"Brian Kelly" wrote
Gary Schafer wrote
No that won't do much good. If you ground the coax shield to the tower
where it bends away from the tower you will have a much better (lower
inductance) to ground with the tower than what the wire would provide.
The wire would do almost no good at all when compared to the much
larger tower in parallel.

This is correct, and why I mentioned even 6" was "too much".

It can be
significant. Especially on a smaller tower.

It took a few seconds to get your point but yes, it's a matter of how
far up the tower the coax departs the tower as a percentage of the
tower height.

The last was not a correct assumption. The distance across a conductor (and
in this case it is also the distance to ground) is what allows inductance to
create deadly voltage potentials. Any conductor in series with a lightning
strike will exhibit the same characteristics. 6" above ground near the base
of a tower can translate to as much as 9800v above ground, with just modest
assumptions of a very average return stroke current of 25Ka with a rise time
of 40Ka/usec. It has no bearing whatsoever how tall or short the tower is.
It's not long (or high above ground) before you could see over 100,000v
potential develop where coax leaves any tower too soon.

Bury it along with the
cables. That will give you more contact with the earth as well as
tying the grounds together.

The wire will be there but I doubt that I'll be able to bury it.

Burying a grounding electrode conductor is normally a code requirement. But
that is not what you have in connecting the tower ground system to the
station ground, AC mains ground, etc. Those are bonding conductors, and they
are in many cases required to be insulated. Not in this case, but I want you
to understand the difference between grounding, voltage division from many
grounds, and a bonding conductor between your station and the tower. The
latter is to maintain equipotential, and will not carry more than just
equalizing currents. It will be well within the capability of a #6 insulated
wire, should you choose to use that. Personally I would go a little larger
but #6 is as largest that NEC or NFPA recommend for a bond in *most* cases.
So burying the bonding conductor is not a requirement, although to protect
it that is exactly what most facilities do. Neither will burying coax
feedlines help in lightning protection, unless you are counting on them by
design to be grounding electrode conductors! Pretty foolish but heh, if
someone tosses feedlines out a window, they may as well short them to a
ground rod and "bring it on". In that case any more than about 5,000v will
breakdown the dialectric both inside and outside the coax, and anything
nearby may be the next target before it ever reaches the ground rod.

The good news is that the soil is eternally damp highly conductive
dark loam . .

Gary K4FMX

That is very good news, and it makes your job easier. But good soil or poor
soil, understanding what bonding provides is equally if not more important
than having a ground rod at all. To rest on the laurels of highly conductive
soil and ignore bonding, would be inviting disaster. Yes commercial tower
design does require many shield "bonds" along the height of towers, but as I
said, I applied a reasonable approach which the average short tower or
mast-only owner could and would be likely to comply with - bonding at the
top, bottom and station entrance. I suspect few go even that far.

You may or may not be interested in all the surge protection diatribe in my
website, but it's there because so many unfortunate souls were mislead in
this area. I do think you might benefit from it's coverage of what bonding
does to protect both you and your station, and it is a lot harder for most
to get a hold of then simple mast or tower grounding. It doesn't have to be.

http://members.cox.net/pc-usa/station/ground0.htm

73,
Jack Painter
Virginia Beach, VA