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Art wrote:
"The computer program is built on those mathematics, and an antenna program will ALLWAYS produce radiators in equalibrium which means at an angle." Arnold B. Bailey disagrees in "TV and Other Receiving Antennas". On page 367 he writes: "The directional action of a rod antenna best can be analyzed by considering the rod as consisting of many tiny sections, connected together to form a metallic circuit. A typical small segment X - X is shown in Fig. 7-28 B; its position in a half-wave center-fed antenna is indicated in part (A) of the figure. Each tiny section may be taken sufficiently short compared to a wavelength so that the electromagnetic wave acts practically instantaneously throughout one section, and hence induces a substantially uniform current in that section. Such a short antenna segment has a simple directional response pattern, indicated in Fig. 7-28B, which is basic for all directivity calculations, since all antenns may be considered to be made up of these tiny segments. This fundamental response pattern varies as the cosine of the angle (which we shall call theta) between the direction of the incoming wave and the perpendicular through the center of the segment X - X, as indicated in part (B) of the figure. If E stands for the value of the field intensity (strength of the electric vector), then we can characterize the directional response by the relation Ecos theta, which gives us the relative magnitude of E for any wave direction relative to the antenna." You probably have seen the figure-eight pattern of a dipole antenna and are already aware that maximum response is broadside to the antenna at its center. If the antenna is tilted away from the perpendicular its response is diminished. Other antennas have a similar response as all are made up of elemental segments. Best regards, Richard Harrison, KB5WZI |
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