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Art Unwin wrote:
"So how does one "create" several conductive surfaces of what ever length on a continuous electrical surface?" First examine the ways it has already been done and ask why? A non-resonant reflector provides a much wider bandwidth than a resonant reflector as used in an array like a yagi, for one thing. Plenty of grid-dish, corner-reflector and similar non-resonant reflector antennas are in use to reduce wind-loading. You have no need at lower frequencies to use solid reflectors. Surface irregularities are not much problem. The solid dishes at 2-GHz are built that way for convenience, not because they need to be. The same is true at lower frequencies. At higher frequencies, the conductors are so close together, there isn`t enough reduction in wind-loading to be worth the construction effort required with grid-reflectors. Grid reflectors only need a collection of conductors parallel with the radiating element(s) illuminating (driving) the antenna, and placed for best results. Reflecting elemants in a grid reflector placed perpendicular to the driven element don`t work. Curvature is used tn dish reflector bars for focus. An angle is used in the corner-reflector for more gain than a flat reflector. None of the reflectors needs cross-connections between the reflector bars anymore than ground radials need their far-ends interconnected. Such connections allow eddy currents which only cause loss. The only current of value is that in the direction of the ground radials or in the direction of the reflector`s parallel conductors, as the case may be. So the eddy currents are bad. Spacing between reflector bars is related to wavelength and capture area.. Measure it in a good grid antenna and scale to your frequency. Or, see Kraus for capture area etc. Best regards, Richard Harrison, KB5WZI |
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