Radio links to West Berlin

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Radio relay system Berlin-Frohnau : The 358 meter high lattice mast on the left was blown up in early February 2009. The smaller (117.5 m) antenna support on the right is still used.

The radio link to West Berlin was created as a result of the Berlin blockade, which began on June 24, 1948, to secure the telephone connections between West Berlin and West Germany , regardless of the existing cable routes. Since the long-distance lines leading westwards from the Berlin Fernamt in Winterfeldtstrasse in the American sector of the enclosed city could be interrupted at any time by the Soviet military administration in Germany (SMAD), solutions were researched and implemented to supplement or replace these with radio link connections.

The establishment of directional radio links was difficult because of the large distances to be bridged (135–190 km) across the territory of the Soviet occupation zone or GDR and was at the limit of what was physically feasible.

history

The main problem was the long distance of around 135 kilometers in the direction of Gartow ( Höhbeck ), which had to be bridged from the Wannsee or Frohnau area in the north of Berlin. It was around 190 kilometers from the Schäferberg on the Wannsee island in the direction of the Upper Harz . These so-called directional radio fields could not be bridged by the radio relay systems available at the time for military use, which came from the Wehrmacht . The decimeter devices of the type DMG 5 K ( code name : "Michael" device) developed by Telefunken for the Luftwaffe at the end of the 1930s worked on frequencies from 502 to 554 MHz with radio fields of a maximum length of 50-100 kilometers.

Since there should be a (quasi) line of sight between the terminals for low -interference transmission , antenna supports ( lattice masts ) around 340 meters high were required on both sides due to the elevation of the earth, even on the shorter Frohnau - Gartow route . This was not realized until the late 1970s.

All radio links to West Berlin were bugged by the Ministry for State Security and the East German NVA .

First temporary arrangements (1948–1950)

In 1948 the British occupying forces carried out the first radio relay test between the Berlin radio tower and the Bocksberg in the Harz Mountains . Initially only three, later eight channels were available for voice transmission.

After the beginning of the Berlin blockade were first with Lorenz - FM - way radios of the type of Munich , which is actually for the police radio were meant conducted experiments. These showed that despite the lack of line of sight and only 100 W transmission power in the frequency range between 35 and 85 MHz, it was possible to establish a radio link between West Berlin and West Germany.

Just a few days after the end of the war , on May 19, 1945, the post and telecommunications system of the later divided city was subordinated to the Berlin magistrate as the "Department of Post and Telecommunications of the Magistrate of Greater Berlin " and thus became a communal matter. In the western sectors from January 1951 the " Senate Department for Post and Telecommunications" (SVPF) was responsible. There was never a Deutsche Bundespost Berlin organization - this term was only found on Berlin postage stamps . See also: Oberpostdirektion - Berlin .

First of all, the Berlin - Torfhaus / Oberharz line was put into operation, which was 190 kilometers longer, but offered the option of placing the antennas higher in the Harz Mountains, which somewhat compensated for the greater distance. A simpler connection to the long-distance telephone network was also possible there. The transmitting and receiving points were spatially separated for better decoupling . In the Harz Mountains, the sending and receiving points were about 600 meters apart on the Lark's Heads , a two-headed ridge in Torfhaus. The (weather-dependent) diffraction effect of radio waves was exploited with large directional antennas and high transmission powers . From October 1948 Torfhaus was transmitting on 38.4 MHz in the direction of Berlin, the return channel worked on 35.5 MHz. Were used frequency-modulated carrier frequency systems (TF) systems with eight channels of type MEK 8 ( M ehrfach- E inzelkanalgerät for K portable and overhead lines), by the AEG were developed in the 1930s.

In Berlin, two 40-meter-high steel lattice masts were erected on the roof of the Heckeshorn bunker at the Wannsee transmitter . The "fir tree antennas" ( dipole fields ) were suspended between the masts. In the Grunewald reception area , there was an identical antenna system on a ruined building of the military technology faculty planned during the Nazi era, southwest of the Olympic Stadium , where the Teufelsberg is today. Both locations were connected to the Berlin remote office in Schöneberg via cable or radio relay .

A second MEK-8 system was operated from December 1948 on the frequencies 41.7 and 44.5 MHz. In August 1949, third connection 15 voice channels maintained 64 and 68 MHz in the VHF band I to the the more powerful TF device MG 15 ( M ehrfach- G 'groups) system used, so that between Berlin and peat now 31 voice channels were available. The MG-15 system with single sideband modulation and suppressed carrier came from Siemens & Halske. All three directional radio links were operated with VHF radio transmitters from Berlin's C. Lorenz AG, type RBS 6 / RBS 7 with 1 kW transmission power. In addition, there was a single-channel service connection via 100 W VHF radio sets with separate directional antennas for operational purposes.

