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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.
TACAMO is a United States military system of survivable communications links designed to be used in nuclear warfare to maintain communications between the decision-makers and the triad of strategic nuclear weapon delivery systems. Its primary mission is serving as a signals relay, where it receives orders from a command plane such as Operation Looking Glass, and verifies and retransmits their Emergency Action Messages (EAMs) to US strategic forces. As it is a dedicated communications post, it features the ability to communicate on virtually every radio frequency band from very low frequency (VLF) up through super high frequency (SHF) using a variety of modulations, encryptions and networks, minimizing the likelihood an emergency message will be jammed by an enemy. This airborne communications capability largely replaced the land-based extremely low frequency (ELF) broadcast sites which became vulnerable to nuclear strike.
Naval Communication Station Harold E. Holt is a joint Australian and United States naval communication station located on the north-west coast of Australia, 6 kilometres (4 mi) north of the town of Exmouth, Western Australia. The station is operated and maintained by the Australian Department of Defence on behalf of Australia and the United States and provides very low frequency (VLF) radio transmission to United States Navy, Royal Australian Navy and allied ships and submarines in the western Pacific Ocean and eastern Indian Ocean. The frequency is 19.8 kHz. With a transmission power of 1 megawatt, it is the most powerful transmission station in the Southern Hemisphere.
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.
Extremely low frequency (ELF) is the ITU designation for electromagnetic radiation with frequencies from 3 to 30 Hz, and corresponding wavelengths of 100,000 to 10,000 kilometers, respectively. In atmospheric science, an alternative definition is usually given, from 3 Hz to 3 kHz. In the related magnetosphere science, the lower frequency electromagnetic oscillations are considered to lie in the ULF range, which is thus also defined differently from the ITU radio bands.
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 a few 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.
An Alexanderson alternator is a rotating machine invented by Ernst Alexanderson in 1904 for the generation of high-frequency alternating current for use as a radio transmitter. It was one of the first devices capable of generating the continuous radio waves needed for transmission of amplitude modulated signals by radio. It was used from about 1910 in a few "superpower" longwave radiotelegraphy stations to transmit transoceanic message traffic by Morse code to similar stations all over the world.
Anthorn Radio Station is a naval and government radio transmitting station located near Anthorn, Cumbria, England, overlooking the Solway Firth, and is operated by Babcock International. It has three transmitters: one VLF; one LF; and an eLORAN transmitter.
Beta is a time signal service in the VLF range in Russia, operated by the Russian Navy. It is controlled by All-Russian Scientific Research Institute for Physical-Engineering and Radiotechnical Metrology. There are 6 transmitter stations, which take turns transmitting time signals and other communications.
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.
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.
In radio communication, a ground dipole, also referred to as an earth dipole antenna, transmission line antenna, and in technical literature as a horizontal electric dipole (HED), is a huge, specialized type of radio antenna that radiates extremely low frequency (ELF) electromagnetic waves. It is the only type of transmitting antenna that can radiate practical amounts of power in the frequency range of 3 Hz to 3 kHz, commonly called ELF waves. A ground dipole consists of two ground electrodes buried in the earth, separated by tens to hundreds of kilometers, linked by overhead transmission lines to a power plant transmitter located between them. Alternating current electricity flows in a giant loop between the electrodes through the ground, radiating ELF waves, so the ground is part of the antenna. To be most effective, ground dipoles must be located over certain types of underground rock formations. The idea was proposed by U.S. Dept. of Defense physicist Nicholas Christofilos in 1959.
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.
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 in 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.
Jim Creek Naval Radio Station is a United States Navy very low frequency (VLF) radio transmitter facility at Jim Creek near Oso, Washington. The primary mission of this site is to communicate orders one-way to submarines of the Pacific fleet. Radio waves in the very low frequency band can penetrate seawater and be received by submerged submarines which cannot be reached by radio communications at other frequencies. Established in 1953, the transmitter radiates on 24.8 kHz with a power of 1.2 megawatts and a callsign of NLK, and is one of the most powerful radio transmitters in the world. Located near Arlington, Washington, in the foothills of the Cascades, north of Seattle, the site has 5,000 largely forested acres.
Project Sanguine was a U.S. Navy project, proposed in 1968 for communication with submerged submarines using extremely low frequency (ELF) radio waves. The originally proposed system, hardened to survive a nuclear attack, would have required a giant antenna covering two fifths of the state of Wisconsin. Because of protests and potential environmental impact, the proposed system was never implemented. A smaller, less hardened system called Project ELF consisting of two linked ELF transmitters located at Clam Lake, Wisconsin 46°05′05.6″N90°55′03.7″W and Republic, Michigan 46°20′10.1″N87°53′04.6″W was built beginning in 1982 and operated from 1989 until 2004. The system transmitted at a frequency of 76 Hz. At ELF frequencies the bandwidth of the transmission is very small, so the system could only send short coded text messages at a very low data rate. These signals were used to summon specific vessels to the surface to receive longer operational orders by ordinary radio or satellite communication.
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.
Naval Radio Transmitter Facility LaMoure is a United States Navy installation located about 3 km west of LaMoure, North Dakota. The site uses a former OMEGA Navigation System station as a VLF transmitter for communications with the US submarine fleet.
PNS Hameed is a very low frequency (VLF) radio transmitter facility of the Pakistan Navy, located near at the coastal areas of Karachi, Sindh, Pakistan. The primary mission of this naval base is to communicate orders with the submerged submarines in the Arabian sea at very low frequency. It is the first of its kind facility with very low frequency transmission capabilities, which will enable the Pakistan Navy to communicate with its submerged submarines.
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.
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Coordinates: 38°22′17″N121°46′32″W / 38.371505°N 121.775569°W
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