I guess that your educated guess may not have much guess in it. Those that work in the electrical
field and the telecommunications field should be familiar with the grounding requirements of the
"National Electrical Code", guidelines from the "NFPA' (National Fire Protection Agency) and what
many call the grounding bible from Motorola, the R56 standard. Plus it wouldn't hurt to check
with your home insurance company.
What this all means is that you want to keep current from flowing between different pieces of
metal, electrical wiring and ground systems during a lightning strike. The best way to reduce and
prevent damage is to have all the different pieces bonded together with a low impedance ground
system. This means no isolated ground rods, as low of a ground resistance on your ground
system, bonding of everything that should be at ground potential together and so on.
if you can take the time, look over a cellular tower site. You might find a few things there that
you never thought of. like the chain link fence around the site has a number of ground wires
attached to it. The gate where you drive into the yard has wire flex jumpers from the support
pipe to the movable gate. the tower has ground wires from each leg, the coax cables are
each individually grounded, the ice bridge where the coax cables go from the tower to the
equipment shelter has a ground wire on each support pipe. the ice bridge is not connected to
either the tower or the shelter. It is self supporting. You can't see the inside of the shelter, but
every metal item inside is bonded to the ground system. Even the door frame and the metal
air conditioner frames are grounded.
Bottom line here is to keep any current flow from occuring durring the strike. If you have 2 different
ground rods on different sides of the house, there is bound to be current flow between them. The
best thing you could do is to run a solid number 2 tinned copper wire from one ground rod to the
other. Bury this wire at least 30 inches below the surface and add additional ground rods along the
run. The rods should be spaced no closer than twice their length. In other words, if you use 8 foot
ground rods, space them at least 16 feet apart. Make no sharp bends in the wire.
There are a number of good documents available here on the web that go into details of all this.
It wouldn't hurt to try a search on the subject. Been in this field of radio site engineering and
construction for better than 40 years now. I can say that grounding a tower site correctly,
the tower can take a direct strike and everything will keep on ticking like nothing happened. Have
seen a number of towers take a strike, steam a little in the rain and the radio equipment just
keeps on doing it's thing.
Jim
My educated guess would be to install a new ground rod, on the side of the house where you intend to locate your radio room. My suggestion, is to isolate a new, proper grounding rod, deep into the soil, on the side closest to that room. The reason I suggest this, is because if you tied all of the grounds together, you are also tying them into the antenna which may act as a lightning attractor, and it may increase or allow a direct hit to back feed into the house TV or Phone system, or Cable TV system. An isolated ground connected to an outdoor mast and antenna sounds like the correct way to go, but I'm not an electrician or electrical contractor, so my suggestion may not be correct. I would hate to see ya loose your phone, cable, TV and other stuff by incorporating an antenna on a tall mast connected together on one shared ground rod... Shared also means they all share the possibility of damage if the antenna is ever hit by lightning. Why introduce those elements to an antenna system, when the antenna acts like a lightning rod by itself attracting lightning. Separation is probably the way to go.
Regarding running the ground wire thru the basement , under the house to get from one side to the other is also probably a poor idea. The best protection during a direct lightning hit, would be to divert the charge down to a ground rod in the shortest possible distance to dispurse it into ground. why bring that hazzard into the house and then out again , especially over a longer attatched ground wire to make the connections... I would buy a super long ground rod, and get it down into the ground as directed, and then attatch a super duti heavy guage ground wire between the mast and the ground rod, and if possible, maybe even attatch a second ground wire from the mast to a metal water supply pipe for additional grounding. Good luck to you.
