7_71_MHz_VFO

Published:2009/7/13 22:51:00 Author:May | From:SeekIC

JFET Q1 serves as oscillator, with frequency determined by C2, L2, CR2, and CR3; diodes operate in reverse-bias regions as voltage-variable capacitors. Amount of reverse bias applied by R2 determines capacitance and frequency. VFO operates on both transmit and receive; on transmit, no voltage is applied to VFO offset circuit R1-C1-CR1 so it has little effect on oscillator, 0n receive, +12 V applied to R1 makes CR1 conduct and places C1 across frequency-determining network to shift VFO about 100 kHz away from operating frequency so receiver will not be blocked. Q2 is buffer between oscillator and transmitter. VR1 provides regulated 9.1 V for oscillator and buffer. (Project was named after chopped beef can in which it was mounted.)-J. Rusgrove, The CB Slider, OST, March 1977, p 15-17.



Reprinted Url Of This Article:
http://www.seekic.com/circuit_diagram/Signal_Processing/Oscillator_Circuit/7_71_MHz_VFO.html

Print this Page | Comments | Reading(3)