Rhauderfehn naval radio station
Rhauderfehn naval radio station
|Use:||Telecommunication system , military use|
|Accessibility:||Transmission system not accessible to the public|
|Owner :||German Navy|
|Data on the transmission system|
|Number of towers / masts:||8th|
|Height of the towers / masts :||8 × 352.8 m|
|Operating time:||since 1982|
|Wavebands :||VLF transmitter, LW transmitter|
|Send type:||Directional radio|
The Rhauderfehn naval radio station with the callsign DHO38 is a long-wave transmitter of the Navy , which is subordinate to the naval support command. The official name of NATO is NATO VLF / MSK Marinefunksendestelle Rhauderfehn . It has had this name since December 18, 1981. The local population knows the complex under the name “The Towers”. It is located within the " Esterweger Dose " nature reserve .
The transmitter is located near Saterland - Ramsloh in the district of Cloppenburg ( Lower Saxony ). The boundaries of the two rural districts of Cloppenburg and Leer run through the premises of the marine radio station . Five antennas are in East Friesland, three in the Cloppenburg area.
The masts of the naval radio station are among the tallest structures used by the military in western continental Europe. At 352.8 meters - since the two 363 m high transmitter masts were blown up in Donebach on March 2, 2018 - they are the second tallest structures in Germany . The eight red and white masts can be seen at a distance of more than 30 kilometers.
The area of the naval radio station covers an area of approximately 540 hectares. The entire site is surrounded by a 12 km long security fence and accessed with a network of paths and roads of around 26 km in length.
The special conductivity of the West Moor played an important role in the choice of location. The damp ground enables the good grounding required for the radiation of longitudinal waves, and the longitudinal waves can spread optimally due to the flat terrain. To establish a transmission connection to submerged submarines, on the one hand, a low transmission frequency and, on the other hand, a high radiated transmission power is required. This is the only way to achieve a sufficient reception field strength in the submerged submarines.
For technical and economic considerations, the antenna system was built as a radiation-coupled system. In order to ensure high availability, the transmitter is available twice. Two antenna groups each with four antennas, two protective structures and two control centers.
The entire building technology with the air and cooling system as well as the water and power supply are designed in such a way that the marine radio transmission system is self-sufficient in the event of disturbances in the public supply . Four diesel generators, one of them as a reserve system, in the basement of each protective structure, each with an output of 550 kVA, automatically take over the entire energy supply in the event of a power failure. Normally, the energy supply of the transmission system is ensured by a 20 kV feed line from the public network of EWE AG . The drinking and service water supply is fed from the public water supply network. A drinking water tank is available in the event of a possible failure. For cooling circuits, extinguishing systems and the sanitary facilities, there are two wells with corresponding pumping systems.
The transmitter system with its eight 100 kW transmitters is designed for long wave (VLF) or long wave (LF) for frequencies from 14 kHz to 50 kHz and currently transmits on 23.4 kHz with a transmission power of 800 kW. The transmitters are broadband amplifiers and do not contain any tuning means. The transmitter output stages each consist of an electron tube with evaporative cooling .
Coded messages are sent to submarines of the Navy and other NATO countries . Due to the very low transmission frequency, combined with high transmission power, the transmitter can be received worldwide and up to a water depth of about 30 m.
The transmitter uses eight identical shield antennas , each supported by 352.8 meter high tubular steel masts. Each mast has a diameter of 2.20 meters. The cylinder constructions have wall thicknesses of 8 mm to 13 mm, depending on the local stress. The individual masts each stand on an approximately 3 meter high cylindrical ceramic insulator , a so-called base point insulator , which consists of 16 ceramic solid core supports in two levels. The foot insulator is designed for a load of 4000 tons and can safely isolate a voltage of 250 kV. The transmitter masts are each fixed on three levels by nine guy ropes ( guys ). These ropes are arranged around the masts on three levels and offset by 120 degrees. The 12 roof ropes are part of the shield antenna and have little influence on the mechanics of the antenna bracing.
