Topband: Insulator problems- Notr og caution

[GeorgeWallner]

On Mon, 16 Dec 2013 14:32:41 -0500
  "Charlie Cunningham" <charlie-cunningham at nc.rr.com> 
wrote:
> Many black plastics are "blackened" by the addition of 
>"carbon black" that
> can make them rather lossy at RF!  "Been there, done 
>that" in my work - at
> 900 MHz.

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. I replaced the burned insulator 
with the a new one and covered all the insulators with 
high voltage putty. That was about two years ago and I had 
zero trouble with any of them since.

George
AA7JV