Topband: Insulator problems- Notr og caution

[Michael Tope]

On 12/16/2013 5:52 PM, GeorgeWallner wrote:
>
> 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

Hi George,

I had the same experience with black delrin insulators for one of my 160 
meter vertical antennas. It was fine until it got wet, then forget it, 
it would breakdown. I kludged up a shroud to keep the rain off it. It's 
been fine ever since.

BTW, I have never heard of high voltage putty. Where do you get it?

73, Mike W4EF.....................