION sets. The F.M circuits, pages of test pat- needed tests, guide you in data covers timers, AM- moments. Use test patterns for quirk adjustment. or terns. response curves, carrying out adjustments, FM combinations, and all look up probable cause of trouble in the pages of hints alignment farts, waveforms, point to probable trouble other types of F.M. cir- after simply observing fault in video picture. No equip- voltage charts, service hints, spots, indicate location of cuits. Most complete in- ment needed with these tests. Or use your voltmeter hundreds of diagrams many all parts, trimmers, and compare values with many voltage in the form of giant and forma lion on various meth- charts included. double controls. includes ods With an oscilloscope spread blueprints. Here you hun- of F.M. alignment A you can get waveforms shnilar have approved factory data dreds of c h a r t s, wave- great deal of material on to hundreds illustrated using test points suggested and on every popular T -V set. forms, photographs, and popular T -V sets including In a flash locate what used -to -be a hard -to -find fault. Large size: 9}.,x11 ", 192 many large 11x16" bl s- RCA 630 -TS. Data on 19.2 These manuals will give you the know- -how of a tele- pages + 9 bluepr nts 11x15 ", prints. t"se coupon below large pages, S %x11 inch- vision expert and will repay for themselves with time -..anal style. Amazing Su- to order, your special es. Sturdy manual -style saved on the first TV job. Order at our risk for a 10- areme value for only $3. price only $3. binding. Price only $2. day trial. Use coupon below.

NEW 1949 DIAGRAM MANUAL SENSATIONAL LOW PRICE AMAZING SUPREME BARGAIN IN Use this newest SUPREME radio manual to re- Be money ahead with SUPREME Manuals. DIAGRAMS AND SERVICE DATA pair quickly all modern 1949 radio receivers. In For the remarkable bargain price lonly $2 for most volumes) you are assured of having in Here is your low- priced, money -saving source of ra- this big single volume, you have clearly -printed, din diagrams and service data for all sets. large schematic diagrams, your shop and on the jot. popular needed alignment data, needed diagrams and other Above is a photograph of these giant -size manuals- - replacement parts lists, voltage values, and in- essential repair data on 4 available to radio servicemen at only $2 for most vol- formation on stage gain, location of trimmers, and out of 5 sets you will ever umes. Let these easy -to -use manuals guide you to dial stringing for almost all recently released sets. service. These manuals pay quick fault finding and simplified repair of any radio A worthy companion to the 8 previous volumes for themselves with time Eliminate guesswork. cut hour -wasting jobs to pleasant used by over 1211,000 shrewd radio servicemen saved on a couple of jobs, moments. These manuals rover every popular radio Like the previous volumes illustrated above, it after that you use them of all makes, from old timers to new 1919 sets Clearly sells at a give -away price and gives you a whole FREE. Don't spend large printed circuits, parts lists, alignment data, and help. ful service hints are the facts vnu need to be more year of radio diagrams for a couple sums for bulky, space -wast- of dollars expert in radio servicing There are nine volumes in total cost -nothing else to buy the rest of the ing manuals of other pub- lishers, don't buy additional all as illustrated above Each manual is 8%411 Inch. year, nothing else to pay Giant size: 81/2x11 drawings Conipuro uy es, sturdy manual style binding, average manual has every few weeks. N Reitman. radio Inches. Includes index. Manual style binding be wise, use SUPREME 194 pages of diagrams and practical service data Use at your or engineer. teacher. Mailable jobber, send coupon, price Manuals to get the most in author a service. coupon below to order on 10 -day no -risk trial or see only $2.60. diagrams for smallest cost man these manuals at your jobber S Record Changers Radio Servicing Course -Book Post -War Manual Here is your practical radio course of NO RISK TRIAL ORDER COUPON Service expertly all modern easy.to-hdlnw lessons. Review fundamentals, (1945 -1948) record changers. learn new servicing tricks, Includes every popular make all about signal tracing, SUPREME PUBLICATIONS, 3127 W. 13th St., Chicago 23, ILL. Just follow simplified factory oscilloscopes, recording. Instructions to make needed P.A., test equipment, and Ship the lolluwiiig manuals on 10 -day Most -Often- Needed adjustments and all repairs T -V Just like a $100 00 trial under your guano, lee of satisfaction Radio Diagram Manuals Hundreds of photographs and correspondence c o u r s e 1049 exploded views. Large size Everything in radio sery New Television Manual $8.00 New 1949 Manual.S2 50 8th "x11 inches. 144 fact -filled icing. With self- testing 17 1046 Television Manual 3.00 1948 pages. Available at your radio PRICED questions and index. 1147 F.S1. and Television, 2.00 jobber, or sent post- $ SO Large size: 8%x11' SOW ' j 19461947 AT ONLY paid, price only New 1949 Post -war Record Edition Price postpaid, only L- Changers 4.50 1942 Radio Servicing Course W,ok 2..10 1941 s2(m LI1940 I am . enclosing 5 sena postpaid. 111 1939 EACH Supreme Puliccztiofs Send COD I am enclosing a deposit. 1926. 1936 -52.50 Name

Sold by all Leading Radio Jobbers Address: NOVEMBER, 1949

www.americanradiohistory.com 72 New Devices -- PORTABLE ANTENNA Tee zew toe rd2 is je e in values from .01 to 2 it and in American Phenolic Corp., ratings of 200, 400. and 600. Size o ih. Chicago, III. capacitors is small, the 2 -pf unit is inch Amphenol Telestar antennas ore a ring only 23/32 diameter new version of the familiar table -top I }ÿ inches long. V. In this one the lengths of the ele- ments aree not adiust,ble but there MARKER GENERATOR are two dipoles. one for the low and another for the high band. The weighted Radio City Products Co., Inc., base is ea.ioped with rubber 'OCT. 152 West 25th Street Single Bay New York I, N. Y. VOLTOHMMETER KIT Model TV -50 is o .. - -e tuency MODEL 114 -005 Heath Co., signal generator with fo ,,r ronges cov- ering 5 to 250 nec. It is used os a with mast, Complete swivel Benton Harbor, Mich. marker in conjunction with standard mounting plate, guy clamp, The new Heath kit Harditester kit has a 3-inch, 400 -pa meter. A.c. and stand -off insulators and 75 d.c. voltage ranges of 0.10 -30- 300 -1,000 ft. Amphenol 300 ohm Twin Lead. MODEL 114 -009 Standard 114.005 TV antes no without Twin -Lead

A MPHENo»,. television and FM sweep generators. Calibration accuracy is within 1%. A self -contained crystal oscillator may be used simultaneously with the v.f.o. or by itself. A phasing control is in- cluded. An internal mixing circuit is TV ANTENNAS arranged so that the output of o sweep be to the TV -50 5,000 volts are available as well as generator may fed and the resistance ronges of 0- 3,000- 300,000 marker's output leads carry both ohms. Two milliampere ronges are in- signals. 0.10 100. TELEVISION LAZY H TV MASTER SYSTEM Technical Appliance Corp., Tronsvision, Inc., Sherburne. N. Y. New Rochelle, N. Y. The Toco Lazy H . 1940, has im- A master antenna system which am- first introduced in been proved. Formerly made only for the plifies the signals is being offered for low- frequency channels, the unit now apartment houses. One antenna is erected for each occupied has changed spacing and high -Ire. channel. whiskers to The amplified signals ore mired and quency give good perform- ance over all 12 channels. An piped throughout the house. Each set addi- has is plugged into getting tional reflector been added espe- an outlet, the high maximum reception on all channels. cially for channels. Construe Two -Bay tien 's all: 1, -- a_.m except at insulotion METAL VIEWING TUBE MODEL 114 -302 Sylvania Electric Products, Inc. ANTENNA ROTATOR Two Bay Antenna with top and New York, N. Y. bottom boy, connecting rods and Crown Controls Co., Sixteen -inch metal tubes are now New Bremen, Ohio two 5 -foot lengths of 1Y," mast available to distributors. The I6AP4 Designed for rotating hos o 6.3 -volt. 600 -ma filament and p' without leod -in. Supplies added television anterr.ss but useful olso for high forward directive gain on ham and other work, this rotator will support 175 pounds. It may be mounted all twelve TV channels.

Amphenol Infine Antennas are manufactured under Patent No. 2,474,480. The best reception of picture and sound on ALL TV CHANNELS is directly dependent upon the me- chanical and electrical construction of the antenna. Amphenol has designed the Model 114 -005 IN- LINE TV ANTENNA after years of study and research to meet the strict demands for optimum antenna per- requires r,agnetic defection, focusing. formance ... this antenna provides the best in high, and on trap. High voltage required is 12.000, focusing -anode voltage 300, near the ground or roof with the an- uniform gain with clear, brilliant reception on all chan- and control grid bias -33 to -77 ro- volts. tenna and mast supported by the nels. The Model 114 -302 TWO -BAY INLINE TV AN- tator. The control unit hos o meter indicating directions. A three -way mo- TENNA provides added high forward gain for TV sets METALLIZED mentary push switch rotates the an- tenna in two directions or lights the in fringe areas. CAPACITORS indicator dial. Castings are aluminum Costly service calls due to antenna maintenance Aerovox Corp., and the drive :s weatherproof. New Bedford, Mass. problems are eliminated with an Amphenol installa- Aerofite metallized -paper capacitors POCKET tion. The faithful, steady performance of Amphenol do not contain metal foil os do con- VOLTOHMMETER ventional units but substitute high- Electronic Measurements Corp., for purity paper tissue coated with o film antennas is the solution excellent picture reception of metal one millionth of an inch thick New York, N. Y. through many years. or less. Model 102 is o pocket tester with a Less space is occupied by the elec- 3-inch sauore meter. Sensitivity is trodes, allowing more insulation and 1,000 ohms per volt. Ranges are: 12, better protection against voltage 120. 600, and 1,200 volts a.c.: 6, 60, AMERICAN PHENOLIC CORPORATION surges. R.f. impedance is lower than in 300, 600, and 6,000 volts d.c.; 6, 30, and 1830 50. 54TH AVENUE standard units. The capacitor is essen- 120 mo, and 1.2 amperes d.c.; 30, ISO, tioliy self -healing alter high surges or and 600 mn a.c. Two ohms ranges are CHICAGO 50, ILLINOIS momentary overloads. also included. RADIO -ELECTRONICS for

www.americanradiohistory.com 73

World's fastest automatic changer -in RCA 45 rpm system - changes records in 5 seconds.

4vic1e c/aì'77e are/se-

Hundreds of thousands are now enjoy- central spindle post on which records 45 rpm system -which was started 11 ing RCA's thrilling new way of playing are so easily stacked. Result: a simpli- years ago at RCA Laboratories -is seen records ... they marvel at its wonderful fied machine, that changes records in in the instant acceptance, by the public, tone ... and the speed with which it 5 seconds. of this better way of playing records. changes records. Remarkable, too, are the new records - Music lovers may now have both the 45 rpm system, and the conventional "78." Prolonged research is behind this achieve- only 6%4 inches in diameter -yet giving as which sought the first much playing time as conventional 12 -inch ment, research -for Development of an entirely new record - of phonograph history-a records. Unbreakable, these compact vinyl time in 70 years playing principle is just one of hundreds of designed for plastic discs use only the distortion -free record and automatic player ways in which RCA research works for you. "quality zone "... for unbelievable beauty each other. Leadership in science and engineering adds of tone. Revolutionary is its record -changing value beyond price to any product of RCA, principle, with mechanism inside the Value of the research behind RCA's or RCA Victor.

RAD/0 CORPORAT/ON AMER/CA lyor/d leader in Rodio -T2/-5/- in Te%Vision

NOVEMBER, 1949

www.americanradiohistory.com 74 Itadio-Electronic Circuits I REVERSIBLE TV BEAM ANTENNA With Each 100 Tubes. $20.00 List Value Filter f-HARD-TO-GET PARTS-N FREE! Condensers. Cornell -Du. A novel 12- channel TV receiving an- 1 bilier Mallory. Aerovoa, POWERFUL ALL. PURPOSE INDUCTION Sprague, Sc,o'. Ten Fast Moving Filters. tenna system, described in a recent is- MOTOR -ue of RCA Review, is a combination IDEAL FOR E%PERIMENTERS-101 USES of Sturdily constructed two- element broadside and taiards this elf t: rtn:er shaded RADIO TUBES end -fire ar- pale A.C. induction lllll tor is io w. 6K6 128A7 35 rays producing Someenough number of use, a unidirectional pattern of lcl,&,e a a: Automatic Tim- 6K7G 12BE6 3585 ing Devices. Current Interrupter. which can be reversed at will. Its ele- Electric Fans. Electric Chimes. 6K8G ì2F5 35C5 Window Displays. Photocell Control EA. 6P5G 12H6 35W4 ments are cut to one -half wavelength Devices. Electric Vib tors. Small 39C 65A7 12J5 3524 Ori . Suffersff and Polishers. near channel 2 to keep the efficiency Miniature Pumps. Mechanical Mod. 1CS 6AL5 6SG7 12J7 35Z5 els. Sirens. and other am,Deatlm,a 106 6AQ5 65147 12K7 36 from falling off at low frequencies. Consumes about 15 tt. of power and has a speed rf a,lUo 1L4 6AT6 6SJ7 12K8 37 down. Since the high -band channels bear a r D m. When g In,. IRS 6AU6 651.7 1258 38 study unit will constantly oper- 154 686 6SK7 125A7 39 3 to 1 frequency ratio to those in the ate an ié -inch turntable loaded with 200 lbs. dead w ioht- TNAT'S POWER! 155 6BA6 6SN7 12SF5 46 low band, a half -wave, low Di, 3 high by 2' wade by Is y d P: 1U5 -band dipole has mounting suds: shaft is Itig 6BD6 6597 125E7 SOBS 4' ant ¡ i -I. will by 3/ 10° diameter. and is In cellaligning 2A5 68E6 65R7 125G7 5076 constitute three half -waves on the rctai ilea bearings. Designed for 110 -20 volts. 50.00 2A7 VT-52 6U6 12SH7 51 eyrie . A.c. only. Shp. Wt. 2 lb.. high band and the radiation pattern ITEM NO. 147 354 6BJ6 6U7 12SJ7 56 YOUR PRICE $1.95 5U4G 6C5 6V6 12SK7 57 will take the form of a four -leaf clover 5W4 6C8 6X4 125N7 58 rather than the figure -eight of the ULTRA MAGNET SX4G 606 6X5 '2597 75 dipole. LIFTS MORE THAN 20 TIMES 573 6F5 6Z4 24A 77 "Vees," added to each dipole as ITS OWN WEIGHT 574 6F6 12A8 251.6 78 shown in Fig. 1, have no effect on the LITTLE GIANT MAGNET 5Z3 6G6 12AT6 30 80 Lifts 5 Iba. easily. Weighs 4 os. 6AC4 6146 12AU6 31 85 low band, but change the high -band steel. with keeper.' World's 6AC5 6J5 12AU7 32 89 clover -leaf into a figure -eight, thus Complete 6AG5 6.16 12A X7 33 Thee expowerfulm ter° end Iho bbyistn vili 6AK5 6J7 12BA6 34 making each dipole bidirectional on all nod hundreds resent s Uiv ,, Measures 1 X Ì4ÿ'1Ç1 Ship. Wt. channels. e/a lbs. 1T[M NO 1511 687 7B6 12J5 TouR rrnee $1 .25 688 7E5 1297 6BG6G 7E6 12SL7 GENUINE MICROPHONE TRANSMITTERS 49 EC a. Regular telephone trant- 7E7 12Z3 6C6 misters taken from a large 6D8 7F7 14N7 telephone supply einnpany' overstock. Work perfectly OZ4 1T5 6F5 7G7 1978 2 ,I n' Cells. Can be 1A5 1V 6F8 7147 20 usedv on P.A. ,stems. call 1A7 1L114 697 7J7 32L7 ii rase et., short-line e. 105 1LN5 6R7 7L7 35L6 lii,lusestle orrufarm-to-farmhouse-to. 1C7 2A3 65F5 7N7 36 phone lines. also to talk 1145 2137 6T7 7Q7 40 through your own concealed wdictaphone 1LA4 3LF4 678 757 43 reerawd 1LE3 5V4 6U7 7T7 50L6 j 1 k s° flatten' 53 rural,ral telephone line.. 1LN5 5Z4 6W7 7W7 ARE. GENUINE 1N5 6A8 676 10Y 11723 r it ANSMITTERS. MADE BY 1P5 6AC7 6Z7 12A7 VR150 KELLOGG. WESTERN ELECTRIC AND STROMIIERG ig yes- aller antenna pattern. i- .11t1.kahl excellent appearance 195 6AV6 7A4 12AT7 XXL-7A4 1-'1 ri a.S Ne value ndn one seldom offerederInl these c. Ship. t. tolb. ° ITEM NO. ISO YOUR PRICE $1.95 91.95 A diagram of the array is shown in Fig. 2. The dipoles of the broadside ar- WATTHOUR METER I 51.29 r'ay- mounted above one another-are forr'overhauled service. ie. for regular 100-1 1 n fed in phase the volt. e0 cycle 2 -wire A.C. Less Than 50 Tubes 5c Per Tube Extra at center of a balanced 2 moires fromsCthethe line and Individually Boned. transmission line. The end -fire elements 2 wires to the load. Stull. aY constructed t heavy Standard Factory Guarantee -in a horizontal plane -are fed in the metal case. deep t Westingh use. P. M. Speakers-5" 51.05, 4' 51.05, same manner; however, one half of the G. F.her . rtal ilable °m eke. Slip. 6- 51.59. Output Transformers for 50L6 line is transposed to provide out -of- WI. IS lbs. ITEM NO. 33 39c, for 6V6.. 45c. phase feed. YOUR RIG[ S4.954.95 A and B are feed points for the AMAZING BLACK LIGHT!! FILTER CONDENSERS broadside and end -fire arrays, respec- P Cornue 25O.W.,It Ultra- Violet Source Very brands. Fresh stock. The 1 .t und most practical best tively. These points are connected to general of ultra -v tolet light for 450 Working Volts experimental and enter- opposite corners of a bridge consisting tainment e. Makes all Snores. 8 -450 V ea. 21c cent 10 V ea. 24c of four one -quarter wavelength lines, transformer.yofurnany -450 kind needed. Fits any adard 10 -450 V with 20.20 -25 V ea. 29c one of which is transposed as shown. 15-450 V ea. 29c l opalescenttren hus I llintifuvarious A 150 -ohm resistor and 300 -ohm trans- types of materials. Swell for 20-450 V ea. 39c amateur parties, playa. etc.- to 30-450 V ea. 49c obtain S lighting effects. Curb onlly, 2 Ills. 30 -450 V with 20.20-25 V ea. 29c NO. 87° 8.8 -450 V ea. 39c YOEMUR PRICE $$1.95 1 5 10.10 -450 V ea. 43c 20- 20-450 V ea. 49c WESTERN ELECTRIC BREAST MIKE 150 Working Volts MODIFIED DIPOLE Tbi- i. Im U. li ...mi.,. 15.15 -150 V ea. 29c or:,ft ,urholi nnrr I nly 1 Ib. 20 -20 -150 V ea. 29c Mike with Srremtplate V ea. 39e mounting has 20.20.20 -150 Inc st°e °t that It a nvehe 30.30 -150 V ea. 39c unmated to any desired position. aroundare ovNes 40.20 -150 V ea. 39c n and around other around 40.30 -150 V- 30.20 -25 V ea. 39c Straps can be snapped o 40.40 V ea. 39c by an ingenious -150 arrangement.a d off qickly 40.40 -150 V-25-25 V ea. 39c his xcellenl mike can he V ea. 39c adapted for horns broadcasting or 50 -30 -150 Private he 50 -50 -150 V ea. 39c mouunting hre.,aitpletSystems.. Itr canrare Used as desk mike. 60.60 -150 V ea. 39c mld,.te with 6-font cited 21e t 15 -150 V ea. INCOMING SIGNAL Coil bord rubber plug. Fmlghed gheranlized plate. 16 V ea. 23e l:llile. SI weight. 2 °Ibs. -150 ITEM I NO. 152 a, 1 .00 20 -150 V ea. 25e YOUR PRICE .7 30-150 V ea. 29e 40 -150 V ea. 29e 150 /.5 HUDSON SPECIALTIES CO. 25 Working Volts in West Broadway, Dept. RE-11-49, New York 7. N.Y. 10 -25 V ea. 166 I have circled below the number of the items I'm ordering. My full remittance pf S. , tln- 20 -25 V ea. 16e EXTRA A LINE slllPnR charges lebrll , (NO C.O.O. 25-25 V ea. 16e 6 O RDERS UNLESS ACCOMPANIED WITN A DEPOSIT., ea. 16e OR my deposit of E la enclosed 12UTD. 100 -25 V inlred,. Ship under C.O.D. for baton-e. NO C.D.D. 20.16 -16 -350 V Sprague type ea. 39e ORDERS FOR LESS THAN $9.00. SE SURE TO IN. V-200-10 V ea. 39e CLUDE SHIPPING CHARGES. 25-25-150 i ,eel, 11em Vii, wanted: Rated Accounts 10 Days; All Others 20 °o Deposit 147 119 160 117 152 33 Balance Minimum Order with Order. C.O.D. Nome 55.00. RCVR

Andrete PREMIER RADIO TUBE CO. A/4 APPROX 413' Reue Print Cleaely 1808 WINNEMAC AVE., CHICAGO 40. ILL. City slate four tube source since 1926 Fig. 2- Antenna :urea? with . RADIO -ELECTRONICS fo

www.americanradiohistory.com 7

ANOTHER SCORE IN THE battle of the inches

It takes many costly buildings to tiny permalloy transformers, and more parts can be housed in a given house your telephone system. Every special assembly techniques, it is space. Telephone buildings and inch saved helps keep down the cost scarcely larger than a single vacuum other installations keep on giving of telephone service. So at Bell Tele- tube used to be. Yet it is able to more service for their size - and phone Laboratories engineers work boost a voice by 35 decibels. keep down.costs. constantly to squeeze the size out Mounted in a bay only two feet The new amplifiers, which will of wide 111 telephone equipment. and /2 feet high, 600 of the soon be used by the thousands new amplifiers do work which once In the picture a new voice fre- throughout the Bell System to keep quency amplifier is being slipped required a room full of equipment. telephone voices up to strength, are into position. Featuring a Western This kind of size reduction but one example of this important Electric miniature vacuum tube, throughout the System means that phase of Laboratories' work.

