Topband: Changes To My Shunt Fed Tower

[Gene Smar]

Bob:

     Before making physical changes to the shunt feed system, can you try 
changing the length of the StepIR element to see if that affects the match? 
If it does or doesn't make a difference, that would be valuable info for the 
group.


73 de
Gene Smar  AD3F


----- Original Message ----- 
From: "Bob Garrett" <rgarrett5 at comcast.net>
To: "'Jim F.'" <j_fitton at yahoo.com>; "'top Band'" <topband at contesting.com>
Sent: Sunday, December 11, 2011 12:21 PM
Subject: Topband: Changes To My Shunt Fed Tower


> Hello Topbanders,
>
> It is getting cold in the Northeast and as I get older, I dislike the cold
> even more.
>
> In April of this year, I replaced my Cush craft D40 40 meter rotable 
> dipole
> with an OptiBeam OB-4030 dipole for 30 and 40 meters right at the top of 
> the
> mast.  The overall length of the antenna is about ten feet longer and I am
> assuming that it has added some additional capacitance to my 100 foot 
> shunt
> fed tower with a Cush craft X7, A3WS, 5 EL M2 6 meter yagi and the new
> OptiBeam dipole.
>
> My match on the tower went from 1.0 x 1. To 1.9 x 1 after I installed the
> new antenna.  In terms of loss, this isn't a huge change but my amplifier
> doesn't like the change.  Before I spend a lot of time running back and
> forth to the tower making random changes, any thoughts as to what I can do
> to improve the match.  I'm currently using one series capacitor 1000PF for
> the matching network.  I have attempted to adjust this capacitor but it
> looks like the 1.9 x 1 is the low point.  Perhaps some thoughts - increase
> or decrease the spacing of the shunt wire?  Move the connection up or down
> on the tower?
>
> Before I get to crazy, just wanted to look to the base of knowledge on 
> this
> reflector for your input.
>
> 73 and tnx in advance.
>
> Bob K3UL
>
>
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