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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.
In telecommunications, the effective height of an antenna is the height of the antenna's center of radiation above the ground. In low-frequency applications involving loaded or nonloaded vertical antennas, the effective height is the moment of the current distribution in the vertical section, divided by the input current. For an antenna with a ...
The typical height of a 'T' antenna is shorter than the quarter wavelength required for resonance. A 'T' antenna is distinguished from the similar 'L' antenna by the place where the dangling, radiating wire attaches to the horizontal cross wire: For the 'T' antenna the dangling wire attaches to the exact center of the top horizontal wire.
Most often, a panel antenna will be constructed as multiple "bays" - each consisting of an individual dipole placed before a shared reflector - with all of these bays connected in parallel to increase received signal strength. These forms of antennae were introduced in the late 1980s as a "C.F.R." by C.F.R. America (Circa 1989).
For transmissions in the shortwave range, there is little to be gained by raising the antenna more than a half to three quarters of a wavelength above ground level, and at lower frequencies and longer wavelengths, the height becomes infeasibly great (greater than 85 metres (279 ft)). Shortwave transmitters rarely use masts taller than about 100 ...
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 ...
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An ideal monopole antenna radiates maximum power in horizontal directions at a height of 225 electrical degrees, about 5 / 8 or 0.625 of a wavelength (this is an approximation valid for a typical finite thickness mast; for an infinitely thin mast the maximum occurs at / = 0.637 [6]) As shown in the diagram, at heights below a half ...