Phase modulator. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Knots of amateur radio equipment. Modulators
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In amateur VHF transmitters, you can use a phase modulator, the circuit of which is shown in the figure. It consists of a microphone amplifier, a quartz master oscillator and a phase modulator.
(click to enlarge)
The signal from the microphone through the low-pass filter (R1C1C2) is fed to the amplifier (circuit A1). and then through another filter (L1C8C10C11) - to the base of the transistor V3, which acts as a phase modulator. The RF voltage from the master crystal oscillator on the transistor V2 is also supplied here. The phase-modulated signal is taken from the collector of transistor V3.
The inductor L1 is wound on a magnetic circuit from the output or matching transformer of the Selga radio receiver and contains 760 turns of wire PEV-1 0,1. In the master oscillator, you can use quartz resonators at a frequency of 6, 8. 9, 12 or 16 MHz. The mode of operation of the phase modulator is set by selecting the resistor R9. The required deviation is set with a trimming resistor R3.
Author: G. Rybakov; Publication: N. Bolshakov, rf.atnn.ru
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