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radio frequency

 
Dictionary: radio frequency
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n. (Abbr. RF)
  1. The frequency of the waves transmitted by a specific radio station.
  2. A frequency in the range within which radio waves may be transmitted, from about 3 kilohertz to about 300,000 megahertz.

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Columbia Encyclopedia: radio frequency
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radio frequency, range of electromagnetic waves with a frequency or wavelength suitable for utilization in radio communication. Some of these waves serve as carriers of the lower-frequency audio waves; others are modulated by video or digital information. Short waves have relatively high frequencies; long waves have relatively low frequencies. Radio waves are identified by their frequencies, expressed in kilohertz (kHz), i.e., thousands of cycles per second, in megahertz (MHz), i.e., millions of cycles per second, or in gigahertz, i.e., billions of cycles per seconds. Signals in the amplitude modulation (AM) broadcast band have frequencies ranging from 540 to 1,800 kHz. Frequency modulation (FM) broadcast frequencies range from 88 MHz to 108 MHz. A range, or band, of radio frequencies is regularly assigned to a broadcasting station or service by the nation in which it operates. In the United States, the Federal Communications Commission is responsible for that task. Countries cooperate on on a worldwide basis through the International Telecommunication Union, which holds periodic conferences. See also the table entitled Radio Frequencies for the classification of radio frequencies.

Medical Dictionary: ra·di·o frequency
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(rā'dē-ō)
n.

A frequency that lies in the range within which radio waves may be transmitted, from about 10 kilohertz per second to about 300,000 megahertz.

WordNet: radio frequency
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Note: click on a word meaning below to see its connections and related words.

The noun has one meaning:

Meaning #1: an electromagnetic wave frequency between audio and infrared

Wikipedia: Radio frequency
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Radio frequency (RF) radiation is a subset of electromagnetic radiation with a wavelength of 100km to 1mm, which is a frequency of 300 Hz to 3000 GHz,[1] respectively. This range of electromagnetic radiation constitutes the radio spectrum and corresponds to the frequency of alternating current electrical signals used to produce and detect radio waves. RF can refer to electromagnetic oscillations in either electrical circuits or radiation through air and space. Like other subsets of electromagnetic radiation, RF travels at the speed of light.

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Radio communication

In order to receive radio signals, for instance from AM/FM radio stations, a radio antenna must be used. However, since the antenna will pick up thousands of radio signals at a time, a radio tuner is necessary to tune in to a particular frequency (or frequency range).[2] This is typically done via a resonator (in its simplest form, a circuit with a capacitor and an inductor). The resonator is configured to resonate at a particular frequency (or frequency band), thus amplifying sine waves at that radio frequency, while ignoring other sine waves. Usually, either the inductor or the capacitor of the resonator is adjustable, allowing the user to change the frequency at which it resonates.[3]

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 they can ionize air to create a conductive path through air. This property is exploited by 'high frequency' units used in electric arc welding, although strictly speaking these machines do not typically employ frequencies within the HF band. 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

See Radio spectrum

In medicine

Radio frequency (RF) energy has been used in medical treatments for over 75 years[4] generally for minimally invasive surgeries and coagulation, including the treatment of sleep apnea.[5]

See also

References

  1. ^ Stan Gibilisco (2002). Physics Demystified. McGraw-Hill. p. 474. ISBN 0071382011. 
  2. ^ Brain, Marshall (2000-12-07). "How Radio Works". HowStuffWorks.com. http://electronics.howstuffworks.com/radio8.htm. Retrieved 2009-09-11. 
  3. ^ Brain, Marshall (2000-12-08). "How Oscillators Work". HowStuffWorks.com. http://electronics.howstuffworks.com/oscillator3.htm. Retrieved 2009-09-11. 
  4. ^ Ruey J. Sung and Michael R. Lauer (2000). Fundamental approaches to the management of cardiac arrhythmias. Springer. p. 153. ISBN 9780792365594. http://books.google.com/books?id=S1fWhl2c5zIC&pg=PA153&dq=rf+coagulation+75-years&lr=&as_brr=3&ei=IIhuSpfBJ6aqlQT-n7nmDg. 
  5. ^ Melvin A. Shiffman, Sid J. Mirrafati, Samuel M. Lam and Chelso G. Cueteaux (2007). Simplified Facial Rejuvenation. Springer. p. 157. ISBN 9783540710967. http://books.google.com/books?id=w1fQK21WK28C&pg=RA1-PA157&dq=rf+coagulation+sleep-apnea&lr=&as_brr=3&ei=ZYduSumzKJCckgT_-bHdDg. 

External links

v • d • e
Radio spectrum

ELF
3 Hz
30 Hz

SLF
30 Hz
300 Hz

ULF
300 Hz
3 kHz

VLF
3 kHz
30 kHz

LF
30 kHz
300 kHz

MF
300 kHz
3 MHz

HF
3 MHz
30 MHz

VHF
30 MHz
300 MHz

UHF
300 MHz
3 GHz

SHF
3 GHz
30 GHz

EHF
30 GHz
300 GHz
v • d • e
Electromagnetic spectrum
← shorter wavelengths       longer wavelengths →
Gamma rays · X-rays · Ultraviolet · Visible · Infrared · Terahertz radiation · Microwave · Radio
Visible (optical)
Violet · Blue · Green · Yellow · Orange · Red
Microwaves
W band · V band · Q band · Ka band · K band · Ku band · X band · S band · C band · L band
Radio
EHF · SHF · UHF · VHF · HF · MF · LF · VLF · ULF · SLF · ELF
Wavelength types

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Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.  Read more
Columbia Encyclopedia. The Columbia Electronic Encyclopedia, Sixth Edition Copyright © 2003, Columbia University Press. Licensed from Columbia University Press. All rights reserved. www.cc.columbia.edu/cu/cup/.  Read more
Medical Dictionary. The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company.  Read more
WordNet. WordNet 1.7.1 Copyright © 2001 by Princeton University. All rights reserved.  Read more
Wikipedia. This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article "Radio frequency".  Read more