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 their 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 Nationwide Differential GPS system.