BELL TELEPHONE LABORATORIES EXPLORING AND INVENTING, DEVISING AND PERFECTING, FOR CONTINUED IMPROVEMENTS AND ECONOMIES IN TELEPHONE SERVICE

NOVEMBER, 1 9 4 9

www.americanradiohistory.com 761_ lindin-Blectronic Circuits

mission line are connected to the re- Your BEST BUY is maining corners of the network. This network is called a diplexer. Assuming that an incoming signal approaches the array from the front TV TEST EQUIPMENT by f see Fig. 2), two main signals will ar- rive at A and B 90 degrees out of phase Originally designed liy McMurdo Stker ... developed because of the spacing between elements

, .. and constantly being improved by McMurdo Silver's stall' I. i;. i - and the transposition in one of the Manufactured of the highest quality, tested et inpouents by the trained feed lines. Since transmission line B -D electronic technicians in McMurdo Silver's modern factory. Compact! is one -quarter wavelength longer than A -C, the signals will di- Low- priced! l'ou can't heat the value that is built into every McMurdo arrive at the plexer in phase. The in -phase voltages Caliber Test Instrument! Silver Laboratory at C and D will buck each other at E because of the transposition in one leg Model 900 -A "Vomaz" of the bridge. Therefore, E is at zero The new VOMAX makes TV, FM, and AM measurements oc. potential, and the resistor will not ab- curotely, at highest meter resistance. Giant meter, nonbreakoble gloss; 45 ranges, new single probe for o.c., d.c, o.f r.f., volts, sorb power. The main waves arrive at ohms, db. and current measurements. " VOMAX ' measures TV I.. in phase and pass through to the power supply potentials up to 30 Kilovolts when used with the receiver. High Voltage Adaptor Probe. A world beater at only S68.50 net. When a signal arrives from behind the array, main waves arrive at C and Model 918 Multiplier Probe It out of phase. out Built for long lile and hard usage, eocl, probe This -of -phase re- has been thoroughly tested: assuring safety of lationship is maintained at F, and no operation on voltages up to 30,000 volts d.c. signal goes to the receiver; instead, it Plug.in tips make it readily attached to your is absorbed by the resistor, the signals VOMAX VTVM, Model 900 or 900A, on which being in phase at this point. direct meter readings con now be mode from If there is a mismatch between the 1 IG ooh to 30.000 volts d.c. Only 59.95 net. receiver and the transmission line, the signal will be reflected back toward the antenna where some of its energy is Model 906 Model 915 Tubeless radiated and the remainder reflected FM -AM hack down the line toward the receiver. Grid Dip Adapter In this case, reflected signals are can- Checks oscillators, on Signal Generator celled in the same manner as signals tenno systems, trans . Choice of the big mitters, trop circuits, engineering labora- from the back of the antenna. without mechanical tories plus thousands The directivity of the beam can be coupling. Determines of service technicians, reversed by connecting a d.p.d.t. trans - value of oll coils and condensers. Requires no 906 stands out as maximum value. 90 kc thru position switch in one of the transmis - power supply or tubes; connects to any signal 210 nier in 8 ranges, 1 uracy: less thon I z

generator. Three calibrated plug -in coils cover microvolt, including strays to c over 1 volt v.t v nx -ion lines. The diplexer can be mounted 100 kc. to 300 mc. Equipped with phone lock for metered output; multiple shielding; adjustable 0 11 spreaders for positioning behind the easy identification of oscillator frequencies. to 100 amplitude modulation, adjustable 0 ro l' \' receiver. Model 915 is only 534.95 net including coils. 1000 kc. FM sweep. Price only 5116.50 net. HI -FI CRYSTAL TUNER Designed for high-quality local broad- cast reception, the new bandpass Model 911 Miller t.r.f. tuner kit should make a hit with Model 905 -A TV FM Sweep crystal receiver fans and high -fidelity "SPARX" Generator audio enthusiasts. The double -tuned Combining signal Here is on all -in- bandpass circuit uses negative mutual tracer and uni- one TV service coupling to provide adequate selectivity versal test speak- center. Continu- for separating most local stations. er ,905-A is amaz- ous range of 2 is 25 kc ingly sensitive yet free of usual tracer hum. G,ru 226 mc. Output from 0 -'1 volt. 1 and Bandwidth approximately at Vacuum -tube prod with r.f. a.f. switching; high - 5 mc. precision crystal markers insure pin -point 2 -db points when measured at 900 kc. gain high -fidelity amplifier, 6" PM speaker; setting of TV i.f, band width, and trop circuits. 18 -watt output transformer gives wide choice Phased 60 cycle sine and 120 cycle sow-tooth PER IN34 /1118 of impedances. Two essential instruments in one, voltages for direct scope control. Sweep from 10.365.40 tl SECTION 905 -A is a value far exceeding 544.50 net 0,10 me An outstanding buy of only 578.50 net. ANT °-I r SEND COUPON TODAY 2° 6ND McMURDO SILVER CO., Inc. Date 1949 2 r 1 PEAK c,35 CONT 1249 Moin Street Hartford 3, Conn. T.OIS 9ROKENLiNEI Please send me - and bill through my jobber - the instruments I have checked below: The 900 -A "VOMAX" 568.50 r- 906 FM -AM Signor Generator á 5116.50 1N34 or 1N48 crystal diode de- tector develops between .05 and 0.5 volt 918 Multiplier Probe re 59.95 905 -A "SPARX" ri 544.50 on stations within a 211 -25-mile radius Dip Adopter 911 TV FM Sweep Generator .: 578.50 915 Tubeless Grid 534.95 when used with a good outside antenna Free catalog of Send 75 to 100 feet long. L1 and L2 are MY JOBBER IS: J Laboratory Caliber Test Instruments Miller 242 -A antenna coils, and L3 is a type EL -55 negative mutual coupling Name Name coil. Available in kit form, this tuner is City City the basis of a high -fidelity AM receiver when coupled to a hi -fi audio system. Address Address A volume control can be connected as shown by the broken lines. If this control is included, the connection be- tween points X must be removed. 7/167/444/0-sX.e.k. (Continued on page 79) RADIO -ELECTRONICS for.

www.americanradiohistory.com 77

FM - AM HALLICRAFTERS CHASSIS MODEL S -59 $32995 HALLICRArTER'S S -56 559.95 HALLICRAFTER'S S -59 S32.95 $110.00 VALUE 11 -TUBE FM -AM CHASSIS 8 -TUBE FM -AM CHASSIS *AUTOMATIC FREQUENCY CONTROL ON F.M. PUSH -PULL AUDIO CONSTRUCTION R.F. STAGE ON F.M. -AC Model S -56 Hanicralters. hurl, liarlliv. I1 tube A11. FM radio receiver Model 5 -59 Haitierallers, high fidelity. 8 Bike c chassie band K receiver chassis. for FM /AM reception. Size 121 °lX frequency controls ln FM holds the Statlstation In tune. PhonoAc 7`/2 x 9'. An excellently engineered chassis. equal to rctiOn on rear of l chassis. Full range tone control with base boost. thole used In 83011.00 commercial sets. Wide range Push pull 108(1 in audio system. Frequency response ! entially BTUBE TM 41111 audio. 80 to 14.000 Cp...1°to. control, phono input Bat from 311 tu 140110 cps. Wide vision accu tely calibrated slide MODEL S -39. 532.95 jack onu Chassis. Receives uroaucant. 5411 to 1700 kc. ode dial. ,u, preooieclim, on broadcast band. Output transformer and FM 88 to 108 Accurately slide rut dial. Any good PM speaker 11 -TUBE FM that matches 500 ohm Irae. 4 Antenna terminals; two and MODEL S -96. for AM two for will this Output transformer voice coil. 559.95 FM. is 11c type know of ith f8 lbs. °4 5p chassispand PricecS32.95. tter get order in early. Designed to usedk commercial 9. PM (O.K. radios Iling M the 5400.00 to 5600.00 glass. The regular dealer's net on this chassis is ccustom with ourr regular 812.95.'bCR.13X IC axial 112' PM speakers. 5100.011. However. lucky purchase enables us tu offer these brand new, factory 1' 00.1 all for 542.95. S -58 Hallicrafte« chassis with tubes aidmid operation inntructlon at only S59.95 leas speaker. in :itching transformer, 500 o .o coil 52.50 .extra. Chassis sise z7 Weight 25i -Combinationlofer -S -S `Hal'icraftersl chassis. speaker match- ing123/4 x 10 st. CONSOLE CABINET FOR S -59 $19.95

N - ! Beautiful blond console cabinet. Sire 17 X 21 33' hi This cabinet DETROLA -COILS, GANG -CHASSIS AND DIAL $2.95 .s intended for use nationally known SÌ20.00 radio-Mono m lunation. The lower half the cabinet is divided for albums. The Upper ,CIr 1Ì1v 18 x 15.1 and I Ia. be covers the Radio t1Iie. I. r1:1 slide oie dial.( 3 Gang 'TU rdered really cut fora Hllleraftnrs -50 or condenser. All'` RF and 'IF coils and hand switch ..'llh a blank panel for Installing your chassis. Changer panel is for standard broadcast ana foreign whorl wave. monk. will hold changer up to 12 14'. Cabinet will hold O. or Hu,' these part for less than the coil value Il 9 speaker. Shipping wt. 40 lbs. Stock No. JR -4 blond cabinet. Ólone. These parts all Bt the chassis properly. easy eut for the 5 -59 H illenfters will not hold 5.581... 519.95 11D- material apictureA and listed above is S x Os-Alnico PM speaker 52.95 95 offered. It is not a complete kit. You supply Stock No. a bol blank panels Unger tubes. speaker resistors, densers. Stock No. 8 -101)0 wninel e do gilt them.tow You the calo and changer e t etc. Stork No. PET -1. Shipping Weight 9 Ilis. area Io oil your e. SI. , is n Is x 15 ana nÁio area 5 Ix Net $2.93. Stock No. efñó9. . na ... 1.. it 40 lb, s1s.9s 6 TUBE TELEVISION PARTS AC DC KIT 12 INCH "COAXIAL" P. M. SPEAKER $12.5 Sarkes Tarzian REGULAR 532.50 LIST at $9.95 13 CHANNEL ub. Sup1rnes. AC -D T.V. TUNER using1 size r ariemtl F'a Kit. RESPONSE 40-17000 C.P.S. orth plastic wA11 slide rule dial. ONLY $9.95 and 5'aspeaker.11This makes a factory like MOLDED ONE PIECE CONE S.libel. Tasman 1$ chnnel tuoir r l'ele- radio. The cadmium chassis is redly punched front end and socket are aided. Thin type of kit ali wired. includinThisulle sockets T V fusually sells for least $15.00. All parts front end as used by several nationally known urnished, including tubes: 12K8. 2.125K7. AVAILABLE IN 12 AND 15" SIZES Offemanufacturers. Built In antenna trimmer. red with printed schematic diagram. diagrams and photon. KtKit Mdl FS- Wt. Priced complete with 3 tubes: OC4 31 o( ioel S9.95 u Sism loathand 8 Newly designed by of America's finest speaker Hourptpricamplifier. iired.. builders. Made for FM °eand AM high fidelity radio and output Is to be fed Into your video channel. 3 -WAY- players. incorporated in radios of It be mounted and used with the Faros. the raO bracket. eat hers worth GVZ.60° chüsl9, advertised below. PICK ME UP 8.8 os.s Alnico V Magnet PM fore the cllow range Woofer Weight 2 Ms. Stock No. SK -T3. Net ice and tally built in 3' Alnico V tweeter for the :rkes.Tarzian. 13 channel tuner with 3 PORTABLE extended high rage. The high pass filter is concealed tole. . $9.95 under Just hook RADIO rormer Will ln place of leeany home °raadio 12' Coaxial Model speaker as most speakers have an 8 Ohm Cou. only G.I. T.V. FRONT END SCOOP ONLY 2 wires tu connect. Will handle 18 Watts peak. Wile CR-13X $12.95 5195 range response 0 to 17.000 Cycles. This speaker should G 1 13 Channel T.V. front end. Require. sell for $35.011. Why buy any ordinary speaker when we 15" Coaxial Model lutes 6C4 a11Á 2- 8AGS. These tune( are offerRer a 12' Coaxial PM for onlyii $12.95. Shipping weight in damaged condition, but are Ideal for the $12.95 Ins. Model CR -13X. SI2.95. Two for 524.95 5 -15X $24.95 and for building TV boosters. K Alexperimenterso for schools as class room ids for train- coller. Radio ing. Stock No. MA -I3XT weight lbs. net tubes pluses Housedot 11 aluminum. leatherette covered case made 51.95: Kit of 3 tubes 99e extra. by Farnsworth. n lid with loop antenna built-In. -Ire 5 x 9 x 63. Build yourself professional looking radio with this kit. 15 INCH "KING COAXIAL" SPEAKER $2495 T. V. SCOOP $5.95 Every piece furnished including tubes; IRS. 174, 1S5. and 3V4, an 'ell s easy to fol- diagram 1d hoto Receives broadcast WORLD'S BEST 15" COAXIAL VALUE Chassis Model GVZBO par. low built up Chassis Size 540 to will full The King Coax. A 21.5 z. 1 5 nnnull Y PM speaker with a bu11t-1ii Sig. frequency Alniv 12x17. 18 Tube sock - gang uperhet. that looks . $4o tweeter. Will respond to from 40 to 17.(100 civics. This is a ruggedly built speaker with Has We h0UId ask S17.í19 for this kit. u o'elenier o1 niece molded cone. Built -in high pass filter. Just hook to v N Ohm 150 small However. line production makes this 512.95 taut. Built by the maker of ever popular 12 inch 1S model CR -13X. This ker Pans priceIce powntbie. .tack No. FP -4X. complete hues a retail list r 880.00.rWeeoffer you our 5.ISX inch coax for olllY 124.11. oils orl Tranafonners or tuningunit.eSweepr less batteries. shipping weight 9 lbs. Shipping weigh 11,5. sync. circuits are all partially wired up. Net price 512.95. Kit of batteries. 671/2 Tdhis T.V. Chassis is .teal for the tudent and exerimenter. Leann T.V. by building t sing this hassle to start from. Furnished with 1048 regular $3.00 Olympic TRANSFORMER Supreme Publications Tel Manual. HIGH FIDELITY which has a omplete schematic of this FM well as 9 Pages of service In. -AM We furnish you with a diagram fo fórmd. Chassis '6" If asyou play with Television here Build a Hi -Fi 6L6 Amplifier want( tog and 12 6600 OHMS PLATE TO PLATE Fainworth GV7.1111 partially built up Chassis Wh. -, 1 fi r Sup" a, slit and high Iand 48 Supreme T.V. Manual all for $5.95. Speaker fidelity outputl Put' transformer.orm luslgneci ugh -pull plates nclude Postage for 1I On. 0557.80 Chassis 12_{1'11. o 2 -SAG?1 classlass AB. to 4. 8115 -250 anda 500 ohms: only 52.95. $47.95 with Bur'- feedback winding. in compound case: 37,kx4V.x3e. Actual net R'eight. 0 Gon. If you want the lest quality from your audio system. order this transformer. TELEVISION POWER TRANS. OD mph. M.rlel " -112- 10 Tube FM-AM esponse ea tially flat 20 to 20.000 cycles. We have tried several high fidelity out- Chassis. Latest 1040 Model with 10 tube.. puts In our lab and find Sin tu be the hest value. Even though your amplifier ly Puts push pull 1001 audio base boost tone control. lut 10 or f5 watts. this 34 watt lob is what v should have. Connectlug Instructions are Inch Dynamic spker. finest heavy Ni,. A.40:1. Nn 12 A.V.C. nd pire. forni.liciI. Stock stlipplol, s,lg, lt.s. Nel prim 55.95 $2.95 construction uporhet with OV2 -80 Power selection both FM and14 AM. Receives550 Transformer. FM to 108 N.C. This -114 3302. A 135 mati tapped to 1700 KC and FM re- REGULAR $35.00 LIST voltag1,emanlli set was designed for fringe area plate ception. Chassis Size 121/2" Iong. filament high. 12' front to back. iced complete for part °of Farnsworth T. V. with tunes. 3, (MAIL 80E0. BAL5. anis 2. Rassis. :175 volts I .C. 8.3 12 Inch speaker. net 5 volt filament. AAlustable voltage. OS07. 20108. 5Y3. na "JUKE BOX" 15 INCH Me.. 31% $995 38g x . blab. tool/Me This Chassis Is the Same as used in weight. 9 his. Scoop bina - mire. GVZOti T. V. Olvmpic's highest prices phono SPEAKER Power Trans former lions. and worth twice prices. Shipping P.M. SALE PRICE 52.95 fight 30 Ifs. Olympic Model 9.925 custom JEFFERSON $47.95 HAS NEW MOLDED CONE T.V. PWR. TRAN chassis ready to play. nit T.V. Power Trans former, similar R.C.A. , A carload iilha se. folio 1 number builder of 1r PM 110 volts, OC cycle. 700 volts speakers. enables U. to offer this lregular n53.5.00 list is speaker D.C..pma. filaments 5 vot t 3 am l.. 5 volts for only 80.95. New one piece molded e. with 8 ohm Ice at 3 amps d 0.3 sits at S ant... Trans. coll. 12 os. uwantla take IS act average Mae 3a. x 41/2 5I/4'. Ship/1111e Ig1.ht. 3 tts peak. Ifsyy to the low 12 Ills. Stork No. MR -4F. Net r,r .1.95.95 buy this model. This is without doubt the culot soaker for the money that is available today. Include postage for II Television Vertical Deflection Output Trans. Ms. stock Nu. 15-KR. Net price 59.95. former. Shipping weight 2 pus. Stock Nu. VD -5000. Net price $1.95 KINGJUKE 50 -WATT 15 -INCH P.M. SPEAKER SCOOP PRICE $16.95 Television Focus Coil. Tap quality for 10 or 12' tubes. Similar to N.C.A. No. 20.2131. Model 15.15 -'thy KING of all juke lox speakers. fre,li'.o'y r1sponse low as 30 Net price 12 KIT 20 WATT KIT cycles. '111 take 50 sans peak audln and a55 watts average, .e. The most effi- 42.49 WATT ciently nt oflan taint iIir . o ohmicekcoil allmChmoldtwice the Transformer. Stock SNo. 1. TM -12 510.95 TM -20 S15.9S aaryasjeaker. Has on piece Hseia Nell scillator Model Amplifier Designed for Include postage for 18 lbs. Stock No. °15 -LS. Ideal for high qualitydh2We cured cone. !to S32l P.A. System or recording a +lifer. Matched RCA Type 21173 Horizontal Deflection Out- punched°paes Put and Voltage Transformer. Sale price qquuHigh control onre fades frontoa b pu t s Variable Reluctance CAPEHART MINIATURE A 203D3r Permanent( Magnet Ion Trap. compensation for G.F. °ke] Sale Price 99e. Dicp. Output atches M ohm Voice Coll. POST BROADCAST 100 Mlll Power Transformer. Complet with TWO Sale tubes. diagram and photos 2-6VO. 2- 12AX7. RECORD STATION Price 20gular2$4 50. Net 113..49.Yoke. c mer. Variable tone control. Model 1011P4 Picture Tube. Manufacturer TMe-I2. Weight 10 ms. Net 510.95. Crystal CHANGER $6.95 KIT $6.95 these tube. are guaranteed perfect except utility mike and desk stand 54.95 extra. t quit up to their rigid specifications. kit Ice. na n,. :L.l io.lue. Net 119.95. wÌ d y to operate n514.9 -I Capehart Changer Scoop. l'sra on famous. eadt tWtepetrS high priced mbinations. These changers OX. Build your own miniature Genuine Picture All In Kit Model TM -20. A high quality 20 Watt Kit Model AC factory Audio Amplifier with 135 been tears. ale Price 0'5.íf putsforrmike pplaced ith twin speed °chan`rers. Require Station 800 to15Ó0Tube . 11B as dia tyfn m Cpvstal or 1 or Compensation Minor Adjustments. These have Capetiart Mike phono record. Wanling: cols traeuuqe TELEVISION COURSE ariable Reluctance pick TO e and fader -untere variable resistance cartridges. aerial. potherwise you wwill broadcast twonor $3.00 controls. Has heavy universal R same three miles,. Complete kit with cules, dia. e Television Course nook. 218 nag to match speakers. ((ridge. Connecting 11 instructions furnished. T\5'. ,Iaiue,I l Noll In eve v,l:1' Inngua'e-ae. nsr Base siz Weight 23 gram and r ting instructions. Weight 4 Ready punched chassis. °Price Includes tubes. IOa. lbs. Model 13E-OX. We think it's the finest r value diagram and photos. 2 -81.0. 2 -787. 77.4 No. NK 3. S6.95 Net 31.91. Net to y.00 Frequency response 50 t 12000 Cs.s. Kit Extra tone arm. with MI.P-I Crystal car- Model DE-0/(WT Miniature Radin Trans. Ward TVS.9 Television ..... s. Stacked 200 Ills. Net tridge and permanent needle. $1.60, extra. muter wired really to mente. Net 58.95. dg1 ana Ins 1 11aÌ fooled .ipo`Ies, with re- Model 7M-20.W eight t Ó5s(15 Extra tolle arm. with G.E. RPX -010 van. flectors and Regular al 5.110 net. to led reads tu prate net 120.95. alie reluctance cartridge. 12.95, extra. Crystal Mike A Desk Stand 54.95 extra. anale unrne lÓ.49 r.i«. F -O.- K.C. send 25% deposit WRITE FOR BARGAIN FLYER. with Order. NI. sent C.D.D. With Parcel 4 McGEE RADIO COMPANY Post orders include e.1.9p 1424 Grand Ave.. Kansas City, Missouri NOVEMBER, 1949

