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[TowerTalk] 2 Vertical Array Question

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Subject: [TowerTalk] 2 Vertical Array Question
From: (Tom Rauch)
Date: Thu, 22 Mar 2001 08:06:24 -0500
> a 2 vertical array (on 40m in this case, and projecting it to be
> switchable), please debate the merits of the "cardiod" pattern by
> feeding 90-degrees out of phase (3db gain by the ON4UN book and best
> f/b) and possibly feeding 135-degrees out of phase (4.9db gain by the
> book and small back lobe)? It's a gain vs. f/b question.  

The F/B ratio of the 135-degree phased antenna will actually be 
more useful and appear higher than the 90-degree phased antenna. 

That's because the 90-degree phased antenna has a single null 
area at ground level directly off the back. That's the last place we 
want a null when working skywave.

When 135-degree phasing is used, the null forms a deep slice in 
the shape of a cone that is at two points off to each side of the rear 
at zero-degree elevation. As you move towards the back, the null is 
elevated and reaches its highest point directly off the back.

The reason the 135-degree phased antenna has more gain is it has 
a wider null area. A wider null area up in the air is much more 
useful to us than a single null directly off the back centered along 
the ground.



73, Tom W8JI 

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