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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.
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.
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 ...
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).
A discone antenna is a monopole version of a biconical antenna, in which one of the cones is replaced by a disc. It is usually mounted vertically, with the disc at the top and the cone beneath. It is usually mounted vertically, with the disc at the top and the cone beneath.
Yagi antenna for UHF TV reception with 22 parasitic elements; 4 reflectors attached to the vertical bracket at left, and 18 directors attached to the horizontal beam at right. The driven element is attached to the black box next to the reflectors. The antenna is most sensitive to radio waves coming from the right, parallel to the antenna's axis.
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The antenna is resonant at this length, so its input impedance is purely resistive. The input impedance has capacitive reactance below 1 / 4 λ and inductive reactance from 1 / 4 to 1 / 2 λ. The gains given in this section are only achieved if the antenna is mounted over a perfectly conducting infinite ground plane ...