50Bd/500 FSK (likely CIS Gov/Mil)

Unid (likely CIS) 50Bd/500 FSK message recorded on 12221 KHz (cf) at 1035z using the KiwiSDR "nsk" located near Novosibirsk, Russia. Notice the LFSR sequences generated by the polynomials x^7 + x^5 +x + 1 (128 bytes length) and x^5 + x^4 + x + 1 (Fig. 1).

Fig. 1 - the two LFSR sequences

Although the shift is an integer multiple of the speed, the two FSK tones do not preserve their phases (Fig. 2).

Fig. 2 - phases of the two FSK tones

https://yadi.sk/d/mZiO7oRcHtQ5-Q