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LORAN-C
Loran-C is a hyperbolic radio navigation system that allows a receiver to determine its position by listening to low frequency radio signals that are transmitted by fixed land-based radio beacons. Loran-C combined two different techniques to provide a signal that was both long-range and highly accurate, features that had been incompatible. Its disadvantage was the expense of the equipment needed to interpret the signals, which meant that Loran-C was used primarily by militaries after it was introduced in 1957. By the 1970s, the cost, weight and size of electronics needed to implement Loran-C had been dramatically reduced because of the introduction of solid-state electronics and, from the mid-1970s, early microcontrollers to process the signal. Low-cost and easy-to-use Loran-C units became common from the late 1970s, especially in the early 1980s, and the earlier LORAN system was discontinued in favor of installing more Loran-C stations around the world. Loran-C became one ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hyperbolic Navigation
Hyperbolic navigation is a class of radio navigation systems in which a navigation receiver instrument is used to determine location based on the difference in timing ( phase) of radio waves received from radio navigation beacon transmitters. Such systems rely on the ability of two widely separated stations to broadcast a signal that is highly correlated in time. Typical systems either broadcast short pulses at the same time, or continual signals that are identical in phase. A receiver located at the midpoint between the two stations will receive the signals at the same time or have identical phase, but at any other location the signal from the closer station will be received first or have a different phase. Determining the location of a receiver requires that the two synchronized stations be tuned in at the same time so the signals can be compared. This reveals a ''difference'' in time, corresponding to a relative distance closer to one station or the other. Plotting all the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radio Navigation
Radio navigation or radionavigation is the application of radio frequencies to determine a position of an object on the Earth, either the vessel or an obstruction. Like radiolocation, it is a type of radiodetermination. The basic principles are measurements from/to electric beacons, especially * Angular directions, e.g. by bearing, radio phases or interferometry, * Distances, e.g. ranging by measurement of time of flight between one transmitter and multiple receivers or vice versa, * Distance ''differences'' by measurement of times of arrival of signals from one transmitter to multiple receivers or vice versa * Partly also velocity, e.g. by means of radio Doppler shift. Combinations of these measurement principles also are important—e.g., many radars measure range and azimuth of a target. Bearing-measurement systems These systems used some form of directional radio antenna to determine the location of a broadcast station on the ground. Conventional navigation techni ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CHAYKA
Chayka (russian: Чайка, lit. "seagull") also known as Radioteknicheskaya Systema Dalyoloiy Navigatsii abbreviated as RSDN (lit. Russian Hyperbolic Radio Navigation System) is a Russian terrestrial radio navigation system, similar to Loran-C. It operates on similar frequencies around 100 kHz, and uses the same techniques of comparing both the envelope and the signal phase to accurately determine location. The systems differ primarily in details. Chayka-Chains Chayka, like LORAN-C, uses different pulse repetition frequencies (Group Repetition Intervals, or GRIs) to allow the identification of different stations operating on the same frequencies. There are 5 Chayka chains in use: *GRI 8000 — Western (European) Russia Chayka Chain (1969, RSDN-3/10) *GRI 7950 — Eastern Russia Chayka Chain (1986, RSDN-4) *GRI 5980 — Russian-American Chayka Chain (1995) *GRI 5960 — Northern Chayka Chain (1996, RSDN-5) *GRI 4970 — North-Western Chayka Ch ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Loran C Navigator
LORAN, short for long range navigation, was a hyperbolic radio navigation system developed in the United States during World War II. It was similar to the UK's Gee system but operated at lower frequencies in order to provide an improved range up to with an accuracy of tens of miles. It was first used for ship convoys crossing the Atlantic Ocean, and then by long-range patrol aircraft, but found its main use on the ships and aircraft operating in the Pacific theater during World War II. LORAN, in its original form, was an expensive system to implement, requiring a cathode ray tube (CRT) display. This limited use to the military and large commercial users. Automated receivers became available in the 1950s, but the same improved electronics also opened the possibility of new systems with higher accuracy. The U.S. Navy began development of Loran-B, which offered accuracy on the order of a few tens of feet, but ran into significant technical problems. The U.S. Air Force worked on a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Low Frequency
Low frequency (LF) is the ITU designation for radio frequencies (RF) in the range of 30–300 kHz. Since its wavelengths range from 10–1 km, respectively, it is also known as the kilometre band or kilometre wave. LF radio waves exhibit low signal attenuation, making them suitable for long-distance communications. In Europe and areas of Northern Africa and Asia, part of the LF spectrum is used for AM broadcasting as the "longwave" band. In the western hemisphere, its main use is for aircraft beacon, navigation (LORAN), information, and weather systems. A number of time signal broadcasts also use this band. Propagation Because of their long wavelength, low frequency radio waves can diffract over obstacles like mountain ranges and travel beyond the horizon, following the contour of the Earth. This mode of propagation, called ''ground wave'', is the main mode in the LF band. Ground waves must be vertically polarized (the electric field is vertical while the mag ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
LORAN
