It consists of 4 conducting long wires connected in the form of rhombus or diamond. The complete antenna structure is placed horizontally above the surface of the ground. A rhombic antenna may also be considered as a combination of 2 V antennas or inverted V antennas forming an obtuse angle. The excitation to the antenna is provided through feed lines. This feed line can be two-wire transmission lines or coaxial wire that excites the whole structure. Also, to avoid reflections of the travelling wave the opposite end of the antenna wrt feed line is terminated with a properly adjusted resistor.
This leads to cause the absence of standing waves in any of the legs of the antenna. While designing the rhombic antenna, necessarily it has to be kept in mind that length of all the four conductive wires must be equal, ranging between quarter to one wavelength or more. However, the opposite acute angles of the rhombus must be equal. The physical form and the size of the antenna are decided by the length of the side and the angle between the vertex.
The feed point and the terminating point of the antenna must be properly aligned as the line joining the two forms the axis of the antenna. Generally, the antenna is terminated with a value equivalent to characteristic impedance thereby causing the non-resonant condition to establish.
My planned curtain , at feet high and feet wide, has Referencing a dipole over earth this is Efficiency PA6Z r hombic 2-wave per leg Not given? Yagi 40m Antenna at W8JI 70 x 50 feet x feet 63 degrees 7. In the 's I actually had a true inverted V antenna on an FM broadcast tower in a swampy area with wet rich black loam soil. The apex of the antenna was around feet high with legs going up and coming down several hundred feet long.
The inverted V antenna or vertically polarized half-rhombic is half of a standard rhombic turned on its side. Theoretically the terminated inverted V antenna uses the ground below the antenna to make up the "missing half" of the rhombic.
It also has a single wire connecting the grounds below the antenna. Gain of the inverted V over perfect earth is Gain is now 7. The antenna has a slight loss from a dipole at optimum height. This is with no conductor or antenna changes.
The only change is the soil type, which went from perfect lossless soil to good soil. This actually agrees with my tests at the broadcast station. After one season I removed my large inverted V antennas and went with a regular dipole antenna about feet in the air. The V-beam antenna is the first part of a rhombic antenna.
It omits the closing end of the rhombic. As such, we can model it by removing the outer half of a rhombic. This is a four wavelength-per-leg meter V-beam antenna:. In practice, half of the power is dissipated in the terminating resistance of the antenna. The rest of the power is radiated. The wasted power contributes to the minor lobes.
Figure 1 shows the construction of rhombic antenna for point-to-point communication in olden days. The maximum gain from a rhombic antenna is along the direction of the main axis, which passes through the feed point to terminate in free space. The polarization obtained from a horizontal rhombic antenna is in the plane of rhombus, which is horizontal. Next Patent Wideband microwave a V-type directional antenna. Directional antenna array. Nonresonant antenna. Device for the alternating voltage supply of a load.
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