These traps have caps on the end opposite the piston. IF the cap is good it
will keep water out. The same for the heat shrink integrity for the piston
end. The original heat shrink has a liner that melts when the heat shrink is
heated. This makes a water tight seal IF the heat shrink was correctly heated
and correctly shrunk (as it was from the factory).
Over time the heat shrink can deteriorate from being out in all kinds of
weather. If someone replaced the heatshrink with the regular heatshrink or
used some other method of repair water can enter the capacitors. In this case
the capacitor must be taken apart and cleaned. There are 2 good websites that
detail this, just google R5 or R7 traps or trap repair. There are cross links
to the sites from several amateur radio sites also. Here is one of the sites:
http://www.iol.ie/~bravo/r7_vertical.htm
The capacitors are plain old coaxial capacitors and there is no electrical
reason to have piston up or piston down. The constraint comes with how the
capacitor will interfere with the trap below it or above it.
The problem would be if the brackets move and you end up with a different
capacitance thus changing the frequency.
I
have an AP8A that is very similar to the R7. I have resonated these
on the bench and find no difference with the direction of mounting the
capacitor since this was my thought on one
that was missing an end cap. However I have found a cap and did not reverse
the capacitor mounting.
73,
Bill
AI4WM
--- On Sat, 9/5/09, Barry Fox <foxbw@comcast.net> wrote:
From: Barry Fox <foxbw@comcast.net>
Subject: [TowerTalk] R7 traps
To: towertalk@contesting.com
Date: Saturday, September 5, 2009, 7:37 AM
I'm no antenna designer, but it seems to me that if the trap capacitor
clamps were swapped such that the center rod were at the bottom, no
water could then enter. Would that work?
Barry - W1HFN
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