One last note on down conductors. You can figure out what the
inductance of a particular gauge of wire is. You can also figure out
what the inductance of a particular size tower is. Just looking at the
size difference you can see that the inductance of the small wire in
comparison to the tower will be many times greater. That equates the
many times greater voltage drop on the small wire. I would say that
carrying 25% to 30% of the total current would be way optimistic. It
is not just the gauge of the wire verses the gauge of the tower legs
but how much inductance each presents. The cross section area of the
face of the tower makes for less inductance as well as the size of the
legs.

RADIALS
Buried radials make an excellent lightning ground system. An AM
broadcast tower ground system is an example. Not only is it an
excellent Radio ground but it is also an excellent lightning ground.

Running radials out from the base of a tower that you want to ground
is a big plus in addition to ground rods I think you will have to
agree.

It is suggested that many shorter radials be used rather than a few
long ones in a lightning ground system. The reason is that the
inductance gets too high to do much good as the length gets long.

Also long ground rods suffer the same fate. Too long and the
inductance is so high. That is one reason why additional shorter rods
are recommended rather than very long rods.

COAX LINES
Only talking about the energy on the OUTER SHIELD of coax here now.
With buried coax lines coming from the tower they serve the same as a
radial tied to the tower. They will dissipate some of the energy just
the same as a radial will. And they do not have to be bare copper
shield lines to do so either.

This was where I was going with the buried insulated single wire long
wire lead.

By the time the energy on the shield of the cable reaches the shack,
part of it has dissipated by the coupling to earth. Also the impedance
seen at that end is much higher than it is at the tower end of the
coax.
Just like the radial. The ground is a choke if you will.
Add ferite beads on a transmission line and you greatly limit the
amount of RF current that gets past on the shield. That is what the
earth does to the coax line buried.

73
Gary K4FMX