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English: Diagram of a J-pole antenna, a vertical end-fed half-wave omnidirectional transmitting antenna used in the shortwave frequency bands. It consists of a vertical element a half wavelength (/) long, fed in series with a quarter wavelength (/) transmission line stub, with the coaxial cable feedline (F) from the transmitter attached along the stub.
Counterpoises are typically used in antenna systems for radio transmitters where a good earth ground connection cannot be constructed.. Monopole antennas used at low frequencies, below 3 MHz, such as the mast radiator antennas used for AM broadcasting, require the radio transmitter to be electrically connected to the Earth under the antenna; this is called a ground (or earth).
The J-pole antenna is an end-fed omnidirectional half-wave antenna that is matched to the feedline by a shorted quarter-wave parallel transmission line stub. [5] [1] [6] For a transmitting antenna to operate efficiently, absorbing all the power provided by its feedline, the antenna must be impedance matched to the line; it must have a resistance equal to the feedline's characteristic impedance.
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A monopole antenna is a class of radio antenna consisting of a straight rod-shaped conductor, often mounted perpendicularly over some type of conductive surface, called a ground plane. [ 1 ] [ 2 ] The current from the transmitter is applied, or for receiving antennas the output signal voltage to the receiver is taken, between the monopole and ...
English: Diagram of a ground plane antenna, a common omnidirectional monopole antenna used at VHF and UHF frequencies. It consists of a vertical whip antenna one quarter wavelength long, with 3 or 4 quarter wave rods extending from the base electrically connected to the ground side of the transmission line.
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The antenna feed system or antenna feed is the cable or conductor, and other associated equipment, which connects the transmitter or receiver with the antenna and makes the two devices compatible. [ 1 ] [ 2 ] In a radio transmitter, the transmitter generates an alternating current of radio frequency , and the feed system feeds the current to ...