Summary: grounding parasitic elements on KT34XA
Lynn D. Osterbur
no9z@prairienet.org
Wed, 9 Oct 1996 20:30:12 -0500 (CDT)
Here is the summary of responses I received regarding grounding parasitic
elemnets on the KT34XA fyi
curious, Lynn. Why are the elements insulated from the boom? 73
Stu Greene WA2MOE
7537 North 28th Avenue
Phoenix, Arizona 85051 USA
wa2moe@doitnow.com
>
>
> Now that I have my KT34XA on the ground for the 3rd time, I was thinking
>of grounding the center of the parasitic elemnts to the boom. The books
>say there will not be any change in performance. I was wondering about
>static build up. Anyone have any experience or comments regarding
>grounding or not grounding the reflector and the directors?
>Thanks 73 Lynn NO9Z
>
I asked Mike Staal K6MYC (the inventor) that same question and he said
"leave it like it is."
Would like to hear what you get back from the many experts on towertalk.
Mine is coming down for the third time in 12 years for new caps and the
second balun. Boy I wish I could find someone with the elements so I could
replace them and fix the old element at my leisure rather than rush to get
them back on. I do have a crank up and take the elements off one at a time
from my roof.
Dave K4JRB
Id advise against it, or at least recommend that you document the VSWR
bandwidth and F/B performance of the antenna before and after your
proposed modification to be sure that no unintended degradation has
occurred!
Multiband Yagis using elements grounded to the boom are subject to
spurious undesired resonances. This is caused by currents flowing in
adjacent elements and the boom - for example 1/2 half of the last
director, the intervening boom section, and the opposite 1/2 of the
adjacent element. The "books" you refer to probably referred to monoband
Yagis where such spurious resonances are much less likely.
I'd don't want to discourage you from trying your idea - but to encourage
you to do so with due attention to detail.
73!
Frank
W3LPL
donovanf@sgate.com
Lynn, I have grounded the end elements on my KT34XA with no change in SWR.
I grounded them at the center via a 2 turn loop of 1/4" copper so they would
act as end loading so the boom could be used as a 40M dipole. I feed the
boom with a gamma match. Works very well (>250 on 40 with it.) GL 73 Clay,
KF4IX (for now.)
curious, Lynn. Why are the elements insulated from the boom? 73
--------------
a postscript...why not ask klm? 73
Stu Greene WA2MOE
7537 North 28th Avenue
Phoenix, Arizona 85051 USA
You might ask Bruce at KLM KLM_ANTENNAS@msn.com he has been most
Shown 90%, press <SPACE> for more, 'q' to quit, or 'h' for helphelpful to me during my resent rebuild. He is THE KT-34 expert.
73s de Ed
Don't even THINK about it....
"Bad Boy! Bad Boy!" <whap , whap, whap, - sound of rolled up newspaper> <g>
Denny
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Thanks to all who responded......
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Now the facts per Bruce at KLM
Bruce recommends not grounding the parasitic elements unless you are
having static build up problems. He noted that this occurrs most
frequently along the coast and in very dry areas like Phenoix, AZ.
In those cases where a popping or crackling noise can be heard on the
receiver, it is then recommended. He was of the opinion that the
antenna is somewhat quieter with non-grounded elements.
I will leave my elements ungrounded, but for those with static problems
you now have the answer.
73 Lynn
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