R. L. Measures wrote>
> >K7GCO wrote:
> >
> >I've run patterns of verticals with radials 10 or more WL long and it
shows
> >some promise. I have a location where I will be able to do that. Has
anyone
> >any experience with this?
>
> >N6RK wrote:
> >I don't know what program you used, but I ran
> >a bunch of simulations on NEC3-GS. The results
> >are fairly discouraging. With 10 WL long radials,
> >you need thousands to be effective.
> Since the end-feed Z of a half-wave vertical is typically c.
> 1000-ohms, even one 1/4 wave counterpoise makes a sufficient ground.
> OTOH, with 1/4 wave verticals, which have a thirty-something ohm feed Z,
> an extensive ground is needed.
We're confusing two different issues. One is the
ground radials as counterpoise, the other is
ground radials to enhance low angle radiation.
A half wave vertical requires virtually no
radials to equal the gain of a 1/4 wave vertical
with radials. However, with either vertical, it
requires an impractically large ground plane to get
substantial enhancement of low angle radiation.
The 1/2 wave and 1/4 wave verticals are no
different in this respect.
It has been pointed out that the ground mounted
half wave has E-field losses because of the
high fields close to the ground. However, it
also has an extra 2 dB of directivity. This
seems to just about balance out the ground losses.
Rick Karlquist N6RK
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