[TowerTalk] Rooftop vertical grounding

[berferd]

Hello everyone.
 
My name is Jeff and I'm a new ham.  I received my general class
license approximately two weeks ago.  Call sign is KC0HEP.  I
live in Colorado.  I'm not putting up a tower (yet), so if this
not the appropriate forum for my questions, please chastise
me and I'll be on my way.
 
My first antenna is going to be a vertical.  The Butternut HF9V
to be exact.  I'm planning on mounting it the roof of my house
with the counterpoise kit on a tripod.  The antenna is about
26 feet in height.
 
I'm trying to figure out the best way to ground this thing in
case Mother Nature decides to zap it.
 
The antenna needs to be mounted in the middle of the roof because
there will be four rope guys going to the corners of the roof.
So the down conductor(s) will have to take a turn when it gets
to the edge of roof.  I understand from reading messages in
the towertalk archive that the turn should be as small as
possible.  Does anyone know how tight I can go?  If I did get
a lightning strike and the bolt reaches the turn, I don't
know where it else it could go (other than down the coaxial
cable).  All the fences around here are wood and there aren't
any above ground utilities.  So wouldn't it continue down
the conductor to ground in spite of the turn?
 
I'm thinking about two down conductors of #1/0 gauge going down
adjacent corners of the house into separate ground rods tied
together.  Is this enough?  Can I get away with only one down
conductor?  It is my understanding that the down conductor
surface area should be at least equal to or larger than the
total surface of the coax.  I'd like to use insulated conductors
if possible.  Any reason why I should use bare conductors?
 
Since my shack will be in the basement, I'm looking at
installing an entrance panel at the top of the wall of the
shack (have to see how much room I have between the top of
the foundation and the floor above to see if I can squeeze
one in there).  So the outside of the entrance panel would
be tied into earth ground and the inside would be tied
into the equipment bus bar.  I have a electrician coming
over to see about moving my service ground (which currently
resides under a concrete patio) somewhere else so I can
tie into it.
 
The part that scares the hell out of me is tying my shack
bus bar into the antenna ground.
 
Let's say I've done everything by the book with respect
to lightning protection.  What if the energy from the
strike isn't dissipated by ground quickly enough?  What's
to stop the energy from finding it's way to my equipment?
I'd like to have a good RF ground for sure, but I'm worried
about protecting my equipment.  I'd like to set something
up where I could not only disconnect the antenna feed
from the shack, but also disconnect the bus bar from
ground when not operating.  I'm thinking that this way,
if a lightning strike does occur (when I'm not operating)
the equipment is isolated.  Of course *all* connections
would be severed (power, etc.)
 
Is this a good idea?  Comments?  Flames?
 
Thanks for reading this far.
 
 
Jeff
KC0HEP                                                                                


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