Yeah, but usually any ground coupling will cause the resonant frequency to be
lower, not higher. Something is wrong with Chad's antenna on 15.
73 es GL Chad, Ty K3MM
-----Original Message-----
From: Jeff Singer <k2kv@reallybig.com>
To: WE9V Chad Kurszewski <Chad_Kurszewski@csg.mot.com>;
towertalk@contesting.com <towertalk@contesting.com>
Cc: k7sv@juno.com <k7sv@juno.com>
To: <towertalk@contesting.com>
Date: Tuesday, September 22, 1998 23:41
Subject: RE: [TowerTalk] KT-34XA tuning (long)
>
>Chad -
>
>I've built (and rebuilt) a number of kt-34A & -XA antennas, and have always
>enjoyed superb swr and performance. Besides the problem of occasionally
>having to dip the tubes into the pool to get everything over to the tower,
>the only difference here is that I NEVER tested them pointing up! You might
>find that, once it is horizontally mounted, it will harmonize with its
>environment in a much more acceptable manner.
>
>Remember, taking readings while the antenna is vertical only gives you an
>"approximation" of how things will be once installed properly. If you had,
>for example, NO resonance on one or more of the bands, you would want to
>know this before going to the trouble of mounting the beast.
>
>Small changes in resonance can be expected for an antenna that is designed
>to be horizontally installed at 60 feet, but which has been installed
>vertically at 9 - 15 feet instead. If it were me, I'd reset all dimensions
>to exact specs in the manual, and put the thing up already. Then you'll know
>for sure.
>
>But don't simply trust me (I am not that smart). Wait until one of the
>accepted gurus tells you the same thing. :-)
>
>Good luck.
>
>73,
>
>Jeff K2KV
>k2kv@reallybig.com
>http://reallybig.com - "The Complete Resource for All Web Builders"
>
>
>
>-----Original Message-----
>> From: owner-towertalk@contesting.com
>> [mailto:owner-towertalk@contesting.com]On Behalf Of WE9V Chad Kurszewski
>> Sent: Tuesday, September 22, 1998 5:02 PM
>> To: towertalk@contesting.com
>> Cc: k7sv@juno.com
>> Subject: [TowerTalk] KT-34XA tuning (long)
>>
>>
>>
>> Hi All,
>>
>> I'm about to put up the first KT-34XA this weekend. Upon checking
>> the SWR, it wasn't too close to the published curves, especially
>> on 15M.
>>
>> The antenna:
>> KT-34XA
>> Brand new Blue Insulators installed
>> ALL connections (strap, cap tube, tubing) thoroughly cleaned & penotroxed
>> All dimensions set, checked, and REchecked to latest dimensions
>> I've read the K3MM "bible" to rebuild
>> I've check the balun with the MFJ-259B and get nearly a 30dB return loss
>> into a 200 ohm load on all bands. (That means less than 1.1:1 SWR.)
>>
>> The test setup:
>> Antenna pointed straight up into the air
>> Reflector off of ground by 9-15'
>> Elements in a plane 90 degrees to tower (perpendicular to a line drawn
>> from boom to tower)
>> Brand new RG-213 coax, cut to 0.5 wavelength on 7.15MHz
>> (multiple of a half wave for 10/15/20)
>> New MFJ-259B
>>
>>
>> The results:
>> 13.875 3.0:1
>> 13.93 2.0
>> 14.0 1.4
>> 14.1 1.1 No complaints here.
>> .
>> .
>> 14.35 1.1
>> 14.44 2.0
>> 14.46 3.0
>>
>>
>> 21.00 3.5 This sucks!
>> 21.018 3.0
>> 21.070 2.0
>> 21.1 1.8
>> 21.2 1.3
>> 21.3 1.0
>> 21.4 1.0
>> 21.62 1.3
>> 21.696 2.0
>> 21.75 3.0
>>
>> 27.8 3
>> 27.966 2
>> 28.0 1.9 Not great.
>> 28.1 1.6
>> .
>> .
>> 29.06 1.1
>> 29.25 2.0
>>
>>
>> So, I've hoisted this thing up in the air (by myself) NINE times,
>> each time changing the tuning a little bit.
>>
>> The goal was to adjust dimension C (10M) and B (15M) to get the SWR
>> down on the bottom of those bands and see what effect that has on 20M.
>>
>> Starting with the reflector (according to KLM's "the horse's mouth",
>> the reflector has the greatest influence on the bottom of the band),
>> I lengthened C and B. Only small improvements. I then went to the
>> 1st driven element (the longer one, which has more to do with the
>> bottom of the band) and adjusted B and C. Small improvment.
>> Next to the first driven and then the first director.
>>
>> I now have B and C maxed out on both the reflector and the 1st driven.
>> (B=47.75 on ref and 48 on rear drvn)(C=28.25 on ref and 27.75 on
>> rear drv.)
>> Both 10 and 20M have better SWR across the band but on 15M the 2:1 point
>> is still only at 21.030.
>>
>> I then started to adjust (lengthen) D, which makes all 3 bands get
>> "longer"/lower in frequency. I lengthened reflector D by 1" and
>> now 2:1 is at 21.007. Lengthened it by a total of 2.5" and now
>> 21.000 is 1.9:1. My last straw was to lengthen it all the way to
>> 3.5" longer and lengthen the rear driven by 1". That resulted in
>> a 21.000MHz SWR of 1.7:1. 10M is 1.2:1 max from 28-29.1, and 20M
>> is 1.2 max for the whole band. The top of 15 is 1.1:1.
>>
>> I'm out of knobs to tweak. Where do I go from here?
>> KG9X also rebuilt one and built it to book specs and the SWR was
>> perfect.
>>
>> Anyone have similar experiences? What did you do? Wasn't there
>> someone on the list that measured the resonances of each of the
>> elements? Larry, K7SV, you have those? I'm thinking that one of
>> my elements is way off for some reason and that data would help.
>>
>> Help!!!
>>
>> Thanks,
>> ---
>> Chad Kurszewski, WE9V e-mail: WE9V@qth.com
>> The Official "Sultans of Shwing" Web Site: http://www.QTH.com/sos
>>
>> --
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>>
>
>
>--
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>
--
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