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Shortwave Bands
Shortwave bands are frequency allocations for use within the shortwave radio spectrum (the upper medium frequency Fband and all of the high frequency Fband). Radio waves in these frequency ranges can be used for very long distance (transcontinental) communication because they can reflect off layers of charged particles in the ionosphere and return to Earth beyond the horizon, a mechanism called skywave or “skip” propagation. They are allocated by the ITU for radio services such as maritime communications, international shortwave broadcasting and worldwide amateur radio. The bands are conventionally named by their wavelength in metres, for example the ‘20 meter band’. Radio propagation and possible communication distances vary depending on the time of day, the season and the level of solar activity. International broadcast bands These bands are used by powerful long range AM radio stations, many operated by governments, which broadcast to multiple countries. Most interna ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shortwave Radio
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 radi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eastern Hemisphere
The Eastern Hemisphere is the half of the planet Earth which is east of the prime meridian (which crosses Greenwich, London, United Kingdom) and west of the antimeridian (which crosses the Pacific Ocean and relatively little land from pole to pole). It is also used to refer to Afro-Eurasia (Africa and Eurasia) and Australia, in contrast with the Western Hemisphere, which includes mainly North and South America. The Eastern Hemisphere may also be called the "Oriental Hemisphere", and may in addition be used in a cultural or geopolitical sense as a synonym for the " Old World." Geography The almost perfect circle (the earth is an oblate that is fatter around the equator), drawn with a line, demarcating the Eastern and Western Hemispheres must be an arbitrarily decided and published convention, unlike the Equator (an imaginary line encircling Earth, equidistant from its poles), which divides the Northern and Southern Hemispheres. The prime meridian at 0° longitude and the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
WTWW
WTWW is a shortwave station located in Lebanon, Tennessee. WTWW broadcasts religious programming from LaPorte Church of Christ, a white-supremacist church with Christian Identity sympathies based in Colorado, carrying that church's Scriptures for America programming service. It is officially licensed to Leap of Faith, Inc. As of December 2022, WTWW has one working transmitter, that on 5.085 MHz, which operates during the evening hours. Until 2022, WTWW had also carried an oldies/classic hits format operated by Ted Randall, who also appeared on several programs on the station, and his wife Holly on the 5.085 MHz and 9.94 MHz frequencies. WTWW went off-air November 10, 2022, with Randall taking the format to WRMI; it returned to the air sporadically in December. WTWW is licensed several other frequencies that are off-air. History WTWW, according to the FCC, was originally licensed a construction permit as WBWW on June 30, 2009. Testing began in January 2010 and end ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Citizens Band Radio
Citizens band radio (also known as CB radio), used in many countries, is a land mobile radio system, a system allowing short-distance person-to-many persons bidirectional voice communication among individuals, using two way radios operating on 40 channels near 27 MHz (11 m) in the high frequency (a.k.a. shortwave) band. Citizens band is distinct from other personal radio service allocations such as FRS, GMRS, MURS, UHF CB and the Amateur Radio Service ( "ham" radio). In many countries, CB operation does not require a license, and (unlike amateur radio) it may be used for business or personal communications. Like many other land mobile radio services, multiple radios in a local area share a single frequency channel, but only one can transmit at a time. The radio is normally in receive mode to receive transmissions of other radios on the channel; when users want to talk they press a " push to talk" button on their radio, which turns on their transmitter. Users ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
2005 In Radio
The year 2005 in radio involved some significant events. __TOC__ Events *April 29 – KFRC 610 AM in San Francisco, switches formats as a result of ownership change. KFRC becomes KEAR, the "Sound of the New Life" (Family Radio), a listener-supported, gospel/religious only station. It had been previously KFRC from September 1924 to this date. KFRC continued to broadcast on its sister station 99.7 FM. *July – Digital Radio Mondiale conducts an extensive test of using the 11 meter (26 MHz) shortwave band for local digital shortwave radio broadcasts in Mexico City. *November 3 – Cumulus-owned KCHZ/Kansas City flips formats from Mainstream Top 40 ("Z 95.7") to Rhythmic Top 40, branded as "95-7 The Vibe." *November 9 – ''Mediaweek'' announces that radio personality Bob Kingsley is stepping down as host of ''American Country Countdown'' after being associated with the program for 31 years (27 of them as host). His last countdown program airs December 24. Kix Brooks (one half ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mexico City
Mexico City ( es, link=no, Ciudad de México, ; abbr.: CDMX; Nahuatl: ''Altepetl Mexico'') is the capital and largest city of Mexico, and the most populous city in North America. One of the world's alpha cities, it is located in the Valley of Mexico within the high Mexican central plateau, at an altitude of . The city has 16 boroughs or ''demarcaciones territoriales'', which are in turn divided into neighborhoods or ''colonias''. The 2020 population for the city proper was 9,209,944, with a land area of . According to the most recent definition agreed upon by the federal and state governments, the population of Greater Mexico City is 21,804,515, which makes it the sixth-largest metropolitan area in the world, the second-largest urban agglomeration in the Western Hemisphere (behind São Paulo, Brazil), and the largest Spanish language, Spanish-speaking city (city proper) in the world. Greater Mexico City has a gross domestic product, GDP of $411 billion in 2011, which makes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Surface Wave
