M17 Project Forum

Full Version: M17 - SDR & GNU Radio
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M17 compatible radio built using RTL-SDR/HackRF and GNU Radio.
Have you made this/are you making this?
I'm working on it. I think SQ3SWF is trying too.
Sorry for double-posting, but if anyone is familiar with GNU Radio - please stand up Smile We need a 4FSK demod block.
I've been meaning to learn GNUradio, maybe this is my motivation.
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.
Can you provide (attach) a .grc file? I have received a HackRF One yesterday and gonna play with it.


[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]
I'm bumping this thread.
If memory serves, there was some movement on github and reddit, where u/mobilinkd was able to provide a working sample.
4FSK with RRC for GNURadio 3.7 can be found here:
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