2 transistor fm voice transmitter

Posted on Feb 6, 2014

This is a circuit for voice transmitter using a pair of BC548 transistors in this circuit. Although not strictly RF transistors, they still give good results. I have used an ECM Mic insert from Maplin Electronics, order code FS43W. It is a two terminal ECM, but ordinary dynamic mic inserts can also be used, simply omit the front 10k resistor. This

2 transistor fm voice transmitter
Click here to download the full size of the above Circuit.

is the figure of the circuit; The coil L1 was again from Maplin, part no. UF68Y and consists 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 my 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.

Leave Comment

characters left:

New Circuits



Popular Circuits

Logic level relay controller
Voltage-Tuned Vhf Oscillator
Protected Intrinsically Safe Op Amp Circuit
Telephone Call Recorder
transistors Mystery circuit: latching relay control with transitor / capacitor why doesnt it work
hv neon lamp multivibrator
versatile micropower battery protector
AM-fidelity wireless microphone circuit