The Ground Wave Emergency Network (GWEN)[1] was a command and control communications system intended for use by the United States government to facilitate military communications before, during and after a nuclear war. Specifically, GWEN was constructed to survive the effects of a high-altitude nuclear explosion electromagnetic pulse to insure that the United States President or his survivors can give a launching order to strategic nuclear bombers.[2][3]
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GWEN was part of the Strategic Modernization Program designed to upgrade the nation's strategic communication system, thereby strengthening the value of nuclear deterrence. The GWEN communication system, established in the late 1980s, was designed to transmit critical messages (i.e. Emergency Action Messages (EAMs)) to United States nuclear forces. EMP, over a large area, can produce a sudden power surge that would overload unprotected electronic equipment and render it inoperable. In addition, EMP would interfere with transmissions that use the ionosphere for propagation. GWEN would use a ground-hugging wave for propagation, being unaffected by the EMP.[2]
The network was conceived as an array of approximately 300 radio transceivers distributed across the continental USA which operated in the Low Frequency (LF) radio band. Later revised for 126 towers, plans again changed to include 56 radio towers linking 38 terminals; it was later expanded to 96 towers linking 49 terminals. Final network towers numbered 58.[3]
Originally conceived during the early days of the Ronald Reagan Presidential Administration, the Air Force placed a tentative initial operating capability for GWEN by January 1992.[3]
GWEN transmitting antennas consist of a concrete foundation 2 feet (0.61 m) above grade, a 3-foot-high (0.91 m) insulator, a 290-foot (88 m) steel tower, and 4-foot (1.2 m) lightning rods enclosed by a 42-foot (13 m) × 47-foot (14 m), 8-foot-high (2.4 m) chain-link fence topped with barbed wire. The tower itself would be supported by 15 guy wires attached to the ground at six anchor locations. Surrounding the tower and attached to it at the top and anchored in the ground by concrete blocks would be 12 top-loading elements (TLEs). The purpose of the TLEs is to enhance the efficiency of the antenna. Anchors for the TLEs and guy wires would be within the site boundaries.
In the GWEN system, originating stations send ultra high frequency (UHF) signals by broadcast towers for line-of-site receipt at Relay Nodes (RNs). The RNs form an unmanned network throughout the US, with individual RNs at spacings of approximately 150 to 200 miles (240 to 320 km). The RNs transmit received messages via LF signals for ultimate receipt by receive-only terminals at existing military communication buildings. By utilizing LF ground transmission the GWEN system minimizes the potential effect of HEMP on military communications.
The network had three types of stations: input/output stations (I/Os), receive-only stations (ROs), and relay nodes (RNs). I/O stations could send and receive messages. ROs only received messages transmitted through I/Os. Dispersed and unmanned RNs, would provide continuous relay links between I/Os and ROs. The I/Os and ROs would reside at locations with strategic military forces, and the RNs would be scattered throughout the country on government or privately leased land. Distance between the relay nodes were determined by the ground wave transmission wavelength, at intervals of approximately 150–200 miles.[2]
During initial operations, the towers would receive and relay brief test messages every 20 minutes.[3] The system had built-in redundancy, using packet switching techniques for reconstruction of connectivity if system damage occurs.[4]
Early in its lifetime, electrical interference problems caused by GWEN system operation began to surface. Since the stations were using LF, the chosen frequency was within 1 kHz of the operating frequency of nearby electrical carrier current systems. With GWEN handling constant voice, teletype and other data traffic, interference was noticed by local power companies on a diagnostic two kilohertz side carrier tone – if the carrier disappeared, the power grid would interpret that as a system fault.[5]
The overall site area of a relay node was approximately 11 acres (4.5 ha), approximately 700 feet (210 m) × 700 feet. Typical site features include a longwave transmitting tower (generally between 290 and 299 feet (88 and 91 m) tall), a backup diesel generator with a two-chambered fuel tank having a capacity of 1,020 US gallons (3,900 l), 8-foot (2.4 m) × 14-foot (4.3 m) × 8-foot antenna-tuning unit (ATU) in the center of the site, and a radio processor; electronic equipment was housed in three shelters. Two of the shelters were located inside the fenced area at the perimeter of the property, and the other at the base of the tower. The equipment area and the tower base were surrounded by locked, 8-foot-high (2.4 m) chain-link fences topped with barbed wire. In addition, each node had a UHF antenna and an LF receive antenna on a ten-foot mast located inside the equipment area. The main GWEN antenna operated intermittently in the LF band at 150 to 175 kilohertz (kHz) (e.g., the bottom of the AM band is 530 kHz). The peak broadcasting power was from 2,000 to 3,000 watts. The UHF antenna operated at 20 watts, between 225 and 400 megahertz (MHz).
The GWEN transmitter sites include:
| Broadcast Site |
Frequency | Power | Field Strength |
Latitude | Longitude | ILC | Notes |
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| Goodland, Kansas |
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| Ronan, Montana |
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| Penobscot, Maine |
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| Kirtland, New Mexico |
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| Appleton, Washington |
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| Macon, Georgia |
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| Medora, North Dakota |
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| Edinburg, North Dakota |
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| Clark, South Dakota |
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| Whitney, Nebraska |
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| Austin, Nevada |
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| Billings, MT |
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| Flagstaff, AZ |
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| Hudson Falls, NY |
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| Pueblo, CO |
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| Savannah, GA |
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| Kensington, SC |
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| Egg Harbor, NJ |
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| Great Falls, MT |
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| Goldwein, VA |
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| Spokane, WA |
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| Summerfield, TX |
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Public perception of the GWEN system was extremely negative. Its surmised purposes ranged from communication nodes for government mind control to giving the Soviet Union additional nuclear targets.
Citizen public protest groups stood up in Massachusetts, Oregon, Pennsylvania and California to band together to fight construction of GWEN towers in their areas. The groups believed that the presence of a GWEN node would increase the community's "strategic worth" in the eyes of the Soviet Union. Responding to the protest groups, the Air Force repeatedly downplayed the importance of the towers, stating they were not worth that kind of attention by the Soviet Union.
Alternative theorists posed the idea that GWEN towers were means by which government mind control messages could be sent.[6]
GWEN's construction became a hot political issue when former Defense Secretary James Schlesinger criticized Governor Michael S. Dukakis for opposing the project.
Amid controversy and world geopolitical changes, GWEN's value diminished greatly in the post-Cold War environment, in addition to its existence being rendered moot by the sustained effectiveness of predecessor and follow-on systems (Survivable Low Frequency Communication System and Minimum Essential Emergency Communication Network respectively). As early as 1990, legislative measures were enacted to terminate the program.[7]
In 1994, new construction of GWEN towers were banned after a defense appropriations bill eliminated any funding for the towers for one year.[8]
A few months later, the United States Air Force announced that they would terminate the construction contract to build the remaining 25 towers,[8] except for monies used to dismantle the system.
Since the fiscal year 1998-1999, the GWEN system has been replaced by Milstar SCAMP terminals and GWEN Operations and Maintenance funding has been terminated.
The United States Coast Guard began outfitting a number of GWEN sites to house the National Differential GPS system. Existing equipment fit the needs of the NDGPS.