[TowerTalk] ground rods for towers

[Tom Rauch]

Hi Tom

> How many ground rods should be used on a tower of 75 feet?

Are you grounding it for lightning or RF? 

 > used only for beams and dipole support. I have a friend who says one is
> enough, I have others who say one on each leg, what say ye me hearties?

Even one on each leg isn't enough if you really want an effective 
ground to protect your equipment. What people are describing to 
you is a ground that offers some minimal personal safety.

To protect radio equipment, a good ground requires a large surface 
area. ALL of your cables should grounded where they enter the 
house, and all telephone, CATV, and power lines should be close-
by and grounded to the same point.

Generally a good lightning ground requires multiple rods and/or 
buried wires. Braiding is a very poor choice for ground cable, 
unless the cable has to be flexed. Smooth wide copper is better.

Braiding has several times the resistance as a smooth conductor 
for RF and lightning.

A couple important things to remember...three ground rods are not 
much better than one if they are spaced closer than the length of 
the rod to each other...and the biggest problem with lighting is 
current loops that flow through equipment from the power and telco 
lines to the tower and antennas.

For RF grounds, you need straight multiple wires spread over a 
wide surface area.


73, Tom W8JI
w8ji@contesting.com

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