FM transmitter (personal device)

This article is concerned with low powered transmitters used in some countries for interfacing personal audio devices. "FM transmitter" can also refer to high powered broadcast equipment used by pirate radio and licensed broadcast stations

An FM transmitter is a portable device that plugs into the headphone jack or proprietary output port of a portable audio or video device, such as a portable media player, CD player, or satellite radio system. The sound is then broadcast through the transmitter, and plays through an FM broadcast band frequency. Purposes for an FM transmitter include playing music from a device through a car stereo, or any radio.

The FM-transmitter plugs into the audio output of audio devices and converts the audio output into an FM radio signal, which can then be picked up by appliances such as car or portable radios. Most devices on the market typically have a short range of up to 30 feet (9 meters) with any average radio (up to about 75 feet (23 meters) with a very good radio under perfect conditions) and can broadcast on any FM frequency from 76.0 to 108.0 MHz (or 88.1 to 107.9 in the US). Some lower-cost transmitters are hard-wired to the 87.7–91.9 MHz band allocated to educational broadcasts in the United States, or a certain other smaller range of frequencies.

FM transmitters are usually battery driven, but some use the cigarette lighter socket in cars, or draw their power from the device itself. They are typically used with portable audio devices such as CD or MP3 players, but are also used to broadcast other outputs (such as that from a computer sound card) throughout a home or other building.