aprs

I first got into radio when I found out about the RTL-SDR dongle. I am an IT guy by trade and have always been interested in programming and hacking, so when I saw that I can get a $10 dongle, hook it up to my computer and pick up rf signals from garage door openers, wireless remotes, and even airplanes, I started reading all I could.

The first thing I did with the dongle was set it to receive ADS-B signals from planes. That was simple to set up and was pretty cool to watch. I thought APRS would be the same. I figured I could hook the radio to a computer or phone and start picking up packets immediately, but I was wrong.

I first tried to rig up a cable to go straight from a Baofeng HT to an android phone running APRSDdroid. I found several different variations on this idea. I started with this one.

I used the crappy headset that comes with the Baofeng radio and the cable from a broken headset.

I wired up the thing, just like in the schematic, but it didn’t work.

I had better luck with this version.

I could receive packets in APRSdroid using this cable and my radio, but I couldn’t transmit. It would start to transmit and then it would key on and off over and over again until I killed it. I figured that going straight from the radio into the phone might be a problem, so I started looking into TNCs and I found this arduino TNC.

I built out the TNC circuit on a breadboard and flashed the firmware on a brand new arduino nano knockoff, but it didn’t work. I scratched my head and fooled around with it for two days. I plugged the nano in for the millionth time and the regulator failed. I guess that’s what I get for buying cheap Chinese clones.

I popped open another nano clone and flashed the firmware and it fired right up. I started picking up packets here and there, but it was slow going. It could be my location or it could be my crappy Baofeng, but I could not receive reliably at all. I tried the stock antenna, a nagoya antenna, and finally my tape measure yagi.

With the yagi, I could receive fairly reliably, but I still can’t transmit. Maybe my ghetto cable isn’t wired up right. It looks like the arduino is triggering correctly, but the radio isn’t keying down. At this point, I am annoyed with the whole situation and I will probably put it aside and try again later. Here was my final setup: