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Encyclopedia > AM broadcasting

AM broadcasting is radio broadcasting using Amplitude Modulation. Note: broadcasting is also the old term for hand sowing. ... [[Amplitude modulation]] (AM) is a technique used in electronic communication, most commonly for transmitting information via a carrier wave wirelessly. ...

Contents

History

Main article: History of radio

AM was the dominant method of broadcasting during the first two thirds of the 20th century and remains widely used into the 21st. // For the controversy about who invented radio, see Invention Of Radio. ... (19th century - 20th century - 21st century - more centuries) Decades: 1900s 1910s 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s As a means of recording the passage of time, the 20th century was that century which lasted from 1901–2000 in the sense of the Gregorian calendar (1900–1999... The 21st century is the present century of the Anno Domini (common) era, in accordance with the Gregorian calendar. ...


AM radio began with the first, experimental broadcast in 1906 by Reginald Fessenden, and was used for small-scale voice and music broadcasts up until World War I. The great increase in the use of AM radio came the following decade. The first licensed commercial radio services began on AM in the 1920s. XWA of Montreal, Quebec (later CFCF) was the first commercial broadcaster in the world, with regular broadcasts commencing on May 20, 1920. The first licensed American radio station was started by Frank Conrad, KDKA in Pittsburgh, Pennsylvania. Radio programming boomed during the "Golden Age of Radio" (1920s1950s). Dramas, comedy and all other forms of entertainment were produced, as well as broadcasts of news and music. 1906 (MCMVI) was a common year starting on Monday (see link for calendar). ... Reginald Aubrey Fessenden (October 6, 1866 – July 22, 1932) was a Canadian-born inventor, best known for his work in early radio. ... This article is becoming very long. ... The 1920s is a decade sometimes referred to as the Jazz Age or the Roaring Twenties, usually applied to America. ... CINW is an English language Canadian radio station located in Montreal, Quebec. ... This article needs cleanup. ... ‹ The template below has been proposed for deletion. ... Dr. Frank Conrad (1874-1941) was a radio broadcasting pioneer who worked as the Assistant Chief Engineer for the Westinghouse Electric Company in Pittsburgh, Pennsylvania. ... KDKA is a U.S. class A clear channel AM radio station located in Pittsburgh, Pennsylvania that operates on 1020 kHz. ... Nickname: Steel City, Iron City, Steel Town, City of Champions, City of Bridges, City of Colleges, The Burgh Motto: Benigno Numine (With the Benevolent Deity) Location in Allegheny County, Pennsylvania Coordinates: Country United States State Pennsylvania County Allegheny County Founded November 25, 1758 Incorporated April 22, 1794 (borough)   March 18... Official language(s) English, Pennsylvania Dutch Capital Harrisburg Largest city Philadelphia Area  Ranked 33rd  - Total 46,055 sq mi (119,283 km²)  - Width 280 miles (455 km)  - Length 160 miles (255 km)  - % water 2. ... Radio broadcasts have been a popular entertainment since the 1910s, though popularity has declined a little in some countries since television became widespread. ... Old-Time Radio (OTR) or The Golden Age of Radio is a term used to refer to radio programs that were broadcast during the 1920s through the late 1950s (with some outlying programs produced earlier and later) in the United States, as well as the United Kingdom and Canada and... The 1920s is a decade sometimes referred to as the Jazz Age or the Roaring Twenties, usually applied to America. ... // Recovering from World War I and its aftermath, the economic miracle emerged in West Germany and Italy. ...


Operation

AM radio technology is simpler than either FM radio or DAB. An AM receiver detects amplitude variations in the radio waves at a particular frequency. It then amplifies changes in the signal voltage to drive a loudspeaker or earphones. The earliest crystal radio receivers used a crystal diode detector with no amplification. Digital Audio Broadcast or DAB is a standard for digital radio broadcast developed by EUREKA as a research project for the European Union. ... It has been suggested that this article or section be merged with light. ... International safety symbol Caution, risk of electric shock (ISO 3864), colloquially known as high voltage symbol. ... “Loudspeaker” redirects here. ... In-ear headphones Headphones (also known as earphones, stereophones, headsets, or the slang term cans) is a transducer that receives an electrical signal from a media player or receiver and uses speakers placed in close proximity to the ears (hence the name earphone) to convert the signal into audible sound... An example of a modern set created by VE6AB The crystal radio receiver (also known as a crystal set) is a passive radio receiver consisting of a variable LC tuned circuit, a diode detector, and audio transducer. ... Types of diodes closeup, showing germanium crystal In electronics, a diode is a component that restricts the direction of movement of charge carriers. ...


