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Due to their omnidirectional radiation pattern, vertical monopole antennas are commonly used in terrestrial radio communication systems in which the direction to the transmitter or receiver is unknown or constantly changing, [7] such as broadcasting, mobile two-way radios, and wireless devices like cellphones and Wi-Fi networks, [8] [4] because they radiate equal radio power in all horizontal ...
The most common monopole is a vertical, 1 / 4 wave tall, which is the minimum size for it to self-resonate. [o] A one-quarter wave monopole has a gain of 5.12 dBi when mounted over a good ground plane.
A 1 / 4 λ monopole antenna and its ground image together form a 1 / 2 λ dipole that radiates only in the upper half of space. The vertical, Marconi, or monopole antenna is a single-element antenna usually fed at the bottom (with the shield side of its unbalanced transmission line connected to ground). It behaves essentially ...
The gain and input impedance of the antenna is dependent on the length of the whip element, compared to a wavelength, but also on the size and shape of the ground plane used (if any). A quarter wave vertical antenna working against a perfectly conducting, infinite ground will have a gain of 5.19 dBi and a radiation resistance of about 36.8 ohms.
The radiation patterns of a vertical half-wave dipole, an omnidirectional antenna. The horizontal and vertical polar patterns are projections of the 3 dimensional pattern onto horizontal and vertical planes, respectively. An omnidirectional antenna radiates equal signal strength in all horizontal directions, so its horizontal pattern is just a ...
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.
For instance, if a radio wave passing a given location has a flux of 1 pW / m 2 (10 −12 Watts per square meter) and an antenna has an effective area of 12 m 2, then the antenna would deliver 12 pW of RF power to the receiver (30 microvolts RMS at 75 ohms). Since the receiving antenna is not equally sensitive to signals received from all ...
The vertical plane is used to plot an antenna's relative field strength perpendicular to the ground (which directly affects a station's coverage area) on a polar graph. Normally, the maximum of 1.000 or 0 dB is at the side (unless there is beam tilt ), which is labeled 0°, to 90° at the top and −90° at the bottom.