Ground Wave Emergency Network (GWEN)

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Appleton Washington

GWEN transmitting antennas consisted of a concrete foundation, 2 feet (0.61 m) above grade, a 3-foot-tall (0.91 m) insulator, a 290-foot (88 m) steel tower, and 4-foot (1.2 m) lightning rods, all 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 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:
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


Relay node[edit]

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)
Diesel backup 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) at the center of the site

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 third 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) (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).