Rca1948FrequencyModu.. - The New Jersey Antique Radio Club

FREQUENCY MODULATION GENERATOR 109quency multiplier stages driving a final amplifier delivering a carrieroutput of approximately two kilowatts.The crystal-controlled oscillator in the transmitter was used as theprimary source of stabilized r-f voltage, the amplifier chain in thetransmitter being broken between the buffer amplifier and the firstdoubler stages for insertion of the cathode ray phase modulator andassociated apparatus, as shown.To obtain the 90° phase relationship between the voltages on thetwo sets of deflecting plates of the cathode ray tube, a phase-splittingnetwork consisting of a capacitive reactance in series with a pureresistance was employed, one set of deflective plates being connectedacross the capacitive reactance and the other set across the resistance.Fig. 8—Spiral anode of five turns, similar to that shown in the tube inFigure 6. The spirals were formed by scribing through a platinum film on amica support, thus separating the surface into two insulated segments.In this set-up the internal capacity between one pair of the deflectingplates was utilized as the capacitive reactance. A parallel tuned circuitwas bridged across the other set of deflecting plates to permit tuningout the reactance of the variable resistor and also that due to thecapacity between these deflecting plates, thus obtaining a purelyresistive impedance. The variable resistor in this circuit was used toadjust the relative amplitudes of the voltages on the two sets of deflectingplates, and the amplitudes of the two deflecting voltages wereadjusted simultaneously by means of the variable resistor R tin serieswith the d-c plate supply to the modulated amplifier.The output circuit connected to the two halves of the target anodewas tuned to the fundamental crystal frequency and coupled inductively