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{{Short description|US Navy research on communicating with submarines}}
{{Use dmy dates|date=September 2017}}
{{Use dmy dates|date=September 2017}}
[[File:Clam Lake ELF.jpg|thumb|225px|Clam Lake, Wisconsin [[Extremely low frequency|ELF]] transmitter in 1982, part of Project ELF, the downsized successor to Sanguine. Sections of the [[right of way (transportation)|right of ways]] for the power lines that make up the two 14-mile-long ground dipole antennas can be seen passing through the forest in lower left. ]]
[[File:Clam Lake ELF.jpg|thumb|225px|Clam Lake, Wisconsin [[Extremely low frequency|ELF]] transmitter in 1982, part of Project ELF, the downsized successor to Sanguine. Sections of the [[right of way (transportation)|rights of way]] for the power lines that make up the two 14-mile-long ground dipole antennas can be seen passing through the forest in the lower left.]]


'''Project Sanguine''' was a [[United States Navy|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]] {{Coord|46|05|05.6|N|90|55|03.7|W|display=inline}} and [[Republic, Michigan]] {{Coord|46|20|10.1|N|87|53|04.6|W|display=inline}} 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 (signal processing)|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.
'''Project Sanguine''' was a [[United States Navy|US Navy]] project proposed in 1968 for communication with submerged submarines using [[extremely low frequency]] (ELF) [[radio wave]]s. The initially proposed system, hardened to survive a nuclear attack, would have required a giant antenna covering two-fifths of the state of Wisconsin. The proposed approach was never implemented because of protests and potential environmental impact. A smaller, less hardened system called '''Project ELF''' consisting of two linked ELF transmitters located at [[Clam Lake, Wisconsin]] {{Coord|46|05|05.6|N|90|55|03.7|W|display=inline}} and [[Republic, Michigan]] {{Coord|46|20|10.1|N|87|53|04.6|W|display=inline}} 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 (signal processing)|bandwidth]] of the transmission was 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.


==Proposed system==
==Proposed system==


The originally proposed system would have had a giant "[[Antenna (radio)|antenna]]" consisting of {{convert|6000|mi|km}} of buried cables in a rectangular grid covering {{convert|22500|sqmi|km2}}, two fifths of the state of Wisconsin,<ref name="Altgelt" /> powered by 100 underground power plants in concrete bunkers.<ref name="Jones" /><ref name="Aldridge"/> The cables were [[Ground (electricity)|grounded]] at their ends, and loops of AC electric current flowed deep in the ground between the ends of the cable, generating ELF waves; this is called a ''[[ground dipole]]''. The original design was projected to cost billions<ref name="Sullivan">{{Cite news |last = Sullivan |first = Walter |title = How Huge Antenna Can Broadcast into the Silence of the Sea |newspaper = The New York Times |date = 13 October 1981 |url = https://www.nytimes.com/1981/10/13/science/how-huge-antenna-can-broadcast-into-the-silence-of-the-sea.html?pagewanted=all |access-date = 22 May 2012 }}</ref> and consume 800 megawatts of power.<ref name="Altgelt" /><ref name="Spinardi" >{{cite book |last = Spinardi |first = Graham |title = From Polaris to Trident: The Development of US Fleet Ballistic Missile Technology |publisher = Cambridge University Press |year = 1994 |location = London |pages = 81–82 |url = https://books.google.com/books?id=8mH-EbdNl0UC&pg=PA81 |isbn = 0-521-41357-5 |via = Google Books }}</ref> The goal was a system that could transmit tactical orders one-way to U.S. nuclear submarines anywhere in the world, and survive a direct nuclear attack.<ref name="Jones" />
The initially proposed system would have had a giant [[Antenna (radio)|antenna]] consisting of {{convert|6000|mi|km}} of buried cables in a rectangular grid covering {{convert|22500|sqmi|km2}}, two-fifths of the state of Wisconsin,<ref name="Altgelt" /> powered by 100 underground power plants in concrete bunkers.<ref name="Jones" /><ref name="Aldridge"/> The cables were [[Ground (electricity)|grounded]] at their ends, and loops of AC electric current flowed deep in the ground between the ends of the cable, generating ELF waves; this is called a ''[[ground dipole]]''. The original design was projected to cost billions<ref name="Sullivan">{{Cite news |last = Sullivan |first = Walter |title = How Huge Antenna Can Broadcast into the Silence of the Sea |newspaper = The New York Times |date = 13 October 1981 |url = https://www.nytimes.com/1981/10/13/science/how-huge-antenna-can-broadcast-into-the-silence-of-the-sea.html?pagewanted=all |access-date = 22 May 2012 }}</ref> and consume 800 megawatts of power.<ref name="Altgelt" /><ref name="Spinardi" >{{cite book |last = Spinardi |first = Graham |title = From Polaris to Trident: The Development of US Fleet Ballistic Missile Technology |publisher = Cambridge University Press |year = 1994 |location = London |pages = 81–82 |url = https://books.google.com/books?id=8mH-EbdNl0UC&pg=PA81 |isbn = 0-521-41357-5 |via = Google Books }}</ref> The goal was a system that could transmit tactical orders one-way to US nuclear submarines anywhere in the world, and survive a direct nuclear attack.<ref name="Jones" />


