3 December 2015

MFSK-4 (double FSK) 96/100Bd 500Hz, Ukraine Military

This waveform is known as Double FSK 96/100 Baud and 500 Hz shift, a dual channel F7B mode used by Ukraine Military, spreading about a 1730Hz bandwidth. 
The signal was heard just this morning (03 December) on 6970.9 KHz on USB, tones at -750, -250, +250 and + 750 Hz. Site radioscanner.ru reports this signal as Ukraine Mil 96-100, the two baudrates indication (96 and 100) is due to (literally) "some difficulties  in determining the speed of manipulation, due to the fact that the transmission channels are not synchronized (or poorly synchronized) with each other".
That issue is verified in the 21Aug15 log: the signal exhibits two baudrate lines at 96 and 100 Hz (pic. 3). That uncertainty is anyway not present in the measurement results of the  03Dec15 signal (96Bd) as in the pic. 2. The perfect 500Hz space among the tones (pic. 3) has ben found in the 96Bd signal, while in the other (96/100Bd) the shift is about 505Hz.

Pic. 1 - 03Dec15 signal, single baudrate line (96Hz)
Pic. 2 - 21Aug15 signal, the two baudrate lines
Pic. 3 03Dec15 signal, perfect 500Hz shift

F7B is a FSK modulation technique with four modulation frequencies, the two transmission channels, termed V1 and V2, are obtained through six possible combinations of the four frequencies and this leads to 6 different modes F7B1 to F7B6:


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