Tuesday, February 18, 2020

2000 symb/sec 8PSK bursts

Today 8PSK bursts with 2000 symb/sec were received on a KiwiSDR in WCNA on 7862 kHz USB (center frequency is 7863.8 kHz).

Starting from the recorded WAV file in I/Q mode, all processing (symbol synchronization, doppler correction, symbol analysis, plotting) was done manually in GNU Octave using signal-analysis for LFSR-detection.

The bursts consist of a BPSK-modulated preamble which is a subsequence of a length-14 LFSR with period 214-1, i.e., a maximal length LFSR. The preamble is followed by 6 720-symbol-long frames, where each frame starts with 72 known 8PSK-modulated symbols, followed by 72 BPSK-modulated unknown symbols and 576 8PSK unknown symbols.

Preamble and frame structure

720 symbol frames