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SE 74/12
Abwehr spy radio set - this page is a stub

SE-74/12 was a clandestine suitcase transceiver, or spy radio set, developed around 1938 by OKW-Aussenstelle Berlin-Stahnsdorf 1 for use during World War II by the German Security Service, the Abwehr. It is believed that this is one of the earliest suitcase radio sets used by the Abwehr.

The set consists of an S-74/12 transmitter with an output power of 12 Watts, an E-74 receiver and a matching mains power supply unit (PSU), mounted together in an unobtrusive suitcase.

At present we do not have a picture of this suit­case radio set, but from surviving documents in the British National Archives, we know some of its properties [1]. When German spy Franz Mayr was arrested in Iran (Persia) in August 1943, he was in possesion of a large quantity of paper­work – including instructions for the SE-74/12 – most of which were translated by MI5/MI6 [1].
  
No image available

It is very likely that these instructions were for the SE-74/12 radio sets that had previously been used by the German Embassy in Tehran (Iran). When the Germans were forced to leave Iran, they handed the radios over to the Japanese, who kept them until they were forced to leave as well. When the radios finally ended up in the hands of the British, they were no longer operational.

It is believed that the circuit diagram of the transmitter is similar to that of the S-87/20 that was released in 1939, given the fact that the same valves (tubes) are used in the design. The output power of the S-74/12 is somewhat lower than that of the S-87/20 — it delivers 12W instead of 20W — because standard valves were used, whilst the S-87/20 came with special selected valves.

  1. OKW = Oberkommando der Wehrmacht (Supreme Command of the Armed Forces) in Nazi Germany during the Second World War. Aussenstelle = Outpost.

PLEASE HELP — At present no further information about the SE-74/12 is available and we have so far never seen a picture of the set. From surviving documents we know that it existed, however. If you have any information, documentation or image(s) that might help us to expand this page, please contact us.

Specifications
Transmitter
  • Output
    12 Watts
  • Valves
    EDD11, 2 x EL11 (or EL12)
  • Stages
    Oscillator, Power Amplifier (PA)
  • Frequency
    4,730 - 7,530 kHz and 8,020 - 12,640 kHz
  • Tuning
    Variable Frequency Oscillator (VFO)
  • Antenna
    Symmetrical dipole (wire)
Receiver
  • Valves
    3 x EF12
  • Stages
    RF amplifier, Detector, AF amplifier
  • Frequency
    4,250 - 13,650 kHz
PSU
  • Input
    220V AC (other voltages available)
  • Valve
    AZ12 (rectifier), GR150 (stabilizer for RX voltage)
  • Fuses
    2 A (input), 500 mA (output)
Documentation
  1. SE-74/12 operating instructions (English)
    Translated by MI5/MI6 [1].

  2. EDD11 valve datasheet 1
    Telefunken. September 1938, April 1939.

  3. EL11 valve datasheet 1
    Telefunken. June 1938, June 1940.

  4. EL12 valve datasheet 1
    Telefunken. August 1939 — July 1943.
  1. Obtained from Frank's Electron Tube Pages [3].

References
  1. MI5/MI6, The Franz Mayr Case
    Translation of documents found in possession of German agent Franz Mayr upon his arrest in August 1942 in Iran (Persia). DSO 1 CICI 2 (SIME) 3 interrogations.
    Crown Copyright. KV 2/1482-7, pp. 77-79. Obtained via [2].

  2. Arthur Bauer, The Franz Mayr Case
    Personal correspondence, March 2018.

  3. Frank Philipse, Valve datasheets
    Website: Frank's Electron tube Pages.
  1. DSO = Defence Security Officer.
  2. CICI = Combined Intelligence Centre Iraq (and Persia).
  3. SIME = Security Intelligence Middle East.

Further information
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Crypto Museum. Created: Friday 30 March 2018. Last changed: Saturday, 12 May 2018 - 16:12 CET.
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