Saturday, January 26, 2019

Listening to DMR without a DMR radio

It's not too hard to listen in to DMR digital radio traffic with just a low cost RTL-SDR dongle and some software.

I can pick up the Sydney repeater on 439.5MHz pretty well, even with a non-resonant antenna. There's a good list of frequencies in Australia on VK DMR Info site.

(Click to enlarge the screen shot).

Here, on Windows 10, I'm using SDRSharp piping audio over to DSD+. I followed the instructions found via the RTL-SDR page but in summary, you need VB-Cable to route audio out of SDRSharp over to the DSD+ program.

Demodulation is set to NFM but the bandwidth is wound out to 12kHz. I turned squelch off and also turning off "Filer Audio" made it work much better. Adjusting the audio output level in SDRSharp is also important for good decode.

Here's how it sounds:

At the home brew group meeting on Sunday I understand there's a talk on DMR so I'll be interested to learn more.

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