Ever since the FCC began a campaign to reign in too-powerful FM transmitters last year, and manufacturers quietly began to change their accessories to comply with the agency’s demands, we’ve been reluctant to make any definitive statements on these devices: as hard as it was last year to know for sure how well a given transmitter would work in a given car, new differences from unit to unit now increase that difficulty. But while the FCC has limited the power of these devices, it hasn’t stopped companies from improving on them in other ways, so today we’re looking at five different in-car iPod accessories with FM transmitters inside. Our standard disclaimers — that your car’s antenna location, the iPod and transmitter’s location, and local radio airwave congestion can radically affect your results — still apply.
The five accessories come from three companies and break down into two categories. Belkin’s TuneBase FM with ClearScan ($90) and Macally’s BTCup ($100)—a more expensive sequel to its earlier FMCup—both combine an FM transmitter with an iPod car mount and car charger, but vary considerably from there. Kensington’s Liquid FM ($80), Liquid FM Plus ($70), and Liquid FM Deluxe ($100) are cables that offer only the FM transmitter and car charger features, leaving you to mount the iPod on your own.
All five of these accessories have three things in common. They’re all made substantially from black plastics, although each has silver and/or gray accents. Their FM transmitter performance was universally good in our testing, with only small variations from unit to unit.
And they are all a little more restricted in frequency tuning than the best pre-2007 devices we tested: all tune from 88.1FM to 107.9FM, rather than up to 87.7 or 87.9FM. This is an issue only in that the latter station has consistently been better than any other in our prior testing—it’s almost always empty in the United States because major broadcasters aren’t allowed to use it.
Belkin and Kensington both have solutions to this problem. Two of Kensington’s transmitters—LiquidFM Plus and Liquid FM Deluxe—as well as the new Belkin TuneBase FM include a feature we first tested last year, which Kensington calls QuickSeek and Belkin calls ClearScan. Most other FM transmitters, including the standard Liquid FM and BTCup, require you to find an unused FM radio station on your own, then tune the transmitter to match that station. QuickSeek and ClearScan simplify that process. With one button press on each device, the screen begins to sweep back and forth as the transmitter searches for a relatively empty FM radio station, displaying its result so that you can tune the radio to it. In our testing, this feature always worked well enough on both the Belkin and Kensington transmitters to produce relatively clear, low-static sound on the chosen stations, though the transmitters didn’t always choose the same stations, and quality typically varied a small bit from pick to pick.
Overall, we think the ClearScan and QuickSeek technology is useful, but we’re not sure that it’s worth paying a huge premium for. Kensington’s assessment of QuickSeek’s value is $20; street prices peg it at $12 and up.
Belkin apparently thinks it’s worth about $10. TuneBase FM with ClearScan is the sequel to the 2006 TuneBase FM, which carried an MSRP of $80 without ClearScan, versus $90 for the new model. Though the new version of TuneBase FM retains its predecessor’s overly modest 4-inch-long gooseneck, it’s otherwise better-looking, easier to use, and more iPod-compatible than before—thanks to its built-in LCD screen, it works with all of the current iPod models, which due to Apple firmware changes, the past version of TuneBase FM doesn’t.

For $10 less than the Liquid FM Deluxe MSRP—and street prices of $57 and up—TuneBase FM does everything that Liquid FM Deluxe does, adding the aforementioned mount and using an even more readable LCD screen. You give up only one feature—Belkin includes two memory presets instead of three—and gain two features, a “Pro” button that cycles through three audio settings to improve the connected iPod’s audio levels relative to your radio, and a line output so that you can pull the iPod’s highest-quality audio signal from its bottom and directly connect to a car stereo with a line-level input. The latter feature was included in an iPod mini version of TuneBase FM years ago, but absent from the prior full-sized iPod version in 2006; its reappearance here is welcome.