www.americanradiohistory.com 7u

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Same

Address

CIt9 State

RADIO -ELECTRONICS for

www.americanradiohistory.com Radio- Electronic Circuits -j 79 BATTERY INTERCOM Operated ft um a battery po :': er sup- ply, this intercom provides for one mas- ter and a single remote station. The remote may call the master by s ounding a buzzer even when the power is off. The master calls the remote by connecting the input of the amplifier to the output and creating a feedback whistle with the switch set at TALK. ONLY $8299 IS THE COST MASTER SPAR o t o rM .-0 I for the sensational- new -improved T O BU22ER I BATTER au22 TALK T E L E K I T

r D L - REMOTE TELEVISION KIT L UNIT Operates the 10'. Ir. IV 15" and I6 picture tube. 105 MISTE= LALL - REMOTE -GT Complete with new builtinpretuned and aligned 13 channel tuner. all and easy step -by -step instruc- _= P8SSW OUT TRANS parts tions and schematics. $82.99 less tubes. complete set of tubes. including 10 8P4 picture tube $49.50, special IH5 -GT .0, .25 designed 10' cabinet $21.50. VC GRID II An amazing value. even a beginner can assemble one of TRANS these fine. new. improved television kits. Uses the new 13 channel tuner. prewired and factory aligned for the en. Same quality and features for 7- v59.50- tire television spectrum. Highest quality parts and excel- kit, tom plate, less tubes lent circuit assure perfect performance. Circuit designed by outstanding TV engineers. Contains R F stage. oscil- A 5 Complete with tubes, $99.50. special designed lator and mixer. Uses new IF coils, providing maximum gain and picture definition. Sound reception is high cabinet .. .. $1950 quality FM for years of listening pleasure. THE MODEL 999 -A COMBINATION

620 0 SIGNAL GENERATOR A- '1.1.5, 8- a +9Ov AND SIGNAL TRACER T -TALK - 0-OFF - _- LISTEN - ALL GANGED Signal Generator Specifications: The circuit is given in the diagram. Frequency Range: 150 Kilocycles to 50 Megacycles. The R.F. Signal Frequency is kept completely constant at all output levels. Modulation is The TALK -LISTEN switch is a five -circuit accomplished by Grid blocking action which is equally effective foe alignment of amplitude and frequency modulation as well as for tele- three- position rotary. The center OFF vision r R.F. obtainable separately or modulated by the position disconnects the batteries to Audio Frequency. save power. Note if the Signal Tracer Specifications: that remote Uses the new Sylvania I N34 Germanium crystal $L%% 8.NE85 buzzes the master when the three -posi- Diode which combined with a resistance -capacity network provides a frequency range of 300 cycles tion switch is not at OFF, the battery to 50 Megacycles. The Model 999 comes complete T with all test leads and operating instructions. current will go through either the input ONLY or output may transformer. It burn up THE NEW MODEL TC -75 TEST CRAFT the transformer and will certainly dis- charge the tuzzer battery. Between A COMBINATION TEST SPEAKER calls, therefore, the switch should al- ways be set at OFF. D. Crisf, F. and SIGNAL TRACER BIGGEST REFLECTOR plus speaker substitution plus substitute 100 V. D.C. B plus resistor tester pew er s p sly plus field bstitutor ee plus condenser tester plus voice coil substitution plus resistor substitutor plus signal tracer plus condenser substitutor plus an experimental one stage audio amplifier 50 plus output indicator plus universal output transformer Complete including signal tracer and full instructions. Z9 NET probe A must for every radio serviceman and engineer.

THE NEW MODEL TC -50 TEST CRAFT

TUBE & SET TESTER A complete laboratory, all purpose test -instrument, this versatile combination tube and set tester will accurately test all up -to -date designed tubes. The multi -meter section affords many necessary measure- ments for everyday's service work.

The New Model TC -50 Tube and Set Tester combines seven instruments, D.C.V., A.C.V., D.C.M.A., Ohms, Out- put Meter, Decibel Meter and Tube Taster. Full scale .0 accuracy to 2 %. English Reading GOOD and BAD scale for testing tubes. Obsolescence reduced to absolute minimum. Simple and quick reading charts for tube testing. Multimeter section affords most popular every - day's measurements. 7 Complete with test leads, tube charts and all detailed, operating instruc- Q 50 Used for recepticn of television signals from tions. field this NET pickup unit:, parabolic receiving - Sine u a 5" 39 6" 10./2" antenna reflector is the largest in the U.S. It operates on a 100 Mt. -foot track atop Lee Immediate delivery from stock. 20% deposit required on C.O.D. orders. in Hollywood. Ca if. Constructed for the Don Lee Broadcasting System, the reflector stands METROPOLITAN ELECTRONICS & INSTRUMENTS COMPANY 16 feet high. It con be pointed at any loca- 106 FIFTH AVE. DEPT. RC -11 NEW YORK 11, N. Y. tion in the surroLnding area to pick up r.f. NOVEMBER. 949

www.americanradiohistory.com 80 Question BOX ALL -WAVE 1 -TUBER should be adjusted for smooth regener- ation control. The average spacing will MID- AMERICA'S ? ¡'Most ¡,riot o rirr'llit of an (ill- icitly one -tube receiver using a 117L7/ be about 1/4 inch. The chassis connects -INBEA -TABLE M7 -GT. I want to wind my own coils, so to one side of the a.c. line, so place the please supply coil data. -A.C.B., Char- set in an insulated cabinet and use lotte, N.C. insulated knobs on the tuning and re- LOW PRICES generation control capacitors. Dead A. This circuit will give good results spots are eliminated with the antenna when used with an efficient antenna. trimmer. FAMOUS -MAKE The coils are to be wound on 11/4-inch RECORD CHANGER plug -in forms. ANTENNA MATCHING ONLY ?Ill a an antenna array consisting of a folded dipole mounted one -half $9.95 wave above a simple dipole. How do I ROCK BOTTOM PRICE match this combination to a 800 -ohm Pekes twelve 10-Inrh I_ Bch records. Smooth, g In transmission line? Please show how Change cycle. Removable metal these be connected and give one the base measures 13!¢-11:4 -; over- can , height 7'. . Complete with high -quality crystal data on which your design is based. - lve anda Imu,nnw lins iiir,. A real Neal al ea, 'u H.L.M F., US Navy A. The antennas can be connected by STANCOR TELEMATCH transforming the impedance of each to Regular List $9.50 $ 600 ohms and paralleling them across NOW ONLY -95 the 300 -ohm transmission line.

Used h, TV set tiers everywhere! Inez , Quarter-wave transmission lines are linos ellImenry, minimizes ghost Images, ten., ad- jacent channel interference. Attaches to antenna the impedance-transforming devices. terminal, of set with :inn nlim twin lead provided: that's all therm is in install, inn. Brand n rig - The impedance (Z1) of the matching Inal di -nlal ar!,n., nnl,l,ne I,o-lnntti u - n section is Z1= VZ.Z3, POWER TRANSFORMER SCOOP! where Z. is the impedance of the trans- Fully shielded: tapped primary for adjustment over iu -, In "an moll .N' Pr., , ide. _]u CI n' at Inn Band Turns Wire Turns WS Suac,ng mission line and Z:t is the impedance of (M I ILII size (La) size (Li) t1.t :n,T , c _ .,,ng hie "I MA -2500 wound the antenna. $2.49 200 -500 126 28 28 34 close When the matching section is con- 135 -270 82 28 16 30 I7/p inches structed from two air- insulated parallel GENUINE DELCO 66-150 38 26 II 30 15/8 inches conductors, its characteristic impedance 29c RADIO TUBES 29C 33 -75 18 24 6 30 I1/2 inches Z1 is equal to 276 log b /a, where bis Every Tube in Original Carton! 17 -41 9 16 5 30 I1/4 inches the center- to-center distance between IT I Pr IT 9 -20 31/2 14 3 30 I inch I.PIG It' conductors and a is the radius of the Terrific Savings! L2 should be wound at the lower end conductor. Note that a and b must be CERAMICON CONDENSERS of Ll. The spacing between windings in the same unit of measurement. \lade in Hi-- Il-rance; rated ',bi \'ill' ,all size WI pigtail leads. 7e each. 10 of one type for 69e. 100 of one type for 66.00 nun( mmf mmf mnmf mmf mmf mmf 2 15 411 68 140 232 4011 2Á7 20 47 70 15n 4711 ,.,-.-,.-::: 1 r0S p 25 50 108 170 2. 11 Poo 0861 1. 10 30 56 125 171 350 N Write For Ff-nlYEpMt BIGBARGAIN BULLETINS gwSES I Substitution receiver ein9 by Sign d.inCOOth *O SerVl SPee AM-TY. Dynamic FM EXTRA SAVING! Modern, problems. S tells HOW in Simple, stment -S -S - The and adjustment learn language. to ho se simple, direct WARD TV ANTENNA alignment to purchase New 9th edition now off the press. \t.t -31:91 T\' -89. 4I to 8s SIC. Cmnplelc with MI No cam equipment of :null -ldltn In-ad-io. Into Ilanitarr non-obsolescent Pn1ent information. fret insulator:. sol -lyOBoslc Eq 100 pages of valuable and Inatruelluns. Regular $12.50 ILst. only 62.95 Test 1 MA -31:12 TVA 88. Sanme s TV-88 but less 3u0- only Employs uiun lead. In and insulators. a . only $2.49 Available from all leading radio parts and ider hmad MA-31:13 TVA -94. 44 to 8$ MC: Ono or directly from factory hand. high gain. ('olnplete with hardware and in- equipment distributors structions. Regular list Wire $10.60 . .52.49 at only 40c per copy. Write for quantify prices on all Ward TV N. Y. antennas above. PRECISION APPARATUS COMPANY, Inc. 92 -27 Horace Hording Blvd., Elmhurst 4, Famous -Make Model 50 ANTENNA CHIMNEY MOUNT

Á -- size shim- \ a inquired, lnoVleu uilh hard,same and instriuMons Save bet' 511'; on this item CONICAL TV RECORD BREAKER MA3135 $ 1 .75 wire. All channels 1 to 13. No booster 300.OHM TWIN LEAD -IN Matches any ohm required. Lightweight-approx. 7 lbs. Immediate delivery. U o'I boss this great boy! Standard 300 -ohm lead- in 'l'\' and F- \I. Rip in quantity and , Users report up to 300 miles reception. per n $13.26 1011" MA -3136 wer Inn ft. 1 .40 t o, r I =n _ .02 ORDER FROM THIS AD! $10.95 DOUBLE STACK All prices f.o.b. Chicago. 25°c deposit required on C.O.D. orders. pay balance plus postage on delivery. Send orders to Desk RC -119. Minimum order 52.50. 8V -TV LIST $37.95

MIDAMERICA CO. Inc. NO JOBBERS. ORDER DIRECT 20% DEPOSIT ON ALL C 0 D ORDERS STORE WAREHOUSE 2412 S. Michigan Ave. 2307 S. Archer Ave. RAYTRON -441 Summit -Toledo, Ohio C a,raao la, 111. ChiCOO la, 111.

RADIO -ELECTRONICS for

www.americanradiohistory.com Question Box 81 If both matching sections are made of 14-inch tubing, the center -to- center spacing should be 1 inch and 4s/a inches for the 208- and 424 -ohm sections, re- spectively.

300e FOLDED DIPOLE SUPERIORITY

AT A GLANCE! 424AMATCHING SECTION SEE TEXT The vertical response of this economy TV á scope is usable to 5000 kc, not 50 kc. Response is flat to 750 kc; down 3 db A L L B R A N D N E W! at 1000 kc. Amplifier 208nMATCHING SEQON INDIVIDUALLY CARTONED! supplies a voltage SEE TEXT AR-3 A GUARANTEED! RUSH DELIVERED! gain of 20 at 5000 kc. e300nTRANSMI5S10N a LINE Check Ihn necessary feature before you buy any scope for TV use. The R.S.E., AR -3 Scope has been built by Ross TUBES Armstrong to our rigid specifications. It's a 72n DIPOLE SPECIAL DISCOUNT: Order( 5t' from each that embodies standard hori- complete unit The electrical length of the quarter - tube when ordering 25 or more assorted tubes! zontal amplifier and sweep circuits with 617 6FSGT SCV, section can be calculated from 150 Ea. 6K66T 606G 8770 normal sensitivity. wave 6K76 88SGT 7a7 2C 8 6K7G 6R7GT 7C5 The case is 8` high x 5` wide x 14" long, 2952 X K 2C34 /RK34 684 T 65767 955 6SA7GT 85L7GT ici attractively finished in "hammered " opal escent L - 1628 65C7 858767 12606 1644 65D76T 655767 12C6 blue enamel. Operates on standard 110 volts 7193 2C24 65FSGT 8VS 1466 E 05F7 8760 25ACS cycles wafts. Tubes, 3BPI -6AC7- where L is length in inches, f is fre- VTS2 6517 7014 /XXL SOCS -60 -40 7As SOCS 6SJ7- 6X5 -5Y3 -884. Instructions included. quency I9c Ea. 680767 786 SOLS in megacycles, and K is the 688 7E5'1201 2050 Complete specifications upon PRICE 57A 80607 7K7 2051 velocity constant (0.95 for open -wire 6VSGT 12876 3506 request. Satisfaction or your 6 %4 126x6 75 lines). X99 6 %SGT 126E6 money bock. 12AH70T 125J7GT 290 Ea. 1223 590 Ea. AVAILABLE TO JOBBERS $4995 Ì2Ás 6 250166 F. O. B. 121767 25L6GT IN QUANTITY TROUBLES IN BC- 223 -AX 2A7 12K7GT 32 LIST DETROIT 2%2 1207°T 34 024 6C4 I25A7GT 35Z4GT 1LA4 (WAG 125FS 43 1LC6 . I have a BC- 223 -AX transmitter SN7G7 12587 4525 1LDS 6511767 12587GT 46 1E1E3 that has been converted for a.c. opera- 6U7G 125LIGT 50760 1LK4 CRYSTALS 794 12581707 55 1LNS tion. There is an indication of r.f. in 12A6 12512707 1686 12ANGT 1978 11723 174 the antenna even when the key is up 12FSGT 24A 4A6 12146 25260T 5V4G 26 27 6111150 when operating c.w. What causes this, 36 32 50e Ea. SAB7 956 35/51 GAGS and how can it be cured ? -C.P.B., Gray, 35L6GT 1ASGT 6BF6 95011/VT90 35W4 156 68066 Maine. 67616 35.5 IA7GT 6866 RK72 3528 lC6G 618 58172 41 1C7G 6186 RKR73 42 107G 695 063 A. VT25 1D5G SW4 I do not know how much the orig- 5085 1E70 BA% OFF 39e Ea. 57 1F4 673 UP TO 77% inal circuit was altered during conver- 76 IFS° 12A 153 78 ILsG 12AT7 sion; therefore, it is somewhat difficult IUR 60 1C6GT Your s Has 1407 choice 185°7 1487 to put a finger on the trouble. It does áé4 1866 22 ASIATIC L72 Hi Output 49 8 /166 70L7GT seem that the final amplifier is not 3014 16562 SHURE P30 Lever Typa EACH s urna 51614 45c Ea. neutralized. The neutralizing capacitors 5X46 3D6 69e Ea. All Less Needle NO LIMIT 5736 165 255 304 are in the tuning units, so you will MGT 354 SAC, 1652 BUY AN ASSORTMENT 5Y40 1R5 3V4 BAG7 have to neutralize each unit. Neutral- 6ÁF50 154 SZ3 SAKS SANS 115 1172607 izing procedure is as follows: SATS ITSGT 656 SAU. 2a5 SACS 1. Bea. 6666 Tune the transmitter to 3,000, 66E6 367 No Ea. .C56r 0507 606 4,500, and 5,200 kc when neutralizing Sc. GALS 6F8G 12307 sOle 0 S.J. 6150 6L66 tuning units TU -17, TU -18, and TU- 8 6070 5305 25, respectively. HARD TO GET TUBES: Our tube stock is 2. Turn on. the transmitter constantly being expanded. If your tube is 3. Adjust the antenna -circuit tun- listed, write mil ing controls for maximum r.f. current not ORDER: E2.50 -Send 25% deposit 5" 450 ohm into a dummy antenna consisting of a MINIMUM Limit of 5 to shipments. Include sufficient DYNAMICS 100 -µµf, 5,000 -volt capacitor between for all C. O. D. customer postage-excess will be refunded. Orders with- Perfect- the ground and antenna terminals of clean- out postage will be shipped express collect. Where else but the BC- 223 -AX. All prices. F.O.B., New York City. at RSE? 99¢ 4. Hold the meter switch in the EACH osc position and close the key. 5. Adjust the neutralizing capacitor tee! NEW 1950 ORDER INSTRUCTIONS (marked PA NEUT COND) for minimum CONDENSER -RESISTOR antenna current. A sensitive neon lamp Minimum order -52.00. 25% deposit COLOR CODE CHART with order required for all C.O.D. ship- or a low- current flashlight lamp in se- post- It's SENCO's way of thank- ments. Be sure to include sufficient and to Demand This age- excess will be refunded. Orders ries with the 100 -µµf capacitor may ing their customers Seal of Quality received without postage will be shipped prove a little more sensitive than the greet new friends. It's yours exoress collect. All prices F.O.B. Detroit. and it's FREE. Just antenna- current meter in indicating send us your name and ad- Quantity and Export complete neutralization. dress on a penny postcard Orders Solicited 6. FREQUENCY CONTROL ... tau! 1 t 1 Rotate throughout its range to make sure that SUPPLY & the amplifier is fully neutralized on all KHVIV frequencies. 5ENCO RADIO.. ENGINEERING CO., Inc. 7. Follow the above precedure on Dept. O. 73 West Broadway New York 7, N. Y.. Tel. BEekman 3 -6498 1 85 SEIDEN AVE. DETROIT 1, MICH. all tuning units.

