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| Fig. 1 - "Serdolik" multimode waveform |
The MFSK segments have the usual 40Bd and 40Hz (channels separation) values which are typical of the Serdolik waveforms family: a long-range radio strategy utilized by the Russian and CIS countries Diplomatic Service, possibly Serdolik V2. It's worth noting in Figure 2 - at least in this example - that although the strategy provides a 33 channels grid, only 32 are the effective (used) ones: specifically, the first 15 lower channels plus the 17 higher ones (the 16th channel is not used).
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| Fig. 2 - MFSK segments |
The FSK inserts besides have usual Serdolik values, i.e. 40Bd/680Hz in this sample, and consist of short "01"s sequences (Figure 3).
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| Fig. 3 - FSK segments |
This example has been recorded on 20.8155 MHz/USB utilizing a distant AirSpy server located in UK.
CIS MFSK-33 waveform is not the only 1 that does not always usage all the available channels of the frequency grid: CIS MFSK-34 (aka Crowd-36) is another example in this respect (Figure 4).
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| Fig. 4 - frequency grid of any CIS MFSK-34 samples |
