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Simple FM Transmitter Projects

Mention FM to most people and there first thought is about radio stations or radio receivers. However, FM transmitters are more common in our modern lives than you might think. And because FM transmitters are relatively simple and inexpensive to build, they make great projects for learning basic electronics. Projects like these can be addictive, so do not be surprised if they become a new hobby for you.

Wireless Microphones
- From simple home karaoke mics to more elaborate devices used in churches and auditoriums, wireless microphones may be the most common FM transmitter projects. The low power requirements of a small FM transmitter mean the device will be light. A few resistors and capacitors, a microphone element, a couple of op-amps or transistors, a battery and a small antenna are all most projects require.
Wireless Audio Links
- If you have ever bought a device that lets your phone or MP3 player be heard over your car radio without a physical attachment, then you are familiar with wireless audio links. Audio links are similar to wireless microphones except the mic element is replaced by the MP3 player or other audio device, usually by means of an audio plug and jack. A very small unit might only transmit a few inches to the car's FM radio or it might broadcast to all the radios in your house with a very small bump in the power level.
Small Scale Radio Stations
- It is only a step up from a home audio broadcast system to a small radio station. It's possible to build your own full-fledged FM broadcast station. Think of "pirate radio stations" and college radio stations that may cover a college campus and no further. These uses are sometimes referred to as "microbroadcasting." Similar broadcast "stations" can be used for other purposes such as broadcasting movie audio at a drive-in theater or as a wireless announcement system for a car lot or local carnival. Or think small---as in surveillance devices like "bugs" or as a one-way monitoring system in a child's bedroom.
FCC Regulations
- The Federal Communications Commission regulates the range of various small FM transmitter types to prevent interference between licensed and unlicensed transmitters. If your project plans do not mention whether they are legal, you may want to check the FCC Rules, Part 15 to make sure. There are websites that provide a basic overview of these rules so you can make a determination before you start. However, if you broadcast on an unused part of the FM band in your area, you will rarely run into problems in the United States.

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