Posted on Dec 5, 2012

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-!l potentiometer in the collector circuit can be adjusted to enable the desired frequency modulation level.

Click here to download the full size of the above Circuit.

The Hartley rfoscillator, 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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