On 13960.0 KHz I tuned an apparently MFSK-4 100Bd/1000 transmission spreading about 3000Hz bandwidth: tones at -1500, -500, +500, +1500. After emails exchange with friends, "cryptomaster" from radioscanner suggested that the signal is a F7B mode actively used by Ukrainian Nets. Usually, the two channels transfer T-207 ciphered data. He also warned me that SA program parses these transmissions as classic MFSK-4 therefore the received result doesn't correspond to the truth. Another F7B signal, this one from Ukrainian Mil, was reported here some times ago.
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| Fig. 1 |
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| Fig. 2 |
http://www.wavecom.ch/content/.../twinplex.htm
The equipment BUK-2D, for example, is one of the equipments used to filter and separate the two channels (thanks to 'cryptomaster').
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| Fig. 3 - BUK-2D equipment |
https://yadi.sk/d/f2PpWmdi3UTaqG