29 July 2017

Russian MFSK-17 125Bd/125Hz burst system (selcall waveform?)

Unid MFSK-17 burst system heard on 11090 KHz/USB, modulation speed 125 symbols/sec and separation between tones is 125 Hz (Figs. 1,2)

Fig. 1
Fig. 2
The waveform-1 seems to have some LMF components and a curious tones format (Fig. 3) maybe used to wake-up receiving modems or  matching a certain known tone-sequence. Waveform-1 is then followed by a Russian male operator calling the other station: "first calling twentieth" (thanks my friend KarapuZ who translated the voice comm).

Fig. 3
Bursts have a duration of ~1080 msec and sent each 4000msec in waveform-2.
The same signal, more precisely the here-termed waveform-1, was reported about one year ago in radioscanner.ru forum. "Sometimes a multi-frequency transmission with spreading has been observed" my friend KarapuZ say.


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