[TowerTalk] A different question (I think) on SPG

[Gary E. Jones]

I have read the threads on SPG over the years, but I think I don't really
understand a couple of concepts that are fundamental. Maybe someone can
help. 

 

I live in a 4000 square foot ranch house which is in the shape of a "U" with
sleeping areas on one end of one leg of the U, and Garage/laundry/den on the
other leg of the U, and the traditional living areas in the center of the U.
The house has two 200A 240 volt distribution panels as the house was all
electric initially. The phone and power services all come into the house on
the garage end of one leg of the U. The shack is one of the bedrooms on the
other leg of the U. 

 

Further, the house is 500' from the two 90' crank up towers, each with two
yagis stacked on them. The towers are grounded through three ground rods per
tower. Further, the feedlines for the yagis (buryflex) enter into
weatherproof boxes mounted on 4x4 weather resistant posts. The boxes have
remote coax switches in them to switch the various yagis on each tower. The
remote switches are grounded and I will be separately grounding each piece
of buryflex at the base of the towers. There is Heliax from the remote
switches (500' for one tower and 600' for the other tower) to the house. 

 

Now, I assume there is no logic of trying to put the house and the two
towers at the same common ground point and that the towers have to be
separately grounded at their base (the way that I have it now). That means
there is a 500 and 600 foot separation between the towers and the house.
Further, the shack is on one side of the house and the common utility
grounds are in the center of the house. I have a separate ground rod right
outside the shack window, so it is not a SPG even for the house. 

 

Now, is the conventional wisdom that I have a problem?

 

I can't see an easy or even possible solution. It seems to me that the
towers have to be grounded separately, and short of running a ground strap a
hundred feet and boring either under my slab or around my swimming pool,
there is no easy way to even have a SPG for the house. 

 

One more thing, it has always seemed to me that at the exact instant that a
tower or antenna gets hit with lightening, the tower ground is going to be
many volts higher than a second ground 500' away as the charge dissipates
into the tower "ground". That is going to put a very large voltage
difference between the two and is my understanding of the whole logic of
SPG. Am I correct or wrong in my assumptions?  However, if they are all tied
together, for that same fraction of a second, isn't everything "hot" (even
the "ground") relative to any other ground that is separated from the common
ground?

 

Straighten out my thinking. 

 

Thanks in advance

 

     73

 

                 Gary      W5FI