November 17th 08, 11:45 PM
posted to rec.radio.amateur.antenna
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First recorded activity by RadioBanter: Jun 2006
Posts: 1,898
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"Unwashed" hams and "washed" hams
David G. Nagel wrote:
wrote:
David G. Nagel wrote:
The last time that I built an antenna I used the formula to get the
appropriate length then I had to adjust it to obtain the optimal
readings for the frequency I was using.
Did "the formula" take into account any insulation, conductor resistivity,
conductor diameter, height above ground, characteristics of the ground,
and objects in the near field including supports?
If not, what is your point?
The point is that those items are not part of "Antenna Theory: The
Science" but are a large part of "Antenna theory: The Art". Art has been
talking as if they are one and the same.
Science is fully accounting for all variables and their effects giving
you exact answers.
Art is experience and rules of thumb that get you close enough.
Something you could answer if you can. I am planning to install a dipole
antenna in NVIS configuration adjacent to a mobile home type structure.
The wire will be within about 10 to 15 feet of the metal covered
structure. How much will the metal warp the radiation pattern of the
antenna. It will be in the 75 to 60 meter bands.
Dave WD9BDZ
I can't but it should be easy enough to model in EZNEC.
--
Jim Pennino
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