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Kaira   Кайра
Covert two-way VHF radio · USSR

Kaira (Russian: Кайра) 1 is a body-wearable covert radio, developed in the USSR in the 1980s. It was used by the MKV 2 and by the KGB for covert operations, surveillance and observations. It has a wire antenna that can be hidden under the operative's clothing, and operates in the 150 MHz band (2 meter). An optional voice scrambler adds a limited level of speech security to the radio.

The radio is housed in a curved enclosure that was shaped in such a way that it could easily be carried on the body of an operative, concealed under the clothing. All connections are at the top of the device and all controls are on a hand­held remote control unit that is at the end of a cable that runs through the sleeve of the user's coat.

The handheld remote control unit also acts as the microphone/speaker, but some units came with a small external speaker that can be hidden under the collar of the coat. It was attached to the clothing by means of a safety pin at the rear.
  
Kaira covert radio

Although it was possible to connect a vertical antenna, most Kaira units came with a special wire antenna that had several safety pins along its length, allowing it to be concealed under the operative's clothing. The radio is powered by a 7.2V battery back, that is installed from the top.

When used by the KGB and other secret services, Kaira was often issued with an (optional) speech scrambler, that protected the communication against the occasional eavesdropper. Contrary to popular believe though, this scrambler is not built-in, but is an optional external add-on [5].

  1. Кайра (Kaira) is Russian for Guillemo. Kaira is sometimes written as Kajra or Kayra.
  2. MKV = Ministry of Internal Affairs of the Soviet Union (USSR). This includes the military police, regular public safety police, traffic police (GAI), customs and interior troups (VV). Often confused with the KGB.

Compete Kaira set Kaira body Kaira body, seen from the rear Wire antenna Remote control with microphone and speaker Microphone/speaker Two batteries Operating the PTT
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Compete Kaira set
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Kaira body
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Kaira body, seen from the rear
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Wire antenna
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Remote control with microphone and speaker
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Microphone/speaker
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Two batteries
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Operating the PTT

Features
The diagram below gives an overview of the components that were part of the Kaira radio station. At the centre is the actual radio body, which has a curved shape so that it can be carried on the body more easily. It is shown here with a battery installed. At the left is the wire antenna, that was concealed under the clothing, using safety pins to attach it to the clothing at various places.


At the right is the handheld controller, of which various designs were available. The one shown here has an external microphone/speaker, which is visible at the bottom left, but there was also a model with a built-in microphone/speaker. The external speaker has a safety-pin at the rear, so that it can be attached below the collar of a coat. The controller was usually carried in the hand, with the flexible cable running through the sleeve of the coat. This allows the user to control the push-to-talk (PTT) switch and adjust the volume, without this being visible to a bystander.

The radio works in the 2-meter radio band, between 152 and 172 MHz, and was usually populated with crystals for two channels. Switching between the two channels is done with the recessed switch at the bottom of the unit. The channel was never changed during an operation.

Compete Kaira set Kaira covert radio Kaira covert radio Kaira covert radio Two types of controls. The one on the left has a built-in microphone/speaker Alternative control unit with built-in microphone/speaker Kaira covert radio Kaira covert radio
kaira top panel Accessory socket Battery slot Accessory plug at the end of the cable of the remote control Accessory socket Kaira and Kaira-M1 Case screw and channel selector at the bottom Channel selector (1/2) at the bottom
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Compete Kaira set
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Kaira covert radio
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Kaira covert radio
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Kaira covert radio
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Two types of controls. The one on the left has a built-in microphone/speaker
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Alternative control unit with built-in microphone/speaker
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Kaira covert radio
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Kaira covert radio
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kaira top panel
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Accessory socket
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Battery slot
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Accessory plug at the end of the cable of the remote control
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Accessory socket
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Kaira and Kaira-M1
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Case screw and channel selector at the bottom
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Channel selector (1/2) at the bottom

Models
As far as we know there were two Kaira models, but the differences are currently unknown. The following models are known:

  • Kaira
    This is the basic Kaira model that was introduced in the 1980s. It was available with three different types of controller, of which two models are featured in this page. It is believed that the Kaira shown here, is the basic model.

  • Kaira-M1
    This was a slightly modified version of the radio, but the exact differences are currently unknown. It is possible that the only difference was the simplified antenna socket, as shown in this image.