The project was controversial from the start and was attacked by politicians, [[Antinuclear movement|antiwar]] and [[Environmental movement|environmental groups]] concerned about the effects of high ground currents and electromagnetic fields on the environment.<ref name="Jones" /><ref name="Aldridge"/><ref name="Brodeur" >{{cite book |last = Brodeur |first = Paul |title = Currents of Death |publisher = Simon and Schuster |year = 2000 |location = New York |url = https://books.google.com/books?id=mke1FlCkIm4C&pg=PA62 |isbn = 0-7432-1308-4 |page = 62 |via = Google Books }}</ref><ref name="TheNuclearResistor" >{{cite magazine |last = Cohen-Joppa |first = Felice |title = Project ELF Closes |magazine = The Nuclear Resistor |issue = 135 |publisher = Felice and Jack Cohen-Joppa |date = 15 October 2004 |url = http://www.nukeresister.org/enwiki/static/nr135/135elfcloses.html |access-date = 10 July 2014 }}</ref> The nuclear survivability of the system was made doubtful by Soviet development of [[Multiple independently targetable reentry vehicle|MIRV]] ballistic missiles.<ref name="Aldridge"/> After an attempt to resite the project in the [[Llano Uplift]] of Texas<ref>{{cite journal |url = http://www.texasmonthly.com/politics/dr-strangelove-is-back/ |first = Grover |last = Ellis |title = Dr. Strangelove is Back! |journal = Texas Monthly |date = September 1973 }}</ref> was also stopped by public opposition,<ref name="Aldridge"/> the Navy abandoned Sanguine and proposed a series of increasingly modest variants: Project Seafarer (1975), Austere ELF (1978), and finally '''Project ELF''' (1981), which was constructed.<ref name="Aldridge"/><ref name="Spinardi" /> This lower power system required 15 minutes to transmit each code group, so it was not used to transmit tactical orders directly but instead served the function of a "bell ringer", ordering a specific vessel to surface and receive further orders by ordinary radio or satellite communication. <ref name="Altgelt" >{{cite web |last = Altgelt |first = Carlos |title = The World's Largest 'Radio' Station |work = The Broadcaster's Desktop Resource |publisher = Barry Mishkind |url = http://www.oldradio.com/archives/jurassic/ELF.doc |format = DOC |access-date = 17 February 2012 }}</ref><ref name="Jones" >{{cite journal |last = Jones |first = David Llanwyn |title = Sending Signals to Submarines |journal = New Scientist |volume = 26 |issue = 1463 |pages = 37–41 |date = 4 July 1985 |url = https://books.google.com/books?id=NOPpwVvNu44C&pg=PA39 |access-date = 17 February 2012 |via = Google Books }}</ref><ref name="Aldridge">{{cite web |last = Aldridge |first = Bob |title = ELF History: Extreme Low Frequency Communication |id = PLRC-941005B |publisher = Pacific Life Research Center |year = 2001 |url = http://www.plrc.org/docs/941005B.pdf |access-date = 23 February 2012 }}</ref> The system became nominally operational in 1989, 20 years after it first went online as "test facility," and was used until 2004, when the US Navy declared it obsolete and it was shut down and dismantled.
The project was controversial from the start and was attacked by politicians, [[Antinuclear movement|antiwar]] and [[Environmental movement|environmental groups]] concerned about the effects of high ground currents and electromagnetic fields on the environment.<ref name="Jones" /><ref name="Aldridge"/><ref name="Brodeur" >{{cite book |last = Brodeur |first = Paul |title = Currents of Death |publisher = Simon and Schuster |year = 2000 |location = New York |url = https://books.google.com/books?id=mke1FlCkIm4C&pg=PA62 |isbn = 0-7432-1308-4 |page = 62 |via = Google Books }}</ref><ref name="TheNuclearResistor" >{{cite magazine |last = Cohen-Joppa |first = Felice |title = Project ELF Closes |magazine = The Nuclear Resistor |issue = 135 |publisher = Felice and Jack Cohen-Joppa |date = 15 October 2004 |url = http://www.nukeresister.org/enwiki/static/nr135/135elfcloses.html |access-date = 10 July 2014 }}</ref> The nuclear survivability of the system was made doubtful by Soviet development of [[Multiple independently targetable reentry vehicle|MIRV]] ballistic missiles.<ref name="Aldridge"/> After an attempt to resite the project in the [[Llano Uplift]] of Texas<ref>{{cite journal |url = http://www.texasmonthly.com/politics/dr-strangelove-is-back/ |first = Grover |last = Ellis |title = Dr. Strangelove is Back! |journal = Texas Monthly |date = September 1973 }}</ref> was also stopped by public opposition,<ref name="Aldridge"/> the Navy abandoned Sanguine and proposed a series of increasingly modest variants: Project Seafarer (1975), Austere ELF (1978), and finally '''Project ELF''' (1981), which was constructed.<ref name="Aldridge"/><ref name="Spinardi" /> This lower power system required 15 minutes to transmit each code group, so it was not used to transmit tactical orders directly but instead served the function of a "bell ringer", ordering a specific vessel to rise near the surface and receive further orders by ordinary radio or satellite communication. <ref name="Altgelt" >{{cite web |last = Altgelt |first = Carlos |title = The World's Largest 'Radio' Station |work = The Broadcaster's Desktop Resource |publisher = Barry Mishkind |url = http://www.oldradio.com/archives/jurassic/ELF.doc |format = DOC |access-date = 17 February 2012 }}</ref><ref name="Jones" >{{cite journal |last = Jones |first = David Llanwyn |title = Sending Signals to Submarines |journal = New Scientist |volume = 26 |issue = 1463 |pages = 37–41 |date = 4 July 1985 |url = https://books.google.com/books?id=NOPpwVvNu44C&pg=PA39 |access-date = 17 February 2012 |via = Google Books }}</ref><ref name="Aldridge">{{cite web |last = Aldridge |first = Bob |title = ELF History: Extreme Low Frequency Communication |id = PLRC-941005B |publisher = Pacific Life Research Center |year = 2001 |url = http://www.plrc.org/docs/941005B.pdf |access-date = 23 February 2012 }}</ref> The system became nominally operational in 1989, 20 years after it first went online as "test facility," and was used until 2004, when the US Navy declared it obsolete and it was shut down and dismantled.


