I am specifically referring to Scotch #27 Glass Cloth Electrical Tape
(or so the box says). Rated to 266 degrees F. Used in furnace, oven
controls and switches.
I use 1/2 inch size because it's easier to wind on the ferrite core.
The specific application put the insulating material inside a 50 watt
resistor,
which would make a mess with ordinary #33 black stiff.
When I built a balun for ladder to coax transition, wound the tape on a
heavy
balun core compliments of "the Wireman", see his catalog. After the balun
was built, I further coated it with several layers of epoxy. Fastened to
perfboard,
mounted about 3/4 " from each wall of a copper box, made from PC material.
Beehive insulator output, type "N" input. Hasn't failed in over 6 years.
I never used the tape outside, inside a UV oven, etc. Just as an
insulator, or in
the case cited as a spacer and insulator.
That's my story and I'm stuck with it ...
73!
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Today's Topics:
1. Re: Glass Tape (Manfred Mornhinweg)
----------------------------------------------------------------------
Message: 1
Date: Sat, 27 Jul 2013 17:23:05 +0000
From: Manfred Mornhinweg <manfred@ludens.cl>
To: amps@contesting.com
Subject: Re: [Amps] Glass Tape
Message-ID: <51F401F9.6070903@ludens.cl>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
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.
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.
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! 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!
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
========================
Visit my hobby homepage!
http://ludens.cl
========================
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