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Kopchik   Копчик
Covert surveillance detection receiver - wanted item

Kopchik (Russian: Копчик) 1 was a aperiodic body-wearable covert VHF surveillance detector, developed in the 1970s in the former Soviet Union (USSR), for use by the intelligence services, such as the KGB, the GRU and the East-German Stasi. It was intended for the detection of nearby adversary agent-to-agent communication, in particular in the 150 and 400 MHz VHF/UHF bands.

The receiver measures 20 x 93 x 25 mm and weights just 280 grams (battery not included). It is powered by a rechargable battery pack that is installed behind a lid at the right side. The unit is designed to be worn under the clothing, with a small speaker attached to the collar of the coat.

The device is operated by means of a handheld remote control unit (RCU) of which the cable is guided through a sleeve of the coat. An external recording device – like the Mezon wire recorder – can be connected, so that intercepted agent conversations can be recorded simultaneously.
  
Kopchik receiver

The recorder allows the conversation — usually in a different language — to be translated and transcribed later. The external recorder can be started and stopped from the RCU, which also allows the speaker to be used as a microphone, so that the agent can add a verbal comment to the recording. The device is normally used with a simple wire antenna that is affixed to the clothing by means of safety pins, and connected to one of the two antenna inputs (25 or 90).

The receiver was used by Soviet and Warsaw Pact field agents, to check whether they were being followed by their foreign counterparts, in which case the adversary agents were most likely using covert radio sets hidden under their clothing.

As the receiver is only sensitive to strong nearby radio signals — in particular transmissions in the 150 and 400 MHz bands — it provides a good means for detecting foreign agents. If a signal is picked up, the speaker produces a 2 kHz tone, which promts the operative to abort the mission, or continue the surveillance detection run. 2
  
Kopchik with remote control unit

Although the receiver can be used for simple direction finding (DF) tasks — using the supplied dipole antenna — a dedicated direction finder like Sinitsa, Soyka or Filin would have been far more appropriate, as these offer better control over frequency and signal strength. Kopchik can be regarded as the Russian equivalent of the same-era SRR-100 receiver of the American CIA.

  1. Копчик (Kopchik) is the russian word for coccyx (tailbone).
  2. In espionage, covert agents commonly follow a complex procedure — consisting of walking, using public transport, changing direction, etc. — to ensure that he or she is not being followed by adversary observers. This procedure is commonly known as a surveillance detection run.

Kopchik receiver Kopchik receiver Kopchik with remote control unit Sockets for remote control unit (RCU) and external receiver Kopchik receiver with remote control unit, antenna and speaker Remote control unit (front) Operating the volume control switch Battery compartment
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Kopchik receiver
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Kopchik receiver
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Kopchik with remote control unit
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Sockets for remote control unit (RCU) and external receiver
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Kopchik receiver with remote control unit, antenna and speaker
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Remote control unit (front)
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Operating the volume control switch
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Battery compartment

Features
The diagram below gives a quick overview of the controls and connections on the body of the Kopchik receiver. The text on the body (БЛ. ПРИЕМНИКА) means RECEIVER BLOCK. The device is powered by a rechargeable NiCd battery pack that should be installed behind the curved lid at one side, or by an external DC source connected to the socket marked ПИТ. (pitaniya, supply). The device is operated by means of a remote control unit (RCU) that is held in one hand, with the cable guided through the sleeve of the coat. It is switched ON/OFF from the remote control unit.


A simple antenna should be connected to the 25-socket (for narrowband) or to the 90-socket (for wideband) reception. It can be fixed to the clothing by means of safety pins. Due to the non-selective (aperiodic) nature of the receiver, it is responsive to strong nearby signals only, in which case it will produce the demodulated sound (AM only) or an audible 2 kHz tone (FM, SSB and CW).

The demodulated sound is reproduced through a standard Soviet NEVA speaker, which can also be used as a microphone, in case the (optional) recorder is connected to the 4-pin socket at the side. The start/stop function of the recorder is under control of an internal miniature relay.

