What Are Radio Stations?
One-way transmitters of information and entertainment to a mass audience.
The classic logo of WMAQ which entertained and informed Chicago and much of the eastern U.S. from 1922-2000 via a clear-channel 50,000 watt AM signal on 670 kHz.
Radio is the transmission of intelligence by modulating waves of electromagnetic radiation at specific frequencies. Radio signals move at the speed of light and are said to travel over the air.
A broadcast is the one-way transmission of program content intended to reach a mass audience. Radio programs transmitted over the air are said to be on the air. Broadcasting of audio to mass audiences also is accomplished via streaming media on the Internet, cable, local wire networks and satellites.
A radio station transmits information and entertainment programs to a mass audience, either over the air or via streaming media.
In the United States, the Federal Communications Commission (FCC) licenses over-the-air AM, FM, LPFM, FM translator and FM booster radio stations. The Audio Division of the FCC's Media Bureau licenses commercial, noncommercial and educational stations.
Radio stations can be linked together as networks to broadcast a common program content.
Amplitude modulation (AM) is a means of encoding audio on an over-the-air radio transmission. AM stations are known as standard broadcast stations because AM was the first form used to broadcast signals to the public. AM stations also are known as mediumwave stations. To restrict signals to local areas, more than half of all AM stations in the U.S. are daytime stations or stations allowed to transmit only low power at night. In the U.S., standard AM broadcasts are in the frequency range 535 kHz-1.7 mHz.
Frequency modulation (FM) is a means of encoding audio on an over-the-air radio frequency transmission. FM full power, low power, translator and booster stations transmit in the 88-108 MHz frequency range. Only non-commercial educational radio stations are licensed in the 88-92 MHz frequency range. Commercial stations and non-commercial educational stations operate in the 92-108 MHz range. FM radio became more popular than AM because of its noise-free reception.
Low Power FM Service
An LPFM radio station uses a low transmitter power to broadcast an FM signal over short distances. They are used mainly by educational institutions and some public safety travelers information groups.
How many U.S. radio stations are on the air?
Radio stations on the air 14,619 AM stations 4,782 FM commercials stations 6,526 FM educational stations 3,311 Low-power FM stations 859 FM translators and boosters 6,131 Source: U.S. Federal Communications Commission, December 31, 2010
Shortwave radio enables long-range communication. International shortwave broadcasts are in the frequency range 5.9-26.1 mHz. While hundreds of shortwave radio stations remain on the air around the globe, the rise of the internet has convinced many broadcasters to discontinue shortwave transmissions.
The program content of Internet radio – aka web radio, streaming radio, net radio, e-radio – is audio information and entertainment webcast across the global Internet, rather than transmitted wirelessly over the air. Some 50,000 stations broadcast on the Internet around the world.
- Internet radio differs from on-demand file serving because Internet radio listeners receive a continuous stream of audio that can't be paused or replayed, which simulates a traditional over-the-air radio broadcast.
- Internet radio is not podcasting, which involves downloading rather than streaming. Many traditional over-the-air radio stations and networks offer Internet radio services.
Digital radio is the transmission and reception of sound that has been processed using the kind of technology used in compact discs (CD). The radio transmitter converts sound into patterns of numbers, or digits, thus the name digital radio.
Tribal and Rural Radio
- FM digital radio provides clear sound comparable in quality to CDs. Digital receivers provide significantly clearer sound than conventional analog radios, just as CDs sound clearer than record albums.
- AM digital radio provides sound quality equivalent to that of standard analog FM, and sounds dramatically better than analog AM broadcasts.
- Digital radio reception is resistant to interference and eliminates many imperfections of analog radio transmission and reception. There is some interference to digital radio signals in areas that are distant from a station's transmitter.
The Tribal and Rural Radio service encourages Native Nations to broadcast radio programming that focuses on tribal culture, language and historic preservation.
Carrier Current Campus Radio Stations
Carrier Current Stations, also known as Campus Radio Stations, do not require an FCC license to operate. A carrier current station transmits an AM radio frequency signal on a frequency between 535-1705 kHz by injecting it into an electrical power line. The coverage area of a carrier current station is 200 feet from the power line.
Part 15 Devices
Unlicensed operation on the AM and FM radio broadcast bands is permitted for extremely low powered devices covered under Part 15 of the FCC's rules. The devices are limited to a range of 200 feet.
Travelers Information Service
Governmental entities, cities, towns, park districts and other authorities may operate a low power AM radio station in the TIS service to disseminate information to travelers.
Pirate radio is the illegal transmission over the air of radio programs.
Learn more . . .
Federal Communications Commission FCC FCC Media Bureau Audio Division FCC Broadcast Station Totals - 1990 to Present FCC Radio and Television Timeline Radio's 90th Anniversary International Broadcasting History Film, Television & the Internet Web and Internet History Over-The-Air Programming Wikipedia Radio Propagation Wikipedia Radio Wikipedia Amplitude Modulation Wikipedia AM Broadcasting Wikipedia Frequency Modulation Wikipedia FM Broadcasting Wikipedia Campus Radio Wikipedia Carrier Current Wikipedia Medium Wave Wikipedia Shortwave Wikipedia Shortwave Listening Wikipedia Internet Radio Wikipedia TuneIn 50,000 radio stations online Reciva Internet Radio Digital Radio Wikipedia Podcasting Wikipedia Streaming Media Wikipedia Satellite Radio Wikipedia Disc Jockey Wikipedia Computer DJ Wikipedia Pirate Radio Wikipedia
Resources for Courses »
© 2011 Dr. Anthony Curtis, Mass Communication Dept., University of North Carolina at Pembroke email home page