Topband: Fw: GAP VERTICAL QUESTION

[Guy Olinger K2AV]

Short version:

 *** WARNING:  Most locations do not have the fortunate circumstances to
support sparse or miscellaneous radial systems without exaggerated loss,
and the builder with constrained circumstances should attempt counterpoise
solutions designed specifically for those circumstances.

Long version:

I think the main point is being missed here.

First of all RBN is showing changes well in excess of 6 dB with the removal
of loss by replacing a faint radial system with an FCP.   Remember that an
FCP HAS NO GAIN.  It only reduces loss.  If the signal went up ten dB, it's
because 10 dB of loss was removed from the system.  Doesn't matter if we
don't know how to calculate it with our stuff.

IF it was a complex change, involving changing the wire overhead (other
than adding the FCP and moving the feed to 8 feet in the air), or moving
the location of the antenna, then the answer clearly cannot be cleanly
attributed to any one issue.  Some reported changes added together MULTIPLE
loss remediations plus improvements to the radiator and produced what can
only be termed stark improvements in overall performance.  A few of these
are easily in excess of 20 dB because of everything that was done at the
same time.  I certainly do not count those as pure ground loss
improvements.

But neither is there any reason to throw away reported results, calling
them anecdotal with a condescending tone of voice as if that were some kind
of disease.  Anytime one can clean up that much cr*p at one time, one
deserves congratulations, not being hounded on the reflector, as has
happened to some.  Nor should starting out with a cr*ppy situation
disqualify the report, or make its numbers "poison".

*I* would fairly agree with a 6 dB limit to the possible change, in
situations that were absent a long list of troublesome loss contributors
linked to ground coupling.  I would agree, given such pristine conditions
as I would expect to measure on your cleared out, flat, expansive, lovely
rural acres of electrically unpolluted farm land.  Nor would I disagree
that there are some with severely restricted radials on small lots that get
away with it to some degree, simply due to serendipitous or deliberately
cleaned-up backyard circumstances.  WX7G I believe has done that and is
getting away with it using NINETY 12 to 24' radials.  But we should note
there are many situations where there is not enough space or the
circumstances to attempt WX7G's successful enough limited method.

What is going wrong is that current ADVICE is telling people that ANY
radials, and even merely a ground rod, will NEVER exceed six dB down from
full size.   And with that guidance, they are putting down faint imitations
of a commercial radial field, expecting with a 1500 watt amp they will be
equal to you, if they could only get you to reduce power to 375 watts.
 There should be SOMEBODY out there like that, as in the story you tell.
 There is a law of averages.

But there are many, many more who have drunk the koolaid, followed the
advice, and had very disappointing results.  Some here maintain that
"disappointing" can't be measured in dB, therefore doesn't count, and
should be ignored, "poisons the database".  "Disappointing" is abstract or
conjectural unless it has happened to oneself.  Then one bristles when
accused of purveying disinformation.

Once someone's backyard has stuff from the list of troublesome loss
contributors, the chances of being penalized ONLY six dB with a faint
radial imitation are getting slim.  The loss contributors include dirt
quality from the poorer end of the spectrum, particularly in urban
circumstances, or where the land has been leveled out for construction with
dirt or even rubble useless for anything else and merely coated with enough
good dirt to support grass.  They include conductors in the ground, or any
conductor close to antenna or radials that couples dirt, the list goes on.
 Getting the bottom of the vertical up 8 feet to an FCP decreases coupling
to all that stuff. Faint radial systems on/in the dirt do not shield an
antenna from heavily coupling  "earth" made of whatever in the immediate
region underneath the feed.

Since an FCP provides no shielding of ground, as there is with a proper
radial installation, there is a last dB or two of ground loss from the
vertical conductor that it cannot mitigate.  So if as you put forth, the
depth of that trouble can ONLY be 6 dB, then the absolute mitigation of
loss from an FCP would be 4 dB, at best 5.

However, RBN changes are 7, 10, 12, 15 and some larger which I keep in the
"reserved for watching" column.   7 to 10 is common.  This far exceeds the
4 or 5 db, meaning that back yards are COMMONLY nastily lossier than the
ideal.  Since I can run models that give ridiculous loss figures
approaching 20 dB over average ground that is perfectly homogenous without
any of the nasties around, there is nothing to keep me from simply hearing
people's stories just as they tell it, with no reason to assume they are
deluded or lying.  I encourage people to watch RBN before and after to keep
up on what is going on.

