That's a great example - thanks for sharing, Jim.
73s Tim EI8IC
----- Original Message -----
From: "Jim Reid" <email@example.com>
To: "Tim Makins, EI8IC" <firstname.lastname@example.org>; "Towertalk"
Sent: Saturday, February 14, 2004 7:37 PM
Subject: Re: [TowerTalk] Radials, elevated, or otherwise
> Here is an excellent photo of exactly the sort of antenna you
> you might have to recopy the above URL into your browser
> "open file" space, it is a bit long for the email.
> This is the 15 mHz phased array here on Kauai out at
> WWVH. The array is designed to proved a cardioid's
> pattern, with max power to the West or out to the far
> Western Pacific ocean areas.
> Note that many ground mounted radials fanning out all
> around, you can see them in the lower foreground of
> the photo. Even though this is a vertical dipole, with
> the downward sloping (and note the insulators to
> provide the correct resonant radial length) the ground
> radials were absolutely necessary to recover the
> ground loss power, and to obtain the total predicted
> field strength out to the far West of the Pacific.
> You just can't turn a dipole vertical with the lower end
> any where near ground and get high efficiency without
> the use of the ground radials, hi. I suppose if you were
> able to get the lower end of the dipole well above even
> 1/4 wave length in height, you would be better off,
> but at WWVH it was far more economical to use the
> ground radials to terminate the high E fields from the
> lower ends of those down sloping fanned radials
> (which, by the way, provide the shielding for the
> coax feed which goes up the center of the lower
> portion of the supporting tower structure).
> The antenna structures were built by Rohn some
> 30 years ago, and now need replacing since they
> are sitting right on/at the beach here on the island.
> When asked, Rohn would not bid again on such
> an elevated and center insulated structure; anyway,
> now, I guess, Rohn is gone.
> 73, Jim KH7M
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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