By February 1950, the first two lines had been converted to the MG-15 devices in VHF Band I, so that a total of 45 telephone channels were available between Berlin and Torfhaus. The daily downtime was only around two percent.

Directional radio station Berlin-Nikolassee (1951–1973)

Radio station Berlin-Nikolassee on a special stamp , 1956

On June 12, 1950, the Berlin magistrate ( Magistrat Reuter ) decided to deposit the rubble that had remained in the city after the Allied air raids and the Battle of Berlin on the area of ​​the unfinished Defense Faculty. Other landfills such as the Insulaner had reached the intended capacity and could no longer be used. By 1972 a total of 26 million cubic meters of rubble had been dumped where the Teufelsberg is today.

After less than two years of operation, the Grunewald radio reception center had to be abandoned. The replacement was an area on the Wannseebadweg around 500 meters east of the Wannsee lido . The radio station Berlin-Nikolassee was set up there in 1950/1951 , called post-internal directional radio station Berlin 2 (RifuSt), which started operations in May 1951. As an antenna carrier of the OTH-radio relay system ( situation ) served three 150 meters high guyed steel lattice masts . Two of them were set up at a distance of 25 meters and formed the shape of an 'H', as they were connected at a height of 120 meters via a steel truss bridge. The opposite station was the Höhbeck radio station in the Lüchow-Dannenberg district, around 135 kilometers away . The system located on the Höhbeck was later called Gartow radio station . From 1957, 78 channels (2 × 15 plus 2 × 24 channels) in VHF band I were in operation in RifuSt Nikolassee , which two years later were supplemented by two new systems with a total of 240 channels, which were set to 300 MHz in the upper range of the Ultra short wave worked. In the final stage, a total of 318 telephone / telex channels ran over the system, which is known in Berlin as “Niko” for short. After the Schäferberg telecommunications tower went into operation in July 1964, RifuSt Nikolassee lost its importance and from 1969 to 1973 only provided a television transmission line (system AM TV / 250). After the masts were dismantled in October 1974 and the technical equipment was dismantled, the site was returned to the State Forestry Administration on May 26, 1975.

Radio relay station Berlin-Schäferberg (1959–1995)

The two 18-meter parabolic mirrors on the Berlin-Schäferberg telecommunications tower , 1971

To relieve the Nikolassee radio station, a 45 meter high freestanding steel lattice tower was built on the Schäferberg in the Wannsee district in 1959 , which carried two parabolic mirrors, each ten meters in diameter. The counterpart was the identical directional radio station Torfhaus in the Upper Harz, about 190 kilometers away . For the first time, the technology of scatter radio transmission was tested and in the 2.2 GHz range it was possible to provide an additional 360 channels (3 × 120). After it was decommissioned in 1991, the steel lattice tower in Torfhaus was completely dismantled, while the 45-meter tower in Berlin is now mainly used for mobile communications .

In mid-March 1961, work began on the foundation for the 216-meter-high Berlin-Schäferberg telecommunications tower . About him (20 x 120 = 2,400 channels in maximum configuration) (also 400 MHz later) ran from July 1964 to 1,991 phone connections to frequencies around 250 MHz for new mast Gartow one of the radio relay station Gartow .

In the late summer of 1966, the FMT Schäferberg received two parabolic mirrors ( Cassegrain antenna ), each 18 meters in diameter, installed on the shaft at a height of 35 and 55 meters, respectively , to enable additional scatter radio links in the 1.9 GHz range to Torfhaus, where two identical parabolic mirrors were attached to each other on a new steel lattice tower 57 meters high. The free-standing tower in the Harz Mountains was made exceptionally massive because of its exposed location with the high wind speeds that often occur there and the two parabolic mirrors, each weighing ten tons. The first directional radio links from the Schäferberg telecommunications tower to Torfhaus (when fully developed 3 × 960 = 2880 channels) were activated in July 1967. Its operation ended at the beginning of 1995.

Up to 5640 channels were available from the entire Berlin-Schäferberg directional radio station in the direction of Gartow and Torfhaus. The two large parabolic mirrors at the FMT Schäferberg were on 11./12. November 1996 dismantled. The steel lattice tower in Torfhaus, whose 18-meter parabolic mirror was also dismantled, continues to serve as a carrier for directional radio and mobile radio antennas.

