In a move similar to what it’s done with its
remote control, Griffin Technology has taken technology originally designed with the iPod in mind and transferred it to a USB device intended for use with a Mac or PC. Specifically, its $40 RocketFM appears to be the first-cousin of the company’s fabled iTrip FM transmitter for iPod. The difference here is that the RocketFM is designed to transmit audio from a computer to a nearby FM receiver.
This isn’t the first time we’ve seen such a device. Last month we looked at a similar product—
Engineered Audio’s $40 Aurius. Like the Aurius, the RocketFM connects to a Mac or PC via the computer’s USB port. And just as similarly, you change the channel the device transmits on via a software utility. And, like the Aurius, the RocketFM offers the same benefits
disadvantages of any FM broadcaster.
Those benefits include inexpensively broadcasting audio to speakers better than what’s attached to your computer and doing so without the lag inherent in Apple’s AirPort Express. Among the disadvantages of these devices is that it’s sometimes difficult to get a clear signal when the FM band is crowded with stations and the quality of the audio broadcast is not nearly as good as you’d get from a direct connection or via an AirPort Express.
Setup and Software
The RocketFM is a little over four inches long and slightly resembles a squat, digital thermometer. Inside it bears one of Griffin’s trademark blue LEDs that lights up when the device is plugged into a powered USB port. Permanently attached to the bottom is a three foot USB cable. Included with the device is a clear plexiglas base that, yes, makes it look just like a 1950s notion of a rocket ship. In short, it’s another attractive piece of gear from Griffin.
Setting up the device is as simple as selecting the RocketFM in the Output tab of OS X’s Sound system preference or the Audio tab of Windows’ Sounds and Audio Devices control panel. Within each of these areas you can adjust the output gain of the RocketFM—something you’ll likely wish to do as running the device at full gain can cause distortion. Thankfully, backing off on the computer’s overall volume or the volume of the currently playing application (iTunes, for example) gets rid of the distortion. Just like with the Aurius, the RocketFM broadcasts any sound that would normally play through your computer’s speakers—sound from an application such as iTunes as well as any system alert sounds.
I mentioned that you change the RocketFM’s station through software. This software isn’t strictly necessary, however. The device is pre-configured to broadcast at 88.1kHz. Should you wish to change its frequency you’ll discover that, unlike with the Aurius, the RocketFM allows you to tune in all available FM frequencies—88.1, 88.2, and 88.3, for example, rather than just the odd point-frequencies (88.1, 88.3, and 88.5, etc.) that the Aurius allows.
The RocketFM software offers a virtual scroll-wheel interface for tuning—helpful for making big jumps across frequencies. You can also use the computer keyboard’s arrow keys to increment from one point-setting to another. I’d like to see the scroll wheel go all the way around—begin anew at 88.1 after you’ve scrolled past 107.9—and the interface allow me to type in the frequency I’d like, but using the controls as they’re currently designed is hardly a chore.
Ups and Downs
The obvious benefits to using an FM transmitter are flexibility and economy—particularly in comparison to Apple’s AirPort Express. While the AirPort Express offers greater range and better fidelity, by default you’re limited to broadcasting only your iTunes library to it (though Rogue Amoeba’s $25
lets you channel any audio you like to the AirPort Express). Also, you can broadcast to only a single AirPort Express at a time. With an FM transmitter, you can broadcast to any FM radio within range for a cost of $40 versus the AirPort Express’ $129 (plus the cost of your computer’s wireless card). Unlike with an AirPort Express that requires the receiving device have a stereo input, you can broadcast a device like the RocketFM to any radio—a boombox, your car’s stereo, and FM headphones.
Additionally, there’s no audio lag when you use an FM transmitter such as the RocketFM—the AirPort Express introduces a slight delay when it encodes and decodes its transmissions, thus throwing a transmitted video’s audio and video tracks out of sync. Without this delay you can watch a movie on your laptop and, though the transmitter, listen to the movie’s audio on a nearby stereo.
As I mentioned earlier, an FM transmitter is only as good as the signal your stereo is capable of receiving. If the FM band is choked with stations, you can have a difficult time getting a clear transmission. Likewise, if that stereo’s antenna isn’t very good, the quality of sound will suffer as well.
To test the RocketFM—and compare it to the like-priced Aurius—I attached each device to an Apple PowerBook and then a Power Mac G5 and broadcast each to a boombox. I tested both inside an office crowded with audio and computer gear. I also tested each transmitter with the PowerBook and the boombox outdoors. I dialed each device and the bookbox into uncluttered FM stations.
Overall, placement was more of an issue with the RocketFM than it was with the Aurius. The Aurius was fairly forgiving about where I placed it, while the signal from the RocketFM exhibited some static unless it was placed in exactly the right spot.
When connected to the PowerBook in the office, the RocketFM occasionally stuttered at a distance of about 15 feet from the boombox whereas the Aurius played cleanly. When I plugged each into a Power Mac G5, both played cleanly. Each of the devices offered better range outside but the RocketFM gave out earlier than the Aurius. Specifically, I was able to walk 25 feet away from the boombox and around the corner of my house and the Aurius maintained a clear signal. The RocketFM’s signal pooped out a couple of feet earlier than the Aurius.
As I mentioned earlier, your mileage will vary depending on the degree to which your FM band is filled with stations and the power of your FM antenna. You could easily get greater or less range from either device depending on conditions. But these test do indicate that when it comes to extreme range, the Aurius offers a little something extra.
The RocketFM offers a way to broadcast your computer’s audio less expensively and more flexibly than an AirPort Express. The tradeoff is that the quality of the resulting sound is not nearly as clean as that from an AirPort Express and the device is susceptible to interference.
While I prefer the look of the RocketFM and Griffin’s software over what’s offered by the Aurius, in my tests the Aurius provided a more consistent signal under varying conditions, which, ultimately, is what you want from this kind of device. If you require an FM transmitter for your computer and your FM radio is within 20 feet or so, either the RocketFM or Aurius will get the job done. If, however, you’re in a trickier environment—one with a lot of interference or with an FM receiver at the extreme ends of these devices’ range—you’re better off with the Aurius.