22 September 2021

19.5Bd/100 FSK: Rus R-397 “IRTYSH” (“ИРТЫШ”)

About one years ago (may 2020) I came across a short 19.5Bd/100 FSK [1] which, at that time, I chalked up to a some Russian-Mil network. Well, an anonymous reader of the blog, whom I thank, left a link about it [2], without further comments or suggestions: the link refers to an interesting topic posted on the airbase.ru forum about the HF R-397LK receiver - "Lapis" (Р- 397ЛК "Ляпис") used by the Navy Special Forces and - likely - not only by the Navy or by Russian forces. 
The translation from Russian is shown below. 

The R-397 LK radio receiver is intended for tuningless and search-free communication with discrete frequency setting in the short-wave range and provides reception and registration of call commands with visual and sound indication in the memory device, as well as auditory reception of messages by Morse code in the RT and AT modes. The radio receiver provides the following modes:
- Auditory reception of telegraph signals with amplitude modulation (AT)
- Auditory reception of telegraph signals with frequency modulation (FM)
- Continuous reception of commands by signals of RF at a rate of 19.53 baud (CALL CONTINUOUS.)
- Reception of commands by signals of RF at a rate of 19.53 baud with periodic switching on and off of the radio receiver power (CALL CYCLE) 

Fig. 1 - 19.5Bd/100 FSK (R-397 OK)

The “IRTYSH” (“ИРТЫШ”) equipment is designed to provide h24, noise-resistant short-wave special radio communication for the purpose of transmitting short messages with up to 50 digital groups and calls and providing auditory telegraph communication.

R-397 OK - special radio transmitter "OKOLYSH"
R-397 LK - special radio receiver "LYAPIS"
R-397 KC - a set of center equipment "KEDON" as part of the R-160P radio receiver, R-397 OTs demodulator and BPA
R-397 OTs - special demodulator "DEER" included in the set of center equipment "KEDON"
Р-397 LC - the generator of calling commands "LUMEN"
BPA - start-stop telegraph apparatus operating with the MTK-2 code

Conventionally, the radio line "IRTYSH" can be divided into two functionally independent directions:
radio link "OKOLYSH" - "KEDON"
radio link "LYUMEN" - "LYAPIS"
Radio direction "OKOLYSH" - "KEDON" works only for the transmission of information with a special broadband low-energy signal from the correspondent to the Center. The radio direction "LYUMEN" - "LYAPIS" provides an urgent call for communication with a source of intelligence or special intelligence at any time and the transfer of information by auditory telegraph from the Center. Thus, it seems I heard just a short transmission in the Lyumen-Lyapis mode, maybe the R-397 OK2 was the used device.

[1] https://yadi.sk/d/z-4ImVGLytR0rQ
[2] http://forums.airbase.ru/2008/10/t62176_10--spetsnaz-vmf.html
[3] https://sdamzavas.net/4-35296.html 

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