AM stations were the earliest broadcasting stations to be developed. AM refers to "amplitude modulation, a mode of broadcasting radio waves by varying the amplitude of the carrier signal in response to the amplitude of the signal to be transmitted. The medium-wave band is used worldwide for AM broadcasting. Europe also uses the "long wave band. In response to the growing popularity of "FM stereo radio stations in the late 1980s and early 1990s, some "North American stations began broadcasting in "AM stereo, though this never gained popularity, and very few receivers were ever sold.
The signal is subject to interference from electrical storms ("lightning) and other "electromagnetic interference (EMI). One advantage of AM radio signal is that it can be detected (turned into sound) with simple equipment. If a signal is strong enough, not even a power source is needed; building an unpowered "crystal radio receiver was a common childhood project in the early decades of AM broadcasting.
AM broadcasts occur on "North American airwaves in the "medium wave frequency range of 525 to 1705 "kHz (known as the “standard broadcast band”). The band was expanded in the 1990s by adding nine "channels from 1605 to 1705 kHz. Channels are spaced every 10 kHz in the "Americas, and generally every 9 kHz everywhere else.
AM transmissions cannot be ionospherically "propagated during the day due to strong absorption in the "D-layer of the ionosphere. In a crowded channel environment, this means that the power of regional channels which share a frequency must be reduced at night or directionally beamed in order to avoid interference, which reduces the potential nighttime audience. Some stations have frequencies unshared with other stations in North America; these are called "clear-channel stations. Many of them can be heard across much of the country at night. During the night, absorption largely disappears and permits signals to travel to much more distant locations via ionospheric reflections. However, fading of the signal can be severe at night.
AM radio transmitters can transmit audio frequencies up to 15 kHz (now limited to 10 kHz in the US due to FCC rules designed to reduce interference), but most receivers are only capable of reproducing frequencies up to 5 kHz or less. At the time that AM broadcasting began in the 1920s, this provided adequate fidelity for existing microphones, 78 rpm recordings, and loudspeakers. The fidelity of sound equipment subsequently improved considerably, but the receivers did not. Reducing the bandwidth of the receivers reduces the cost of manufacturing and makes them less prone to interference. AM stations are never assigned adjacent channels in the same service area. This prevents the sideband power generated by two stations from interfering with each other. "Bob Carver created an "AM stereo tuner employing "notch filtering that demonstrated that an AM broadcast can meet or exceed the 15 kHz baseband bandwidth allotted to "FM stations without objectionable interference. After several years, the tuner was discontinued. Bob Carver had left the company and the Carver Corporation later cut the number of models produced before discontinuing production completely.["citation needed]
FM refers to "frequency modulation, and occurs on "VHF airwaves in the frequency range of 88 to 108 "MHz everywhere except "Japan and "Russia. Russia, like the former Soviet Union, uses 65.9 to 74 MHz frequencies in addition to the world standard. Japan uses the 76 to 90 MHz frequency band.
"Edwin Howard Armstrong invented FM radio to overcome the problem of "radio-frequency interference (RFI), which plagued AM radio reception. At the same time, greater fidelity was made possible by spacing stations further apart in the "radio frequency spectrum. Instead of 10 kHz apart, as on the AM band in the US, FM channels are 200 kHz (0.2 MHz) apart. In other countries, greater spacing is sometimes mandatory, such as in New Zealand, which uses 700 kHz spacing (previously 800 kHz). The improved fidelity made available was far in advance of the audio equipment of the 1940s, but wide interchannel spacing was chosen to take advantage of the noise-suppressing feature of wideband FM.
Bandwidth of 200 "kHz is not needed to accommodate an audio signal — 20 kHz to 30 kHz is all that is necessary for a narrowband FM signal. The 200 kHz bandwidth allowed room for ±75 kHz signal deviation from the assigned frequency, plus guard bands to reduce or eliminate adjacent channel interference. The larger bandwidth allows for broadcasting a 15 kHz bandwidth audio signal plus a 38 kHz stereo "subcarrier"—a piggyback signal that rides on the main signal. Additional unused capacity is used by some broadcasters to transmit utility functions such as background "music for public areas, "GPS auxiliary signals, or financial market data.
The AM radio problem of interference at night was addressed in a different way. At the time FM was set up, the available frequencies were far higher in the spectrum than those used for AM radio - by a factor of approximately 100. Using these frequencies meant that even at far higher power, the range of a given FM signal was much shorter; thus its market was more local than for AM radio. The reception range at night is the same as in the daytime. All FM broadcast transmissions are line-of-sight, and ionospheric bounce is not viable. The much larger bandwidths, compared to AM and SSB, are more susceptible to phase dispersion. Propagation speeds (celerities) are fastest in the ionosphere at the lowest sideband frequency. The celerity difference between the highest and lowest sidebands is quite apparent to the listener. Such distortion occurs up to frequencies of approximately 50 MHz. Higher frequencies do not reflect from the ionosphere, nor from storm clouds. Moon reflections have been used in some experiments, but require impractical power levels.
