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Topband: Dual Tophats

To: <topband@contesting.com>
Subject: Topband: Dual Tophats
From: w7iuv@earthlink.net (Larry Molitor)
Date: Mon, 13 Aug 2001 23:00:01 +0000
At 04:14 PM 8/13/01 -0400, Doug Waller wrote:
>According to some authorities, any "whip" added above a tophat will receive
>minimal current.  I am thinking the added capacity hat will function
>normally however, adding its capacity to that of the beam's, for the total
>of 50 elec. degrees.

In my experience, the top hat will pretty much be invisible unless you make 
it several times the area of the beam below it. For an example, with a TH6 
at 72 feet, adding a 402BA at 82 feet made almost no difference in the 
measured resonant point of the shunt fed tower.

On a positive note, even though the elements of the beam are insulated, 
there is capacitance through the insulators and brackets that will 
contribute much more than you expect.

I suggest you measure the thing first with only the beam and then decide 
what to do next.

Larry - W7IUV




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