NOVEMBER, 1 9 4 9

www.americanradiohistory.com 82

RADIOMEN'S HEADQUARTERS + WORLD WIDE MAIL ORDER SERVICE ! ! 2.95 FOR BIG BARGAIN V. GENERAL ELECTRIC )50 WATT TRANSMITTER 1950 MODEL 51 L (ATI 3 items listed below) COST THE MUTUAL I. SENSATIONAL, FASCINATING. GOVERNMENT $1800.00 MYSTERIOUS SELSYNS. brand new CONDUCTANCE COST TO YOU -BRAND NEW- EXPORT PACKED 5100,00 E_ Srlsyns made by 1:. E. Company. Two or TUBE TESTER Tltin is lite famous transmitter , ea :: l'..S. Arm)' bombers rod more alai hart n_ connected to- wee. of :, . the Ils design and , ur t have been proved lt-It.- all kolas of 556.95 gether work per- r -r Anions, all then world. lT Ile entire frequency ange nt is,, ell by means fectly on IIOV AC. of oing -ir. which are included. Each taming unit has r w- its own oscillator ap ,Isle :n : :Ol ease Any rotation of the lie,,tcoilunits nd t- tm Itots,rs. and adent. using circuits Atli within -all tdesigned to "Perataaral toll dit - shaft nit une Selsyu leltey its particular frequency ange. Transmitter :mil :tyres -e Ilnlnhed un bl:wk crackle. and tithe ttnilliantmtter. voltmeter. - 1 Calibrated Inn n 1,1110 anale and all others connected to it will rotate n Ire' ammeter a e ...... s rl , the front t.tf ter" panel. lien are the specifications: FREQUENCY RANGE:h' 11 too 500 KC and Lilts to as weir as Rad -Graal scale exactly as Many udegrees ht the s me di- e 2) mt K fuse . fen-thin. following unerringly as If the units Front panel b and wilhhl sight moJ li ëe Individual socket: for all heeled together by shafting instead t Ion forr which dliagninis are fur - t uhe hase Ida wire. This is true whether you twist Ished. OSCILLATOR: S If.exrited. IYp,'s. Crone.' tberoto comsnsated. d filament voltage supplied In test the shaft of the master unit a fraction u hand cali- any tube etlr brated. POWER AMPLIFIER:I Neu - made. Unequalled switching flexibility al- a erulul loo or many revolutions. Useful trahaed class stage. using C" 211 lots all present :und future ill/Ws lu br tested for e indicating direction of t rather vanes. coupling circuit regardless of location of elrmeuts on tul,, rotating direct tonal antenna,. : n control- which a practically any length antenna. base. gas content. Detects ling innumerableu opera) inns it a dis- ndleate shirts MODULATOR: Class N" -uses two or ituens oI nv element of any tance. Complete with diagram and in- 211 tubes. POWER SUPPLY: Sup. tale. T,sls structions. Per /latched pair $4.95. dynamotor CON cathode. mach' eye and voltage recula - which furnishes 1000V at :1.1) MA tnr tubes as well as all ballast. amplilhct 2. ALUMINUM GEAR BOX IaxxxT that 12 or 24 volts. Com- and rectifier types. ,o rains two powerful electric and plete are to motors instructions furnished Model tso matched gear trains. 62 gears in ail Ferale e from i0V AC. SIZE:: "C "- doping 'front counter 21 t x23xtli 4e. case Winìng in size i3 4 s Total shipping ugt, $56.95 from to inches in di- 300 lbs., complete with all tubes ner. This unit is readily conterted In Including n full set of spares be- Model "P" - Ilandsome hand -rubbed

a . rotate beam antenna or any other similar sides necessary operation. portable corse ...... _ . 59.95 use amtorh poersuppl t . seven tu- $5.00 I units. antenna tuning milt and Moil- in roll hart with .rill, of 3. HOME WORKSHOP AT BARGAIN t ie essential plugs. above x $5.00 extra. PRICE, Accurate and precise ' speed hubby lathe, the essential ma- chine for the hone workallop. Sturdy VACUUM TUBE enough for light pnaluctlon work or fac- FCC AUTHORIZES RADIO FOR PRIVATE SERVICE!!!! tory standby service. Supplied with 56' of VOLT- OHM -CAPACITY METER belting for connecting to any available (The FCC announced that effective June 1, any American over 18 el. -irk motor or longer takt -off. Also in- years of age is eligible for a 5 year station permit. In the Then "Citizens" Illia a cluded In this unbelievable offer a e such ll -0lp lo "e ttslralnent than in a0)' other ice' band, neither code test nor technical knowledge is necessary.) nn accessories as a drill chuck with spe- Instrument the market, reg,, rd less of price. cially hardened tad steel a GENERAL ELECTRIC 15 TUBE TRANSMITTER- RECEIVER SET. This brand here acv a feu of jaws, 4' electric for the many features of this l uniate high speed grinding wheel. a cot - new 15 tube transmitter- receiver was designed mobile storage battery powered outstanding meter: tun hafting wheel and a large supply serviee. It will operate in the "Citizens" band where no amateur license to transmit of 5 Inch easy to read meter. buffing , [...nil. and a 4' sleet wire is necessary. It's a cinch for any experimenter to connect this unit for 130 V AC wrath Your cost $6.00. Sole ex- Operation by following the instructions and diagrams supplied, which cover numerous 6 DC voltage ranges from port a., Ili stributor inquiries Invited. appplications, including television. For those intending to use on car or boat, a new 0 to 1000 V (Input resist- dynamotor. exactly as originally supplied, costs only $15.00. Don't fail to write for ance as high as I megohm FREE descriptive bulletin. Order our RT -1248 for only $29.95, or two for $53.90. pr volt.) SENSATIONAL VALUE IN 5 AC voltage ranges from AC -DC POCKET 0 to 1000 V (No dry disc TESTER HEAT GUN MICROPHONES rectifier to age and de- This analyzer. featuring a selaithe repul- troy the accuracy of Mis ni,' pet .tl -Il ipb VACUUM TUBE BOLT ion type meter housed In a bakelite rase. Streantlned pistol grip rd ualiq all Ch aime represents heal gun. "hid era hous- METER). the Culmination of 15 years tidlrt shaped t - 251 ruble teen min- lJdryrultlit In the Instrument field by a ing. per .x1. >I ut top- 6 Resistance ranges from at lhk tnp- arge company specializing in electronic ute blast of lint air 101° 2 10 ohm to 1000 megohms. - flightfllght nationally test equipment. Fahrenhe 1 t. tirdina ry blow known brand rs have smell fan motors. -- $5.95. 4 Capacity ranges from .000025 to 20 RFD. Spre1111-atinns of the AC Model Bullet UVN.AOIII -lit' but this has a lifetime - A zero F: MIKE center range for balancing FM )volt -Olnn -Mi ll iammeter. lubricated At' -DC motor of the rugged yllh $7.95. discriminators. AC Volts -0.25, 50. 125. 250 .Ir -60e. l.l'S11-Tl1- :mourn cleaner type. that produces a hurri- Isolating DC Volts -0 -25. 50, 125, 250 either hot or cold air. Blow out tint TAI.K 5111(E midi resistor built into probe. s tell On handle 311111amperes AC -0 to 50 u fntln radio chassis. Dry out ignition Sturdy natural finish hard wood case. "r De Milliamperes Ick 98e. LAPEL M Ih I:S - srdustitems. Heat carburetors. till -dry paint. -- (Specify whether This outstanding development of one of the 0 to 50 nun o water etc. Thaw radiators or pipes. carbon or maghete leading fir l acumen+ tot test equipment Ohms Full Scale Warning:-Keep obi: away from your wife. cost., only $39.50 motilete With all leads, - because 93e. 100.000 Site will use it to dry her hair it 111u tr ted Ohms Center Scale will do It in halt the time of her ordinary - hair rin'rr, to say nothing Of her using it to T-32 Microphone o ilh desk or table 20.0110 ohm per volt SI'PERTESTER. 2400 stand Similar and made by same Capacity- dy stockings or clothing. or defrost the $2.95 in appearance ntiliterate i, -,antlr. Only $12.95. Satis- manufacturerh as Vacuum Tube V-0 Ca 05 to 15 Mfd. ad or money refunded if AUDIO AMPLIFIER -Brand new dual partly Meter pictured above. Specifica- Total lice. prepaid ¡thin 5 days. stage triade amplifier having 2 of the valu - tions as follows: ¡nowhere in the USA ble and scare, nr r type audio trans- DC volts at 20.000 ohms per volt; --$7.00. Stange in' formers that sell u (nt, over $10.00 a piece. Meter. lacking the AC Our PE -109 Power Plant Neat aluminum case. fully enclosed (larg- 0 -3v, 15v. 60v. 300v, 1500v. 6000v operated nges of Direct C t est dimension 6 Indiesl. Perfect for Inter- AC welts at 10.000 ohms per volt: alms,. com $5.50 Prepaid. gasoline engine coupled to a watt system. phono amplifier. mike unpll- 0 -6v. 30v, 120v. 600v, 3000v, 6000v 32 volt DCgnerator. Can lie adjusted ter or signal tracer amplifier for testing cive 12 to 40 V. output. Ideal for w radio sets. A sensational bargain at only Current: 0 -60 Microamps, 0 -6MA. 60 SCR 274N Command Set in locations not serviced by commercial or w run of the surnlus items $3.40 each MA, 600MA, 6 Amperes operation. (Made by Western Electric) that er nuire 24.32v DC for The Resistance: 0.3000. 300.000, 3 Mein, price of this power plant tested and in good condition is only 579.95. We SIGNAL GENERATOR 300 Mega THE GREATEST RADIO EQUIP- Aso a ply a converter that will rsupply 110v AC front the above milt n ffrr Genuine Laboratory -type precision lgnl Decibels: Minus 4 to plus 77 DB MENT VALUE IN HISTORY any DC generator. Manufactured and sold for $68.00 divided into 6 ranges Oev o each in large quantities during the war by Ali special 52.55. Northeastern Engineering Corp.. one M the 1'; accurate multipliers used. We also have No external source of power required for a limit s top a facturers of electronic ettuinment At ents brand nU.S. Govt. bands although there Is pu now of for the Five fundamental frequency. error in the range from PE -1098 in starting at 150 KC. Strong harmonics up to 30 cycles to 1 megacycle. original factory 120 MC. Five step ladder type atenualor as 9125.008 each, well as potentiometer output control. Regular This Sl'l'ERTESTER has valuable features F.O.B. Buffalo. 1000 cycle audio oscillator us ng vacuum tube. found in no other tester on the market. not a cheap neon sawtooth audio oscillator. such as WIDEST resistance range coverage. Audio output separately available externally. III[ ;HEST At' voltage sensitivity, WIDEST Weight without packing power level I1)Iti coverage, and the lowest SUPER SPECIAL material 16 Iba. which prive -only $29.95. We urge comparison yaa...,..... should show what with this instrument before buying env New 1950 Mtu.1 e1 +a,... aa.rm /oca//xm..,._.. on. world of difference exists other tester. M1a0SinalGen-Po Kit. Mod. between this signal gen- Mallon On -Off erator and the ordinary switch. Internal cheap oscillator used by modulation d "DRILLMASTER" external modu- the average serviceman. Complete lation Jack t with fused plug ELECTRIC DRILL sided.Internal and coaxial output lead. 40o ycle w'- Super Special $38.75. LISS- priced electric drill. ideal for hobbyists. Ì udl u availableva fores. Complete with sander. buffers. grinding testing 4 I . t . Thl i. bankrupt stock and only ndarnal fidelity checks on re.celvers. a few are available. Prevision roils for greater accuracy and POWER RHEOSTAT A sensational bargain max imum salrrility all 5 bands Dial calibrations Exceptionally Rugged.Trouble- at $9.95. Satisfaction from 150 K.C. to 104 M.C. This or y .,l t signal (ree design. Withstands severe guaranteed money I.,. .:, ti .: iI;le ia.ho iii 1e.: 1 In- r is 115 V.A.C. 80 cycle edrand e with everything. In- overloading to many times the refunded If returned tiudrs 3 !visit ale tbnl 1 l ratinas Receivers. a-iodine complete detailedretailed instructions. As- nominal 25 watt rating without prepaid within 8 covering up to 9.1 III',aa2 separate 40 watt , is ea lob. even for the least burning or smoking. Perfect for days. Transmitters including crystals. 4 -28v exmhtyperienced.nTheainweat price and the hest Dynamotor. (easily converted to 110v A(' 5)mal generator on the market for only motor speed control or line available factory-assembled collage adjustment. 3 sizes 50, operation/. Pre - Amplifier and Modulator. 2 15,75. available Pte 7Also fill and 200 Ohms. Regular price PURPOSE NEON BO te Tuning Control Boxes. and I Antenna 90.20. A L TESTER. 51) Coupling Box complete with R.F. Ammeter. Special $1.00. DCor RF. and cá complete Wtth.mslrur. 29 tubes supplied In all. Receivers and LINE FILTERS tient lnklet outlining' v s teats on adi, sets. Including Me location of fading. dead Transmitters Instantly detached from mount- Each unit contains two 4 mfd oil Oiled con- RT1655 sages. shorts. and making screen-grid, and ing racks for use in separate locations. densers and a high inductance 5o amp choke plate circuit tests. 35e ea. Per dos. co Removed from unused ireraft and In anar- In fully shielded case. Suitable heavy Only 5, 495 attractive display card- 13.50. anteed electrical condition. A super value rent connectors are nroviden to attach to at $59.95 complete. the input and connectors at d of frontty rand 11 tube.. nn dl cA super -heterodyn alters with innumerable uses oil reeeiver h:d FM Mann. The ultra Universal 4 lead broadcast hand Bayonet type radio pilot light sockets for DI A. R, automobiles latest tuhe oscillator coil (can be converted model and wherever isert is to pea's re . rcaluafng.nd .Beautiful railroad enthusiasts. etc. $5.00 a Interference abolished. A 912.00 value for chassis tluiminai cabinet. Tubes and to 3 lead type by addition of hundred. Marna licensed hulls. per 18 50e. 51.99. includa. Jumper). Ten for $1.00 BUFFALO RADIO SUPPLY, 219 -221 Genesee St., Dept... )¡BUFFALO 3, N. Y. RADIO -ELECTRONICS for

www.americanradiohistory.com Try This One

HUM DETECTOR It is often 11111101 ant to know whether Dynamic Mutual or not a potentiometer on an amplifier chassis is free of magnetic fields. To de- Conductance termine this, wind a small choke of about 100 turns on a core made of a thin iron nail. Connect the two leads from the choke to the amplifier input, IWN1\,,,,, T lJ BE TESTERS or connect one to the grid of the first a.f. amplifier tube and the other to re Dependable Income Builders ground (in a receiver). Hold the choke on the spot being tested. If any hum is present, it will be heard in the loud speaker. This method can also be applied to oscilloscope construction when it is necessary to locate and eliminate elec- tro- magnetic fields which may distort the pattern on the cathode -ray tube. A. A. BOSCHAART, Amsterdam, Holland of the Experts RELAY CHECKER In electronic circuits where relay for contacts carry currents in the order of Accuracy a few microamperes, it is essential that the contact resistance be less than 0.1 and ohm. Ohmmeters and resistance bridges Speed being unsatisfactory measuring de- vices for production work, this system was devised. MODEL 600 Never in the history of radio ser- vicing have HICKOK Tube Testers 1. New, smaller, portable, lower ever been excelled. Their Dynamic cost tester. Mutual Conductance Circuit has long been an exclusive HICKOK 2. Tests for gas content. development. Available in a com- 3. Reads directly in micromhos. plete line of portable, counter, and The meter M is a laboratory -type display models. Specially designed galvanometer having a deflection of 4. Separate voltage applied to professional features. The choice .004 pa per millimeter, and R is the contact resistance. Deflections of 10 to each element. of leading radio service techni- with good cians throughout the world. 12 millimeters are obtained S. Detects more weak tubes. contacts. Heavy low -resistance con- See them at your jobber's now, or ductors should be used between the write for latest free literature. contacts and the test circuit. The loop resistance effect can be observed by (401X1E0L5E3 shorting the conductors and taking a CTRI CAL INSTRUMENT COMPANY reading. 8, OHIO WILLARD MOODY, 1 DUPONT AVENUE CLEVELAND Washington, D. C. Please send me latest literature on SAFE HOME -MADE TV SETS your line of Hickok Tube Testers: It is a good idea to use separate a.c: NAME line cords on the high- and low- voltage ADDRESS power supplies in home -made TV re- ceivers, oscilloscopes, and other similar CITY STATE__ equipment. This makes it possible to re- l move all unnecessary voltage from the equipment when it is being serviced or adjusted. In KANSAS CITY , MO. the exact Center of America CHARLES ERWIN COHN, 1 CAYS CLOSER TO EVERYWHERE Chicago, Ill. A FAST RELIABLE ONE STOP SOURCE ' EVERY T1,NG I N RADIO- TELEVISION- ELECTRONIC BE YOUR OWN BOSS! Catalog No. 501, 144 big pages now being made Schoci MAKE MORE MONEY to Dealers, Servicemen, Broadcast Stations, Factories, Public Utilities, Laboratories, Engineer. In "DASD IN" you $1.00 now get THE nil Amateurs, Experimenters VALUE money- maters - doz- ens of on:Cable tested Its FREE . . . Write us if you haven't received it. mall order plan,. con- nasals' business ee- 1 aets, dozens of eme- 25c ticsi tested formulas, BURSTEIN.APPLEBEE CO. 1012 McGee St., Kansas City 6, Mo. 40.000 successful tested schemes - actual ex- WORDS periences men Send me your FREE catalog. started mon aloe- IN sWaf -with Ins than ., i TEXT $10 capital. 25e May Mrlyald. Send NAME U. S. tam^.. money rn- w.'"r( - NO ADS order, , . ADDRESS ALL Money Back y°'>.0 swall "MEAT"I Guarantee TOWN STATE NATIONAL PLANS COMPANY 1966 R Broadway New York 23. N. Y. NOVEMBER, 1949

www.americanradiohistory.com Association News NEW ,1,«!RADIOE LECTRONthe ICS MAGAZINE LIBRARY

INGENIOUS, CUSTOM -BUILT STORAGE FILE Another WALTER ASHE Value Scoop! each plus 6c each to cover packing and postage (any- where in U. S.) Holds 12 complete Issues of magazine in its present SO to 90 page size. Measures 12" x 81/2' x 23/s' Here's the brae I new, grand new way to preserve each issue of RADIO -ELECTR )NICS Magazine! Made of high quality Kraft fibre board, printed e nd constructed to look like a Buckram -bound book. Affords neat, o derly. flick-of-the-finger convenience. Handy Refer - once Index, p: nted on back, records the location of selected articles, wiring Pogroms, etc. A "must" for every bargain -conscious reader of Radie Electronics Magazine. At the low price you'll want several of thes serviceable, attractive Magazine Libraries. Order now for immediate delivery. Walter Ashe Radio Co. AE 11-48 1125 Pine St., St. Louis 1, Mo. Use the handy coupon. Rush my order (or: FREE!

_ Radio -Electronics Magazine Library at NEW (quantity) 25c each (plus 6c each to cover postage and packing) 1950 Remittance for $ is enclosed Catalog (amount) of Radio, Electronics Mail my Free Copy of new 1950 Walter Ashe Catalog and Television. 160 pages. The Treasure Name Chest of Values! Address .._ _.. _. ... RADIO CO. -._. - Order your copy City ...... Zone State today. 1 1125 PINE ST. ST. LOUIS 1, MO.

AID FOR ORGANIZERS outstandingly well organized grout: eluded such points as general transmis- One of the important stumbling The reprints are offered wit out sion and reception problems, modulated blocks in the path of new association charge to any service organization for waveforms and high- frequency propa- organizers is the formation of a set of use as a gir. L . gation and reception. rules, bylaws, and procedures. Howard ESFETA LECTURES The opening meeting was attended W. Sams & Co., Inc., publisher of the The Empire State Federation of by several hundred radio-television tech- Photofact Service, has reprinted the Electronic Technicians opened its 1 )49- nicians, including a number from points Manual of Procedure, the application 1950 lecture season September 7. The outside New York City. These were blank, and the technical examination set initial lecture was given in New ' ork largely from the Long Island Television up by the Radio Electronic Technicians City by John F. Rider, who spok on and Radio Technicians Guild and the Association of Ontario. Canada, an "The Nature of TV." The lecturt in- Independent Radio -Television Techni- cians of Westchester County. The meeting is the first of 16 lecture - sessions, each of which will be held in four areas in New York State -New York City, Poughkeepsie, Binghamton - Endicott, and Rochester. The complete program will extend to May, ending with a final examination- meeting.

Association Officials at September 7th ARSNY; Karl Nelson, Karl Richter, and meeting. Left to right: Joseph D. McNa- C. E. Cypher, Independent Radio-' ele- mara and John A. Wheaton, Long Island vision Technicians of Westchester; ioel Television and Radio Technicians Guild; Payne, ARSNY; Pat Avery and 'aul Arthur Silverberg, ARSNY; John Rider; Prochnau of the Westchester technb fans Sant Marshall and Max Leibowitz, association. Attendance figures ran igh. John F. Rider gives first ESFETA talk. RADIO -ELECTRONICS for

www.americanradiohistory.com1' 'rCCh1111tCS- PHILCO 48 -700. 48.1000 AND OTHERS These and several other Philco TV sets have a center -tapped primary on the antenna transformer. The input impedance is 300 ohms across the ends of the primary and 75 ohms between the grounded center tap and either out- side Co lead -ins are con- terminal. -axial your 1; nected between one terminal and ground. Signal strength and picture Moneys Wort

PR, OF ANT COIL ies GO" - 75n pNID ANT PLUG

ANT SOCKET ON SET TEfrEr100~

300n set."'

