A_ONE_TRANSISTOR_FM_TRANSMITTER

Published:2009/7/8 22:40:00 Author:May | From:SeekIC

The 2N2222 circuitry is a three-element, phase-shift oscillator circuit, designed to yield a 1,000-Hz sine wave. The 1,000-Hz sine wave is then applied to the TCG-610 varactor diode, 6 pF at 4 V, which changes the tank capacitance, thus varying the rf oscillator frequency at a 1,000-Hz rate. The 1,000-Ω potentiometer in the collector circuit can be adjusted to enable the desired frequency modulation level.The Hartley rf oscillator, designed around a readily available MPF-102 JFET, has an output that should be relatively stable if it is enclosed in a metal box, thus minimizing changes in tank capacitance. The completed transmitter has a range of 30 feet when not enclosed-without an antenna.



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