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Re: [TowerTalk] Vertical vs Beam

To: lists@subich.com
Subject: Re: [TowerTalk] Vertical vs Beam
From: Michael Tope <W4EF@dellroy.com>
Date: Mon, 06 Apr 2009 21:02:07 -0700
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
Joe Subich, W4TV wrote:

>  
>
>>Thanks, much. It is interesting that, as far as I can recall, 
>>yours is the first reference (Directly) to the QST article. I 
>>had forgotten it (Senior moment?) I must go back and re-read.
>>    
>>
>
>The radials were added at WWVH after field strength testing showed 
>that the half wave verticals failed to produce the expected field 
>strength due to e-field losses in the ground below the bottom end 
>of the antenna.  While the radials did not effect the feed point 
>impedance they provided a significant improvement in field strength. 
>
>  
>
Thanks for that clarification, Joe. My vague recollection was that W8JI 
had pointed this out in a Towertalk post a number of years ago, but I 
couldn't recall if it was WWV or WWVH that used radials under their 1/2 
wave vertical dipoles. It makes sense that there will be ground lossess 
even with a 1/2 wave vertical dipole. Any antenna in close proximity to 
ground will couple some energy to the lossy ground and induce some 
current there. The hard questions to answer are whether these ground 
losses are small enough to ignore and whether the additional field 
strength to be gained is worth the effort and expense of a ground 
screen. The suspect the answer to those questions will vary depending on 
the ground characteristics and the requirements/motivation of the user 
(i.e. do I just want something with decent performance or do I want to 
squeeze out every last dB?).

73, Mike W4EF.............
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