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Re: Topband: Shunt-fed tower vs. T-vertical

To: Rudy Bakalov <r_bakalov@yahoo.com>
Subject: Re: Topband: Shunt-fed tower vs. T-vertical
From: Herb Schoenbohm <herbs@vitelcom.net>
Date: Tue, 13 Jul 2010 06:48:20 -0400
List-post: <topband@contesting.com">mailto:topband@contesting.com>
Rudy Bakalov wrote:
> I have never model an antenna before and thus have no idea what the 
> electrical length of the tower is. Furthermore, I plan on adding 2 more 
> tribanders next year, at 68' and 30' so the loading will change. Finally, all 
> the books I have read on shunt-feeding a tower have created an impression 
> that doing so is not as trivial and certainly not plug-and-play.  Thus, I am 
> considering the much simpler and more predictable T-vertical.
>
> Remember there will most likely be some interaction between the "T" and the 
> grounded tower distorting the pattern, if one end of the T is supported by 
> your tower.  I have found the easist way to tame a shunt fed tower is to feed 
> it with a three or four wire cage rather than a single wire shunt and the 
> complexities of feedlines and rotor cables being part of the mix.  The cage 
> does the radiation essentially decoupling a lot of what is run inside it.  
> Chokes and grounding at the base is still imortant however.
>   


Herb Schoenbohm, KV4FZ

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