Code to decode QPSK signals

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Joined: Wed Aug 16, 2017 6:50 am

Code to decode QPSK signals

Post by AussieSusan » Wed Dec 20, 2017 1:50 am

I've written code to take the IQ data from the RSP2 (running at 2MHz sampling) to select the specific frequency of interest (actually picking up the NOAA POES signals) and then perform an FM decode. All of this is working well.
I'm looking to decode the QPSK signals from the METEOR-M2 satellite and I've been looking at a number of sites on the internet for QPSK decoding of IQ signals. I think I can see what to do but most of the examples I've seem (in a variety of coding languages) use an IQ stream that they have generated without further modulation.
As yet I'm not picking up the satellite signal (for some unknown reason - I've used a number of radios and antennae but I can't find any signal during a pass - but that is another story) so I'm not able to experiment with the received data stream.
I'm not clear if I need to do an FM decode (or some other decoding) of some sort of if I can use the IQ signal directly to feed into the QPSK decoder.
Just wondering if anyone else is doing this and can give me a bit of guidance?

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