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Yachta   Яхта
Soviet clone of Nagra SNST

Yachta-1M (Russian: Яхта-1М) is a miniature stereo covert audio tape recorder, developed in 1987 by the special machinery factory of Kiev 1 (Ukraine) and used by the intelligence community of the USSR during the final years of the Cold War, in particular by the Russian KGB. The device is basically a clone of the highly acclaimed Swiss Nagra SNST of 1977, which was a beloved item of the American services. Yachta-1M 2 is also known by its factory designator Yavir-1 (Явiр-1) 3 [1].

The recorder is built on a machined aluminium chassis, that is nearly a 1:1 copy of Nagra's SNST design, with small differences in the position of some screws, and the meter replaced by an LED.

The tape heads and the tape track specifications are identical to those of Nagra, so that tapes and other accessories could be used straight away. The sockets at the left side are made of bakelite rather than plastic, but are fully compatible with Nagra's plugs. Even the supplied covert micro­phones can be used on both recorders. Yachta's interior was completely redesigned however.
  
Yachta covert tape recorder

The design of the recorder is based on the Nagra SNST, which is the stereo version of the Nagra SN. It was developed in Ukraine — at the time part of the USSR — around 1987, 10 years after the introduction of the Nagra SNST, and nearly 16 years after the original Nagra SN. The latter was developed during the 1960s 4 especially for the US intelligence and law enforcement community.

Although it must have cost them a fortune to develop Yachta — a single unit was probably more expensive than an original Nagra SNST — the Soviets didn't want to order equipment from Nagra, as that would likely have become known to US intelligence, given the good relationship between them and Nagra. Production started in 1987/88, and lasted for ~10 years, during which time it was a popular item of Soviet intelligence services like the Russian KGB. After the fall of the Soviet Union in 1992, the Ukrainian factory kept producing the recorder, but designated it Yavir-1 [1].

  1. Also known as the Research Institute Manuilsky, today known as the Space Research Institute (SRI).
  2. Яхта (Yachta) is Russian for Boat or Yacht. It was the KGB code name for the recorder. Note that Yachta was also used as the codename of the T-219 voice encryption device.
  3. Явiр (Yavir) is Ukrainian for Sycamore, the European species of a maple tree.
  4. The prototype of the Nagra SN was made in 1960, but production first started in 1971.
    The stereo version – Nagra SNST – was first produced in 1977.

Yachta record with top cover in place Yachta with top cover off Yachta seen from the front left Yachta covert tape recorder Top view Yachta (front) versus Nagra SN (rear) Microphones External battery box with remote control button
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Yachta record with top cover in place
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Yachta with top cover off
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Yachta seen from the front left
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Yachta covert tape recorder
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Top view
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Yachta (front) versus Nagra SN (rear)
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Microphones
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External battery box with remote control button

Features
The diagram below gives an overview of the controls and connections of the Yachta recorder. The sockets for connection of the peripherals are all at the sides, with those for the microphones and the external battery/remote control unit at the left, and the busses for the earphones at the front. All text on the recorder's body is in Russian and is engraved in black, rather than screen-printed.


The tape heads and the routing of the tape past the guides, are similar to those of the Nagra SN and SNST, with the most obvious difference being the absence of a meter at the bottom right. The meter — which on the Nagra is used for checking the audio level as well as the battery level — is replaced here by a simple LED indicator that starts flashing when the voltage drops below 2.1V.

Another indicator (КНЗ) is present at the top left, aside the leftmost Bakelite socket. The indicator is controlled by three push-buttons that are located at the right side, and can be used to check the presence of a signal on microphones (1) and (2), or a sufficient battery voltage (КН).

A small adjustment tool is stored inside the top cover, close to the case lock. It can be used to adjust the height of the tape heads, as shown in the image on the right. In this case, the tool is made of plastic, but later builds of the recorder were sometimes supplied with a metal version.
  
Adjusting the heads

Yachta was commonly used in combination with a special playback device — in Russian known as устройство воспроизвдения — which is actually a clone of the Nagra DSP-1 amplifier. This device features audio expanders which match the audio compressors inside the recorder.

