What are we looking at here? This is a near real-time map of all APRS stations in the rally area. APRS – Automatic Position Reporting System, is used to transmit the exact location of an object (vehicle) over amateur radio frequencies. A data packet can contain a number of additional items, such as direction, speed, altitude, temperature, etc. Short text messages can also be attached. These messages are transmitted on 144.390MHz and re-transmitted by local repeaters called digipeaters. Some of these digi’s are on the internet, and this is how you are able to see the data above!
Stations use their call-sign and a status message to identify them. You can click on the station to get more info. Be on the lookout for things like “HDT Zero Car” or “Car #761″ or “Sweep”. These are vehicles on the stages right now! You might also be able to tell based on their speed.
The rally car has a ham radio, a TNC (Terminal Node Connector), and a GPS receiver. A TNC is a little data device that talks to the GPS and sends its information to a radio. Every few minutes the TNC gets the position from the GPS receiver and transmits it over the airwaves with the VHF FM radio. The TNC we use is the OpenTracker+ made by Argent Data Systems.
Service has a scanner and a laptop. The audio from the scanner is hooked to the laptop sound card. The software, AGW Packet Engine + AGW Tracker, receives the data and converts it to a little icon on a map. Key features: Service knows where we are at all times. There is a ham radio in the car for emergencies and the crew doesn’t have to be ham licensed. We encourage you to learn more, get your amateur radio license, and get an APRS tracker in your rally vehicle!