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Mosley trap test?

Subject: Mosley trap test?
From: sdelling@facstaff.wisc.edu (Scott Ellington)
Date: Tue Feb 11 10:13:27 1997
Jeffrey W. Withers wrote:
> 
> What a frustrating day with my tri-bander.
> SWR was 2.5:1 and the antenna only resonated
> below the CW portions of the bands.
> I replaced the feedline and the problem improved
> somewhat, about 1.5:1 on 20M .. flat at bottom of 10/15.
> So if I bring down the driven element, how should I test
> for bad trap? Can a bad trap just a little off
> allow a load of 1500 watts? Anyone else remember
> having a sudden change in the resonent freq?
> This antenna had flat SWR, but something has changed
> since that last ice storm. Ideas? tnx/73  Jeffrey@WLN.com

My guess is that a trap is full of ice or water, and may work
again when it dries out.  Another possibility is that the ground
connection to one of the coils is open.  Mosley's grounding method
is poor.  The problem is probably obvious once you open up the trap
and look at it.

But you can test the traps with a dip meter.  Remove the trap from
the element and take off the cover.  You should see a very sharp dip
near the band on which the trap is active.  (The innermost traps should
dip near 28 MHz.)  The traps from the two sides should dip at almost
exactly the same frequency.  
-- 
73,

Scott  K9MA
sdelling@facstaff.wisc.edu

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