==Project ELF==
==Project ELF==
[[Image:US Navy ELF transmitter map.png|thumb|upright=2.0|Map showing location of the US Navy ELF transmitters. The <span style="color:red;">red lines</span> show the paths of the ground dipole antennas. The Clam Lake facility ''(left)'' had two crossed 14 mi. ground dipoles. The Republic facility had two 14 mi. dipoles oriented east–west, and one 28 mi. dipole oriented north–south.]]
[[Image:US Navy ELF transmitter map.png|thumb|upright=2.0|Map showing location of the US Navy ELF transmitters. The <span style="color:red;">red lines</span> show the paths of the ground dipole antennas. The Clam Lake facility ''(left)'' had two crossed 14 mi. ground dipoles. The Republic facility had two 14 mi. dipoles oriented east–west, and one 28 mi. dipole oriented north–south.]]


The scaled-down system the Navy constructed in 1969, called Project ELF, began official testing in 1982 and became officially operational in 1989.<ref name="NavyFactSheet" >{{cite web |title = Extremely Low Frequency Transmitter Site, Clam Lake, Wisconsin |work = Navy Fact File |publisher = United States Navy |date = 28 June 2001 |url = http://www.fas.org/nuke/guide/usa/c3i/fs_clam_lake_elf2003.pdf |access-date = 17 February 2012 |via = Federation of American Scientists }}</ref> It consisted of two transmitter facilities, one at [[Clam Lake, Wisconsin]] and one at [[Republic, Michigan]].<ref name="NavyFactSheet" /> with a total of {{convert|84|mi|km}}<ref name="Friedman" >{{cite book |last = Friedman |first = Norman |title = The Naval Institute guide to world naval weapons systems, 1997-1998 |publisher = Naval Institute Press |year = 1997 |location = New York |pages = 41–42 |url = https://books.google.com/books?id=l-DzknmTgDUC&pg=PA42 |isbn = 1-55750-268-4 |via = Google Books }}</ref> of above-ground transmission line antenna. The two transmitters normally operated synchronized together as one antenna for greater range, but could also operate independently. The scaled down system was not designed to survive a nuclear attack.
The scaled-down system the Navy constructed in 1969, called Project ELF, began official testing in 1982 and became officially operational in 1989.<ref name="NavyFactSheet" >{{cite web |title = Extremely Low Frequency Transmitter Site, Clam Lake, Wisconsin |work = Navy Fact File |publisher = United States Navy |date = 28 June 2001 |url = http://www.fas.org/nuke/guide/usa/c3i/fs_clam_lake_elf2003.pdf |access-date = 17 February 2012 |via = Federation of American Scientists }}</ref> It consisted of two transmitter facilities, one at [[Clam Lake, Wisconsin]] and one at [[Republic, Michigan]].<ref name="NavyFactSheet" /> with a total of {{convert|84|mi|km}}<ref name="Friedman" >{{cite book |last = Friedman |first = Norman |title = The Naval Institute guide to world naval weapons systems, 1997-1998 |publisher = Naval Institute Press |year = 1997 |location = New York |pages = 41–42 |url = https://books.google.com/books?id=l-DzknmTgDUC&pg=PA42 |isbn = 1-55750-268-4 |via = Google Books }}</ref> of above-ground transmission line antenna. The two transmitters normally operated synchronized as one antenna for greater range but could also operate independently. The scaled-down system was not designed to survive a nuclear attack.


The Clam Lake facility, which served as the test site and was originally called the Wisconsin Test Facility (WTF) consisted of two {{convert|14|mi|km|adj=on}} transmission line antennas (called [[ground dipole]]s) in the shape of a cross, with the transmitter station at their intersection.<ref name="Altgelt" /><ref name="Heppenheimer" >{{cite journal |last = Heppenheimer |first = T. A. |title = Signaling Subs |journal = Popular Science |volume = 230 |issue = 4 |pages = 44–48 |date = April 1987 |url = https://books.google.com/books?id=IAEAAAAAMBAJ&pg=PA44 |access-date = 17 February 2012 |via = Google Books }}</ref> The Republic facility consisted of three transmission lines, two {{convert|14|mi|km|adj=on}} and one {{convert|28|mi|km|adj=on}},<ref name="Altgelt" /> in the shape of the letter "F" (the shape is not significant and was dictated by land availability).<ref name="Heppenheimer" /> The lines, made of {{convert|1.5|cm|in|adj=on|sp=us}} aluminum cable supported on insulators on {{convert|40|ft|m|adj=on}} wooden utility poles, resembled ordinary power transmission lines.<ref name="Jones" /> The ends of the transmission lines were [[ground (electricity)|grounded]] by {{convert|1|to|3|mi|km}} of buried copper cable and ground rods,<ref name="Jones" /> later replaced by arrays of electrodes in deep {{convert|300|ft|m|adj=on}} boreholes<ref name="Altgelt" /> The transmitters sent [[alternating current]]s of 300 amperes through the lines, which passed through the buried electrodes deep into the Earth.<ref name="Jones" />
The Clam Lake facility, which served as the test site and was originally called the Wisconsin Test Facility (WTF), consisted of two {{convert|14|mi|km|adj=on}} transmission line antennas (called [[ground dipole]]s) in the shape of a cross, with the transmitter station at their intersection.<ref name="Altgelt" /><ref name="Heppenheimer" >{{cite journal |last = Heppenheimer |first = T. A. |title = Signaling Subs |journal = Popular Science |volume = 230 |issue = 4 |pages = 44–48 |date = April 1987 |url = https://books.google.com/books?id=IAEAAAAAMBAJ&pg=PA44 |access-date = 17 February 2012 |via = Google Books }}</ref> The Republic facility consisted of three transmission lines, two {{convert|14|mi|km|adj=on}} and one {{convert|28|mi|km|adj=on}},<ref name="Altgelt" /> in the shape of the letter "F" (the shape is not significant and was dictated by land availability).<ref name="Heppenheimer" /> The lines, made of {{convert|1.5|cm|in|adj=on|sp=us}} aluminum cable supported on insulators on {{convert|40|ft|m|adj=on}} wooden utility poles, resembled ordinary power transmission lines.<ref name="Jones" /> The ends of the transmission lines were [[ground (electricity)|grounded]] by {{convert|1|to|3|mi|km}} of buried copper cable and ground rods,<ref name="Jones" /> later replaced by arrays of electrodes in deep {{convert|300|ft|m|adj=on}} boreholes<ref name="Altgelt" /> The transmitters sent [[alternating current]]s of 300 amperes through the lines, which passed through the buried electrodes deep into the Earth.<ref name="Jones" />


