FSK-2 1200Bd/800Hz waveform, approximately 1500 Hz bandwidth, used by Italian Military; in this record it's used by Italian Navy HQ (IDR Rome) on 12200.6 KHz/USB as unusual intro before STANAG-4285 1200bps/L transmission, receive peer had the tactical callsign AZWL. Since the PtP nature of that tansmission it could be that the initial FSK part act as a squelch ...but it's only a mine speculation.
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| fig. 1 ~1500 Hz bandwidth |
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| fig. 2 - baudrate line |
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| fig. 3 - involution module and shift between carriers |
The main features of this signal are what seems a polarity change that occurs each 8 bits (fig. 4), as reported by radioscanner.ru and confirmed in this analysis, and, at least in this sample, its quite pronounced 232-bit period shown in figure 5.
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| fig. 4 - polarity change |
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| fig. 5 - 232-bit period (fisrt part looks like a sort of preamble) |
https://yadi.sk/d/MAaPeQIRuHX7J