Frequency Bands

AM radio is broadcast on several frequency bands:

  • Long wave is 153–279 kHz; it is not available far into the Western Hemisphere, and European 9 kHz channel spacing is generally used (historically frequencies as high as 413 kHz were used but currently there are no terrestrial LW broadcasters above 279 kHz).
  • Medium wave is 520–1,610 kHz. In the Americas (ITU region 2) 10 kHz spacing is used; elsewhere it is 9 kHz. ITU region 2 also authorizes the Extended AM broadcast band between 1610 and 1710 kHz.
  • Short wave is 2,300–26,100 kHz, divided into 15 broadcast bands. Shortwave broadcasts generally use a narrow 5 kHz channel spacing.

The allocation of these bands is governed by the ITU's Radio Regulations and, on the national level, by each country's telecommunications administration (the FCC in the U.S., for example) subject to international agreements. Longwave can also refer to the economics concept of Kondratiev waves, or to the rock band Longwave The Longwave radio broadcasting band is the range of frequencies between 148. ... A kilohertz (kHz) is a unit of frequency equal to 1,000 hertz (1,000 cycles per second). ... Mediumwave radio transmissions serves as the most common band for broadcasting. ... The International Telecommunication Union (ITU), in its International Radio Regulations, divides the world into three ITU regions for the purposes of managing the global radio spectrum. ... The extended AM broadband is a medium wave broadcast allocation (1620-1710 KHz -- sometimes known as the X-band) available only in ITU Region 2 (North and South America) that became available c. ... A solid-state, analog shortwave receiver Shortwave radio operates between the frequencies of 3,000 kHz and 30 MHz (30,000 kHz) [1] and came to be referred to as such in the early days of radio because the wavelengths associated with this frequency range were shorter than those commonly... The International Telecommunication Union (ITU; French: Union internationale des télécommunications, Spanish: Unión Internacional de Telecomunicaciones) is an international organization established to standardize and regulate international radio and telecommunications. ... The Radio Regulations is an intergovernmental treaty text of the International Telecommunication Union (ITU), the Geneva based specialised agency of the United Nations which coordinates and standardises the operation of telecommunication networks and services and advances the development of communications technology. ... The FCCs official seal. ... Motto: (Out Of Many, One) (traditional) In God We Trust (1956 to date) Anthem: The Star-Spangled Banner Capital Washington D.C. Largest city New York City None at federal level (English de facto) Government Federal constitutional republic  - President George Walker Bush (R)  - Vice President Dick Cheney (R) Independence from...

  • Long wave is used for radio broadcasting in Europe, Africa, Oceania and parts of Asia (ITU regions 1 and 3). In the United States and Canada, Bermuda and U.S. territories this band is mainly reserved for aeronautics, though a small section of the band could theoretically be used for microbroadcasting under the United States Part 15 rules. Due to the propagation characteristics of long wave signals, the frequencies are used most effectively in latitudes north of 50°.
  • Medium wave is by far the most heavily used band for commercial broadcasting. This is the "AM radio" that most people are familiar with.
  • Short wave is used by audio services intended to be heard at great distances from the transmitting station. The long range of short wave broadcasts comes at the expense of lower audio fidelity. The mode of propagation for short wave is different (see high frequency). AM is used mostly by broadcast services — other shortwave users may use a modified version of AM such as SSB or an AM-compatible version of SSB such as SSB with carrier reinserted. In many parts of the world short wave radio also carries audible, encoded messages of unknown purpose from numbers stations.

Frequencies between the broadcast bands are used for other forms of radio communication, such as baby monitors, walkie talkies, cordless telephones, radio control, "ham" radio, etc. Six F-16 Fighting Falcons with the U.S. Air Force Thunderbirds aerial demonstration team fly in delta formation in front of the Empire State Building. ... Microbroadcasting is the process of broadcasting a message to a relatively small audience. ... In the U.S., Part 15 is an often-quoted section of Federal Communications Commission (FCC) rules and regulations, regarding unlicensed transmissions. ... High frequency (HF) radio frequencies are between 3 and 30 MHz. ... Single-sideband modulation (SSB) is a refinement of the technique of amplitude modulation designed to be more efficient in its use of electrical power and bandwidth. ... The German Lorenz cipher machine, used in World War II for encryption of very high-level general staff messages Cryptography (or cryptology; derived from Greek κρυπτός kryptós hidden, and the verb γράφω gráfo write) is the study of message secrecy. ... This article or section is not written in the formal tone expected of an encyclopedia article. ... Ham radio station with modern solid-state transceiver featuring LCD display and DSP capabilities Ham radio station with vintage vacuum tube gear featuring separate transmitter, receiver and power supply Amateur radio, often called Ham radio, is a hobby and public service enjoyed by about 6 million people throughout the world. ...


