Sfruicing AUDIO

NOVEMBER 1951 tAl) 1 o K

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LATEST IN TELEVISION SFRUIcING AUDIO

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No. 8411 No. 8401 No. 8422 No. 8410 No. 8412 No. 8423 No. 8424 Nominal Capaci- Nominal Capaci- Nominal Capaci- Nominal Capaci- Nominal Capaci- Nominal Capaci- Use for inter- tance 37 mmf per tance 25 mmf per tance 32 mmf per tance 33 mmf per tance 68 mmf per tance 54 mmf per connecting power ft. Use partic- ft. For crystal, ft. Use specially ft. For crystal, ft. Use specially ft. Use particu- cable for all elec- ularly for lapel ribbon, carbon fo- carbon micro- ribbon, carbon for carbon micro- larly for carbon tronic uses. Also microphone. microphones. phones. microphones. phones. microphones. microphone cable.

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AUDIT BUREAU OF CIRCULATIONS RE Hugo Gernsback, Editor -in -Chief ABOUT M. Harvey Gernsback, Editorial Director Fred Shunaman, Managing Editor Robert F. Scott. W2PWG, Technical Editor Angie Pascale, Production Manager I. Queen, Cal:arial Associate SPRAGUE Wm. Lyon McLaughlin, Tech. Illustration Director LOK`tV Lee Robinson, General Manager G. Aliquo, Circulation Manager TWIST- John J. Lamson, Sales Manager Robert Fallath, Promotion Manager CONTENTS NOVEMBER, 1951 CpPpCITORS

Editorial (Page 21) Radio -Electronic Giant by Hugo Gernsback 23 Television (Pages 24 -33) CBS-Columbia--First Commercial Color plus Black and White Set by I. J. Melman, E. S. White & S. Kuker 24 Remote Controls for TV Promote Viewer Comfort by Robert F. Scott 28 Television Service Clinic by Matt Mandl 32 Television dx Forecast for November 33 Moreore twist - Servicing -Test Instruments (Pages 34 -38) Audio Signal Generator with Calibrated Output. prong electrolytic capacitors by Lawrence Fleming 34 are made by Sprague than Fundamentals of Voltage Regulation by Allan Lytel 37 by any other manufacturer Theory and Engineering (Pages 39-43) ... And Sprague naturally Discone- Broadband Antenna (Cover Article) lists the largest, most com- by Fred Shunaman 39 Magnetic Phenomenon by Alvin B. Kaufman 41 plete line for exact TV re- New Design (Pages 44-45) placement applications. lonophone by E. Aisberg and M. Bonhomme 44 And when you use a Electronics (Pages 46 -50) Sprague Twist -Lok TV Ca- Ultrasonics and Therapy by Dr. F. Van den Bosch 46 pacitor, you can be sure it's Audio (Pages 52 -74) dependable. No costly Birds and call- Ultrasonics 52 backs will jeopardize Filter Facts and Faddle by James R. Longham 54 your Electronics and Music, Part XVII by Richard H. Dorf 60 profit or your reputation. Audio Feedback Design, Part XIII ..by George Fletcher Cooper 70 Your business judgment will Construction (Pages 78 -80) tell you to accept no sub- Versatile Intercom Unit "Rings Up" Called Party. by Bob White 78 stitutes. Amateur (Pages 85 -89) *Trademark Converting the Mork II by Louis H. Hippo, W6APQ 85 Broadcasting and Communications (Pages 89 -92) Your Tape Recordings Are Not Negotiable Francis George 89 Universal Tester for Field Use by Lyman E. Gray 90 Departments GET YOUR Radio Month 12 Try This One 109 Radio Business 16 Question Box III New Devices 82 With The Technicians 113 New Patents 101 Miscellany 120 SPRAGUE TV CAPACITOR Technotes 104 People 122 REPLACEMENT MANUAL TODAY! Radio -Electronic Communications 126 Circuits 106 Book Reviews 129 Just off press, this NEW 3rd edition of the famous Sprague Man- ON THE COVER: Paul Chirlian, New York University, and the ual is jam -packed with up- to -the- antenna designed by the university's Electrical minute replacement recommen- for Engineering College to range from 100 kc to dations critical capacitors in 4,000 mc. practically every TV set on the Ektachrome original by Avery Slack market today! FREE from your Sprague parts distributor or send 10¢ directly to Sprague to cover November, 1951 RADIO -ELECTRONICS Vol XXIII, No. 2 handling and mailing costs. Published monthly by Radcraft Publications, Inc., at Erie Ave., F to G Streets, Philaaelpnia 32, Pa. EXECUTIVE. EDITORIAL and ADVERTISING OFFICES: 25 West Broadway. New York 7. N. Y. Telephone 1(Ectur 2 -8630. Hugo Gernsback, President; M. Harvey Gernsback. Vice -President; G. Allow, Secretary. SUBSCRIPTIONS: Address Correspondence to Radio- Electronics. Subscription Dept.. Erie Avenue. F to G Ste., Philadelphia 32. Pa., or 25 West Broadway, New York 7. N. Y. When ordering a change please furnish an address stencil impression from a recent wrapper. Allow one month for change of address. SUBSCRIPTION RATES: 1n U. S. and Canada, in U. S. possessions, Mexico. South and Central American countries. $3.50 for one year, $8.00 for two years; $8.00 for three years; single copies 30c. All other foreign countries $4.50 a year, $8.00 for two years; $11.00 for three years. Entered as second class matter September 27, 1948 at the poet office at Philadelphia, Pa., under the Act of March 3, 1879. Printed in U. S. A Copyright 1951 by Radcraft Publica- tions, Inc. Text and illustrations must not be reproduced without permission of copyright owners. BRANCH ADVERTISING OFFICES: Chicago: 520 N. Michigan Ave. Telephone SUperior 7 -1798. Los Angeles: Ralph W. Harker, 1127 Wilshire Blvd., Tel. MA 6 -1271. San Francisco: Ralph W. Harker. 582 Market St.. Tel, GArfield 1 -2481. FOREIGN AGENTS: Great Britain: Atlas Publishing and Distributing Co., Ltd., London E.C.4. P ODUCTS COMPANY Australia: McGill's Agency. Melbourne. France: Brentano's. Paris 2e. Holland: Trilectron. Heemetede. Greece: International Book & News Agency. Athens. So. Africa: Central News Agency, Ltd., Johannesburg; Capetown: Durban, 81 Marshall Sf. Natal. Universal Book Agency, Johannesburg. Middle East: Steimataky Middle East Agency. Jerusalem. India: Broadway NORTH ?.DAMS, MASSACHUSETTS News Centre, Dador, Bombay 414. K. L. Kannappa Mudallar, Madras 2. Pakistan: Paradise Book Stall. Karachi 3. POSTMASTER: It undeliverable send form 3575 to: RADIO-ELECTRONICS, 25 West Broadway. New York T. N. Y. (Distributors' Division of the Sprague Electric Company) RADIO -ELECTRONICS for

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This Western Electric employee mounts a transmitter in the test fixture which is swung down to face an artificial mouth at 45- degree angle, just as transmitters are held in use. More than a million transmitters are tested each year.

his mouth speaks to millions

To serve the changing needs of scientists, Western Electric engi- telephone subscribers millions of neers developed the practical tester telephone sets have to be moved in the illustration. each year. Before being put back into The transmitter is removed from service most of them are returned the handset and put in front of an to. the Western Electric Company's artificial mouth which emits a tone Distributing Houses where they that swings several times per second receive a thorough checkup. over a band of frequencies. A signal Western Electric engineers needed lamp tells whether the transmitter a rapid method of testing trans- is good. Each test takes 5 seconds. mitters over a range of frequencies. This new tester illustrates bow At Bell Telephone Laboratories, Bell Laboratories research and scientists had just the thing -a Western Electric. manufacturing At Bell Laboratories a scientist employs a technique they had devised for skill team up to maintain your tele- condenser microphone to check the sound level fundamental research on trans- phone service high in quality yet from another type of artificial mouth, used in transmitter research. mitters. In co- operation with these low in cost.

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www.americanradiohistory.com 12 The Radio Month FM RADIO SNOW GAUGES, de- The phosphor color plate can be pro- veloped by the U.S. Weather Bureau duced by silk- screen printing methods and the Corps of Engineers, are now with sufficient accuracy and at low cost. being used to measure the water con- According to the inventor, the new tent of snow fields on mountain tops tube can be adapted to receive either and other isolated points. The depth of CBS or RCA color, as well as black -and- the snow is measured by burying radio- white programs. To receive CBS pro- active isotopes of common metals below grams only three additional tubes are the ground surface and using a Geiger- needed, plus an adapter somewhat similar to those now sold to make standard receivers compatible with CBS 405 -line transmissions. Dr. Lawrence worked with Chromatic Television Laboratories, Inc., a Paramount Pictures subsidiary, in the development of the tube.

SHIPBOARD RADIO OPERATORS who have been drafted into the armed services will be discharged and returned to civilian status if recommendations of the Federal Maritime Administration are followed. The recommendation was made at a recent conference of representatives of the FCC, Maritime Ad- Courtesy Motorola Inc. ministration, radio -operator unions, The sensing unit (foreground) with its Coast Guard, and maritime industry at Geiger tube slips into housing (rear). a meeting called to determine means of easing the shortage of qualified marine Mueller tube to measure the intensity of radio operators which developed when radiation after passing through the nearly 300 merchant ships were with- snow. The strength of the radiation is drawn from the "moth -ball fleet." an indication of water content of the Proposals were made to alter the FCC snow. regulations to permit employment of Since the measuring apparatus is lo- men not now eligible for the licenses cated at remote points, battery- operated required for shipboard service. The FM transmitters are used to transmit changes would make available men in the data to a central recording station. two new categories. One group includes men who held limited radiotelegrapher's licenses came before 1935 and who would be PHONE BOOTH TELEVISION eligible if they could prove to a recently in previous close being reality shipboard service. The second group in- a New York City pay station. Pick- cludes men ing receiver to make a a those who obtained licenses Q up the call, since 1935 and who operated shipboard keeps pace with the would -be telephonist heard voices. radio installations -that he was a conver- under temporary Thinking interrupting limited licenses during the war. In both growth of the electronic sation, he hung up and tried again a instances, voices the operators would have to few minutes later. The were still pass a code test. industry there, and were apparently following the script of some kind of a play. With- in a few minutes the program was iden- U.H.F. TELEVISION was advocated by tified as that of WABD, channel 5. FCC chairman Wayne Coy as being a Quosia A call to an official of the telephone means of bringing about a nation -wide resulted in repair men being -that meets fully the per- company system of competitive television. Speak - rushed to the scene. The company offi- ink at RCA's one -day u.h.f. seminar in formance requirements of cial stated that while such happenings Bridgeport, Conn., Mr. Coy went all out are rare, they can be caused by a cross- for u.h.f. TV. He said that he is sold on all radio and tv set manu- talk between the regular phone lines u.h.f. and that he would lil:e to see all facturers and those used for the TV broadcast. TV in the u.h.f. channels. Mr. Coy pointed out that the "TV NEW TV COLOR TUBE, that can be freeze" came about when the FCC real- manufactured at a cost comparable to ized that the existing 12 v.h.f. channels

present black- and -white tubes, was are . not sufficient to provide for a com- Q demonstrated by Professor Ernest O. petitive TV service in the nation's 168 -that safeguards dealer Lawrence of the University of Cali- metropolitan areas with populations of fornia. Dr. Lawrence is the inventor over 50,000. He proposed using the en- service work of the cyclotron and a Nobel prize win- tire band between 480 and 890 me for ner for his work in electronic and u.h.f. TV assignments and asserted that atomic physics. when the freeze is over, two -thirds to The new tube has a screen built up of three -quarters of all TV station as- phosphor strips which glow alternately signments will be in the u.h.f. region. in blue, green and red. Before reaching These would make possible the ulti- TUNG-SO L this screen, the electrons pass through a mate establishment of nearly 3,000 TV RADIO, TV TUBES, DIAL LAMPS multiple -wire grid which acts both as a stations in this country. accelerating electrode and a deflecting U.h.f. TV reception was described as lens. By alternately raising and lower- excellent. This was based on the fact ing the voltage on this grid a few hun- that the signal from Bridgeport's u.h.f. TUNG -SOL ELECTRIC INC , Newark 4, N. J. dred volts above and below its steady TV station was as good in New Haven Sales Offices: Atlanta Chicago Dallas Denver Detroit Los Angeles Newark state, the beam is directed to the de- -25 miles away -as that of New Ha- sired color. ven's channel 6 station, WNHC -TV. RADIO -ELECTRONICS for

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TELLS HOW - TELLS HOW - WE GUARANTEE Our Amazingly Effective JOB -FINDING SERVICE TO TRAIN AND COACH YOU AT HOME Helps CIRE Students Get Better Jobs IN SPARE TIME UNTIL YOU GET Here are a few recent examples of Job -Finding results: GETS CIVIL SERVICE JOB YOUR FCC LICENSE "Thanks to your course I obtained my 2nd phone license, and am now employed by Civil Service at Great Lakes Naval Training Station as an Equipment Specialist." If you have had any practical experience- Amateur, Army. Kenneth R. Leiser, Fair Oaks. Mtd. Del., McHenry, Ill. Navy, Radio repair, or experimenting. GETS STATE POLICE JOB "I have obtained my Ist class ticket (thanks to your school) and since receiving same I have held good jobs at all times. I am now Chief Radio Operator with the Kentucky TELLS HOW- Employers make State Police." Edwin P. Healy, 264 E. 3rd St., London. Ky. GETS BROADCAST JOB "I wish to thank your lob- Finding Service for the help in securing for me the position JOB OFFERS like These of transmitter operator here at WCAE, in Pittsburgh." Walter Koschik, 1442 Ridge Ave., N. Braddock, Pa. to Our Graduates Every Month OURS IS THE ONLY HOME STUDY GETS AIRLINE JOB Telegram, August 9, 1950, from Chief Engineer, Broadcast Station, Pennsylvania, COURSE WHICH "Due to your Job- Finding Service, I have been getting many - "Have ¡ob opening for one transmitter operator to start immediately, contact SUPPLIES FCC offers from all over the country, and I have taken a job with me at once." TYPE EXAMINA- Capital Airlines in Chicago, as a Radio Mechanic. TIONS WITH ALL Harry Clare, 4537 S. Drexel Blvd., Chicago, Ill. Letter, LESSONS AND August 12, 1950, from Dir. Radio Div. State Highway Patrol, "We have two FINAL TESTS. vacancies in our Radio Communication Division. Starting pay $200; $250 after six Your FCC Ticket is always recognized in alll months' satisfactory service. Will you recommend graduates of your school." radio fields as proof of your technical ability. These are just a few examples of the job offers that come to our office periodi- tally. Some licensed radiomen filled each of these jobs . if might have been you!

HERE'S PROOF FCC LICENSES ARE OFTEN MAIL COUPON NOW SECURED IN A FEW HOURS OF STUDY With CLEVELAND INSTITUTE OF RADIO ELECTRONICS OUR Coaching AT HOME in Spare Time. Desk RE -35 -4900 Euclid Bldg., Cleveland 3. Ohio (Address to Desk No. to avoid delay.) Name and Address License Lessons Approved For Veteran Training Under G. I. Bill Lee Worthy, 2nd Phone 16 22101/4 Wilshire St., Bakersfield. Calif. I want to know now I can get my FCC ticket in a minimum of tune. me your FREE booklet, "flow to lass FCC License Examina- Clifford E. Vogt. let Phone 20 Send Box 1016. Dania, Fla. tions" (does not rover exams for Amateur License), as well as a sample FCC-type exam and the valuable new booklet, "Money-Making Francis X. Foerch, Ist Phone 38 38 Beucler PL., Bergenfield, N. J. FCC License Information." S "Sgt. Ben H. Davis, Ist Phone 28 Name 317 North Roosevelt. Lebanon, III. Albert Schoell, 2nd Phone 23 Address 110 West Ilth St., Escondido, Calif. CLEVELAND City Zone State INSTITUTE OF RADIO ELECTRONICS Paste on penny postcard or send air mail. Desk RE -35, 4900 Euclid Bldg., Cleveland 3, Ohio NOVEMBER, 1951

www.americanradiohistory.com 141 The Radio Month ELECTRONIC SCALES are now be- AUDIO FAIR, the third annual con- ing used to weigh giant electrical trans- vention of the Audio Engineering So- formers and other equipment too mas- ciety, will be held on November 1, 2, and sive and heavy to be weighed by ordi- 3 in the Hotel New Yorker, in New M ERIT nary means. The operation of the new York City. Audio equipment and acces- scale is based on the use of a resistance - sories will be displayed and demon- Best for Better TV Service wire strain gage which changes its re- strated by manufacturers, distributors, sistance in proportion to its length. and manufacturers' agents. High lights The gage is connected to the upper of the Audio Fair will be a series of part of a gigantic crane hook which technical papers delivered by authori- supports the object to be weighed. It is ties in the field. The tentative lecture cemented to a member on the crane's program is as follows: structure where the weight of the ob- "Problems of Ultra -Speed Recording ject develops a compression strain Techniques," by C. J. LaBel, of Audio which produces an imperceptible re- Instrument Co. duction in the length of the member. "Magnetic Recording Equipment for This compression is transmitted to the Motion Picture Production," by Bruce strain gage which changes its resist- Denny and William L. Thayer, of Para- ance according to the applied force. mount Pictures, Inc. Electronic circuits convert the change in "Modern Recording Installation That resistance directly into pounds or tons Emphasizes Tape," by W. O. - MDF -30 -nw 70° Summer "f ull foc us "dish bused on the dial of a portable meter. lin, of Audio -Video Recording Co. winding "cosine" "An Artificial Reverberation Genera- yoke - complete with network. For dircl RADAR FISH PATROL in use by tor," by Lewis S. Goodfriend, of Audio drive tubes up te 2e. California's Division of Fish and Game Facilities Corp. is rapidly driving illegal fishing from "Magnetic Tape Recording for In- the coastal waters of that state. Before strumentation and Data Storage," by radar equipment was installed on the Kenneth B. Boothe, of Audio and Video commission's four patrol boats, fog and Products Corp. darkness severely handicapped the sea- "Loudspeaker Enclosures," by Daniel going wardens whose duty is to prevent J. Plach and Philip B. Williams, of commercial fishing inside the 3 -mile Jensen Mfg. Co. limit. Under these conditions, standard "Multiple- Speaker Systems," by Harry operating procedure was to stop the pa- F. Olson, of RCA Laboratories. trol boat and listen for other boat en- "Design Principles as Applied to gines and watch for lights aboard boats Radio and Loudspeaker Cabinets," by of careless violators. Jeff Markell, New Horizons Furniture. Now, with radar, the patrol can al- "New Amplifier Design," by Herbert ways spot violators miles away, at any I. Keroes, of Acro Products Co. time of day or night. After a few boats "Industrial Sound Systems," by H. S. were captured and many warned, the Morris, of Altec Lansing. word has gotten around that there can "Transistors in Audio Use." Speaker Merit TV full -line* Components be no escape so there are few attempts from Bell Telephone Laboratories. For Conversion or Replacement at fishing inside closed waters. During "Magnetic Amplifiers for Audio Ap- 1949 and 1950, 25 boats were caught plications." Speaker from Bureau of Merit... HQ for TV Service Aids and 284 crewmen arrested. This year's Ships, U. S. Navy. Keep ahead of TV conversion and com- catch is one boat and nine men. -end- ponent replacement service problems- write MERIT, HQ for TV Service Aids.

FREE Sept. 1951 Issue #404

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*Merit is meeting the TV replacement component and conversion demand with a line as complete as our advance information warrants) Courtesy General Electric Co. MERIT TRANSFORMER CORPORATION Captain Hooker scans the radar screen aboard the 63 -foot patrol boat Bonito. 4425 N. Clark St., Chicago 40, Illinois Seagoing game and fish warden uses radar to spot violators off California coast. RADIO -ELECTRONICS for

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Merchandising and Promotion Brach Manufacturing Corp., Newark, INDISPENSABLE! Merit Transformer Corp., Chicago, N. J., is sponsoring a joint advertising has published a new "TV Replacement campaign with Dynamic Stores over Guide and Catalog" which lists all New York's WOR -TV. Built around the PHOTOFACT BOOKS makes and models of TV sets with man- theme, "Two Sets for Every Happy ufacturers' numbers and Merit replace- Home," the campaign features the ments. The catalog is available through Brach two -set coupler. the company or its distributors. The South River Metal Products, Inc., company also introduced a new con- South River, N. J., has prepared a new version and replacement kit for distrib- catalog on its antenna mounting acces- utors' sales departments, featuring a sories. "Day -Glo" card. Edwin I. Guthman Co., Inc., Chicago, Astatic Corp., Conneaut, Ohio, has has published a new booklet illustrating issued two new phonograph cartridge its production facilities. The company is a fabricator of electrical and TV components. Photofant Television Course. Covers TV principles, oper- Columbia ation and practice. 216 pages; profusely illustrated; 81/2 Wire & Supply Co., Chi- x 11 ". Order TV -1 Only $3.00 cago, published a new booklet describing its facilities and products Television Ant . New 2nd edition. Describes all which it TV antenna types; tells how to select, install, solve troubles. manufactures, including all types of Saves time; helps you earn more. 200 pages; illustrated. electrical insulating Order TAG -1 Only wire, cords, cable, $2.00 wire kits, etc. Columbia is also a na- Television Tube Location Guide. Volume 2. Accurate tional warehouse and distributor for diagrams show position and function of all tubes in hundreds of TV sets; helps you diagnose trouble without removing Anaconda Densheath television and chassis. 224 pages; pocket -size. Order TGL -2. Only $2.00 radio wire and cable.

Television Tube Location Guide. Vol. 1. Over 200 Sangamo Electric Co., Springfield, Ill., pages of TV receiver tube position diagrams on hundreds released its first TV capacitor replace- of models. Order TGL-1 Only $1.50 ment catalog. The 28 -page booklet lists 1949 -1950 Record Changer Manual. Vol 3. Covers not only Sangamo capacitors but types 44 models made in 1949, including multi -speed changers comparable and wire and tape recorders. Original data based on actual to them made by other analysis of equipment. 286 pages; 81/2 x 11 "; paper- manufacturers. The booklet may be had bound. Order CM -3 Only $3.00 from the company or its distributors. 1948 -1949 Changer Manual. Vol. 2. Covers 45 models made in 1948 -49. Paper bound. Order CM- 2.Only $4.95 replacement guides. One lists the proper Servicing Business Astatic replacements for Columbia pho- 1947 -1948 The RCA Service Co., Changer Manual. Vol. 1. Covers 40 post- nographs and record changers, Camden, N. J., war models up to 1948. Order CM -1 Only $3.95 and the added new other gives similar data two protection plans to its on Philco full- coverage service contracts. One Recording & Reproduction of Sound. A complete au. models. Recommended Astatic car- thoritative treatment of all phases of recording and amplifi- plan provides protection for the picture cation. 6 x 9". Order RR -1 Only $5.00 tridges and needle types are illustrated and a numerical designation tube only; guarantees the tube for one given. year from the date of purchase by the Allen B. Du Mont Laboratories' user. Cathode -Ray Tube Division advertising Cost of the plan varies according manager, to the size of the tube. The second plan Jake Ruiter, outlined the features complete installation, instruc- largest and most comprehensive advertising tions to the customer and a one -year campaign the division has yet and tube undertaken. The campaign parts warranty plus one serv- will include ice call during the year. Additional calls advertisements in leading trade and service publications are charged at the rate of $3.95 if the as well as exten- set is brought to RCA sive use of point -of -sale the Service Com- material for pany, and $5.95 if it is a home call. Audio Amplifiers. Vol. 3. Clear, uniform, accurate data on distributors, dealers, and service tech- 50 important audio amplifiers, plus full coverage of 22 FM nicians. and AM tuners, produced during 1950. 362 pages, Production and Sales 81/2 x 1 1 ". Order AA-3 Only The Division $3.95 also issued a new pocket - 'l'he size TV Picture Tube Replacement RTMA announced that sales of Audio Amplifiers. Vol. 2. A complete analysis of 104 Se- receiving tubes by manufacturers dur- well -known audio amplifiers and 12 tuners made 1949 -50. lector which indicates the correct re- 368 pages, 81/2 x 11". Order ing the month AA -2 Only $3.95 placement type for worn of July dropped to -out Du Mont 13,185,567, almost 50% less picture tubes. The circular cardboard than the Audio Amplifiers. Vol. 1. Covers 102 amplifiers and FM June figure. An analysis of sales showed tuners made through 1948. 352 pages. Order indicator is available free through the AA -1 Only $3.95 company and its Teletron that 7,117,435 were for new equipment, distributors. 4,625,314 were for replacements, and Auto Radio Manual. Complete service data on more than Allied Radio Corp., Chicago, has pub- 100 the balance for export and Government post -war auto radio models. Covers over 24 mfrs. lished its 1952 catalog. The new 212 - 350 pages, 81/2 x 11 ". Order AR-I Only $4.95 agencies. page book lists radio, television and The Communications Receiver Manual. Complete analysis RTMA also announced that of 50 popular communications models. 246 pages, 81/z x 89,144 cathode -ray tubes were sold to 1 I". Order CR -1 Only $3.00 TV receiver manufacturers during July Radio Receiver Tube Placement Guide. Accurate dia- as compared with 221,759 during June. grams show where to replace each tube in 5500 radio Of the July total, 99% were rectan- models, covering 1938 -1947 receivers. 192 pages, pocket - size. Order TP -1 Only $1.25 gular and 16 inches or larger in size. The NBC -TV Sales Planning and Dial Cord Stringing Guide. Vol. 2. Covers receivers made from 1947 through 1949. Shows you the one right way to Research Bureau announced that there string a dial cord in thousands of models. Pocket -size. Order were 13,271,700 TV DC -2 sets installed in the Only $1.00 United States as of August 1. There Dial Cord Guide. Vol. 1. Covers sets produced 1938 were 2,455,000 in New York City, through 1946. Order DC -1 Only $1.00 1,003,000 in Los Angeles, 942,000 in Making Money in TV Servicing. Tested proved methods Chicago, 874,000 in Philadelphia, 754,- of operating a profitable TV service business. Covers all 000 in Boston, 526,000 in Detroit, important phases. Authoritative, valuable guide to success. Over 130 pages. Order MM -1 Only $1.25 486,000 in Cleveland, 312,000 in Pitts- burgh, and 308,000 in Baltimore. Order from your Parts Jobber or write direct to electronic parts, test equipment, P.A. NOWARD W. SAMS 8 CO., INC., 2201 E. 46th St., Indianapolis 5, Indiana I systems and many other items to meet Show Notes the requirements & Equip- HOWARD of the radio -tele- The Radio Parts Electronic W. SAMS & CO., INC. vision -electronics field. ment Shows, Inc., Board of Directors RADIO -ELECTRONICS for

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approved a three -point program for For a basic changes in the future conduct of the show. The board was increased BETTER PICTURE from nine to fourteen members to include seven NEDA members and seven members of cosponsoring manufactur- on the TV Screen ers' associations, including the RTMA, Association of Electronic Parts & ..And Atop the TV Equipment Mfrs., Sales Managers Club, Eastern Division, and West Coast Elec- Receiver Cabinet tronic Mfrs. Association. Other changes in the bylaws provided that at least the first two days of shows be exclusive ASIATIC TV and FM BOOSTERS distributor days and that no individual may serve and no company may be represented on the board for more than IT'S better viewing two consecutive years. As a result of these changes, the NEDA Board of Di- all around, with one of the rectors decided that beginning in 1952, four Astatic TV and FM and every year thereafter, there would Booster models. Advanced be an Annual NEDA Convention and Manufacturers' Conference without a engineering principles and trade exhibit. famous Astatic manufac- The Eighth Annual Pacific Electronic Exhibit Show Committee increased its turing quality assure better perform- membership to eight. This increase of Model BT -I three ance ... brighter, clearer pictures .. . members was made to include List Price representatives of the I.R.E. who will $32.50 crisp, clear sound. Handsome, lux- cosponsor the show with the West urious cabinets -in a va- Coast Electronic Manufacturers' Asso- ciation in 1952. riety of styles and finishes -permit selection to suit New Plants and Expansions The American the style of the TV receiver. Phenolic Corp. is erect- ing its fourth plant on Chicago's west No matter how you Iook at side to permit a greater expansion of it, the better booster is AN and RF connector assembly production at the main plant. The new 65,000 - an Astatic. Write for full square -foot plant will house all syn- details. thetic operations. Model BT -2 General Electric Company's Tube List Price Department leased the Garden State THE Lines bus $ 34.95 terminal in Clifton, N. J., for use as its electronic tube warehouse and as headquarters for the depart- AST TIC CORPORATION ment's eastern commercial service op- CONNEAUT, OHIO erations. MEN IN CANADA. CANADIAN ASTAT C LTD, TORONTO, ONTARIO Haydu Brothers, Plainfield, N. J., Model AT-I manufacturer of TV tubes and other electronic products, is adding a new List Price $54.50 wing to its plant. (Also available in Helipot Corp. added a second plant blond wood cabinet to its facilities in Pasadena, -Model AT -IB Cal. It comprises 15,000 List Price $56.50.) square feet of floor space with facilities for over 150 employees. The Hi -Lo TV Antenna Corp. constructed an additional plant immediately adjacent to its present plant in Chicago. Veri -Best Electronics Co. is now in full production in its new plant at Westbury, N. Y. The company plans a new series of electronic products in addition to its current line of TV antennas. North American Philips Co., Inc., New York City, purchased the capital stock of the A. W. Haydon Co., Water- bury, Conn. Collins Radio Co., Cedar Rapids, Iowa, has established a Procurement Division which will be headed by Max W. Bur- rell, former general sales manager. Electronic Devices, Inc., Brooklyn, N. Y., purchased the Precision Rectifier Corp., which will now operate as the Precision Rectifier Division of Elec- tronic Devices. The division will manufacture selenium -end-rectifiers. RADIO -ELECTRONICS for

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www.americanradiohistory.com 20 EQUIPMENT EME AT SPECIAL SAVINGS THAT FAMOUS QUALITY RECOGNIZED AND PRAISED BY ELECTRONIC TECHNICIANS FOR OVER 24 YEARS NO REDUCTION OF COMPONENTS NO REDUCTION IN QUALITY ONLY A REDUCTION IN PRICE TO YOU AM - FM - TV MULTI -METER MEASURES DC VOLTAGE TO 86,000 VOLTS AT 25,000 OHMS PER VOLT! The popular Supreme Model 592 has been extended for television. It now measures up to 35,000 volts DC with input resistance of the high range being 875 megohms. Many VTVMs are below this. Once you have used the Supreme 692, you would not trade it for all the rest. Lt's simple to operate and gives the user speed he never dreamed of. After test leads are inserted in the two pin jacks, it is not necessary to move them again (except on the 14 ampere and 35,000 volt ranges). Fifteen DC VOLTAGE ranges -two sensitivities -8 ranges at 25,000 ohms /volt and 7 ranges at 1000 ohms/ volt -0/3.5/7/35/140/350 /700/1400 volts DC. External extension unit included for 35,000 volt range at 25,000 ohms/volt. Six OHMMETER ranges -0/500/5000/50,000 /500,000/5 meg./50 meg. No ranges omitted to confuse operator. All readings are made on easy -to -read single scale by simply adding zeros. Ohmmeter uses standard type batteries -simple, economical replacement. No external power required, even for the 60 megohm range! Six AC VOLTAGE ranges -0/7/35/140'350/700 /1400 volts. Temperature compensated double bridge rectifier circuit provides maximum accuracy and protection. Seven DIRECT CURRENT ranges -0/70 microamperes, 0/7/35/140/350 milliamperes, 0/1.4/14 amperes. Six OUTPUT VOLTAGE ranges -0/7/35/140/350700 /1400. No external blocking condenser required when used as output meter in alignment. Four DECIBEL ranges -0 to plus 16, plus 10 to plus 26, plus 26 to plus 36, plus 36 to plus 46 db. All decibel ranges calibrated for direct reading on 500 ohm line. Full- vision, Supreme built, four inch meter with 40 microampere movement and sturdy pointer. Instrument housed in attractive, sturdy, metallic carrying case with leather handle, test lead compartment, and detachable lid. Shipped complete with instruction manual, test leads, batteries, and high voltage extension unit. Approx. dimensions 81 x 12 x 5 inches. Shipping Weight 13 pounds.

YOUR COST DURING Regular Value $69" THIS SPECIAL OFFER '3695

ALL SUPREME INSTRUMENTS ARE COMPLETELY WIRED. TESTED AND CALIBRATED AGAINST RELIABLE STANDARDS BY SKILLED INSTRUMENT TECHNICIANS. THEY ARE NOT KITS. EACH SUPREME INSTRUMENT IS BRAND NEW FRESH EQUIP.. MENT -NOT SURPLUS OR REBUILT. TUBE AND BATTERY TESTER CHECKS AM -FM -TV RECEIVING TUBES AND PORTABLE RADIO BATTERIES. The SUPREME Model 616 cannot be beat for efficient bench or counter tube testing. Incorporating that famous tube test circuit and patented regulated neon leakage test, both pioneered and developed by Supreme. Have set tube rejection standards for years. Minimized obsolescence by use of Supreme patented element selector system. Thousands of testers using this circuit have been in use over ten years. Socket facilities for all AM, FM and TV receiving tubes. ILLUMINATED ROLL CHART with hundreds of types listed. TUBE SETTING DATA on future tubes supplied by Supreme as they come into use. Quality test readings for both tubes and batteries on "Replace- Good" scales of beautiful BIG SEVEN INCH FULL VISION METER designed and built by SUPREME. Non -breakable window. Most people can read this meter ten feet away. Also checks portable radio batteries UNDER PROPER LOAD. Tests batteries with rated voltages of 11/2, 43,5, 6, 45, 671, 90 volts. Hammerloid finished metallic case with detachable cover. Approx. dimensions 11 x 15 x 61/2 inches. Shipping weight 20 pounds. YOUR COST DURING 55495 Regular Value $875° THIS SPECIAL OFFER SUPREME MODEL 600 is also being made available during this special sale offer. Similar in appearance to Model 616, with all the features listed above plus 31 multi-meter ranges (1000 ohms /volt). Regular Value 511750 Your Cost during this Special Offer $7495 ORDER TODAY -THIS OFFER IS SUBJECT TO WITHDRAWAL IN 60 DAYS, OR BEFORE IF ANY MODEL IS SOLD OUT AND NOT AVAILABLE FOR IMMEDIATE DELIVERY. PRICES APPLY ONLY TO ORDERS FROM INSIDE THE CONTINENTAL U. S. A. A DEPENDABLE SIGNAL GENERATOR RF TO 82 MC-400 CYCLE AF- COVERS TV IF MARKERS Supreme pioneered in the development of all wave signal generators and the Model 661 is the result of many years of development and research to find the most stable circuits and provide the most simple operation. Many circuits were explored and the one used in the 661 was declared the best of all. Many dial arrangements were investigated; many calibration methods checked; many attenuators and modulation methods carefully analyzed. There is no better service oscillator on the market than the Model 661. Only 2 dial scales but 5 bands. All ranges are read simply on two basic scales that are accurately calibrated- - even at both ends. Impregnated iron core tuned inductors and air dielectric trimmers provide the maximum frequency stability. Guards against shift due to line voltage fluctuation, aging, temperature and humidity. Continuously variable output in a 4 step ladder attenuator. Double shielding to minimize leakage. Shielded line cord, illuminated hair line dial. RF ranges from 65kc to 82 megacycles (65kc to 20.5 Mc on fundamentals). Audio frequency output, continuously variable from minimum to maximum. Internal modulation of RF signal approximately 50%. Jack provided for external amplitude modulation. Housed in heavy steel case, attractive finish. Complete with instruction manual and shielded connector. Approx. dimensions 934 x 8% z 71 inches. Shipping weight 16 pounds.

Regular Value $7250 THIS SPECIAL ER 53475 EVERY SUPREME INSTRUMENT IS BACKED BY OUR COURTEOUS AND EFFICIENT SERV- ICE ORGANIZATION. NO "ORPHAN" INSTRUMENTS. FULL ONE YEAR GUARANTEE, BACKED BY THE FACTORY. ANY SUPREME INSTRUMENTS SHIPPED DIRECTLY FROM THE FACTORY ARE SOLD STRICTLY ON A "MONEY- BACK -IF- NOT -SATISFIED" BASIS. TRY ANY OF THEM FOR 10 DAYS. IF NOT COMPLETELY SATISFIED, RETURN FOR FULL REFUND OF PURCHASE PRICE. MAIL YOUR ORDER TO SUPREME, INC., BOX A552, GREENWOOD, MISSISSIPPI -ORDER TODAY

I WANT TO TAKE ADVANTAGE OF TH!5 SPECIAL SUPREME SAYINGS OFFER- PLEASE RUSH THE MODELS CHECKED- -_ Model 592 @ $36.95 $ Ship to Model 616 @ $54.95 $ _ Address Model 600 @a $74.95 $ City State Model 661 @ $34.75 $ $ Deposit ship balance C O D $ Payment in full Enclose full payment with order or send 2O% deposit with C.O.D. orders. (Full payment orders are the quickest to handle and save you C.O.D. fees). NOTE: If you do not want to cut this page, copy above on separate sheet of paper and mail. It will receive same prompt handling. RADIO -ELECTRONICS for

www.americanradiohistory.com 21 \ \\\ I ,

for men in radio -electronics to prepare for better pay jobs in

No vocational field offers more opportuni- RCA INSTITUTES Home Study ties for "career" jobs and good pay than Course television- America's fastest growing in TELEVISION SERVICING - industry. The demand for TRAINED and EXPERIENCED TV SERVICEMEN is growing. A Service to the Industry YOU STUDY AT HOME There is a big shortage of such men now In your spare time, you learn pre -tested Because of the critical shortage TRAINED "How- todo-it" techniques with "How and will be for several years to come. of -it- and EXPERIENCED TV SERVICEMEN, RCA In- works" information in easy -to -study lessons. stitutes is offering this highly The course is based on the experience of the PLENTY OF GOOD JOBS OPEN TODAY specialized and RCA Service Company in servicing thousands practical home study course as a service to of home television receivers. Radio-Television jobbers, dealers and serv- the working members of the radio- televi- ice companies offer lifelong opportunities sion -electronics industry. Its object is to with excellent salaries for qualified service train more good servicemen and to help technicians. Manufacturers of television re- make good servicemen better. ceivers are looking for men with good serv- Never before has this course been ice training avail- as inspectors, testers and trouble- able to anyone outside of RCA. It is now shooters. Many experienced servicemen go offered to you, through RCA Institutes, one into business for themselves. Others hold of America's oldest and most their respected tech- regular jobs and earn extra money nical training schools. The course covers servicing TV receivers in their spare time. most major makes and types of TV receivers. Radio -electronics manufacturers busy Available exclusively to men in the radio - with defense equipment contracts offer ex- television- electronics field. Not offered to cellent job opportunities for men with a the general public, or under G.I. Bill. television technician background. Service- The cost is low . .. only $9 a unit for 10 YOU KEEP WORKING ON YOUR JOB men called into military service are further units or $90 total, on an easy pay- as-you- reducing Because you work in the radio- television- the supply of skilled TV service- learn plan. At successful completion electronics industry, men of the your job provides the available for civilian activities. Think course you earn an RCA Institutes certificate laboratory work of the course. There are no what kits, parts or television servicing offers you in terms that can lead straight to a better job at equipment to buy. Self - of a lifetime career and financial security. employed independent radio and television higher pay. servicemen are eligible for enrollment.

* SEND FOR FREE BOOKLET. Find out complete details * of the RCA INSTITUTES Home Study Course in TELE- RCA Institutes conducts a resident VISION SERVICING. Don't pass up this opportunity to school in New prepare York City offering day and yourself for a money - making career in the television evening courses in industry. Illustrated booklet Radio and TV Servicing, Radio Code and Radio explains all the features of the course. Mail coupon in an envelope or paste on a penny Operating, Radio Broadcasting, Advanced Tech- postcard -NOW! nology. Write for free catalog on resident courses.

RCA INSTITUTES, INC. Home Study Department, RE -1151 350 West Fourth Street, New York 14, N.Y. Without obligation on my part, please send me copy of booklet "RCA INSTITUTES Home Study Course in TELEVISION SERVICING." (No salesman will call.)

Name (Please Print) RCA INSTITUTES, INC. Address A SERVICE OF RADIO CORPORATION ofAMERICA City Zone Stare 350 WEST FOURTH STREET, NEW YORKIR, N.): L J NOVEMBER 1951

www.americanradiohistory.com 22

M. AI Goldberg, Assistant Chief Engineer of CBS- In the CBS.Columbia design, lebaratories, Al Goldberg Columbia, and Harry R. Ashley, President of EICO, takes some Important readings ohm the EICO Model 221 inspecting the use of the EICO Model 221 Vocuum Tube Vacuum Tube Voltmeter and Model 555 Multimeter, as Voltmeter and Model HVP-1 High Voltage Probe at the Harry R. Ashley looks on. Sweep Frequency Troubleshooting Position on the CBS- 'ts 11E4co Columbia Color Television production lines. KITS for laboratory Precision at lowest Cost- WIRED INSTRUMENT S the leaa:ers look to EICO! 4e. NEW does CBS-Columbia, Inc., today's headline-maker in Color 221K VTVM KIT $25.95 WHY Television set production, use EICO Test Instruments on WIRED $49.95 its new Color Television production lines and in its design laboratories? HIGH VOLTAGE BECAUSE - like Emerson, Tele-King, Teletone, and many PROBE $6.95 another famous TV manufacturer coast to coast, CBS-Columbia knows that Only EMT! Test Equipment delivers W Al/ 10 EICO nomical features!

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www.americanradiohistory.com Editorial 23 Radio -Electronic Giant

... The radio -electronic industry will soon be one of the top three .. .

By HUGO GERNSBACK

ometimes the members of our industry do not realize industrial revolutions, few people get hurt in the process. the giant strides that it has made in recent years. The workers are simply released for other and more im- Dr. Allen B. Du Mont last month stated that more portant jobs, which usually pay better. Surprisingly than $7,600,000,000 will have been awarded for radio - enough, radio -electronics has been a huge factor in not electronic contracts by the end of 1951, ranking the in- only increasing the prosperity of the country but in a dustry next to steel and aircraft in importance during large measure is responsible for higher wages. In our the present military buildup. ownindustry, when radio -electronic workers are eliminated Military contracts are, however, only a single facet in in one branch these same workers, practically without the new giant industry. At the moment, no accurate exception, command higher wages on their next jobs. statistics as to the total volume of radio -electronic dollar This is true in many of the allied industries as well. volume can be compiled. The industry is too young and The machine age has now been replaced by the radio - is growing so fast that no sooner have the first set of electronic age. Heretofore, men tended the machines. figures been computed than they are already obsolete. The Soon the machines will tend themselves, purely due to the industry is so huge and goes into so many ramifications- magic of radio -electronics. Modern plants have already at times overlapping other industries -that it is often begun robotizing. Some plants where formerly hundreds difficult to formulate a true overall picture. Take for in- of employees were needed, today require only a handful stance, two of the largest radio -electronic manufacturers of engineers to supervise a series of complex procedures. in the country, General Electric and Westinghouse, who This tendency is now on the march and will continue to do not report their radio -electronic sales separately. These expand during the next few decades at an ever- accelerat- concerns manufacture many other items of electrical or ing rate. It would seem that there are few manufactured other nature, (not radio or electronic) which makes it items which cannot be made successfully in a practically impossible to get accurate figures. While the radio -elec- manless plant. tronics industry is now some thirty years old, even the These tendencies will make man freer than he ever was U. S. Department of Commerce still lumps its radio - before. The drift toward shorter hours which has been electronic figures under a heading: "Manufacturing, going on for the past 30 years is still in evidence and will electrical machinery." continue at an increasing rate, due primarily to radio - If we estimate that radio and electronic items represent electronics and its labor- saving devices. only 15% of the total production of such huge firms as The new uses for radio -electronics are so astonishing General Electric and Westinghouse in 1950, we can obtain that even men within the industry are hard put to keep an approximate figure of their radio -electronic dollar track of them. Every day brings new applications which volume. If then we add the twenty topmost radio -elec- in turn increase the power of the industry. One of the tronic firms manufacturing radios, television sets, and newest huge additions is the electronic computer-the various electronic items, we find that the income of these robot mathematician. The manufacture of computers in firms during 1950 came to around $3,000,000,000. (Three itself is becoming quite an industry and these computers billion dollars.) will be one of the big factors in the automatic factories This isn't, however, the whole story and does still not of the future. give us a correct perspective. The point is that there are Radio -electronics has successfully invaded other in- hundreds of lesser firms who manufacture all sorts of dustries such as plastics. Some solid plastics are now made radio -electronic devices, both for peace and military from liquids. Cathode rays, similar to those we use in tele- purposes. Many of these firms are young and have as yet vision, convert liquid raw materials into solid plastics. to make their way. New firms spring up in the industry Another unsung radio -electronic achievement is the every week and while many manufacture radio -electronic assorting machine, which nowadays is doing almost devices exclusively, there are equally as many firms who magical jobs. It would seem impossible that a machine manufacture other products as well. could accurately sort thousands of different unlabeled The war effort has also blurred the picture somewhat, cans, containing dozens of different foods; nevertheless, because it is difficult to disentangle war orders from this has been done recently in a very striking manner. others throughout the industry. One thing is quite certain: There is no visible identification on the cans, but then even with no war orders it seems likely that annual non- radio -electronics doesn't need any. Before the cans are military sales of the entire radio-electronic industry by packed with the various foods they are magnetized in 1960 should reach no less than $10,000,000,000. certain spots in a special code. The radio -electronic sorter So much for the dollars and cents aspect of the giant segregates the various cans using the magnetic code on industry. People on the outside sometimes find it difficult their rims. Then the machine selects the correct label, to understand that our industry has made such tremendous affixes it and sends it down the conveyor. strides, particularly during the past ten years. The answer is simple. In nearly every endeavor that one Wonders such as these are becoming commonplace in can think of radio -electronics has a part nowadays. There our blasé world -which expects them. Nothing seems im- is hardly any household, office, or factory today which is possible today for radio -electronics. It improves our health, untouched by the magic wand of radio -electronics. This it gives us more and purer foods, it gives us more leisure tendency is certain to increase and will keep on increasing and far greater wealth. It is the key to interplanetary during the next few decades. travel-impossible without it. Radio -electronics to future Indeed, radio -electronics has created a new industrial ages will be known as the Ultimate Emancipator, for it, and revolution far greater than any of us realize today. It it alone holds the key to man's peace on earth -the final keeps on eliminating many jobs throughout this country elimination of war. and, indeed, the world at an astonishing rate. Unlike other -end--

NOV EM BER. 1951

www.americanradiohistory.com 24 Television

CBSColllmbia First Commei'iaI Color Plus BlaukalldlVhite Sel.

By I. J. MELMAN,*

E. S. WHITE,*

Fig. 1 -New receiver looks S. CUKER* like standard set, has only one more control. Wheel is invisible and inaudible.

ACOMPLETELY self- contained fear its supposed complexity and won- television receiver which can re- der about its reliability and serviceabil- 1.0 ceive both black- and -white trans- ity. It should be made quite clear, there- mission and CBS color trans- fore, that with the exception of the VIDEO associated 2215 CARRIER mission is an important advance in the scanning mechanism and its 2575 television field. The console unit shown 3 -tube disc control circuit, the funda- in Fig. 1 contains -within an exterior mental circuitry in every section of this no larger than most current black -and- receiver is already well known to the .032 - - - white television models-what the view- television industry. Unlike rival color ing public looks at as a somewhat magi- television systems, the CBS color -mono- 21.25 (SOUND CARRIER) cal device which reproduces either color chrome receiver uses circuits which Fig. 2-Video detector output response. or monochrome pictures with the flick have been production- and field-tested Sound carrier is maintained at a level of one simple switch. for many years. Special consideration approximately 30 db below video carrier. The dealer and service technician may has been given in the design of the various sections to bring out the full CBS color system; 1.0 3.6 *CBS- Columbia, Inc., Advanced Development potentialities of the Laboratory however, these special considerations represent only refinements of currently z "known art." <0.5 4.0 128H7 It might be suspected that the quality SYNC VERT PULSE TO CONTROL picture produced SEP CIRCUIT of the monochrome n VERT VERT BO by this dual -type receiver would be INTEG VERT OUT - YOKE TRANS MH CKT , .005 PUT TRANS 50 neglected in concentrating upon repro- FREQUENCY 4.5 ducing a good color picture. As will be .005 6 later in this article, design re- Fig. 3- Response of the combined out- shown puts of video detector and amplifier. quirements for a good color picture are Half -power points are near 4 me on the more stringent than for a good mono- highs and 30 cycles at the lower end. chrome picture. Since the same basic 005 K2 2_ circuits are used for both color and I ) 500 00 monochrome, however, the natural con- PULSE INFORMATION NOT SHOWN IN DETAIL. TO 1.8 MEG VERT sequence is not only good color, but also RED CENT INFORMATION VERT HOLD C-M very good black- and -white reproduction...... i BLUE The design and operation of the com- M INFORMATION 1.5 MEG plete color- monochrome receiver will be 1 GREEN 3K under the following headings: ^^'1 INFORMATION discussed H ` H 1. Tuner and i.f. amplifier. K 3.95 1K 'VERT 1 2.2 MEG MEG amplifier, d.c. restorer, and - V LIN 2. Video IV I TO BOOSTED HV intercarrier sound system. H----144S--I `BLACK LEVEL ON SWITCHES -C = COLOR 3. Synchronization, sweep, and high - 1,1= MONOCHROME voltage circuits. Fig. 4 -Signa at video amplifier grid. vertical sweep circuit, in- 4. Disc -control circuit. The amplification of each color must be Fig. 5 -The motor assembly. equal regardless of frequency or level. cluding color- monochrome switching. 5. Scanning disc and RADIO -ELECTRONICS for

www.americanradiohistory.com Television 25

Receives black-and-white at 525 lines or full color at 405 lines. ut the flick of a switch. and is completely self -contained. Its design features are described in the article belote.

Items 1 and 2 are the same in both the video -detector output is shown in Fig. 2. shown in Fig. 4, arriving at the input color and monochrome positions; switch- Two staggered pairs,' with CCB6 ampli- grid of the final video -amplifier tube. ing of circuit elements between color fier tubes, are used because of simplicity The scene depicted is a solid color con- and monochrome operation is necessary and cost considerations. Almost any i.f. sisting mainly of red, with some blue only in 3; 4, and 5 operate only during amplifier interstage coupling arrange- and less green components. If the tube color reception. ment may be used as long as the re- characteristics are not linear, the rela- sponse obtained is as shown. Overload- Tuner and i.f. amplifier tive amplification of the three fields may ing and departures from linearity must be considerably different, resulting in Since the r.f. tuner or "front end" be avoided. poor color reproduction. Furthermore, is not called upon to perform any un- this color distortion will be a function usual function in the color -monochrome Video amplifier of over -all signal level. To avoid this receiver, almost any well- designed tuner A combined video amplifier and video difficulty, an output swing of approxi- is suitable. The usual conside-:at:ons of detector response flat out to 3.6 me is mately 100 volts with a maximum of noise factor, gain, oscillator radiation, used to retain picture information. The 10% departure from linearity has been spurious responses, etc., are applicable. response is shown in Fig. 3. A good designed into the receiver. In the CBS color system, both the low- frequency response, down to 30 vertical and horizontal scanning fre- cycles, is also desirable. D.c. restorer quencies are increased over current Although high-frequency peaking of- The theoretically desirable type of standard monochrome scanning frequen- ten is employed in monochrome televis- d.c. restorer, from the point of view of cies. To retain as much picture informa- ion receivers to "crispen up" the picture, color fidelity, is highly efficient and has tion as possible in the color position, a its desirability is questionable in color a speed of response of the order of a minimum over -all r.f. and i.f. 6 -db reception. To obtain the proper color few lines. The instantaneous position bandwidth of 3.6 me is employed. A balance, as transmitted, the detailed of the video amplitude on the kinescope high -Q accompanying sound trap is ca- color information in the red, blue, and amplification characteristic will, of pacitively- coupled to the first i.f. ampli- green fields should be amplified equally course, determine the degree of faithful- fier tube grid, so that at the output of the regardless of frequency. ness of reproduction of the color. Since video detector, the sound carrier is at- The output linearity of the video am- this position is determined, in great tenuated 30 db relative to the pass -band. plifier is particularly important. Con- part, by the value of d.c. component The over -all relative response at the sider the highly simplified signal, present at that instant, one can ap-

TO VERT. AMPL. C =COLOR (2) 1X2' 128H7 100K M= MONOCHROME PLATER 500uuf/20 KV 8 TO 6AG7 ALL SECTIONS OF C -M SWITCH GANGED. 006 GRID i -(4) 470K 0051 12BH7 HORIZ DRIVE 6B(26 -GT 1W T

1 220 K 1 1 MEG MEG 3 270 K ^ 70-350uut 0 KV 15 270uufti _ A TONE GENERATOR .005 ; 6Et K MEG AFC 4701( DET 7 (PAPER) 390 D 6AG7 PP( 470 SCRÉEN C ~ BOOST 33 200 250 K ANTI - HUNT 390 3 B+ mot llld MEG 035 uuf fy Ì-+ II tf212BH7 IT _ CONTROL _ Co M 47 6AX4 3.9 2.7 47 100K Fig. Source of the control voltage. .os; 9- K K 1(

C DIRECTION OF ROTATION 820 HORIZ N CENT 50 HORIZ4 3900 W r C -M HORIZ YOKE At OSC T T put HOR I Z 6 8 33K COIL 8.3 MN 25 -300 HOLD 401 put ' B+ 120K 18K .002 "-100 K 8+ +150 COMP SAW TOOTH H 4111ShIABAMina TO AFC DET Fig. 6 -The receiver's horizontal sweep circuits, with switching- for color and monochrome. Note that component values change in the same ratio as sweep rates. 5. . 16 .n20* 1-SYNC INFORMATION 6AG7 SAT. RED 4 PHASE MAGNETIC MOTOR REACT. AND DETECTOR AMPLIFIER DC91 AC MOTOR WHEEL CLEAR LUCITE NO FILTERS OR BALANCE r FEDBACK WHEEL SPEED INFORMATION WEIGHTS Fig. 7 -Disc control circuit diagram. Phase detector and magnetic amplifier DISC CLEARb schematics appear in Figs. 8 and 9, and the motor photograph in Fig. 13. I17V 22W AC 22 44" Fig. 8 -The magnetic control amplifier. Fig. 10 -The two- section color disc.

NOVEMBER, 1951

www.americanradiohistory.com 26 Television

light reduction, it is necessary to raise the high voltage and average beam current. The energy storage in the 53° de- BALANCING flection yoke for the lORP4 picture tube WEIGHT is insufficient to produce over 10 kv with a single rectifier without excessive retrace time or excessive 6BG6 cathode current. Therefore, a voltage doubler is used to meet the 14 kv, 250 µa requirements. The high voltage could have GROOVES been obtained with a single rectifier only at the cost of excessive retrace time, or with a high- current horizontal deflection amplifier. Obviously, the design of the horizontal output transformer would be a function of the sweep frequency. Neverthe- PINS less, the same transformer, in conjunction with a single yoke, is called upon to operate satisfactorily in both color and monochrome performance. This is accomplished by a simple autotrans- former design with an extra tap for REAR DISC-FRONT VIEW FRONT DISC - REAR VIEW switching the horizontal yoke. Since the losses go up as frequency squared, a ferrite yoke must be used. Ferrite yokes give increased width and high voltage at 15,750 cycles, and at Fig. 11 -Some details of the discs and hubs, showing the pins and grooves which reproduce color while in motion but permit black- and -white reception when still. preciate the reasons for the d.c. restorer noteworthy improvement, the double requirements stated above. time constant input, is incorporated in To meet these requirements at the the sync circuit of this receiver. This present time would involve complex and addition to the conventional sync circuit costly circuitry (the simple direct - improves the noise immunity of the sync coupling arrangements employed in cur- by providing a fast discharge path for rent monochrome receivers do not meet the undesirable noise energy stored up these requirements), and so a simple in the grid -coupling capacitor, thus pre- diode d.c. restorer circuit has been used, venting the effects of impulse noise pending further developments. bursts from "hanging on." The problems of converting to color Fig. 12 -The black- and -white window. Intercarrier sound system sweep frequencies have been brought to The intercarrier sound system, al- the attention of the public and the in- 29,160 cycles the advantages gained by though not critical, requires more care dustry' and still remain a point of in- using a ferrite yoke are even more sig- in its design. In the color position, 144 - terest. To produce the color sweep fre- nificant. cycle sync buzz is more readily ampli- quencies of 144 and 29,160 cycles per fied by the audio system and more ac- second, the time constants of the ver- Disc control circuit curately reproduced by the loudspeaker tical blocking oscillator and the hori- In the CBS field -sequential system than is 60 -cycle sync buzz in mono- zontal multivibrator must be switched. the color information is transmitted in chrome reception. Application of well - The ratios by which the time constants the order red -blue -green. To reproduce known principles, however, is sufficient must be decreased are: the color information on the viewer's to eliminate any audible buzz. screen, the color disc must be in exact 144 Most important of these are : Vertical = 2.4 synchronism with the transmitter. Fur- 1. The sound carrier should be at- thermore, the red field and the red tenuated at least 26 db relative to the filter on the disc must coincide. The pass -band at the video detector. 29,160 circuit which keeps the disc in step Horizontal : 1.85 2. The video detector should operate 15,750 with the transmitter is dubbed the "disc - with as high a signal level as possible control circuit." without overloading the last i.f. ampli- If the reader checks the circuits shown For the purpose of analysis, the cir- fier stage. in Figs. 5 and 6, he will see that the cuit will be divided into several simple 3. Operation of the video amplifier values which are switched are approxi- circuits whose individual functions are with the composite video signal sync mately in the ratios of these numbers. more readily apparent. A block diagram tips close to the cutoff region must be It is interesting to note that the higher is shown in Fig. 7. avoided. vertical sweep frequency requires a re- The magnetic amplifier consists of a 4. Picture i.f. amplifier overloading trace time of about 40% of that for high -gain pentode whose plate current must be prevented. monochrome, hence the large peaking flows through the d.c. winding of a 5. Adequate amplitude modulation re- resistor. saturable reactor. The a.c. winding of jection must be provided by the ratio No changes are required in the verti- this reactor is in series with the motor detector or by whatever other FM de- cal amplifier stage. Since the vertical which drives the disc. See Fig. 8. Op- tector and limiting device is used. output transformer is designed for 60- eration is as follows: cycle sweep, it will operate at least as If the control bias becomes less nega- Sync, sweep, and high -voltage well at 144 cycles. The vertical winding tive, the plate current increases. The The synchronizing circuits require no of the yoke will likewise perform well. increased plate current in the d.c. wind- basic changes to accommodate the verti- The horizontal output and high -volt- ing drives the reactor into saturation cal sweep at 144 cycles and the horizon- age circuits merit some special attention and hence decreases the a.c. voltage tal sweep at 29,160 cycles. However, a in connection with color. Because of the drop across the reactor a.c. winding, RADIO -ELECTRONICS for

www.americanradiohistory.com Television I27

horseshoe thus making a larger share or the line arms, and the ends of the generated wave - voltage available for the motor. There- magnet determine the The voltage is then ap- a reduction in negative bias at the shape. sawtooth fore, disc control circuit for com- control tube grid speeds up the motor, plied to the in the negative bias parison with the vertical sweep pulses and an increase in the section on slows down the motor. However, we are as explained previously of disc cóntrol. not interested in varying the speed is thrown we are interested in keeping When the selector switch the disc; monochrome position, a mechanical its speed constant at 1,440 r.p.m. This to control bias must be brake (Fig. 13) is applied. This slows implies that the motion of the discs. by a circuit which will insure down the forward furnished time, the current through that at every instant the proper control At the same speed one of the motor windings is reversed. bias is present to keep the motor with re- regardless of line As the driven disc slows down absolutely constant free disc, its relative po- of any line frequency fluctua- spect to the voltage or sition with respect to the free disc is tions. by 120 °, where the is just such a cir- allowed to change The phase detector free disc is again held in position by cuit. Two signals are furnished to the vertical the indexing pins which ride in the phase detector, one from the disc hub (Fig. 11). which is in sync grooves of the free output of the receiver In this position there is 120° of clear with the transmitter, and the other. one When the reverse cur- generator. After the area (Fig. 12). from the disc tone rent in one of the motor windings re- two signals are compared by the phase detector, a d.c. output whose magnitude is a function of the relative phase re- Fig. 13 motor and motor control. sults. A schematic diagram is given in -The Fig. 9. By obtaining the proper polarity from the phase dexed (as explained later) so that the the sawtooth tone generator, in detector can be made to produce a d.c. clear area of each disc is stationary bias which whl keep the front of the raster (Fig. 12). correction discs may color disc exactly in step with the ver- The filters used in these Thus the color be the red, green, and blue Monsanto tical amplifier pulse. Eastman disc is held in dynamic synchronism by "E" filters or the following electronic control Kodak television filters: a straightforward Red circuit. Blue -# 451, Green -# 610, - # 260 are Scanning disc and motor To avoid flicker, the two discs paired so that the comparative filters One of the advantages of the field- for similar color segment areas do not sequential system for color transmission vary more than ±1 %o for green, ±2.5% of and reception is that the frequency for red, and ±3.5 %n for blue in their color switching is low enough to render color transmission. The discs are static- it practical to use either electronic, elec- ally balanced to within 0.1 inch -ounce. tromechanical, or comparatively simple The rotating disc and motor are gen- mechanical devices. The simplest tech- erally not discernible by the viewing nique thus far used is that of the ro- audience. It has been the experience of tating color disc. The disc is used in the writers, while demonstrating the the present production receiver. (Other receiver to various groups, that invari- methods have been used or are now in ably the question is raised, "Is there a Fig. 14 -Rear view, complete receiver. the laboratory stage). The color drum disc in the cabinet ?" The audience (in- is a mechanical means for obtaining a cluding engineers and service techni- larger color picture. The tricolor tube cians) coule neither see nor hear the verses the direction of rotation of the is being investigated as a possibility for disc about which they had been hearing disc, a stop latch on the hub of the free an electronic field -sequential system. and reading. disc moves up against a stop on the Other mechanical means for converting With the proper motor and shock mounting assembly and both discs are present 17- and 20 -inch black- and -white mounting (Figs. 13 and 14), the opera- stopped in the correct position (clear sets to receive color are under investigation is essentially noiseless. The motor sections in front of raster). When the tion. used in this receiver is a split -phase discs are in the correct position, a micro - To date, the most faithful color re- capacitor type which has a torque of 21 switch behind the stop latch turns the producticn has been obtained with the inch -ounces. Its speed is 1,748 r.p.m. motor current off. This changeover from disc. The discs used in the current re- and it is geared down with belt and color to monochrome takes less than 8 ceiver are shown in Figs. 10, 11, and 12. sprockets (Fig. 13) to 1,440 r.p.m. The seconds. The shape of the color segments is de- operating voltage of the motor is ap- A magnifying lens enlarges the 10- termined by: proximately 85. inch tube image to the equivalent of a 1. The requirement that the color seg- The disc shaft is rigidly connected 121/2 -inch tube. ment follow the scanning lines vertical- to the front disc. When this disc rotates Acknowledgment is gratefully given ly down the raster. it pulls the other, or free, disc along to the CBS Engineering Staff, and par- 2. The position of the center of the with the indexing pins (Fig. 11) which ticularly to Dr. Peter Goldmark, John disc relative to the raster. are engaged in the grooves of the "free" Christianson, and Al Goldberg who The color- monochrome receiver uses disc hub. It takes the discs approxi- worked closely with the authors in the two discs. Each of the discs have three mately 20 seconds to reach the operat- development of this receiver. color segments and a 50% clear section. ing speed from the off position. When the selector switch is in color po- Mounted on the rear of the disc shaft REFERENCES sition, the color segments of the rotat- (Fig. 13) is a tone -generator disc. As 1 "Vacuum Tube Amplifiers," Valley and Wall- ing discs are 180° opposite each other, each pair of arms of this disc passes man; Chapter 4. and the effect is that of a conventional under the ends of the horseshoe magnet, 2 "Field Sequential Color Companion," Cohen and 6- segment disc. When the switch is in a sawtooth voltage is generated in the Easton; Electronics. May 1951. monochrome position, the discs are in- coils. The spacing, the shape of the -end-- NOVEMBER, 1951

www.americanradiohistory.com Television 28 ` Remote Controls For TV Promote viewer Comfort

elecsromechanical and electronic systems are used

By ROBERT F. SCOTT

BUILT -IN and large- screen television installations are usually placed where the screen can be seen clearly by a maximum number of viewers, who may be seated 10 or 15 feet away. If the host sits among his guests, he blocks their view each time he gets up to adjust the volume, tuning, or contrast. If he sits beside the set where he won't block the view of others, he will probably go to bed with a neck cramp from trying to see the screen and with a headache from watching it from too near. One TV owner even sits beside the set and watches the screen in a mirror on the opposite wall. Some TV set manufacturers have produced remote viewers and remote -control systems which permit control of the set from a convenient viewing spot. Some of the following systems are elec- 'O 'JE4E COW TIROL tronic, others are electromechanical. ;lOLuME CL)TìN t4VTROL Zenith "Lazy Bones" The Zenith remote-control system, Pheta A- Remote coat -ol ur.iL on ?hilco dual- chassis receiver. called "Lazy Bones," is optional on the 1951 series H chassis. It consists of a ARMATURE motor -driven tuning mechanism bolted AN?' SOLEFIOI to the rear of the tuner and controlled by two push switches on the end of a 17 -foot 3- conductor cable. A schematic of this system is shown in Fig. 1 and a d- awing of two views of the mechanical arrangement is shown in Fig. 2. The essential parts of the system are a low- voltage a.c. motor, step -down transformer, a high -ratio reduction gear, an electromagnetic clutch, and a small control box on the end of the 17 -foot cable. The drawings in Fig. 2 show the drive mechanism in the un- en_ergized position. Gear G1 has a D- shaped hole which fits the shaft extension on the rear of the tuner turret. The worm gear G2, mounted in bearings on the armature of the electromagnet EM, is coupled to the motor shaft through a flexible coupling made of rubber tubing or similar material. Pressure on S1 or S2 applies power to the motor and the electromagnet s . cu-o== MJTIV6 SS' TC which is in series with it. When the motor starts, the magnet attracts the armature holding G2 and pulls in until Plato B- Close -up of drive snit of Philec's remote control. G1 and G2 are meshed. Because of the gear ratio, G1 turns slowly. This slow RADIO -ELECTRONICS for

www.americanradiohistory.com Television I29 motion and a heavy detent causes the the speaker voice coil and the cycling on the back of the tarret tuner. stations to click in one after the other switch S2. Photo C shows the exploded as long as S1 or S2 is closed. All the view of the cycling switch and detent Operation operator need do to chang3 channels is assembly and Photo D is the detent and When the STATION SELECTOR Switch iS press either switch until the detent roller assembly which fits over a shaft pressed, the motor and corresponding drops into the right channel. S1 causes the turret to turn clockwise and S2 r ARMATURE G 2 BEARING BEARINGEARINGHAFT turns it counterclockwise. No provisions any controls MOTOR !HINGE are made for operating 27V A.0 FLEXIBLE other than the channel selector. COUPLING MOT Philco control RC -1 control turns GI The Philco remote EM on or off, selects any channel, TRANS the set REAR VIEW and adjusts volume, contrast, and fine - SIDE VIEW tuning controls from any distance up Fig. 1, left-Diagram of Zenith's Lazy Bones remote control. Fig. 2, above - to 30 feet from the receiver. The control When motor starts, electromagnet EM cable fits on a spring roller reel -up pulls armature down bringing gear G2 drum. Proper length is pulled out. into mesh with drive gear G1 which is Shown schematically in Fig. 3, it con- mounted on a shaft projecting from the sists of four self- centering d.p.d.t. rear of the turret -type tuner. A heavy switches on the end of a 30 -foot 8 -con- SOCKET PLUG detent action provides positive tuning. ductor cable, a 24 -volt reversible a.c. motor and step -down transformer, and a clutch -gear assembly which turns the shafts of the volume, contrast, station - Fig. 3- Schematic of the Philco remote control. 24 V MOTOR selector, and fine -tuning controls. Photo All controls can be adjusted from 30 feet away. A shows the front of one of the recent Philco models with the gear assembly and motor in place. Photo B is a close - SLIP RING up of the gear mechanism. ASSEMBLY The major portion of the remote - control mechanism -the clutch -gear- IWo CYCLING solenoid assembly-is mounted on the LP1UG SOCKET SWITCH I ° RED r--3 II The volume control I o r.f. -i.f. chassis. -on 1.1 !_s YFFLLOW I the power and deflection chassis -is STATION .I1 ORANGE I 1 0

to its mechanism through I 1 coupled drive I WHITE 1. 1 041 a pulley and drive cords (see Photo A). o BROWN OUTPUT All controls on the set have concentric 11-11°21- TRANS BLACK I.° 41o61 shafts. Only those controls on the outer Si shafts are operated by the remote -con- r-: GREEN ,JL_JLo110 - L o BLUE SPARE LEAD trol system. One gear in the train is VOLUME driven by a belt from the motor. This ON-OFF O 1 belt- driven gear is coupled to the others o through small transfer gears. See Photo ISO A. 1 ° I ° -o There are four solenoid -clutch- driver FINE assemblies. The clutch -gear assembly is TUNING ° CUTOFF SW. _ S a one -piece unit which revolves con- = MUTING SW. ° CONTRAST tinuously as long as the motor is turn- VOLUME ing. When the solenoid is excited, the SOLENOID SOLENOID clutch moves back approximately % 24 V 17 V. A. C inch so one of its cogs engages the TUNING STATION toggle on the driver and the shaft starts i. SOLENOID SOLENOID to turn. A spring returns the armature CONTROL BOX J and clutch to their resting position when `SWITCHES NORMAL CENTER POSITION, SPRING RETURN the solenoid circuit is opened. A safety device on all controls except the channel selector is a spring toggle 6CB6 6C86 VIDEO AMP which maintains sufficient pressure to VIDEO AMP turn the control throughout its range .I and slips with a audible clicking when .1 the control reaches the end of its range. IN60 OR IN64 I N60 OR IN64 The channel selector can be rotated con- VI DEO DET. VIDEO GET. I MEG tinuously so it does not have such a 22K MEG IME slip -type clutch. 56 56 K I MEG Referring to Fig. 3, we see that K I. MEG throwing any switch on the control box CONTRAST CONTROL starts the motor and excites the solenoid 1.5K which transfers the motion -130V. rotary to 330 -130V. ACC 330 the shaft corresponding to the switch. AG.0 C9 .I The switches have a dead center posi- I MEG CONTRAST b tion with a spring return. The rotation CONTROL can be reversed by sliding the switch 1005 a in TO TUNER a IST 8 2ND the opposite direction. TO TUNER B I ST B 2ND I.F. AMPLIFIERS The channel -selector mechanism is I.F. AMPLIFIERS coupled directly to a normally open cutoff and muting switch S1 placed across Fig. 4 -a -Tele -Tone contrast control; 4 -b -as modified for remote control. NOVEMBER, 1951

www.americanradiohistory.com 301 Television

solenoid are energized and the turret close the cycling switch S2. This switch parallel the STATION SELECTOR in the shaft starts to rotate. The detent rollers is in series with the cutoff section of S1 control box. Therefore, during the time (see Photos C and D) are subjected to which was closed earlier by the clutch that the detent roller is riding up on the sideways and upward thrusts by the gear as it moved backward to conduct star wheel, the centering lever holds S2 star wheel on the detent -plate assembly. the driver. closed. The centering lever moves sideways to These two series- connected switches The cycling switch S2 closes, even on one sharp pulse from the station selector Fig. 5- Diagram of the 151V2W switch. Thus the station selector switch synchronizing and a.g.c. does not have to be held down once the circuits and contrast 280V AGG tuner to rotate. PPf starts S2 has two posi- and black -level controls -ìl TO R.F. AMPL. tions; as shown, because the motor ro- employed in the Pre- tates in one of two directions, cision (Hertner) L -10 47 MEG 270K and proper phasing must be maintained. The de- projection -type televi- 65N7-GT (3) SYNC. CLAMP 5 a tent cam throws S2 in one of the two sion receiver. SYNC. A T' + 25V AMPLIFIER positions, depending on the initial di- 2 3.9 SYNC CLIP rection of rotation. R o LINE f UGC DRIVER LIMI "E The tuner continues to revolve until the detent roller (see Photo D) dips down to the next depression in the star wheel. The centering lever returns to its normal position and opens S2 so all voltage is removed from the motor and solenoid. The armature returns to its SYNC OUTPUT TO SWEEP CHASSIS resting position and opens Si which

