Radio Broadcast (May 1928-Apr 1929)

152 RADIO BROADCAST ADVERTISER S-M 720 Screen Grid Six (See description on opposite page.) Read What They Say About It — Gentlemen: I have had this kit in actual operation for over a month and am astounded with the results. . . Stations which my friends and myself had given up as "lost at sea'* have come thru like a ghost from the grave, and dance volume from a loudspeaker from the Pacific coast is a reality instead of 3 wiIl*o-the-wisp. And knife-edge selectivity. What a treat! F. Lordan, Galveston, Texas. Gentlemen: On my set, which is a Silver Marshall Screen Grid Six, I am using a loop, and it might be interesting to you to know that in testing with the loop for distance this last week I received (at Rochester, N. Y.) Los Angeles, Hot Springs, Arkansas; Davenport, Iowa; Jacksonville, Florida and Omaha, Nebraska. Clayton R. Bragg, Rochester, N. Y. Gentlemen: Between 4:30 P.M. and 9:00 P.M. — knocking off about an hour for supper — I logged 63 stations within a radius of 2000 miles. Calgary, Alta., Canada, came in with pretty good volume and an Army band in St. Paul, Minn, nearly tore the speaker apart. Jos. H. Malkin, South Norwalk, Conn. If you build professionally, write us about the Service Station franchises. Or if you don't build, yet want your radio to be custom-made, S-M will gladly refer your inquiry to an Authorized Silver-M.ar shall Service Station near you. Are you receiving "The Radiobuilder" regularly? Every issue describes new and interesting radio developments. To all Authorized S-M Service Stations, it comes free of charge; to others a nominal charge is made. Use this coupon. Silver-Marshall, Inc. 838 W. Jackson Blvd., Chicago, U. S. A. ....Please send me, free, the complete S-M Catalog; also sample copy of The Radiobuilder. For enclosed in stamps, send me the following; . 50c Next 12 issues of The Radiobuilder . Si. 00 Next 25 issues of The Radiobuilder S-M DATA SHEETS as follows, at 2c each: .No. 1. 670B. 670ABC Reservoir Power Units .No. 2. 685 Public Address Unipac .No. 3. 730, 731, 732 " Round-theWorld" Short Wave Sets ..No. 4. 223, 225, 226, 256, 251 Audio Transformers . .No. 5. 720 Screen Grid Six Receiver . .No. 6. 740 " Coast-to-Coast" Screen Grid Four ..No. 7. 675ABC High-Voltage Power Supply and 676 Dynamic Speaker Amplifier . .No. 8. Sargent-Ray ment Seven . .No. 9. 678PD Phonograph Amplifier I Name 1 Address 1 Huge Amplifying Power — 250 type tubes, singly or in pushpull, with unbeatable S-M tone quality — built into an existing receiver, or separately for radio and phonograph amplification — at prices below all competition — this is the S-M power amplifier story! As a separate two-stage amplifier for homes and small theatres, working from radio or phonograph into a dynamic speaker, using one each '50, '26 and '81 tubes, the S-M 678PD far outclasses, in qualitv and price, any competitive amplifiers at prices up to double that of the 678PD: WIRED $73; KIT complete $65. For portable use, to cover 2,000-seat or larger auditoriums, oroutdoor crowds of up to 15,000, with optional voice, radio or record input — the S-M 685 three-stage Public-Address Amplifier is ideal. WIRED $160, KIT $125. Conversion of any existing receiver to use '10 or '50 type power tubes is accomplished with no change of wiring, by using S-M 675ABC power supply which supplies all ABC power for the power tube, and receiver B as well. WIRED, $58; KIT, $54. For large theatres, schools, hospitals, auditoriums or stadiums requiring the finest amplifying equipment, the S-M "PA" Rack-and-Panel Amplifiers, consisting of any required number of standard or special unit panels, will provide for any class of coverage. The system illustrated allows optional selection of one of two microphones, radio, or record input, with master gain control, visual volume level indicator, three-stage input amplifier, test meter panel, input amplifier power supply, and two socketpowered push-pull output panels of 15 watts undistorted power output each. With a voltage gain of over 5,000 times, a frequency characteristic flat to 2 T.U.'s from 30 to 4,000 cycles (with cut-off at 4,500 cycles) and with hysteretic distortion practically eliminated, the perform,' ance of S-M "PA" type amplifiers is unconditionally guaranteed equal or superior to any and all competitive American equipment. Full information on these new amplifiers, as well as on the 720 Screen Grid Six and other S-M sets and kits, is contained in the new December edition of the S-M 24-page general catalog. Ask for it, or send two cents for Data Sheet No. 9 covering the 678PD Amplifier. New Push-Pull Apparatus And now, S-M is glad to announce new super-quality push-pull audio transformers built on the Clough system, all offering curves flat from below 50 cycles to well above 5,000 cycles — transformers that give to "push-pull" a new and really startling significance. And their prices like their quality are unbeatable! The new 257 is a push-pull input type, to operate from one amplifier tube into two 171A, 210, or 250 tubes, and lists at the low price of only $7.00. Type 227 is a push-pull inter-stage transformer, to feed from two 112A, 226, or 227 tubes into two 112A, 226, 227 or 171 A, 210 or 250 tubes, and lists at $8.00. Type 258 tapped output impedance is intended to feed from two 171 A tubes into any standard speakers. Price $5.00. Type 248 Universal output choke is designed to feed out of two 210 or 250 tubes into one to six or more standard speakers, and is provided with several impedance-matching taps. It will handle over 20 watts without core saturation. Price, 248 open mounted $7.00; or 228 (in same case as 227) $8.00. Remember — S-M guarantees these push-pull transformers to have a finer frequency characteristic than any and all competitive types — bar none. SILVER-MARSHALL, Inc. 838 West Jackson Blvd., Chicago, U. S. A.