The Argent Data OpenTracker USB is a fully-featured KISS TNC – and it’s one of the least expensive, clocking in at $45 at the time this article was written. If you’re going to build an APRS digipeater or igate, or just use it on your home station in KISS mode, it’s a great solution. Motorola radios make excellent APRS radios, especially the CDM series – which has a VHF range of 136-174MHz, placing the APRS frequency of 144.39MHz squarely inside its bandsplit. My home APRS station currently uses a CDM750 4-channel model.
The problem is that the OpenTracker USB’s audio level is just too low for the Motorola. Some users were reporting as little as 1.5Kc of deviation even with the audio levels turned all the way up.
The solution? Simple. Short resistor R6. I simply placed a gob of solder over top of it. It was a quick mod and I did not measure the deviation like I should have, but it seems to be working well.