Re: [amsat-bb] coax seal

["JC Smith" <jc-smith@xxxxxxxxxxxxxxxx>]

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,
http://www.championradio.com
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
<w7lrd@juno.com>
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
scotch
> > coat and then put another wrap of 33 on it and seal the whole thing up
with
> > scotch coat again making sure you get a good coat at both ends of the
tape,
> > 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
connector.
> > 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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