CHASSIS GND CONDUCOR

OUTER CONDUCTOR COAX ANTENNA I EAD-IN SHIELD quality will be improved if the unused part of the coil is shorted out by grounding the remaining terminal. This connection can be made on the antenna plug by connecting the co -ax across the 300 -ohm terminals and grounding the outer conductor to the chassis as shown in the drawings. CLARENCE J. JONES, Ch reland 9, Ohio NAar° AND INpN BIRDIES IN A.C. -D.C. SETS -... Squeals and birdies may be elimi- nated from compact a.c: d.c. sets by replacing the i.f. tube. The old tube may test perfect and can be used in another set. ALAN MCFARLANE. Aberdeen, S. Dak. Give customers a new appreciation BRUSH B.K.401 SOUNDMIRROR Intermittent noise on playback and of your service facilities recording has, on several occasions, been traced to a bad plate resistor Get the better, more profitable (220,000 ohms) in the first 6SJ7 am-1 plifier. A 'z -watt resistor was used in service calls the original circuit. Replace it with a i 1 -watt unit. Every radio service magazine raved about this latest ALBERT HOWE, Vancouver, B.C. business builder from the makers and distributors of:

TELEVISION INTERFERENCE Look around for old-fashioned clear tungsten lamps when unable to identify SPRAGUE CAPACITORS of television in- or localize the source Here is just the kind of adver- cu.tI equipment needed to re- terference. One such lamp caused two tising for your service business pair complicated modern re- entirely different interference patterns that you've been looking for! ceivers properly. And it demon- on two receivers in one installation. The "Your Money's Worth in Good strates to set owners exactly why offending lamp was removed to the Radio and Television Service" is and how the best service is service shop where it produced a third a handsomely 2 -color litho- cheapest in the long run. Each interference pattern on a set there. graphed 16-page booklet that copy can he prominently im- tells customers a lot about serv- printed with your name and R. L. CONHAIM, ice they probably never realized address. Fill in and mail the Donlon, Ohio before. It shows why good serv- coupon for sample copies and ice is worth good money. It details -or see your Sprague STABILIZING THE MODEL 900 VOMAX explains the large amount of distributor. Early models are unstable on the 3 -, 12 -, and 30 -volt a.c. ranges. This instability can be cured by inserting a Dept. RE-Ill. Sprague Products Company 1 -ohm resistor in series with one of the North Adams, Mass. 6.3 -volt heater leads. This reduces the and increases the life of the Please rush mea free copy of your new booklet "Your Money's voltage Worth in Good Rodio and Television Service" and explain how tubes. I can obtain additional copies for distribution to my customers. WILBUR HANTZ, Write for Columbus, Ohio (The McMurdo Silver Co. has in- FREE Name stalled a 0.9 -ohm, 1' -watt resistor in Address the filament lead of the latest models SAMPLE City Zone Stole of the Vomax.-Editor) L J NOVEMBER. 1949

www.americanradiohistory.com Earnings . . .. .:! LEARN RADIO-EIECTRONICS

This fast -growing science of RADIO, TELEVISION, RADAR and ELECTRONICS, offers tremendous opportunities, and in no industry is f RADIO -ELECTRONICS more important than in aviation. A skilled technician I who knows the modern application of electronic devices, as used in the aircraft I industry, is always in demand ... not only in aviation, but in many other / industries. Many large organizations call on Spartan regularly for graduates.

Often, students are hired months before graduation. / Don't confuse the RADIO -ELECTRONICS course offered by / SPARTAN with other courses, offered anywhere! As a graduate from this I famous school you will know the application to industrial control devices; / to the search for petroleum; and the important uses of radar, television I and other electronic equipment. / SPARTAN offers two complete and thorough courses. You will work on the most modern and complete equipment. You will / build equipment. You may join the SPARTAN "Ham" Club. Either / SPARTANS 21 years of teaching civilian and army personnel is your assurance of receiving the course prepares you for Federal Communication Commission license / best possible training in the least possible time. tests -first class radio telephone, second class radio telegraph, or class / You'll not need MORE than Spartan training -you "B" radio amateur. I cannot afford to take LESS.

NAME _ TAN AGE SPAA SCHOOL OF RADIO AND ELECTRONICS

ADDRESS

SCIIIL et ALR/NAIfICS CILLECE al ENCINEERINC MAXWELL W. CITY STATE eALfOUR. DIRECTO* ADDAESSDVr. "e a se Dept. RE -I19 TULSA, OKLAHOMA G. I. APPROVED -Write TODAY for Complete Information

ELECTRONIC LITERATURE CARTRIDGEREPLACEABLE STYLUS Any or all of these catalogs, bulletins, and periodicals are available to you if you write to us on your letterhead (do not use postcards) and request them by number. A STYLUS FOR EVERY PURPOSE It is necessary to send only the number of Here's the wide range variable reluctance pickup you have been '1 item you want. We will forward the request waiting for. It features a removable and replaceable stylus to permit to the manufacturers, who in turn will send use of the cartridge with all types of recordings, LP microgroove rec- the literature directly to you. This offer ords and commercial pressings. Change the size of the ball point as void after six months. desired without altering the fine quality performance of this pickup. A high fidelity pickup offering flat response (meets FM specifications). low distortion and featherweight needle force. Response is velocity NV- I-VIBRATOR GUIDE responsive to above 12000 cps. Needles available with .0010" ball The Mallory Vibrator Guide is a point radius for microgroove records, or .0015 ", .0022", .0025", .0030" for conventional recordings and 40 -page book listing receivers using vi- pressings. The cartridge has standard holes for mounting on tone arm. See it at your jobber brators, with the correct type of vibra- or write for Bulletin No. 141M. tor for each. Notes are included on installation, building a vibrator tester, and servicing auto radios. -15f B10/120 NV -2- ROTATOR FOLDER This 4 -page folder -published by the E. F. Johnson Co. describes their Roto - matic beam rotator and amateur an- tenna.-Gratis

.i NV -3 -PARTS CATALOG THE ARM WITH THE SLIDE -IN CLARKSTAN "INDIVIDUALLY This is a 128 -page catalog of standard CARTRIDGE HOLDER SHADOWGRAPHED" STYLII radio parts of many manufacturers sold Ballbearing Record Arms with the new Clarkston finer quality stylii are the result of by Bill Sutton's Wholesale Electronics expert craftsmanship and repeated checking Slide -in Cartridge holder requires no in Fort Worth, Tex., at standard "net" for close tolerances after each cutting and pol- prices. -Gratis soldering and fits all types cartridges. ishing operation. Only highest quality sapphire Quick acting weight adjustment for all rod is used. Entire cone h polished and tip is NV -4- SPEECH CLIPPER BULLETIN type records, standard and super-polished. Only Clarkston No. 145 offers a wide selection of tip The Electro -Voice Bulletin LP. Made in two sizes for radii accurate to .0001 ". Our describes the advantages in limiting points are made from records up to 12" and 17 ". diamond audio modulation peaks in amateur and CLRRKsTQN only the finest entire small dia- It See your jobber or write CORP monds available. See your job - emergency communication services. 170M. 1,000 for Bulletin 172M. 11927 W. P,e Blvd. berorwritefor BulletinNo. describes the uses of the Model Les Angles 34, Cal. Speech Clipper.- Gratis RADIO -ELECTRONICS for

www.americanradiohistory.com Miscellany I 87 NV -S- RESEARCH WORKER Aerovox Corporation has resumed CE MIDGET CONDENSER publication of The Aerovox Research Double Bearing Worker, a monthly technical publica- Min. rap. 8 mmfd. Max

ACORN 75 . nimbi Sic ea; 3 for S2.40 tion dealing with various aspects of HEADQUARTERS FOR TOP VALUES radio and electronics.-Available to manufacturers upon request. Gratis to TRANSFORMERS FILTER CHOKES Stock .21.100. 21. Hv In1 ohms DC I.m.red in Dumont These are NUT ' ISo -400 52.49 interested with indorsement T. Stock .21 -135. Ili I1. le 1511 n a -2011 ohms 1.49 parties of nnm.lit surplus hilt brand new nails:- DC Stock .21329. 111 Iiv 4J 17S n - 70 ohms DC 1.97 a radio parts deale. Innlurs used by Umnont in their TV sel. Stock .21.330. 12 11v is 110 asst 4(10 ohms DC 1.19 '11ií e 1110 183012 sold at a irarlI ll Stock . 21.331. II 11y I.) 325 ,na -1115 ohms DC 2.95 Stock .20.401. 11 their ufilifal lost. Ili Hi 4a ;11111 nia -11111 ohms í7C 3.29 Stock .21C- 12976. 5, ilv La 400 na -110 ohms IIC 2.95 Stock .21.129. nn Ili is :10 n a -2200 ohms tR' 1.59 NV -6-FOR TV TECHNICIANS POWER TRANSFORMERS Audio Reactor Stock .:20-11 Stock .21 -390. 1:1,', (Iv 4a The Care of Television Customers, 10i. 110 '0.611 Ce. 1u usa Inafnnnt -n 500 ohms DC .90 4500 V. ins. a handbook on courtesy and proper See. 111011 -11 -11)01 0. 10 ma. NATIONAL RF CHOKE 6' r' SP AK s. V. ac 3 amp. Almeo S - 1..4r 2, H u1110ve $2.'39 handling of television customers, has 4 V. Winding $4.95 Ií-1,4 r 41, Imp PO Stock .20 -304 I,,'ti1er' " "'d IIII II: RCA DEFLECTION YOKE been prepared by the RCA Service 49c ea. 3 for Iri. 1111 -51060 CF. $1.35 201.02 usell for 5TP4 proieeu'. ars. Very Special Company for use by TV technicians. Sic. 00 0 V.V et . I IT) ma. $3.89 5 V. rt. In, 3 amp. III 3 sud). S9.79 FILAMENT TRANSFORMERS .... k _ 2OC -4933 Stock .200 -4707 Stock _ 2004716 t'ri. 1111-5U l'y. secs. .:i 1. ,u T all Prl. 110 -SO /60 Cy. NV- CLAROSTAT CATALOG Pri. 11n-50/60 ; See. 7- .I 6.3 V. 8 mp. W i dins.. 0 -101111 Ser. 560 V. rl. (á 325 ma. $5.95 11$2.95 V. Test Catalog No. 49 has 15 pages describ- 25101 V. Ted Stock 20C -11056 6.3 v. n 3 amp.-1000 Stock .20D -4921 V. Test .e. aár,0 V. et. C I0 ing and illustrating the various types 110 Cy. anp.$3.19 5.0 V. et. Q 6 p.- Iri. -50'60 1500 V. Test $2.95 of fixed, adjustable, variable, and flex- Su. ROO V. cf. (a. 325 ma Stock ní20.307 5.0 V. et. cr O amp. l'ri. 110_50 60 Cs. Stock 1(20.120 C 3 to R ama. ible resistors made by Clarostat Manu- V. 110 V. (d 1 slop. Tapped asallm..sptroni e' rrl. -50/60 CY. 6.3 11.44 See. l' 3 V. et.t. lm 500 V. Test slY 7 a to as. facturing Company, Inc. Also included a 7.,1,1 r..I c.. icon s'. Stack .200-11325 Tnor1l,r.on .T'IIIF!la 52.95 is a description of the Clarostat beam Fri. 110 -50 60 I's. Sec. 850 V. et. (sail 275 ma. bender designed for use with 10 -inch (Winding tanned al 760 V A.F. VERTICAL HORIZONTAL SWEEP C -R tubes. -Gratis at. Im 175 ma.) OUTPUT TRANS. OUTPUT TRANS. 6.3 V. (a 1.5 amn. Stock .20.374 Stock 1(200 -4706 5 V. (d r, amp. $1.95 I.' With Ileflrcti.m .pke For use with Deflection woke 5V.w3amp. 211 D1 $2.95 RCA 201 DI Sa.s NV- 8- WORKSHOP TV ANTENNAS HIGH VOLTAGE TRANSFORMER HORIZONTAL BLOCKING STEP -UP. STEP -DOWN Stock .20011086 TRANSFORMERS An eight -page illustrated catalog de- Electrostatically Shielded OSCILLATOR TRANS. 110/220-220 /110 Stock -20 -17 í2.S9 Fri. 110 -50/60 (y. inning. :121 Toros _20. ISO W scribes the TV antennas and acces- a' S 110 3.39 See. 4400 V. ma. 1'names ui ar. 0 Trans. 230 W 3.95 sories made by The Asso- 2.5 V. 1.75 amp.-122 KV Test _. 22Trt i7.í9 400 W .59 Workshop 2.5 V. (d 1.75 amp. -12 KV Teal ciates, Inc. A short section on tele- Perfect for High Voltage AUDIO TRANSFORMERS Power SouD)s for orniet tans $18.95 616 parallel 30 watts ctout. Voice C CO vision receiving problems illustrates ''nl,l1n Itoéil038r. -15 -010p. mp. pr. mount. $2.69 B.T.O. TRANSFORMERS .Jilt n , tOut transformer. 20 output. V.C. tapped some trc 4.R -15 -2 511 of the antennas that may be re- Stock .20 -58 -5oo ohms imp. Up,. mt 52.19 quired for good reception in certain lo- Illrix. puise trails. nler-smCe ,rani /o mar. p.o plate grids. Electrician 51621. S1.47 irtOtm 51.39 calities. Graphs illustrate the radiation PHONE: WORTH 4 -3270 pattern and standing -wave character- ACORN ELECTRONICS CORP. TERMS: 20r7. rash with order. Balance C.0.lt. istics of the antenna systems.- Gratis All penes F.O.R. our warehouse in New Salk VESEY RE 1 76 ST.. DEPT. -11 NEW YORK 7. N. Y. I, o I nleri under 52.50.

All merchandise subject to prior sale, minimum order $2.00. No C.O.D. or- ders accepted. Michigan resident. must add 3 Percent State Sales Tax 525 feet Brand New Telephone Wire. 3 conductor braided insulated copper and steel telephone wire. It is of copper for conductivity and steel for strength. Worth at least 3c per foot, yet due to Brand New in original cartons C -30, an exceptional buy we can now offer CATHODE RAY TUBE ARC -5 Push Button control box with it at less than lc per foot. (Shipped 7 push buttons and selector switch. POST Express. Charges Collect). BARGAINS

ALL NEW GUARANTEED 3 TRIPLE TUN /NG HEADS CP I (Indicator Screen) $ .75 3FP7 -A LOO BC 450 triple remote control 3HP7 box for 1.25 Command Receivers (SCR 274 N Se- 5 B 1 Brand new, compact, spill -proof with 2.4S ries). Equipped with 3 tuning dials, 3 5 CP I dry charged (just 1.95 built in hydrometer, volume controls, and 6 selector swit- 5FP7 Add 35c each 1.00 add acid) $1.25 eac4ii. ches. Used, but in excellent 5HP1 condition, 2.45 to cover Postage and Handling. a steal 7BP7 at only $1.50 Each. (Add 25c 2.50 each to cover postage and handling). 7 CP 1 3.25 908 . 2.45 9GP7 3.50 NEW ANTENNAS

-131 Add 25c each to postage and handling New AN -A Collapsible 10 feet. 8 New Broadcast Band Push Button Tu- on ell 3" tubes, 35c each on all 5" tubes, inches steel antennas 97c each plus 35c ner (used in 1947 Studebaker Radios) S0c each on 7" tubes. 9GP7 shipped Eapreu, charges collect. each to cover Postage and Handling. $1.26. Add 35c each to cover Postage and Handling.

BRAND NEW FLAMEPROOF TELEGRAPH KEY 95c POSTPAID 6532 E4McNichols "1 Detroit-I2-Mich NOVEMBER, 1949

www.americanradiohistory.com 88

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Dual 1rp11t 2.2v o, 40 40040 150 .20 55OVCT .01e "r/3 2.95 1.54: Out w..0.5 V 30 20 ISO 40 MTR 3 Prong Bar 100w for scie 20040 20 80 á 7u0YCT .017 rr/3A 2.25 Sptl -lu 722. Prue $1.'2 2410 15025 40 25,200 20 50 .40 51.19 2x20 25 2440 150 24 350 .30 2300V .14141 'A 8.49 .15411 14.8.18 M C. 500w 30-IS ISO 1114(1Y'T 1 4017.1 CRYSTAL DIODES 8 400 .30 I T/I0. 3.49 $1.19 150 .15 N: % .1 1421 for f 1'T/.1.16.6/.1.6.3/.1 154R 8.3.10 MC. 500w $1.00 10 56.30 25c ea. 10 For $2.25 151111V .160 rT/12, 301-/.01 6.95 11423 1.30 10 for 14.00 100 150 .15 61.19 1826 3.00 10 for 27.50 2410 300 50 IDlOVCT 4 .l0 TAP. p5n /LO} 6.95 .C538 2.3.5 MC 300w Fix 20/20 350/25 4 150 .14 400V5 Link $1.19 -81' áiO4 1.79 DYNAMOTORS 20 30 25O0 V/2 .1735 2 -3.5 MC. 300w Var. 2430 SO 25VCT 3.95 OS TYPE CARDBOARD 1"I'/3A Link 30.20 150 $1.49 >L,1rn . _ _ x44441'l`T .190 ' :;.t 2.5/IA 3.95 30 /2O 350:25 w /LONG PIGTAILS 2c3o0V i 45V/3.5 *C390 5 -7 MC. 300w Fix. al 10'SO'100 450 100 50 .042 1t5, 3.95 Link 53 49 Mro. 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Each 926 -68 928 _ fra rI RadlADnn. 150 .78 Can he used w1h ISO 3440/10 41 5V .500 $1.49 701' sí.95 9266 -16 12wá 60 -40-30 100150 25 1.25 926 * -14 ea. 131e i44r:rce.nulesrent IIKIrt 8-8126 544 75 1.25 5nl'5'l'T- l 144441' 3. 1.95 926C -19 100 for 25 1.25 .14t'l'T .1.40 -.4(15 3.00 ^020í-1'T 512.00 10 450 30-20/20 450 f 11.95 928* 20 525 25 .50 2XISOV 21 -910 4.25 2IOV'CT 3.95 for Dal:- 50--30_10 350 .S5 :8 75c 50 25 2221í'T- i .ull,5 2.49 12ík 1 . 400.20.20 150 24 izo -.0771 CNDSR SPECIALSI 450 .35 2544í0'r ¡ J 1226.25y - I 1.5A 2.25 1619 40 20 150 25 MF VOLT PRICE -1819 -1619 20 450 r,40V .452 4.95 1 0 O 800DC 5.29 30 1500, 5 20 .18 177210T 1,2 24.00 21c I0 50 100 350,100 50 20 450 40 600DC .30 Aversatile High 25;150 -150 4000C Tube. New. S for 51.00 1O 10 -10 Filament Trans formers-113t' /50 -60 cos input SOODC .11 6 50 330ÁC 1.83 20 ROTARY 250 BEAM Ratite Each Ratina Each 200DC 1.00 Higain Dyn 1SOODC 1.05 Mike Xfinr MrD. 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KIT LUGS LARGE 25 400.25 .59 -+:: RADIO Elee ape 40-40 M549 4. *550 fn. ICAT1qN54'T 1óó 1.00 40-10 80 450 150 .69 Mobdeo Dipole 74" 131LÌBCirTYST.emc BARGAINS KIT LUG SMALL 40-40-10 450 .89 qU1PMENT NEW TORII 7. .Y- RADIOTvpK300 for 1.00 40-30-10 450 .79 KIT 1011. FORMS 3xIS-30 300 .69 see 49c N OMpANY ,..7Hw.,.==4.1.wr1 GALORE 1.00 2430,20410 450 .98 .niai IIF....50 for

