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In article ,
(Richard Harrison) wrote:
I`ve built and used many rhombics. They all were satisfactory in spite
of somewhat ragged patterns. They are capableof high gain and extreme
bandwidth. They require much space and 4 supports but construction is
simple for the minimalist model.
How critical was the aiming of the antenna? I'm asking because if I
build one, many wavelengths long, it probably won't be easy to move the
poles.
The bigger it is, the more critical. Longest rhombics have the highest gain
and, by necessity, the narrowest beamwidths.
Beamwidth is usually specified as the angle between the two 3 dB points on
the left and right sides of the beam. Most designs either specify the
beamwidth or show you a polar plot from which you can arrive at the
beamwidth by inspection.
It is not inconceivable to make a rhombic structure that pivoted about a
single point at the feed and was supported at the terminated end. An
insulating structure would be needed but if you were to confine it to UHF, a
five-wavelength rhombic would be about 15 feet long. Awkward but not
imposssible; we already do it (or close to it) with some of the larger quad
antennas