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Re: [TowerTalk] Phasing two GAP monoband verticals

To: towertalk@xxxxxxxxxxxxxx
Subject: Re: [TowerTalk] Phasing two GAP monoband verticals
From: Gary Johnson <gwj@xxxxxxxxxx>
Date: Fri, 2 Jun 2017 18:56:02 -0700
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> I want to phase two of the 40M monogaps, to get some F/B away from a noise 
> source that has shown
> up lately. I have had extensive experience with ComTek and Array Solutions 
> classic 4 square setups
> using 1/4 wave verticals.
> Has anyone done this with the DX Engineering or Array Solutions boxes and GAP 
> verticals? No need
> to discuss the GAP antenna theory but they are not 1/4 verticals.

Phasing a pair of arbitrary verticals will work fine, but not with the 
commercial boxes. Performance of any array is highly dependent upon feedpoint 
impedances and mutual coupling between the antennas. The commercial boxes will 
work properly only with a very specific antenna pair. But you can build your 
own. I’m doing it right now, at N6RO. The references you need are ON4UN’s book, 
in the chapter on phased arrays, and also look at the ARRL Antenna Book because 
it’s more concise and it comes with a very nice application called Arrayfeed1 
that is very easy to use. You will have to measure your feedpoint impedances (X 
and R) for a single antenna and when both are present in their final locations 
to obtain the mutual coupling data. Then you can decide what kind of phasing 
network you want to build. Examples are in both books and they are not very 
complicated. You can also add some relays if you want to switch directions. 
Note that you are not stuck with any particular spacing or phasing. Pick a 
pattern that suits your purpose, and build to that. EZNEC is great for 
predicting how things will work, but only if you have a good model for the GAP 

Gary NA6O

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