Ti you doort zeceeoe ouz The only book that covers 33abio birty=lfibe Dears Ago the entire field BARGAIN 3hl éSrrn9bark Vublitaiion9l CATALOGS ELEMENTS OF you ze lo4túúg mo'ce y HUGO GERNSBACK Founder SOUND RECORDING A RADIONIC SPECIAL! Modern Eleetrin 1908 Electrical Experimenter 1913 By John G. Frayne and Halley Wolfe Stacked, All Bond Conical Radio News.. 1919 Science A invention 1920 A comprehensive and up -to -date work- TV Array... at Lowest Cos} Television 1927 T's harr! Scientifically Radio -Craft. 1929 ing tool for use on basic sound prerislnn made, all-band conical Short -Wave Craft 1930 designer, operating TV array -giving nimumtremendous In- Television News 1931 problems by the 1908 and absolutec nllno ter Wireless Association of Anuries engineer or technician. enre at no greater The authors present in detail those the using dipole. 150 or direct to 72. 150 or Some of the larger libraries in the country still have subjects which belong to the restricted :41144 ohm Ifne with minimum loss. All ducal con- ELECTRICAL EXPERIMENTER on Ole for struction. 30 foot mast copies of field of sound recording and repro. included, Amazingly $11.95 interested readers. Ion' of ono 1F duction, and which are not discussed price aIII lots of 3. $11.45 euh devoted to the allied fields in books «4 100 In the November 1915 issue of radio engineering, etc. l st, $1.25.6.l00Ó feet S11.251 of electronics, 211F deposit with order. balanq C.O.D. Other closely related subjects such as ELECTRICAL EXPERIMENTER electromechanical analogies, acou/tics, vacuum tubes, and R A D I O N I C audio amplifiers EQUIPMENT CORPORATION Increasing Wireless Range by Kites are also treated. Tribune Theater Entrance Wireless Telephony Now From Wash- 170Y NASSatI Street New York 7. N. Y ington to Honolulu 1949 íí'4401h 2 -0422/ Open dalla 9 bs 6--Sa, ,,L, 4- 686 pages Construction of an Inductive Tuner by 483 illus. MAIL TODAY! Milton B. Sleeper $8.50 C valw+ The Amateur Radio Station Which 10DAY EXAMINATION 1 Aided Uncle Sam OIT Y.8F8arA8vO[féRUOb° p.r4atla --.. I A Machine That Captures and Holds ON APPROVAL COUPON olRA13SO ]g11 Te CUltl`., Ue t0. 1 Wireless Talk E SONS, INC. 1 JOHN WILEY EQUIPNIEN'ti t 440 Fourth Ave., New York 16, N. Y. --_-N1C 1 N Y' The Smallest Loose Coupler YorK 1 Please of ; UIO TleReg: ßar5asn send nie. on IO days' approval. a copy r,c $treet. 1 latest Pa1A s 1 How Wireless Waves Travel Around Frayne and Wolfe's ELEMENTS OF SOUND Nassau éf Y° ut 1 13OY seU. 1 decide to keep the book. I 1 levt5ion Earth's Curvature RECORDING. If u5h T'ree a T the will remit plus postage; otherwise 1 wilI $8.50 Please of Rador1e.. Meter by Samuel V 4 asalog Acce How to Build a Wave return the book postpaid. and 1 ...... Name cabe...... Cohen ...... 1 - Mounted on Slider Address 71,\36£...... Loading Coil £SS...... Si --- City Zone State ADDRESS - A Home -Made Tuning Coil by Samuel Employed F'. F. Dunn I I 1'lt' (Offer .i L I' . i' An Efficient Detector by William Guier Tm

www.americanradiohistory.com People 89 Dr. Oliver D. Sledge ha, b& en ap- pointed to the staff of the NATIONAL BUREAU OF STANDARDS, where he will do research in the Microwave Stand- AMPERITE ards Section of the Bureau's Central Studio Microphones Laboratories. Formerly a professor of electrical SOLVES EVERYDAY at P.A. Prices School of PROBLEMS engineering at the Georgia HELPS YOU GET Technology, Dr. Sledge will engage in AHEAD IN LIFE limes have you lost research on microwave attenuation How many money because of mis- Ideal for 300 me take in figuring? Do you know how to figure quickly and standards for frequencies above correctly? Can you figure discounts. interest rates. taxes BROADCASTING and on radio measurement methods. and all the other calculatit's you meet up with in your He has done extensive work in elec- daily life? RECORDING Are you having trouble qualifying for Civil Service Exams PUBLIC ADDRESS tronic and radio engineering, including or Armed Services Promotions, because you're not up on electronic digital computer circuits and mathematics? "The ultimate in micro- he joined the Here is the book that sines you a good background In phon quality," says radar equipment. Before mathematics: that takes all the irritation and drudgery Evan Rushing, sound out of it. You don't need Bureau, Dr. Sledge was Associate Pro- to be scared of mathematics. engineer of the Hotel because here's the subject explained without frills, with fessor of Electrical Engineering at the out useless computations. Here's the book for men in radio New Yorker. Georgia Institute of Technology, where Jabs; for business men: technicians and craftsmen, explain- Shout right into the ing and answering everyday mathematic problems In easy new Amperite Micro - he also conducted radar research. to- understand words and illustrations. phone-or stand 2 'sot Yes, it's the key to simple understanding Octave Blake. president of CORNELL- of loathe. away -reproduction IS matics. It's a real homestudy course in mathematics for always perfect. DUBILIER ELECTRIC CORP., South Plain- the man who's alert le its importance in the world today. Not affected by Models field, N. J., was elected chairman of the ELEMENTARY MATHEMATICS any climatic conditions. RBLG -200 board of RADIART CORP. of Cleveland, EASY - SIMPLIFIED - PRACTICAL Guaranteed to with- ohms of stand severe "knocking RBHG -Hi -imp. Ohio, a wholly owned subsidiary CONTENTS OF BOOK - - --1 Wildberg, for- CHAPTER I. Arithmetic _ Addition Subtraction around." List Cornell- Dubilier. L. K. tIFactoringl - $42.00 and general man- CH Amen iji1iIl and Cancellation -Fractions merly vice president -Decimals-Percentage-Ratio-and Proportion. III. The Metric System. "Kontok" Mikes ager, has been advanced to the post of IV. How to Measure Surfaces and Caper - Geametryl. SKH, list Radiart president. CHAPTER V. Powers and Model $12.00 lotion. Involution -Roots and Evo. The parent com- CNA Mathematics Model KKH, list $18.00 Manual and echnicl Craftsman all -Thermometer con ve rs one- pany bought the Graphs or Curve Plotting-Log. ONLY anthills-Use of the Slide Rule. Offer. stock of Radiart CHAPTERPT VII. special Mathematbre Special Introductory for the Radio Technician. folder. from Maguire In- t CHAPTER VIII. Commercial Calcula- Special 4-page illustrated tions - Interests Discounts $1. and dustries in 1948, Arithmetic.- - CHAPTER IX.Wg and Mean. and continued its u re s-S rseftll Tables. operation as a man- Send Stamps. Cash or Money Order. AMPERITECompany Irle trarrod, :adit. ufacturer of tele- Ir Can M. r' rri.d Rraddy TFCHNIFex Sol BROADWAY NEW YORK 12 N Y :s Year Pork. vision 110 N. Frankkn St., Clime, 6. Ill. King W Toronto and automo- . ur 6, 9 In.) Conodo Allos Radio Corp Ltd 560 St bile antennas and -J automobile radio vibrators, with Mr. LItARN Wildberg as vice president.

John V. L. Hogan, president of Sta- tion WQXR, New York, has with- drawn from the management of the Interstate Broad- casting Company, operator of the sta- HOW TO GET THE tion. He will con- TRAIN QUICKLY! centrate his efforts MOST FROM OLDEST, BEST EQUIPPED on facsimile and YOUR RADIO SCHOOL of ITS KIND in U.S. other fields. "KNOW -HOW" 2 Oppadmallil4 Melds Learn all about new. way of , fixing Come to the Great Show of COYNE in Chicago dur- William Warren ramplifieddios. Nothing complex ing our 50th Anniversary Year! Get quick. practical Davis has been ap- to learn. lating. training in RADIO- TELEVISION or ELECTRIC - sed by n and e U beg ñ 1T1V. G 1 Approved. Finance for non-veterans. pointed to the Electronics Division of pet. Send fora FREE plan manual: "THE INSIDE Atoll Coupon Today for complete details. the NATIONAL BUREAU OF STANDARDS, RY.' today. as pages -easy to d! Shows how NOT "HOME- STUDY" COURSESI where he will do research on the high- obsolete methods preventve full N I \'o11 learnle o 'dl. full equipment. not by mall. your real ability. Explain a1 NEW Fi '.t nof tr.' iinstructors to help techniques. You ow it to you and your rolare to 'd y'nu get speed electrostatic memory of the elec- "gel out in front" n work. ready quickly for a better job. a fine future. your computing Clip coupon for big illustrated tronic digital machines. His SEND COUPON OR FREE BOOKS Coyne book on either ELEC- work will include tube characteristics PENNY POSTCARD FOR TRICITY or RADIO -TELEVISION. Both books afili sent FREE if yon wish. No obligation; no ealesman and general applications. FREE MANUAL TODAY! will cull. Act NOW? Before he came 9 to the FEILER ENGINEERING CO., Dept. IIRC9 O . W. COOKE, Pre.. Bureau, 945 George St.. Chicago 14, Illin.i COYNE Electrical& Radie School. Dept 139 -81H 500 S. Street, Chicago 12. Illinois he was engaged in Please 111'511 my FIREF. copy of "The Inside Sale," Paulin research on com- Send FREE BOOK and full details on: ponents for electric Name ELECTRICITY RADIO- TELEVISION NAME fuzes and has de- AdOH'ss signed and devel- ADDRESS City Zone. . Stnte oped equipment for CITY STATE vacuum -tube meas- George Ra Sommers, formerly direc- ments. Davis was tor of Pacific Coast sales for SYLVANIA f'IASHTHAT VOL TA GE Turn let altar Extinguish the mon on the staff of the ELECTRIC PRODUCTS, INC., has been ap- a al r Instantly ad toltsee N,nt on d1.tAC. or Naval Ordnance pointed assistant to C. W. Shaw, gen- AlsoYIIH. Tells Mother ACe 04 Virtually bunwutpront °wean Plastic Md., teed 1 !sct boon' opetanun Laboratory at White Oak, from eral sales manager of the radio tube test r se it- ileatble test lods and 1947 to 1949. He was an electronics division, according to an announcement orals. A "must" In Recuira I and ,.dlu en- .arcs. Only 12.75 eatnla! gineer with the Naval Research Lab- by R. H. Bishop, vice -president in IMOUSIRIAL OfYIC1S INC N oratory from 1942 to 1947. charge of sales. EOGEWAIEA 3 J

NOVEMBER, I 9 4 9

www.americanradiohistory.com People

George K. Konz has been appointed assistant manager of advertising and ISOLATION sales promotion of NATIONAL UNION SUPPLIES 1 to 20 AMPS CORP., Orange, N. J., according to an announcement by Emil J. Maginot, sales BENCH TRANSFORMER manager of the 6 Volts D C, Continuous Duty company. Konz, formerly with National Union's advertis- ing department, has since served as as- sistant director of public relations for the American In- surance Co. of Newark.

Lloyd M. Hershey has been appointed

Pater 1 director of research for GENERAL IN- STRUMENT CORP., Elizabeth, N. J. it was REGULATE YOUR LINE VOLTAGE Conduction Cooling announced today by Richard E. Laux, Increases Rectifier president. TO FIT YOUR REQUIREMENTS Power Rating 11/2 Times Hershey previ- ously was assistant New Electro Model "B"' costs no to the chief engi- N -303 VARI -VOLT JUNIOR more than the conventional type. neer at the Halli- Completely different application crafters Co. in Chi- $15.00 DEALER NET cago, and of selenium rectifiers aided by prior to that was in charge A voltage trans- conduction cooling, dissipates over regulating isolation of development re- former to make your bench test volt- heat. The Electro 3 times the search operations age exactly what you want...on 117V Model "B" has proved itself the for the Hazeltine line, variable from 95 to 145 volts... most efficient direct current source Corp. if line drops to 90, variable from 75 of power known. Gives instant to I I5V....output adjustable in It/z C. readings, and offers ample power G. Roberts has been appointed volt steps...metered output voltage product manager for broadcast to operate any receiver. Peak in- and ...capacity up to 250 Watts inter television equipment for GENERAL ELEC- mittant, 50 -60 cycles...for radio and stantaneous current rating of 35 TRIC'S transmitter division, Syracuse, television receiver resting at under or amperes (from 50 to 60 cycle N. Y. over voltage...to isolate "hash" and 115 volt power source), permits Edward Maged has been appointed live ground from AC -DC equipment operation of two receivers with ...controled voltage for meter calibra- sales . manager of RACON ELECTRIC push button solenoids. tion...speed up or retard heating of Co., INC., New York City, where he light soldering iron...and for many APPLICATIONS will coordinate sales advertising and sales promotion, other similar uses. Test or operate auto radios, re- according to the an- nouncement by Mr. A. I. Abrahams, See your local Halldorson distrib- lays, telephone circuits, laboratory president. Maged was formerly sales utor for complete line of replacement instruments and many other low manager of the distributor division of transformers...exact duplicates televi- voltage requirements. University Loudspeakers, Inc. sion and auto Vibrator transformer replacements, or write direct to us for Frank A. Hinners has joined the staff complete information. THE HALL - ONLY ELECTRO HAS of JEWEL RADIO and TELEVISION CORP., DORSON COMPANY, 4500 Ravens- Long Island City, Y., ALL THESE FEATURES N. it was an- wood Avenue, Chicago 40, Ill. nounced by Don J. Ferraro, president of the company. *1 to 20 amperes at 6 volts con- tinuous duty Walter L. Stickel has been appointed national sales manager for the re- Damped volt and ammeters * ceiver sales division of ALLEN B. DU (no wiggling) voltmeter 3% MONT LABORATORIES, INC. He was for- accuracy merly manager in charge of the RCA - * Less than 3% A. C. rippleorhum Victor Division of the Leo Mayberg * Heavy duty selenium rectifiers Company, located in Los Angeles. BUILD IT Yourse/fe' *8 heavy duty power tap ad- William R. Kennatigh, who has been justments Os scO associated with the radio and television TX -9 * Heavy duty transformer and production field for more than 19 years, choke has been appointed chief process engi- GEIGER * 6000 mfd. filter condenser neer at JOHN MECK INDUSTRIES, INC., COUNTER UNMATCHED NET PRICE $43.50 Plymouth, Indiana, manufacturers of and radio receivers. 4 }-.... n; 'ril;utur nr If "tih l television KIT! Here it i.' A regular production model TX -9 Geiger counter construction kit. No jumble of tricky parts -all sub -assemblies completed. Just fit it together. One hour's work for an experienced man. This port- able Geiger counter is the type preferred by professional prospectors. Send for com- plete details now! Fnnccr ALmw.,.tutca f It.,ncn El mun.in i. ELECTRO PRODUCTS LABORATORIES Omaha Scientific Supply CO. Jemen Industries, Inc., 329 5. Wood St., Chicogo 12,111. 4507 N. RAVENSW00D AVENUE. CHICAGO 40. ILL. 3601 N. 24th, OMAHA 10, NEBR. RADIO -ELECTRONICS for

www.americanradiohistory.com COMIllunicatio99s 91 DON'T STOP TV DOPE! A BETTER SURPLUS PRICES SLASHED! CONE-BUY .. Q Dear Editor: a N William Krider (July issue, page 97) 12" DE LUXE SPEAKER BAFFLES --Dynamotor ioorer. Shp$. t. 6 lbs 52.9i had better find himself a hole and crawl P-23 HEADSETS , . 5 cord & FL + 1.29 NS -30 HEADBANDS 15 into it, because he's going to get jumped D-2 PL -54 PLUG with 13' tipped dole and .15 n I..; 1 00 L D YoAthn DYNAMIC HEADSET A HAND MIKE tSIU 51K on! " IU Sluppitlg w tacit 3 lbs. 195 tn He says there is no possibility of TV minutes. Ma- NE -48 NEON BULBS . . . 115V 19e Ill for I.ú9 r - lnrlad NE20 NEONS . Min. bay. 115V & 15 fit 1.00 in gram his town for at least ten years as he L e mains 4 TUBE AMPLIFIES FOUNDATION . . Mack I box cackle cabinet slide 1 Integral near li -in chassis. Contains: is over 90 miles from any city of 50,000. having tally poem ti ass, a eideiiset's, t4' esisOors. eut. drive shafts turn- Slips. wt. 4 Ina My Rand -McNally map shows that he 511W25 OHM "UIVIDOHM" ADJ. RESISTOR ing simultane- is less than 90 miles from Tulsa, Okla. ously at the following speeds: Uhmttel ea. 29e 1 ter LOO 4000 Grinders, buffers, etc. SOW -15 OHM RPM- flexible shaft tools. RHEOSTAT (IRC) " shalt ...50 And if he can't get the station Tulsa 150 RPSI- wrapping fishing rods. slow speed tools. JACK BOX BG -1566 (3661 Leas kuuh. ...89 HIGH 25 RPM-Der. tray rocker for photo darkroom. FIDELITY CRYSTAL MICROPHONES.., will have pretty soon, he really does 5 HPM-Turning barbecue spits. Sensitive diapitt Jam. high flamed. typ.. Adv. Dlep. Beams Thousand Other $95 t l is "U.D.x ie" near. Rubber 611c/eta-mid. need TV articles. 981: Uses Around the Work Shop. ONLY Lean housing. ONLY 90 ' fed to 110 volts A.C. ALUMINUM HOUSING for crystal mike...... 15 We are over miles from one sta- $7.45 PILOT ASSEMBLY . Faceted Red jewel. tion and more than 130 miles from an- plated brass hsë With bay. bulb 2st ' tut 1.00 DYNAMOTOR D -1 =30 P.E. MAGNET WIRE . 400 FT. ROLL:: .19 other. We get them every night, and 0-1 Convert, to I to V .U' in ten minutes. 6V. D.C. COOK RELAY Makes 6, inteak I. 12 liagram in- ... cluded. has shaft whit squirrel cage ohm coil .913 television is pretty popular in our town. 2 blower. also gear reducer with shafts 110V. AC RELAY (W -L) . . , SPST. Noun. oneu .95 I and al the other end. 1001 2ÚA. contacts .98 have repaired several TV receivers, pulley's uses. NEW 4' PRECISION ETCHED DIAL... O- t00uuv 10U'. installed antennas, and checked sets. 11'11'. ' non:. Plated brass .29 RM -Y9 PORTABLE FIELD TELEPHONE 8 mod /500WV ELECTROLYTIC . . . can, 2xs. " a CHAR! FS F. JOHNSON .. r 49 1 teal portable litId telephone. nM -4 RECORDING MOTOR (6.1.) Adoptable Denison, Tex. . plote In a rugged steel rase for /a: Tj .d neat. Ringer !Sr WWi either 33 -113 or 78 RPM. Silent oi,erstmg circuit and l9 IIIE. TAPE or DISC RECORDING-PLAYBACK. handset No leather rase to .1 ar e. /'rampart I111V. AI' 3- 1h, -.q 524. ". Less turntable. LIKES READING ABOUT TV :f 36'x9'- J as remote control .Il i we wheel A rid, glair.plaie. el. 9 5 on se -7,.,--, .. 4.95 11 _e I. Simple two wire pera- 7RI COIL, WIRE RECORD-PLAYBACK HEAD Dear Editor: 15 miles distance and up- ! Call be used for television I Itio11 standard I Pin Ping-in I I S nr. Item go. \ \l Rewty, rte.). disagree with William Krider. hot. intercom system. c 695 nnantes outside and Inside work. etc. Light SEK.KtE, 11 . x"ef' .PECIAL don't think you publish enough about TO WIRE HEAD lbs. Excellent nd itlo r'. - I Ll CO1 ANo AST SECTIONSea. r television! LOW EACll.. FWEV lbs. 3 fu 1.00 2 for {1R.1á MOST POPuLAR KIT OUR 22 EAR XIS- On a set which I installed myself : LEO v "JUJUS() 1A rr. PLUGS after reading TV articles I get good re- aid CONNECTORS each Lrr. " YOU CAN'T CO WRONG G FULL TOUR CHOICE for only -wU POUNDS at selected-r new & dismantled Radio r. ception from all Detroit stations, 53 Electronic parts event Service, Amateur, Iul For the NCR -522 PLQ -167, 1'L -172 For the BC-34e , t TRANSFORMERS. :AREit ALCES - miles away. Even if certain articles PLQ -t ll RESISTORS. For the BC -733 PLIJ_'1 l P. CONDENSERS, ETC. ETC. don't help me personally, I get a kick For 269 -F Radio Compass Inserter. PL- 3ío8 -.. For the SCR -274 -N THESEí O w:. Ihs) ND MUCH 2.95 100 >u 11E FOR NLti out of them, as do at least out of PL-147, 148, 151, 152. 153, 1:,4A. 156. For the BC -375 l'L- 59- PL- 61- 1'1. -6t RADIO HARDWARE TREASURE . , FULL the 1,200 in my high school -many of PUL'NP Screws, Nuts. Washers. bugs. For the ART -13 U -SC. U -1011. C -1811 of etc, For the ARC -I a BANDY SELF- SEALING BINGED11 whom borrow my copy of R -E just to U-1511. U -181 l MC -203A coupling Coax Fittings 1 iu SIE'TAL CAN. Shpg. wt. 2 Iba read about TV. Anyone who tells you PI. -259A (83- 1SP)- 1-0- 21U- UO -22U GT TUBE SHIELDS . . . utniversal slip-on PL -184 M -359 U -11/U es. 5c 21 fur 1.00 there is too much about TV in the mag- AN- 3108 -28 -191' I MEGI% PRECISION RESISTOR (IRC). Wire - AN- 31118 -12S 7 Combination and 69 Male ,,mil azine when it is the coming thing must AN- 3100- 1274-33 f Female .65 -400WV OIL CONDENSERS 10c 12 for 1.00 PL -63 SQ -44 L -82 RADIO NOISE FILTER . 6- 30V UC. IO auiri. want to live in the old era of silent 1'1.56 SQ -86 Em. for Mobile e'lpt. 2 "sq.xl" 59 RADIO- AMPLIFIER STEEL CABINETS Ifrom movies. ... BC -733 D M'.\ scut radios). GLISTENING C111t11S11: t Hl t.LE LARRY SHAW c SIDE: 'TRIAL. Marine grey finish. Will HE.tITIPV .t 10 -tube a perliet receiver for lateral blind 15n hoc guidance (CAA type certificate) -1045. Excellent ry KLECTItUNII. TES -r, INDUSTRIAL Port Harar. 1 / -1'h. Tl' or MEDIC.tl. EUI'T. 101/2'x9Y "x10',' 1.98 condition lÚ8 -110 MC. Tube plement: I- 12SÚ7; Shoe. wt. 12 tbs. (BRAND NEW. -12SH7; 1 -1 ^t6; 1- 12AII1GT: 2 -1"567 ; í- 1.511 717A -tubes alone worth more than tills DC -AC ROTARY CONVERTER (G.E.) . . SOME DO ADVERTISE low SCHEMATIC FURNISHED. 63.95 aio runt dbl). II5V.DC to 7Ut'.At'. 3ar "ylle -sit ." price. Each high. Shpg. wt. I, lbs 7.95 AN /CRW Y.H.F. 110V.AC INDUCTION MOTORS Seltstarning Dear Editor: -2 RECEIVER 6 651,7. 1 I:70 RPM. Free. Ill'. _?í'U. U.i! ". Slips. tubes: 3-- -sSN7, 1 651:7, I -6J5 Dyna- Ili, 1.25 I would like to express my views on motor. plug -in ails and sensitive relays. This was one of the Army's "Secret" V.ILF. remote control re- SPIRIT LEVELS . . . Red etehrd graduation:. ceivers. .- I..m...... _..39 your article, "Manufacturers Versus Operating at about 110 MC. A thousand d one uses. Like new in a metal ease. NEEULE CONTACT BINDING POSTS . . Plated $4.95 Knurled. not -removable head 9e 15 for 1.00 Service Technicians." Each SERVICERS' BARGAIN KITS I notice that Stevens, Jensen, Brooks, COMPLETE BEAM ROTATOR ASSEMBLY = 1 -R.F., ANT. 6 OSC. COILS Kit or to 98 LP 1 -2-SPEAKER CONES 12 asstd. 4' to l'!" banddr Meissner, Browning, and others of the -21A AND -82A A 1 hr I i y fire -dgr Its r oils . 1.98 large ! indicator -a2.\. ud and L1' -21 3- SPEAKER REPAIR KIT a IHoF :S- same caliber do advertise directly to loop (removed from aircraft). A i complete perfect beam n1ON.tI. KIT TII.bT g. SAVE YOU 581 those who know. As schematic rotator system with indicator. Loop Is low .ul it ias: 25 assi t. nttg. rings. IO spider. 2 regards Impedance- contains sels,n transmitter, etc. C7'P 95 .oil forms. 3 yds. tell strip. 2. chamois leather .eg- diagrams, I must give Philco due credit Loop alone 35.95 Indicator alune $4.25 ebr. skit of IG ,rims A tube ammo.en tt'Ith IN- FILAMENT TRANSFORMERS ALI. FOR ...... 219 for getting out diagrams for their new See. SPECIAL OFFER.: BOTH KITS :2 6 Fully- shielded Pri. 100 V. 1 =1 inding 10.2 V -3 FOR ONLY 395lei models. Yes, I have seen some of those w A A. C. T.; le winding 10.2 V C. 10 A. C. T.1 =a- MOULDED BAKELITE CONDENSERS (Rua. before the radios. I also 2cundna winding can be tonnerted in series to ruppiy appreciate 55 V. with a line Voltage of Volts mold) :) : std....col to .2 sad. 2 i,ctnnihn. .2.49 III $2.95 -8- KNOBS .. asstd. wood A Laken lr Inn their stand for the technician in regard 60 Cyc. New. Each. wet strew Kit of _- ..98 )'pea- 6 VOLT MOTOR \9 -WAFER SOCKETS ... 4 to s o I: you .25 to TV. A real beauty. removed from aircraft. Type =10- VOLTAGE DIVIDERS . to an -.I 1,75 $1.29 E. RICE used for auto fan. 12 -MICA PADDERS A TRIMMERS I C. Each. colt. Multiple A Ceramle Incl. Ku .69 Newport, Vt. x-I4-VOLUME A TONE CONTROLS \car* BC -4336 o.oitol A Carbon Iss Switches. Kit ei I,, 1.39 15 -tube superhet radio compass receiver 2 -15 -WIRE -WOUND RESISTORS 98 Kr; CW- tone- voice. Like new. Similar b $19.95 cc", KR of 15. .. .98 LOOKS AHEAD TO TV H5 /AIIN7. Only x=18- BAKELITE COIL FORMS di.im. TUBES Gil of le asstd. . .98 Dear Editor: 1625...3 for 51.10 5BltI Scope tubes (r $1.95 1'73 -RADIO CEMENT A SOLVENT KIT . 6V6 .... lt. .35 5111'1 Scope tubes 1., 2.50 e. albnurnosr cement A 1111 nner ss üh blush .69 The last two issues of your magazine 31)6 ..... 1,' .35 3525 (a' 49 w -26 -WIRE A CABLE CLAMP KIT . . r to I" -.0 were especially good. I like :rssfd...... 59 particularly 6" PM SPEAKER -FACTORY REPAIR 'SERVICE ON ALL the way Beautiful new stock. Alnico l.95 SPEAKERS" articles are headed under dif- magnet. Each $á Min. Order S2.00 20% Deposit on all COD's ferent classifications such as FM, TV, T -17 D MIKE Pirate add cuffs lent postage -extess refunded Test Equipment, etc. Let us have more The lesi rahle single button carbon mike. With press the Ninon to talk switch. 4' cord and l'L 611 plug. $2.49 articles on transmission lines, wire re- mike rover. Features non -echo eifert. New corders, and FM. DM -53A DYNAMOTOR 24V.. In.. 220V- SOMA. out, used, good Television has not yet come to this condi tion. $1.39 city, but I am trying to keep up with it WRITE FOR NEW CATALOG MAKERS OF CONES AND FIELD COILS through your magazine. I hope you will Minimum order $2.00, F.O.B. Chicago 65 -67 DEY STREET. NEW YORK 7. N.Y. keep up the good work. 20% deposit required on all C.O.D. orders WORTH 2- 0284 -5 NESCORP ELECTRONICS, Dept. A 12.000 SO FT OF RADIO RICHARD COOVERT PARTS Portland, Oregon 2635 W. Grand Ave., Chicago 12, III. NOVEMBER. 1949

