Interesting fleet broadcast from the MHFCS (Modernised High Frequency Communications System) site in Humpty Doo, Northern Territory - Australia. The transmissions use STANAG-4285 600bps/L in ISB mode and are audible on 11145.0 KHz (Figure 1).
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| Fig. 1 |
Bitstream of the LSB channel (Figure 2) is a "classic" broadcast which is encrypted using KW-46 (or compatible) cipher device given the presence of the m-sequence generated by the polinomyal x^31 + x^3 +1 (KW-46T uses that M-sequences to synch the KW-46R receive devices).
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| Fig. 2 - bitstream of the LSB channel |
The bitstream of the USB channel is more interesting since it consists of 12-bit strings where all the bits have the same logical value, likely originated by the GA-205 12-channel time division multiplexer: I already met such signal some years ago [1] but that time from the "Naval Communication Station Harold E. Holt" (NCS HEH) 6 km north of Exmouth. USB channel too transports a KW-46 secured traffic: as shown in Figure 3, I filtered out 11 channels and reshaped a single "column" into a 7-bit pattern then I successfully checked the presence of the x^31 + x^3 +1 m-sequence.
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| Fig. 3 - bitstream of the USB channel |
As said, in this case the transmission is source by a Tx located in Humpty Doo, Northern Territory Australia.
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| Fig. 4 - DirectionFinding results (TDoA algorithm) |
https://disk.yandex.com/d/cd6YKgpc18NPrw
[1] http://i56578-swl.blogspot.com/2019/05/kw-46kiv-7m-secured-fleet-broadcast.html
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