Definition

radio frequency (RF, rf)

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.

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.

RF technology

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.

Designation

Abbreviation

Frequencies

Free-space wavelengths

Very Low Frequency

VLF

9 kHz to 30 kHz

33 km to 10 km

Low Frequency

LF

30 kHz to 300 kHz

10 km to 1 km

Medium Frequency

MF

300 kHz to 3 MHz

1 km to 100 m

High Frequency

HF

3 MHz to 30 MHz

100 m to 10 m

Very High Frequency

VHF

30 MHz to 300 MHz

10 m to 1 m

Ultra High Frequency

UHF

300 MHz to 3 GHz

1 m to 100 mm

Super High Frequency

SHF

3 GHz to 30 GHz

100 mm to 10 mm

Extremely High Frequency

EHF

30 GHz to 300 GHz

10 mm to 1 mm

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.

This was last updated in February 2017

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What kinds of radio frequency interference have you had to address in terms of troubleshooting your Wi-Fi network?
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Well written!!! I enjoyed this article very much. Learned a few things too! Thanx!
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