Not exactly an "Arduino TNC" because he doesn't use the Arduino libraries at all, but he uses the standard Arduino board with a few resistors to get signals in and out. http://sites.google.com/site/ki4mcw/Home/arduino-tnc I know we've talked about this in the past, and maybe you've seen this guy. But he's got updates as new as January reporting success sending and receiving APRS data with his stuff hooked up to a VHF handheld transceiver. This could be the basis for an APRS node on a balloon, car, boat, etc. It could also mean that you have an APRS node waiting to be built sitting in your parts drawer if you have an HT and an Arduino. Ed