27 December 2020

async 5N1.5 STANAG-4481F in cleartext

Yet another interesting STANAG-4481F signal, this time operated in async 5N1.5 mode and in cleartext(!): first time I see a not encrypted S-4481F transmission (obviously except FABs/CARBs). Signal spotted on 11123.55 KHz (CF) at 2220Z a few days ago (24th Dec) thanks to the AI6VN/KH6 KiwiSDR at Kahakuloa, Maui, HI.

Fig. 1

Curiously, since the poor quality of the signal, the bitstream sometimes appears as 5N1 and sometimes as 5N2 (Figure 2).

Fig. 2 - 5N1 and 5N2 bitstreams

The decoded text concerns the AOMSW exercise in the Arabian Gulf on December 21 [1] and since the title ("Navy News Stories of the day" ) and the text, I think it's probably a kind of "press review" for the fleet at sea. 

Fig. 3 - decoded text

Don't know which USN/NATO station operates on that frequency (11223.55 KHz, CF) and unfortunately I went late on that transmission so I didn't have time to DF the signal.

[1] https://www.centcom.mil/MEDIA/NEWS-ARTICLES/


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