Limitations of AM radio

Because of its susceptibility to atmospheric interference and generally lower-fidelity sound, AM broadcasting is better suited to talk radio and news programming, while music radio and public radio mostly shifted to FM broadcasting in the late 1960s and 1970s. Previously, in the UK during the 1980s, BBC Radio 4 (a largely speech channel) had an FM location whereas BBC Radio 1 (a music channel) was confined to AM broadcasts over much of the UK. Frequency response is typically 40 Hz–7 kHz with a 50 dB S/N ratio. Talk radio is a radio format which features discussion of topical issues. ... For other uses, see News (disambiguation). ... This article or section does not adequately cite its references or sources. ... Public broadcasting (also known as public service broadcasting or PSB) is the dominant form of broadcasting around the world, where radio, television, and potentially other electronic media outlets receive funding from the public. ... FM broadcasting is a broadcast technology invented by Edwin Howard Armstrong that uses frequency modulation (FM) to provide high-fidelity sound over broadcast radio. ... The 1960s decade refers to the years from January 1, 1960 to December 31, 1969, inclusive. ... The 1970s decade refers to the years from 1970 to 1979, inclusive. ... BBC Radio 4 is a British domestic radio station which broadcasts a wide variety of chiefly spoken-word programmes including news, drama, comedy, science and history. ... “Radio 1” redirects here. ... The decibel (dB) is a logarithmic unit of measurement that expresses the magnitude of a physical quantity (usually power) relative to a specified or implied reference level. ... The phrase signal-to-noise ratio, often abbreviated SNR or S/N, is an engineering term for the ratio between the magnitude of a signal (meaningful information) and the magnitude of background noise. ...


Part of the limitation on AM fidelity, however, comes from current receiver design. Most modern receivers do not pass the full spectrum of audio that AM radio is capable of transmitting, while older receivers designed at the peak of AM's popularity may sound quite good by comparison.[citation needed]


Medium wave and short wave radio signals act differently during daytime and nighttime. During the day, AM signals travel by groundwave, diffracting around the curve of the earth over a distance up to a few hundred miles (or kilometers) from the signal transmitter. However, after sunset, changes in the ionosphere cause AM signals to travel by skywave, enabling AM radio stations to be heard much farther from their point of origin than is normal during the day. This phenomenon can be easily observed by scanning an AM radio dial at night. As a result, many broadcast stations are required as a condition of license to reduce their broadcasting power significantly (or use directional antennas) after sunset, or even to suspend broadcasting entirely during nighttime hours. (Such stations are commonly referred to as daytimers.) Groundwave is the propagation of radio waves close to the surface of the Earth. ... A mile is a unit of length, usually used to measure distance, in a number of different systems, including Imperial units, United States customary units and Norwegian/Swedish mil. ... A kilometre (American spelling: kilometer) (symbol: km) is a unit of length equal to 1000 metres (from the Greek words khilia = thousand and metro = count/measure). ... Relationship of the atmosphere and ionosphere The ionosphere is the part of the atmosphere that is ionized by solar radiation. ... It has been suggested that this article or section be merged with Ionosphere. ... Clear channel stations are AM radio stations that are designated as such so that only one or two 50,000 watt powerhouses operate at night on each designated frequency, covering a wide area via sky wave propagation. ...


Some other radio stations are granted clear channel rights, meaning that they broadcast on frequencies whose use is more restricted and thus relatively unaffected by interference from other stations. Nowadays relatively few stations enjoy clear channel status. Clear channel stations are AM radio stations that are designated as such so that only one or two 50,000 watt powerhouses operate at night on each designated frequency, covering a wide area via sky wave propagation. ...


