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The radials at the antenna base provide a proper ground plane for the types of radio antennas used for long wavelengths. These "half dipole" antennas require grounding or earthing wires in order to function well, since the virtual image of the antenna electrically reflected by the mirror-like ground system is an essential part of the operation ...
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).
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.
If the ground plane is large enough, the radio waves from the remaining upper half of the dipole (a) reflected from the ground plane will seem to come from an image antenna (b) forming the missing half of the dipole, which adds to the direct radiation to form a dipole radiation pattern. So the pattern of a monopole with a perfectly conducting ...
Buried in the ground under the antenna is an enormous radial ground system, which forms the bottom 'plate' of the capacitor with the overhead top load. The antenna must be very large at the VLF frequencies used; the supporting masts are 250–300 metres (820–980 ft) high, and the topload is about 1,900 metres (6,200 ft) in diameter.
The ground plane rods attach to the ground wire of the feedline, the other wire feeds the whip. Since the whip is mounted above ground, the horizontal rods form an elevated ground plane just below the whip to reflect its radiation away from the earth and increase its gain. [2] Used for elevated base station antennas for land mobile radio ...
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