High-speed data encoders
During WWII and during the Cold War, wireless communication over long
distances was often done on the HF radio bands (short wave)
using morse code.
As the enemy was continuously trying to intercept and track down such
messages using radio direction finding (RDF),
it was necessary to be on the air as little and as short as possible.
Furthermore, it was important to make effective use of the limited
frequency space that was available, especially when sending long messages.
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
increased drastically and new methods had to be devised to avoid detection.
This resulted in the development of Burst Encoders
and high-speed morse keyers.
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,
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
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
1973Morxe coder/keyer (compatible with ➤ RS-59)
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© Crypto Museum. Created: Monday 03 August 2009. Last changed: Saturday, 08 December 2018 - 14:20 CET.