How the radio spectrum works



How the radio spectrum works

The radio spectrum is the lower portion of the electromagnetic spectrum.  The radio spectrum is below both the infrared spectrum and the visible spectrum.  The sections of the radio spectrum are called bands.  These bands are subdivided into frequencies and even further divided into channels.  Channels are frequently set aside for certain purposes, but can be changed by one of the regulatory agencies that monitor and regulate the radio spectrum.   Use of the various bands and frequencies is usually determined by individual government agencies on a country by country basis.  In many cases, such as in the United States, these frequencies are leased, sold or licensed to private radio operators. 

Frequency Division

The radio spectrum is subdivided into sub frequencies.  Very low frequencies (VLF) range from 3-30 kHz.  Very low frequencies are used for communication with submarines, heart rate monitors and avalanche beacons.  Low frequencies range from 30-300 kHz are used for navigation signals, AM long wave broadcasting and amateur radio.  300-3,000 kHz are medium frequencies are used for amateur radio and AM medium wave broadcasts.  3,000-10,000 kHz are high frequencies and are used for FM broadcasts, television broadcasts, ground to aircraft communications, maritime mobile communications and weather radio.  Very high frequencies are 30,000 to 300,000 kHz.  Finally, Ultra high frequencies are 300,000-3,000,000 kHz.  These ultra high frequencies broadcast mobile phones, GPS, two way radios, microwave ovens and television broadcasts.

Regulations and Restrictions

All radio transmissions in the United States are monitored and regulated by two separate agencies, the Federal Communications Commission and the National Telecommunications and Information Administration.  The Federal Communications Commission (FCC) regulates the use of the radio spectrum for nongovernmental use.  All use of the radio spectrum by the federal government is controlled by the National Telecommunications and Information Administration (NTIA.)  

The use and redistribution of bands and frequencies can change frequently.  Public use of certain bandwidth can rise to the forefront of public debate when large companies move to purchase the bandwidths or frequencies.  There are a number of groups in the United States that advocate opening access to the radio spectrum, arguing that this would create a greater free market.  Opponents of such open access are necessary to prevent any one entity from controlling the spectrum. 

Additional Readings and Resources

US Frequency Allocation Chart

http://www.ntia.doc.gov/osmhome/allochrt.pdf

The Radio Spectrum for Beginners

http://www.cromwell-intl.com/radio/rf-spectrum.html

Radio Spectrum Allocations 101

http://www.unwantedemissions.com/wp/allocations101.p df

FCC Nods to New Use of Airwaves

http://www.nytimes.com/2008/11/05/technology/interne t/05spectrum.html

Managing the radio spectrum in the new environment

http://www.google.com/url?sa=t&source=web&cd=35&ved=0CD8QFjAEOB4&url=http%3A%2F%2Flirne.net%2Fresources%2Ftr%2Fchapte r11.pdf&rct=j&q=radio%20spectrum&ei=V3BHTcyuIovfgQfFzoD-BQ&usg=AFQjCNFmF-4VW2dyWJ1ng-IE6X2G9aKU6A&cad=rja

Radio spectrum management

http://www.google.com/url?sa=t&source=web&cd=37&ved=0CFAQFjAGOB4&url=http%3A%2F%2Fwww.iop.org%2Feducation%2Fhigher_ed ucation%2Ffellowship%2Ffile_43353.pdf&rct=j&q=radio%20spectrum&ei=V3BHTcyuIovfgQfFzoD-BQ&usg=AFQjCNHeYZLTyKrjBrs-4TwaNGbxSWbG3Q&cad=rja


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