Parts
Remote control unit External concealable speaker Rechargeable battery pack Concealable wire antenna Vertical  wave antenna Optional (external) speech scrambler Cloth body harness
Remote control unit
All functions of the radio are controlled with the externally connected remote control unit, or controller. It is shaped in such a way that it nicely fits inside the hand. It is connected to the radio by means of a 1 metre flexible cable, that is usually guided through the sleeve of the coat.

The controller holds the push-to-talk switch (PTT), the volume adjustment, and a switch to select silent operation. Some versions of the controller had a built-in microphone rather than an external one.

  
Operating the PTT

Microphone/speaker   PDM-1
For covert use, the radio was usually supplied with a concealable microphone/speaker, such as the PDM-1 model shown in the image on the right. It has a safety pin at the rear, so that it can be attached to the clothing, for example under the collar of a coat.

When a controller with built-in speaker was used, the external speaker was omitted.

  
Microphone/speaker

Battery pack
The radio is powered by six rechargeable 1.2V AA-size NiCd battery cells, that are housed in the long rectangular battery packet shown in the image on the right. It should be installed in the battery slot at the top of the Kaira radio, and does not go all the way in. About 2 cm of the battery pack will be sticking out from the top.

Kaira uses the same batteries as Chaika. It is currently unknown how they were charged, but this was probably done with an external battery charger. Spare battery packs must have been available to power the radio in the meantime.

  
Battery pack

Covert antenna
For the best performance, the radio should be used with a vertical antenna, that can freely radiate in all directions. When concealing the radio on the body however, this is not possible.

For such situations, the wire antenna shown in the image on the right is used as a compromise. It decreases the performance of the radio, but has the advantage to be completely invisible. The wire has safety pins at various points, so that it can be easily attached to the clothing.

  
Wire antenna

Vertical ¼λ antenna
In non-covert (i.e. overt) situations – such as common police surveillance – where good performance was important, a straight vertical ¼λ antenna could be fitted to the radio.

The antenna is shown in the image on the right. It consists of two pieces: a flexible part in a rubber sleeve, and a shorter thin piece that can be mounted on top. The antenna shown here can only be fitted to the Kaira-M1.

  
Flexible 1/4 lambda antenna

Speech scrambler   wanted item
To add some level of voice security, an optional speech scrambler could be installed externally. It was connected between the handset (controller) and the 16-pin socket on top of the radio. The image on the right shows an original Kaira Voice Scrambler, as it is held in the collection of the KGB Spy Museum in Lithuania [5].

It is implemented as a simple frequency inverter, that was only intended for protection against an occasional or accidental eavesdropper. It offers no protection against a professional interceptor, as speech scramblers in general are insecure.

 More about speech scramblers

  
Optional speech scrambler. Photograph kindly supplied by KGB Spy Museum [5].

Body harness   wanted item
For covert operations, a special cloth body harness was usually supplied with the radio. It allowed the radio to be carried inconspicuously under the operative's clothing. The radio is fitted inside one of the pockets of the harness, as shown in the image on the right [5].

The image also shows the optional external speech scrambler, which is described above. Both the harness and the scrambler are currently missing from our collection. If you have spare items, please contact us.
  
Cloth harness with Kaira radio and optional speech scrambler. Photograph kindly supplied by KGB Spy Museum [5].

Controller - front Operating the PTT Volume setting and slide switch Setting the volume level Microphone/speaker Safety pin at the rear Two batteries Battery pack
Installing the battery pack Battery pack locked in place Wire antenna Antenna detail Antenna plug Safety pins for mounting the antenna Safety pin at the end of the wire antenna Kaira with 1/4 lambda vertical antenna
With vertical antenna With vertical antenna 1/4 lambda vertical antenna Flexible 1/4 lambda antenna Optional speech scrambler. Photograph kindly supplied by KGB Spy Museum [5]. Kaira cover radio in cloth harness, with optional speech scrambler. Photograph kindly supplied by KGB Spy Museum [5].
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Controller - front
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Operating the PTT
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Volume setting and slide switch
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Setting the volume level
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Microphone/speaker
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Safety pin at the rear
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Two batteries
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Battery pack
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Installing the battery pack
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Battery pack locked in place
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Wire antenna
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Antenna detail
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Antenna plug
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Safety pins for mounting the antenna
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Safety pin at the end of the wire antenna
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Kaira with 1/4 lambda vertical antenna
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With vertical antenna
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With vertical antenna
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1/4 lambda vertical antenna
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Flexible 1/4 lambda antenna
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Optional speech scrambler. Photograph kindly supplied by KGB Spy Museum [5].
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Kaira cover radio in cloth harness, with optional speech scrambler. Photograph kindly supplied by KGB Spy Museum [5].




