Radio relay system Berlin-Frohnau

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Radio relay system Berlin-Frohnau
Image of the object
Steel lattice tower and the lattice mast that was blown up in 2009
Basic data
Place: Berlin-Frohnau
Country: Berlin
Country: Germany
Coordinates: 52 ° 39 ′ 10.6 ″  N , 13 ° 17 ′ 45.4 ″  E
Use: Telecommunication system
Accessibility: Transmission system not accessible to the public
Owner : German radio tower
Data on the transmission system
Tower / mast 1
Height: 117.5 m
Construction time: 1971-1972
Operating time: since 1972


Tower / mast 2
Height: 358.6 m
Construction time: 1978-1979
Operating time: 1980-2000
Send types: Directional radio , cellular radio
Shutdown : February 8, 2009 (blown up)
Position map
Radio relay system Berlin-Frohnau (Berlin)
Radio relay system Berlin-Frohnau
Radio relay system Berlin-Frohnau
Localization of Berlin in Germany

The directional radio system Berlin-Frohnau (internal radio transmission center Berlin 25 ) in the north of Berlin in the district Frohnau was built in the 1970s by the Landespostdirektion Berlin in order to create additional radio link connections to West Germany . It consisted of a 117.5 meter high free-standing steel lattice tower and a later built, over 358 meter high, guyed lattice mast . After the television tower, it was the second tallest building in Berlin and the fourth tallest in Germany .

Both antenna supports were only used for directional radio and at no time for broadcasting radio programs . Up to 12,600 telephone connections to the federal territory ( Clenze and Gartow ) could be transmitted via the Frohnau system . Its capacity was therefore more than twice as large as that of the Berlin 3 radio link on the Schäferberg . The steel lattice tower that has stood there since 1959, together with the Schäferberg telecommunications tower, enabled up to 5,640 connections in the direction of Gartow or Torfhaus . Alternatively, television broadcasting channels (two in Frohnau and up to seven on Schäferberg) could be switched.

The facility was owned by Deutsche Funkturm GmbH (DFMG), a subsidiary of Deutsche Telekom based in Münster . Since Telekom was no longer used for the facility after German reunification , the lattice mast was blown up in February 2009. Today, the steel lattice tower is mainly used for mobile communications.

Steel lattice tower

In the summer of 1970, work began on a new scatter radio link between Frohnau and Clenze , a place in Lower Drawehn . The steel lattice tower was built from 1971 to 1972 for 2.5 million marks (adjusted for purchasing power in today's currency: around 4.06 million euros). It has a dead weight of 400  tons . 100 m³ of concrete was placed on each of the four foundation blocks. The 92-meter-high tower was given grating platforms at heights of 40, 61 and 82 meters for the installation of the feeder directional antennae. With the tubular mast attached , it reached a height of 117.5 meters.

Two parabolic mirrors ( Cassegrain antennas ) with a diameter of 18 meters each were installed at both locations for the 164 kilometer long radio link to the new Clenze 1 radio transmission point , where an identical steel lattice tower stood. The directional radio devices FM960-TV / 1900 , already tried and tested on the Schäferberg - Torfhaus route, should be used. The radio equipment was set up from autumn 1973. During commissioning, however, it turned out that the transmission quality was very poor, despite the high transmission power of 1000 watts. Interference pulses and level fluctuations were recorded, presumably because of the considerably low altitude above sea ​​level (Clenze 123 m compared to 800 m in Torfhaus, Frohnau 49 m compared to around 100 m at Schäferberg) in connection with the high transmission frequency in the 1.9 GHz range . At the turn of the year 1974/1975 only 360 telephone channels could be switched, followed by the same number a year later. From 1976 to 1993, instead of the planned 3000 telephone channels, only 720 channels were in operation between Frohnau and Clenze.

Lattice mast

The initially 344 meter high lattice mast enabled for the first time, at the same time and structurally constructed mast Gartow 2 on the Höhbeck in the Lüchow-Dannenberg district , a (quasi) line of sight for a low-interference radio link across the territory of the former GDR to the western federal territory . Until this system was commissioned, this was only possible with the help of the complex technology of over- the- horizon radio transmission, which exploited the (weather-dependent) diffraction effect of radio waves with large directional antennas and high transmission powers . With the air line between Frohnau and Gartow, the approximate smallest distance between West Berlin and West Germany was used, it is around 133 kilometers. The height of both towers resulted from the need to overcome the curvature of the earth .

