Three new fleet broadcast channels spotted in these days, all STANAG-4481F:
4987.0 KHz (cf) 50Bd from NSS Davidsonville
7455,5 KHz (cf) 75Bd from NSY Niscemi
7457.0 KHz (cf) 50Bd from NAU Isabela
All the the broadcast are KW-46 secured(!), although 75Bd/850 usually run KIV-7/KG-84 devices.
These and other recent catches seem to confirm a change in some transmission frequencies, mostly of 2000 Hz or , even stranger, of 1300 Hz. "There is currently a Navy exercise in progress off the east coast, so the shift may perhaps be supporting that effort or maybe to avoid interference or harmonics on other services at the sites", my friend Mike mco say.
I have updated the page related to the BRASS STANAG-4481F page, it is even more evident that all the transmissions that use the waveform 50Bd / 850 are protected with KW-46.
https://disk.yandex.com/d/XJVGUnkI4D4etg
6759 St Eval UK
ReplyDelete8788 Turkey
8792 Turkey
Thanks for the comments, updated the BRASS page :)
DeleteHi Antonio, excellent analysis, thank you very much for sharing it.
ReplyDeleteI’m trying to replicate your study on FSK 50Bd/850 transmissions related to STANAG-4481F and KW-46 encryption. I already have the demodulated signal (bitstream) and have arranged it into 7-bit frames as you mentioned. I also generated the LFSR sequence using the polynomial x^31 + x^3 + 1, but I would like to know a bit more about your method:
How did you determine in which column the sync bit appears? Did you compare the LFSR sequence with each column by shifting bit by bit and calculating the percentage of matches? Did you use any special metric or threshold? Are you using any external software (Octave/Matlab/Python) or only “BEE”?
I would really appreciate if you could share a few more details. I’m learning a lot thanks to your work.
Best regards from Chile!