[TowerTalk] Lightning protection - length of grounding rods runs from tower?

[Ray Benny]

I am about to start the grounding system for my 90ft free standing tower. I
do have the Ufer ground / rebars connected to the tower. The next part is
to run 'spokes' of ground rods out a distance from the base of the tower.
Ground rods are connected with #4 copper wire with Cadwell thermal devices,

My question, or request for your thoughts, is it better to run 3 grounding
wires out 40, 50 or 60 ft (8 ft ground rods about every 16 ft connected
with bare #4 wire) or to run say 6 ground wires out, perhaps 30 - 40 ft
outwards? I have room in all but one direction to trench out a 100 ft if
that would be even better yet.

I'm in the Arizona high desert, at 5000 ft. My soil is hard packed dirt and
conductivity is very low, with no moisture at all, except during our winter
storms and summer monsoons. Its takes about 5 minutes to drive an 8 ft
ground rod with an electric impact driver. Water level is about 350 ft.

Your thoughts and knowledge please.

Tnx,

Ray,
N6VR