Homepage
Crypto
Spy radio
Index
Glossary
USA
USSR
UK
Germany
Poland
Czechoslovakia
Hungary
Yugoslavia
OWVL
Stay-Behind
Receivers
Other
Burst encoders
Intercept
Covert
Radio
PC
Telex
People
Agencies
Manufacturers
• • • Donate • • •
Kits
Shop
News
Events
Wanted
Contact
About
Links
   Click for homepage
MA-444
Swedish superhet receiver

The MA-444 was a valve-based superheterodyne receiver, developed during WW-II by MILORG/SOE-Section Norway and built by an unknown company in Sweden. The receiver was mainly intended for use by the Norwegian resistance (MILORG/SOE-Section Norway), for listening to the coded messages that were hidden in the news broadcasts of the BBC in London.
 
During WW-II, the Norwegian resistance MILORG listened to the news broadcasts of the BBC in London. Hidden in these broadcasts were coded messages, informing them about droppings of weapons and other equipment and giving them further instructions for sabotage actions, etc.

In September 1941 however, the Germans ordered everyone who was not a member of the Nazi Party, to hand in their receivers. As a substitue, the MA-444 was developed by the SOE-Section Norway (i.e. MILORG technical personnel operating from the UK).
  
MA-444 receiver with original headphones and mains lead

The MA-444 was built by an unknown company in Sweden and is also known as Svenskesuperen (the Swedisch superhet). The picture above shows a pristine example of the MA-444. The receiver was connected directly to the 220C AC mains and had a connection for a high-impedant pair of headphones (2000 ohm) at the rear. A single wire antenna was connected to a socket at the top.
 
The image on the right shows how the head-phones were connected at the rear of the unit. A correct polarity is important, which is why one of the sockets is marked with a red dot. The circuit diagram, reconstructed by Tor Marthinsen in 2000 [3] reveils that the speakers are connected in series with the anode of the 6Q7 valve.

In order to keep the price of the unit down, it was built on a simple chassis and consists of just 4 valves. The frequency dial is visible through a circular window at the front, but is in fact a simple piece of printed paper glued onto a disc.
  
Headphones connected to the rear of the MA-444

The components are protected by a perforated metal case, that is similar to a case that Siemens used at the time for antenna amplifiers [2]. The case provides sufficient shielding and ventilation at the same time. The radio was suitable for the reception of phone (AM) and telegraphy signals on frequencies between 15 and 50MHz. The two knobs at the front are for tuning and volume.

The MA-444 was produced towards the end of WW-II and most units were delivered by the so-called borderpilots to Norway [1] [2], where they were used alongside other clandestine receivers such as the Norwegian Sweetheart. The Sweetheart was a battery powered device, intended for use in the field, whereas the MA-444 was a desktop mains-powered receiver.
 
MA-444 receiver with original headphones and mains lead Rear view of the MA-444 Close-up of the tuning dial MA-444 receiver with the front panel removed Close-up of the tuning dial 2000 Ohm headphones with red and black banana-type plug Headphones connected to the rear of the MA-444 Antenna socket on top of the MA-444
MA-444 receiver Front view of the MA-444 Close-up of the tuning dial Tuning in MA-444 receiver with the front panel removed Close-up of the headphones Rear view of the MA-444 Mains connection at the rear

 
Circuit
The circuit of the MA-444 is build around three valves: A 6J8 as HF mixer and oscillator, a 6K7 for the IF stage and a 6Q7 for the detector and the AF output. The IF frequency is at 432kHz. A fourth valve (25Z6) is used as rectifier. The 2000 ohm headphones are connected in series with the anode of the 6Q7 AF-amplifier.
 
References
  1. Louis Meulstee, Wireless for the Warrior, volume 4
    ISBN 0952063-36-0, September 2004.

  2. Erling Langemyr, Svenskprodusert radioutstyr benyttet i Norge 1940-45
    Hallo Hallo, Nr. 67 (3/99), September 1999, p. 17.

  3. Erling Langemyr, 'Svenskesuperen' MA-444
    MA-444 circuit diagram reconstructed by Tor Marthinsen (2000).
    Hallo Hallo, Nr. 78 (2/02), May 2002, pp. 20-22.

Further information

Any links shown in red are currently unavailable. If you like the information on this website, why not make a donation?
Crypto Museum. Created: Tuesday 25 September 2012. Last changed: Monday, 04 July 2016 - 21:09 CET.
Click for homepage