[TowerTalk] SWR Problem with Tri-Bander - help!

[Keith Dutson]

This symptom is likely heat-related which would explain the variance over
time on 500 watts.  Simple fact, heat is generated by power that is consumed
but not radiated.  It could be that this heat is affecting the physical
connections to the balun, which of course has the strong likelihood of
changing impedance.

Keith NM5G

-----Original Message-----
From: towertalk-bounces at contesting.com
[mailto:towertalk-bounces at contesting.com] On Behalf Of RLVZ at aol.com
Sent: Tuesday, February 22, 2005 3:11 PM
To: towertalk at contesting.com
Subject: [TowerTalk] SWR Problem with Tri-Bander - help!

Hi Guys,

I've got a Hy-Gain TH3-Mark4 that has a rather unusual SWR problem and
wonder if you have any thoughts on fixing the problem.  Here's the scoop:

1) The SWR is always fine on 10 and 20 meters.
2) On 15-meters the SWR starts out fine but the longer I transmit the higher
it goes.  Such as, when running 500 watts the beginning SWR is 1.3 to 1 but
after 45 minutes it's 2 to 1. 

Here's various things I've tried but they didn't fix the problem:
1) Replaced the coax.
2) Replaced the balun.
3) Replaced the 15-meter traps on the driven element.
4) Took all traps apart and checked for solid connections. 
5) Locked the elements together with aluminum screws.

This is not my main antenna so it's not a life or death matter.  But I
really like the antenna and want to correct the problem so I have a working
backup and multiplier antenna.

Any idears?

Thanks!   Dick- K9OM  
_______________________________________________

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