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Naval Radio Transmitter Facility Grindavik
Naval Radio Transmitter Facility Grindavik (NRTF Grindavik) is a transmission facility of the US Navy at Grindavík, Iceland, maintained by the N62 Division. It is active on shortwave and longwave under the callsign TFK on 37.5 kHz. NRTF Grindavik originally had two towers for its longwave service – the west tower with a height of and the east tower with a height of – which were, when built, the tallest man-made objects in Iceland. In 1983, the east tower was replaced by a new tower of the same height. The west tower was replaced by a new guyed mast and helix house, now the second tallest structure in Iceland. Before all these improvements were made, in about 1976, the station was tasked to operate its tower on a very low frequency, much lower than any frequency on which it had ever before been operated. There was some concern about running the shorter tower on such a low frequency, but the tower was already tasked with a higher priority mission. Wh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Naval Radio Transmitter Facility Grindavík
A navy, naval force, or maritime force is the branch of a nation's armed forces principally designated for naval and amphibious warfare; namely, lake-borne, riverine, littoral, or ocean-borne combat operations and related functions. It includes anything conducted by surface ships, amphibious ships, submarines, and seaborne aviation, as well as ancillary support, communications, training, and other fields. The strategic offensive role of a navy is projection of force into areas beyond a country's shores (for example, to protect sea-lanes, deter or confront piracy, ferry troops, or attack other navies, ports, or shore installations). The strategic defensive purpose of a navy is to frustrate seaborne projection-of-force by enemies. The strategic task of the navy also may incorporate nuclear deterrence by use of submarine-launched ballistic missiles. Naval operations can be broadly divided between riverine and littoral applications (brown-water navy), open-ocean applicati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
US 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 of its active battle fleet alone exceeding the next 13 navies combined, including 11 allies or partner nations of the United States as of 2015. It has the highest combined battle fleet tonnage (4,635,628 tonnes as of 2019) and the world's largest aircraft carrier fleet, with eleven in service, two new carriers under construction, and five other carriers planned. With 336,978 personnel on active duty and 101,583 in the Ready Reserve, the United States Navy is the third largest of the United States military service branches in terms of personnel. It has 290 deployable combat vessels and more than 2,623 operational aircraft . The United States Navy traces its origins to the Continental Navy, which was established during the American Revolut ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Grindavík
Grindavík () is a fishing town on the Southern Peninsula (Iceland), Southern Peninsula of Iceland not far from the tuya Þorbjörn (mountain), Þorbjörn. It is one of the few cities with a harbour on this coast. Most of the inhabitants work in the fishing industry. The Blue Lagoon (geothermal spa), Blue Lagoon, Grindavík's premiere attraction, is located from the town centre. History Landnáma or ''The Book of Settlements'' mentions that around 934, two Viking settlers, Molda-Gnúpur Hrólfsson and Þórir Haustmyrkur Vígbjóðsson , arrived in the Reykjanes area. Þórir settled in Selvogur and Krísuvík and Molda-Gnúpur in Grindaví The sons of Moldar-Gnúpur established three settlements; Þórkötlustaðahverfi , Járngerðarstaðarhverfi and Staðarhverfi . The modern version of Grindavik is situated mainly in what was Járngerðarstaðarhverfi. In June 1627 Grindavik was raided by Barbary Pirates in an event known as the Turkish Abductions. Twelve Icelanders and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shortwave
Shortwave radio is radio transmission using shortwave (SW) radio frequencies. There is no official definition of the band, but the range always includes all of the high frequency band (HF), which extends from 3 to 30 MHz (100 to 10 metres); above the medium frequency band (MF), to the bottom of the VHF band. Radio waves in the shortwave band can be reflected or refracted from a layer of electrically charged atoms in the atmosphere called the ionosphere. Therefore, short waves directed at an angle into the sky can be reflected back to Earth at great distances, beyond the horizon. This is called skywave or "skip" propagation. Thus shortwave radio can be used for communication over very long distances, in contrast to radio waves of higher frequency, which travel in straight lines (line-of-sight propagation) and are limited by the visual horizon, about 64 km (40 miles). Shortwave broadcasts of radio programs played an important role in the early days of radio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Longwave
In radio, longwave, long wave or long-wave, and commonly abbreviated LW, refers to parts of the radio spectrum with wavelengths longer than what was originally called the medium-wave broadcasting band. The term is historic, dating from the early 20th century, when the radio spectrum was considered to consist of longwave (LW), medium-wave (MW), and short-wave (SW) radio bands. Most modern radio systems and devices use wavelengths which would then have been considered 'ultra-short'. In contemporary usage, the term ''longwave'' is not defined precisely, and its intended meaning varies. It may be used for radio wavelengths longer than 1,000 m i.e. frequencies up to 300 kilohertz (kHz), including the International Telecommunication Union's (ITU's) low frequency (LF, 30–300 kHz) and very low frequency (VLF, 3–30 kHz) bands. Sometimes the upper limit is taken to be higher than 300 kHz, but not above the start of the medium wave broadcast band at 520&nb ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Callsign
In broadcasting and radio communications, a call sign (also known as a call name or call letters—and historically as a call signal—or abbreviated as a call) is a unique identifier for a transmitter station. A call sign can be formally assigned by a government agency, informally adopted by individuals or organizations, or even cryptographically encoded to disguise a station's identity. The use of call signs as unique identifiers dates to the landline railroad telegraph system. Because there was only one telegraph line linking all railroad stations, there needed to be a way to address each one when sending a telegram. In order to save time, two-letter identifiers were adopted for this purpose. This pattern continued in radiotelegraph operation; radio companies initially assigned two-letter identifiers to coastal stations and stations onboard ships at sea. These were not globally unique, so a one-letter company identifier (for instance, 'M' and two letters as a Marconi station ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
