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Re: [VHFcontesting] Tech Help needed

To: 'Jim Worsham' <wa4kxy@bellsouth.net>, Paul Rollinson <Paulrollinson@sbcglobal.net>
Subject: Re: [VHFcontesting] Tech Help needed
From: Dan Evans via VHFcontesting <vhfcontesting@contesting.com>
Reply-to: Dan Evans <k9zf@yahoo.com>
Date: Sun, 3 Jan 2021 00:58:31 +0000 (UTC)
List-post: <mailto:vhfcontesting@contesting.com>
Hi Paul,No help here with the issue, but I wanted to thank you and the list for 
the topic.
I currently have a CC 6 element on a small tower.  I have a bigger tower I hope 
to put up soon, and I've been wanting to upgrade to the 6M7 if I ever get the 
tower project off the ground.  So I will likely face the same issues.
I've been following with interest.
-- K9ZF  President, Clark County Amateur Radio Club,Amateur Radio Emergency 
Service, Clark County Indiana. EM78el The once and future K9ZF /R no budget 
Rover  ***QRP-l #1269 Check out the Rover Resource Page at:  List Administrator 
for: InHam+grid-loc+ham-books  Ask me how to join the Indiana Ham Mailing list! 

    On Saturday, January 2, 2021, 11:55:03 AM EST, Paul Rollinson 
<paulrollinson@sbcglobal.net> wrote:  
 Good morning all,

It appears that I'm not alone with this issue. It's a great antenna until you 
try to push up the band for the digital modes, with potential for more to come.

So far I've learned this from this list and other friends in the VHF spectrum:

The theory behind moving the shorting bars out to more the freq up the band may 
be based on simple J pole type design, when you short higher up the driven 
element, it increases in resonate freq.
The 70 ohm (RG-6) phasing line might be able to raise the center freq if 
shortened. If anyone has done this, please reply with length to attempt.
The driven element might be able to be sleeved increasing the diameter and 
potential bandwidth, which is the biggest problem with this design.
Electrically lengthening the T match bars using  retaining rings at the end may 
create an aching point at hi power and wet environment. This may be 
catastrophic for an amp and will not be explored.
Repositioning D1 may help but this has unknown effect of performance.
Finding a better, free space test range will be first on the list. I have 90Ft 
trees here so spanning 2 trees and hanging the antenna in the middle show be 
I still plan on calling M2 on Monday to see if I'm missing something

I will say this, great responses from the VHF community. Thanks to all.


Paul Rollinson, KE1LI
Rollinson Associates
860-208-8814 Cell/Text

Representing Component Part 
Manufacturers for over 35 years

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