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A horizontal rhombic antenna radiates horizontally polarized radio waves at a low elevation angle off the pointy ends of the antenna. If the sections are joined by a resistor at either of the acute (pointy) ends, then the antenna will receive from and transmit to only the direction the end with the resistor points at.
The rhombic is a travelling wave antenna, Each segment of the rhombus has a radiation pattern as shown (grey) having two lobes pointed forward at a certain angle. By making the corner angle equal to twice the tilt angle, the main lobes of each of the 4 sides point in the same direction and reinforce each other, increasing the gain.
In most antennas, the radiation from the different parts of the antenna interferes at some angles; the radiation pattern of the antenna can be considered an interference pattern. This results in minimum or zero radiation at certain angles where the radio waves from the different parts arrive out of phase , and local maxima of radiation at other ...
The rhombic is a nonresonant traveling wave antenna so the length of the elements is not critical, each of the 4 sides is several UHF wavelengths long. The antenna is composed of two wires which are connected at the near end (upper left) with a resistor equal to the characteristic impedance of 470 - 500 ohms, and at the far end to the 300 ohm ...
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 antenna acts similarly to an electrically short dipole or monopole, equivalent to a 1 / 4 wave vertical and the radiation pattern, [citation needed] similar to these antennas is omnidirectional, with maximum radiation at right angles to the helix axis. For monofilar designs the radiation is linearly polarized parallel to
The amount of reflection at these two sites varies with the flare angle of the horn (the angle the sides make with the axis). In narrow horns with small flare angles most of the reflection occurs at the mouth of the horn. The gain of the antenna is low because the small mouth approximates an open-ended waveguide, with a large impedance step. As ...
For most antennas the boresight is the axis of symmetry of the antenna. For example, for axial-fed dish antennas, the antenna boresight is the axis of symmetry of the parabolic dish, and the antenna radiation pattern (the main lobe) is symmetrical about the boresight axis. Most antennas boresight axis is fixed by their shape and cannot be changed.