Radio frequency
42852
224561679
2008-07-09T12:35:00Z
66.53.215.173
/* Frequencies */
'''Radio frequency''' ('''RF''') is a [[frequency]] or rate of [[oscillation]] within the range of about 3 [[Hz]] to 300 GHz. This range corresponds to frequency of [[alternating current]] [[electrical signal]]s used to produce and detect [[radio waves]]. Since most of this range is beyond the vibration rate that most mechanical systems can respond to, RF usually refers to oscillations in [[electrical circuit]]s or [[electromagnetic radiation]].
== Special properties of RF electrical signals ==
Electrical currents that oscillate at RF have special properties not shared by [[direct current]] signals. One such property is the ease with which it can ionize air to create a conductive path through air. This property is exploited by 'high frequency' units used in electric [[arc welding]]. Another special property is an electromagnetic force that drives the RF current to the surface of conductors, known as the [[skin effect]]. Another property is the ability to appear to flow through paths that contain insulating material, like the [[dielectric]] insulator of a capacitor. The degree of effect of these properties depends on the frequency of the signals.
== Frequencies ==
{| class="wikitable sortable"
|-
! Name !! Symbol !! Frequency !! Wavelength !! Applications
|-
| [[Extremely low frequency]] || ELF || {{sort|a|3 to 30 Hz}} || {{sort|k|10,000 km to 100,000 km}} || directly audible when converted to [[sound]], [[communication with submarines]]
|-
| [[Super low frequency]] || SLF || {{sort|b|30 to 300 Hz}} || {{sort|j|1,000 km to 10,000 km}} || directly audible when converted to sound, [[AC power grids]] (50 hertz and 60 hertz)
|-
| [[Ultra low frequency]] || ULF || {{sort|c|300 to 3000 Hz}} || {{sort|i|100 km to 1,000 km}} || directly audible when converted to sound, communication with [[Mining|mines]]
|-
| [[Very low frequency]] || VLF || {{sort|d|3 to 30 kHz}} || {{sort|h|10 km to 100 km}} || directly audible when converted to sound
|-
| [[Low frequency]] || LF || {{sort|e|30 to 300 kHz}} || {{sort|g|1 km to 10 km}} || [[international broadcasting]], [[non-directional beacon|navigational beacons]], [[lowFER]]
|-
| [[Medium frequency]] || MF || {{sort|f|300 to 3000 kHz}} || {{sort|f|10 m to 1 km}} || [[Non-directional beacon|navigational beacons]], [[AM broadcasting]], maritime and aviation communication
|-
| [[High frequency]] || HF || {{sort|g|3 to 30 MHz}} || {{sort|e|10 m to 100 m}} || [[shortwave]], [[citizens' band radio]]
|-
| [[Very high frequency]] || VHF || {{sort|h|30 to 300 MHz}} || {{sort|d|1 m to 10 m}} || [[FM broadcasting]], [[broadcast television]], [[airband|aviation]], [[Ground-penetrating radar|GPR]]
|-
| [[Ultra high frequency]] || UHF || {{sort|i|300 to 3000 MHz}} || {{sort|c|10 cm to 100 cm}} || [[broadcast television]], [[mobile telephones]], [[wireless networking]], [[remote keyless entry]] for automobiles, [[microwave oven]]s, [[Ground-penetrating radar|GPR]]
|-
| [[Super high frequency]] || SHF || {{sort|j|3 to 30 GHz}} || {{sort|b|1 cm to 10 cm}} || [[wireless networking]], satellite links, microwave links, Satellite television, door openers.
|-
| [[Extremely high frequency]] || EHF || {{sort|k|30 to 300 GHz}} || {{sort|a|1 mm to 10 mm}} || [[microwave]] data links, [[radio astronomy]], [[remote sensing]], advanced weapons systems, advanced [[security scan]]ning
|}
==See also==
* [[Radio waves]]
* [[Frequency allocation]]
* [[Plastic Sealing/Welding Technologies]]
* [[Ultrasound]]
* [[RF connector]]
== External links ==
*[http://www.vlf.it/frequency/bands.html Definition of frequency bands (VLF, ELF … etc.) IK1QFK Home Page (vlf.it)]
*[http://www.sengpielaudio.com/calculator-wavelength.htm Radio, light, and sound waves, conversion between wavelength and frequency]
*[http://www.rfzone.org/free-rf-ebooks/ RF eBooks - Some free RF related eBooks]
*[http://www.myrf.org RF and Telecommunication eBooks]
*[http://www.sunmantechnology.com/resources_gls_rfts.html RF Terms Glossary]
{{radio_spectrum}}
{{EMSpectrum}}
[[Category:Radio spectrum]]
[[Category:Radio technology|Radio waves]]
[[Category:Waves|Radio waves]]
[[Category:Electromagnetic spectrum|Radio waves]]
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[[pt:Ondas de rádio]]
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