Because electromagnetic radiation such as normal radio communication cannot travel through thick conductors such as salt water, communication with submarines when they are submerged is a difficult technological task which requires specific techniques and devices. Electromagnetic radiation is a propagating wave in space with electric and magnetic components. ... It has been suggested that Conductor (power engineering) be merged into this article or section. ... USS Los Angeles A submarine is a specialized watercraft that can operate underwater. ...

In many cases, the obvious solution is to surface and raise an antenna above the water surface to use standard technology. This is not sufficient, however, for nuclear-powered submarines. These vessels, developed during the Cold War by the major military powers, are capable of staying submerged and hidden for weeks or months. Yet, they are supposed to launch ballistic missiles in case of a nuclear war. How could such an order be sent to a submarine which is well hidden but also out of communication reach? The mushroom cloud of the atomic bombing of Nagasaki, Japan, in 1945 lifted nuclear fallout some 18 km (60,000 feet) above the epicenter. ... This map shows two essential global spheres during the Cold War up until 1959. ... Polish missile wz. ... Nuclear War is a card game designed by Douglas Malewicki, and originally published in 1966. ...

Several technologies have been developed and deployed:

Acoustic transmission

Sound travels far in water, and underwater loudspeakers and hydrophones can cover quite a gap. Apparently, both the American and the Russian Navy have placed communication-by-sound equipment in the seabed of areas frequently travelled by their submarines and connected it by submarine communications cables to their land stations. If a submarine hides near such a device, it can stay in contact with its headquarters. A schematic representation of auditory signaling Sound is vibration, as perceived by the sense of hearing. ... Closeup of a loudspeaker driver A loudspeaker is a device which converts an electrical signal into sound. ... A hydrophone is a sound-to-electricity transducer for use in water or other liquids, analogous to a microphone for air. ... Russian Navy Jack Russian Navy Ensign The Russian Navy (Russian: Военно Морской Флот (ВМФ) - Voyenno Morskoy Flot (VMF) or Military Maritime Fleet) is the naval arm of the Russian armed forces. ... A submarine communications cable is a cable laid beneath the sea to carry telecommunications between countries. ...

Very low frequency

VLF radio waves (3–30 kHz) can penetrate sea water down to a depth of roughly 20 meters. Hence a submarine staying at shallow depth can use these frequencies. Even a vessel hiding in deeper water might use a buoy on a long cable equipped with an antenna. The buoy mounts up to a few meters below the surface and is hopefully small enough to be overlooked by the enemy's sonar. Very low frequency or VLF refers to radio frequencies (RF) in the range of 3 to 30 kHz. ... A kilohertz (kHz) is a unit of frequency equal to 1,000 hertz (1,000 cycles per second). ... metre or meter, see meter (disambiguation) The metre is the basic unit of length in the International System of Units. ... A seal on a buoy in San Diego Harbor A buoy is a floating device that can have various purposes, which determine whether the buoy is tethered (stationary) or allowed to drift: The word is derived from the Dutch boei. sea mark - aids pilotage by marking a maritime channel, hazard... The F70 type frigates (here, La Motte-Picquet) are fitted with VDS (Variable Depth Sonar) type DUBV43 or DUBV43C tugged sonars Sonar (sound navigation and ranging) is a technique that uses sound propagation under water to navigate or to detect other watercraft. ...

