[TowerTalk] TH3MK4 15M SWR fluctuation

[George Cortez Jr]

they are pretty easy to disassemble Use new ss hardware and clean them out. Insects love these traps and make nests in them.

George NE2I

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?
> 
> 73,
> 
> Gary
> KA1J
> 
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