[TowerTalk] R7 traps

[AI4WM Bill]

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 at comcast.net> wrote:

From: Barry Fox <foxbw at comcast.net>
Subject: [TowerTalk] R7 traps
To: towertalk at 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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