[[File:Ground dipole ELF antenna.svg|thumb|upright=1.5|Clam Lake ground dipole antenna, showing how it works. The alternating current I in the line is shown flowing in only one direction for clarity.]]
[[File:Ground dipole ELF antenna.svg|thumb|upright=1.5|Clam Lake ground dipole antenna, showing how it works. The alternating current I in the line is shown flowing in only one direction for clarity.]]


The transmitters operated at a [[frequency]] of 76&nbsp;Hz in the [[extremely low frequency]] band, with an alternate capability at 45&nbsp;Hz<ref name="Jones" /> and used a combined power of 2.6 megawatts.<ref name="Spinardi" /> They were able to communicate with submarines over about half the world's surface. The system transmitted continuously, 24 hours a day, sending an "idle" message when it was not being used, so that submarines could verify they were within communication range.<ref name="NavyFactSheet" /><ref name="Heppenheimer" />
The transmitters operated at a [[frequency]] of 76&nbsp;Hz in the [[extremely low frequency]] band, with an alternate capability at 45&nbsp;Hz<ref name="Jones" /> and used a combined power of 2.6 megawatts.<ref name="Spinardi" /> They could communicate with submarines over about half the world's surface. The system transmitted continuously, 24 hours a day, sending an "idle" message when it was not being used so that submarines could verify they were within communication range.<ref name="NavyFactSheet" /><ref name="Heppenheimer" />


Because of the extremely small [[bandwidth (signal processing)|bandwidth]] of the ELF band, the transmitters had a very slow [[Bit rate|data rate]]. They couldn't transmit voice ([[audio signal|audio]]) but only short coded text messages of a few letters.<ref name="Spinardi" /><ref name="Friedman" /> Reportedly it took 15 minutes to transmit a single three-letter code group.<ref name="Friedman" /><ref name="Heppenheimer" /> Therefore the system was not used to relay operational orders, but served a "bell-ringer" function, ordering specific submarines to the surface to receive detailed orders by ordinary radio and satellite communications links.<ref name="Friedman" />
Because of the extremely small [[bandwidth (signal processing)|bandwidth]] of the ELF band, the transmitters had a very slow [[Bit rate|data rate]]. They couldn't transmit voice ([[audio signal|audio]]) but only short coded text messages of a few letters.<ref name="Spinardi" /><ref name="Friedman" /> Reportedly, it took 15 minutes to transmit a single three-letter code group.<ref name="Friedman" /><ref name="Heppenheimer" />


The system was controversial, and was the target of legal attacks, suits and protests throughout its operating life.<ref name="Brodeur" /><ref name="TheNuclearResistor" /> On five occasions protesters cut down transmission line poles, interrupting operation briefly.<ref name="TheNuclearResistor" />
The system was controversial and was the target of legal attacks, suits, and protests throughout its operating life.<ref name="Brodeur" /><ref name="TheNuclearResistor" /> On five occasions, protesters cut down transmission line poles, interrupting operation briefly.<ref name="TheNuclearResistor" />


In 2004, the Navy shut down both transmitters, with the explanation that [[very low frequency]] (VLF) communication systems had improved to the point that the ELF system was unnecessary.<ref name="TheNuclearResistor" />
In 2004, the Navy shut down both transmitters, with the explanation that [[very low frequency]] (VLF) communication systems had improved to the point that the ELF system was unnecessary.<ref name="TheNuclearResistor" />
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==How ELF communication works==
==How ELF communication works==
{{main|Communication with submarines#Extremely low frequency}}
{{main|Communication with submarines#Extremely low frequency}}
Submarines are shielded by seawater from all ordinary radio signals, and therefore are cut off from communication with military command authorities while submerged.<ref name="Heppenheimer" /> However radio waves of very low [[frequency]] can penetrate seawater; the lower the frequency the deeper in the ocean they can penetrate.<ref name="NavyFactSheet" /> Waves in the VLF range of 3&nbsp;kHz to 30&nbsp;kHz are able to penetrate to a depth of about 10 to 30 meters,<ref name="Friedman" /> and since WWII navies have used VLF transmitters to communicate with submarines. To receive VLF signals subs must rise to just under the surface or trail a shallow antenna buoy, making them vulnerable to detection by the enemy.<ref name="Spinardi" /><ref name="Friedman" />
Submarines are shielded by seawater from all ordinary radio signals and, therefore, are cut off from communication with military command authorities while submerged.<ref name="Heppenheimer" /> However, radio waves of very low [[frequency]] can penetrate seawater; the lower the frequency, the deeper in the ocean they can penetrate.<ref name="NavyFactSheet" /> Waves in the [[very low frequency|VLF]] range of 3&nbsp;kHz to 30&nbsp;kHz can penetrate to a depth of about 10 to 30 meters,<ref name="Friedman" /> and since WWII navies have used VLF transmitters to communicate with submarines. To receive VLF signals, subs must rise to just under the surface or trail a shallow antenna buoy, making them vulnerable to detection by the enemy.<ref name="Spinardi" /><ref name="Friedman" />


