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AN/GRA-71
Is a Burst coder, used first in combination with the GRC-109.
It was used with spyradios and radios for special units to send out morse code very fast with
300 WPM (words per minute); in order to to lower the possibility of intercept,
and to lessen the time the enemy has to "DF" your location.
(A message of one minute duration was compressed to 1.5 seconds).
The bandwidth of the transceiver had to be broadened. That made listening in by conventional receivers more difficult.
Morsecode is copied to a magnetic tape. All components, to write the code and to read it and send it to the transmitter,
are in the watertight housing of the GRA-71:
MX-4498/GRA-71, the power supply for the "Keyer" . One of the cables on the upper side of the front goes to the
transceiver, the other to the keyer.
Two magnetic tape cassettes MA-9/GRA-71 belong to the GRA-71 (in my case they are lost). A magnetic tape of abt 3 meters length is used to copy the message. It is automatically rewound by a spring
when the cassette is removed from any other component. The tape runs for 32 seconds, or 125 groups of 5 letters.
MX-4495/GRA-71 Dot Dash Coder is one of two devices that writes data to the cassettes. It has three pushbuttons:
. (dot), S (space), and - (dash) . Dot and dash write morse code, space advances the tape without a sign.
MX-4496/GRA-71 Wheel Coder is the second device to write data to the tape (also lost). Letters are written to the tape with the aid of two letter disks.
The Keyer KY-468/GRA-71 reads the magnetic tapes and sends the data to the transceiver, it also deletes the data on the tapes. It
is connected to the cable end "keyer " of the power supply
MX-4498/GRA-71.
A second letter wheel and a camel hair pencil are also part of the
GRA-71.
The collection's radios that can work togehter with the GRA-71:
GRC-109,
RS-6,
PRC-64
PRC-74 B
PRC-104.
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RBZ
GRC-109