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Long Delayed Echo
Long delayed echoes (LDEs) are radio echoes which return to the sender several seconds after a radio transmission has occurred. Delays of longer than 2.7 seconds are considered LDEs. ARRL: Stan Horzepa, ''Radio Ghosts'' (dead link. use https://web.archive.org/web/20031105155129/http://www.arrl.org/news/features/2003/10/31/1/) LDEs have a number of proposed scientific origins. History These echoes were first observed in 1927 by civil engineer and operator Jørgen Hals from his home near , |
Radio
Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmitter connected to an antenna which radiates the waves, and received by another antenna connected to a radio receiver. Radio is very widely used in modern technology, in radio communication, radar, radio navigation, remote control, remote sensing, and other applications. In radio communication, used in radio and television broadcasting, cell phones, two-way radios, wireless networking, and satellite communication, among numerous other uses, radio waves are used to carry information across space from a transmitter to a receiver, by modulating the radio signal (impressing an information signal on the radio wave by varying some aspect of the wave) in the transmitter. In radar, used to locate and track objects like aircraft, ships, spacecraf ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radio Propagation
Radio propagation is the behavior of radio waves as they travel, or are propagated, from one point to another in vacuum, or into various parts of the atmosphere. As a form of electromagnetic radiation, like light waves, radio waves are affected by the phenomena of reflection, refraction, diffraction, absorption, polarization, and scattering. Understanding the effects of varying conditions on radio propagation has many practical applications, from choosing frequencies for amateur radio communications, international shortwave broadcasters, to designing reliable mobile telephone systems, to radio navigation, to operation of radar systems. Several different types of propagation are used in practical radio transmission systems. ''Line-of-sight propagation'' means radio waves which travel in a straight line from the transmitting antenna to the receiving antenna. Line of sight transmission is used for medium-distance radio transmission, such as cell phones, cordless phones, walkie- ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radio Frequency Propagation
Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmitter connected to an antenna which radiates the waves, and received by another antenna connected to a radio receiver. Radio is very widely used in modern technology, in radio communication, radar, radio navigation, remote control, remote sensing, and other applications. In radio communication, used in radio and television broadcasting, cell phones, two-way radios, wireless networking, and satellite communication, among numerous other uses, radio waves are used to carry information across space from a transmitter to a receiver, by modulating the radio signal (impressing an information signal on the radio wave by varying some aspect of the wave) in the transmitter. In radar, used to locate and track objects like aircraft, ships, spacecraft ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Propagation Mode
Radio propagation is the behavior of radio waves as they travel, or are propagated, from one point to another in vacuum, or into various parts of the atmosphere. As a form of electromagnetic radiation, like light waves, radio waves are affected by the phenomena of reflection, refraction, diffraction, absorption, polarization, and scattering. Understanding the effects of varying conditions on radio propagation has many practical applications, from choosing frequencies for amateur radio communications, international shortwave broadcasters, to designing reliable mobile telephone systems, to radio navigation, to operation of radar systems. Several different types of propagation are used in practical radio transmission systems. ''Line-of-sight propagation'' means radio waves which travel in a straight line from the transmitting antenna to the receiving antenna. Line of sight transmission is used for medium-distance radio transmission, such as cell phones, cordless phones, walkie-tal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Duncan Lunan
Duncan Alasdair Lunan, born October 1945, is a Scottish people, Scottish author with emphasis on astronomy, spaceflight and science fiction, undertaking a wide range of writing and speaking on those and other topics as a researcher, tutor, critic, editor, lecturer and broadcaster. He is known for his Science journalist, science writingshttp://www.jeffhawkeclub.com/cv_pubwork.pdf as well as for his work on the Sighthill, Glasgow, Sighthill stone circle. His 1970s report of a possible space probe orbiting around the Moon sent by the inhabitants of a planet orbiting Epsilon Boötis"Spaceprobe from Epsilon Bootes" by Duncan Lunan, in "Spaceflight" (British Interplanetary Society), 1973 brought him to international notice. Background Lunan, who grew up in Troon, claims descent from an Legitimacy (family law), illegitimate son of King Robert II of Scotland, Alexander Stuart, who owned the "Lands of Lunaine" near Aberdeen, and, more distantly, from the astronomers of ancient Chaldea "wh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nature (journal)
''Nature'' is a British weekly scientific journal founded and based in London, England. As a multidisciplinary publication, ''Nature'' features peer-reviewed research from a variety of academic disciplines, mainly in science and technology. It has core editorial offices across the United States, continental Europe, and Asia under the international scientific publishing company Springer Nature. ''Nature'' was one of the world's most cited scientific journals by the Science Edition of the 2019 ''Journal Citation Reports'' (with an ascribed impact factor of 42.778), making it one of the world's most-read and most prestigious academic journals. , it claimed an online readership of about three million unique readers per month. Founded in autumn 1869, ''Nature'' was first circulated by Norman Lockyer and Alexander Macmillan as a public forum for scientific innovations. The mid-20th century facilitated an editorial expansion for the journal; ''Nature'' redoubled its efforts in exp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ronald Bracewell
