High-speed data encoders
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
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
and the use of various military and civil
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.
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
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 :
1959Coder/Keyer (military: AN/UGT-1)
1959Coder/Keyer (military: AN/GRA-71)
1960Coder/Keyer (used with RT-6)
1964Coder/Keyer (special version of CK-8)
1965Coder/Keyer (compatible with RT-49)
1965Coder/Keyer (used with AS-12)
1966Coder/Keyer (used with ASR-100 transceiver)
1970Morse coder/keyer (film-based)
1973Baudot version of CK-33
1974Baudot coder/keyer with built-in encryption
1973Baudot coder/keyer with built-in encryption
1973Morse coder/keyer (compatible with ➤ RS-59)
Burst encoders are known by the following names
- Burst encoder
- Burst transmitter
- Burst keyer
- Burst coder
- High-speed burst transmitter
- High-speed morse transmitter
- High-speed keyer
- Morse burst-keyer
- Squirt transmitter
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© Crypto Museum. Created: Monday 03 August 2009. Last changed: Sunday, 04 February 2024 - 09:46 CET.