3 July 2015

Unid FSK 1200Bd/600 (MSK)

I heard this signal on 14747.0 USB at 0645 (30 Jun 15), it's a  500 mS bursts transmission with Br = 1200 Baud (Fig. 1) and 500 Hz Shift.  The source/user is unidentified. 
According to http://signals.radioscanner.ru/info/item68/ the waveform looks like a classic MSK modulation with Shift = 1/2 * Br, as clearly visible in Fig. 2.
The second harmonic of the MSK waveform (Fig. 4) has two bright spectral lines, the spacing between these lines is equal to Br, that is one of the signs of these modes. This is the necessary condition of their definition at the analysis, but not the sufficient: two lines in the second degree/power can be also given by both SDPSK and OQPSK modes; the constellation (transitions) of the signal is shown in Fig. 5.

Fig. 1

Fig. 2
Fig. 4
Fig. 5

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