12 K removes the short from across the TO 1ST &3RD PIX I.F speaker voice coil. ?-4.+135V During manual operation, S2 is closed by rotation of the tuner shaft but the 47K 22 K 001 47K motor and solenoid are not excited be- 1---MNb cause Sl -in series with the hot lead 6 NC from the transformer-is open. AGG PEAKDET SYNC UGC AG.C. AMP a SYNC.SEP. SEPARATOR AM Tele 2 2 -tone control 47K 26AL5 Tele -Tone .X+.05 SYNC B A.GC. DET. type TAP chassis are used 5 I MEG 4 in some remote installations. The 1'1'1 ."*. tuner is removed from the set and installed in 00K .01 .25 a small control box. The converter and 01 F- first i.f. transformers have low- imped- -400V V TO CATHODE OF ance secondaries and 93 ?H VIDEO DETECTOR primaries, respectively, which are link -coupled with 72- 20 K RFC 18K IK 10 ohm coax. The volume -control circuit is brought to the control box through .0015 stûndard 2- conductor shielded cable. When the TAP chassis is used in a 50K -50V. 50 K straight console or table model, the con- CONTRAST 10K BLACK-LEVEL trast control is a 1,500 -ohm potenti- CONTROL CONTROL ometer in the cathode TO SUPPRESSOR TO return of the OF 6AU6 VIDEO RESTOTORER C 6CB6 video -amplifier stage shown in Fig. 4 -a. Since the control is in a signal circuit, it is not practical to extend to 4.5MC TRAP 150 PH the control box for remote -control in- ó5ö' -7 a DON- stallations. Therefore, the control is re- 8.2 K moved from the circuit and the cathode 47j4 f of the video amplifier is returned di- 1509 05 rectly to ground. The modified PH circuit 100K is Fig. 4 -b. The video amplifier operates at full gain as it does with the original 6AU6 s 6V6 - GT 5 contrast control at minimum resistance. VI 3KAow 6AL5 DEO-IN IST VIDEO 2ND VIDEO N.I. I MEG The a.g.c. lead is disconnected from .05 2 AMP AMP D.C. 39K RESTORER the junction of R14 and C9 and con- 6 nected to the arm of a 1- megohm poten- 7 tiometer shunted across C9. Placing the IMEG 3.9K contrast control in a d.c. circuit makes

560 100 5 it possible to extend its leads to the W 45pv control box without disturbing the op- .01 05* eration of the circuit. The Hertner system An electronic remote -control system is used in the Precision (Hertner) L -10, N I. NONINDUCTIVE a projection model which has the tuner, i i.f. strips, sync circuits, and audio am- 2 3 1 2 4 3 plifier on I the remote -control or receiver 63V 6 3V GA N +250 B GNO. 6.3V 63V ONO 250 VÍDEO chassis. The 30 -kv r.f. power supply, sweep circuits, video FROM REC. TO GRT. and amplifier are all on separate chassis. The tuner and Fig. 6 -Video circuit of the L -10. Lead B from the d.c. restorer plate goes to audio amplifier are on subchassis which the brightness control. The contrast control varies suppressor bias on the 6AU6. can be taken off the receiver chassis RADIO -ELECTRONICS for

www.americanradiohistory.com Television 31 and mounted in other remote locations. The tuner, a Standard Coil Products CYCLING DETENT SWITCH, unit, has a converter transformer de- PLATE DETENT DETENT ASSEMBLY S2 signed to connect to the first i.f. trans- SPRING ROLLERS former through a low- impedance link. The connecting cable (standard 90 -ohm coax) may be 50 feet long without affecting the performance of the tuner. This system of chassis and subchassis makes possible a large number of physical arrangements which can be adapted to almost any custom installation. The composite circuit is very much TUNER like that of a 630 which has been modi- SPACER STAR fied to make it possible to separate the BUSHING WHEEL WASHER CENTERING various chassis. LEVER The contrast, black -level, horizontal ASSEMBLY and vertical hold, volume, and tone con- main chassis. All except Photo C- Exploded view of the cycling switch and detent assembly used in the trols are on the for 1951 models. the last two are in d.c. circuits which Philco RC -1 remote control which is optional equipment it to extend control leads make possible and coaxial cable. Although 600 ohms tube chassis through 8- conductor shielded to any remote point without taking to be unusually high for a cable. No. 16 wire is used for the fila- to avoid signal may seem elaborate precautions long video line, hum and spurious sig- ment lead to prevent excessive voltage distortion. The sync and a.g.c. circuits up do not ap- drop. The loudspeaker is normally controls nals which may be picked and contrast and black-level pear in the picture because the video mounted on the control chassis but it are shown in Fig. 5. level is very high at this point. The only can be moved to any convenient point The video amplifier shown in Fig. 6 precaution is to make sure that the un- by extending the voice -coil leads. prevents the high input capacitance of video line is at least IA inch Many of the circuit innovations shown a in the shielded the 5TP4 from causing loss any of the others. The video out- here can be successfully incorporated the video from high- frequency components of put circuit of the LD -120 is shown in into sets of other makes and models. Contrast is by vary- signal. controlled Fig. 7. High voltage (14,000 volts) for Before trying to use any of these cir- on the 6AU6, ing the suppressor voltage the picture tube (a 19 -inch round or 20- cuits, carefully study the complete and the black -level is controlled by ad- inch rectangular) is fed to the anode schematic of the receiver using the cir- on of the justing the bias the plate through RG /59 -U cable. The hot side cuit you want to use in your set. Pay 6AL5 d.c. restorer. of the horizontal deflection circuit is fed particular attention to d.c. operating polarity of video and Cascade remote system to the yoke through a separate lead in- voltages and to sulated for 6,000 volts or more. All synchronizing signals. The circuit of Cascade's LD -120 re- other voltages are fed to the picture- -end- mote system is surisingly simple. In this system, all voltages and signals are developed on the control chassis-a modified 630 -and "piped" into the picture - 6V6 470K 470 K 6Y6 -G tube chassis over special cables and 2NÁMPLEO lines which may run up to 65 feet. The second video amplifier (usually a 6K6 -GT in the 630) is replaced by a 6ÁOU6 6V6 followed by a 6Y6 cathode -follower IOW which works into a video line having 820K an impedance of approximately 600 8 +240V 3K X .5 ohms. This video lead is made by strip- 5W ping the outer conductor from a stand- 470 r1,.f 100K HORIZONTAL OUT. PIN 4 OF 50K BRIGHTNESS FLYBACK TRANS I MEG CONTROL

B+135V 47K 150K FEMALE -60V 125 BLACK a WHITE PLUG CONTRAST MALE CONTROL 1 3 SOCKET í) SWITCH HANDLE ORANGE BUSHING t FOR S2 ) 1 WHITE BLACK 12 GREEN

CENTERING +135 FOCUS 2 VIDEO LEAD LEVER COIL (SEE TEXT) 1330

425 1 DETENT ROLLERSC-f -f VERT

C.R.T. FIL. 6.3V GND. 56 PIN HEIGHT HORIZ CONTROL 14 KV. ALDEN 560 PIN 2 -HOR CENT. VERT CAL CENTERING 810 1 M CONTROL CONTROL PIN 2 FEMA 8101E C.R.T. GREEN VERTICAL ACROSS R183 MALE 19"OR 20" OUTPUT TRANS AT FOCUS CONTROL 1 83 FIL.H.V. L RG -59/U Photo D- Detent rollers and centering lever fitted on back of Philco tuner. Fig. 7 -Video output circuit of the Cascade LD -120. Remote may be 65 feet away. NOVEMBER, 1951

www.americanradiohistory.com :t1 Television Television Service Clinic Conducted by MATTHEW MANDL

AN of receivers However, the oscillator for channel high -pitched squeal. Evidently the 15,- make use of a sound i.f. of 6 produces harmonics as well as the 750 sweep is now very audible and I 21.25 megacycles and a pic- fundamental 109 mc. The second har- would appreciate suggestions for its ture i.f. of 25.75 megacycles. monic is 218 mc, which is so close to the reduction. F. S., South Attleboro, Mass. These sets normally give good service channel 10 oscillator frequency (219 Your new horizontal output in most transfor- signal areas, but use of these mc) that channel 10 will ride into the mer is the offender. Some transformers i.f.'s sometimes can cause considerable i.f. system and cause interference on produce more singing than others. If trouble. channel 6. the transformer windings are vibrating, A reader in Tucson, Arizona, reports Other such interference problems little can be done except boiling the fringe -area reception of channel 5 re- have arisen and manufacturers have core in a sealing compound. A reduction sulted in finely- spaced horizontal lines subsequently used 25.5 mc for the pic- in the drive- control setting sometimes which look like thickened horizontal ture i.f. and 21 mc for the sound i.f. is helpful; excessive drive aggravates trace lines. Fine tuning adjustment in their later receivers. Many tech- singing. Reduce drive as much as pos- caused such lines to rotate from their nicians have realigned such receivers sible, but check horizontal horizontal linearity to position to vertical. They dis- slightly to rid them of this type inter- prevent picture distortion. Also check appear when the station signal strength ference. When this is done the tuner to see that width is proper. increases. A booster or 4.5 -mc trap ad- must be tracked to produce the new i.f. justment did not help. frequencies and the i.f. stages must be Reduced picture size In these receivers the source of aligned for proper acceptance of the On a G -E model 806 the picture does trouble is the third harmonic of the new resultant. This was done by our not fill the screen. There is about % inch video i.f. falling on channel 5 picture Tucson reader. It resulted in complete border all around the picture and carrier frequency: I absence of the interfering lines. have been unable to fill the mask. G. L., Channel 5 picture carrier 77.25 New Brunswick, N. J. Receiver picture i.f. Adjacent channel interference If both height and width controls are 25.75 X 3 77.25 What unable to bring the picture to full size, With the slightest can be done to reduce adjacent deviation of oscillator channel interference in this area? one of several things may be wrong, as frequency (such as 25.72 i.f. resultant) Local stations are strong and spill over listed : heterodyning action can take place when be- the more distant ones are tuned in. 1. Defective low- voltage supply. Re- tween channel 5 picture carrier and the A. D., Wèst Orange, N. J. place the low-voltage rectifier and third harmonic of the i.f. which is pres- check filter capacitors to see ent When local stations are extremely that because of low -Q circuits and non- high in signal strength, leakage resistance is not draining too linear mixing systems. The not much can resultant be done to reduce adjacent channel in- much current. frequencies, if slightly below the 15,750 2. Excessive high voltage. This could sweep, terference. Adjacent channel traps can will produce the effect shown in be installed be caused by a gassy horizontal out- the photo. in receivers which do not have them, or additional ones can be put tube or high -voltage rectifier. Re- put into receivers which have single place each to see if picture expands. ones. Poor i.f. alignment will cause ad- 3. Improper placement of yoke on jacent channel spill-over and so will a neck of tube. If yoke is too far back poorly tracked tuner. A good booster, from the flare of the picture tube, the with its added selectivity, will also help. beam cannot sweep fully. Also check antenna orientation and use Picture stretch multielement reflectors fog better screening from the rear. I have a receiver with excessive stretching of the picture at the left. Reversed picture The outer circle of the test pattern is After almost pointed. conversion of an RCA receiver I have tried to remedy this condition from a 10 -inch tube to a 14 -inch, the by replacing the damping tube and ad- picture appeared reversed in a hori- justing controls, zontal direction. without success. R. S., Would this be caused New York, N. Y. Horizontal lines are due to video i.f. by the newly installed yoke? C. H., Normally this condition is caused by Varying the fine tuning may change Cleveland, Ohio. an incorrectly adjusted "drive" control the difference frequency enough to pro- If you get a reversed picture along which, in conjunction with the horizon- duce a resultant above the 15,750 sweep. the horizontal plane it indicates that tal linearity and width controls, must The interfering lines will then be ver- you have the two leads to the horizon- be properly set for a perfectly rounded tical. If the incoming signal is strong, tal coils of the yoke reversed. circle. If adjustment of these controls the visible line structure will be less Interchange these leads. When the fails to reduce leads left -side stretch, the dis- noticeable. are reversed on the horizontal charge tube should be replaced and a The 25.75 -mc picture i.f. can also pro- coils, sweep starts from the right and check made of the associated circuit. An duce interference in localities with dif- goes to the left instead of vice versa. incorrect value voltage -boost capacitor ferent station allocations. For instance, If you had reversed the vertical -coil in the cathode circuit of the damper a fairly strong channel 10 carrier can leads your picture would have appeared tube may also cause this condition. ride in on channel 6. upside -down. To tune channel 6, the local oscilla- Defective picture tube tor in sets using an i.f. of 25.75 will Transformer sing I have a receiver using a 12LP4 tube. have to generate a frequency of 109 mc. After conversion of an Admiral to a When the set is turned on, sound is all Similarly, to tune channel 10 it would 14 -inch screen everything worked all right but the picture takes about 15 have to generate a frequency of 219 mc. right except for the presence of a very minutes to come up to proper bright- RADIO- ELECTRONICS for

www.americanradiohistory.com Television 33 ness. During this time the screen has no brilliancy, and as the picture appears Television dx Forecast for November it is badly out of focus and double -seasons of moderately cool will be getting good ex- and The between character images appear. Eventually focus November is reflected in the nature of tended -range reception on the lower normal levels. I have brilliancy reach TV dx conditions that may b, expected channels in fair calm weather. High - tried receiver-tube changes but this as in weather, band tropospheric DX occasionally ob- this receiver is during the month. Just didn't help. The trap in November provides samplings of both served in early fall will be rare after a single- magnet type -could this cause the latter part of October. Birmingham, summer and winter in its v.h.f. propa- such symptoms? H. P., gation conditions. Average signal strengths on all chan- Ala. Sporadic -E skip is not uncommon at nels will deteriorate somewhat, increas- All indications point to a defective the openings are usual- ing "fringe -area jitters" on the part of in receiver. The 12LP4 this season, but picture tube this ly of short duration and reception is TV service technicians. Viewers who tube requires a double- magnet type of in have had their first TV experience in has been likely to be highly erratic character. ion trap, and if this receiver be more pre- the favorable conditions of summer and time with a TV dx of this sort will in use for any appreciable valent in the lower latitudes. Viewers early fall will be needling their tech- single -magnet ion trap, damage to the nicians to fix up their snowy reception, has probably 500 to 1200 miles from either Mexico gun structure of the tube will be occa- and educational as well as technical ion trap City or Havana getting occurred. Try a double- magnet 4 methods will be required to pacify them. for brightest sional looks at the Channel trans- and carefully position it from these two cities. Sta- This may be a little trying to a bus This may make some difference missions raster. in the southern parts of this coun- man's patience, but it can be good for in performance, though if the damage tions try will be received at similar distances the booster and high -gain antenna busi- is extensive, the tube will have to be with the ness. will regain normal several times in November, replaced before you more northerly stations affected less The aurora borealis is likely to pro- operation. often. Little dx will be observed on TV vide a show or two for residents of that portion of the U.S.A. above Latitude 40 No picture or sound channels above 4. Tropospheric propagation will run (approximately Washington to Reno), In an Air -King model A -1000 both the gamut from very good to near the and we again request that propagation sound' and picture are missing, but the winter minimum, and these variations effects observed on the TV frequencies raster is present. Inasmuch as this is will follow the weather pattern closely. during auroral disturbances be reported no an intercarrier receiver I suspected Parts of the country where November's in detail for study. the tuner. I replaced all the tube. in the days are still warm and the nights only -end- tuner with new ones without result and finally changed the entire tuner but to no avail. Where else could the trouble lie? M. G., Cementon, Pa. WOR'S "Television Square" Opens Next Month receiver has the same cir- This model -TV's new accommodate about twelve performers cuit as the RCA 630 and the sound take- Television Square, WOR block- square studio, is scheduled to be each. Each studio has access to 5,000 - off is right between the mixer tube and square -foot storage area used for scen- the first i.f. stage. Absence of both pic- opened for occupancy about December 1, a month ahead of schedule. The two - ery and properties. ture and sound usually indicates tuner The second floor is equipped for you replaced the front story structure-New York's first to be trouble. Since studio filmed productions. There are editing, end, it is quite possible that you have erected solely as a TV -runs from Broadway to Columbus Avenue cutting, and projection rooms, master a bad tube or defective part in both the and a small studio for forum There is and occupies practically the entire block control, video and the sound section. and news telecasts. also a bare possibility that there was between 67th and 68th Streets. The building, which will contain ap- The roof of the building has clear some defect in the new tuner that you to WOR -TV's transmitting tower installed. proximately 50,000 square feet of floor range space, will enable WOR -TV to place in North Bergen, N. J., thus making it If the tubes check all right in both relay between stage nearly all their production facilities possible to use microwave these stages, localize the defective studios and transmitter. The entire in the sound i.f., detector, and audio under one roof. Incorporated in the studios are many new design features building is acoustically treated, air-con- amplifier by signal- tracing methods. against fire. the suggested by competitive engineers ditioned, and protected Repeat for the video section from An ingenious system is devised to tuner to the picture tube. from Du Mont, ABC, CBS, and NBC. The live -production facilities consist of discourage gate- crashing and trespass- and to prevent unauthorized per- Conversion to 20 -inch tube two 4,000- and one 6,000- square -foot ing Each sons from entering or leaving except receiver, studios on the first floor. is entire- I have a Radio Craftsman with its own control through the main entrance. An indi- 16AP.4A pic- ly self- contained model RC- 100 -A, using a room, sponsor's and announcer's booths, cator board is located at the recep- tube. Am I right in assuming that ture and a 400 -square -foot rehearsal room. tionist's desk. If any door, except the my present high- voltage system would main one-is opened, a light flashes and I The largest studio has a spectator's bal- be suitable for the 20CP4 conversion nearly 250 persons. The a buzzer sounds until the door has been the yoke the cony seating have in mind? Is changing studios are adjacent to four dressing closed and locked. item? O. M., only major conversion rooms for stars and two others which -end- Moosup, Conn. You would need more high voltage for the 20CP4 than your present supply furnishes to get best results. Besides Underwater TV Spots Submarine's Remains a new yoke, the horizontal output transformer also should be changed for a Underwater television was used by on the salvage ship Reclaim. proper impedance match. The focus coil the British Navy to locate and positively Underwater soundings taken over also will have to be replaced. The identify the wreck of the submarine many square miles of sea located many 16AP4 -A is a 53° deflection tube using Affray lost with '75 men aboard during wrecks which were investigated with a double-magnet ion trap and metal - a practice dive last April. the undersea TV equipment. After sev- cone lip, high -voltage connection. The equipment consisted of a porta- eral weeks of intensive investigation, The 20CP4 is a glass tube (70° de- ble TV camera equipped with remote the search was climaxed when viewers flection) and the high -voltage connec- controls and sealed in a watertight con- aboard the Reclaim were able to read tion is of the cavity type. A single -mag- tainer. The camera assembly was fitted the name Affray on the wreckage 250 net ion trap is needed. with powerful lights designed for un- feet below the English Channel surface. -end- derwater photography. It was installed -end- NOVEMBER. 1951

www.americanradiohistory.com Servicing-Test Instruments

GENERATOR UDiO SIIÌtI* tM.IBRMED OUTPUT

%Ili -R1.07 .107k MEO 2X RESISTORS RESISTORS 1/2 MATT UNLESS MOTS 10.7 SEE TEXT By 10.7 0.2 KEG 8/8008 RI 6K6 -GT 6AC7 OSCILLATOR RARER. CS LAWRENCE CATHODE FOLLOWER FLEMING 80 V IOOV 1 100p - C2 CM CI `" _- 100 V 0.E LL audio measurements SEE and test- TEXT ing require a calibrated signal C8 V7k -20/400V source. Very few audio IV oscilla- 10.7 oloN tors are equipped CO R7 to tell just IOOuV 47 IOW Iók 1126 2V how many volts or millivolts they 10.7 1113 . IV are 26k Ik R27 delivering to their terminals, and 33k OW with- R12 .IV I17V-3W V.7k A17 out 107k RE knowing this we are in no position - 2V ROOVM.CI W.7k 8"' 00 828 52 to measure, for instance, the gain of R25 .01V an 5Z4, 5Y3 .120 V 10 029 amplifier. YO .350`_`V If we R2R 001V want to feed the input of an .1 R30 V.T.V.R. experimental SEE 100k 2 amplifier, say 10 .C12 C13. TEXT IV millivolts RIO 2,500 33Y at cycles, we usually need T2O/VOOVM 2.2 RE0 a regu- - R23 R2I lar oscillator plus an auxiliary output 1.54 184 meter and a calibrated .280 o attenuator. Most CIO OUTW amateur, PA, and allied work doesn't jß.01 RIB require 1% IREO laboratory precision. This 0.3 V 1Xill. instrument does the job with 5 to 10% i O accuracy, is easy to build, uses stand- Oscillator is a Wien bridge with wide -range amplifier and calibrated attenuator. FLEXIBLE TUNING and parts throughout and is completely self- contained. COUPLING CAP. C I An output meter and attenuator are built into the same case with a conventional VI resistance -tuned METER audio oscillator. The output is isolated from the oscillator proper by a cathode- follower stage. V2 RANGE The frequency range is 2) cycles to SWITCH, SI 200 kc, covered in 4 ranges. The same dial calibration serves for all ranges. The output voltage is variable V from 3 WATT BULB 100 microvolts to 10 volts. The output impedance varies with the setting of V4 C II the attenuator switch, but is always lower than 900 ohms.

12, 13 C 3-0- General layout TRIMMER The instrument is built on a standard C2 10 x 12 x 3 -inch chassis, which fits into an 11 x 12 x 8 -inch utility box. As shown -POWER TRANS. in the photo, the main tuning capacitor, Cl, is mounted down the middle of the chassis. It is a 4 -gang, 365- µµf -per -section unit. The sections are paralleled STANDOFF in pairs, giving in effect a two -gang INSULATORS capacitor having 730 µµf per section. SHIELD 5Z4 The range selection switch S1 and its V5 associated resistors, as well as the 6J7 tube V are mounted to the left of the tuning capacitor. Layout of the generator. Variable capacitor must be insulated from chassis. The power supply occupies the back RADIO -ELECTRONICS for

www.americanradiohistory.com Servicinl1-Test Instruments

An instrument with calibrated out-

put variable from 100 microvolts to

10 volts and frequency range from

20 cycles to 200 kc in four bands.

the chassis (filter capacitor is mounted on External appear- left -hand corner of ance of the generator. choke L, is under the chassis), and the small ceramic standoffs remaining tubes and the output meter and the dial is con- an are mounted to the right of the tuning nected to it through the coupling. The frame -to- uator S_, R.ry, -R,,, mounted below capacitor. V, is nearest the panel, and insulating level down out- ground capacitance is across the lower chassis, knocks the output next to V,. The cathode -follower steps of 10. This atten- in line, and the section of C1. The purpose of the 100- in successive put stage V3 is next this uation at the output insures a good v.t.v.m. tube V for output metering, µµf air trimmer C2 is to balance and its normal setting signal /hum ratio at low output levels. the rearmost. capacitance, a simple voltage should be about 60% of maximum. The step attenuator is impedance looking back Circuit operation To prevent electrostatic hum pickup divider. The circuit of the 6J'7, shielding into the output terminals accordingly The oscillator is the Wien bridge in the grid attenuator setting, but components are is necessary. The metal cabinet is varies with the type and its principal this disadvantage is outweighed by the bridge itself, R1-R, and the two sufficient shielding from 60 -cycle electro- the C outside the gain in simplicity for nearly all practi- stage amplifier V V2. With resistors R, static fields orginating frequency 'range is chassis. In the chassis the only offender cal work. switched in, the The choice of the over -all resistance cycles; with R2, 200-2,000 is the rectifier tube V,. If a glass tube, 20-200 a tin of the divider is controlled by the fol- R3, 2,000-20,000 cycles; such as a 5Y3 -GT, is employed, cycles; with : If it is too high, This last baffle shield will be required between lowing considerations with R 20,000- 200,000 cycles. the output impedance on those taps range is easy to include and is useful the tube and C1. Use of the metal 5Z4 shield less necessary, near (but not at) the top will be ex- in getting the bugs out of feedback makes the baffle load the still advisable. A shield was added cessive; if too low, it will amplifiers, which often oscillate up but much. to the present unit after the photo was output stage too above 30 or 40 kc. Leakage in the electrolytic capacitor The amplifier part of the oscillator taken. All a.c. wiring should be below the 6J7 grid lead, range C used for output coupling sometimes system has to have wide -range response the chassis, and d.c. to and its resistors R,-R, all causes a fraction of a volt of and low phase- shift, which is the rea- switch S, the output terminals. bypass capa- should be above the chassis to assure appear across son for not using screen This is a difficulty common to most com- citors. The 6J7 and 6K6 tubes get their elimination of hum. shows up as beats be- mercial resistance -tuned oscillators, too. screen voltage from voltage dividers Hum pickup to the oscillator frequency and 60 Hence it is not advisable connect R , R7, R,,, R1, instead. This is the rea- tween to a grid without of interstage cycles and its harmonics. Thus when the output directly son too for the large 0.5 an intervening capacitor, since it might capacitor C, and the very large the dial of C, is set within a few cycles coupling will appear upset the bias. C3 for coupling the output of 60 or 120 cycles the beats capacitor amplitude back to the positive and negative feed- as an oscillation of the output Output metering back networks. C, and C are for high - at the difference frequency. The effect when the instrument The output meter circuit consists of frequency equalization, such as is used is very noticeable one half used is operated with the cabinet removed. a double triode V, with in oscilloscope amplifiers. -wave diode rectifier and the loop extends Normally the effect is hardly percep- as a half The negative feedback half as a d.c. vacuum -tube volt- C3, tible. other from the plate of V2 through meter. It is stable, low in cost and potentiometer R5 to through feedback -follower stage does not load the output circuit enough the cathode of the first stage V,. The Cathode normal amplitude of oscillation to cause any distortion due to clipping. 3 -watt lamp, which acts as a cathode The is needed other as the auto- at the plate of V, is about 15 volts. To No zero adjustment resistor for V, serves also than the mechanical zero on the 500 - matic amplitude control. If the output isolate the oscillator section and provide lower output impedance, a cathode - microampere d.c. meter. voltage rises, the signal voltage fed a works into a 1- will and follower is used for the output stage. The diode rectifier back across the lamp rise R,,. The positive d.c. volt- consume some A 6AC7 tube, V operates at about.12 megohm load the lamp filament will developed across it is fed through When the filament gets hotter, milliamperes plate current and about age energy. a filter R,,,. C, to the grid of the other increases, so that 60 volts drop across its load resistor its average resistance triode section, which operates as a feedback factor increases R11. Our maximum useable output is the negative cathode -follower type voltmeter. The too and the gain drops. about 10 volts. This is fully adequate for all applications of supplying input full -scale voltage is 10 volts r.m.s. The The positive feedback extends from by the multiplier the Wein to an amplifier. For testing speakers, sensitivity is adjusted the plate of V, through C R,,, and the zero is governed by to the grid of the tube cutting heads, etc., a power amplifier resistor bridge, and back the ohmage of the voltage divider resis- V,. is needed anyway, external to the sig- capa- nal generator. tor R33. The rotor of the main tuning meter of higher sen- is precautions have to Potentiometer R. gives continuous An indicating citor C, hot and than 500 microamperes full - also for stray capacitances control of the signal level to the grid sitivity be taken scale can be used at M merely by in- and hum pickup. The variable tuning of the output stage, and the step atten- NOVEMBER, 1951

www.americanradiohistory.com Servicing-Test Instruments

creasing the series multiplier R.,,, but a Incidentally, less the interstage coupling output of the sensitive movement such as 0 -1 standard to the horizontal capacitor C, should be a good one. Leak- input of milliampere will not work without re- age an oscilloscope, and the newly - designing here is about the commonest cause built unit to the vertical the whole circuit. Once cali- of trouble in plates. Identity brated, this commercial instruments. of the two frequencies is shown v.t.v.m. is quite accurate Calibration of by a and stable, because the output meter circle or ellipse on the screen. the over -all sensi- merely consists of connecting tivity depends only very slightly a 1,000 The instrument can be calibrated on ohm -per -volt a.c. meter to the output, with tube characteristics. With 10 volts Lissajous figures on an oscillo- r.m.s. setting output control and S2 for 10 volts, scope screen, a.c. input to the diode, the recti- and using the 60 -cycle power selecting or padding multiplier R21 frequency fied d.c. applied to the grid of the tri- until as a standard. Frequencies ode meter M reads full scale. The fre- such as 20, section is 14.14 volts. This voltage quency should 30, 60, 90, 120, and 180 is applied to the meter be low, say 100 cycles. cycles are easy to spot, but frequencies through an effec- If the meter does not zero properly, tive resistance made up of multiplier with more complicated ratios to 60 adjust the 1,500 -ohm divider resistor cycles (such 112 voltage divider resistors R;, and until as 50 and 200) are more IL, and the output R2, the electrical zero and me- difficult to identify. impedance of the chanical zero coincide. The meter triode which appears across cathode scale A piano that is reasonably well in is linear. tune might resistor R,0. This last is only a few Trimmer be used as a standard, but hundred C, is best adjusted with the the frequencies are all ohms, whereas the fixed resis- chassis in the cabinet, rather odd tors total 28,000 ohms. through a hole values. The lining -up of the oscillator in the top of the box. The procedure The output voltages appearing across is frequency with the piano notes is best merely to adjust C2 until the output done by the attenuator switch S2 are 10, 1, 0.1, voltage ear, even if a microphone and .01, of the oscillator is most nearly a scope are available, and .001 volts. The photo showing the same because the piano at both ends of the dial. This tones have very high harmonic obtains on the three content. lower frequency Middle C is 261.6, A one octave above ranges only. On the 20- 200 -kilocycle range middle C is 440, and 2 octaves below it it is normal for the output volt- is 110 c.p.s. age to rise 20% or so at the high - frequency end. On the high end of this Materials for generator: range, too, the frequency Resistors: calibration is 2-10.7, 2 -1.07, 2-0.107 megohms, 2- somewhat 10,700 ohms, 1- 10,000, 1,000, dependent on the value of 1- 1- 1,000, 1 -100, I -10, 1 -1.1 ohms, V2 waft, 2% accuracy; 1 -300, the small capacitor C, 5,000, across the lamp 2- 1- 10,000, 1- 18,000 (see text), I- 39,000, 1- 150,000, 500,000 bulb. Ordinarily I- ohms, I -1, 1 megohm, /2 not much accuracy is watt, -2 10% accuracy; 1-500, I- 30,000, 50,000, required up there, but 100,000 I- I- if it is desired C; ohms, I watt; I-55,000, I- 22,000, 1- 50,000 ohms, 2 watts; can be adjusted by beating the output I- 25,000 ohms, 5 watts; 1- 10,000 against a ohms, noninductive, 10 watts; Potentiometers; 1- signal generator at 200 kc. 3,000. I- 1,500, 1- 25,000 ohms. Capacitors (Electrolytic) Frequency calibration 2 -20 µf, I -20 µf, 450 volts. I (Mica) -150 µµf, 1 -.002 µf. (Paper) 1-01, I 1 µf, 400 Barring a serious -.I, -.25 volts. 1 -.5, I-8 µf, 600 volts. inaccuracy in the (Variable) I-4-gang, 365 µµf per section, 1 -100 µµf. Wein bridge resistors, there is no reason why the Inductors: I -15 h, 65 ma choke, (approx. 500 ohms dial calibration for one d.c. resistance. I -power transformer, 600 volts, c.t., range will not hold precisely for the 55 ma. other ranges. Miscellaneous: Tubes: The 200 -2,000 -cycle range I-6J7, I- 6K6 -GT, I -6AC7, I- 6SL7 -GT, I -5Z4 or 5Y3 -GT (see An is the most convenient for text). I -SI, underchassis view of the generator calibration. 2- circuit, 4- position rotary switch, shorting type, I- The following methods may be used, 52, I- circuit, 5- position rotary switch, shorting type, the easiest requiring the I- s.p.s.t. toggle switch. 1-6-volt pilot lamp and most appara- socket, I -3 -watt, 117 -volt lamp, I -1 ampere fuse the front of the panel shows an addi- tus and vice versa. The easiest way is and fuse holder, I-0 -500 microampere d.c. meter, tional .0001 -volt to use another 2 /2-inch diameter, Tube sockets, Chassis. Hard- section on S2. This audio oscillator which ware. Solder. Wire. was added by the author, but in most you trust, as a standard. Apply the -end- cases is not necessary. If desired, an additional resistor, 0.11 ohms in value, can be used to give this scale reading. However, great accuracy at this level should not be expected. If used, the re- DU MONT MAKES sistor is inserted between R30 and 405 -LINE ADAPTER ground, and an additional switch section is necessary for S. Calibration and adjustment When construction is completed, the first thing to check is the d.c. potentials at the various plates, screens, and cathodes, and they should be within about 20% of the values marked on the schematic. The amplitude of oscillation is controlled by the 110 -volt 3 -watt lamp bulb and by the negative feedback potentiometer R5. An oscilloscope is necessary, and the first thing to do is to increase R6 until flat -tops just become A number of "color noticeable on the sinusoidal output adapters" which make possible black- and -white of reception of CBS color broadcasts have been put on the market recently. the oscillator. Then decrease R6 until Du Mont is possibly the first large the amplitude television manufacturer to produce has dropped to about such an adapter. It is intended for use with standard Du Mont receivers two -thirds of its former value. If R6 is to receive 405 -line programs. The front and rear appearance of the unit too high, overloading and distortion is well shown by the two photographs. It is attached to a convenient place will result; if too low, oscillation will on the rear of the receiver, and is said to take only one hour for installa- tend to die out. Individual tion. selection or This adapter will make padding of R6 is necessary possible reception of CBS color programs in because the black- and -white. Adding a color wheel would lamp bulbs vary quite a bit in permit reception in full color. characteristics. RADIO -ELECTRONICS for

www.americanradiohistory.com Servicing-Test Instruments 37

V -R systems are important in many new developments

OLTAGE- REGULATION sys- If the line voltage should drop and resistor R1 also prevents excessive cur- tems are used to maintain a the d.c. output from the rectifier circuit rent flow to the regulator tube which constant voltage output over a tends to decrease, the voltage -regulator would shorten its life. Tubes must range of varying load require- tube will draw less current. This de- operate within their proper range to ments. There are two fundamental cir- creases the current flow and the voltage regulate properly. Less than 5 ma., regulation action is poor. With cuit types : one uses gas -filled tubes and drop across resistor Rl. This action their is based upon the ionization of the gas tends to keep the output voltage con- more than 40 ma. their life span is particles; the second utilizes vacuum stant. The same regulatory action shortened. tubes and is based upon the changing occurs as the current drawn by the load Several of these tubes may be plate resistance. changes. If the output voltage from operated in series to obtain a higher Gas regulator tubes can maintain a the regulator circuit tends to decrease voltage output. Two 0C3's will give a fixed voltage output over a range be- d.c. operating voltage of 210 for in- tween 5 and 40 milliamperes. Fig. 1 stance. Parallel operation is impossible, illustrates the OD3 (VR -150) gas -filled since one tube will ionize first and re- voltage -regulator tube. A d.c. potential duce the voltage across the second of 180 volts is necessary to ionize the below the ionization potential. inert gas and start the tube in opera- If the regulator tube is removed from tion. The tube has a voltage of 150 its socket, the voltage output from the between plate and cathode after ioniza- power supply rises to a higher value tion; operating current is 5 -40 ma. than normal, due to the current taken Fig. 2 shows the operating characteris- by the operating voltage -regulator tube. tics of the OD3. The table shows how In some of these tubes, a jumper is this tube compares with two other gas used as an additional safety device, tubes. Fig. 4. This jumper is connected in series with the voltage output to the How gas tube regulates load. If the tube is removed no voltage A typical gas diode voltage regula- output can be obtained. tor circuit may be seen in Fig. 3. As- REGULATION CHARACTERISTICS sume that the d.c. output voltage from the power supply filter tends to rise; TYPE 003 this may be because the line voltage Fig. 1 -Cold- cathode gas tube OD3. increases. As the line voltage increases, The small tube beside it is an 0A2. the d.c. output from the rectifier will 10 increase and the output voltage across because of increased load, the regulator / STARTING VOLTAGE the load would also have a tendency to tube draws less current and keeps the rise. But the voltage regulator tube output voltage constant. will now draw more current which in- V -R tubes must have an applied volt- 160 creases the voltage drop across the age greater than their operating volt- series resistor Rl. This increased voltage before they will ionize. This voltage S=1. age drop decreases the voltage output occurs during the initial surge when the '-- OPERATING RANGE to the load. power supply is turned on. The series 150 CC

0A3 /YR -75 0B3/YR -90 0C3 /VR -105 0D3 /VRI50 D.c. starting supply voltage (min.) 105v 125v 133v 180v 140 D.c. operating voltage (approx.) 75v 90v 105v 150v 0 10 20 30 D.c. operating current (min.) 5ma 5ma 5ma 5ma OPERAI NC MILLIAMPERES D C 40ma 40ma 40ma 40ma Fig. 2- 0D3 /VR -150 operating charac- D.c. operating current (max.) terestics. Note the operating range. NOVEMBER, 1951

www.americanradiohistory.com 38 Servicing- Test Instruments

Vacuum tube regulators to the plate voltage, the tube conducts resistor string Rl, R2, and R3. Since Where only small currents (up to heavily and acts like a very low series the 2A3 is conducting, it appears as a 40 ma.) need to be regulated, it is pos- resistance. A negative grid voltage (less fixed resistance in the circuit and there sible to use a gas tube. For higher current flow with the same applied is a voltage drop from cathode to plate voltage), will make the tube act as a of this tube. This is the reason the out- SERIES RESISTOR R1 higher resistance. If we apply a nega- put voltage is 250 rather than 350 volts.

OUTPUT + tive voltage great enough to prevent Assume now that the input voltage R2 FROM VOLTAGE current flow entirely, the 2A3 acts as a to this circuit increases, (this may be REGULATED LOAD FILTER REGULATOR VOLTAGE RESISTANCE very high resistance. caused by an increase in the applied TUBE A 6J7 is used as the voltage amplifier line voltage). As the output voltage tube V2 ; it supplies the control voltage tends to increase, the voltage on the Fig. 3 -Gas diode regulator circuit. for the grid of Vl. V3 (0C3) supplies control grid of the 6J7 will also in- a fixed reference voltage. The currents and better regulation, vacuum output crease. This will decrease the bias on load resistors in series are Rl, R2, and this tube and decrease the voltage dif- tubes are used. Fig. 5 is a simplified is variable. circuit demonstrating vacuum tube volt- R3. R3 ference between E2 and E3. The 6J7 now age regulator action. conducts more heavily, and more cur- Tube regulator action (6J7) rent flows through R4. The larger volt- R2 is the resistance which represents The cathode of V2 (6J7) is fixed at a the load; the regulated output voltage age now developed across this resistor definite value above ground by V3. V2 increases 2A3 appears across it. A voltmeter, is the bias on the tube; V, acts as an amplifier, feeding back the this tube conducts less and becomes a placed across the regulated voltage out- changes in output voltage to the vari- put. The higher resistance. More voltage is now regulation occurs in the ele- able resistor, Vl. As this resistance dropped across ment marked Rl, a vacuum tube in this higher resistance changes, the output is held constant. and the voltage tends ìo practice, but here shown as a variable output drop. Assume that the circuit is turned on. Assume the input voltage decreases. series resistor; A small series resistor The complete path for the current flow Less voltage appears across Rl, R2, and for V3 is through V2, R4, PLATE 5 and Vl to R3. There will be a decrease in voltage the positive side of the input voltage. on the grid of the 6J7 which will in- CAS As 0C3 ionizes, will 105 the it have crease the negative grid bias on this JUMPER COLD volts from cathode to plate. This is : CATHODE tube (because its cathode is held at a shown as E2 in Fig. 6. The plate volt- Fig. 4 -Base connections for 0A3, OB3, constant . age potential by V3) Less current 0C3 and OD3. See text for jumper use. of the regulator tube is exactly the flows through R4. A smaller same as bias volt- the cathode voltage of V2. age is applied to the 2A3 which con- means a small voltage drop, a high The grid V2 is of connected to the ducts more readily, becoming a lower series resistor a high voltage drop. An junction of R2 and R3. Its grid voltage actual variable resistor is not used in resistance. A smaller voltage drop ap- is 100 volts d.c. Since grid bias is the pears across this lower resistance and the circuit; by means of vacuum tubes' voltage difference between grid and plate resistance the same effect is ob- the output voltage rises. Thus constant cathode, if the V2 cathode has 105 volts voltage output is maintained. tained. The value of this variable resist- and its grid 100, the bias is volts 5 A 6J7 is used for ance changes as the d.c. supply voltage d.c. This is not enough to cut the tube the control tube since it has high gain and small changes VARIABLE SERIES RESISTOR off but acts as a control voltage. in output voltage give close The suppressor grid of V2 is tied to regulation. Vl must be a tube able to carry large R2 its cathode; the screen is attached to D.C. SUPPLY currents since all of the current used LOAD the bleeder network at the junction of VOLTAGE VOLTMETER in load flows Rl and R2, with between 100 and 250 the through this tube. volts d.c. on it. A type 2A3 is used in regulators which supply Fig. 5- Simplified vacuum tube regulator The plate voltage of V2 is also the up to approximately 50 milli- circuit where Rl is the tube resistance. grid voltage of Vl. Current for the 6J7 amperes. Power amplifier triodes of this flows through R4 and the 2A3. The type are often used; by means of changes. This same variable resistor current flow through this resistor es- parallel connections, several tubes may also changes value when the current tablishes a potential so that the grid be used and this multiplies the effective drawn by the load changes. This circuit of the 2A3 is more negative than the current by the number of tubes being effectively keeps thé output voltage cathode. used. One control tube of the 6J7 constant in spite of changes in the line variety can be used with several 2A3 voltage and changes in the load current. Regulator action (2A3) tubes in parallel. A 6Y6 -G tube is used + 2 The circuit is placed in operation by in parallel to obtain load currents of up VI 2A3 connecting it to a power supply with an to 250 milliamperes. Other types of R4 output of 350 volts. Conduction is es- control tubes are the 6SF5 triode or 111EC tablished through the 3 tubes in the the 6AC7 pentode. 1 circuit, and current flows through the -end- ci RI o (4) 6L6 o á 5R 4 GY LIJ so c- 39oK 390A 50 100 50 2 o 4 6 INEC 6SH7

HOUTPUT O I { sa 3 OC3 v R3 o BA 105V IOOV + + TO olo FIL.OF 65NT Fig. 6 -A simple voltage regulator. , 6.3V TO FILS. 5N F-. OF 616 0 I05-I~ OUTPUT.D.C..RECULATED A vacuum tube voltage -regulator cir- 25° !NEC 2506 cuit shown in Fig. 6 uses two vacuum 60+ a 200-500V 200NA tubes and one gas tube. V1, a 2A3 500 MA power amplifier triode, acts as the series 4 AMP 406 40 4 0A3 NA resistance Rl of Fig. 5. The plate re- 506 sistance of a triode tube can be said 's? 0.25 to vary as the grid bias varies if other 40T 40T voltages are constant. If the grid volt- 6RAS511 )I age is positive, and approximately equal The Kepco model 245 supply uses series regulator like that shown in Fig. 6. RADIO- ELECTRONICS for

www.americanradiohistory.com Theory and Engineering :i!f IJISCONE - BROADBAND ANTENNA

This antenna, using discones in two of its three switching positions, goes from 100 kilocycles to 4,000 megacycles in only three tuning ranges

By FRED SHUNAMAN

THE antenna on our cover is pos- Lester Saporta, one sibly unique among its kind both of the designers of it is able to in the size of the job the antenna, tunes do and in the special design features that permit it to do that work. It up the whip section resulted from the need of the Air Force's Air Development Center for an antenna that would cover the almost unbelievable bandwidth of 100 kc to Courtesy New York University 4000 mc. A research project with the coaxial transmission line (for conveni- often rated in terms of the percentage objective of designing such an antenna encl placed at right angles to a vertical of center frequency at which response was let to Camburn, Inc., who sublet it feeder, Fig. 1 -z) we check the radiation. is 3 decibels down. The bandwidth of to the College of Engineering of New It is negligible. Now, if we flare the the discone is so great that its useful York University. The resulting antenna outer conductor out into a sort of horn frequency range is usually stated in is largely the work of two students in (Fig. 1 -b), it begins to radiate effici- terms of octaves rather than percent- that college, Lester Saporta and Paul ently at frequencies above a certain ages. The smaller (upper) antenna in Chirlian. cutoff point. Our flared coaxial line be- the photograph is used over the region Even this antenna does not cover the comes a radiator with a wide frequency between 600 and 4000 mc, while the big band in one continuous sweep without range, but good in one direction only. one works over the enormous frequency switching. But only three switch posi- Four such "coaxial horns" would range of 12 to 600.mc. tions are necessary to work across the make an omnidirectional antenna, A vertically polarized wave is trans- whole spectrum. The lower band, from though the field pattern would be irreg- mitted (or received best) anc: the bulk 100 ke to 12 mc, is handled prosaically ular, because radiation naturally would of the signal is radiated almost parallel with a 22 -foot whip antenna and tun- be best directly ahead of each horn. But with the earth at the lower end of each able loading coil. It is in the upper there is a simpler and better way to antenna's spectrum, the angle tipping reaches of its spectrum that the an- get a perfect omnidirectiona: pattern. slightly upward as the frequency is tenna departs from tradition. To cover Imagine rotating our "coaxial horn" raised. For greater flattening of the the extended frequency range, it was around the end of its feeder through a signal area, two or more discones may necessary to use the peculiar qualities complete circle (360 degrees). The inner be stacked one above the other, com- of the discone. conductor would, as they say in geom- pressing the radiation pattern into a The discone antenna is not new. De- etry, "generate" a disc, and the top and thin disc which puts most of the power veloped by Armig G. Kandoian of Fed- bottom of the horn would each "gener- near the earth's surface where it is era'. Telephone and Radio Corporation, ate" a cone. This would be equivalent needed. it was first described by him to the to an infinite number of these "horns" Institute of Radio Engineers in 1945. or at least such a large number that At frequencies near cutoff, the in- Its inventor says that it "may be visual- the central conductors would be close ventor states, we can think of the an- ized as a radiator intermediate between enough together to become a disc. See terna as a dipole. Of course, since we a conventional dipole and an electro- Fig. 2. are dealing with the space between two magnetic horn "' The radio technician The top half of this antenna merely surfaces instead of a conductor, we will studying it for the first time may also duplicates the lower half, and can be have to think in terms of electric fields see it as a combination of transmission abandoned, and we have a discone-a instead of currents. As the waves move line, matching section, and radiator. horn thr.t presents a mouth in all di- out from the center of the discone, the It may be difficult to conceive of how rections. electrostatic lines of force extend be- an antenna can combine all these fea- tween disc and cone as in Fig. 3. For tures, but the actual operation of the Frequency range any given frequency, there is a point discone is rather easy to understand. The frequency range of the discone where the wave finds it easy to "take Starting with it as a piece of standard is phenomenal. Antenna bandwidth is off" into space. Our imaginary dipole, NOVEMBER, 1951

www.americanradiohistory.com 401 Theory 81141 Engineering then, can be taken as a ring around the The gradually increasing distance be- appearance has prevented is more gen- cone and one around the disc, on which tween upper and lower plate of the dis- eral acceptance. Search through the the ends of the electrostatic lines of cone acts as just such a transmission standard antenna handbooks turns up force rest at the point where they are line matching section, increasing gradu- very little about it, and that little usu- being radiated out into space. Cutoff ally in impedance as the space between ally buried in the section on ground - comes at the point where the lines ex- them increases, down to the point where plane antennas. Its vertical polariza- tend from the disc to the extreme lower the wave takes off into space. That edge of the cone. again can be considered a matter of matching impedances. At the critical Automatic impedance match point, the impedance of the antenna for i Here is where the matching section the given frequency is similar to that feature of this antenna comes in. The of space. The impedance just before discone acts not only as a radiator for that (toward the center of the antenna) is lower, and toward the edge is higher. Therefore the wave finds it easier just to depart into space than to stay on the 1 cone. -I The critical point moves outward as frequency is lowered, making it neces- Fig. 4- Discone dimension references. sary to build a bigger antenna for lower frequencies. Kandoian gives the fol- tion the position most convenient 90 mc Fig. -in lowing dimensions for (see for mounting -may keep it out of the 4) : A, 9 inches; B, 24 inches; C, 10 b television field. Yet it might be the so- inches. For 200 mc, the figure' are: A, lution to the problem of perfect match- 41/2 12% 7 l'ig. 1-Evolution of a coaxial horn. inches; B, inches; and C, ing at both high and low frequencies, inches. Amateurs' have found it safe which might compensate for the diffi- to consider the cutoff frequency that at culties of horizontal mounting. In size, which the height of the cone (D slant such an antenna could be kept within in Fig. 4) is wavelength. a quarter about 4 feet in height and diameter and The larger antenna in the photo- '%74,t--- it could be built of copper screen on a graph may not seem to be a true dis- metal (or insulating) framework, to cone. The difference is one of detail. keep down wind resistance. The designers found that by making a The amateurs, as already noted, are cylinder out of the lower part of the beginning to use the discone for v.h.f. cone, they could retain most of the ad- and u.h.f. work. As frequencies continue /;;; . vantages of the conical shape while to rise, we may expect to see these an- saving a great deal of the space that tennas more and more often. .- would otherwise be occupied by the flaring lower edge. 1 Proceedings I.R.E., Waves and Electrons Sec- Fig. 2- Discone is derived front horn. Vol. 1, The discone has not come into as com- tion. No. 2, February, 1946. 2 Diacone -40 to 500 Mc Skywire, Joseph M. mon use as its qualities would seem to Boyer, W6UYH, CQ. July. 1949. I justify. Possibly its peculiar and novel -end- An Interesting Mixer Circuit Needing a mixer having special char- superposed r.f. This is no modulated acteristics, we thought of a combination wave. The choke must be chosen in ac- of two cathode followers, tying the cath- cordance with the r.f. range of the odes together to deliver the modulated mixer. output voltage. The circuit shown was Fig. I Fig. 2 Fig. 3- Electrostatic field on discone. tried and worked nicely at on e. A 6J6 tube was used, but equally good results a given frequency, but as a matching were obtained with 6SN7 -GT and 6F8 -G transformer between the transmission tubes. The scheme is extremely simple line and that point on the antenna at and involves no critical parts. which that frequency finds conditions A scope was used to ,ee how this suitable for transfer between antenna works. The F1 input posts were tied to and space. an oscillator working on 200 kc, and As a matching transformer, it resem- the F2 ones to an audio oscillator. Fig. bles closely the old delta- or V -match 1 shows the output wave modulated at section of the lead -in of a Bout -let -that 60%; the modulation is rather good. This circuit features several out- section which is fanned out to match A radio- frequency choke RFC is re- standing advantages: quired to provide a low impedance path line to flat -top. The V- section matches 1 -Very low input capacity. As a cath- a lower to a higher impedance because for the audio component. When RFC ode follower, the amplification of the of the gradualness with which its im- was omitted, the pattern of Fig. 2 was tube is less than unity, and there is pedance increases as it opens. If a 52- obtained, showing the audio wave with no Miller effect. ohm line were connected to the ter- 8+100-250V. 2 -High input impedance. The grid re- minals of a 300 -ohm antenna, waves sistors are of 0.2 to 2 megohms. would be reflected back along the line, .05 3 -Low output impedance. A good char- and the match would be bad. But if the IE--o acteristic for signal generators. 52-ohm line opens into a very short sec- F2 4-High stability. The B- voltage can tion of 53 -ohm line, and that into an INPUT vary widely without any change in 220K equally short section of 54 -ohm line, modulation quality. Resistors and and so on out to the 300 -ohm points capacitors are in no way critical. on the antenna, the mismatch at any 5- Economy. Minimum of components. one point is slight, reflection is mini- Alfred Haas mized, and the match is considered good. -end- RADIO- ELECTRONICS for

www.americanradiohistory.com Theory ni4s1 Engineering agneticl PHENOMENON

Strange action of bismuth in a magnetic field opens up new range

of possibilities in future electronic discoveries and applications

By ALVIN B. KAUFMAN

NE of the most unusual of all magnetic phenomena now open to experimentation is the 0 change of resistance of bismuth wire when placed in magnetic fields of different intensities. This change of resistance is as high as 100 to 1. Bismuth is well known in the laboratory, but because of its limited availability up to now it is not familiar to the average person. The advent of com- mercially available ductile bismuth wire opens up new fields to the experimenter. Last January the Fitzpatrick Electric Supply Company, 444 Irwin St., Muske- gon, Mich., offered the market the first ductile bismuth wire and alloys. Photo A -'rhe simplest equipment used. Photo B- Construction of pickup coil. Bismuth is a white metal. It is a poor conductor of heat and electricity, ap- change of resistance with a magnetic values of 0 to 35,000 gauss, and for dif- proximately 1/80 of copper, and is very field, see Table I. Bismuth Las a change ferent temperatures; assuming 100% diamagnetic in comparison with other of resistance of approximately 300% (or 1 ohm) resistance at 0° C with no metals (Diamagnetic means that metal, at 18° C when subject to a zero to 35; field. instead of being attracted to the poles 000 -gauss field. At -192° C when sub- The Hall effect, Fig. 1, is the genera- of a magnet, rather is repelled by the ject to the same field, the change is close tion of minute output potentials when a magnet. This is opposite in effect to to 9,000%, or about a 100 to 1 change! flat strip of metal is placed within a paramagnetic material which is at- Table I shows the proportional values of magnetic field with its planar surfaces tracted to the magnet. -Editor). Bis- bismuth resistance for magretic field at right angles to the direction of the muth is the most diamagnetic metal known, a sphere or bar of it being force- Table I fully repelled by a magnet. Electrically, bismuth has some fas- H Gauss -192° C 18° cinating qualities, some highly desir- -135° C -37° C 0° C C 60° C 100° C able, some very unsatisfactory. When 0 0.40 0.60 0.88 1.00 1.08 1.25 1.42 present in other metals, even in minute 2,000 1.16 0.87 0.96 1.08 1.11 1.26 1.43 quantities, bismuth renders them 4,000 2.32 1.35 1.10 1.18 1.21 1.31 1.46 brit- 6,000 tle and decreases their electrical con- 4.00 2.06 1.29 1.30 1.32 1.39 1.51 ductivity. 8,000 5.90 2.88 1.50 1.43 1.42 1.46 1.57 Further notable effects are: 10,000 8.60 3.80 1.72 1.57 1.54 1.54 1.62 a. Resistance change with magnetic 12,000 10.8 4.76 1.94 1.71 1.67 1.62 1.67 field (Gauss effect). 14,000 12.9 5.82 2.16 1.87 1.80 1.70 1.73 b. Voltage change due to Hall effect. 16,000 15.2 6.95 2.38 2.02 1.93 1.79 1.80 c. Resistive change with temperature. t8,000 17.5 8.15 2.60 2.18 2.06 1.88 1.87 d. Highest known thermoelectric po- 0,000 19.8 9.50 2.81 2.38 2.20 1.97 1.95 tentials. 5,000 25.5 13.3 3.50 2.73 2.52 2.22 2.10 Possibly the effect most 0,000 30.7 18.2 4.20 3.17 2.86 2.46 2.28 interesting to 35,000 those concerned with electronics is the 35.5 20.35 4.95 3.62 3.25 2.69 2.45 NOVEMBER, 1951

www.americanradiohistory.com and -12 Theory Engineering

obtained by subtracting column 2 from are much higher than normally avail- DC -I column 3. A longitudinal current of 1.5 able in laboratories. High field PASSING THROUGH amateur .012 - MAGNETIC FIELD -H BISMUTH STRIP amperes was used with a sprayed strengths are normally found only in cm -thick bismuth film for obtaining the close -gap apparatus. A conventional above data. d.c. motor, for example, generally has DG As a resistance material with a high a 6,000 -gauss field, or about 40,000 lines coefficient of thermal electric resistance per square inch. Low- to medium - strength fields are not high enough to TABLE II give more than a fraction of 1% to several percent in resistance BISMUTH HALL EFFECT IN BISMUTH FOR change of STRIP the bismuth at normal ambient temper- A SINGLE PICKUP atures. Field Residual Residual Net Hall Fig. 1 -How Hall effect (generation of Strength e.m.f. Hall e.m.f. voltage at right angles to magnetic field Gauss (A Volts) e.m.f. (µ Volta) (µ Volts) Simple tests and current) is studied. The Hall effect .08 14.0 15.5 11.5 is extraordinarily strong in this metal. The author, using the equipment .10 14.2 15.8 1.6 shown in Photo A, about three feet of .25 14.0 16.4 2.4 .011 Fitzpatrick bismuth wire wound .30 14.5 19.8 5.3 MAGNETIC FIELD -H on a 24 -turn pregrooved % -inch form .50 14.6 22.7 8.1 AC -I and an Alnico horseshoe magnet, could 1.00 14.6 20.6 15.0 deflect the galvanometer on an imped- 1,000. 14.0 1,889.0 1,875.0 ance bridge. The deflection was not mo- TIME 2,500. 14.0 7,514.0 7,500.0 mentary, as will occur due to generator 4,220. 14.0 15,320.0 15,300.0 effect with a coil of copper wire, but BISMUTH WIRE permanent until the magnet was re- change Fitzpatrick bismuth wire is ex- moved. The galvanometer deflection was cellent, running 720 ohms /mil foot. In slight, but easily visible. With a strong- is nega- Fig. 2- Idealized illustration, setup this respect, bismuth the most er field (800 -2,800 gauss such as pro- to study change in b'smuth's resistance tiv3 material known for thermocouples, duced by a surplus magnetron magnet), as surrounding magnetic field is varied. exceeding all others by over 100%, giv- the effect is much greater and more reading 69 microvolts per degree Centigrade able in terms of resistance change. The field and with a current passed through change from 0 to 100° C compared with change in resistance is easily visible and the length of the strip. The difference platinum. possible to read when a more sensitive of potential occurs between the top Wheatstone bridge is used. and bottom surfaces of the strip. Bis- The Gauss effect In all tests employing a galvanometer muth exhibits this property to an un- The Gauss effect is very interest- for indication, the coil was first discon- usual degree, and many physicists have ing. Probably the most important char- nected and the magnet brought close explored the phenomenon. Output micro- acteristic of bismuth wire is its large to it while the galvanometer was ob- volts may vary from several microvolts increase in resistance when placed in served to be sure that the magnetic to over 15,000 for a field strength of a magnetic field (Fig. 2) . Between the field of the magnet was not directly af- 4,200 gauss (See Table II). The residual values of 2,000 and 35,000 gauss, its fecting the galvanometer. It was also e.m.f is the potential difference caused proportionate response is approximately noted that the thermal effect was much by the fact that the pickup fingers 214% at 18° C. From 300 to 2,000 gauss, greater than the magnetic effect for a which pick up the transverse Hall po- the proportionate response is less ow gauss field. In measuring the change tential cannot possibly be placed at ex- though sensitive enough for electrical of resistance on a bridge, a change of actly equipotential spots with regard to instrumentation. 0.2% (about .04 ohms, 16 -ohm coil) the longitudinal current (with present The gauss fields indicated in tables, was visibly induced by the horseshoe techniques). The net Hall e.m.f. was Fig. 3, and in the article to this point, alnico magnet. This small magnet had about a 200 -gauss field. Later a magnetron magnet of 2,800 gauss was used. The same pickup coil with 16.37 ohms ambient resistance increased to 17.20 ohms when placed in this field. This was an increase of 5',Ç %. Putting the fingers on the coil resulted in a thermal resistive change of possibly several times this magnitude. Measuring errors It is preferable then, in design, to obtain a strong enough field to reduce any thermal change to a small percentage of the gauss resistive change. Otherwise it is necessary to introduce a thermal compensating coil in series or parallel with the bismuth coil to prevent thermal effects from introducing errors. It must also be noted that the wire changes electrical resistance with the passage of current due to the resultant thermal I'R heating. If, the current is held to a low value, this effect may be negligible. For higher currents, but below the fusing value, the wire may change its resistance by approximately 50% as indicated in Table III. The .011 Photo C- Equipment of Fig. 4, used to detect effect of magnetism on resistance. wire used for these preliminary experi- RADIO -ELECTRONICS for

www.americanradiohistory.com Theory Mid Engineering' 43 ments ran warm at % ampere, and fused at 11/2 amperes. TABLE III Current Resistance (Amperes) (Ohms) 0 24.0 .4 25.5 .45 25.75 .5 .6 3l .7 22 .8 35

Consideration must be taken when Photo D -This simplified setup follows Fig. 5, with a meter instead of 'scope. making bridge measurements not to exceed these currents and to allow the bridge to stabilize until the thermal conditions in the coil ale completely equalized before making any gauss this it is comparatively easy to wind or ion traps and probably to many other measurements. any type of coil. A typical coil wound similar uses. by the author had an ambient resistance The bismuth probe is small, about 1/4 inch 1/2 inch. The coated wire Care in handling of 60 ohms which increased to 63 ohms by when subjected to a 2,800 -gauss field must be handled carefully the same as In handling the wire, do not make from a surplus magnet. the bare wire. The insulating coating is sharp bends or flex the wire. The wire Since the coil resistance will increase easily removable with the use of ace- is not as ductile as copper; it will break directly in proportion to the intensity tone. after a few bends. After the pickup coil of the field beginning with about 2,000 It must be noted that although an is made, cement the wires in place and gauss (under that the resistance analyzer, as the Simpson 260, may be connect the bismuth wires to light - changes are low and not linear), the used for the bridge meter, its much gauge, flexible, extension leads (see use of this measurement method appar- higher internal resistance, even if it is Photo B). The melting point of bismuth ently is limited to high- intensity fields. used on the 1C0- microampere scale, will is 520° F, so conventional solder cannot Where high-intensity fields are avail- cause the bridge to be comparatively be used. Instead, a low- temperature- able, the measurement i_eed not be insensitive. melting alloy must be used. The author limited to a Wheatstone bridge. The A bridge supply voltage of 71/2 volts used Cero -bend, but Woods metal or change of resistance may be used to is optimum when measuring high -in- others of the same class are applicable. operate electronic control equipment. tensity fields. For low- intensity PM The joint between the bismuth wire Slight changes of this high- intensity speaker field measurements, etc., the and the tinned -copper wire strictly field by ferrous materials on a person bridge sensitivity may Le increased speaking is not a soldered joint, as the or in material might well be detectable threefold by raising the bridge voltage Cero -bend does not bond to the copper by this means. to 22% volts. The bridge supply voltage wire. These low-temperature joints are directly regulates its sensitivity-the mechanical. If a soldering iron is used to Sample experiments higher the supply the greater the sensi- melt the low-temperature alloy, allow the For low- intensity fields where the tivity. The maximum supply is limited melted metal to cool before use or its maximum resistance change might be by the heating in the bridge arms. With higher- than -500° temperature will cause 0.2 %, (in strain gauges, typical carrier the bismuth wire used, 45 volts input the bismuth wire to melt. The joint in or phase sensitive amplifiers) designers should not be exceeded; higher level any case will look dirty and like a very might make use of bismuth's peculiar causes high thermal temperatures to poor cold solder connection. properties. A scope indication of the un- develop in the coil. balanced bridge carrier output is shown -end Noting field intensities - in Photo C. Here (see Fig. 4 for the 120V -120V With the fine bare bismuth wire schematic) 60 -cycle a.c. is fed into a ISOLATION wound into a flat coil or on a rod to Wheatstone bridge, and the u-nbalanced SCOPE form a prod, it may be used directly with output is connected to a 5 -inch oscillo- a high- sensitivity Wheatstone bridge scope. After potential is applied to the 25 25 for exploring the 117 V IO W IO W intensity of magnetic bridge for several minutes and the four 608, 10-20V fields in many types of magnetically legs resistively thermal -stabilized, the o 60N operated apparatus. Coated bismuth bridge is balanced. The oscilloscope 500 25 wire also may be obtained, and with amplifier used supplied enough gain to VARIAC WW LVERTCAL OR secure a change in the sine wave ampli- POT. 10 W INPUT 3.2 POWERSTAT I I I I 1 I I I I I I tude when the bridge balance was upset 24 .n. BISMUTH IN J., 3.0 FROM SMITHSONIAN TABLES by placing a 200 -gauss magnet next to BRIDGE AC OR DC FIELD z 2.8 VARIAI ON OF RESISTANCE the bismuth pickup coil. For a.c., the BALANCE o OF BISMUTH IN 3 2.6 coil must be noninductively wound. A Fig. 4- Experimenta setup with 'scope. A MAGNETIC FIELD bifilar winding with opposing bucking zú 2.4 fields is constructed. a 2.2 The experimental setup shown in Fig. ¡Nj, 2.0 TEMP 8 °C - 5 and Photo D is the simplest circuit for BRIDGE ¢ 1.8 RI.OAT0 °C_ the experimenter to construct. A 50- z BALANCE 50 1.6 ohm coil is wound, using coated bismuth 7.5 V wire, and hooked into a bridge circuit PROBE a 1.4 W as shown. It has extremely high sensi- COIL ú 1.2 tivity, giving as much as half -scale de- 501L 1 z WW 1.0 flection using a surplus magnetron mag- 27 6 10 14 18 22 26 30 34 net. This MAGNETIC FIELD H -IN 1000 GAUSSES circuit is adaptable to measuring and comparing the field strengths of 9 MAY BE 0.5 WATT IRC FOR TEST PURPOSES Fig. 3 -Gauss effect in strong fields. PM or dynamic speakers, TV focus coils Fig. 5- Simplest experimental hookup. NOVEM BER, 1961

www.americanradiohistory.com 411 New Design IONOPHONE

By E. AISBERG* and M. BONHOMME **

Long the dream of engineers, the inertialess loudspeaker is now reality. It produces sound from electric current with ionized air molecules The inventor, S. Klein, demonstrates his new and revolutionary loudspeaker.

