During December 2006 it became legal to use portable FM radio transmitters in the UK. You are most likely to have heard of this concept in the shape of the iTrip FM transmitter for Apple's iPod, but there are plenty of other options available, both for iPods and for other portable music players.

As long as your portable player has a 3.5mm headset jack and you have an FM radio, you can take advantage of Belkin's TuneCast II Mobile FM Transmitter. You could use it, for example, with a portable CD player if your vehicle does not have one of these built-in, or with an FM radio at home.

We used SanDisk's excellent Sansa e280 8GB portable music player with Belkin's TuneCast II Mobile FM Transmitter to test the concept in action in our car.

The Belkin transmitter is small - it tops out at about 75mm wide, 50mm tall and 25mm thick. It has rounded edges, rather like a small bar of soap. There is an LCD screen on its front which displays the frequency at which it is transmitting. It is powered by either two AAA cells or your vehicle power jack; a vehicle power cable and two batteries are provided.

Buttons to the left and right of the screen are used to control the transmitter, which switches itself off if no audio signal is detected for 60 seconds. A cable hard-wired to the transmitter connects to your music player's 3.5mm headset jack.

Tuning is a simple matter of finding an empty frequency on your radio, then setting the transmitter to that frequency using the two buttons which move up and down the device's range of 88.1MHz to 107.9MHz.

The transmitter can remember four broadcasting channels so that you can switch if you encounter interference from normal broadcast radio or other transmitters. The TuneCast II has a range of 30 feet, though for best reception it is suggested that you put the transmitter within 10 feet of the FM antenna.

We tested our review device over the Christmas break and it certainly did what it claims to, sending music from our music player to our car's radio. Setup was extremely easy and importantly the quality of delivery was fine. We did experience a couple of issues, though.

When using the windscreen wipers we got a bit of interference on the broadcast. The effect was no greater than you might normally encounter when listening to the radio while driving, and was not always noticeable.

Also, volume had to be set quite high on our car radio, though we had it at the top of the dial on the Sansa player. Ideally volume should be set lower than its maximum on the portable player to avoid any sound distortion.

You may find your preferred setting causes problems if you switch over to a standard radio broadcast without altering the volume, as it could come through louder than you'd prefer. We didn't find the difference eardrum-shattering, but it was noticeable.

Belkin's TuneCast II Mobile FM Transmitter certainly delivers what it claims to, opening up new opportunities for music fans, particularly when travelling by car.