A few years ago, after a severe thunderstorm, I noticed that all the
johnny-ball insulators in the bottom set of guys on my tower were shattered.
I have 4 sets of guys, and the upper sets were all intact, but every
insulator in the lower set was destroyed.
The original insulators are the small "500" size, military surplus about 3"
X 1 1/4" in size, connected using 3 u-bolt clamps at each termination with
the strands wrapped (served) in addition. I replaced the shattered
insulators with larger "502" size from the power company, and used Guy
Grips, aka pre-forms, which are much easier to install than the cable
clamps.
I still have the 500's on the upper guy wires, but have never had any more
lightning damage.
My insulators are all the older brown glazed ceramic. I notice that
insulators made the past 30 years or so are light bluish-grey. I was once
told that the newer blue-grey power company insulators are not the best to
use as guy wire insulators, because the ceramic is not designed to be
rf-transparent, and that currently, insulators are made in two grades, for
rf and non-rf applications. Supposedly, the older brown glazed ones from
the power company are OK, because back then they used only one grade of
ceramic. Wonder if anyone else has heard this? I had always just assumed
that ceramic strain insulators were ceramic strain insulators regardless,
and in never even occurred to me that any insulator might be unsatisfactory
for rf use.
I do recall reading about special strain insulators manufactured with some
impurity added to the ceramic to make them have a very high electrical
resistance, but not infinite, in order to bleed off static charge build-up
in the insulated sections of guy wires, thus avoiding noise that would
interfere with reception.
Don k4kyv
_______________________________________________________________
This message was typed using the DVORAK keyboard layout. Try it - you'll
like it.
http://www.mwbrooks.com/dvorak/
http://gigliwood.com/abcd/
_______________________________________________
Topband mailing list
Topband@contesting.com
http://lists.contesting.com/mailman/listinfo/topband
|