"TX/RX synchronisation" would reduce the time occupied by FFT by 100 or more (from several FFT/sec to 1 FFT/min). The "calculation power" that becomes available could be used to improve SNR. But How
My point is that there has been a lot of discussion about locking to GPS, or Loran, or some other standard, and it has failed to attract any practical interest because it is more complex than most am