page_title: AN/URC-117 Ground Wave Emergency Network
hierarchical_section_title: AN/URC-117 Ground Wave Emergency Network
caption_attribution_description: English: Diagram of a Ground Wave Emergency Network relay node. GWEN was a survivable command and control communications network operated by the US military between 1982 and 1993 designed to ensure that messages from national command authority, such as nuclear launch orders, would reach US military facilities in the aftermath of a nuclear strike. It consisted of a network of unmanned radio relay "nodes" at 150-200 mile intervals throughout the US which forwarded messages on 150-175 kilohertz in the low frequency (LF) band. Radio transmissions in this band are relatively unaffected by the W:electromagnetic pulse (EMP) created by nuclear weapons that disrupt other electronic devices. The node consists of a UHF receiver and a 2&#160;kilowatt low frequency transmitter driving a 299 ft high, umbrella antenna.
context_page_description: The Ground Wave Emergency Network 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, the GWEN network was intended to survive the effects of an electromagnetic pulse from a high-altitude nuclear explosion and ensure that the United States President or his survivors could issue a launch order to Strategic Air Command bombers by radio.
  AN/URC-117 was the system's Joint Electronics Type Designation System identifier, which signified various radio components installed in different locations. Each GWEN Relay Node site featured a longwave transmitting tower, generally between 290 and 299 feet tall, and emitting an RF output of between 2,000 and 3,000 watts. Of 240 planned GWEN towers, only 58 were built. In 1994, a defense appropriations bill banned the funding of new GWEN tower construction, and a few months later, the GWEN program was cancelled by the US Air Force. The United States Coast Guard later outfitted a number of former GWEN sites to house the National Differential GPS system.
context_section_description: 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, the GWEN network was intended to survive the effects of an electromagnetic pulse from a high-altitude nuclear explosion and ensure that the United States President or his survivors could issue a launch order to Strategic Air Command bombers by radio.
  AN/URC-117 was the system's Joint Electronics Type Designation System identifier, which signified various radio components installed in different locations. Each GWEN Relay Node site featured a longwave transmitting tower, generally between 290 and 299 feet (88 and 91 m) tall, and emitting an RF output of between 2,000 and 3,000 watts. Of 240 planned GWEN towers, only 58 were built. In 1994, a defense appropriations bill banned the funding of new GWEN tower construction, and a few months later, the GWEN program was cancelled by the US Air Force. The United States Coast Guard later outfitted a number of former GWEN sites to house the National Differential GPS system.
caption: Typical GWEN relay node
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