Smaller FM transmitters can sound good for playing music in the car; the iPod dock is a built-in advantage.
Satellite radio is great when traveling, but it cuts out if you're driving in the mountains - or in a tunnel, for that matter - and of course, FM radio can be crackly or downright irritating, depending on the DJ. Instead of fiddling around with burning CDs, bring the device that already has your music on it: these FM transmitters let you listen to an iPod on your car radio. There's no expensive installation, either; you just plug in, tune to an empty frequency and play. Just remember not to start skipping tracks or changing playlists while you're driving...
We looked at a selection of FM transmitters, some of which only work with iPods, while others transmit from any MP3 player. Some only work in the car, but others you can use with your home stereo as well.
Be sure to check how the transmitter connects. Some plug into an iPod dock, which gives you a line out signal for better sound quality than you get from the headphone socket. It also means that you can turn the volume right down and save on iPod power, because you control the volume you hear through the radio. You don't get those advantages if a transmitter plugs into the headphone socket, but this does mean that you can transmit music from more than just an iPod.
The radio and speakers in your car will also have a big impact on the sound quality you hear, as will the number of strong radio signals already being broadcast. Also, bear in mind that while the enclosed space in a car is a reasonable audio environment, road noise will diminish the listening experience to some extent.
All of the transmitters we're looking at work in both the UK and the US, as well as other locations. However, just because FM transmitters are now legal to use in the UK - previously, they were only legal to buy - that doesn't mean you can just order any transmitter. Legally, devices to be used in the UK need CE certification. Practically, different countries tend to use slightly different ranges of FM frequencies, so a transmitter set for one region may broadcast on too few or too many frequencies for a car radio from another region. The option to switch from US to international frequencies means that you can take your transmitter with you when you travel, and have the best chance of finding an unused frequency.
Memory settings for frequencies mean that you can quickly switch to a frequency you think will be free if you travel to an area where the current frequency is in use; this is most helpful if you have regular routes and take the time to pick the most useful frequencies yourself. If the transmitter doesn't remember the last frequency you tuned it to after it's been unplugged, you'll need at least one memory location to stop you from having to tune to it every time you drive.