18 July 2015

Unid MFSK-7 200Bd 400Hz

This waveform is an MFSK-7 running at 200 baud, the seven tones are 400 Hz spaced. The ACF is 350 mSec then 70 bits long. Looking at its frame (pic. 3,4,5) it seems that 7 bits transport something like data while the other 63 bits have a constant sequence (Sync?).
It looks like a "selective call" and the only think that I could find in the web is a reference to the "AirCal": an MFSK 7 tone system by the old Racal (!?): http://www.scancat.com/rvw-faqc.html 
Well, Racal was taken over by Thomson-CSF and now it's Thales. Although Thales has continued part of the former Racal product line, most products have gradually disappeared along with the name 'Racal' itself. 
The signal was caught by KarapuZ on 10150.0 KHz on USB, around 1540z on 15 July (present year): it's available on request for your further analysis: just email me.

pic.1 - speed

pic.2 grid
pic.3 ACF

pic.4 frame structure

pic.5 FSK demod

No comments:

Post a Comment