Having worked in the cellular market for many years, one thing I learned was that a good ground is very important. With that said, ground rods do not last forever. Depending on the acidity of your soil, you might want to consider replacing your house electrical ground rod if the house is more than say 10 years or so.
The ground rods tend to get surface oxidation and if that happens, they will loose the low resistance grounding they are being relied on to protect everything and everyone. Reason being is that my house had sustained damage from a lightning strike to a tree near the house. Did all sorts of damage to electronic equipment in the house. Even though I had surge protection on many of the outlets feeding the individual items.
Having a ground resistance tester available to me, I got curious about the actual resistance of my house electrical ground rod. I killed the main circuit breaker, disconnected the electrical meter ground from the ground rod and proceeded to measure it's resistance. What I found was not a 5 Ohm resistance to ground or even 25 Ohms, but on the order of over 200 Ohms.
So now I know why so much electronic damage was done by the near strike to the house. I went out and bought 2 new ground rods. Installed them 16 feet apart and bonded them together and tied the electrical meter to the new ground rods. One quick comment about multiple ground rods. There is a cone of influence around each ground rod. If you space them closer than twice their length, your not obtaining the lowest resistance for the amount of money you have spent on each ground rod. Go do your own homework if you think I am just blowing smoke about the ground rod spacing of twice their length.
I did do another ground resistance measurement before connecting the electrical meter ground wire back to the ground rod under the meter. It measured about 2 Ohms. So now I knew that there was a low resistance ground available to the electrical meter and the neutral / ground at the electrical meter. Your type of soil will effect the resistance. In sandy soil, it might take ground rods that go 40 feet down to get a good low resistance.
Most people never think about the age or ground resistance of the most important portion of the house electrical wiring. You can never have a better ground than a new one. Age works against low resistance grounding. The type of connections also make an important portion of your grounding. I like to use an exothermic weld type of connection. But for the average person, this is not cost effective.
Never use bare copper against a galvanized surface. The copper will etch the zinc out of the galvanization over time and with the normal moisture that occurs outdoors. This is why you will always see a bronze connector used to connect a copper wire to a galvanized surface.
Hope this little tid bit of information gives some of you food for thought. Another old wives tale you constantly hear in the radio chat groups is you can't survive a direct hit on a tower. This too is not true. I have been at a number of towers that have taken a direct hit. The equipment has stayed operational with no damage. But you can be sure the tower legs will produce steam from the high current of the strike going through them in the rain.
The reason the equipment has stayed operational is due to a good low resistance grounding system. The system operators could not stand to keep replacing equipment after every storm that rolls through. It would not be financially practical. So they do spend some money and put in a good, low resistance grounding system. You will notice that I said grounding system. This includes surge suppression, good bonding between equipment racks and a good grounding system inside the equipment shelter or equipment building.
