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 as the wavelengths range from one to ten myriameters. Due to its limited bandwidth, audio (voice) transmission is highly impractical in this band, and therefore only low data rate coded signals are used. The VLF band is used for a few radio navigation services, government time radio stations and for secure military communication. Since VLF waves can penetrate at least 40 meters (131 ft) into saltwater, they are used for military communication with submarines.
Low frequency (LF) is the ITU designation for radio frequencies (RF) in the range of 30–300 kHz. Since its wavelengths range from 10–1 km, respectively, it is also known as the kilometre band or kilometre waves.
Communication with submarines is a field within military communications that presents technical challenges and requires specialized technology. Because radio waves do not travel well through good electrical conductors like salt water, submerged submarines are cut off from radio communication with their command authorities at ordinary radio frequencies. Submarines can surface and raise an antenna above the sea level, or float a tethered buoy carrying an antenna, then use ordinary radio transmissions; however, this makes them vulnerable to detection by anti-submarine warfare forces.
Sender Zehlendorf or Zehlendorf (radio) transmission facility was a radio transmission facility which was in service since 1936, when a short wave transmitter was built on the occasion of the Berlin 1936 Summer Olympics in Zehlendorf as part of the establishment of permanent radio services. This Zehlendorf site, which until the end of World War II was referred to as the Rehmate Radio Transmission Centre, had 26 different antennas at the time.
The Roumoules transmitter is the main broadcasting facility for longwave and mediumwave broadcasting of Radio Monte Carlo near Roumoules, France and is owned by Monaco Media Diffusion. The 1000 and 2000kW transmitters installed are among the most powerful in the world and can be received well at nighttime throughout Europe.
The Mühlacker Broadcasting Transmission Facility is a radio transmission facility near Mühlacker, Germany, first put into service on November 21, 1930. It uses two guyed steel tube masts as aerials and one guyed steel framework mast, which are insulated against ground. It has two transmission aerials for shortwave and one free standing steel framework tower for directional radio services. The shortwave transmitter was shut off on October 19, 2004. The medium wave transmitter was switched off in January 2012.
The AM transmitter in Burg, near Magdeburg, Germany, is a huge facility for longwave and mediumwave broadcasting. Its most dominant constructions are a 324-metre guyed radio mast and two 210 metre guyed steel tube masts.
The Langenberg transmission tower is a broadcasting station for ananlog FM Radio and Digital-TV signals. It is located in Langenberg, Velbert, Germany and owned and operated by Westdeutscher Rundfunk, WDR.
The VLF transmitter DHO38 is a VLF transmitter used by the German Navy near Rhauderfehn, Saterland, Germany. It is used to transmit coded orders to submarines of the German Navy and navies of other NATO countries.
The Skelton Transmitting Station is a radio transmitter site at grid reference NY433376 near Skelton, Cumbria, England, about 5 miles (8 km) north-west of Penrith, run by Babcock International and owned by the Ministry of Defence. Since the Belmont Mast in Lincolnshire was shortened in 2010, the mast at Skelton has been the tallest structure in the United Kingdom.
Grimeton Radio Station in southern Sweden, close to Varberg in Halland, is an early longwave transatlantic wireless telegraphy station built in 1922–1924, that has been preserved as a historical site. From the 1920s through the 1940s it was used to transmit telegram traffic by Morse code to North America and other countries, and during World War II was Sweden's only telecommunication link with the rest of the world. It is the only remaining example of an early pre-electronic radio transmitter technology called an Alexanderson alternator. It was added to the UNESCO World Heritage List in 2004, with the statement: "Grimeton Radio Station, Varberg is an exceptionally well preserved example of a type of telecommunication centre, representing the technological achievements by the early 1920s, as well as documenting the further development over some three decades." The radio station is also an anchor site for the European Route of Industrial Heritage. The transmitter is still in operational condition, and each year on a day called Alexanderson Day is started up and transmits brief Morse code test transmissions, which can be received all over Europe.
Eilvese transmitter was an early long-distance radiotelegraphy station at Eilvese, Germany owned by Transradio AG, used for transmission of telegrams. It went into service in 1913, exchanging commercial and diplomatic Morse code traffic on VLF frequencies with Germany's colonies, and a similar station at Tuckerton, New Jersey, USA. During World War I when the allies cut Germany's submarine telegraph cables it was one of two long-distance radiotelegraphy stations which maintained Germany's contact with the rest of the world, and was used for diplomatic negotiations between Woodrow Wilson and Kaiser Wilhelm II leading to the 1918 Armistice which ended World War I.