www.americanradiohistory.com 92 4:0111111uOiciltioOs SENSATIONAL TELEVISION RADIO WILL CLEAN HOUSE Dear Editor: 1x3.10 worth of mponent s ALL 53950 OFFER far the famous =03co0 chassi s FOR I thoroughly agree with your editor- Similar to List ial in your June issue. I believe, with RCA No. Description price you, that TV will compel radio to clean STATION 201T6 -POWER TRANSFORMER 526.50 house. No other or 21171 -TRANSFORMER, horizontal output 9.00 means arguments 201 D1- DEFLECTION YOKE 7.50 have been able to achieve that. INTERCOM KIT 20202 -FOCUS COIL 6.00 It will be another crowning A must item for offices, 20472- TRANSFORMER, vertical output 4.75 achieve- schools, churches, etc. A 20872- TRANSFORMER, vertical blocking 2.25 ment of television if, by its competi- wonderful bargain at the 20301 -ION TRAP BEAM BENDER 1.90 tion, radio is impelled to give us more price. COMPLETE 201X1 -YOKE MOUNTING HOOD 1.10 PARTS. TUBES TS630- PUNCHED CHASSIS PAN 10.00 of the high -class, worth -while music, 59.9 5 204x2 -VIDEO 6 I.F. KIT. consisting of e peaking and less of the drip and ffads. S filament chokes, 2 sound IF trans- gutter stuff ormes and I of each of the cathode trap, which has befouled our loudspeakers 25 WATT r -G6.1.: discriminator and the 1st. 2nd, 3rd and 4th IF AMPLIFIER KIT coils IS.IO for the past 15 years. A wonderful buy' Make up worth $311 to TOTAL LIST PRICE 555.10 Of course, the soap operas for Mag- an amplifier I / e you. Powerful All ports listed including gie and Maisie and housewives gener- enough for all- ít630 circuit diagram- (Mori.. seating 13110 People. Sepa- For . ally must endure as long as such can rately controlled Mike A Phono Inputs. $39 S 0 All parts. Incl. chassis. hard endure to listen. There TV cannot com- 'are, solder. circuit diagram. ete. SUPERIOR POCKET SIZE Lus Wee VOLT -OHM MILLIAMETER pete-at least if we want to have Ship. tot. housework carried on with any appre- 12 lb,. SENSITIVITY -1000 ohm. PER VOLT corp SIX -A.C. VOLTAGE RANGES ciable degree of efficiency! Unlversutseneral t 0- 15/30. 250 300 1500 3000 volts SIX -D.C. VOLTAGE ANGES LEE DE FOREST 365 J CANAL ST, N. Y. 13, 0-7.5 29 75 150 790.1500 volts Chicago, Ill. FOUR -D.C. CURRENT RANGES WAlker 5-9642 0.1.3 1S 150 MA 01.9 Amps TWO -RESISTANCE RANGES 0-500 Ohms 01 Menonm $10,000 REWARD PLASTIC CASE -31 a S7;. a 21.- VALIANT DEFENDER Rare the government bongs toll locating Radin - Adios with Orr. complete m<4ries.$13.90 Dear 7h a at lead.. ,n.tuceonn 7 Editor: .. d factory duaranty. You have published many good letters P.R.I. GEIGER COUNTER and articles defending the radio \e eight sol, 2 IL, l'rt^.I front 119 S0 tech- -I QUALITY RADIO & TELEVISION pb'r. hr m0,. sen:lth'e ;eI r l nician's reputation for U^rable . nur'ers insit integrity, but I PRECISION RADIATION INSTRUMENTS, INC. TUBULAR TUBES think the best was "Why Pick on Radio 1101 -L N. Poulina St. Chicago 22, Ill. STANDARD BEST NUMBERS Technicians ?" which lam Dealer Inquiries Invited CONDENSERS RCA Neorad Sylvani appeared in the Tungsol etc. August issue. PER HUNDRED All New , . Money Back Why indeed? Just call in a plumber, .001 - 600V ...S 3.95 Guarantee! .002 600V ... - 3.95 5OL6GT 55. carpenter, or electrician to have a re- .003 - 600V ... 4.40 pair job done, and see what the charge .005 - 600V ... 4.40 35Z5GT 39e .01 - 600V ... 4.40 is. And some of these repairs aren't .02 - 600V ... 4.95 12S97GT 49e exactly perfect .03 600V either. - ... 4.95 125K7GT 54r .05 - 600V ... 4.95 It doesn't seem probable that licens- .1 600V ... 7.20 - 12SA7GT 55e ing is the answer. The "better mouse- Assembled for your convenience EACH SOBS 55. trap" theory ought to work so that the .25 - 600V ... .12 technician who does good work will be Facts, standards .5 600V ... .17 35W4 390 - patronized and the ones who 10 - e0V ... .12 12AT6 49e don't or practices, data 16 - 150V ... .18 who charge too much will go out of 20 - 150V ... .24 12BA6 54r 20/20 -150V ... .26 business. for the whole field 30 - 150V .28 128E6 550 GRANT R. BERKEBILE 40/20/20.150V -25V .44 25L6GT 69e q/ radio engineering 40/40/20.15019.25V Johnstown, Pa. .44 25Z6GT 50 /30 49. -150V .44 (But does it? -and do they ? -Editor) 8 - 450V .27 6S97GT 490 16 - 450V .36 16/16-450V .49 6SK7GT 54.. 20 - 450V .39 6SA7GT 55. PHILCO HELPS TECHNICIANS 30 450V Radio Engineering - .47 790 40 - 450V .59 35AS Dear Editor: 80 - 450V .97 50A5 79. .005 I just finished -1700V .13 35Y4 69e reading "Manufactur- .008 -1700V .15 ers Versus Service Technicians" in your Library .01 - 1700V .17 14A7 49e .02 1700V .19 August issue, and I want to thank you DA, I,. a ?L i.r,a 11111 publication - e, lected books I 14B6 490 tho fur tide library as thuv for going to bat for the men who make giving the most complete. NEW LOW PRICES 1497 49e dependable overage of their livings in service work. farts needed by engineers ON TELEVISION 0Z4 54e Library includes: My own experience is I whose pecil fields CONDENSERS 6XSGT 49e that never grounded on radio funda- I. Fundamentals of fail to speak well of and have con- mentals. They cover circuit Vacuum Tubes - .05 - 2500V .52 5Y3GT 44. phenomena, tube theory. Eastman .1 2500V .57 fidence in the products of the company networks, measurements, - and .25 2500V .72 80 39. other eublect... . give 2. Radio Engineering - that treats me as a businessman rather speriallged treatment ar all -Terman .05 - 3000V .54 6AG5 69.- fields of practical design .003 6000V than a necessary evil. 3. Communication - 49 6AK5 89e and application. .005 - 6000V .52 Radio manufacturers could benefit by Engineering- .01 - 6000V .58 6AL5 69e * Special Low Price Everitt .0005 .48 the example of Philco Corp., which sup- 4. High -Frequency -7500V 6J6 69e * ouumt moots, the five .003 - 7500V .52 plies full technical data to all mem- woulde ost Measurements- .0005- 10000V .54 6K6GT 49, 530.50. Under this offer Hund bers of its service organization you .eve $3.00. -of 5. Radio Engineering Pay n ea y ,netaoment. WHITE TUBE CARTONS which I am extremely proud to be a * Handbook -H enney member. 3559 pages! 100 -SMALL PEANUT. . S .75 FREE IO Day Trial 2558 illustrations! During my wartime service in the 100 -LARGE PEANUT. I "xl "x23/4 "... .85 RCAF I serviced sets for people where McGraw -Hill Book Co., 330 W. 42nd St., N.Y.C. 18 100 -GT TYPE, I 4 "gl14 "x33/8" .95 I was stationed. Running into a problem end me Radio Engineering Library, 5 cols.. for 10 days on approval. in 10 days 1 will send $2.311 100 -SMALL G. II /2 "x11/2 "x41/2" 1.25 ` with a Philco set, I wrote to Philco lfewplusdnation rents postage. and $3.00 monthly till $27.30 i or return books 100-LARGE G. 1.45 Corp. of Canada. By return mail I re- paid. postpaid. ONE POUND ROSIN SOLDER S .49 ceived a circuit diagram plus complete alignment and service Name TWIN LEAD -IN. 300 ohms, 100 feet 1.39 instructions. I have been a Philco booster ever since A ad teen CO -AX CABLE, ,ß59U. 100 feet . 3.95 that experience. City Zone State BROOKS RADIO DIST. CORP. CHARLES E. BEAN Company 80 VESEY ST., DEPT. A, NEW YORK 1, N. Y. Toronto, Ontario Position lic-11 . A'í a- RADIO-ELECTRON ICS for

www.americanradiohistory.com e OPPORTUNITY AD -LETS rtisementn in this Section cost i cord tor II Insertion. Name, addres. and initials must be WHERE RADIOMEN MEET, EAT and SLEEP tided at the shove rate. Cash should accompany r lanited advertisements unless placed by an Visit the ((silted advertising agency. No advertisement for FAMOUS . than ten words accepted. Ten percent discount ()Mee - FIESTA i -:ues, twenty percent tor twelve issues. fo'l'F' 1. r TRANT) ...ahle nr ml.lca'ni m aeremed LOUNGE rï j 1ensementa for December. 1949. issue. must reach Renowned for not later than October 24. 1949. Fine Food RadieEleetronies, 25 W. Broadway. New Tart 7. N.Y. Atlantic City's Hotel of Distinction

t11ATECR RADIO LICENSES. COMPLETE THEORY The Ideal Hotel for Rest and Relaxation preparation for passing amateur radio examination. Home Beautiful Rooms Salt Water Baths Glass ankh and resident course. . American Radin Institute. tot West 83rd St., New York City. See our ad in Page 94. inclosed Sun Porches Open Sun Decks atop Delightful Cuisine Garage on NI:N6t7.INES (BACK DATI:SI- FOREIGN. DOMESTIC. premises. Moderate Rate Schedule. lets. Books, booklets, subscriptions, pin-ups. etc. Catalog. OPEN Dur (refunded). Cicerones. 863 First Ave., New York 17. N. Y. ALL YEAR Exclusive Pennsylvania Ave. and Boardwalk

RECORD CHANGER PARTS for leading makes. We ship rceryrhere. Friends Wholesale Distributors, 106 North sixth Street, Philadelphia 6. Pa. AMAZING "SNOOPERSCOPE" TUBE LISTED AND DESCRIBED IN OCTOBER RADIO- ELECTRONICS HERMAN LEWIS GORDON, REGISTERED PATENT Attorney. Patent Investigation. and Opinions. Warner Building. Washington. D. C. An Infra -Red Image Con Tube (B h) that enabled combat men to see in the dark and through camouflage. No scanning or amplifiers WE REPAIR ALL TYPES OF ELECTRICAL INSTRU- necessary! Uses only infra -red light source and simple high. voltage supply. menta. tube checkers and analyzers. Hazleton Instrument Shows image in greenish -white color on 1 Vs" screen. Has wonderful pos- Co. (Electric Meter Laboratory). 140 Liberty Street. New sibilities for darkroom work, fog penetration devices, night photograph.. York. N. Y. Telephone -BArcI" 7 -4239. etc. With technical data and diagrams. All NEW tubes. BARGAINS: NEW AND RECONDITIONED HALLI- PRICE, EACH crafters. National, Collins, Hammarlund, Melasner, ItME. $8.00 other receivers, tuner., television receivers, transmitters, TWO FOR $15.00, QUANTITIES OF SIX OR MORE $6.00 EACH etc. Wholesale prices. Terms. Shipped on trial. Liberal "Snooperscope" lens unit front. Baruch Lomb 3.5 in. E. F. each trade -In allowance. Henry Radio, & F /2.1, $12.00 Write. Boller. Missouri at and 11i40 West Olympic, Los Angela, California. Mounted lens unit. Results as good as B & L unit. Speed F 1.9, F.L. 91.44 MM. Outside dm. one end 60 MM. Length of mount 64 MM. PRICED, EACH $9.00 BARGAIN HUNTING? RADIO SERVICEMEN WRITE, 25 % Deposit with All C.O.D.'s. All prices F.O.B. N. Y. C. Sensational catalog. Renshaw Radio Supply. 3619 Troost, All Materials Offered Subject to Prior Sale. Kanuas City 3. Missouri. thane- TELEMARINE COMMUNICATIONS CO. 280 Ninth Ave. RADIO PARTS FOR SALE. Details. Knight, Radio, LORgocre 4.4410.1 N. Y. 1. N. Y. 9118 Ave. A.. Brooklyn 12. N. Y.

LANCASTER. ALLWINE & ROMMEL. 438 BOWEN Building, Washington. D. C. Registered Patent Attorneys. Practice before United States Patent Office. Validity and infringement Investigations and Opinions. Booklet and form 'Evidence of Conception" forwarded upon request. $1,000 A MONTH BIG MONEYTELEVISION 15 TESTED ONE -TUBE CIRCUITS. including "Radio - .t,. builder." Catalog 25c. Laboratorleu, 578 -B, San Carlos, New 7- Volume Set California. - That's what JUST ONE of the many plan. In this book brought in -over $1.000 SURPLUS TUBES: 80% off List F.O.B. Pittsburgh, Pa. month, steadily. from radio eu il obtained from army signal turps in original carton. all service alone. HOW TO YIAKE FREE 017 ceav guaranteed perfect. Follosing types available: GF6. 6J5, Ñrr MORE MONEY IN RADIO 01:61:7. 77 78, 6AC7. 6ÁG5, 65117, 6L6, 351. INS. 136G. SER%'ICE it so full of money- APPLIED PRACTICAL C115721.1, CTL954. 1299. Minimum quantity $5.00 net. making plane and ideas it will send ail orders to Monarch Electric Company, 411 Wood amaze you. tt'hy wort for RADIO- TELEVISION Street. Pittsburgh 22, l'a. wages? Why not become your own boss and make more With Televisien Servicing Aluminum tubing. etc. )teams for Amateurs, Tt'. F31. imoney? EVEN BEGINNERS the Radio-Televisiyon Ex- Lists free. Willard Radcliff, Fostoria. Ohio. ho used some of the easier pertpSpeee plans in this book averaged tyoure oughest Ser`v`ice Jobs. This new,, 7 volume A 27 years experience radio repairing. Simplified system. WAY OVER $100 WEEK et given y solid king working from home. This knowledge Radio No calculations. No formulas. Total price $2.00 postpaid Just of and Tele. mi book is making money for vision. ery latest on Tele. or COD. Moneyback guarantee. Rosa Radio. 14615 Grand- vision - servicemen and beginners. Covent rater, Detroit 27. Mich. ge fromr' fu ametls everywhere - U.S.A.. Canada to newest in FM. Television. Puerto Rico. Mexico, So. America. Hawaii, Philippine., Electronics. etc. Clear. practical. Tell Sensational You how to construct. Install. serves "TAB" BV CARTER Dynamotor. 400V /1I0ma, and other countile.. Letters of thanks are continually Short-cut $8.98. 2501'/100mä $4.98, 110TH $12.49. Guaranteed Tube trouble shooting methods. ti.u,,h Jot coming in. R:ntioman. Hendbotr Included. More than 2500 1200 Bargains! 836, 6AK5. BAGS. ea. 37c -6C4. 21c -368A. 40c LAST! illustration.. charts. diagram.. pages. -nli, 14c -955, 16c. 1N34 Crystal. Bic. GE2J1G1 SEL- AT The real w01111)-making secrets 1 radio service are given SYNS Used Tested PAIR $1.49 Tuning Meter final 98e. FREE TRIAL OFFER L;a;nq DonkeeforgTediyisf 30('m Mobile out In this book. /129.'lI1, HAMRAND Antenna AT5/ARR1 -Rook very, -best of It. kind that have expense. Just mall coupon below, 39e, 4/$1. Hi -Gain Dynamic Mike Transformer PLUS Ex- Inc advice In the lowk earned a ver been printed. RADIO-TELEVISION cellent Fidelity Dynamic Mike. ROTH $1.49. Write for high as $100 a k radio W. Ueadloed. F r R E E Bargain repairing, in my apartm rat E. Cnicaee. Indiana MBOOK 'TAIIOGRAM" TAB," Dept. TIRE, 8 Church kl St., NYC. C. C. soldier. Have book -only week Act at once and get. with APPLIED RADIO - N -,, - TELEVISION hook of '1s0 Radio.Televeeion 10 couldn't ooy It. -In buslnes years-re. made readingY tl E our It many Vp ont- Wire Recorder, table top. Sllvertone, with radio & record relved eina' motln.y w [omen. you d tlhenát back expense e d It 3 times. Would 7 days. If you kern the set. send Unger, Box 188. Salamanca, Y. ffoor player. $100.00. N. take twice the price Carthage. N. Y. either 522 rash. e3 In 7 days and 53 month until iof0...... aeW.gWa. 23 50 is paid. Either way- Diagrams hook Is yours! Send W.iaa. In bualnese 17 year.. Book TODAY! its not an order-Just a to see the Build your own Geiger Counter. Save money! Write for -in radio 15 'ears-Rook contain. m ny things which Set and get the Diegram. book Free. Act now! free parts lin and diagram. Woodwid Industries, 5217 -G far more Informa tok me many years to learn Itottysvwd Rlvd., Hollywood 27, Calif. Úown.m, than xpected. Every the harA way. Book worth radioman should have this many times its small cost. GOOD FOR FREE TR /AL and FREE SOON! book. Liment. N. Y. ElmwoodF lllino, Educational Rack Publishing Division 25 years experience are packed in thlr 83 page book, COYNE ELECTRICAL i Rani°o SCHOOL RADIO- ELECTRONICS will 500 S. Dent. Chicago 12. 111. print -without charge 8V, x 10%. by V. Gale. for servicemen, beginner.. stu- hullo. at.. WWII. -small classified advertisements for radiomen dents. Among MANY OTHER THINGS It shows you Ñ4f7 postpaid. for da va pTMxaodFREE Examination per yuroffer.oe who live in exchange -restricted countries and where the money is and how to get it FAST; How to Include FREE Book of 150 Radio- Television Diagrams. who wish to swap something available in their get plenty of customers; How to test seta without taking countries for American radio parts or books. them out of cabinets and give estimates QUICKLY; How Nome Age American radio men may then correspond with to operate spare time and build to full time: How much to charge; How to connect with certain BIG MONEY Address the advertisers direct. RADIO- ELECTRONICS concerns; 110w to Increase butanes. and expand.

