AN / URC - 117 Ground Wave Emergency Network The Ground Wave Emergency Network ( GWEN ) 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 generated electromagnetic pulse ( HEMP ) to ensure that the United States President or his survivors could issue a launch order to strategic nuclear bombers . Overview . 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 Emergency Action Message s ( EAM ) to United States nuclear forces . EMP can produce a sudden power surge over a widespread area , that could overload unprotected electronic equipment and render it inoperable . In addition , EMP would interfere with radio transmissions that use the ionosphere for propagation . GWEN would use a ground - hugging wave for propagation , being unaffected by the EMP . 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 . History . Analysis showed that low frequency ( 150 - 190 kilohertz ) radio transmissions were largely unaffected by high altitude EMP , and the Air Force Weapons Laboratory ( Kirtland Air Force Base ) tested a small scale ' groundwave ' transmission system in 1978 - 1982 . Based on the groundwave concept ' s promise , USAF Headquarters issued a draft Program Management Directive ( PMD ) for a " Proliferated Groundwave Communications System ( PGCS ) " on 25 August 1981 . The name of this proposed network system was changed from PGCS to Groundwave Emergency Network in February 1982 The Air Force placed a tentative initial operating capability for GWEN by January 1992 . Operations . 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 . Originating stations would send ultra high frequency ( UHF ) signals by broadcast towers for line - of - site receipt at Relay Nodes ( RNs ) . The RNs would retransmit received messages via LF signals for ultimate reception by receive - only ( RO ) terminals at existing military communication buildings . During initial operations , the towers would receive and relay brief test messages every 20 minutes . The system had built - in redundancy , using packet switching techniques for reconstruction of connectivity if system damage occurs . Problems . 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 . Site layout . GWEN transmitter sites . GWEN transmitting antennas consisted of a concrete foundation , above grade , a insulator , a steel tower , and lightning rods , all enclosed by a × , chain link fence topped with barbed wire . The tower itself would be supported by 15 guy wires attached to the ground at six anchor points . 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 improve antenna efficiency . Anchors for the TLEs and guy wires were within the site boundaries . The GWEN transmitter sites include : Relay Node . The overall site area of a relay node was approximately , approximately × 700 feet . Typical site features include a 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 third at the base of the tower . The equipment area and the tower base were surrounded by locked , 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 ) ( below the bottom of the AM broadcast band at 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 ) . Controversies . 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 . 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 . Health effects . Conspiracy theorist s posed the idea that GWEN towers were means by which government mind control messages could be sent . GWEN ' s construction became a hot political issue when former Defense Secretary James Schlesinger criticized Governor Michael S . Dukakis for opposing the project . Termination . 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 . In 1994 , new construction of GWEN towers were banned after a defense appropriations bill eliminated any funding for the towers for one year . A few months later , the United States Air Force announced that they would terminate the construction contract to build the remaining 25 towers , except for monies used to dismantle the system . Since fiscal year 1998 - 1999 , the GWEN system has been replaced by Milstar SCAMP terminals and GWEN Operations and Maintenance funding has been terminated . Disposition . 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