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Very high frequency (VHF) is the ITU designation [1] for the range of radio frequency electromagnetic waves (radio waves) from 30 to 300 megahertz (MHz), with corresponding wavelengths of ten meters to one meter.
Radio waves are defined by the ITU as: "electromagnetic waves of frequencies arbitrarily lower than 3000 GHz, propagated in space without artificial guide". [5] At the high frequency end the radio spectrum is bounded by the infrared band. The boundary between radio waves and infrared waves is defined at different frequencies in different ...
waves: EHF Extremely high frequency: 1 cm: 30 GHz 124 μeV: SHF Super high frequency: 1 dm: 3 GHz 12.4 μeV UHF Ultra high frequency: 1 m: 300 MHz: 1.24 μeV Radio waves: VHF Very high frequency: 10 m 30 MHz 124 neV: HF High frequency: 100 m 3 MHz 12.4 neV MF Medium frequency: 1 km: 300 kHz: 1.24 neV LF Low frequency: 10 km 30 kHz 124 peV: VLF ...
HF's position in the electromagnetic spectrum.. High frequency (HF) is the ITU designation [1] for the band of radio waves with frequency between 3 and 30 megahertz (MHz). It is also known as the decameter band or decameter wave as its wavelengths range from one to ten decameters (ten to one hundred meters).
Extremely high frequency or commonly known as "EHF", is a large broadband that span a radius of about (30 GHz to 300 GHz) for the molecular spectra of radio frequencies. It lies between the super high frequency (3 GHz to 30 GHz) band and the far infrared band (300 GHz to 10 15 ), for which the lower part is the terahertz band .
Radio propagation is the behavior of radio waves as they travel, or are propagated, from one point to another in vacuum, or into various parts of the atmosphere. [1]: 26‑1 As a form of electromagnetic radiation, like light waves, radio waves are affected by the phenomena of reflection, refraction, diffraction, absorption, polarization, and scattering. [2]
Radio waves in vacuum travel at the speed of light. [9] [10] When passing through a material medium, they are slowed depending on the medium's permeability and permittivity. Air is tenuous enough that in the Earth's atmosphere radio waves travel at very nearly the speed of light.
Medical applications of radio frequency (RF) energy, in the form of electromagnetic waves (radio waves) or electrical currents, have existed for over 125 years, [9] and now include diathermy, hyperthermy treatment of cancer, electrosurgery scalpels used to cut and cauterize in operations, and radiofrequency ablation. [10]