I have to confess at the beginning that I was only interested in how they
handled a lightning strike. I didn't think until later that I should have
asked about equipment rf grounding and so on. In fact there were a bunch of
things I wish I had asked but you can't think of everything. Anyway, medium
wave broadcast stations in the U.S. seem to all have antenna designs that
happen to be great for dissipating strike energy because they have these
really good radial systems. This one was a relatively low power station
(around 250 watts). The tower was 5/8 w. & made by Rohn, around 370 to 400
feet tall with a beacon on top and lights halfway down. Each side was about
a 15" wide. Can't remember if it was 3 or 4 sides. It tapered down to the
insulator which went from about 8" down to 6" in diameter and 4 or 5 inches
thick. Instead of spark balls they had a short rod about the size of a
railroad spike coming up from the ground to within 3 to 5 mm of the tower.
I guess the gap could be that small because of the low tx power. The
insulator sat on a concrete base about 3' square. there were four 4" wide
metal straps going down around the base to a buried loop around the base
that the radials were tied to. They had a radial every 3 degrees & all were
one or two inch wide heavy gauge braid buried under the grass. So it looked
like when the tower got hit all of the energy would simply come down, jump
the gap and fan out on the radials.
Assuming a ham with a tower has the room, I wonder how much more protected
his station would be if he (this assumes he's not using the tower as a
radiator) buried 120 heavy guage radials all one or two hundred feet long
and bonded them to the base of his tower? Would this divert most or all of
the current? Sorry I didn't come up with more useful information.
73,
Rob Atkinson
K5UJ
k5uj@hotmail.com
----Original Message Follows----
From: "Bill Hider \(N3RR\)" <n3rr@erols.com>
To: "Rob Atkinson, K5UJ" <k5uj@hotmail.com>,<towertalk@contesting.com>
Subject: Re: [Towertalk] MW BC tower insulator swap method
To: <towertalk@contesting.com>
Date: Thu, 16 May 2002 08:58:31 -0400
Rob,
So tell us about how they did their grounding!!
Bill, N3RR
----- Original Message -----
From: "Rob Atkinson, K5UJ" <k5uj@hotmail.com>
To: <towertalk@contesting.com>
Sent: Wednesday, May 15, 2002 2:19 PM
Subject: [Towertalk] MW BC tower insulator swap method
> Hi you guys:
> stuff deleted
. I wanted to see how the
> pros did their grounding, counterpoise connections, and insulation of the
> tower. I expected to be told we couldn't get close because of liability
but
> to my surprise the guy showing us around let us gather around the tower
> base.
stuff deleted
> 73,
> Rob Atkinson
> K5UJ
> k5uj@hotmail.com
>
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