Jim,
When you do that calculation for a 1/4 ground mounted
vertical, what do you use for the effective height when
doing the ray trace for the distance to the reflection zone?
I posed that question on the topband reflector (in the context
of siting a 160 meter antenna near salt water) and nobody
seemed to have a good answer. Using the ray tracing
simplification the calculation is rather simple, but the answer
you get depends strongly on where you define the phase
center of the antenna. On the site I had in mind, it could
make a big difference because of the limited extent of the
salt water in certain directions.
73 de Mike, W4EF............................................
----- Original Message -----
From: "Jim Lux" <jimlux@earthlink.net>
To: "RICHARD BOYD" <ke3q@msn.com>; "Towertalk" <towertalk@contesting.com>;
"Michael Harris" <mike.harris@horizon.co.fk>
Sent: Friday, December 03, 2004 9:02 PM
Subject: Re: [TowerTalk] Stacking
>
> ----- Original Message -----
> From: "RICHARD BOYD" <ke3q@msn.com>
> To: "Towertalk" <towertalk@contesting.com>; "Michael Harris"
> <mike.harris@horizon.co.fk>
> Sent: Friday, December 03, 2004 7:38 PM
> >
> > On verticals on the beach (or not)... my recollection of the Force 12
> "Team
> > Vertical" guys, what they said in a Dayton Antenna Forum presentation
> (about
> > one of their 6Y, Jamaica, operations), is that they found signals peaked
> at
> > 1/4 wavelength back from the water's edge, apparently not at the water's
> > edge or out on a dock or something.
> >
> > Also, others have told me, empirically (seat of the pants) that they
> thought
> > the advantageous salt water effects on vertically-polarized antennas
might
> > be noticed up to a mile inland from the water. I assume they diminish
the
> > farther away you get after that first 1/4 wavelength.
> >
> > 73 - Rich, KE3Q
>
> The beneficial effects from the high conductivity aren't so much from the
> good ground plane close to the antenna, but because a bit farther out, it
> supports a low angle reflection. Consider, for example, a takeoff angle of
> 10 degrees. If your antenna is, say, 20 feet off the ground, the "ground"
> location where the reflection hits (and will reflect at 10 degrees) is 113
> feet away. For 5 degrees, 230 ft, and so forth. If you've got an antenna
> that's up a few hundred feet (say on a hill or bluff overlooking the sea),
> then you can be quite a ways inland.
>
> _______________________________________________
>
> See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
questions and ask for Sherman, W2FLA.
>
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>
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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