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MA-4010
High-speed morse unit

The MA-4010 was a tape-based burst encoder, developed in the 1970s by Racal Datacom Ltd in Salisbury (UK). It was used for recording morse code signals and transmitting them at high speed over a radio channel, in order to minimize the risk of detection and radio direction finding (RDF).

The electronic device is partly mechanical. It has a fixed internal ferro-magnetic audio tape that can hold just over 10 minutes of data in morse code, which is entered by means of a morse key that is connected to one of the audio sockets.

Once a morse coded message has been recorded at regular speed, it can be played back through a connected transceiver and 10 times the speed. This minimises the time that the transmitter is on air and, hence, the chance of interception and detection. As a result it will be more difficult to locate the station by means of direction finding.
  
Racal MA-4010 burst encoder

A signal that is sent at high speed, is known as a burst transmission. Unlike many other burst encoders, the MA-4010 can not only be used for initiating burst transmissions, but also for receiving them. When recording a message, the clock indicator at the centre of the front panel shows how much tape is used (in minutes). The device's status is shown by three red LEDs.

It is currently unknown who the primary user of the MA-4010 was, but it is likely that they were used by special military services, such as the Special Forces (SF). The model number tag suggests that there were several variants of the device, which might explain the inconsistency between the service manual [A] and the actual AUDIO sockets of the MA-4010/8 featured on this page. It is one of the last electromechanical burst encoders, before the arrival of fully electronic ones.

Racal MA-4010 burst encoder Rear view Racal MA-4010 burst encoder Front panel MODE selector Tape position indicator (10 minutes) and three LED indicators Connections Serial number tag
A
×
A
1 / 8
Racal MA-4010 burst encoder
A
2 / 8
Rear view
A
3 / 8
Racal MA-4010 burst encoder
A
4 / 8
Front panel
A
5 / 8
MODE selector
A
6 / 8
Tape position indicator (10 minutes) and three LED indicators
A
7 / 8
Connections
A
8 / 8
Serial number tag

Controls
All controls and connections of the MA-4010 are located at the front panel, with the exception of the power terminals, which are at the rear. The unit is suitable for connection to a short wave (SW) radio, and should be inserted between the handset and the transceiver. It requires a morse key to be connected to the second audio socket. Ensure the tape is fully wound back to the start.


The required mode of operation is selected with the 9-position knob at the bottom right. In the centre position, the device is turned OFF. The 4 positions on the left are used for entering and transmitting a message. Likewise, the 4 positions on the right are used for receiving a message. When recording a message, the clock indicator at the center shows the tape progress. The current status of the device is reflected in three LEDs, REC, AUX and RUN, just below the clock indicator.





Interior
The MA-4010 is housed in a metal enclosure that is nearly identical to that of the Racal MA-4204 time domain voice scrambler, that was developed around the same time. It consists of a metal frame that holds all mechanical and electronic circuits, and that is attached to the front panel.

The device is enclosed by a metal case shell, that can be removed by loosening the two large bolts at the rear and sliding it off. The front half of the interior is occupied by the mechanics of the tape recorder that also holds the ferro-magnetic tape.

The rear half of the frame contains the electronic circuits, which are divided over three densely populated printed circuit boards (PCBs), two of which are hinged and can be tilted outwards as demonstrated in the diagram above this section. This makes the device very service-friendly. The boards are interconnected by bundled wiring.
  
Mechanical construction

The mechanical section is more difficult to access. It consists of several high-precision machined parts, that are driven by a small electromotor via a series of nylon cogwheels. The device can be powered by an external battery that is attached at the rear side. Alternatively, it can be powered directly from the transceiver, via the 6-pin Clansman-standard TCVR socket on the front panel.

Interior - top view Interior - bottom view Wiring PCB - solder side Top PCB up Bottom PCB up Interior with unfolded PCBs Interior with unfolded PCBs
PCB detail Mechanical construction Mechanics Mechanics Detail Wiring detail Motor Fuses
B
×
B
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Interior - top view
B
2 / 16
Interior - bottom view
B
3 / 16
Wiring
B
4 / 16
PCB - solder side
B
5 / 16
Top PCB up
B
6 / 16
Bottom PCB up
B
7 / 16
Interior with unfolded PCBs
B
8 / 16
Interior with unfolded PCBs
B
9 / 16
PCB detail
B
10 / 16
Mechanical construction
B
11 / 16
Mechanics
B
12 / 16
Mechanics
B
13 / 16
Detail
B
14 / 16
Wiring detail
B
15 / 16
Motor
B
16 / 16
Fuses

Connections
All connections of the MA-4010 are at the front panel. In total, there are three audio sockets — one of which connects the unit to the transceiver — and a ground terminal. The pinout of the three sockets is given below. Note that the pinout of the two 6-pin audio connectors is different from the 8-pin audio sockets of the MA-4010/8 that is featured on this page.

Audio 1
  1. Mic (input)
  2. Battery charging (+)
  3. PTT (input, switched to ground)
  4. Ground (battery charging –)
  5. Key
  6. Speaker (output)
    6-pin female socket
Audio 2
  1. Mic (input)
  2. Power supply to ancillary (+)
  3. PTT (input, switched to ground)
  4. Ground (ancillary –)
  5. Key
  6. Speaker (output)
    6-pin female socket
Transceiver   TCVR
  1. High speed key output (or microphone output)
  2. Auxiliary power input (+)
  3. PTT (output)
  4. Ground
  5. Key (output) 1
  6. Speaker (output)
    6-pin male socket
  1. Except in KEY, CHECK, REPLAY or during high-speed transmission.

MA-4010/8 model
The MA-4010/8 version of the device, which is featured on this page, has two 8-pin female audio sockets, rather than the 6-pin Clansman type specified in the manual (and in the tables above). The wiring of these sockets is currently unknown.

Audio 1
  1. ?
  2. ?
  3. ?
  4. ?
  5. ?
  6. ?
  7. ?
  8. ?
    8-pin female socket
Audio 2
  1. ?
  2. ?
  3. ?
  4. ?
  5. ?
  6. ?
  7. ?
  8. ?
    8-pin female socket
Help required
At present we have no further information about the Racal MA-4010. If you have any additional information, such as a user manual or the pinout of the 8-pin audio sockets, please contact us.

Documentation
  1. MA-4010 circuit diagrams and parts list 1
    Racal Datacom Ltd. Date unknown.
  1. Obtained from jdosher@blueyonder.co.uk

Further information
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Crypto Museum. Created: Friday 30 June 2017. Last changed: Saturday, 01 July 2017 - 08:35 CET.
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