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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.
A horizontal rhombic antenna radiates horizontally polarized radio waves at a low elevation angle off the acute end of the antenna opposite the feedline. Its principal advantages over other types of antenna are its simplicity, high forward gain and wide bandwidth , the ability to operate over a wide range of frequencies.
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 ...
4nec2 - A free NEC2/NEC4 implementation for Microsoft Windows. It is a tool for designing 2D and 3D antennas and modeling their near-field/far-field radiation patterns. Numerical Electromagnetics Code NEC2 unofficial home page - NEC2 documentation and code examples; MMANA-GAL basic - A free antenna modeling program based on MININEC. Opens .MAA ...
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 ...
Omnidirectional radiation patterns are produced by the simplest practical antennas, monopole and dipole antennas, consisting of one or two straight rod conductors on a common axis. Antenna gain (G) is defined as antenna efficiency (e) multiplied by antenna directivity (D) which is expressed mathematically as: =.
Radiant intensity is used to characterize the emission of radiation by an antenna: [2], = (), where E e is the irradiance of the antenna;; r is the distance from the antenna.; Unlike power density, radiant intensity does not depend on distance: because radiant intensity is defined as the power through a solid angle, the decreasing power density over distance due to the inverse-square law is ...