XPA2 waveform uses a combination of 12 out of 16 possible tones: the lower tone (#1) acts as synch, or maybe as a separator/space between data, and is issued each 768 ms or each five symbols (Fig. 2). The eleven contiguous(!) tones from 6 to 16 are used for data. Room for the (possible) four tones 2-5 is not used. Notice that the tones #4 and #6 are used as EOM sequence. tones #1 and #16 as initial synch sequence.
Manipulation speed is 7.8Bd while the separation between the "active" tones is 15.66Hz (Fig. 1). XPA2 is a Russian mode believed to be used by at least one of the Russian intelligence services.
Manipulation speed is 7.8Bd while the separation between the "active" tones is 15.66Hz (Fig. 1). XPA2 is a Russian mode believed to be used by at least one of the Russian intelligence services.
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| Fig. 1 |
Assuming that the tone #1 acts as a separator/space between five 4-bit symbols (Fig. 2), the transmission could be interpreted as a commonly used five LGs/FGs off-line encrypted message.
https://yadi.sk/d/Jmkm0ehj2omkRA
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| Fig. 2 |
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