Qz currently supports the following tuner devices:
|ADS||Instant Music FM||USB OTG||Based on the Si4701, see there|
|GNS||9830 and related||Bluetooth||Untested|
|GNS||FM9BT||Bluetooth||Supported, see notes|
|GNS||FM9||UART/Bluetooth||Supported with homebrew Bluetooth header|
|Silicon Labs||Si4701/Si4703||USB OTG||Supported, see also #4|
Some Android devices come with built-in FM radios. These are currently not supported. If you have such a device and are willing to help out, patches are welcome! Some older Samsung devices use the Si4709 tuner, which is related to the Si4701/Si4703, possibly allowing you to build upon work already done.
Do not expect too much of reception, though: most of these devices use the headphone cable as a pigtail antenna, thus signal strength and quality might not be sufficient to reliably pick up TMC information. See information on the other devices.
These are combined GPS/Bluetooth devices. Since their command set is slightly different from the FM9 series, they might work but have never been tested—if you have one and are willing to help out, you are more than welcome to! Most of the command set is implemented, except for querying signal strength.
These devices are/were frequently bundled with sat-nav devices. They come in a bunch of flavors, with a bunch of interfaces:
Some have genuine USB interfaces, which (presumably) emulate a serial port. These are currently not supported by Qz.
Some have USB connectors on both ends (and are inserted between a sat-nav and its USB charger) but the interface is actually UART and just happens to (ab)use a USB connector. The device they came with knows how to “talk” to them, but they will not work on an ordinary USB port. See below.
Some have UART interfaces with a variety of connectors. The primary differences are the connectors used (some use USB, others have a proprietary connector for the device they came with) and the signal level, which can be either 3.3V or 5V. The 3.3V type usually gets 5V through the USB connector but will also work on a 3.3V power supply.
These devices can easily be hooked up to a UART-Bluetooth device (such as the HC-05, which can be picked up for a few bucks on ebay). This setup is essentially equivalent to what GNS markets as the FM9BT (see below) and is supported by Qz in the same way.
One major drawback of these devices is the pigtail antenna they come with. Reception is really poor with these, especially in a car, which is full of electronics which may interfere with radio reception. You might be able to get a Y adapter for your car antenna for those (allowing you to splice into the antenna of your car), which might give you better reception.
If you’re into soldering: the devices use a 2.5 mm headphone jack as their antenna input. The tip contact is the antenna connection; ring and sleeve are not connected on the stock pigtail antenna. Anecdotal evidence suggests that using a mono jack, or connecting the sleeve to ground, may cause a short somewhere and prevent the device from picking up anything. If anyone could shed some more light on that, it would be appreciated.
Altogether, given the somewhat dubious antenna setup, reception with these devices is disappointing, especially when you’ve seen one of the Silicon Labs devices in action before.
These devices feature a Bluetooth interface and are fully supported by Qz. They come in two main flavors.
One variant plugs into the 12V outlet in your vehicle, which is convenient if you change vehicles frequently or don’t feel comfortable tinkering with the wiring harnesses behind your dash. They feature a convenient USB outlet to power your phone or sat-nav. However, they come with a tiny stub antenna, with the same headphone jack connector as the devices above and likely the same poor performance.
The other variant is inserted between the car radio and its antenna. It is available with two types of plugs, ISO or Fakra. Check which connector type your car uses before you buy.
Power is supplied through an extra cable. A clamp is provided to splice into the wiring harness of your radio.
Pay attention if your car uses phantom power for the antenna amplifier (Audi/VW and some other brands do): Car antennas typically have an amplifier, which needs a 12V power supply. With phantom power, this power is supplied through the antenna cable (+12V on the core, ground on the shielding).
The FM9 claims to work with such setups, drawing its power from the antenna cable (eliminating the need to connect the power wire) and supplying power to the antenna. In practice, however, this did not work for me: The FM9 apparently did not get powered (Bluetooth discovery did not find it) and there was no power to the antenna, thus radio reception was seriously degraded.
If you experience these symptoms (degraded radio reception, FM9 is not discovered via Bluetooth), lack of phantom power might be the issue. Check with a multimeter if you have 12V between the core and shielding of the antenna cable on the antenna side of the FM9-BT. If not, insert a phantom power adapter between the FM9BT and the antenna.
You can get a phantom power adapter from most car hifi stores, prices should be in the €10–20 range. Models with ISO connectors seem to be more common than Fakra ones—there are also adapters with an ISO plug on the radio side and a Fakra plug on the antenna side. If you’re getting the phantom power adapter with the FM9BT, consider going for the ISO FM9 (which is slightly cheaper), an ISO/Fakra phantom power adapter and a Fakra to ISO adapter.
Splice into the wiring harness: Your radio might supply +12V on one of its pins when ignition or radio is on; check with a multimeter. (This pin might still supply +12V for some time after you pull the key; unplug the connector before you measure.) If not, try splicing into a power source coupled with the ignition of your car. You’ll need to connect both the FM9BT and the phantom power adapter to that power source.
Results were very encouraging: with the phantom power adapter, radio reception is similar to before, and the FM9BT picks up way more than its siblings with a pigtail antenna.
The Si4701 is the core of a couple of FM tuner USB sticks, whereas the Si4703 is common in the single-board computer community. Both share the same command set. They are the de-facto standard FM tuners in the Linux/single-board community, due to their fairly good documentation and availability of open-source drivers.
Qz supports the FM tuner sticks, which are sold under various names. A prerequisite is that your Android device supports USB OTG. There are occasionally issues with the devices not being recognized properly upon being plugged in, which is still being investigated (#4). When that happens, unplug the device, wait a bit and plug it back in.
Some sticks, such as the ADS Instant FM Music, come with a pigtail antenna, which is in fact a poor excuse for an antenna, with disappointing performance. You can significantly improve reception by getting a MCX-to-Belling-Lee adapter and hooking the stick up to your building antenna. This has worked very well in some buldings. Surprisingly, in other buildings results were better with a stub antenna (from a DVB-T receiver) plugged into the adapter. This setup might work for car antennas in the same way—try at your own risk. Wrapping the stick in aluminium foil for shielding has also improved reception.