My TH7 is acting up on 10 meters. I wonder if the same things have
happened. It's time to take it down and find out. I have a couple of tips
that are bent as well.
Mike
W0MU
-----Original Message-----
From: John Schaffner Jr.,- K8LN [mailto:k8ln@neo.rr.com]
Sent: Friday, July 23, 1999 10:58 AM
To: TowerTalk
Subject: [TowerTalk] trapped
Tower Talkies.........there is a picture on contesting .com of a fire
truck taking down a TH7. Let me explain why the TH7 had to come down
and also show you a picture of what was found to be the problem with
fluctuating swr. After CQWWSSB 97 I began noticing the swr changed after
a rain. Only on 15 meters at first. If the rain lasted for more that a
day the swr would start to lower frequency on 20. Prolong the rain, the
swr would change on 10 also. The dip on 15 would occur around 20825. I
was puzzled. After a few days of dry everything returned to normal. Got
the glasses out and looked at the drain holes, all open and ok. Checked
the coax, it was ok. Called high-gain, they said change the balun, I
was told that a balun should last longer than 14 years and they mailed a
free one. Scott, K8DX the "Tower man of Louisville" changed the balun
and no change. Wonder if will get the same service from MFJ? I
cornered the "High-gain man at Dayton hamvention and explained the
problem and without hesitation he said that the trap ends of the driven
elements are not draining. This is a problem we know happens and the fix
is a cleaning the trap out and a 1/4 inch hole drilled in the black
plastic trap cap, tip element end. This will allow and water settling in
the cap to drain. Water collecting in the tip end of the driven
elements will lower the sweet spot of your swr.
WELL.............he was exactly right. the picture will show that over
14 years critters took up house keeping in the tip ends of the driven
elements. There was some build up in the other traps but the driven
elements were the worst. I found mostly wings, legs and small blades of
grass, this caused the water to collect and act like a piece of wet
cloth around the element and the trap.
One trap showed that some arcing occurred.
After the beam was down the traps were blown out and every element was
cleaned and re-greased. I was amazed at the condition of the elements
and the plastic hardware. Only made two modifications. 1.philly strand
for boom support. 2.stainless steel strut clams on the boom. The old
ones rusted and I didn't want to re use them.
The Fire Truck is so heave that it would have left deep ruts in my yard
so the re-hanging of the TH7 had to be done when the ground is very
dry. Friday the16th, no rain for two weeks, Scott, K8DX had the time,
Don and his truck was available and I was ready. My wife, Kathy didn't
think my timing was the best for putting it back up. The problem in
Kathy's eyes was my daughters wedding was on Sat the 17th. Everything
was in place for the wedding, the time slot was open. I told her I am
ready, I have wrote the check and have rehearsed my line for the
wedding. Right in the middle of putting the TH7 back up she got a call
that the lettuce for the dinner never got placed....Kathy said "WE HAVE
to leave now there is only one store around that has that much lettuce
and it closes at 9pm". As I tell the story the beam was up and working,
the lettuce was bought and I had a half hour to spare. Randy, KD8JN
say's it's all about getting your priorities in order!
I am very pleased with the TH7. The wedding was GREAT. I am very proud
of my daughter and son-in-law.
73
K8LN
John Schaffner
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