Practical_Antenna_Handbook_0071639586

CHAPTER 30
Grounding for Safety
and Performance
In most radio transmitting or receiving installations there will be four different types
of ground systems to consider and implement:
• Grounding for lightning protection
• Grounding for power distribution safety
• Grounding all station equipment together
• Grounding for maximum antenna efficiency
The first three are absolutely necessary; the fourth may be important, depending on the
type(s) of antenna(s) in use.
Note The single most important message to take away from this chapter is this: A good
lightning ground is not necessarily a good radio ground, and neither of them provides a safe
power distribution or equipment ground in and of itself. In short, for a proper communications
installation, all four types of ground systems must be independently considered, designed,
and installed. Nonetheless, in many installations, components of any of these ground
systems may well function as components of one or more of the other three systems.
Grounding for Lightning Protection
Although lightning figured prominently in early electricity experiments—especially
those conducted (pardon the pun) by Benjamin Franklin—it remains one of the most
unpredictable and incompletely understood phenomena in electromagnetics today.
But despite some remaining gaps in our understanding of lightning, the scientific
body of knowledge is sufficiently mature today that lightning experts are able to provide
valuable guidance to all of us for protection of our lives and our property—usually
couched in terms of a statistical “probability”. In other words, predicting exactly what
lightning will do is difficult, if not impossible, but predicting what it is likely to do is
helpful most of the time. The problem is akin to that of weather prediction—the scope
of the system is enormous, and the number of variables not under our control is mind-Â
numbing.
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