Hinge Three push-buttons on the right side for checking microphone signal (1) and (2), and battery voltage (KH). Play control Power check LED Bakelite Nagra-compatible sockets Close-up of a bakelite socket External power/remote plug Looking into a 'cloned' plug
Microphone fitted to the recorder Capstan and pinch roller Erase, record and playback heads Adjustment tool stored inside the top cover Adjusting the heads Break Earphone connected to the leftmost output External battery box
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Hinge
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Three push-buttons on the right side for checking microphone signal (1) and (2), and battery voltage (KH).
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Play control
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Power check LED
B
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Bakelite Nagra-compatible sockets
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Close-up of a bakelite socket
B
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External power/remote plug
B
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Looking into a 'cloned' plug
B
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Microphone fitted to the recorder
B
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Capstan and pinch roller
B
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Erase, record and playback heads
B
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Adjustment tool stored inside the top cover
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Adjusting the heads
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Break
B
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Earphone connected to the leftmost output
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External battery box

Yachta vs. Nagra
The designers of the Yachta recorder went through great length to copy every detail of the Nagra SNST. As first sight, one might be led to believe that it was actually manufactured by Nagra. When looking closer however, there are some differences in quality, materials, tolerances in sizes, the position of screws, etc. In addition, the interior is completely different as will be shown below.


The image above shows both the Yachta (front) and Nagra (rear). As we do not have a Nagra SNST in our collection, we are showing the Nagra SN instead. The most obvious difference between the two recorders is no doubt the absence of the meter at the bottom right. On Yachta, it is replaced by a power check indicator (LED) that starts blinking when the battery voltage drops below 2.1V.

Furthermore, the shape of the transport locking knob is different. On the Nagra it has the shape of a quarter circle, whilst on Yachta it has an oval shape. Although the individual parts, such as the tape heads and guides, are at exactly the same position on both recorders, the position of some of the recessed screws is slightly different. One example is the screw in the yellow circle above.

The springs that are used for the spring-loaded items, such as the tape tension arm at the left, have a different strength, as a result of which these parts will behave somewhat differently.
  
Yachta power LED (top) versus Magra power meter (bottom)

The spring that is used for the case lock is slightly too strong, as a result of which the case lid can not be closed as easily as on the Nagra. The overal impression is that some parts are less well finished and that the quality of the materials is slightly lower. Nevertheless, the result is amazing.

The recorder is built on a machined chassis that is milled-out of a solid block of aluminium. The outer case is eloxed, whilst the top surface is also brushed. It is hard to tell the difference.

At the left side are the sockets for connection of an external power source, a remote control unit and the microphones, all custom made to Nagra specifications. On the Nagra, these sockets are made of green plastic, whilst for Yachta brown bakelite is used. Bakelite — a brand name for a thermosetting phenol formaldehyde resin — was one of the first plastics, developed in 1907 [4].
  
Microphone fitted to the recorder

In the West, Bakelite was largely replaced by modern polymer plastics during the 1960s, but in the USSR is was used throughout the Cold War, until well after the fall of the Soviet Union. In fact, many connectors and sockets that are used in the Russian space program today (2017) are still made of Bakelite, probably because of its proven reliability and its heat-resistant properties.

Yachta (front) versus Nagra SN (rear) Yachta power LED (top) versus Magra power meter (bottom) Bakelite Nagra-compatible sockets Microphone fitted to the recorder Green plastic sockets at the left side of the Nagra SN
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Yachta (front) versus Nagra SN (rear)
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Yachta power LED (top) versus Magra power meter (bottom)
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Bakelite Nagra-compatible sockets
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Microphone fitted to the recorder
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Green plastic sockets at the left side of the Nagra SN

Parts
External microphone(s)
Mic
Fixed (internal) microphone(s) Earphones External battery box Magnetic tape and spools Audio adapter External self-contained amplifier Telephone pickup coil
Cable tapping coil
Tap
External microphone(s)
Yachta was supplied with two covert electret microphones — one for each channel — that could easily be hidden under the operative's clothing. They are protected by a rubber sleeve, and are shown in the image on the right.

