Information Technology

I managed to use APRSDroid (v1.6.2b) on a BlackView BV9900pro (Android 10) with a Kenwood TH-D72E TRX. It works, with a few caveats.

The HT itself needs to be set to the same APRS settings as the TM-D710, which are:

• Com Port
  • Baud Rate (screen 330): 9600 bps
  • Input (331): Off
  • Output (332): Waypoint
• Waypoint
  • Format (340): KENWOOD
  • Length (341): 9-Char
  • Output (342): All

One difference to the TM-D710 is that the TH-D72 has got native USB. Therefore, I also set PC Port Output (screen 350) to On.

I connected the HT with a Mini-USB cable to a USB-OTG adapter which had a Micro-USB plug. Using a USB-C adapter, I connected it to the BV9900pro. A simple USB OTG app didn’t list any USB devices connected, though. I noticed I had to switch on “OTG data exchange” in Settings > System. Now APRSDroid showed a USB device connected, and I could start tracking.

I noticed two caveats, which might be completely the smartphone’s fault. (It performs aggressive internal task killing which can’t even be entirely neutralized by rooting and modding.) Note that the “OTG data exchange” setting shows a description that it would be switched off when unused for 15 minutes. In my case, it switches off anyway, even if the phone’s screen is on and APRSDroid is tracking. The second issue is that when I switch to map mode while the USB connection is on, the app freezes and is cumbersome to stop and restart. I always have to switch off OTG first, then study the map, switch back to list view, activate OTG and start tracking again.

Additional thoughts: The TH-D72 is an aging device. It was introduced in 2010, I bought it new when I got licensed in 2018, and it was discontinued soon after. It is still the only device available [besides the TH-D74] that offers an all-in-one solution for Packet/APRS/GPS that also works perfectly from Linux and Android. Although I’m a ham for a little time now, it always puzzles me how information can be so inaccessible to newbies: Only recently I managed to use Packet Radio at 1200 baud to

• send WinLink messages directly from the HT (called APRSLink),
• send ordinary e-mails directly from the HT,
• receive(!) ordinary e-mails directly on the HT, via APRS radio (what is endgame-awesome), and
• use AX.25 on a Linux machine to connect to WinLink via a Packet node,

all of which are actually old-school meanwhile. It also took me four years to figure out APRS works directly between the HT and a smartphone or tablet. At least I established these options for me now.

The TM-D710 disappeared from the market last year, and I was caught by surprise. After months of searching I could finally buy one used. This mobile TRX also offers APRS on-board which can be directly accessed from Linux.