Just make sure that no one is confused that this rough equivalence of
a freshwater takeoff to what I would term halfway decent dirt is NOT
to be confused or ranked ANYWHERE NEAR the spectacular low angle
performance of vertical antennas at the edge of salt water.
That seemed to be the question behind the question of the original
post, wondering if a fresh water edge would do as well.
73, Guy.
----- Original Message -----
From: "John Petrich" <petrich@u.washington.edu>
To: "FireBrick" <w9ol@billnjudy.com>; "TowerTalk List"
<towertalk@contesting.com>
Sent: Saturday, April 20, 2002 8:14 PM
Subject: Re: [Towertalk] antennas near water
> Bill and the rest,
>
> A lot can be said about antenna performance in a fresh water
> environment. It seems to me that the distinguishing impact of a
fresh water
> environment on antenna performance involves consideration of both
the
> conductivity and dielectric properties and the physical (macro)
properties
> in the far field reflection zone or first reflection zone and
beyond. A
> narrow river in a steep valley is not a fresh water enviroment in
this
> context. A large river, large lake, or a large swamp in a
relatively flat
> area are what I think you are describing in your question.
>
> A fresh water environment has modeled out for me, and is
described in
> the ARRL Antenna Handbook and in W7XC's original QST article, as
equivalent
> to a "very good" ground. The result is that the Pseudo-Brewester
angle is
> about 6 degrees through the HF spectrum. My modeling attempts
suggest a
> significant improvement in low angle radiation from a vertical
antenna over
> fresh water compared to a vertical over "average" ground at all
elevation
> angles below 10 degrees.
>
> A fresh water environment CAN be physically flat, homogenous,
and have a
> low radio horizon at distances that correspond to the far field
reflection
> zone and beyond for our HF antennas. This uniformity can contrast
with the
> relatively cluttered and irregular far field reflection zone and
beyond that
> characterize so many real world regular earth enviroments. A smooth
and
> uniform far field reflection zone and low radio horizon could be
expected to
> aid beam forming and contribute to low angle propagation efficiency.
>
> The performance of horizontal antennas are relatively little
effected by
> the electrical characteristics of any ground in the far field
reflection
> zone. Vertical antenna performance is significantly affected by
these
> properties. Both are benefited by efficient beam forming and a low
radio
> horizon if DX is a priority.
>
> I'd say that a fresh water environment can contribute to the
performance
> of any antenna to the extent that the far field reflection zone is
uniform
> and the radio horizon low. Vertical antennas get the additional
benefits,
> unique to vertical antennas, that come from a "very good" ground.
>
> Regards,
>
> John Petrich, W7FU
>
>
> ----- Original Message -----
> From: "FireBrick" <w9ol@billnjudy.com>
> To: "TowerTalk List" <towertalk@contesting.com>
> Sent: Friday, April 19, 2002 5:18 PM
> Subject: [Towertalk] antennas near water
>
>
> > I've seen many postings about the improvement having an antenna
near the
> > shoreline.
> >
> > Just wondering...would having a tower and antenna on the shoreline
of a
> > large river provide a similar improvement?
> > In ME where I would love to move to, there are MANY large rivers
emptying
> > into the bays and harbors.
> >
> > Would any gain be dependent on the direction/route of the river?
> >
> > Just curious.
> >
> >
> > ------------------------------------------------------------
> > A hangover is the wrath of grapes.
> > ------------------------------------------------------------
> >
> > Bill H. in Chicagoland
> > w9ol@billnjudy.com
> >
> >
> > _______________________________________________
> > Towertalk mailing list
> > Towertalk@contesting.com
> > http://lists.contesting.com/mailman/listinfo/towertalk
> >
>
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