Resurrecting KM7N-10

     This idea all started innocently enough----I was cleaning the shack, and found a Mobilinkd TNC2 that I was not actively using, plus an unused Baofeng UV-5R. So that quiet voice in the back of my brain started getting louder….”You haven’t had aDigi/iGate online in a while, and you really want one”…”Hmmmm, what if?”

    The seed had been sown, and it was time to see what would germinate. I realized that I had the guts of what I needed a TNC, a radio, and a computer (Raspberry Pi). I had tried previously to build an RTL-SDR RX-Only iGate, but that was unsuccessful because I could not get any software to “see” the RTL-SDR. So that RPi 2B and RTL-SDR combo ended up as an ADS-B receiver feeding FlightAware, and has been faithfully pumping out aircraft tracks constantly for over a year now…

     The easy first step was connecting the Mobilinkd to the Baofeng UV-5R, and then connecting to the config software on an old android phone to set noise levels appropriately. I was doing well!

After that, it got a little harder. My first challenge was to decide on a software platform to do the decoding, displaying, digipeating and iGating. Based on my research, I saw DireWolf, Xastir, and YAAC often used with an RPi. I tried all of them, and throughout the testing process of each, I had to dig way back in my memory banks to my days as an undergrad computer science major (there were very few of those days, as I quickly learned early on that it was not the escape from college-level math that I thought it would be, so I changed my major after my first year :-D ), because installing and running software on an RPi is NOT a plug-and-play affair that a Windows user like me is used to. You need to understand some basic coding. Fortunately, the Google Machine is quite adept at pointing a newbie to resources and guides that walk you through the steps. I ultimately settled on Xastir as the software of choice due to its easier handling of the Mobilinkd data via Bluetooth.

Now, with the Mobilinkd connected to the HT and talking to the RPi, and Xastir running as advertised, I was off to the races, digipeating and iGating like a champ.

Result: It’s doable! It’s small and portable. Moreover, it works. However…

I used APRS.fi to monitor iGate and digi performance, and adjusted my setup over the period of about 7 months, primarily focused on the antenna. The Baofeng is not known for its highly discriminating receiver, and the volume and squelch settings are critical (I settled on mid-range volume and open squelch). I tried the stock rubber ducky, a high-gain ducky, and a J-pole, and finally a small roll-up J-pole designed for the UV-5R. Over the course of about 7 months, my best results were withthe roll-up J-pole, and my best month showed me receiving just over 3,000 packets via RF, but an average receiver range of only about 15 miles, though anecdotally I believed it to be significantly smaller. I compared this with a nearby neighbor who was also running a digi/iGate with a KPC-3 and an external antenna, and he was doing much better than I was, receiving even closer in signals than my setup was (but should have been).

Thanks to a green paper Christmas gift, I have replaced this setup with a more permanent one, using a Microsat WX3in1 Mini and my old Alinco ALR-22 2M radio. Happy to say, it receives, decodes and generally behaves much more strongly and reliably, and I do not anticipate making any substantive changes to my APRS digi/iGate setup.