K1TTT Technical Reference

K3MM on the KT34XA:

 

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

>

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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