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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 signals 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 circuits 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
Name
Symbol
Frequency
Wavelength
Applications
Extremely low frequency ELF
a 3 to 30 Hz k 10,000 km to 100,000 km directly audible when converted to sound , communication with submarines
Super low frequency SLF
b 30 to 300 Hz 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
c 300 to 3000 Hz i 100 km to 1,000 km directly audible when converted to sound, communication with mines
Very low frequency VLF
d 3 to 30 kHz h 10 km to 100 km directly audible when converted to sound (below ca. 18-20 kHz; or "ultrasound " 20-30+ kHz)
Low frequency LF
e 30 to 300 kHz g 1 km to 10 km AM broadcasting , navigational beacons , lowFER
Medium frequency MF
f 300 to 3000 kHz f 100 m to 1 km navigational beacons , AM broadcasting , maritime and aviation communication
High frequency HF
g 3 to 30 MHz e 10 m to 100 m shortwave , amateur radio , citizens' band radio
Very high frequency VHF
h 30 to 300 MHz d 1 m to 10 m FM broadcasting , broadcast television , aviation , GPR
Ultra high frequency UHF
i 300 to 3000 MHz c 10 cm to 100 cm broadcast television , mobile telephones , cordless telephones , wireless networking , remote keyless entry for automobiles, microwave ovens , GPR
Super high frequency SHF
j 3 to 30 GHz b 1 cm to 10 cm wireless networking , satellite links, microwave links, Satellite television, door openers.
Extremely high frequency EHF
k 30 to 300 GHz a 1 mm to 10 mm microwave data links, radio astronomy , remote sensing , advanced weapons systems, advanced security scanning
See also
External links
