Radio Broadcast (May 1928-Apr 1929)

RADIO BROADCAST ADVERTISER 81 e)Vew/ 5 -Prong S-M Plug -In Coils Economy — Efficiency and 1% of types Why plus les meter; For the popular "tube base" short wave receiver Silver-Marshall will have ready on June 1st, new types of moulded Bakelite coil forms and wound coils designed to fit any standard 5-prong tube socket, such as S-M 512. These forms have ample winding space for all short wave or broadcast band coils, and a tickler slot at the base. Their small size particularly adapts them to short wave sets to provide the smooth regeneration necessary to telephone or rebroadcast reception, and their cost is as low as their efficiency and flexibility is high. Type 13 0 blank forms can be had with smooth winding space IV2" in diameter ' long, with tickler slot and pins at .50 each, or with threaded winding space (98 threads) if preferred. A variety wound for different purposes can be had at $1.25 each list. Type 512 socket which fits these coils is priced at 75c pay $8.00 to $12.00 for a set of short wave coils when four 130 forms and a 512 socket costing $2.75 altogether, s than a pound of wire and an hour's fun will give you as pretty a little set of coils, tuning from 17 to over 200 as you'd ever want to see. The Famous S-M 240 Audio Transformer At $6.00 S-M 240 Audio transformers, containing more actual material than competitive $8.00 transformers, give such fine performance that they are being increasingly chosen in preference to other makes. The Peridyne used them, the LC 2 8 Unipac was built around them, the Universal Tuners rely on 2 40's for the fine tone that has made them so popular. Radio Broadcast Laboratory has reported most favorably on them. Small, compact, rugged and above all possessed of the qualities that have made S-M leader in the audio field in two short years, they are your guarantee of fine tone quality in any set you buy or build. Price, 240 audio, 3:1 ratio, $6.00; 241 output, $5.00. ABC and B Power Units to Fit in Your Set Cabinet The new S-M "670" Reservoir Power Units are but 13" long, 3%" wide and 6%" high over the 2 80 rectifier tube they use. Both are housed in attractive brown crystaline steel cases, and have the features that made the older 652 and 656 Reservoir B's the most popular kits of their type. The Clough selective flilter and a new voltage divider system provide unusually quietness and freedom from motorboating on any set of one to ten tubes. 670B supplies fixed voltages of 22V2, 90, 135 and 180 to 200 volts, with a variable tap giving from 22% to 90 volts. 6 70ABC supplies the same B power and A and C power to any AC tube set — 1.5 volts, 2.25 and 5.0 volts A for up to seven tubes, with the necessary C bias for the tubes used obtained by suitable resistors in the set. 670B is priced at $35.50 wired, ready to use, or $33.00 in kit form, with cabinet, ready to assemble. 670ABC is priced at $38.50 wired, or $35.00 for the complete kit with all instructions. New Unipacs for 250 Tubes Two Unipacs taking full advantage of the new 2 50 type tube are ready, one a single stage light socket power amplifier and B supply, and the second a two stage amplifier for radio or phonograph. Each uses one UX-250 amplifier tube to furnish 4650 milliwatts of undistorted power output, which means just about the sweetest, fullest tone you've ever heard — just a shade better than you can get with the next best. Both Unipacs are peers in their fields, operate from 105 to 120 volt 60 cycle alternating current, and deliver 450 volts B and 84 volts C to the self contained 250 tube which develops more undistorted power output than two 210's in push pull. 681-250 is the single stage model using one 250 tube, two 281 rectifiers and one 874 voltage regulator. Besides a stage of 250 amplification for any radio set. it also furnishes 45. 90 and 135 volts of B power Price wired $98.25, or in kit form ready to assemble. $83.25. 682-250 is the single stage model with a 22b first stage tube added. It supplies two stages of power A. F. amplification— enough for dance hall volume using the output of a record pick-up or radio set detector tube. It gives 45, 90 and 135 volts of B and 1.5 and 2.25 volts of A for receiver operation. Price wired. $107.75, or as a kit, ready to assemble $92.75. SILVER-MARSHALL, Inc. 838 West Jackson Blvd., Chicago, Illinois SILVER-MARSHALL. Inc., 838 West Jackson Blvd., Chicago, III. ....I enclose 10c for which please send me full information on the S-M audio transformers, power supply units, unipacs. and the S-M receivers. ....I enclose 2 5c for instructions for building the S-M unipacs. ....I enclose 25c for instructions and blueprints for building the Shielded Grid Sixes. ....I enclose 25c for instructions and blueprints for building the S-M wave tuners. Name Addrcs P.adio Broadcast. June. 192 Published monthly. Garden City, N. Vol. XIII. No. 2. Published at Garden City, N. Y. Subscription price $4 00 a year Y., as second class mail matter. Doubleday, Doran & Company. Inc., Garden City. N. Y. ' Entered at the post orrlc