10 April 2014

XPA2


XPA2 is another Russian polytonic mode and as well as XPA, its believed to be used by Russian intelligence services. It transmits data at 7.5 Baud using 16 tone MFSK system, the whole pool of the available frequencies, although only 14 of those are used, sumarizing the initial sync part and the message part of an XPA2 transmission (Pic.1). There are "holes" related to frequencies that are not in use or have special/unknown functions.

Pic. 1
Measuring the frequency grid inside  the message you get the same value, but only eleven are used to transfer messages (Pic. 2) 

Pic. 2
This system is very symilar to the Russian Intel Multitone System 1+12 described in radioscanner.ru here

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