[TowerTalk] TH3MK4 15M SWR fluctuation
George Cortez Jr
ne2i at optonline.net
Wed Apr 2 10:45:20 EDT 2014
they are pretty easy to disassemble Use new ss hardware and clean them out. Insects love these traps and make nests in them.
On Apr 2, 2014, at 7:21 AM, Gary Smith <Gary at ka1j.com> wrote:
> I rehabbed my father's old TH3MK4, renewing the electrical contacts,
> replacing the traps and installing a new DXE-BAL050-H10-A balun. It
> worked well on all three bands for the last week and its really a
> pleasure to have access to a beam again as I've only been able to use
> vertical wires since 1995.
> But last night I noticed the SWR was wildly swinging up to 5:1 on 15M
> when using the amp and when running barefoot it dropped back to 1.2
> as it had been at before. More testing finds that anything over
> 70-80W raises the SWR and it remains stable at 1.2 below that power
> level. 10 & 20 are unaffected and have a 1.2 SWR. I ran the amp into
> a separate 15M antenna and there was no issue with SWR so it appears
> isolated to the TH3.
> I'm suspecting a 15M trap has failed and I either need to replace it
> or rehab it. I don't know how to tell if it is the driven element
> trap or one of the parasitic traps that has failed. Deciding which
> trap is involved is the first problem, my guess is it would be the
> driven element trap.
> Once I have that sorted out, are these traps easily reparable & if
> so, any caveats? I've done a google search but haven't found that
> answer yet.
> Suggestions on how to determine which trap & how to best rehab it?
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