W9OY:
>It made me think of a radial field in a whole new
light. It's more about effective coupling into a
volume of ground and less about absolute numbers and
such.
Yes, maximize surface area coverage, but no
need to make the ground screen any finer than 0.025
wavelengths at the end points (however far out they are).
In a nutshell, that is what Rudy, W8JI, etc are saying.
Ground rods are meaningless for RF and I would not be
using them if they weren't necessary for lightning
protection of my tower.
This concept makes it very simple to put
down an effective radial system in any area using
the minimum effective amount of wire. From page 9-15
of ON4UN's 4th edition:
############################################
In actual practice, when laying radials on an irregular
lot where the limits are the boundaries of the lot, the most
practical way to make best use of the wire you have is just
walk the perimeter of the lot and start a radial from the
perimeter (inward toward the base of the antenna) every
0.015 . (1.3 meters for 80 meters or 2.5 meters for 160) as
you walk along the perimeter.
############################################
Since that was published, the thinking is now that
0.025 wl will get you within 0.5 dB of "perfect ground"
(near field that is). This is equivalent to ~60 1/4 wave
radials instead of the ~100 used in ON4UN's book.
This rule-of-thumb is based on actual field strength
measurements by W8JI, N6LF, etc. Apparently W8JI
and W7EL (Eznec author) will be publishing a paper
about their radial system measurements in the future:
http://lists.contesting.com/archives//html/Topband/2006-08/msg00023.html
73, Bill W4ZV
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