Radio broadcast .. (1922-30)

RADIO BROADCAST ADVERTISER 247 UNI PA C for Power The Silver-Marshall laborat- ories now offer a series of power packs absolutely without com- parison. Type 660-210 Unipac, a push-pull amplifier using two UX-210 tubes, will deliver from 100 to 300 times more power than a 201-A tube, or from 4 to 17 times more power than aver- age 210 power packs. Type 660- 171 Unipac, with two 171 tubes will deliver equal or greater power than average 210 packs at far lower cost! There is a Unipac for every need, from the most powerful receiving am- plifier ever developed down to a low power 171 power pack. There are models for phonograph amplification, turning any old phonograph into a new electric type actually superior to com- mercial models costing from five hun- dred to several thousand dollars. And every Unipac, operating entirely from the light socket, supplies receiver "B" voltage as well. 112 K. C. Long Wave Time Amplifier Type 440 Jewelers Time Amplifier, accurately tuned and measured to ex- actly 112 K. C., 2677 meters (NAA's exact time signal wave) makes avail- able a three-stage R. F. amplifier and detector that is a laboratory product. It simplifies receiver construction, and eliminates all guess work in transformer matching. Price, completely shielded, $35.00. Silver-Marshall, Inc. 838 West Jackson Blvd. Chicago, 111. Complete A. C. Operation A Practical Reality For the past several seasons the trend has been toward complete battery elimination. Many satisfactory plate supply units oper- ating from A. C. have been developed but filament operation from an A. C. source has presented more of a problem due to the larger currents required and increased expense in the rectifier and filter circuits. The newly announced A. C. tubes offer an excellent solution to this problem. The above diagram shows how to adapt the filament wiring of the popular type of receiver to A. C. op- eration by use of General Radio parts especially designed for this purpose. Type 410 Rheostats The new A. C. tubes require low resistance rheostats capable of car- rying appreciably more current than those used with D. C. tubes. Current price 3.5 amp. J1.25 2.0 amp. 1.25 Type 438 Socket The new type UY-227 or CX-3 2 7 detector tube has a separate heating ele- ment and requires a socket designed to take the new five prong base. Type 438 socket . . $.50 The various types of A. C amplifier tubes are designed with standard UX or CX base having four prongs. Type 349 Socket ' J.50 Type 440-A Low Voltage Transformer The alternating current tubes require a source of low voltage capable of delivering large cur- rent. The various types of tubes require several different voltaRes. The Type 440-A Transformer supplies voltages for all popular tubes and sufficient current for all ordinary receiver re- quirements. Filament supply is provided for fila- ment, separate heater, power amplifier and recti- fier tubes. The following voltages and currents are available. Pri. 115 V (for lines 105-125 volts) 60 cycles. Sec. I volts 8 amperes 3.5 volts 2 amperes 5 volts 2.5 amperes 7.5 volts 2 amperes Prfnr J10.00 Type 439 Center Tap Resistance HH HL All the new A. C. / ^^ tubes require a resistance f : with center tap across the filament as shown in the • • diagram. The Type 439 Resistance is adaptable to any socket in which the new A. C. tubes may be used. Type 439 Center Tap Resistance Price $.60 Your local <1>al>r .tlioiilii hav th- nrcmsory parts in stock. If Tic JH utitihli- t" supply tfou with all the ittms required, we shall fie glad to send them to you prepaid pon nciiitt of list i-rii-i. GENERAL RADIO CO. Cambridge, Mass. GENERAL itaDio PARTS and ACCESSORIES