1.5 Volt Tracking FM Transmitter

Operates from 87-109MHz. The current draw for this tracker is 3.7mA, so the 1.5V button cell will last a while. My experimental version was tuned to 87.6MHz and worked as expected on only 1.5 volts.

When your circuit is working you should see the LED flash quite fast. Take your FM radio and search for the low-beat ‘thumpe-thumpe-thumpe-etc’ equal to the flash of the LED (probably around the 100Mhz). Found it? If that position is interfering with a radio station you can fine-tune it with the variable capacitor. If you like to have the tracker around the 88Mhz (or lower) you can do that by keeping the windings from the home-made coil close together. Anyways, play with it and learn. It may take alot of patience to find the signal but once you know where it is it becomes simple. It is a nice learning project.

Read More Source:
http://www.uoguelph.ca/~antoon/circ/tx15trak.htm

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