GWEN Towers

Post date: Dec 13, 2013 4:5:57 PM

Tidbits From:https://en.wikipedia.org/wiki/AN/URC-117_Ground_Wave_Emergency_Network

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 Messages (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.^[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][clarification needed]}

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.^[6]

The GWEN transmitter sites include:

• • A 299-foot (91 m) broadcast antenna tower

  • A large ground plane, designed for ground conductivity conditions at the site

  • An antenna tuning unit enclosure at the base of the tower

  • Two equipment shelters

  • Electronic racks that will accept the DGPS equipment

  • All utilities that are required for operation of the DGPS broadcast site

  • Air conditioning and environmental controls

  • Back-up power generators

  • Above ground fuel storage tanks

  • Security enclosures with intrusion alarms

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^[4] The Air Force placed a tentative initial operating capability for GWEN by January 1992.^[3]

Tidbits From:https://en.wikipedia.org/wiki/AN/URC-117_Ground_Wave_Emergency_Network