On 3/23/2021 12:11 AM, Ron Hylton via TowerTalk wrote:
I'm contemplating the best route for the coax and control cables from a new tower to
my single-point ground and shack. The easiest and shortest way to get the
cables to my entry point is by running them through the crawl space of my house
(diagonal across the span of the house), and then back outside to the entry point.
My concern about doing this is bringing the cables into the house (albeit the crawl
space) without lightning protection. Certainly I could install protection at
the base of this tower for all lines before making the run under the house, but this
doesn't really adhere to the single point ground notion.
Trying to run the cables underground in conduit to the entry point would be
quite a hassle for multiple reasons - a retaining wall in the path, sprinkler
system, septic drain field, etc.
One other note - I'm in the Pacific Northwest, so lightning is not a real
common occurrence, but I still want to do this the safe and right way.
Ward Silver and I are currently working our way through this sort of
issue for the 2nd edition of his ARRL book and Grounding and Bonding. My
current thinking is that, for lightning protection, the safest solution
is to bring cables to ground level below the shack and bond their
shields to your home's ground system there, then extend them to your
shack entry point where coax lightning protectors are installed, with
that panel bonded with a direct run to your home ground system. That
entry point and the protectors should ideally be in a wall plate "pass
through" as close as practical to your operating desk.
The logic for protectors at the entry panel very close to your radios is
that lightning-induced currents in coax shields will induce a
differential voltage inside the coax, which can fry your rigs.
Protectors operate by shorting center to shield, and that short should
be as close as practical to the rigs.
73, Jim K9YC
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|