Topband: Insulator problems- Notr og caution

[Tom W8JI]

> I have been using 3" black Derlin (Acetal)insulators at the base of my 160 
> m vertical. Because the antenna is only 91 foot tall, there are 
> substantial voltages on the insulators at legal limit. Indeed, one them 
> caught fire just after a rain-shower, when water got between the insulator 
> and the metal.

You are had that issue because you have no leakage path length. Aggravating 
that, you probably have contaminated water from the metal tower legs, 
although anything can tear up when wet unless it has a pretty long surface 
path.  You can have Teflon or anything there and you will tear it up.

That problem can be cured with rubber ribs, or by using a larger insulator 
and turning ribs or skirts in it. Next time, just find rubber panel grommets 
that fit tight and string them over the rod.   They make shrink to fit 
sealing grommets that are 5" OD. They make dandy skirts, or you can 
improvise with other materials like you did.

They put polymer ribs over fiberglass rod insulators for good reason. :-)

http://www.victorinsulators.com/polymerindex.htm


 73 Tom