Wednesday, July 10, 2019

Decoding APRS via SDR

APRS uses packet radio and FLDIGI doesnt support it for some ungodly reason. You can chain a few tools together to get the decoded output.

  1. Plug in and attach your RTLSDR, or whatever, to your VM
  2. start up GQRX, start receiving
  3. Tune to 144.390 to get an APRS signal (North American calling freq for APRS)
  4. Set the following: 
    • Filter Width: Wide
    • Filter Shape: Sharp
    • Mode: Narrow FM
    • AGC: Fast
    • set the squelch to silence the noise
  5. In the audio section, hit the "UDP" button which should start streaming the audio over UDP port 7355.
  6. In another tab: apt install direwolf
  7. direwolf -r 48000 udp:7355
You should get output like below:

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