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Meter Band
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 intern ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shortwave Radio
Shortwave radio is radio transmission using radio frequencies in the shortwave bands (SW). There is no official definition of the band range, but it always includes all of the High frequency, high frequency band (HF), which extends from 3 to 30 MHz (approximately 100 to 10 metres in wavelength). It lies between the Medium frequency, medium frequency band (MF) and the bottom of the Very high frequency, 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" radio propagation, 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 generally limited by the visual horizon, ... [...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 European term, "Old World." Geography The almost perfect circle (the earth is an oblate that is wider 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° longit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Citizens Band Radio
Citizens band radio (CB radio) is a land mobile radio system, a system allowing short-distance one-to-many bidirectional voice communication among individuals, using two-way radios operating near 27 MHz (or the 11-m wavelength) in the high frequency or 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 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 communicate they press a "push to talk" button on their radio, which turns on their transmitter. Users on a channel must take turns transmitting. In the US and Canada, and in the EU and th ... [...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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mexico City
Mexico City is the capital city, capital and List of cities in Mexico, largest city of Mexico, as well as the List of North American cities by population, most populous city in North America. It is one of the most important cultural and financial centers in the world, and is classified as an Globalization and World Cities Research Network, Alpha world city according to the Globalization and World Cities Research Network (GaWC) 2024 ranking. Mexico City is located in the Valley of Mexico within the high Mexican central plateau, at an altitude of . The city has 16 Boroughs of Mexico City, boroughs or , which are in turn divided into List of neighborhoods in Mexico City, neighborhoods or . 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 list of largest cities#List, sixth-largest metropolitan ... [...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. Historically, it was only possible to detect sunspots on the far side of the Sun indirectly using helioseismology. Since 2006, NASA's STEREO spacecrafts allow their direct observation. 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 f ... [...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 codecs and Opus 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
WWV (radio Station)
WWV is a Shortwave radio, 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, 20, and 25 Hertz, 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. The term WWV is not an abbreviation and does not stand for anything (see WWV (radio station)#Establishment, below). 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 i ... [...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 w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Critical Hours
Critical hours for radio stations is the time from sunrise to two hours after sunrise, and from two hours before sunset until sunset, local time. During this time, certain American radio stations may be operating with reduced power as a result of Section 73.187 of the Federal Communications Commission's rules. Canadian restricted hours are similar to critical hours, except that the restriction results from the January 17, 1984, U.S.-Canadian AM Agreement. Canadian restricted hours are called "critical hours" in the U.S.-Canadian Agreement, but in the AM Engineering database, the FCC calls them "Canadian restricted hours" to distinguish them from the domestically defined critical hours. Canadian restricted hours is that time from sunrise to one and one-half hours after sunrise, and from one and one-half hours before sunset until sunset, local time. U.S. stations operate with restricted hours because of Canadian stations, and vice versa. Those radio stations that must lower their powe ... [...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 7.000-7.200 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) and intercontinental 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
