From: "Mike Dennison" <mike.dennison@rsgb.org.uk>
To: rsgb_lf_group@blacksheep.org
Date: Tue, 23 Jan 2001 16:53:52 -0000
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Subject: Re: LF: Pyrotechnic insulators
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G3YXM wrote:
> > I sympathise about the insulators, with QRO it's a battle just to
> > keep things running...

Keen subscribers to this group may remember that my cable-tie 
insulators failed last weekend, and that I assumed this was due to 
them becoming brittle in the sub-zero temperatures.

I took the mast down on Sunday and found that the insulators had 
been sparking and had burnt through. Since they had worked fine 
up to then, I assume this was because they were coated in ice and 
snow. I have replaced them with 100mm lengths of 5mm thick 
perspex (that's Plexiglass for those divided by our common 
language) cut from a large piece that I picked up at the Puckeridge 
LF site. I did wonder whether the cable ties had been sparking 
before they became iced up, and expected to see an increase in 
current at the feed point caused by an increased voltage at the far 
end. However, there was no change so cable ties make perfectly 
good insulators when not icy.

I have taken some photographs of the dead insulators, and will post 
on my web site soon.


Mike, G3XDV (IO91VT)
http://www.lf.thersgb.net