Radio frequency
Oscillation rate enabling radio wave radiation and technology.
Radio frequency (RF) refers to the oscillation rate of an alternating electric current, voltage, or electromagnetic field within the range from around 20 kHz to around 300 GHz. These frequencies enable energy from an oscillating current to radiate off a conductor into space as radio waves, forming the basis of radio technology and numerous other applications.
- frequency_range
- ~20 kHz to ~300 GHz
- lower_bound_note
- Different sources specify different upper and lower bounds
- key_property
- Energy from RF currents can radiate as electromagnetic waves (radio waves)
- governing_body
- International Telecommunication Union (ITU)
- related_bands
- Microwave (≥1 GHz), Millimeter wave (≥30 GHz)
- applications
- Broadcasting, voice communication, data communication, radar, radiolocation, medical treatments, remote control
Lore & Background
Electric currents oscillating at radio frequencies exhibit properties distinct from direct current or lower-frequency alternating current. RF currents can radiate energy into space as electromagnetic waves, which is the foundation of radio technology. They also display the skin effect, flowing along the surface of conductors rather than penetrating deeply. When applied to the body, RF currents often do not cause the painful sensation or muscular contraction of lower-frequency electric shock, as the rapid direction change prevents nerve membrane depolarization; however, they can cause internal injury and serious superficial burns known as RF burns.
Reader's Guide
Radio frequency is central to modern communications and technology. Its ability to radiate energy as radio waves enables broadcasting, voice and data communication, radar, radiolocation, medical treatments, and remote control. The radio spectrum is divided into bands by the ITU, with frequencies above 1 GHz termed microwave and above 30 GHz designated millimeter wave. RF currents exhibit unique behaviors: they can ionize air (used in electric arc welding), appear to flow through insulating materials due to decreasing capacitive reactance at higher frequencies, and can be blocked by coils due to increasing inductive reactance. They also reflect from discontinuities in cables, causing standing waves, and are efficiently carried by transmission lines like coaxial cables. Test equipment for RF becomes more specialized at higher frequencies, with signal generators commonly used for testing and calibration.
Did You Know?
- RF currents do not penetrate deeply into conductors but flow along surfaces, known as the skin effect.
- RF currents can ionize air, creating a conductive path exploited in electric arc welding.
- RF currents can appear to flow through insulating materials because capacitive reactance decreases with increasing frequency.
- RF currents can be blocked by a coil of wire because inductive reactance increases with increasing frequency.
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