The QStarz BT-Q818XT bluetooth GPS receiver is a 10Hz unit that is 100% compatible with RaceChrono. It also offers high poll rates, DGPS (differential GPS), AGPS (almanac GPS) and long battery life.
While most decent GPS units use the SiRFstarIII chipset, the 818 uses the relatively unknown and new MKT II chipset.
My experience with the 818XT has all been positive. It acquires satellites very quickly, and I’ve not had any bluetooth issues with the connection to my Android phone. However, I was confused by a few of the features and settings when I first started using it, so hopefully this blog post will help answers some of the questions I originally had … as you might be having them too.
There is a 3 position on-off switch on one side of the unit; those positions being Off, 1Hz and 10Hz. The differential (DGPS) capability is not enabled when operating at 10Hz, but is available when the switch is in the 1Hz (middle) position. However, 1Hz is not really fast enough for reliable lap timing, so what can be done?
Well, you can download the Windows drivers and the GPS View application (for Windows only) which will allow you to reconfigure the 1Hz switch setting to a frequency between 1 and 5Hz. You can find the downloads for the 818XT at QStarz Downloads page – select “GPS Receiver” as your product type and choose your exact model from the secondary (right hand) menu. There are also links to a quick quide and full user manual.
After installing the driver and application, connect your Q818XT to your computer and switch it on to the 1Hz setting. Open Settings->Control Panels and select the System control panel. Switch to the Hardware tab and look to see which LPT/COM port the 818 is listed as being connected to. Launch the GPS View application and set the appropriate COM port at the top of the window. You should then see the GPS messages scrolling in the top left panel of the window – if you don’t then you have probably selected the wrong COM port.
If you switch to the Setup tab, you can change the frequency for the middle (1Hz) switch position. Look for the section that says “Fix Update Rate” and hit the Query button. It should report 1Hz in the Data Bandwidth box to the right. Since we want 5Hz instead of 1Hz, all you need to do is change the rate in the pulldown menu from 1 to 5 and hit the Set button. That’s it, the 1Hz switch position will now operate the unit at 5Hz with full DGPS capabilities. It will remain at 5Hz until you pull the battery out of the unit or possibly until the battery runs completely flat.
Just remember to make sure you select the middle (1Hz) setting instead of the 10Hz switch position before you head out on track! In my opinion, a 5Hz refresh rate with DGPS is more valuable than a 10Hz rate without DGPS as the position reports will be both frequent enough and have a greater accuracy.
The AGPS feature is less important for accuracy as it primarily affects how long the unit takes to get its first fix. It does this by updating its internal almanac which enables it to locate the appropriate satellites more quickly. You can use the Update button in the lower panel to download a new almanac automatically from the internet. The new almanac will last for 6 days, and you can update it as often as you like.
Pairing this unit with your phone should be simple. Enable Bluetooth on your phone, switch on the Q818XT and it should show up in the list of available devices. The pairing code will be “0000” (four zeroes).
Make sure you change the “GPS receiver type” setting in RaceChrono to be “Bluetooth device” and select the QStarz 818XT as the external GPS device.
In order to give the unit decent line of sight with the satellites in the sky, I mount the unit on the tail of the bike. The 818XT has a rubberised bottom which is placed on the tail unit, and the whole thing is then taped to the tail.
I used a lot of tape; firstly to ensure that the receiver doesn’t fall off (?!) and secondly to try and form a waterproof barrier around the switch and the USB connector. Since the device lasts for 24-40 hours on a single charge you can switch it on before taping it to the bike, and then leave it on for the full track day.
Pre Track Day Preparation
I usually charge the unit for 2-3 hours before a track day. Using QStarz’s GPS View software, I also upload the latest almanac(which lasts for 6 days) and double-check that the 1Hz switch position is still re-mapped to 5Hz.
That’s really all you need to know about this receiver.
If you want background on using the QStarz 818XT then have a read of this post on how to set up and use a lap timer.
Update Summer 2014
You might be interested in reading a comparison between the QStarz 818XT and the Garmin Glo.