3 x 250Bd/500 FSK, likely Ukr nets

3 x 250Bd/500 FSK channels, probably Ukrainian-Mil broadcast, already met here in october 2020. This sample shows a 334-bit period with interesting preambles consisting of a repeated pattern followed by a "counter/progressive" binary field.

 

 https://disk.yandex.com/d/3wTfrevGpVvJ9A

250Bd/500 FSK embedded channels, likely Ukr nets

Three 250Bd/500 FSK "embedded" channels, 1000 Hz spaced, spotted on 6775.0 KHz (CF) and originating north of Rivne, Ukraine; probably trials or experimental transmissions.

Fig. 1

 It's to notice that the 105-bit streams share the same 43-bit preamble/sequence:

00111111111111011110001011000110011001101110
00111111111111011110001011000110011001101110
00111111111111011110001011000110011001101110

Fig. 2

My friend cryptomaster informed me that he too listened to a similar signal (3 x 250Bd/500 FSK), but spacing between channels was 500 Hz); his analysis can be read here:
http://www.radioscanner.ru/forum/topic36750-202.html#msg1463633

https://yadi.sk/d/gQhScJMvESFlIg

MFSK-4with mixed offsets mode (likely Ukr nets)

Some days ago my friend Mike (mco) sent me an interesting record about a seeming MFSK-4 signal (fig. 1) originating north of Rivne, Ukraine; such (duplex) transmissions are frequently heard on 13873.55, 15833.55, 15863.55, 16354.55, 17412.55, 17442.55 & 17469.55 KHz (Rivne TX).

Fig. 1

This sample I think it's a  combined mode in which the used offsets and speeds are: -1200 -400 +400 +1200 400Bd, -750 -250 +250 +750 250Bd, and -600 -200 +200 +600 200Bd; anyway, it's to be noticed a change of the center frequency between the first and the second mode (Figs 2,3).

Fig. 2

Fig. 3

"They use a wide range of frequencies and I've not noted all of them. This list seems ok but it certainly include Main stn freqs and also side B stations ones and some are missing. They are working full duplex with abroad stations according to multiple TDoAs. So far I've seen them using MFSK-4 with 50/100 80/160 100/200 125/250 160/320 200/400 250/500 400/800 500/1000 settings" my friend Linkz say.

Fig. 4 - TDoA Tx site (thanks to Mike)

https://yadi.sk/d/WQrHjOlxMkH48A
[1] http://resources.rohde-schwarz-usa.com/c/manual-of-transmissi-2

FSK two channels in F7B mode, likely an UKR-Net

On 13960.0 KHz I tuned  an apparently MFSK-4 100Bd/1000 transmission spreading about 3000Hz bandwidth: tones at -1500, -500, +500, +1500. After emails exchange with friends, "cryptomaster" from radioscanner suggested that the signal is a F7B mode actively used by Ukrainian Nets. Usually, the two channels transfer T-207 ciphered data. He also warned me that SA program parses these transmissions as classic MFSK-4 therefore the received result doesn't correspond to the truth. Another F7B signal, this one from Ukrainian Mil, was reported here some times ago.

Fig. 1

Fig. 2

The F7B transmission mode deals with signals consisting of two independent, but synchronous channels carrying teletype signals. Modulation used is MFSK-4 (more precisely, FSK2 on 2 independent channels).

The equipment BUK-2D, for example, is one of the equipments used to filter and separate the two channels (thanks to 'cryptomaster').

Fig. 3 - BUK-2D equipment

https://yadi.sk/d/f2PpWmdi3UTaqG

MFSK-4 (double FSK) 96/100Bd 500Hz, Ukraine Military

This waveform is known as Double FSK 96/100 Baud and 500 Hz shift, a dual channel  mode used by Ukraine Military, spreading about a 1730Hz bandwidth and tones at -750, -250, +250 and + 750 Hz. Actually, there are two versions of this waveform:

96Bd-100Bd/500 heard on August 21th on 8008 KHz/usb (likely F7W mode?)
96Bd/500 heard on December 3rd on 6968 KHz/usb (F7B mode)

Site radioscanner.ru reports the first signal (08/21) as Ukraine Mil 96-100, the two baudrates indication (96 and 100) is due to some difficulties  in determining the speed of manipulation, due to the fact that the two transmission channels are not synchronized  with each other. The "double" speed is not present in the measurement results of the first signal (12/03): most likely the two channels are in sync and transmitted according to the F7B mode.

Fig. 1

Fig. 2

96Bd-100Bd/500 waveform (likely F7W mode?)
https://yadi.sk/d/SvmC1_ajzVzAAw

96Bd/500 waveform (F7B mode)
https://yadi.sk/d/VHJYHLgg7ATdeA