Well a aerial/antenna ground may have a very different purpose. I was a radio broadcast engineer. In the 1 MHz range, one half of the transmitting antenna is buried in the dirt. That's right, 1/2 of the local area radio signal flows through the dirt. That's 20 to 40 miles from the towers. The ground system is 100 or more radial wires buried in the dirt, each about the same length as the tower is tall.
Getting back to US NEC code requirements about ground rods. There is a trick rule in the book. The rule is that you may have one 8 foot rod if the earth/ground/dirt resistance is less than 25 Ohms, but to make that measurement requires a $2500 meter and about 1/2 hour time. So almost all electricians use the other rule that only requires two 8 foot ground rods separated by more than 6 feet. This is a simple summary because nothing in the NEC code book is simple. Almost every rule has hidden exceptions or requirements.
In the US more than 99 % of all homes have a 3 wire single phase 120.240V system.
The wires are
Neutral/Ground. Yep. over here, Neutral & Ground are the very same wire.
In residential wiring, Neutral and Ground are bonded together in the Service Entrance Panel.
At the Service Entrance Panel a Ground Wire is run to Earth to bond Neutral to earth via cold water pipe, a ground rod or buried ground wire.
From that point on, Neutral and Ground are separate conductors.
From that point on, the Ground Wire is more properly called a Bonding Conductor.
Neutral is a current carrying conductor.
The Bonding Conductor is a non-current carrying conductor, unless it is carrying ground fault current or other exceptions.
Edited by Chris J - 8/14/13 at 3:29pm