Joe Humet wrote:
>
> Ok all you antenna experts out there..
> This is were I'm at with this thing. I have replaced the balun (made no
> change)and cleaned all the joints and connections, checked and cleaned
> all of the cap tubes,reset all dimensions to factory spec.
> With it 25 feet in the air the swr sucks. On 20 the swr goes from
> 1.7 @ 14.000 to at best 1.5 at 14.300 and seems to be flat @ 14.277, too
> high in the band. On 15 it is flat at 20.603 (a bit out of the band)
> and the srw goes from 1.7 @ 21.000 to 2.0 @ 21.200 then back to 1.8 @
> 21.300. This is the biggest problem. On 10 its 2.6 @ 28.000 drops to 1.5
> @ 28.500 and goes back up to 1.8 @ 29.000.
> I have tried everything I can think of.
> I know we have some real sharp people on here and some have the same
> antenna. Please H E L P, before I cut this thing up and put up a g5rv
> (ugg).
> Thanks a bunch......
> Joe
>
> --
> FAQ on WWW: http://www.contesting.com/towertalkfaq.html
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Since there are a few guys out there having troubles with KT34XA's at
the moment, I thought I'd take the time to pass along my experience with
this antenna in hopes that it may shine some light on the problems that
guys are having with it.
Joe, I've rebuilt 3 of them now from used antennas in various condition,
and by being very meticulous and replacing questionable parts, etc., all
3 have come out very close to the same and very close to the published
specs.
First off, make sure you have the blue capacitor tube end caps and that
the tubes you have do not have drain holes on the outside. The holes
should be on the top side of the inner 3/8" tubes. If either of these
conditions have not been met, you should purchase the "capacitor tube
update kit" for an XA. It's about $45 US I think. This includes the
latest dimension sheet, modification instructions, new cap tubes and
blue end caps, and some new conductive grease, 10 meter element
extensions in case you have a really old one, and a couple of worm
clamps for that.
Other things I'd look at replacing are the clamps that go over the cap
tubes, examine the element to boom mounting blocks for cracks and
replace as needed or just replace them all if you feel like...they've
recently been redesigned out of a little different material that should
hold up better. Replace the no-doubt rusted balun clip. Replace the
plastic standoff for the dual-driven crossover feed.
You know those black plastic spacer things they put out on the element
to preserve spacing? Slide them all the way to the center and put a few
wraps of electrical tape behind them so they cant move out toward the
tip, where they wont support the element as well.
Although I havent had any trouble yet, I didnt like the loose fit of
the old shorting clamps all over the place, so once I cleaned them all
up, I ran a #6 SS sheet metal screw through all of those joints on each
element on the last one I rebuilt. Note that you DONT want to do that
into the cap tube joint. That's why I recommend replacing THOSE straps
with new ones to make sure you get a tight connection without screws.
Do everything exactly as they tell you on the dimensions, and that means
checking EVERYTHING, such as position of the cap tubes along the 3/8"
inner tube...when you replace the cap tubes, check to make sure they are
exactly the right length as listed in the manual, and that the are
positioned correctly. Mark the "top" of the inner tubing with the vent
holes to make sure they are facing up after you slide the cap tubes over
them. I use a fine line permanent marker pen to draw a little line on
the top side of that tube right at the end, so that I can double check
it later (and I've messed that up several times and had to go back and
correct that!). I also mark the tube where the 2 cap tube assy's are
supposed to butt together ( and note that that position is different for
different elements).
When you are rebuilding the elements make sure you note which part of
the element goes forward, and again when you mount them on the boom.
Certain elements get mounted with the cap tubes "trailing" (towards the
rear) and others go to the front.
When you make your A,B,C,And D measurements, they should be made from
the OUTSIDE edge of the straps involved (ie, the longest length you
could measure from those two "points"). So take your tape measure, hang
the hook on the appropriate cap tube strap and then measure to the far
edge of the shorting strap that's involved. You'll have to eyeball
these carefully as the inner straps arent on the same plane. Also make
sure you get them perfectly perpendicular. This is easier to see if you
take the black plastic spacer and push it right up against the strap.
Well, I've probably forgotten half of the other things to check, but it
all boils down to complete and thorough rebuilding and at least double
checking every single dimension that they give you, both in the
dimension sheet and in the assembly instructions and the modification
sheet.
It'll take "forever", but if you do all that, I can guarantee you the
thing will play at least very close to the published specs.
That said, I think if I have to rebuild one more KLM tribander I think
I'll go insane!! It'll be F12's next time...if there is a next time!
I'm sorry I cant provide any insight into your specific problem, but
I've never had to deal with any myself. They all worked perfectly the
first time. ...and now you know why! hi!
73, Tyler K3MM
--
FAQ on WWW: http://www.contesting.com/towertalkfaq.html
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com
Search: http://www.contesting.com/km9p/search
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