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DAB-3
Radio Direction Finder - not in collection

The DAB-3 was a complete Radio Direction Finding System, or Radio Direction Finder (RDF), developed in 1942 by the Collins Radio Company in Cedar Rapids (Iowa, USA), for the US Navy. The unit is suitable for the 2000 to 18,100 kHz range, and was used during WWII for locating German U-Boats. After the war they were used in Europe as a Cold War radio countermeasure.

DAB consisted of a double receiver with two long horizontal arms. At the end of each arm was a cross-connected loop antenna. By measuring the phase difference between the two antennas and displaying it on an oscilloscope, it was possible to get an accurate bearing of a radio signal [B].

The system can be seen as a shore based variant of the spaced loop direction finding system, that was developed by the Marconi Company and the UK National Physical Laboratories. In practice, it was the US variant of the UK's HF/DF (Huf-Duf).
  
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The DAB system was installed in a two-floor wooden building that also acted as its concealment. A description of the dimensions and materials were supplied in the instruction manual [A]. It was constructed in such a way that the building had minimal effects on the quality and bearing of the intercepted radio signal. The antenna had to be rotated manually by an operator standing behind the receiver, in order to obtain a bearing. The DAB system was developed by Collins during WWII.

Four variants were manufactured, known as DAB, DAB-1, DAB-2 and DAB-3, all of which are more or less identical. Once the war was over, several DAB stations were installed along the European North Sea coast, in order to be prepared for the event of a potential war with the Soviet Union.

In the Netherlands, 7 DAB stations were erected. They were used in the early years of the Cold War for monitoring East-European radio traffic and following the movements of troops behind the Iron Curtain. The Dutch Radio Monitoring Service RCD was responsible for their operation.
  
Original DAB-hut, now serving as the amateur radio station of Radio Club De Bevelanden in Goes (Netherlands). Image via Google Maps [2].

Over time, the DAB systems were gradually replaced by modern alternatives, that were installed in the existing DAB houses. As far as we know, two of the seven DAB locations in the Netherlands have survived: Post GOLF in Wilhelminadorp (near Goes, Netherlands) – now the home base of Radio Club De Bevelanden [2] – and Post HOTEL in Hoogezand, which has recently been restored.

Parts
A complete DAB-3 system consisted of the following major units:

  1. 55A-2
    Tuner Unit A 2
  2. 55B-2
    Tuner Unit B 2
  3. 55C-2
    Oscillator Unit 2
  4. 55D-2
    Mixer Unit 2
  5. 347A-2
    IF Amplifier 2
  6. 409R-2
    Power Supply
  7. 347E-2 1
    Commutator 2
  8. 26R-2
    Audio Amplifier
  9. 54G-2
    Monitor Unit 2
  10. 82S-2
    Meter Panel
  11. 101T-2
    Control Panel
  12. -
    Miscellaneous Equipment
  13. 347B-2
    Oscilloscope Amp. & Motor Relay
  14. 348E-3
    Right Loop Assembly
  15. 348E-4
    Left Loop Assembly
  1. From serial number 17 onwards, Commutator Unit 347E-3 was used.
  2. Spares available for sale.



Available for sale
A number of modules of a DAB-3 system are held in the collection of an associated museum in the Netherlands. At present it is not possible to build a complete DAB-3 system from these modules, but they could be of use to another museum or a private collector when restoring an existing DAB-3 installation or for displaying purposes. If you are interested, please contact us.

Spares available for sale
  • 54G-2
  • 55A-2
  • 55B-2
  • 55C-2
  • 55D-2
  • 347A-2
  • 347E-3 (2 pieces)
Some examples
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Documentation
  1. Instruction book for the Navy Model DAB-3 Radio Direction Finder - Part 1
    Instruction book for the Navy Model DAB-3 Radio Direction Finder - Part 2
    Full description and circuit diagrams (in two parts). Restricted.
    Collins Radio Company, 10 December 1942 - 18 May 1943. CM302612.
     Circuit diagrams in high resolution (600 dpi)

  2. DAB, DAB-1, DAB-2 and DAB-3 Radio Direction-Finding Equipments
    Catalogue of Naval Electronic Equipment. April 1946. Unclassified.

  3. Section 4, Direction-Finding Equipment, D-Series
    Communication Equipment Maintenance Bulletin.
References
  1. Wikipedia, Direction finding
    Retrieved April 2017.

  2. Google Maps, Radioclub de Bevelanden, Wilhelminadorp
    Retrieved April 2017.
Further information
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Crypto Museum. Created: Friday 07 April 2017. Last changed: Monday, 09 January 2023 - 13:00 CET.
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