Four masts each form a common antenna that are not connected to one another above ground. It is fed via coaxial cables that go from the transmission bunker to the voting houses below the masts. There the power of the transmitter is adapted to the impedance of the antennas and fed into the mast near the base.
As with transmitters, where the antenna is much smaller than the wavelength used, the antenna structure does not have a pronounced directional diagram . The wavelength at DHO38 is 12.82 km at the currently used transmission frequency.
Inside the antennas there is an elevator and a ladder for inspection and maintenance work. The elevator is moved up and down via a worm gear that engages in a rack located inside the mast. A trip from the base to the roof hatch of the transmission tower takes 18 minutes. It is mandatory that people who use the elevator wear rescue harnesses on their bodies. The elevator is intended for a maximum of three people. Every 60 meters there are grid levels in the mast on which abseiling material and bandages are stored.
Between the three anchoring points and the active roof ropes, four vibration dampers (shown as bulges in the pictures), so-called vibration dampers , are attached to the outside of the masts . These are filled with a special granulate and reduce the generation of vibrations that could occur even at relatively low wind speeds. They are necessary for the stability of the construction even in storms . The total mass of a mast including the fixtures and ropes is 475 tons each.
To tune the antennas, there is an antenna tuner house the size of a small apartment block next to each mast. These contain meter-high capacitors and inductors as well as other devices. This means that the antennas, which are mechanically too short in relation to the wavelength, can be electrically "extended". The tuning means are used to adapt the input resistance of the antenna to the impedance of the transmitter amplifier.
The earth network should ensure the best possible introduction of the antenna current into the earth. Around 30 cm below the surface of the earth, 200 earth wires are laid out in a radial pattern around each of the eight mast antennas. These copper wires, each 400 m to 450 m long, have a diameter of 3.5 mm and end in a 3 m long earthing rod made of stainless steel. A 1.5 mm thick lead jacket serves as corrosion protection , which ensures the resistance of the earth network against the aggressive bog water. The entire floor area around the area of influence of the shield antennas is covered by the earth network. The ends of the earth wires that meet between two adjacent masts are welded together and use a common earth connection.
|January 1966||Start planning|
|September 1977||Start of construction|
|May 1, 1982||Start of trial operation|
|December 9, 1982||Commissioning|
|January 1, 1984||Start of operations|
|development||7.4 million DM|
|Procurement of the devices||47.8 million DM|
|Infrastructure||126.6 million DM|
|total||181.8 million DM|
The signal from DHO38 is an MSK -coded signal with 200 baud on all 4 channels. The transmitter can be received with any receiver or converter that picks up the frequency 23.4 kHz. An AM receiver makes a chirping sound .
Since all transmissions from DHO38 are encrypted and they presumably do not contain any information for civil users at the moment, the civil use of the signal from DHO38 is limited to very rudimentary purposes, such as radio direction finding, investigation of the propagation conditions for radio weather forecasting, for example, and the detection of larger metal accumulations in the ground, there these influence the direction of propagation and polarization of the waves of DHO38.
For military reasons, the naval radio station remained a blank spot on the map for a long time. In 1973 the Saterlanders were still happy that they had prevented a bombing site planned at the same place, but now there is concern that the radiation exposure caused by the building could pose a health risk. There is also the risk of being a target in the event of a crisis or war.
During the planning and construction phase of the transmitter, concerns about the environmental impact of the facility were raised by various organizations. Due to the extremely restrictive access restrictions, however, many animal and plant species have settled in this part of the Westermoor over the years that are not or only rarely found elsewhere. The Federation for Bird Protection states that it has counted 34 breeding bird species.
- List of tallest structures in Europe
- Longest wave transmitter HWU (similar system in France)
- VLF transmitter Skelton (similar system in Great Britain)
- Literature: Elektrotechnische Zeitschr., Berlin 1919, Issues 11 and 26. - Telefunken-Ztg. Berlin 1919, Issue 15. - Yearbook of wireless telegraphy, Berlin, Vol. 4.
- Europaschule Schulzentrum Saterland - press archive - historical, mixed media - documents of the citizens' initiative ( memento of October 4, 2013 in the internet archive )