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Super Low Frequency
Super low frequency (SLF) is the ITU designation for electromagnetic waves (radio waves) in the frequency range between 30 hertz and 300 hertz. They have corresponding wavelengths of 10,000 to 1,000 kilometers. This frequency range includes the frequencies of AC power grids (50 hertz and 60 hertz). Another conflicting designation which includes this frequency range is Extremely Low Frequency (ELF), which in some contexts refers to all frequencies up to 300 hertz. Because of the extreme difficulty of building transmitters that can generate such long waves, frequencies in this range have been used in very few artificial communication systems. However, SLF waves can penetrate seawater to a depth of hundreds of meters. Therefore, in recent decades the U.S., Russian and Indian militaries have built huge radio transmitters using SLF frequencies to communicate with their submarines. The U.S. naval service is called Seafarer and operates at 76 hertz. It became operational in 1989 b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hertz
The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that one hertz is the reciprocal of one second. It is named after Heinrich Rudolf Hertz (1857–1894), the first person to provide conclusive proof of the existence of electromagnetic waves. Hertz are commonly expressed in multiples: kilohertz (kHz), megahertz (MHz), gigahertz (GHz), terahertz (THz). Some of the unit's most common uses are in the description of periodic waveforms and musical tones, particularly those used in radio- and audio-related applications. It is also used to describe the clock speeds at which computers and other electronics are driven. The units are sometimes also used as a representation of the energy of a photon, via the Planck relation ''E'' = ''hν'', where ''E'' is the photon's energy, ''ν'' is its freq ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ZEVS (transmitter)
ZEVS is a facility of the Russian Navy to transmit messages to submerged submarines in deep water using ELF waves. It is located near Murmansk on the Kola Peninsula. As ZEVS works on 82 hertz, it can be only used for very rudimentary transmissions. Due to its extreme low frequency the techniques used by ZEVS are quite different from those of standard transmitters. The antenna used by ZEVS is a ground dipole. This is simply an arrangement of two widely separated electrodes, through which the transmission current is fed into the ground. As ZEVS is a location of high strategic importance, nearly no official information of the facility is available. Nearly all of the following information was obtained from satellite imagery, which can be seen on Wikimapia. ZEVS consists of 2 units, situated at and at . They are supplied by Kolenergo with electricity and have there the designation PS-373 (Cyrillic: ПС-373) and PS-393 (Cyrillic: ПС-393). These Kolenergo substations are designed ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fast Fourier Transform
A fast Fourier transform (FFT) is an algorithm that computes the discrete Fourier transform (DFT) of a sequence, or its inverse (IDFT). Fourier analysis converts a signal from its original domain (often time or space) to a representation in the frequency domain and vice versa. The DFT is obtained by decomposing a sequence of values into components of different frequencies. This operation is useful in many fields, but computing it directly from the definition is often too slow to be practical. An FFT rapidly computes such transformations by factorizing the DFT matrix into a product of sparse (mostly zero) factors. As a result, it manages to reduce the complexity of computing the DFT from O\left(N^2\right), which arises if one simply applies the definition of DFT, to O(N \log N), where N is the data size. The difference in speed can be enormous, especially for long data sets where ''N'' may be in the thousands or millions. In the presence of round-off error, many FFT algorithm ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sound Card
A sound card (also known as an audio card) is an internal expansion card that provides input and output of audio signals to and from a computer under the control of computer programs. The term ''sound card'' is also applied to external audio interfaces used for professional audio applications. Sound functionality can also be integrated onto the motherboard, using components similar to those found on plug-in cards. The integrated sound system is often still referred to as a ''sound card''. Sound processing hardware is also present on modern video cards with HDMI to output sound along with the video using that connector; previously they used a S/PDIF connection to the motherboard or sound card. Typical uses of sound cards or sound card functionality include providing the audio component for multimedia applications such as music composition, editing video or audio, presentation, education and entertainment (games) and video projection. Sound cards are also used for computer-base ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Personal Computer
A personal computer (PC) is a multi-purpose microcomputer whose size, capabilities, and price make it feasible for individual use. Personal computers are intended to be operated directly by an end user, rather than by a computer expert or technician. Unlike large, costly minicomputers and mainframes, time-sharing by many people at the same time is not used with personal computers. Primarily in the late 1970s and 1980s, the term home computer was also used. Institutional or corporate computer owners in the 1960s had to write their own programs to do any useful work with the machines. While personal computer users may develop their own applications, usually these systems run commercial software, free-of-charge software ("freeware"), which is most often proprietary, or free and open-source software, which is provided in "ready-to-run", or binary, form. Software for personal computers is typically developed and distributed independently from the hardware or operating system ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radio Amateur
An amateur radio operator is someone who uses equipment at an amateur radio station to engage in two-way personal communications with other amateur operators on radio frequencies assigned to the amateur radio service. Amateur radio operators have been granted an amateur radio license by a governmental regulatory authority after passing an examination on applicable regulations, electronics, radio theory, and radio operation. As a component of their license, amateur radio operators are assigned a call sign that they use to identify themselves during communication. About three million amateur radio operators are currently active worldwide. Amateur radio operators are also known as radio amateurs or hams. The term "ham" as a nickname for amateur radio operators originated in a pejorative usage (like "ham actor") by operators in commercial and professional radio communities, and dates to wired telegraphy. The word was subsequently adopted by amateur radio operators. Demographics { ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antenna (radio)
