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[TowerTalk] C4XL Tuning

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Subject: [TowerTalk] C4XL Tuning
From: (
Date: Wed, 5 Nov 1997 16:23:25 -0500
Hi Rich,

        I went through a similar process with an EF -420/240 
about a month ago.  I posted a few notes to the reflector, and 
traded e-mail with Tom & Natan at Force-12.

        I tried tuning the driver & reflector individually.  
Basically I hauled the 6ft piece of boom with the element on it, 
up to the top of the tower and then checked SWR.  My first mistake
was not putting the hairpin coil on the single elements....SWR was
awful at first.  After I added the coil, things acted better.  
What I found was that the dimensions were off by about 3 

        Then when I put the whole thing together and got it to the
top of the tower, I checked SWR once again before mounting onto the 
mast.  The tuning was low...about 7.040 when I was aiming for 7.120!!!  
So back down the tower it comes, and it turns out that putting 
the jumpers back to their original positions (as suggested in the book)
was the right place to be.

        It may be a pain, but the only right way to do it is with the
beam fully assembled.  It seems that interaction between the elements
can really throw things off.

        Hope this helps.
        --Lee - KT4ZX
        Georgetown, KY

> From  Mon Nov  3 
> 19:41:53 1997
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> Date: Mon, 03 Nov 1997 18:36:28 -0800
> From: Richard Thorne <>
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> Need some advice from experienced C4XL antenna users on tuning the 40
> meter portion of the antenna. (C4 users could probably help to).
> I have my antenna ready to go at the base of the tower.  I raised the
> antenna to about 15' off the ground and attempted to tune the reflector
> so it would reasonate at 6.9mhz.  However, the lowest dip I could get
> on the mfj analyzer was 3 to 1 at 7.3 mhz.  So I'm assuming the low
> height and the close guy wires is screwing things up.
> So, the question is, how accurate are the settings given in the
> construction book?  Its going to be a bear to get the antenna to the
> top of the tower and want to keep the up and down to a minimum.  The
> antenna is going to be at 60' above my office building roof and will
> be the only antenna mounted at the apex.  No stacking of other antennas.
> Thanks in advance.
> -- 
> 73,
> Rich Thorne - WB5M
> Amarillo, TX
> --
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