I know what you're thinking, because I'm thinking it too. "It's 2013 -- are FM transmitters even still relevant?"
Well, yes...kind of. Cars have a much longer shelf life than your average consumer electronic product, so there are still thousands of cars on the road that lack the 3.5mm analog auxiliary input or Bluetooth wireless connection that we here at Car Tech have come to know as ubiquitous. For drivers of these cars, the only way to get their increasingly digital music library on the road is to either replace their car stereo or pick up an inexpensive FM transmitter like the Gogroove Smartmini BT.
In design, the Smartmini is similar to the Gogroove FlexSmart X2 that we've reviewed previously. It uses a similar control scheme consisting of a control knob that can be twisted and pressed like a button. Around this controller are buttons for Play/Pause, Skip Forward, and Skip Backward. To the right of the knob is a simple red LED display for readouts, on either side of which you'll find a phone button, one red, one blue, which we'll address in a bit.
You mount a Smartmini in your car by plugging its arm directly into a 12-volt power point. You can orient the device different ways by twisting this connection 360 degrees within the circular power point, and it has a few degrees of tilt adjustment via a hinge where the arm, which is short, connects to the body of the device.
Many ways to connect (inputs)
Along one edge of the device, you'll find a pair of 3.5mm analog auxiliary audio connections, one for input and another for output. Along the other edge, you'll find a powered USB port with labeled output of 5 volts and 1A. That's enough current to charge most smartphones on the market, but likely not enough power to charge most tablets that I've encountered. So, those looking to use an iPad's large screen to navigate with the Smartmini will be disappointed.
The remaining connections are of the invisible sort: FM radio and Bluetooth.
The Gogroove Smartmini can make a wireless, one-way audio connection by broadcasting to an empty frequency on the FM radio spectrum, which you can then listen to by tuning a nearby radio (preferably the one in your car's dashboard) to the same frequency.
The device also features a Bluetooth 2.1 connection that enables it to receive hands-free calls and A2DP stereo audio streaming. Pairing is simple and didn't even require a PIN for my Samsung Galaxy Nexus running Android 4.2.x.
The Smartmini's primary function is to act as a bridge between your high-tech mobile device and a low-tech car stereo radio. It can do this in a number of ways. Bluetooth-to-FM transmission is the primary advertised mode, but there's also Bluetooth-to-auxiliary input for cars with a 3.5mm connection, and headphone-jack-output-to-FM transmission for devices without Bluetooth. You could probably even go from headphone jack to audio input to audio output to auxiliary input if you were feeling needlessly complex, but I don't advise it.
Automatic FM tuning
Because the broadcasting strength is limited by the FCC, the effectiveness of any FM tuner is mostly dependent on your ability to find a clear frequency that is not otherwise occupied by a local radio station. In some areas, this is relatively easy to do. In other areas, like the San Francisco Bay Area, it's nearly impossible.
You can manually select a blank FM station by twisting the control knob on the Smartmini's face until your chosen frequency is displayed, but the easiest way to get a clear signal is to let the device do it for you. Press and hold the control knob like a button for 2 to 3 seconds, and it will automatically seek the nearest empty channel. Then it's just up to you to tune your car's radio to match.
Interestingly, the Gogroove is able to tune even as well as odd decimal frequencies (88.4, 88.5, 88.6), whereas most American car stereos that I've encountered can only tune to odd increments (88.5, 88.7, 88.9). This means that occasionally the Smartmini will return a frequency like 104.4FM that your car won't be able to match. Sometimes twisting the knob to jump up or down one decimal place will help. Other times, I just had to try autotuning again.