ULY 27,1951 will remain a red -letter loud enough to raise his invention above radio receivers be required to pass the day in the memory of two authors the category of a mere scientific toy. audio frequency currents which have of this article. On that day they He has succeeded, and at present the been carefully protected against distor- J heard for the first time sounds from biggest French manufacturer of loud- tion through a part which -by its very a loudspeaker that did not have a single speakers is tooling up for mass produc- nature-cannot but distort the sounds mechanical part in movement and was tion of lonophones, as the new speakers it engenders? designed on an absolutely new principle. are called. The best diaphragm has its natural The device is the fruit of years of Yesterday's dreams make tomorrow's vibration period and enough weight to patient research by S. Klein, a young inventions. Electronicians always dislike be a factor, without possessing that French physicist, who for years struggled to use moving parts, and nowhere more ideal rigidity which forms the piston over the problem of producing sounds than in loudspeakers, where they result described in manuals on acoustics. In in an efficiency of less than 5 per cent spite of setting the resonant points be- *Publisher of Toute La Radio **Chief Editor of Toute La Radio and in imperfect fidelity. Why should yond the limits of the frequencies being reproduced, all diaphragms cause linear and nonlinear distortion, not to mention bad reproduction of transient phenomena. Inventors have long tried to get rid of the unfortunate diaphragm. One of the earliest attempts was probably Edi- son's Thermophone. Duddell's singing arc and the talking flame also might be mentioned. Hugo Gernsback, whose ideas seem so fanciful but whose predictions usually come true, called for a speaker without moving parts' ten years ago.

1Molecular music is another subject which as yet has not been exploited at all. Years ago, it was discovered that it is possible to make dynamos sing or talk by merely vibrating the dynamo's molecules. In this case, nothing moves. There are no diaphragms, no loudspeakers, but the entire iron frame of the machine gives forth sounds, speech, or music. I can visualize, therefore, a future all-steel auditorium giving forth super-music by energizing the entire auditorium in such a manner that the walls, ceiling, and floor will have their molecules vi- brated. Entirely new effects undreamed of today will thus be obtained. C1oseup vier' of the ionization unit. me opening is down, in the aluminuul c o11a1. (From an editorial in Radio- Craft, April, 1941.) RADIO -ELECTRONICS for

www.americanradiohistory.com New Ilcsitin I45

wire comes very In this formula, the platinum (which emitter with its central platinum This new loudspeaker shield. Between these being the fulfilment of that pre- is the principal source of ions) reaches and the exterior close to which plates there is a cloud of ionized par- diction. It is based on the phenomenon a state of extremely fine division, the tempera- favors both the emission of ions and ticles, which are in a state of agitation of ionization. By raising are in an alternating field bodies they can be made the renewal of the emitting surface. because they ture of certain end acts on all bodies, whether posi- to emit ions. Under the influence of in- This tube is sealed to the lower which agitation, not only are of a short exponential horn (likewise tense thermal in- electrons torn off but also some mole- of quartz) which has a double wall cules, which because of the fact that side of which a high vacuum is main- they have lost electrons, become ionized tained. The assembly is then placed in- positively. The action becomes compli- side a cylindrical shield, the bottom of cated because the electrons meet air which is steatite, so that the emitter is and tear off further electrons. held in place. The mouth of the small molecules ex- We therefore have a complex mixture quartz horn connects with a large of ions from the emitting substance and ponential horn of the type ordinarily ionized molecules from the gases of used for compressed -air public address which the air is composed. loudspeakers. Creation of the lonophone How it operates The first model was made several A high- frequency (about 400 kc) and years ago. It can be compared to a diode high-voltage (10,000 to 12,000) field is operating in free air. An indirectly set up between the outside cylindrical heated "cathode" emitted positive ions shielding and the platinum wire which toward a "plate" which was maintained When an at a high negative potential. The speaker unit with its r.f. exciter. alternating audio -frequency voltage was on the direct voltage between impressed tively or negatively charged. the two electrodes, the number of ions of the al- according to If we change the strength in circulation would vary field, we also alter the the alternating voltage ternating electric the rhythm of amplitude of the individual oscillations and determine the corresponding move- Now, molecular molecules, which were of each of these bodies. ment of the air and heat are two words to in the form of sound waves movement propagated describe the same phenomenon. There- at the audio frequency. the strength of the model was designed in the fore, by varying A better electric field, we can obtain correspond- form of a triode where the alternating variations of tem- voltage was applied to a sort of cylin- ing instantaneous emitter and the perature. drical grid between the is easier to the radioman outer cylindrical shield (Fig. 1). Nothing II the strength of a high - sound generated by both these lit than to vary The a frequency field at a low- frequency rate. was very weak and the high -voltage P The inventor of the Ionophone simply d.c. heating required a power in the Fig. 2- Idealized cross -section of the C the modulated his high- frequency field at speaker. P is the platinum wire, in quartz cylinder, V ithe vacuum space in audio frequencies. The temperature the horn walls and A the outer shield. the vicinity of the emitter was varied in proportion to the low frequency. the This takes us back to Edison's original is the axis of the emitter. Through that action of dielectric losses, the quartz Thermophone, with the exception wire reaches where Edison's heated wire was limited surrounding the platinum Iono- a temperature of 1,000 degrees within to the lower audio frequencies, the one or two minutes. phone reproduces with equal exactitude field which is established all frequencies within the audio range. The strong sound between the platinum wire and the (The old Thermophone produced shielding produces emissions by expansion and contraction of the air cylindrical which of which also produce heat in leaving the surrounding a heated wire, I I emitter, thereby assisting to maintain course had considerable thermal lag.) a high temperature. The heat is con- Each variation in temperature pro- because the vacuum chamber duces an expansion of air, followed by centrated a of the evacuated quartz horn prevents a contraction, thereby producing - 700V + - I5V its spread by conduction. Secondarily, sound wave. These sound waves spread enclosure prevents along the length of the exponential horn with the vacuum of this F'g. 1 -The developmental model, the passage of electrical charges through without friction and manifest their heater H, "cathode" C, grid G, and out- presence by sounds of the strength, er shield A at a high negative voltage. the material. Because of the concentrated effect of form, and frequency desired. not permit details of the order of 500 watts. A decisive step for- heat and the electrical discharge rich Space does in ultraviolet radiation, the emitter re- rather special circuits used for the ward was made when Klein gave up loud- heated cathode and con- leases a flow of ions. The high tempera- operation of this unconventional the indirectly to point out that while ceived the idea of a self -heating one. ture in the neighborhood rarefies the speaker, except it can be used with present types of That idea was developed in the form air ; consequently, the molecules are far a enough apart to enable the ions leaving radios, it also opens up the possibility of a cylinder of quartz into which either platinum wire was sealed along its axis. the cathode to follow a free course of having radio receivers without was then coated with an longer than they could in dense, cold audio amplification or detection -the The cylinder of the receiver ion -emitting substance, composed as air. It is nonetheless true that some intermediate frequency collision being sufficie:,t to operate the loud follows : air molecules are ionized by 50% with ions and electrons coming from the speaker. Precipitated platinum in a Aluminum phosphate 40% emitter. All these points will be covered Graphite 5 % In short, we have before us a kind succeeding article. Precipitated iridium 5% of capacitor whose plates are the coated -end- NOVEMBER, 1951

www.americanradiohistory.com .dgl Electronics ULTRASONICS AND THERAPY Medical application of ultrasonics -both in diag- specific heat depends on frequency). Ultrasonic waves are sound waves. nosis and for treatment -has made great strides, They are thus absorbed as well as reflected. Absorption depends upon the especially in Europe, as this article testifies. medium the wave travels in, and attenuation can run in the order of several decibels per meter wavelength. In CO. for instance, this value sometimes reaches 300 db per meter, which is extremely large. Transducer types Electrical energy is changed into ultrasonic energy by means of transducers. These act as matching devices and permit maximum transfer of energy to the medium, in addition to acting as a converter of one type of energy into another. There are two types of transducers, magnetostriction and piezo- electric. Magnetostriction transducers utilize the principle that a rod of iron or other magnetic material undergoes a change of length when magnetized. Piezo -electricity is based on the fact that if a slice is cut from a quartz crystal and pressures applied on the opposite faces of the slice, then these faces will develop equal and opposite electrical charges. This effect is also reversible : by placing the quartz in an electric field elastic deformations are developed in it. If the field is an alternating one of frequency f, the quartz will be subject to f oscillations along its electric axis. This principle is used in generating Part of the laboratories at the Institut Medical Bunge. Guinea pig, left, is wired up ultrasonic waves. A crystal which will for simultaneous notation of myograms, electro- encephalograms, and cardiograms. resonate at a desired frequency is chosen. One face of the crystal is fixed, and the other side, S, left free to By DR. F. VAN DEN BOSCH* vibrate when acted on by the electric field. If this face S is in contact with air, water, oil, or any other fluid, waves LTRASONIC waves are sound measuring the pressure in dynes per will be generated in the fluid. waves generated beyond the square centimeter and the velocity in The natural frequency of upper limit of human hearing. centimeters per second, Z would have vibration They are not electromagnetic one value for air and another for liq- of the crystal is determined by its di- waves like radio waves. Generation of uids. The units used are sometimes mension parallel to the direction of heat in tissues by using them is funda- referred to as "acoustical ohms." vibration. Using quartz, frequencies of mentally different from dielectric heat- In the study of transmission of acous- 5 X 10' c.p.s. may be attained, but if ing, for instance. Sound waves are a tic and ultrasonic energy, the charac- this is the fundamental frequency the special kind of elastic wave. They travel teristic impedances of the material or plate is only .055 millimeters thick and in media which have two properties: medium used is important. Reflection very fragile. Higher frequencies are inertia and elasticity. Sound waves in of sound waves is a function of reflect- attainable by using partial tones or air are longitudinal waves; they con- ing surface and wavelength. When harmonics, and this has the further sist of condensations and rarefactions ultrasonic energy is transmitted through advantage that a number of different of the air. two materials the influx of energy into frequencies may be obtained from the The characteristic field terms are the second medium will be smaller by same plate although the intensity is pressure, P, and particle velocity V. the amount that reflection is greater in less. If the surface of the crystal plate This gives rise to a kind of Ohms law of the first medium. is large compared with the thickness, Comparing mechanical energy to acoustics : = Z. the partial tones are very nearly V analogous electrical circuitry, mass re- harmonic. sistance in the mechanical system is Z is (in the case of plane waves) the The photos on page 48 show different characteristic impedance of the mate- analogous to an inductance. Ultrasonic sound energy can be measured by the practical forms of quartz transducers. rial and is equal to DV° where D is the The quartz transducer is in every case density and V° propagation sound radiation pressure, for which the veloc- the same, the only difference being ity. Z is a constant of the medium. By Lord Rayleigh calculated the formula the P = 1 /2RD; D represents energy den- special mounting on top of the quartz sity, P the measured for specialized applications. Generally Chief of Physical and Electronic Laboratories, radiation pres- Institut Medical Bunge, Berchem- Antwerp, Bel- sure, and R the ratio of the specific speaking, quartz transducers are water - gium. heat constants (the effective value of cooled when they have to dissipate a RADIO -ELECTRONICS for

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www.americanradiohistory.com 481 Electronics certain amount of power and are her- waves; the disintegration of polymer- be detected by ultrasonics based upon metically sealed so that they may be ized molecules and acceleration of pep - pure reflection phenomena. Kidney and used to treat cases under water or in tization (convert 'into colloidal solutions bladder stones are easily detectable, for immersion baths. If they use trans- and sols). In contrast to the dispersive their size is usually greater than gall- ducers in liquids, operators must take effect which the waves produce in the stones. Abnormal bone structures can precautions to protect their hands from casa of liquids or hydrosols is the coagu- also thus be mapped where the patient's the ultrasonic vibrations of the liquid. lative effect which they produce in the sensitivity to X -ray radiation makes Specially adapted thick rubber gloves case of aerosols (suspensions in gases). radiography impossible or inadvisable. are often used. Smoke is quickly coagulated into larger particles. These cannot remain in sus- Medical therapy Ultrasonic generator pension and drop out of the air. Medical ultrasonic therapy has been The oscillators which drive the trans- extensively used in recent years. Ultra- ducers are generally of relatively low Biological effects sonic therapy is as yet in its infancy, power compared to other industrial The biological actions of ultrasonic as the application is varied and results high- frequency generators. They range radiation are sometimes astonishing, are sometimes contested. Medical prac- from the 50 -watt type to about 1 kw witness the rupture of small organisms titioners should start ultrasonic ther- (output power). The circuit shown is such as protozoa, the tearing -off of the apy with small power so as to avoid simple to build, efficient in operation, gills of Triturus larvae, the complete injury. To avoid injury to the patient, and has the advantage of being self disintegration of Arbaciae eggs, and it is generally accepted that the thresh- rectifying, thus giving a pulse type of the killing of fish and frogs. Tobacco - old of pain indicates a maximum limit power which presents an advantage in mosaic virus can be inactivated and of power dosage. This should never be ultrasonic therapy. the virulence of certain bacteria dimin- exceeded. For deep therapy it is advis- The frequency is determined by the ished. These effects seem to be due to able to use the fundamental wavelength, tank circuit: the transducer parallels the immense pressure changes which while harmonics are more useful for Cl, the main tank capacitor. It may accompany the radiations. surface treatment. Since attenuation in be difficult to get stability of the oscil- In medical diagnostics ultrasonics un- tissues is rather large, intensity should lator as such. In this event, adjust the doubtedly will present certain unde- be proportional to the depth which it decoupling capacitor C2 between grids niable advantages. For example where is desired to attain, while the time will and cathodes. Coil RFC 1 is made by ordinary means fail, using ultrasonics be a function of the area to be treated. winding 16 turns of No. 22 gauge wire it i : easy to detect an empty or full or- Here are some successful cases using on a coil form 1% inches in diameter gan, such as the projection of the heart, ultrasonic therapy which have been re- and 2 inches long. RFC 2 is 14 turns spleen, liver, bladder, kidneys, and the ported, mainly in Germany and France. of No. 12 wire on same size coil form. stomach. G. Barth and F. Wachsmann (Medical The rest of the circuit is self- explana- By its nature ultrasonics allows the University Clinic Erlangen) have pub- tory. differentiation between a normal and lished in Strahlentherapie 78 (1948) abnormal organ. An enlarged liver some Ultrasonic uses can of their results which follow: be diagnosed as being an ordinary en- Neuralgia: Patients were neglected Among the reported chemical effects largement-or a tumor, for the tumor cases. No results had been obtained of ultrasonic vibration are: The trans- will present a different coefficient of through other methods. Good results formation of immiscible liquids such as absorption than the liver itself. Ultra- were obtained especially with sciatica, water and oil into homogeneous, stable sonics is probably most useful in this with a decrease in the pain noted. emulsions; the dispersion of metals type of field since the basis of medical Myalgia: After one to three treatments, during the process of electrolysis by therapy is correct diagnosis. pain subsides. bombarding the anode with ultrasonic Solid objects such as gallstones can Arthritis: Arthritis, especially of ar- ticulations, reacts favorably with ultrasonics. Infections : Abscess and maxilar em- pyema generally respond well to ultrasonic treatment. Prostates: Relief of individual pain. Carriers of Diphtheria microbe: Among 21 cases treated, only twa did not react; it was not possible to eject the microbes in vitro even with large intensities. Malignant Tumors: In the cases of small tumors these have disappeared, while in some cases they disappeared to re -form again later on. The authors cannot recommend the use of ultrasonics as a therai y, but they seem of the opinion that results justify further investigation and research. These results are confirmed by the Röntgenabteilung der Chirurgisches Universitätsklinik Würzburg. Ulcer therapy A. Stoltz of the Strahlenabteilung des Medische Klinik, Giessen (Strahlenther- apie 79- 1949;4.641) has experimented with ultrasonic therapy on gastric and duodenal ulcers. 93 persons, sufferers from ulcers (47 ulc. ventr. and 45 ulc. Four quartz transducer ultrasonic applicators. The vibrating quartz units duod.) have been treated. Without spe- in these are identical; their difference is due to the specialized mounts, cial diet or medical therapy, 89 cases which make them convenient to apply to different parts of the human body. felt total relief, after the sixth treat- RADIO -ELECTRONICS for

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ment. Weight increased and in all cases ultrasonic intensity. The effect is imme- the ulcers were cured by the end of diate as in the case of adrenaline in- the treatment. Frequent examinations jection. The only complication some- failed to find hemorrhages az a result times is dizziness. of the treatment. Only in 4 cases was These results have been confirmed by T'S a recurrence noted, and there the fail- A. Denier and H. Desgrez, and in Ger- ures have been explained by other many by W. Bunse and R. Muller of AUTO -RADIO causes. the Poloclinique Medicale Wirzburg. Ti RANSDUCER Conclusions from results TIME -l--.---. After looking at all the published 6µyf à T-I2 5 data on ultrasonic therapy one has to OR come to the conclusion TANK COIL o°L TW-I50(2) that efficient and lasting results are obtained RFC! only when RFC I full advantage is I taken of the peculiar I characteristics ultrasonics possess. For \200µpf example, Yes sir, summer and 10KV the cases of ulcers treated use fall are auto -radio the dispersional properties of ultrason- time. Thousands of ics to effect the cure. The same can be auto-radio sets to be said for asthmatical treatment. Expe- repaired. riments on animals have Millions to C2 borne out that be kept perking. And 40µµf ultrasonic therapy will be most bene- fast ... for car owners n ficial and meet real success if therapists are impatient folks. =" RFC 2 will base their treatments on the fun-

RFC I damental properties of ultrasonic en- It ergy, and if when starting, they always use the smallest possible intensities. OV/ IOA On the other hand there seems to be 2K an unlimited field of application in 20w diagnostics. Ultimately ultrasonics will 1/4 A 1/4 A contribute to what is bound to come 2.6KV 2.6KV one day. Complete 000 and rational elec- 44Q9 tronic diagnosis, wherein the site of /A. Aerovox every ailment will be correctly located Vibrator POWER and the ailment evaluated by appropri- Buffer LINE ate electronic apparatus. Capacitors, This kind of The schematic of the oscillator used to qualitative and quantitative analysis Type VBC, generate energy will give a faultless are for the transducer unit. and unmistakable especially diagnosis. From the pure physical and designed for electronic vibrator Treatment technique: The region angle there is not the slight- buffer marked est reason why this could not applications as by X -ray examination was be treated with vaseline (to insure achieved even today. It can be achieved well as coupling good fastest and many other contact) and a vigorous ultrasonic mas- by the fullest co- operation sage was given, each treatment lasting among members of the medical pro- circuits where high -qual- fession. ity tubulars are required. 10 minutes. The first six treatments were given daily, then -end- Your local Aerovox job- six treatments ber carries a complete every 2 or 3 days, finally 3 to 8 weekly line treatments after the disappearance of of VBC capacitors the Thunderstorm Recorder? plus a wide assortment of symptoms. During and before treat- auto - radio suppressors ment patients had to drink ry4 to 1 liter hot Thunderstorms are located both in and filters especially con- camomile tea. Britain and structed to These results have the U. S. by using withstand the been further con- networks of radar stations to determine high temperatures en- firmed by other workers such as Ebert countered in auto by triangulation the location of the -radio of the Innere abteilung Stadtkranken- storm. The present operation. Your local haus Wolfsburg. American network Aerovox jobber can fill covers an area with a diameter of 4,000 ALL your auto -radio ca- Asthma therapy miles in the Caribbean region. pacitor needs. The British Other interesting have now worked out a results are the method, however, which uses an auto- cases reported by P. Anstett of Lyon, matic recorder to pick France (Lyon up and compute Medical, 1948). signals received by a single radar. They The report deals with sixty cases of measure the asthma time interval between re- treated with ultrasonics, 29 ception of a wave from a lightning flash cases without complication (25 cases as it travels along the with bronchitis ground and an- and emphysema have other wave from the same flash as it also reacted ; favorably) 39 cases were bounces off the ionosphere high in the completely cured (observed during 10 sky. months) ; 13 cases improved to a point Signal Corps scientists at Fort Mon- of being negligible; 1 case slightly im- mouth, N. J., have analyzed similar proved ; and 1 case resisted treatment. experimental tests conducted for them FOR RADIO- ELECTRONIC The impression is gained that only the by University of Florida scientists spasmodical fraction is influenced and working under contract INDUSTRIAL APPLICATIONS with the Army. not the inflammatory fraction. How- and declare that the method is not AEROVOX CORPORATION ever, this has been improved sometimes feasible. Wave shapes from lightning NEW with BEDFORD, MASS., U. S. A. the injection of autovaccin. patterns were not clear enough, to accu- Export: 41 E. Treatment : 42nd St., New York, N. Y. technique 10 minutes ev- rately place the thunderstorms, but Cable Address, AEROCAP, N. Y. ery day, 12 treatments in all, both sides they used human calculation rather In of Canada: AEROVOX CANADA LTD. the sternum at the height of the than the automatic recorder developed Hamilton, Ont. ganglium stellatum. This treatment by the British. used the highest possible and bearable -end - RADIO- ELECTRONICS for

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BIRDS AND ULTRASONICS There has been much difference of opinion about the value of ultrasonic "scarecrows," though a number of attempts have been made to use ultra- sound to scare birds away from roosting places. The rather negative results of such attempts have led many to believe that ultrasonics is not the answer to the problem. Therefore, special interest attaches to the following letter, written by a Detroit radio engineer who is also interested in the work of the Audubon Society. It was addressed to Hugo Gernsback, in reply to a request for information on the successful experiments on bird- scaring, of which he had heard. "The martin -starling experiment we have been working on here in Detroit has been keeping us quite busy checking and re- checking data on the effects of the various frequencies used. THE Turner Television Booster Model TV -1 has been on the market for less than a year, but "Inasmuch as this was the sponta- already is making booster history. neous application Reports from fringe areas all of a theory, the equip- over the country are loud in their ment used was all standard praise of the consistently -oscillator, superior performance of the TV -1. Wher- amplifier, and speakers. No special ever boosters are compared the Turner TV -1 produces the sharpest, ec;uipntent was developed and therefore clearest picture ... the crisp, natural sound TV viewers seek. no special circuits were involved. The Turner's advanced electronic engineering, plus solid, quality last five years we have recorded on tape construction make the difference. The low- noise -level Cascode some 135 '..alf-hour reels of bird, animal, circuit stabilizes the picture, reduces noise and snow to a minimum, and insect sounds made throughout and produces an excellent picture under fringe area receiving Michigan, on the East Coast and in con- Canada. ditions that nullify the best efforts of many other boosters. Single knob continuous tuning permits fine "Our findings in this work contributed adjustment for best to the possible reception of both picture and sound. idea of using high frequencies Three position control in forcing the movement switch turns on TV set only, TV set and booster, shuts of concentra- or off both tions of birds from areas in which they set and -1 booster. The TV may also be used to amplify FM, mobile come to roost each night. These concen- and aviation radio signals. trations, or flockings, always precede The unit is quickly and easily installed. Attaches to any tele- actual migration. Two or more species vision set. Attractive styling and neutral finish harmonize with any may gang up in this flocking; therefore furniture design.Contact your Turner representative or write direct. the two above -named species of birds make up this particular flock of some List price $57.50 hundred thousand individuals. The mar- For the best possible TV reception, turn to tins particularly are of inestimable value as insect killers and are protected by Federal law throughout the land. THE Where they have become a nuisance, TURNER BOOSTER however, such as in great concentra- tions in the middle of residential sections, wholesale killing has been quite THE TURNER COMPANY, generally sanctioned by local authorities -thoughtlessly, of course, as they 933 17th Street, N.E. Cedar Rapids, Iowa might as well try to stop a hurricane or In Canada: Canodian Marconi Co., Toronto, Ont., and Branches flood or any other natural happening. Export: Ad. Auriema, Inc., 89 Broad Street, New York 4. "We have quite effectively proven that frequencies varied quite rapidly, learned from approximately 9,500 Technicians Have to 11,000 Over 43,000 cycles per second with substantial level MOWS as determined by distance involved, will GET THE MOST HOW TO . v..0 . :.N rtWN definitely keep the birds on the wing, EOUIP UT forcing them to go elsewhere. With stra- OF BASIC TEST tegically located Too? speakers in the usually Why Not You, small areas involved the entire flock could be discouraged from landing in SUBS TITUTION the area affected. These areas are usu- by SIGNAI 12TH EDITION) SERVICING UP TO DATE. ally thickly covered with old tall elms. 9 YEARS! (NEW. ELLER FOR OVER A BEST "We are desirous that Approach To Re- this informa- Dynamic Speed tion be made available wherever and to The Simple, Modern, Problems, AM-FM-TV and Alignment whomever it may be of practical inter- ceiver Adjustment Universal - non.obsolescent est, in the hope that the final to learn results Nothing compter Basic Test Equipment Employs Only 100 may save the lives of countless thou- to purchase pages. Invaluable No extra equipment information that will help sands of one of our most valuable Ask for ".5..5.5." at your local you re- double the value of species of birds. "-Ed. G. Boyes your basic test equipment. Radio Parts Jobber or order direct from factory. -end- PRECISION APPARATUS COMPANY. INC. 9227 Horace Harding Blvd Elmhurst 4, N Y RADIO -ELECTRONICS for

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www.americanradiohistory.com Audio Filter Facts And Faddle Filters are widely used in radio, video, and audio work. The author shows how to design many of the various types.

By JAMES R. LANGHAM

WE FIRST began fooling with mered down after awhile and wondered I dug into books then while the XYL filters 'way back when we what I should have wondered straight played records. I soon decided my books had just managed to get our away: "Do you suppose that could be weren't adequate so I called on a friend tuner's over -all response up a beat frequency between stations ?" (hah!) for help. This man was a high - past 10 kc -up into the range where the We didn't immediately jump into fil- fidelity fan who was also a physics 10 -kc beat -frequency squeals between ter design. We followed our usual (ex- major, and he handed me a book. broadcast stations were coming through cuse the expression) engineering tech- There's no question that it's a fine very well. nique. We first tried several sections of book but it surely wasn't for me. Lordy, For a long time I was sure I had resistor- capacitor tone control between I could barely count over ten without oscillation in the tuner-I don't know the tuner and amplifier; we added R -C taking off my socks -and this book . . . why an r.f. beat frequency didn't occur sections until the highs were sounding Around midnight the XYL peeked to me -and I had beat my head against muffled and the squeal still came over my shoulder on her way to bed. the wall for several evenings in a row through. Then I remember padding the "Hmmm," she yawned. "I didn't know trying to de- squeal that little t.r.f. I inside of the boom box (I still thought I you liked mathematics, dear." remember dashing into the bedroom, liked them then) and even suggesting "I find it extremely fascinating," I late one evening, to wake up the XYL that we use cotton upholstery padding snarled at her. and tell her the squeal had disappeared for grill cloth. It was the XYL who Her laugh was silvery and gay, so I and I hadn't done anything to it. I got us started. "Listen," she said. "Why added: "- especially with you playing also remember her remarks. She sim- don't you design a filter? I'll build it." Pictures At An Exhibition at a 34-db level." She trilled a merry goodnight in my T FILTER PI FILTER HALF SECTION direction and went in to bed, yawning CONSTANT . . o-- loudly and sighing luxuriously as she re- (m =1.0) Ro 2C 2C Ro Re C Re 2C 2L 2L 21. laxed. I ground my teeth, made more (BASIC TYPE) --- coffee and tried to think. I couldn't find o o the information for the mathematics, as %2L, %2 L, L the author had done a beautiful job of SHUNT TYPEm hiding it. I finally gave up that night Ro I some more. Ro 2L, but the next day tried 2C, : L: 2Ci 2C, I wasn't curious about how the formu- o o las were derived-I just wanted to 2C, 2C, 2C, know how to work it. After awhile I SERIES TYPE m o o-)1 tried other books, looking for answers. became bloodshot, the circles 2 Ro 21.2 2L2 Ro RD 2121 My eyes Ro RD underneath them became bags, and my 1/2C2T T %2C2 hC: T took on the tone of a slightly o 0 0 skin o soiled mushroom. Ro OHMS FORMULAS, Re LI 2 4L L2 The M business bothered me a great L 4fo m2 m L , L,,L2 HENRIES IOo deal because I couldn't find out what C, m C2 T2 2 4C C.C2.C2xf C 4>fo Ro it meant. I was very annoyed at myself for not learning how to apply the 1 -pass filters: T, Pi, Half sections. These can Fig. -Three classes of high I Nowhere be Constant -k, Shunt type no, or Series type m. Note formulas for their use. math didn't understand. could I find any explicit directions

T FILTER (a) PI FILTER (b) HALF SECTION (D) about filter design.

N Actually, the design of a simple low - CONSTANT DDD

(m =I.0) R L pass (or high -pass) filter is quite easy %L R R /L2 o (BASIC TYPE) -+ 2 T ° c I47 -now that I know how to do it. o ''2 2 T 0 L, Filter types r D88 SHUNT TYPE m The main classes of filters are: T, Ro Ro Ro 1 yi RO Pi, and half sections. There are others 2C, 2C, 2 2C, CI Val' -0 )/2C2T o o o 0 but they are mostly versions of these

L also con - 1/2L, L, r2 L, doubled or folded. There are SERIES TYPE m stant-k filters and m- derived filters: in the vo-derived category there are shunt Ro 2L2 Ro Ro 21.2 Ro ó L2 Ro 4-- and series types.

-' 1 2 1/2 C2 The T and Pi filters are called that 1/2C2T o C2 o Co o ~0 o because their configurations look like

Ra -m2 L the Latin letter T and the Greek letter R, =OHMS FORMULAS. L2= L = L,= mL ff fo m 2 4 3t. The half sections are also called =HENRIES 2 1.1.1.L2 104 C C, Ca . MC half -tees, half -Pi's, and ladders. C.C,,C2..f vfoRo Im T Constant-k filters are also called con- Fig. 2- Low -pass filters also fall into several classes. The math is very easy. stant z, basic type, and m =1 filters. RADIO -ELECTRONICS for

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www.americanradiohistory.com 561 Audio

type you're likely to need. It makes the 4 4 I ; f1iÌ best impedance match to any circuit I \ with a critical source impedance, and 4 4 /r A for this reason it is very often used 1 L A in two half sections, one at the input

35 i 3 end / i end and the other at the output / I.\ - of a complex, multi -element filter. / . % \N% 30 30 Those of you who have delved into r . \ .N. this stuff before might be confused as 44 r m 0.6-+ %-m0.6 m 0.8 m0.8 I was in the matter of impedance `- 25 5. 25 matching. Just from the name, I ,.. thought that a constant -k (which I 20 20 f W i think was called a constant -z in that 112. / :.._. particular book) would be better to 15 / 15 use for impedance matching. Not so. / m 1.0 CONSTAN N) 4- CONSTANT K m .0) / / Don't regard that name, constant -k, as / / : 10 : 10 having any more meaning than if it / 0 IOO(d0.01) 0=30(d=0.033) el... were called George or Terence. For im- ! m 0.6 m0.6 - - pedance matching, forget names and m 0.8 m0.8 5 - 5 % - m I.0(CONSTANTI) m 1.0 ( CONSTANT K) use the m - 0.6 filter. In the case that started me off, a 0 0 111 0.6 0 10 12 I4 1.6 1.8 20 0.6 08 1.0 12 1.4 1.6 1.1 2.0 single m =0.6 section is fine, but, as you FRE00ENCY RATIO f/foefc/f FREQUENCY RATIO = /ifs PTO can see by the curve, the attenuation simmers down once the peak is passed. Fig. 3- Characteristics of high and low Fig. 4 -Same conditions as Fig. 3, but There are many applications where the pass filter where Q Q is now 100. Note sharp cutoff points sections equals 30. attenuation must continue and in one of those cases an m =0.8 section is very They are fundamental to the evaluation lator, and I made some silly remarks fine: its peak is farther away and its of constants for the m- derived filters. about the XYL's fabrication which attenuation is higher except in the cut- The term m is best regarded as simply turned out to be very unwise after we off region. The basic constant -k type a dimensionless number that is used both checked the circuit constants on is also popular for providing attenua- in filter work. It can be defined as the the bridge. With the bad filter design, tion at an even greater distance from square root of the quantity one minus my headaches, and the XYL's remarks, cutoff. These three types are by far the square ratio of cutoff frequency I was having a pretty unhappy time all the most useful of all and you can do to peak- attenuation frequency, thus: around. nearly any filter job quite easily with combinations of these three. m =V1- c/fp)2. The Q's you are likely to encounter around the audio band range from 30 Combining them is quite practicable In simpler language, m is a mumber and it is common to use sections between zero to 100 for the coils and you can stop of and one; the closer to one m =0.8, m =0.6, and constant -k all in it is, the is worrying about the capacitors. Away sharper the attenuation the same filter with an m =0.6 section curve and the closer together are the up in the ridiculous frequencies where they have things like television, I am split so that half is used at either end cutoff and peak- attenuation frequencies. for impedance m- told conditions are likely to be opposite matching. The attenua- The derived filters are simply filters tions are in decibels and merely add using m in calculation of the capacity -the capacitor Q's are the worry items and the coils pretty much forgotten. arithmetically like apples and pigs. and inductance values. The values across the bottoms of All of these filters are in Down in the high -fidelity band, the critical re- Figs. 3 and 4 are frequency ratios that gard to impedances and resistances coil Q is the circuit Q and there's no nonsense about it. permit you to place the curves any- across either the input or the output. where you wish to in the band. All the If you want to use a particular filter Practical filters values are referred to the cutoff fre- on a 500 -ohm line, you must design it quency. for that particular impedance or it Fig. 1 shows high -pass filters and won't play. Fig. 2 illustrates the low -pass units. In each case, the formulas are right there Designing a filter Filters and Q too, and about the only item to worry Now let's do some. Let's assume we Now there were two major faults you is grade school arithmetic. want a filter to fit in a 500 -ohm speaker with all those books I struggled with Fig. 3 and 4 show the curves you line and attenuate a strong 10 -kc that time long ago: (1) Their con- will get from practical filters. In Fig. 3 whistle. In this case a single M =0.6 stants were all pure reactances without are the attenuation characteristics of section will do nicely. The cutoff is resistive components, which is to say a basic constant -k, an m =0.6 and an sharp and the peak attenuation comes that their Q's were infinite. I was m =0.8 filter with a Q of 30. Fig. 4 is at 1.25 times the cutoff frequency so we further confused in that the books did the same except that there the Q is 100. can set f= at 8 kc. A single section not mention Q explicitly either. They You can see a strong resemblance be- should be sufficient, and, because coils used another term, d, which they de- tween the two sets of curves but I'm are more expensive than capacitors, fined badly but which I later discovered sure you can also see quite a difference, we'll make it a shunt type Pi section, to be nothing more than 1 /Q. (2) The especially in the cutoff region for the Fig. 2, shunt type m, (b), which uses books had been written for people who m =0.6 filter. one inductor and three capacitors. study rather than people who just read; Now the m =0.6 filter is about the First we must calculate the L and C and one very important matter, the con- handiest and the most commonly used as of a constant -k filter because the m version between T, Pi, and half sections, was buried in a mass of mathematics. LI The filter I ended up with that time 11.93 NH 5.96511H 5.985RH was about an octave out of kilter. In- stead of attenuating the 10 -kc whistles, IgCt 5.304 NH 500A y'/KCt C y 500a 500A 500A it had a nominal cutoff of 20 kc. I say To238T .02122 .0238TT -r.04114 nominal because the difference between b TTYPE: m= 0.6 i f2.800 infinite Q and the Q of the filter made SERIES T TYPE for such a sloppy cutoff that I couldn't Fig. 5 -Shunt Pi low -pass filter design- Fig. 6- Characteristics of the series - find it on my 20 -to- 20,000 -cycle oscil- ed for m of 0.6 and for 8 -kc cutoff. T filter are similar to those of Fig. 5. RADIO -ELECTRONICS for

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www.americanradiohistory.com 581 Audio types are derived from these. Using tions. The sections are combined by ad- Specially low -pass formulas, see Fig. 2: ding the parallel capacitors into single Designed 500 units-this is just to save space and L = 0.01989 h or 19.89 mh expense. If we had formed -a X 8000 = our filter 10° of T sections we would combine them for d.07957 µf by adding the reactances of the pro- C a X 8000 X 500 - truding arms; inductances arithmeti- L, = 0.6 X 19.89 = 11.93 mh cally, L, L L, etc., and capaci- C, = 1 - 0.62 X 0.07957 = 0.0'2122 µf tances by using: 1 /CT = 1 /C, + 1 /C2. 0.6 4 Fig. 8 shows the over -all character- TV 1/2 C2 = 1/2 X 0.6X 0.07957 = 0.02387 if istic of our filter. The solid line is the The filter section is shown in Fig. 5 curve for using coils with Q's of 30, as a shunt type ni. Compare with Fig. 2, while the dotted line shows how the Technicians and you will see that the center part of attenuation is with Q's of 100.

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WELLEJI HALF SECTION FULL CONSTANT K HALF SECTION m =0.6 m49.8 SOLDERING m =0.6 GUN 5.965 NH 15.91 NH 5.965 NH 19.89 NH For ticklish 1'V soldering, there's no 500s. .04244 008951 .04244 SOlOn tool like the new 135 -watt Weller T0557 T01162 T06366 Gun. Dual spotlights eliminate ó (b) shadows. Precision balance Fig. 7- Design for a low -pass filter, (b) is combined from the elements of (a). assures accurate soldering. Long length reaches deep the Pi is really a simple tuned circuit There are other ways of designing s\\ \\ into chassis. 5- second resonant at 10 kc. The capacitors on filters. One of the more rigorous ways N N\\\ heating saves time each side true up the impedance match involves the consideration of various \ so that the complete section looks like resonances and antiresonances or (if and current. Your \ Weller Gun pays 500 ohms from either side. The trans- you'd like to keep in style) "poles" and for itself in a mission characteristic will be like the "zeroes." If you like doing things the solid line in either Fig. 3 or Fig. 4, de- hard way that's fine, but this method few months. pending on whether the Q of the 11.93 - will get your filters to come out as you millihenry coil is closer to 30 or to 100. want them and without any great strain. This particular filter configuration The design of filters isn't hard (as was selected because we preferred using you can see) but filter building is a cow Check This capacitors. If a chap likes to mess from another barn. You can buy almost Exclusive around with inductors, he could get any value of capacitor but the inductors exactly the same results for the series aren't quite so easy to come by. If you Combination type T section shown in Fig. 6. are poor you can wind them yourself. Suppose now that a single m = 0.6 Actually coil winding is,0't nearly so of Features section should not be sufficient. Suppose hard as you might think. You should you wanted about 60 db of attenuation have a bridge to check the reactances. from here on up. You could add an These can usually be borrowed. 5- SECOND HEATING m = 0.8 section and, to ensure imped- As I look back, I do believe a lot of -No waiting. Saves ance matching in and out, split the my filter headaches at first were caused power. m = 0.6 section into halves and use half by nothing more than awe for a lot of mathematics that were away beyond .. OVER on each side of the m = 0.8 section. /UNDER DESIGN -Tube construction me. There's no need for that. gives bracing action to tip, and improves visibility. The m = 0.8 constants are computed in exactly the same way as were those -end- DUAL SOLDERLITE Prefocused spotlights com- - for the M = 0.6 section: pletely eliminate shadows -let you see clearly. L,= 0.8X19.89 =15.91 mh 90 LONGER REACH -Slides easily into the most C, = i - 0.8k X 0.07957 complicated set -up. Reaches tight corners. 0.008951 µf 1 0.8 4 to COMPACT DESIGN -Streamlined and precision 1/2C2 = 1/2 X 0.8 X 0.07957 = 0.03183 µf balanced for delicate "pin- point" soldering. 0-i00-.0 Our values for the m = 0.6 section 10 TRIGGER -SWITCH CONTROL -Adjusts heat to are for a full section, and by referring the job. No need to unplug gun between jobs. to Fig. 2 type m, (c), we see that shunt 60 DUAL HEAT -Single heat 100 watts; dual heat we want to use 1/2L, and 2C, so we 0=30 100/135 watts; 120 volts, 60 cycles. Handles all double our reactances in the center of light -duty soldering. the Pi. This of course does not change 50 See new Model WD -135 of your dis- the resonant frequency. tributor, or write for bulletin direct. A combination of the m = 0.6 and the 40 SOLDERING GUIDE. Get your new copy of m = 0.8 sections provides a lot of at- "Soldering Tips " -revised, up -to -date tenuation close to cutoff, but, if we 30 and fully illustrated 20 -page booklet wish to maintain a full 60 -db blank

of practical soldering suggestions. from here on up, we must add still 20 Price 10c at your distributor, or another section. A constant -k filter will order direct. do nicely here and we already have 10 the values of L and C worked out so 0 =30-x; -0 =100 all we have to do to make a Pi section WELLER is halve the capacitance according 0 to 4.91e UAA, He 8.6114 11.211e 129Áe NM Ms ELECTRIC CORP. Fig. 2 constant -k, (C). FREQUENT 828 Packer Street, Easton, Pa. Fig. 7 shows the lineup of filter sec- Fig. 8- Curves of filter shown in Fig. 7 RADIO -ELECTRONICS for

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www.americanradiohistory.com 60 Electronics and Music

Part XVII -This and next month's article describe the Baldwin, an instrument of the all- electronic type.

By RICHARD H. DORF

Vibrato (frequency -modulation type) effects both manual and pedals and is adjustable. There are 25 stops and two couplers. The console is 52% inches wide a._d 29 inches deep. The Baldwin uses Model 10 is a newer and larger model, no moving parts to with additional stops and couplers and generate or color stop musical with pistons to select preset com- the tones. binations. It operates like Model 5. Baldwin has also introduced a new DELIBERATELY introducing dis- designed using the formant principle model which operates on the photoelec- tortion in an amplifier is con- discussed here two months ago. While tric principle. In this article we shall trary to most audio principles. no electronic or electrical organ per- discuss the Model 5. When the amplifier must trans- fectly duplicates a pipe organ, the Bald- mit music, distortion is especially un- win comes so close that most lay hearers General functioning desirable. However, when discrimina- are deceived. It is used in a 1p,rge num- The organ is an all- electronic device ting circuits are used in an instrument ber of churches. It is also used for with no moving parts except keys, ped- which generates musical tones, results serious recital work. Some prominent als, and stop tabs. It generates a series may justify altering the fidelity of the concert organists and conductors pre- of sawtooth- shaped waves which are amplifier. fer it to the run -of- the -mill pipe organ. passed through fixed filters to modify The Baldwin electronic organ, built Two Baldwin electronic models are them and reproduce various tone colors. by the Baldwin Piano Company, Cin- manufactured. Model 5, (photo left) is Fig. 1 is an over -all block diagram. cinnati, uses this principle ol tone varia- the smaller one. It has a standard The generator assembly generates tones. tion with filters to produce tone colora- AGO (American Guild of Organists) A vibrato oscillator modifies the tone tion almost like that of a true pipe or- console, with great pedal and swell man- frequencies at the vibrato rate when the gan. The filters in the Baldwin were uals and a 32 -note radial pedal clavier. vibrato switch is operated. The gen-

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www.americanradiohistory.com 62 ARMY -NAVY AIR FORCE- MARINES SERVICEMEN TECHNICIANS Here's Help!

Now IN 1$00 PAGES Fig. 2-This rear view of the Baldwin shows the bank of generator subchassis. THE BASIC KNOWLEDGE AND DATA OF erators operate continuously. When a balance with the manual tones, depend- key on the swell manual or pedal clavier ing on room acoustics, at the time of RADIO & TELEVISION is pressed, two gradual- contact switches installation. connect two tones to the busses for that The expression pedal operates a DIGESTED INTO 32 SECTIONS keyboard. On the swell, for example, if volume control which affects the entire . . . IN A COMPLETE, QUICK - the key for A -440 is pressed, a tone of instrument. The main -echo switch trans- TO -FIND, EASY -TO -READ A -440 is connected to the swell 8 -foot fers the output of the console to either HANDBOOK FORM. bus and a tone of A -880 is connected to or both of two power amplifiers located the swell 4 -foot bus. You can plan every operation in TV -Radio & Elec- at different places in the auditorium. tronics with the Library Set. These handbooks are your Each bus is connected in parallel to Tone cabinets containing power lifelong tools -use there every day on the board. at the ampli- bench, or in the field -for construction, production. servic- the input ends of a number of tone fil- fiers and speakers produce the music. ing, installation or operation -for adjusting, troubleshooting, measuring and testing. Your invaluable aid in service, ters. As shown in Fig. 1, for example, research. development, design. manufacturing and mainte- the swell 8 Tone generators nance. With all data & servicing procedures, these handy -foot bus goes to five filters, books work better, faster and easier. and the swell 4 -foot bus goes to three Fig. 2 shows In addition. you get complete coverage of everything the rear of the organ you need in TV, Radio & Electronics -in practical form filters. At the output of each filter is a with the wooden back removed. The everything presented in plain talk, all terms explained;- schematics, working diagrams and pietures all clearly stop switch. It is normally open, but metal frame holds 13 subchassis, the illustrated for your quick and easy reference. These books are works of complete authority prepared when closed it connects the output of first 12 of which are generators and the by the well known engineers, Joseph J. Roche and Morton its filter to the common bus to Scheraga, under the direction of William F. Boyce, famous leading last the power supply. Each generator for the preparation of hundreds of handbooks and manuals the mixer amplifier. Thus, to set up a chassis generates a single alphabetical for the U. S. Signal Corps, U. S. Navy, (T, S. Air Force. Western Electric ('o., General Electric Co., Bell Labora- certain combination of tone colors, the note of the scale, six notes similar in tories, National Radio Co. and many others. These Handbooks are endorsed by leading schools for player presses the required stop tabs, tone but an octave apart. The chassis, instruction and reference. The armed services make them connecting the outputs of in available to their technicians in libraries, schools, and the desired when place, are connected to the sys- in the field. Engineers. Draftsmen, Laboratory and Pro- filters to the amplifying system. The tem through bus bars and plugs. duction men in every Industry have purchased over 50,000 of these books for use in their work. pedal -balance switch adjusts the out- Fig. 3 is a schematic diagram of one 500 Radio jobbers keep them constantly in stock for the convenience of their service and industrial customers. puts of the pedal -tone filters for best generator chassis. The left triode of the These are the most commonly used books in Radio & TV. Whether you use these Handbooks for general reference, scientific instruction or education, one thing is certain; the practical help, the daily usefulness you will derive SIG. I from them will prove to be worth many times their price. 1.8K 1 47K Contents are too long & complete to describe here, so see the books at your Radio Jobber, your bookstore, or .Y 3- 6SNT- GT's MULTIPLE SEND FOR TEN DAY R PULSE TRANSFORMER FREE TRIAL EXAMINATION. +165V RADIO ç ELECTRONICS HANDBOOK $7.00 VIBRATO VOLTAGE VIDEO HANDBOOK 57.00 9K - SPECIAL OFFER! SAVE $2.00 15.115 or The LIBRARY - SET (both books) $12.00 65-350 ppt II II II J BOYCE -ROCHE BOOK CO. 270 K Caldwell 51, New Jersey send Library Set (2 books) @ $12.00 .05 01-0.15 Radio Electronics Handbook @ $7.00 .075 Video Handbook @ $7.00 In ten days I will send price plus postage, or I will return honks postpaid. RI (Offer good in U.S.A. and to men in Armed Services overseas only.) 4.7K 4.7K 4.7K 4.7K Natile 06-.08 0.24.7K 0.5-0.75 1 -1.5 +15V Address SIG.2 SIG.3 SIG.4 5I6.5 SIG.6 Employed by Save postage -we pay postage and packing if you send money NOW. Money back on same return privilege. Fig. 3 -One of the 12 generator chassis. An L -C master oscillator followed by five frequency dividing blocking oscillators cover the Baldwin's six octaves. RADIO -ELECTRONICS for

www.americanradiohistory.com 63

Did you know that Rauland's Replace- Did you know that Rauland offers Il ment Picture Tube Warranty and Ad- 23 valuable premium points for the prompt justment Policy provides a 6 months warranty return of warranty registration cards? Each from the date of purchase by the consumer? card returned promptly entitles dealer and And that all Rauland replacement tubes now distributor to premium points redeemable in carry a triple registration card providing pro- valuable merchandise prizes. tection for jobber, dealer and consumer?

Did you know that Rauland provides If you have not received full details on a full 120 -day price protection on dis- all of the above, write, phone or wire tributor inventory of replacement picture your distributing contact on Rauland tubes? That Rauland distributors can carry tubes. If you have not received your a stock adequate for their territories without prize merchandise catalog, use the cou- risk of loss through price adjustment? pon below today.

The Rauland Corporation THE RAULAND 4245 N. Knox Ave., Chicago 41, Illinois Please rush premium merchandise catalog and full information on CORPORATION Ei Earning Premium Prizes 6 Months Warranty D Distributor Price Protection Name Penfer-a- an- Tlrunt9 k, Rez.e..42A.C.A. Address 4245 N. KNOX AVE. CHICAGO 41, ILLINOIS City State L NOV EM BER, 1951

www.americanradiohistory.com 64 Audio

COMMON CORE

5 DIVIDER TRANSFORMERS

Fig. 4 -The multiple pulse transformer construction is well shown in this view.

left 6SN7 -GT is a self -controlled, grid - grid winding of the top oscillator is tuned, L -C oscillator tuned to one note grounded through the vibrato oscillator of the octave between 1,108.7 and 2,- grid circuit. The vibrato oscillator, lo- 093.0 cycles. Oscillation is caused by cated on the power -supply chassis, fur- positive signal feedback from plate to nishes a signal at about 7 cycles, which grid through the transformer, which serves to vary the top -oscillator bias at has a turns ratio of 6:1. The trimmer the same rate. Since the bias affects the across the grid winding is used for frequency, there is a small frequency tuning. The output of this oscillat r, change at the vibrato rate. signal 1, furnishes the top -octave tone The five frequency dividers which for the instrument. It is taken from the follow the top oscillator are identical in voltage divider R to furnish a correct principle, all being blocking oscillators. load impedance for the oscillator snd a Like the top oscillator, each is a tuned - good source impedance for the follow- grid oscillating circuit. It has no tun - ing keying circuits. ing capacitor, however, and its natural R2 passes part of the oscillator signal resonant frequency, dependent on dis- to the plate of the first frequency di- tributed capacitance of the transformer vider and also provides plate voltage for windings, is around 100 kc. It has a the top oscillator. The low side of the high L -C ratio and a very high. grid -

UDIO VOLTS AT PLATE OF leak resistance R1. (Values for R1 and TOP OCTAVE OSCILLATOR the unmarked capacitor are carefully

R.F. PULSE VOLTAGE AT GRIS_J adjusted at the factory.) OF FIRST BLOCKING The plus 15 volts applied to the di- OSCILLATOR vider cathodes biases them so that they R.F. PULSE VOLTAGE AT will not normally oscillate. The first PLATE OF FIRST BLOCKING OSCILLATOR wave transmitted through R2 to the first blocking oscillator supplies enough SIGNAL NO. 2 MOST OUTPUT VOLTAGE extra voltage to start the divider os- Fig. 5- Waveshapes at various points. cillating at its high resonant frequency.

POWERFUL B+ T0 OFF TONE COLOR I o 5Y3-GT +260 V BOX MED. COMBINATION Q(9 r R2 R7 'FULL 5.6K 2K Pp for R3 II° IBOK C2 C3 LT 10K C5 6SN7-GT o R4 80 2 R9 SINGLE 5K 5 1K C6 0.15 o

CHANNEL I 5.6K

1 VI V2 L 6 R8 RECEPTION 0.15 270K TONE COLOR BOX .5

GND T 4.7 K 6,3V TO TONE C8 COLOR BOX T2 T o 17V VIBRATO AC bI VOLTAGE I- o o VIE-Et t15 V +165V 619.7 (C) TO DIVIDER TEST 2 PLUG THE LaPOINTE-PLASCOMOLD CORPORATION TO GENERATORS j Windsor Locks, Conn. Fig. 6-The power supply also contains bottom C and the vibrato oscillator. RADIO- ELECTRONICS for

www.americanradiohistory.com 65

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NOVEMBER. 1951

www.americanradiohistory.com Within a single cycle of this oscillation, however, the grid draws so much current through the high -value grid leak that the triode is biased beyond cutoff, and it stops oscillating. The resulting charge on Cl discharges relatively slowly through Rl until the bias becomes less than cutoff value. Then another wave from the top oscillator starts the cycle over. The number of waves from the top oscillator between successive discharges of Cl depends on the time constant of Rl and Cl -C2. Because the Baldwin uses frequency division, the first divider discharges its capacitance once for every two cycles of the top oscillator. The charge and discharge is in the form of the characteristic sawtooth, which is the waveform appearing across Cl -C2. The two capacitors are used as a voltage divider, with the output signal voltage taken from the junction. The output, signal 2, is 1 /10 of the voltage appearing across the combination and is at a frequency just half that of the top oscillator. The five divider transformers are all wound on a common core, as can be seen in Fig. 4. Thus, while there is no electrical connection between the dividers, the top- octave signal fed through R2 into the multiple transformer affects them all in the same way. Each divider must, of course, lock at some submul- tiple of the top octave. Fig. 5 shows simultaneous wave - shapes at various points in the generator circuits. The output of the top - A satisfied customer -the keystone of any successful business! octave oscillator is not very complex, You endanger customer good will when you use "just -as- good" but this is unimportant for the later tone -shaping circuits because the funda- replacement parts on your repair jobs. Use quality OHMITE mentals are so high that most of the components -known the world over for dependability among higher -order harmonics would be inau- servicemen, amateurs, and design engineers -and you can be sure dible anyway. The waveform at the plate of the first blocking oscillator of customer satisfaction every time. It's just good business! shows the effect of the synchronizing OHMITE MANUFACTURING COMPANY waves supplied from the top oscillator -large pulses of high- frequency oscil- 4895 Flournoy St., Chicago 44, III. lation. The grid waveform of the blocking oscillator shows the resulting pulse of grid voltage caused by the grid current, followed by the gradual fall of Ve R4t coia voltage as the capacitance discharges. The signal 2 output voltage taken from WAITE, the capacitive voltage divider is a simple RHEOSTATS RESISTORS TAP SWITCHES sawtooth because of the capacitors' filtering action. The schematic of Fig. 3 shows for several components a range of values rather than a single one. Components so marked are dependent for their values on the particular note to be generated by the chassis in which they are placed. Power supply The power supply diagrammed in Fig. 6 also holds the vibrato oscillator WZrete and an extra tone generator for the FOR lowest C of the instrument. The primary of the power trans- STOCK former is provided with three taps, one CATALOG of which is selected in accordance with the average a.c. line voltage in the location. The d.c. power is supplied by the 5Y3 -GT rectifier and a filter consisting of choke L and capacitors C2 and C3. The filtered 260 -volt line is fed to tubes RADIO -ELECTRONICS for

www.americanradiohistory.com fil

Easy- acting, q u i c k l y locked swivel permits simple adjustment for the best reception.

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three -way bracket mounting 7e-a-aq k listed at just $4.95. For the single bay array, the ENTERPRISES, INCORPORATED suggested list price BOX 332E, HENDERSON, KENTUCKY $ 14.95.

TRADEMARK

NOVEMBER, 1951

www.americanradiohistory.com 68 Audio in the tonecolor box, where there are additional filter sections. Resistors R2, R4, and R5 form a voltage divider to supply plate and cathode voltages to the generator chassis. The B -plus, 165 volts, comes from the junction of R2 -R4, and the cathode voltage comes from R4 -R5. The ratio of 11:1 between the plate and cathode voltages must be maintained exactly to keep the oscillators dividing correctly. C5 provides additional filtering for these two voltages. C4 provides still more cathode filtering. There are three different filament windings on the power transformer. The first is a 5 -volt winding for the 5Y3 -GT. The next supplies 6.3 -volt power for the 37 tubes (see next para- graph) in the generator assembly. The center -tap of that one is connected to the plus -15-volt line so that the cathodes and heaters of the divider tubes are at the same potential and heater - Here is a fine instrument you can always depend upon for cathode leakage is minimized. The last furnishes power for the tubes in the engineering service or laboratory use. Its tuned fundamental tone color box. The center -tap is con- frequency circuit provides a permanently locked calibration. nected to plus 15 volts to minimize Just look at these specifications: hum, and R10 -C1 filters the connection so that no signal from the generators FULL RANGE -Sine wave, 20 cycles single selector switch. is transferred to the tone-color tubes. to 200 KC with continuously vari- OUTPUT POWER -500 milliwatts. The left section of the 6SN7 -GT Vl (Fig. is the able frequency selection. Improved OUTPUT CONTROL- Continuously 6), blocking oscillator for the lowest C of the instrument. Each logarithmic calibration means no variable from zero to maximum. tone -generator chassis has three tubes crowding at either end of dial. Four WAVEFORM -Less than 5% Har- and can put out only six tones, one for decade ranges provide over 33 monic Distortion at all frequencies each octave of the organ. The C series inches of linear calibration. between 30 and 15,000 cycles. must have an additional note (there are ACCURACY- Frequency calibration FREQUENCY CHARACTERISTIC-Plus 7 C's in six octaves), so that each man- accurate to within 3% or 1 cycle. or minus 1 db between 30 and ual will go from C to C. The divider is Complete stability is accomplished 15,000 cycles. identical to the others except that it receives synchronizing signals from the with a constant waveform -even at Hum LEVEL -Down more than 60 plate of the lowest C on the C chassis the extreme ends of the range. db of maximum power output. through a 180,000 -ohm resistor rather Spurious "beats" or signals are im- VOLTAGE -For 105/120 volts, 50/ than through the coupling of a common possible in the output. 60 cycles AC; 60 watts. transformer core. The output tone is OUTPUT IMPEDANCE-Five values: DIMENSIONS -13" wide, 91/2" high, obtained as in the other dividers. 10, 250, 500, or 5,000 ohms im- 95/e" deep. Net weight, 26 lbs. V2 is the vibrato oscillator. The pedance as well as additional re- Furnished complete with all tubes. feedback circuit includes the trans- sistive range, all controlled by a Model 655. Users' Net Price, $135.00 former T, C6, and R8 and R9. The vibrato frequency is largely controlled by the inductance of T and the combined capacitance of C7 and C8. C8 is selected at the factory as a final frequency adjustment, to fix vibrato rate. The grids of all the oscillators are grounded through the grid winding of MODEL CRO -2 MODEL TVG -2 . ' the vibrato transformer. OSCILLOSCOPE GENERATOR The depth (amount of frequency swing) of the vibrato and the on -off control are combined in a 3- 5 -inch oscilloscope having a vertical Sweep Oscillator in three ranges position switch in the tone -color box (see sensitivity of .018 RMS v.p.i. and from 2 Mc thru 216 Mc, all on fun- Fig. 6). With the switch in the off band width flat within 1.5 damentals. Reversible sweep direc- position, db from the vibrato oscillator plate is discon- 20 cycles thru 4.5 Mc. Linear saw - tion. Sweep width variable .1 Mc nected from the power supply. In the 18 Mc. Marker 4 Mc tooth sweep oscillator 20 cycles thru thru covers center or medium position, plate cur- 50 KC per second in 5 steps. A stand- thru 216 Mc. Crystal Oscillator to rent passes through R7 and other ard voltage provided for determining use as Marker or Calibrator. Video components, to from external source for the plate of Vi. At the unknown Peak to Peak potentials of Modulation same time the second portion of video signal for check, the all waveforms. Has reversible ver- using actual switch shunts the plate of V2 with for use with Audio Oscillator to tical polarity and return trace blank- or 5,600 ohms and 0.15 µf to lower the ing. produce bars for linearity checks. frequency somewhat to correspond with the lowered amplitude. In the full position, the 5,600 -ohm series resistor is bypassed and there is no shunt. R7 is a J AC SON ELECTRICAL INSTRUMENT CO. permanent current -limiting resistor selected at the factory to limit the rrvice Engineered" In Canada: DAYTON 2 OHIO maximum vibrato amplitude. Test Equipment r The Canadian Marconi Co. (continued next month) RADIO -ELECTRONICS for

www.americanradiohistory.com 69

RCA engineers. New portable radiotelephone, of less weight but longer range, designed and built by

¿o,79er rai9e, é/,L 4%7'ec wei#f- - /e "'Tke -a/on9 Rad,b,m4 one" You've read how useful our Armed weighing only 29 pounds. Its range is Forces found their portable radio- double that of the World War II model. telephones. Now this indispensable in- Even more important, under present condi- beat the most optimistic even more efficient. tions, RCA was able to strument has become estimate of the time needed to design such an At the Signal Corps' request, RCA engi- instrument by nearly three months. Signal neers undertook to streamline the older, Corps engineers have called this "A major heavier model -which many a soldier of engineering and production achievement." World War II called "the backie- breakie." Following principles of sub -miniaturization See the latest wonders of radio, television, and -pioneered at RCA Laboratories -every one electronics at RCA Exhibition Hall, 36 West Comparison with the older model of its hundreds of parts was redesigned. 49th St., New York. Admission is free. Radio portable radiotelephone shows how Models were built, tested, rebuilt, and Corporation of America, RCA Building, Radio RCA engineers have reduced its size finally RCA came up with an instrument City, New York 20, N. Y. with their new instrument. RAO /O CORPORATION of AMER /CA oft .k/or/d Leader if? Radio - /first in 7 /evision Vvir NOVEMBER. 1961

www.americanradiohistory.com 70 Aiidili Audio Feedback Design

Part XIII- "Fifty to Five Hundred" -the story of an amplifier which should solve By many of the public- address man's problems GEORGE FLETCHER COOPER

HIS is the last article of this series watt supply, and loads down to 5 ohms This sort of installation is ideal for on audio feedback design. Unlike to a 500 -watt supply. If 10 -watt speak- the ordinary public- address operator, the poet, I propose to end, not with ers are used, each is bridged across the because with 500 watts of amplifier T a whimper but a bang. The topic line, with a transformer giving a pri- power he either can use it all at the one of feedback amplifier design is by no mary impedance of 250 ohms. big show -the county fair, say-or he means exhausted, even though the The power supply engineer provides a can put in 200 watts for one job, 100 reader and the author may be, and I low- impedance source, then monitors the watts for another, 50 watts in some hope to discuss in some separate ar- output so that the voltage does not vary small hall, and still hold one unit in ticles some special topics which do not more than about 5% as the. load is reserve. The equipment load factor can fit into the framework of this series. To changed. We shall use negative feed- be kept high, and he never has to use a finish up the series, however, I propose back to keep the audio level from vary- big amplifier for a small job, where tube to describe an amplifier which has been ing more than about 20% as the load wear would eat away his profit. designed to act as a general -purpose changes from one loudspeaker to the public- address unit. This is not an am- maximum system load. A "see -saw" circuit plifier for the home, at least not for my Perhaps it is time to explain the title The amplifier circuit is a very simple idea of a home; it was designed for use of this particular article. Recently I have one, consisting merely of a see -saw in a sound -distribution network, feeding had to design a number of public- address phase splitter driving a class -B push - from 5 to 50 loudspeakers in parallel. systems, of different sizes. Like most pull output stage. In consequence, the The particular merit 01 the design is ingenious engineers, I am a lazy man, grid input voltage is high, by the usual its flexibility. and I decided to design one basic am- standards of power amplifiers (we need For public address work in which a plifier which could be used as a standard 15 volts to drive the amplifiers to full number of loudspeakers are to be driven brick in building up any size of public - power.) This is only a few milliwatts, from a common audio line we are in address system. The standard unit however, and is easily obtained from a rather the same position as the power which fitted into the scheme best turned normal 3 -stage microphone amplifier. engineer who provides 60 -cycle supply out to be a 100 -watt amplifier, using The voltage deliberately was made high at a number of outlets, to drive the four tubes in the output stage. When so that the long connections used in radio and the lamps, the vacuum cleaner operated with only two tubes it is a paralleling amplifiers would not pick and the electric heater. He provides us 50 -watt amplifier, the power consump- up serious amounts of hum and noise. with a fixed voltage from a low -im- tion is halved, and the two tubes which Class B has been getting a bad press pedance source, so that the level at one are taken out are not wearing out. lately, and I have read quite a lot about outlet does not depend on the load at When more power is needed, several notch effect. This is the small step at another. The nominal level of the 60- amplifiers can be connected in parallel the crossover point where both sides of cycle supply is 117 volts r.m.s. In dis- without any more precaut :on than the the push -pull circuit seem to be cut off. tributing speech and music to a number obvious check of keeping the polarities With a bad transformer all sorts of of outlets it is very convenient to follow the same. So far only five have been run curious effects can occur in the gap, and this example, but to use 50 volts r.m.s. in parallel, but there are very few jobs if the transformer is included in the as the nominal level. Loads of down to for which more than 500 watts of audio feedback path, trouble is in store for the 50 ohms then can be connected to a 50- is needed. designer. A good transformer, which 12AT7 EL34 must be symmetrical, seems to prevent 4 -42V (4) 425V. (AT FULL LOAD) all this sort of trouble, and in this amplifier, at any rate, the waveform looks perfectly good until the level is high 22K 10K enough for the peaks to start limiting. 470 K 22 I can get the notch effect by using the wrong bias, but so long as I use the values given by the tube maker I have no trouble. Anyone who is suspicious about this might ponder on the number of AM broadcast. transmitters which 50V use high -power class B modulators. They do this in Europe, too, where state broadcasting means that low distortion is demanded with all the vigor that any taxpayer puts behind what he considers his rights. The output tube, which is the key to the amplifier design, is a European type, the Dutch Philips EL34. There

22 just doesn't seem to be any other tube M. which will do all that this excellent tube 2.2K will do. It is a 6.3 -volt indirectly heated Fig. 1-The amplifier schematic. Feedback is from a special output winding. tube, on an octal base, with a transcon- RADIO- ELECTRONICS for

www.americanradiohistory.com 71

NEW PARACON ANTENNA COMBINES PARABOLIC & CONICAL PRINCIPLES Solves 9 out of 10 Installation Sight Problems-Challenges Comparison Sells It Two best features are incorporated into one BEST antenna. The After all, people praiseworthy features conical type aerials possess for supplying full buy TV sets to en- audio and full video bandwidth reception are used with a parabolic joy the picture. It design that gives the Para -Con a concentration of signals. Para -Con .just makes sense is engineered to concentrate the maximum wave energy on the that the antenna antenna by providing all- around, unmatched performance ... perfect bringing in the picture clarity ... long customer satisfaction. best picture brings in the best entertainment and the most customer satisfaction. Hook a Para -Con onto any set and you'll agree -it sells on sight.

