Re: Challenger Ant. and Gap products

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From: AA3RL (m9bw990@ix.netcom.com)
Date: Tue Jun 01 1999 - 20:14:43 EDT


David:

As I mentioned in my reply to Stuart's post, I have addressed exactly
this question via modeling and A/B testing. Partial results can be
viewed on my web site:
http://www.qsl.net/aa3rl/

Any questions or comments are welcomed.
73 de Mike Banz, AA3RL
------------------------------------------------------------------

david fouchey wrote:
>
> I wonder then how working on an Islet in a salt water location with a
> GAP style half wave vertical antenna would effect performance? How would
> it compare to the 1/4 wave ground mounted vertical with the near
> infinite highly conductive ground plane that the bay or ocean would
> represent?
>
> Dave
> WA4EMR
> Sterling Heights, MI
>
> "L. B. Cebik" wrote:
> >
> > >
> > > However, you probably should put your improvements in RF conductive earth out
> > >from the antenna, where the angle of takeoff has a component hitting the
> > >ground. This issue is addressed in some texts in discussing the horizontal
> > >dipole and its image plane, but I don't believe I have seen anyone do anything
> > >about providing better conductivity this way. We mostly have little control
> > >out from our antennas at the distances that would help, but those living on a
> > >true antenna farm could do some woderous things with ground reflection
> > >improvement. Those living on a cliff over the sea already enjoy this effect
> > >in the seaward direction.
> >
> > Stuart,
> >
> > The issue of conductivity and its effect on initial reflections in the
> > Fresnel zone is discussed by ON4UN in Low Band DXing. It is also
> > discussed briefly in the SCV series I did for NCJ (which is on line also).
> >
> > In effect, you are correct that for self-complete antennas, such as the
> > vertical dipole (even the very short ZR-3s produced by Force 12), local
> > ground plays a role in RF ground returns, but does not play the same role
> > it plays with a GP monopole. ON4UN concludes that it is a couple of
> > wavelength's distant that begin the Fresnel zone for verticals--and this
> > area is rarely controllable by an inland homeowner when using the low HF
> > region. Relocating to an island or peninsula is feasible for only a very
> > few. Also, the water must be salt water; fresh water is just not that
> > much of a help. The effect can be modeled. And, as well, the team that
> > broke the CQ multi-multi score record a couple of years back did an
> > article on their vertical antenna farm on the coast of Jamaica for CQ's
> > contest journal. So there is both quantitative and qualitative to be had
> > on vertical dipole (and other complete) antenna performance relative to
> > ground conditions and some of the variables, such as height above ground.
> >
> > -73-
> >
> > LB, W4RNL


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