Radio waves in the [[extremely low frequency]] (ELF) band of 30 to 300&nbsp;Hz can penetrate to a depth of hundreds of meters, allowing them to communicate with submarines at their normal operating depth.<ref name="Spinardi" /> The lower the frequency, the longer the [[wavelength]] of the radio waves, and transmitters require longer [[antenna (radio)|antenna]] structures to generate them. ELF transmitters use huge antennas called [[ground dipole]]s consisting of tens to hundreds of kilometers of overhead cables resembling ordinary power transmission lines. The transmission lines are [[ground (electricity)|ground]]ed at the ends, and looping currents deep in the Earth form part of the antenna. Because even these huge antennas are much smaller than the ELF wavelengths, they are extremely inefficient; only a tiny fraction of the input power is radiated as ELF waves, with the rest dissipated as heat in antenna resistance. At their full input power of 2.6 MW, both US ELF transmitters working together only generated about 8 watts of ELF radiation. This weak signal was able to reach submarines over half the globe only because of the extremely low attenuation of ELF waves of 1–2 dB per 1000 kilometers. ELF transmitters are most efficient when sited over certain low [[Electrical resistivity and conductivity|conductivity]] underground rock formations, which forces the currents to spread deeper through a larger volume of rock, forming a larger "antenna".<ref name="Jones" /> The US system was located in Wisconsin and the Upper Peninsula of Michigan over the [[Laurentian Shield]] formation, for that reason.<ref name="Jones" />
Radio waves in the [[extremely low frequency]] (ELF) band of 30 to 300&nbsp;Hz can penetrate to a depth of hundreds of meters, allowing them to communicate with submarines at their normal operating depth.<ref name="Spinardi" /> The lower the frequency, the longer the [[wavelength]] of the radio waves, and transmitters require longer [[antenna (radio)|antenna]] structures to generate them. ELF transmitters use huge antennas called [[ground dipole]]s consisting of tens to hundreds of kilometers of overhead cables resembling ordinary power transmission lines. The transmission lines are [[ground (electricity)|ground]]ed at the ends, and looping currents deep in the Earth form part of the antenna. Because even these huge antennas are much smaller than the ELF wavelengths, they are extremely inefficient; only a tiny fraction of the input power is radiated as ELF waves, with the rest dissipated as heat in antenna resistance. At their full input power of 2.6 MW, both US ELF transmitters working together only generated about 8 watts of ELF radiation. This weak signal reached submarines over half the globe only because of the extremely low attenuation of ELF waves of 1–2 dB per 1000 kilometers. ELF transmitters are most efficient when sited over certain low [[Electrical resistivity and conductivity|conductivity]] underground rock formations, which forces the currents to spread deeper through a larger volume of rock, forming a larger "antenna".<ref name="Jones" /> The US system was located in Wisconsin and the Upper Peninsula of Michigan over the [[Laurentian Shield]] formation, for that reason.<ref name="Jones" />


Such ELF transmitters cannot be installed on submarines, because of the size of the antenna and high power requirements. So ELF communication is one-way, with a receiver in the submarine receiving orders from a shore station, but unable to reply. The low attenuation of ELF waves with distance allows a single ELF station to send messages to submarines all over the world.
Such ELF transmitters cannot be installed on submarines because of the antenna size and high power requirements. So ELF communication is one-way, with a receiver in the submarine receiving orders from a shore station but unable to reply. The low attenuation of ELF waves with distance allows a single ELF station to send messages to submarines worldwide.


Another drawback of ELF is that the ELF band has very small [[bandwidth (signal processing)|bandwidth]], and therefore can only transmit very simple messages, very slowly.<ref name="Spinardi" /><ref name="Friedman" /> ELF signals cannot carry [[audio signal|audio]] (voice) like other types of radio, and can only carry short text messages consisting of a few letters. The US Navy system (above) reportedly uses three-letter code groups and requires 15 minutes to transmit one group.<ref name="Friedman" /><ref name="Heppenheimer" /> So current systems are not used to transmit detailed orders, but serve a "bell ringer" function, to order a specific vessel to surface and receive further orders by ordinary radio or satellite communication.<ref name="Friedman" />
Another drawback of ELF is that the ELF band has very small [[bandwidth (signal processing)|bandwidth]] and, therefore, can only transmit very simple messages very slowly.<ref name="Spinardi" /><ref name="Friedman" /> ELF signals cannot carry [[audio signal|audio]] (voice) like other types of radio and can only carry short text messages consisting of a few letters. The US Navy system (above) reportedly uses three-letter code groups and requires 15 minutes to transmit one group.<ref name="Friedman" /><ref name="Heppenheimer" />


