Thanks for all the reply so far, I'm sure there's more to come...
keep them coming!
To answer/dispell some questions:
Antenna pointing straight up:
I have used the antennas pointing straight up method before on many antennas.
It works wonderfully, quite accurately, and can even be (and has been)
modeled with AO, EZNEC, etc. to show that it does work.
K3MM also correctly stated that ground effect, if any, "would cause the
resonant frequency to be lower, not higher". My antenna is resonant too
high on 15M. Lastly, KG9X, who also just finished his XA, measured his
with the same method, same 1/2 WL @ 7.15MHz line, and a MFJ-259B. He
had EXCELLENT results. Again, pointing up, approximately 9' off the ground.
Element linear sections don't all go the same way:
My antenna is built with the 10M sections alternating forward and backward,
as pictured in the KLM manual.
Balun:
Is attached to the front driven element.
I mentioned previously that I used a 200 ohm resistor on the output
and measured the return loss to be better than 25dB across 13-30MHz.
25dB return loss is equivalent to a 1.1:1 SWR.
SWR Measurements:
Taken with a MFJ-259B, as did KG9X a couple days ago. His numbers are
great, mine not. K6LL suggests using a low power SWR bridge or a radio
to check SWR due to possible local RF pickup. I will try that tonight
(except I hate carrying around the FT-1000...too heavy!)
Continuity check:
I've checked (and rechecked) continuity between the 10M cap can and 15M
cap can. I also checked from the 15M cap can to the "D" dimension area,
where the whole assembly mounts into the larger element section. I also
checked from element half to element half to insure the shorting strap
was working.
Phasing straps:
Are crossed, tight and secure. Due to the tightness, they cannot short
to each other or the boom.
Coax:
Someone mentioned using a coax feed that wasn't tuned. First thing
that comes to mind is that SWR is constant for a 50 ohm line and
50 ohm SWR meter, regardless of coax length. Secondly, KG9X also
measured his with a same length line, no problems. Lastly, there
could be some sort of radiation problem with that length of line.
ie. that length could either be picking up the antennas radiation
or it can be affecting the near field. I will try an extension.
Tower/Guys:
I forgot to mention that the tower is guyed 100% with Phillystran.
I also forgot to mention that the boom is 15-20' away from the tower
when measurements are taken. Again, the reflector is 10-15' off the
ground.
Progress, or lack thereof:
I have an antenna crew coming on Sunday. I need this thing fixed ASAP!
So I just remembered (duh) that I have another KT-34XA in the garage
that is supposed to go at the 50' level on the 100' tower. I could
just finish assembling that one. But I wouldn't figure out what is
wrong with this one.
So here's the plan: Reset all dimensions back to factory spec.
One by one, replace each element with an element from the garage.
When problem goes away, I know which element(s) is the culprit.
Since the reflector (and rear driven) has the most to do with the
bottom of the band, I started back there. I replaced the reflector,
hoisted the antenna back in the air, and.....same. 2:1 at 21.040
Lower the antenna. Replace the rear driven....son of a gun. That
sucks too. Because the front driven element from the garage
wasn't completed yet, I skipped up to the first director. Replaced
that (still with the "garage" reflector and rear driven) and same
SWR curves. Well, at least I built repeatable elements!! By now
it was completely dark and I had to have/make dinner with my fiancee
or suffer some other kind of pain. After dinner I started to
finish off the "garage" front driven element.
Next:
Tonight I will replace the front driven element and balun with the
"garage" element and balun. The antenna will then have all 4 rear
elements replace with the "garage" elements. I will again hoist it
up and take SWR measurements. Then I will add a length of coax and
repeat the measurements. If that's not the ticket, I will replace
that last remaining triband element, the 3rd director. If that doesn't
work, I will get my 9mm and shoot something, I'm not sure what.
If I end up plugging something other than myself or the antenna, W9II
forwarded a copy of K1KP's element resonances. I will then start
attacking each element, making sure the resonances are near his.
Lastly, if time permits, I will homebrew a brand new 4:1 balun and
try that.
If there are no other breakthroughs, Saturday night I will restore
everything back to factory specs and install it as is at 100'.
Antenna season doesn't last long around here (Wisconsin) and contest
season is upon us. I will cross my fingers and hopefully the curve
will shift downward (I'll go to church before installing it) when it's
up there. If not, I'll have to live with it for this winter and
continue building the rest of the station. This XA is only 1 of
13 antennas that have to go up yet this year. Don't know if I'll
make it to the lucky #13 this year.
Thanks guys. If anyone else has some words of wisdom, let me know!!
---
Chad Kurszewski, WE9V e-mail: WE9V@qth.com
The Official "Sultans of Shwing" Web Site: http://www.QTH.com/sos
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