Jim Creek Naval Radio Station is a

United States Navy The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage ...

very low frequency Very low frequency or VLF is the ITU designation for radio frequencies (RF) in the range of 3–30 kHz, corresponding to wavelengths from 100 to 10 km, respectively. The band is also known as the myriameter band or myriameter wave a ...

(VLF) radio

transmitter In electronics and telecommunications, a radio transmitter or just transmitter is an electronic device which produces radio waves with an antenna. The transmitter itself generates a radio frequency alternating current, which is applied to the ...

facility at Jim Creek near

Oso, Washington Oso is a census-designated place (CDP) in Snohomish County, Washington, United States. It is located to the west of Darrington, south of the North Fork of the Stillaguamish River and approximately 50 air miles (80 km) from Seattle. The popu ...

. The primary mission of this site is to communicate orders one-way to submarines of the Pacific fleet. Radio waves in the

band can penetrate seawater and be received by submerged submarines which cannot be reached by radio communications at other frequencies. Established in 1953, the transmitter radiates on 24.8 kHz with a power of 1.2 megawatts and a callsign of NLK, and is one of the most powerful radio transmitters in the world. Located near

Arlington, Washington Arlington is a city in northern Snohomish County, Washington, United States, part of the Seattle metropolitan area. The city lies on the Stillaguamish River in the western foothills of the Cascade Range, adjacent to the city of Marysville. It i ...

, in the foothills of the Cascades, north of Seattle, the site has 5,000 largely forested acres.

Antenna

Much of the site is devoted to the enormous overhead wire antenna array that is necessary to efficiently radiate the VLF waves. The antenna, shown above, consists of ten

catenary In physics and geometry, a catenary (, ) is the curve that an idealized hanging chain or cable assumes under its own weight when supported only at its ends in a uniform gravitational field. The catenary curve has a U-like shape, superfici ...

cables, 5,640–8,700 ft (1,719–2,652 m, 1.1–1.6 miles) long, suspended in a zigzag pattern over the valley between Wheeler mountain and Blue mountain on twelve 200 ft. towers on the mountains' crests. Each cable receives energy from a vertical cable attached at the center, which drops down to the valley floor where it is fed by one of two "bus"

transmission line In electrical engineering, a transmission line is a specialized cable or other structure designed to conduct electromagnetic waves in a contained manner. The term applies when the conductors are long enough that the wave nature of the transmi ...

s which extend along the valley from the transmitter building in the center. This type of antenna, called a "valley-span" antenna, functions as a capacitively top-loaded electrically short

monopole antenna A monopole antenna is a class of radio antenna consisting of a straight rod-shaped conductor, often mounted perpendicularly over some type of conductive surface, called a ground plane. The driving signal from the transmitter is applied, o ...

. The vertical cables are the main radiating elements, and the horizontal cables serve to add capacitance to the top of the antenna, to increase the power radiated. The antenna is divided into 2 sections of 5 elements, each fed with its own transmission line. These normally operate together as one antenna, but can operate separately so one section can be shut down for maintenance without interrupting transmission. The floor of the valley under the antenna is covered with an elaborate network of buried cables that serve as the ground system for the transmitter. This station is part of the command system which, in the event of a nuclear war, would transmit launch orders to US ballistic missile submarines in the Pacific fleet. The station was listed as a potential target for a Russian attack by a Russian state media report in early 2019.

Gallery

File:Jim Creek Naval Radio Station - Transmitter building (120815-N-XS652-021).jpg, Transmitter building. From the two bushings on the roof cables supply power to two feed buses which extend both directions along the valley, connected to the overhead antenna wires. File:Jim Creek Naval Radio Station - Antenna feed bus towers (120813-N-XS652-046).jpg, Towers supporting one of two antenna feed bus cables extending from the transmitter building. From each 145 ft. tower a vertical feedline (faintly visible, top of picture) extends up 900 ft. to attach to the midpoint of each horizontal valleyspan cable. File:Jim Creek Naval Radio Station - work on feed bus tower (120815-N-XS652-003).jpg, Contractors working on feed bus tower. The long insulator strings and

corona ring A corona ring, more correctly referred to as an anti-corona ring, is a toroid of conductive material, usually metal, which is attached to a terminal or other irregular hardware piece of high voltage equipment. The purpose of the corona ring is t ...

s are needed to withstand the very high voltage on the antenna File:Contractors work on lowered antenna span as part of the 2012 Antenna Replacement Project at Jim Creek Naval Radio Station near Oso, Wash., Aug. 9, 2012 120809-N-XS652-008.jpg, Contractors repairing one of the mile-long antenna wires that span the valley, which here is lowered to the ground for access.

Recreation area

Jim Creek includes a regional outdoor recreation area for active duty personnel, reservists, retirees, DoD civilians, and sponsored guests. It offers a variety of recreational opportunities, including trout fishing, boating, and wildlife viewing. A group lodge is used for retreats and seminars; camping and picnic sites and other amenities are available. The area also includes hiking/bike riding trails and scenic viewpoints. Programs include environmental education, outdoor recreation, and leadership training. Navy Legacy projects include trail construction and a salmon hatchery built in cooperation with the Stillaguamish Indian Tribe to restock the salmon spawning stream.

Resource management

In 1991, the Navy purchased rights to of

old growth forest An old-growth forestalso termed primary forest, virgin forest, late seral forest, primeval forest, or first-growth forestis a forest that has attained great age without significant disturbance, and thereby exhibits unique ecological feature ...

, associated lakes, creeks, and wetlands, using $3 million of Legacy Resource Management Program to protect the largest remaining old-growth spruce and cedar forest in the Puget Sound trough. Natural mountain lakes provide a habitat for wildlife including

beavers Beavers are large, semiaquatic rodents in the genus ''Castor'' native to the temperate Northern Hemisphere. There are two extant species: the North American beaver (''Castor canadensis'') and the Eurasian beaver (''C. fiber''). Beavers a ...

, river otters,

waterfowl Anseriformes is an order of birds also known as waterfowl that comprises about 180 living species of birds in three families: Anhimidae (three species of screamers), Anseranatidae (the magpie goose), and Anatidae, the largest family, which i ...

, and bald eagles. Many trees in the are estimated to be up to 1,500–1,700 years old, with some over tall and in diameter. Jim Creek provides habitat for the marbled murrelet and other threatened species.

References

External links