This grounded mast of 357 m, called "I mast" with 5 levels of guy ropes has a predecessor of the same height. It collapsed due to a Sovjet MiG fighter which hit one of the guy ropes in May 1978.
The former mast together with a cage of 12 ropes (flare skirt), erected between 1960 and 1962, was also used as LW antenna.
The present mast is rebuild in 1979. After the collapse of the wall in Berlin the mast was refurbished but it had no rope cage. The guy insulators with narrow spacings referred to the wavelength correspond to the insulation of the predecessor.
The speedy extension ot the transmitting site in Zehlendorf was pushed under the dynamic and optimistic leadership of Dieter Schacht, the chief in charge at that time.
The operating data of today are: frequency = 177 kHz and power= 500 kW. The dimensioning of the antenne and the antenna tuning unit was carried out for the power of 1000 kW.
When reconstructing the here presented cage antenna only six ropes were used, in particular to minimize the stress forces on the mast caused by the rope cage. A large sag for the cage ropes was tolerated in order to reduce the forces on the mast during wind without having big changes of antenna impedances.
Mast and cage form a kind of folded monopole. The cage is fed and the mast is grounded. To be clear: the cage ropes are connecte to the top of the mast directly.
Only a few insulators are needed.
The pull-off ropes, which keeps the cage ropes distant to the mast, are provided with two rod insulators (length 814 mm). They are in parallel due to the high stress forces.
The maximum peak voltage of 70 kV for 1000 kW and 100 % modulation require corona rings for these rod insulators.
All parts of the antenna except the lower guys of the mast are statically grounded.
The existing guy insulation was modified for the upper guys. All guy insulators except for two,- the uppermost and the lowest-, have been bridged in order to ground the guys statically. The lowest insulator of the uppermost guy was bridged by a coil representing a statical short circuit. The coil is a rectance for the operating frequency. The value of the reactance determines the current distribution on the guy. By choosing the right value the current distibution of the antenna remains nearly unchanged comparing to the one with the original insulations.
The rod insulators needed for the feeding of the rope cage at the bottom of the mast are of the same size like the others although due to lower maximum voltages of 16 kV at this point smaller insulators could have been used. These larger insulators were available.