German Naval Radar

Updated 17 October 1999
2. Initial Development
In Germany, it was the Reichsmarine which showed interest in the development of this new ranging device, which could 'see behind the clouds", although they entered the field of electromagnetic echo-ranging from a totally different direction. As early as 1929 the Nachrichten-Versuchsabteilung (NVA: Communication trials department) at Kiel were working on a horizontal sound-plummet capable of detecting submerged targets by measuring returning sound echoes; this was the German forerunner of sonar. NVA's scientific director, Dr. Rudolf Kühnhold, decided to use the same basic principles above water by employing electromagnetic waves, and in 1933 NVA managed to pick up echoes from 13.5cm short-wave transmissions via a parabolic dish aerial. However, due to the rather primitive technical possibilities of the time (a transmitting power of only 100 milliwatts), no return echoes were obtained from metallic objects. At the same time, one of the leading firms in this field. Philips Eindhoven, produced a 50W magnetron for general sales and the German scientist purchased a few to boost their transmitters to 80W. Unfortunately the transmitting system proved unstable.

Dr. Kühnhold now contacted Telefunken to ask if they could take over the development in their highly skilled experimental laboratories. As they rejected this approach, he initiated the foundation of the Gesellschaft für Elektroakustische und Mechanische Apparate (GEMA) in 1934 specifically for this promising field of research. GEMA took over the trials sets, which worked on a wavelength of 48cm (630MHz), and found, in trials on the old battleship Hessen, that the transmitting impulse had to be pulsed to 'clear' the receiver to allow range as well as bearing information to be obtained.

NVA's original civilian contractor, Pintsch (at Berlin), was in the meantime stimulated by the appearance of this new competitor. After feverish work, they succeeded in trebling the emitting power of the 13.5cm valve to 300mW. With the transmitter and receiver spaced 10m (30.4 ft) apart, the echo of the trails vessel Welle (ex. Grille) could be picked up to 2km range but beyond this it faded away due to limited transmitting energy. Parallel trails with one-way communication (UHF-radio telephone) produced results at over 43km range - from Heligoland to Wangerooge!

These results led to heavy competition between the two contractors, with each trying to overtake the achievements of the other. GEMA now succeeded in producing results at 300m (914 ft) range with their improved 48cm set, and later, in October 1934, they managed to obtain a clear echo from Welle at over 12km (6.48nm). GEMA trails at the beginning of 1925 showed that longer waves resulted in clearer echoes with no fading effects, and it was realized that the quality of the echo depended substantially on the silhouette of the target ship (broadside versus end-on). It was therefore decided to build a radar set working on a 2m wavelength (150MHz) and push forward the development of the 13.5cm Pintsch set, although the technical development of the necessary high-energy valves for the latter was proceeding only slowly. Work also continued on the 48cm set, and on 26 September 1935 the improved version was demonstrated in the presence of the German C in C Admiral Raeder; his Commander of the Fleet, Admiral Carls; the head of the Marinewaffenamt (Naval Ordnance Department), Admiral Witzell; and other high-ranking naval engineers. The large gunnery training ship Bremse was obtained to serve as a radar target and good results were produced. As a result of the ensuing discussion, a number of important development decisions were made, together with a decision to replace the existing term for the system, electric bearing, by the less obvious codename Dezimeter Telegraphie (DeTe: decimetric telegraphy). Therefore, all naval radar sets were initially known to the German sailors as DeTe-Gerät which, as they did not know its true meaning, the sometimes misinterpreted as Deutsches Technisches Gerät (German technical device)! Hence we find this term used for the German naval radar sets in the German literature of the first half of the war. The whole matter was so secret that only a handful of specialists actually knew the purpose of the 'grey switchboard' and the curious mattress antenna which began to appear in their ships.

Before being returned to GEMA, the 48cm set was placed on Welle and she thus became the first German naval unit to carry a radar set. To improve its efficiency and bearing accuracy, this set was modified to a wavelength of 82cm (368-370MHz), and thus became the ancestor of the German Seetakt set. 

During February 1936 GEMA finished the above-mentioned 2m set, on a final wavelength of 1.8m (165MHz), and with a peak power output of 8kW. By chance this set obtained a clear return from an aircraft at 28 km (15.1nm) range and it was, therefore, decided to develop it as an air-warning radar, ultimately leading to the generation of sets known as the Freyas

Although it had no direct connection with naval radar, it should be mentioned that Telefunken also entered te field of radar development in 1935. Their 50cm set, characterized by its parabolic dish and spinning lobe, was the ancestor if the air-warning Würzburg radar. This was a land service set but at a later date a few were adapted for naval use - of which more will be said later.

Various small German firms became involved in the development of radar and valve technology expanded rapidly, but, due to the need for secrecy and to the limited finance with which to follow up the many proposals made, development was concentrated mainly with the firms GEMA, Telefunken, Siemens, Lorenz and AEG. In the years immediately before the the Second World War German scientists tended towards the employment of the fixed frequencies, one for each of the three services, in order to facilitate IFF-definitions: 125MHz for aircraft reconnaissance, 368MHz for the navy and 560MHz for AA-ranging.

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