[TowerTalk] lightning ground & cet.

[Jim Jarvis]

Here we go again...but it was recently asked.

1)  Braid, as k3na says, will corrode and quickly become useless.

2)  Surface area is important, both for RF grounds, and for lightning
dissipation grounds.  Copper strap run radially or linearly from the
common ground point will carry much of the current.

3) The utility of ground rods will vary, depending on mineral content
and moisture content of the soil.  In general, however, a lightning pulse
will see the rod as somewhat inductive...depending on the soil situation.

4)  As a result, broadcast tower folks tend to use a combination of
techniques.  Laterally run copper strap, plus a combination of rods
cad-welded to them, at 10' distances.
    For really tall towers, they'll run 8" or 10" strap down around the
foundations, 10-15' into the earth, and maybe drive some rods in the
bottom of the holes.
    The idea is to give the current lots of parallel paths to follow, so
the voltage doesn't build to high levels on any one path, and things
dissipate over as large an area as possible.
    Remember, you're also dissipating charge BEFORE a strike, to avoid one
taking place.  Low inductance grounds are important for this.

5) SO:  What's practical for an amateur?  Recognize that it's a prophilactic
treatment we're discussing.  The answer is as much copper of reasonable
surface area and as many ground rods as you can reasonably organize, given
your budget.
   At the same time, I don't leave my gear connected to anything in a storm,
and I do mean anything.  The entire station is unconnected...power, phone,
rf....all gone.  Even earth ground gets pulled from the gear.
   But between the RF service entrance to the house and where the antenna
feedlines come to earth...there are as many connections as I can manage.
I want to dissipate direct strikes and induced currents from nearby strikes
before they get into the house to cause damage.

Like potato chips,  " One is never enough!"

Good luck!

Jim/n2ea