Ronald Newbold Bracewell AO (22 July 1921 – 12 August 2007) was the Lewis M. Terman Professor of Electrical Engineering of the Space, Telecommunications, and Radioscience Laboratory at Stanford University. Education Bracewell was born in Sydney, in 1921, and educated at Sydney Boys High School. He graduated from the University of Sydney in 1941 with the BSc degree in mathematics and physics, later receiving the degrees of B.E. (1943), and M.E. (1948) with first class honours, and while working in the Engineering Department became the President of the Oxometrical society. During World War II he designed and developed microwave radar equipment in the Radiophysics Laboratory of the Commonwealth Scientific and Industrial Research Organisation, Sydney under the direction of Joseph L. Pawsey and Edward G. Bowen and from 1946 to 1949 was a research student at Sidney Sussex College, Cambridge, engaged in ionospheric research in the Cavendish Laboratory, where in 1949 he r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Extraterrestrial Life
Extraterrestrial life, colloquially referred to as alien life, is life that may occur outside Earth and which did not originate on Earth. No extraterrestrial life has yet been conclusively detected, although efforts are underway. Such life might range from simple forms like prokaryotes to intelligent beings, possibly bringing forth civilizations that might be far more advanced than humankind. The Drake equation speculates about the existence of sapient life elsewhere in the universe. The science of extraterrestrial life is known as astrobiology. Speculation about the possibility of inhabited "worlds" outside the planet Earth dates back to antiquity. Multiple early Christian writers discussed the idea of a "plurality of worlds" as proposed by earlier thinkers such as Democritus; Augustine references Epicurus's idea of innumerable worlds "throughout the boundless immensity of space" (originally expressed in his Letter to Herodotus) in ''The City of God''. In his first century p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bracewell Probe
A Bracewell probe is a hypothetical concept for an autonomous interstellar space probe dispatched for the express purpose of communication with one or more alien civilizations. It was proposed by Ronald N. Bracewell in a 1960 paper, as an alternative to interstellar radio communication between widely separated civilizations. Description A Bracewell probe would be constructed as an autonomous robotic interstellar space probe with a high level of artificial intelligence, and all relevant information that its home civilization might wish to communicate to another culture. It would seek out technological civilizations—or alternatively monitor worlds where there is a likelihood of technological civilizations arising—and communicate over "short" distances (compared to the interstellar distances between inhabited worlds) once it discovered a civilization that meets its contact criteria. It would make its presence known, carry out a dialogue with the contacted culture, and presum ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Moon
The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of Australia). The Moon is a planetary-mass object with a differentiated rocky body, making it a satellite planet under the geophysical definitions of the term and larger than all known dwarf planets of the Solar System. It lacks any significant atmosphere, hydrosphere, or magnetic field. Its surface gravity is about one-sixth of Earth's at , with Jupiter's moon Io being the only satellite in the Solar System known to have a higher surface gravity and density. The Moon orbits Earth at an average distance of , or about 30 times Earth's diameter. Its gravitational influence is the main driver of Earth's tides and very slowly lengthens Earth's day. The Moon's orbit around Earth has a sidereal period of 27.3 days. During each synodic period ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
EME (communications)
EME may refer to: Companies and organizations * Edison Mission Energy, a defunct American power company * Emcor, an American construction company * College of Electrical and Mechanical Engineering, a constituent college of National University of Sciences and Technology, Pakistan * Corps of Royal Canadian Electrical and Mechanical Engineers, of the Canadian Forces * Indian Army Corps of EME, of Electronics and Mechanical Engineers * Pakistan Army Corps of Electrical and Mechanical Engineering Science * ECB-mask-ECB, a block cipher mode of operation used for disk encryption * EME (psychedelic), a drug * Early myoclonic encephalopathy * Earth–Moon–Earth communication * Eigenmode expansion * Electromagnetic environment * Electromembrane extraction * Early Medieval Europe (journal) Other * EME Temple, in Gujarat, India * Encrypted Media Extensions Encrypted Media Extensions (EME) is a W3C specification for providing a communication channel between web browsers and the Content ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solar Flare
A solar flare is an intense localized eruption of electromagnetic radiation in the Sun's atmosphere. Flares occur in active regions and are often, but not always, accompanied by coronal mass ejections, solar particle events, and other solar phenomena. The occurrence of solar flares varies with the 11-year solar cycle. Solar flares are thought to occur when stored magnetic energy in the Sun's atmosphere accelerates charged particles in the surrounding plasma. This results in the emission of electromagnetic radiation across the electromagnetic spectrum. High-energy electromagnetic radiation from solar flares is absorbed by the daylight side of Earth's upper atmosphere, in particular the ionosphere, and does not reach the surface. This absorption can temporarily increase the ionization of the ionosphere which may interfere with short-wave radio communication. The prediction of solar flares is an active area of research. Flares also occur on other stars, where the term ''stellar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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