I am currently working on a BPSK demodulator and decoder for a satellite communication system using GnuRadio.
The system uses a BPSK modulation at roughly 2GHz with a symbol rate of 200 ksymb/s. I recorded the signal directly from the transceiver module connected to my Ettus b200mini via a coax cable and some attenuation in-between using 2.4 MS/s and therefore 12 SPS.
I create the following graph for demodulating the signal, which works while using it between different SDRs for sending and receiving. But when I try to demodulate the signal from the transceiver module, I get a really noisy constellation figure (see screenshot).
I already tried different ways of filtering, different levels of attenuation between the sender and receiver, and many different settings for the used blocks, so far nothing helped.
Can anyone help me here? Even some hints on what I could try would already be nice.