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Weird RF Part 3: Communication with Submerged Subs Barry Manz

There is no shortage of stories about bizarre Department of Defense programs, but this one is surely in the top tier. Extremely Low Frequency (ELF) signal propagation (we’re talking 3 to 30Hz) allows signals to pass through the earth and throughout the oceans to depths of several hundred feet, allowing a system at a single location to communicate nearly anywhere on the planet. This made it rather appealing for communicating with submerged submarines and might be able to function in the event of a nuclear strike. The idea was championed not just by the U.S., but by the Soviet Union and India as well. Signals degrade rapidly in the ocean, so when a submarine is submerged, it is less likely to receive communication. The purpose of Elf was to reach deeply submerged subs sufficiently to let them know to surface to receive communications through normal (and better) radio communications.

Exploration of the concept began in 1958 according to some sources but was first revealed a decade later when the first test facility was built in the Chequamegon National Forest near Clam Lake, Wisconsin. This area as chosen because of the low conductivity of its soil, to reduce attenuation as the signals penetrated the earth. These efforts resulted in a plan to create a deployed system called Sanguine, which would consist of more than 100 buried transmitters measuring about 20ft x 60ft, along with 6000 miles of underground cable covering 6500mi², buried 4 to 6ft deep.

 

The Navy’s ELF transmitter sites. At the Clam Lake facility there were two 14-mi. in-ground dipoles. At the Republic (MI) facility there were two 14 mi. dipoles oriented east-west and one 28 mi. dipole oriented north-south. 

The project almost immediately ran into stiff opposition over possible damaging health effects, although the Navy maintained its studies concluded that health issues should not be a problem. It’s interesting to note studies about health effects of high-voltage, 50-60 Hz overhead transmission lines have indicated the very real possibility of such effects, and is still a topic of study and concern for some. The project in Wisconsin was canceled but not before Sen. William Proxmire bestowed one of his famous Golden Fleece Awards (dedicated to egregious examples of government waste) to the project’s keeping a bull on the facility to keep track of health effects. The Navy next approach the state of Texas, which also gave the program a thumbs down.

Not an agency to be dissuaded, the Navy resurrected the project in the early 1970s, this time under the name Surface ELF Antenna for Addressing Remotely Employed Receivers (SEAFARER). After evaluating several sites, Michigan’s Upper Peninsula was selected. This time the system used three transmitters and 2,400 miles of cable covering an area of 4,700 mi2. As the project was about to reach full development in 1977, it took a major hit from then Gov. William Millikin who vetoed the project, telling Defense Secretary Harold Brown that “The people of Michigan do not want SEAFARER, nor do I”. President Jimmy Carter then terminated the program.

Nevertheless, the Navy persevered to get an ELF system built, this time in Michigan, using a single transmitter at the K. I. Sawyer Air Force Base and 130 miles of cable buried along roads and right-of-ways. The now mothballed Clam Lake facility 165 miles distant was to be slaved to the Michigan system using leased telephone lines. The system would then consist of 158 miles of cable. The new program name was Austere ELF, presumably reflecting its diminished nature. As usual, the program ran into significant resistance, this time accompanied by budget cuts and the perception in some defense circles that an ELF system wasn’t actually necessary, and Defense Secretary Caspar Weinberger recommended it be scrapped.

 

ELF communication at 76 Hz with submarines was possible thanks to the wave propagation characteristics at this very low frequency. The submarines received signals bounced from low layers of the ionosphere as well as through the Earth and the oceans.

 

The Reagan Administration disagreed with the DoD’s recommendation, and authorized an even smaller version called Project ELF that would upgrade the Clam Lake facility, add a second transmitter to the one in Michigan, and install ELF receivers in submarines. This system would use only 56 miles of cable, this time above ground. The system became partially operational in the late 1980s and fully functional in the 1990s when all submarines had been fitted with ELF receivers. These ELF system operated in some form through 2004.

Other ELF system variants were also developed and systems were deployed by the Soviet Union and India. If you’re interested in reading more about these programs, you can find more information in the following sources:

1. “ELF History: Extreme Low Frequency Communication”, Pacific Life Research Center, Compiled by Bob Aldridge, February 2001. https://www.plrc.org/docs/941005B.pdf

2. “Zevs, The Russian 82 Hz ELF Transmitter,” Trond Jacobsen, ALFLAB, Halden, Norway https://www.vlf.it/zevs/zevs.htm

3. “SEAFARER Extremely Low Frequency (ELF) Submarine Command and Control Communications System records”, MSS-249, Central Upper Peninsula and Northern Michigan University Archives, Northern Michigan University https://www.nmu.edu/archives/sites/DrupalArchives/files/UserFiles/MSS-249.html

4. “Extremely Low Frequency Transmitter Site, Clam Lake, Wisconsin,” U.S. Navy Fact file,  https://fas.org/nuke/guide/usa/c3i/fs_clam_lake_elf2003.pdf

5. The World’s Largest “Radio” Station, Carlos A. Altgelt https://www.hep.wisc.edu/~prepost/ELF.pdf



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Barry Manz is president of Manz Communications, Inc., a technical media relations agency he founded in 1987. He has since worked with more than 100 companies in the RF and microwave, defense, test and measurement, semiconductor, embedded systems, lightwave, and other markets. Barry writes articles for print and online trade publications, as well as white papers, application notes, symposium papers, technical references guides, and Web content. He is also a contributing editor for the Journal of Electronic Defense, editor of Military Microwave Digest, co-founder of MilCOTS Digest magazine, and was editor in chief of Microwaves & RF magazine.


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