For those who are not familiar with APRS (automatic packet reporting system), it is a system that employs amateur radio stations to pickup and relay packets broadcast by remote stations. When a repeater station picks up a broadcasted packet, it relays via the internet to a central server. What has this to do with experimental aviation, you ask? Well, the primary use of APRS is to allow tracking. APRS-equipped radio can include positional (i.e. from an attached GPS) and other telemetry data in its packet. The equipment for this is very inexpensive, and once you have it all setup, there’s no user fees. I bought a ready-to-go system from Byonics. If you like, you can assemble your own system for cheaper, but for $200, its a pretty good deal. The only other thing you need before you turn it on is an amateur radio license. Not tough to get, just an exam that you can take from your local HAM radio club. Websites like http://aprs.fi show all reporting APRS stations on a google map.
So, to install an APRS system in my plane, I decided to mount the APRS unit behind the panel, and provide a switch on the panel to turn it on. Also, the APRS unit has an 2-color indicator status LED that lets you know if you have a GPS lock, and gives a blink every time it transmits a packet. It thought it’d be cool to move that LED out of the APRS unit and put it on the panel beside the switch. You can see in the pictures that I removed the LED in the box and soldered wires so I could remote it. There was also a connection on the board to allow you to wire a switch that would allow you to select the APRS broadcast profile, so I wired that in as well. That might allow me to add a switch on the panel to select a different message (i.e. parked/taxiing or flying). The Byonics APRS unit came with an antenna, but it was a vertically polarized whip antenna. I put a copper strip bipolar antenna (2 x 17.7″ strips for the 2M amateur radio band) under the front passenger seat, instead.
I tested the APRS unit by driving around with it in my truck before I ripped it apart to install it in my plane – worked great. The minute I turned it on it got a GPS lock and started spitting out packets that I could see on the APRS website. Pretty amazing technology.
