This 16-tones signal occupy a bandwidth of about 2700 Hz, from 385Hz of the lower tone to 3010Hz of the top tone (dF = 2625Hz), with 175Hz increment steps as shonw in pics. 1,2:
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| pic. 1 - spectrum of the MFSK-16 signal |
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| pic. 2 - the 16 tones grid |
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| 32.84Bd |
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| 49.32Bd |
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| 65.8Bd |
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| 131.59Bd |
It could be that the symbol rate varies according to the transmission channel conditions, or most likely these are just transmission tests to evaluate the better waveform that allow acceptable performaces in presence of varying channel conditions. Source is suggested to be CIS Intelligence/Diplomatic services.