Herzogstand Radio Station
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The radio station at the Duke booth was a radio system that was built from 1920 to 1946 at Duke stand near Kochel am See in Bavaria and operated. The plant was designed by the C. Lorenz AG as an independent resource for wireless communications on long waves between Germany and the Far East, as the existing major radio stations primarily related to the transport to the west.
As of 1930, the facility was used as a research and experimental station of the Technical University of Munich for ionospheric research.
The construction of the mountain antenna
Since the cost of the poles of a large station for the company were prohibitive, the antenna system should be hung in the mountains. The 1735 m high Herzogstandbahn between Lake Kochel and Walchensee in the Bavarian Alps seemed particularly suitable for several reasons: The peak is accessible all year round, at the station square drinking water and cooling water was plentiful and the nearby Walchenseekraftwerk promised a safe, cost-effective energy supply.
For the intended design of the antenna, there was no experience. As a free span, there was a distance of over 2.5 km, with a vertical drop of 800 m. In order to achieve a sufficient height of the antenna above ground, the rope should run up horizontally at the bottom of suspension, which required a tremendous tension of the rope. Due to the additional load expected from the wind, but also by snow and ice only steel wire highest strength came into question.
A first thin steel cable was stretched in the summer of 1920. Radiation measurements revealed at wavelengths of 12.6 km and 9.7 km in comparison to the large radio station Nauen 1.3 times radiation or 1.6 times compared to overseas stations Eilvese. By early summer of 1925, three antennas were drawn in a fan shape to the summit of the Duke article. In order to achieve better conductivity, the steel cord has been provided with a sheath of aluminum. The ropes were manufactured in a specially built Seilereianlage in the summit area. In the area of the summit, the antennas were fixed to cast- steel anchors. At the bottom anchor point a movable suspension was used to allow yielding of the ropes when loaded with snow and ice.
The station building
The station building for the transmitting equipment and a house were built by the main post office in Munich under the direction of Robert Vorhoelzer and Walther Schmidt in 1927 in Vallelunga above the Kochel. Here also extensive grounding systems were built.
After the completion of a further expansion and operation of the station appeared technically and economically not meaningful, since now worldwide radio compounds could be performed on shortwave cheaper with much smaller antennas.
Ionospheric
The facilities were made available for research from 1930 to the Physical Institute of the Technical University of Munich. Under the direction of Jonathan Zenneck here was the first German Ionosphärenforschungs station. Zennecks assistant Georg Goubau used outside its program times the Munich Radio stations for broadcast short characters (pulses) on medium wave. The echo signals were initially a few kilometers away in Kochel, then registered at the station itself. Later pulse programs were, in particular by Walter Dieminger performed with their own transmitters, which were well received at greater distances. For your own antennas were built; the mountain antenna was dismantled in 1934. Kochel Berlin was the first impulse remote connection, established explanations about the various propagation paths of the short waves between the ionosphere and the earth with the Rudolf Eyfrig. A transmitter-receiver system with variable frequency was created by Georg Goubau and Theo Netzer, put into operation in 1937 and operated until 1946 by an ongoing basis. The results of an image of the switched -free electron density as a function of the amount that has been helpful for predicting the propagation conditions.
The end of the station
After the Second World War, the station operation was continued under U.S. supervision until 1946, but spent all existing registrations to America. Because ionospheric research was banned in the occupation era, the operation of all systems was then prohibited, removed, demolished the premises.
Today you can find next to a memorial stone near the Walchenseekraftwerk work only remnants of the anchorages of the antenna cables as well as some foundations of the station building in the woods. The remains of the aerial anchors were taken from the Bavarian State Conservation Office, as a historic monument in the Bavarian list.
Similar systems
A long wave radio station with a mountain antenna was taken in 1923 in Malabar on the island of Java in Indonesia today for wireless communications with Holland in operation.
Similar transmitting antennas were built after the Second World War for three transmitters of the Omega navigation method ( in Aldra, Hawaii and Trinidad ), for the VLF transmitter JXN at Aldra, for the Jim Creek Naval Radio Station and for the VLF transmitter ICV Tavolara.