Any TV Set Performs One Antenna Covers All Channels Better With a The Para -Con antenna reaches out and grasps all channels. The Para -Con Antenna Ward Para -Con has an excep- Every set performs better tionally low standing wave ratio when conditions are better. In- combined with a spectacular high stall Para -Con when older sets gain advantage on all channels. Ob 5, SINGLE BAY PAM-CON are starving for a stronger sig- so so nal. Install a Para -Con when any set is being drowned in a 35 30 sea of local interference. In the 25 majority of set installations, Para -Con makes both old and 1.0 I new sets perform at their peak. To be on the safe side every time, install the sensationally Db x, performing new Para -Con antenna and forestall TV troubles at both the reception and the ss 160 :: To service end. {o The First In TV Use Parabolic Principle

35 10 Parabolic antennas have long been used in special applications for Proved in Thousands 15 concentrating weak signals onto driven elements. The brilliant .+.c ,.e , . 1ee roo I . , N 302 :oe , o ae results of Ward Para -Con are now setting new performance standards on all channels and in most every area. Ward's Para -Con Of Installations Antenna is different. It's new. Now it is possible for one antenna No Ghost Hunts to meet and solve many of the local problems of installation and Spectacular success has been No more skeletons in your reception. achieved in practically every in- customer's TV closets. Scientif- stallation. Even in locations far ically determined direct imped- Ideal For All Band removed and in difficult terrain ance matching characteristics Fringe Areas where other more elaborate eliminate many ghosts. Para - arrays were tried and failed, Con's revolutionary design In fringe areas where selection PARA -CON aerials not only transfers the maximum power of a number of channels is avail- bring in brighter, clearer pic- from the antenna to the receiver able, Ward's stacked Para -Con tures but seize and channel in with a minimum of reflections. models provide the ideal com- stations where dependable recep- promise antenna for maximum tion has not been possible with results on all bands. Stacked in an ordinary antenna. Ward's Profit -Wise Dealers either two or four bay arrays, new PARA -CON Antenna has Diagramatic ske ch showing how the Parabolic design reflectors parabolic reflectors gather in and been field tested in thousands of Prefer Para -Con* reach out, gather and concen- concentrate energy on conical installations ... proved far and trate maximum energy on the elements. away better. The antenna is one of the most antenna elements. important end critical components of a TV receiver. Nearly Singles Out The Stations 20% of all TV service calls result from faulty antennas. The gen- High Front to Back Ratio eral all- around, high perform- The new Para - ance of Ward's Para -Con an- Con design tenna gives customer satisfac- achieves an un- tion right from the initial instal- usual capacity lation. Expensive call -backs due PARA -CON to obtain sharp to antennas are slashed. Rug- and Conical Principles) directivity over gedly built for long lasting (Combining Parabolic all the television trouble -free service Para-Con spectrum. Para - withstands winds and weather. Con principles Easy to handle and quick to in- ANTENNAS afford greater stall ... saves time and expense. power and less See your distributor for THE WARD PRODUCTS CORPORATION, Division of The Gabriel Co. interfering noise Ward's answer to your antenna 1523 E. 45th Street, Cleveland 3, Ohio on each channel. problems. *Trade Mark IN CANADA: ATLAS RADIO CORP., LTD., TORONTO, ONT. NOVEMBER, 1951

www.americanradiohistory.com Audio zs 1 ductance of 10,000 µmhos and can be The output transformer run in class B with 0.5 megohm in the The design of the output transformer grid circuit. The full details are sup- is the first and most important stage in Elul] plied in the appendix. Four of these the detailed design of the amplifier, tubes give a rated power oitput of 116 once the framework of the amplifier is watts at 425 volts plate sr pply, and fixed. In designing this transformer for they can be driven by a single 12AT7. class B it is imperative Every to keep the other tube seems to need a low - inductances low and the balance be- impedance driver stage, or an extrava- tween the two sides good. Balanced gantly high plate voltage. To us who have to get American tubes in spite of import prohibitions and exchange regulations, it would seem to be simple indeed for an American to get EL34's. What sort of a performance will this amplifier give? Measured at 10 volts 26 output into a 25 -ohm load, the frequency response is flat within ±1 db from 20 to over 10,000 cycles. At 100 watts the distortion is less than 2% at frequencies between 300 and 1,000 cycles. It is not much more even at '75 cycles, but this is not important, because we do not expect high levels at extreme frequencies. a Negative feedback keeps the output impedance low, so that when the load 260 is disconnected the output line voltage rises less than 20%, which is hardly to be detected by a listener. The circuit diagram is shown in Fig. 1. The input tube a 12AT7 double PLATE PLATE triode, operates as a see -saw type phase -splitter. The first triode is a nor- +475ví mal amplifier, with 47,000 -ohm plate b load. Cathode bias is provided by a 2,000 -ohm cathode resistor together TURNS SIZE NO. TURNS SIZE NO. with 2,000 -ohm 65 18 65 18 the feedback resistor, 65 30 65 30 making 1,000 ohms in all. This tube 65 18 65 18 drives the lower half of the push -pull 300 24 300 24 stage directly. The second triode is a 300 24 300 24 unity gain amplifier with a large c amount of feedback from plate to grid, which gets its input through the first Fig. 2 -The output transformer design. 470,000 -ohm resistor. That, at least, is one way of looking at it. Another way direct -current polarization cannot be of thinking of the circuit is that the assumed, because we do not want to grid drive of the second tube is the dif- run into instability if a tube fails. We ference in the plate swings of the two can make use of our assumption that triodes, so that the center point of the we do not want high levels at low fre- two 470,000 -ohm resistors acts as the quencies, and in designing the trans- fulcrum of a see -saw. An exact balance' former I have allowed the rolloff at low of the plate swings is obtained by re- frequencies to begin at 125 cycles so ducing the left -hand 470,000 -ohm re- that the plate load is almost purely resistor slightly, and if you do want to sistive down to 300 cycles, while the balance the stage closely you can try response is 6 db down at 60 cycles. In something of the order of 5 megohms these circumstances the high- frequency in parallel with this resistor, or some response of the transformer alone is tens of kilohms in series with the right - good up to beyond 30 kc. The inductance hand resistor. The second triode drives is easily calculated: The optimum plate - the upper half o1 the push -pull stage. to -plate load for two tubes is 4,000 The plate -supply voltage, about 250 ohms, so that for 4 tubes it will be 2,000 volt- ohm- milliammeter that volts, for the twin triode is derived ohms. The inductance is 2,000.2m125= outsells all others combined. from the main high -voltage supply of 2.54 henries. With the core size 425 -475 volts by a potential d'vider and shown in Fig. 2, and an air gap of .040 decoupling capacitor. inch, ordinary 14 mil silicon steel lami- In the power stage all cathodes are nations, we need 1,200 turns to give an grounded. Plate stoppers of 22 ohms are inductance of 2.5 h. The exact core size mounted close to each tube, to kill any is not critical, of course, an any core parasitic oscillations which may other- of about the same size may be used. wise be produced in the wiring. Each Fig. 2 -a is a rough drawing of the core. push -pull pair has its own 800 -ohm The plate windings are put on as four common screen resistor, which is not de- separate windings of 300 turns each, coupled. The screen voltage comes two in each section of a twin former. straight from the high -voltage supply. They are cross- connected as shown in 260 Feedback is taken from a special wind- Fig. 2 -b. A layer of insulation, rated at ing on the output transformer. With 42 2,000 volts, is then applied. This can be volts bias on the output stage, a drive supplemented with an ordinary split of 29.5 volts r.m.s. is needed to give screen of copper foil. full output. Over the plate windings three addi- RADIO- ELECTRONICS for

www.americanradiohistory.com Audio 7:l tional windings are added on each half of the former. These are output, feedback, and output in that order. No. 18 AWG wire is used for the output wind- We CHALLENGE the performance ings, while 30 AWG is used for the any 12" speaker with a feedback winding. Each of these six of coils contain 65 turns. A series -parallel connection of the output windings and series feedback windings provide very close and balanced coupling between the output circuit and the feedback winding. The window cross -section appears in Fig. 2 -C. ROYAL EIGHT" Although this sort of amplifier is usually considered to be a 2 -stage cir- SAYS.PERMOFLUX'S MR. HY-FY cuit, which must be stable at low frequencies, it must not be forgotten that in one half of the push -pull This avero the signal reed m _ áMEP stage passes through three stages. Ade- xéie RVr low- frequency stability is ob- ( spouse quate curve of tained by choosing the coupling capaci- the rmoftex tors so that the response is flat to well P, below the 125 cycles used in the output prov e s . transformer design. I have used 0.1 µf, with which with the 100,000 -ohm grid resis- less size PQest SECOND peakers tors gives a characteristic frequency regard- below 16 cycles per second. This value -Fi Fans the country over of capacitance can be reduced to 0.05 uf Hi without danger, and could probably be have accepted this challenge -have reduced even more. asked their "soundman" for a demonstration -then, have installed a Permoflux Royal Eight" in their High- frequency problems own audio equipment. Now they possess a magnifi- At the high- frequency en,1 the decent speaker at a reasonable price which repro- sigi presented a lot of difficulties, main- duces sound with superior sensitivity and fidelity as ly because of the need for flexibility. An well as tonal qualities which YOU too will want to amplifier to work into a normal load is add to perfect the excellence of your own equipment. quite straightforward, but if you want to be able to remove the loarì or to at- Send for beautifully illustrated catalog No. J201 to tach a long capacitive cable with no address listed below for further information in- termination the problems of design be- cluding a full page devoted to correct baffling of come much more complicated. Separate Royal Eight" and other size speakers. responses must be plotted for each possible load condition, and any circuit change must be checked in at least Cheek These EXelusive features three different plots. To add to the diffi- Permoflux's exclusive slotted, treated cone culty a really good safety margin gives the following results which makes seemed to be desirable to meet the spe- their speaker comparable to any 12" speaker: cial conditions of parallel operation. Two shunt R -C circuits, one in each Soft -suspended cone and extra -large spider stage, and duplicated because of the provide extended low frequency response. push -pull operation, were found to give Deeper, curvilinear cone greatly extends satisfactory results. Across each half of high - frequency response. the transformer primary a .02 -uf capacitor (1,000 -volt d.c. wkg. paper tubu- High permeante yoke increases output. lar) is connected to prevent the load on watt voice coil. the output side affecting the high-fre- 8 ohm -10 quency response. The phase shift pro- Big speaker performance in a small frame duced by this capacitànce is brought allows smaller more economical baffle. hack to zero in the dangerous region -clean, re- Here's BIG SPEAKER performance above 25 kc by connecting 4C9-ohm but at a sen- sistors in series with each capacitor. brilliant, musical reproduction level. Your customers will ap- An additional pair of high-frequency sible price prove and buy. response control circuits across the in- PERMOF LUX terstage circuits of the amplifier, con- ROYAL EIGHT" WITH ORDER FROM YOUR LOCAL INDEPEND- sisting each of a 4,700 -ohm resistor in THE FAMOUS ENT PARTS JOBBERS BLUE CONE series with .002 uf, was found to be Hear the AMAZING ROYAL EIGHT" necessary. It would probably be suffi- SPEAKER demonstrated at the AUDIO cient to combine these into a single FAIR, November 1, 2, 3. Hotel New 10,000 -ohm resistor and .001 uf, leav- Yorker -Suite 640. ing out the ground point at the center. One disadvantage of the stabilizing 'MADE "PK system used must be noted. At high frequencies all the power can pass into the two 400 -ohm resistors across the transformer primary. Any attempt to measure the frequency response at full P E R M O F L U X C O R P O R A T I O N 5, CALIF. power will lead to a burn -out here, un- 49121(W. GRAND AVE., CHICAGO 39, ILL. 236 S. VERDUGO RD., GLENDALE less you use unreasonably large resis- Canadian Licensee . . . Campbell Mfg. Company, Toronto, Canada tors. I have used 5 -watt wire -wound re- NOVEMBER. 1951

www.americanradiohistory.com 14I

sistors, which do not even get warm under normal working conditions. The only other resistors with any power in Look close ...and SAVE! them are the 800 -ohm screen resistors, RECEIVING SPECIAL PURPOSE TV TUBES which should be 2 -watt types. The layout follow the Standard brands such as RCA, Sylvania, Tung -Sol, Ken -Rad, Notional Union, GE, Motorola, Hytron and physical can Philco. ALL TUBES BRAND NEW- INDIVIDUALLY BOXED. RMA. Guarantee. circuit diagram. The only precautions are keep and Buy 10 or more, deduct 5 %. Buy 100 or more, deduct 10 %. to the stages separate, to 19808/0 . 2.99 35L6GT .. .86 53 1.85 keep the plate stopper resistors in the RECEIVING TUBES 19.18 1.59 35W4 19T8 .... . 1.34 OZ4A .59 . . 1.85 . 574 . . .68 57 output stage the Do not for- 6AW6 6YGG . .84 .... .76 near tubes. 1A3 .85 6AXSGT . , 1.15 62YSG ,. 1.54 3523 .. 1.26 58 .99 1A4P 1.89 684G .... 1.50 7A4 .89 250105/0T 1.42 35Z4OT ' .. 1.05 70A70T 2.73 get that the output line must carry 2 1ASGT .87 685 2.24 7AS 2526G ... 1.89 3525 .57 70L7 1.95 1.08 258018 ... 146 .99 666G .. 1.54 766 .88 ... 1.49 amperes. 1A70T .98 6B7 1.21 767 251.601' . . .86 37 .59 756 1.4 0 1B3GT 1.02 668 1.46 768 .... 1.26 25W46T .. .88 38 1B4P 1.51 6846 .... .69 7AD7 2.24 25Y5 1.74 9/40 .79 77 .99 185/25 1.51 6847 .... 1.18 7AF7 .. .86 41 1.40 78 1.40 Important details 1.7C 1C5GT 1.09 6BC5 ... .86 7607 . . 1.54 2525GT'.. 42 1.40 80 .89 106 .74 6806 .... 1.35 7AH7 .. 1.09 43 1.09 81 3.38 is 27 The power supply unit required to 1C7G . .74 68E6 .... .82 784 .86 .29 45 .99 82 1.85 1D5GP .73 6BF6 ... 69 785 1.26 . . . 1.29 4523 1.26 83 1.85 provide 6.3 amp at 6.3 volts for the , . 328070 .76 1070 . .74 68G6G 1.79 768 .89 46 1.62 83V 2.24 1DSGT .75 6886 . .99 787 1.26 47 1.44 84/6Z4 .. 1.28 32L7GT 1.59 heaters, a plate supply of about 550 ma 1F4 .74 66.16 . . .78 788 1.26 5065 .96 85 .99 1F5G .74 68K8 .... 1.05 7C4 1.49 33 .98 5085 ... .96 117L /M7GT 1.48 load, to about 100 ma 1F6 .73 6BN6 . 1.32 7C5 34 SOCS ... .89 117N7GT . 1.48 at full dropping .89 35/51 1F7G .73 6BQBGT .. 1.44 7C6 1.19 1.54 50L6 ... .72 117P7ß7 . 1.48 1G4GT .74 6676 .... 1.05 7C7 1.26 35A4 .96 50X8 .. 1.54 117Z3 .88 at no input, with a smoothed voltage of 1G6GT .74 6BU6 .... 1.15 7E5/1201 1.21 3585 .... .99 50Y8GT .. 1.26 11724ßT' . 2.03 ,. 1H4G 1.04 6C4 .81 7E6 1.49 3505 .... .99 50Y7GT 1.40 117Z6GT . 1.54 425 volts at full load. In addition a 1H5GT .69 fiC5 .80 7E7 .99 1H6GT 1.59 6C6 1.05 7F7 1.01 smoothed grid supply of 42 volts is IJ6G .74 6C8G .... 1.55 1.79 SPECIAL PURPOSE TUBES 1L4 .74 8Ce6 ... .88 707/1232 1.33 AB -150 1.12 BCD6G ... 2.29 767 .. 2.75 SAP1 .. 3.25 808 4.69 needed. For the grid supply a ger- 1L4A .87 CBJ 5.85 58111 811 1.99 1LA6 1.12 808 1.54 7J7 1.48 CE -1 79 4.69 1LB4 1.12 6080 .... 1.94 7K7 ... 1.19 58P4 .. 813 7.95 manium, copper oxide, or selenium rec- 1.12 6E5 1.54 7L7 CEP -220 . 1.29 5CP1 .. 3.69 3.90 1LC5 1.29 CKSO7AX . 1.95 ILC6 1.12 6F5 .75 7N7 1.05 5021 ..19.95 5is° 2.95 tifier may be used, and it is a good idea 6F5GT .75 7Q7 CRP -72 . 49 SFP7 .. 6.95 826 .25 1LD5 1.12 .89 001290 8.95 6C21 ..15.50 828 11.50 1LE3 1.12 6F6 1.10 7n/ 1.04 EC -1 4.45 to take this and the heater supply from 11.65 1.12 6F6G .88 757 1.19 10Y .79 829 9.95 ILH4 1.12 6F6GT ... .88 7V7 1.19 F1236 ... 7.95 15E 1.09 8298 12.74 . The 1LN5 1.12 6F8G .... 1.94 7W7 1.19 GL -134 9.95 15R .69 8308 3.69 one transformer. grid -bias voltage .87 6G6G 1.32 7X7 HF100 ...11.95 18C .49 832 5.95 1N5GT .... 1.85 RK34 .... .59 24R 4.95 832A 12.50 can be used to operate a relay in the 1P5GT 1.25 7Y4 .89 RK72 .49 100TH 7.99 836 1Q5GT .74 6JS . .59 724 .84 .... 3.49 .74 6J5GT... 10Y VR90 .. 1.32 21.58 1.59 837 1,36 high-voltage supply transformer pri- 1R4 .59 .85 VR -105 .. 1.22 211 .48 838 2.45 1115 .82 616 1.09 1246 . .99 .74 617 .81 12A7 VR120 ... .69 217A 7.95 841 .44 so 154 1.52 VR -150 .. 1.09 217C 8.89 843 .39 mary, that you cannot get plate volt- 155 .79 6J7GT ... .81 12A8GT'. .86 1623 5.85 174 .83 6.580 .... 1.49 12AH7GT 1.85 ... 218 9.95 84S 4.49 age without bias. More trouble, 1827 . . . 6.95 1.44 849 true, 1T5GT .74 6KSGT ... .75 12AL5 .. 1.19 221A 28.75 .79 6K6GT ... .78 1 829 ... 6.95 2310 1.69 851 44.50 lU4 12AT6 .. 65 ... 7.95 but so is for new .78 6K7 .82 12477 .. 1832 2506 9.75 860 5.90 paying tubes if the lU5 1.09 1838 ...18.95 2536 12.95 864 1V .75 687G .99 12AU6 , 1.40 1V2 687GT ... .99 12AU7 .96 2A4S ... .84 254 12.95 865 1.15 bias supply fails. The bias must be ad- 688 1.48 2ÁP1 ... 8.95 264C 10.95 866A 1X26 .5 6 12ÁV6 .99 2622 4.44 2748 3.50 872A 243 1.49 688GT ... 1.48 12AV7 . 1.48 ... 2 39 justed to 42 volts with a resistor in the 2C21 ... 1.63 2764 .. 9.75 876 .27 2A4G .84 6L5G .... 1.45 12AW6 . . 1.59 .84 6L6 2.75 126X7 2C2 .45 282B .. 7.95 878 1.59 2A5 .99 .32 ..12.95 bias -rectifier circuit. The high voltage 2A6 .39 6L6GA 1.98 12846 .. 84 2C34 304TH 902P1 8.95 2C28 .. .44 304TL ..11.95 905 . 2.29 2A] .39 61.7 1.19 128A7 1.16 4.85 4.85 is supplied by a 550 -0- 550 -voit winding 364 .89 6L7G 1.19 128E6 .86 2C40 307A .. 913 .89 2043 19.95 3718 .. .93 918 1.39 345 1.55 BNBG .... 2.73 12887 . 1.17 2C51 2.95 393A .. 5.95 924 1.39 and a pair of 5Z3 rectifiers. It is a good 3A8GT 1.39 887 1.19 128N7 . 2.03 2 E22 1.95 417A .. 8.99 954 3LF4 1.85 6N7GT . . 1.19 12C8 89 .27 6P5GT ... 1.68 12F5GT 2J21A 9.50 446A .. 4.19 955 .38 idea to make it three 5Z3's, to keep the 3Q4 .89 1..26 2122 7.90 489 12.00 956 3Q5GT 1.02 12316 . .89 .38 .78 8Q7G .... .88 12J5GT 2128 ...17.95 471A 2.65 957 .39 system working through a failure. A 354 .79 2127 ...19.94 531 4.95 958A 3V4 .99 60767 .. .88 12K7GT . 1.54 .95 1.72 666G .... 1.28 1288 2J30 ...29.95 5326 7.95 959 1.21 5T4 1.32 .19 choke input filter, using a single 10 -µf . 2131 ...24.50 HY61S 966A .. 1.98 5U4G . . .65 667 .90 12K8G' 1.20 2.132 ...24.95 702A 2.49 CK1005 .48 5V4G . . 1.10 6R7GT 1.85 120767 .70 capacitor, provides sufficient smoothing, 5W4 .83 654 .81 12567 .77 ...26.50 7036 6.89 . .98 1.15 6570 1.94 12SA7GT 2332J334 ...47.50 704A 1616 1.85 5W4GT .77 705A 1.29 1619 and the regulation is such that the volt- . . .32 5X40 . .89 65867 1.32 125F5 .90 ...23.95 707A ..12.95 1624 1.38 5V3G . .47 6567 .68 125FSGT .99 125 SY3GT .47 65A7GT .68 125F7 .92 2:K28 ...29.50 7078 ..11.95 1625 .38 age at no load rises to 475 volts. 7086 .. 4.69 1626 5Y4G ... .75 8587Y , . 1.19 12SF7GT .92 229 ..21.50 .38 . . .74 713A 1629 5Z3G ... .89 6SC7 .99 125G7 . .89 2X2-879 .34 An additional continuity of service 5Z4 1.12 6507GT .. .97 12587 1.10 3024 . 1.99 714Y ..11.95 1630 .75 643 1.59 65F5 .. .98 125H7GT 1.10 3827 ... 3.49 7154 .. 6.95 1632 .75 precaution is the connection of a second 666 1.08 65F5GT .. .98 125J7 .7a 36P1 6.95 7158 .. 8.95 1633 .62 3C28 ... 9.50 715C 1639 647 1.04 65F7 . .99 125J7GT .78 ..18.95 1.55 12AT7 in parallel with the one shown. 648 1.10 6SG7 ... .99 1251(] .77 3C34 7.50 718ÁY ..48.50 1641 .95 3DP1 ... 4.45 71887 ..48.00 1642 .69 . . 6A8G . . 1.54 6587 .84 125K7GT .77 6SH7GT.. .84 125L7GT 3028 ... 4.75 71807 ..48.50 1851 1.69 When used as a 100 -watt amplifier 6A8GT .. 1.54 1.20 ...12.95 720EL 96 6517 . .76 125N7GT 1.49 3829 ..14.99 2050 .99 5.29 721A . 4.89 2./51 all be 6487 1.39 65J7GT . .76 12507 .68 3EP1 ... .. 1.22 tubes should in place, and the 6ACSGT 1.44 6587 . .90 1250767 .78 3ßP1 8012 1.25 6AC7 .. 1.21 65K7GT .. .90 12567 .. .89 30X2 ... 6.95 723A/B . -14.95 8020 load impedance should be 25 ohms. It is, 64076 2.24 65L7GT ,. 1.19 .82 4A -11 .. .39 725A . .. 7.49 FG-17 ... 2.95 .. 1.28 GT 14A4 1.19 4825 ... 7.69 BOO 1.69 FG-104 ..17.50 of course, quite in 6AF6G .59 9001 .... 1.39 order to work with AAG5 .86 6507 . . .7z 1447 1.03 4038 8016 ...19.15 803 2.40 9002 .... 1.39 6AG7 ... 1.59 65070T .. .72 14ÁF7 46P19 ... 4.45 higher load impedances, but you will not 6486 1.49 65R7 .. .86 1468 1.03 804 8.69 9003 .. . 1.39 4023 ... 7.65 Bos 2.55 9004 .... .75 6485 .. 1.49 65R7GT .. .86 1468 1.10 4827 100 6486 1.10 14C5 1.31 ....14.95 807 1.74 9006 .... .39 get watts, but only (50)1/R watts, .68 65V7 . .. 2.03 14C7 .99 6AL7GT 1.85 6T7G ....1.89 14E6 1.31 where R is the load impedance. If you 6AQ5 .72 14E7 1.31 Special on 5 Tube All American Kit 6ÁQ6 1.26 8Ú4GT 1.39 14F7 .89 50L6 35Z5 - 125A7 - 12SA7 - 123017 need only 50 watts, pull out two of the 66ß70T 1.68 BUS 14F8 1.09 - 64125 ... .67 6U70 1.44 1467 1.04 STANDARD BRANDS $3.70 EL34 tubes and one of the rectifiers, if .... .99 6V6 1.89 14J7 1.31 per kit 6655 Buy 10 Kits or more and save 5% 6457 .... 5.39 eVBG .88 14H7 1.05 you are using three. That is all. If you .72 6V6GT .86 1407 .99 666467 . .68 1467 1.02 6AUSGT .. need 200 1.59 6W6GT .84 1457 1.32 TV PICTURE TUBES watts, connect two amplifiers 6AU6 . . .76 6X4 74 14W7 1.27 .. in parallel, 6AVSGT 1.31 6X50 . .74 1474 1.19 Sheldon. Zetka and other Standard Brands after checking that they are 6ÁV6 ... .62 6X50T .74 19 .33 set to have the same gain. The load im- 14BP4 21.95 17HP4 24.95 LATEST 30 TUBE 630 TV 16HP4 23.95 19AP4A 31.95 pedance may then be 12.5 ohms. And so CHASSIS . Ready to Work. 16KP4 27.75 19EP4 32.95 on for higher powers. .. 16ßP4 29.95 Exceptionally 19DP4 39.50 It is with some regret that I come to Fine for Fringe 16LP4A 32.95 20CP4 32.95 Areas. All high 17BP4A 22.90 24AP4 65.50 the end of this series of articles. I have quality parts. All standard brand endeavored in this series to provide a tubes pretested Battery Operated sound fundamental background before shipment. TRACER for the RCA Licensed. SIGNAL KIT Complete With steel cabinet, speaker, 3 designer and constructor of feedback Takes all picture tubes, all other components, and easy - tubes from 16 "- 50.10110w instructions. circuits, without exceeding the rigid 24" round or rec- $9.45 (Less Batteries) tangular. Stand limit of mathematics set by the editor. and RMA Guar- antee. Free re- Automatic 3 -Speed RECORD CHANGER In sorting out my knowledge I myself placement on de- Special have learned quite a lot. I can only hope fective parts. - - Terrific - Complete with Webster or Milwaukee Plays 12, to, 7 loch records that the readers have found the series RCA 12" Speaker, Knobs & Hardware standard coil at 335,9, 45 or 78 RPM. Twist - tuner $127.50 (Less C.R.T.) Needle tip (included) for stand- of some value. Fed. Tax Paid. ard or micro- grooved records. Appendix. Available with DuMont Input Tuner Pick-up arm comes to rest -position after last record has Philips EL34 tube: Heater: 6.3 volts, 1.5 amps. $138.50 (Less C.R.T.) played. New and in original Fed. Tax Paid. factory cartons. a.c. or d.c. Class B operation, 2 tubes: List $47.50. Common screen resistor 800 ohms Chassis Mounting Bracket for Picture Tube Our Price $23.40 $4.95 Extra. 3 for ...565.00 Bias - 42 volts Grid drive 0 29.5 volts Terms: 20, cash with order, balance C.O.D. Prices F.O.B. N.Y. City warehouse. Min. order $5. (Allow for postage) Supply voltage 425 425 volts NOTE: Availability of merchandise subject to prior sale. Prices subject to change without notice. Optimum load 4,400 ohms Ip 2 x 20 2x 106 ma 212 197 2 x 2.4 2 x 28 ma 56 STEVE -EL ELECTRONICS CORP. Power 0 58 watts E Distortion - 4.5% Dept. -11, 65 READE ST., NEW YORK 7, N. Y. COrtlandt 7 -0086 * Free Catalog. -end - RADIO- ELECTRONICS for

www.americanradiohistory.com New Supreme 1951 TV Manual - Often - Needed Most INCLUDES ALL POPULAR SETS AMAZING BARGAIN OFFER The new 1951 TV manual has complete The new 1951 TV service manual is the 1951 service material on every popular television most remarkable value offered by Supreme _---- set of every important manufacturer. Here Publications in their 18 years of business. This is helpful, practical, factory -prepared data giant -size television servicing manual at only Teievision that will make servicing and adjustment easy $3, or the four TV volumes for previous years for you. This new giant manual, as well as for only $3 and $2 each, are amazing bargains S:rriciny Information the previous four volumes listed at left, has and defy competition. There is nothing else complete circuit diagrams, alignment facts, like them. Each manual is a virtual treatise on test patterns, response curves, service hints, practical television repairs. 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I am enclosing $ deposit. 1947194 su reute Publications 1941 ó Name: 19193940 á EACH Sold by all Leading Radio Jobbers Address: 1826 -1938 Manual. $2.50 NOVEMBER, I951

www.americanradiohistory.com 76 HERE'S THE POWER RESISTOR THAT NEEDS NO DE-RATING

IRC PWW's Carry Full Wattage in ANY Range!

What is the function of this type of resistor? To handle POWER! Power rating of many power resistors is derated sharply -as much as 75% -in the higher resistance values -to prevent voltage breakdown between winding turns and resultant turnouts. IRC PWW's need no derating because of resistance value! These rugged, full size power wire wounds carry full wattage rating -even in the highest stock resistance values- without failure. Ample core sizes produce larger heat -radiating surface areas and the special rough, dark coatings dissipate heat fast -so IRC PWW's operate at lower temperatures. Low temperature processing preserves fine wires and prevents turns of windings from shifting- reduces likelihood of hot spots and voltage breakdowns.

THERE JUST ISN'T A BETTER POWER WIRE WOUND FOR CONTINUOUS OPERATION AT FULL RATED POWER OR LONG, DEPENDABLE TROUBLE -FREE PERFORMANC

You can get fixed and adjustable IRC PWW's in a full range of power ratings, resistance values, sizes and terminal types ... adcatable to any rig or use. In adjustable types, contact is made by a metal band which can be positioned anywhere along the resistor. By using additional bands, various taps can be obtained For exacting, heavy -duty applications-high- - permitting the resistor to be used as a voltage voltage bleeders, bias supply, grid and fila- divider. Tolerances: Fixed types- standard tolerance ment- dropping resistors -leading technicians ± 5% for 50 ohms and over, ±10% below 50 ohms. and industrial users have specified IRC PWW'S Adjustable types- standard tolerance ±10 %. for more than 15 years.

www.americanradiohistory.com COMPARE IRC PWW's WITH ANY OTHER POWER RESISTOR

Feature by feature, IRC PWW's prove their superi- 5, Unusually Alloy Winding elongation,aly give balanced Hi g h -grade value, diameter, ority over ordinary resistors. PWW's Uniform, resistance and 9govern with uniform sspacing Here's why... rigid specifications are wound performance in every characteristic. ResistorRe elements and mechanically. and weights. to terminal electrically wire is secured tension, and -+-mormodllIM Special Rugged Steatite Heat -dissipating Winding Forms. exclusive dark, Cement steatite tubes have Carefully selected rough coatings Coatings. IRC'S superior mechanical (1) They are used for variations strength, withstand sudden can be processed 3 specific reasons: in temperature, are at lower tem impervious to moisture. harm the wire windings or cause them oes not provides a larger to shift. (2)r The area for faster rtoughssurface cement coatings heat radiation. do not trap (3) The porous corrode. moistureure which might cause windings

fitted with are re, ble PWW's t pressure. Adjustable constant button, IRC maintain Bands, or Ample size is essential open circuits for Cooler Operation. they specially spring couse Full Size PWW's full-size steel gspr to Because IRC able b°e cannot to fast heat dissipation. ale. un its, adjustable ° temp feature and at much lower critical components Bonds free also safeguards e oxidation of contact. the resistor, and which at point operatelong life for high resistance mounted nearby.

UNIQUE LUG -AND -LEAD DESIGN GIVES FLEXIBILITY IN MOUNTING An exclusive feature of IRC 10- and 20 -watt Power Wire Wound Resistors is the combination lug - and -lead terminal for flexibility in mounting. In tight space applications, lugs may be cut off without disturbing lead, and in other installations the leads may be removed. Leads are a full 13/1 " and all terminals are hot tin dipped for easy soldering.

INTERNATIONAL SEND TODAY RESISTANCE COMPANY

417 N. Broad St., Phila. 8, Pa.

Please send me full information on IRC Fixed and Adjustable Wire Wound Resistors,

NAME INTERNATIONAL COMPANY RESISTANCE COMPAN r 401 N. Broad Street, Philadelphia 8, Pa. ADDRESS

In Corrodo: International Resi.tonce Co., Ltd., Toronto, Licensee J. F. ARNDT e CO.. ADV. AGENCY

www.americanradiohistory.com Construction 78 _ Versatile Intercom Unit "Rings Up" Called Party

PORTABLE short -range carrier - By BOB WHITE current telephone system can be a useful thing to have. Two units were constructed using 0A4-G this principle. Each unit is plugged into 20-20µF 1619 a standard power outlet and is then 450V L I ready for operation without additional connecting wires. 5Y3-GT C3 When the power switch is turned on in one unit, an alarm is sounded in the L3 other. Telephone handsets are used and simultaneous operation of receivers and transmitters provides duplex operation. The warmup period for each telephone unit is less than one second because tubes with directly heated cathodes are used. Each unit uses five tubes in a circuit that includes an alarm, a power supply, a receiver, and a modulated transmitter built on a single chassis measuring 11 x 4% x 5 inches. Signalling A type 0A4 -G cold- cathode, gas -filled ON-OFF tube operates an alarm relay when a SWITCH carrier -current signal of a certain fre- SI quency is impressed across the series - HANDSET PLUGS resonant circuit including Cl and Ll. POWER CORD Ll was made from a standard 455 kc i.f. transformer; one of its coils was TELEPHONE removed for later use by careful heat- HANDSET ing to soften the wax. The trimmers provided with the transformer are The complete equipment is mounted on this easily transported chassis. Note shunted across especially construction the remaining coil to and mounting of the oscillation transformer L3. tune the series circuit. (See Fig. 1.) A sufficient voltage is developed across the coil (when a carrier -current 26 /60NÁ 5Y3 -GT 0A4 -G signal of the correct frequency is ap- DI y 6V/2A T 00.0 RELAY plied) to initiate a glow discharge [ 6 A 6.86 be- 6-1 2 MA tween the starter -anode and cathode 006 wg RECEPTACLE through the 100 -µµf coupling capacitor. 17v A The potentiometer Rl is adjusted to 1 provide an a.c. bias so that less r.f. volt- 117V -6000 OR LAMP age is required for conduction of the 80/I 0W SEE TEXT 6. DMEF tube. When the starter -anode ionizes 0.06 0. SPECIFICATIONS FOR PARTS NOT RATED the gas, conduction from the main anode CARBON PESISTORS -0.26 WATT MINIMUM EM Mul CAPACITORS -600 VOLTS MINIMUM to the cathode occurs and a current A X 0.6 /2.IA 20/26V PI CAPACIIORS-400 VOLTS MINIMUM A B flows through the relay coil. Fig. 1 -The alarm or ringing circuit and power supply appear in this diagram. Since the cathode is so much larger than the anode, a greater flow of electrons can take place toward the anode than toward the cathode with the impressed a.c. so that a rectified voltage is produced for the d.c. relay. The 0.2- PHONE n V µf capacitor shunting the relay coil eliminates relay chatter. The relay contacts can control an alarm bell or signal lamp. EXTRA HANDSET If desired, the relay mechanism itself TERMINALS can serve as a buzzer by merely removing the shunting capacitor. With the contacts in vibration the controlled out-

CARBON put should not be used because of the arcing would in "' "E *See text that result. With S1 the off position the 0A4 -G circuit will Fig. 2- Transmitter -receiver. Leads with same letter are connected together. signal when a carrier -current signal is RADIO -ELECTRONICS for

www.americanradiohistory.com Construction 79 present. With S1 on, the 0A4 -G circuit is shunted and inoperative. A toggle switch was used by the author, but a CENTERING micro -switch operated by hanging up PICTURE the telephone handset could be used. CTR0_STATIC TUBES oR QERFE ESE Power supply i 1N When S1 is turned on, the power transformer is energized and in less Use the NEW than one second the four directly - heated- cathode tubes become operative. PERFECTION The 5Y3 -GT acts as a full -wave rectifier. Two plates are connected to the AAe- ends of the high -voltage winding as is e` e«e standard practice. The 20 -gf capacitors Here is the simplest of all centering and 12 -henry choke provide adequate devices for the new electrostatic tubes. It smoothing of the direct current for the is also the most efficient and positive -as carrier -current receiver and transmit- your own tests will prove. ter. The 100,000-ohm Lleoder resistor the aids voltage regulation. The 80 -ohm car- Quickly Mounted. Slip Kine- Center over the tube neck bon resistor connected from the center - holding screw. It tap of the 2.5 -volt filament winding to and tighten the ground carries the current from the stays firm. No wobble. No wiggle. cathode circuits of the detector, modu- Finger -Tip Control. Picture is lator, and oscillator tubes and develops centered by rotating the two rings a small potential of about 2 volts. This MORE EFFICIENT either independently or together. acts as grid bias for all three stages and Rings are closer to Positive Centering. Once ad- also as a d.c. source in the carbon mi- deflection yoke (the justed, the rings stay put. crophone circuit. This resistor is shunted most effective operating by two to prevent audio os- area) and to the tube No Distortion of Focus as with capacitors neck. They are stabil- cillation and loss of gain. ized magnetically. many other centering devices. The receiver Order today from your supplier! The receiver uses a sir.gle 3Q5 -GT, see Fig. 2, in a grid -bias detector circuit. The tuning coil L2 was made from PERFECTION ELECTRIC COMPANY a 455 -kc i.f. transformer plus the wind- 2635 South Wabash Avenue, 16, ing removed in making Ll. The added Chicago Illinois winding was slipped next to one of MAKERS OF PERFECTION SPEAKERS AND TELEVISION COMPONENTS the two coils in the can. Then, the trimmer capacitor was disconnected from the coil closest to the added winding two were in ON-THE and these windings joined BATTERY RECORDER pEveage series so that their magnetic fields aid Every RADIOMAN "Horyw to Si-mof 8 plify Radio Re- each other. WALKIERECORDALL RECORDER -el AYHRYACK Continuous, permanent, accurate, indexes recording can use these pairs" is pack- The trimmer across the primary at only 5c per hr. instantaneous. permanent play- with -the- back. Picks up sound up to 80 ft. Reccrds confer- HINTS! ed on winding does the tuning. This primary ences, lectures, dictation, 2 -way phone & sales talks; SERVICE bench, practical bwhile walking, riding or a vine. Recorde in closed Valuable Manual Yours -FREE ideas. winding was moved closer to the sec- riefcase with "hitlden mike "! Write or details. Write today-no obligation coils for greater transfer of MILES REPRODUCER CO., INC. FEILER ENGINEERING CO. Dept. 11 RC1 -1 ondary 8026 N. Monticello Ave.. Skokie, I I I (Suburb of Chicago) energy. The primary which is connected 812 BROADWAY ,..0 Ft Ell NEW YORK 3. N. Y.

www.americanradiohistory.com 801 Construction across the line through C2 resembles mica capacitor C3 which is chosen to charge of the 0A4 -G's and the relays the 0A4 -G resonant circuit except for fix the frequency of resonance. C5 are just about to close. the inductive coupling which is neces- shunts the grid -leak resistor and sup- Next, one unit is turned on and the sary to isolate the chassis from the presses harmonics that might otherwise trimmer shunting Li of the other unit power line. C2 is made of 2 ceramic interfere with nearby radio and TV re- is adjusted for glow discharge and capacitors, one 240- and one 100 -µ1f ceivers. The reactance of a capacitor relay closing. The most sensitive point capacitor, paralleled. Detection is ac- varies inversely with frequency so that is found by tuning for the glow to cover complished by amplification of the posi- the higher frequencies are shunted to as much of the cathode electrode as pos- tive half of the received carrier -current a very much greater extent than the sible. The procedure is next repeated signal only. The negative portion of fundamental low- frequency carrier-cur- with opposite units the on and off. signal added to the negative bias rent signal. Now, with both units on, the receivers causes negligible plate current to flow Connected directly to the screen grid of each unit are adjusted for loudest in comparison to the positive signal of the 1619 tube is the plate of the signals from the other transmitter portion. The audio signal produced in triode- connected 3Q5 -GT tube. The 10,- unit. Receiver tuning is the plate done with the circuit is coupled to the head- 000 -ohm dropping resistor applies a L2 trimmers. An audio tone applied to phone by a 0.1 -µf capacitor. The receiver voltage to the screen which is fluctuated the modulator is a good is sound source, tuned to the same frequency as the according to the signal applied to the and a sensitive a.c. voltmeter 0A4 -G alarm. across modulator. The phono input shown is the phone terminals makes a better for high impedance The transmitter sound sources; it is alignment indicator than the ear. After isolated from the microphone trans- the initial The alignment, the telephone carrier -current transmitter uses former by the 220,000 -ohm resistor. units can be plugged into outlets sepa- a 1619 tube connected as a Hartley oscil- The operating frequencies and values rated by a greater lator using distance and the series feed and a type 3Q5- for Cl, C2, and C3 are included in Table process repeated with weaker signals GT triode -connected modulator. The coil 1. Small ceramic or mica capacitors are for finer adjustment. L3 is wound on form 2 inches a in di- suitable for Cl and C2, while mica The power -line medium is an un- ameter and 2% inches in length with 55 capacitors of 1,200 -volt rating should be known variable, turns of since different electrical No. 26 enameled wire. A tap used for C3. loads that are connected is provided at about the and discon- center for nected from the line tend to absorb connection to the positive side of Alignment procedure r.f. the energy and change the useful range of power supply. Two turns of well -insu- With both telephone units plugged lated hookup wire are communication. In most cases it should wrapped around into nearby electrical outlets the align- be possible to use the units satisfac- the center of this winding to couple the ing procedure can be started. The first torily for operation generated signal to between any two the power line step is to adjust the potentiometers locations in the home, or any locations through C4. The windings are fastened (Rl) on each unit with both power where meters to the form with dope. or other bypassing devices switches (S1) turned off. They are set do not intervene. Also mounted on the form is the to the position at which a glow dis- To use more than two of these phones

TABLE I some experimentation would be necessary. A frequency -selector switch might be added, Frequency of Mica Mica Mica and undoubtedly there would Iinit Alarm Circuit Frequency of Cl C2 C3 be a question of choosing frequencies and Receiver Transmitter 170-215 kc 181 -209 kc that would not interfere with one another. 1 186 kc 207 kc 300 µµf 340 µµf 0.005µf (In some cases, signals from the (240 +100) transmitter may be strong enough to block the receiver in the same station 2 207 kc 186 kc 300 µµf 340 µµf 0.006.µf unit even though (240 their frequencies are +100) 20 kc or more apart. If this happens, it is advisable to install a spring-return CARBON CI 300µµF 2MA /6.5K type s.p.d.t. send -receive switch in series 220K MICROPHONE RELAY ON -OFF PHONE JACK 100µµF with the B -plus leads to the transmitter JACK SWITCH and receiver circuits. 0.2µF ,! S The B -plus lead MICROPHONE from the power supply connects TRANSFORMER 250/4/,F to the O.iµF 6.S MEG arm of the switch, the normally closed 20µF 1. contact to the B -plus lead of the receiver. The normally open contact goes 0.1 µ F to the B -plus lead to the transmitter. 5µf G2340µµFa If your handset has a talk -listen switch ( 240p.taF+IOOµµ F) like that shown in the photo, this switch can be used to control a send -receive 0.05µF relay connected in place of the switch 5Y3 -GT in the B -plus lead. Editor) SOCKET 1619. Materials for telephone unit OCKE1 Resistors: I -.I, I -.15, I -.22, I -3.9. 1-6.8 megohms, I/2 watt; 1- 10,000 ohm. 2 watt; 1- 10,000 ohm, 10 watt; I -80 ohm, watt; I- 100,000 ohm potentiometer.

0O01µ F Capacitors: (Ceramic) I -240, 1-100 opt. (Electrolyt- 10Oµµ F 0.0Iµ F LEADS ic) 1 -20 of, 25 volts; 2-20 µf, 450 volts. (Mica) 2- FROM 100, 1 -250, 1 -300, 1 -.005, 1 -.006 µf, 1,200 volts. 101.C/2W O.02µ F (Paper) 1 -.001, 1 -.006, I 2 1 LEADS 0.006µF L1 -301, -.I, -.2 µf, 400 volts; 2 -.02, 3 -.05 µf, 600 volts. FROM .9 MEG. L2 Inductors: I- choke, 12 h, 50 ma; I -power trans- HANDSET former, 300 -0 -300 volts, 50 ma with 2.5- and 5 -volt 150 K TERMINALS windings. 1 -mike transformer, for 117 V OUTPUT carbon mike. 2- i.f. transformers, 455 kc. PHONO 3Q5 -GT Miscellaneous: Tubes: 1-0A4-G, I -5Y3 -GT, I -1619, JACK SOCKET 2- 305 -GT, and sockets for same. I- Relay, 2 ma, 6,500 -ohm coil, s.p.s.t., contacts heavy enough to control lamp or bell 1- s.p.s.t. toggle switch. (- Compactness the equipment coil form, 2 -inch diameter, 2;/4- inches long. I -Phone of and the large number of components mounted on jack. I -Mike jack. I -Phono jack. I- terminal strip, the chassis make for a rather crowded underchassis layout. However, the 3-terminals. Chassis. Hardware. Wire. constructor will be aided by the rather complete callout of components. -end- RADIO -ELECTRONICS for

www.americanradiohistory.com 81

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EASY TERMS 20 -Inch MDWEST "CONSTELLATION" -TO -YOU CHASSIS Television Console FACTORY TELEVISION 20 -Inch For Easy Installation In Your Own Cabinet 0/./W-ad WRITE or PHONE ede 1952 20 -Inch TELEVISION - RADIO - For This NEW PHONOGRAPH CONSOLE MIDWEST A luxurious instrum_nt that offers the Mam- moth 20 -Inch Rectangular Picture Telev.sion, FREE TELEVISION plus powerful AM -FM Radio, plus 3 -Speed Automatic Intermix Record-Charging Phono- RADIO CATALOG graph in a beautiful mahogany veneer console. If You Live In One of These Cities Phone and Ask for Your Catalog World- Ranging NEW YORK MUrray Hill 2 -6810 Alsa-Pwerful New 1952 CHICAGO STate 2 -5600 PITTSBURGH GRant 1 -0609 MIDWEST Series of RADIOS CLEVELAND PRospect 1 -7450 For Beautifll Consoles and Complete Chassis DETROIT WOodward 3 -1233 ST. LOUIS GRand 1161 An entirely new line of PHILADELPHIA LOcust 4 -1035 radios featuring the powerful Series 16 five or Send Coupon Below wave band AM -FM Radio Chassis and the WRITE IN NAME AND ADDRESS (PLEASE magnificent Symphony PRINT) ON COUPON OR lc POSTCARD Grand Radio -Phonograph with 3 -Speed Automatic Intermix Record Player. MIDWEST RADIO & TELEVISION CORP. Dept. 384. 909 BROADWAY CINCINNATI 2, OHIO Please send me your new FREE 1952 Catalog.

NAME

ADDRESS

CITY ZONE -STATE ll NOVEMBER. 1951

www.americanradiohistory.com New Devices -INLINE SEALED RECTIFIERS range of vacuum -tube voltmeters and International signal generators. Its extended low - Rectifier Corp., 6809 5. frequency responses permit accurate Victoria Ave., Los Angeles 43, has developed analysis of television signals. Sixty - a new line of hermetically cycle square waves are passed with sealed selenium rectifiers. They are less than 5% tilt. assembled in half -wave cartridges with current ratings from 300 so up to 60 mo. The individual cartridges accom- 4 -WAY SWITCH modate up to 400 cell elements with JFD Manufacturing Co., Inc., 6101 Six- d.c. voltage ratings up to 8,000 volts teenth Ave., Brooklyn 4, N. Y., is proper cartridge. By connecting a num- ducing a new four -way antenna switch. ber of cartridges in series, voltages The new accessory supplies swift, low - up to 250,000 have been obtained. loss switching facilities in any TV installation, local or remote, where up to four antennas are used. A constant - impedance rotary switch with low - loss- resistance silver-to- silver contacts provides maximum energy transfer. The new JFD accessory is housed in a compact bakelite case.

The assembly is rugged and impervious to the effects of outside atmos- phere. The units are capable of with- standing 100 G's of acceleration, and ore ideally suited for airborne applications. They can be operated in ambient temperatures up to 100° C. Out- side diameters vary from 3/16 -inch up to 11/4- inches, depending upon current rating. These rectifiers are designed for applications such as air -borne radar'corn- TEST PROD ADAPTER ponente, guided missiles, bias supplies, United Technical Laboratories, Morris- inverse peak clippers, oscilloscope town, N. J., announce a new test prod power supplies, solenoid power sup- adapter specially designed for use with plies, modulators, etc. standard R.T.M.A. test points or the phonograph needle type so that any BROADBAND point in miniaturized or other compact electronic circuits may be conveniently TV BOOSTER contacted by a self -holding prod. Electro- Voice, Inc., Buchanan, Mich., The new Klipzon type L Longie announces the new model 3002 Tune -O- adapter provides a slender, insulated Matic two -stage broad -band automa- point for reaching into crowded cir- tic self -tuning TV booster, for fringe cuits without danger of shorts, shock, and intermediate areas. It uses two or accidental disconect. A unique self - type 6BK7 tubes (one on the high bands holding point permits measurements and one on the low) in an exclusive with both hands free for circuit adjust- low -noise circuit, and provides uni- ment, soldering, or other work. formly high usable gain with very low Klipzon type L adapters, which are internal noise, on all channels, 2 -13. about 3 inches long and are available in red and black, clip onto wires ranging from the finest to No. 12 AWG. Prod points are made of nonmagnetic alloy steel and are needle sharp for easy piercing of insulation, protective coatings, and fungus. The adapters are easily slipped onto standard test prods.

Tuning is automatic -no booster dials to turn--and it is turned on or off by the TV receiver switch. The all-electronic circuit is a.c: powered and has high stability, insur- ing long, trouble -free service. BASIC CHASSIS The booster is finished in baked Alden Products Company, 117 North lacquer copper tone. It is 67/8x3 /ex3s/8- Main St., Brockton 64, Mass., has de- inches and weighs I pound, 13 ounces. signed a new basic chassis on which It has rubber grommet feet to protect most circuit elements can be laid out polished surfaces. and easily fabricated as unit subassemblies. is Heart of the chassis is the terminal VIDEO AMPLIFIER mounting board system whereby tube antenna construction means superior electrical Polaroid Electronics Corp., 100 Metro- sockets and all associated circuitry are politan Avenue, Brooklyn II, N. Y., mounted and interwired as an individu- announces a new, improved wide -band al subassembly for mounting in basic characteristics i.e., a single forward lobe to "pick up" the video amplifier, model V-2. It has a chassis. Mounted on both sides of the flat amplitude response ± 1.5 db chassis, terminal boards are instant- from below 10 cycles to 20 megacycles. ly accessible for inspection or removal. strongest signal - no minor lobes to receive reflected It is designed for use as an oscillo- Hundreds of prepunched holes on the scope deflection amplifier for the mea- terminal boards permit an almost un- surement and viewing of pulses of limited number of circuit patterns to or spurious radiations. When this single lobe is accurately extremely short duration and rise time. be wired without modification of any It is a tool for laboratory and in- sort. Alden miniature terminals staked pointed to the desired signal by dustrial use to extend the amplitude into holes as per optimum pattern Amphenol's "Auto -Dial" hold components firmly for soldering without time- consuming wrap -around antenna rotator, technical men know what any layman of leads. The simplified production methods made possible by the new chassis can see ... the picture is the best there is! speed up production. When an electronic design is ready to go into production, the schematic is divided into For the best TV picture on any channel, from any direction, functional blocks of circuitry. These blocks can readily be laid out on the standard components of the Alden Amphenol's -Wine" antenna and Auto -Dial rotator ....i basic chassis. Costly intermediate steps of housing design, modification of the phototype, tooling, ordering of the unbeatable combination by special connectors, plugs, etc., are -B 14 eliminated. On the production line, terminal boards, front panel, back connectors, and cabling are all wired as subassemblies, resulting in increased production efficiency. AMERICAN PHENOLIC CORPORATION All specifications given on these pages are from manufacturers' data. ti6?ß SOUTH 54th AVENUE CHICAGO 5C, ILLINOIS RADIO -ELECTRONICS for

www.americanradiohistory.com New Devices 83 sibility. Entire cabinet is a welded DEFLECTION YOKE ossembly with dark grey hammertone Cleveland Electronics, Inc., 6612 Euclid finish, and has provision in rear for Avenue, Cleveland 3, Ohio, has de- nine 1/2 -inch conduits. A removable signed a deflection yoke with anastig- terminal -strip mounting plate is in- matically corrected coils to provide a cluded near conduit inlets. Dimensions sharper focus over the entire picture are 591/2- x 23- x 16- inches. area. Insulated against high temperature throughout with materials to with- PICK -UP STICK stand temperatures up to 90 degrees Co., Celsius. Quadruple Formvar wire insul- Hytron Radio and Electronics hos brought out on ination used on all horizontal coils for Salem, Mass., maximum protection against high voltage. Easily installed with a floating type cage nut that permits rapid and accurate adjustment. teresting and elteful novelty in the form of a pencil with an adhesive wax tip in place of the eraser. This special wax tip picks up screws, nuts, etc., dropped into inacressibie spots in radio chassis. It also holds head of screw in those impossible -to -reach spots while starting nuts. Just a slight pressure of the special wax tip does the trick. The Pick -Up Stick doubles in brass as a pencil too. CHIMNEY MOUNT The Radiart Corporation, Cleveland 2, Ohio, announces the development of an entirely new idea in chimney mounts for TV antennas. Known as the Spee -Dee chimney mount, it is swiftly installed WILLIAMSON without the usual nuts and bolts for ABSOLUTELY NO KNOWLEDGE OF RADIO NECESSARY COMPONENTS tightening the straps around the chim- FREE TOOLS WITH KIT NO ADDITIONAL PARTS NEEDED ney. A slip -proof aluminum ratchet Standard Transformer Corp., 3580 Els- `EMI. EXCELLENT BACKGROUND FOR TELEVISION ton Ave., Chicago 18, announces Stan - 10 DAY MONEY -BACK GUARANTEE cor components for the famous William- son amplifier, designed to make high - fidelity audio available at low cost. The new Stancor components include a WHAT THE PROGRESSIVE RADIO high -fidelity output transformer A -8054, "EDU -KIT" OFFERS YOU power transformer PC8412, and filter The Progressive Radio "Edu -Kit" offers you a home study course at a rock choke C -1411. bottom price. Our kit is designed to train Radio Technicians, with the basic facts of Radio Theory and Construction Practice expressetl i mply d clearly. You will gain a knowledge of basic Radio Principles involved Radio Reception, Radio Transmission and Audio Amplification. You will learn how to identify Radio Symbols and Diagrams; how to build radios,, using regular radio circuit schematics; how to mount various radio parts; how to and solder in a ' professional manner. You will learn how to operate Receivers, rTransmitters, and Audio Amplifiers. You will learn how to service and lock winds up the straps and locks trouble -shoot radios. In brief, you will receive a basic education in Radio exactly them tightly in place. like the kind you would expect to receive in a Radio Course costing several hun- Use with masts up to IN inch O.D. dreds of dollars. is made possible by the large U -bolt. THE KIT FOR EVERYONE The Progressive Radio "Edu -Kit" was specifically prepared for any person who has a desire to learn Radio. The Kit has been used successfully by young JUNIOR VOLTOHMYST and old in all parts of the world. It is not necessary that you have even the RCA, Harrison, N. J. announce the slightest background in science or radio. The Progressive Radio "Edu -Kit" is sed by many Radio Schools and Clubs latest addition to RCA's Blue Ribbon in this country and abroad. It is used byu the Veterans Administration for Voca- Tests made by an independent test- test equipment line, the new WV -77A tional Guidance and Training. ing laboratory on a unit built from The Progressive Radio "Edu -Kit" requires no instructor. All instructions Junior VoltOhmyst meter, measuring are included. All parts are individually boxed, and identified by nam photograph standard stock parts show zero db a.c. volts, d.c. volts, and resistance and diagram. Every step involved in building these sets it carefully explained. You cannot make a mistake. frequency response from 20 cycles to in five different ranges. The all -elec- 50 kc at the 8 -watt level, remaining tronic meter features a high -impe- unchanged at the low level of 0.5 watts. dance diode tube as a signal rectifier, PROGRESSIVE TEACHING METHOD Intermodulation distortion measures The Progressive Radio "Edu -Kit" comes complete with instructions. These an electronic bridge circuit similar to instructions are arranged in a clear, simple and progressive manner. The theory 3% at 8 watts output. Total harmonic of Radio Transmission, Radio Reception and Audio Amplification is clearly ex- at 1,000 cycles is extremely plained. Every part is identified by photograph and diagram; you will learn the distortion function and theory of every part used. low and may be considered nonexis- The Progressive Radio "Edu -Kit" uses the principle of "Learn By Doing ". tent below the 10 -watt power level, Therefore you will build radios to illustrate the principles which you learn. These radios are designed in modern manner, according to the best principles of the tests showed. present -day educational practice. You begin by building a simple radio. The next set that you build is slightly more advanced. Gradually, in a progressive manner, you will find yourself constructing still ore advanced radio sets, and doing wor like a professional Radio Technician. Altogether you will build fifteen radios, RACK ASSEMBLIES including Receivers. Amplifiers and Transmitters. Newcomb Audio Products Co., 6824 Lex- ington Ave., Hollywood 38, Cal., offers The Progressive Radio "EDU -KIT" Is Complete basic elements for custom, cabinet - You will receive y part necessary to build 15 different radio sets. This includes tubes, tube sockets, variable s condensers, electrolytic condensers, mica type rock systems. Designed for flexi- condensers, paper condensers, resistors, tie strips, coils, tubing, hardware, etc. bility, these assemblies enable the en- Every part that you need is ncluded. In addition these parts are individually gineer to install PA equipment to meet packaged, so that you can easily identify every item. individual requirements. All standard Newcomb amplifiers are available TROUBLE -SHOOTING LESSONS Trouble- shooting and servicing lessons are included. You will be taught to mounted in panels, as well as a record recognize and repair troubles. While you are learning in this practical way, you changer, rodio, intercom amplifier, and will be able to do many a repair job for your neighbors and friends, and charge ... atilt Iir, fees which will far exceed the cost of the Kit. Here is an opportunity for you to other special equipment. Mounting learn radio and have others pay for it. holes are RMA standard 11/4- 1/2- and the one used in RCA's Senior Volt - inch spacings. Panel mounting holes Ohmyst meter, a 200- microampere FREE EXTRAS IN 1951 ore tapped in 1/2-inch stock. Fully ven- movement, and carbon -film multiplier ELECTRICAL AND RADIO TESTER tilated rear door provides easy acces- RADIO TROUBLE -SHOOTING GUIDE resistors. BOOK ON TELEVISION MEMBERSHIP IN RADIO- TELEVISION CLUB ELECTRIC SOLDERING IRON CONSULTATION SERVICE QUIZZES PIC TUBE TESTER PUBLIC Oak Ridge Products, 37 -01 Vernon Blvd., THE APPROVES! COMMENTS FROM SATISFIED USERS OF THE PROGRESSIVE RADIO "EDU- KIT ": Long Island City I, N. Y., announces VETERANS ADMINISTRATION. the Cofhette, a tester for checking C-R PHYSICAL MEDICINE REHABILITATION SERVICE, D. tubes in the television set under high - WASHINGTON, C. This Morning I was showing the Pro ive Radio 'Edu -Kit' to one of our voltage operating conditions. representatives from ouru Branch Office in Richmond, nd already he wants me to This compact tester measures only purchase some for his As Indicated in previous correspondence. I took the Progressive Radio F.du -Kit' to our Veterans Administration Hospital 51 /2x31/sx21 /4 inches. It checks all magne- at Fort Thomas, Kentucky. Both Instructors and patients worked them, and they tic and electrostatic focused tubes proved quite satisfactory." ROBERT L. SNUFF, and has a large full -scale meter, cal- 1534 Monroe Ave., Huntington, W. Va. ibrated with GOOD -BAD scales. "Thought I would drop you a few lines to say that I have bought a Progressive Radio 'Edu -Kit' and was really amazed that such a bargain can be had at such a low price. I have already started repairing radios and adio- phonographs. Friends were really surprised to see me get into the swing of it quickly. The trouble -shooting tester that came with the kit Is really swell. and finds the trouble if there is any to be found. Everything you say about your kit to true." DOMINICK STRACUZZA, 111 Clarence St.. London, Ontario "I am very satisfied with the Progressive Radio 'Edu -Kit' which I bought from You. I did not know ything about radio, but now I feel as though I have been in the radio business afor years. Your kit is simple and working with It." educational. I enjoy Order your Progressive Radio "EDU -KIT" Today, or send for further information. Postage prepaid on cnxh orders-O.O.D, orders accepted in U. 8. A. PROGRESSIVE ELECTRONICS CO. 497 UNION AVE., Dept. RE -53, Brooklyn 11, N. Y.

NOVEMBER. 1951

www.americanradiohistory.com 81 New Devices SIGNAL BOOSTER ALL -CHANNEL The Grayburne Corporation, 103 La- fayette St., New York 13, N. Y., has AMPLIFIER produced a new TV i.f. signal booster Blonder- Tongue Laboratories, 38 N. specifically designed for use in near- Second Ave., Mt. Vernon, N. Y., has fringe as well as metropolitan or just introduced a new type commer- suburban areas where a moderate in- cial TV amplifier. crease in signal will produce satis- Their new unit, called the Commer- factory results on "those weak stations" cial Antensifier, is a 4 -tube, 4 -stage TV present in every TV locality. signal amplifier that will suppy a gain of 30 db on all channels simultaneously. Operation is automatic, without any tuning or adjustment whatever. This unit can be used with the Blon- der- Tongue, and every other master antenna distribution system, to overcome line losses at any point in the system. In weak signal areas, it can be used as a preamplifier for the distribution system.

ttr 'One Blonder-Tongue antensifer replaces 12 ordinary boosters. Automatically amplifies all channels 16 times

TV SERVICE TOOLS By increasing video and oudio sig- Insuline Corporation of America, 36- nals approximately 25 %, the booster can often change unsatisfactory pic- 02 35th Ave., Long Island City I, N. Y., tures into pleasing TV reception at hos placed on the market two new nominal cost. tools designed to speed up television and rodio servicing operations. The Designated the model TSB -I, the new is the No. 6247 Kleer booster is a complete i.f. stage ready first dual -bladed This is a rod -loss for insertion in the receiver circuit in aligner. of low transparent plastic, 41/2 a matter of minutes. No external cabi- inches long and net to house the unit is needed, and no on -off or channel switches are required. TV boosters and master antenna systems BREAK LOCATOR Easy -Up Tower Co., Racine, Wis., has introduced o testing device for quickly When you write please mention RADIO-ELECTRONICS I locating breaks in 300 -ohm twin line. Sold under the trade name Twin - Test, it indicates the exact location of the break by a light. Twin line can be tested while connected to any type of antenna, whether open- or closed - circuit. How Bing Crosby's Shaver

Speeds up Electric Shaving 7/32 inch in diameter, fitted with corro- sion -proof steel blades .018 inch and .025 inch thick, respectively. The second of these instruments is the No. 6249 tuning wand, which is a brown phenolic rod 43/4 inches long and 1/4 inch in diameter. One end contains a molded powdered iron core having a permeability tolerance of 2% and a O tolerance of 10 %; the other end of the rod contains a silver -plated brass core.

V.T. VOLTMETER C -R TUBE TESTER Precise Development Corp., Oceanside, N. Y., has commenced delivering its Trojan Electronics, 3706 North Halstead new vacuum -tube voltmeter, the mo- has St., Chicago, developed a new del 909. It has six voltage ranges for tube tester which enables the television both o.c. and d.c., five for resistance, service technician to determine the and one decibel range. Ranges are: condition of a picture tube without Volts: 0- 5- 25 -50- 250 -500 -1,000. removing it from the chassis. ...THANKS TO VERSATILE SELETRON will Ohms: .01 to I billion in five ranges. The model 601 check all the more Db: -20 to +55. SELENIUM RECTIFIERS commonly used direct -view tubes made since 1946. Condition of the tube is A wonderful /won to faster whisker removal as smooth as Bing's voice is the Crosby. Shaves' indicated by the fractional milliam- which changes household alternating cunent to D.C., thus boosting the power and speed pere reading of the meter, of any electric razor as much as 40% ... And built into each unit is a miniature The tester is designed for durability. SELEIRON Selenium Rectifier No. 5M4 for trouble -free operation. Its meter is protected with a 5 -ma fuse, and it is light in weight 3 The Shaver is very small, and excessive heating within such a compact enclosure could be a problem. (just under Yet President William H. Burgess of Shaver Division, Electronic Specialty Co., pounds). Los Angeles 39, says that extensive temperature tests under full load show SELL-MOM rectifiers operate mrich cooler than other rectifiers tested ... and Ser.c-rnaN's reliability has been confirmed by successful use of the Shaves under varied conditions of temperature and humidity over a period of several years. So.ernos builds 'em midget size for radio, TV and other electronic circuits, all the may up to the giant stack assemblies for industrial use. Perhaps the unusual Shaves application may give you an idea for putting these versatile selenium rectifiers to work in some other unique spot ... If so, Serrrnon engineers can be of real assistance. Write us today, and request your copy of bulletin 104 -R -11. .n.e. TM rMCnonk Specialb ta MATRON DIVISION LLJ Ln _i L1 The voltmeter is available in kit RADIO RECEPTOR COMPANY, INC. or factory -wired form. The instrument .,.....,,,....,.mod .re,....k. (VD Seletron measures 91/2 x 6 z 5 inches and its shipping weight is 10 pounds. Sain DO.: 231 R. 111N SI., 114 York II, N. T. Wog. 54 N. SD St., Iroetlrn 1I, N. T. -end- RADIO -ELECTRONICS for

www.americanradiohistory.com Amateur its Converting the Mirk II Minor changes improve the equipment. The By author increased the output on phone with LOUIS H. HIPPE, W6APQ speech amplification and plate modulation

THE No. 19 Mark II radio set is Plate modulation lated. To do this would entail further you work c.w. Lack of one of the most beautifully en- on phone operation input modifications if However, screen modulation does not seem to gineered and built pieces of radio to the 807 is only 5 watts as compared equipment to be offered to date By affect the modulation quality, however, to the 30 watts input on c.w. con- the air indicate. on the surplus market. Designed to op- verting to plate modulation the power as reports on erate in combat tanks, its construction be Finding sufficient room to mount the input for phone operation can transformer may seem is rugged enough to stand up under brought up to the level of that possible plate -modulation almost any amateur use. In addition, its to be a hopeless task. However, you can for c.w. This, too is a simple operation the size makes it ideally suited to portable in an evening. We find sufficient space by shifting and can be completed located between the 807 and or mobile use. As for versatility, it is by the output of the inter- shield do this using T6A. Move it back against actually two complete ham stations in com as a modulator for the 807 plate. transformer the side of T6A and swing the small one. Set A covers the 3.5- and 7 -mc Make all changes as described in 1 and T2A back so the edge of its bands. Set B is a high- frequency trans- 3 are con- transformer above. After these completed, can slip under the ceiver that operates on 235 mc. Both tinue as follows: mounting bracket sets are tuned by variable-frequency edge of T6A. Its opposite mounting oscillators, which adds to their useful- 4. Replace the 6V6 -G (V8B) with a bracket is fastened to the chassis by a ness. 6L6. (V8B is the tube at the left bolt through the extra hole drilled in For phone operation set A employs rear as you face the set from the the chassis. Location of the modulation low -level grid modulation. The oscilla- front top.) transformer is shown in Photo B Lon tor is modulated in set B. 5. Replace R39A, the cathode resistor next page. We used the rig on 75 -meter phone of V8B, with a 500 -ohm, 10 -watt Since with plate modulation the form- for several months without modifica- resistor bypassed with a 4 -µf, 50- er speech input transformer T3A is tions. Reports indicated that unless we volt electrolytic capacitor. no longer needed, it can be removed to a -by input shouted into the microphone the result- 6. Disconnect the plate of the 6L6 provide room for stand ant modulation was insufficient to kick (V8B) from the primary of T6A. transformer for use with other equip- the 807 final anywhere near a useable ment you might build. Remove the 7. Use a 10 -watt modulation trans- tubes in the receiver section opposite level. W6ABM suggested we use the former (Hadley S- 588 -D, Peerless intercom amplifier in the rig as a pre - the transformer. With a long, thin M2103X, or equivalent, provided it screwdriver carefully reach back be- amp to increase the output of the modu- is physically small) to couple the lator. The changes are very simple and tween the variable tuning capacitor and output of V8B (the 6L6) to the remove the two screws that hold T3A the changeover can be made in three plate circuit of the 807 final. Use easy steps. to the chassis shield. You may have to the entire primary winding of the remove the screws that hold this shield 1. Reverse the leads to prongs 3 and modulation transformer. Connect to the plate 1 on power socket PL2A, on lower one side of the primary left corner of front panel. of the 6L6 (V8B). Leave the other 2. Disconnect the center wire of the side of the primary floating until shielded lead from the microphone step 8 is completed. input transformer T3A, leaving the 8. Break the 500 -volt lead to the plate shield connected to ground. To the coil of the 807 final amplifier. Con- center wire of the shielded line just nect the 807 plate coil to one of the disconnected, solder another length secondary leads on the modulation MCW-CW -PHONE SWITCH of shielded wire which is in turn transformer. The other lead from to be connected to the secondary of the secondary and the remaining the intercom output transformer. wire across from it on the primary This is the tap on the left front of side are both 'connected to the 500 - T6A having the white lead soldered volt lead to the power supply. to it. 9. Replace C33B with an .002 -pf, It is not necessary to discon- 1,500 -volt paper capacitor. (C33B nect the white wire from T6A, once is connected from the lower end of the new shielded wire is soldered to the 807 plate -tank coil to ground.) this terminal the output of the in- 10. Short out the two bottom pins on tercom will drive the grid of V3A the contacts nearest to the back of and thus modulate the 807 final the set on the MCW -CW -PHONE stage. switch. See Photo A. This increases 3. Resistor R23D (22,000 ohms), lo- the power input on phone to 30 cated on the grid cap of V1F can watts. be left as is or it may be shorted 11. Change resistor R8F (from grid of out, whichever seems to give the V8B to ground) to 470,000 ohms, best results. 1/i watt. The above will give added kick to the 12. Use set in normal manner. Be sure grid of the 807 and set A may be used the ALL switch is in the oN position according to operating instructions to place the former intercom ampli- JUMPE fier in operation modulator. without having to shout into the mi- as the Photo A- Underside, MCW -CW -PHONE crophone. The screen of the 807 is not modu- switch. Install jumper as shown. NOVEMBER, 1951

www.americanradiohistory.com 86 Amateur in place so that it may be raised to permit removal of the transformer. A.C. operation NOW! COLOR TELEVISION If you build an a.c. power pack for the unit, either you must provide 12- volts d.c. for the heaters and relays or you can cut loose the filaments so that ON YOUR PRESENT SET! a.c. may be used on them, thus reducing the d.c. drain so a lighter d.c. source can be used for the relays. The relays must be operated from d.c. Surplus selenium rectifiers solve this problem nicely. Note Sensational New Tri -Col- that the filament and relay circuits can $ 6 5 be operated on 6 volts by reconnecting ored Film, will bring you col- them in parallel instead of series 10 INCH and ored pictures on all block and white series parallel as they are hooked up broadcasts. Brings in any TV pro- at present. The voltage which supplies the 807 gram in glorious color, on any TV screen, speech amplifier, and receiver is set. Anybody can Your attach in less than Retail Cost fairly critical. The voltage on the high - one minute. Greatest development 10" $4.95 $1.65 voltage section should not run over 600; the voltage for the low- voltage section 12' /2" 5.95 1.95 since advent of television. Send for should read not less 300. 14" than These yours today. Start selling this red 6.95 2.30 readings should be made at the voltage 16 &17 " 7.95 2.55 hot item at once. When your cus- divider with the power pack under full 19 & 20" 8.95 2.85 load. If the low- voltage reading is too tomers see color programs with Ray low, downward modulation will result. Vision you will be swamped with This is indicated by the down kick of orders. ADD 15e SINGLE the panel meter in AE position or the ORDERS WE PREPAY glow of 1/2 watt neon bulb. SIX OR MORE The power supply is connected in the conventional manner but should be capable of delivering 250 ma. Be sure the components used are capable of 441 Summit Immediate handling the total load without over- RAY CO TOLEDO, OHIO Delivery load or excessive voltage drop. Mobile operation If the set is intended for mobile operation, the first three steps of the con- Good lobs for trained men -in version are all that is necessary. This limits the set to 5 watts input which is RADIO-TV-ELECTRONICS about the limit WILL BUY OR TRADE In minimum time, CREI trains you of the capabilities of the this -expanding NEED BC -611 or BC -721 Hondie- Talkie for fast field. Start studying now at CREI Residence School, (or any part; ART -13; ARC -I; ARC -3; and win your place in these fields that need trained men so DY -17; TS -12; TS -13; MN -26 J or K; desperately. Average time required: 22 months. BC -342; BC -312; I -100; BC -348; BC -788 Located in historic Washington, D.C., CREI has a 24-year history of successful technical training. A, AM, B or C; I -152A, AM, B or C; Industry asks for CREI grads, and uses CREI TS -67; Teletype, test or any other training for their own technicians. equipment. Cash or trade. What have SEND FOR ILLUSTRATED FREE CATALOG Write today for your copy of new descriptive cata- you? log, with survey of opportunities. and details of course and school. New classes start twice a Write: BOB month. SANETT (W6REX) CAPITOL RADIO ENGINEERING INSTITUTE 4668 Dockweiler, Los Angeles, California in _r ce,,,Iiled nehi r,l Institute Founded in 1927 Dept. 3011, 16th & Park Rd., N.W.. Wash. 10, D.C.

