[TenTec] A grounding question

[Stuart Rohre]

Think of RF grounding as providing a low inductance path for the RF return 
currents.   Wide, flat solid copper conductor provides this.  Braid may not 
be as good if you get a direct or near direct lightning hit, as the magnetic 
fields are so intense, you will even get the strands repelling each other, 
and not all conducting in unison, thus they will not carry the surge current 
a solid copper conductor will carry.

Rods are an imperfect way to couple RF to earth.  They are typically too 
short except at 10 meters, where they may be too long, (8 feet is after all, 
a quarter wavelength.)  They seldom are long compared to wavelength, and 
thus are augmented by radials, which may be resonant, or cover more area to 
gather return currents from the antenna above. Rods are specified from the 
DC view of lightning, but even lightning contains many frequencies.  Mainly, 
the rod provides a solid conductor of low AC impedance vs. what it looks 
like at HF RF frequencies.  It is always specified as power regulation is 
based on 60 Hz good practice.

A rod in the basement may or may not be a good ground, depending on the 
level of the water table, and hence, the moisture level of soil underlying 
the basement.

For RF grounding, you likely would benefit from some insulated counterpoise 
or radial wires, unless you are using balanced antennas such as beams, 
doublets, dipoles, loops, and thus do not have the single ended problem of 
short verticals needing a "completion element", (The missing quarter wave in 
the case of common quarter wave ground mounted or elevated vertical without 
radial or ground plane field.)

-Stuart
K5KVH