I am sure you already did this, but check it with an SWR bridge and transmitter
before making the climb.
My MFJ259 (any small signal analyzer for that matter) has issues in the
presence of strong RF. Really noticeable when that RF is CW or SSB but can
fool you if it is from a constant source such as an AM broadcast station. I
have an an AM array a couple of miles from my house that makes my MFJ259 almost
useless.
You are right, its always the top one that goes. I put my KT34XA 10 feet above
my 2 el 40 meter figuring the 40M was going to have element droop and would
probably break first. Guess which one isn't working? I built steps to go on
my mast but it adds a whole new element to tower climbing when you step off the
flat top and start going up the pipe.
Earl
N8SS
To:TOWERTALK@contesting.com
Subject:[TowerTalk] 20 meter stack problem
From:Cqtestk4xs@aol.com
Date:Sun, 2 Feb 2014 21:10:33 -0500 (EST)
List-post:<towertalk@contesting.com">mailto:towertalk@contesting.com>
I came back from vacation to find my 20 meter stack not working right. To
make it short, the bottom stack 100/50 is fine, SWR is the nominal
1.2-1.5. Of course if one part has to go, it is the top one.
The top stack, 200/150 is the problem. Directly connected at the base of
the tower the SWR is around 3.5 and drops to around 1.7 at around 15.6 mHz.
I have not gone up the tower yet to check it out hoping to get a couple
of suggestions before doing so. Physically, from the ground, the antennas
look fine, and with the SWR at least getting near a "normal" reading, even
if out of the band, I think the baluns are good. The antennas are M2 with
1:1 baluns.
I do have a phasing harness made up of a tee-connector with two 1/4 wave
75 ohm matches leading to the two antennas as well as a couple of a other
coax connectors. My hope and thinking is that perhaps one of these
suffered
some water intrusion even though they were pretty well waterprooofed.
Since I wasn't home, and we did have t-storms, lightning could also be a
source
of the problem. By the way since the antennas do have baluns I checked
the resistance and it was about 1 ohm....pretty much what you expect, but
that could be due to a short on the line.
Any ideas before I climb? I plan to take my trusty MFJ259 and a
multimeter and check all connectors that I can reach.
Bill K4XS
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