The VLF transmitter DHO38 (known as ''VLF/MSK Marinefunksendestelle Rhauderfehn'' or ''Marinefunksendestelle Saterland-Ramsloh'') is a very low frequency (

VLF Very low frequency or VLF is the ITU designation for radio frequencies (RF) in the range of 3–30 kHz, corresponding to wavelengths from 100 to 10 km, respectively. The band is also known as the myriameter band or myriameter wave ...

) transmitter used by the

German Navy The German Navy (, ) is part of the unified (Federal Defense), the German Armed Forces. The German Navy was originally known as the ''Bundesmarine'' (Federal Navy) from 1956 to 1995, when ''Deutsche Marine'' (German Navy) became the official ...

near Rhauderfehn,

Saterland Saterland (; Saterland Frisian: , ) is a municipality in the district of Cloppenburg, in Lower Saxony, Germany. It is situated between the cities of Leer, Cloppenburg, and Oldenburg. It is home to Saterland Frisians, who speak Frisian in addi ...

Germany Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...

. It is used to transmit coded orders to

submarine A submarine (often shortened to sub) is a watercraft capable of independent operation underwater. (It differs from a submersible, which has more limited underwater capability.) The term "submarine" is also sometimes used historically or infor ...

s of the

and navies of other

NATO The North Atlantic Treaty Organization (NATO ; , OTAN), also called the North Atlantic Alliance, is an intergovernmental organization, intergovernmental Transnationalism, transnational military alliance of 32 Member states of NATO, member s ...

countries. DHO38 has transmitted since 1982 on 23.4

kHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), often described as being equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose formal expression in terms of SI base uni ...

with a power of up to 800

kilowatts The watt (symbol: W) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantify the rate of energy transfer. The watt is named in honor of ...

, although other sources says 300kW is the usual power. Each mast is powered by 100kW transmitter but all masts operate at once. The transmitter is able to transmit signals in a range from 14 to 50 kHz. DHO38 uses an

umbrella antenna An umbrella antenna is a capacitively top-loaded wire monopole antenna, consisting in most cases of a mast fed at the ground end, to which a number of radial wires are connected at the top, sloping downwards. One side of the feedline supplying po ...

which is carried from eight steel tube masts each with a height of . Each pylon stands on three-metre-tall

ceramic A ceramic is any of the various hard, brittle, heat-resistant, and corrosion-resistant materials made by shaping and then firing an inorganic, nonmetallic material, such as clay, at a high temperature. Common examples are earthenware, porcela ...

cylinders, which serve as insulators for voltages up to 300 kV. The masts are equipped with cylindrical

oscillation Oscillation is the repetitive or periodic variation, typically in time, of some measure about a central value (often a point of equilibrium) or between two or more different states. Familiar examples of oscillation include a swinging pendulum ...

dampers for better protection against storms. Each mast has an

antenna tuning hut An antenna tuning hut or helix house is a small shed at the base of a longwave or mediumwave radio transmitting antenna. It contains antenna tuner — radio equipment for coupling the power from the feedline to the antenna. Alternative names inc ...

and sits on a copper mat 30cm under the ground. The site is wet which helps improve the performance of the antenna. The transmitter is capable of transmitting signals to submarines worldwide to depths of approx. 30 metres. In 2016 the transmitters were updated to semi-conductor technology from the previous

valve A valve is a device or natural object that regulates, directs or controls the flow of a fluid (gases, liquids, fluidized solids, or Slurry, slurries) by opening, closing, or partially obstructing various passageways. Valves are technically Pip ...

based ones.

Transmission

The signal from DHO38 is an MSK-coded signal with 4 x 50 baud on all 4 channels on frequency 23.4 kHz. All transmissions from DHO38 are encrypted. The messages transmitted via DHO38 are processed at the naval telecommunications center

Glücksburg Glücksburg (; ) is a small town northeast of Flensburg in the district of Schleswig-Flensburg, in Schleswig-Holstein, Germany. It is Germany's northernmost town. It is situated on the south side of the Flensburg Fjord, Flensborg Fjord, an inlet ...

. They are sent "by cable" from German and NATO offices to the protective structure there and are prepared for transmission by the responsible telecommunications operators.

References

External links

* * http://skyscraperpage.com/diagrams/?b45289 {{coord, 53, 04, 55, N, 7, 36, 59, E, region:DE-NI_type:landmark, display=title Radio masts and towers in Germany Military radio systems 1982 establishments in West Germany Towers completed in 1982 Buildings and structures in Leer (district)