Extremely low frequency

Electromagnetic waves in the ELF frequency range (see also SLF) can travel through the oceans and reach submarines anywhere. However, building an ELF transmitter is a formidable challenge, as they have to work at incredibly long wavelengths: The US Navy's system (called Seafarer) operates at 76 hertz, the Soviet/Russian system (called ZEVS) at 82 hertz. The latter, for example, corresponds to a wavelength of 3658.5 kilometers. That is more than a quarter of the Earth's diameter. Obviously, you cannot build a usual half-wavelength dipole antenna, as it would spread all across a large country. Extremely low frequency (ELF) is the band of radio frequencies from 3 to 300 Hz. ... Super Low Frequency (SLF) is the frequency range between 30 Hertz and 300 Hertz. ... The wavelength is the distance between repeating units of a wave pattern. ... The United States Navy (USN) is the branch of the United States armed forces responsible for naval operations. ... The hertz (symbol Hz) is the SI unit of frequency. ... A kilometre (American spelling: kilometer) (symbol: km) is a unit of length equal to 1000 metres (from the Greek words khilia = thousand and metro = count/measure). ... A dipole antenna is an antenna with two driven elements. ...

Instead, one has to find an area with very low ground conductivity (a requirement opposite to usual radio transmitter sites) and dig two huge electrodes into the ground at different sites separated by about 60 km, and feed-lines (just wires on poles) reaching them from some station in the middle. Although other separations are possible, 60 km is the distance used for the ZEVS transmitter which is located near Murmansk. As the ground conductivity is so poor, the current between the electrodes will penetrate deep into the interior of the Earth, basically using a large part of the globe as antenna. The antenna is very inefficient; to drive it, a small dedicated power plant seems to be required although the power actually emitted as radiation is only a few watts. But its transmission can be received virtually anywhere: Even a station at Antarctica noticed when the Russian Navy put their ZEVS antenna into operation for the first time. Murmansk, Archangelsk, Dikson, Tiksi, on the Arctic Ocean Murmansk coin Murmansk (Му́рманск) is a city in the extreme northwest of Russia (north of the Arctic circle) with a seaport on the Kola Gulf, 20 miles from the Barents Sea on the northern shore of the Kola Peninsula, not far from... The watt (symbol: W) is the SI derived unit for power. ...

Due to the extreme technical difficulty of building an ELF transmitter, only the US and the Russian Navy owned such systems. Until it was dismantled in late September 2004, the American Seafarer system (76 Hz) consisted of two antennas, located at Clam Lake, Wisconsin (since 1977) and at Sawyer Air Force Base near Gwinn, Michigan (since 1980). Before 1977, the Sanguine system was used, placed in the Laurentian Shield in Wisconsin. The Russian antenna (ZEVS, 82 Hz) is installed at the Kola peninsula near Murmansk. It was noticed in the West in the early 1990s. The British Royal Navy once considered building their own transmitter at Glengarry Forest, Scotland, but the project was cancelled. 2004 is a leap year starting on Thursday of the Gregorian calendar. ... 1977 was a common year starting on Saturday (the link is to a full 1977 calendar). ... Gwinn is an unincorporated community located in Marquette County, Michigan. ... 1980 is a leap year starting on Tuesday. ... The Canadian Shield is a large geographic area in eastern and central Canada and adjacent portions of the United States, composed of bare rock dating to the Precambrian Era (between 4. ... One of the periods of glaciation was also termed the Wisconsin glaciation. ... Kola can refer to: Kola nut Kola Peninsula, in the far north of Russia Kola Island, part of the Aru Islands of Indonesia This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... Murmansk, Archangelsk, Dikson, Tiksi, on the Arctic Ocean Murmansk coin Murmansk (Му́рманск) is a city in the extreme northwest of Russia (north of the Arctic circle) with a seaport on the Kola Gulf, 20 miles from the Barents Sea on the northern shore of the Kola Peninsula, not far from... // Events and trends The 1990s are generally classified as having moved slightly away from the more conservative 1980s, but keeping the same mind-set. ... The Royal Navy of the United Kingdom is the senior service of the armed services, being the oldest of its three branches. ... Clan MacDonell of Glengarry is a branch of Clan Macdonald, taking its name from Glen Garry where the river Garry runs eastwards through Loch Garry to join the Great Glen about 16 miles (25 km) north of Fort William. ... Scotland (Alba in Scottish Gaelic) is a country in northwest Europe and a constituent nation of the United Kingdom. ...

