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Re: Topband: Shunt fed T

To: "john" <jb@beaumonts.karoo.co.uk>, <topband@contesting.com>
Subject: Re: Topband: Shunt fed T
From: "John G3PQA" <g3pqa@onetel.com>
Date: Tue, 5 Jan 2010 05:53:06 -0000
List-post: <topband@contesting.com">mailto:topband@contesting.com>

From: "john" <jb@beaumonts.karoo.co.uk>

Could anyone advise me about top loading when 4 wires are use as an alternative to 2 with this type of antenna. My present antenna is 82ft vertical with 4 top lading wires each 35ft long, I have been told only 1 wires counts as the loading/lengthening on this type of antenna which I dont fully agree/understand. Is it not that a 2 wire tee you calculate the missing portion of your vertical lets say I needed 127 ft for 1.83mhz and my vert is 82ft so 45ft too short, so lets say 60% of 45ft = 27ft I would need 2 top wires 27ft or maybe 70% of 45ft = 2 x 31.5 ft.


According to EZNEC a tophat of 4 x 35ft wires gives resonance on about 1.6MHz , assuming single wire vert.
If the wires are shortened to 22ft resonance is 1830kHz
John
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