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English: Graph of the measured base feed resistance and reactance of a typical mast radiator antenna vs the height of the mast. A mast radiator antenna consists of a guyed lattice mast in which the steel mast structure itself is connected to the transmitter and functions as the antenna. It is mounted on a ceramic insulator which keeps it ...
Antenna directivity is the ratio of maximum radiation intensity (power per unit surface) radiated by the antenna in the maximum direction divided by the intensity radiated by a hypothetical isotropic antenna radiating the same total power as that antenna. For example, a hypothetical antenna which had a radiated pattern of a hemisphere (1/2 ...
The category of simple antennas consists of dipoles, monopoles, and loop antennas. Nearly all can be made with a single segment of wire (ignoring the break made in the wire for the feedline connection). [citation needed] Dipoles and monopoles called linear antennas (or straight wire antennas) since their radiating parts lie along a single ...
The antenna can have a smaller or larger number of rod elements; in general, the more elements, the higher the gain and the more directional. Another design used mainly for UHF reception is the reflective array antenna, consisting of a vertical metal screen with multiple dipole elements mounted in front of it.
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 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.
Panel antennas are common at Ultra high frequencies or UHF, where they are often used for cellular/mobile base stations or wireless networking due to their size and directional properties. At very high frequencies, such an antenna would be impractically large for most receiving applications unless implemented as no more than a two-bay design.
The receiving antenna height of 10m dates from the 1950s when receivers were relatively insensitive and used rooftop antennas. Although this may seem unrealistic for typical situations today, when combined with the above threshold it is considered a good proxy for providing coverage to more sensitive modern receivers used without external ...