My wife and I spent a lot of time in our vehicles this summer, traveling around PST and the broader USA. Our Creative Labs Zen Micro and iRiver H10 portable players, and the Yahoo Music Unlimited subscription service that powers them, therefore got quite a workout. Ordinarily I'd use a cassette adapter to pipe their audio output over the car's sound system (among other reasons, because a well-maintained cassette head has a wider frequency response than a broacast FM signal, although arguably an auto's high ambient noise makes any theoretical cassette adapter advantage moot....or is that mute?), but our '01 Volkswagen Eurovan Camper's Pioneer-branded radio integrates a CD player, not a tape deck. So I had the chance to try out several FM transmitters.

I'd used a Belkin TuneCast in the past, and it worked pretty well in the Eurovan. But it chewed up AAA batteries at a rapid clip. Belkin's followon TuneCast II had several advantages over its predecessor, at least on paper; it could alternatively be powered via a cigarette lighter socket, and it supported a greatly expanded range of broadcast frequencies. But its broadcast signal intensity seemed to be very weak, judging from the fact that even a far-away radio station on the same frequency would overwhelm it and, in the absence of any other comparable-frequency signal, its output was still 'hissy'. Plus its monochrome LCD display was hard to read and annoyingly flickered, especially after the unit was exposed to sunlight for a few minutes.

The iRiver AFT-100, on the other hand, is an outstanding FM transmitter. At the time I bought one for the Eurovan, it was $29.99 at Amazon.com (right now it's $36.39). It's got a very strong broadcast signal, with a wide range of user-selectable broadcast frequencies, and its blue-background illuminated LCD is easy on the eyes. It plugs directly into the cigarette lighter socket, minimizing the number of wires cluttering the car's interior. And it automatically turns on and off based on the presence or absence of a signal coming from whatever device is connected to the AFT-100's headphone plug.

I don't know why the TuneCast II is such a feeble performer. Maybe I have a bad unit, although other reviews I've read on it echo my observations. Similarly, I don't know why there's such a stark contrast between it and the AFT-100. Perhaps the iRiver unit's broadcasting beyond FCC-specified signal strength; some of Sirius and XM Radio's units recently got busted for such a transgression. Although given how long the AFT-100's been in the market, I doubt it's misbehaving.