6 August 2016

Unid PSK-2 signals 125.3Bd and 127.3Bd


These two PSK-2 signals has been heard on 12499.0 KHz (06 August, 2016) and 22499.0 KHz (10 May, 2016) on USB. Perhaps a coincidence but, unless a little variance of ~ 140 Hz, their central frequencies differ of 10KHz: for that reason I shifted up the 22499 KHz signal of just 140 Hz in order to find differences and similarities.

The two signals exhibit different manipulation speeds: 125.3 and 127.3 Baud, although the sub-carrier frequency have (reasonably) the same value of 830 Hz (it's to note the better recording quality of the 22499 KHz signal).

fig. 1 - manipulation speeds
fig. 2 - sub-carrier and harmonics

For what concerns the modulation, both the two signals use the PSK-2 technique (figs. 3,4)

fig. 3
fig. 4
 
The analysis of the demodulated bitstreams show a 141-bit period for the 22499 KHz signals and a 14-bit period for the 12499 KHz signal (fig. 5).

fig. 5- perdios of the two bitstreams
These signals are perhaps produced by the same modem/equipment running at different speeds, but it's only my supposition. As far as I know, user(s) is unidentified: comments and help in this direction are welcome.


bpsk-125.3 Bd https://yadi.sk/d/VCAq0bBktzER8 
bpsk-127.3 Bd https://yadi.sk/d/buRS-WngtzEKn 

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