Jim, you've opened a real can of worms.
You can't say there is "data" to the contrary ... there may be
legend, anecdote or even model studies but there are no validly
conducted field strength studies that show elevated radials to
outperform a reasonable (16 - 32 radials) in ground system when
the length of the in ground radials are "sufficient" <snip>
-0-
Joe,
You're right. IF you have a reasonable, 16-32 radial system
to work with. I believe there was a stipulation that that wouldn't be
possible. I DID say better than an 'insufficient' system.
Of greater importance...and it supports your argument, actually...
is that the field strength data, was taken with 4 elevated radials...
over the remains of a previous 120 radial system.... NOT really
relevant to the amateur case. I was reminded of this off-reflector by
a chap from EU.
It IS true that a larger ground system would be more stable...and
probably that an in-ground one is even more so, as shifts are swamped by
the earth losses.
However, in the initial broadcast submission, they were still able to
attain 190mV at a mile...which was the same field they had with
the buried system. (and I'm sure there were 'holes' in between the
radials where they didn't achieve that, but didn't report it!)
Here in suburbia, I'm constrained to use onground radials, stapled down,
for aesthetic reasons. Up in VT, I was free to fly radials, which worked
reasonably well. Hardly quantified, admittedly, but good enough to work
Campbell Island on top band in 99.
Jim
-----Original Message-----
From: Joe Subich, W4TV [mailto:w4tv@subich.com]
Sent: Friday, August 04, 2006 4:03 PM
To: 'Jim Jarvis'; topband@contesting.com
Subject: RE: Topband: Grounded Tower
Jim Jarvis writes:
> I disagree. There is data to the contrary...that is, that a
> few elevated radials work better than an insufficient on/in
> ground system. I am sure this depends on the conductivity of
> the earth involved, to some degree.
Jim, you've opened a real can of worms.
You can't say there is "data" to the contrary ... there may be
legend, anecdote or even model studies but there are no validly
conducted field strength studies that show elevated radials to
outperform a reasonable (16 - 32 radials) in ground system when
the length of the in ground radials are "sufficient" (e.g.,
separation of .03 wave at the tips). Quite the opposite in
those cases where before and after measurements were taken where
elevated radials were replaced by a reasonable in ground system
in broadcast service, the in ground system outperformed (and were
more stable) the elevated radials that were replaced.
73,
... Joe, W4TV
> -----Original Message-----
> From: topband-bounces@contesting.com
> [mailto:topband-bounces@contesting.com] On Behalf Of Jim Jarvis
> Sent: Friday, August 04, 2006 12:27 PM
> To: topband@contesting.com
> Subject: Re: Topband: Grounded Tower
>
>
>
> Quoth N9RF:
>
> "I would opt for a known performer -- the shunt-fed tower with in/on
> ground radials. Regardless of claims that 4 elevetaed radials
> outperforms many on/in ground radials, the opposite has been proven by
> field strength measurements."
>
> I disagree. There is data to the contrary...that is, that a
> few elevated
> radials work better than an insufficient on/in ground system.
> I am sure
> this
> depends on the conductivity of the earth involved, to some degree.
>
> At the same time, I would favor in-ground on the basis of
> aesthetics. If
> you can get in 12-24 radials, even of varying lengths, you'll
> be better off.
> If not, then you should consider flying 4 radials @ 10' or so up.
>
> On the topic of eliminating coupling between the tower and a
> k9ay loop which
> is only .6 lambda away? Only way to decouple is to ACTIVELY
> do so...that
> is, to
> use a relay to switch in (or out) tuning components for the
> tower which
> would
> result in it being resonant well away from 1.830.
>
> n2ea
> jimjarvis@ieee.org
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