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 power from the transmitter is connected to the mast, and the other side to a ground (Earthing) system of radial wires buried in the earth under the antenna. They are used as transmitting antennas below 1 MHz, in the MF, LF and particularly the VLF bands, at frequencies sufficiently low that it is impractical or infeasible to build a full size quarter-wave monopole antenna. The outer end of each radial wire, sloping down from the top of the antenna, is connected by an insulator to a supporting rope or cable anchored to the ground; the radial wires can also support the mast as guy wires. The radial wires make the antenna look like the wire frame of a giant umbrella hence the name.
The Wiederau transmitter is the oldest broadcasting facility in Saxony. It is located near Wiederau, a village which is part of the municipality of Pegau, and is used for medium-wave, FM and Television broadcasting.
Marnach transmitter was a broadcasting facility of RTL near Marnach in the commune of Clervaux, in northern Luxembourg. The Marnach transmitter was built in 1955 for improving the transmission of the English-speaking program on 1439 kHz, which was transmitted from 1951 with an omnidirectional antenna from Junglinster, to the British Isles and for a better transmission on this frequency to Germany at daytime. Therefore, it was given a directional antenna with a switchable directional characteristic pointing North-northeast towards the Rhine-Ruhr area, Germany's most populated area, and West-northwest in the direction of the UK. This antenna was implemented in form of a directional antenna consisting of three ground-fed 105-metre (350') tall guyed mast antennas arranged in the form of an isosceles triangle with a 90 degree angle. As transmitters, two 100 kW units switched in parallel were used when it went in service in December 1955.
Dillberg transmitter is a transmitting facility of the Bavarian Broadcasting Company on the 595-metre-high Dillberg mountain west of Neumarkt in der Oberpfalz, Bavaria, Germany. Dillberg transmitter went into service in 1955 for serving the area of Nuremberg with TV and FM radio programmes from a 198-metre-tall guyed mast.
VLF transmitter Lualualei is a facility of the United States Navy near Lualualei, Hawaii transmitting orders to submerged submarines in the very low frequency (VLF) range.
Nauen Transmitter Station in Nauen, Havelland district, Brandenburg, Germany, is the oldest continuously operating radio transmitting installation in the world. Germany's first high power radio transmitter, it was founded on 1 April 1906 by Telefunken corporation and operated as a longwave radiotelegraphy station through World War II, and during World War I became Germany's main link with the outside world when its submarine communications cables were cut. Upgraded with shortwave transmitters in the 1920s it was Germany's most advanced long range radio station, continually upgraded with the latest equipment and serving as an experimental station for Telefunken to test new technology. At the end of World War II, invading Russian troops dismantled and removed the transmitting equipment. During the Cold War it served as the GDR's international shortwave station Radio Berlin International (RBI), and was the East Bloc's second most powerful radio station, disseminating Communist propaganda to other countries. Since German Reunification in 1991 it has been operated by Deutsche Telekom, Germany's state telecommunication service. The original 1920 transmitter building designed by architect Herman Muthesius is still used; it is one of the many remaining buildings designed by that architect that is a protected cultural heritage site.
The VLF Transmitter Cutler is the United States Navy's very low frequency (VLF) shore radio station at Cutler, Maine. The station provides one-way communication to submarines of the Navy's Atlantic Fleet, both on the surface and submerged. It transmits with call sign NAA, at a frequency of 24 kHz and input power of up to 1.8 megawatts, and is one of the most powerful radio transmitters in the world.
The Sainte-Assise transmitter is a very low frequency (VLF) radio transmitter and military installation located on the grounds of the Château de Sainte-Assise in the communes of Seine-Port, Boissise-la-Bertrand, and Cesson in the Seine-et-Marne department of the Île-de-France region of France. The transmitter's original equipment was inaugurated on 9 January 1921, at the time being the most powerful radio transmitter on Earth. On 26 November 1921 the first French radio program was transmitted from Sainte-Assise. In 1965 the transmitter was used to send VLF signals to FR-1, the first French satellite. Since 1998 the French Navy has used the transmitter to communicate with submerged submarines.