==Other ELF transmitters==
==Other ELF transmitters==
The US, Russia, India, and China are the only nations known to have constructed ELF communication facilities. The [[Indian Navy]] has an operational ELF communication facility at the [[INS Kattabomman]] naval base to communicate with its [[Arihant-class submarine|Arihant class]] and [[Akula-class submarine|Akula class]] submarines.<ref>{{cite web |url = http://timesofindia.indiatimes.com/india/Navy-gets-new-facility-to-communicate-with-nuclear-submarines-prowling-underwater/articleshow/39371121.cms |title = Navy Gets New Facility to Communicate with Nuclear Submarines Prowling Underwater |date = 31 July 2014 |work = [[The Times of India]] }}</ref><ref>{{cite web |url = http://www.janes.com/article/11147/india-makes-headway-with-elf-site-construction |archive-url = https://web.archive.org/web/20140223135343/http://www.janes.com/article/11147/india-makes-headway-with-elf-site-construction |archive-date = 23 February 2014 |first = James |last = Hardy |date = 28 February 2013 |title = India Makes Headway with ELF Site Construction |work = IHS Jane's Defence Weekly }}</ref> The [[Russian Navy]] reportedly operates an ELF transmitter, [[ZEVS (transmitter)|ZEVS]], located northwest of [[Murmansk]] on the [[Kola Peninsula]] in northern Russia.<ref name="Trond">{{cite web |last = Jacobsen |first = Trond|title = ZEVS, The Russian 82 Hz ELF Transmitter |work = Radio Waves Below 22 kHz |publisher = Renato Romero webpage |year = 2001 |url = http://www.vlf.it/zevs/zevs.htm |access-date = 17 February 2012 }}</ref>
The US, Russia, India, and China are the only nations that have constructed ELF communication facilities. The [[Indian Navy]] has an operational ELF communication facility at the [[INS Kattabomman]] naval base to communicate with its [[Arihant-class submarine|Arihant class]] and [[Akula-class submarine|Akula class]] submarines.<ref>{{cite web |url = http://timesofindia.indiatimes.com/india/Navy-gets-new-facility-to-communicate-with-nuclear-submarines-prowling-underwater/articleshow/39371121.cms |title = Navy Gets New Facility to Communicate with Nuclear Submarines Prowling Underwater |date = 31 July 2014 |work = [[The Times of India]] }}</ref><ref>{{cite web |url = http://www.janes.com/article/11147/india-makes-headway-with-elf-site-construction |archive-url = https://web.archive.org/web/20140223135343/http://www.janes.com/article/11147/india-makes-headway-with-elf-site-construction |archive-date = 23 February 2014 |first = James |last = Hardy |date = 28 February 2013 |title = India Makes Headway with ELF Site Construction |work = IHS Jane's Defence Weekly }}</ref> The [[Russian Navy]] reportedly operates an ELF transmitter, [[ZEVS (transmitter)|ZEVS]], located northwest of [[Murmansk]] on the [[Kola Peninsula]] in northern Russia.<ref name="Trond">{{cite web |last = Jacobsen |first = Trond|title = ZEVS, The Russian 82 Hz ELF Transmitter |work = Radio Waves Below 22 kHz |publisher = Renato Romero webpage |year = 2001 |url = http://www.vlf.it/zevs/zevs.htm |access-date = 17 February 2012 }}</ref>


==See also==
==See also==
Line 56: Line 57:
* {{cite book |first = Robert O. |last = Becker |title = Cross Currents: The Promise of Electromedicine, the Perils of Electropollution |pages = [https://archive.org/details/crosscurrentspro00beck/page/201 201–2, 233–4] |location = Los Angeles |publisher = J.P. Tarcher |year = 1990 |edition = 1st |isbn = 9780874775365 |url-access = registration |url = https://archive.org/details/crosscurrentspro00beck/page/201 }}
* {{cite book |first = Robert O. |last = Becker |title = Cross Currents: The Promise of Electromedicine, the Perils of Electropollution |pages = [https://archive.org/details/crosscurrentspro00beck/page/201 201–2, 233–4] |location = Los Angeles |publisher = J.P. Tarcher |year = 1990 |edition = 1st |isbn = 9780874775365 |url-access = registration |url = https://archive.org/details/crosscurrentspro00beck/page/201 }}
*{{cite journal |last = Jones |first = David Llanwyn |title = Sending signals to submarines |journal = New Scientist |volume = 26 |issue = 1463 |pages = 37–41 |date = 4 July 1985 |url = https://books.google.com/books?id=NOPpwVvNu44C&pg=PA39 |issn = 0262-4079 |access-date = 17 February 2012 |via = Google Books }}
*{{cite journal |last = Jones |first = David Llanwyn |title = Sending signals to submarines |journal = New Scientist |volume = 26 |issue = 1463 |pages = 37–41 |date = 4 July 1985 |url = https://books.google.com/books?id=NOPpwVvNu44C&pg=PA39 |issn = 0262-4079 |access-date = 17 February 2012 |via = Google Books }}
*{{cite journal |first = James R. |last = Wait |author-link = James R. Wait |title = Project Sanguine |journal = Science |date = 20 October 1972 |volume = 178 |issue = 4058 |pages = 272–5 |issn = 0036-8075 |doi = 10.1126/science.178.4058.272 |pmid = 17735468 }}
*{{cite journal |first = James R. |last = Wait |author-link = James R. Wait |title = Project Sanguine |journal = Science |date = 20 October 1972 |volume = 178 |issue = 4058 |pages = 272–5 |issn = 0036-8075 |doi = 10.1126/science.178.4058.272 |pmid = 17735468 |bibcode = 1972Sci...178..272W }}
*{{cite journal |first = James R. |last = Wait |title = Propagation of ELF Electromagnetic Waves and Project Sanguine / Seafarer |journal = IEEE Journal of Oceanic Engineering |volume = 2 |issue = 2 |date = April 1977 |pages = 161–72 |issn = 0364-9059 |doi = 10.1109/JOE.1977.1145337 }}
*{{cite journal |first = James R. |last = Wait |title = Propagation of ELF Electromagnetic Waves and Project Sanguine / Seafarer |journal = IEEE Journal of Oceanic Engineering |volume = 2 |issue = 2 |date = April 1977 |pages = 161–72 |issn = 0364-9059 |doi = 10.1109/JOE.1977.1145337 |bibcode = 1977IJOE....2..161W }}
{{refend}}
{{refend}}


Latest revision as of 15:30, 7 June 2024

Clam Lake, Wisconsin ELF transmitter in 1982, part of Project ELF, the downsized successor to Sanguine. Sections of the rights of way for the power lines that make up the two 14-mile-long ground dipole antennas can be seen passing through the forest in the lower left.

