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Burst encoders
High-speed data encoders

During WWII and also during the Cold War, secret agents operating on enemy territory commonly used clandestine transmitters to send messages to the spy centre in their home country, via the short-wave radio bands (SW or HF), using morse code. As the enemy was continuously trying to intercept such messages and determine the location of the rogue transmitter by means of Radio Direction Finding (RDF), it was necessary to be on-the-air as little and as short as possible. This was also necessary to make effective use of the limited frequency spectrum that was available.

Over the years, different systems were developed to reduce the length of a message. One method that was commonly used, was to replace long sentences and frequently-used expressions by a predetermined code. Examples of such short messages are the international Q-codes and the use of various military and civil code books.

As the Cold War progressed, the need to send more and longer messages gradually increased and new methods had to be devised to avoid detection. This resulted in the development of high-speed morse keyers and Burst Encoders.
Burst encoder with various tape cassettes

A Burst Encoder is a device that allows messages to be stored on a recording medium first. The pre-recorded message is then sent over the air at very high speed using a high-speed keyer. A wide range of solutions was developed for this, using a variety of media, such as paper, audio tape, metal tape, mechanical drums, rods, photographic film and finally electronic memory chips.

Messages that are sent this way often sound like a short tone or burst, which is why it is called a Burst Transmission. This part of the website describes a number of solutions that were developed for high-speed burst transmission of messages. Use the buttons on the left, check the index of burst encoders, or click any of the thumbnails below for more information on a particular device.

 Index of burst encoders

Burst encoders on this website
SQUIRT WWII rod-based burst encoder
Kurzsignalgeber (KSG) developed by the BND for the KSG-Sender
CIA coder/keyer CK-8
USA: AN/GRA-71 external automatic tape-based burst encoder
Racal MA-4010/8 tape-based burst encoder
Europe: Manual (mechanical) burst encoder
Europe: Digital burst encoder used by West-European Gladio Forces
Europe: fully electronic hight-speed burst encoder (1980)
French burst transmitter with metal tape and nail polish (name unknown)
UK (SAS): crypto burst transmitter for the PRC-319 radio
EMU Alpha - Alphanumeric version of the BA-1304 (EMU)
Nokia Sanla - Sanomalaite
Nokia Parsa - Partiosanomalaite
Philips UA-8295 short-burst terminal with encryption
Racal MA-4230 morse encoder and MA-4231 morse decoder
DDR: Digital burst encoder built in the DDR (East-Germany) during the Cold War
Racal MA-4450 Message Entry and Read-Out Device (MEROD)
Czechoslovakian Mesic tape-based morse burst encoder (1966)
East-German manually operated tape puncher
East-German Handschnellgeber (manual fast keyer)
Message Exchange Device (MED)
TCU-7000 controller and message encryptor for HRM-7000 (HF-7000)
R-350 manual film-based burst encoder
R-353 automatic metal-tape-based burst encoder
R-354 automatic film-based burst encoder
R-014D, the first fully electronic burst encoder developed by the USSR
R-394K built-in digital burst encoder
R-394KM digital integrated burst encoder
DKM-S digital burst encoder (USSR)
Russian R-355 Base Station Controller
Czechoslovakian TI-485 (Davac) tape-based morse burst encoder (1962)
American baudot coder/keyer with built-in encryption
Known CIA keyers
Over the years, the US Central Intelligence Agency (CIA) developed an impressive range of burst encoders for a variety of radios and applications. These encoders were commonly identified with the letters 'CK' for 'Coder/Keyer'. Some of them were also used by the Army under a different designator. The following CIA burst encoders are currently known [1]:

  • CK-7
    Coder/Keyer (military: AN/UGT-1)
  • CK-8
    Coder/Keyer (military: AN/GRA-71)
  • CK-12
    Coder/Keyer (used with RT-6)
  • CK-100
    Coder/Keyer (special version of CK-8)
  • CK-30
    Coder/Keyer (compatible with RT-49)
  • CK-34
    Coder/Keyer (used with AS-12)
  • CK-36
    Coder/Keyer (used with ASR-100 transceiver)
  • CK-33
    Morse coder/keyer (film-based)
  • CK/A-33
    Baudot version of CK-33
  • CK-42
    Baudot coder/keyer with built-in encryption
  • CK-43
    Baudot coder/keyer with built-in encryption
  • CK-45
    Morse coder/keyer (compatible with  RS-59)
Burst encoders are known by the following names

  • Burst encoder
  • Burst transmitter
  • Burst keyer
  • Burst coder
  • Coder/keyer
  • High-speed burst transmitter
  • High-speed morse transmitter
  • High-speed keyer
  • Morse burst-keyer
  • Squirt
  • Squirt transmitter
  1. Peter McCollum, The CK-8 Coder/Keyer
    Website 1999-2017. Retrieved November 2017.
Further information
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Crypto Museum. Created: Monday 03 August 2009. Last changed: Wednesday, 10 July 2024 - 16:15 CET.
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