This article explains how to find the best FM frequencies for your car's transmitter. Instructions apply to all FM transmitters that are compatible with mobile devices.

FM transmitters are one of the easiest and most affordable ways to listen to music from your mobile device on your car stereo, but they have one major drawback: FM interference. In order to use them effectively, you need to find a frequency that is free of interference. This process is easy if you live in a rural area where there is not much competition for radio frequencies. However, if you live in a city, it will be more difficult to find a clear frequency.

FM transmitters work like tiny radios, broadcasting audio from your iPhone or mobile music player over a standard FM frequency that you tune into your car stereo. Set the transmitter to broadcast on 89.9 FM, tune your radio to that frequency, and you should hear your music.

The transmitters are weak and can only transmit a few feet. This is both good and bad. It is good because you don’t want a transmitter in the car next to you on the highway drowning out your signal. It is bad because weak signals are susceptible to interference. If there is a radio station broadcasting on the frequency you choose, it will likely prevent you from hearing your music. The interference can even occur on nearby frequencies. For example, a radio station on 89.9 can make 89.7 and 90.1 unusable for transmitter audio as well.