The microphones are connected to the recorder by means of a 3-pin plug at the end of its cable, and are fully compatible with Nagra ones. The electret elements are known as M1-B2 Sosna (Russian: Сосна), which means Pine [2].
  
Microphones

Fixed microphone(s)   wanted item
As an alternative to the external microphones shown above, the set also came with two fixed microphones, in which the electret element is mounted inside an enlarged plug.

The microphones can be attached to the side of the recorder, jut like an ordinary microphone connector. Photograph kindly supplied by [1].
  
Fixed microphones. Photograph kindly supplied by [1].

Earphone
The recorded audio could be played back on Yachta via virtually any type of earphones, such as the one shown in the image on the right, that was commonly used in the USSR at the time.

Note that the audio volume is relatively low and that there is no volume control. It was also possible to play the audio back via the special self-contained audio amplifier, or via any other amplifier by using the external adapter box.
  
Earphone

External battery
In order to extent the battery life of the recorder – for example in situations where the record and playback function had to be used uninterrupted for several hours – the external battery box shown in the image on the right was available.

The box accepts two large 1.5V C-size batteries (also known as mono-cells), and has a long cable that connects to the remote socket of the recorder by means of the 5-pin plug at the end. The cable also holds a power switch that can be used as a hand-held start/stop button.
  
External battery box with remote control button

Magnetic tape
The magnetic tape on which the audio signal is recorded, is identical to that of the Nagra SN. It is 3.81 mm wide and is divided into two tracks.

The tape is supplied on a plastic reel, such as the one shown in the image on the right. As the dimensions are identical, it was also possible to use Nagra tapes and spools, which were also available in eloxed aluminium.

 See available tapes

  
Magnetic tape

Adapter   wanted item
An external audio adapter, or galvanic separator, was available for connecting Yachta's output to an external stereo audio amplifier, but it should be noted that the audio signal on the tape is compressed and that most amplifiers do not have a suitable expander.

The adapter contains two 1:1 transformers and delivers the outputs on a 5-pin 180° DIN socket.
  
Adapter for external amplifier. Photograph kindly supplied by [1].

Amplifier   wanted item
The recorded signal can be played back via an external amplifier that can be connected to the earphone sockets at the front of the recorder.

It was recommended to use the original Nagra DSP-1 or its Russian clone – which was named устройство воспроизвдения (playback device) – as these have a built-in expander that properly recovers the recorder's compressed audio signal.

 More information

  
Nagra DSP-1

Telephone pickup coil   wanted item
For covertly recording a telephone conversation, the pickup coil shown in the image on the right was supplied as part of the kit. The rectangular coil is placed under the (analogue) telephone set and picks up the stray magnetic field produced by the transformer inside the telephone set.

Note that this is only suitable for old analogue telephone sets. Modern (electronic) ones, do not have a transformer that produces an exploitable stray field. Photograph kindly supplied by [1].
  
Telephone pickup coil. Photograph kindly supplied by [1].

Wire tap
In some situations it was not possible to use the pickup coil shown above for covertly recording a telephone conversation. For such situations, the wire tapping tool shown on the right was used.

The tool is not electrically connected to the wires of the telephone line, but is clamped around the cable, where it picks up the (weak) mangnetic stray field that surrounds the cable during a conversation. The weak signal is then amplified to normal microphone level. Photograph kindly supplied by [1].

  
Wire tapping tool. Photograph kindly supplied by [1].

