US INTELLIGENCE FSK-SYSTEM

100 Bd / 800 Hz SHIFT

ACF 

The 100 Bd FSK used by one the US-intelligence agencies, shows a distinctive
16 bit pattern during the message call-up procedure:


 

At the start of the actual message, the 16 bit pattern disappears and is replaced by a distinctive 64 bit pattern:


 
 
 

During tfc. condition, the system shows characteristic spikes every 4 bits:

Speed bit analysis view of the system with all 3 phases:



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