Directional radio station Berlin-Frohnau (1974-2000)

In the summer of 1970, work began on a scatter radio link between Berlin-Frohnau and Clenze , a place in Drawehn . A freestanding steel lattice tower with a height of 92 meters served as antenna support for the Berlin-Frohnau radio relay system (internal: radio transmission center Berlin 25 ), with grating platforms at 40, 60 and 82 meters for the installation of the feeder directional radio antennas. With the tubular mast attached, the antenna carrier reached a height of 117.5 meters. Two Cassegrain antennas with a diameter of 18 meters were installed at both locations for the 164 km long radio link to the new Clenze 1 radio transmission point . A total of 720 channels were in operation in the 1.9 GHz range between Berlin and Clenze from 1976 to 1993.

From the beginning of 1980, a directional radio link between West Berlin and the Federal Republic was implemented for the first time using a line of sight . For this purpose, a 344 meter high guyed steel lattice mast was erected in Frohnau between 1977 and 1979. The counter station was the Gartow 2 steel lattice mast, which was being built at the same time on the Höhbeck . The total transmission capacity of these radio links working with frequencies of 5.9 and 8.2 GHz was 11,880 telephone channels, so that together with the smaller lattice tower, the Frohnau system had a total capacity of 12,600 telephone channels. The directional radio operation in Frohnau ended in early 2000.

The operating pulpit in Frohnau was expanded in 1982 to make room for eavesdropping technology for the French and US occupying forces, which could better record VHF and UHF radio operations in the Warsaw Pact area from there . Since the installation of the antennas also required space, the mast had to be increased by around 14 meters to 358.58 meters.

Radio and cable routes through GDR territory (from 1987)

In the mid-1980s, agreements between the two German states were able to be made which, in return for payments to the GDR in " convertible currency " ( West Mark ), allowed a directional radio link from Schäferberg in Berlin to Gartow in Wendland over four normal radio fields, each 30 to 45 kilometers in length build up. On the telecommunications towers of the GDR post office in Perwenitz , Rhinow and Dequede , directional radio systems of the type DRS 140/3900 (digital Rifu system for 140  Mbit / s ) from West German production were installed, which from mid-March 1987 digital 1920 telephone channels in 3.9 GHz Broadcast area. Maintenance work in the three GDR radio relay stations was carried out by the Deutsche Post staff there.

The laying of a cable with optical fibers between Uelzen and Berlin over GDR territory was also agreed . The operation was initially partially started in mid-1987; the full extension was only completed two months before the fall of the wall in early November 1989. Each of the 60  gradient fibers was suitable for the transmission of digital signals at 140 Mbit / s. This would have allowed a total of 57,600 telephone channels to be transmitted, but the cable was mixed with electrical circuits for data services , telephony and video conferencing .

Wannsee earth station (from 1987)

At the Deutsche Bundespost, planning began in 1986 for the Wannsee earth station . A  system with eight parabolic mirrors with a diameter of between 5 and 18 meters was built on the site of a former garbage dump at Roedenbecksteig 11 in Wannsee. In February 1987 the first antennas went into operation; Only after German reunification was the final completion of the satellite radio station ( location ), which today belongs to KB Impuls Satellite GmbH , in 1991 .

After reunification

The 324 meter high transmission mast Gartow 1 was blown up on August 20, 2009

After the establishment of German unity, West Berlin could again be connected to West Germany via long-distance cable routes. Some of the antenna carriers used for the radio link to West Berlin are still available in Clenze, Gartow and Torfhaus and are used for radio relay and radio and mobile radio transmitters. The large steel lattice mast in Berlin-Frohnau was blown up on February 8, 2009, the 324 meter high mast Gartow 1 on August 20, 2009. The 344 meter high Gartow 2 mast will continue to be used, as will the 57 meter high steel lattice tower in Torfhaus.

Web links

Individual evidence

  1. ^ The main department III of the MfS , on manfred-bischoff.de, accessed on July 15, 2019
  2. ↑ photograph of the receiving agency to forst-grunewald.de
  3. ^ Günter Erler: Telephoning in Berlin. 50 years of Fernamt Winterfeldtstrasse. Series: Berliner Forum , Press and Information Office of the State of Berlin, 1979
  4. ↑ FTZ , vol. 3 issue 7 (July 1950) p. 221 ff.
  5. ^ Anniversary publication 75 Years Lorenz 1880–1955 , p. 112 ff.
  6. ↑ Richtfunkstelle Berlin 2 , on forst-grunewald.de, accessed on July 12, 2019
  7. ↑ Directional radio links from West Germany to West Berlin at manfred-bischoff.de, accessed on July 31, 2019
  8. ↑ "Explosive Mixture" . In: Der Spiegel . No. 31 , 1986, pp. 78-80 ( online ).