[Elecraft] Verticals

[Guy Olinger K2AV]

In Jim's second linked PDF, he makes reference to W6GJB's (Glen) ground as
being very poor, presumably because these measurements show so much more
loss than "average" ground in the model. The question is what do you have
to do to get the model to hand you 13.5 dB differentiation with those same
changes in height IN THE MODEL. The assumption is that Glen's ground is
abnormally bad. Suppose Glen's ground is very ordinary and speaks for a
majority of space challenged situations. What then?

NEC4 underestimates ground loss for all but commercial grade dense ground
radial fields. One will be well-served by taking the W6GJB measured results
as the RULE rather than the exception for any vertically polarized RF
current near ground. There is a very good lead on why and what is not taken
into account in NEC program code regarding ground losses in compromised ham
situations, but it will not be published until it's absolutely nailed to
the wall, and the NEC fix coded and tested. That may be quite a while.

In the meantime, to better model ground losses for comparison use in
optimizing an antenna configuration, always use WORST TERRIBLE ground in
the model. You will be far closer to the truth. WORST TERRIBLE ground =
(0.0007,1). Yes, that's point ZERO, ZERO, ZERO seven, not a mistake.  But
even as vicious a correction as that is, it does not work out as bad as a
pile of anecdota indicate.

WORST TERRIBLE ground will demonstrate ground sensitivities as you make
adjustments to an antenna system. If you are doing modeling and intend to
pass results along to anyone else ever, then assume that most people have
terrible ground circumstances. This will be largely true, because vertical
users are most frequently driven to those circumstances because of cramped
erection possibilities so common to us folks with ordinary limited space.
Cramped spaces are usually full of ground defiling lossy stuff like
concrete, "rubble fill", asphalt, concrete slabs, rusty buried pipes,
basements, and other stuff that turns ground type into WORST TERRIBLE.

Your design maximized over WORST TERRIBLE ground will minimizing coupling
current into all-too-common RF sucking stuff in typical hamdom "ground".
This will take care of the ground-challenged mass majority of hams, without
inconveniencing or harming in any way those awful spoiled people who live
over super-dirt.

In Bill Clinton's first presidential campaign, the famous (infamous?) motto
was "It's the economy, stupid!". In affairs regarding verticals the
parallel motto is "It's the ground losses, stupid!"

The solution which maximizes results over WORST TERRIBLE ground is the one
you tell friends you want to keep and publish abroad.

This is why we picked FCP dimensions that were non-resonant (5/16 wave
single wire folded counterpoise for use in situations where commercial
grade 80m or 160m radials are not practical.) It was a compromise between
high counterpoise feed reactance and ground loss. A couple dB were at stake
in the choice of dimensions over WORST TERRIBLE ground.

Jim is showing a 13.5 dB variation with varying heights at W6GJB, all
related to ground losses, or relative lack thereof. Raising 100 watts to
1500 watts is only 11.8 dB. On the wrong side of that range and you waste
all your amp power, and more, in ground losses. And it WILL be seen at some
time in the future that Glen is the norm and not the exception.

Note to self: "It's the ground losses, stupid!"

Think about how the vertical on the roof at K9OR avoids at least some
amount of ground losses. In the 60's I had a trap vertical over raised
radials 1 foot up from a copper roof on a 3 story row house. It worked
GREAT. The same antenna later turned into a ghastly dummy load near the
grass after I moved to the suburbs and had to put it somewhere behind the
house where it couldn't be seen.

73, Guy.

On Thu, Sep 11, 2014 at 12:10 PM, Jim Brown <jim at audiosystemsgroup.com>
wrote:

> On Thu,9/11/2014 6:50 AM, Hisashi T Fujinaka wrote:
>
>> I use a AV-640 and I would suggest it over NO ANTENNA any day. And it
>> fits on a city lot without too many complaints
>>
>
> Yes, and that's something that blanket criticisms of antenna choices fail
> to consider. On his tiny Evanston, IL city lot, my friend K9OR has an
> AV-640 on his roof and a low 80M dipole between trees. He has a lot of fun
> with it.
>
> On Thu,9/11/2014 8:56 AM, Joe Subich, W4TV wrote:
>
>  I need to agree with Jim and others in support of the verticals.
>>
>
> Here's my take on this sort of antenna decision -- with a limited number
> of possibilities, which are likely to work the best?
>
> http://k9yc.com/VertOrHorizontal-Slides.pdf
>
> http://k9yc.com/VerticalHeight.pdf
>
> 73, Jim K9YC
>
>
>
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