26 October 2015

MIL 188-110C App.D: BW15 KHz, SR12000 Bd, PSK-8

signals were heard at different days and times, around 1100-1200z, on 18270.KHz (f0) by KarapuZ.
Waveform Number 7: PSK-8, 15 KHz bandwidth 


The waveform (WID7-15Khz) occupies a bandwidth of 15 kHz, providing 24000 bps user data rate. Modulation used is PSK-8 at 12000 symbols/sec. Reading the MIL 188-110C App.D documentation, a frame for this waveform consists of 1280 unkown symbols (data) + 160 known symbols (mini probe), so 1440 symbols. Since the 12000 symbols/sec of this waveform, the frame should be 120 ms long but I get a 240 ms ACF: just the double of the expected lenght. More likely ACF value is generated by the cyclic rotation of the mini-probes, as specified in the standard, and the interleaving of this sample needs one rotation after 2 data blocks and so the 8640 bits period (240 ms).

1 comment: