my configuartion is based on 2 usb limesdr cards. One contains the transmitter: board number1 + 2 receivers the other 2 other receivers and provides its clock 30.72Mhz to the clock REF input to board number1.
Also the transmitter emits 1 BPSK modulation. By doing the intercorrelation of the signals we see that the phase between two signals of 2 receivers of the same card is constant in time however between 2 receivers of 2 different cards the phase turns quite and or quickly. In addition, the greater the carrier frequency, the faster the phase turns.
My configuration is the default one to which I add the line of code to program the clock ref at 30.72Mhz.
Have you got one idea to program the board to suppress phase shift? Write register or ini file?