Tuesday, January 19, 2010

FM Transmitter with one transistor

This is clearly shown in the diagram. For best performance the circuit should be built on a PC board with all components fitted close to each other. The photo below shows the circuit using a coil etched on the board. This type of coil is totally unsuitable. It does not have a high "Q" and the range is very poor. The board cannot be touched as the capacitance of your body causes the circuit to drift. A wound coil will improve the stability considerably. See photos below for the details of a wound coil.

A one transistor circuit

Do not use an etched coil
Here is the 1-transistor circuit produced by GuEsTyE.net on a home-made PC board and heat-shrunk so the air-trimmer is adjustable via a small hole.
The PC board drilled ready for fitting the components
The 10 components (plus heatshrink, battery and wire)

The components mounted on the board
The board ready for fitting into heatshrink

The finished bug with "studs" for the battery
and a cut-out for the air trimmer
At On Air

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