FM Wireless Microphone Circuit Using Single Transistor

This FM Wireless Microphone circuit huses only a single transistor with few additional passive components and has range over 30-50m (under good conditions). This FM transmitter is very compact and need only a single cell 1.5Volt battery, even works on 1.2V rechargeable battery.

Simple FM Wireless Microphone Circuit

 The inductance L is the critical part and should be handmade. Use an AWG24 (0.5mm) enameled copper wire and make 2-4 loose turns with about 4-5mm diameter. Try to loosen or tighten the coil, or trim the variable capacitor, and try to receive the signal on around 90MHz. Don’t forget to tighten the coil using a glue to fix the coil, avoiding mechanical deformation that change its inductance value.