GNURadio

Have a graph!

Some not long time ago, gcndevelopment released a bundle of binaries for x64 Windows 10 at http://www.gcndevelopment.com/gnuradio/downloads.htm, and this created a great opportunity to play with GNURadio from a native Windows environment perspective.

I always had doubts regarding the quality of the demodulated data fed into Scytale-C by demodulating audio, either from a device, from a recorded sound file, or recently from audio served through a plugin. Using the GNURadio kit I created a couple of Inmarsat-C BPSK demodulator graphs. Internally they have the same structure, however one is fed with audio data and the other one with true IQ.

I left the IQ decoder running for a while on live input and saved the generated Inmarsat-C frames. I also recorded the same data as audio and the next day I ran the audio decoder and also saved the frames. The results were pretty revealing. While the IQ decoder had lost about 12 frames, the audio decoder showed 92 lost.

Here is a graph I made that serves two BPSK demodulated streams over tcpip. One can copy/paste the decoding chain and demodulate as many channels as one wishes. I intend to wrap the Scytale-C decoder into a console app for one to be able to use these types of GNURadio demodulated streams of bytes to decode the Inmarsat-C signals:

scytalec_inmarsat-c_bpsk_48000_x2

 

When locked, this is what one is expected to see:

Enjoy!

 

Sources:

http://aaronscher.com/GNU_Radio_Companion_Collection/Audio_modem.html

https://wiki.gnuradio.org/index.php/Guided_Tutorial_GRC

 

This is a continuation to: https://thinair.aelogic.com/another-idea/

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