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A common type of monopole antenna at these frequencies for mounting on masts or structures consists of a quarter-wave whip antenna with a ground plane consisting of 3 or 4 wires or rods a quarter-wave long radiating horizontally or diagonally from its base connected to the ground side of the feedline; this is called a ground-plane antenna.
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.
Another mobile antenna is the continuously loaded half-wave version. They do not require a ground plane to present a near-50 ohm load to the radio, and are often used on fiberglass vehicles such as snowmobiles or boats. They are also useful in base stations where circumstances preclude the use of a ground-plane antenna.
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 ...
Whips mounted on vehicles use the metal skin of the vehicle as a ground plane. In hand-held devices usually no explicit ground plane is provided, and the ground side of the antenna's feed line is just connected to the ground (common) on the device's circuit board. [2] Therefore, the radio itself serves as a rudimentary ground plane.
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 ...