As the costs of erecting a sufficiently high mast were exorbitant, a suspended antenna system in the mountains was conceived. The Herzogstand mountain between the Kochelsee and Walchensee in the Bavarian alps seemed particularly suitable for several reasons: the summit is accessible all year round, sufficient water for drinking and cooling was available, and the conveniently nearby Lake Walchen Power Plant promised a safe, economical power supply. The design of the antenna was unprecedented. As free span a distance of over 2,5 km resulted to reach with a difference in height of 800 m. around a sufficient height of the antenna above ground should the rope at the lower point of suspension horizontally accumulate, which required an enormous tension of the rope. Due to that load by wind, in addition, by snow and ice, additionally which can be expected, only steel wire of highest firmness was applicable. A first thin steel cable became strained in the summer 1920. Radiation measurements resulted in the 1.3 subject radiation and/or the 1.6 subject in the comparison to the overseas Eilvese transmitter in the case of wavelengths of 12,6 km and 9.7 km in the comparison to the high-power radio station Nauen. Up to the early summer 1925 3 antennas were pulled fan-like for the summit burr of the duke conditions. In order to improve conductivity, the steel cable was coated with aluminum. The rope in a particularly developed Seilereianlage within the summit range were manufactured. Around the summit the antennas were fixed to concreted steel anchors. At the lower tie points a mobile suspension system was used, in order to allow the cables to stretch when loaded with snow and ice.
The station building for the transmitting plants and a house was established in the long valley above the Kochelsees, and extensive grounding systems were built. After completion, further development and operation of the station became uneconomic, since advances in short-wave radio communications allowed the use of substantially smaller antennas.
Ionospheric research
The plants were finally placed for research work at the Physical Institute of the Technical University of Munich, where under the direction of Professor J. Zenneck, the first German ionosphere research station developed. Using high-performance emitters of variable frequencies, scientists investigated the propagation of radio waves and their reflections based on the layers of the ionosphere. But as personal antennas were used, the mountain antenna was again diminished in 1934. The slave station was some km distance away in the "office for amplifier" in Kochel. Occasionally additional transmitting plants in Berlin eagle yard, Amberg and Swan Village were used.
End of facility
After the end of the Second World War the ionosphere research continued until 1946. Subsequently, the plant were dismantled, and the factory was torn off. At the Gedenkstein for ionosphere research station today one finds, beside Gedenkstein in the proximity of the Walchenseekraftwerkes, only remainders of the anchorages to that antenna rope as well as some foundations of the station buildings in the forest.
