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Radio frequency (RF) is a frequency or rate of oscillation within the range of about 3 Hz to 300 GHz. Frequency is a measure of the number of occurrences of a repeating event per unit Time. Oscillation is the repetitive variation typically in Time, of some measure about a central value (often a point of Equilibrium) or between two or more different states This range corresponds to frequency of alternating current electrical signals used to produce and detect radio waves. An alternating current ( AC) is an Electric current whose direction reverses cyclically as opposed to Direct current, whose direction remains constant In the fields of communications, Signal processing, and in Electrical engineering more generally a signal is any time-varying or spatial-varying quantity Radio waves are electromagnetic waves occurring on the Radio frequency portion of the Electromagnetic spectrum. Since most of this range is beyond the vibration rate that most mechanical systems can respond to, RF usually refers to oscillations in electrical circuits or electromagnetic radiation. An electrical network is an interconnection of Electrical elements such as Resistors Inductors Capacitors Transmission lines Voltage Electromagnetic radiation takes the form of self-propagating Waves in a Vacuum or in Matter.

Contents

Special properties of RF electrical signals

Electrical currents that oscillate at RF have special properties not shared by direct current signals. Direct current ( DC) is the unidirectional flow of Electric charge. 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. Arc welding uses a Welding power supply to create an Electric arc between an electrode and the base material to melt the metals at the welding point Another special property is an electromagnetic force that drives the RF current to the surface of conductors, known as the skin effect. The skin effect is the tendency of an alternating electric current (AC to distribute itself within a conductor so that the current density near the surface of the Another property is the ability to appear to flow through paths that contain insulating material, like the dielectric insulator of a capacitor. A dielectric is a nonconducting substance ie an insulator. The term was coined by William Whewell in response to a request from Michael Faraday. The degree of effect of these properties depends on the frequency of the signals.

Frequencies

Name Symbol Frequency Wavelength Applications
Extremely low frequency ELF 3 to 30 Hz 10,000 km to 100,000 km audible 20+ Hz, communication with submarines
Super low frequency SLF 30 to 300 Hz 1,000 km to 10,000 km audible, AC power grids (50 hertz and 60 hertz)
Ultra low frequency ULF 300 to 3000 Hz 100 to 1000 km audible, communication with mines
Very low frequency VLF 3 to 30 kHz 10 to 100 km audible range 20 Hz to 20 kHz (to be audible, energy must be simply converted to sound)
Low frequency LF 30 to 300 kHz 1 to 10 km international broadcasting, navigational beacons, lowFER
Medium frequency MF 300 to 3000 kHz 100 m to 1 km navigational beacons, AM broadcasting, maritime and aviation communication
High frequency HF 3 to 30 MHz 10 to 100 m shortwave, citizens' band radio
Very high frequency VHF 30 to 300 MHz 1 to 10 m FM broadcasting, broadcast television, aviation
Ultra high frequency UHF 300 to 3000 MHz 10 to 100 cm broadcast television, mobile telephones, wireless networking, microwave ovens
Super high frequency SHF 3 to 30 GHz 1 to 10 cm wireless networking, satellite links. Extremely low frequency (ELF is the band of Radio frequencies from 3 to 30 Hz. Communication with submarines when they are submerged is a difficult technological task which requires specific techniques and devices Super Low Frequency (SLF is the Frequency range between 30 Hertz and 300 hertz Electric power transmission, a process in the delivery of Electricity to consumers is the bulk transfer of electrical power The Ultra Low Frequency (ULF is the Frequency range between 300 Hertz and 3 kilohertz Mining is the extraction of valuable Minerals or other geological materials from the earth usually (but not always from an Ore body Very low frequency or VLF refers to radio frequencies (RF in the range of 3 KHz to 30 KHz. Sound' is Vibration transmitted through a Solid, Liquid, or Gas; particularly sound means those vibrations composed of Frequencies Low Frequency or LF refers to Radio Frequencies (RF in the range of 30 kHz&ndash300 kHz International broadcasting is Broadcasting that is deliberately aimed at a foreign rather than a domestic audience A Non-directional beacon ( NDB) is a Radio transmitter at a known location used as an aviation or marine Navigational aid LowFER ( Low - F requency E xperimental R adio is a license-free form of two-way radio communications practiced on frequencies below 500 kHz Medium frequency ( MF) refers to radio frequencies (RF in the range of 300  kHz to 3000 kHz A Non-directional beacon ( NDB) is a Radio transmitter at a known location used as an aviation or marine Navigational aid High frequency (HF radio frequencies are between 3 and 30 MHz. Shortwave Radio operates between the frequencies of 3000 KHz (3 Citizens' Band radio ( CB) is in many countries a system of short-distance simplex radio communications between individuals on a selection of 40 channels within Very high frequency (VHF is the Radio frequency range from 30 MHz to 300 MHz. See also Frequency modulation, FM band FM broadcasting is a broadcast Technology invented by Edwin Howard Armstrong that Terrestrial television is a term which refers to modes of television broadcasting which do not involve satellite transmission The airband or air band is the band of frequencies used for radio communication in Aviation. Terrestrial television is a term which refers to modes of television broadcasting which do not involve satellite transmission Wireless network refers to any type of Computer network that is Wireless, and is commonly associated with a Telecommunications network whose interconnections A microwave oven, or a microwave, is a Kitchen appliance that cooks or heats Food by Dielectric heating. Super high frequency (or SHF) refers to radio frequencies (RF in the range of 3  GHz and 30 GHz Wireless network refers to any type of Computer network that is Wireless, and is commonly associated with a Telecommunications network whose interconnections
Extremely high frequency EHF 30 to 300 GHz 1 to 10 mm microwave data links, radio astronomy, remote sensing, advanced weapons systems, advanced security scanning

See also

External links

Extremely high frequency is the highest Radio frequency band. Microwaves are electromagnetic waves with Wavelengths ranging from 1 mm to 1 m or frequencies between 0 Radio astronomy is a subfield of Astronomy that studies celestial objects at radio frequencies. Remote sensing is the small or large-scale acquisition of information of an object or phenomenon by the use of either recording or real-time sensing device(s that is not in physical The security scan is a device to frisk a person without making physical contact Radio waves are electromagnetic waves occurring on the Radio frequency portion of the Electromagnetic spectrum. The purpose of this article is to outline the most commonly used heat sealing technologies in the Industrial Fabrics market using Engineered Textiles with Polymer coatings Not to be confused with Supersonic. Ultrasound is cyclic Sound pressure with a Frequency greater than the upper

Dictionary

radio frequency

-noun

  1. (uncountable) That part of the electromagnetic spectrum, between about 3 kHz and 300 MHz, within which radio waves are transmitted.
  2. (countable) A frequency in this range.
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