WGS84
The World Geodetic System (WGS) is a standard used in cartography, geodesy, and satellite navigation including GPS. The current version, WGS 84, defines an Earth-centered, Earth-fixed coordinate system and a geodetic datum, and also describes the associated Earth Gravitational Model (EGM) and World Magnetic Model (WMM). The standard is published and maintained by the United States National Geospatial-Intelligence Agency. Definition The coordinate origin of WGS 84 is meant to be located at the Earth's center of mass; the uncertainty is believed to be less than . The WGS 84 meridian of zero longitude is the IERS Reference Meridian,European Organisation for the Safety of Air Navigation and IfEN: WGS 84 Implementation Manual, p. 13. 1998 5.3 arc seconds or east of the Greenwich meridian at the latitude of the Royal Observatory. (This is related to the fact that the local gravity field at Greenwich doesn't point exactly through the Earth's center of mass, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radio Tower
Radio masts and towers are typically tall structures designed to support antennas for telecommunications and broadcasting, including television. There are two main types: guyed and self-supporting structures. They are among the tallest human-made structures. Masts are often named after the broadcasting organizations that originally built them or currently use them. In the case of a mast radiator or radiating tower, the whole mast or tower is itself the transmitting antenna. Terminology The terms "mast" and "tower" are often used interchangeably. However, in structural engineering terms, a tower is a self-supporting or cantilevered structure, while a mast is held up by stays or guys. Broadcast engineers in the UK use the same terminology. A mast is a ground-based or rooftop structure that supports antennas at a height where they can satisfactorily send or receive radio waves. Typical masts are of steel lattice or tubular steel construction. Masts themselves play no part in t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Guyed Mast
A guyed mast or guyed tower is a tall thin vertical structure that depends on guy lines (diagonal tensioned cables attached to the ground) for stability. The mast itself has the compressive strength to support its own weight, but does not have the shear strength to stand unsupported. It requires guy lines to stay upright and to resist lateral forces such as wind loads. Guy lines are usually spaced at equal angles about the structure's base. Guyed masts are used for telecommunications, sailing, and meteorology. The tallest guyed mast in the world is currently the KVLY-TV mast near Blanchard, North Dakota, USA. Two subtypes exist. A ''partially guyed tower'' is a structure consisting of a guyed mast on top of a freestanding tower. The guys may be anchored to the top of the freestanding structure, or to the ground. A famous tower of this type is the Gerbrandy Tower. An ''additionally guyed tower'' is a freestanding tower which either has guys attached temporarily to add stab ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Helix Building
An antenna tuning hut or helix house is a small shed at the base of a longwave or mediumwave radio transmitting antenna. It contains antenna tuner – radio equipment for coupling the power from the feedline to the antenna. Alternative names include ''antenna tuning house'', ''coupling hut'', and ''dog house''. Equipment The radio frequency current from the transmitter is supplied to the antenna through a cable called the feedline. The antenna tuning hut contains a matching network made of high wattage capacitors and inductors (coils) that in combination match the antenna's impedance to the feedline, to efficiently transfer power into the antenna. The inductors, made of large helixes of wire, give the name ''helix house''. The powerful radio waves near the antenna can be a hazard for workers, so the interior of the antenna tuning hut is typically shielded with copper or aluminum sheeting or wire mesh, in order to reduce radiation from the tower. In operation the components c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Iceland
Iceland ( is, Ísland; ) is a Nordic island country in the North Atlantic Ocean and in the Arctic Ocean. Iceland is the most sparsely populated country in Europe. Iceland's capital and largest city is Reykjavík, which (along with its surrounding areas) is home to over 65% of the population. Iceland is the biggest part of the Mid-Atlantic Ridge that rises above sea level, and its central volcanic plateau is erupting almost constantly. The interior consists of a plateau characterised by sand and lava fields, mountains, and glaciers, and many glacial rivers flow to the sea through the lowlands. Iceland is warmed by the Gulf Stream and has a temperate climate, despite a high latitude just outside the Arctic Circle. Its high latitude and marine influence keep summers chilly, and most of its islands have a polar climate. According to the ancient manuscript , the settlement of Iceland began in 874 AD when the Norwegian chieftain Ingólfr Arnarson became the first p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Defense Information Systems Agency
The Defense Information Systems Agency (DISA), known as the Defense Communications Agency (DCA) until 1991, is a United States Department of Defense (DoD) combat support agency composed of military, federal civilians, and contractors. DISA provides information technology (IT) and communications support to the President, Vice President, Secretary of Defense, the military services, the combatant commands, and any individual or system contributing to the defense of the United States. Headquarters From January to July 2011, DISA relocated more than 4,500 military and civilian employees and supporting onsite contractors, 700 workstation suites with 11,000 pieces of IT equipment, and 58,000 square feet of lab equipment in accordance with the Base Realignment and Closure legislation of 2005. The relocation to Fort George G. Meade, Md., consolidated DISA headquarters elements that were housed in multiple locations in Arlington and Falls Church, Va. In April 2011, DISA held a ribbo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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