FM Transmitter with 2 Transistors


Here the simple and cheap FM transmitter which powered using two transistors. This circuit may be tuned to operate over the range 87-108MHz with a range of 20 or 30 metres.

Electronic circuit

The coil L1 was consist of 7 turns on a quarter inch plastic former with a tuning slug. The tuning slug is adjusted to tune the transmitter. Actual range on this prototype tuned from 70MHz to around 120MHz. The aerial is a few inches of wire. Lengths of wire greater than 2 feet may damp oscillations and not allow the circuit to work.
Although RF circuits are best constructed on a PCB, you can get away with veroboard, keep all leads short, and break tracks at appropriate points.

One final point, don’t hold the circuit in your hand and try to speak. Body capacitance is equivalent to a 200pF capacitor shunted to earth, damping all oscillations.


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