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R-394KM   Strizh - Стриж
USSR spy radio set - Swift Mark III

The R-394KM was the last Russian spy radio set for HF, before the fall of the Iron Curtain in 1989. It was developed in the USSR in the early 1980s and was used during the final stages of the Cold War by the Warsaw Pact countries. The device is the successor to the short-lived R-394K and features a digital messaging system as well as a digital frequency readout. It was used by agents abroad as well as by Special Forces and was available with Russian or English text on its front panel. The spy version of this set is known by its Russian code name Strizh (English: Swift).

The complete radio, except for the batteries, is housed in a small water-tight case that can be carried on the back. For that, the rear of the radio is padded with some soft material. A canvas pocket, mounted at the right side, contains the antenna and counterpoise wires.

The interior of the case is painted in the usual grey hammerite, whilst the exterior of the case is in the common Russian army sand colour. The lid contains a screwdriver and a small work light that can be inserted into a socket at the top edge of the radio, to the right of the fuse.
  

In older versions of this radio, some additional accessories, such as the headphones, are also stored inside the top lid. In the version shown here (built in July 1988), these accessories are supplied separately. The radio is completely mounted inside the carrying case, and consists of 4 major blocks. From left to right: the spare parts storage compartment, the receiver (RX), the digital storage unit (DSU) and the transmitter (TX). It is shown here with translated inscriptions:


The spares compartment contains some lamps, fuses, etc. (see below for a full description). The receiver (RX) and transmitter (TX) are pretty straight forward in operation, but the Digital Storage Unit (DSU) is slightly more complex. TX and RX frequencies can be set individually from the DSU. Any pre-coded messages are stored in the DSU's memory and can be transmitted at will.

Three displays are present at the center of the DSU: one for displaying the coded message (in groups of 5 digits), one for the RX frequency and one for the TX frequency. The currently set frequencies can be checked by pressing the corresponding CHECK key (K). The CLEAR button (C) is used to clear the display prior to entering a new setting. Please note that RX and TX each have their own CLEAR and CHECK buttons. For a detailed description, look here.

Just above the displays is a table with frequency ranges and the corresponding settings for the RX preselector and the TX antenna matcher. Fine tuning is done separately by following the procedure described in the user manual. The table also specifies the required length of the wire antenna and the counterpoise wire. A suitable antenna is supplied with the kit. For more details about this radio, please refer to the page about the spy version known as Strizh.

 More about Strizh (the spy-version)

Wooden transit case Contents of the wooden box The closed (water-tight) case The padded back of the radio Full radio with opened lid Control panel of the R-394KM Shown with the work light in place Manual operation of the morse key

Transmitter
The radio operated on the HF band, covering all frequencies between 1.5 and 13.5 MHz. The transmitter (TX) is mounted to the right of the Digital Storage Unit (DSU). It is synthesizer controlled and produces an HF output of 10W (CW only). The TX frequency is set in the rightmost display of the DSU. In order to obtain maximum TX output, the antenna matcher on the TX-unit should be set appropriately for the selected frequency. A fine control is used, in combination with a meter at the top right (and an antenna current light), to adjust for maximum antenna current.

At the bottom right is a built-in morse key that can be used to send messages manually. To the right of the morse key is a small oval lid that is held in place by two bolts. It gives access to a 9V battery that is used to retain the messages in the memory of the Digital Storage Unit (DSU).

The image on the right shows the battery compartment after removing the lid. The holder accepts a cylindrical Acacia battery (Russian: Акация), which is actually a stack of 6 circular 1.5V cells. Without this battery the memory of the DSU will be cleared when the radio is off.
  
Memory battery compartment

With the battery in place, the contents of the DSU's memory will be retained, as slong as the MEMORY selector is set to STORE, even when the set is switched off. The memory can be cleared by turning the set off and placing the memory selector in the OFF position. Wait a few seconds before turning it on again. The OFF-position can only be engaged when pressing the small metal button (to the left of the MEMORY selector) simultaneously.

Memory battery compartment Memory battery compartment Looking inside the battery compartment. The pertinax clip allows a standard 9V battery to be used.

