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Electronic morse burst encoder

The MG-80 was a high-speed burst encoder developed by RFT in Zwonitz (East-Germany, DDR) and was used by the East-German Army (NVA). It is suitable for the transmission of morse and teletype signals and entered service in July 1986, close towards the end of the Cold War (1989).

It's a fully electronic transistorised device, that was built to very high quality standards. It features a high quality keyboard that supports both the Latin and the Cyrillic (Russian) alphabet. All settings (e.g. transmission speed) are controlled via the keyboard. The output level and tone pitch can be adjusted with the knobs just above the keyboard.

The built-in memory allowed 6 messages to be stored simultaneously with a total capacity of 768 characters. When sending directly from the keyboard, a 16-character buffer allowed typing at a higher speed and prevented overruns.
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Morse signals can be transmitted at 30, 40, 50, 60, etc. up to 999 characters per minute, which is equivalent to 10...99 groups per minute in four different formats. Teletype signals are transmitted at 45, 50, 100, 200 or 300 baud from two separate outputs.

The MG-80 was used for transmitting messages at very high speed in order to minimise the risk of detection, but also as a training device for future morse code operators. When used for training purposes, the space between characters and words could be extended.

There are two versions of the MG-80:

  • MG-80
    The basic MG-80 is suitable for transmission of morse code signals only, either in Latin or Cyrillic. It can be used for high-speed (burst) transmissions, but also for training purposes. The MG-80 featured here, is of this type.

  • MG-80M
    In addition to transmission, this version has a built-in receiver, which makes the device also suitable for the reception of morse code and teletype signals.
A complete MG-80 setup consists of a power supply unit (PSU) and a separate main unit, with its own pair of headphones. It was not classified as a secret device and was therefore not destroyed at the end of the Cold War. As a result, many units ended up at the European surplus market. Most of these were in used condition, but the one shown here was found it it's original packaging on a German flea market in 2009. It was built in December 1988 and never saw service.

The drawing above shows a typical MG-80 setup. On the left are the optional morse key and telex unit (e.g. the F-2000). On the right are the transmitter (TX) and the receiver (RX). Please note that a receiver can only be used on an MG-80M version. The MG-80 can be used at temperatures of 0°C and higher. When turned on, it can be operated after the self-test has completed (approx. 3 seconds). When used at temperatures below 0°C, an optional SV80 or SV81 heater has to be used, which is controlled from the MG-80. It takes 15 minutes before the MG-80 can be used reliably.

Z-80 clone
At the heart of the MG-80 is a Central Processing Unit, or CPU (German: Zentrale RechenEinheit, or ZRE), based on the Robotron Z-2521 board (part of the K-1520 computer systems). It features a UA880 processor, which was in fact a Cold War clone of the Zilog Z-80.

The block diagram above roughly shows what is inside the MG-80. At the heart is the Z-80 based K-2521 CPU board. The keyboard is on the left and is connected to PIO-B (PIO: Peripherial Input Output). The LEDs and the data interface are both connected to PIO-A. Some filtering is added to the I/O lines to prevent radio interference. At the bottom right is the temperature control unit that drives the (optional) SV-80 heater. As the CPU can't reliably be operated at low temperatures, the K-2521 board inside the MG-80 is kept in reset at temperatures below 0°C.

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  1. RFT, VEB Messgerätewerk Swönitz. MG-80 Bedieningsanleitung - Nutzung
    MG-80 User Manual (German). Date unknown, but probably between 1986 and 1988.

  2. RFT, VEB Messgerätewerk Swönitz. MG-80 Werkprüfprotocoll mit Garantieurkunde
    Warranty card (example), serial number M1840. December 1988.
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Crypto Museum. Created: Sunday 01 November 2009. Last changed: Wednesday, 11 May 2022 - 06:25 CET.
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