Nokia msg terminal + Tadiran HF equipment

Transmission picked up some days ago by my friend AngazU using the SM2BYC Kiwi sdr. The signal is composed of an initial tone followed by a preamble consisting of F7B modulation (apparently MFSK-4) and two simultaneous FSK modulations (Fig. 1). As suggest by cryptomaster and KarapuZ, this is an interesting example of a Nokia Adaptive MSG Terminal which is used along with a Tadiran HF equipment that presumably provides an active noise cancellation feature (Tadiran DCS, Digital-Coded Squelch).

Fig. 1 - waveforms

The upper FSK 125Bd/290 delivers the same 84-bit pattern and it's interesting to note that the last 84-bit sequence is sent in opposite polarity:  perhaps signalling the last group/block of data (sent in the lower FSK).  The same parameters (FSK and 84-bit pattern length) has been discussed here in radioscanner:

http://www.radioscanner.ru/forum/topic39959-69.html#msg1080112

Although, of course, we can be wrong because a specific description of this function was not found TADIRAN HF modems.

The lower FSK 300Bd/780, after the initial 1-0 sync sequence pattern, delivers data and seems to have a 16-bit period. After differential demodulation the stream exhibits 8 solid bits columns in a 16-bit period and once removed the stream does not have a clearly defined period (Fig. 2).

Fig. 2 - bitstreams

Cryptomaster is inclined to the Machester modulation but I get errors in both the phase conventions (G.E.Thomas and IEEE 802), and he pointed me that the signal has a constant preamble whicH is not coded using Manchester (Fig. 3) and causes mistakes in decoding.

Fig. 3

As for as I can see, the same F7B + FSK125Bd structure is sent first but without the lower FSK300Bd (Fig. 4). The patterns are the same in the two FSK125Bd streams, perhaps it is used to initialize the (supposed) Tadiran noise blanker function?

Fig.4

Nokia M/90 (Panasonic CF-U1): FSK 301-151Bd 780Hz shift

I reported Nokia M/90 / Panasonic CF-U1 301-401Bd/780Hz in this post, this time I copied the 301-151Bd waveform on 10737.7 KHz (cf) around 1235 UTC. In this sample the initial 301Bd burst seems to be used with a different functionality (fig. 1).
Sanomalaite M/90 (SANLA) (Literally "Message device M/90") is a digital, portable and encrypted text-based communications device developed by Nokia and used by all branches of Finnish Defence Forces. From 2013 onward, these devices are being replaced with Panasonic CF-U1 Toughbook.

Fig. 1

Note that also in this case, the preamble is always modulated at 301Bd (fig. 2).

Fig. 2

For what concerns the characteristics of the demodulated stream, refer to the mentioned post.

https://yadi.sk/d/DhKXi9ga3NLzFg 

Nokia M/90 (Panasonic CF-U1): FSK 301-401Bd 780Hz shift

This is an interesting copy of FSK-2 transmissions in dual 401 (401.5) and 301 Baud mode, both running with constant 780 Hz shift and heard on 10225.0 KHz/USB (offset = 1700 Hz) at 0605 UTC.  This waveform was originally used in Nokia Adaptive MSG-Terminal "Sanomalaite M/90" [1] used by all branches of Finnish Defence Forces but from 2013 onward,  these devices are being replaced with Panasonic CF-U1 Toughbook tablet computers [2].

Fig. 1

The three transmissions resemble a PtP ARQ system where the caller station use the 401Bd mode to send data and the called station use the 301 Bd mode for ACKs, also note that in the second transmission the 401Bd frame is sent without the preamble: maybe it is a segment which belongs to the first transmission. However, during that same recording the 401Bd mode has been used also as stand-alone (Fig. 2).

Fig. 2

Just the preamble is probably the "business card" of this waveform: talking with my friend KarapuZ about this device, he pointed the fact that the preamble it's always modulated at a speed of 301 Baud.  Indeed, at a first glance the speed seem to be constant in the two modes: 401 and 301 Baud (Fig. 3)

Fig. 3

but trying to demodulate the 401Bd signal it's possible notice some distorsions in the preamble which are not present when the stream is forced to 301 Baud (Fig. 4)

Fig. 4

These distorsions are not present in the case of the 301Bd signal (Fig. 5)

Fig. 5

In order to prove this characteristic, KarapuZ sent me a recording of the Nokia M/90 running at 151 (150.5) Bd and also in this case it's possibile notice that same behavior in the preamble (Figs. 6,7)

Fig. 6

Fig. 7

KarapuZ also suggested to demodulate the 151Bd signal using the differential decoding: after the removal of the synchronization bits (vertical solid columns in the 4-bit period stream) and inverting the polarity, a period of 8 bits with 1 stop bit is obtained.  (Fig. 8). Next, it's difficult to state how to process the information, as a rule, such terminals use off-line encryption. Since the removal of 2 bits of four, the data signaling rate is 150/2 = 75 bps.

Fig. 8

https://yadi.sk/d/htVJdKCj3G5aHc
https://yadi.sk/d/QP1c4nli3G5afh

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[1] http://www.radioscanner.ru/forum/topic39959-51.html
[2] https://en.wikipedia.org/wiki/Sanomalaite_M/90