How to Find the Best FM Frequencies For Your Car Transmitter

finding the best signal for your fm transmitter
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FM transmitters are one of the easiest and most affordable ways to listen to your iPhone's music on your car stereo, but they have one big drawback: FM interference. In order to use them well, you have to find a frequency free of interference.

Interference and How FM Tuners Work

These transmitters work like tiny radios, broadcasting audio from your iPhone or iPod over a standard FM frequency that you then tune in on your car stereo to hear.

Set the transmitter to broadcast on 89.9, tune your radio to that, and you should hear your music.

The transmitters are relatively weak, though, and can only broadcast a few feet (this is a good idea; otherwise, a transmitter in the car next to you on the highway could override your signal). Because they're weak, they're prone to interference. If there's a radio station broadcasting on the frequency you choose, it will likely prevent you from hearing your music. In fact, that interference can even happen on nearby frequencies (a radio station on 89.9 can make 89.7 and 90.1 unusable, too).

Finding interference-free frequencies isn't that hard if you're stationary, but in a moving car, the frequencies that work well with FM transmitters change constantly as you drive. Finding a reliable frequency can be a challenge. Unless you use these tools.

Tools To Find Open FM Frequencies

The three tools listed below help you find open frequencies to use with your FM transmitter wherever you are, based on your location and their databases of open channels.

Use them when traveling to find a frequency for your music.



This free app uses the GPS features built into your iPhone to determine your location and give you the best open frequencies in your current area. For iPhone users, the simplicity of one-touch searching and the performance of an app, combined with not needing to visit a website, make this an appealing option.


This website can help you find open signals by city, state, and zip code. If you visit it on your smartphone, it can also use your smartphone's GPS to determine your exact location and suggest stations based on where you are.

SiriusXM Channel Finder


SiriusXM satellite radio offers this tool for owners of their portable and otherwise not-in-dash radios. But you don't have to have a satellite radio to use it. Just enter your zip code and the site will offer 5 suggestions for clear stations near you.

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