The hobby of listening to long distance signals is known as DX or DX'ing, from an old telegraph abbreviation for "distance unknown". Several non-profit hobbyist clubs are devoted exclusively to DXing the AM broadcast band, including the National Radio Club and International Radio Club of America. Similarly, people listening to short wave transmissions are SWLing. DX communication is communication over great distances using the ionosphere to refract the transmitted radio beam. ... Optical Telegraf of Claude Chappe on the Litermont near Nalbach, Germany Telegraph and telegram redirect here. ... This article or section does not adequately cite its references or sources. ... A non-profit organization (often called non-profit org or simply non-profit or not-for-profit) can be seen as an organization that doesnt have a goal to make a profit. ... A hobby is a spare-time recreational pursuit. ... Drake R8B communications receiver. ... The National Radio Club (frequently abbreviated NRC) is a non-profit hobbyist organization formed in 1933 and is devoted to the activity of DXing on the AM broadcast band. ... Shortwaves can be heard using a cheap world band receiver. ...


AM radio signals can be severely disrupted in large urban centres by concrete bridges with metal reinforcements, other Faraday cage structures, tall buildings and sources of radio frequency interference (RFI) and electrical noise. As a result, AM radio in many countries has lost its dominance as a music broadcasting service, and in many cities is now relegated to news, sports, religious and talk radio stations although some musical genres — particularly country, oldies, nostalgia and ethnic/world music — survive on AM, especially in areas where FM frequencies are in short supply or in thinly populated or mountainous areas where FM coverage is poor. Entrance to a Faraday room A Faraday cage or Faraday shield is an enclosure formed by conducting material, or by a mesh of such material. ... Radio Frequency Interference (RFI) is electromagnetic radiation which is emitted by electrical circuits carrying rapidly changing signals, as a by-product of their normal operation, and which causes unwanted signals (interference or noise) to be induced in other circuits. ... Talk radio is a radio format which features discussion of topical issues. ...


Other distribution methods

Stereo transmissions are possible (see AM stereo), and there is work underway to add digital radio services to currently existing AM transmissions. In the United States, the iBiquity company is developing a proprietary standard for medium wave transmissions, while Digital Radio Mondiale is a more open effort often used on the shortwave bands, and can be used alongside many AM broadcasts. Label for 2. ... AM stereo is any of a number of mutually-incompatible techniques for broadcasting two_channel audio in the mediumwave band in a manner that is compatible with receivers designed for standard amplitude modulation. ... This article needs to be cleaned up to conform to a higher standard of quality. ... iBiquity is a company formed by the merger of USA Digital Radio and Lucent Digital Radio, with the goal of creating an in-band on-channel (IBOC) digital radio system for the United States. ... Digital Radio Mondiale (DRM) is a set of digital audio broadcasting technologies designed to work over the bands currently used for AM broadcast, particularly shortwave. ... Shortwave bands are frequency allocations for use within the high frequency radio spectrum. ...


While FM radio can also be received by cable, AM radio generally cannot be, although an AM station can be converted into an FM cable signal. In Canada, cable operators that offer FM cable services are required by the CRTC to distribute all locally available AM stations in this manner. In Switzerland a system known as "wire broadcasting" transmits AM signals over telephone lines in the longwave band. Cable radio or cable FM is a complementary concept to that of cable television, bringing radio transmissions into homes and businesses via coaxial cable. ... The Canadian Radio-television and Telecommunications Commission (CRTC, in French Conseil de la radiodiffusion et des télécommunications canadiennes) was established in 1968 by the Canadian Parliament to replace the Board of Broadcast Governors. ... Longwave can also refer to the economics concept of Kondratiev waves, or to the rock band Longwave The Longwave radio broadcasting band is the range of frequencies between 148. ...


Amateur AM & microbroadcasting

Increasingly, amateur radio operators are giving a second life to retired AM broadcast transmitters, donated or sold cheaply to hobbyists by stations with no further need. The attraction is part of a vintage amateur radio specialty in the hobby, and it resembles old car collecting. There are often large gatherings on the shortwave amateur bands, where the transmitters are used for 2-way contacts among aficionados. Nighttime propagation is especially reminiscent of the early days of radio, as individual stations warm up their transmitters for hours of storytelling and technical discussion with other "ham" enthusiasts far and near. These amateur stations often place an emphasis on high-fidelity reception as well as striving toward good transmitted audio. Some amateurs listen on the big speaker of an antique floor console with shortwave bands such as those from Philco, GE, Crosley and Zenith. Occasionally, an amateur using AM gets reception reports from an "SWL," a shortwave listener who has picked up their signals on an antique radio, or perhaps with a modern "world-band" receiver.[1] Ham radio station with modern solid-state transceiver featuring LCD display and DSP capabilities Ham radio station with vintage vacuum tube gear featuring separate transmitter, receiver and power supply Amateur radio, often called Ham radio, is a hobby and public service enjoyed by about 6 million people throughout the world. ... Vintage amateur gear at station W1GFH Vintage amateur radio is a subset of the amateur radio hobby, considered a form of nostalgia much like antique car collecting, where enthusiasts collect, restore, preserve, build, and operate amateur radio equipment from bygone years, most notably those using vacuum tube technology. ... A solid-state, analog shortwave receiver Shortwave radio operates between the frequencies of 3,000 kHz and 30 MHz (30,000 kHz) [1] and came to be referred to as such in the early days of radio because the wavelengths associated with this frequency range were shorter than those commonly... Shortwave bands are frequency allocations for use within the high frequency radio spectrum. ...


