![]() This geological formation channels ELF currents deep into the ground and effectively increases the size of the antenna for more efficient signal transmission. They are located geographically to take advantage of the bedrock layer (Precambrian metamorphic) and overlying rocks (Paleozoic) of the Superior Upland shield. The two ELF transmitting sites synchronize their transmissions to provide greater coverage to most of the earth’s oceans in which United States submarines operate. The result is that ELF waves penetrate seawater to depths of hundreds of feet, permitting submarine communication while maintaining stealth.Įach ELF antenna works as an independent horizontal electric dipole. The Navy’s ELF system operates at about 76 Hz, approximately two orders of magnitude lower than VLF. Radio waves in the Very Low Frequency (VLF) band at frequencies of about 20,000 Hertz (Hz) penetrate seawater to depths of only tens of feet. This means that the lower the frequency a radio transmission, the deeper into the ocean a useable signal will travel. Thus, the ELF system represents a critical safeguard against a scientific breakthrough in submarine detection by another nation using aircraft or satellite systems that exploit non-acoustic phenomena such as kelvin wakes and internal waves near the surface.ĮLF submarine communication systems make use of a principle in physics where the attenuation of radio signals (electromagnetic waves) from seawater increases with the frequency of the signal. The ELF submarine communication system permits submarines to receive communications without reducing speed or operating at the surface. This requirement imposes an enormous restriction upon the submarine's operating depth and its speed, as well as increasing its exposure to detection. With other submarine communication systems, continuous communication is possible only when submarines deploy a receiving antenna while operating at or near the surface. It is a critical part of America’s national security in that it allows the submarine fleet to remain at depth and speed and maintain its stealth while remaining in communication with the national command authority. ![]() The Navy’s ELF submarine communication system is the only operational communications system that can penetrate seawater to great depths and is virtually jam proof from both natural and man-made interference. submarine fleet to perform its mission, it must remain silent and be undetectable. The Clam Lake ELF radio station broadcasts messages to the fleet as required by the Navy Submarine Broadcast Control Authority in Norfolk, Virginia or Pearl Harbor, Hawaii. The submarine communication site has more than 28 miles of over-head signal transmission line that form part of the “electrical” antenna to radiate the ELF signal from the two-acre transmitting facility. The Clam Lake site, located in the Chequamegon National Forest in Northern Wisconsin, is the site where testing began for ELF communications more than 30 years ago. The sites at Clam Lake, Wisconsin and Republic, Michigan are operated by the Naval Computer and Telecommunications Area Master Station – Atlantic. Navy operates two extremely low frequency (ELF) radio transmitters to communicate with its deep diving submarines.
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