On 1/2/2011 11:38 PM, RLVZ@aol.com wrote:
> Hi Guys,
> I've used Hy-Gain TH3's, TH6's, and TH7's for the past 40 years that were
> made by the original Hy-Gain Company. I like to use them in small stacks.
> During the past 5 years, I've purchased 2 new TH3-Mk4's from the new
> Hy-Gain/MFJ Company and they each have the exact same problem and I can't
> out how to fix them. Perhaps you have had a similar problem? Here's my
Try to borrow (or purchase) one of the IR heat sensors and watch, or
have someone watch the thing while running like that.
You might be able to rent one at one of the home supply rental places.
> Both of these newer TH3-Mk4's work fine and have excellent SWR's at 1,000
> watts when first using them. In fact, I can contest with them and "run"
> stations for hours at 1,000 watts on CW and the SWR is fine when operating on
> 10 or 20 meters. But on 15-meters only, after 15 minutes of use at the
> same 1,000 watts, the SWR starts to climbing on both antennas, by 30 minutes
> of use the SWR is over 2 to 1, and by 45 minutes the SWR is 3 to 1. (which
> requires me to QSY from 15-meters until they cool off)
> Things I have tried and it didn't correct the problem:
> 1) Replaced the 15-meter traps with original Hy-Gain Company traps.
> 2) Replaced the Balun.
> 3) Made sure all elements and traps had electrical contact.
> 4) Took the antenna down and looked for discoloring but didn't find much.
> 1) Could I have a bad 10-meter or 20-meter trap that only effects
> 2) The driven element has plastic boots to insulate it from the boom.
> Could a plastic boot be cracked and only effect 15-meters?
> 3) If the problem is a trap, do you think the defective trap is on the
> Driven Element... or could it be on the Director or Reflector as well?
> I need to get one of the TH3's back up this week... so I'd sure appreciate
> your thoughts on how to fix this problem.
> Dick- K9OM
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