Interior
Kaira is housed in a plastic enclosure that consists of two plastic case shells, held together by a molded metal cover at the top and at the bottom. Opening the radio is really simple and involves the removal of just three screws. First remove the two recessed screws from the rear panel.

Next, remove the single screw at the centre of the bottom cover. Note that this screw may be sealed and be prepared to remove the wax if necessary. After the bottom cover is removed, the plastic front and rear case shells can also be removed. The interior will now be exposed.

The radio consists of two printed circuit boards (PCBs): a bigger one that holds the receiver, and a smaller one – with the transmitter – at the side. The image on the right shows Kaira's interior, with the receiver at the front and the top panel at the left. At the right is the channel selector.
  
Interior

The empty space at the front is normally taken by the battery pack, for which two spring-loaded contacts are present. The radio consists of a large number of modules that are housed in a metal enclosure that is very similar to a crystal. The function of each module can be determined from the number at the top, e.g. M06-20. The radio shown here was manufactured in January 1990.

Opening the radio Rear panel removed Interior Interior Top view Spring-loaded battery contacts Solder side of the two PCBs PCB wiring detail
Transmitter PA transistor Transmitter PA transistor Output transformer and connector wiring Antenna relay IF filter Channel selector (1/2)
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Opening the radio
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Rear panel removed
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Interior
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Interior
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Top view
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Spring-loaded battery contacts
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Solder side of the two PCBs
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PCB wiring detail
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Transmitter PA transistor
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Transmitter PA transistor
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Output transformer and connector wiring
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Antenna relay
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IF filter
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Channel selector (1/2)

Connections
Apart from the antenna socket, there is only one socket at the top panel. It is a typical 16-pin USSR bus to which the controller should be connected. All control and audio signals are available on this socket. The wiring of the socket can be determined from the circuit diagram. Note that the optional voice scrambler should be connected between the controller and this socket.


Specifications
  • Voltage
    7.2V DC
  • Current
    20 mA (RX), 350 mA (TX)
  • Power output
    0.3 - 0.5 Watts
  • Frequency
    148 - 173 MHz   see table
  • Channels
    2
  • Dimensions
    177 x 115 x 23 mm
  • Weight
    336 grams (without battery and control unit)
Frequency bands
Depending on the customer and the application, the radio was manufactured and aligned for a specific frequency band, as assigned by the USSR Ministry of Internal Affairs (MVD). Three MVD bands are known — A, Б and X — covering the following frequencies (40 channels each) [4]:

  • A
    148.000 - 148.975 MHz
  • B
    172.000 - 172.975 MHz
  • X
    171.100 - 172.100 MHz (mixed) 1
The Kaira radios in our collection all have the same two channels in the A-band: 11 (148.125) and 31 (148.175). Althoug in the frequency table, channel two is 20 steps away from channel 1, the actual frequencies are just 50 kHz apart. This is because the frequencies are not contiguous.

  1. Band B and band X share three channels: 00 (172.000), 01 (172.100) and 20 (172.050).

Help wanted
We are still looking for additional information about this radio, such as manuals, circuit diagrams, technical details, and backgrounds on where and how this radio was used. We are also looking for the optional speech scrambler – that was connected externally – and the body harness, that allowed the radio to be carried on the body. If you can help us in any way, please contact us.


Documentation
  1. Радиостанция Кайра - Kaira user manual (Russian)
    ЯЕ 2.000.151 TO. Date unknown. Available via [1].

  2. Kaira circuit diagram
    Retrieved December 2017 [3].
References
  1. Radioscanner.ru, Кайра
    6 February 2006. Retrieved December 2017.

  2. User: Alexandr, Радиостанция Кайра
    12 August 2015. Retrieved December 2017.

  3. Website CQHAM.RU, Schematics of radios
    Retrieved December 2017.

  4. Radioscanner.ru, Numbering and frequencies of MVD channels in bands A, B and X
    Retrieved December 2017.

  5. KGB Spy Museum, Kaira covert radio with speech scrambler
    Lithuania, January 2018. Personal correspondence. 1
  1. Images reproduced here by kind permission from the author.

Further information
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Crypto Museum. Created: Monday 05 May 2014. Last changed: Friday, 16 November 2018 - 13:12 CET.
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