Microphone Microphone close-up Microphone External battery box with remote control button Operating the remote button Open battery box battery box close-up Internal microphone
Internal microphone connected to the recorder Audio output adapter Cable tapping coil Telephone pickup coil
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Microphone
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Microphone close-up
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Microphone
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External battery box with remote control button
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Operating the remote button
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Open battery box
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battery box close-up
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Internal microphone
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Internal microphone connected to the recorder
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Audio output adapter
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Cable tapping coil
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Telephone pickup coil

Block diagram
Below is the block diagram of the electronic circuits inside the recorder. At the bottom left is the power supply, with is provided either by two internal 1.5V AA-size batteries, or an external 3V DC power source. A small micro-switch senses the presence of the external power plug, and switches between the two sources. The power source is converted by a step-up and stabilization circuit, to a constant +5V DC level. The direct battery voltage is monitored by a warning circuit.


At the top left are two audio compressors, each of which amplifies the signal from one of the microphones and compresses its dynamic range. The outputs of the compressors are fed to the recording head, where they are mixed with the signal from the bias generator. The latter also drives the separate erase head. The recording circuit is activated by a small micro-switch that is located at the side of the recorder. It senses the presence of one/both of the microphone plugs.

The playback circuit is always ON, so that the recorded signal can be checked immediately, either through the earphones (output) or via the check indicator, by pressing one of the signal check push-buttons (1) or (2). The check indicator can also be used to check the internal +5V DC level.


The block diagram above shows the motor driving circuit, which is completely independent from the audio circuits. It consists of a motor, a motor driver (20001) and a speed stabilization circuit (38004). A tacho generator – mounted to the body of the motor – delivers pulses to the input of a phase comparator, that compares it with the signal from a crystal-driven reference oscillator. The error signal from the phase comparator is fed to the driver, which controls the motor voltage.




Interior
Although the exterior of Yachta is nearly identical to that of the Nagra SNST, the interior, and the electronic circuits in particular, are completely different. The circuits are based on the Nagra SN design, but are built with Russian components, including eight so-called micro-assemblies (ICs).

The interior of the Yachta can be accessed in the same way as Nagra: simply by loosening the three large bolts at the sides, and taking off the bottom cover. This reveals the rear end of the motor and the solder side of two circuit boards.

The smaller PCB holds the motor driving circuit, whilst the larger one contains the audio circuit and the power converter. The image on the right shows the interior of the recorder after tilting the larger hinged board. The smaller board to the right of the motor is the playback amplifier, that delivers the signals for the two jack sockets.
  
Interior

The circuits are nicely built, using first class Soviet parts, and are interconnected by means of the typical Soviet pink Teflon wire bundles. Although the magnetic heads and the amplifier circuits are based on the Swiss Nagra designs, Yachta's frequency response is less good and the recorder does certainly not meet Nagra's design criteria. According to markings on the PCBs, the recorder featured here was built in June 1991, and shows the state of technology in the USSR just before its collapse. By that time, the world had moved on to SMD components, and Nagra had its JBR.

Yachta with rear cover removed Interior Motor control board Interior with raised audio board Interior Interior detail Power circuit Wiring detail
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Yachta with rear cover removed
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Interior
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Motor control board
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Interior with raised audio board
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Interior
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Interior detail
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Power circuit
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Wiring detail

Restoration
Judging from the usage marks on the recorder featured here, this Yachta has seen quite some action. When we first loaded the recorder with fresh batteries, it didn't work and the batteries became hot immediately. Fortunately, this was just an intermittent failure that was easily fixed.

The pink wire of the (+) terminal of the battery compartment, was broken. Further­more, the (+) terminal could be shorted to ground, due to two manufacturing flaws that will only expose them­selves when using modern 1.5V AA batteries.

As modern AA-size batteries are about 0.5 mm longer than the batteries of the 1980s, they will hardly fit the battery compartment, as there is no tolerance whatsover. As a result, the spring of the (+) terminal will be fully compressed, and the (+) is pushed all the way towards the chassis where it touches a metal supporting bracket.
  
(+) terminal of the battery compartment resoldered. Chassis bracket isolated with Maylar tape.

This problem can easily be fixed. The wire can be resoldered to the spring of the (+) terminal, and a piece of Mylar tape can be used to isolate the metal support bracket, as shown in the image above. The latter can also be fixed by milling off the corner of the metal support bracket.

