Radio is the technology of using radio waves to carry information, such as sound and images, by systematically modulating properties of electromagnetic energy waves transmitted through space, such as their amplitude, frequency, phase, or pulse width. When radio waves strike an electrical conductor, the oscillating fields induce an alternating current in the conductor. The information in the waves can be extracted and transformed back into its original form.
Radio systems need a transmitter to modulate (change) some property of the energy produced to impress a signal on it, for example using amplitude modulation or angle modulation (which can be frequency modulation or phase modulation). Radio systems also need an antenna to convert electric currents into radio waves, and radio waves into an electric current. An antenna can be used for both transmitting and receiving. The electrical resonance of tuned circuits in radios allow individual frequencies to be selected. The electromagnetic wave is intercepted by a tuned receiving antenna. A radio receiver receives its input from an antenna and converts it into a form that is usable for the consumer, such as sound, pictures, digital data, measurement values, navigational positions, etc. Radio frequencies occupy the range from a 30 Hz to 300 GHz, although commercially important uses of radio use only a small part of this spectrum.
Amateur radio or ham radio is a hobby that is practised by over 16,000 licensed users in India.
Licences are granted by the Wireless and Planning and Coordination Wing (WPC), a branch of the Ministry of Communications and Information Technology. In addition, the WPC allocates frequency spectrum in India. The Indian Wireless Telegraphs (Amateur Service) Rules, 1978 lists five licence categories:
To obtain a licence in the first four categories, candidates must pass the Amateur Station Operator's Certificate examination conducted by the WPC. This exam is held monthly in Delhi, Mumbai, Kolkata and Chennai, every two months in Ahmedabad, Nagpur and Hyderabad, and every four months in some smaller cities. The examination consists of two 50-mark written sections: Radio theory and practice, Regulations; and a practical test consisting of a demonstration of Morse code proficiency in sending and receiving. After passing the examination, the candidate must clear a police interview. After clearance, the WPC grants the licence along with the user-chosen call sign. This procedure can take up to one year. This licence is valid for up to five years.
Each licence category has certain privileges allotted to it, including the allotment of frequencies, output power, and the emission modes. This article list the various frequencies allotted to various classes, and the corresponding emission modes and input DC power.
Degen DE1103, an advanced world mini-receiver with single sideband modulation and dual conversion
A Fisher 500 AM/FM hi-fi receiver from 1959.
2008 Pure One Classic digital radio
An audio signal (top) may be carried by an AM or FM radio wave.
Radio communication. Information such as sound is converted by a transducer such as a microphone to an electrical signal, which modulates a radio wave sent from a transmitter. A receiver intercepts the radio wave and extracts the information-bearing electronic signal, which is converted back using another transducer such as a speaker.
Bakelite radio at the Bakelite Museum, Orchard Mill, Williton, Somerset, UK.
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.
||Being a famous print journalist is like being the best-dressed woman on radio.
Howard Stern (born Howard Allen Stern on January 12, 1954) is an American radio and TV personality, media mogul, humorist, actor, and author. He is best known for his national radio show, which for many years was syndicated on FM radio stations (and a few AM stations) throughout the United States until his last terrestrial radio broadcast on December 16, 2005. He began broadcasting on the subscription-based Sirius satellite radio service on January 9, 2006.
The self-proclaimed "King of All Media" (a humorous reference to Michael Jackson's appellation "The King of Pop") has been dubbed a shock jock for his highly controversial use of scatological, sexual and racial humor. Stern has said that the show was never about shocking people, but primarily intended to offer his honest opinions on a gamut of issues (ranging from world affairs to problems among his own staff). Though controversial, he is one of the highest-paid radio personalities in the United States and the most fined personality in radio broadcast history.
- 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