I'd like to get the group's opinion on lightning protection for my new tower
project. My property layout may be a bit different than most situations. I'll
try to paint a picture.
The tower base is 10 ft to the right (I'll call it "east") from the front of a
detached garage. The garage has underground electric service (240vac). The
garage load panel is tied to a ground rod on the side nearest the tower, which
is about 9 ft away. The garage feeder's ground wire is bonded to this load
panel and also tied to the ground bus in the house main service panel.
The house itself is 75 feet "south" of the garage. The house main electric
service panel (on another underground feeder from the utility) is on the
opposite side of the house from the garage, about 145 feet straight line
distance "south" of the garage and tower. The house service panel is tied to a
ground rod at the feeder entry.
In addition to the usual tower radial grounding scheme with multiple rods, I
believe the tower radial system must be bonded to the nearby garage electric
service ground rod, and I also need to run a separate #4 or larger copper wire
underground from the tower (probably with more rods along the way) all the way
back to the ground rod at the house electric service entrance. This would be
about 180 ft of wire, keeping a gentle turning radius around the "southeast"
end of the house. Near the tower, this wire run would be about 10 feet away
from the garage power feeder for the first 75-80 ft.
Coax and rotor lines will run in a PVC conduit either in the same trench as the
bare #4 or a nearby trench. The shack coax entry panel will be mid way along
the "east" wall of the house. In addition to ground rods there, I plan to tie
the coax entrance panel into the #4 wire mentioned above.
Anything wrong with this plan?
My main concern is that electric feeder to the garage. The feeder enters the
house basement on the "north" side and runs to the main service panel along the
unfinished basement ceiling. Don't want lightning currents to prefer that
route. The second concern is routing the coax conduit near the #4 bonding wire
between the tower and house service panel. Possible inductive coupling during a
lightning event?
OBTW ... Up until now, I've just used wire antennas at this QTH, hung in the
80+ foot trees. When QRT, I always disconnect the feedlines (window line) and
anchor the ends in the yard about 40 feet from the house. A few years ago one
of the wire antennas took a direct strike. All the copper in the window line
was vaporized and the antenna (a V-beam) fell to the ground. Had a foot deep
crater in the yard where the window line was anchored. Nothing in the house
suffered any ill effects except the cat, who hated thunderstorms ever since
then.
Thanks in advance.
Shawn - N3AE
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|