M17 - SDR & GNU Radio

[SP5WWP]

M17 compatible radio built using RTL-SDR/HackRF and GNU Radio.

[faydrus]

Have you made this/are you making this?

[SP5WWP]

I'm working on it. I think SQ3SWF is trying too.

[SP5WWP]

Sorry for double-posting, but if anyone is familiar with GNU Radio - please stand up We need a 4FSK demod block.

[KE0WVA]

I've been meaning to learn GNUradio, maybe this is my motivation.

[KE0WVA]

Been busy with work lately but had some time to start learning GNURadio and sketching out a flowgraph

At the moment all it does is encode audio to raw Codec2, transmit it as 4FSK symbols over FM, simulate a noisy channel, and demodulate it back into bits. Currently missing: Framing that would let me plug those bits back into Codec2 and get audio out of it. When I manually find the correct offset it decodes fine, though, even down to some pretty low SNRs (constellation diagram is basically just 4 pinprick dots even down to 10dB SNR or so). I expect this to get worse with higher symbol rates, but it's a pretty good start. I wager that with ECC we should be able to get quite acceptable decode performance down to 4-5 dB SNR.

It would probably be a good idea to design the function that accomplishes framing and ECC in the M17 codebase, to also work as a GNURadio plugin so that it doesn't need to be written twice and we can be assured that what we are simulating is actually reality.

[SP5WWP]

Can you provide (attach) a .grc file? I have received a HackRF One yesterday and gonna play with it.

EDIT:

[img width=300]https://i.imgur.com/Qq6CX1B.png[/img][img width=300]https://i.imgur.com/E0vDcpD.png[/img][img width=300]https://i.imgur.com/nhiDAsC.png[/img]

[SP5WWP]

I'm bumping this thread.

[tarxvf]

If memory serves, there was some movement on github and reddit, where u/mobilinkd was able to provide a working sample.

[SP5WWP]

4FSK with RRC for GNURadio 3.7 can be found here:
https://github.com/M17-Project/gr-m17/bl...SK_RRC.grc