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Small rhombic UHF television antenna from 1952. Its broad bandwidth allowed it to cover the 470 to 890 MHz UHF television band. A rhombic antenna is made of four sections of wire suspended parallel to the ground in a diamond or "rhombus" shape. Each of the four sides is the same length – about a quarter-wavelength to one wavelength per ...
The antenna consists of a wire suspended above the ground in the shape of a rhombus, terminated at one end by a resistor equal the the wire's characteristic impedance, about 400 to 600 ohms, and at the other end connected to the feedline to the receiver. The rhombic is a travelling wave antenna, Each segment of the rhombus has a radiation ...
Similar to how a vertical monopole uses its ground system to produce a "phantom" image of the rest of a dipole, the missing lower half of the half-loop is replaced by its ground-plane image. If shaped like a half of a square, a half-loop can operate either as a loop antenna or on its first harmonic as a dipole antenna whose ends have been bent ...
It is a simple half-wave dipole antenna used to receive the VHF television bands, consisting in the US of 54 to 88 MHz and 174 to 216 MHz , with wavelengths of 5.5 to 1.4 m (18 to 5 feet). It is constructed of two telescoping rods attached to a base, which extend out to about 1 m (3.3 feet) length (approximately one-quarter wavelength at 54 MHz ...
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 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.
An antenna focuses the radio waves in a certain direction. Usually, this is called the main direction. Because of that, in other directions less energy will be emitted. The gain of an antenna, in a given direction, is usually referenced to an (hypothetical) isotropic antenna, which emits the radiation evenly strong in all directions.
The coaxial collinear (COCO) antenna uses transposed coaxial sections to produce in-phase half-wavelength radiators. [5] A Franklin array uses short U-shaped half-wavelength sections whose radiation cancels in the far-field to bring each half-wavelength dipole section into equal phase. Another type is the omnidirectional microstrip antenna (OMA ...