Project Sanguine was a US Navy project proposed in 1968 for communication with submerged submarines using extremely low frequency (ELF) radio waves. The initially proposed system, hardened to survive a nuclear attack, would have required a giant antenna covering two-fifths of the state of Wisconsin. The proposed approach was never implemented because of protests and potential environmental impact. A smaller, less hardened system called Project ELF consisting of two linked ELF transmitters located at Clam Lake, Wisconsin 46°05′05.6″N 90°55′03.7″W / 46.084889°N 90.917694°W / 46.084889; -90.917694 and Republic, Michigan 46°20′10.1″N 87°53′04.6″W / 46.336139°N 87.884611°W / 46.336139; -87.884611 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 was 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.

Proposed system

[edit]

The initially proposed system would have had a giant antenna consisting of 6,000 miles (9,700 km) of buried cables in a rectangular grid covering 22,500 square miles (58,000 km2), two-fifths of the state of Wisconsin,[1] powered by 100 underground power plants in concrete bunkers.[2][3] The cables were grounded at their ends, and loops of AC electric current flowed deep in the ground between the ends of the cable, generating ELF waves; this is called a ground dipole. The original design was projected to cost billions[4] and consume 800 megawatts of power.[1][5] The goal was a system that could transmit tactical orders one-way to US nuclear submarines anywhere in the world, and survive a direct nuclear attack.[2]

The project was controversial from the start and was attacked by politicians, antiwar and environmental groups concerned about the effects of high ground currents and electromagnetic fields on the environment.[2][3][6][7] The nuclear survivability of the system was made doubtful by Soviet development of MIRV ballistic missiles.[3] After an attempt to resite the project in the Llano Uplift of Texas[8] was also stopped by public opposition,[3] the Navy abandoned Sanguine and proposed a series of increasingly modest variants: Project Seafarer (1975), Austere ELF (1978), and finally Project ELF (1981), which was constructed.[3][5] This lower power system required 15 minutes to transmit each code group, so it was not used to transmit tactical orders directly but instead served the function of a "bell ringer", ordering a specific vessel to rise near the surface and receive further orders by ordinary radio or satellite communication. [1][2][3] The system became nominally operational in 1989, 20 years after it first went online as "test facility," and was used until 2004, when the US Navy declared it obsolete and it was shut down and dismantled.

Project ELF

[edit]
Map showing location of the US Navy ELF transmitters. The red lines show the paths of the ground dipole antennas. The Clam Lake facility (left) had two crossed 14 mi. ground dipoles. The Republic facility had two 14 mi. dipoles oriented east–west, and one 28 mi. dipole oriented north–south.

The scaled-down system the Navy constructed in 1969, called Project ELF, began official testing in 1982 and became officially operational in 1989.[9] It consisted of two transmitter facilities, one at Clam Lake, Wisconsin and one at Republic, Michigan.[9] with a total of 84 miles (135 km)[10] of above-ground transmission line antenna. The two transmitters normally operated synchronized as one antenna for greater range but could also operate independently. The scaled-down system was not designed to survive a nuclear attack.

The Clam Lake facility, which served as the test site and was originally called the Wisconsin Test Facility (WTF), consisted of two 14-mile (23 km) transmission line antennas (called ground dipoles) in the shape of a cross, with the transmitter station at their intersection.[1][11] The Republic facility consisted of three transmission lines, two 14-mile (23 km) and one 28-mile (45 km),[1] in the shape of the letter "F" (the shape is not significant and was dictated by land availability).[11] The lines, made of 1.5-centimeter (0.59 in) aluminum cable supported on insulators on 40-foot (12 m) wooden utility poles, resembled ordinary power transmission lines.[2] The ends of the transmission lines were grounded by 1 to 3 miles (1.6 to 4.8 km) of buried copper cable and ground rods,[2] later replaced by arrays of electrodes in deep 300-foot (91 m) boreholes[1] The transmitters sent alternating currents of 300 amperes through the lines, which passed through the buried electrodes deep into the Earth.[2]

Clam Lake ground dipole antenna, showing how it works. The alternating current I in the line is shown flowing in only one direction for clarity.

The transmitters operated at a frequency of 76 Hz in the extremely low frequency band, with an alternate capability at 45 Hz[2] and used a combined power of 2.6 megawatts.[5] They could communicate with submarines over about half the world's surface. The system transmitted continuously, 24 hours a day, sending an "idle" message when it was not being used so that submarines could verify they were within communication range.[9][11]

Because of the extremely small bandwidth of the ELF band, the transmitters had a very slow data rate. They couldn't transmit voice (audio) but only short coded text messages of a few letters.[5][10] Reportedly, it took 15 minutes to transmit a single three-letter code group.[10][11]

The system was controversial and was the target of legal attacks, suits, and protests throughout its operating life.[6][7] On five occasions, protesters cut down transmission line poles, interrupting operation briefly.[7]

In 2004, the Navy shut down both transmitters, with the explanation that very low frequency (VLF) communication systems had improved to the point that the ELF system was unnecessary.[7]

