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 a radio receiver connected to another antenna. 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 and missiles, a beam of radio waves emitted by a radar transmitter reflects off the target object, and the reflected waves reveal the object's location. In radio navigation systems such as GPS and VOR, a mobile receiver receives radio signals from navigational radio beacons whose position is known, and by precisely measuring the arrival time of the radio waves the receiver can calculate its position on Earth. In wireless radio remote control devices like drones, garage door openers, and keyless entry systems, radio signals transmitted from a controller device control the actions of a remote device. (Full article...)
The electromagnetic spectrum
is the range of all possible electromagnetic radiation
. Also, the "electromagnetic spectrum" (usually just spectrum
) of an object is the range of electromagnetic radiation that it emits
, or transmits.
The electromagnetic spectrum, extends from the frequencies used in electric power grids (at the long-wavelength end) to gamma radiation (at the short-wavelength end), covering wavelengths from thousands of kilometres down to fractions of the size of an atom. It is commonly said that EM waves beyond these limits are uncommon, although this is not actually true. The 22-year sunspot cycle, for instance, produces radiation with a period of 22 years, or a frequency of 1.4*10−9 Hz. At the other extreme, photons of arbitrarily high frequency may be produced by colliding electrons with positrons at appropriate energy. 1024 Hz photons can be produced today with man-made accelerators. In our universe the short wavelength limit is likely to be the Planck length, and the long wavelength limit is the size of the universe itself (see physical cosmology), though in principle the spectrum is infinite.
Comparison of AM and FM modulated radio waves
Frequency spectrum of a typical modulated AM or FM radio signal. It consists of a component C at the carrier wave frequency with the information (modulation) contained in two narrow bands of frequencies called sidebands (SB) just above and below the carrier frequency.
Neighborhood wireless WAN router on telephone pole
Wildlife officer tracking radio tagged mountain lion
Radio communication. Information such as sound is converted by a transducer such as a microphone to an electrical signal, which modulates a radio wave produced by the transmitter. A receiver intercepts the radio wave and extracts the information-bearing modulation signal, which is converted back to a human usable form with another transducer such as a loudspeaker.
Rotating marine radar antenna on ship.
Laptop computer and typical home wireless router (right) connecting it to the Internet
BBC Local Radio is the BBC's regional radio service for England and the Channel Islands, consisting of 40 stations. Initially, stations had to be co-funded by the BBC and local authorities, which only some Labour-controlled areas proved willing to do. Radio Leicester was the first to launch on 8 November 1967, followed by Sheffield, Merseyside and Nottingham. By the early 1970s, the local authority funding requirement was dropped, and stations spread across the country; many city-based stations later expand their remit to cover an entire county. Today, stations are asked to target their coverage to Dave and Sue, two fictional fifty-five-year-olds.
Fred Allen (born John Florence Sullivan on May 31, 1894 in Cambridge, Massachusetts, died March 17, 1956 in New York City) was an American comedian whose absurdist, pointed radio show (1934–1949) made him one of the most popular and forward-looking humorists in the so-called classic era of American radio.
His best-remembered gag may be his long-running mock feud with friend and fellow comedian Jack Benny. Allen has been considered one of the more accomplished, daring and relevant humorists of his time. A master ad libber, he constantly battled censorship and developed routines the style and substance of which influenced future comic talents. Perhaps more than any of his generation, Fred Allen wielded influence that outlived both his contemporaries and the medium that made him famous.
- Radio December 12, 2006 "...to create, expand, and maintain wikipedia articles related to radio, including radio propagation and reception, radio programming, radio personalities, and the business of radio." (Example: Mutual Broadcasting System)
- Amateur Radio August 24, 2006 "...to improve Wikipedia's articles related to Amateur radio, maintain the amateur radio category and its sub-categories for clean organization, and to produce and maintain templates for Amateur radio-related topic identification." (Example: Amateur radio)
- Radio Stations February 15, 2005 "...to coordinate the activities of creating and maintaining articles about radio stations." (Example: Pulse FM Kingborough & Huon)
- Podcasting January 21, 2007 "...to make Wikipedia's knowledge of notable Podcast and podcast-related information as complete as possible." (Example: Podcast)
||Music radio, Old-time radio, Radio comedy, Radio documentary, Radio drama, Top 40
||BBC Radio, Blue Network, Columbia Broadcasting System, Mutual Broadcasting System, National Broadcasting Company, Sirius Satellite Radio, XM Satellite Radio
||Fred Allen, Gracie Allen, Don Ameche, Jack Benny, Edgar Bergen, Jagadish Chandra Bose, George Burns, Ronald Colman, Jim Connors, Frank Conrad, Norman Corwin, Frankie Crocker, Alice Faye, Stan Freberg, Vaughn Harper, Phil Harris, Bob Hope, Hal Jackson, Spike Jones, Hans von Kaltenborn, Kay Kyser, Frances Langford, Guglielmo Marconi, Elizabeth McLeod, J. Carrol Naish, Ozzie Nelson, Arch Oboler, Dorothy Parker, Virginia Payne, Harold Peary, David Sarnoff, Red Skelton, Kate Smith, Howard Stern, Nikola Tesla, Jonathan Toubin, Lurene Tuttle, Rudy Vallée, Fred Waring, Orson Welles
||Abbott and Costello, Amos 'n' Andy, Arch Oboler's Plays, Burns and Allen, Cavalcade of America, CBS Radio Mystery Theater, Dragnet, Duffy's Tavern, Fibber McGee and Molly, The Goldbergs, The Howard Stern Show, Inner Sanctum Mysteries, The Jack Benny Program, Life with Luigi, Lights Out, Lux Radio Theater, Opie and Anthony, The Archers, The Hitchhiker's Guide to the Galaxy, The Phil Harris-Alice Faye Show, Quiz Kids, The Screen Guild Theater, The Shadow, Suspense, Theater Guild on the Air, Twenty Questions, The Whistler, Yours Truly, Johnny Dollar
||Amateur radio, AM broadcasting, FM broadcasting, International broadcasting, Internet Radio, Digital Radio Mondiale, HD Radio, Digital Audio Broadcasting and GNU Radio, Software-defined radio, Transistor radio, Vacuum tube