Hi Sylvain,
Thank you for your quick reply. Much appreciated!
I will try your suggestions and come back to you when I have more results.
Best regards, Johann
On Thu, Apr 30, 2020 at 6:53 PM Sylvain Munaut 246tnt@gmail.com wrote:
Hi Johann,
So, first wrt to different formula, the spec is definitely right ... (I mean it's the spec ...). However they are narrow channels and if your B210 is not GPS disciplined, its oscillator could be out quite a bit. It's default xtal is only rated to +- 20ppm and that's a 30 kHz error at 1.5 GHz ... so you can be off by a full channel just with that.
Second, the frequency you give to gmr1_rx_sdr.py is where to tune. In reality you want to tune not to the channel directly but a bit to the side so that the DC offset and 1/f noise at the center of the capture don't mess up the data. The script will automatically filter and recenter the proper frequency depending on the -a argument you passed to it.
Finally that python script only does the sample and channelization, and saves to a cfile in /tmp it doesn't do any of the decoding at all. For that you need to also run gmr1_rx binary ( or gmr1_rx_live , see the live branch ) on the recording. And it's that one that will take the raw samples do all the demod and decoding of the channels and send the data to wireshark.
Cheers,
Sylvain