I have a similar situation and I received the following advice from two
Polyphaser application engineers: three lightning arrestors on each line
from tower to house. One arrestor at the top of the tower to catch the
strike energy as close to the source as possible. Another arrestor at the
bottom of the tower where the cables make the 90 degree turn from vertical
to horizontal. Finally, a bulkhead arrestor at the SPG ground panel going
into the house.
Another professional feature is that there are approximately 25 separate
runs of #12 copper wire bonded to the SPG entrance panel. This bundle of
25 ground wires were then routed into the ham shack to individually ground
each piece of equipment as required. No daisy chaining of grounds, no buss
bar along the back, but individual and separate ground wires all leading
back to their common SPG panel.
Just make sure your underground buried conduit and all utility enclosures
are at least three times larger than they need to be and that drain rock is
placed in the bottom of the conduit trench. Finally, use perforated septic
tank conduit to allow water and condescension to drain out into the drain rock.
73, Dick
From: "Bill Ralston" <n7vm@lgcy.com>
To: <towertalk@contesting.com>
>Date: Tue, 3 Dec 2002 20:06:07 -0700
>Subject: [Towertalk] Lighting arrester placement
>
>Tower is 300' from the house, with a buried conduit from house to tower
>about 1-2' underground. I am planning to put a set of lighting arresters at
>the tower base where the coax will enter a small utility enclosure
>containing remote switching equipment. A second set of arrestors will be on
>a bulkhead feed through panel at the entrance to the house.
>
>Here is my thinking:
>
>The 300' of cable from the house to tower, even though it is buried, seems
>like a good candidate to pick up induced currents from nearby lightning
>strikes. Hence, I want lightning arrestors on the entry panel to the house
>(which will be the single point ground for all of the indoor equipment).
>
>But, the most likely lightning strike is to the tower. By putting a set of
>arrestors at the tower base before entering the utility enclosure, this will
>protect the remote switching equipment and limit any coax damage to coax
>runs on the tower.
>
>Is this overkill? Is this counter productive? (I've never seen anything
>about 2 arrestors in series in the reading I've done). Adding the second
>set of arrestors at the tower base certainly adds lots of $$ (On the antenna
>side of the remote switch there are 6 arrestors required, only are 2
>required back at the house).
>
>-- Bill N7VM
--
Dick Flanagan W6OLD OOTC CFII Minden, Nevada
Visit http://www.cvrc.net
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