RADAR: The Range and Direction Finder (RDF) Type 289

 

The Range and Direction Finder (RDF) Type 289

 

Von Weiler went to work at the Admiralty Signal Establishment (ASE) at Portsmouth. This was renamed the Admiralty Radar Establishment and later the Admiralty Surface Weapon Establishment (ASWE). Under Von Weiler’s direction, using parts from the aforementioned third device, another fully electric listening device was made, equipped with two English Yagi antennas (‘fishbone aerials’) placed in parallel without a hybrid circuit (i.e. 3 dB splitter). The antenna structural elements were made of synthetic-resin laminated wood. The system was named Range and Direction Finding Type 289 (RDF 289), also known as the ‘Dutch RDF’.

On the 9th of October 1940, the Experimental Captain’s Conference took place in Portsmouth discussing the fitting of type 289 and other RDF sets on the HNLMS Isaac Sweers and the HNLMS Jacob van Heemskerck. The book Radar at Sea [Derek Howse, p343] provides some outline details on the RDF 289 and says it was fitted in both the HNLMS Isaac Sweers and the HNLMS Jacob van Heemskerck. No confirmation, however, has been found on the RDF type 289 installation on the Jacob van Heemskerck.

Two modern, stabilised Hazemeyer fire controls (one at the B-tower and one at the AA platform) were installed on the HNLMS Isaac Sweers. The two fire controls controlled a double-mounted 40 mm anti-aircraft Bofors machine gun. Each fire control was linked to an RDF 289 serving as a range and direction finder. The two sets were located in a forward and an aft RDF hut. A unique combination that was the first of its kind in the world. Sea trials and operational use succeeded: when Italian or German attacking craft appeared, all guns were pointed in the right direction.

In September 1941, the HMLMS Isaac Sweers sailed to Malta as an escort ship for a convoy. Von Weiler wanted to make this journey on board. For that, he had to become a military. On the spot, he was appointed Lieutenant commander (LTZ1), received a uniform and was sworn in onboard [Rollema].

Unfortunately, the HNLMS Isaac Sweers was lost on the morning of 13 November 1942 northwest of Algiers by two enemy torpedoes fired by the German submarine U-431 under the command of Wilhelm Dommes.

Royal Netherlands Navy officers who had to operate the RDF 289 system received a SECRET manual that explained the basic principle of radar technology understandably as well as operating instructions. The manual also contained instructions for resolving system malfunctions. Neither system parts nor the manual was allowed to be taken ashore.

(note: in its archives, the Museum has detailed electronic and construction drawings of the RDF 289 installation and the Yagi antenna on the HNLMS Isaac Sweers)

 

Electric listening device transmitter-receiver on the HNLMS Isaac Sweers with the J-scope and headphones
Electric listening device transmitter-receiver on the HNLMS Isaac Sweers with the J-scope and headphones (a.k.a. RDF 289)

 

The fire-control radar transmitter
The RDF 289 fire-control radar transmitter

 

The schematics of the transmitter with the Kolster circuit
The schematics of the RDF 289 transmitter with the Kolster circuit

 

Bouwtekening van het voedingsapparaat
Schematics of the RDF 289 power rectifier (including a power safety switch) 

 

Fire control antenna of the HNLMS Isaac Sweers mounted with the Bofors twin mounted 40 mm anti-aircraft guns
The fire control antenna of the HNLMS Isaac Sweers mounted with the Bofors twin-mounted 40 mm anti-aircraft guns

 

Fire control antenna of the HNLMS Isaac Sweers mounted with the Bofors anti-aircraft guns (backside)
Fire control antenna of the HNLMS Isaac Sweers mounted with the twin mounted 40 mm Bofors anti-aircraft guns (backside)

 

De dubbelloops 40mm-mitrailleur met radar van Hr. Ms. Isaac Sweers
The twin-mounted Bofors 40 mm machine guns with the RDF289 radar of the HNLMS Isaac Sweers

 

Systeemtekening RDF 289 (tweede versie met een goniometer boven de kathodestraalbuis) uit 1941 door Von Weiler
The RDF 289 system – second version with a goniometer above the cathode ray tube  (1941)

 

Hr.Ms. Isaac Sweers near Southampton
HNLMS. Isaac Sweers near Southampton

 

Sources
  • To a large part, this text is a translation of Van Soest’s contribution to the book Physisch Laboratorium 1927 – 1977. Details are clarified with information from Van Soest’s article in the Ingenieur jrg. 84. nr 9, 3 maart 1972 (Dutch). Moreover, some details were clarified by Ir. Max Staal’s in “Hoe de radar naar Hengelo kwam” set of articles in Roering 1996-1998, and several other articles.
  • Von Weiler and Staal, Electromagnetic Range and Direction Finder, 82 Zeer Geheim/Top Secret (expired classification), June 1940 – a description of the workings and performance of the Dutch Electric listening device 
  • Archives Electric Listening Device/Von Weiler’s and Admiralty’s HM Signal School drawings at Museum Waalsdorp
  • [Dutch] “De bewogen en kortstondige loopbaan van de “Sweers”, hoofdstuk VII in  K.W.L. Bezemer (1954), Zij vochten op de Zeven Zeeën: verrichtingen en avonturen der Koninklijke Marine in de Tweede Wereldoorlog.
  • [Dutch] prof. dr.ir. J.L. van  Soest (1972). IIa. Radar en Von Weiler, Symposium Elektronische Navigatie, NERG, pdf
  • [Dutch] R. van der Hulst en E. Goldbohm, Radar: een vergeten stuk geschiedenis, De Ingenieur, 2(1985)52-59
  • [Dutch] Over Von Weiler, Roering jg 33, nr 1, p.72, 1996.
  • [Dutch] Ir. D.W. Rollema (1983), Radarontwikkeling vóór de Tweede Wereldoorlog, Radio Bulletin, 12/1983, pp 493-494