Some microbroadcasters and pirate radio broadcasters, especially those in the United States under the FCC's Part 15 rules, broadcast on AM to achieve greater range than is possible on the FM band. On mediumwave (AM), such radio stations are often found between 1610 kHz and 1710 kHz. Hobbyists also use low-power AM transmitters to provide local programming for antique radio equipment in areas where AM programming is not widely available or is of questionable quality; in such cases the transmitter, which is designed to cover only the immediate property and perhaps nearby areas, is hooked up to a computer or music player. Microbroadcasting is the process of broadcasting a message to a relatively small audience. ... The term pirate radio usually refers to illegal or unregulated radio broadcasting. ... In the U.S., Part 15 is an often-quoted section of Federal Communications Commission (FCC) rules and regulations, regarding unlicensed transmissions. ... FM broadcasting is a broadcast technology invented by Edwin Howard Armstrong that uses frequency modulation (FM) to provide high-fidelity sound over broadcast radio. ...


Notes

  1. ^ Courson, Paul. "Chrome and Glass Shine Again: Hams Give Second Life to Legendary Transmitters With Names Like RCA, Collins, Gates and Raytheon", Radio World, 2001-06-20. Retrieved on 2007-04-06. 

2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the Anno Domini (common) era. ... April 6 is the 96th day of the year in the Gregorian calendar (97th in leap years). ...

See also

Superscript text
Ň==External links== [[Amplitude modulation]] (AM) is a technique used in electronic communication, most commonly for transmitting information via a carrier wave wirelessly. ... Drake R8B communications receiver. ... FM broadcasting is a broadcast technology invented by Edwin Howard Armstrong that uses frequency modulation (FM) to provide high-fidelity sound over broadcast radio. ... Analog transmission is a method of conveying voice, data, image, signal or video information using a continuous signal which varies in amplitude, phase, or some other property in proportion to that of a variable. ... The extended AM broadband is a medium wave broadcast allocation (1620-1710 KHz -- sometimes known as the X-band) available only in ITU Region 2 (North and South America) that became available c. ... Compatible Amplitude Modulation - Digital or CAM-D is a proposed hybrid digital radio format for AM broadcasting, put forth by respected broadcast engineer Leonard Kahn. ... The following is a listing of radio stations in North and Central America: // United States As of June 2004, the FCC had licensed 4,771 AM stations, 6,218 commercial FM stations, and 2,497 educational FM stations. ... This article is a list of radio stations that are located on Earth. ... // The title of Oldest Radio Station is a controversial one, but can be assumed from several in Europe (particularly of England and Germany), and in the United States and Canada. ...

  • "Building the Broadcast Band" the development of the 520-1700 kHz MW (AM) band
  • Listen to live AM radio transmissions.
  • How Products Are Made
  • Listen to Online Radio.

  Results from FactBites:
 
AM broadcasting at AllExperts (1190 words)
AM was the dominant method of broadcasting during the first two thirds of the 20th century and remains widely used into the 21st.
AM radio began with the first, experimental broadcast in 1906 by Reginald Fessenden, and was used for small-scale voice and music broadcasts up until World War I.
AM is used mostly by broadcast services — other shortwave users may use a modified version of AM such as SSB or an AM-compatible version of SSB such as SSB with carrier reinserted.
AM broadcasting - ArticleWorld (247 words)
The radio waves used in broadcasting have to be modulated before being transmitted, a process in which audio-frequency waves are super-imposed over carrier waves.
AM was the most dominant method of radio broadcasting initially and continues to be popular today.
AM radio broadcasting, as explained above, involves the modification of the amplitude of audio frequency signal received from the microphone.
  More results at FactBites »

 
 

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