LORAN, short for long range navigation, was a hyperbolic radio navigation system developed in the United States during World War II. It was similar to the UK's Gee system but operated at lower frequencies in order to provide an improved range up to with an accuracy of tens of miles. It was first used for ship convoys crossing the Atlantic Ocean, and then by long-range patrol aircraft, but found its main use on the ships and aircraft operating in the Pacific theater during World War II. LORAN, in its original form, was an expensive system to implement, requiring a cathode ray tube (CRT) display. This limited use to the military and large commercial users. Automated receivers became available in the 1950s, but the same improved electronics also opened the possibility of new systems with higher accuracy. The U.S. Navy began development of Loran-B, which offered accuracy on the order of a few tens of feet, but ran into significant technical problems. The U.S. Air Force worked o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alfred Lee Loomis
Alfred Lee Loomis (November 4, 1887 – August 11, 1975) was an American attorney, investment banker, philanthropist, scientist, physicist, inventor of the LORAN Long Range Navigation System and a lifelong patron of scientific research. He established the Loomis Laboratory in Tuxedo Park, New York, and his role in the development of radar and the atomic bomb contributed to the Allied victory in World War II. He invented the Aberdeen Chronograph for measuring muzzle velocities, contributed significantly (perhaps critically, according to Luis Alvarez) to the development of a ground-controlled approach technology for aircraft, and participated in preliminary meetings of the Manhattan Project. Loomis also made contributions to biological instrumentation. Working with Edmund Newton Harvey he co-invented the microscope centrifuge, and pioneered techniques for electroencephalography. In 1937, he discovered the sleep K-complex brainwave. During the Great Depression, Loomis anonymous ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Center Frequency
In electrical engineering and telecommunications, the center frequency of a filter or channel is a measure of a central frequency between the upper and lower cutoff frequencies. It is usually defined as either the arithmetic mean or the geometric mean of the lower cutoff frequency and the upper cutoff frequency of a band-pass system or a band-stop system. Typically, the geometric mean is used in systems based on certain transformations of lowpass filter designs, where the frequency response is constructed to be symmetric on a logarithmic frequency scale. The geometric center frequency corresponds to a mapping of the DC response of the prototype lowpass filter, which is a resonant frequency sometimes equal to the peak frequency of such systems, for example as in a Butterworth filter. The arithmetic definition is used in more general situations, such as in describing passband telecommunication systems, where filters are not necessarily symmetric but are treated on a linear fre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ionosphere
The ionosphere () is the ionized part of the upper atmosphere of Earth, from about to above sea level, a region that includes the thermosphere and parts of the mesosphere and exosphere. The ionosphere is ionized by solar radiation. It plays an important role in atmospheric electricity and forms the inner edge of the magnetosphere. It has practical importance because, among other functions, it influences radio propagation to distant places on Earth. History of discovery As early as 1839, the German mathematician and physicist Carl Friedrich Gauss postulated that an electrically conducting region of the atmosphere could account for observed variations of Earth's magnetic field. Sixty years later, Guglielmo Marconi received the first trans-Atlantic radio signal on December 12, 1901, in St. John's, Newfoundland (now in Canada) using a kite-supported antenna for reception. The transmitting station in Poldhu, Cornwall, used a spark-gap transmitter to produce a signal with a f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
United States Coast Guard
The United States Coast Guard (USCG) is the maritime security, search and rescue, and law enforcement service branch of the United States Armed Forces and one of the country's eight uniformed services. The service is a maritime, military, multi-mission service unique among the United States military branches for having a maritime law enforcement mission with jurisdiction in both domestic and international waters and a federal regulatory agency mission as part of its duties. It is the largest and most powerful coast guard in the world, rivaling the capabilities and size of most navies. The U.S. Coast Guard is a humanitarian and security service. It protects the United States' borders and economic and security interests abroad; and defends its sovereignty by safeguarding sea lines of communication and commerce across vast territorial waters spanning 95,000 miles of coastline and its Exclusive Economic Zone. With national and economic security depending upon open global t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Decca Navigator System
The Decca Navigator System was a hyperbolic radio navigation system which allowed ships and aircraft to determine their position by using radio signals from a dedicated system of static radio transmitters. The system used phase comparison of two low frequency signals between 70 and 129 kHz, as opposed to pulse timing systems like Gee and LORAN. This made it much easier to design receivers using 1940s electronics, and operation was simplified by giving a direct readout of Decca coordinates without the complexity of a cathode ray tube and highly skilled operator. The system was invented in the U.S., but development was carried out by Decca in the UK. It was first deployed by the Royal Navy during World War II for the vital task of clearing the minefields to enable the D-Day landings. The Allied forces needed an accurate system not known to the Germans and thus free of jamming. After the war, it came off the secret list and was commercially developed by the Decca Company and deplo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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