How ELF communication works

[edit]
Main article: Communication with submarines § Extremely low frequency

Submarines are shielded by seawater from all ordinary radio signals and, therefore, are cut off from communication with military command authorities while submerged.[11] However, radio waves of very low frequency can penetrate seawater; the lower the frequency, the deeper in the ocean they can penetrate.[9] Waves in the VLF range of 3 kHz to 30 kHz can penetrate to a depth of about 10 to 30 meters,[10] and since WWII navies have used VLF transmitters to communicate with submarines. To receive VLF signals, subs must rise to just under the surface or trail a shallow antenna buoy, making them vulnerable to detection by the enemy.[5][10]

Radio waves in the extremely low frequency (ELF) band of 30 to 300 Hz can penetrate to a depth of hundreds of meters, allowing them to communicate with submarines at their normal operating depth.[5] The lower the frequency, the longer the wavelength of the radio waves, and transmitters require longer antenna structures to generate them. ELF transmitters use huge antennas called ground dipoles consisting of tens to hundreds of kilometers of overhead cables resembling ordinary power transmission lines. The transmission lines are grounded at the ends, and looping currents deep in the Earth form part of the antenna. Because even these huge antennas are much smaller than the ELF wavelengths, they are extremely inefficient; only a tiny fraction of the input power is radiated as ELF waves, with the rest dissipated as heat in antenna resistance. At their full input power of 2.6 MW, both US ELF transmitters working together only generated about 8 watts of ELF radiation. This weak signal reached submarines over half the globe only because of the extremely low attenuation of ELF waves of 1–2 dB per 1000 kilometers. ELF transmitters are most efficient when sited over certain low conductivity underground rock formations, which forces the currents to spread deeper through a larger volume of rock, forming a larger "antenna".[2] The US system was located in Wisconsin and the Upper Peninsula of Michigan over the Laurentian Shield formation, for that reason.[2]

Such ELF transmitters cannot be installed on submarines because of the antenna size and high power requirements. So ELF communication is one-way, with a receiver in the submarine receiving orders from a shore station but unable to reply. The low attenuation of ELF waves with distance allows a single ELF station to send messages to submarines worldwide.

Another drawback of ELF is that the ELF band has very small bandwidth and, therefore, can only transmit very simple messages very slowly.[5][10] ELF signals cannot carry audio (voice) like other types of radio and can only carry short text messages consisting of a few letters. The US Navy system (above) reportedly uses three-letter code groups and requires 15 minutes to transmit one group.[10][11]

Other ELF transmitters

[edit]

The US, Russia, India, and China are the only nations that have constructed ELF communication facilities. The Indian Navy has an operational ELF communication facility at the INS Kattabomman naval base to communicate with its Arihant class and Akula class submarines.[12][13] The Russian Navy reportedly operates an ELF transmitter, ZEVS, located northwest of Murmansk on the Kola Peninsula in northern Russia.[14]

See also

[edit]

References

[edit]

Footnotes

[edit]
  1. ^ a b c d e f Altgelt, Carlos. "The World's Largest 'Radio' Station" (DOC). The Broadcaster's Desktop Resource. Barry Mishkind. Retrieved 17 February 2012.
  2. ^ a b c d e f g h i j Jones, David Llanwyn (4 July 1985). "Sending Signals to Submarines". New Scientist. 26 (1463): 37–41. Retrieved 17 February 2012 – via Google Books.
  3. ^ a b c d e f Aldridge, Bob (2001). "ELF History: Extreme Low Frequency Communication" (PDF). Pacific Life Research Center. PLRC-941005B. Retrieved 23 February 2012.
  4. ^ Sullivan, Walter (13 October 1981). "How Huge Antenna Can Broadcast into the Silence of the Sea". The New York Times. Retrieved 22 May 2012.
  5. ^ a b c d e f g Spinardi, Graham (1994). From Polaris to Trident: The Development of US Fleet Ballistic Missile Technology. London: Cambridge University Press. pp. 81–82. ISBN 0-521-41357-5 – via Google Books.
  6. ^ a b Brodeur, Paul (2000). Currents of Death. New York: Simon and Schuster. p. 62. ISBN 0-7432-1308-4 – via Google Books.
  7. ^ a b c d Cohen-Joppa, Felice (15 October 2004). "Project ELF Closes". The Nuclear Resistor. No. 135. Felice and Jack Cohen-Joppa. Retrieved 10 July 2014.
  8. ^ Ellis, Grover (September 1973). "Dr. Strangelove is Back!". Texas Monthly.
  9. ^ a b c d "Extremely Low Frequency Transmitter Site, Clam Lake, Wisconsin" (PDF). Navy Fact File. United States Navy. 28 June 2001. Retrieved 17 February 2012 – via Federation of American Scientists.
  10. ^ a b c d e f g Friedman, Norman (1997). The Naval Institute guide to world naval weapons systems, 1997-1998. New York: Naval Institute Press. pp. 41–42. ISBN 1-55750-268-4 – via Google Books.
  11. ^ a b c d e f Heppenheimer, T. A. (April 1987). "Signaling Subs". Popular Science. 230 (4): 44–48. Retrieved 17 February 2012 – via Google Books.
  12. ^ "Navy Gets New Facility to Communicate with Nuclear Submarines Prowling Underwater". The Times of India. 31 July 2014.
  13. ^ Hardy, James (28 February 2013). "India Makes Headway with ELF Site Construction". IHS Jane's Defence Weekly. Archived from the original on 23 February 2014.
  14. ^ Jacobsen, Trond (2001). "ZEVS, The Russian 82 Hz ELF Transmitter". Radio Waves Below 22 kHz. Renato Romero webpage. Retrieved 17 February 2012.

Bibliography

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