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GRU R-397 LK → ← IRTYSH
Spy radio transmitter
R-397-OK (Russian: P-397), codenamed OKOLSH (Russian: ОКОЛЫШ),
was a transistorised short wave (SW) spy radio transmitter,
used from 1975 onwards in counter-intelligence operations
by the Russian military intelligence service GRU,
and by the Russian special forces - the Spetsnaz.
It is part of the IRTYSH (Russian: ИРТЫШ)
radio system, which is highly resilient against jamming.
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The transmitter measures 200 x 120 x 55 mm and weighs 1200 grams.
It covers the short wave radio band from 2.5 to 20 MHz, and has a range
of approx. 1500 km, using just 1 Watt of power. It has a built-in
digital memory (RAM) that can hold up to 20 groups of 5 characters.
To make it resistant against jamming, a relatively high
bandwidth is used and a low data transfer rate of just 5 baud. 1
This means that to send a long 20-group message,
the transmitter would be on the
air for more than 3 minutes, making it vulnerable to
radio direction finding (RDF).
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Apparently, data integrity and resilience against
jamming were more important than the risk of being detected and located.
This is the opposite of what a burst encoder
does in most other spy radio sets: reduce the risk
of detection by sending the message at very high speed, at the cost
of data integrity.
The R-397-OK was commonly used in combination with
the R-394-LK receiver.
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5 baud = 6 groups/minute. Each group consists of 5 characters.
Each character consists of 10 bits.
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PLEASE HELP —
At present we have no further information about the R-397-OK or about
any other part of the IRTISH communication system. If you have additional
information that you can share, please help us to expand and improve
this page. We are looking in particular for circuit diagrams, manuals
and photographs (and stories) about the use of the device in practice.
We are also looking for a complete R-397-LK receiver.
➤ Contact us
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IRTYSH communication system
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The R-397-OK was part of the IRTYSH radio system,
which is shown in the diagram below. The transmitter was part of a
radio link between the base station — the Centre – and the agent
in the field — the Correspondent.
The R-397-OK (OKOLSH) transmitter is shown in blue at the top left.
Most components of the IRTYSH radio system have a model number
that starts with R-397, followed by a two-letter suffix that determines the
actual device. The first letter of the suffix indicates the name of the device
(e.g. 'O' = OKOLSH), whilst the
second letter tells us at which end of the radio link the equipment was used —
field (agent) or base station (centre).
➤ More about IRTYSH
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Device Digital spy radio transmitter Purpose Low-power high-confidence agent communication Model R-397-OK (Р-397-ОК) Codename OKOLSH (ОКОЛЫШ) Country Soviet Union (USSR) Year 1975 Users GRU, Spetsnaz Principle Digital Frequency 2.5 - 20 MHz in 10 kHz steps Modulation MFSK 5ЦТ-20 Deviation 4 kHz Output 1 to 1.8 W Range 1500 km Memory 20 groups 1 Data rate 6 groups per minute 1 Bit rate 5 baud Power Battery, 12.8V, 0.8A (external) Battery 10НКГЦ–1Д Temperature -10 to +45°C Dimensions 202 x 122 x 62 mm Weight 1.3 kg (3 kg with accessories)
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1 group consists of 5 characters.
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This website was no longer available in 2024.
Data retrieved via WayBack machine.
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© Crypto Museum. Created: Sunday 14 February 2021. Last changed: Wednesday, 05 November 2025 - 12:10 CET.
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