Radio frequency

Radio Frequency

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Radio frequency

Radio frequency (RF) is a frequency

Frequency

Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency....
or rate of oscillation

Oscillation

Oscillation is the repetitive variation, typically in time, of some measure about a central value or between two or more different states. Familiar examples include a swinging pendulum and Alternating current power....
within the range of about 3 Hz

Hz or hz may mean:*Herero language *Hertz, unit of frequency*Hamilton Zoo, New Zealand...
to 300 GHz. This range corresponds to frequency of alternating current

Alternating current

In alternating current the movement of electric charge periodically reverses direction. An electric charge would for instance move forward, then backward, then forward, then backward, over and over again....
electrical signals used to produce and detect radio waves

Radio waves

Radio waves are Electromagnetic radiation 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.

trical currents that oscillate at RF have special properties not shared by direct current

Direct current

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Encyclopedia

Radio frequency (RF) is a frequency

Frequency

Oscillation

Hz or hz may mean:*Herero language *Hertz, unit of frequency*Hamilton Zoo, New Zealand...
to 300 GHz. This range corresponds to frequency of alternating current

Alternating current

Radio waves

Special properties of RF electrical signals

Electrical currents that oscillate at RF have special properties not shared by direct current

Direct current

Direct current is the unidirectional flow of electric charge. Direct current is produced by such sources as battery , thermocouples, solar cells, and commutator-type electric machines of the dynamo type....
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

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....
, 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

Skin effect

The skin effect is the tendency of an alternating current to distribute itself within a Conductor so that the current density near the surface of the conductor is greater than that at its core....
. Another property is the ability to appear to flow through paths that contain insulating material, like the dielectric

Dielectric

A dielectric is a nonconducting substance, i.e. an Insulator . The term was coined by William Whewell in response to a request from Michael Faraday....
insulator of a capacitor. The degree of effect of these properties depends on the frequency of the signals.

