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The radio spectrum is the part of the electromagnetic spectrum with frequencies from 3 Hz to 3,000 GHz (3 THz).Electromagnetic waves in this frequency range, called radio waves, are widely used in modern technology, particularly in telecommunication.
The International Telecommunication Union uses an internationally agreed system for classifying radio frequency signals. Each type of radio emission is classified according to its bandwidth, method of modulation, nature of the modulating signal, and type of information transmitted on the carrier signal.
Radio frequency (RF) is the oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency [1] range from around 20 kHz to around 300 GHz.
The copper cables (transmission lines) which are used to carry lower-frequency radio waves to antennas have excessive power losses at microwave frequencies, and metal pipes called waveguides are used to carry them. Although at the low end of the band the atmosphere is mainly transparent, at the upper end of the band absorption of microwaves by ...
Class B and D stations can be found on any frequencies from 540 kHz to 1700 kHz except where frequencies have been reserved for Class C stations. Class C stations can be found in the lower 48 US states on the frequencies of 1230 kHz, 1240 kHz, 1340 kHz, 1400 kHz, 1450 kHz, and 1490 kHz (commonly known as "graveyard" frequencies).
Extremely high frequency (EHF) is the International Telecommunication Union designation for the band of radio frequencies in the electromagnetic spectrum from 30 to 300 gigahertz (GHz). [ 1 ] [ 2 ] It is in the microwave part of the radio spectrum, between the super high frequency band and the terahertz band .
A discone is exceptionally wideband, offering a frequency range ratio of up to approximately 10:1 , over three octaves above the antenna's lowest frequency, but otherwise only functions just as well as other quarter-wave monopoles: It is omnidirectional, vertically polarized, equally efficient as a monopole, and has gain similar to a ground ...
The radio frequency of bremsstrahlung emission is related to a plasma's electron density through the electron plasma frequency from Equation 1. [17] A plasma with a density n e {\displaystyle n_{e}} can produce emission only at or below the corresponding f p {\displaystyle f_{p}} . [ 18 ]