Simple FM Transmitter Circuit With Mic

If you are interested in learning basic RF electronics, this simple FM transmitter circuit is a fun small project to build at home. The circuit uses a single transistor and a few common electronic components to transmit audio signals over the FM band. You can receive the signal using a normal FM radio nearby.

The design is very simple and works well for beginners who want to experiment with wireless audio transmission. A small microphone captures sound and the transistor amplifies and modulates the signal. The tuned LC circuit helps generate the FM frequency, while the antenna sends the signal through the air.

The transmitter operates roughly between 88MHz and 108MHz depending on the tuning capacitor adjustment. You can slowly tune the variable capacitor until you find the signal on an FM radio.

Main components used in this project:

• 2N3904 transistor
• Electret microphone
• 47k resistor
• 10k resistor
• 1k resistor
• 10nF capacitor
• 10uF capacitor
• 4.7pF capacitor
• 5-30pF variable capacitor
• Coil/inductor
• 9V battery

The coil is one of the important parts of the circuit. You can make it by winding a few turns of copper wire around a small object like a pen refill or screwdriver shaft. Small adjustments in the coil spacing can slightly change the transmission frequency.

This project is mainly for educational and experimental purposes. The transmission range depends on antenna length, coil quality, power supply, and component placement. Keeping the circuit compact usually gives better stability.