> i presume that eznec pro v3.0/nec4 would allow full modelling and avoid
the
> above
> limitations, has anyone actually done a comparison? provision for buried
> radials
> i guess allows full vertical lead ins & terminations to real earth
Sam,
There is no need at all to go through all of that. Just run the vertical
leads and model a small radial system just above ground at each end, or
ignore the warnings and connect a wire directly to earth. I've always found
the ONLY error connecting wires to earth will be in termination and feed
impedances. The pattern is fine.
The T counterpoise is a BAD idea, since even a 180-degree in-line wire fed
as a T radiates much more than a vertical drop would. While I've seen it
claimed that termination method works in models and life without radiation,
that just isn't true.
The effects of the vertical ends, like many things we hear about, are over
exaggerated non-issues when the Beverage is very long compared to the
height. Sloping the ends does nothing at all discernable, except change the
mechanics.
Same for verticals, just model the radials a foot or so above ground. Keep
in mind NEC programs DO have a problem with wires close to earth, and will
not give the exact results. The fewer the wires, the larger the possible
error. The earth is not homogenous like the model, and we really have no
idea what the earth is like under our antennas.
Also remember most programs we use, unless they allow us to set pattern
distance, calculate pattern at large enough distances to be considered
infinite. That means the really low angle signals from verticals appear to
be more attenuated than they actually are in real life. So don't rely on TOA
or groundwave patterns as absolute.
73 Tom
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