1982 aerial
view of the Clam Lake, Wisconsin ELF facility.
Communicating with submarines at sea has always presented
special problems. As submarine capabilities improved after the mid- 1950s
thanks to nuclear power, the vessels could stay deeply submerged for extended
periods, making detection of their location nearly impossible. But if they had
to rise to the surface for communication, much of that capability disappeared.
During World Wars I and II, the only way a submarine could
communicate with its home base was to surface in order to use shortwave or
other radio signaling. This made the vessels vulnerable, and after the British
broke the German Enigma codes, many submarines were located (and some sunk)
through their regular signaling process. After the war, though submarines
improved, means of signaling from a land base through deep water remained
impossible.
In the late 1950s, to resolve the submarine problem, the
Navy proposed an extremely low frequency (ELF) antenna system, which would face
strong opposition throughout its proposal and development and into its
operational stages. The Navy first became interested in ELF signals in 1958
when it was discovered that low-frequency radio waves could penetrate seawater
deep enough to send one-way signals to submerged submarines. Tests in the early
1960s proved the idea to be practical. The original project would have required
a grid of cables over 22,500 square miles of northern Wisconsin and the Upper
Peninsula of Michigan (an area larger than Belgium and Holland combined), as
well as 240 transmitters and 800 megawatts of power, and would have cost
billions of dollars to build. In 1969, a more modest replacement, “Project
Seafarer,” was proposed, relying on newer technology to eliminate the need for
such a huge grid. But with both projects, concern over potential harmful
effects on fish, birds, and animals, as well as delayed effects on humans, was
at the heart of concerted public opposition.
In the end, the further downsized $400- million “Project
ELF” became operational in October 1989, consisting of just two transmitters in
Wisconsin and Michigan, connected by a 165-mile underground cable. Operated for
twenty-four hours a day, each transmitter consisted of a 14-mile-long antenna
strung on hundreds of 40-foot poles across dozens of miles of forest. Annual
operating costs for both ELF transmitters was $13 million. Consideration was
given to a mobile ELF system (using trucks on land or balloons in the air to
avoid enemy attack), but cost precluded implementation. The Soviet Navy
developed a similar system, called the ZEVS, located on the Kola Peninsula near
Murmansk. It was first detected in the 1990s and, unlike the American system,
is also used for geophysical research. The British Royal Navy also considered
building such a system in Scotland, but decided against it given the high cost.
As is evident from the huge size of the ground antennas
used, the ELF communication link was obviously one way. Further, on such low
frequency, information can only be transmitted very slowly, on the order of a
few characters per minute. Although the actual codes used were secret, the
transmissions could be received all over the world. Naturally, when a submarine
is on the surface, it can use ordinary radio communications. Today, this
usually means use of dedicated military communication satellites (the U.S. Navy
calls its system Submarine Satellite Information Exchange Sub-System).
The Navy’s ELF system was closed in September 2004, the
official explanation being that technological progress in very low frequencies
had made use of the huge ELF antenna no longer necessary.
Sources
Aldridge, Bob. 2001. “ELF History: Extreme Low Frequency
Communication.” Santa Clara, CA: Pacific Life Research Center.
Jacobsen, Trond. “ZEVS, the Russian 82 Hz ELF Transmitter:
A[n] Extrem[e] Low Frequency
Transmission System.”
Merrill, John. 2003. A History of Extremely Low Frequency
(ELF) Submarine Radio Communications. Southington, CT: Publishing
Directions.
Navy Extremely Low Frequency Communications System
Facilities Closure. 2004.
“The Wireless Equipped Sub marine.” 1916. Wireless Age III
(9): 605–616.