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Re: [CQ-Contest] 80 mtr antenna

To: CQ-Contest@contesting.com
Subject: Re: [CQ-Contest] 80 mtr antenna
From: Sinisa Hristov <shristov@ptt.yu>
Date: Wed, 04 Jul 2007 13:47:26 +0200
List-post: <mailto:cq-contest@contesting.com>
Glenn VA3DX wrote:

 > I currently use a standard Inv V on 80 meters.
 > I would like to change this to a Delta Loop.

 > I have been told the total length should be around
 > 265 feet., and for vertical polarization it should be fed
 > at the bottom corner.

For vertical polarization it should be fed a quarterwave from the top.

There is substantial difficulty in feeding such an antenna correctly.
The problem of supressing common mode currents on the feedline
is much more pronounced than with symmetrical antennas.

 > Currently the Inv V is fed at the top of the tower, at 70'.
 > If I lengthen the Inv V across the bottom to the required
 > length and thus make a Delta Loop., what sort of
 > polarization would I expect to see if it is fed at the top
 > of the tower ?????

You'd get horizontal polarization and low angle radiation
would be much weaker than with Inv V alone, due to reduced
average height of the antenna. Noise coupling from the
neighborhood is likely to increase.

 > My interest is in DX , contesting, and a low takeoff angle.
 > Local ragchewing is not a priority.

Avoid horizontally polarized loops at low height,
they will be worse than your Inv V.


Sinisa  YT1NT, VE3EA

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