LAFAYETTE RADIO, Dept. JK Free NE 100 Sixth Avenue, N. Y. 13 BIG RADIO Please rush Free catalog to:

CATALOG Name Ready now. Complete with everything in radio, television and electronics. Newest Address parts, as well as old, standard lines. Paste coupon on penny postcard and mail today! City State Q DIVISION: RADIO WIRE TELEVISION, INC. Photo B- Shield and transformer T2A NEW YORK 13 NEWARK 2 BOSTON 10 BRONX SR 100 Sixth Ave. 24 Central Ave. 110 Federal St. 542 E. Fordham Rd. are moved back to make room for trans- PASTE ON PENNY POSTCARD former needed for plate modulation. RADIO -ELECTRONICS for

www.americanradiohistory.com 87

ALL RANGES WITH THIS ONE CONTROL

Just one knob -extra large -easy to turn -flush with the panel, Model controls all ranges. This one knob saves your time - minimizes the chances of "burn- outs" because you don't 630 have to remember to set another control. You can work fast with Model 630 with your eyes as well as your hands. Look at that scale -wide open -easy to read, accurately. Yes, this is a smooth TV tester. Fast, safe, no projecting knobs, or jacks, or meter case. Get your hand on that single control and you'll see why thousands of "Model 630's" are already in use in almost every kind of electrical testing FOR THE MAN WHO TAKES PRIDE IN HIS WORK

ONLY $39.50 AT YOUR DISTRIBUTORS Prices Subject to Change Triplett

TRIPLETT ELECTRICAL INSTRUMENT COMPANY BLUFFTON, OHIO, U.S.A. NOVEMBER, 1951

www.americanradiohistory.com 88 Amateur

dynamotor for phone operation. The 3. Solder the new coil in the trans- NEW a "must" book 500 -volt section is rated at only 65 ma; ceiver, using the same connections the 275 -volt section at 125 ma. If you as on the previous coil. for every use the dynamotor after conversion to 4. The transceiver is now on two plate modulation, be sure the resistor meters and may be operated exactly TV Service Technician placed in the cathode of V8B (step 5 the same as before conversion. Be above) does not fall below the specified sure and check with 2 -meter sta- value otherwise the 6L6 will draw so tions for band -edge limits on the much current that the dynamotor will tuning dial. Adjustments can be overheat. The low -voltage section of the made by stretching or squeezing dynamotor is well filtered (32 µf) but the coil. See Photo C. "Servicing TV the high -voltage section is not. The 0.1- The low- voltage (300 -volt) µf capacitor, C33A, is much too small. tap from This the power supply also feeds the four in the probably explains why the c.w. tubes in note is rough. Heavier filtering the transceiver. If the plate helps to voltage falls 275 clear up this as well as help remove below the sensitivity of Customer's Home" carrier hum. the B set receiver will suffer and a reduction in output when transmitting Puffing the B set on 2 meters will result. The versatility oî the Mark II can Antennas for the Mark II be increased by further conversion of the B set for 2 -meter operation. This A 123 -foot off- center fed Hertz or is an even simpler conversion than the Marconi works best on 75. Use a trans- Servicing one just described for the A set. The mitting -type variable capacitor (about conversion 80 µµf) in series with TV I, .,..., .,... is simplest when following the antenna lead. in the these steps: Set capacitor to half capacitance and 1. Remove the present coil from the peak the circuit with the variometer. Customer's transceiver. Home SAVES TIME (Note its connections The 2 -meter antenna used at W6APQ «,.;.,. carefully before TV «,. SAVES WORK removal.) is a commercial 5- element Yagi fed with 2. Wind 5 Earns More a -turn coil, % inch inside 52 -ohm coax and coupled directly into wJ..q diameter, 10 sello tlM for You with No. antenna wire. the transceiver through the connector on Outside Space the coil to a length of 11/16 provided on set B. Service Calls inch. -end-

shows how to diagnose trouble using capacitor probe and VTVM Here's the book you've been asking for-practical, proved help to make your outside TV servicing really eflèctive and profitable. Saves time, work and chassis hauling ... shows you how to make successful repairs on the spot. You learn the following: 1. A simple, effective method for tracing down trouble, using your VTVM and a simple capacitor probe. 2. Methods for finding your way around a strange circuit - shows you how to "pull tubes" and diagnose trouble by observing audio and picture effects. 3. How to judge set performance by analysis of TV for the test pattern. 4. Methods making adjustments in the field. You'll want this essential, profit - building book. Handy pocket size; sturdy cover. $150 ORDER TC -1. Only Pays for itself on the very first job.

HOWARD W. SAMS & CO., INC.

Order from your Parts ORDER Jobber, or write direct to HOWARD W. SAMS & CO., TODAY 2201 E. 46th St., Indianapolis 5, Ind. Send ... copy(ies) of "SERVICING TV IN THE CUSTOMER'S HOME," $1.50 per copy.

(Check) (money order) for $ enclosed

Name

Address

City State t_ J Photo C- V.h.f. compartment showing the location of the coil used for 2 meters. RADIO -ELECTRONICS for

www.americanradiohistory.com Broadcasting and Communications 811 Your Tape Recordings Are Not Negotiable! If you cut your own records or make tapes from radio broadcasts with your own recorder, don't try to sell them! The Metropolitan Opera Association and Columbia Records got a New York dealer into a lot of trouble because of that. The dealer tuned in the opera every Saturday afternoon, cut a master plate from the broadcast, stamped out a lot of records and sold them cheap, without paying royalties and without much overhead. The Metropolitan Opera Association didn't like it because it was a poor recording job and made the opera sound bad. Columbia Records didn't like it because they had exclusive rights to record the Metropolitan operas and the exclusive right to use the Metropolitan name on records. They had to have expensive special performances to record an opera. The pirate recorder made a good case in court and almost got away with it. AUTOMATIC SELF -TUNING The copyright on all the operas expired long ago; anyone can perform Lohen- grin or Tannhauser or Carmen or almost anything else the Metropolitan does without paying any royalty. So he claimed that he had not violated any copyright law. NO The pirate said that he wasn't com- peting with the Metropolitan, as he TV BOOSTER wasn't trying to run a rival opera or Connect it...and forget it! Anyone... steal customers from them, so they had get his favorite no grounds to complain. And he hadn't even a child...can stolen anything from Columbia; com- programs with a clarity o' picture and petition is legal in this country, and a sound like never before...on any channel business rival has no right to sue you if ... automatically ... without any booster you are able to produce cheaper than tuning! he can. As far as this particu'ar dealer was concerned, it was simply a matter Exclusive E -V all- electronic broadband of free enterprise. circuit gives superb low -noise performance Paul Whiteman once sued RCA for ...provides higher effective gain on all using some of his music without pay- channels...works where o'hers have ing him, but the court said that White- failed, even in tough fringe areas. not in man and RCA were the same Furthermore, the booster can be easily business ( Whiteman is a musician and is and simple. RCA a manufacturer) and dismissed concealed. Installation quick the action. Plugs into 50 -60 cycle a.c. outlet. That argument was used here, but it Thousands of installations have proved didn't work this time. The New York it completely trouble -free. There's Supreme Court said that the Metro- nothing like it! politan program had been "misappro- priated and one doesn't have to be in First all- channel, low- noise, Model 3000 TUNE -O- MATIC. List. $59.50 competition with a thief to stop him antenna- mounted, self - from stealing the product of your ex- tuning TV Booster! Mounts penditure and industry." The answer to on antenna mast ahead of this was that when a program is broad- the lead -in. Automatically is cast, it published and abandoned; boosts the signal -not any TV BOOSTERS MICROPHONES HI -fl SPE* BERS PHONO-PICKUPS interpretive ideas are not subject to local noise picked up by the Pole, Pend,g copyright; the Metropolitan didn't own lead -in. Clearly brings in the score, and by spreading the pro- Electro- telecasts you could never get Voice, Inc., gram all over the country by radio 421 Carroll Dept. Ell -5l _- ______before. Finest booster for St., Buchanan, - where anyone could listen to it free, Send Michigan tough fringe areas or noisy Free Bulletin they lost all exclusive right to that pro- No. locations in primary areas. 153 gram. But the court wasn't having any. I Nome i , They laid down the law that a radio Model 3010 TENNA -TOP. Address (PLEASE PRINT) / performance doesn't endanger a per- List Price $89.50 i I former's ownership of the material used i City I and it is against the law to copy a radio I / / Serviceman Zone show and then sell records of it even Instar S+ate I if you give credit to the show. Francis lle Deal wTVPan / George I -end- FREE BULLETIN TODAY! I NOVEMBER, 1951

www.americanradiohistory.com 90 Itroadcasting and Communications 4 SENSATIONAL Universal Tester Foi Field Use VALUES for immediate delivery from stock TEST -CRAFT Model TC -10 Quality Multifester

Only $12.85 AC and DC Voltage Ranges: 0- 5/15/150/1500/ 3000 Volts. DC Current Ranges: 0 -5/50 ma. 0.1. 5 Amps. Resistance Ranges: 0 -100 ohms, 0 -100 K. Size: 6 "x31/2"x2 ". Complete with batteries and full instructions. TEST -CRAFT Model TC -15 Combination Test Speaker and Signal Tracer

Photo of plus speaker substitution Only . 50 the tester. Provisions are made for multiconductor test cable and test plus resistor tester plus field substitut$29or leads with phone or tip type plugs. All jacks are insulated from the metal panel. plus condenser tester plus voice coil substi- plus output indicator tution Complete with full instructions By LYMAN E. GRAY TEST -CRAFT M-odel Tube andTCSet Te50ster A communication technician does most This simple meter was designed for tests all tubes up -to- of his work in the field. His test equip- flexible field use. It has few parts and date incl. 4, 5, 6, 7L, octets, loctals, televi- ment is necessarily limited. One way can check alignment and operation of sion, magic eye thyra- to overcome this disadvantage is to most communication sets. A crystal - tors sinnded,e, floating filgleament, mer- carry spare units; the defective unit controlled frequency meter is necessary + tory va,or new can go back to the shop for repairs. --- too. (The Link 2051 frequency meter, miniaturesp, etc. This method is not often economical. a dual -channel battery- operated 0 Multimeter Specifi- unit, Some manufacturers supply is 41 ,li\fl, cations: AC and special ideal. It supplies a crystal -controlled ;\ tf DC Voltage Ranges: test apparatus for their equipment. Un- signal for receiver alignment and also 0- I - 100 - 1000 - 5000. DC Current Ranges: fortunately, such test apparatus seldom can be used to check carrier frequency, -' 0 -10 /100 /1 Amp. can be used with other manufacturers' radiated power and frequency swing of ,,,,j Low Resistance Range: 0- 10,000 products. the modulator in FM equipment. Ohms. Medium Re- sistance Range: Only $39,50 0- 100,000 Ohms. MI M2 High Resistance Range: 0 -1 megohm. Complete with test leads and full instructions 0-200 us MODEL 999 Combination F.M. and A.M. Signal Generator and Signal Tracer DISC

o o o o 0-101.1A 02 20 o3 o o4 o 5 o o -06 20ó .-0 1 0-200 MA o 6 -o 9 Only $28.85 o o Generates R.F. frequencies from ISO kilocycles to I1 50 megacycles. Battery operated, no external source of current required. Positive action at- 0-200pa tenuator provides effective output control at all times. R.F. is obtainable separately or modulated by the Audio Frequency. Complete with test leads and full instructions 6 25% with order, balance C.O.D. or full check with order. 0-S00ua METROPOLITAN 666 ELECTRONICS & INSTRUMENTS CO. Dept. C 106 Fifth Ave., New York, N.Y. Schematic of the tester designed for Link FMTR ED7A and similar 2 -way sets. RADIO -ELECTRONICS for

www.americanradiohistory.com Broadcasting and Communications

The instrument shown in the diagram and photograph is designed especially for testing Link FMTR ED7A equipment, but it can be used with other types as well. The 9 -pin socket shown TRA NoIELEVISIOil between the meters is used for connections to the circuits in the FMTR ED7A. Test leads fitted with phone in 3 easy steps! plugs or standard pin tips are used when testing other types of equipment. .. of the amazingly The main advantage of this test set is that discriminator voltage and limiter low price grid currents can be metered simultane- of... ously. This is an important feature when checking equipment in the field and also when complete realignment is ONLY necessary. Two meters are used. Ml is a zero- center 100 -0 -100 microammeter used to $1550 measure discriminator voltage. We used a meter of this type to eliminate the for the complete need for a polarity-reversing switch. training (all 3 books) M2 is a standard 200 -µa instrument. The need for a polarity-reversing switch is eliminated here by using two test cables, one of which has connections to 5 Months one plug reversed. A 3- circuit, 11-position switch is to Pay! used for switching M2. The meter ranges and functions corresponding to switch positions are given in the table. Positions 5 through 11 are used for metering circuits in type FMTR ED7A equipment. 1- FREQUENCY MODULATION ...FOR BETTER JOBS! Switch Position Range and Function The "heart" of television sound Here, for the first time, is a com- ...FOR BETTER PAY! 1 0 -200 pa and 0 -500 na (0.5 ma) plete, easily understood description of Frequency Modulation (F -M) the These 3 great books offer you a really outstanding 0 - 2 -200 ma circuit system by which TV sound is LOW -PRICED OPPORTUNITY to get ahead in the 8 0 -10 ma transmitted and on which many other greatest, fastest -growing electronics field of them all - 4 Not used important electronic developments are TELEVISION! based. You learn all about basic F -M 16 million television receivers 5 First limiter grid current theory, control circuits, receivers, Already, there are almost 6 Second. limiter grid current transmitters, mobile equipment, trans- in U.S. homes. Each TV set uses from 4 to ro times as radio. Within a few months TV 7 First doubler grid current mitters, detectors, amplitude limiters, many parts as an average antennas and dozens of related sub - reception will be extended to many parts of the country 8 Quadrupler grid current Concise, clear explanations of that never had it before. This famous library helps you get 9 Second doubler grid current Fecte. -M test equipment and its use plus in on the "ground floor" of this giant TV business -paves 10 Power amplifier grid current specific F -M service problems are in- your way to bigger pay and better jobs! valuable to busy service men. Price an authentic, easy-to-under- 11 Power amplifier plate current $5.00 if bought separately. Read singly, each book is stand guide to a special phase of Television. Add all s PRACTICAL TV together and you have a specialized training that might The meter used for M2 has an inter- 2- well spell the turning point in your life toward bigger nal resistance of 1,000 ohms so the cur- SERVICING and better things! rent shunts were constructed accord- Complete "how -todo -if" data ingly. When using a meter having a After studying this famous book, SAVE $1 pay as you learn you'll find even the most puzzling TV lower resistance, compute the values of servicing problems greatly simplified. Now - for the first time - this RINEHART TV shunts from the formula: You'll work better, faster -more prof- LIBRARY is offered on ro -DAY FREE EXAMINATION. itably! Actual service case histories Read the books for ro days before you decide-then make Rmeter make things amazingly clear. Dozens a worthwhile cash saving if you buy. Bought singly, these Reliant = N 1 of illustrations and pattern photos ex- famous books would cost you $16.5o. Under this offer, plain details step by step. You learn you save $ n-and you have the privilege of paying in how TV differs from radio, how re- where N is the factor by which the ceivers operate and, above all, how to easy monthly installments. service them properly. Other subjects basic meter range is to be multiplied. include wiring details, component re- You can't lose on this offer! Thus, if you have a 100-microampere placement data, testing tips, fringe area reception hints, improving picture meter and want to make it read 1 milli- linearity and dozens of other vital TV ampere, N is 10 and N 1 is 9. So the service subjects. Price $4.00 if bought shunt required is 1/9 the resistance of separately. the meter. PRACTICAL TV Dept. RE -111, RINEHART BOOKS, INC., Technical If the resistance is near 1,000 ohms, 3- Division, 232 Madison Ave., New York 16, N. Y. ENGINEERING SAVE sl -ORDER THE COMPLETE SET! simply put a resistor in series to bring Send me the famous RINEHART TV LIBRARY (all 3 books) Basic training for the "big for 10 -DAY FREE EXAMINATION. If the books are not what I the total resistance up to the proper want, I will return them to you postpaid in good condition at money" field the end of 10 days without any further obligation on my part. value. If I decide to keep them, I will then enclose $3.50 as my first The "know how" so clearly present- payment and will end you 53 a month for 4 months until the ed in this big 700 -page book can quickly total special price of $15.50 is paid. Materials for test set help you forge many steps ahead of TO ORDER BOOKS SINGLY the average television student ! Starts Enclosed find for books checked; or send C.O.D. 5 in Resistors: (For 1 000 -ohm meter) 2 2 and I will pay postman. In either case. I may return booke -I, -20, 1-666 right at the beginning with an easy ex- to refund my money. ohms, 5% or smaller tolerance. good condition in IO days and you guarantee planation of all TV receiving and FREQUENCY MODULATION PRACTICAL TELEVISION Meters: 1- 100 -0 -100 (ta, d.c.; I -200 pa, 1,000 ohms, transmitting components and just how $5.00 ($5.50 outside U.S.A.) SERVICING d.c. they are combined in the complete 54.00 (54.50 outside USA) PRACTICAL TELEVISION ENGINEERING Miscellaneous: I -9 -Pin socket (Amphenol 77MIP9 television system. Progresses logically $7.50 (58.00 outside U.S.A.) or equivalent). 4 -Tip jacks, black: 4 -tip jacks, red. through every phase of the work in- 4 -Phone jacks, open -circuit type; I -phone jack with cluding transmission fundamentals, all Name separate make -contact springs (Utah -Carter type about the cathode ray tube and how 103, Mallory type 703, or equivalent). 1- Switch, it works, camera chains, studio work, Address rotary, 4 circuits, II positions. Insulating washers lenses, oscilloscopes, synchronizing gen- City, Zone, State for jacks, hookup wire, panel, carrying case, etc. erators, video amplifiers, power supplies, etc. 385 illustrations. Price $7.50 Your employer -end- separately. L

NOVEMBER, I 9 5 1

www.americanradiohistory.com 92 Broadcasting and Counnunicntions A -Bomb Position Locator Radiation lampshade is a new device civil defense authorities may use to quickly and accurately determine the exact position of an atomic blast within a given target area. Such data is required immediately after the explosion MEETS ^ ll@ NEED to enable rescue workers to proceed with the greatest efficiency. Developed by the Mohawk Association of Scientists and Engineers, in co -oper- IN INDUSTRY, RESEARCH ation with Schenectady, N. Y. civil defense authorities, the instrument will determine the height as well as ground - And DEFENSE PROGRAM zero -the point directly under the burst. The instrument resembles a standard lampshade approximately 12 inches in diameter at the bottom and somewhat smaller at the top. It is made of metal FOR TESTING and is painted white inside and out. On its inside surface is a grid consisting of and SERVICING numbered vertical and lettered horizon- A pointed rod Aircraft, tank, ma- Telephone circuits tal lines. brass projects rine radios and Laboratory instru- upward inside the "shade." electronic equip- ments, research ment Low voltage devices Relays and solen- For plating opera- oids tions

CONTINUOUSLY VARIABLE 0 -28 VOLTS AT 15 AMPERES

NEW MODEL "N" UNIVERSAL y tieneres riseccne t:o. Heat generated by an atomic blast DC POWER SUPPLY within a few miles of the device will Never before has a DC power supply with this output range and dependability scorch the painted inside surface. Since heat radiation travels in straight lines, been available at this moderate price. The new Model "N" utilizes the "Electra" it casts shadows of objects in its path application of selenium rectifiers. This exclusive feature increases the rectifier in the same way that light rays cast power rating and provides lower cost per ampere output. A single control provides shadows. The upper edge of the device continuous voltage adjustments for different load conditions over the specified and the pointed rod will cast shadows and which appear as unscorched areas on range. Highest quality components special design withstand high overloads. the calibrated grid. MODEL "B" MODEL "BJ" The lampshade will be inspected im- Send for mediately after an atomic explosion. DC POWER SUPPLY Literature DC POWER SUPPLY 6 VOLTS 1 -20 AMPS. 6 VOLTS I -12.5 AMPS. Shadows on the grid will indicate the direction and elevation of the blast. It is planned to install the devices so there will be at least four within one /ectro or two miles of any blast that may occur in a target area. By taking the readings of two or more indicators, a headquarters unit can, by triangulation, deter- ELECTRO PRODUCTS LABORATORIES 4501 -R Ravenswood Ave., Chicago 40, III. mine the elevation and ground -zero of the blast. Crystal Quartz in U.S.A. Quartz crystals of electronic quality $52,000.00 have been discovered in appreciable Finds Intermittent quantity in the United States. Formerly AVAILABLE Condensers Instantly we were dependent chiefly on Brazil for TO BUY NEEDED SURPLUS NET these important items. The new source ELECTRONIC EQUIPMENT Pres -probe's sliding tip with variable resistance of crystal quartz is on a high mesa in Top Dollar Paid! Send description, condition prevents condenser the Gosiute Indian reservation in Utah. and asking price. Prompt replies! healing. Tests with power on. Requires Preparations are being made by a no adjustment. Stops Western mining company to excavate URGENT! NEEDED AT ONCE: BC -61I guesswork. Saves the quartz, the Indians to receive 10% Handie -Talkies, ARC -I, ART -13, I -152C, BC- time. Convenient -348. Complete 788C, BC units or ports. probe size ( 734 " long) . of the company's profits. The U.S. Gov- Satisfaction guaranteed. ernment (General Services Adminis- See Your Dist. or Order Direct WEST REGION ELECTRONICS tration) has ordered the full output 1437 S. Norton Ave., Los Angeles 19, Calif. PRES-PROBE CO. for the next year. 4034 N. Sixth St., Milwaukee 12, Wisc. -end- RADIO -ELECTRONICS for

www.americanradiohistory.com #; Q CL t W i e2 OF T H E NEW 1952

NEW 0 -7 OSCILLOSCOPE'S PROOF OF THE PERFORMANCE OUTSTANDING showing the outstand- P,photographs HEATH- are actual, unretouched O- the KC Below the left is2 a ing frequency To 4 MC sine gODEwaveMODEL to the rig i KITKI OSCILLOSCOPE. on the screen. they actually appear wave as tests Two highly severe (only the scopecopmake will best of scopes show traces like these) O.7 really comes through.

NEW STYLE AND BEAUTY Style that's modern, yet functional that's the trend of today - kits - and Heath- are right up to the minute. Note the cut showing the new cabinet V -5 and AV -1 and panel construction. The front panel and rear over cover slide right the recessed flange of the case thereby eliminating sharp pointed edges and corners. The voltmeter kits aren't "shelf" or "mounted" ments instru- - they're moved about on the bench a lot and thus the new compact size and specially designed cabinets - Another 1952 Heathkit feature.

A STATEMENT FROM TRANSFORMER CHICAGO the outstand gratifying to note A STATEMENT It is indeed are building with you FROM ing sales records you SIMPSON ELECTRIC Heathkits. is readily understand CO. This sales success high In choosing are cognizant Simpson Meters for their since ave established kit VTVM, the Heath Heath- quality standards you standard Co. has set a new high component suppliers. proud that of kit meter quality. The same high your Transformer are P quality of material, workmanship We at Chicago contributed to the sign that has given and de- 'our product has p P rec of for Simpson the reputation and increasing building "Instruments That nized quality rate" is found Stay Accu- Heathkits.. in the Heathkit Meter Move- DIVISION ment. CHICAGO TRANSFORMER SIGNED Essex Wire Corporation SIMPSON ELECTRIC CO. Manager Vice-President and Sales

COLLEGES RESISTORS USE PRECISION HEATHKITS HEATHKIT for Colleges and Universities values are required out the through- resistance spared country are using Where exact Heath Co. has kits in their Heath - accuracy, the il- ,radio. electrical engineering, instrument the finesanuistors aby and physics laboratories in supplying Heathkits are no effort test the answer to good Precision resistInc., d Wilcor Corp., equipment at able. being rugged, low cost, plus Carbon (Jointoint Army-Navy) dependable, and Continental JAN extremely curare. Trade schools ac- meet the rigorous small their students are having ahi are have tem- obtain build Heathkits tle, to a first hand to -turc cee, 8 held knowledge of working non-inductive,pen nog at test equipment and accuseperature coefficient, quality components Bet the practical experience find gained by construction. accuracy. kits fill Heath- Heathkits. school needs.

YOU SAVE BY ORDERING DIRECT FROM MANUFACTURER -USE ORDER BLANK ON LAST PAGE

ROCKE INTERNATIONAL CORP. 13 S..6111 ST. NEW YORK CITY (16) ... BENTON HARBOR 20, MICHIGAN

NOVEMBER, 1951

www.americanradiohistory.com 94

OSCILLOSCOPE

MODEL O -7 SHIPPING WEIGHT 24 LBS.

earivted New "spot shape" control for spot adjustment - to give really sharp focusing. A total of ten tubes including CR tube and five miniatures. Cascaded vertical amplifiers followed by phase splitter and balanced push -pull deflection amplifiers. The performance of the NEW, IMPROVED, Greatly reduced retrace time. HEATHKIT 5" OSCILLOSCOPE KIT is truly amazing. The O -7 not only compares favorably: Step attenuated - frequency compensated - cathode follower vertical input. with equipment costing 4 and 5 times as much, but in many cases literally surpasses the really expensive equipment. The new, and carefully en- Low impedance vertical gain control for minimum distortion. gineered circuit incorporates the best in electronic design - and a multi- New mounting of phase splitter and deflection amplifier tubes near CR tude of excellent features all contribute to the outstanding performance tube base. of the new scope. Greatly simplified wiring layout. The VERTICAL CHANNEL has a step attenuated, frequency cotn- Increased frequency response - useful to 5 Mc. pensated vertical input which fecds a cathode follower stage - this Tremendous sensitivity .03V RMS per inch Vertical - .6V RMS per inch accomplishes improved frequency response, presents a high impedance Horizontal. input, and places the vertical gain control in a low impedance circuit for Dual control in vernier sweep frequency circuit smoother acting. minimum distortion. Following the cathode follower stage is a twin triode - cascaded amplifiers to contribute to the scope's extremely high sensi- Positive or negative peak internal synchronization. - tivity. Next comes a phase splitter stage which properly drives the push - pull, hi -gain, deflection amplifiers (whose plates are directly coupled to the vertical deflection plates). This fine tube lineup and circuitry give a sensitivity of .03V per inch RMS vertical and useful frequency response to 5 Mc. 1reeet`t The HORIZONTAL CHANNEL consists of a triode phase split - NEW INEXPENSIVE ter with a dual potentiometer ( horizontal gain control) in its plate KIT and cathode circuits for smooth, proper driving of the push -pull ANIC horizontal deflection amplifiers. As in the vertical channel, horizon- SWITCH tal deflection amplifier plates are direct coupled to the CR tube R horizontal deflection plates (for improved frequency response). ELECT The WIDE-RANGE SWEEP GENERATOR circuit incorporates a twin triode multivibrator stage for producing a good saw -tooth sweep frequency ( with faster retrace to a scope -- reed time). Has both coarse and anion piece switch, con - vernier sweep frequency controls. comp into the chu And scope has The signalsvals y can the internal synchronization which operates on different scope. and either positive or negative peaks of the input signal both high two as an indi- - its output each and low voltage rectifiers -Z axis modulation ( intensity modu- signals - is easily both lation) new spot ( e of ea ch input the - shape astigmatism) control for spot ad- Gain controls), justment provisions for external synchronization vertical trace. and le to - - vidualvictual A gain adjust centering and horizontal centering controls, wide range focus ( gain is simple set frequencyefrequency and control - and an intensity control for giving plenty of trace switching controls) com- . brilliance. and hue for I coarse The Model O.7 EVEN HAS GREAT NEW MECHANICAL can superimposed study' the traces or individual FEATURES -A special extra -wide CR tube mounting bracket or separated is provided so that the vertical cascade amplifier, vertical phase parson control) splitter, vertical deflection amplifier, and horizontal deflection position see distortion. l switch to bias, both 5-2. amplifier can mount near the base of the CR tube. This per- Use the to improper - Model lb> of an ampli Wt. l i mits close connection between the above stages and to the clippingand traces 5hlppnq deflection plates; distributed wiring is shift, and output over capacity greatly re- the - ut wave $generator duced, thereby affording increased high frequency. response. as a squareq The power transformer is specially designed so as to keep tier - switches, limited range all tubes, otheer its electrostatic and electromagnetic fields to a minimum The kit is complete; an $195a (- also has an internal shield with external ground lead. power transformer construction You'll like the complete instructions showing all details cabinet, lear detailed for easily building the kit includes pictorials, step -by- lus a - parts, P step construction procedure, numerous sketches, schematic, manual. circuit description. All necessary components included- transformer, cabinet, all tubes ( including CR tube) , completely punched and formed chassis -nothing else to buy.

E BY ORDERING DIRECT FROM MANUFACTURER -USE ORDER BLANK ON LAST PAGE

ROCKE INTERNATIONAL CORP. 13 E. 4001 ST. NEW YORK CITY 06) ... BENTON HARBOR 20, MICHIGAN RADIO -ELECTRONICS for

www.americanradiohistory.com 95

9eareeted

New styling, - formed case for beauty. New truly compact size. Cabinet 41/4" deep by 4. 11/16" wide by 73/s" high. Quality 200 microamp meter. A real beauty - you'll have only highest praise for this NEW MODEL New ohms battery holding clamp and spring clip - assurance of good VACUUM TUBE VOLTMETER. Truly a beautiful little instrument - and electrical contact. it's more compact than any of our previous models. Note the new rounded Highest quality precision resistors in multiplier circuit. edges on the front panel and rear cover. The size is greatly reduced to occupy Calibrates on both AC and DC for maximum accuracy. a minimum of space on your workbench yet the meter remains the same - Terrific coverage - reads from 1/2V to 1000V AC, 1/2V to 1000V DC, and large size with plainly marked scales. .1 to over 1 billion ohms resistance. A set of specially designed control mounting brackets permit calibration Large, clearly marked meter scales indicate ohms, AC Volts, DC Volts, to be performed with greatest ease - also makes for ease in wiring. New and DB - has zero set mark for FM alignment. battery mounting clamp holds ohms battery tightly into place, and base New styling presents attractive and professional appearance. spring clip insures a good connection to the ohms string of resistors. The circuitry employs two vacuum tubes -A duo diode operating when AC voltage measurements are taken, and a twin triode in the circuit at all times. The cathode balancing circuit of the twin triode assures sensitive measurements, and yet offers complete protection to the meter movement. Makes the meter burn -put proof in a properly constructed instrument. Quality components are used throughout -1% precision resistors io the multiplier circuit -conservatively rated power transformer -Simpson meter movement - excellent positive detent, smooth acting switches - sturdy cabinet, etc. . And you can make a tremendous range of measurements - V to 1000V AC, 1/2V to 1000V DC, .1 to over 1 billion ohms. and DB. Has mid -scale zero level marking for quick FM alignment. DB scale in red for easy identification - all other scales a sharp, .crisp black for for easy reading. A four position selector switch allows operator to rapidly set the instrument for type or reading desired - positions include ACV,DC+V, DC -V, and Ohms. DC- position allows negative voltage to be rapidly taken. Zero adjust and ohms adjust controls are conveniently located on front panel. Enjoy the numerous advantages of using a VTVM. Its high input impedance doesn't "load" circuits under test - therefore, assures more accurate and dependable readings in high impedance circuits such as resistance coupled amplifiers, AVC circuits, etc. Note the 30,000 VDC probe kit and the RF probe kit - available: at low extra cost and specially designed for use with this instrument. With these two probes, you can make DC voltage measurements up to 30,000V, or make RF measurements - added usefulness to an already highly useful instrument. The instruction manual is absolutely complete - contains a host of figures, pictorials, schematic, detailed step -by -step instructions, and circuit description. These clear, detailed instructions make assembly a cinch. And every part is included - meter, all controls, pilot light, switches. test leads, cabinet, instruction manual, etc.

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fX /Off AGENT ROCKE INTERNATIONAL CORP. IJ f. 6,1, Si. NEW YORK CITY (16) /te HEATH COMPA IVY ... BENTON HARBOR 20, MICHIGAN

NOVEMBER, 1951

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Model SG -6 Shipping Wt. 7 lbs.

The new Heathkit Signal Generator Kit has dozens of improvements. Covers the extended range of 160 Kc to 50 megacycles on fundamentals and up to 150 megacycles on useful calibrated harmonics; makes this Heathkit ideal as a marker oscillator for TV. Output level can be conveniently set by means of both step attenuator and continuously variable output controls. Instrument has new miniature HF tubes to easily handle the high frequencies covered. Uses 6C4 master oscillator and 6C4 sine wave audio oscillator. The kit is transformer operated and a husky selenium rectifier is used in the power supply. All coils are precision wound and checked for calibration making only one adjustment necessary for all bands. New sine wave audio oscillator provides internal modulation and is also available for external audio testing. Switch provided allows the oscillator to be modulated by an external audio oscillator for fidelity testing of receivers. Comes complete, all tubes, cabinet, test leads, every part. The instruction manual has step -by -step instructions and pictorials. It's easy and fun to build a Heathkit Model SG -6 Signal Generator.

geaddeet SIG NEwe KIT EST "I'ERSA` CHECKER Su PEAKER TRAC E CONDENSER $'950KIT R

$1950 Shipping Wt. 7lbs. The popular Tracer Model C -2 has now Signal Wt. 6 lbs. biped been ¡ Shipping with a universal I¿J speaker at test 11110 i of condensers no increase all types The same in price. ' Checks ceramic high quality `, paper mica follows ® j j - signal Y tenter condenserfer from ` - electrolytic. All to speaker _ antenna - direct reading saves tes intermittents scales are dre- valuablc finds no charts or multipliers. hour. Works Service time - e quire .00001 MFD one can read. A leakage The gives greater parts range of that test speaker well onn income' Covers Measures peaker broadcast, 1 per Molar A Condenser aí500 V provided.read. has a assortment °Come service tò 1000 oltage for 20 reads re- ke or ment of or and polarizing 0%U o and 50% ph e teusp- singlea switching test electrolyttcs between magic eye indicator and g to power factor of megohms. The 60 PA systes. Also from é0 ohms to 5 and detailed transformer, mesáomplcomplete: tests ststancesistance and comes com- instructions tubes, test cabinet, testing operatedrated for probe, all 110V maTh be cycleCY transformer c and assemblyas is 110V cabinet, and use. necessary The kit is eye tube, and and Pans, herharts. tube, instructions for assembly allot Has clear detailed all other parts. Has qeaddet TUBE CHECKER KIT

The Tube Checker is a MUST for radio repair men. Often customers want to SEE tubes checked, and a checker like this builds customer confidence. In your repairing, you will have a multitude of tubes to check - quickly. The Heathkit tube checker will serve all these functions - it's good looking (with a polished birch cabinet and an attractive two color panel) - checks 4, 5, 6, 7 prong Octals, Loctals, 7 prong miniatures, 9 prong miniatures, pilot lights, and the Hytron 5 prong types. AND ITS FAST TO OPERATE - the gear driven, f ree- running roll chart lists hundreds of tubes, and the smooth. acting, simplified switching arrangement gives really rapid set -ups. The testing arrangement is designed so that you will be able to test new tubes of the future - without even waiting for factory data - protection against obsolescence. You can give tubes a thorough testing - checks for opens, shorts, each element S individually, emission, and for filament continuity. A large BAD-? -GOOD meter scale is in three colors for easy reading and also has a "line -set" mark. Model TC -1 Shipping Wt. 12 lbs. 2950 You'll find this tube checker kit a good investment - and it's only $29.50.

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84.f Y

RADIO -ELECTRONICS for

www.americanradiohistory.com 97 Time LABORATORY LINE HEATHKITS

NEW qeatitieet -` Q.C. VACUUM TUBE VOLTMETER KIT

Now - as a Heathkit - at a price anyone can afford, an AC VTVM. A new kit to make possible those sensitive AC measurements required by audio enthusiasts, laboratories, and experimenters. Here is the kit that the audio men have been looking for. Its tremendous range of coverage makes possible measurements of audio amplifier frequency response - gain or loss of audio stages - characteristics of audio filters and attenuators - hum investigation - and literally a multitude of others. Ten ranges consisting of full scale .01, .03, .1, .3, 1, 3, 10, 30, 100, 300 volts RMS assure easy and more accurate readings. Ten ranges on DB provide for measurements from -52 to +52 DB. Frequency response within 1 DB from 20 cycles to 50 KC. The ingen ious circuitry incorporates precision multiplier resistors fox accuracy, two amplifier stages using miniature tubes, a unique bridge rectifier meter circuit, quality Simpson meter with 200 microampere movement, and a clean layou: of parts for easy wiring. A high degree of inverse feedback provides for stability and linearity. Simple operation is accomplished by the use of only one control, a range MODEL AV -1 switch which changes the voltage ranges in multiples of 1 and 3, and DB Shipping weight 5 lbs. ranges in steps of 10. The instrument is extremely compact, cabinet size - 41A" deep x 4- 11/16" wide x 7%g" high, and the newly designed cabinet makes this the companion piece to the VTVM. For audio work, this kit is a natural. NEW r7'ecteft(ae AUDIO FREQUENCY N E W qateveie AE -1 METER Shipping KITIT weight 12 lbs. A NEW Heathkit Audio INTERMODULATION the ideal instrument Frequency Meter from 20 for determining frequencies- KIT cycles to 100 KC. switch to the proper Set the selector ANALYZERaudio into the range feed testing of input terminals - the signal lntermodulation being ui - from the meter - and read the fre- ment is rapidly and audio gperaty, and - completely and more engineers ° yet dependable simple to more way determine results. experts as the best amers, hasQtwoty plainly Simpson 200 microampere of audio marked scales meter characteristics networks, etc. - These scales, read in ( 0 -100 0-300. recording character- position selector conjunction with the up those undesirable of switch, give full seven shows 100, 300, 1000, 3000, scale readings istics tfail. 100,000 cycles, 10,000, when all otherumethods easy Convenient ranges and e readings. forfor and The Heathkit ofewo high fre- 450 For greatest supplies choice fre- accuracy. a higher S3 ranges the 1 -3 cycles and is maintained -10 ratio (3000 and each range of quenciesquencles one low frequency (60 lib has indi. quency) and ratios of low voltagenput mpe high Both 1:1 or 4:1 MODEL IM -1 a ceis 2( for ne ligiblteeircuit cycles) . set up for and a change in signal I 300V can be fed loading high frequencies set wt. 18 lbs. reading. voltage between directly into the to nd the y Shipping In addition, input these limits will instrument testing, and the in- frequency of wave shape is not affect the of a Ppanel control either sine wave not critical (the meter by means m; An output level The tube complement or square wave input). unit will read the own Vhe $ 395.0 clipper, consists of a 6SJ7 6H6 meter pulse amplifier and clipper, control supplies impedance of OD3 /VR150 voltage rectifier, 6X5 Peer, 6V6 amplifier level with output section Construction regulator. Power supply desired The Analyzer is simple, rectifier, and two thousand ohms. proper i P and quality components level control and to and are used throughout. has input instruments VTVM of 30hf lOr10 circuits feeding the for operating iuilt duly all cnecessary voltages read suPP Y furn shed 3ofe. Built-in Powerpower of testing and efficient means NEW the instrument. be without this new You won't want to "e4 & SQUARE WAVE GENERATOR KIT The new Heathkit Square Wave Generator Kit with its 100 KC square wave opens an entirely new field of audio testing. Square wave testing over this wide range will quickly-show high and low frequency response characteristics of circuits - permit easy adjustment of high frequency compensating networks used in vidio amplifiers - identify ringing in circuits - demonstrate transformer characteristics, etc. The circuitry consists of a multivibrator stage, a clipping and squaring stage, and a cathode follower output stage. The power supply is transformer operated and utilizes a full wave rectifier tube with 2 sections of LC filtering. MODEL SC)-1 As a multivibrator cannot be accurately calibrated, a provision is provided to allow the instru- Shipping wt. 14 lbs. ment to be accurately synchronized with an accurate external source when extreme accuracy is required. The low impedance output is continuously variable between 0 and 25 volts and operation is simple. You'll really appreciate the wide range of this instrument, 10 cycles to 100 kilocycles - 950 continuously variable. Kit is complete with all parts and instruction manual, and is easy to build.

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wo.r AOENI ROCKE INTERNATIONAL CORP. Is E. 4016 ST. NEW YORK, IT..(16) ... BENTON HARBOR 20, MICHIGAN NOVEMBER, 1951

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This Impedance Bridge Kit is really a favorite with schools, industrial laboratories, and serious experimenters. An invaluable instrument for those doing electrical measurements work. Reads resistance from .01 Ohms to 10 meg., capacitance from .00001 to 100 MED. inductance from 10 microhenries to 100 henries. dissipation factor from .002 to 1, and storage factor from 1 to 1000. And you don't have to worry about selecting the proper bridge circuit for the various measurements - the instrument automatically makes the correct circuit when you set up for taking the measurement you want. Bridge utilizes Wheatstone, Hay, Maxwell, and capacitance comparison circuits for the wide range and types of measurements possible. And its self powered - has internal battery and 1000 cycle hummer. No external generator required - has provisions for external generator if measurements at other than 1000 cycles are desired. Kit utilizes only highest quality parts, General Radio main calibrated control. Mallory ceramic switches, excellent 200 microamp zero center galvanometer, laboratory type binding posts with standard 3 inch centers, 1% precision ceramic -body type multiplier resistors, beauti- Model 18 -18 $695° ful birch cabinet and ready calibrated panel. (Headphones not Shipping Wt. 15 lbs. included.) Take the guesswork out of electrical measurements -order your Heathkit Impedance Bridge kit today -you'll like it. feat LABORATORY ie-ez 4er LABORATORY KIT RESISTANCE DECADE POWER SUPPLY KITS piece An indispensable No load Variable equipment 1 of laboratory 25 MA 50 -400V DC Resis- Variable - the Heathkit 50 MA 30 -310V DC Variable 25 tance Decade Kit gives Higher loads. Voltage -250V DC drops off proportionally you resistance settings Every experimenter needs a good t to 99.999 ohms ply for electronic setups power sup- from unit has been of all kinds. OHM STEPS. Hy expressly designed This IN ONE supply and a 6.3 to act as a accuracy, source. Voltage V filament voltage For greatest HV control allows ceramic - output desired (continuouslyselection of Irk precision within limits outlined), variable body type resistors and provides and a Volts-Ma s large of output ceramic plainly marked and metering $195: highest quality meter scale indicates direct reading 950 are used. put in Volts either voltage Wt 4 lbs. wafer switches or DC current out- Shipping (Range of meter output to Bridge above, D 0 -S UOV D.C.. Ma. Medal the Impedance C) InstrumentI has 0 20 U M ° PS. (.....Ship Designed to match birch convenienttent stand Wt YD lbs.s has a beautiful Comes withw' power -b position and Decade Kit bi- twot 1619IG1 transformer, pilot light. the Resistance and comes control completely filament transformer, oiled 9construction punched t and attractivewith Pant manual manual, and and formed chassis, rectifier. parts andconstruction all other parts to panel, biner, complete all le / make the kit complete

qieeidr HIGH FIDELITY . . . 20 WATT

ECONOMY . . . 6 WATT AMPLIFIER KIT Our latest and finest amplifier - the model A -6 AMPLIFIER KIT (or A -6A) is capable of a full 20 Watts of high fidelity output - good faithful reproduction made possible through careful circuit de. sign and the use of only highest quality components. Frequency response within ± 1 db from 20-20.000 cycles. Distortion at 3 db ' J below maximum power output (at 1000 cycles No. 304 12 inch is only .8 %. The power transformer is rugged speaker ... $6.95 and conservatively rated and will deliver full -I-his fine Heathkit Am- plate and filament supply with ease. The output transformer was selected because of its plifier was designed to exceptionally good frequency response and wide give quality reproduction range of output impedances (4.8 -16. 150.600 ohms). Both are Chicago Transformers in Model A -4 and yet remain low in $335? drawn steel case for shielding and maximum Ship. Wt. 8 lbs. price. Has two preamp protection to windings. The unit has dual tone Shipping Wt. 18 lbs. stages, phase inverter controls to set the output for the tonal quality desired - treble control attentuates up db at 50 stage, and push -pull beam to 15 db at 10,000 cycles - bass control gives bass boost up to 10 cycles. Tube complement consists of 5Ú4G rectifier, 6537 voltage amplifier, 6SN7 amplifier power output. Comes complete with six tubes, quality and phase splitter, and two 6L6's in push-pull output. Comes complete with all parts output transformer (to 3 -4 ohm voice coil) . husky and detailed construction manual. ( Speaker not included. ) MODEL A -6: For tuner and crystal phono inputs. Has two position selector switch for cased power transformer and all other parts. Has tone Convenient switching to type of input desired. and volume controls. Instruction manual has pictorial for easy assembly. Six watts output with response flat MODEL A -6A: Features an added 6SJ7 stage (preamplifier) for operating from variable reluctance cartridge phono pickup, mike input, and either tuner or standard crystal phone 11/2 db from 50 to 15,000 cycles. A quality ampli- pickup. A three position selector switch provides flexible switching. fier kit at a low price. Better build one. Shipping Wt. 18 lbs. $35.50 YOU SAVE BY ORDERING DIRECT FROM MANUFACTURER -USE ORDER BLANK ON LAST PAGE

ROCKE INTCINATIONAI CORP. NEW Ótí:irr MI

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BATTERY ELIMINATOR KIT Can be used as battery charger. Continuously variable output 0 - 8 Volts - not switch type. Heavy duty Mallory 17 disk type magnesium copper sulfide rectifier. Automatic overload relay for maximum protection. Self -resett ng type. Ideal for battery, aircraft and marine radios. Dual Volt and Ammeters read both voltage and amperage continually - no switching. The new Heathkit Model BE -2 incorporates the best. Continiously variable output control is of the variable transformer type with smooth wiper type contacts. There are no switches or steps and voltage between 0 and 8 Volts is available at 10 Amperes continuous and 15 Amperes intermittent. Maximum safety from overloads and shorts provided by automatic overload relay which resets itself when overload is removed. The new rectifier is a 17 plate Mallory magnesium copper sulfide type. This is the most rugged type available for long trouble -free use. Output is continuously metered by both a 0 - 10 Volt Voltmeter and a 0 - 15 Amp Ammeter. Shorted vibrators indicated instantly by ammeter. Equip now for all types of service - aircraft - marine - auto ar d battery radios - this inexpensive instrument vastly increases service possibilities - better be ready when the customer walks in. Model BE -3 Shipping Wt. 17 lbs.

N E W qeGtddeie THE NEW erect SINE AND SQUARE KIT HANDITESTERprecision KITT ohm portable GENERATOR meter. volt-y AUDIO high quality Uses only -' usefulness, «n w. mim All versatility. cisionhighs 1 o parts - pre- Designed with the resistors in mind' wave deck switch three and dependabilitytwo most needed _ for trouble gives You the fingertips _ mounting -fret right ave; specially nd the squarea cali- designeding batteryof parts, sine ewave switch and plainly bracket, mounting The range give rapid and smooth frequency scale and the output adjust acting brated selection, to control, ohm easy frequency the output molded beautiful permits setting Bakelite .4 control sets micro any desired level: switch -am . ante p meter A high-low for etc, movement, instrument fore r high to con- the output and on DC and . - impedance edance load, I() AC volta nettnect high low impedance Model AG -7 - 30 - 300 - ` into a re- 1000 - low to work negligible DC Wt. 15 lbs. Ohms range 0 500ÓV with Shipping 300,000. -3000 and to 20,000 0 - siscCove. from . 20 peres Milliam- Coverage is peres 0 -10 ange really trusts wave 0 - yo, and the output Y assembled you can realty 4S? from - con - plete instructions corn_ shape. 4 gang tuning circuit, tubes, qquality cased . determining and tall torial diagrams. and pic- Six transformer, metal in the frequency manual - denser. power precision resistors complete construction condenser, 1% i a come with the low. other the price is truly lnendous kit, NEW fQ%QGt., T.V. ALIGNMENT GENERATOR KIT A few auto radio repair jobs will pay for the Heathkit Battery Eliminator Kit. It's fast for service. The voltage can be lowered to find sticky vibrators or raised to ferret out intermittents. Provides variable DC voltage 5 to 71/ Volts at 10 Amps. continuous or 15 Amps. intermittent. Also serves as storage battery charger. A well filtered, rugged power supply uses heavy duty selenium rectifier, a husky choke, and a 4000 MFD DC. 0 -15V voltmeter electrolytic condenser for clean Model TS -2 indicates output which is variable in eight steps. Better Shipping Wt. 20 lbs. be equipped for all types of service - it means more income.

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ROCHE INTERNATIONAL CORP. Il F. 4100, ST. NEW YORK CITY (10 .. BENTON HARBOR 20, MICHIGAN

NOVEMBER, 1951

www.americanradiohistory.com 1011

1eatitieee- RECEIVER & TUNER KITS for AM and FM

Model BR -1 Broadcast Model Kit covers 550 Model AR -1 3 Band to 1600 Kc. Shipping Receiver Kit covers 550 Kc. to over 20 Mc. con- Wt. 10 lbs. tinuous. Extremely high sensitivity. Shipping Wt. 10 lbs. TWO HIGH QUALITY eea ar SUPERHETRODYNE RECEIVER KITS Two excellent Heathkits. Ideal for schools, replacement of worn out receivers, amateur and custom installations. Both are transformer operated quality units. The best of materials used throughout - six inch calibrated slide rule dial - quality power output transformers - dual iron core shielded. I.F. coils - metal cased filter condenser. The chassis has phono input jacks, 110 Volt output for phono motor and there is a phono -radio switch on panel. A large metal panel simplifying installation in used console cabinets is included. Comes complete with tubes and instruction manual incorporating pictorials and step -by -step instructions (less speaker and cabinet). The three band model has simple coil turret which is assembled separately for ease of construction.

T R U E F M FROM ea t l t FM TUNER K I T The Heathkit FM Tuner Model FM -2 was designed for best tonal reproduction. The a', circuit incorporates the most desirable FM features - true FM. Ol tete Utilizes 8 tubes: 7E5 Oscillator, 6S1-17 mixer, two 6SH7 IF amplifiers, 6SH7 limiter, two 7C4 diodes as discriminator, and 6X5 rectifier. The instrument is transformer operated making it safe for connection to any type Model FM -2 receiver or amplifier. Has ready wound and adjusted RF coils, and 2 stages of 10.7 Mc IF (including Ship. Wt. 9 lbs. limiter). A calibrated six inch slide rule dial has vernier drive for easy tun- $22 :° ing. All parts and complete construction manual furnished.

MAIL TO THE O R D E R B L A N K SHIP VIA HEATH COMPANY 20, Parcel Post BENTON HARBOR Express MICHIGAN Freight Best Way

Quantity Item Price Quantity Item Price

Heathkit Oscilloscope Kit - Model O -7 Heathkit H.V. Probe Kit - No. 336 Heathkit VTVM Kit - Model V -5 Heathkit R.F. Signal Gen. Kit - Model SG -6 Heathkit FM Tuner Kit - FM -2 Heathkit Condenser Checker Kit - Model C -2 Heathkit Broadcast Receiver Kit - Model BR -1 Heathkit Handitester Kit - Model M -1 Heathkit Three Band Receiver Kit -Model AR-1 Heathkit Power Supply Kit - Model PS -1 Heathkit Amplifier Kit - Model A -4 Heathkit Resistance Decade Kit - Model RD -1 Heathkit Amplifier Kit - Model A -6 (or A -6A) Heathkit Impedance Bridge Kit - Model 1B-1B Heathkit Tube Checker Kit - Model TC -1 Heathkit A.C. VTVM -KIT - Model AV -1 Heathkit Audio Generator Kit - Model AG -7 Heathkit Intermodul. Analyzer Kit -Model IM -1 Heathkit Battery Eliminator Kit - Model BE -2 Heathkit Audio Freq. Meter Kit - Model AF -1 Heathkit Electronic Switch Kit - Model S -2 Heathkit Square Wave Gen. Kit - Model SQ -1 Heathkit T.V. Alignment Gen. Kit - TS -2 Heathkit Signal Tracer Kit - Model T -2 Heathkit R.F. Probe Kit - No. 309 On Parcel Post Orders, include postage for weight shown and insur- ance. (We insure all shipments.) Enclosed find Check Money Order for On Express Orders, do not include transportation charges - they will be collected by the Express Agency at time of delivery. Please ship C.O.D. Postage enclosed for lbs ALL PRICES SUBJECT TO CHANGE WITHOUT NOTICE

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www.americanradiohistory.com New Patents 101 SIDEBAND GENERATOR Patent No. 2,545,250 Kurt E. Appert, San Francisco, Calif. (Assigned to Lenkurt Electric Co., Inc.) This circuit mixes two signals, for example a.f. modulation with an r.f. carrier. Both signals are balanced out and do not appear, only the side - bands remain. No tubes are needed in this circuit. The carrier is connected between Pl and P2. It divides equally and flows in opposite directions through the windings of the T2 primary. Thus the carrier is balanced out. Modulation is fed to Tl which has 2 secondaries, Ll and L2. Each is shunted by a center -tapped resistor. The carrier voltage is made much larger than the modulation. Therefore the conductivity of the four rectifiers is determined solely by the carrier. During one -half cycle of the carrier, while P1

TRANS -BOTH ON SAME CORE

I I

TI T2

MOD OUT II

CARRIER is positive and P2 negative, A and B are biased for full conduction while C and D are blocked. During this period Ll delivers its voltage to T2 but L2 is effectively isolated. During the next half- cycle, L2 delivers its voltage to T2 while A and B are blocked by the large negative voltage on their anodes. Modulation voltage is thus transmitted to T2 but it is reversed rapidly (at the carrier rate). Therefore the audio envelope has simultaneous positive and negative components, and the modulation (like the carrier) is cancelled out. Sidebands are generated because of the non- linearity of the rectifiers. These are available at the output terminals. HIGH -VOLTAGE REGULATOR Patent No. 2,548,452 Clarence M. Turner, Stony Brook, N. Y. . SERVICEMEN, AMATEURS, (Assigned to United States of America as represented by U. S. Atomic Energy Committee) TECHNICIANS SELECT- It is difficult to regulate the output of an electrostatic generator like the Van de Graaff because of the high voltages involved. This invention permits control without a direct connection to the hot terminal. There are no moving parts. Hmericzan Beauty

TANK WALL SOLDERING IRONS t for

POSITIVE HI VOLTAGE ELECTRODE OF GEN TOP SOLDERING

AMPLIFIER PS Vi 1111 PERFORMANCE!

}ERROR SIGNAL Outstanding performance coupled with Resistors R act as load resistors and stabilize durability of construction make Ameri- corona discharge from the end of needles N. can Beauty electric soldering irons the Metal needles N are fixed near a screen S. The all screen substitutes for part of the tank wall of the choice of discriminating users in fields generator. As usual, the wall is the grounded negative terminal. The power supply PS is sufficient to generate a corona discharge between N and S. This discharge is formed when electrons TEMPERATURE REGULATING STAND are drawn from the points N under influence of the positive screen. Providing heat -regulation for all sizes The elements N. S, and P act as a triode. Some of electric soldering irons, this stand electrons pass through S and continue on to P. is adjustable for all heats up to full This flow loads the generator and lowers its out- working- temperature. Assures longer put voltage E. life of An amplified error -signal controls tube T and iron and tip. therefore determines the emission from N. This For descriptive catalog pages write Dept. S -23 signal may be a small fraction of the generator 122 output. If E rises for any reason, there is a greater error-signal and a more intense corona AMERICAN ELECTRICAL HEATER CO. discharge. The increased flow between S and P reduces the generator output to normal. DETROIT 2, MICH. NOVEMBER, 1951

www.americanradiohistory.com r New Patents GAS FLAME PROTECTION Patent No. 2,528,589 New 5 Inch George P. Frick, Wayne, Pa. (Assigned to Minneapolis -Honeywell Regulator Co., Minneapolis, Minn.)

This invention automatically shuts off a gas the relay there is no average d.c. component to supply if the flame goes out. Its operation is based energize it. The a.c. is bypassed by a 2 -Mf capaci- Oscilloscope on the conductivity of a flame. tor across RY. The relay contacts control the gas Winding T of the power transformer feeds rectifier VI. Rectified voltage appears across R, and PAPER FOR half -waves of current flow downward through } TELEVISION, 1 R .2K 2.i )RV relay RY. Load resistor R is shunted by a 2.2- ^c 22MECi 7N7 e megohm resistor and a flame B in series. When AM & FM 1T SERVICING the flame is on, its conductivity completes a volt- 1001( I V2 o age divider across R and C becomes charged. When the flame goes out, there is infinite resist- o0 ance between electrode A and ground. There is no voltage division in this case and C loses its charge. Grid and cathode of triode V2 are across C (through a grid resistor). When the flame is on, the voltage from C biases the triode beyond cutoff, and the only relay current is due to the half - waves flowing downward. When the flame goes out, there is no charge on C, and V2 conducts to feed to the flame so that gas flows only in the send half -waves of current upward through RY. energized position. This external control circuit Since both alternations of the a.c. pass through is not illustrated here.

CONDUCTANCE METER Patent No. 2,547,650 William A. McCool, Hyattsville, Md. (assigned to Boonton Radio Corp.)

Measuring conductance and susceptance at any when resonance occurs and measures the voltage desired r.f. this device is applicable to coils, trans- across the secondary. D is a diode rectifier of the mission lines, transformers and similar equipment. 6H6 type. With terminals A left open, the oscillator is set When the unknown network (shown here as to the desired frequency. Then the secondary cir- Gx, Bx) is added, the secondary is detuned and cuit is resonated by means of C. Meter V shows shunted. Resonance may be re-established by varying C. The difference in scale reading of C shows the value of Bx. If the first reading is the higher one, then Bx is a capacitor. Otherwise it is an inductor. C may be calibrated in terms of capaci- 1 1 tance (or inductance) across A so Bx can be read directly. )( Gx shunts the secondary so the second maximum Available of V is lower than the first. The original maxi- (TONABL mum can be restored by increasing R. This con- an monthly only RF OSC trol may be calibrated in terms of resistance $121! terms across A. Then Gx is found directly by reading PERFORMANCE EQUALS SCOPES the dial. MUCH HIGHER PRICED

WIDE -BAND VERTICAL AMPLIFIER -3 db from FREQUENCY CONTROL 10 cps to 4.5 mc on any attenuator setting; useful Patent No. 2,551,848 to 7 mc. Billy E. Parker, Quincy, Ill. VERTICAL SENSITIVITY-.014 volt (RMS) per inch.