Another problem is caused by the metal case shell of a micro-assembly (IC), that is located close to the (+) terminal of the battery. Although the case is isolated with a conformal coating, it is pretty sharp and can easily damage the thin isolation of an AA-size battery when inserting it.

Depending on the construction of the battery, either the (+) or the (-) side becomes connected to the IC's case shell and will cause a full short circuit. In addition, Alkaline batteries have a high energy density and may catch fire. This problem can be avoided by installing them as described.
  
Short circuit between battery shell and IC enclosure

Although the battery compartment is copied from the Nagra design, the dimensions are slightly different, and the battery compartment of the Yachta is far less tolerant to battery size variations. Always be careful when installing new batteries and do it as shown in the images below. Avoid using excessive force and metal aids, such as a screwdriver, as this will damage the isolation.

Repaired battery terminal (+) terminal of the battery compartment resoldered. Chassis bracket isolated with Maylar tape. Short circuit between battery shell and IC enclosure Bettery (+) terminal with fully inserted batteries Install batteries Pushing-in the batteries
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Repaired battery terminal
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(+) terminal of the battery compartment resoldered. Chassis bracket isolated with Maylar tape.
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Short circuit between battery shell and IC enclosure
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Bettery (+) terminal with fully inserted batteries
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Install batteries
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Pushing-in the batteries

Accessories
The following accessories were available for the Yachta/Yavir recorder:

Specifications 1
  • Voltage
    2 - 3V
  • Current
    120 mA (at 2.5V)
  • Batteries
    2 x 1.5V AA-size
  • Tape width
    3.81 mm
  • Tape speed
    2.38 cm/s
  • Tape thickness
     see table
  • Recording time
     see table
  • Frequency response
    170 Hz - 6000 Hz 2
  • Harmonic distortion
    ≤ 3%
  • Wow & flutter
    ≤ 0.35%
  • Dimensions
    156 x 103 x 27 mm (body: 148 x 101 x 27 mm)
  • Weight
    600 grams (without batteries and tape)
  1. Obtained from Vintage Technics website [1].
  2. The frequency response is reported by some sources as 280 Hz - 3950 Hz ±3dB [2].

Tapes
  • 9 µm
    270 m
    3:08 hrs
  • 12.5 µm
    217 m
    2:32 hrs
  • 18 µm
    150 m
    1:44 hrs
Wanted
We are still looking for the following items. If you can supply any of these, please contact us.

  • Internal microphones
  • Telephone pickup coils
  • Remote control unit
  • Playback device
  • Power supply unit
  • Audio adapter
Documentation
  1. Yavir-1 (Yachta-1M) Operating instructions (PDF)
    Kiev, 1991 (Russian). Kindly supplied by Alexander Yurinov [3] via [1].

  2. Yavir-1 (Yachta-1M) Service manual (PDF)
    Kiev, 1991 (Russian). Kindly supplied by [1].

     Main circuit diagram (annotated)
     Speed controller circuit diagram
     Assembly drawing 1
     Assembly drawing 2

  3. Micro-assemblies (ICs) used in Yachta/Yavir (PDF)
    Kindly supplied by [1].

     
    30002
    Power controller

     
    23003
    Bias generator

     
    38006
    Audio compressor

     
    21059
    Amplifier

     
    38004
    Speed control PLL

     
    20001
    Motor driver

     
    20003
    Comparator (not available)

     
    38005
    Audio expander 1
  1. Used in the playback device.

References
  1. Vintage Technics, Яхта-1М / Явiр-1
    Retrieved December 2017.

  2. User 'Blarrer' et al., Yavir-1 - Soviet clone of Nagra SNST
    Forum Tapeheads.Net. Retrieved December 2017.

  3. Alexander Yurinov, Yavir-1 Operating instructions
    1992. Obtained via [1]. December 2017.

  4. Wikipedia, Bakelite
    Retrieved December 2017.
Further information
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Crypto Museum. Created: Thursday 21 December 2017. Last changed: Saturday, 13 January 2018 - 11:29 CET.
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