Date: Sat, 11 Sep 2010 22:22:35 -0700
From: "Jim Brown" <jim@audiosystemsgroup.com>
Subject: Re: [TowerTalk] Lightning Protection Question
Gene,
I didn't misread or overlook it at all. The function of an arrestor is to
protect sensitive (and expensive) electronics from a strike. ALL IT DOES IS
SHORT THE COAX. That remote switch is neither sensitive nor expensive.
Although, as K8RI noted, it's easy to do that with the switch, the coax isn't
connected to the shack, so it doesn't matter. So I'm sticking with my (and
K1TTT's) advice. Arrestors go as close as practical to the sensitive
electronics that they protect. Anywhere else is a waste of money.
73, Jim K9YC
## Some folks will use SPDT vac relays for the remote coax switch. [ IMO,
this makes for the
ultimate, reliable remote coax switch, esp if a gigavac G-2 is used]. I wire
those
things so when the relay is DE-energized, the center conductor is grnded to the
remote switch box
which in my case, is at the top of the tower..where it belongs. Yagi's with
hairpin match's will have the
center conductors grnded anyway. [ since the braid of the same cable is bonded
to
top of tower..via the remote coax switch. ] Now whether the super duper,
type 31 cookbook
5 k+ ohm balun will impede the lightning is debatable. OK, now we have ALL
the braids
of the remote switch box grnded to top of the tower... and ditto with all the
center
conductors. [ excluding OWA designs].
## In this one example... there is now a single coax coming down the side of
the crank up tower.
In my own case, that smaller cable, then has to interface into a larger
cable..which heads back
to the basement [aprx 60'] . Since the small cable has to be interfaced into
a larger cable,
I decided to install a bulkhead lightning arrestor at base of tower. You can
now kill 3 x birds with
one stone! [A] interface 2 x different cable types. [B] grnd the shield of
BOTH the small + big
coax cable. [C] have a lightning arrestor at the base of the well grnded
tower.
## I install a 2nd lightning arrestor at the SPG. I use this lightning
arrestor to [A] bond
braid to SPG. [B] interface back to a small coax cable. [ C] lightning
arrestor. I also run a
2 ga Cu wire between base of tower, and SPG.
## In previous tower install's, [ not crank ups] I also ran ALL coax, and
control lines down the
INSIDE of the tower, on the inside of the big V shaped legs. Those were all
big face width towers,
one was 32", top to bottom. Other's were even bigger. I don't think I would
want to try running 7/8" heliax
up the inside of Rohn-45.
## in this one case... since big and small coax cables have to be interfaced at
base of tower, plus braids
need to also be grnded... a lightning arrestor, imo, is a wise choice. It's
easily accessible, and also provides
a demarcation point, and / or test access point. IE: insert test gear and
either look up the tower... or look back
towards the shack. In some cases, I can see where the 'base of tower arrestor'
would take the brunt of the damage.
Later... Jim VE7RF
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