The method employed was a 64-ary Reed-Solomon, meaning that the alphabet had 64 symbols, each one represented by a very long pseudo-random sequence. The entire transmission, of course, was then encrypted. The advantages of such a technique are first, that by correlating multiple transmissions, a message could be completed even with very low signal-to-noise ratios, and because only a very few pseudo-random sequences represented actual message characters, there was a very high probability that if a message was successfully received, it was a valid message (anti-spoofing). Reed-Solomon error correction is a coding scheme which works by first constructing a polynomial from the data symbols to be transmitted and then sending an over-sampled plot of the polynomial instead of the original symbols themselves. ... A pseudo-random number is a number belonging to a sequence which appears to be random, but can in fact be generated by a finite computation. ... This article is about algorithms for encryption and decryption. ... Signal-to-noise ratio (often abbreviated SNR or S/N) is meaningful both in the context of information theory and, informally, for Usenet or other newsgroup-like services. ... A spoofing attack, in computer security terms, refers to a situation in which one person or program is able to masquerade successfully as another. ...

Two facts should be noted: First, the communication link is obviously one-way. No submarine could have its own ELF transmitter on board, due to the sheer size of such a device. Attempts to design a transmitter which can be immersed into the sea, hanging from an aircraft, were soon given up.

Second, on such low frequency, information can be transmitted only very slowly, on the order of a few characters per minute (see Shannon's coding theorem). Although the actual codes used are of course secret (well, their meaning only—the actual transmissions can be received all over the world and even some radio amateurs do listen) it is reasonable to assume that no specific orders are given but rather only commands like "surface and await orders by satellite radio." In information theory, the Shannon-Hartley theorem states the maximum amount of error-free digital data (that is, information) that can be transmitted over a communication link with a specified bandwidth in the presence of noise interference. ... Amateur radio, commonly called ham radio, is a hobby enjoyed by many people throughout the world (as of 2004 about 3 million worldwide, 70,000 in Germany, 5,000 in Norway, 57,000 in Canada, and 700,000 in the USA). ...

Standard radio technology

As long as the submarine is surfaced, it can obviously use ordinary radio communications as any other marine vessel. Today, this usually means no longer shortwave but rather the use of communication satellites -- for military use of course not the usual public ones like the Inmarsat system, but dedicated military communication satellites. (The US Navy calls their system Submarine Satellite Information Exchange Sub-System (SSIXS), which is a part of the Navy Ultra High Frequency Satellite Communications System (UHF SATCOM).) A Grundig Shortwave receiver Shortwave radio operates between the frequencies of 3,000 kHz and 30 MHz (30,000 kHz) and came to be referred to as such in the early days of radio because the wavelengths associated with this frequency range were shorter than those commonly in use at... U.S. military MILSTAR communications satellite A communications satellite (sometimes abbreviated to comsat) is an artificial satellite stationed in space for the purposes of telecommunications using radio at microwave frequencies. ... INMARSAT, is an international telecommunications company founded in 1979, originally as an intergovernmental organisation. ...

See also

submarine, extremely low frequency, super low frequency, TACAMO USS Los Angeles A submarine is a specialized watercraft that can operate underwater. ... Extremely low frequency (ELF) is the band of radio frequencies from 3 to 300 Hz. ... Super Low Frequency (SLF) is the frequency range between 30 Hertz and 300 Hertz. ... TACAMO is a US military term literally meaning Take Charge and Move Out. TACAMO actually refers to a system of survivable communications links designed to be used in nuclear war to maintain communications between the decision-makers (the National Command Authority) and the triad of strategic nuclear weapon delivery systems. ...

External links

• About the U.S. ELF projects
• ZEVS, The Russian 82 Hz ELF Transmitter By Trond Jacobsen at ALFLAB, Halden in Norway
• Extremely Low Frequency Transmitter Site Clam Lake, Wisconsin, a "Fact File" published by the US Navy (PDF File)