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T-219 Yachta   ЯХТА
Voice scrambler - not in collection

T-219, codenamed Yachta 1 (Russian: ЯХТА), is an analogue voice scrambler, released during the Cold War by the Soviet Union, and used by the armies of the countries of the former Warsaw Pact, for tactical communication in the (combat) field. The unit was also part of the R-142 radio setup — as found inside the radio shelter of a GAZ-66 truck — but was only issued in the event of war.

Yachta consists of two units: the actual voice scrambler device, and a remote control panel. It is usually connected to a short-wave (SW) radio station, but can also be used over analogue telephone lines. The image on the right shows the rather big and heavy PU-1 control panel [1].

The system was coded by means of a key card that was installed in the main unit. An external heater was used to keep the device warm in the winter. Although voice scramblers are inherently insecure, Yachta was used by the Russian Army until long after the fall of the Soviet Union [6].
  
PU-1 remote control unit of the T-219 (Yachta) voice encryptor

Yachta is characterized by a Frequency Shift Keying (FSK) signal that is transmitted in the middle of the main signal, with the scrambled voice stream split above and below the FSK signal. The FSK signal is transmitted at 100 Baud and uses an 150 Hz shift [3]. One of the frequencies on which Yachta signals were known to be transmitted, was 28.347 MHz. Yachta was succeeded by CIS-12.

  1. Yachta, sometimes written as Yakhta, is Russian for Boat or Yacht. Note that the name Yachta is also used as the codename for a covert body recorder that was a Soviet copy of the Swiss Nagra-SN.

PU-1 remote control unit of the T-219 (Yachta) voice encryptor
Front view
Front panel
Rear view
Connections at the rear
Serial number tag
Cable filtering
The two main units of the KU-27M
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PU-1 remote control unit of the T-219 (Yachta) voice encryptor
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Front view
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Front panel
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Rear view
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Connections at the rear
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Serial number tag
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Cable filtering
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The two main units of the KU-27M

Test and alignment
Especially for test, repair and alignment of the T-219 (and similar voice scramblers), the Soviets developed a comprehensive test setup, known as KU-27 and KU-27M (Russian: КУ-27М).

The installation consists of two large cabinets (both of which are shown here) and two storage containers with spare parts, documentation and tools, enough for setting up a repair workshop.

The device can be configured for a particular test or alignment, by installing one of the building blocks of the Yachta scrambler into one of the slots at the front, and inserting the appropriate program card in the receptacle above the slot.

 More information

  
The two main units of the KU-27M

Decoding
Yachta signals can be decoded with the following software:

Specifications
  • Frequency
    3 - 30 MHz
  • Mode
    USB
  • Bandwidth
    2700 Hz
  • Modulation
    FSK
  • Speed
    100 Baud
  • Shift
    150 Hz
References
  1. Immo Hahn, Yachta control panel PU-1
    April 2013, September 2019.

  2. SAS Fernsprechgerät T-219, T-219 M, T-817 N
    Retrieved May 2017.

  3. Signal Identification Guide, Yachta T-219 Voice Scrambler
    Retrieved May 2019.

  4. Signal Identification Guide, High Frequency (HF)
    Retrieved May 2019.

  5. Radioscanner.RU, Yachta T-219
    Retrieved May 2017.

  6. Southgate, Russian vocoder Yakhta back on 21 MHz
    9 October 2013.
Further information
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Crypto Museum. Created: Friday 12 May 2017. Last changed: Monday, 30 September 2019 - 08:11 CET.
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