Radio frequency (RF) is a measurement representing the oscillation rate of electromagnetic radiation spectrum, or electromagnetic radio waves, from frequencies ranging from 300 GHz to as low as 9 kHz. With the use of antennas and transmitters, an RF field can be used for various types of wireless broadcasting and communications.
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How radio frequency works
Radio frequency is measured in units called hertz, which represent the number of cycles per second when a radio wave is transmitted. One hertz equals one cycle per second; radio waves range from thousands (kilohertz) to millions (megahertz) to billions (gigahertz) of cycles per second. Microwaves are a type of radio wave with higher frequencies. Radio frequencies are not visible to the human eye.
In a radio wave, the wavelength is inversely proportional to the frequency. If f is the frequency in megahertz and s is the wavelength in meters, then
s = 300/f
As the frequency is increased beyond that of the RF spectrum, electromagnetic energy takes the form of infrared (IR), visible, ultraviolet, X-rays and gamma rays.
Many types of wireless devices make use of RF fields. Cordless and cellphones, radio and television broadcast stations, Wi-Fi and Bluetooth, satellite communications systems, and two-way radios all operate in the RF spectrum. In addition, other appliances outside of communications, including microwave ovens and garage-door openers, operate at radio frequencies. Some wireless devices, like TV remote controls, some cordless computer keyboards and computer mice, operate at IR frequencies, which have shorter electromagnetic wavelengths.
The RF spectrum is divided into several ranges, or bands. With the exception of the lowest-frequency segment, each band represents an increase of frequency corresponding to an order of magnitude (power of 10). The following table depicts the eight bands in the RF spectrum, showing frequency and bandwidth ranges. The super high frequency (SHF) and extremely high frequency (EHF) bands are often referred to as the microwave spectrum.
In the United States, radio frequencies are divided into licensed and unlicensed bands. The Federal Communications Commission issues licenses that permit a commercial entity to have exclusive use of a frequency band in a given location. Unlicensed frequencies are free for public use, but remain a shared medium.