Cannot, of course, act as intermediary in or be Send for this hook today and tart making more money Town Zone . Slse. responsible for any deals that may be made. almost as soon you get it. The full price is only $3 Ads must be under 40 words in length. State (any convenient asform) postpaid; or C.O.D. at $3 plus your needs exactly and give name few cents postal charge.. You have nothing to lose. Ex- full and amine it for 5 days. If you aren't positively delighted address. return It and we will refund your $3 promptly. If Note that most countries (including the U.S.A.) want more information about the book send for literature have import and export regulations and duties. 52 -RE. It's free. RADIO MADE EASY! Both correspondents should check with their customs authorities before arranging that any MERIT PRODUCTS, DEPT. RE. A JRI Home Trainer goods be shipped to them. 216.32 132 Avenue. Springfield Gardena 13, N. Y. A NEW APPROACH to radio repairing. Here Is SIM- PLIFIED METHOD of repairing radio. that can be LEARNED QUICKLY-Begin repairing immediately! NEED FOR G -E 260 2 A PORTABLE: The -volt ibrator. COMPLETE KIT OF ALIGNMENT TOOLS INCLUDED! tADIII New. 8 x 12 Inches. 2.-volt 2 DATA B/H)K. with more than storage battery, rectifier cells and 3 pushy buttons Balance ANY RADIO with '06 diagrams of European receivers. Will exchange Iooff- charge). Will return genuine Edam these tools. Prepare for for cheese. or GOOD INCOME. NOW! Send for the JIM llome Trainer Essentiale of Radio. or American Radio Data book. Jaro what do you want from Holland? Radio Peelers. van TODAY Kober. Jlfin 56. Czechoslovakia. Woustraat- Amsterdam Z. Holland. and get Alignment Tool Kit -ROTH FOR ONLY $9.75 postpaid. or plus c.o.d. charge. Pays for itself almost immediately! SATISFACTION GUARANTEED. WANT: Genuine E. IL Scott spares, G.E. pickup with ENGLISH READER wishes to exchange British radio and THE rm. Rill swap custom-built audios to your specs, ffrr other goods for stinted American Darts and books. Thomas JRI TRAINERS rcdinea. etc. Austen Graham. 33 Warrlalotn Crescent, G. Sutcliffe. 20 Granville Rd. Frininghall. Bradford, York- P. O. lox 2011. Dept. 15-11. Chicago T. III. 4 M inhurgh 4. Scotland. shire. England. NOVEMBER, 1949

www.americanradiohistory.com ADVERTISING INDEX Acorn Electronics 87 OUTSTANDING Allied Rodio Corporation 49 SIX TUBE SUPER American Phenolic Corporation 72 Three Gang Condenser Amperite Company 89 Amplifier Corporation of America .. 97 TELEVISION VALUES Wolter Ashe Radio Company 84 Bell Telephone labs., Inc. 75 $33.30NET Factory wired and tested type 630 tele- Boland & Boyce, Inc...... 10 Brooks Radio Dist. 92 Crowe Panel vision Company chassis, complete with 29 tubes, Buffalo Radio Supply 82 ready for installation in cabinet. Will Burstein- Applebee Company .. .. 83 Kit Included operate 16" picture tube or smaller. Price Jock Cantor 97 Cargille 66 (Less picture tube) $157.50 Capitol Radio Engineering Institute ...... _ 7 Certified Television Laboratories .. ... 97 Cinex. Inc ...... 97 SPECIAL G. E. 9" TELEVISION Clarkston Corporation 86 TUBE Cleveland Institute of Radio Electronics ...... 18 Communications Equipment Company . 86 White screen electromagnetic deflection Coyne Electrical School 89, 93 DeForest's Training, Inc. 11 and focus. Brand new type MW 22 -2. Electric Auto -Life Company 8 Price $13.95 Electro Products Laboratories .... 90 Electronic Instrument Company . 62 Electronic Wholesalers 96 Espey Rodio ...... 69 Panel kit to fit most all makes (Please specify TELEVISION TRANSFORMER Feller Engineering Company 189 make of car and year model). New up -to -date 115V /60 cycles, secondary 2500 volts of General Electronic Dist. Co. 51 latest prices. Catalog ovailable. General Test Equipment Company ... 69 2 MA., 2.5 volts at I.75Á. 6.3V at .6A, Greenwich Sales Company ... 95 /Kill Sutton's Price $3.85 Greylock Electronic Supply Co. .. 95 Gould Green 69 Wholesale Electronics Halldorson Company ... 90 5th at Commerce Fort Worth. Ten. -X Heath Company .. 13, 14, 15, 16, 17 HIGH GAIN CONICAL Hershel Radio .... 53, 54, 55 TELEVISION ANTENNAS Hickok Electrical Inst. Co. 83 Hudson Specialties 74 Covers channels 2 to 13 without separate Industrial Devices, Inc. 189 section. Constant non -varying center im- Instructogroph Company 69 International Resistance Company .. . 57 pedance. Better than 12Db front to back FREE! Jersey Specialty Company 96 ratio. Can be used with 72, 150 or 300 ohm Jensen Industries Inc. 90 line. Works well in weak areas and gives The 1121 Trainers 93 MONTHLY BULLETIN Kronenberg ... .. 97 a Price each sharp conical beam. $5.95 Lafayette- Concord .... 67 No strings attached. Just send us your less mast. Extra for 6 ft. mast $1.35 Lectronic Research Laboratories 69 name and you'll receive our bulletin free Leotone Rodio Corporotion .. .. 91 Liberty Electronics 96 of charge each month. It's crammed with FRINGE AREA ANTENNA McGee Radio Company 77 red -hot specials at spectacular prices! McGraw -Hill Book Company, Inc. 92 Stocked X Antennas for estro gain in McMurdo Silver Company 76 fringe areas including heavy ICI ft. mast. Merit Products 93 Elec i ron mJio lesale rs. inc : Price Metropolitan Electric & Inst. Co. 79 f is $14.95 Mid -America Company 80 Midwest Radio Corporation Back Cover 2010 14th STREET, N.W. Murray Hill Books, Inc. 61 PORTABLE RECORD PLAYERS National Company 6 WASHINGTON 9, D. C. National Rodio Institute .. 3 Dual Speed, AC /DC. U. S. government Notional Schools . 5 & surplus. Used but reconditioned. 33 1/3 Nescorp Corporation . .. . 91 78 R.P.M. adjustable speed control, em- Niagara Radio Supply 78 Ohmite Manufacturing Company 58 bodies a 3 tube phono amplifier with elec- Omaha Scientific Supply Company 90 TELEVISION trodynamic speaker, housed in portable, Opportunity Adlets 93 black leatherette case. Price $16.95 Plastics d Electronics Company 66 Precision Apparatus Company 80 Precision Radiation Inst., Inc. 92 MFGS.- DISTRIBUTORS PHONO MOTORS AC DC Premier Tube ...... 74 Progressive Electronics Company 97 INSTALLERS! ! DUAL SPEED We Manufacture Green Flyer type reconditioned and guar- RADIO SCHOOL DIRECTORY anteed. Complete with 12" turntable. (Pages 94 -95) 300 OHM TV TWIN $8.95 American Radio Inst. Hollywood Sound Inst. LEAD TRANSMISSION WIRE Baltimore Technical Inst. Milwaukee School AC PHONO MOTOR Candler System Co. of Engineering Commercial Radio Inst. RCA Inst. AT THE WORLD'S 33 1 3 RPM Commercial Trades Inst. Radio Inst. Don Martin Tri -State College School LOWEST PRICES ! ! I Price $2.45 of Rodio Arts Valparaiso Tech. Inst. Western Radio- Television Institute YMCA Trade f Technical Schools MODEL NFRD -RADIO NOISE We supply over 5O% of oll FILTER Radio City Products Company, Inc. 70 Twin Lead used in the Rodio Corporotion of America . 73 made to U.S. government specifications Radio Dealers Supply Company . 96 Metropolitan Area will eliminate all line noises when properly Radio Supply 6 Engineering Company 81 connected fo radio television, motors, and Radionic Equipment Company ...... 88 Raytron 80 electric appliances. Will carry up to 12 John F. Rider, Inc. Publishing 65 amps. Price $1.95 Howard W. Sams 6 Co., Inc. 59 WRITE FOR QUANTITY Sanders Electronics 9 PRICES TODAY! ! ! Senco Radio, Inc. 81 SPECIAL N. Silverstein 87 Simpson Electric Company 12 Mammoth assortment of radio & electronic Soverign Television Company 69 JERSEY SPECIALTY CO. parts of such items as transformers Spartan School of Radio Electronics 86 Sprague Products Company 85 Little Falls, N. Y. chokes, condensers resistors wire, coils, Sprayberry Academy of Rodio. .. Inside Bock Cover Phones: L.F. 4 -0784 -1258 hardware etc. of not less than 10 pounds. Hotel Strand 93 Price Supreme Publications . . . $1.25 Bill Sutton's Wholesale Electronics 96 Sylvania Electric Products 63 Tech -Master Products Company 70 HEADQUARTERS FOR ELECTRONIC TUBES Satisfaction guaranteed on all merchandise Technifax 189 Telemarine Communications Company .. 93 All prices F. O. N. New York City IN ALL QUANTITIES Telrea, Inc. 66 5000 Magnetrons, 1000 Kylstrons WRITE FOR FREE CATALOGUE T11 Transvision 68 United Surplus Materials 64 500,000 other tubes. Write for Universal General Corporotion 92 our Bulletin and Prices. Word Products Inside Front Cover RADIO DEALERS SUPPLY CO. Weller Manufacturing Company 4 EL R e NICS. INC. Wells Sales, Inc. 98 135 LIBERTY STREET NEW YORK 6, N. Y 154 Greenwich St. New York 6, N. T. Wholesale Rodio Parts Company, Inc. 60 F.o.. wo.,. -2032 John Wiley E Sons 88 7 RADIO- ELECTRONICS for

www.americanradiohistory.com Rook Reviews 97 RADIO AND TELEVISION MATHEMATICS. by Bernhard Fischer. Published by the Macmillan SUCH A PHENOMENAL Co., New York. 51A z 81/4 inches, 484 pages. Price NEVER VARIETY OF FINE $6. PROM:06111E TAPE RECORDERS This book is not a text but a tool - and one of the most useful this re- AlTS BEFORE within these pages: the viewer has ever seen. The woods are The best qualify tape recorder you want, full of volumes explaining mathe- - the largest variety . of o popular price. (com- matics; there are even plenty which For Beginner, Technician or Engineer plete data on 2 -speed re. carry right through with radio -elec- FREE Gift with Each Kit corders, 24 hour recorders, tronic examples for each explanation. plus FREE MEMBERSHIP conference recorders, and many But there are very few, if any, to in PROGRESSIVE Radio others. Accessories included. which the designer may turn in his & Television Club: Write today for your free copy! moment of need and be reasonably cer- Provides FREE Consultation Service. tain that full instructions for whatever NOW, AMPLIFIER CORP. OF AMERICA calculation he needs to make will be ,:, 75 15 R aDos 398-10 Broadway New York 13. N. T. spread before him like a blueprint. This BUILD comer,, /rot, slay is such a book. j 348 up with - Absolutely No Knowledge The first pages are .aken _. of Radio Necessary. You CABINETS -CONSOLES actual problems, about three to the Need No Additional Parts. FOR page, such as, "What is the secondary EXCELLENT FOR BACKGROUND voltage of a transformer which has a IN TELEVISION... Conta,na s eryttliny Y need. n book. metal RADIO TELEVISION primary voltage of 100, primary turns chassis, tubes. condenser,, fry all o - .ry radio parts. The Instruction Rook ritten by JACK CANTOR expertexpen dio instructors and engineers teaches you to 200, and secondary turns 40 ?" Then the radios in a professional manner. The circuits are designed to de excellent performance. 171 A. Wasiington St.. N. Y. 7 formula is given and the answer worked Each of the la radios you ll build operate. on 110.120 The PROGRESSIVE out in the necessary number of stages ttforC l earning R céver - Tri miner and Amplifier design. It i ,ed l any so that all the reader need do is substi- Radio Schools and colleges in U.S.A. andu abroad. It i, used by the V lnielration for veteran train. rood TELEVISION RECEIVER-SI.00 tute the values of his own problem for ELECTRICAL FREE Memrhi e Progressive) Radio Television Complete instructions for building your own television those of the illustrative one and follow Club. You will be entitled to FREE experti advice and recom er. le pages -11'617' of pictures. pictorial dla- consultation service with licensed radio technician,. grams. clarified schematic.. 17'122' complete schematic the author's footsteps. The problem ORDER YOUR KIT NOW! diagram & chants layout. Also booklet of alignment quoted is one of the simplest; the re- instruction,. voltage & renlaenre tables and trouble - 7 " -10" TELEVISION KITS shooting hints. -All far $1.01. mainder run the gamut from the lowest Factory -built and aligned 13 channel Tuner -IS Tube Kit CERTIFIED TELEVISION LABORATORIES level to the highest and cover almost Kit - Dept. C, 5507 -13th Ave., Brooklyn 19. N. Y. r $59.50 every common case the radioman is like- Complete set of tubes, including ly to run into. Cathode Rey Tube. $41.58 Ferlory -built and aligned 13 channel DYNAMOTORS Only a few mathematical points are Tuner. 10' Kit. less tubes $82,99 Complete set of tubes. Including Cathode 655.88 for DY 12 -Power .upply actually explained. A chapter each is ltay Tube for Art -13 given to powers of 10, the principle of Cabinet for 7' or 10' $24.50 Special $9.95 the slide rule, the j- operator, and polar FREE: Television Servicing Noies vectors. Each of these is short and in- Bal. C.O.D. 204á deposit with order. formative. There are 27 of num- 5" OSCILLOSCOPE KIT Boa =11RE ers Radio-Electronics pages AM -FM TELEVISION 1111 absolute mpeaa today's radio- 25 West Broadway, New York, N. Y. bered formulas (which are referred to "for nlan.1111111. Input Impedance: 1 553. and 50 in the problems) and 18 pages of SImfF. Tubez -2 -6537, 2 -51'3, 1 -884. 1 -5BP1. FREE: Hook on Ca- $39.95 tables. Both index and contents table thole Ray Oscillascolm 'e . are unusually complete, the latter list- ing each problem to save time in using IIIVACUUM TUBE VOLTMETER KIT the book. A professional piece of test equipment you need for FM and TV. Attractive steel FLASH The cut -and -try experimenter will case. FREE: Book on Ad- $23.95 PHOTO probably find little use for this book, maned Servicing Technique.. EQUIPMENT but it is recommended to the more seri-

ous radioman and the engineer as a SIGNAL TRACER KIT . 1 "' -- "- ---," An Invaluable aid In trouble -shooting COMES COMP. f TF WITH G' candidate for the place of honor be- }... FREE: Book on Radio $21.95 EDGERTON side its natural partner the slide rule. Test luit ruments. FLASH TUBES I 4 A REFLECTORS -R.H.D. EASY TO SWEEP GENERATOR KIT CONVERT INTO ELEMENTS OF SOUND RECORDING. by John A necessity for television work .- Tube circuit. IMC to 226 Sir. A 2 -WAY PHOTO G. Frayne and Halley Wolfe. Published by John FLASH UNIT Sweep width 0 to 10 MC. Verlabl, Wiley & Sons. Inc.. New York. 6 x 9! s inches. phasing control . . . 110r 411 OPERATES ON 110V. AC L 12V. BATTERY 686 pages. Price $8.50. e paonT Brand new at a fraction of origina cost. Contains lG' le eledelon & !M $22.95 ' Notes finest component pans available. All necessary This book is remarkable for parts and complete instructions included. After -among xrsion, works on ItOV AC or other things -its exhaustive treatment SIGNAL GENERATOR KIT AM & F51 alignment and trouble- I12V battery by a flick of a switch. of film recording. Of the 32 chapters, shooting marker for sweep genera` - - Immediate $68M delivery on all mall weirs COMPLETE tor. Ei0kc to 34 MC on fundamen- 14 are devoted to the techniques of tais. Over 100 SIC on strong har- CINEX. INC.. 165 W. 44th St., N. Y. It N. Y., 0ept.pE-lI Ci sound -on -film. monies. 4,10 cycle audio. 110V 60e. 0 operation. r c ^ Disc recording is analyzed in detail, FREE: Books on radio test $18.95 Instruments and several chapters are devoted to the Î techniques TOOL KIT and equipment which are Consists of Diagonal cutter. combi- TELEVISION TODAY! associated with recording -the nature nation long-nose pliers and cutters, amber-handle screwdriver. 75 Watt Learn all the interesting of sound, amplifiers, filters, tubes, speak- soldering iron, and supply of solder. facts about TV., how it ers, acoustics, and so on. The method FREE: works, instal'ation aids, soldering manly of analysis is not entirely mathematical d of hook-up wire buyers needs. etc., written in language anyone will so that the book may be read for gen- understand. OTHER KITS eral information. Vast quantities of 7 -Tube FM Receiver. Battery portable receiver. 3 -way ORDERYOUR Portable Receiver, 5 -Tube Broadcast Bond Superbet $1.00 formulas, graphs, and quantitative Receiver, 6-tube 2 -band ouperhet receiver. multl- COPY TO. te +ter. amplifier, signal tracer probe. DAY! data are given, however, making this a FURTHER INFORMATION ON REQUEST. MARVIN KRONENBERG thoroughly informative text and hand- Deduct Sop if full payment ...meanies order. orders aceeeeed in U.S.A. 82 -27 217th Street, 9 Village, New York book. A single chapter on magnetic re- C.O.D. Etichiseti is 61.00 Check for my copy o,TV TODAY cording is included, but the treatment PROGRESSIVE ELECTRONICS CO. Name is rather superficial in comparison to 497 Union Ave., Brooklyn 11, New York Address CIU Zone the attention accorded the other sys- Dept. RE -31 Phone: Evergreen 8.0054 4 State tems mentioned. -R.H.D. NOVEMBER, 1949

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WELLS RADIO-ELECTRONIC Components by the Thousands: TOGGLE AND PUSH SWITCHES Micro Switches

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PRECISION AND POWER CONTROLS

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PUISTE0 111 T.3 U. S. A. I? T16 CUNEO PRESS, ING.

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