Receiver
The receiver (RX) is mounted to the left of the DSU. It is also synthesizer operated and covers the same range as the transmitter. It is a double-superheterodyne receiver with intermediate frequencies of 40.5 MHz and 500 kHz. The RX frequency is set in the middle display on the DSU and can be adjusted in steps of 1 kHz. A 4-position pre-selector is used to select the appropriate frequency range.

Digital Storage Unit
The middle section of the radio set is also the largest. It contains the so-called Digital Storage Unit (DSU) that consists of a synthesized transceiver and a digital burst encoder. Control of these two functions is more or less integrated, in that they share the same numerical keypad.

Antenna
The antenna should be connected to the transmitter. Usually a long-wire antenna is used with sufficient counterpoise. The counterpoise is connected to the topmost connector. Like most Russian spy radio sets of this era, the receiver only performs satisfactory when a decent counterpoise is used. The manual describes how to setup the supplied antenna for use with this radio. One end could be tied to, say, a tree, whilst the other end is held high with a light-weight telescopic fibre mast.

Power Supply
Power is supplied by a battery belt that was usually supplied with the set. It is also possible to connect any other 12V source to the radio, via the 4-way connector on its front panel. A short cable is supplied to connect the R-394KM to an ordinary car battery. According to [1] the R-394KM was powered by an internal battery. Although this was quite likely, as the earlier R-394K also had an internal 12V battery, no evidence for this has been found to date.

Theoretically, a battery might be fitted in the leftmost compartment (normally used for spares), but in none of the R-394KMs we have seen so far, was there a power connection present in that compartment. Nevertheless it might have been present on earlier models, or it might have been used with an external cable. There are also reports of an R-394KM that was found completely intact in a field in Germany in the late 2000s. According to eye witness accounts, the radio had a built-in battery that was still fully charged when it was found [3]. This story might be related to the Strizh, the spy-version of the R-394KM.

Accessories
A new R-394KM radio station was supplied in a wooden box, complete with a set of accessories and manuals. Apart from the radio, the box contained batteries, a battery charger, a hand-operated power generator, antenna, telescopic mast, etc. The wooden box was of rather poor quality and was only used for storing the equipment in military depots until needed.

Some of the supplied items are described in more detail below.
  

Battery belt
By default, the radio is powered from a set of batteries, mounted together in a canvas belt with suitable webbing. The belt consists of two sets of five cells each (one set on either side). As each cell produces 1.2V, the total voltage delivered by the belt is 12V.

The battery belt can be charged with any 13.5V power source, such as the mains battery charger below.
  

The battery belt as packed in the wooden transit case Close-up of the packed belt A typical view of the battery belt Opening the belt The cells inside the belt Close-up of the cells Spare battery cells Battery fluid pippet

Battery charger
The above battery belt can be recharged with the mains power supply unit shown here. The PSU is suitable for connection to either 220V (as depicted here) or 110V mains networks. The mains plug is stored inside the top lid.

The charger can be connected to the battery belt by using the supplied 4-pin Power cable (see further down).
  

The closed battery charger The battery charger with opened lid Close-up of the control panel The mains cable stored inside the lid

Hand-operated generator
If no mains power is available, the battery can also be charged using a small crank-operated power generator. Charging the batteries is not an easy task and takes several hours, for just a few minutes of operation.

The generator is normally stored inside a carrying case with a canvas strap. The connection cables are stored inside the top lid of the case. New generators were generally supplied in grease paper, stored inside in a green wooden box, together with a checklist and instructions.
  

Generator in closed storage cage Generator storage case with opened lid The generator with retracted crank The generator with the crank folded out

Power cable
This cable should be used to connect the R-394KM to a suitable power source such as the 12V battery belt (see above). The cable is about 1 meter long and has a standard 4-female plug at one end and a matching male connector at the other end.   

External battery cable
This cable is used to connect the R-394KM directly to an external power source, such as a car battery.

One end of the cable contains the standard 4-pin female power plug that goes straight into the power socket of the radio. The other end of the cable contains two clamps. The red wire is the positive (+) terminal and the blue wire is the negative (-) one.
  

Headset
Almost any type of headset can be used with the R-394KM. In most cases, a common USSR military headset was supplied, with rubber ear pads and elastic head bands. Such headsets are commonly used with military radio sets in tanks etc. Headsets are connected to the two-pin socket on the left of the front panel of the radio.   

