[CQ-Contest] sealing contest feedlines

Charles Harpole hs0zcw at gmail.com
Thu Dec 8 00:02:53 EST 2016

Planning and putting new feedlines for my contest antennas, I researched
joint sealing techniques.
1.  Wraps of black electrical tape, even Scotch 33+ for example, is
inadequate.  I have cut mine open yrs later, many wraps, and there it is
damp or even wet inside.  Oh, also do not, for any use, PULL that tape to
break it... that creates a stretch which will later come loose and wave
like a little flag in the wind.

2.  One good method...  wrap the joint (coupling coax cables together, for
example) with one turn of good electrical tape, cover that and the whole
joint with CoaxSeal.  Removal is made easier with the one wrap of
electrical tape.   Excellent seal, examined years later.
However, pulling CoaxSeal joints over other cables or whatever can easily
dislodge the CoaxSeal.  Definitely, do not cover the CoaxSeal with wraps of
electrical tape because as you pull that tape, it can easily dislodge the
CoaxSeal.... better to top CoaxSeal with heat shrink tubing that hopefully
shrinks equally and presses equally on the underlying CoaxSeal.

3.  Use a good quality heat shrink wrap that has goo or glue inside which
also activates semi-liquid.  The goo inside dries and really seals while
the heat shrink tube pulls tight over that.

For fun, investigate the many products made to water-tight seal cable
joints.  3M has many including Scotch 33+ but also caulking compounds,
etc.  Silicone, like that sold to seal around automobile windshields, is
not good if put in as one large blob... in that case, I witnessed, the
liquefying plasticizer chemical in this product will ooze out UNDER the
seal, leaving the joint immersed in liquid later.  Silicone can be applied
in thin layers, each drying before another is put on top, but there are
better ways to seal.

Water will get into most things, of course.  73, Charly

Charly, HS0ZCW

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