9 January 2019

unid 1200Bd (G)FSK bursts recorded in Japan


This signal was recorded at different periods using some the KiwiSDRs located in Japan (http://103.2.34.7:8073 http://222.7.151.84:8073 http://kiwisdr-jp7fso.ddns.net:8073), it was observed, at least, in three frequencies: 4765, 4626 and 4584 KHz. During night-time good results are also obtained with the KiwiSDR at Irkutsk (Russia), so the origin of the signal seems to be Japan or surroundings. 
My spanish friends ANgazu and Rapidbit (from radiofrecuencias group) did a brief analysis measuring the speed (1200Bd) and the shift between tones (825-890 KHz) and suggesting the GFSK mode (Fig. 1). On my behalf, I veried their measurements and verified that the bursts are 26 secs spaced and carry the same (encrypted?) text sent in async 8N1 mode (Fig. 2), although there are some difference among old recordings and new ones. The stream obtained after removal the start/stop bits does not offer useful information (encryption? not-standard 8-bit alphabet?), same results after descrambled the stream using the polynomial x^3+x^2+x+1. 

Fig. 1
Fig. 2
Maybe some kind of beacon? We thinked that a reference could help others to record and study the signal.



2 comments:

  1. What software are you using?

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  2. mostly SA (Signals Analyzer http://signals.radioscanner.ru/info/item21/) and a bit editor

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