CIS-60 30Bd, π/2-DBPSK

this CIS OFDM 60-tone modem, probably also it belonging to the CIS HDR family, was heard on 29 September at 0600z on 14259.0 KHz on USB. It exhibits a rather intriguing waveform:

1) manipulation speed is 30Bd and channel step 44.4Hz (Pic. 1), values are reasonably approximated since the signal was not sampled at its native frequency (look at "k" parameters);

Pic. 1

2) modulation format is DBPSK with these features: 

a) a service-tone (w/out modulation) is sent each 3 symbols in all (!) the carriers

b) 24 tones (say black-carriers) have π/2-DBPSK (Pic. 2);

c) 24 tones (say blue-carriers) have the same π/2-DBPSK modulation but with the evidence of the service tone (Pc. 3);

d) 12 tones (say red-carriers) have regular DBPSK (Pic. 4).

Pic. 2 - 24 (black) carriers: π/2-DBPSK

Pic. 3 - 24 (blue) carriers: π/2-DBPSK and service-tone

Pic. 4 -  12 (red) carriers: DBPSK

Pic.5 - phase angles in black/blue and red carriers

By writing the 60 coloured carriers in a 10x6 array, it's interesting to note that they are are arranged in a sort of diagonals format (Pic. 6):

Pic. 6 - carriers arrangement

About the ACF value, it is 200 ms, that makes 6 symbols although the real measure is 202.3 (Pic. 7) ms but you must consider that the signal is not perfectly in-frequency: infact the measured baudrate is not the expected 30.0 Bd but rather 29.9 Bd. Anyway, calculating the mathematical proportion:

(symbols-per-second : 1000) = (symbols : ACF)
(29.9 : 1000) = (x : 202.3) ; x = 6.04 

you get 6.04 symbols per frame. Then, given the exact 30Bd baudrate, I think the real ACF is 200. A further evidence in this direction is that just each 6 symbols the service-tone occupies the same position (Pic. 8).

Pic. 7 - 6 symbols ACF (200 ms)

Pic. 8 - each 6 symbols causes 200 ms ACF

CISwitching...

September, 30 at 0711z on 15812.0 KHz on USB: on-the-fly switch from CIS-45 to CIS-60, both belonging to HDR (High Data Rate) family modem. Maybe tests or fast (auto) adatpion to the channel conditions ?

a CIS-20 variant (37.5Bd, 60Hz)

the so-called CIS-20, in its standard format, is an OFDM 20-tone waveform characterised by π/4-DQPSK modulation at 75 symbols per second and 120Hz channel separation, as described here. CIS-20 is supposed to be the successor of CIS-12.
This variant exhibits the same modulation format but speed and channel separation are exactly the half of the ones of the standard version, i.e. 37.5Bd and 60Hz channel step. The signal bandwidth is unchanged (~2800Hz).

CIS-20 variant - OFDM parameters

CIS-20 single channel analysis

Note, once again, the differences between PSK-8 and π/4-DQPSK constellations (in absolute and relative mode, Diff=0 and Diff=1):

in a real PSK-8 the paths cross the origin of axis

VEZHA-S (ВЕЖА-С), Russian Telegraph

This is a very old Russian telegraph system carrying information possibly for radio check of lines or for other (uknown) purposes. I could not find news about this signal and Russian monitors too do not have detailed informations about it; asking Karapuz and digging radioscanner forum I found the same signal than mine, and then its name "VEZHA-C" (ВЕЖА-С)[1].

The transmission was heard (and monitored for tens of minutes) at 0725z on 12165.0 KHz cf on September 22, and it did not change its format, sending the same "train" of bits and sometimes something like a "sync" signal . My measurements match the ones obtained by the Russian friends: baudrate 100Bd and 500 Hz frequency shift, frame is 162 bits and the the length of the codeword could be 6 bits. It's interesting to notice that - looking at the spectrum as at a Morse code -  the points are exactly 3 times shorter than the dashes.

[1] http://www.radioscanner.ru/forum/topic29556.html

CIS-48 probe/marker signal

heard today on 17289.0 KHz on USB (on May 21 also, but on 17234.0 KHz there) from 1140z, this is the so-called 'CIS-48 probe/marker of channel' signal, according as defined here in radioscanner forum. 
The probes are sent every ~16 Sec - at least in this sample - in quite long sessions w/out any other signal during the monitored time (more than 1 hour) and consist of 4 x DPSK 50 baud modulated tones, located at 500 Hz, 1250 Hz, 1750 Hz, 2500 Hz and spaced by 750, 500 and 750 Hz, bandwidth is 2000 Hz. A short recording is available.