Guys, the adhesive is NOT an issue: after being over wound with the wire
it
is irrelevant!
There are 2 kinds of tape : fiberglass, which is an organic material and
glass fiber which is not. Corvettes are made of the latter!
Alex 4Z5KS
-----Original Message-----
From: Amps [mailto:amps-bounces@contesting.com] On Behalf Of Carl
Sent: Monday, July 29, 2013 5:09 AM
To: Jim Thomson; amps@contesting.com
Subject: Re: [Amps] Glass Tape
----- Original Message -----
From: "Jim Thomson" <jim.thom@telus.net>
To: <amps@contesting.com>
Sent: Sunday, July 28, 2013 6:27 PM
Subject: [Amps] Glass Tape
Date: Sat, 27 Jul 2013 17:23:05 +0000
From: Manfred Mornhinweg <manfred@ludens.cl>
To: amps@contesting.com
Subject: Re: [Amps] Glass Tape
Hi,
Glass tape usually turns to dust in UV sunlight.
I think Carl means that glass fiber reinforced, plastic adhesive tape.
That stuff indeed turns to dust rather quickly. Dust with loosely
embedded glass fibers. Even when used indoors, in dry climates the glue
crumbles rather soon, in my experience.
But I'm under the impression that Ed means a different material, one
that is just glass fiber fabric, without any plastic or glue in it. Is
that right? Such a material should survive UV without trouble.
** The glass tape Im referring to is strong and used for package
wrapping.
A tape without an adhesive is simply a wrap and in some cases rather
useless.
For winding baluns, I use one of two different techniques to avoid the
wire insulation chafing through. One is to wind the balun with
plastic-insulated wire, with the insulation being thick and hard enough
that it won't puncture. Common THHN house wiring stuff is fine. It also
gives me more confidence when working under high power, elevated SWR
conditions, when the voltage between wires can reach the kilovolt level.
** THHN is thick and has a high capacity between turns because of the
dielectric. Ive seen THHN turn to a melted mess in a couple of commercial
vertical antenna baluns at well nder 1000W.
I use Teflon sleeving over bare copper wire or stranded, silver plated,
Teflon covered wire.
The other technique is to wrap the core, but instead of glass tape, I
use several layers of black vinyl insulating tape. This tape MUST be
good quality. Since about 30 years I use Scotch Super 33+, and I can
fully recommend it. There must be other good tapes available, but when I
tried, this was the one that worked best among all the ones I tried, and
as long as it is available, I see no reason to search for another!
** Vinyl tape is a poor choice for a toroid if any heat much over ambient
is
expected.
I
have some antennas that are over 20 years old, fully exposed to the
weather, with this tape used in several locations, and it's still fine!
** You combined 2 completely different subjects in one paragraph. I agree
that Scotch 33 is great for outdoor cables and connectors and Ive been
using
it since the 1960's.
I have read lots of warning about using PVC in RF fields. This
insulating tape, and most plastic wire insulations, are PVC. So I was
always a bit scared that something terrible might happen, like an
insulation meltdown, but so far it hasn't. I wouldn't use a thin sheet
of PVC as a capacitor dielectric, but in the form of wire insulation or
a toroid core wrap it seems to do fine enough.
Black is best, for the wire insulation too. It blocks UV and largely
prevents degradation beyond the surface layer of a plastic.
Manfred
** That all depends upon the tape composition, Ive seen some import black
tape that curls up and splits in the UV AND in frigid temperatures which
are
common here. Scotch 33 is the most weather insensitive tape Ive ever used.
PL-259 connectors and barrel
splices I did over 20 years ago looked like new when I took various
antennas
down. I tried Scotch 88 but it didnt handle the cold as well which can
get
to -25 to -30F here at times.
Carl
KM1H
: 07/28/13
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