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Re: coax seal

Hi John,

What you say makes sense, and I'm going to find some 130C and give it a try.
I have, however, seen the problem of coax being crushed by tape wrapped too
tight.  It would seem to be even more of a problem with some of the low loss
cables we use on the higher freqs.  I don't know what kind of tape it was
nor the specific cable, but I do recall seeing it more than once.

Another product I might throw in for consideration is LET (liquid electrical
tape).  It can be purchased on line at Champion Radio Products,
It is similar to Scotchkote, but is not supposed to deteriorate in sunlight.
I have not tried it myself, but plan to as soon as my current can of
Scotchkote runs out.  Champion also carries other items such as vapor seal
and Scotch 33+ and 88 vinyl tapes.

73 - JC,k0hps@amsat.org

----- Original Message -----
From: John Harrington <johnh@ih2000.net>
To: B Sinbine <stonehaven@webcombo.net>
Cc: Franklin Antonio <antonio@qualcomm.com>; JC Smith
<jc-smith@worldnet.att.net>; <amsat-bb@AMSAT.Org>; Bob W7LRD
Sent: Thursday, April 20, 2000 6:16 PM
Subject: Re: [amsat-bb] coax seal

> Hi, Bill.  I haven't ever had that problem (compressing coax by
> overstreching the tape) in over 40 years of doing it that way,
> nor have I ever heard of it happening to anyone I know.  I'm
> not arguing with you, I just never had the problem.  Scotch 130C
> is a very soft tape, and takes very little force to stretch it
> to the recommended half width.  On a "hard" tape like 33 or 33+,
> you MUST stretch it, at least a moderate amount, or it will not
> conform to an irregular surface.  Unstreched tape leaves wrinkles,
> and water or other contaminants can get under it.   Scotch Coat
> might seal up the holes from wrinkled tape and give you a good
> seal, but I've never seen the need for it if the tape is properly
> applied in the first place.   By the way, a neat trick on a cold
> day at the top of a tall tower is to carry your roll of tape under
> your armpit, under your coat or jacket.  Your body heat will keep
> the roll of tape soft and easy to work with.   73  John  W5EME
> B Sinbine wrote:
> >
> > At 22:24 2000-04-19 , John Harrington wrote:
> > >I agree- very good tips.  You also may want to consider using Scotch
> > >130C
> > >self-sealing tape in the first few layers.  This tape, when streched
> > >tightly, fuses to the layers underneath and makes an almost perfectly
> > >sealed covering.  The technique is to stretch the tape to about half
> > >its' original width when taping, and overlaying the new turn over
> > >about half of the previous turn.  This is called "half-lapping".
> > >The 130C should be covered with an overwrap of tightly-streched
> > >Scotch 33, 33+, or 88 tape.  Relax the tension on the last few
> > >turns, to eliminate the tendancy to unravel.  You can get any of
> > >the 3M tapes at any electrical wholesale house.
> > >  John  W5EME
> >
> > Hi All
> >
> > I want to warn everyone about stretching the tape tight. When you make
the tape
> > that tight you are adding several hundred pounds of clamping force on
the coax
> > and you WILL compress the coax in time and start to have problems with
it. The
> > best way is to just use 33 and just pull it snug and apply a coat of
> > coat and then put another wrap of 33 on it and seal the whole thing up
> > scotch coat again making sure you get a good coat at both ends of the
> > i.e.: coax and connector. If you do it this way all you have to do to
remove it
> > is cut the tape and it will just peal off and you will have a clean
> > Don't put the scotch coat on the coax or connector first as you will
never get
> > it cleaned off if you need to take the connector apart.
> >
> > 73, Bill N4XEO
> >
> > E- Mail        mailto:n4xeo@amsat.org
> > home page: http://www.qsl.net/n4xeo
> > F.A.D.C.A.: http://www.fcrosby.com/fadca
> > FPAC         http://www.qsl.net/fpac
> > ICQ: 19219163
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