Figure 1: Christian Hülsmeyer
Christian Hülsmeyer (☆ 25. December 1881 in Eydelstedt, Lower Saxony - † 31. January 1957 in Ahrweiler, Rhineland-Palatinate) is a German inventor and is considered the discoverer of the radar principle.
Hülsmeyer comes from a poor family. His teacher enabled him to study in Bremen. After primary school, he was sent to a school for teacher training in Bremen. In the laboratory there he studied the basics of electricity. After finishing his studies he found a job at Siemens-Schuckert. He worked there for about two years and was responsible for the electrical equipment of ships. On the occasion of the death of a friend who died in a ship collision, he left this company to found a company in Düsseldorf which was engaged in the construction of an apparatus for the detection of maritime obstacles with the help of radio waves.
In 1904 he acquired a patent (Reichspatent Nr. 1655461) for a device which he called “Telemobiloskop”. It used a spark gap as a transmitter, which emitted a directional radio wave via a multipolar antenna. When it hit a metallic obstacle, such as a ship, this wave was partially reflected back to the location of the transmitter, where two dipole receiving antennas were used to set off an electric bell. This system could determine the approximate side angle of ships up to a distance of 3 km but was not yet able to measure a distance.
Hülsmeyer successfully demonstrated the system in Germany and in the Netherlands. However, this did not impress the representatives of the German Navy or any shipping companies. One of the problems was the multiple reflections, which are also possible in case of intensive maritime traffic. Furthermore, the device was quite difficult to operate and the bell was hard to hear because of the engine noise of a ship. Hülsmeyer went back to work and on January 16, 1906, he received a second patent in America for an improved version that allowed false echoes to be filtered out.
The lack of interest of the authorities in this improvement made the device sink into oblivion.