CALIBRATED THREE STEP VERTICAL ATTENUATOR MAGNETOSTRICTIVE MATERIAL (Frequency Compensated) -gives peak -to -peak volt- This control varies the physical dimensions of a ages direct. quartz plate. The opposite surfaces of the quartz BALANCED PUSH -PULL DEFLECTION AMPLIFIERS are coated with a thin layer of nickel or other -used for both horizontal and vertical deflection. magnetostrictive material. External connections are made by leads soldered to the metal surfaces. WIDE -RANGE HORIZONTAL SWEEP cps to 100 -10 A crystal may be used to control the frequency 0. kc in four overlapping ranges; will sync with 3 mc sine wave. of an oscillator or as a filter element. However, if a coil L is added near the nickel layers, current LIAD THIRTEEN TUBES including SUPI CR Tube. through L sets up a magnetic field which expands LEAD As a VOLTAGE REGULATED FUSED POWER SUPPLY. or contracts the nickel. result the dimensions of the quartz plate also vary to alter the resonant frequency. DESCRIPTIVE CIRCULAR FREE REZO- ELECTRIC XTAL Servicemen, investigate this scope before you buy another. Save yourself money, keep down your investment in equipment. Mail coupòn or postcard for free descriptive circular giving details regard- LINEAR SINGLE -SWEEP ing its operation, specifications, and terms. You'll agree that this scope is just what you wont for TV, Patent No. 2,539,007 and FM is an AM, servicing jobs -that it exceptional Laurens Blok value. Send coupon in envelope or paste on penny and George Philip Roszbach, postal. Eindhoven, Netherlands. MAIL NOW (assigned to Hartford Nat'l Bank) NATIONAL RADIO INSTITUTE. DEPT. 502 A single -sweep time base such as needed to dis- zero to its final value. This is due to the fact that 16th & U STS.. N.W., WASHINGTON 9. D. C. play a transient signal on a scope is provided by when bias is removed, the grid does not reach this circuit. It is not easy to attain linearity when cathode potential instantaneously. Send me, without obligation, descriptive circu- such a sweep is very rapid. Compensation is The new (see a lar regarding the NRI 5" Professional TV Scope. circuit diagram) has variable added here to obtain a sweep which is rapid resistor R (about 120 ohms) in series with the and linear. usual capacitor C. Normally the tube is blocked NAME A single-sweep is often generated by discharg- (SW open). When SW is closed, the bias is ing a capacitor through a pentode. Normally the removed and the sweep starts. SW may be closed ADDRESS tube is blocked, and when the bias is removed the manually as shown, or electronically by the trans- discharge current flows through it. Although a ient to be observed. In either case C discharges CITY ZONE. .STATE pentode tends to pass constant current, it is found through R and the tube. that the current actually rises gradually from The discharge current (I) increases gradually RADIO -ELECTRONICS for

www.americanradiohistory.com New Patents

before reaching its steady value. Therefore ER (which is proportional to I) has the shape shown in the figure. Since I is the current withdrawn from the capacitor during discharge, Ec will L1i.IlIl1 Sensational Offer! T 2 Yr. GUARANTEE on PICTURE TUBES Pro -Rated

Transvision is the first and only manufacturer to offer you this Learn Radio amazing 2 yr. guarantee. Top quality rectangular and round TELEVISION tubes; all sizes. through this NEW Write for UNIT CHASSIS SYSTEM LOW PRICES The exclusive "Unit Chassis System" of teaching television was developed at this 48- year -old College of Electrical Engineering. The TV set is divided into stages on separate chassis. You study one stage at a time, inti- FEED up to 5 TV SETS mately learning the functions of every component of all types and makes of receivers. You are fully prepared to cope with future from 1 Antenna with design changes, including the advent of color TRA NSVISION'S TIME television. By enrolling NOW you will be ready for engineering employment oppor- MULTI-SET decay as shown by the curve. If R is correctly tunities predicted to reach a new high level in 1954. CONNECTORS chosen, the rise in ER will be similar to the decay of Ec. The sweep voltage is the difference between Ec You can become a Radio and Elt. It is shown by the straight line Eowhich Technician in 12 months indicates a linear sweep. The first third of the College of Electrical En- gineering program trains you for such positions as Radio Shop Operator or Serviceman, Supervisor of Service Personnel. The Radio POWER FACTOR METER Technician's certificate is awarded. You may then advance immediately or at a future date Patent No. 2,543,640 into courses described below. Novai P. Millar, Danvers, Mass. and Russell A. Warner, Schenectady, N. Y. Radio -Television Certificate (assigned to General Electric Co.) in 6 additional months Increase Sales with Multi -Set Connectors. Be prepared for such work as Radio TV Ideal for homes, garden apartments, TV dealers, The Hall effect is utilized in this instrument to Service -Audio, Transmitter or Communica- in time and labor. bars, etc. Big savings measure power factor in an a.c. line. If current tion Technician -and Broadcast Operator PRICES: Multi -Set Conn. for 2 sets $4.95 liste (upon passing FCC flows through a plate of germanium while in a examination). " " for 3 or 4 sets $7.95 list' FULLY GUARANTEED magnetic field. the germanium generates a potential difference. The voltage will be perpendicular Also Your Technician Courses are *Dealers, write for discounts to both the current and the field, and will be pro- credited toward the B. S. Degree portional to their product. in ELECTRICAL ENGINEERING. CR Tube REACTIVATOR M is an electromagnet supplied with a.c. through ¡ REVIVES a phase-shifter. L and R produce a 90° shift. The The Radio Technician course, while complete Hall plate (1) is fixed between the magnet pole in itself, is one -third of the college program DIM TV (major in electronics). Further, you may se- pieces. Current flows through the plate by means lect as an elective: design, research, manu- CR TUBES of conductors (2). The generated voltage is avail- facturing and production, or engineering able from leads (3) and is measured by the gal- sales and management. It's profitable -first use often pays for instrument. vanometer. Reactivates may CR B.S. dim of shifter, the field is Degree in 36 months. Tubes, or tubes with low Because the phase 90° Military, practical or prior light output, if there's no out of phase with the current to the germanium, mechanical defect. 110V- academic, training evalu- 60 cycles; weighs 3 lbs. under conditions of unity power factor in the line. ated for advanced credit. $ 14a95 The product of two vectors with 90° phase differ- Terms open January, April, ence is zero. Therefore the meter shows a reading July, October. of zero -center if the power factor is unity. As the FIELD STRENGTH METER factor lags or leads, the needle will deflect in one MILWAUKEE at NEW direction or the other. The meter may be calibrated in terms of power factor. SCHOOL of ENGINEERING LOW PRICE: Technical Institute e College of Electrical Engineering only net FREE -Write for -Occupational Gui- $59 dance Manual" and 1951 Catalog. Improves TV Installations; saves 1/a the work. Model FSM -I, complete with tubes 550 net MILWAUKEE SCHOOL OF ENGINEERING Dept. RE -1151, 1025 N. B'way, Write for details on amazing Transvision Milwaukee, Wisconsin FACTORY AGENT PLAN! Without obligation, mail Your Career Bulletin, 1951 Catalog, Occupational Guidance Bulletin on Ell Radio-TV, Electrical Engineering, B.S. se ,at Degree in Electronics, Electrical Power. E 3 on Electrical Service, Weld- BE FLEL goo Also bulletin 4or °'ttce. CONSTANT VOLTAGE ing, Refrigeration, Heating, Air Condi- ltotd et TRANS '"wtresales, 6eN ., tioning. slop Name Age TRANSVISION, INC. Address State DEPT. RE NEW ROCHELLE, N. Y. City LINE If Veteran, indicate date of discharge NOVEMBER, 1951

www.americanradiohistory.com 1041 Tcchnoitcs INCREASING PICTURE WIDTH If the width control of a TV set cannot be adjusted so the picture completely fills the screen, or if the set has no width control, the picture width can be extended to a satisfactory degree by

IB3

Thousands read the best -seller! Millions have seen and will see the thrilling movie! fil) IeII 6866 -G III D-AMPER III i Bt IIÌ ADD 4+:wNTH CANT connecting a .05 -µf, 600 -volt capacitor across terminals 5 and 6 of the horizontal output transformer. -L. H. Casto ADMIRAL 24 -TUBE CHASSIS Strong 60 -cycle hum in the 24D1, 24E1, 24F1, 24G1, and 24H1 chassis is generally caused by one of the following, and can be corrected easily: (1) The cold side of the volume control may be connected to the grounded heater lug of the first a.f. amplifier tube instead of to the grounded cathode lug on the same socket. Make sure that the volume control grounds to the cathode lug. (2) The a.c. leads to the switch on the volume control may be too close to the grid lead of the first a.f. tube. Dress the a.c. leads well away from the by the makers of professional radio grid lead. Later production models have a retaining lug to keep the a.c. leads dressed against the chassis. (3) The coupling capacitor between the volume control and first a.f. grid may be reversed. -Admiral Radio & TV Service Bulletin HALLICRAFTERS T -54 greatest adventure of our time! Failure of sound and video circuits is sometimes caused by a short in the Despite 101 days of salt spray and .02 -µf capacitor between ground and even total immersion, a National the plate of the 25L6 -GT audio output transmitter and receiver kept the world famed Kon -Tiki Expedition tube. The short circut reduces the plate in touch with the world! Now the same rugged dependability is yours voltages to the point where the video in the amazing SW-54, the circuits are inoperative. Replace this capacitor with a .02 -µf, 600 -volt unit. "Mighty Midget" broadcast and To improve the sensitivity of this shortwave receiver (540 kcs. to set, remove the 10,000 -ohm resistor be- 30 mcs.). Measures only 11" x tween the plate and screen grid of the 7" x 7 ". Write for details and 6AG5 r.f. amplifier. -Wilber J. Hantz name of nearest supplier! EMERSON 650D, 654DF, AND 654F NATIONAL COMPANY, Inc. If the set does not work and several M A L D E N , M A S S A C H U S E T T S of the tubes do not light, check the filament-dropping resistors. These usually go bad after the set has been in service for about a year. After repairing the set, check the line voltage at the outlet supplying the receiver. HAVE YOU A JOB FOR A Do not confuse models 650D and OYO! 654D (chassis 120123 -B) and 650E and TRAINED TECHNICIAN? 654F (chassis 120138-B)- transform- erless types -with the 650 and 654 i'J/: We have a number of alert young men who have Simply attach TELECOLOR FILTER to front completed intensive training in Radio and Tele- (chassis 120118 -B) which have power and in glorious color of set enjoy programs Repairing. They learned their trades thor- transformers.-Wilbur J. Hantz tones Instead of dull black and white- GUAR- vision ANTEED to give genuine color tone. Can also oughly by working on actual equipment under be used with any other filter. Once tried, personal, expert supervision. If you need a AIRLINE MODEL 62.901 you will go bock to old black and trained man, we invite you to write for an out- If you find the 6A7 screen bypass white. for FREE Information. ORDER Write the Er MAIL. NEW REDUCED PRICES! line of our course, and for a prospectus of capacitor C31 shorted, check the screen - Send check, M,O., cash, COO to Dept. RE -I graduate. No fees, of course. Address: dropping resistor R21 to make sure 10 in. $1 16, 17 in. $3 Placement Manager, Dept. P10811 that its value has not changed from 12 14 in. 2 19 21 in. 5 INSTITUTE 30,000 ohms. This set will not track COMMERCIAL TRADES has changed. Chicago 26 properly if the value - 1400 Greenleaf HARVARD LMb, B R O O K L Y N" NSY. Clarence J. Tabor RADIO -ELECTRONICS for

www.americanradiohistory.com TeCI111i/teS 105 PIX TUBES FOR SENTINEL 420TV The Sentinel model 420TV was originally shipped with a 16 -inch rectangular picture tube bearing the manufacturer's part number 57E5 or 57E6. When exact replacements sre not available, 16TP4 or 16RP4 tubes can be used as replacements. After installing the 16TP4 or 16RP4, REGISTERED set the horizontal drive control as de- "tONRA4YI6EAMS TRADE MARK scribed on page 4 of the service manual for this model. If neck -shadow is present, remove it by adjusting the four NOT JUST A WISE CHOICE - mounting screws on the focus -coil mounting assembly. Adjust the focus :w, BUT THE ONLY CHOICE control for proper focus. SUPERIOR PERFORMANCE "CONICAL-V- BEAMS" FOR THE ULTIMATE IN TV RECEPTION

Full Audio and Video Bandpass

STEEL SHUNTS HERE (ON EACH) TO REDUCE STRENGTH High Gain and High ON FOCUS MAGNET a Signal to Noise Ratio TO C79 IK 3K Telrex designs and TO C82 R97 manufactures antennas 3 for all requirements. See FOCUS COIL your Telrex distributor.

R89 ------TO C78 DELUXE SERIES -World's most ADD RESISTOR TO INCREASE FOCUS CURRENT famous, most powerful, most b sturdily constructed antenna. Su- perior to any for TV -FM and UHF If focus improves but is not perfect reception. WRITE today for your when the control is in the full counter Telrex catalog. clockwise position, the focus magnet is too strong. Correct this by placing four "CONICALV -BEAMS "are produced under Re -issue s/4 I/a x x Me -inch steel strips around Patent No. 23,346. THE SKILL the focus magnet as shown in the draw- TO DESIGN.. ing at a. If these shunts do not bring CANADIAN THE FACILITIES focus AND FOREIGN TO PRODUCE.. proper within the range of the PATENTS control, use additional shunts. PENDING THE ABILITY If you must turn the focus control TO DELIVER clockwise for improved focus but perfect focus is not attained before the control reaches the full clockwise position, the focus magnet is too weak. Connect a 20,000 -ohm, 5 -watt resistor between ground and the junction of resistors R97, R98, and R99 as shown in the partial schematic at b.-Sentinel Service Dept. CARE OF FOCUSING MAGNETS The PM and EM -PM type focus magnet assemblies used in many TV sets can be permanently damaged by improper handling or storage. A slight jar Immediate or striking with a metal tool may cause EASY TO LEARN CODE the unit to lose its magnetism and af- Delivery of SCARCE It is easy to learn or increase speed fect its ability to properly focus the with an Instructograph Code Teacher. RADIO Affords the quickest and most Prac- electron beam on the screen of the pic- tical method yet developed. For beginners or advanced students. Avail- ture tube. TV TUBES able tapes for beginner's alphabet Always use a brass or nonmetallic to typical message. on all subjects. Complete Line of Speed range 5 to 40 WPM. Always QBM. screwdriver when making adjustments T U B E S TELEVISION PICTURE TUBES ready -co on the unit. When storing, do not leave Radio and TV service men, ex- BOUGHT. perimenters. amateurs . we ENDORSED BY THOUSANDS! them in contact with each other or with hare many types of scarce tubes The Instructograph Cod* Teacher S O L D a n d ready for immediate shipment. literally take. the place of an oper- any metal material such as tools, other Don't use make -shifts or spend ator- instructor and enable. anyone to TRADED. Send learn and master code without fur- components, or Do not store valuable time looking for tube ther assistance. Thousands of successful operators have shelving. Your Want and sources. Try Electro FIRST . . "acquired the code" with the Instructograph system. and get the tubes you need with- Write today for convenient rental and purchase plans. them where they will be subjected to Trade List! out delay. Get complete list and severe mechanical shock or vibration. Electro's low prices. Its FREE - . . . write Stromberg-Carlson Service Dept. today! INSTRUCTOGRAPN COMPANY RRandolph St.,

-end- ELECTRO -S ALES 425 W. 47[) I Sheridan Rd., Dept. RC. Chicago 40. III. NOVEMBER, 1951

www.americanradiohistory.com 'Radio-Electronic Circuits 106 I TWO DYNAMIC NOISE SUPPRESSORS FOR HI -FI MUSIC FANS USE PHOTOFACT A number of dynamic noise- suppres- in a special potted unit called the LS -8. sor circuits have been published -some The variable low -pass scratch sup- of them have been incorporated in com- pressor is shown in Fig. 2. It is basic- the world's best Radio -TV mercial audio equipment. Until a short ally a two -section, constant -K filter with while ago, constructors were unable to variable capacitance elements Cl and service data -it pays for duplicate the published circuits without C2 connected between grid and cathode winding special high -Q inductors or of cathode -followers V2 -a and V2 -b. itself every working day having them made to order. The incoming signal is amplified by o +250V 250K IOOK .002 S250K 470K }250K 13°K 6SG7 -41--- 6SG7 .05 7R7 .05 * I( o L I /.02H CUTOUT-o o .0005"' 470K 1 .001 6

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4°O°''1775K 25K; Try PHOTOFACT:

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WE'LL PROVE YOU'LL SAVE TIME 1.50 and EARN MORE WITH PHOTOFACT NOW-learn for yourself-at our expense- TI 2.2MEG .005 how PHOTOFACT makes your Radio and TV work quicker, easier, more profitable! Examine 2.2 MEG IMEG .0025 470K an actual PHOTOFACT Folder. Use it. You'll learn first -hand why over 35,000 successful service technicians use PHOTOFACT daily. You'll Fig.1 -A 4 -tube noise suppressor. Frequency response is variable in four steps. learn that no other service gives you PHOTO - FACT'S completeness, accuracy, uniformity, and A four -tube dynamic noise suppressor V1 -a. The amplified signal passes lowest cost. PHOTOFACT is the only radio and and a two -tube dynamic scratch sup- through the low -pass filter to the output TV service data prepared from laboratory pressor are described in UTC Circuits, terminals. A part of the signal developed analysis of the actual equipment. Know the published by United Transformer Com- by VI-a is fed to the diode rectifier Vl -b facts-get your FREE Folder now. Examine, pany. The noise suppressor, Fig. 1, is which develops a bias voltage for the use, compare-learn why no modern service controlled by a four -position switch and grids of the variable- capacitance tubes shop can afford to be without PHOTOFACT! the suppression control. It is similar V2 -a and V2 -b. The bias voltage varies in Except those followed by asterisk ( *) or letter A. to the circuit shown in Fig. 1 of the accordance with the average signal level. 1 PAY AS YOU EARN! Ask. article "Noise Reduction in A.F. Cir- When the bias increases, the effective your distributor about this amaz -' cuit" in the May, 1948, issue of RADIO - capacitance of Cl and C2 varies and ing plan. Only $18.39 puts the, CRAFT. When the switch is in position changes the cutoff frequency of the fil- entire profit- boosting Photofact! 1, the gate section is cut out and the ter. The response of the filter is 3 db library in your now! shop circuit response is flat within 1 db from down at 3,500 cycles for a weak input 20 cycles to 20 kc. The remaining switch signal and 9,000 cycles for a strong one. NOTE: Our FREE Folder is limited to offer positions provide different degrees of The suppression control is a 250,000 - Service Technicians only. Attach coupon be- high- and low- frequency suppression ohm dual potentiometer with linear re- low to your letterhead and mention your which are determined somewhat by the sistance elements. Connections to the jobber's name. If you have no letterhead, strength of the input signal. The sup- left- and right -hand terminals are made send coupon to your jobber. Experimenters pression control varies the suppression as shown so the output level remains and others may obtain The Photofact Folder between limits determined by the switch constant at all settings of the control. by remitting amount shown below. setting. Inductors Ll, L2, and L3 are Inductors Ll and L2, 0.8 and 2.4 .02, .06, and .06 henry, respectively. henries, respectively, are combined in HOWARD W. SAMS & CO., INC. These three inductors are made by UTC one unit in UTC's CG -50. 2201 E. 46th St., Indianapolis 5, Ind.

Send FREE Photofact Cumulative Index AMPL VI-a RECT VI-b 6SL7-GT t 2) V2-a V2-b +300r Send Full Easy -Pay Details 270K LI L2 Á5/4000 820K .25 .05/400V lam a Service Technician: 270K Send FREE Folder for set model 2 OUTPUT 1 am an Experimenter: Enclosed $

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www.americanradiohistory.com Circuits Radio-Electronic 107 NOVEL 3 -TUBE SUPERHETERODYNE FROM AUSTRIA THE A glance at the circuit of this 3 -tube grid. The trimmer capacitor C serves as superhet receiver will show that it is a blocking capacitor as well as a means RIGHT rather unusual when compared to typi- of tuning the trap (neutralizing) cir- cal American circuits. This set was cuit. ANTENNA described in Radiotechnik (Vienna, The UBL21 is the second detector Austria) . and power amplifier tube. The output can do wonders for any TV set The receiver uses a UCH21 triode - section is a beam power amplifier hav- heptode, UBL21 duodiode -power am- ing comparatively high sensitivity. plifier, and a UY1N half -wave recti- With 100, 180, or 200 volts on plate and fier. In most European circuits, the screen, grid bias is 5.3, 10, or 13 volts Television & ANT. FM Antenna -1-.001 IKV Guide ANT. COIL Shows you how to get the most out of the antenna system at any location.

Remember the TV broadcasts from the San Fran- cisco conference in August? Special antennas made them possible. To het the most out of any TV receiver at any location, a thorough knowledge of 2206 the best type of antenna to use and how to install it is essential This book gives you that knowledge. 33K UYIN UBL2I UCH2I It tells you how to determine, quickly and accu- OI 950 IOW UYIN rately, the best spot and direction for the antenna ÌKY and what type to use; how to minimize noise from TIKIV the transmission line; when and why to use booster o MA. amplifiers. 220V AC 150 4W oa Includes UHF It explains antennas for the new UHF band and is heptode respectively. shows how to attach a UHF antenna to a VHF UCH21 connected with the model. Everything you want to know about an- section working as a mixer and the The UY1N is a half -wave rectifier tennas is here, in the most convenient handbook the high- frequency oscillator having a 20 -volt heater. In other form for quick on-the -job reference. Get a copy triode as tube without cost and see for yourself. Use the coupon in a converter circuit similar to that respects, it is very much like the 35Z3 below. which we commonly use with a 6K8. In and similar American types. this circuit, the heptode section is This circuit can be used as the basis used as a pentagrid converter and the for a number of interesting experi- FOR THE RIGHT SOLU- triode section as a neutralized i.f. am- mental circuits. For example, you may YOUR plifier. try a 6X8 as the converter and i.f. am- TIONS TO The triode section of the UCH21 is plifier, a germanium diode as the second PROBLEMS neutralized to prevent oscillation. In- detector, a sensitive power amplifier ductive neutralization is used. The tube as the output stage, and a selen- use these most helpful books inductance of L is paralleled by the ium rectifier in the power supply cir- grid -plate capacitance of the triode to cuit. Note that this set operates from form a parallel- resonant circuit tuned a 220 -volt line. It might be advisable Radio and TV to the intermediate frequency. The high to use a voltage doubler type power impedance of the tuned circuit prevents supply to obtain comparable plate and Mathematics the flow of current from plate back to screen voltages. A Handbook of Prob. SIMPLE SHORTWAVE RECEIVER CONVERSIONS lems & Solutions home over a range of 10 or 15 kc on each side 721 sample problems and solutions show you There are a number of -type what formulas to use, what numerical values to all -wave receivers which compare fa- of the receiver's intermediate frequen- substitute, and each step in working out any prob- in cy. The coil L may be one winding of lem you may encounter in radio. television or in- vorably with communications sets dustrial electronics, conveniently arranged and selectivity and sensitivity. Such sets can an i.f. transformer designed for a fre- thoroughly indexed by radio topics sp you can be converted amateur use by adding quency equal to the receiver's i.f. with quickly find the solution to for YOUR problem. a b.f.o. and S- meter. The b.f.o. circuit a 30 -turn cathode winding close to the shown at a and the S -meter at b can ground end of the i.f. coil. No. 28 or 30 be added to most receivers without wire may be used for the cathode wind- making any changes in the original ing. Reverse the connections to this Television for wiring. These circuits were described winding if the circuit does not oscillate. in an article on an 11 -tube communica- C is the usual i.f. tuning capacitor. Its Radiomen tions receiver in La Radio Profession- value should be adjusted so the circuit Clear, non -mathematical explanations of the oper- nelle (Paris, France). oscillates at the receiver's i.f. when ating principles and function of every part and cir- is cuit in today's TV receivers. with full instruction Both circuits are designed to use a the pitch control set at midrange. on installation, alignment, testing, adjusting and medium-mu triode such as a 6C4 or Shield the entire b.f.o. circuit and use trouble shooting. 6C5. You can conserve space by using minimum coupling to the second detec- the separate triodes of a 6SN7 -GT or tor. SEE THEM ON APPROVAL tg a 12AU7. The S -meter circuit is a triode The b.f.o. is an oscillator which tunes v.t.v.m. which measures the a.v.c. vol- The Macmillan Co., 00 Filth Ave., N. T. 11 tage and uses this as a measure of Please send me copies of the books checked be- TO DIODE OF 6C4,6C5,ETC. low. I will either remit in full or return the SECOND DET. 470 books in 10 days. F.0 6C4, 6C5, ETC B. Television L FM Antenna Guide $5.50 ON OFF NA n S- METER TUBE Radio L TV Mathematics $6.00 [117K B.F.O. Television for Radiomen $7.00 SWITCH APPROI.Sµµf TO AYC LINE ZERO ADJUST I WW 3.9 K Signed

a. 8 2 150 Address E 250 V b 250 V IMOONO=MOMMIMIIIIMIIMMIMMIUM. NOVEMBER, 951

www.americanradiohistory.com 108 Radio-Electronic Circuits signal strength. The meter should be adjusted to zero with the antenna posts grounded and the sensitivity control turned to maximum. The conversion can be completed by installing a switch which grounds the a.v.c. line when the b.f.o. is turned on to receive c.w. This switch is connected between ground and the grid returns on the grid side of the a.v.c. isolating resistor. A bandspread capacitor is another desirable feature. A good approximation is a 15- or 20 -µµf variable connected across the high- frequency oscillator trimmer in the receiver. Fitted with a knob, it will act as the bandspread tuner. The set should be aligned with NEW GOODLINE AIRLEAD has everything you want! it in the half -in position, which should be clearly marked, so that stations will Sharp, clean, "snow- free" pictures. come in at the same point on the main Correct impedence for "ghost- free" reception. Nominal 300 tuning dial. ohms. A noise limiter is often used in communications receivers. One may be Lower in cost than other leadlines purported to accomplish added, using the circuits shown in the same results. June, 1951, issue of RADIO- ELECTRONICS. Correct spacing for minimum radiation loss -Less than 1% of operating wave length. A.F. OUTPUT METER Fully An output meter like that shown in insulated- approved by safety experts. the diagram is a handy piece of equip- Pure, unadulterated polyethylene insulation - specially ment to have on the aligning bench of treated by our chemists for extreme weather. a busy radio service shop. The average service technician uses the a.c. volts High -efficiency conductors : Flexible, stranded to insure - or output range of a multimeter, thus long life. tying up the instrument so it cannot Easily installed -with standard insulators. be used for more essential work. in Popu- Packaged in convenient lengths : 100', 250', 500', 1,000', This instrument, described 2,500'. ular Radio (Stockholm, Sweden) works without being connected to the set. AT YOUR DEALERS, or Write For Free Samples and Sound is picked up by a microphone- Literature. a small loudspeaker -and fed through a rectifier to a 200 -ga d.c. meter. An *Patent Pending *Trade Mark U.S.and Foreign Patents Pending output transformer having a turns ra- EXCLUSIVE LICENSEE AND SOLE MANUFACTURER tio of 60 to 1 provides a high output voltage. A transformer designed to match a 4 -ohm voice coil to a 14,000 - 1014 FAIR OAKS AVENUE or 15,000 -ohm plate should work nicely. ,INC. Tivn SOUTH PASADENA, CALIFORNIA The rectifier may be a germanium diode or an instrument rectifier.

OUTPUT SENSITIVITY OTHER OUTSTANDING GOODLINE PRODUCTS: TRANS. CONT. VARIABLE TELETRAPS -2: Highly effective for eliminating interference from FM STATIONS, and DIATHERMY and AMATEUR SIGNALS within its tuning range. HI -PASS FILTER: Eliminates or greatly reduces interference picked up by I. F. AMPLIFIER or TV RECEIVER - interference arising from strong, When aligning sets, the output meter local low- frequency fields: X -Ray, Diathermy Equipment, Neon Lights, is placed in front of the speaker on the Etc., Etc. set. The volume control and the 5,000 - ohm sensitivity control are adjusted for a low reading on the meter. Receiver circuits are then aligned for maximum swing on the meter. TELEVISION RECEIVER-$I.00 When working with audio circuits Complete instructions for building your own television and filters, the volume control or input receiver. 16 pages -11"x17" of pictures, pictorial dia- WANTED grams. clarified schematics. 17"x22" complete schematic to the circuit and the sensitivity con- diagram & chassie layout. Also booklet of alignment meter are adjusted instructions, voltage & resistance tables and trouble- trol on the output TO BUY shooting hints. -All for $1.00. Write for free catalogue. so the meter reads zero db. Changes CERTIFIED TELEVISION LABORATORIES in volume level can then be read direct- Large and small quantities o` new or Dept. C, 5507 -13th Ave.. Brooklyn 19. N. Y. ly from the meter which is calibrated used electronic government or manu- in decibels. facturers' surplus tubes and equipment. The meter is calibrated with zero db Highest prices paid. State quantity, at the 80-ga point. Above zero db, +2, condition and best price in first letter. +4, +6, and +8 db are at 100, 126, 159, and 200 µa respectively, on the Box No. F -2 c/o Radio -Electronics SURPLUS meter. Below zero db, 63, 50, 35, and 25 West Broadway BOUGHT & SOLD New York 7. N. Y. 25 ga are marked -2, -4, -7, and 252 Greenwich St. -10 db respectively. GOULD CREE N WOrth 4.8044 -NYC 7 -end- RADIO -ELECTRONICS for

www.americanradiohistory.com Try This One

NOVEL CROSSOVER NETWORK I find that the circuit shown is an ac- ceptable substitute for the more expensive dividing or crossover networks used with most high -fidelity reproduc- ing systems. It is particularly useful in small receivers which do not have sufficient baffling to warrant the ex- PUSH-PULL OUTPUT TUBES 8 INCH WOOFER

6 INCH TWEETER 8+ pense of a more elaborate system. The crossover frequency is approximately 400 cycles. T1 is the regular output transformer of the receiver or amplifier. Its secondary is not used. T2 and T3 are small output transformers. The primary impedance of each is equal to the plate-to -plate load impedance of the output tubes. R1 serves as a tone con- ALL -NEW trol by cutting the highs fed to the tweeter. I use a 500,000 -ohm unit, but COMPLETE probably a lower value will work bet- BUYING GUIDE ter.-G. Borchert for Every Need! SUBSTITUTION BLOCK This little gadget is as handy as it is simple to construct. I find it lots easier FAMOUS PRODUCTS -VAST STOCKS - LOWEST PRICES to use than a decade box. The component leads are clamped firmly to Fahne- HIGH FIDELITY TV RADIO ELECTRONICS stock clips on a heavy wooden block, so TV & RADIOS PHONOS & RECORDERS You save time and money -with this bigger, SOUND SYSTEMS better 1952 Buying Guide! Here is HAM GEAR page- after -page full of the latest and greatest TEST EQUIPMENT values in Television, Radio and Electronics. BLOCK Of WOOD TEST CAP OR RESISTOR ELECTRONIC TUBES DUAL It brings right to your finger tips one of the FAHNESTOCK CLIPS PARTS, BOOKS, KITS world's largest stocks of nationally known TEST PRODS WITH POINTS OR ALLIGATOR CLIPS guaranteed quality parts and equipment. You Y FAST DELIVERY large and varied stocks in- find it quick and easy to get whatever you there is little danger of short -circuits sure quick shipment on thou- need -at the very lowest prices! Send or If sands of items. an accidental shock. test leads are for your FREE Concord Catalog today! fitted with alligator clips, the setup can HELPFUL SERVICE be used when trying different com- Our technical experts give Have it handy for quick reference! personal attention to your ponents in experimental circuits. Any problems! Supplies for Industry, TV and Broadcast resistor, or other two -ter- capacitor, Stations, Schools, Servicemen, Hams, minal device can then be inserted for INDUSTRIAL DIVISION Experienced staff and central- Government, Experimenters and Builders test or substitution. -M. J. Kolo ized efficiency speed service on supplies to Industry! TOM THUMB 3 -WAY SET HIGH FIDELITY The customer reported that severe Complete systems and cus- CONCORD RADIO tom components for finest BLVD. CHICAGO distortion appeared in the set after he reproductionl 901 W. JACKSON had installed five new 1.5 -volt A- cells. Over 30 Years of Service to the Radio World The distortion sounded like that pro- EXPORT DIVISION X1/1./ Special Export Division gives ./1./1./\./1.1. \ ../1'1 duced by improper bias or a bad coupl- prompt service on orders and ing capacitor. Examination showed that inquiries. CONCORD RADIO CORP., Dept. JL -51 1\ 901 W. Jackson Blvd., Chicago 7, Illinois the new cells had been inserted incor- POSITIVE SATISFACTION rectly. The trouble cleared up when CONCORD'S policy of quality Rush FREE Big, New 1952 CONCORD Catalog No. 951 and value assures you of the cells were properly installed. complete satisfaction! l Bias for the various stages is ob- Name tained by returning the grids to points on the series -connected filament string. Address Reversing the polarity of one or more ll cells will cause severe distortion as City Zone State ) will one or two bad or low cells. David Gnessin ./ ` /` /```` /h./r` /`/ \J'`./`J NOVEMBER, 1951

www.americanradiohistory.com 110 Try Tliis One HANDY SOLDER SUPPLY Forgetting to take along a supply of solder when going on a service call or running out of solder just when you Model need it most, can be prevented by wrap- M -51

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for emergency communications USED BY HUNDREDS OF MUNICIPALITIES FROM BOSTON, MASS., TO ALHAMBRA, CAL. ping a foot or two of wire solder around one end of the soldering -iron cord as shown in the photo. Here, it is out of poucALARm MONIìAoIO the way, yet always available when needed. -Louis H. Yates 5 Models For All Systems 6 VOLT MOBILE Says S. L. Grant, City Manager, Winchester, Virginia.. M -51 DEFECTIVE TUBES ARE USEFUL Tuneable 30.50 MC Frequently amateurs and radio ex- "I think you have a receiver that is well M -1O1 built, and I see no reason why it should not É Tuneable 152 -163 MC perimenters are called on to repair a be in demand by all public works depart- RCC -1 small a.c.-d.c. set for a friend or rela- ments that have a transmitter available." Fixed Frequency tive. Usually, the trouble is a burned - in both bonds out indicated by 115 VOLT AC-DC tube as the complaint, Users of FM 2 -Way Radio Communications PR -31 "the set won't light ". equipment throughout the entire nation, find Tuneable 30 -50 MC To quickly locate the tube with the PR -8 open filament, a collection of Tuneable 152 -163 MC make dif- Polk-Alarm and Monitoradio a welcome in- ferent types of tubes which have good -cost AIRCRAFT novation to low mobile communications AR -I filaments but are otherwise defective. radio . AM Tuneable 100.132 MC Snip off all the pins except those for 115 Volt AC -DC the heater. Now, when you get a set to For Complete Information: See Your Jobber -Or Write Us Today repair, you can quickly find the defective tube by substituting a dummy. RADIO APPARATUS CORPORATION I have also found the dummy tubes 55 N. NEW JERSEY ST., INDIANAPOLIS 4, IND., PHONE: ATLANTIC 1624 handy substitutes for line-dropping resistors in experimental a.c.-d.c. circuits. For example, I built a code oscillator using a 35Z5 -GT and 50L6 -GT. I didn't have a resistor which could be used in series with the heaters so I wired in an extra socket and inserted a dummy 35Z5- GT. -C. Tierney

LINE FILTERS IN A.C. SETS Many a.c. receivers have filter capacitors-usually about 0.1 µf- connected from the chassis to one or both sides of the a.c. power line. Although these capacitors are effective in removing stray line noises, they have the disadvantage of reducing the line -isolating capabilities of the power transformer. The current passed by these capacitors is not sufficient to damage any of the set's MODEL 2430 -Designed specifically The new Gold Medal Series incor- components but it can give you a for all picture tubes requiring from porates all the latest Tech -Master fea- healthy jolt if you happen to get be- 65 to 70 degrees horizontal deflection, (such as 24AP4, 20CP4, tures which have made this improved tween the chassis and a good ground. 19AP4, etc.) Supplied with 5X7 630 type chassis the standard by which You can avoid it by removing one speaker and Universal Picture Tube custom -built TV is measured perform- Mounting Brackets. $109.50 ... capacitor and connecting the other ance and service are assured because across the line. -Charles Erwin Cohn Tech -Master design and construction are MODEL 2431P - Similar to model 2430, but with Push -Pull Audio, as fine as human hands and brains CARRIER -CURRENT NOTES Phono Jack, 12" PM Speaker and can produce. All chassis are supplied Universal Picture Tube Mounting I - Brackets. $199.95 completely wired, aligned and tested Recently, constructed the carrier with all tubes (less picture tube). current relay described in the Septem- MODEL 2431C Basically same as ber, 1950 issue. While experimenting - LOOK for your Tech -Master registra- Model 2430 but with Continuous with it, I found that it will not work if Tuner, Push -Pull Audio, Phono Jack, tion and guarantee card attached to a receiver or other device having a by- 12" PM Speaker and Universal each chassis ... it is your assurance that Picture Tube Mounting Brackets. pass capacitor across its line cord is Allows complete coverage of both you are buying a genuine Tech -Master TV and FM bands. $199.95 receiver. plugged into the power line. The capacitor short -circuits the line for r.f. so the See the Gold Medal Series and other quality Tech -Master products at your favorite Radio Parts Jobber or write direct to Tech -Master relay will not work. The same applies to Products Co. Dept. RE -11 for complete descriptive literature. most carrier- current or wired -wireless devices. -Walter R. Sherman TECH -MASTER PRODUCTS CO. -end- RADIO -ELECTRONICS for

www.americanradiohistory.com question Box

A CRYSTAL -CONTROLLED MARINE TRANSMITTER ? Please print a circuit of a 4 -chan- c.w. position, this relay closes when the nel, 100 -watt phone -c.w. transmitter for c.w. send -receive switch S3 is in the send use in a small fishing launch. The position. RY2 is controlled by the A Recd-- transmitter should have a single con- microphone switch when using radio- trol which can be used to select one of telephony. RY3 is a 12 -volt antenna Aid to a four frequencies in the 2-3 -me range change -over relay having auxiliary con- while simultaneously switching in the tacts for muting the receiver while STRONGER correct power- amplifier tuning and transmitting. TV SIGNAL antenna -loading capacitors. Power is The parasitic suppressors in the plate supplied by a 12 -volt dynamotor which circuits of the 829 are 10 turns of ANY Receive delivers 600 to 625 volts at 225 ma. No. 18 enameled wire wound around a for When using phone, I want to control 100 -ohm, 2 -watt resistor. The power - the dynamotor with a switch on the amplifier tank and antenna loading coil R T-17 microphone. Separate send -receive consists of approximately 15 turns of and dynamotor switches must be used No. 12 wire spaced to 3 inches on a for c.w. operation. E. N., Port 21/2 -inch form. The winding should be Arkansas, Texas. tapped every three turns. A shorting strap is adjusted to the point where the TV Roo A. The circuit of the transmitter is shown. By using a Pierce crystal oscil- inductance is optimum for the four later and a Pi -type antenna coupler, channels. Sections of the channel selec- tuning adjustments are limited to a tor select the proper preset variable Mount single stage. The 6Y6 -G clamp -tube capacitors connected across the ends prevents excessive dissipation in the of the coil. final under key -up conditions. The coil winding data given for the Tower. The modulator is an 815 driven by a loading coil is typical for most whip - The world's leading triode -connected 6F6 which is excited type antennas. However, it may be producer of towers directly by a T -17 or similar carbon necessary to use considerably more presents a new microphone. Microphone excitation volt- turns with some antennas, depending on superior TV ROOF age is tapped off the cathode resistor their length. MOUNT TOWER for the 6F6. Modulator bias is devel- TV LEAD -IN PROBLEM UTILITY - Adjustable feet oped across a resistor in series with roof slope. Adjust. be- for any the negative leg of the high -voltage ? I have a run of over 500 feet able clamps for pipe or fit- supply. tween my TV antenna and the receiver. tings -11 to 134 inches. RY1 is the dynamotor starting relay. I want to use No. 18 wire in an open - Ten foot tower plus ten foot has heavy contacts capable of carry- wire line. What spacing shall I use for pipe provides a 19 foot It installa more and is controlled a 300 -ohm line ? -R. R., Hartford, Conn. SELF -SUPPORTING ing 40 amp or tower plus 30 300 -ohm line, the spacing is fion. Ten foot through dynamotor switch Sl. When A. For a foot pipe provides a 40 foot the switch is in the position shown, the 0.3 inch for No. 18 wire, 0.5 inch for installation with guys at 20 dynamotor is stopped and started by No. 12, and 0.6 inch for No. 10. Such and 40 foot levels. the switch on the mike. When it is in spacii g5 are too small to maintain with May be used as a ground the opposite position, RY1 closes aiid any degree of accuracy, particularly installation. 18 wire on a 500 -foot starts the relay. when using No. APPEARANCE - Baked on RY2 makes and breaks the high - run. black enamel finish. All voltage supply circuit. The contacts Why not use a 600 -ohm open -wire line hardware electro -plate gal- should be wide -spaced and insulated for and match it to the receiver and an- vanized. 1 kv or more. We recommend that you tenna through 425 -ohm quarter -wave SAFETY -All steel, sturdily use a d.p.s.t. relay with two sets of stubs? The 600 -ohm line can be made braced construction. Weight contacts in series. When S2 is in the from No. 18 wire spaced 3 inches on is evenly distributed on all four feet. 15F6 829-8 SHORTING 10 TURNS NO.18 LINK CONVENIENCE -Will fit DYNAMOTOR CHANNEL SELECTOR WIRE AROUND} RESISTOR r -t any roof. One man can 005 0j2 /10KV easily and quickly erect MICA 1'KV either the five or ten foot tower plus mast and an- is easily = 25 ALL- tenna. Mount MH 250 climbed for service and uul Comes packed _I15 I KV maintenance. SPAC in a flat carton for easy TT G storage. 100 J IODw TT ECONOMY Low erection -15V - IIIV-- °I2 Va costs. No special tools re- 0) 12V 11_ssK 600V I quired. RYI DYNAMOTOR SWITCH in Price. +600V TO 625 V +200 Low eoce52 1 St 500uut 151I/25W 471 Phone° I America's top distributors and dealers 1° send " g25 TO ANT. POST ON lj12V ' carry the Wincharger RCVR RY2 500 MA rcv TV Roof Mount Tow 0-S RF AMP er. For complete dis TO ANT DRIVER OD tributor and dealer TRANS 006 815 I TIRA information, write to: Wincharger Cor- MIKE +150V oq RCVR STAND-BY _ t 12V .i, TRANS 4 Depart- TERMINALS RY3 T, _ 3 poration, 6 MIKE ment (l), Sioux 815 Z 4K 1 /AB JACK .- Í7 City 2, Iowa. n. T 829B op 6 toll zsw -ISV Write today . I1 70 11EG 50 50V NOW! FIL. SWITCH 1- 2 7 +600V® Corp. 20 W Wincharger 6Y6G +12V 100/25 V SIOUX CITY, IOWA NOTE-POINTS HAVING THE SAME NUMBER ARE CONNECTED TOGETHER OD3 NOVEMBER, 1951

www.americanradiohistory.com 112 question Ilex centers. The quarter -wavelength match- WORLD'S FASTEST SELLING ing stubs may be No. 12 wire spaced inches, or 1/4 -inch tubing or rod spaced 41/z inches. VOLT -OHM MILLIAMMETER The length of the matching stubs is calculated from the formula: L = 246 X V /f, Sensitivity where L is the length of the stub in per vol feet, V is the velocity factor (approxi- 1000 ohms mately 0.975 for open -wire lines), and f is frequency in megacycles. If the Uses latest design 2% accurate 1 Mil. D'Arsonval antenna is cut for a single channel, type meter. substitute for f the center frequency Same zero adjustment holds for both resistance of that channel. For an all- channel ranges. It is not necessary to readjust when switch- antenna, use the average of the fre- ing from one resistance range to another. This is quencies of an important time -saving feature never before the highest and lowest local included in a V.O.M. in this price range. channels or use the center frequency of the weakest local channel. * Housed in round- cornered, molded case. * Beautiful black etched panel. Depressed letters ADDING A TUNING INDICATOR filled with permanent white, insures long -life even ? Please show me how to connect an with constant use. electron-ray tuning indicator tube to an The Model 770 comes complete with a.c. -d.c. receiver which uses a 35Z5 -GT, self -contained batteries, test leads 50L6 -GT, 12SQ7, 12SA7, and 12SK7. I and all operating instructions. NTTNET would like to use either a 6AF6 -G or a $14 6AB5 Specifications: /6N5. -C. M., Maracaibo, Vene- 6 A.C. VOLTAGE RANGES: zuela 0- 15/30/150/300/1500 /3000 Volts. A. Your set requires approximately 6 D C VOLTAGE RANGES 0- 7.5/15/75/150/750 /1500 Vol ts. 120 volts across the series- connected Model 770 4 D.C. CURRENT RANGES: heater string for proper operation. If 0- 1.5/15/150 MA. 0-1.5 Amp s. is an accurate pocket-size V.O.M. 2 RESISTANCE RANGES: you use the set on a.c. only, then you Measures only 3té" x 57/e" x 21/4 ". 0 -500 Ohms 0 -1 Megohm. can connect the indicator tube as shown at a and supply its Write Dept. RC -11 for catalog of complete line. heater voltage from 6AB5/6N5 Manufactured and Guaranteed by 270K SUPERIOR INSTRUMENTS B+ 135V

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B- Just For a DID YOU CET IT' IF NOT I vV 2111,3¢3/32 ,axle Examining 50L6GT 6SK7 elCYDSX 8911 SEND NOW FOR B -A's 3525GT 6A85/6N5 1 125A7 12507 ea'rraWna I 136 BIG PAGE 1 Get this Book COYNE'S i TO AC /DC of TV l' I C- CATALOG LINE 200A IOW TUIt E PAT - New 5- Volume Set TERNS & WAVE TO B- FORMS FREE. Gives you or CHASSIS dozens of actual TV Test Pat- APPLIED D terns and wave forms -tells how to use them to shoot trouble and 35Z GT 12$57 12507 repair TV sets quicker . . PRACTICAL easier. Money- making short outs TOA 50L6GT I25Á7 that help you get ahead In Tele- 1952 LC/DCCI vision. It's yours FREE! gp010 Complete RADIO - Practical . . . UptoDatel tELEU1S10n a small 6.3 -volt, 1- ampere filament This book is our gift to you for TELEVISION examining Coyne's brand net, LELTR0111t5 transformer. If the set is used on d.c., 5- volume set APPLIED PRAC- TICAL RADIO- TELEVISION. you may substitute a 6SK7 for the Itere is the most completely up to -date set of reference books in 12SK7 and connect the heater of the America! 1500 easy-to- under- 6AB5/6N5 in the filament string as stand pages; 1000 illustrations. Covers all phases of radio and shown at b. The 6SK7 draws 300 ma, television. Tells you how to install, service trouble shoot. align so resistors must be shunted around all types of radio and television sets. "Break- down" photos help the sections of the string which con- you understand quicker. tain the 150 -ma tubes. The drawing at 5 tional Free Book Offer c shows the Seed No Money! heater circuit of the av- Mail coupon now to get this great ne" erage 5 -tube receiver using the tubes 5 volume set and the FREE Book of FREE Picture Patterns. Use the set 7 days you have listed or their equivalents. If If you keep the set, pay Just $3.00 after 7 days and $3.00 a month until 7 DAYS a 35L6 can be used for the 50L6, the $10.50 plus postage is paid. (Cash l'' price $15.00., If not 10Orge satisfied TRIAL INC[UDING 21 PACES OF 6AB5 can be inserted without other with set send it back and owe us noth- changes. ing. EITHER WAY THE BOOK ON TV , DOLLAR-SAYING BARGAINS! PICTURE PATTERNS IS YOURS FREE. (' Coupon Is just request to see set and get Free book of Some receivers develop considerably picture patterns. This offer Is limited. ACT NOW more a.v.c. voltage BURSTEIN- APPLEBEE CO. -r than others for a MAIL 4 McGee St. given signal input to the antenna, there- COUPON NOW! Kansas City St. `is COYNE ELECTRICAL 0. TELEVISION -RADIO SCHOOL FREE fore allowance must be made for indi- SOO S. Pauline St.. Dept. B1 -T1, Chicago 12, III. Send your 1952 catalog to Ip vidual receiver peculiarities. Rush "APPLIED PRACTICAL RADIO -TELEVISION" on 7 days' FREE TRIAL, per offer above. Name E In this circuit, 10 volts must be ap- NAME Age plied to the grid of the 6AB5 for zero Address.. Address shadow angle. Therefore, it may be City Zone.... State City State J necessary to add a cathode biasing re- Where Employed sistor. A resistor of approximately ()Check here if you want net sent C.O.D. You pay postman $15.00 plus C.O.D. postage. Same money- BURSTEIN-APPLEBEE CO. 2,000 ohms will be about right. back guarantee of satisfaction. -end - RADIO- ELECTRONICS for

www.americanradiohistory.com With the Technician 113 RTMA ANSWERS TECHNICIANS r 1 The Radio -Television Manufacturers You'll find it Association's Service Committee met September 18 at New York. Delegates of several radio -TV service technicians' and TV contractors' associations were also present. The committee made a formal reply to the proposals made by in the the service technicians' representatives at the committee's Chicago meeting (RADIO- ELECTRONICS. Aug. 1951, page MASTER 87 and Sept. 1951, page 119). On the question of design the RTMA committee stated that the majority of member manufacturers were in favor No More of, and had already complied with, re- Files of quests such as stamping model and Small serial numbers on the chassis, providing tube layouts in each set, providing pro- Catalogs and This yeeial offer avail- covers on metal picture tubes, able ONLY thru Di - Loose tective utors (publisher' price view, utor .50). The engineering sets with servicing in he's bulk Literature of the cost for the priv- and that practically all their other mem- ilege of printing their bers had "set wheels in motion" in that The Industry's OFFI- ad on the front cover. CIAL Buying Guide of direction. The committee did not quite Radio- Electronic-Tele- When you BUY -- SELL -- SPECIFY see its way clear, however, to promise vision parts and equip- that such problems as tubes and fuses ment. you must have the MASTER placed under the chassis would be set- 1100 Pages This single volume replaces all other small catalogs Hard Cover Over 90% of the products manufactured in the Radio -Electronic -Television tled immediately. in this BIG 1100 page Permanently Bound Parts and Equipment Industry are catalogued Even after it was pointed out by ser- MASTER Buying Guide. Complete descriptions, with specifications and vice delegates present that large manu- Fully Indexed illustrations are written and compiled by each manufacturer covering Over 75,000 Items such products as: tubes, instruments, TV parts, transformers, capacitors, with relays, coils and antenna equipment. Also, re- ufacturers had marketed receivers Over illustra- resistors, test equipment, 7000 intercoms, tools, hardware, switches and thou- glass, so that the face tions cording and PA systems, removable safety sands of associated products. ITS YOUR "RADIO BIBLE" -SAVES YOU of the picture tube could be cleaned, Weight-5 lbs. TIME AND MONEY. Size -8%y x 103/4" the committee insisted that the under- BE MASTER -Minded -GET your copy NOW writers have not approved the practice. Serving the Industry 16 years from local Distributor The "more liberal program" in supplying service notes was "economically Sà ONLY available thru Distribu unfeasible" the committee stated. tors at this special $1.95 pricj Krantz of Philadelphia, representing - to - -a NETSDA, pointed out that much of the present distribution of service data is wasted, going into the hands of dealers SHOOT TROUBLE and distributors who neither under- Tv stood nor used the data, and that if AMPERITE such data were in the hands of the FAST! Studio Microphones it would re- active service technician With H. G. CISIN's at P.A. Prices sult in an increase in components sales Copyrighted Rapid cover the cost of probably sufficient to "TV TROUBLE SHOOTING METHOD" distributing the service data. The ser- EARN more money! Locate television troubles vice technician, it was pointed out, by this quick, entirely new method. Rapid Ideal for use the cor- checks applied in simple, logical steps enable BROADCASTING would naturally prefer to you to classify, sub -classify, diagnose and lo- rect replacement part, which could be cate all faults in record- breaking time regard- RECORDING less of make or model! installed without difficulty, if he had PUBLIC ADDRESS would permit him A. G. CISIN Is well -known to radio and tele- the information which vision men as a recognized electronic engineer, inventor, "The ultimate in micro- to order it. This point evoked consider- technical author and educator. He has trained thou- phone quality," says sands of television technicians, many of them now able interest, and it is felt that future owning their own prosperous TV service organizations Evan Rushing, sound or holding important positions in television. The re- engineer of the Hotel policies of RTMA members may favor sults of his years of experience are embodied in this remarkable TV TROUBLE SHOOTING METHOD. New Yorker. wider data distribution than envisaged Shout right into the HERE'S PROOF! J. B. Seiler, Chicago, writes: "Rush by the committee's statement. another copy. Am tickled to death with results. Your new Amperite Micro - book hasn't failed me yet." G. E. Hirsch, Jamaica, phone-or stand 2 feet It appeared that the manufacturers N. Y.: "Congratulations! Your book extremely under- had not been able to make progress on priced. Very ingenoius in its logical use of cause and away- reproduction is effect, should be in every TV tool kit." the proposal for an effective training always perfect. INCREASE your earning power with the Not affected by Models program on u.h.f. and color, for techni- most valuable aid to TV servicing ever any climatic conditions. written ! cians to whom these fields are new, as Guaranteed to with- RBLG -200 ohms requested at the June meeting. Instead, Guaranteed, Money Back in 5 Days If Not Satisfied! stand severe "knocking RBHG -Hi -imp. some progress had been madé in a plan Send Your Name & Address Today. $ around." List $42.00 to have a television technician's train- POSTPAID - - - ing course included in the curriculum "Kontak" Mikes RUSH COUPON NOW! Model SKH, list $12.00 2,500 vocational schools. of Model KKH, list $18.00 Service technician representatives H. G. CISIN- CONSULTING ENGINEER attending the meeting expressed the E -7, 200 St.,Brooklyn2, N.Y. Offer, Dept. Clinton Introductory feeling while much asked for at Write for Special folder. that Enclosed is S for which please Special illustrated the Chicago meeting had not material- rush copies (postpaid) of your and 4.page TROUBLE SHOOTING METHOD. Offer: ized, considerable progress had been TV I Name made. The very fact that manufacturers AMPER/TE i mpany Inc and service technicians are at last work- IAddress 561 BROADWAY NEW YORK 12. N. Y. ing together for their mutual benefit is I Zone.... State Canada: Allas Radio Corp., Ltd., 560 King St. W., Toronto a great step forward, they pointed out. LCityy NOVEMBER. 1951

www.americanradiohistory.com 114 11'itli the Technician NETSDA MEETS IN PHILLY The first fall meeting of the National Electronic Technicians and Service Dealers Associations (NETSDA) was held September 9, in Philadelphia. Del- egates from fifteen member Chapters were present. Delegations from the Ra- dio and Television Servicemen's Asso- ciation of Pittsburgh, Inc. and the Tele- vision Contractors Association of Phila- delphia were also present as guests. The delegation headed by David Van Nest of Trenton presented application for membership to NETSDA, which was voted on and accepted, making the Trenton Radio and Television Service- Special men's Association the sixteenth Chap- Offer On This ter in NETSDA. Dave Krantz then reported on the Complete Chicago June meeting of the RTMA service committee, which he had at- RADIO tended as representative of NETSDA, and informed the delegates of the coming meeting in New York, to which a ENGINEERING representative was also invited. Krantz and Max Liebowitz were elected to at- tend that meeting. (See P. ;13.) Delegates then voted to add to LIBRARY NETSDA's Industry Relations Com- Only $2.25 New, Up -To -Date Edition of Fam- mittee Max Leibowitz of New York and 176 Pages 131) Illustrations ous Library Covers Whole Field Dave Krantz Philadelphia of Radio of to assist Engineering. Places Norman Selinger, vice -president of First Gernsback Library Book with Latest Facts, Standards, Data, Durable hard -cloth cover Practice, and Theory At Your NETSDA, in Washington, D. C. in Fingertips making a representation to the Federal One of the finest books on fundamentals Trade Commission on September 26th. ever written for the practical service tech- The five big volumes of the new edition oí nician. BASIC RADIO COURSE starts the Radio Engineering NETSDA will join with other service Library now include groups in making representation. with Ohm's law, then takes you through the very latest facts, standards, data, and prac- this the circuits of a modern radio set and tice. This Library will help solve hundreds of NETSDA voted unanimously approv- tells you how and why they work. It's problems for designers, researchers, engi- ing Sylvania's action regarding its ad- actually a pleasure to read because the neers, and students in any field based on vertising policy in regard to Look Mag- author believes learning should be fun. radio. azine and suggested that other members He talks the service technician's language Written by leading radio engineers, these of the electronic manufacturing indus- and isn't afraid to make you smile once books cover circuit phenomena, networks, in a while. But BASIC RADIO COURSE tube theory, vacuum tubes, try follow Sylvania, in the protest to amplification, Look Magazine, thus assisting doesn't skimp on facts. It gives you all the measurements, etc. give specialized treat- the elec- technical information you'll find in a ment of all fields of practical design and ap- tronic Servicing profession. (See R. higher priced book. But, you'll enjoy read- plication. They provide you with a complete 116.) ing it and you'll save money. and dependable encyclopedia of facts. A committee was appointed under the PUBLISHED BY REQUEST 5 Volumes, 3872 Pages, 2770 Illustrations chairmanship of Mr. James Daly of the BASIC was Eastman's FUNDAMENTALS Philadelphia Radio Servicemen's Asso- RADIO COURSE published OF VACUUM at the request of many radio men TUBES, 3rd Edition. ciation to formulate a national code of who Terman's RADIO ENGINEERING, 3rd Edi- read, enjoyed and learned from John tion. ethics for NETSDA. Frye's series on the fundamentals of radio Everitt's COMMUNICATION ENGINEER- The next meeting was set for Octo- servicing which concluded only recently ING, 2nd Edition. ber 7, at New York City. in RADIO -ELECTRONICS. It can help Hund's HIGH FREQUENCY MEASURE- the experienced technician as well MENTS, as the 2nd Edition. beginner. Order your copy today. Henney's RADIO ENGINEERING HAND- MARYLAND'S TECHNICIANS BOOK, 4th Edition. FACE LICENSING PROBLEM TWENTY -SIX CHAPTERS SEND NO The Electron Theory Ohm's Law and the Resis- MONEY Some Maryland believers in the value tor What is Induction? Capacitance How Capacitors are Mode Reactance, Special of Impedance Low Price -Easy Terms licensing to the service industry have and Phase Resonant Circuits Transformers - recently been inclined to admit that How They Work The Diode Vacuum Tube Tri- On this special offer you get this Library ode and Tetrode Tubas The Pentode Vacuum for $34.50, instead of $39.00. You save $4.50 even a good thing can be carried to ab- Tube Vacuum Tube Characteristics The Power and may pay on easy terms. Mail surdity. Cause of the opinion was a Supply Power Supply Types Sound and Loud - coupon be- Speakers The Power Output Stage The Volt- low to examine the Library FREE for 10 days. "Notice to the Public" recently issued age Amplifier Demodulating the R. F. Re- No obligation. These books are recognized as by the Electrical Administrative Board ceiver Selectivity The Converter Stage Some standard works; you are Oscillator Circuits How To Trop a Signal bound to need them. of Baltimore County, Maryland (Balti- Signals in Space Receiver Refinements Instru- So take advantage of this special money - more County surrounds ments and Tools Service Techniques. aving offer. Mail the city on three coupon at once! sides, but Baltimore proper is not part of it). Order your copy from your distributor or McGraw -Hill Book Co., Dept. RE -11 -51 j 327 West 41st St., New York 18, N. Y. i The notice read: MAIL THIS COUPON TODAY Send for 10 days' FREE trial, the RADIO i is illegal to perform ENGINEERING LIBRARY. If not satisfied I It or have per- Radcraft Publications, Inc., Dept. Ill 25 Broadway will return books. Otherwise I will send $4.50, B formed any electrical repairs, instal- West plus delivery charges, then; and $5 a month for I lations, or electrically operated ap- New York 7, N. Y. 6 months. (Reg. price $39.00; you save $4.50) I My remittance for $2.25 is enclosed. Please send paratus including television and radio, me a copy of Book No. 44, BASIC RADIO Name Ii except by a person holding an elec- COURSE postpaid. B trician's license as set forth in the Home Address I RE-11-51 i 1949 Acts of the General Assembly NAME City & State i of Maryland. Persons violating this We'll Pay Delivery Charges if you enclose i law will be prosecuted... . STREET $4.50 first payment WITH coupon. Same return I privilege for full refund, i Shortly thereafter, a meeting was held by the board, before a surprisingly CITY ZONE STATE RADIO -ELECTRONICS for

www.americanradiohistory.com 11'itlt the Technician large body (more than 200) of interested radio -TV service technicians, radio amateurs, and experimenters. The board's chairman, Louis E. Susemihl, a local electrical contractor, declared that his business had improved 25 per cent eL 1.YOU NEED PRACTI since these new rulings had gone into OF effect. He continued by urging radio TO DO THE KIND and TV service technicians to obtain TRAINING their licenses. "It lahesactual practic on real equipment to "I want practical To obtain one of these licenses, how- learn any job well" facts, not long- ever, it is necessary to have worked for winded lectures and complicated a master electrician for a period of at mathematics." least two years, and to pay various fees TV SERIIICINIC!YI and pass an examination. This would limit licensing to a very small group of LEARN BY DOING WITH the persons now working in the field of I "If want to learn a I lI MILTON "I learn taster, easier trade S. KIVERI* electronics as it is generally accepted. and remember longer go to someone in that busines, sic Active president for practical of T. when my hands help help. They kno, professional engineer, C. I., registered High points of the meeting included from experience." Internationally Television me think." known Consultant. magazine author of several questions as to the fitness of articles. TV books and You the board members to pass on the quali- * build and train Prepare Now for Color TV and UHF! screen on modern large fications of electronics technicians whose TV set. You can't learn Television Servicing from books alone. skills are quite different from those of leading weeks experience The right way . . the only way to learn to test, trouble * servicet organization. with shoot, repair and adjust television sets is by actually You learn electricians. * testing trouble doing this work. That's how you learn with T.C.I. of all types shooting, re- As a result of the meeting, a second of TV sets. PRACTICAL TELEVISION TRAINING! This easy -to- * You learn on COLOR TV, including meeting was held between the board follow training is based practical experience. version and con UHF. We guarantee - supply. to and representatives of a combine of you with latest facts Look How Practical This Course Is! Phases of television. on these radio amateur clubs. James F. Gordon You train on a large screen modern television receiver, and Willis Jones, of Bendix Radio Di- furnished as Dart of the course. You build this set . . service it ... trouble shoot it ... adjust it .. . keep it! vision of Bendix Aviation Corporation, As an optional feature you can get two weeks of actual Towson, field experience with Chicago's largest independent TV Maryland, announced after the servicing organization. You learn set conversion. master meeting that the board had agreed to antenna installation, COLOR TV. COLOR CONVERSION, Milton S. Kiver, President money -saving short cuts practiced by expert TV servicemen. TELEVISION COMMUNICATIONS INSTITUTE interpret the rulings in such a way as 205 W. Wacker Dr., Dept. RE8, Chicago 6, 111. SEE FOR YOURSELF bow this practical training can help 5 "ES, MR. RIVER! Rush FREE Catalog and Sample to eliminate the requirement for radio you get ahead faster in the big -money TV field. Write for Lesson on your practical course in TV Servicing. 1 am not obligated. Salesman will not call. FREE Catalog and SAMPLE LESSONS. Age is no barrier. amateurs and radio broadcasting sta- Many T.C.I. students are over 40. ACT NOW! tion operators to hold County Electri- Name Age cian's Licenses. This was not exactly a Address COMMUNICATIONS victory, since these classes of operators TELEVISION City Zone State are protected in their rights by the (BEGINNERS: Check here for facts on Pre-TV 205 W. Wacker Dr., Dept. RE -6 radio course. Federal no Chicago 6, Illinois Government, and doubt the 115I IIEB =I =I NMI=...... ME Ma board had learned that fact. At the present time, according to N Paul D. Rockwell, principal engineer at DYNAMOTORS Type Input Output Radio Bendix Radio Division and president of Volts Amps. Volts Amps. PE86 28 1.25 250 .060 RC 36 the Chesapeake Amateur Radio Club, (TELEVISION DM418 14 6.2 330 .170 RU 19 DM33A 28 7 S40 .250 BC 456 DM42 14 46 515 .110 SCR 506 there are some indications that the en- 1030 .050 tire set of rules and regulations may be PElO1C 13/26 12.6 400 .135 SCR S1S 6.3 800 .020 changed, but the ruling continues to re- BD AR 93 28 3.25 375 .150 SERVICING 23350 285 .075 APN -1 quire electrician's licenses for radio and ZA0515 ii/24 á/ï 500 .050 B -19 pack 12 9.4 275 .110 MARK 11 television repairmen. by Walter H. Buchsbaum 500 .050 D -104 12 225 .100 Get this brand new, complete 440 .200 DA-3A 28 10 300 .089 SCR 522 handbook for sure -fire working 150 .010 14.5 .5 PITTSBURGH'S CREDIT UNION knowledge of TV installation, 5053 28 1.4 250 .060 APN -1 PE73CM 28 19 1000 .350 BC 375 maintenance and troubleshoot - CW21AAX 13 12.6 400 .135 The Radio and Television Service- 26 6.3 800 .020 3.40 pages ing. Tells you step -by -step pro - 9 1.12 men's Association of Pittsburgh, Inc., 170 illustrations PE94 28 10 300 .200 SCR 522 cedures for audio IF alignment, 150 .101 14.5 .5 applied for membership in the Federa- video IF alignment, aligning DY2/ARR2 DY22 ARC tion of Radio Servicemen's Association RF amplifiers, mixers, oscil- of Pennsylvania. lators, etc. All possible defects INVERTERS is believed to classified for ready reference, PE 218 -E: Input: 25 28 vdc. 92 amp. Output: 115 v. Pittsburgh be the first 350 -500 cy 1500 volt- amperes. Dim: 17"x61/2'910". association in the country to set up a thoroughly analyzed to show New 549.50 PE 218 -H: Same as above except size: I81/a °x8x10 ". Federal Credit Union. This was done to what is wrong and why . . . New 549.50 help the small shop owners and the in- and what to do to correct the Symptoms of de- POWER TRANSFORMERS dependent service technicians to obtain fective operation defect. No mathematical knowl- easily recognized. edge needed! Practical, author- ALL PRIMARIES 115Y, 60 CYCLES additional financing for their business quickly corrected STOCK lt RATINGS PRICE by illustrations. itative, up -to -the minute, the CT-458 39OVCT/30 MA, 6.3V/1.3A, 5V/3A. 53.45 and the purchasing of test equipment. diagrams and how- CT100 800VCT/100 MA, 8.3V/1.2A. 5V/3A.. 4.95 perfect handbook for set own - CT-319 680VCT/.085A, 5V/2A, 6.3/7.5A, to-do-it facts in 6.3/3A. 3.25 this new book. e1-c, trainees, and repairmen. CT-931 585VCT/86 MA, 5V/3A, 6.3V/6A 4.95 CT-441 50.46V/200 MA, IOVCT/2A. . 2.75 NETSDA ADOPTS EMBLEM CT-442 525VCT/75 MA, 5V/2A,., 10VCT/2A, USE IT 10 DAYS FREE 50V/200 MA 3.85 CT-828 1500V .180 2.5/12,30/.100. 9.95 Coupon below brings you "Television Servicing" CT-15A 350VCT .070 16.x3/.8, 8.3/1.8, 3 on FREE trial for 10 days, without obligation. 2.95 CT-071 110V .200 323/5./1000, 5V/10. Mail it NOW. 4 9S CT 378 2300V 4 MA 2.S/2 6.95 CT-387 580VCT .050 5VCT/3A 2.25 CT-721 550VCT .100 8.3/1, 2.SVCT/2. 2.95 PRENTICE -HALL, Inc., Dept. M -RE -1151 CT-99A 2x1IOVCT .010 8.3/1A,2.5VCT/7A3.25 CT-403 35OVCT .028 MA 5V/3A ...... 2.75 70 Fifth Ave., New York 11, N. Y. CT-931 585VCT .038 5V/3A, 8.3V/8A. 4.25 CT-610 1250 .002 MA 2.5V /2.1A. 2.5V/ Send roe, for 10 DAYS' FREE TRIAL, "Television 4.95 Servicing." I will return It to ten days and pay noth- CT-137 350VCT .026 MA 5/3Á 2.75 ing-or keep it and send $1.35 down (plus postage) CT888 330V .065 8.3V/1.2, 8.3V/ and $2 monthly for 2 months. 600 MA 1.75 Rated Concerns Send P.O. Above is the new emblem of the National NAME Electronic Technicians and Service Deal- Send M.O. or CH K. Mdse. Guartd. Shoe. Charges ADDRESS ers Associations, adopted in Washington Sent C.O.D. Price F.O.B. N.Y.C. Phone Di. 9 -4114 last spring. It will be supplied CITY STATE to all COMMUNICATIONS EQUIPMENT CO. chapters in the form of mats and decals. SAVE! Send $5.35 with this coupon, and we'll pay postage and packing. 131 Liberty St.. Dept. C- I I Nes York City 7. N. Y. NOVEMBER, 1951

www.americanradiohistory.com With the Technician

_Avel'ere,z_ RADIO -TV EMPLOYMENT BUILDERS OF QUnlliv RADIO INDUCTANCES SINCE 1924 PROSPECTS ARE GOOD The U.S. Labor Department predicts NOW AVAILABLE strong demand for skilled electronic TO THE SERVICEMAN ' technicians throughout the early 1950's. AND EXPERIMENTER Chief demand will be in the fields of THE FAMOUS home radio and television servicing and in manufacturing and servicing military, industrial, and household electronic equipment. The prediction, which appears in an "Occupational Outlook THE FINEST Handbook" issued by the Department in MINIATURE co-operation with the Veterans Admin- I. F. TRANSFORMER istration, continues to state that service EVER work will increase with the increase of MANUFACTURED! automatic control and automatically op- ONLY 2 Vs" HIGH erated appliances and equipment. Such BY 1/4" SQUARE control is predominantly electronic. SHELL CORE PERMEABILITY TUNED. STABLE SILVER One note of warning was sounded: MICA FIXED CONDENSERS - NOT MICA COM- PRESSION TUNED. The radio service shop owners who do UNIQUE SNAP CLIP MOUNTING FOR ROUND HOLES IN CHASSIS. not intend to go into television may

455 KC in ut transformer gain 50. Band width at 2 times have to prepare to go out of business, 16 KC; at 10 times 40 KC. according to the report. 455 KC output transformer gain 110. Band width at 2 times 18 KC; at 10 times 50 KC. 262 KC Input transformer gain 65. Band width at 2 times 9 KC; at 10 times 23 KC. ETHICS AND WARRANTIES 262 KC output transformer gain 130. Band width at 2 times DISCUSSED IN JERSEY 10 KC; at 10 times 27 KC. CAT. No ITEM NET PRICE The Television Contractors Associa- RADIO TUBE 12 -HI 262 KC Input I. F. Trans. 12 -H3 262 KC Output I. F. Trans. tion of New Jersey made business ethics 12 -CI 455 KC Input I. F. Trans. and warrantie3 the of FUNDAMENTALS 12 -C2 456 parts subjects KC Output I. F. Trans. discussion The"K- TRANis distributed at an August meeting at the by George J. Christ nationally the American Legion Home in East Orange. Instructor, Div. of General Education, to jobber only New York University by J. W. Miller Company. President Gus Friedman pointed out 96 pages Menufect.nd under "K- TRANS" Patent that the problem of parts warranties is Only $1.00 Numbers 2435630 and 2429466 of Automatic 74 illustrations Manufacturing Core. becoming a serious matter, and that in What! You never went to college? You don't some cases warranties on some compo- understand calculus backwards (and forwards)? J. W. MILLER COMPANY nents were on the point of expiration You can't outperform an electronic computer? Really deep down you don't understand radio 5917 S. MAIN ST. LOS ANGELES, CALIF. when the equipment containing them tubes? reached the customer, thus creating a Don't worry about it, for here's a brand new i/ARN difficult situation for contractor, dealer, book whose sole object is to make you understand just what radio tubes are, how they work, and and distributor. just how you can expect them to behave in a The Association advertises in two radio circuit. The author, with years of radio Newark Sunday newspapers, tube teaching experience for a background, takes asking TV the complicated subject of radio tubes and makes service contract holders to make any it so simple and easy to understand that you'll legitimate complaints to the associa- just naturally wonder why you didn't understand it all by yourself. tion's grievance so committee, that any If you're a beginner, then this book is a instances of dishonesty or incompetence definite must, and if you've been in the business may be investigated and rectified. more years than you can (or care to) remember, then this book will give you a fresh new approach to the subject. SYLVANIA CANCELS LOOK RADIO TUBE FUNDAMENTALS goes all the way from diodes on through multi -purpose Among the indignant respcnses to the tubes, and then into circuits. Don't worry about getting lost -the author is with you all the way. Look article, "Pop Is a Moral Slacker," Get it today. It's the biggest dollar's worth of was one that came from Sylvania Elec- radio info you can possibly buy. tric Products, Inc. Sylvania had been running its well -known series of ads USED AS A REFERENCE TEXT Radio Course. Div. of General promoting the skill and reliability of Education, New York University TRAIN QUICKLY! the radio service technician in that OLDEST, BEST EQUIPPED magazine, and by coincidence part of Partial list of Contents SCHOOL of ITS KIND in U.S. the article describing "radio repair ex- Electrons in motion. Thermionic emission perts" as crooks and cheats appeared The cathode Plate current Space charge au . czncl Olcie4 Mess Diode load voltage on the same page. Ionization Voltage Come to the Great Shops of Coyne in Chicago. Get regulators The triode Plate resistance practical training in TEL EVISION-RADIOor ELEC- Although no part of the television Amplification factor Oscillation Gas tri- TRICITY- vital in Defense Program. Prepare now odes Tetrodas Pentode characteristics for a better job or better service rating. industry would deny that the servicing Multipurpose tubes Vacuum and gas photo - START NOW -PAY LATER field includes some dishonest individ- tubes Vacuum-tube grid bias Radio Tube You can finance most of your tuition, pay for it later applications Voltage doublers Detectors in easy monthly payments. Special plan for men of uals, this article stated that "America's Automatic volume control FM detection Draft Age. Part time employment service available. radio repair experts and garage me- Oscillators Converters Conversion gain. GI APPROVED Clip coupon for Big Free Illustrated chanics, almost to a man, have cheated FREE BOOK Book. Indicate below, course that the set owners and interests you. No salesman will call. Act NOW. car drivers. In near- See Your Distributor -or use coupon An Institution not for Profit ly every case, though they did diagnose and repair the trouble, they gave it a RADCRAFT PUBLICATIONS, INC, B. W. COOKE, Pres. fancy name and charged a fancy price." COYNE Electrical & Television -Radio School. 500 S. 12,111. felt Paulina St., Chicago Dept, 81 -81H I Sylvania that such an article did Radcraft Publications, Inc., Dept. 1Il Send FREE BOOK and full details on: not fairly represent the service tech- 25 West Broadway, New York 7, N. Y. TELEVISION -RADIO ELECTRICITY I nician and that Look in publishing it My remittance of SI.00 is enclosed. Please send me postpaid a copy of RADIO TUBE FUNDA- NAME had acted in a manner harmful to the MENTALS, Gernsback Library Book No. 45. service industry. To make the protest Name - I ADDRESS more impressive, all future Sylvania ad- Street vertising in Look was cancelled. CITY STATE (Italics ours. Editor) City Zone.. .State RADIO- ELECTRONICS for

www.americanradiohistory.com 117 SPECIAL OFFER! Save up to $2.50 over regular rates.

