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 wave.
OMEGA was the first global-range radio navigation system, operated by the United States in cooperation with six partner nations. It was a hyperbolic navigation system, enabling ships and aircraft to determine their position by receiving very low frequency (VLF) radio signals in the range 10 to 14 kHz, transmitted by a global network of eight fixed terrestrial radio beacons, using a navigation receiver unit. It became operational around 1971 and was shut down in 1997 in favour of the Global Positioning System.
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. Early submarines during World War II mostly traveled on the surface because of their limited underwater speed and endurance, and dove mainly to evade immediate threats or for stealthy approach to their targets. During the Cold War, however, nuclear-powered submarines were developed that could stay submerged for months. In the event of a nuclear war, submerged ballistic missile submarines have to be ordered quickly to launch their missiles. Transmitting messages to these submarines is an active area of research. Very low frequency (VLF) radio waves can penetrate seawater just over one hundred feet (10–40 meters), and many navies use powerful shore VLF transmitters for submarine communications. A few nations have built transmitters which use extremely low frequency (ELF) radio waves, which can penetrate seawater to reach submarines at operating depths, but these require huge antennas. Other techniques that have been used include sonar and blue lasers.
Saterland 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 addition to German.
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 outstanding monument representing the process of development of communication technology in the period following the First World War." 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.
NSS Annapolis, officially known as Naval Communications Station Washington, D.C. Transmitter or NavCommStaWashingtonDC(T), was a Very Low Frequency (VLF) and High Frequency (HF) transmitter station operated by the United States Navy.
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.
Goliath transmitter was a very low frequency (VLF) transmitter for communicating with submarines, built by Nazi Germany's Kriegsmarine navy near Kalbe an der Milde in Saxony-Anhalt, Germany, which was in service from 1943 to 1945. It was capable of transmission power of between 100 and 1000 kW and was the most powerful transmitter of its time.
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. 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 (usually) insulated 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.
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.
Yosami Transmitting Station was a very large transmitting station for intercontinental communication and for submarine communication in the VLF-range at Kariya, Aichi, Japan. Yosami Transmitting Station used as antenna a wire antenna system, which was spun between 8 guyed masts, each 250 metres tall and insulated against ground. The masts of Yosami transmitting station were at its completion in 1929 Japan's tallest architectural structure. Yosami Transmitting Station played an important role in World War II for transmitting news to Germany and Italy and for transmitting messages to submarines under water.
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.
Torreta de Guardamar or Torre de los Americanos is a 380-metre tall guyed radio mast erected by the US Navy near Guardamar del Segura, Spain. It was built in 1962 and is the tallest architectural structure in both the Iberian peninsula and the European Union, and the tallest military structure in Europe. Its base is situated 64 metres above sea level at a distance of 1.4 km from the sea.
The "Vileyka" VLF transmitter is the site of the 43rd Communications Center of the Russian Navy, located west of the town of Vileyka in Belarus. The "Vileyka" VLF transmitter is an important facility for transmitting orders to submarines in the very low frequency range. Beside this, it is used for transmitting the time signal RJH69 at certain times.
Ebino VLF transmitter is a large transmitter for transmitting orders to submerged submarines, situated near Ebino, Miyazaki in Japan. Ebino VLF transmitter, which was completed in 1991, is used by the Japanese Navy to transmit orders to submerged submarines on the frequency 22.1 kHz with the callsign JJI. The antenna system is carried by eight masts, each 270 metres tall, which are arranged in two rows.
Aguada transmission station is a tall guyed radio mast erected by the US Navy. It is used as a facility of the US Navy for transmitting orders to submerged submarines near Aguada, Puerto Rico at 18°23′55″N67°10′38″W by using radio waves in the very low frequency range.
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.
