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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.
Consists of a long horizontal wire crossing the gap between two towers, with a vertical wire attached to the center of the horizontal wire, hanging down from its center; the dangling vertical wire is the radiating part of the antenna.
An omnidirectional antenna radiates equal signal strength in all horizontal directions, so its horizontal pattern is just a circle. It is a fundamental property of antennas that the receiving pattern (sensitivity as a function of direction) of an antenna when used for receiving is identical to the far-field radiation pattern of the antenna when ...
So the vertical portion of the antennas are much shorter than λ/4. These "electrically short" antennas have low radiation resistance and can't radiate much power. The horizontal wire in the T antenna doesn't radiate radio waves but instead functions as a "capacitive top-load" to add capacitance to the antenna, increasing the current in the top ...
The words antenna and aerial are used interchangeably. Occasionally the equivalent term "aerial" is used to specifically mean an elevated horizontal wire antenna. The origin of the word antenna relative to wireless apparatus is attributed to Italian radio pioneer Guglielmo Marconi.
Omnidirectional antennas oriented vertically are widely used for nondirectional antennas on the surface of the Earth because they radiate equally in all horizontal directions, while the power radiated drops off with elevation angle so little radio energy is aimed into the sky or down toward the earth and wasted.
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A closely related antenna is the inverted-L antenna. This is similar to the T-antenna except that the vertical feeder wire, instead of being attached to the center of the horizontal topload wires, is attached at one end. The name comes from its resemblance to an inverted letter "L" (Γ).