Seetakt (Radar)

The Funkmessgerät FuMG 38G Seetakt was an early naval radar of the German Navy in World War II. It was developed in the 1930s.

Development

In the German Reich Hans Erich Hollmann began in the late 1920s, with work in the field of microwaves, which should form the basis of most radar systems around the world later. During this time he was interested particularly the use of microwaves for communications, but his partner Hans -Karl von Willisen and he also worked in the field of radar-like systems.

In the year 1934, Hollmann, of Willisen and Paul Guenther Erbsloh a company called GEMA ( Society for Electro- Acoustic and Mechanical appliances mbH). In the fall of 1934, the company GEMA built the first commercial radar for the detection of ships. It worked on a wavelength of 50 cm and was able to capture ships within up to 10 km away. The system was similar to the development of Christian Hülsmeyer, it could also show no distance information.

On behalf of the Navy, a pulse radar was developed, which enabled them to capture the summer of 1935 the light cruiser Königsberg at a distance of 8 km with an accuracy of 50 m. That was good enough for the fire control system for ships. The same system was also able to detect an aircraft at 28 km distance and 500 m height. The military utility was not allowed at this time ignored. The development of a land-based version of successes under the name Freya that the sea-based versions under the name Seetakt. For the Navy, the focus of the development was first on the distance measurement, the view of objectives and obstacles at night and in bad weather was the next point in the priority list. The use of radar as a target for which the Würzburg radar was developed for the Wehrmacht, was initially irrelevant for the Navy.

The first prototype used nor the wavelength of 50 cm or 600 MHz. Since these frequencies, however, were still difficult to control at that time, and GEMA also have little experience in the series production, especially for rough use on vessels owned, the first device worked from the production series at 60 cm or 500 MHz and was January 1938 is installed on the battleship Admiral Graf Spee. Thus, the Navy decreed due to the initiative of some predictive officers well before the Royal Navy and the U.S. Navy have functioning radars on their ships. The further development was delayed because both the Navy and the GEMA project when ate not a high priority. Moreover, few people were for reasons of secrecy always informed and detailed documentation for error suppression (eg circuit diagrams) not on board.

Technology

Later devices (eg FMG 41gU or FuMO 29) were then run on 82 cm to 77 cm and 368 MHz to 390 MHz. With a peak power of 8 kW, a pulse length of three microseconds and a pulse frequency of 500 Hz goals in a ship's size could be detected at sea on a good day in up to 220 km away, but normally the maximum detection distance was only 110 km. The accuracy was approximately 70 m and three degrees off-axis.

Approximately 200 Seetakt devices were prepared and surface ships, submarines and - used on land for coastal defense - in greater numbers. On submarines, the range was due to the lower antenna structure with 7 km far below, and the detection range was limited to 60 degrees.

Discovery

At the end of 1939, only four Seetakt devices were due to the Entwicklungshemnisse and the still low reliability in use, one of which was on the plunder from September to December 1939 the battleship Admiral Graf Spee been of great benefit. On 13 December 1939, she was involved in a naval battle against Montevideo, where it was so damaged that the port of Montevideo in neutral Uruguay had to be started. Since there was threatened with internment and the damage could not be repaired sufficiently to be able to continue the use can, the Admiral Graf Spee was after three days port stay outside the Uruguayan territorial waters to be scuttled by demolition. The crew had previously left the ship and was interned. The ship was not very deep sunk and not completely covered in its upper parts of water. Therefore, the antenna of the device Seetakt still sticking out of the water and was noted after a visit by the Royal Navy in its report to the home office. Few took note of the report, with the exception of Reginald Victor Jones, a scientific expert in the British military intelligence for which this report was very revealing: allow but already the antenna dimensions conclusions on the frequency ranges used.

After the fall of 1940, due to targeted attacks on nightly convoys in the channel region suspicions about a British Chain Home system similar system arose in the Royal Navy, who knew nothing of the German radar equipment on the German side, NE Davis, a communications engineer the company Marconi, responsible for further investigation. With a wide- band receiver, he succeeded in recording the Seetakt broadcasts and in February 1941 six jammers were installed on these frequencies at Dover on the Channel coast: the radar war began.