STANAG-4481 PSK (4481-P) is basically a STANAG-4285 sub-mode which adopts fixed 300 bps data-rate and long interleaving. 4481-P is used by for the NATO Naval BRASS (BRoadcast And Ship-Shore) project. BRASS uses 300bps for continuous broadcasting over wide coverage areas due to its repeated preamble data for which supports maintaining sync during long transmissions as well as late entry where a station can start to receive at any point during the transmission as long as their terminal is not set to begin on the SOM sequence.
In the heard transmission, spotted on 8322.2 KHz/USB, it's interesting to note the presence of the 64-bit KG84 sync sequence into the demodulated bitstream that denotes an encrypted message (Fig. 2)
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| Fig. 1 |
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| Fig. 2 |