Work on the foundations , in which a total of 2000 m³ of concrete was built, began on March 16, 1977. On May 30, 1978 the topping-out ceremony took place. The square mast with a side length of 4.3 meters was held in place by 15 guy ropes ( guys ). These were 3.8 kilometers long and between 50 and 82 mm thick. There was a load of 22,000 kilonewtons on the spherical bearing of the mast foot  , resulting from the mast weight of approx. 920 tons and the tension of the guys, who themselves weighed 250 tons.

Commissioning was on May 16, 1980; The official handover by Federal Post Minister Kurt Gscheidle was on September 8, 1980. The construction of the mast cost 11.5 million marks (adjusted for purchasing power in today's currency: around 12.65 million euros), plus three million marks for the telecommunications equipment. Initially 1,800 channels were provided, later when fully expanded, the eight radio frequency pairs in the 5.9 and 8.2  gigahertz range could transmit up to 11,880 channels simultaneously, so that the Frohnau system, together with the smaller lattice tower, had a capacity of 12,600 telephone channels.

It took over eight minutes to take the elevator to the operating floor at a height of 324 meters . Its rooms were - together with those of the Gartow 2 mast - the highest closed rooms above the ground of all structures in the EU area . The elevator car could be reached via a steel staircase, as the drive motor was installed at the base of the mast.

The 11-meter-wide operating pulpit was extended from eight to 14 meters in 1982 to create three additional rooms (a total of approx. 65 m²). The relevant agencies of the French and US occupation forces wanted to install eavesdropping technology for the VHF and UHF areas there in order to be able to better record radio operations in the Warsaw Pact area . Since the installation of the antennas also required space, the mast had to be increased by around 14 meters to 358.58 meters.

The security against eavesdropping that was expected of the system later turned out to be an illusion. All radio links to West Berlin were bugged by the Ministry for State Security and the East German NVA . The low-maintenance radio link in the 5.9 and 8.2 GHz range running over the high mast was not taken out of service until the spring of 1999 and the beginning of 2000. In the first half of the 1990s, the mast was also used for the directional radio of the Bundeswehr .

As the maintenance of the lattice mast caused high maintenance costs and there were no more possibilities of use, the owner applied for a demolition permit in 2008 . The mast was blown up on February 8, 2009.

  • The radio relay system in April 2005

  • The lattice mast was blown up on February 8, 2009

AM antenna

Two "stacked total suspended matter (TSP) heads"

During IFA 2001, test broadcasts in DRM mode on the medium wave frequency 1485 kHz took place in Frohnau . Since neither of the two antenna supports in Frohnau was designed for the emission of medium waves, a long wire antenna was installed on a ten meter high mast. The broadcasts were carried out in simulcast from Schäferberg and Rüdersdorf .

See also

Web links

Commons : Funkanlage Berlin-Frohnau  - collection of pictures, videos and audio files

Individual evidence

  1. ↑ a b Details on the mobile radio transmitters ( memento of the original from August 22, 2007 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / funk.breloehr.de
  2. ↑ Peiner Sendemast Frohnau , Technical Information of Peiner Maschinen- und Schraubenwerke AG, Dept. Tower Construction Steffens & Nölle , on richtfunkmast-frohnau.de, accessed on July 17, 2019
  3. ↑ Press release of the Landespostdirektion Berlin on richtfunkmast-frohnau.de, accessed on July 17, 2019
  4. ↑ Press release Bundespostministerium , on richtfunkmast-frohnau.de, accessed on July 17, 2019
  5. ↑ Directional radio links from West Germany to West Berlin at manfred-bischoff.de, accessed on July 17, 2019
  6. ^ The main department III of the MfS , on manfred-bischoff.de, accessed on July 15, 2019
  7. ↑ Report on the demolition of the rbb transmitter mast - evening show from February 8, 2009 on YouTube
  8. ↑ Markus Richter: Explosion on richtfunkmast-frohnau.de, accessed on July 17, 2019