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For a monopole antenna (a), the Earth acts as a ground plane to reflect radio waves directed downwards, making them seem to come from a virtual "image antenna" (b).In Telecommunications, a ground plane is a flat or nearly flat horizontal conducting surface that serves as part of an antenna, to reflect the radio waves from the other antenna elements.
[17] [8] A common type for mounting on masts or stationary structures is the ground plane antenna, consisting of a quarter-wave whip antenna with a ground plane of 3 or 4 wires or rods a quarter-wavelength long radiating horizontally or diagonally from its base, connected to the ground side of the feedline. [18]
The ground rods create a ground plane under the antenna which increases the gain. The ground rods may extend horizontally from the base, but in antennas fed by coaxial cable as shown here they are usually sloped downward to increase the radiation resistance of the antenna from the 36 ohms of a quarter wave monopole closer to 50 ohms, so the ...
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).
A whip antenna with several rods extending horizontally from base of the whip in a star-shaped pattern, similar to an upside-down radiate crown, that form the artificial, elevated ground plane that gives the antenna its name. The ground plane rods attach to the ground wire of the feedline, the other wire feeds the whip. Since the whip is ...
In telecommunications and antenna design, an image antenna is an electrical mirror-image of an antenna element formed by the radio waves reflecting from a conductive surface called a ground plane, such as the surface of the earth. It is used as a geometrical technique in calculating the radiation pattern of the antenna.
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The inverted-L antenna is a monopole antenna bent over to run parallel to the ground plane. It has the advantage of compactness and a shorter length than the 1 4 λ {\displaystyle {\tfrac {1}{4}}\lambda } monopole, but the disadvantage of a very low impedance, typically just a few ohms if fed at the base, while a base fed 1 4 λ {\displaystyle ...