In Amateur УSW transmitters can use a phase modulator, whose scheme is shown in the figure. It consists of a microphone amplifier, a quartz oscillator and phase modulator.
The microphone signal through a low pass filter (R1C1C2) is supplied to the amplifier (A1 chip). and then another one filter (L1C8C10C11) - to the base of transistor V3, which performs the function of the phase modulator Here moves and RF voltage to the master oscillator transistor V2. A phase modulated signal is taken from the collector of transistor V3.
The inductor L1 is wound on the yoke from the output or matching transformer radio "Selga" and contains 760 turns of PEV-1 to 0.1. In the master oscillator, you can use quartz resonators at frequency 6, 8. 9, 12 or 16 MHz. The mode of operation of the phase modulator set selection resistor R9. The necessary deviation set trimming resistor R3.
Author: G. Fishermen; Publication: N. Bolshakov, rf.atnn.ru