Let’s see if I can explain it they way I understand it…
Let’s start backwards…:-
For proper ground configuration. Every location needs two grounds (Electrical Ground, and Earth Ground). And both(all of them if multiple exist) of these Two Grounds should be bonded together.
Every tall structure with any kind of lighting protection will have some sort of a Earth Ground on it.
Grounding the Radio, is normally protection for any kind of lighting NOT to go thru the radio (to the electrical ground ).
Shielded cable is grounded simply for ESD protection (not lighting, wire is too thin, it will act as a fuse).
If the Earth Ground and System(Electical) Ground are not bonded together, then you will loose ethernet ports due to electricity flowing between the two grounds via the cable and Electronics…
Moral of the story is:-
- Find the Earth ground on the structure, and ground your hardware, radio, mast, surge protector to it.
- Find the Electrical ground and make sure your electronic equipment is grounded to it.
MOST important: Check the resistance (ohm meter) between the electrical ground and the earth ground, and make sure that it is less than 5ohms… otherwise you are asking for trouble.
BTW (Water Tanks, are metal structures, they are most likley using all of the structure as the earth ground).
I have seen folks run a separate ground wire (earth ground), I believe it is simply because they don’t / cannot trust the quality of the earth ground at the top of the structure, and they want to make sure that they earth ground at the bottom of the structure is connected (very low resistance) to the earth ground at the top of the tower.
Also, coiling Ethernet wire at the top, won’t do much to the resistance, it could create some impedance … but overall in my opinion it does not contribute anything to the ‘protection’ of the system, other than you have some excess cable…