The original FM radio service in the U.S. was the "Yankee Network, located in "New England. Regular FM broadcasting began in 1939 but did not pose a significant threat to the AM broadcasting industry. It required purchase of a special receiver. The frequencies used, 42 to 50 MHz, were not those used today. The change to the current frequencies, 88 to 108 MHz, began after the end of "World War II and was to some extent imposed by AM broadcasters as an attempt to cripple what was by now realized to be a potentially serious threat.
FM radio on the new band had to begin from the ground floor. As a commercial venture, it remained a little-used audio enthusiasts' medium until the 1960s. The more prosperous AM stations, or their owners, acquired FM licenses and often broadcast the same programming on the FM station as on the AM station (""simulcasting"). The FCC limited this practice in the 1960s. By the 1980s, since almost all new radios included both AM and FM tuners, FM became the dominant medium, especially in cities. Because of its greater range, AM remained more common in rural environments.
Pirate radio is illegal or non-regulated radio transmission. It is most commonly used to describe illegal broadcasting for entertainment or political purposes. Sometimes it is used for illegal two-way radio operation. Its history can be traced back to the unlicensed nature of the transmission, but historically there has been occasional use of sea vessels—fitting the most common perception of a pirate—as broadcasting bases. Rules and regulations vary largely from country to country, but often the term pirate radio generally describes the unlicensed broadcast of FM radio, AM radio, or shortwave signals over a wide range. In some places, radio stations are legal where the signal is transmitted, but illegal where the signals are received—especially when the signals cross a national boundary. In other cases, a broadcast may be considered "pirate" due to the type of content, its transmission format, or the transmitting power (wattage) of the station, even if the transmission is not technically illegal (such as a webcast or an amateur radio transmission). Pirate radio stations are sometimes referred to as bootleg radio or clandestine stations.
Terrestrial digital radio
"Digital radio broadcasting has emerged, first in "Europe (the "UK in 1995 and "Germany in 1999), and later in the United States, France, the Netherlands, South Africa, and many other countries worldwide. The most simple system is named DAB Digital Radio, for "Digital Audio Broadcasting, and uses the "public domain "EUREKA 147 (Band III) system. DAB is used mainly in the UK and South Africa. Germany and the Netherlands use the DAB and DAB+ systems, and France uses the L-Band system of DAB Digital Radio.
In the United States, digital radio isn't used in the same way as Europe and South Africa. Instead, the "IBOC system is named "HD Radio and owned by a "consortium of private companies that is called "iBiquity. An international "non-profit consortium "Digital Radio Mondiale (DRM), has introduced the "public domain DRM system.
|""||This section needs expansion. You can help by adding to it. (November 2008)|
"Satellite radio broadcasters are slowly emerging, but the enormous entry costs of space-based satellite transmitters and restrictions on available "radio spectrum licenses has restricted growth of this market. In the USA and "Canada, just two services, "XM Satellite Radio and "Sirius Satellite Radio exist. Both XM and Sirius are owned by "Sirius XM Radio, which was formed by the merger of XM and Sirius on July 29, "2008, whereas in "Canada, "XM Radio Canada and "Sirius Canada remained separate companies until 2010. "Worldspace in Africa and Asia, and "MobaHO! in Japan and the ROK were two unsuccessful satellite radio operators which have gone out of business.
Radio program formats differ by country, regulation, and markets. For instance, the U.S. "Federal Communications Commission designates the 88–92 megahertz band in the U.S. for non-profit or educational programming, with advertising prohibited.
In addition, formats change in popularity as time passes and technology improves. Early radio equipment only allowed program material to be broadcast in real time, known as live broadcasting. As technology for "sound recording improved, an increasing proportion of broadcast programming used pre-recorded material. A current trend is the "automation of radio stations. Some stations now operate without direct human intervention by using entirely pre-recorded material sequenced by "computer control.
- Guarnieri, M. (2012). "The age of vacuum tubes: Early devices and the rise of radio communications". IEEE Ind. Electron. M.: 41–43. "doi:10.1109/MIE.2012.2182822.
-  DRP 179807
- Tapan K. Sarkar (ed.) "History of wireless", John Wiley and Sons, 2006. "ISBN 0-471-71814-9, p.335
- Sōgo Okamura (ed), History of Electron Tubes, IOS Press, 1994 "ISBN 90-5199-145-2 page 20
-  Patent US841387 from 10/25/1906
- U.S. Patent 879,532
- Nebeker, Frederik (2009). Dawn of the Electronic Age: Electrical Technologies in the Shaping of the Modern World, 1914 to 1945. John Wiley & Sons. pp. 14–15. "ISBN "0470409746.
- "The Invention of Radio".
- Guarnieri, M. (2012). "The age of vacuum tubes: the conquest of analog communications". IEEE Ind. Electron. M.: 52–54. "doi:10.1109/MIE.2012.2193274.
- Fessenden — The Next Chapter RWonline.com
- Baudino, Joseph E; John M. Kittross (Winter 1977). "Broadcasting's Oldest Stations: An Examination of Four Claimants". Journal of Broadcasting: 61–82. Archived from the original on 2008-03-06. Retrieved 2013-01-18.
- "Callsign 2MT & New Street".