Kopchik receiver Sockets at the upper surface Sockets for remote control unit (RCU) and external receiver Remote control unit (front) Remote control unit (rear) Operating the volume control switch
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Kopchik receiver
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Sockets at the upper surface
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Sockets for remote control unit (RCU) and external receiver
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Remote control unit (front)
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Remote control unit (rear)
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Operating the volume control switch

Parts
Kopchik surveillance detection receiver Remote control unit NEVA speaker Simple wire antenna Simple (wire) dipole antenna with filter Wire recorder Rechargeable NiCd battery pack Cloth body harness
Receiver
The image on the right shows the bare Kopchik receiver, which was identified in the checklist as RECEIVER BLOK (БЛ. ПРИЕМНИКА). It could be carried in a pocket of the coat, but was usually worn directly on the body, using a cloth harness.

The receiver is powered by an internal battery or by an external power source, such as a mains power supply unit (PSU) or the battery of a car. As a bare minimum for operation, it needs an antenna, a speaker and the remote control unit.
  
Kopchik receiver

Remote control unit
The receiver can only by used when the original remote control unit (RCU) is installed in the 12-pin socket at the left side. It is usually carried in the hand. The receiver is powered by sliding the switch towards the bottom of the RCU to the left.

For a first check, it is recommended to shift the Volume switch (Р.Г.) to the loudest position (Б = Больше, more) and the reception switch (ПРИЕМ) to the centre position. At the rear is a switch for selecting ТЛГ (telegraphy, morse, tone), or ТЛФ (phone) for demodulating AM.

  
Remote control unit (front)

Speaker
For reproduction of the demodulated sound, a Soviet standard-issue NEVA speaker is supplied with the receiver. It is the same speaker that was supplied with nearly all direction finders and covert radios of the era.

NEVA can be affixed under the collar of, say, a coat, and can also be used as a microphone, which in this case might be usefull when using an (optional) external recorder.
  
NEVA spekaer

Antenna
As Kopchik is only intended for detection of radio signals in close proximity of the operator, a simple short wire will usually be sufficient as an antenna. The image on the right shows a typical 50 cm wire that can be connected to either of the inputs (25 or 90).

The wire antenna has several safety pins, to allow it to be affixed to the clothing. In most cases, it should be worn vertically.
  
Standard wire antenna

Dipole antenna
For simple direction finding tasks, and for the detection of horizontally polarised signals, the simple (wire) dipole antenna shown in the image on the right might be used as an alternative to the regualar antenna.

The antenna shown here, has a built-in adjustable blocking filter, that can be used to block a specific frequency.
  
Dipole (wire) antenna with blocking filter

Battery pack
Kopchik was powered by a rechargeable NiCd battery pack, that should be installed behind the curved hinged lid at the side. We are currently unable to show a picture of the original battery, as it is missing from the device featured here.

As an alternative, the device can also be powered via the ПИТ. socket at the top. Note that the (+) terminal should be connected to ground (i.e. to the metal of the case).
  

Body harness
During a covert operation – for example during a surveillance detection run – Kopchik was usually carried in a purpose-made cloth harness, that allows it to be hidden easily under the clothing.

We are currently unable to show a picture of the cloth harness, as it is missing from the device featured here.
  

Standard wire antenna Dipole (wire) antenna with blocking filter Dipole (wire) antenna with filter Adjusting the blocking filter Antenna filter Remote control unit (front) Remote control unit (rear) Operating the volume control switch
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Standard wire antenna
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Dipole (wire) antenna with blocking filter
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Dipole (wire) antenna with filter
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Adjusting the blocking filter
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Antenna filter
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Remote control unit (front)
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Remote control unit (rear)
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Operating the volume control switch

Recording devices
Kopchik has a 4-pin socket at its side — just below the 12-pin socket for the remote control unit — that is intended for the connection of an external recording device, such as a body-wearable wire or tape recorder. The recorder can be started/stopped from the remote control unit (RCU).

Mezon   Мезон
Although Kopchik can be used with virtually any type of audio recorder, it was most likely used in combination with the body wearable Mezon wire recorder shown in the image on the right.

Mezon can record many hours of sound onto a very thin steel wire, and was also developed especially for the Soviet intelligence services.

