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Re: Topband: Elevated Radials

To: topband <>
Subject: Re: Topband: Elevated Radials
From: Dan Zimmerman N3OX <>
Date: Sun, 31 Oct 2010 13:28:07 -0400
List-post: <">>
> What does someone DO who is trying honestly to compare alternatives

and the FIRST TIME AROUND squeeze the last dB out of what is going to

be a considerable project, because they don't have the time to try

five different things, one at a time, each one occupying all available

space?  Even if they did it, what beyond QSO count affected by highly

variable conditions would they have to compare sky-wave effectiveness?

You can't do anything.  We need to recognize that there is NO silver-bullet
advice.  You can't optimize without optimizing, and we only have PIECES of
the puzzle put together here, because no one has the time to be a full-time
radial theorist.  If we had such a luxury, we could come up with a system
where you take ground cores to determine your soil's conductivity and
permittivity profile with depth, azimuth, etc and then have a computer
program spit out the best configuration that will fit in a certain space.
 But we don't have that, and we won't, so we need to do the best we can with
incomplete information.
The best we can do is develop a good understanding of the upper bounds on
performance improvement.  Look at lots of sources.... models, measurements,
etc, and find out what the *typical prediction* of switching systems is.

Sure, you've got that one guy who insists that everything is 10dB better now
that he's got elevated radials instead of on-ground radials.  But is his
result TYPICAL or is it an OUTLIER?  Do the measurements seem careful and
correct enough for you to spend your precious time on them?  Or is it just
someone who "feels" stronger because they tried something else?  And we need
to be realistic.  Should we even consider doing something to a painstakingly
installed radial field to gain us 1-2dB based on typical predictions?  No
way!  At that point it is "buckle down and measure the best you can, or
you're never going to e sure you're not wasting your time."

 What comes up over and over and over and over in correspondence

(way, way more times than you guys that are happy with yours) is that

people don't have the space for traditional radials and what they have

tried just plain sucks

The most important question here is "does it actually suck?"

In other words, is there a measurable difference?  How can we figure that
out without measuring?  We can't.  So it doesn't matter how many times
someone tells you that a small backyard full of short radials sucks.  If
they can't tell you how much it sucks, there's no way to assess whether it's
worth any work to try to make it better.

If it seems to "suck" because you get beat in the pileups all the time,
that's just not a useful measurement.   The thing that I don't understand is
this: without a comparison, how are people determining that their radial
setup is at fault for the perceived deficiency in the station?

 I know that in the world of 160m ground systems, my setup MUST be pretty
darn bad (30 radials, only 6 of them longer than about 40 feet, many as
short as 15 feet).  My base impedance measurements are consistent with
rather high ground loss, about 12 ohms.   I did that two ways, with an
analyzer an then a high level measurement with a calibrated current meter.
 Based on comparison with model, the peak gain should be something like
-6dBi or soi.   But I feel like I more or less hold my own with the
medium-sized East Coast stations I compete with, and I don't feel like I get
shut out of 160m DX.

I only run 400W, too, so it's not like I've even maximized my radiated
signal given my ground system.  For a long time I ran 100W, and I didn't
feel too badly.  And I don't just THINK apropos of nothing that my system
sucks.  I have at least some evidence (though not the best kind of evidence)
that I have lots of ground loss for my small radiation resistance antenna
(60 feet straight up, base loaded).  But I don't have any major problems
with it on air.

So I kind of wonder: what is it that people are saying when they're blaming
their ground system for poor performance?  My ground system, as far as I can
tell, is awful.  It uses just 1500 feet of 18ga wire in a 50 foot square
layout.  Cheap, and not hard to duplicate.  Both the impedance measured at
the feedpoint and the current in the bottom six or eight feet of the
vertical are consistent with 12 ohms of ground loss, which for a ~5 ohm
antenna is not so hot.

So are we saying that everyone is managing to knock off another 3, 6, or
10dB vs. my awful setup?  Seems like you'd need to install nothing but a
ground rod, no?  It is possible that my patch of dirt is just a really good
place to put radials and also I have a strange impedance transformation
happening such that my 5 ohm Rrad gets transformed up to 17 ohms.  Such
weird things can happen.

But it doesn't seem likely to me.  It seems more likely that people are
blaming some on-air frustration on a bad antenna system in a way that's not
justified by reliable evidence.  I've tried to measure my system, but the
way I've done it is fraught with large errors.  I spent enough time at 100W
before going to 400W to suggest that while 6dB helps a lot, it's not going
to keep me from doing most of what I want to do.

So are we being realistic when we feel that our radials are limiting us, or
are we just using "bad radial systems" as a scapegoat?  Can we tell the
difference without first making some difficult measurements?
UR RST IS ... ... ..9 QSB QSB - hw? BK

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