17 July 2020

CIS-14 FSK 100Bd/2000 (CIS 3x100)

Interesting 100Bd/2000 FSK signal spotted on 16059.5 KHz (CF), most likely a Russian Governative transmission. This signal is not a separate one, actually it must be considered as part of the CIS 3x100 "system" visible on the left in figure 1. Indeed, the main station operates a VFT 3x100bd/1440 signal and works simultaneously three outstations which in turn run the FSK 100Bd/2000 waveform (outstations are usually not far apart in frequency).

Fig. 1
As well as the mainstation (VFT 3x100Bd/1140), outstations too use CIS-14/T-207 (as from the analysis of the demodulated stream in figure 2); all use the same checksum mode [0312].
Fig. 2
A clearer illustration of this "system" is visible in the spectrum of figure 3, the IQ recording of which was provided by my friend KarapuZ [1] who discussed the signal here.

Fig. 3

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