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A SUBSCRIPTION NOW WILL INCLUDE THE BIG 500 JANUARY SPECIAL TELEVISION ISSUE! RADIO - __...l, .ICONICS NOVEMBER, 1951

www.americanradiohistory.com 118 With the Technician.

BAR WESTERN UNION? A "good possibility" that Western Union might be prevented from continu- STAN-BURN ing in the television service field was stated to exist by Frank Moch of Chi- cago, president of the National Alliance of Television and Electronic Service As- CONDENSER SPECIALS sociations, in a bulletin issued to the BY PASS -ALL GUARANTEED PROVE ...001-400001 -400 Stan Burn .04 .002 -600 Stan Burn .O8 association's membership in late sum- .01-600 Stan Burn .07 .005 -600 Stan Burn . 12 .02.600 Stan Burn .09 .005 -6000 Stan Burn .59 mer. 05.600 Stan Burn .10 .1.600 Stan Burn . 19 -600 Stan Burn .Ó0I .07 20x20.150 Stan Burn .4 I The bulletin refers to the FTC (Fed- I 25.600 Stan Burn . 6 Burn .4 9 005.200 Stan Burn .07 50x30-150 Stan Trade Commission) investigation Stan Burn .3 2 EMC eral .004 -200 Stan Burn .07 20-150 into radio -television industry practices, 6 CHASSIS-630 -K2- Famous make 139.50 SUPERIORITY! and says that the FTC is especially in- CATHODE RAY TUBE SPECIALS terested in: 10BP4 $14.95 I6RP4A 26.00 1. Forced sales of parts warranties. 12LP4 19.95 I7BP4A 27.00 Model 201 12LP4A 19.95 20CP4 39.95 2. Failure to stock replacements. I9AP4AA mutual conductance tube tester r 14BP4 I9.95Í 47.95 Checks mutual conductance on 3. Use by distributors and manufac- I6DP4A 26.00 24AP4A 83.20 calibrated michromo scale Checks off and 16GP4 33.00 Single ion traps ... .39 tubes for gas content Detects both turers of -brand tubes parts. 16AP4A 39.00 Double ion traps .. ,59 shorted and open elements Tests 4. Charge by distributors and manu- 111 all tubes from .75V to 117 Filament RAM TRANSFORMERS r volts Tests all !octal, octal, and facturers of shipping costs in cases RCA type far IB" to 24" 70° DEFLECTION r miniature tubes Checks Individual YOKES purpose where are back -ordered. G. Type for 16" to 24" sections of multi- tubes parts Todd wired replacement Built -in roll chart X045 $3.85 5. Misrepresentation in advertising. These are very special for RCA, GE, etc. Spe- Model R201BC - 4V2" meter-sloping Oat ...... 13.05 counter 6. Failure of distributors and manu- prices. While they last- $69.50 facturers to co- operate in the sup- ANTENNAS Model R201BP - 41/2" meter hand Conlcals, less mast, 10 element S 2.98 rubbed oak plying of service data. Circle X, less mast 2.98 carrying case $73.50 Double V. less mast 2.98 7. Copies of written parts warranties Chimney Mounts -1 -12 .95 12 or more .89 100 ft. roll strapping .. 2.98 issued by distributors and manu- Mast standoffs .03 Model 204 facturers. 10 ft. masts, each I .59 M 12 or more. each 1 .49 m tube- battery -ohm capacity tester The bulletin then goes on to state: 55 mil. 300 ohm wire white or black, 1000 ft 1 9.97 Tests all tubes Including Novel & carry a complete line of popular makes of Radio sub -miniature Tests all batteries "You will undoubtedly be interested We and TV tubes, at 50/ discount. Also many other` under rated load Emission testing types. and all elect- direct readings to know that the Western Union at- special purpose and transmitting method gives easy, tronic parts and equipment at lowest prices. Send usr Tests resistance to 4 megohms tempt to enter the service field is also a list of your requests for quantities and prices. 1 mfd. Tests condensers from .01 to COD. All prices Uses four -position lever type being investigated, and we believe a Terms: 20% with order. Balance switches Checks condenser FOB. New York Warehouse. Minimum order 55.00. leakage very good possibility exists that West- Write for our latest price list to Dept. RE-11 Model 204 - portable oak case, will be barred removable ern Union eventually cover $55.90 from the service field." RADIO and STAN -BURN ELECTRONICS CO. f C.B.S. THEATRE BLDG.) Model 120 NEW STATE ASSOCIATION 1697 BROADWAY NEW YORK 19, N.Y. 120,000 ohms per) (volt meter) A new State federation came into be- 4 Resistance ranges from .2 ohm ing with the formation of the Texas to 300 Megs. S Current ranges to Replace Your Old TV Aerial 6 Amps. Uses 1% precision re.. Electronic Association June 3, 1951. It sistors 6 AC & DC voltage ranges With The NEW Snyder to 6,000 volts AC volts at 10,000 was founded at a meeting at Austin, ohms /volt. which delegates from the Dallas Model 120 - at open face $31,95 Radio Sales and Service Association, Moel Electronic Technicians As- Portable2oak case..... $36.95 the Texas MOTORLESS sociation of Houston, the San Antonio 360° Radio and Television Association, and the Texas Radio Service Association of Write Dept. RE -11 for Free Complete Catalog Austin were present. Representatives TV AERIAL of these and other Instruments. from Fort Worth, Galveston, and Lock- hart also attended the meeting. SAME CLEAR PIX AS click of switch -See them at your Jobbers- clears picture Two earlier meetings, at which the MOTOR ROTATING AERI- instantly proposed setup was thoroughly dis- AL SYSTEMS COSTING cussed, had been held. TRIPLE THIS PRICE ' Electronic The charter permanent officers are: ' Measurements Corp. president, Frank J. Humpola, Houston; Only $18-95

280 Lafayette St. , New York 12, N. Y. vice -president, Forrest Baker, San An- Complete with 3 I1/s" mast sections, 75 ft. of 3 cond. (,port Dept. 303 w. 42nd St.. N r f, tonio; secretary, Luther Bradley, Dal- cable. Electronic beam se- las; and treasurer, J. D. Huff. T. P. lector switch. Connecting stubs, guy ring mounting Robinson of Dallas was appointed pub- base, "U" clamps. C] lic relations representative. For Ultra Fringe Electronically Deems In complete Consecrated to Quality Output 360° rotation to give clear picture on all channels. You choose direction with D hi-tnic selector switch. and Golden Rule Service Object of the association is to unify Mounted on or near TV et. 18 hl- tenuti all. aluminum and bring together the programs of the alloy element.. Complete ready to Install. AX599 DIRECTRONIC ARRAY FOR FRINGE Same local groups into a co- operative effort, as TX -599 less mast 16.95 AX -56 DIRECTRONIC ARRAY FOR CITY AREA to advance the cause of the radio and with switch, lead -in less mast $9.50 foi television technicians of Texas, and to 6 element array .° °l°9c° STEEL MAST SECTIONS weather treated. iPfia provide a means for watching for any 10 Ft. I /4" di. $2.10 end 1.35 255 Grant Are., East Newark, N. J. 5 Ft. ly4" di. crimped ASTRON CORPORATION proposed legislation that would affect Chimney Mount Brackets CM -100 1.59 - -2, Adj. to 18" Wall Mount Brackets WB the welfare of these technical men. Heavy Duty 3.75

In a communication after the date Order from Dept. RE -I I or call Mulberry 2134 of the meeting, the Fort Worth group WRITE FOR FREE F.Y.I. BULLETIN PEN -OSCIL -LITE notified the secretary of the completion Extremely convenient test oscillator for all radio of their own local organization and servicing; alignment Small as a pen Self WHOLESALE powered Range from 700 cycles audio to over their intention to apply for membership 600 megacycles u.h.f. Output from zero to 125 RADIO PARTS CO., Inc, v. Low in cost Used by Signal Corps in the Texas Electronic Association at LI Write for information. which was to held 311 W. Baltimore St. GENERAL TEST EQUIPMENT the next meeting, be 38 Argyle Ave. Buffalo 9, N. Y. in September. It was anticipated that BALTIMORE 1, MD. other associations would join then. RADIO -ELECTRONICS for

www.americanradiohistory.com With the Technician 119

SOUTH JERSEY SEEKS MEMBERS Membership Committee of the Allied Television Technicians Association of South Jersey has designed a program to extend its membership drive to all of P4RAP/S7 South Jersey. 1wM6NNa Present officers are Rodger Haines, THE RADIO- MINDED MAN president, Paul vice -president; EVERYTHING FOR Matlack, ************************* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * ** Bob Blazer, secretary; and Gordon * Laney, treasurer. At the last meeting * * * a nominating committee was appointed * to select the list of candidates for elec- * DOES YOUR TV DROOP tion of officers for the October meeting. * 01, Paul Matlack, vice -president of the * éíooP Association, has just received the con- * FROM TVI* BLOOP? * tract for the Inter -Communication Sys- * SAP WITH tern on the New Jersey Super Highway. BANISH INTERFERENCE

**. HIGH PASS FILTER ppC NIAGARA'S FAMOUS TRENTON, N. J. NOMINATES * Wired and tested...$2.95 * At its recent election the following * Postpaid if entire amount is Positive protection against interference from amateur transmitters, included with order. diathermy, and all other devices generating rodio frequency inter- * : George Owens, * officers were chosen * ference below 40 MCS. Designed for 300 ohm leadin. No loss in * president; Francis Wolf, vice- presi- * Television interference brightness or clarity. .* Redman, secretary; dent; Charles * * while David Van Nest was elected dele- * * * * * * * * * * * * * * * * * * * * * * * * * * * * * ** gate to the NETSDA. Trenton's ************************* * * 80 MTR TRANSMITTING STATION delegates were requested to present * ORIGINAL 630 TYPE KIT NOVICE $15.95 application for membership to * * 1- TRANSMIT ER * NETSDA. The Trenton association will * * (as described in May QST) also co- operate with other groups in * ', * 2 -POWER SUPPLY KIT (for above) 9.95** * t1' New Jersey State in meeting and dis- - * (see June QST) * cussing State problems. * ° j * ANTENNA KIT (80 mtrs) 2.95 * * * $28.85 * D. REPORT * t * COMBINATION SPECIAL WASHINGTON, C., * .. íJ * ALL THREE KITS Q * * 4' ,. .- . * All kits are available separately at * Under supervision of J. T. Burns, * prices indicated beside each kit. Coco- L * - 3-* * pieta instructions with each kit. íiL.V * president, and Norman Selinger, vice /i president, we are preparing a new and * '* +.q3 s` * * * ** * * * * * * * * * * * * * * * * * * * * * ** complete series of technical lectures * ', ',? * REMOTE CONTROL FOR * and business forms. Membership Corn - * THE THING.. a drive to ob- mittee is contemplating * $1 t * (PLUS 51.00 BOOK FREE) * tain membership from all service *, The answer ta the "Re - * * mote Control" experiment- * organizations in Washington, D. C. A s dreamt A completely , wired, 3 tube remote con- * amt' originally used committee will investigate all licensing Brain for re- * * * 1 as Electronic bills are being presented in the * Manufacturer's * to-',1,0 . ote thermo- static control * that 2900* of electric blankets. Can * be used, with slight various municipalities and states as an * Closeout -Brand New * J , trans, a control model * * .i ,, trains, planes, trucks, re- aid in formulating a licensing bill for mote for rage open TV RECEIVER * and close garage doors * Washington, D. C. 16 " -20" * from your car, or to InnCacc control any device * the Tele- Completely Wired, Aligned and Tested- * + accordance with your * Joe Burns, president of * * w m enuitr- Ready to Install With Big 12" High Quality * ae ? And that's not all! With vision Associates, is also Chairman each snit we will give you * * PM Speaker. * absolutely free, one copy * of the Membership Committee for ; fib of Gernsback Library's * .a * 3 Rectifiers)! popular new book "Model NETSDA and is kept busy meeting * 30 TUBES (including , Control by Radio." 112 High Efficiency High Voltage Circuit! * -'' pages, containing more than * diagrams, tables and formulas, delegates from numerous associations * Advanced Model 12 Channel Tuner! 125 illustrations, Elec- Area Reception! * crammed fun of theory and practical uses for and answering mail from others who AGC for Fringe *ironic Remote ontrol. * Magnificent TV Performance! Remote Control Unit, including Fil. Xfmr.. 300 ohm are interested either in forming an as- Plate wired. circuit * * * * * * * * * * * * * * * * * * * * * * * * * ** amñreult above described booketely sociation or obtaining membership in * * * less tubes. * ALL FOR ONLY $5.50! NETSDA. * WEBSTER CHICAGO * Shipping Wgt. 3 Lbs. * AUTOMATIC 3 SPEED * * * * * * * * * * * * * * * * * * * * * * * * * * ** * ARTSNY GETS CLUBROOM * RECORD * WESTERN ARTSNY has obtained a new club * CHANGER ** ELECTRIC 25 ., * room consisting of 3,000 square feet. , TYPE 100-16 " ** WATT AUDIO In addition to being a club room, it will * * SERIES * REPRODUCER * have a complete Service Clinic and of- * A fortunate fices at 5 Rutgers Street, New York * purchase makes .<. *AMAZING FREQUENCY RE- *us t000aerlihese SPONSE! 25 WATT RECEIVER * City. fine, new record changers at * the famous * less roan regular manufactur- Made by W. E., no D- 173246. for * Made byweneedron * systems used in A large group of ARTSNY members, * era coed. a few months BEECHMASTER 250 watt P. A. * * cago and only introduced on the marketyt * for landings and for * backing, now male * guiding blind aircraft in with the Association's * iñcharecords ett33ii 84 t,;;;I IR. P1,aM. 1N2,,, These P. M. dynamic lowers unpiayed record stack. Balanced arm * P. A. from flying aircraft. have a large ad in the classified tele- * carefully have an impedance load of 8 ohms to * nmiero g wear. r=1é. * receivers * as ures geálneedlstéesrdr or any adjustment. the output of any amplifier. DUAL CO -AXIAL phone directory. inside -out records played without * use as * Pickup arm comes to rest position after last record has *MAGNETS weigh 23 ounces. Perfect for * co -axial high power * * played. 7Whilrmallyaast. ngacatd * horn type drive speaker or ITHACA AIDS CAUSE * $47.50 -While they last. * tweeters. Shipping wgt. 7 lbs. $12.50 Each ,* Shipping Wgt. 15 lbs. Z4 85 Ben De Young of the Ithaca RSA has ****** * * * * * * * * * * * * * * * * * * * * * * * * * * * * * ** *fir * * * * * * * * * * * * * * * ** all the members helping him on a fund raising campaign for a cause close to * ONE OF AMERICA'S GREAT RADIO STORES * his heart -The Cerebral Palsy Fund. The Program Committee has developed * new educational and business training * lectures that will be presented to the C4 CORP. Deo * membership at its meetings. 160 Greenwichala Street;" New -end- NOVEMBER. 195

www.americanradiohistory.com 120( Miscellany

Rabío Tfjírtp = Jibe pearg Ago SENSATIONAL 7In ßerngtlick Publtcntiono RESULTS! HUGO GERNSBACK Founder

Modern Electries 1908 Wireless Association of America 1908 Electrical Experimenter 1913 Radio News 1919 Science & Invention 1920 Television 1927 Radio -Craft 1929 Short -Wave Craft 1930 Television News 1931

Some of the larger libraries still have copies of ELEC- NEW! TRICAL EXPERIMENTER on file for interested readers. MULTI - IN NOVEMBER, 1917 RESONANT DIPOLE PAT. PENDING ELECTRICAL EXPERIMENTER OÑE r TRUE COMBINATION YACI ANTENNA Seeing Wireless Signals NOW! for the first time-a TV antenna with all these powerful advantages! Unequalled in relation to gain and size! Just a few Yagi antennas cover the entire high and low bands! All elements work Microphones in Trench Warfare, by H. in their true fashion! When incorporated in the Yogi Antenna as a driven element, the multi -resonant Gernsback dipole assumes the aspects of two or more separate Yogi Antennas in one! Eliminates troublesome and frequency sensitive phasing lines! Flexible to channel changes, and especially adaptable to any locality! Something New in Microphones Light, rigid, easy to install! New Radio The Multi Resonant Dipole Combination Yogi Antenna is the only true answer to difficult reception Submarine to Foil U -Boats problems. Order today from your jobber or write for prices and descriptive folder. Construction of a Laboratory Vacuum TELEVISION ACCESSORY MFGS. Pump by Raymond Francis Yates WELLS & WINECARD BURLINGTON, IOWA First Woman Radio Operator Development of Aircraft Radio in the Navy by Benjamin F. Miessner You can't beat RADIO -ELECTRONICS Efficiency in Radio Transmitting Cir- for complete eorerare of cuits by Bayard Shumate Locating Underground Ores by Elec- RADIO, TELEVISION tricity and AUDIO -end-

W PRReceivingLO- T tJ B E SYERY TransmitEST ting -ICESTY RMA GUARANTEED -ALL STANDARD BRANDS Full Year's OZ4 ...$ .596AK5 ..$1.89 6BN6 ..$1.39'12AX7 .$1.19 35A5 ..$ .98 TV PICTURE Guarantee 1A5 .6966K6 TUBES Black Face ... 1.19'66$6 .. 1.59 12BH1 . 1.19 35L6 .. .89 1Al 1.09 Brand New, Standard Brands, Sealed Cartons ... 6AL5 .79 6C4 ... .79 12SA1 . .19 35W4 . .69 1B3 1.19 10BP4 $22.95 16GP4 $29.95 19AP4A $29.95 ... 6AQ5 .8916CB6 .. .89 12SK1 . .19 35Y4 .. .98 12LP4 22.95 16HP4 1R5 .19 31.95 20CP4 33.95 6AT6 .6916CD6 .. 2.19 12SQ1 . .69 35Z5 .. .59 14BP4 22.95 11BP4 24.95 24ÁP4 69.95 1X2A .. 1.19 6AU6 .7916H6 ... .19 19BG6 . 2.89 39/44 . .49 Terrific Value, 5U4 ... .19 6AV6 .69, 6J6 ... 1.19 19T8 .. 1.39 50A5 .. 1,19 Order Now & Save! 5V4 1.39'6BA6 New 630 Super Chassis ... .79 6K6 ... .69 256Q6 . 1.2e 50B5 .. .98 5Y3 .49 30- Tubes -RCA lic. -For 16" to 24" Picture Tubes ... 6BC5 .896K1 ... .59135/51 . .89 50L6 .. .15 6A34 .. .99 6906 1.09'6L6 1.191 High efficiency high voltage circuit ... TRANSMITTING TUBES Keyed AGC 6AC7 .. 1.29 6BG6 1.89 6S4 . .19 OB2 ...$1.69,803 ...$2.49 6AG5 .. 1.29 6BH6 .89 6SA1 .69OC3/VR105 805 ... 2.99 Automatic brightness control 807 1.79 Special standard 6AH6 .. 1.89 6BJ6 .89 6SK1 . .19 1.29 extra high gain coil tuner 0D3 /VR 15 809 ... 1.79 6SN1 1.09 Directly adaptable for color 1.19813 7.49 12" Speaker GENUINE MOLDED 6SQ7 . .6912X2 .. .59 872A .. 2.39 CONDENSERS 6T8 .. 1.39 3éP1 .. 5.39 885 ... 1.29 Factory wired, aligned & tested Fresh Stock -All Mineral Oil ,89 3HP1 .. 3.49 905 ... 2.29 Complete, ready to Filled -10V Centigrade - Meets 6V6 play Jan. C9I Tests. 5FP14 .16.99 954 ... .29 7C4 ... 89 Including all hardware & knobs All 600 Volts 1 B P7 .. 1.89 1616 .. 1.1E Cap. per 10 per 100 7F8 ... 1.59 7CP1 ..12.49 1624 .. 1.49 .001 $0.79 $6.90 .002 .. .. .79 6.90 12AL5 . .89 211 .59 1629 .. .3E { CRT) .005 $1 .79 6.90 12ÁT7. 1.29 304TH .12.49'2051 .. 1.19 33.95 .01 .89 7.90 GL411 A . 2.15 1193 .. .29 .02 .99 630 DX 8.90 12AÚ7 . 1.19I CHASSIS! 3 times normal reception-designed expressly for fringe areas. 12A6 .. .69 8020 .. 1.25 Needs no complicated .05 1.09 9.90 booster or antenna. $149.955 .1 1.25 11.50 12AV1 . 1.29; 717A .. 1.19 9006 .29 FREE OFFER! Schematic free with any chassis .. diagram ordered! (ieon CRT) FREE! IVrite for new catalog including complete Iisting of tubes, parts and accessories for radio and TV ! Also special electronic instrumenta catalog. THEROSe COMPANY Minimum Order: $5.00. 25% deposit with order. balance C.O.D. Include postage with order. All merchandise subject to prior sale, F.O.B., New York City.

1 100 Park Place Dept. E -11, New York 7, N.Y. COrtland 7-6195 RADIO -ELECTRONICS for

www.americanradiohistory.com Miscellany 121

THE FUND TOPS $8,700. 25 WEST BROADWAY New York 7, New York

FAMILY CIRCLE CONTRIBUTIONS Balance os of August 20, 1951 $434.70 Mrs. I. U. Bollard, Wilmington, Calif 1.00 Miss Norma Cole, Orange, Mass. 5.00 Mrs. Donald Newton, El Cajon, Calif. 1.00 Mary Anne & Tom Rooney, Balti- more, Md. 2.00 We are happy to inform our readers Mrs. J. D. Sims and the Beginners' that the Freddie Fund last month Class of the 9th Street Methodist reached a grand total of $8,672.62. Church, Decatur, Alabama 3.80 As a number of our readers know by Mrs. Dail C. West, Miami, Oklahoma 10.00 this time, little Freddie was born com- FAMILY CIRCLE contributions re- pletely legless and armless. There are ceived up to September 18, 1951. $457.50 not even any vestiges of limbs on his RADIO -ELECTRONICS CONTRIBUTIONS body. He is the three -year -old son of Balance as of August 20, 1951 $8,118.93 Herschel Thomason, well -known Arkan- Anonymous, Glendale, Calif. 1.00 sas radio technician. Anonymous, Stratford, Conn. 5.00 We Anonymous, Atlanta, Ga. 5.00 were exceptionally pleased to re- Anonymous, ceive a letter from Mr. Herbert F. Oak Lawn, Ill. 1.00 DIRECTRONIC MOTORLESS Anonymous, Short Hills, N. J. 1.00 36 0° Electronically Switched Beam Dengler, No Motors No Electric Power Radio Engineer, Voice of Anonymous, New York, N. Y. 2.00 No Roof Orientation No Ghosts Munich, 'l'he Directronic 18 element 360" antenna is the finest America, Germany. He not Anonymous, East Pittsburgh, Pa 1.00 for ultrafringe or metropolitan reception. The Hi -PAC molded insulator is a material of extreme tensile only enclosed his own check for $5.00 Anonymous, Seattle, Washington 10.00 strength not affected by weather or temperature, either mechanically or electrically. Included 'n the AX599 as a contribution, but also forwarded Joe Anso, Seaside, Calif. 1.00 "Servicemen's Array" are; Bradway Locker Plant, New 18 hi-tensile aluminum alloy elements a check for $10.00 as well from the Castle, 1 set of connecting stubs (3) focr to 31/2" members of the German technical staff Ind. 5.00 Directronic Beam J. 75 feet of Tri -X Cable James Cassidy, So. Boston, Mass 3.00 1 stacked array per carton of the Voice of America Receiving Sta- AX -599 Direetronic 516.95 Charles Cerami, Newark, N. J. . 1.00 Weight 8 lbs. tion at Munich, Germany. Ten dollars AX-56 Directronic, 6 element Single 9.95 Richard A. Davis, Collingswood, N. J. 10.00 Weight 4a /4 lbs. may not seem like a large sum of money AX -566 Directronic, 12 element Stacked 14.95 H. F. Déngler, Munich, Germany 5.00 Weight 7 lbs. to Americans, but coming from Ger- AX -59 Directronic, 9 element Single 11.95 Harold Eagen, Philadelphia, Pa. . 10.00 Weight 51/4 lbs. All above antenna prices include Tri -X Cable and many it means a very fine contribution. W. A. Gilmartin, San Francisco, Calif. 5.00 Switch. We take this opportunity to thank the Herbert Goldstein, New York, N. Y. 5.00 5 ELEMENT staff of Voice of . Hurst Radio Service, Trenton, Neb 10.00 the America. TV ANTENNA E. G. Kohl, Richmond Hill, N. Y 3.00 We are also pleased to report a spe- Excellent Pictures Aurora Mares, Seaside, Calif. 1.00 in Fringe Areas cial contribution of $3.80 from the Be- Here ,s a highly directive antenna that is the real so- Roy Mares, Seaside, Calif. 1.00 lution to perfect pictures in fringe areas because It is ginners' Class (5 -6- year --lds) of the closely tuned to each channel and cuts interference Pfc. John Martindale, c/o P.M., N.Y.C 10.00 and noise to the minimum. Five elements include one 9th Street Methodist Church, Decatur, folded dipole. three directors and one reflector. Sup- Members of the German technical plied less mast. Specify number of channel desired. Alabama, collected by Mrs. D. Channels 2 to 6 -96.95 Channels 7 to 13 -$3.95 J. Sims. staff of "Voice of America" Re- Shipping Weight-51/2 lbs. Low Band. Our readers will also be interested in ceiving Station, Munich, Germany 10.00 Shipping Weight-3 lbs. Hi -Band. a very important four -page article in Stephen Nester, Keyport, N. J. 5.00 ALL CHANNEL Look magazine, issue of October 9th. Charles Prichard, Gerard, III. 5.00 CONICALS H. B. Scroogs, Baltimore, Md. 1.00 This conical TV is de- It contains many excellent photographs signed for broad -band Robert B. Sheehan, Williamstown, reception on all TV of Freddie. Do not miss it. channels plus FM. Mass. 5.00 The conical has proved Please send your further contribu- high signal. to noise W4RTI, Birmingham, Ala 10.00 ratio and excellent from front - to - back ratio; tions time to time -even the small- matches 72. 150 or RADIO -ELECTRONICS 300 p est amount will be highly welcome. quality TV antennae ié engineeredrfoprrsuperaper- Contributions $8,250.93 formance. The all- aluminum construction provides Make all checks, money orCers, etc., maximum strength and eliminates rust and weight FAMILY CIRCLE Contributions 457.50 problems. The XA44 Is built solid and cannot slip or payable to Herschel Thomason, and twist on the mast. Single Bay ...$3.75 each Stocked Array with Tie please address all letters to 18, Shipping Weight 31/2 lbs. Rods ...98 20 each TOTAL RECEIPTS TO September Lots of 6, single Shipping Weight 7t /e lbs. carton Lots of 6, single HELP-FREDDIE -WALK FUND 1951 $8,708.43 $21.00- per carton carton 523.10 c/o RADIO -ELECTRONICS -end- Shipping Weight 18 lbs. Shipping Weight 19 lbs. 11/4" O.D. Mast Steel (Dualcoted) 5' Crimped $ 1.05 Mast Steel oled) 10' 1.95 Mast Steel (Zinc Plated) 10' 1.59 Mast Connectors for 11/4" O.D. Mast- Motors-Alliance ATR 20.53 Alliance DIR 26.43 Radiart TR2 29.70 Walco WRO -4 28.50 Motor Wire 3- Conductor (Walco) .03 ft. 4- Conductor (Alliance) .04 ft. 8- Conductor (Radiart( .06 ft. PeaakDRoof Saddles (will take up to 11/2" 1 O9 Twin Lead 300 Ohm -tt70 Mil -Solid .02 ft. Twin 300 Ohm-g 60 MIl -7/28 Stranded ,021/2 ft. Side Wall Mounts- 3" Extension .75 Side Wall Mounts- 6" Extension 1.25 Side Wall Mounts -12" Extension 1.75 Side Wall Mounts-18" Adj. 3.50 Tie Roda for Stocking Antennas .70 pr. Double Stacking Assembly -for stacking 2 -XX arrays 1.70 net Aluminum Guy Line 7/18- Stranded- 300' coil 4.95 Arrestors (TV- Lightning) .69 Auto Radio (6 tube Universal Underdash) 34.97 Chimney Mount-Complete with Straps 1.19 Coax -72 Ohm .06 ft. Elements a/u" x 44" or 46^ .90 pr. Elements 1,2" x 45" or 48" 1.20 pr. Guy Wire -Galvanized- 4 Strand ír20 .001/2 ft. Guy Wire -Galvanized- 6 Strand 220 .003/a ft. Guy Wire -Galvanized -11 Strand 520 .011/2 ft. Indoor Antennas (Popular Brands) Rah - hit Ears 1.75 Boosters -Anchor- 101 -75 22.50 Astatic-BT -1 19.50 Tee-S -505 26.97 Stand -off Screw Insulators- 3" for 300 Ohm 2.75 C Stand -off Screw Insulators- ? "for 300 Ohm...... 5.50 C Strap Clamp Stand -off Insulators.-7^.... 8.50 C PRICES SUBJECT TO CHANGE WITHOUT NOTICE. ALL PRICES F.O.B. CLEVELAND. OHIO &ea. 4019 PROSPECT AVENUE

Three -year -old Freddie gazes admiringly at the addition to the Thomason family. Cleveland 3, Ohio Phone EX 1 -8723 NOVEMBER, 1951

www.americanradiohistory.com People 122 SURPLUS Dr. Charles B. Jolliffe was elected to

the newly . created position of vice - NOVEMBER SPECIALS president and technical director of FOR BARGAIN! NEW! RCA. Dr. E. W. Engstrom was elected ® PREVIEW '52 CRAMER TIMER vice -president in charge of RCA Labo- ADJUSTABLE TIME DELAY RELAY. RE- LAY adjustable from 1 /30 sec. S.F. D.T. with starting relay for remote control motor contac¢ts and separate. Stock No. Just out! Our new 1952 Coil resistance. Contacts SPST (N0) or tNC) 10 Amps. EACH S9Y 9S.7 catalog, featuring the most VERTICAL ANTENNA advanced- design and wid- MAST KITS TWIN- est variety of tape record- Fully AEau tatbol e 5 5 Feet S ers ever offered. FOR FM, TELEVISION AND ROTARY BEAM than 20 popular Doublet Antenna Kit used ith the famous Hain- More crafters BC -810, consisting of 7 steel -alloy mast sec- including models tions in a handy canvas bag. Each section is 5'80 TRAX* recorders, long, 11/2. OD with the last 8^ rolled to a smaller OD to telescope into the end of the preceding section. for the broadcaster, tech- No taper. Assemble into mast up to 35' high or shorter by any multiple of 5'. Finished in weatherproof olive nician, experimenter, and drab. Ideal for erection of FM and Television Beams! Drop your coaxial cable right through the Dr. C. B. Jolliffe Dr. E. W. Engstrom high -fidelity enthusiast. center! Brand new. EACH .95 TAPE TUBE SPECIALS ratories Division. Dr. Jolliffe previously 1626 .... .49 1616 .89 12SL7GT . .99 was executive vice -president of the RCA `Trade Mark 1629 .39 81 .49 41 .49 F0104 /5581 919 .99 837 .99 Laboratories Division. Dr. Engstrom RECORDERS Reg. U.S. Pat. Off. .99 2051 1.29 RK73 .99 843 .39 G.E. 211 .98 was previously vice -president in charge ISR .79 803 2.95 12A6 .. .69 Write today for your free copy of Catalog =5272. 801 .79 9001 .... .99 6SJ7 . .69 OAKS 1.49 SBP4 .. 1.95 307ARK73. 4.95 of research of the RCA Laboratories 2506 3.95 1625 .... .39 1E7G .. .69 111,615 .49 1OY .39 EF5O .... .69 Division. AMPLIFIER CORP. of AMERICA MANY OTHER ITEMS NOT LISTED Julius Fine was appointed commer- 398 BROADWAY NEW YORK 13. N. Y. FUSES 3t each,$1.95 per C 3AG -1 amp, 4 amp. 15 amp 4AG -35 amp, 40 amp SAG- 2Oamp,40,50,70amp cial products sales manager of both GP -7 TRANSMITTER WARD PRODUCTS and WORKSHOP ASSO- TUNING UNITS CIATES, Electronic Divisions of the Ga- LOPE T/MT Ideal Basis for E.C.O. Rig briel Co. He will direct all distributor Tuning units for TCE A OPT in the following frequencies: ken A -350 to 800 kcs; B-800 to 1500 kcs; 0- OWN-WEDGE! 1500 to 3000 kcs: E-4525 to 8500 ken: F -6200 to 9050 kcs. Contains all coils etc.. for these frequencies. I use it instead of e Used units are in A -1 condition. Units C.F. each $3.95 `conventional screwdriver! Write for our Bargain Bulletin S DOW RADIO. INC. 1759 E. Colorado St. Pasadena 4, Calif. Phone: SYcamore 3-1196 $2.00 min. order 25% deposit with orders Send full remittance to save C.O.D. charges All merchandise fully guaranteed. Subject to prior sale. Quick -Wedge

J. Fine K. S. Brock SCREW - sales. The company also announced the appointment of Kenneth S. Brock as HOLDING advertising and sales promotion man- SCREWDRIVER 'MODEL 50 ager for the two divisions. Mr. Fine is currently sales manager of Ward unconditionally guaranteed Products. Mr. Brock was previously MultiFrequency ASK FOR IT AT YOUR DEALER commercial sales manager for Work- KEDMAN CO. 233 S. 5th WEST SAL! LAKE CITY, UTAH Crystal Oscillator shop Associates. Both Mr. Fine and Mr. Brock will maintain their headquarters at the general offices of the OPPORTUNITY AD -LETS Gabriel Company in Cleveland, O. Advertisements In this section cost 35c a word for There will be no change in the policies each insertion. Name, address and Initials must be included at the above rate. Cash should accompany all of either division as a result of these classified advertisements unless placed by an accredited advertising agency. No advertisement for less than ten promotions. words accepted. Ten percent discount six issues. twenty percent for twelve issues. Objectionable or misleading advertisements not accepted. Advertisements fee Tan. Charles A. Hansen of the JENSEN issue muet reach us not later than November 21. 1951. MANUFACTURING CO., Chicago, was Radle-Eleetronles. 25 W. Broadway. New `fork 7, N.Y. elected president of the Board of Di SPEAKERS REPAIRED at wholesale prices. Guaranteed A Must for I.F. Alignment, rectors of the Radio Parts & Electronic workmanship. Fast service. Amprite Speaker Service. Equipment Shows, Inc. Sam L. Baraf, 70 Vesey St., New York 7. N. Y. for Factory or Service Lab. United Transformer Co., was elected MAGAZINES (BACK DATED) -FOREIGN, DOMESTIC -Arte. Books. booklets, aubecrlptione, etc. Catalog 10e vice -president; W. D. Jenkins, Radio (refunded). Cicerone's. 89 -21 Northern Blvd. Jackson Supply Co., Richmond Va., secretary, Relents, N. Y. SPECIFICATIONS WE REPAIR. EXCHANGE. SELL, ALL TYI'Ea and Lew W. Howard, Triad Transformer electrical instruments, tube checkers and analyzers, Bari'. Manufacturing Co., Los Angeles, treas- ton Instrument Co. (Electric Meter Laboratory), 140 Liberty HIGH OUTPUT -1 volt Street, New York, N. Y. Telephone -BArclay 7 -4239. OUTPUTS xtal fregs. urer. -5 WANTED: AN /APR -4, other "APR-", "ARR.". 'TS -". RANGE to 50 M C -1. ARC -3. ART -13. everything Surplus -4 W. of the CROSLEY DIvI- IE -" ARC ACCURACY -±.01% John Craig Special tubes, Tech Manuals, Lab quality Test Equipment. SION, Avco MANUFACTURING CORP., WaS etc. Describe, price in first letter. Littell, Farhilla Bon 26. MODULATION -400 Cycles Dayton 9. Ohio. reappointed chairman of the RTMA Five Element TV. Yaei Reams. Aluminum Tubing Etc. Price net with terminated FM Policy Committee. Other RTMA Write for prices. Willard Radcliff. Fostoria, Ohio. output cable, less crystals $VU include: Les- Committee appointments SPEAKERS RECONED: FIELD COILS manufactured Write for illustrated brochure lie E. Woods, Raytheon Manufacturing to specifications. Guaranteed workmanship. Wholesale only. Box 594. Riverside Drive, Mobile. Co., as chairman of the RTMA Indus- S & S Mfg. Co., Et. -1, CREST LABORATORIES INC. Alabama. Whitehall Building trial Relations Committee; Harvey AMATEUR -RADIO AND ELECTRICAL RESEARCH Engineering. Hy Twlllmann. R.6.ß1. Chesterfield. Mo. Far Rockaway, L. I.. N. Y. Stephens, International Resistance Co., vice -chairman; John B. Swan, Philco LONG DISTANCE TV AND FM ANTENNAS. Tag! beanie, stacks, etc. Wholesale Supply Co.. Lunenburg, Corp., as chairman of the Traffic Com- Mass. RADIO -ELECTRONICS for

www.americanradiohistory.com People

mittee; W. L. Fogelson, P. R. Mallory & Co., Inc., vice -chairman; A. M. Free- SOUNDTRONICS man, RCA Victor Division, as chairman GE THYRATRON FG -105 of the Tax Committee; J. B. Elliot, SPECIALS RCA Victor Division, as chairman of STANDARD the Sports Broadcasting Committee; BRAND and Frank W. Mansfield, Sylvania RESISTORS Electric Products Inc., as chairman of the Industry Statistics Committee. 1/3 W tot W - 5% - 10% - 20% Brand New MERCURY RECTIFIER WEDEMEYER Individually boxed in factory seated Q Jobbers Quantities George Wedemeyer, cartons. List Price $60.00. Your coat.. 1 ,g5 While They Las t V8 Labs -We will make up small assortments for ELECTRONIC SUPPLY Co., Ann Arbor, For continuous rectifier and welder con- e your stock at lowest prices. trot ice. Tetrode type, indirectly heated cathode: Mich., was elected president of the Na- 10000 V peak, 10000 V peak Inverse. Av. Max. current 6.4 amps continuous,2.4 to 4 amps welder control service. 14 PIN TV SOCKETS for 3BP1, 7JP4, etc. tional Electronic Distributors Associa- Black Bakelite 150 Mica Filled 280 tion. Other officers are: Harry D. Stark, 1B3 ..., 1.25 6K8 ,.,. 1.25 12SK7 .. .88 1H5GT . .99 6L6G .. 1.75 I2SL7 .. .95 TOP BRAND TUBULAR CONDENSERS Stark Radio Supply Co., Minneapolis, ILA4 ... 1.12 6L6M .. 2.65 12SN7 . 1.25 .I MFD 1000 Working Volts 6g ILA6 .. 1.20 6Q7 . , . .65 12597 . 1.10 .05 MFD 400V 70 .25 MFD 4007 70 secretary; H. E. Ruble, SREPCO, Inc., 1 L84 . . . 1.22 6SA7 .. 1.10 12SR7 . .90 .035 MFD 600V 60 .035 MFD 10007 80 Dayton, treasurer ; W. D. Jenkins, Radio 1LC5 .. 1.05 65C7 .. 1.10 12Z3 .. . .85 1.05 MUTER CERAMIC CONDENSERS, 600 VOLT Supply Co., Richmond, Va., first vice - 1LC6 .. 1.15 6SF5GT .90 14A7 1LD5 1.22 65F7 . . 1.05 IS, 22, 33, 56, 75, 82, 180, 220 M M FD ... .95 1466 .. president; C. 1LE3 . . . 1.15 . . 1.10 5g each $4.50 per C and Byron Deadman, 6SG7 .85 14F8 Northern Radio & Television Co., Green 1LG5 .. 1.10 65J7 . . . 1.00 14F7 1.05 U.T.C. CHOKES P.A. CASES 1LH4 .. 1.45 65K7 .85 14J7 ... 1.10 10 HY @ 66 MA ..$ .97 10 HY @ 110 MA $1.40 Bay, Wisc., second vice -president. 1LN5 . 1.22 6SL7GT 1.15 14H7 1.05 . 1.10 5 HY @ 150 MA . 1.85 10 HY @ 150 MA.. 2.25 1N5GT 1.20 65N7GT 1.45 14N7 .. Barton K. Wickstrum was elected to 195G7 . 1.15 6597 .. .80 14Q7 1.00 SPECIAL ASSORTMENTS 1R5 .... .95 6557 .. .85 I4R7 .. 1.05 50 new pop. type coded res. 50 small - . . . . . YOUR CHOICE the post of vice 154 . . . . .95 678 1.25 19 .85 pop. ceramic cond., all voltages 155 6V6GT . 1.05 24A . . . .79 each asst, president and di- .... .95 & cap. 50 postage stamp mica cond. 1T4 . . . . .95 6W4 . . . 1.05 25L6 . . . .90 rector of sales of 1T5GT . 1.15 6X5 .... .75 2525 .85 F. W. SEL. BRIDGE RECTIFIERS SYLVANIA ELECTRIC 1U4 .... .95 6Y6G . 1.10 25Z6GT 1.00 18 V. IN..14 V. OUT 40 V. IN..34 V. OUT 1V .75 7A4/XXL 1.05 26 .59 1.3 Amps $ 2.90 .6 amps Si 3.30 PRODUCTS, INC. Mr. 2A3 .... 1.45 7A5 ... 1.05 27 .59 .2.4 3.85 1.2 Amps 4.40 Amps 2A5 . . . .95 7A6 . . . 1.05 28D7 . .90 6.6 5.45 3.2 6.55 Wickstrum, who Amps Amps 2A6 . , , .75 7A7 . . . 1.05 30 .75 13.0 Amps 9.80 6.0 Amps 11.70 had been general 2A7 - . . .75 7A8 ... 1.05 31 .65 17.5 Amps 12.50 9.0 Amps 13.75 2B7 ... .95 7B4 1.05 32 .75 - -- sales- manager of ,,,. ------2X2A .. .88 765 .... 1.05 33 .79 ARC 5 RECEIVER Sylvania's Light- 3Q5GT . 1.15 7B6 , , , , 1.05 34 .89 ing Division since 354 .... .90 7B7 .... 1.05 35/51 .75 I. F. Strip -6.9 MEG. I.F. 3V4 . . . . .90 7B8 . . . . 1.05 35A5 . . .90 1946, succeeds Rob- 1.45 1.05 1.00 Contains the following circuits: Mixer, 1st I.F. Amp., 5T4 .... 7C4 ... 35B5 . . 1.05 1.05 2nd I.F. Amp. Detector AVC and Squelch Rectifier. ert H. Bishop, who 5U4G .75 7C5 ... 35C5 1.65 7C6 1.10 35L6 1.10 1st A.F. and Squelch Amp and 2nd A.F. 5V4G .. ... ONLY! resigned from the 5W4 ... .95 7C7 ,,, 1.00 35W4 1.00 Complete I.F. STRIP, less tubes and output $.49 SX4G .. 1.10 7E8 1.00 35Y4 .95 transformer L company. B. K. Wickstrum .... 5Y3GT . .75 7E7 .... 1.00 35Z3 ,, .88 . . .75 WIRE KIT-OVER 100 FT. 5Y4G .75 7F7 . .. , 1.00 Dr. Edward U. Condon was appointed 5Z3 . . . . .95 7F8 , . 1.75 .95 Contains over 100 ft. of #12, #14, #16 H.D. wire .. 1.15 7H7 . . . 1.40 36 .65 for Pri & Fil. Wiring ONLY 69g director of research and development 6A3 ... 1.25 7K7 .... 1.10 ,65 POWER TRANSFORMER SPECIALS of CORNING GLASS WORKS, Dr. Condon, 6A6 ... 1.15 7L7 .... 1.10 38 .65 6A7 1.05 7N7 .,. 1.25 39/44 .65 700 V. CT @ 70 MA, 6.3 V @ 2.5 A. 5 @ 2 Amp. $2.29 one of the country's outstanding phys- ... 6A8 ... 1.10 797 . . . 1.00 41 .75 700V.CT @150MA,6.3V. @á.5 -AT 5 @2 Amp. $4.95 icists, was previously director of the 6AC5GT 1.15 7V7 , .. 1.10 42 .75 National Bureau of Standards. 6AC7 . . 1.35 7Y4 ... .89 43 .82 TV OR SCOPE TRANSFORMERS 6AG5 .. 1.25 117L7 . 1.45 45 . . . , .75 I800V @5 MA, 2.5V @2Amps $3.95 6AH6 , , 1.65 117N7 . *1.45 46 .85 ... George C. Mercer, former pur- 6AJ5 .. 1.65 117P7 . 1.45 47 .95 435/870/1625 W3.514.-AT 6.3 V -6-51774A. 6.3 V @ 1.3 6AK5 .. 1.65 117Z3 . .85 48 2.25 2 2.5 5 V @ 2 A chasing agent of P. R. MALLORY & CO., A, V @ Amps, $4.95 6AK6 .. 1.25 117Z6 . 1.05 49 .95 ...... 85 1.00 3600 V @ 2 MA, 1.25 V @ 300 MA, 750 V CT @ 200 INC , Indianapolis, Ind., was promoted 6AL5 .90 12A 50A5 6AL7 .. 1.60 12A6 . .70 son . , 1.15 MA, 6,3 V @ 8.7 Amps, 5 V @ 3 Amps $7.95 to le position of director of purchas- t 6A95 .. 1.15 12A8GT .95 SOCS . , 1.10 8 HY @ 75 MA CHOKE -500 OHM D.C.R....490 ing. W. J. Topmiller, Jr., former assist- 6AT6 .. .99 12AH7GT 1.25 50L6 . . 1.00 ------ant purchasing agent, succeeds Mr. 6AU6 .. .90 12AT6 . 1.00 50Y6 . . 1.25 TRANSFORMER 6AV6 .. 1.00 12AT7 . 1.45 53 1.05 POWER SUPPLY Mercer as purchasing agent. 6BA6 .. 1.00 12AU6 . 1.20 56 .70 . 57 .85 115 V. 60 CY., 300 V. @ 55 MA., 6BE6 . 1.00 12AU7 1.20 6BC6G . 2.20 12AV6 . 1.05 58 .85 6.3 V. @ 2 Amps. Has 5Y3, 2.8HY. E. W. Olson was appointed to the ... 6BH6 . . 1.05 12AW6 . 1.75 59 1.05 Chokes, 2 -30 MFD Filters, Pilot . .95 7pL7 , 1.10 Term. Strip, Meas. 5 "x5 "x8 " newly created position of sales promo- 6C4 ... .95 128A6 Completely wired $6.85 tion manager for component products 6C6 ... .85 12BE6 .. ,95 )l .,., .90 6D6 . . . . .85 12J7 , . . .95 75 .85 TERMS -25% w/order. balance C.O.D. of WEBSTER- CHICAGO CORP. He was pre- 6E5 . . . . .95 12K7 .. .95 76 .85 viously field promotional representative 6F5 .... .70 12K8 .. 1.00 77 .85 6F6 . . 1.05 12Q7 .. .75 78 .85 SOUNDTRONICS LABS. for the company. H. R. Letzter con- 6F6G7 . .95 125A7 . .95 80 1.05 6J5 .... .70 12SC7 . 1.25 82 1.10 632 Arch St., Phila. 6. Pa. -MA 7 -2775 tinues as the company's sales promotion 6J6 ..., 1.25 12SF7 .. .85 83 1.25 manager for all products. 6J7 . . .. 1.05 125G7 . .90 83V , , 1.15 6K6 . . . . .85 12SH7 . .95 84/LJ4 90 Howard Rowland was named chief 6K7 ..,. .80 125J7 .. .95 85 .95 research engineer of The WORKSHOP WILLARD 2 -VOLT STORAGE BATTERY Exact replacement for GE portables for ASSOCIATES, division of The Gabriel LB -500 - $2. 69U.7 BE YOUR OWN BOSS! BRAND NEW. Each Co., Needham Heights, Mass. He was WILLARD MIDGET 6 -V STORAGE BATTERY the division's chief electrical engineer. 3 amp hour rating. Transparent plastic case. Brand MAKE MORE MONEY new. 35g x 1 13/10 x 23/8. high. Uses standard electrolyte. I. $2.L. 65v.7 s1.00 .:.ii I\ you Each VALUE iiiia gel THE real ... George Siegel was promoted to the money -makers doz- ONE-QUART BOTTLE BATTERY ELECTROLYTE - Made by Willard. for above storage batteries. 1 quart ens of profitable tested position of sales promotion manager of sufficient for two 2 -volt cells. Hermetically A C mail order plans. con- sealed. SPECIAL. $la CJ fidential business se- JOHN F. RIDER, Publisher, Inc., New per qt. bottle crets, dozens, of prac- 25' York City. Mr. Siegel has been with the 7 -PRONG 2 -VOLT RADIO VIBRATOR tical tested formulas. for Portable and Farm Pats Replacement $1. 95 40.000 successful tested Rider Advertising and Sales Depart- for GE .77d7 schemes - actual ex- LB 530 periences of men who ments for the past five years. WORDS Please include 25% Deposit with order- Balance IN have started on a shoe- C.O.D. MINIMUM ORDER $3.00. All Shipments F.O.B. string -with less than Our Warehouse N.Y C. TEXT $10 capital. 25e a ... Max Cohn, president of SOUTH copy postpaid. Send U. S. stamps, money RIVER METAL PRODUCTS Co., INC., South RADCLAIM MAJESTIC NO ADS order. or coin. River, N. J., will supervise the com- ALL _ Money Back RADCLAIMIO PARTS SERVICE "MEAT "! Guarantee pany's Sales Department in addition G NATIONAL PLANS COMPANY to his duties as general manager. 53 YESEY STREET NEW YORK 7, N.Y. 19660 BROADWAY, NEW YORK 23, N. Y. -end- NOV EM BER. 1951

www.americanradiohistory.com 124

DOLLAR FOR DOLLAR WE BRING YOU YOUR BEST BUYS IN TV! WE ARE HEADQUARTERS FOR #630 TELEVISION CHASSIS, KITS & PARTS All Items are STANDARD BRANDS All Prices Are WHOLESALE (FEDERAL TAXES PAID) Do Not Be Misled By Any Lower Offers!

#630 SUPER DELUXE 31 -TUBE TV CHASSIS #630 DE ULPUEXRE TV KIT COMPLETE SET OF PARTS the OPERATES ALL 16 f TO 24 71 PICTURE TUBES for 31-TUBE 16" to 24" CHASSIS Complete with all tubes, hardware Engineered in strict adherence to the genuine and instructions. (less CRT & wire) $146.49 RCA _630, plus added features * * 7t * * NOTHING BETTER AT ANY PRICE! Standard Turret Tuner #630 STANDARD TV KIT Original 630 Synch. Chain for Stability COMPLETE SET OF PARTS 16,5 KV for Clarity and Brilliance for the FAMOUS ORIGINAL RCA 630 Peak Sensitivity for Fringe Areas 29 -TUBE 10" TO 121/2" CHASSIS 4 Megacycle Bandwidth for Definition Complete with all tubes, hardware and instructions. (less CRT & wire) 4 Larger Power Trans. & Voltage Doubler $119.74 Fast Action Pulse Keyed AGC Large Concert-tone 12" PM Speaker STANDARD Complete ready to play with all tubes, Si 67.97 GUARANTEED PICTURE TUBES KNOWN MFR.... LICENSED BY RCA hardware, knobs, etc. (less CRT) 24AP4 -(Round, Metal, Black) $79.49 20CP4 -( Rectangular, Black) 49.74

19AP4A -( Round, Metal, Black ) 49.74 CUSTOM -BUILT CABINETS R AN TV #630 HT SETS 17BP4A-( Rectangular, Black) 34.63 4 leading styles in genuine mahogany or walnut (Blonde 10% extra). WINDSOR when open looks like STREAMLINER. Ready drilled for #630 chassis and any 16" to 20" picture tube at no extras in price. Also 16TP4 -(Rectangular, Black) 32.97 supplied with blank panel to fit any make TV set. Delivered complete as pictured including hardware, 16DP4A- (Round, Black) supports and safety glass. Information on cabinets for the 24" picture tube, on request. 32.97 16AP4A- (Round, Metal, Black) 32.97 The VOGUE The MANHATTAN The STREAMLINER The WINDSOR Most Popular It Has Everything Center Drop Panel Aristocrat of Cabinets 16GP4A- (Short Round, Metal, Black) 32.97 Table Model. Style, Quality, Price Conceals Tuning Knobs. Doors In Genuine Leather 14DP4A- (Rectangular, Hand Tooled In Gold Black) 29.38 12LP4A- (Round, Black) 26.72 10BP4A- (Round, Black) 22.36

COLOR TELEVISION Good practical COLOR TELEVISION is still a long way off . The NEW TONIC TIMES, June 24, 1951 reports . "CBS executives are no better equipped to sit at home and watch color broadcasts 16"-H -24", W -24", D -24" than is the general Public " Waiting for color TV only deprives you of the world's greatest pleasure . Hardly anyone hesitates 17" -H -24", W -24", D -24" to see a movie in black and white ... For those who want to experiment with color TV, we have the following Items: 20"-H-27",W-24",D-24" H-41". W-23", D-25" H-42". W-26", D-25" H -42", W -26", D -25" COLOR ADAPTER Brings in color programs $47.45 $39.37 $74.98 in black and white from $117.46 all stations. Easy to install to any TV set. Complete with instructions .. $1330 #630 TV PARTS ... TOP QUALITY ... LOW PRICES Specify make of your TV set. RCA FRONT END TUNER, compi. w /tubes..522.49 PUNCHED CHASSIS PAN, cadmium plated $4.87 STANDARD TURRET TUNER, corn. w /tubes.. 22.49 630KIT, screws, nuts, rivets, washers 1.69 COLOR WHEEL PLATE, for either tuner .69 TV with plugs ESCUTCHEON 6' LINE CORD, both .29 Solid DUMONT 1NPUTUNER, complete w /tubes 22.49 INTERLOCK SAFETY CONNECTOR, (input) .17 one -piece product. Matched for true color. COMPLETE SET OF KNOBS, incl. decals 1.34 CATHODE RAY TUBE SOCKET, 18" leads .39 Balanced for smooth per- COMPLETE SET OF KNOBS, gold incl. decals 2.49 AMPHENOL CONNECTOR PLUGS, set .48 formance. CBS specifica- POWER TRANSFORMER, 295ma. 20176 9.97 OVAL PM SPEAKER, 5"x7" 2.49 tions. VERTICAL OUTPUT TRANS. 20472 2.69 8" PM SPEAKER, heavy alnico #5 magnet 3.97 VERTICAL BLOCKING TRANS. 205T2 1.32 12" PM SPEAKER, heavy alnico #5 magnet 6.94 7 ". 15ri¢" Diem. $13.36 HORIZONTAL OUTPUT TRANS. 21 1 T3 2.98 10 ". 22" Dtam. 17.69 HORIZONTAL OUTPUT TRANS. 21175 3.98 PARTS #630 COMPLETE SETS 121/2 "271/2" FOCUS COIL, 247 ohms, 202D1 2.29 R Ñ Diana. 29.47 FOCUS COIL, 470 ohms, 202D2 3.42 VIDEO AND I.F. KIT, 19 items 7.84 DEFLECTION YOKE, 60° 20ID1 2.97 ELECTROLYTIC CONDENSER KIT. 6 Cond 7.37 COLOR WHEEL HUB $2.43 DEFLECTION YOKE, 70° 206D1 3.98 TUBULAR CONDENSER KIT, 37 condensers 4.28 HORIZONTAL DISCRIM. TRANS. 208T8 1.49 CERAMIC CONDENSER KIT, 28 condensers 3.37 FILTER CHOKE, 62 ohms 1.47 MICA CONDENSER KIT, II condensers 1.38 COL WIDTH CONTROL COIL, 201R1 .44 CARBON RESISTOR KIT, 107 resistors 6.98 MOTOR 110V. -50/40 WIDTH CONTROL COIL, keyed AGC .79 WIREWOUND RESISTOR KIT, 4 resistors 2.31 Cycle. Type pictured or type HORIZONTAL LINEARITY COIL, 201R3 .39 OCTAL WAFER SOCKET KIT, 13 sockets .72 superseding it (which- ION TRAP BEAM BENDER, (single) 203D1 .79 MIN. WAFER SOCKET KIT, IO sockets .63 ever is better) will be ION TRAP BEAM BENDER, (double) 203D3 .98 MIN. MOLDED SOCKET KIT, 2 sockets .22 delivered. AUDIO OUTPUT TRANSFORMER (6K6) .69 BRACKET AND SHIELD KIT, 18 items 8.63 Including $J0,16 HV RECTIFIER, SOCKET ASSEMBLY, single .79 TERMINAL STRIP KIT, 18 strips .59 rheostat J HV RECTIFIER, SOCKET ASSEMBLY, double 1.37 VARIABLE CONTROL KIT, 9 controls 5.83 HV KINESCOPE LEAD, with clip .39 COMPLETE SET OF TUBES, 29 tubes 30.31

TELEPHONE BROOKS RADIO & TV CORP., 84 Vesey St., Dept. A, New York 1, N. Y. COrtlandt 7-2359

RADIO- ELECTRONICS for

www.americanradiohistory.com 12

MOST POPULAR RADIO & TV TUBES At Better Than 50(( Off List Price! HOTTEST TV PACKAGE for "ONE BUCK "! STANDARD BRANDS - FULLY GUARANTEED EVERYONE INTERESTED IN TELEVISION should own this TV literature package . The information will be found useful OZ4 $ .77 65G7 .94 on any make TV set. Its different and right to the point! minute and not yet 1.04 It carries instructions that are up to the 1A5G9 .94 65H7 found in expensive text books. Indispensable to the TV tech- 1A7GT 1.03 6SJ7GT .77 nician yet easy enough for anyone with even a limited knowl- 1B3GT 1.27 6SK7GT .84 edge of TV to understand and follow. 1H5GT .77 6SL7GT 1.14 Just think of being able to convert any 10" TV set into a life -size 20" receiver in as little as one hour . . The 1 LA6 1.27 6SN7GT 1.04 ILLUSTRATED TV CONVERSION MANUAL makes that pos- 1184 1.27 6SQ7GT .69 sible. 1LC5 1.27 6557 .94 SAVE MONEY ON REPAIRS -Important common occurrences sug- 1 LC6 1.27 6T8 1.39 are carefully analyzed and corrective procedures are 1LD5 1.27 6U5 .94 gested. You are told what to do -WHEN THE RECEIVER FAILS TO OPERATE, WHEN THERE ARE GHOSTS. INTER- 1LE3 1.27 6V6GT .94 FERENCE NO PICTURE, PICTURE FOLD -OVER, NO RASTER, 1 LH4 1.27 6W4GT .84 PICTURE BLOOMS, DISTORTED PICTURE, PICTURE ROLLS, 1LN5 1.27 6X4 .69 NO SOUND, DISTORTED SOUND, CORONA EFFECTS. ETC. PICTURE TUBE ASSEMBLY and PATTERN ADJUSTMENTS are 1N5GT .94 6X5GT .69 outlined in detail (the ion trap adjustment caution may save 1Q5GT 1.27 7A5 1.04 you the price of a new picture tube). The HORIZONTAL step by step IRS .94 7A8 .84 SYNC, RCA TUNER and STANDARD TUNER adjustments alone are worth many times the cost of this 154 1.03 7B4 .84 package. 155 .84 785 .84 TUNING GUIDANCE and ANTENNA ADVICE will enable you 1T4 .94 7B6 .84 to enjoy peak performance at its best. The HIGH VOLTAGE 1T5GT 1.27 7B7 .84 CAUTION will give you that free and easy feeling of safety while handling the chassis or any of its parts. 1U4 .94 7C5 .84 AGC DIAGRAM, RE- 1U5 .84 7C6 .84 The 1630 CIRCUIT DIAGRAM, KEYED SISTOR & MICA CODE CHARTS need no emphasis as to their 1X2 1.27 7F7 1.04 usefulness. 3Q4 1.04 7F8 1.54 You will also receive our latest catalog and flyers with hun- 3Q5GT 1.14 7Q7 .84 dreds of special offers in Television, Chassis, Cabinets, Pic- .84 ture Tubes, Parts, Radios. Portables, Auto Radios, Radio 354 .94 7Y4 Tubes, Test Equipment, Accessories, Latest in Color Equip- 3V4 .94 12AH7GT 1.27 ment, Etc., at WHOLESALE PRICES. 5T4 1.16 12AL5 .94 5U4G .69 12AT6 .69 )...... USE HANDY COUPON 1.39 5V4G 1.14 12AT7 BROOKS RADIO & TELEVISION CORP. 5W4 .77 12AU7 1.14 84 Vesey St., New York 7, N. Y. 1.14 5Y3GT .52 12AX7 Send complete package of TV literature .84 5Y4G .69 12BA6 I. HINTS FOR BETTER PICTURES ON 630TV Cash Check M.O. .84 6A7 1.04 128E6 2. 630TV DIAGRAM WITH MODIFICATIONS Enclosed find $1.00 .69 6A8GT 1.04 12J5GT 3. ILLUSTRATEDTVCONVEHSION MANUAL NAME 6AB4 .94 12K7GT ... 1.04 4. PULSE KEYED AGC CIRCUIT DIAGRAM 6AB7 1.56 125A7GT .84 3. RMA RESISTOR & MICA CODE CHARTS ADDRESS 6AC7 1.39 12SF5 .94 6AG5 1.27 12SF7 .94 $1 CITY STATE ALL FOR ONLY .00 POSTPAID u. 6AG7 1.54 125G7 .94 .M.E 6AH6 1.89 125J7GT .77 6AK5 1.89 125K7GT .84 AUTO RADIOS 6.415 .94 12SL7GT 1.14 CUSTOM -BUILT KEYED AGC KIT 6AL7GT 1.27 125N7GT 1.04 Known Mfr. Licensed By RCA Keyed pulse, fast action AUTOMATIC GAIN .94 .77 CONTROL KIT to modernize a =630 or any 6AQ5 125A7GT 6 -TUBE SUPER -HET. (8 -tube performance) 6A96 .84 125127 1.04 other TV receiver. Improves performance, giv- 6AQ7GT 1.14 14A7 1.04 FORD 1949 -50 -51 PLYMOUTH 1949 -50 -51 ing a steady picture on all channels. Elimin- 49 -50 -51 flutter and picture jumping. Com- 3.98 1.04 DODGE 49 -50 -51 CHEVROLET ates airplane 6A57G 14B6 plete set of parts includes: CONDENSERS, STUDEBAKER ..50 -51 HUDSON . 48- 49 -50 -51 6AT6 .69 1497 1.04 RESISTORS, 6AU6 TUBE, SOCKET, WIDTH HENRY J. 51 All List at $59.95 6AU6 .84 19BG6G 2.94 CONTROL COIL, HARDWARE, ETCH. .69 19T8 1.39 6AV6 ¡¡ Complete with easy to follow step -by- 6AX5GT .77 25A6 1.27 step assembly instructions and dia- W Your Price . .. (Any Model) $41.91 $4.59 .84 Complete ready to install grams. 6BA6 .84 25L6GT Net ONLY 6BE6 84 25W4GT .94 Including Easy Instructions.. 2.32 25Z5 .77 6BG6G CRCYLEARSTAL- 6BC5 .94 25Z6GT .69 LUCITE MASKS 45) 6BH6 .94 35A5 .84 PM SPEAKERS (ALNICO Framed in Beautiful Rich Gold Leaf Finish 6BQ6GT 1.54 35L6GT .84 Overall ai,oosiom mag. on 8" & 12" -Round 9 /e" x 1 11/4" ....S 3.47 6C4 .77 35W4 .62 1 oz. mag. on 3" to 6", heavier 10" 117/s "n 131/4" 4.78 .77 .84 12)/1" -Round 6C5GT 35Y4 Brand New -Factory Guaranteed Stock -Rectangular I 11/8" x 14" 4,52 .84 14" 6C6 1.04 35Z3 16" -Round 13 -I I/16" x 161/4" . 5.97 6CD6G 2.94 35Z5GT .62 3" $ .98 6" 1.98 16" -Rectangular 123/4" x l61 /e" 5.84 6D6 1.04 41 .94 17" -Rectangular 13- 9/16" x 167/8" .. 5,97 6E5 1.04 42 .94 4" 1.29 8" 3.97 19" -Round (5s/8" x 195 /e" .... 7.69 6F5GT .77 43 .94 20" Rectangular I53/4" x 19°/a" .. 7.98 '1.49 12" 6.94 44" Round 20/2" n 26i/4" 14.65 6F6GT .77 45 .94 5" (including Set of Rosettes) 6H6GT .84 47 1.39 6J5GT .69 50A5 1.04 6J6 1.39 50135 .94 TUBE CARTONS in LOTS of 100 NO GLARE TV FILTERS 6J7GT .94 50L6GT .77 For better, More Clearly Defined Pictures, Improves h" x I" x 21/4" $ .77 .77 SMALL PEANUT .89 Contrast, Eliminates TV Glare, Sharpens Picture 6K6GT 75 Image, Sizes To Fit All Sets In Smoke Or Blue Colors. .77 6K7GT 1.04 76 LARGE PEANUT i' x i" x 2V.:- .98 6L6G 1.72 77 .94 10" 8" x 101/2" $ .89 6N7GT 1.14 78 .94 GT TYPE ly4" x I1/4" x 33/9" 1.06 121/2" 9" n 121/2" 1.26 6Q7GT .84 80 .61 14" 101/2" x 15" 1.47 G 1/2" x r /2" X 41/2" 1.39 65A7GT .84 117L7GT 1.89 SMALL 16" 12' x 163/8" 1.92 x 173/8" 2.16 6SC7 .94 117N7GT 1.89 LARGE G 2" x 2" x 5" 1.59 17" 133/8" 6SF5GT .84 11.7Z3 .69 19" or 20 "- 151/2" x 191/2" 2.44 65F7 .94 117Z6GT 1.14 EXTRA LARGE 2l /4" X 21/4" x 61/2" 2.97 24" 20" x 24" 3.87

COT} BROOKS RADIO & TV CORP., 84 Vesey St., Dept. A, New York 1, N. Y. +O7 2359

NOVEMBER, 1951

www.americanradiohistory.com 1261 Communications PERFORMANCE Not HINTS ON SYNCHRODYNE T U B E Sat Mfr's. COST Size Dear Editor: IS Thanks WHAT COUNTS for forwarding me the corre- Standard Brands- Unbranded- spondence from readers who have been Guaranteed having difficulties with the Synchro- 183 ..,.51.35 613E5 .. . .60 6W4GT .49 dyne. The 1L4 .60 6BG6G . 1.48 6X4 .36 most common appears to be L6 .80 6BN7 , 6X5 .36 ILN5 .. .85 6006 .. .94 6766 . squealing. Some possible causes are : IRS .60 6BQ7 , 012116 . 70 lU4 .60 6C4 .39 12AT6 1. Due to insufficient shielding or U5 -so 6C86 .S .S6 12AT7 2A3 . 1.2S 6CD6G 1.93 12AU6 common in O 2X2 : -60 6N6GT .48 12AU7 coupling a power supply 3Q4 .66 6H6M ,. .75 12AV7 or in 3V4 .62 6.1567 .44 +2AX7 the tuning gang, the r.f. stage is O 5V4 . . 1.20 6J6 .73 12/177 .95 1.09 12BA6 S .48 included in a positive feedback loop 5Z 3.T . .85 666 . .65 128E6 .49 6AC7 . . 1.25 01167M . .85 125K7GT., .53 and the whistles are caused by oscilla- 6A05 . . . .57 6J7M . 1.05 125N7GT. .58 6L6G 1.05 125127 . . .65 tion in the 6AH6 . 1.75 6L6GA 1.05'19T8 .86 r.f. or r.f. plus demodulator 6AK5 .. 1.10 8N7M ., 1.20 25L6GT .50 O 6R6 1.50 ' 025W4 . . .90 circuit. To check this try the untuned 6A05 ... .51 654 .51 35L6GT . .53 6AT6 ... .40 65C7 . 1.10 35W4 .37 input circuit shown below. 611U6 ... .45 65F5GT .75 35Z5GT., .39 "LITTLE GIANT" 6AV6 .40 B5K7GT .53 ... SOBS . .53 6134G ... 1.35 651.767 .65 5005 . . .53 6BA6 65N7GT . .58 OL6GT .53 R. F. TUBE woes 678 .86 059 1.50 LIGHTNING 60ER ... .49 6V6GT .51 0891( .75 ARRESTER UNBRANDED -Lots of 50 only °STANDARD BRANDS-Any Quantify PROTECTS 5 000 or 16000 ,Against Lightning Hazards J SPECIAL PURPOSE TUBES No. AT 105 $125 1N23A ...52.75 211C /VT4C 1.75 1632 ... .65 For ribbon -type and oval 1N236 . .. 4.95 3508 . 5.50 1633 .65 LIST 2C51 . .. . 5.95 394A ... 5.50 8025 jumbo twin lead. 2. Some American 6J8 -G tubes may 2E25 .. .. 5.95 7158 ...15.00 9001 2E30 . . 2.00 721A ... 3.95 9002 be different in 2021 . . . 1.65 726A6 ...16.50 9005 ... 4.95 ONLY JFD Lightning Arresters offer you these construction from the 3821/1 . . 12.50 726A ... 6.50 CK10 ..54.95 exclusive patented 3824 . . 5.50 807 2.25 .0 features... Australian ones. North American Phil- 3821 .56.93 809 2.25 T20 1.50 654 7.4É. 1.75 8320 13.95 T20 2.25 1. Strain -relief Retaining Lip prevents pulling ips should be able to supply an ECH35, 444 6.75 832A .11.95 T200 ..13.95 or straining of lead 446Á 2.25 837 1.95 T . 3.95 against contact points. 755 .35 1603 TZ2O or alternatively you could use more ... 5.90 Z40 . . . . 2.25 2. You actually see positive contact made with 75TH 6.75 1620 ... 6.30 7240 .... 3.25 lead -in wire. turns on the triode grid oscillator coil IMMEDIATE DELIVERY! 3. No wire stripping or cutting. together with lower values for the Write for quotation.. many other types Write for available. All form No. 84 showing the damage anode and grid resistors between the prices subject to prior sale. lightring ran do to a Television Installation. and demodulator ri. tubes. WRITE, WIRE, CALL- TODAY! 3. Insufficient signal from the r.f. will not give enough sync signal. Is the r.f. JFD MANUFACTURING CO., Inc. 6101 -L 16th stage defective? Check tube /VENN, BROOKLYN 4, N. Y. and a.v.c. Nat Adelman liAll Ps r.t.rlri.. Amens.. An.. i.. voltages. 168 Washington St. New York 6, N. Y. 4. The potentiometer giving the syn- CO, 7-6091 chronizing signal may have a high - resistance contact and this combined with excessive shielding may bypass AUTOMATIC M -90 AUTO RADIO TALK TO THE WORLD! too much of the sync voltage. PREPARE FOR F.C.C. NOVICE fULCE JOHN WM. STRAEDE ONLY Victoria, Australia AMATEUR RADIO LICENSE $2695 COMPLETly MULTIPLE 405 -LINE TV! terms Dear Editor: Be a "Horn" in a Few Days -No Experience Needed! Operate Your Own Station - Enjoy the Recently while adjusting my televis- "Hobby with a Future" ion receiver, a 630 model by Philmore, -er CBS started to transmit color. By ad- Six Tube Superheterodyne Three Gang Con- justing the synchrolock control at rear, denser Powerful, Long- Distance Reception Fits All Cars, Easy Installation I received the CBS color picture in black- and- white. Mounting Brackets Included But, best of all, I 6 Tube model M90 *533.87 received not one 5 Tube Model A -15 $28.76 *Above price includes Federal 'l'ax picture but four ! One in each quarter Excise of a 17 -inch picture tube. Now each Approx. shipping weight either radio (11) eleven pounds member of our family has an individual MAIL US YOUR ORDERS All orders filled within 24 hours. picture when Columbia transmits a Standard Brand tubes 50% off list color program! JOHN CODY Wholesale Bronx, N. Y. ,,Safewl Electronics Fifth at Commerce Fort Worth, SOME NOTES ON THE YAGI Texas 36 4.min. code recordings (olphobet thru 6 wpm) 2 12. record albums Telegraph Key Tone Record for Sending Practice Dear Editor: Instruction on Sending, Rodio Theory, 8 F.C.C. Regulations. Pre - We have been reading with interest F.C.C. Exams graded FREE by E.T.I. MONEY -BACK GUARANTEE With PHOTOSOUND, you SEE the material & HEAR your instructor! the answers to the many questions which appear in the Question Box each 5 -DAY TRIAL- -SEND NO MONEY month. You are definitely providing a BIG MAIL COUPON NOW! ELECTRONIC TECHNICAL INSTITUTE Dept. RE Ill much -needed service to your readers. 830 Venice Boulevard, Los Angeles 15, California The July, August, and September is- D Pleose send NOVICE LICENSE COURSE for 5 -day No -Risk Exam- sues contained articles of particular in- BOOK ination. On arrival 1 will pay the postman $26.95 plus C.O.D. charges. Check here if you endose $26.95 -We pay delivery charges. terest to our company. Vee -D-X, as you Send, are probably aware, has made certain information en: Novice License Advanced Amateur License contributions to the television antenna NEWS Commercial License market. Name Age_ In the July issue a question was asked See page 116 Address relative to the matching of a channel lone City State 13 Yagi antenna with a conical. Vee-D- RADIO -ELECTRONICS for

www.americanradiohistory.com Communications 127 X markets a divider network known as the MM -2 Mighty Match. This device will provide the desired isolation of the IN two antennas. When connected to a ALL ONE! single transmission line with an MM -2 AMAZING BLACK LIGHT installed, the conical will not pass high - with RCP's new 250 -watt ultraviolet light source. Makes fluorescent channel signals to the transmission line. articles glow in the dark. The MM -2 will present no insertion loss Fits any lamp socket. For experimenting, entertain- and will prevent detuning effect of the ing, unusual lighting effects. two antennas. A minimum separation Ship. wt. 2 lbs. HEM HI of 36 inches is recommended between A SAVISNG AT 52.45 the two antennas. Your and September issues an- SERVISHOP MOTOR July POWERFUL ALL PURPOSE swered questions relative to the stack- Sturdy shaded pole A.C.induction motor. 15 watts, 3000 rpm. ing of four and eight Yagi antennas. 3 "x2 "x1.14"; 4 mounting studs; Vee -D -X markets such harness kits for 7/e" shaft, 3/16" diameter; 110- 120 volts. 50 -60 cycles. A.C. use with our antennas which will pro- only. When geared down, this vide either vertical or horizontal stack- unit can operate an it turn- table with a 200 lb. dead ing of four Yagis. We have constructed weight. Use it 'for fans, dis- and experimented with the stacking of plays, timers and other purposes. Ship. wt. 2 lbs. eight Yagi antennas. This array, as ITEM NO. 147 pointed out in your article, provided UNUSUAL BUY $2.45 extremely sharp patterns and due to its massive size is not recommended. WATTHOUR METER Such harness kits are not available. Leading makes - com- experience re- pletely overhauled, It has been our that ready for service. 100- gardless of the number of antennas 110 volts, 60 cycles, 2- stacked, the band -width of the array wire A.C. 5 amp. Heavy metal case Byt" will not change from that of a single x 6 y¡ x 5 ". Easy to in- Yagi. We have found that six -element stall. Ship. wt. 14 lbs. Yagis with a band -width of 5 me may ITEM NO 33 EQUIVALENT TO A COMPLETE NOW ONLY $4.50 be multistacked and still maintain their SERVICE SHOP! band -width. WESTERN ELECTRICBREAST MIKE We hope that this information is re- TUBE TESTER Lightweight I lb. carbon micro- in was SET TESTER phone. Aircraft type. Breastplate ceived in the spirit which it A.M. GENERATOR mountings adjustable 2 -way given; is, to assist you in compiling swivel. Easily fastened straps. For that F.M. GENERATOR home broadcasts, communica- information. A.F. GENERATOR tions etc. Complete with 6 foot THE LA POINTE-PLASCOMOLD CORP. CONDENSER cord hard rubber plug. Sherd- dived plate, non -rusting finish. F. A. Hess, Sales Manager TESTER Ship. wt. 2 lbs. FUSE PROTECTED METER ITEM NO. 152 Windsor Locks, Conn. NFW LOW PRICE $1.75 F.vcry square inch solid- packed with value! Look what you get in this phenomenally low UNPAID ETHICAL SERVICE priced tester: a complete latest model obso- TELEPHONE TRANSMITTERS lescent proof tube tester with approximately Genuine transmitters 1000 listings on improved roll chart together made by Kellogg KEt.t.o Dear Editor: with an elaborate multitester for measuring all Western Electric I have just read Walter R. Rogers' AC & DC voltage DC currents- resistance in Stromberg Carbon. article, "Ethical Service Pays," in the ohms and megohms-output in decibels-con- Work on two dry cells denser leakage -signal generators for audio - For P.A. systems, in- September issue, and agree with his radio AM and radio FM signals. tercoms, other prat conclusions. DC Voltmeter : 0- 10- 50- 500-1000 -2500 tical uses. Shippingipping AC Voltmeter: 0 -10 -50 -500- 1000 -2500 weight I lb. But what got me was the lad working DC Milliammeter: 0 -10- 100 -1000 DC 0 -10 ITEM 160 after hours and at a rate of only $1.50 Ammeter: REAL VALUE $2'45 Decibel Meter: -S to +15, 15 to 29, 29 to 49, for replacing a capacitor and alignment 32 to 55 LENS KIT too. I guess that explains why he works Ohmmeter: 0 -500-5000 ohms, 0-0.1 -1 -10 meg- 250 POWER TELESCOPE ohms high powered 6 ft. telescope! make a by Make your own at night-he couldn't living Complete batteries, test leide. output 75" focal length, ground with tubes. Kit contains 3" diem., I, -ads. etc.. In beautiful natural finish oak case. and polished objective day giving away work at that price. lens and necessary eye Standard rates here allow at least $2.50 BUY FROM YOUR JOBBER. INSIST ON RCP pieces. Magnifies 50x to INSTRUMENTS WRITE FOR CATALOG RE -11 250x. Full instructions. for capacitor installation, plus cost of Ship. wt. I lb. the unit at list price. Alignment would ve1 RADIO CITY PRODUCTS CO., INC. .pp75 YOU SAVE I AT $1. be added to that. I believe an item featuring low 152 West 27th St- New York I1, N. Y. charges such as this example is as bad HUDSON SPECIALTIES CO. as too high charges, and only adds to the 40 West Broadway. Dept. RE -11 -51 New York 7, N. Y. confusion of the repair man following I :.n . I, .. ull; n,I ,e :nul :,o' rr hems circled allow. lie 'sure to include ,.fIpI â¢ chargea.) the middle of the road and who is man- balance O.O.D. to keep his business on a paying -8e10 aging MRINIMUM eC.ppnnO1D.n ORDIR $5.00. -VEND WITH 20% DIPOSIr will the aver- VIDEO C.O.D. ORDERS ACCIPTID ONLY basis at fair prices. What INCLUDE SHIPPING S. I.'ire le Items Worsted age technician think after reading of COIN OPERATED TELEVISION e7 147 22 152 IGO 122 who render repairs such as a man can Get in on the ground floor of this Name article listed $1.50? Flew Print Clearly the -for SENSATIONAL. PROFITABLE busi- J. W. ESSEX ness. For small investment we can Address Industrial Sound, Reg'd show you large returns. Requires a week. Write City zone.... Stan Bridgewater, Nova Scotia only a few hours - Coin Radio & Television Corp. (Mr. Essex has an important point here. Dept. RE New York City S3.00 FOR CARTOON Many shops which operate till 10 every 190A Duane St. IDEAS night could close at a decent hour if RADIO -ELECTRONICS prints several radio cartoons every month. Readers are Invited to the owners would only charge what contribute humorous radio Ideas which can be HELP THE DEFENSE EFFORT used in cartoon form. It L not necessary that their work is worth. They'd probably you draw a sketch, unless you wish. increase their prestige thereby and so by turning over old copies of RADIO -ELEC- Address TRONICS and all other waste paper to paper RADIO CARTOONS. RADIO. ELECTRONICS get more business, too!- Editor) collecting agencies in your community. 25 West Broadway. New York 7. N. Y. -end- NOVEMBER, 1951

www.americanradiohistory.com 128 RADIO SCHOOL DIRECTORY

ATTENTION... F.C.C. COMMERCIAL RADIO A NEW department of the DON MARTIN SCHOOL RADIO OPERATORS LICENSE OF RADIO AND TELEVISION ARTS AND Critical Shortage of Licensed Operators Exists!!! SCIENCES . . . for Instruction and training In- :t wonderful future is yours with an F.C.C. commer- COURSES TE LE V ISION- Incorpnrattng: cial radio telephone or telegraph operators license, leading Preparatory Mathematics, to top -salaried Jobs in aviation, broadcasting, Serv- Production: Writing, Directing, Producing, Acting, transportation and Civil Service. Sensational ew ice, Broadcast, Television, Ma- simplified HOME STUDY course teaches you in ti the rine Operating, Aeronautical, Staging, Lighting. shortest possible time at lowest possible cost. NO OTHER COURSE LIKE IT! Proven valuable during Frequency Modulation, Radar. Engineering: Transmission, Receiving, Camera and World War II in speedily training thousands of men, eliminates tedious schooling, Classes now forming for the Studio, Operation, Theory of Video. exam, papers, wading through books. Each page of text directly related to Fall term beginning Feb. 1st Pickup and Reproduction. official F.C.C. exam. questions, thus assuring you of all theory requirements. Entrance exam. Jan. 15th Approved for veterans. The entire course, nothing else to buy, containing Veterans. Literature. 230 pages of complete material, diagrams, etc., yours for only 59.95. Send check or money order: or pay COMMERCIAL RADIO INSTITUTE THE DON MARTIN SCHOOL OF RADIO postman 59.95 upon receipt, plus C.O.U. charges. (Founded 1920) Complete satisfaction or money refunded within ten dogs. 38 West Biddle Street, Baltimore I, Md. AND TELEVISION ARTS AND SCIENCES STREAMLINED SELF STUDY COURSES 1 655 No. Cherokee, Hollywood 28, Calif. HU. 2328L 509 5th Ave. Dept. A New York, N. Y.

AUDIO (SOUND) ENGINEERING COURSE Complete Nome -Study HOME STUDY TRAINING RADIO Course for Passing FCC Amateur Radio Examinations Prepare yourself, in your spare time for a BIG PAY JOB as an AUDIO ENGINEER. Practical, ENGINEERING LOW COST easy -to- understand lessons, written by nationally recognized Audio Engineers and Educators. PERSONAL COACHING B. S. DEGREE IN 27 MONTHS MONEY -BACK GUARANTEE Prepare for a SUCCESSFUL CAREER in the TEL- Write for Detail. EVISION, RADIO, DISC AND TAPE RECORD- Complete Radio Engineering course incl. Telev Mech., FEDERAL ELECTRONICS INSTITUTE ING, ELECTRONICS AND MOTION PICTURE U.H.F. and F.M. BS Degree Courses also in 34 East Putnam Ave.. (Dept. FI. Greenwich, Conn. I NDUSTRI ES. Civil, Elect., Chem, and Aero Env.; Bus. Adm., Acct. well Training will not interfere with present employ- Extensive campus, modern buildings, equipped ment. labs. Low cost. Prep. courses. Personalized instruc- Placement serv- EARN WHILE YOU LEARN tian. Heavy demand for graduates. Founded 1884. Prepare now for the civil and WRITE FOR COMPLETE DETAILS ice. in -TODAY military opportunities ahead. Enter Jan., March, B. M. Klekner, D.Sc.,Ph.D, June, Sept. Write for Catalog. RAPlOchEGREERINGI/ MONTHS HOLLWOOD TECHNICAL INSTITUTE TRI -STATE COLLEGE 3359 Cahuenga Boulevard Intensive, specialized course including strong bails 24111 COLLEGE AVE. ANGOLA, INDIANA In mathematics and electrical engineering, advanced Hollywood 28. California radio theory and design, television. Modern lab. Low tuition, Self -help opportunities. Also 27 -month courses in Aeronautical, Chemical. Civil, Electrical. and Mechanical Engineering. Approved for O,L'e. Enter, Dec., March. June. Sept. Catalogue. DAY a,.i EVENING CLASSES INDIANA TECHNICAL COLLEGE 1511 E. Washington Blvd.. Fort Wayne 2, Indiana

Be a "key.' man. Learn how to send and receive messages In code by telegraph ELECTRONICS -RADIO and radio. Commerce needs thousands of Modern Laboratory men for Jobs. Good pay. adventure- in. RADIO and TELEVISION teresting work. Learn at home quickly Instruction In through famous Candler System. Qual- 11,1 Thorough Training For Men ify for Amateur or Commercial Li- SERVICING and Women in All Technical Phases cense. Write for FREE ROOK. BROADCAST CANDLER SYSTEM CO. APPROVED FOR ELIGIBLE VETERANS Dept. 3 -M, Box 928. Beaver I .Colo., U. S. A. OPERATING DAY- EVENINGS WEEKLY RATES ELECTRONIC and FREE PLACEMENT SERVICE FOR GRADUATES For Free Catalog Write Dept. RC -61 TV ENGINEERING RCA INSTITUTES, Ince f ILLUSTRATED A Service of Radio Corporation of America 350 WEST 4TH STREET NEW YORK 14. N. Y. I7$FO CATALOG EVERY ELECTRONICS INSTITUTE, Inc. 21 HENRY, DETROIT 1, MICH. RADIOMAN RADIO COURSES Can Use These RADIO OPERATING CODE RADIO SERVICING ELECTRONICS F.M. TELEVISION RADIO ENGINEERING Preparation for Civilian, Maritime, Army and SERVICE HINTS! Eon Navy license requirements. FM-Television- Broadcast Write for Catalog TE Valuable Manual Police Radio, Yours -FREE! Marine Radio, Radio Servicing, Avia- 15 W. 63 St., tion Radio and N. Y. 23 Ultra High mobile applications. ENdicott Thorough training in all branches of Radio and Elec- 2-8117 Every page of How to Slm- tronics. Modern laboratories and equipment. Old p11fY R a d t o Repaire" ta es- packed with on -the- bench, tablished school. Ample housing facilities. 7 acre practical ideas. Contains campus. Small classes, enrollments limited. Our photos, charte, diagrams- graduates are in demand. Write for catalog. no suit-no vague theory. In plain every-day language it Approved for Veterans gives you priceless sugges- servicing ideas. 1ou'll use and benefit from VALPARAISO TECHNICAL INSTITUTE LEARN the experience of experts. Dept. C VALPARAISO, Partiel list of contente: Haw INDIANA to Localize Trouble; How to AMATEUR RADIO Service Amplifiers; How to Test far Distortion; How to Test Audio Circuits; How to Radio Television lest Speakers; How to Find Faults in Oscillators; How to Teat Radio Parts-and it's Communications Elec- all yours-FREE! No WI- Lotion., TELEVISION trical inspector courses. FCC License preparation. SEND COUPON OR PENNY (PREPARE FOR A GOOD JOB! POSTCARD FOR YOUR Amateur Radio Station COMMERCIAL OPERATOR (CODE) FREE COPY TODAY! RADIO SERVICEMAN on premises. IFEILER ENGINEERING CO., Dept. 11RC1 TELEVISION Build your own equipment I8026 N. Monticello Ave., SERVICING Skokie- 111. (Suburb of Chicago) BROADCAST ENGINEER in our Laboratories. Please RUSH my FREE copy of "How to Simplify IRadio Repairs." Approved for Veterans C. Gallo W2AWI (Director) Name SEND FOR FREE LITERATURE LINCOLN SCHOOL OF RADIO & TV INC. IAddress BALTIMORE TECHNICAL INSTITUTE 1425 Eutaw Place, Dept. 1851 B'way 161st St.) New York, N. Y. LCity Zone.... State C. Baltimore 17, Md. RADIO -ELECTRONICS fori

www.americanradiohistory.com Book Reviews 129 FUNDAMENTALS OF ELECTRICAL of an obsolete map of proposed coaxial ENGINEERING, by Fred H. Pumphrey. and microwave TV network routes) or Published by Prentice -Hall, Inc., 70 has appeared in manufacturers' litera- SPECIAL!! Fifth Ave., New York, N. Y. 5% x 8% ture previously, the book will be useful inches, 668 pages. Price $7.65 This book is designed for those taking to students and beginners who wish a a full -year's course in basic electrical practical introduction to television. 6 TUBE AC -DC KIT A comprehensive glossary and index engineering. Similar in many respects At Last! A low- priced kit designed for to existing books on the subject, the also are included. -MHG high sensitivity, excellent selectivity and author departs from the usual treat- good tone quality. Uses 25L6, 25Z6, 6SQ7, ment by trying to make the reader un- AUTOMOTIVE MANUAL- ELECTRI- 6SA7, 6SK7, 6$K7 in an easily constructed derstand electrical principles through CAL -RADIO WIRING DIAGRAMS. circuit. The 6 Tube Kit is shipped with all simple explanation and the use of illus- Published by the E. I. Electrical Press, parts, including punched chassis, resistors, trative examples. The book has the Hinsdale, Ill. 81/2 x 11 inches, 87 pages. condensers, coil, sockets, PM Speaker, further Price $2.00. hardware, etc. advantage that numerous addi- The main objective in preparing this And at a closeout price of only $6.95 tional topics such as non -linear resistors manual, according to its foreword, was X182 less tubes and cabinet (varistors), stabilized amplifiers and to supply electrical wiring diagrams electronic instruments have been added. X183 Extra for matched set of and radio schematics for leading auto- six tubes for kit $377 .25LJ A good working knowledge of alge- mobiles in use since World War II. It bra and calculus on a college level is was originally compiled for the use of 5 TUBE AC -DC SUPERHET KIT required. Considerable material is de- students in the E -I Electrical School. Five tube superheterodyne kit, A.C.-D.C. voted to power engineering, not always contains all components required to con- The book consists of wiring diagrams struct this latest design, highly sensitive of interest to those in the communica- of automobiles and schematics of their tions field. Evidently intended as a superheterodyne broadcast receiver com- radios. Since there are cases where sev- plete with book black bakelite cabinet (ex- requiring supplementary classroom eral madels may use the same radio, the cludes wire and solder) Price $7.95 instruction, the section on vacuum pages of wiring diagrams are more nu- Extra for a kit of five tubes (I- 12SK7, tubes particularly calls for additional I merous than those of radio schematics. I- 12SA7, I- 12SQ7, -35Z5 and I -50L6) reading and guidance. MC However, no less than seven schematics $2.95. of various Ford -Lincoln -Mercury ra- YOUR MONEY AUDEL'S TELEVISION SERVICE dios appear, and 12 of General Motors RETURNED IN FULL- MANUAL, by E. P. Anderson. Pub- radios. In all, diagrams of radios used If the New Regency Television Booster fails to improve your television enjoyment! Bring your lished by Theo. Audel Co., 49 W. 23 in cars of 11 manufacturers are printed, picture out of the snow and reduce interference! St., New York 10, N. Y. 5 x 6% inches, as well as electrical wiring diagrams of Push -Pull Neutralized triode design assures 396 pages. Price $2.00. high gain without adding snow. the cars. FS No external impedance matchg devices Although this book is titled a TV required. Service Manual, only 3 chapters are di- TO LARGE PICTURE Inductive tuning assures same high -gain wide - rectly with servicing. Actual- CONVERTING band operation on all channels. concerned TUBES. Published by the American Single knob tuning control. ly it covers the whole range of TV re- Co., 1810 Winchester Underwriters approved with 90 day RMA Distributing guarantee. ception from placement of TV receivers Street, Baltimore, Md. 81/2 X 11 inches, in the home, through adjustment of re- 42 pages, 1951. Price $1.50. LOWEST Price -ONLY $19.11 ceiver controls and antenna installation This manual covers the conversion of to a discussion of color TV conversion 16 TV sets, including Admiral, Crosley, MODEL NFRD -RADIO NOISE FILTER If it doesn't work. send it back! methods. G -E, and RCA. It is written in notebook We absolutely guarantee that our Model NFRD Despite the fact that some material style with instructions printed as Step will eliminate all line noises when properly con- is dated (notably the chapter on TV re- 1, Step 2, etc. Steps of mechanical nected to radios, television sets, short wave sets, motors, electric shavers, refrigerators, vibrators, ceiver fundamentals and the inclusion change are listed in greater detail than oil burners, transmitters, and all other sources of interference. This unit will carry up to 12 amperes or 11/4 KW of power and may be used right at the source of interference or at the radio. Small size only 3 "xl '/2 "x71/z ". Very low price only Each $1.95

A SCIENTIFICALLY DESIGNED PHONO SCRATCH FILTER 4500 4ECGF1 t7 Resonated at approximately cycles effectively reducing objectionable needle scratch without altering the brilliancy of reproduction. BV,LUES! Contains a HI -Q SERIES resonated circuit. Tested by means of an audio oscillator and an oscilloscope / to give 22 db attenuation with very low signal loss EASY TO ATTACH Just two wires to clip on. Compact $1.98 vaeaa Price -

THREE TUBE PHONO AMPLIFIER An assembled unit ready for rnstallation using tone and volume control and six feet of rubber cord $2.95 (Not including Tubes) With Complete Set of Tubes $3.95

PHONO OSCILLATOR Wireless phono oscillator transmits recording for crystal pick -ups or voice from carbon mike through radio without wires. Can also be used as an inter - Comm by using P.M. speaker as mike. Price (excluding tubes) $2.95 With Complete Set of Tubes $3.95 CRYSTAL DIODES Std. makes IN34 75 IN34A .75 IN23B 2.25

Satisfaction guaranteed on all merchandise All prices subject to change without notice. RADIO DEALERS SUPPLY CO. Suggested by Chas. Erwin Cohn 154 Greenwich St. New York 6, N. Y.

NOVEMBER, 1 95I

www.americanradiohistory.com 1:30

/ That's ADVERTISING INDEX THE WORLD'S SMALLEST, YET Adelman, Nat 128 A Bu ! Aerovox Corporttion SO "TA B Alliance Manufacturing Co. 65 866A Allied Radio Corp. 15 KIT and XFORMER American Electrical Heater Co. 101 2 Tubes. tickts, ximr 115v 60cyc Irmo!. American Phenolic Corp. 82 Most Powerful Radio outpt 2.5 t /IOa /10 Kvins...... $6.98 Amperite Company, Inc. 113 DIODE PROBE TUBE! Amplifier Corporation of America 122 Unexcelled for NO -LOSS UFH Testing. Anchor Radio Corp. 17 Ultra- sensitive Sub - Miniature- Envelope Astatie /4 +xa/a Corporation 18 APP. 11 . Element & Probe at Tip. Astron Corporation 118 Low Pwr. Eft. BRAND NEW W /Data, Barry Electronics Corp. 130 Vß92 25F 5 for $1.00 Belden Manufacturing Co. 5 Loop Antenna Bell Telephone Labs. 10 FULL -WAVE BRIDGE RECTIFIERS Blonder- Tongue Labs. .. -84 18 VAC Input 14 VDC Output Boyce -Roche Book Co. 62 2 Amps ...S 2.40 12 Amps ..$ 7.50 Brach Manufacturing Co. 55 4 Amps ...S 2.8S 24 Amps ..514.00 Brooks Radio E Television Corp. 124, 125 8 Amps ...S 5.65 Burstein- Appiebee Co. 112 36 VAC Input 28 VDC Output Capitol Radio Engineering Institute 9 86 2 Amps ...5 3.75 8 Amps ..5 9.95 Certified Television Labs. 108 4 Amps ...S 7.00 12 Amps ..514.00 Cisin, H. G. 113 Institute of Radio Electronics 13 "WILLIAMSON" 10W HI -FI KIT Coin Radio Si Television Corp. 127 10 to 20000 cycles with Easel Internationally Famous: Commercial Trades Institute 104 For HiFi enthusiasts. Intl Pwr supply, RCA Chassis, Communications Equipment Co. 115 I.ess Pre -Amp & outpt xfmr. Preselected parts, Balanced Concord Radio Corp . resists pwr. supply & S tubes $29.95 Coyne Electrical E TV Radio School 112, 116 W'mson PreAmp Kit & Tone boost Amplifier chassis Crest Laboratories, lee. 122 Parts, pwr supply & 5 tubes 534.95 DeForest's Training, Inc. SUPER -Wide -Range HiFi TRIODE 10W KIT Dow Radio, Inc...... al 10 to 20000 cycles, 61340's. Max Harmonic Distortion DuMOnt, Allen B. Labs. - Inside Front Cover t/sgp Electra Products Labs. 13/4% at full outpt & only at 5W outpt. In- Electro 95 ludes Bass & Treble tube boost & Tone ckta @ Sales PreAmp 4 C.E. pickup 5 dual & 2 output (7) tube.. Electro- Voice, Inc. 189 Parts, RCA chassis & info., less outpt xformer Electronic Instrument Co., Ine. 22 Length: 2 ". Diameter: 1/2" $29.95 Electronics Measurements . UTC H!FI Outpt Xfmr for P.P. 2A3, 664. BAS & 61.6. Corp 118 Csd Cap 30 W: Sec. 5 taps 21/2 to 250 ohms $ 6.98 Electronic Technical Institute 126 GE Relue Cartridge perm needle $ 1.98 Feiler Engineering Co. 79, 128 (1K Dual Relue Freshman Si Company, Charles 121 HIGHEST EFFICIENCY: Has a Q of 240 -275; Cartridge RPX 050 S 7.29 G 6 G Radio Parts Service GE Relue Cartridge RPX40 or 041 5 7.29 General 123 ordinary loops have only 110. (:E S1201D Hi -Ft Hvy dty 12- PM Spkr $18.98 Electric Co. 53 (Measure- Sensational 10" HIFISpkr Ideal 10 Watt Home Size. General Test Equipment 118 ments made with Boonton Q- Concentric, Separate Good, Inc., Don 108 Meter.) Driver Woofer & Horn Driver Gould Green 108 Tweeter -30 to 16000 cps Range $18.98 Grayburne Corporation Electro Voice EV 16H dual twill Cart $ 3.98 Harvard Laboratories 130 OMNI- DIRECTIONAL: Equally sensitive and Extra dual needle for Twill Cart S 1.20 104 "1.P" Anti -Static Heath Company 93. 94, 95, 96, 97, 98, 99, 100 efficient fluid Good 100 play ¢ S .69 Hudson Specialties Co. 127 at every angle. Needs no orientation. Hytron Radio A Electronics Co. 59 Sell Your SURPLUS TUBES & Gear Instruetograph Compan International Resistance Co. 76 1 77 GREATER RECEIVING RANGE: Boosts sensitiv- To "TAB" -Send List & Best Prices JFD Manufacturing Co., Ina. 126 ity and signal -to -noise Jackson Electrical Instrument Co. 68 ratio -of special im- APS13 /RT34 30mo If Less Tubes As Is $7.98 Kedman Company 122 portance to portables. RADIO COMP RCVR Less Tubes As In-- - - - 5.98 Lafayette Radio 86 Selsyns GE2J1G1 UFIXM no returns, 2 for .49 La Pointe- Plascomold Corp. 64 Tuning MTR GE21/3- DC 5ma. Spel 1.29 Leotone Radio Co. 131 INCREASED ANT- AT5 /ARRI with Coax- Cnctn, 4 for 1.00 Macmillan Co. BUSINESS: Ferri -Loopstick im- RSTR KIT 100 asstd 1/.s &IW to 2megs 100 for 3.98 Mallory Si Co., Inc. P. R. Inside Back Cover, 61 proves set performance so amazingly, your CIRCULAR SLIDE RULE Plastic Rd e99uiv 12" rule .98 -Hill Book Co. 114 customers 6" Sharpening Stone Carbrndm Co. $22 Spl .25 McGrawMerit Transformer Corp. . will call you a "miracle man." Metropolitan ..... PL259 Coax Plu $.55 50239 Coax Jack .55 Electronics Si Instrument Co ...... 94 Every AM Midwest Radio 6 Tel. Corp. 81 set -owner is a HOT PROSPECT! SNOOPERSCOPE Miles Reproducer CO., Inn. 79 Image-Converter Hi simplified Milwaukee School of Engineering - 103 2^n Willemite screen-ResolutionResolution upo 350 lines/ Miller Company, J. W. 116 LOW COST: Consumer List Price only 75c. inch Complete datas &Q1 tube Ea. $4.98; 2 for $9.49 Moss Electronics 131 Liberal BALL PENS red or bl. 5 for$1.; Draftsman hlk.2 for $1. National Company, Inc. 104 discounts. RADIOACTIVE MARKERS 11/2" DD: 5 for .25 National Plans 123 DIAG CUTTERS 61/2" Hvv dty Eng. Shfld steel 1.69 National Radio IN34 Xtals EI $.69; 1N34A II@ 5.891 1835 4 1.95 Institute...... Insert facing Inside Front Cover and 102 SERVICEMEN: For name of your nearest Ferri - CIRCULAR SLIDE RULE, 12" quiv 2t /R" Radius 980 National Schools 7 Loopstick 6.16 P $1 or 12 for 10; 6X4 Q $.49 or 12 for 5.00 Niagara Radio Supply Corp. 119 distributor, write to us NOW! KITS Ohmite Manufacturing Co. 66 1 Opportunity Adlets 122 Silver 6 Mica Cndsrs 30 for 52.50 Perfection Electric Co. 79 Controls, 50 ohm to 2 Meg. 10 for 2.98 Permoflux Corporation 73 1/I Resistors, & 1 W, to 2 Megs ....100 for 5.98 Precision Apparatus Co., Ino. 52 Vitreous WW Resistors S for .69 Prentice Hall, Inc. 115 GRAY BURNE Sockets, Asstd, 8, 7, 5, 4P 25 for 2.49 Co. C O R P O R A T I O N P- Rotary Switches, Ass. 6 for 1.75 og ressCiive lectronics Co. 83 Gap Tube Caps, Asstd SO for 1.49 RCA Institutes, Inc. 21 103 LAFAYETTE ST. NEW YORK 13, N.Y. Coil Forms, Th'tl Sm HF 50 for 1.00 RCA Victor Division (Redio Corporation of Iron Core Slub Si Screw 50 for 1.00 America) Back Cover Knobs, Asstd, w /insert 10 for .98 Radiart Corporation 49. 57 Spaghetti Sleeving, Asstd 75 ft. for 1.00 Radio Apparatus Corp. 110 Ceramicon Cndsrs, Asstd 12 for 1.00 Radio City Products Company, Inc. 127 Fuses, Asstd, LE & Buss 75 for 1.95 Radio Corporation of America 69 CARTER DYNAMOTORS Grommets, Rubber Asstd 50 for 1.00 Radin Dealers Supply Co. 129 Resistors, 2 W Asstd 25 for 3.98 Radio Receptor Co., Inc. 84 BRAND NEW -ORIGINAL MFR'S SEALED BUILD A BANTAM CARTONS . . 6V. INP. -400 V.D.C. out 6V 375 Ma. List 1 -WATT XMITTER $71.40 With This Bargain Foundation Unit Only $28.00 Free Instructions. Takes 2 Plug -In FT- RADIO SCHOOL DIRECTORY 6V. INP. -590 V.D.C. out @ 250 Ma. List 573.50 243 Xtals A Coil -W/140 Mmf ender & Only $33.00 Xtal Socket 2 for 0.49 Page 128 Complete w /Xtals & Coil 2 for $1.69 ULTRA- COMPACT FINEST MADE Baltimore Tech. MERCURY THERMO- REGULATOR Inst. Quality, tested tubes -new & guaranteed in stock DualCkt. 105 °F & 32 °F. Extremely Sensitive A Accu- rate for Most Exacting Requirements-RESEARCH, FIRE Candler System Company now: many others not listed (XMTG, etc.) PREY. - FREEZE PT CONTROL o MAX -MIN TEMP Con- Commercial Radio Inst. Write for low, low bids on your requirements - trol. Brand New. Indlvid. Boxed /data & ckt. List over $20. Specify $ 98./ 12 for 510.00 Electronics Institute, Inc. 1N21 ..5 .80 6AU6 $ .55 12AV6 .5 .55 1H21-B . 3.00 6AV6 .50 12AÚ7 . .80 HEINEMANN MAGN. BRKRS I CIRCUIT BREAKERS Federal Electronics Inst. Amps: 0.22, 1, 2, 3, 3, 7, 8, 12, 15, 20. 25, 30. 1H23 .95 6BA6 . .65 12AT7 . .95 35, 40, 50, 70 100, 180 each $1.69 Hollywood Technical Inst. 1N23 -A . 2.75 6BD6 .. .50 12BA6 . .65 Sq. O 6 Ch Toggle Sw Brks. Amps: 5, 10, 15.$20, 25, 30, each 98 Indiana Techincal College 1N23-B . 4.00 68E6 .5512ßE6 .. .65 Mixon Theral Push Button Brkrs, Amps: 5, 10.$185. 1N34 .. .70 6BQ6GT .85 12BH7 . .75 20, 30, each Lincoln School of Radio & TV, Inc. IB3GT . .85 6CD6G . 1.50 25L6GT .50 BLOWERS I Martin School, Don 1R5 .... .65 6SH7 .. .6035C5 .65 Cool That Tube: 175 CFM 220 V AC...... $11.98 1U4 - .65 40 CFM 28V AC DC $5.98' 70CFM115V /400 eye. $4.49 RCA Institutes, Inc. -.- 6J56T -. .5035Z5GT .50 40 CFM BLOWER 24VDC Exceptional buy .$6.98 3A5 ... .65 6J6 .90 5005 .60 250 Streamlined Self -Study Course ...... CFM 28V AC DC $9.95: w /Matching 115V 3D6 - - AC Trans 11.95 .. .50 6R8 .75 5OL6GT .60 Tri -State College 354 .... .90 6SD7GT .75 80 .50 NEW THRIFT -LITE 3Q4 .55 Lifetime Photo -Flash Not a kit. Inc., Valparaiso Technical Inst. ... 6SN7GT .65 4-125 -A 27.50 Pwr pck, Life gtd Lamp, RHctr & 15' 5Ú4G .. .60 611 . .80 304TH .11.50 cord 1 /1000 Sec Bash every 7 sec. YMCA Trade & Technical Schools 5V4G 1.05 True daylite color. Usable all cameras .. 6U4GT . .75 304TL .11.50 Oper 115VAC milite Type AC4O $41.98 5Y3GT . .40 6V6GT . .55 813 8.95 Complete Outfit for AC & Battery opr. 6AB4 .. .75 6W4GT . .50 955 .45 Incl. AC40&9P25 pprtopak & all acessrs Rauland Corporation 63 for Kodak&Compur shutters, Cotn- Ray Company 86 6AG5 .. .65 6X4 .... .55 9004 .40 lete $69.95 Raytheon Mfg. Co. 8 6AL5 .. .40 6Y6G , . .75 9005 1.35 Write for Complete "THRIFTLITF" Regency Div. (I.D.E.A., Inc.) Data 79 6AS5 .75 6X5GT . -45 . - - Boosterpacks, Ext lites, Units for Focal plane Rinehart Inc. 91 .. 0A2 1.10 shutters & accessories. We buy, sell & swap. Rose Company 120 0132 1.20 Sams 6 Co., Inc., Howard W 18, 88. 106 TAB "SUN- FLASH" LAMPS Sanett, Bob 86 'TAB" No. Replaces W -Sec. Max. Each Simpson Electric Co. 72 NEW SELENIUM RECTIFIERS U10 GE FT110 100 $11.79 Soundtronics Labs., Inc. 123 No. 1 AMGL.O 5804 100 11.98 Sprague Products do. Full -Wave Bridge Types 23ST GE FT114 200 10.98 Sprayberry Academy of Radio 47 CURRENT 18/14 110 53GT GE FT403 500 16.98 Stan -Burn Radio S. Electronics Corp. 11s 36/28 54/40 /100 VA SYLV. 4330 200 12.98 Steve-El Electronics Corp. 74 (CON'TI VOLTS VOLTS VOLTS VOLTS R4340 FLASH TUBE -Nationally AdVtsd 15 57.$36.00 Superior Instruments Co. 112 35mm FILM & microfilm 20 exp. P /cart. 5 for 1.00 Supreme Incorporated 20 1 AMP. ... $ 2.75 ...... X -400 Air Corps Lamp P /01188 &1169ANequip 14.98 Supreme Publications 75 2 AMP. $ 2.40 3.75 $ 6.95 510.50 Sutton's Wholesale oducts, Bill 126 STORAGE BATTERIES Electric Products, Inc.in 51 4 AMP. 3.85 7.00 9.00 ... 38 volt WILLARD Minl -BRAND NEW! 5 oz. Designed Tab 119130 6 AMP. 5.85 9.00 Portable Equip Models 98e; 4 for $3 Tech Inc., duc ...... 2V /27AH Willard ßB54 PLUS 2 Volt Vibrator $1.98 Tech-Master Products Co. 10 AMP. 5.90 12.50 ...... 6V 110 /6AH Wind NT6 /BB214U 1.75 Tel -A-Rax 167 12 AMP. 8.50 14.00 . . . 6V /40AH Willd ER40 -6 6.98 Televisio Enterprises. Inc. .. Battery Acid. (R -Exp) 1pt. 59e; 2 pts. .98 Television Communications Institute 105 24 AMP. 14.00 27.00 ... Hydrometer 1.06 to 1.24 Sp Gray 1.98 Telrax Inc. 187 Electrolyte Meas Tube, 12" lg .25 Triplett ion, Inc. We can manufacture other rectifiers to Specs." We Spec Gray Ind & Merc. Thermom .98 Triplett Electrical Instrument Co. 112 have an interesting inventory of equipment. Turner l Inc. 52 DRY BATTERIES Turner Company 13 Sig Corps -BRAND NEW-Tested, Shelf Dated-Guaranteed. United Catalog Publishers, Inc. 113 8A43 90/45/11/2 Volts ...... 89e; 8 for $6.49 Ward Products Corp. 71 45/30 Volt NEW 1949 Batty Sim BURGESS XX30E, Weller Electric Corp. 20 loSn,bx41/4" 79c; 3 for $2.00 Wells S 120 ELE[TROfII[S CORP. Wells Sales. 132 $5 Min. 25% Dep. F.O.B. NYC. West Region C 92 136 Liberty Street New York 6, N. Y. Prices Subject to change. Wholesale Radio Co., Inc. 118 W ìnchar ger RE cfor 2 -2563 Dept. II RE, 6 Corp. 111 Church Street Terms: 25% with orde,, balance C.O.D.-Add few New York 6. N. Y.. U. S. A. cents for postage -ALL MERCHANDISE GUARANTEED "TAB" Cor. Church & Liberty Sts. Radio -Electronics does not assume responsibility Room 200. Phone Worth 2 -7230 for any errors appearing in above index. RADIO -ELECTRONICS for

www.americanradiohistory.com Book ltcricwc 1131

the necessary electronic changes although these are likewise included. An THE JUNIOR introductory chapter covers fundamental problems in changing over to large Bulletins draw- SUPER -METER Technical picture tubes. Photographs and The most complete and compact multi- ings included make this a helpful book service instrument ever designed! Postpaid Foreign $1.25 EACH $1.00 for the service technician. Measures: Voltage Electrical Design and Construction RADIO VALVE DATA. Compiled by World. Published by Iliffe & Current Wireless agent: Resistance These bulletins give you easy, accurate, depend- Sons Ltd., London (American of designing and building electrical 122 East 55th St., Capacity able methods tables British Book Centre, equipment. You just follow simple charts, York 22, N. Y.). 81/2 x 11 inches, Reactance and step -by -step instructions that tell how to New Inductance units to meet specific require- 80 pages. Price 80 cents. figure correct size manual covers Decibels ments. This British radio tube Plus Good -Bad and American tubes, in- scale for check. Electric Motors-Enables anyone 2,000 British 106 Rewinding re- tubes. It is divided ing the quality without electrical training to locate trouble. cluding cathode -ray of electrolytic rewind a.c. or d.c. motors and generators to functions pair and coils. into sections according condensers. ; to figure wire size and wind of all kinds how (tetrodes, output tubes, frequency all Specifications: 111 Transformers -How to design and build changers, etc.) and further subdivided Volts. including specials D.C. Volts: 0-7.5/75/150/750/1500 types and sizes of transformers (for British tubes) and A.C. Volts: 0- 15/150/300/1500 /3000 Volts. for Neon tubes and ultraviolet lamps. Easy meth- into brands dimensions and wire size. Listing is alphabetical Resistance: ods of determining core American tubes. 0- 10,000 /100,000 ohms. 0.10 Megohms. and numerical under these subheadings, D.C. Current: 0-7.5/75 Ma. 0 -7.5 amperes. -Safe, approved way to wire Mfd. .1 Mfd. -20 Mfd. 152 House Wiring cir- tubes are further divided Capacity: .001 Mfd. -.2 new and old buildings. Shows many different and British Electrolytic Leakage: Reads qualit of electro- cuits. Explains how to use latest type of materials into obsolete, replacement and current lytics at 150 Volt test potential. estimating Db. +10 Db. to including fittings. fixtures. Also gives types. Decibels: -10 Db. to +18 methods. as +38 Db. +38 Db. to +58 Db. Complete characteristics are given, Reactance: 15 ohms -25 K ohms 15 K ohms - and 101 Resistance Wire -How to use Nichrome well as basing diagrams (obtained from 2.5 Megohms. similar wire in heating devices. rheostats and re- Inductance: .5 Henry-50 Henries 30 Henries - ; space but is a sistance coils. Figuring wire size and length how a table which economizes 10 K Henries. to wind elements and test. Also supply directory. bit complex to operate). FS Handsome round cornered molded bakelite complete 140 -How to make case 31/2" x 5 %s" x 21/4" sfL 113 Solenoids & Plunger Magnets instructions. these a.c. and d.c. magnets having movable with all test leads and plungers to control other equipment. How to figure PRINCIPLES, by Ro- wire size, etc. TELEVISION EASY PAYMENTS dimensions, plunger stroke, bert B. Dome. Published by McGraw - SOLD ON 42 St., U2 Electromagnets -How to design and build all Hill Book Co., Inc., 330 West AT THE NET CASH PRICE types and sizes for a.c. and d.c. How to figure New York, N. Y. 6 x 91/2 inches, 291 lifting power, wire size. $5.50. No interest or carrying charges added. Simply pages. Price remit S5.40 with order, pay balance 54.00 d.c. Written primarily for radio engineers four months. 148 Relays- Designing and building a.c. and as per month for relays of any size for various purposes where by an author recognized by engineers DIST. CO., INC. voltages must control heavy MOSS ELECTRONIC small currents and in the field, this book dif- New York. 7, N. Y. circuits. Includes control systems for motors and an authority Dept. B -2, 38 Murray St., machines. fers considerably from others with similar titles. Possibly the most striking is LEOTONE LEOTONE LEOTONE LEOTONE . . FULL LB. CAN of 137 Meters -Designing and building ammeters. Radio Hardware Treasure 694 3/1.98 book contains fewer pages Id Nuts. Screws, Lugs, Washers. etc. voltmeters, wattmeters, for a.c. and d.c. Includes brevity. The 2 'RELAYSPECIALS!! r the G.E. PLATE RELAY complete information on calibrating. than most of its type. Surprisingly, (CR2791- B109P36). 0 o DPST. 30,000 -,.- 15/ex Z as clear and complete 1a -to- build. explanations seem aLe 11.x2/4 5.96 127 Small Electric Light Plants -Easy J eo o/ .69 camps. etc. more verbose parallels. (GE S#CR2791- B100C3) .. 175,,_ low -cost installations for cottages, as some of their SPST Keying Dble. Brk./ -lamp system; SPST Keying (Allied SSCNSX -1) . . 1.29 Includes a 110 -volt, seven 25- watt is rather freely used in contacts 1010)3. r auto Mathematics N.O. lOA. N.O. al also a 6 -volt system using generator. most Z DPST Keying (Efcor #42]030) .95 explaining circuit action. However, O coots. 150_,.. 1 BF) . . 3A. N.C. au- K e ye ng (Leah 1.29 Z 151 Electric Power from Streams -How to survey of it is simple algebra (though the cDSTs. xt VN' Relay 12V. DC. 1/cx1 a/S r .79 m streams, estimate requirements and available in at least one j aDT An tenna sects. Sliv er build dams, select and install thor went into calculus Condenser 4/250mmf $1.29 power, design and like the plated. 7½53523/s ,59 the control system and electrical equipment. chapter) and the mathematics, ST eL tons 2 sect. 100/ .98 . 31/3' L. Printed W 6T Tube Cartons RPM, Vu r as to be most Z Motor (stew: 2 ) 11750 O text, is so organized 2t codes/a- 161 Burglar Alarms & Time Switches -Dependable O haft. O.D. 69e ioie.so g Time switches made easily understood. FS F 3N21 Crystal Diodes Z types for various purposes. e R tor alarm clocks and arranged to control lights, KITS!! New ".JUMBO RADIO -I III !!BARGAIN COILS. sprinkler systems, motors and other devices. PARTS KIT " -17 FULL LBS. of: a I WIRE. SOCKETS, RESISTORS, CONDENSERS.S3.95 . . 00001 to BASES (second edition) by O. S. Moulded Bakelite Condensers 1.98 e r TIME al 2mfd, 200.300V- Kit of 50 asstd...... 144 Choke Coils -How to design and build for & Switches . Incl. multi- Published by John Wiley 2 Rotary Selector astd. 75 .. How to use these instead Puckle. O e leek, multi -contact, Kit of 6 many different purposes. York, 5 -2óW. 12 asstd ,96 O safely and with Inc., 440 Fourth Ave., New I- wire -Wound Resistors .79 Z of rheostats for voltage control, Sons, O 1W. Carbon Resistors .. ferrule -end ...25 Price Ia setscrew. Kit of 25 asstd. Is much less loss of electricity. N. Y. 53/4 x 83/4 inches, 387 pages. ., Knobs spring, asstd. -49 1 E Wafer Sockets .. 4 to 8 pin. 12 Nigh Fidelity Crystal Mike . HI- Imied. $5.00 I m91. 11/4 -x1/4'. Le housing. 1.29 131 Remote Control of Electrical Devices -Cir- Rubber shock mike.. .15 g base is a means of measuring E Aluminum HOYe i n9 for crystal How to use telephone dial A time Id powerful Bar, Block, r cuits and applications. "AlniC0 Magnet Kit" .. 10 asstd. 1.98 0 and model- in a crude way by the Z "U ", Rod, etc., types. Kit of ... and Stroger switch. For experimenters time. Performed 0 Z railroad switching purposes. divisions of time orossummoEomIIRADIO CABINET SPECIALS!! Z sun dial, more accurate m .1 _ -.- Wood, slide -dial by a modern watch. For .1 - - Type "A'- IVOry. Inside' 134 A.C. Electrical Experiments- Fascinating. can be obtained l0t/4'x6%4'x51/s', Dial: 3 $1.49 experiments for education and entertain- up into millionths of a { i i /4'x6,° ...... harmless splitting time Type B "- Mahog, Inside: r uses. m Dial : in ment. Also practical are required. -._ _ 17"x81/4.x101/4.. a second, electronic means - - /2.x . 2.49 O Type C"= Mahog. Inside: Time base circuits form a necessary I- 14y4 °x63/4' en. Dial: G D 13/4.x8. 1.95 oscillo- ' For m part of electronic equipment- J G. E. Tungar Bulbs (#206501) . . 2 Amps. Bat. Cha gers A DC Supplies...... 1.49 photography, Circuit Breaker , . Type PLAS 120. 520 N. Michigan Ave. scopes, television, radar, Klixon 24V. 494 6/2.49 r Ri -amps. 23/8' mtg. 494 6/2.49 T E C H N I FAX Chicago 11, Ill. to mention just a few of the al SOLS P.P. Outputs computers, NE Bulbs (GE) . 114W. DC bay 29e 10/2.49 a Z -48 Neon .4 O DC Bayonet Socket flush panel mtg 23f 5/1.00 Now appear- or the following more obvious applications. I- BC Tuning Units (SCR -511) . 3655 O Enclosed find $ for which send -746A SSC 3 /1.98 Z $1.25) as book cov- O 4780 KO. BRAND NEW . Less Stelo Technical Bulletins at $1.00 each (Foreign ing in its second edition, this Cabinet Drawer Slides Ball- bearing: 13' R .1 pr.: 15' (11 ")- $2.25: 161 /s indicated by numbers: ers the design and development of time (9" egt) -52.10 2.39 Hvy. duty, all -steel 161 (121/2') 3.25 base scanning generators. Thoroughly is Chassis 6 Cover Foundation .. punched 5 tubes- 11 ^x91/2'043/' 1 29 r the author has Z Cad. plated. /450V. Can....49f 6/2.49 familiar with his subject, e Electrolyties 32mfd. 6/2.49 OI I- IOmfd. /450V. . . can, octal base....49t nut mtg. 39C 6/1.98 Z the field carefully and pains- O Smfd. /475V. .. can, R searched W 30mfd. /300V. .. paper, tubular 294 4/1.00 and has produced an exhaus- -. (WRITE FOR "ALNICO MAGNET" SUPPLEMENT) takingly "FACTORY SPEAKER REPAIRS SINCE 1927" book. Ency- Min. Order $3.00 20% deposit on all COD's Name tive (but not exhausting) Please add sufficient stage -excess refunded r in content (and well indexed) zY Full remittance with foreign orders Aa Address clopedic using time RADI O CORP: ó it is a mighty tool for those Z 87 Street 0 City & State J L York 7, N.R Y. RE-II-SI base circuits.-MC O New -end- 3NO1031 3N01031 3NO1O31 3N01031 NOVEMBER, ISS!

www.americanradiohistory.com 132

...... Over a Million in Stock! The following list represents Each relay is brand new, standard only a portion of our relay make, inspected, stock. Write or wire us for information on types individually boxed and fully guaranteed. shown. not Stock D.C. No. Voltage l'nit Stock D.C. Unit Stock D.C. Ohmage Contacts Price No. Voltage Ohmage Contacts Unit Price No. Voltage Ohmage Contacts Price STANDARD DC TELEPHONE RELAYS ROTARY RELAYS MIDGET RELAYS R-806 115* 900 lA $2.05 R -709 6/8 1 12 Pos. 3 2B & lA 1.10 Water $3.90 R-572 24 256 1C R-100 24 600 R -197 9/16 70 20 2.05 R-857 $1.25 2A & IC 2.45 R -713 9/14 125 IC 24 260 1 Make Before Make 1.75 R-518 85/125 6500 1C 3.60 & IA 2.05 R-912 4/5 20 R-633 180/350 10,000 R-616 28 7 5BB & lA 2.40 3A-1C Ceramie 2.50 1C & 5 Amps. 2.90 R- 712 24 200 R-291 6 5 IA 1.25 Oct. Skt. 2.45 R -711 2.05 R-921 R-667 6 .75 IB/10 24 200 2C & 1B 2.05 6.7 18 IA Dbl.Brk4.10 Amp. 1.45 Amps. R-573 28 200 IC & R-738 12 60 3A IA/3 Amps. 1.45 R-766 lB 2.05 1.20 R-632 6 12 24 230 12 Pos. 8 Deck 4.90 R-922 12 75 IA Dbl.Brk.@10 5A &1C 1.25 R -809 28 7 Amp. 1.45 R-154 6/12 200 lA 1.50 1B & 12 Pos.W/ 2.45 R-144 12 228 lA 1.45 R-517 12 250 2A 1.50 7' Shaft for Wafers R-145 18/24 250 2A Ceramic 1.45 3000 lB 3.05 R-298 21 300 R-531 IA 1.25 100/125 3300 2A 1.90 DIFFERENTIAL RELAYS R-298 21 300 IA 1.25 R-545 110/250 7000 IC 2.45 R-124 300 R -208 120 2000 2('/3 Amps. $2.45 R-586 21 300 IA & IC 1.25 12,000 lA 1.55 R -209 220/250 8000 R-137 24 300 R-160 12 3C & 3A 1.30 1C /3 Amps. 3.10 1C 1.45 R-591 0 40 SEALED RELAYS R-142 24 400 2C 1.50 1B & 1C 1.35 R -658 6 35 2C 100 4A & 413 1.45 /Octal Plug $3.45 R-785 24 200 2C/10 Amps. 2.00 R-520 R -125 24 300 2C/Octal Plug 3.45 R-607 24* IA 200/3Ó8 14,000 2C 3.45 R -261 12/24 1900 1.20 9 50 2A 10/5 Pin Plug 3.75 R-606 24* - IA & 1B 1.35 R-673 48/150 7500 1.20 R-158 6 50 4A 1.35 10/5 Amps. 2.80 R-605 24* - R-576 12 VOLTAGE REGULATORS 1.20 200 2A 1.55 R-745 6 R-728 6 -30 lA 1.25 2 R-153 12 200 IC & lA 1.55 lA /10 Amps. $1.05 R-149 R-780 24 3 1.05 6/8 45 IB 1.50 R -509 6/12 R-732 12 120 SHORT TELEPHONE RELAYS 35 1B /2 Amps. 1.05 IA 1.45 R-281 12 126 2A 1.25 R-635 R-818 12 100 IC & 1A $1.35 SPECIAL RELAYS 18/24 300 1B 1.30 R-648 12 170 lE 1.35 11-135 24 250 1B 1.45 R-826 12 150 2C, lB 1.55 R-503 12/32 100 3A, R-133 24 300 None R-770 24 2C $13.50 .75 150 1A /10 Amps. 1.45 R-749 600 Max. 28 Amps. 7.45 R-138 24 300 4A 1.45 lA /10 Amps. 1.45 R-804 550* - 1B/38 Amps. R-132 24 300 20 1.50 4.35 R03 18/24 400 2A 1.55 R-250 115* - Adj. Cir. Bk.-.04-.16A R-731 24 300 2C R-575 24 50 2C 2.40 R-579 220* - lB 17.50 1.55 R-764 48 8.70 R-292 24 350 1C 1.25 1000 2C & 2A 2.00 R-294 27.5 -200 5.35 R-563 60/120 7500 lA 1.70 R-686 115* 2C R-626 24 400 IA/5 Amps. 1.55 R-801 115* None R-246 6.10 R-786 60 1300 2C 1.45 115* - 1 B 11.20 2.00 R,213 512* R-588 8 2A 3.10 R-246A 115* - lA 11.20 90/125 6500 40 2.70 R-589 125 2A 1.30 R-611 24* - 1A /30 Amps. R-755 24 300 lA 1.45 5.35 4A 1.55 R-283 12 -125 1C/10 Amps. R-150 6 30 lA R89 12/24 255 R-614 4.35 1.50 1C 1.55 18/24 60 lA/15 Amps. 4.35 R-893 14 150 1A, 1C 2.50 R-799 24 500 None 1.00 R-245 12 25 4' Micalez R-15 2 Lever 3.20 R-895 14 150 2A, 1B, 10 2.50 500 IC 1.70 R-527 6/12 50/50 In Serles 1.20 R-110 24/32 1C 1.70 R-544 12/24 60/60 1C R-121 150 5000 2A & 1C R-255 2.05 R-634 150/250 2.05 lA 3.50 6000 IA & IB. 2.45 R-669 75* 400 Cy. 1B, lA 1.20 SPECIAL RELAYS -Cont'd R-800 12 150 2C & IA 1.55 R-537 12/24 150 2C & 1B 2.00 KEYING. R-660 6 yf' Stroke $1.20 R-750 24 400 lA 1.60 RELAYS R-651 24 -100 Solenoid Valve 3.10 CONTACTORS R-714 9/14 65 20/5 Amps. $1.55 R -295 12 275 Annunciator Drop 2.70 R-850 12 450 IA /1.5 Amps. 1.50 R -230 5/8 2 2A, 1C 2.70 R-188 24 200 R-721 18/21 290 20/5 Amps. 1.55 R -813 12 12 Wafer IA/75 Amps. $3.70 R-694 24 300 5.35 R-183 24 60 IA/50 Amps. 3.45 1A/5 Amps. 1.50 R -275 12 750 IA, 111, 10 3.45 R-187 24 100 lA /50 R-935 28 1000 10/1.5 Amps 1.65 R -716 24 70 Amps. 3.70 R-949 2.4* 600y. 1A/5 Amps. 2A/5 Amps. 1.80 R-554 24 85 2A/100 Amps. 5.90 1.95 R-620 6/12 35 2C, lA 1.30 R-788 100* 3B & R-704 2/8 25 2B/5 Amps. 1.35 2A 5.45 R-173 2/6 2 R-629 9/14 40 1C/10 Amps. 1.55 R-682 115* -35 5A /10 Amps. 6.10 lA 3.00 R-720 24 50 2C R-767 24* 20 2A /10 R-280 6/8 77 IA Dble. Brk. 2.45 Ceramic 1.70 Amps. 4.95 R-647 6/12 15 R-500 12 10 /10 2C /6 Amps. R-180 12 25 1A/50 Amps. 4.05 1B /20 Amps. 1.45 3.55 R-657 24 50 4A /100 Amps. R-273 20 160 2A/15A Dble. Brk. 3.55 R -816 12 10/15 2C /6 Amps. 3.55 6.95 R-169 24 200 R- * R-265 24 60 IA/100 Amps. 3.45 lA 2.45 524 24 *- 1.20 R-535 24 70 R-570 24 230 IB Dble. Brk. 2.70 R -566 115* Coil Only lA /100 Amps. 4.80 R-960 24 1.00 R-556 24 70 lA /100 Amps. 4.80 230 3C/15 Amps. 2.95 R -710 150 Coll Only .75 R-557 24 100 R-529 24/48 1020 2C 3.10 *A('. * *AC/DC. IA/50 Amps. 3.85 R-715 24 - R-178 24 100 lA /100 Amps. 4.80 2C Ceramic 3.70 R-727 10 R-584 6 -20 IA Dble. Brk. 1.30 20 lA /20 Amps. R-608 2.00 R-192 12 44 3C /10 Amps. 24 125 1A /200 Amps. 2.80 R-204 1.70 R-184 28 50 lA /100 Amps. 12 66 2A 1.45 R-719 4.90 R-224 12 85 IA 24 10 1A /200 Amps. 4.95 R-221 1.45 R-182 28 80 1A/25 Amps. 2.40 18/24 5000 lA 2.00 R-244 75* 265 1A/20 R-205 24 260 2C 1.55 S PECIAL! Amps. 2.20 R-891 24 475 1C Amps. R-659 12 7.2 2A/20 Amps. 1.70 5 CO R-552 24 70 4A/50 R-536 27 230 2C / 1.55 -AXIAL RELAY Amps. 5.35 R-858 27.5 250 lA Dble. Brk. R-185 24 100 lA /50 Amps. 3.45 1.45 D 153766 SPDT, 6 VDC. R-186 24 132 R-833 6.5 1300 2C 3.05 1A /50 Amps. 4.35 R-220 75 5000 19 Ohm coil. Designed R-817 24 150 IA /50 Amps. 3.45 1C 1.50 R-534 14 45 IA /30 R-828 42 lA 1.50 to accommodate 75 watts maxi- Amps. 2.05 R-627 615* Dble. R-223 28 150 1A /40 Amps. /48 VDC. 1.70 lB Brk. 3.10 mum. Perfect for all types of R-68 6 3 R-734 - 3C /10 Amps. 1.30 antenna 1A/50 Amps. switching. Designed for using 3.90 5 98 24 185 2C 1.30 standard 6 3.5 1A/50 Amps. 3.90 83 -1SP coaxial fittings. Part RAX -1 R-532 6 R-622 20/30 200 3A & 2C/10 Amps. 1.45 of equipment. 15 1A/50 Amps. 3.90 R-274 No. R- 846 Ea. R-676 12 16 1A/50 24* 2A 1.55 -$6.95 Amps. R-855 110.600y160- lA Dble. Brk/15A 3.25 IAUX/25A 3.90 R-277 12 30 20 -D Break Cera 2.20 BASIC CONTACT ASSEMBLIES SHOWN IN UNOPERATED NORMAL POSITION o O

O O Form A- "Make" Form B- "Break" o (Single Throw, f (Single-Throw, Form C- "Break- Make" Form -"Make O Normally Open) Normally Closed) D (Double- Throw) Before- Break" Form E- "Break- Make- Before -Break" MANUFACTURERS AND DISTRIBUTORS: WRITE FOR THE Telephone WELLS NEW WELLS CATALOG SEeley 8 -4143 SALES, /NC. 833 W. CHICAGO AVE. DEPT. Y, CHICAGO 22, ILL.

PRINTED IN MR U. S. A. BY TUB CURIO , tat.

www.americanradiohistory.com \i

In Volume Controls, too . e fast, sure fit is important

In a survey of hundreds of servicemen, the importance of fast, sure installation was emphasized time after time in connection with volume controls. If you want a control that lets you do the job fast ... and do it right . . . Make Sure: Make it Mallory!

When you use the Mallory Midgetrol *, you get a removing the control housing. Positive indexing combination of features that can't be matched. assures proper position.

First, you get a permanently fixed, tubular brass Third, you get exceptionally accurate resistance shaft that can be adapted for split -knurl or values and taper curves. flatted type knobs in a few seconds by inserting Fourth, you can be sure of years of quiet, one of the steel shaft ends supplied in every satisfactory service life through extremes of package. This means utmost convenience with- humidity and temperature. out sacrificing the stability of permanent, two -point shaft suspension. Make it Mallory and make sure! Ask your distributor to show you the time -proved Mallory Second, you get the convenience of AC switch Midgetrol with the new features that make design that permits secure attachment, without installation faster and simpler than ever.

Depend on your Mallory Distributor for precision quality at competitive prices

Single Section Control Illustrated Dual con cen tric MalloryMidgetrols Ïr M1toTIP can be made up easily by com- CAPACITORS CONTROLS VIBRATORS SWITCHES RESISTORS bining factory- assembled front RECTIFIERS VIBRAPACK* and rear sections of desired POWER SUPPLIES FILTERS resis- *Reg. U.S. Pat. Off. tance values. Ask your Mallory Distributor for details! PPROVED PRECISION PRODUCTS P. R. MALLORY & CO., Inc., INDIANAPOLIS *Rep. U. S. Pat. Oß. 6, INDIANA

www.americanradiohistory.com THE QUALITY OF RCA TUBES IS UNQUESTIONED

ELECTRON TUBE EIE six ,%awfflow as a matter of course ... with RCA tubes

The RCA -developed "A" frame con- plays an important role in reducing struction -used in 6 of the metal -type microphonics and maintaining uniform r -f amplifiers -is one of the many im- tube characteristics. provements that contribute to the extra In addition to imparting rigidity to performance of RCA tubes. the tube elements, the top and bottom The "A" frame -shown in red -con- members of the "A" frame serve as sists of a top member, two vertical mem- shields. The two ears on the top member bers, and a bottom cross member. The add to its effectiveness in reducing grid - ribbed uprights are welded to the cross to -plate capacitance ... the tab on the member ... the feet of the uprights are lower member -which extends down to welded to the grounded metal header. In the stem - provides additional shielding leads. effect a truss, this rigid "A" frame acts between grid and plate as the supporting member for the tube The extra performance built into RCA elements. Its increased resistance to tubes accounts for their high quality, vibration reduces the possibility of elec- long life, and dependability. They cost trode displacement due to wear on the no more. Why not use them for your holes in the mica spacers ... and thereby daily tube requirements?

Keep informed -keep in touch with your RCA Tube Distributor

01014 RADIO CORPORATION of AMERICA ELECTRON TUBES HARRISON, N.J.