Rca1948FrequencyModu.. - The New Jersey Antique Radio Club

154 FREQUENCY MODULATION, Volume Icircuit operated at 1/V2 times its resonant frequency. An investigationof the operation of this circuit together with following frequencymultipliers was made with the aid of the afore-described frequencymodulationmonitor. The basic principle of operation of the circuitis as follows : A parallel resonant circuit, tuned to V2 times the frequencyof an unmodulated low-frequency carrier (generally about 100kc) is used as the plate load in a pentode whose grid is fed with voltageat the source frequency (100 kc). See Figure 5. The phase of theplate voltage of the pentode is then varied by changes in the seriesresistance of the resonant circuit. Figure 6 shows the manner ofvariation of