 More information
  
MEZON covert wire recorder with open lid

Yachta   Яхта
It is possible that in later years, Kopchik was used with a covert tape recorder, such as the Yachta device shown in the image on the right.

Yachta is in fact a clone of the 1960s Swiss Nagra SN, and was released in 1987, at a time when the original Nagra SN had been replaced by smaller devices and was no longer in production.

 More information
  
Yachta covert tape recorder


Interior
Kopchik is housed in a hamerite-painted die-case aluminium enclosure that measures 120 x 93 x 25 mm and weights just 280 grams (without the battery). The interior of the unit can be accessed by removing a narrow panel at the front (three screws) and a larger one at the rear (four screws).

The narrow panel at the front gives access to the solder terminals of the 4 sockets at the top, and to the input filters of the 25/90 antenna inputs.

The rear panel gives access to 2 circuit boards: one that holds the mixers and the band filters, and one that holds the oscillators and the audio circuits. The latter is actually a carrier board for a number of pre-assembled sub-circuits that are mounted at the other side. The image on the right shows a close-up of one of these circuits — probably one of the oscillators. The components are moisture protected by a conformal coating.
  
Close-up of one of the audio circuits

All sub-circuits are interconnected by means of typical (Soviet) pink teflon wiring, largely via the 12-pin remote control socket at the side of the receiver. Inside the remote control unit (RCU) are a number of Soviet-made microswitches, operated by sliding metal frames. The construction is very similar to that of the more versatile Sinitsa, which is also a body-wearable aperiodic receiver.

Interior Filters (left) and audio section (right) Mixers and filters Audio section (bottom view) Filters Audio circuits Close-up of one of the audio circuits Audio board lifted from the enclosure
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Interior
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Filters (left) and audio section (right)
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Mixers and filters
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Audio section (bottom view)
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Filters
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Audio circuits
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Close-up of one of the audio circuits
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Audio board lifted from the enclosure

Block diagram
Below is the simplified block diagram of the Kopchik receiver. At the left are the antenna inputs; one for each bandwidth: 25 kHz (narrowband) or 90 kHz (wideband). The antenna signal is mixed with the square wave signal from a free-running low-frequency (LF) generator, running at 2 kHz or 20 kHz. The 2 kHz signal is in the audible range and is used when the slide switch (S2) at the rear of the remote unit is set to ТЛГ (TLG, telegraphy, CW). It can also be used for the detection of FM signals. The 20 kHz generator is selected when the switch is set to ТЛФ (TLF, telephony, AM).

Kopchik simplified block diagram

The output of the mixer is passed through a bandpass filter onto a diode detector. There are two separate input branches, optimised for narrowband (25 kHz) and wideband (90 kHz) respectively, selectable with a slide switch (S3) on the body of the receiver, marked 25-90. The resulting audio signal is then optionally muted (S4), amplified and passed to the speaker. The audio signal is also available for an externally connected recorder, under control of a 3-position switch (S5) (ПРИЕМ).

When the switch is set to МАГН (MAGN, recorder), the demodulated audio signal is passed to the recorder. In the position МКФ (MKF, Microphone), the speaker is used as a microphone, so that the operator can add a spoken message to the recording. The receiver is powered by an internal battery, or by an external 4.5 to 7.4V DC voltage, connected to the socket marked ПИТ. (PIT, pitaniya, supply). Note that the (+) terminal of the battery is connected to the case (ground).

Frequency response
Due to the way in which the antenna input circuits of the receiver are dimensioned, the device is particularly sensitive to signals in the 150 MHz VHF band and the 400 MHz UHF band, both frequencies that were commonly used at the time for covert agent-to-agent communication.

Kopchik frequency response curve

The diagram above provides a rough indication of the sensitivity of the receiver.


References
  1. Günter Hütter, Копчик receiver
    Retrieved October 2016, June 2019.

  2. USSR Special Forces Intelligence Secret Radios, Копчик
    Website. Retrieved October 2016.

  3. Louis Meulstee, Kopchik
    Wireless for the Warrior, Volume 4, Supplement Chapter 190.
    Retrieved June 2019.
Further information
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Crypto Museum. Created: Saturday 22 October 2016. Last changed: Friday, 26 July 2019 - 04:21 CET.
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