I'm trusting RBN, with some careful statistical attention to obvious
sources of variation, and to methods for presenting a single summary
number.  RBN is good enough to see people switch directions with a 4 square
in the middle of a contest.   RBN is good enough to see that one of the
frequent players has made a significant improvement in their station.  RBN
is good enough to see people kick in illegal amplifiers.   (The illegals
really don't know how easy-to-see that is now :>) )

So this is a kind of impasse:  You say it can only be 6 dB, unless ....
 and I don't really disagree that much, except...

I am saying that your ....  is the order of the day for most, and as such,
recommendations of radials less than full size, dense and uniform all
around need to be made with a big asterisk:

 *** WARNING:  Most locations do not have the fortunate circumstances to
support sparse or miscellaneous radial systems without exaggerated loss,
and the builder with constrained circumstances should attempt counterpoise
solutions designed specifically for those circumstances.

I no longer trust the conglomeration of influences that got us where we are
in our ham-wide assumptions about sparse or miscellaneous radial solutions.
 If they had been thinking about small lot hams, they would have invented
the FCP themselves about the same time they started pulling the plug on
LORAN, and I would have learned about it from my Elmer.  Instead, when I
got on 160, the "informed wisdom of the day" recommended to me two 1/4 wave
radials on the ground plus a ground rod.  It was awful.  It stunk.  And
even if you pushed a loaded shotgun between my eyes, I wouldn't agree that
the difference between what I have now and then was only 6 dB.

73, Guy.


Visits to the FCP page still over 1k per month.
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On Thu, Dec 13, 2012 at 11:49 AM, Tom W8JI <w8ji at w8ji.com> wrote:

> This is ~true only for a "far field" analysis (as defined by NEC software)
>> for a vertical monopole -- which includes the propagation losses present
>> in
>> the radiated fields from that monopole, over an infinite, FLAT, real-earth
>> ground plane.
>>
>> However that is not reality.
>>
>
> I think what is going here is we have a bunch of anecdotal results based
> on one unknown compromised system compared to another compromised system
> when dozens of things are changed, and we are trying to generate physics to
> support one thing as being the cause.
>
> I am 100% sure, based on dozens of comparisons with three stations located
> not too far from me, that it is "pretty difficult" to make an antenna of
> reasonable size and construction -20dB based on ground system shortfalls.
>
> Some of this has gone beyond reasonable or logical, and is poisoning our
> knowledge base.
>
> In Toledo, a good friend lived on a small city lot behind a restaurant.
> His backyard, the only place for an antenna, was just a few feet deep and
> maybe 100 feet long. He tied in everything he could; heating ducts,
> plumbing, short radials, a short chain link fence. He was consistently,
> over many years, within a few dB of my full size quarter wave in an ideal
> soil and ground system. This was night after night, DX or local, over and
> over again.
>
> Another fellow in a neighborhood had a short TV tower with inverted L, and
> his radials ran to a sidewalk maybe ten or fifteen feet away. He had
> radials crossing the ceiling of his basement. His signal was the same way.
>
> Another station, W8KWN, just had driven rods.
>
> NONE of these stations were even close to 20 dB down. It was more like 5
> dB to maybe a just little more at times, and a little less at times. The
> driven rods were the worse system, but even they were not -20 dB.
>
> Now there was one station who had bad luck. He had bigger back yard, and
> it was just full of wires and antennas. He had all these bamboo supports
> and quads and other things, a yard full of "stuff". His signal was so weak
> he actually would swear and cuss at the other guys and accuse them of
> illegal power because his antennas "were so good" in his own mind that
> there was not way these other guys would beat him so badly unless they were
> cheating. No amount of conversation could convince him he had the problem.
>
> In my experience, it is more about having a neat, clean, uncluttered
> installation and not doing things grossly wrong, like using coaxial stubs
> for loading inductance or packing 900 pounds of antennas into a two pound
> back yard area, than any sort of grounding issue.
>
> The only -10 dB or -20 dB things I ever see are people who jam too much in
> small area, or have some other serious system error they created but just
> cannot see.
>
> My ten foot tall mobile antenna with a pickup truck for a ground is about
> 20 dB down from my TX antenna. If someone else has that issue with a 50
> foot tall inverted L, they better look at something other than a
> compromised ground system. They have a more serious issue.
>
> 73 Tom
> ______________________________**_________________
> Topband reflector - topband at contesting.com
>