An FM transmitter allows you to stream audio from your phone through your car speakers using Bluetooth.
It effectively turns your phone or other portable device into a mini radio station that only broadcasts a few metres.
To work, the FM transmitter needs to be tuned to a free FM frequency on your car radio that doesn’t have a radio station broadcasting on it.
Some FM transmitters, such as the Belkin TuneCast will automatically select the clearest FM frequency for you.
However, with others you will need to set the frequency yourself. This can be difficult if you live in a city, as most of the frequencies will have been used up.
Best FM Transmitter Frequency in the UK
The best frequency for an FM transmitter in the UK is usually 87.5. This is because frequencies from 87.5-88 are reserved for short-term services using a Restricted Service Licence, so regular stations don’t use them.
In London, however, this frequency is often used by pirate radio stations and it might be harder to find a free frequency.
Another good frequency to try is 108, but again this might be used up in London.
If you have any suggestions for free frequencies in your area, please leave a comment below.
How FM transmitters work
Most FM transmitters on the market at the moment work using Bluetooth. Using a Bluetooth FM transmitter typically involves four steps:
- Plug the transmitter into a power source (usually the cigarette lighter socket)
- Tune your car radio to an unused frequency
- Tune the FM transmitter to the same frequency
- Pair your phone or other device with the FM transmitter using Bluetooth
Some older FM transmitters don’t use Bluetooth, and instead plug into your phone or iPod’s headphone socket.
For some recommended FM transmitters, see our roundup of the best Bluetooth FM transmitters.