Trapped Again

K2MM at MasPar.COM K2MM at MasPar.COM
Tue Apr 13 18:53:23 EDT 1993

The discussion here on Cq-Contest about fixing traps was, for me, very
timely.  I managed to blow up my CushCraft R-7's 30-meter trap for the
second time Sunday night.  (Amazing what you can do with three 811-A's
running 200 Watts.)  CushCraft sent me a warranty replacement the first
time, but that was more than a year ago.  I was wondering how much
they'd charge me for a new one, but I decided instead to try to fix it,
having taken encouragement from remarks made by Tom/WB4IUX, Scott/K9MA,
Mike/N6MZ, Tim/K3LR, Dave/KT5V, Fred/K1VR, and Bill/KM9P.

When I slit open the heat-shrink tubing covering the trap coil, I found
it was full of water.  I hadn't expected that.  The heat-shrink tubing
seemed to make a fine seal against the aluminum.  I conclude that the
water must have gotten in through the inside of the upper aluminum tube.
The same thing almost certainly happened the first time.

By removing the top trap and fully extending the aluminum below it, the
antenna is working again on 30 meters as an "R-6".  Forty will have to
wait for repairs, though.  When I've gotten the coil rewound, I'm going
to make sure I seal the joint where the top of the fiberglass dowel is
inserted into the upper aluminum.  I expect this will keep water out of
the trap for good.

If I were erecting a new R-7, or replacing its 30-meter trap with one
from the factory, I'd consider doing the seal job as preventative
maintenance.  But the logistics of getting the sealant into the right
place without trashing the original heat-shrink covering is unclear.
Anybody else have experience with blown R-7 traps?  Thanks.  --John/K2MM

More information about the CQ-Contest mailing list