In radio engineering, an antenna or aerial is the interface between radio waves propagating through space and electric currents moving in metal conductors, used with a transmitter or receiver. In transmission, a radio transmitter supplies an electric current to the antenna's terminals, and the antenna radiates the energy from the current as electromagnetic wave In physics, electromagnetic radiation (EMR) consists of waves of the electromagnetic (EM) field, which propagate through space and carry momentum and electromagnetic radiant energy. It includes radio waves, microwaves, infrared, (visib ...s (radio waves). In Receiver (radio), reception, an antenna intercepts some of the power of a radio wave in order to produce an electric current at its terminals, that is applied to a receiver to be Amplifier, amplified. Antennas are essential components of all radio equipment. An antenna is an array of conductor (material), conductors (Driven element, elements), elect ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
The Times Of India
''The Times of India'', also known by its abbreviation ''TOI'', is an Indian English-language daily newspaper and digital news media owned and managed by The Times Group. It is the third-largest newspaper in India by circulation and largest selling English-language daily in the world. It is the oldest English-language newspaper in India, and the second-oldest Indian newspaper still in circulation, with its first edition published in 1838. It is nicknamed as "The Old Lady of Bori Bunder", and is an Indian " newspaper of record". Near the beginning of the 20th century, Lord Curzon, the Viceroy of India, called ''TOI'' "the leading paper in Asia". In 1991, the BBC ranked ''TOI'' among the world's six best newspapers. It is owned and published by Bennett, Coleman & Co. Ltd. (B.C.C.L.), which is owned by the Sahu Jain family. In the Brand Trust Report India study 2019, ''TOI'' was rated as the most trusted English newspaper in India. Reuters rated ''TOI'' as India's most trus ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Akula-class Submarine
The ''Akula'' class, Soviet designation Project 971 ''Shchuka-B'' (russian: Щука-Б, , Pike-B, NATO reporting name ''Akula'') are a series of fourth generation nuclear-powered attack submarines (SSNs) first deployed by the Soviet Navy in 1986. There are four sub-classes or flights of Shchuka-B, consisting of the original seven Project 971 boats (codenamed ''Akula I''), commissioned between 1984 and 1990; six Project 971Is (Improved ''Akula''s), commissioned between 1991 and 2009; one Project 971U (''Akula II''), commissioned in 1995; and one Project 971M (''Akula III''), commissioned in 2001. The Russians call all of the submarines ''Shchuka-B'', regardless of modifications. Some confusion may exist as the name ''Akula'' (russian: Акула, meaning "shark" in Russian) was used by the Soviets for a different class of submarines, the Project 941, which is known in the West as the . The Project 971 was named ''Shchuka-B'' by the Soviets but given the designation ''Akula'' b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arihant-class Submarine
The ''Arihant''-class ( in Sanskrit) is a class of Indian nuclear-powered ballistic missile submarines being built for the Indian Navy. They were developed under the ''Advanced Technology Vessel'' (ATV) project to design and build nuclear-powered submarines. These vessels are classified as 'strategic strike nuclear submarines' by India. The lead vessel of the class, was launched in 2009, and after extensive sea trials, was confirmed to be commissioned in August 2016. ''Arihant'' holds the distinction of being the first ballistic missile submarine to have been built by a country other than one of the five permanent members of the United Nations Security Council. History In December 1971, during the Indo-Pakistani War of 1971, US President Richard Nixon sent a carrier battle group named Task Force 74, led by the nuclear-powered into the international waters of the Bay of Bengal in a show of force. Task Force 74 remained in international waters, where it was legally entitled t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
INS Kattabomman
INS Kattabomman is the designation of the VLF-transmission facility of the Indian Navy situated at Vijayanarayanam near Tirunelveli in Tamil Nadu. The facility spread over 3,000 acres has 13 masts, which are arranged in two rings around the central mast. The centre mast has a height of 301 metres, the masts on the inner ring measure 276.4 metres, that on the outer ring measure 227.4 metres. Two further masts of the station carrying an umbrella antenna, the INS Kattabomman is 471 metres tall and the tallest structure in India. They are also the tallest military structure in the world. The facility opened an ELF transmission facility in 2014. History Development and construction of INS Kattabomman started in 1984 as Project Skylark and costed . It was commissioned into service by Indian President Ramaswamy Venkataraman on 20 October 1990. It is named after king Veera Pandya Kattabomman, who died during the Indian independence movement. After operationalising the base, India ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Indian Navy
The Indian Navy is the maritime branch of the Indian Armed Forces. The President of India is the Supreme Commander of the Indian Navy. The Chief of Naval Staff, a four-star admiral, commands the navy. As a blue-water navy, it operates significantly in the Persian Gulf Region, the Horn of Africa, the Strait of Malacca, and routinely conducts anti-piracy operations and partners with other navies in the region. It also conducts routine two to three month-long deployments in the South and East China seas as well as the western Mediterranean sea simultaneously. The primary objective of the navy is to safeguard the nation's maritime borders, and in conjunction with other Armed Forces of the union, act to deter or defeat any threats or aggression against the territory, people or maritime interests of India, both in war and peace. Through joint exercises, goodwill visits and humanitarian missions, including disaster relief, the Indian Navy promotes bilateral relations between n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
