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With help from KA1GJU, I got my OpenTracker 1m (Rev 2) APRS unit connected to my Yaesu VX-6R HT. It took a bit of soldering, testing and troubleshooting. GJU discovered that the blue wire on the VX-170 HT cable wasn’t connected to any pin on the 4 conductor 3.5mm waterproof connector. We installed the 10uF cap to pin 1 on the DB-9 and the 2K Ohm resistor to pin 3 on the DB-9, connected them to the white wire (Mic audio) and the tracker came to life!

So far, the set up works fine using only 5 watts from the HT. Once I get the mobile antenna mounted on the car, it should perform even better. Here is a picture of the OpenTracker, GPS receiver and HT.

So what does all this mean? What is APRS? To paraphrase Wikipedia, “APRS is the Automatic Packet Reporting System which uses amateur radio to automatically report the position of a person or object…” In my case, the tracker is used to report on the position of my car. I connect a small GPS receiver to the serial port on the back of OpenTracker and the HT transceiver, a Yaesu VX-6R, is connected to the radio port. The tracker itself is DC powered by a 3 amp fused cigarette lighter adapter. Using configuration software specifically for the OpenTracker, the tracker stores my ham callsign and other parameters controlling tracker behavior. Once everything is powered on and the GPS receiver has a satellite fix (about 10 seconds or less in my testing), the tracker takes the lat and lon from the GPS, bundles the data into a packet that is then passed to the transceiver. The transceiver sends out the data in a burst on 144.390 MHz (in the USA) that is picked up by a local digital repeater, or “digipeater”, for retransmission. An IGate, internet gateway software for APRS data, takes the incoming radio frequency data (the packet) and passes it to the APRS-Internet Service. So as I drive, I send out GPS position reports at periodic intervals that appear on the ‘net. You can view my position in real-time using FindU.com or APRS.fi. I prefer the latter, so go here to view the last transmitted position of my car. Here is a map of a short drive around town I took yesterday while testing the tracker.