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Re: [TowerTalk] Why horizontally polarized antennas?

To: "Tower Talk List" <towertalk@contesting.com>
Subject: Re: [TowerTalk] Why horizontally polarized antennas?
From: "Larry Banks" <larryb.w1dyj@verizon.net>
Date: Sat, 3 Jul 2010 10:52:29 -0400
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
Thanks Steve -- I stand corrected.

I've never played with that part of EZNEC before!

73 -- Larry -- W1DYJ


----- Original Message ----- 
From: "Steve Hunt" <steve@karinya.net>
To: "Tower Talk List" <towertalk@contesting.com>
Sent: Saturday, July 03, 2010 3:58 AM
Subject: Re: [TowerTalk] Why horizontally polarized antennas?


> No - it IS the polarization of the far field signal resolved as separate 
> horizontal and vertical components.
> 
> Take a look at the two components for a hexbeam as predicted by EZNEC:
> http://www.karinya.net/g3txq/temp/hexbeam_vandh.png
> 
> Note the shape of the vertically polarized (red) component.
> 
> Now take a look at the actual MEASURED azimuth response of a hexbeam, 
> using a vertically-polarized sense antenna:
> http://www.karinya.net/g3txq/temp/hexbeam_vpolarisation.png
> 
> The "skew" in the vertically polarized component is caused by 
> common-mode current in the vertical coaxial band interconnects; I was 
> making the measurements to understand the effect of alternative choke 
> positions.
> 
> It demonstrates how careful you need to be when trying to plot radiation 
> patterns. Depending on the polarization of the sense antenna, you can 
> achieve quite different results. You would have to combine the results 
> from a vertical and a horizontal sense antenna to produce the "normal" 
> EZNEC "Total Field" plot. You also need to take care to avoid 
> common-mode current on the sense antenna feedline if you want to be sure 
> what you are actually measuring.
> 
> Steve G3TXQ
> 
> Larry Banks wrote:
>> If memory serves me well -- that is simply a vertical or horizontal cut 
>> through the plot 3D plot.  It is not the polarization of the field.
>>
>> 73 -- Larry -- W1DYJ
>>   
> 
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