If you are constructing a new tower you can use the tower base as a “ground rod”.  This is called a Ufer ground and it utilizes the rebar that reinforces the concrete base as an excellent ground connection.  The rebar must have at least four inches of concrete between the rebar and the surrounding earth.  If this is done, then a wire can be brought out from the rebar and attached to the tower leg.  A great big ground rod!  No, you will not blow up your concrete!  The other radials with ground rods will handle most of the strike energy.  Since you must put rebar in the concrete anyway, why not use it to augment your ground system.

There are two more items that need to be noticed in the sketch.  The first item is that the SPGP (Bulkhead Entrance in the drawing) is connected to the tower ground radial system.  This connection should use the same material and ground rods as is used for the radials and should be connected via a buried path.  However, if the distance between the tower and the SPGP ground point is more than approximately one hundred and fifty feet then it is not cost effective to inter-connect the tower ground system with the SPGP ground system.  In this case the ground system that would have been supplied by the tower ground system must be duplicated for the SPGP ground system.

The second item is the perimeter ground, shown in the sketch as going completely around the radio building structure (better known as the house).  This perimeter ground serves two purposes; first, it helps to conduct the surge energy around the house, thus minimizes the ground potential differences under the house during the strike event and second, it enhances the basic ground system by providing more connection points to the earth.  Also, note the existing utility ground is connected to the perimeter ground.  This is a must!

Well, that’s how it should be done; now here are some general guidelines for adapting this to your specific situation.

·        In general, it will take twice as many radial to lower the impedance of the ground system by one half (parallel rule plus 10%). 

·        Radials don’t have to go in a straight line; they can follow the contour of your property or flow around obstacles.  Just make the turns gradually (12-inch radius or larger).

·        A perimeter ground that only goes three-quarters or half way around the house is better than no perimeter ground at all.  Although flowerbeds, walkways and driveways frequently present insurmountable obstacles, do your best to get most of the way around.  The perimeter ground must at least connect to the utility ground.

·        Short ground rods are better than none at all.  Just place them closer together – twice the length.

·        Soil doping can improve soil conductivity.  But, be aware that some additives may cause ground and water pollution, and can shorten the life of the grounding materials.

·        Where possible when installing a new tower, place the tower at least twenty-five feet from the house; thirty feet is even better.  By placing the tower at some distance from the house, you minimize the amount of magnetic energy that will be radiated by the tower into the wiring of the house.  In addition, you take advantage of the inductance of the coax line in limiting the surge energy headed toward your equipment.  Don’t get too carried away with the distance, remember the added coax length also attenuates your signals.

If you are fortunate enough to have multiple towers, each tower should have its own ground system of radials and ground rods.  If the towers are within one hundred feet of each other then a radial should be used to interconnect the towers.