- "BBC History – The BBC takes to the Airwaves". BBC News.
- Atgelt, Carlos A. "Early History of Radio Broadcasting in Argentina." The Broadcast Archive (Oldradio.com).
- "What is a Radio Station?". "Radio World. p. 6.
- Grodkowski, Paul (2015-08-24). Beginning Shortwave Radio Listening. Booktango. "ISBN "9781468964240.
- Based on the "interference" entry of The Concise Oxford English Dictionary, 11th edition, online
- Halper, Donna L. "John Shepard's FM Stations—America's first FM network." Boston Radio Archives (BostonRadio.org).
- "The Yankee Network in 1936." Boston Radio Archives (BostonRadio.org)
- Miller, Jeff. "FM Broadcasting Chronology." Rev. 2005-12-27.
- Briggs Asa. The History of Broadcasting in the United Kingdom (Oxford University Press, 1961).
- Crisell, Andrew. An Introductory History of British Broadcasting (2002) excerpt
- Ewbank Henry and Lawton Sherman P. Broadcasting: Radio and Television (Harper & Brothers, 1952).
- Fisher, Marc. Something In The Air: Radio, Rock, and the Revolution That Shaped A Generation (Random House, 2007).
- "Hausman, Carl, Messere, Fritz, Benoit, Philip, and O'Donnell, Lewis, Modern Radio Production, 9th ed., (Cengage, 2013)
- Head, Sydney W., Christopher W. Sterling, and Lemuel B. Schofield. Broadcasting in America." (7th ed. 1994).
- Lewis, Tom, Empire of the Air: The Men Who Made Radio, 1st ed., New York : E. Burlingame Books, 1991. "ISBN 0-06-018215-6. ""Empire of the Air: The Men Who Made Radio" (1992) by "Ken Burns was a PBS documentary based on the book.
- Pilon, Robert, Isabelle Lamoureux, and Gilles Turcotte. Le Marché de la radio au Québec: document de reference. [Montréal]: Association québécoise de l'industrie du dique, du spectacle et de la video, 1991. unpaged. N.B.: Comprises: Robert Pilon's and Isabelle Lamoureux' Profil du marché de radio au Québec: un analyse de Média-culture. -- Gilles Turcotte's Analyse comparative de l'écoute des principals stations de Montréal: prepare par Info Cible.
- Ray, William B. FCC: The Ups and Downs of Radio-TV Regulation (Iowa State University Press, 1990).
- Russo, Alexan der. Points on the Dial: Golden Age Radio Beyond the Networks (Duke University Press; 2010) 278 pages; discusses regional and local radio as forms that "complicate" the image of the medium as a national unifier from the 1920s to the 1950s.
- Scannell, Paddy, and Cardiff, David. A Social History of British Broadcasting, Volume One, 1922-1939 (Basil Blackwell, 1991).
- Schramm, Wilbur, ed. The Process and Effects of Mass Communication (1955 and later editions) articles by social scientists
- Schramm, Wilbur, ed. Mass Communication (1950, 2nd ed. 1960); more popular essays
- Schwoch James. The American Radio Industry and Its Latin American Activities, 1900-1939 (University of Illinois Press, 1990).
- Stewart, Sandy. From Coast to Coast: a Personal History of Radio in Canada (Entreprises Radio-Canada, 1985). xi, 191 p., ill., chiefly with b&w photos. "ISBN 0-88794-147-8
- Stewart, Sandy. A Pictorial History of Radio in Canada (Gage Publishing, 1975). v, , 154 p., amply ill. in b&w mostly with photos. SBN 7715-9948-X
- White Llewellyn. The American Radio (University of Chicago Press, 1947).
|""||Look up radio broadcasting in Wiktionary, the free dictionary.|
- U.S. Patent 1,082,221, "Georg Graf von Arco, "Radiotelegraphic station" (December 1913)
- U.S. Patent 1,116,111, Richard Pfund, "Station for the transmission and reception of electromagnetic wave energy". (November 1914)
- U.S. Patent 1,214,591, Gustav Reuthe, "Antenna for radiotelegraph station" (February 1917)
- Federal Communications Commission website - fcc.gov
- DXing.info - Information about radio stations worldwide
- Radio-Locator.com- Links to 13,000 radio stations worldwide
- BBC reception advice
- DXradio.50webs.com "The SWDXER" - with general SWL information and radio antenna tips
- RadioStationZone.com - 10.000+ radio stations worldwide with ratings, comments and listen live links
- RadioBeta.com, search for stations around the globe
- Online-Radio-Stations.org - The Web Radio Tuner has a comprehensive list of over 50.000 radio stations
- RadioStations.com has a directory of radio stations and real-time music listings
- ZoZanga.com List of radio stations and real-time music listings
- UnwantedEmissions.com - A general reference to radio spectrum allocations
- Radio stanice - Search for radio stations throughout the Europe
- Radio Emisoras Latinas - has a directory with thousands of Latin America Radio Stations
- NEC Lab - A tool to design and test antennas for Radio broadcasting
- autocww.colorado.edu - Broadcasting, Radio and Television
- MY FM Radio Live - MY FM Radio Live - Internet radio broadcast