A Complete Phone Transmitter

Author: J.B. Hoag

Fig. 31 H. The circuits of a complete transmitter. The r.f. units are at the top, a.f. in the middle and power supplies at the bottom. (Courtesy The " Radio " Handbook, Eighth Edition, Santa Barbara, Calif.)

Figure 31 H shows the wiring diagram of a 400-watt plate-modulated phone transmitter. The radio frequency units are across the top portion of the figure. The crystal-controlled oscillator in the upper left-hand corner is capacitively-coupled to the HK54 or 35T amplifier, which is link-coupled to the Class C modulated output amplifier stage containing the 100TH or HK254 tubes.

In the central portion of the figure, the output of a crystal microphone is amplified by the 6J7 and 6C5G tube circuits to operate a push-pull 2A3 circuit which drives the modulator (203Z tubes).

The various voltage supplies are shown in the bottom portion of the figure. Circuit constants and assembly details of this transmitter will be found on pages 369 to 374 of The Radio Handbook (eighth edition) .