[Amps] Glass Tape

[Manfred Mornhinweg]

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

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