On 1/11/01 12:55, Ken Hirschberg at calav@flash.net wrote:
>The traditional broadcast radial field has 120 radials because the radials
>go out
>to 0.4 wavelengths, not 0.25.
Hmm. 0.4 * 2 * pi / 0.025 = about a 100, not 120. If you keep the 0.025
wavelength spacing at the perimeter, you have to go out to nearly 0.5
wavelength radials to require 120 radials.
>BTW, if one would like the radials to
>behave like
>a solid screen, 0.015 wavelength maximum spacing between wires would be a
>good
>number to use.
>Yes ...that's a LOT of wire! (and a lot of performance)
For 1/4 wave radials, that would mean about 100 radials.
>
> A somewhat more complex approach that would save some wire, would be to
>go out
>with say, 30 radials until the 0.015 spacing between wires was obtained,
>connect
>a circumferential wire to each radial, then add radial wires between the
>original
>30 radials, from that ring outward. When the spacing between wires again
>gets to
>0.015, then add another ring, and so on, until the desired radial length is
>reached.
This thought had occurred to me as well. I think the difficulty of laying
the circumferential wire, as well as maintaining the connections at
ground level makes laying more radials seem like a better idea.
You could dispense with the circumferential wire, and merely fork off an
additional wire once you reached the maximum spacing point.
Bill Coleman, AA4LR, PP-ASEL Mail: aa4lr@arrl.net
Quote: "Not within a thousand years will man ever fly!"
-- Wilbur Wright, 1901
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