Frequencies

Name	Symbol	Applications
Extremely low frequency Extremely low frequency Extremely low frequency is the band of radio frequencies from 3 to 30 Hertz, at one time used by the United States and Soviet Navy/Russian Navy to Communication with submarines....	ELF	Directly audible when converted to sound Sound Sound is vibration transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a threshold of hearing to be heard, or the sensation stimulated in organs of hearing by such vibrations.... , communication with submarines Communication with submarines Communication with submarines when they are submerged is a difficult technological task which requires specific techniques and devices. This is because electromagnetic radiation used in radio communication cannot travel through thick Electrical conductors such as salt water....
Super low frequency Super low frequency Super Low Frequency is the frequency range between 30 hertz and 300 hertz. This frequency range includes the frequencies of Alternating current Electric power transmission ....	SLF	Directly audible when converted to sound, AC power grids Electric power transmission Electric power transmission is the bulk transfer of electrical power , a process in the delivery of electricity to consumers. A power transmission grid typically connects power plants to multiple Electrical substation near a populated area.... (50–60 Hz)
Ultra low frequency Ultra low frequency The Ultra Low Frequency is the frequency range between 300 hertz and 3 kilohertz. Many types of waves in the ULF frequency band can be observed in the magnetosphere and on the ground....	ULF	Directly audible when converted to sound, communication with mines Mining Mining is the extraction of value minerals or other geology materials from the earth, usually from an ore body, vein or seam. Materials recovered by mining include base metals, precious metals, iron, uranium, coal, diamonds, limestone, oil shale, Sodium chloride and potash....
Very low frequency Very low frequency Very low frequency or VLF refers to radio frequency in the range of 3 kHz to 30 kHz. Since there is not much Bandwidth in this band of the radio spectrum, only the very simplest signals are used, such as for radio navigation....	VLF	Directly audible when converted to sound (below ca. 20 kHz; or ultrasound Ultrasound Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing . Although this limit varies from person to person, it is approximately 20 Hertz in healthy, young adults and thus, 20 kHz serves as a useful lower limit in describing ultrasound.... otherwise)
Low frequency Low frequency Low Frequency or LF refers to Radio Frequency in the range of 30 kHz–300 kHz. In Europe, and parts of North Africa and of Asia, part of the LF spectrum is used for longwave service....	LF	AM broadcasting AM broadcasting AM broadcasting is the process of radio broadcasting using amplitude modulation.... , navigational beacons Non-directional beacon A Non-directional beacon is a radio transmitter at a known location, used as an aviation or marine navigational aid. As the name implies, the signal transmitted does not include inherent directional information, in contrast to other navigational aids such as VHF omnidirectional range and TACAN.... , lowFER LowFER LowFER is a license-free form of two-way radio communications practiced on frequencies below 500 kHz....
Medium frequency Medium frequency Medium frequency refers to radio frequency in the range of 300 Hertz to 3000 kHz. Part of this band is the medium wave AM broadcast band....	MF	Navigational beacons, AM broadcasting AM broadcasting AM broadcasting is the process of radio broadcasting using amplitude modulation.... , maritime and aviation communication
High frequency High frequency High frequency radio frequency are between 3 and 30 Megahertz. Also known as the decameter band or decameter wave as the wavelengths range from one to ten decameters ....	HF	Shortwave Shortwave Shortwave radio operates in the frequency range of 3,000 kHz to 30,000 kHz . In radio, short wavelength corresponds to high frequency given the inverse relationship between frequency and wavelength, thus, ?shortwave radio? is denominated so, because its wavelengths are shorter than the long wave-lengths used in early radio communications; m... , amateur radio Amateur radio Amateur radio, often called Etymology of ham radio, is both a hobby and a service in which participants, called "hams," use various types of radio communications equipment to communicate with other radio amateurs for Public services, recreation and self-training.... , citizens' band radio Citizens' band radio Citizens' Band radio is, in many countries, a system of short-distance radio communications between individuals on a selection of 40 channels within the 27-Hertz band.... , skywave propagation
Very high frequency Very high frequency VHF is the radio frequency range from 30 megahertz to 300 megahertz. Frequencies immediately below VHF are denoted High frequency , and the next higher frequencies are known as Ultra high frequency ....	VHF	FM broadcasting FM broadcasting FM broadcasting is a broadcasting technology invented by Edwin Howard Armstrong that uses frequency modulation to provide high-fidelity sound over broadcast radio.... , amateur radio Amateur radio Amateur radio, often called Etymology of ham radio, is both a hobby and a service in which participants, called "hams," use various types of radio communications equipment to communicate with other radio amateurs for Public services, recreation and self-training.... , broadcast television, aviation Airband The airband or air band is the band of frequency used for radio communication in aviation. Airband is used to mean the VHF band between 108 Hertz and 137 MHz, which covers its use for commercial aviation and general aviation aviation, radio navigations, air traffic control and other uses.... , GPR Ground-penetrating radar Ground-penetrating radar is a Geophysics method that uses radar pulses to image the subsurface. This non-destructive method uses electromagnetic radiation in the microwave band of the radio spectrum, and detects the reflected signals from subsurface structures.... , MRI
Ultra high frequency Ultra high frequency Ultra high frequency designates a range of Electromagnetic radiation waves with frequency between 300 megahertz and 3 gigahertz . Also known as the decimetre band or decimetre wave as the wavelengths range from ten to one decimetres....	UHF	Broadcast television, amateur radio Amateur radio Amateur radio, often called Etymology of ham radio, is both a hobby and a service in which participants, called "hams," use various types of radio communications equipment to communicate with other radio amateurs for Public services, recreation and self-training.... , mobile telephones, cordless telephones, wireless network Wireless network Wireless network refers to any type of computer network that is wireless, and is commonly associated with a telecommunications network whose interconnections between Node is implemented without the use of wires.... ing, remote keyless entry for automobiles, microwave oven Microwave oven A microwave oven, or a microwave, is a kitchen appliance that cookings or heats food by dielectric heating. This is accomplished by using microwave radiation to heat water and other dipole within the food.... s, GPR
Super high frequency Super high frequency Super high frequency refers to radio frequency in the range of 3 Hertz and 30 GHz. Also known as the centimeter band or centimeter wave as the wavelengths range from ten to one centimeters....	SHF	Wireless networking, satellite links, microwave links, satellite television, door openers
Extremely high frequency Extremely high frequency Extremely high frequency is the highest radio frequency band . EHF runs the range of frequencies from 30 to 300 gigahertz, above which electromagnetic radiation is considered to be low infrared light, also referred to as terahertz radiation....	EHF	Microwave Microwave Microwaves are electromagnetic radiation with wavelengths ranging from 1 mm to 1 m, or frequency between 0.3 hertz and 300 GHz.... data links, radio astronomy Radio astronomy Radio astronomy is a subfield of astronomy that studies Astronomical object at radio frequency. The initial detection of radio waves from an astronomical object was made in the 1930s, but subsequent advances have identified a number of different sources of radio emission.... , remote sensing Remote sensing 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 that is not in physical or intimate contact with the object .... , advanced weapons systems, advanced security scan Security scan The security scan is a device to frisking a person without making physical contact.One technology is the millimeter wave scanner, in which extremely high frequency radio waves are reflected off the body to make an image on which one can see anything hidden under the clothes.... ning

Radio frequency

Special properties of RF electrical signals

Frequencies

See also

External links