Antenna
The antenna is usually stored inside a cavas packet to the right of the radio. Depending on the way the radio is used, a second antenna might be needed as a counterpoise. The second antenna (see the images below) can be stored in the same pocket.   

Antenna mast
In order to setup the antenna as required, a light-weight telescopic glass fibre mast is supplied. It allows the antenna wire to be mounted free from obstacles and the earth. A ground pin is supplied to prevent the mast from sliding away.

The mast and the ground pin are stored inside a canvas bag that can be strapped to the radio or the canvas raincoat (see below).
  

Canvas raincoat
The radio is already painted in the usual Russian 'sand colour' camouflage tint and has suitable padding at the bottom to allow the radio to be carried on the back of the radio operator.

The lid of the unit is firmly closed with clamps and a gasket, to protect the radio against dirt and water. Further camouflage is possible by fitting the canvas raincoat shown on the right.
  

Power cable External battery cable Headset Antenna Extra antenna The packed mast Telescopic antenna mast Canvas raincoat

Spare parts
A set of spare parts is supplied with each R-394KM radio station. Usually, these spares are stored in the special spares compartment of the radio itself, hidden behind the leftmost panel.

The spares compartments contains a variety of fuses, lamps, bolts, etc. as detailed in the checklist.
  

The lid of the spares compartment partly removed The spares

Manuals
A complete R-394KM radio station comes with an an extensive set of documents that are usually stored inside the large wooden storage box. The documents include the operator's manual and full circuit diagrams of the analog and digital parts. Some of the books are marked 'Secret'.

The following documents were supplied:
  • Checklist
  • R-394KM Operating Manual
  • R-394KM Technical Description (analog)
  • R-394KM Technical Description (digital)
  • R-394KM Maintenance Book
  • Battery Technical Instructions (2x)
  • Battery Maintenance Book (2x)
Below are some close-ups of the various books and the checklist. Two of the black books are marked 'Secret' in the top right corner.
  

Connections
Power supply
  1. n.c.
  2. n.c.
  3. 0V
  4. 12V
Expansion connector
A 10-pin expansion connector is present at the center of the DSU, between the MEMORY and MODE selectors. This socket is sometimes protected by a black plastic cap and is intended for the connection of additional equipment such as an external morse keyer. It allows the transceiver to be partly remote-controlled by the external device. The connector has the following pin-out:

pinout of the 10-pin expansion socket, when looking into the socket.

An external key can be connected between KEY and GND. Please note that the radio has two KEY inputs: one used for AM (amplitude modulation) and one for PM (phase modulation). Also note that the pin-out of this socket is different from the same socket on the earlier R-394K radio. Connecting an accessory that was designed for one radio may cause permanent damage when being connected to the wrong radio. So, be careful when connecting an external device here!

  1. This contact is NOT wired on most R-394KM/Strizh units. When wired, it provides a clock signal for an external keyer. In A2 mode, the clock signal is 100 Hz. In F1 mode it is 250 Hz.

Documentation
  1. Radio Station R-394KM Technical Description and Operating Instructions
    Full circuit description, block diagrams and wiring diagram (Russian).
    IV1.106 007 TO. 1988. SECRET. Serial number 10.
     Drawings and diagrams for this manual

  2. Radio Station R-394KM Technical Description and Operating Instructions. Appendix.
    Components list and circuit diagrams (Russian).
    IV1.106 007 TO1. 1988.

  3. Block NMU (Russian: Блок НМУ) Technical Description
    Circuit description and diagrams of the burst encoder (Russian).
    2.082.046 TO. 1988. SECRET. Serial number: 31.
References
  1. Louis Meulstee, R-394KM
    Wireless for the Warrier. Volume 4. September 2004. ISBN 0952063-36-0.

  2. R-394KM Operating Instructions and Technical Description
    Original documentation supplied with the R-394KM. See above [A].

  3. Anonymous source, Eye witness account of R-394KM found in Germany
    Interview with Crypto Museum, 2009.
Further information
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Crypto Museum. Created: Monday 28 December 2009. Last changed: Sunday, 02 October 2016 - 09:10 CET.
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