Wooferhound,
The point of a single earth ground is to ground one of the current carrying conductors at only one point. It doesn't mean you can't have more than one ground rod. There are 2 distinct grounding systems. One is the "grounding electrode" system. This is the single point bonded system of one of the current carrying conductors (negative wire) to the grounding electrode. This grounding electrode can be a system of interconnected ground rods, water pipes, buried wire, etc. It also can be as simple as a single round rod. The point is to only have one tie-in point to the grounded negative conductor. The other system is the "equipment grounding". This is usually the bare wire. It is attached to the grounding electrode system only at the same point as the grounded negative conductor. This equipment ground should also be tied to every metal part of electrical equipment. This includes towers, computer frames, metal buildings, etc. In addition, supplemental ground rods can be driven for a bit of added protection from lightning and short circuits. The tower would be a likely place. This is often done in tall parking lot lighting systems. Since this is only a 12vdc system, there won't be the dangers involved if this was a 120 vac or higher dc system. Good grounding can still help protect equipment and prevent a lot of strange electrical behaviors, especially involving electronics.
David