This was our first experience of any FM transmitter. But, once testing got under way, we quickly realised that an FM transmitter was one in-car accessory we'd no longer want to live without. It really is a must-have for any driver wanting to make use of a portable music player.
First a couple of general observations. The performance of these products is highly dependant on how cluttered the FM band is in the area in which you're travelling.
Ideally, you'd try to use a frequency where there is just static and no interference from other radio stations.
But no matter how carefully you set things up, an unoccupied and interference-free frequency at the beginning of a journey is unlikely to stay that way if you move very far from your starting point.
Even on a drive of 40 or 50 miles you may have to retune the transmitter (and the radio) a couple times to maintain peak performance. And that's where transmitters with multiple channel presets make life a lot easier.
Presets allow you to store different broadcast frequency on the transmitter and switch from one to another - rather than having to manually retune and save each time reception starts to get iffy.
You can cut down a little on the retuning by switching to mono mode on the radio or the transmitter if they have that option. Makers of in-car audio kit call that DX mode - stereo is termed LX. Opting for mono sound produces a stronger and cleaner signal that is less prone to interference but you obviously lose stereo (LX) reproduction.
When these transmitters are performing at their best – and under during normal driving conditions – most people will find it hard to tell the iPod radio station from anything else on the FM band.
The five products reviewed all have backlit LCD screens, a radio bandwidth of 88.1 to 107.9MHz and switch off automatically about 60 seconds after the audio signal stops.
All have claimed frequency responses of 50Hz to 15000Hz except for the Kensington transmitter (100Hz to 15000Hz) and the icast (30Hz to 15000Hz).
So, let's get started, looking first at in-car-only FM transmitters...