In physics, a surface wave is a mechanical wave that propagates along the Interface (chemistry), interface between differing media. A common example is gravity waves along the surface of liquids, such as ocean waves. Gravity waves can also occur within liquids, at the interface between two fluids with different densities. Elastic surface waves can travel along the surface of solids, such as ''Rayleigh wave, Rayleigh'' or ''Love wave, Love'' waves. Electromagnetic waves can also propagate as "surface waves" in that they can be guided along with a refractive index gradient or along an interface between two media having different dielectric constants. In radio transmission (telecommunications), transmission, a ''ground wave'' is a guided wave that propagates close to the surface of the Earth. Mechanical waves In seismology, several types of surface waves are encountered. Surface waves, in this mechanical sense, are commonly known as either ''Love waves'' (L waves) or ''Rayleigh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wolf Number
The Wolf number (also known as the relative sunspot number or Zürich number) is a quantity that measures the number of sunspots and groups of sunspots present on the surface of the Sun. History Astronomers have been observing the Sun recording information about sunspots since the advent of the telescope in 1609. However, the idea of compiling the information about the sunspot number from various observers originates in Rudolf Wolf in 1848 in Zürich, Switzerland. The produced series initially had his name, but now it is more commonly referred to as the international sunspot number series. The international sunspot number series is still being produced today at the observatory of Brussels. The international number series shows an approximate periodicity of 11 years, the solar cycle, which was first found by Heinrich Schwabe in 1843, thus sometimes it is also referred to as the Schwabe cycle. The periodicity is not constant but varies roughly in the range 9.5 to 11 years. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Digital Radio Mondiale
Digital Radio Mondiale (DRM; ''mondiale'' being Italian and French for "worldwide") is a set of digital audio broadcasting technologies designed to work over the bands currently used for analogue radio broadcasting including AM broadcasting—particularly shortwave—and FM broadcasting. DRM is more spectrally efficient than AM and FM, allowing more stations, at higher quality, into a given amount of bandwidth, using xHE-AAC audio coding format. Various other MPEG-4 and Opus codecs are also compatible, but the standard now specifies xHE-AAC. Digital Radio Mondiale is also the name of the international non-profit consortium that has designed the platform and is now promoting its introduction. Radio France Internationale, TéléDiffusion de France, BBC World Service, Deutsche Welle, Voice of America, Telefunken (now Transradio) and Thomcast (now Ampegon) took part at the formation of the DRM consortium. The principle of DRM is that bandwidth is the limiting factor, and comp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
WWV (radio Station)
WWV is a shortwave ("high frequency" or HF) radio station, located near Fort Collins, Colorado. It has broadcast a continuous time signal since 1945, and implements United States government frequency standards, with transmitters operating on 2.5, 5, 10, 15, and 20 MHz. WWV is operated by the U.S. National Institute of Standards and Technology (NIST), under the oversight of its Time and Frequency Division, which is part of NIST's Physical Measurement Laboratory based in Gaithersburg, Maryland. WWV was established in 1919 by the Bureau of Standards in Washington, D.C., making it one of the oldest continuously-operating radio stations in the United States. NIST celebrated WWV's centennial on October 1, 2019. In 1931, the station relocated to the first of three suburban Maryland sites, before moving to a location near Fort Collins in 1966. WWV shares this site with longwave (also known as "low frequency" or LF) station WWVB, which transmits carrier and time code (no voice) at 60 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Time Signal
A time signal is a visible, audible, mechanical, or electronic signal used as a reference to determine the time of day. Church bells or voices announcing hours of prayer gave way to automatically operated chimes on public clocks; however, audible signals (even signal guns) have limited range. Busy seaports used a visual signal, the dropping of a ball, to allow mariners to check the chronometers used for navigation. The advent of electrical telegraphs allowed widespread and precise distribution of time signals from central observatories. Railways were among the first customers for time signals, which allowed synchronization of their operations over wide geographic areas. Dedicated radio time signal stations transmit a signal that allows automatic synchronization of clocks, and commercial broadcasters still include time signals in their programming. Today, global navigation satellite systems (GNSS) radio signals are used to precisely distribute time signals over much of the world ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
40-meter Band
The 40-meter or 7-MHz band is an amateur radio frequency band, spanning 7.000-7.300 MHz in ITU Region 2, and 7.000-7.200 MHz in Regions 1 & 3. It is allocated to radio amateurs worldwide on a primary basis; however, only 7.000-7.100 MHz is exclusively allocated to amateur radio worldwide. Shortwave broadcasters and land mobile users also have primary allocations in some countries, and amateur stations must share the band with these users. 40 meters is considered one of the most reliable all-season long distance communication ( DX) bands. History The 40-meter band was made available to amateurs in the United States by the Third National Radio Conference on October 10, 1924, ''Recommendations for Regulation of Radio Adopted by the Third National Radio Conferen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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