> NEC has ALWAYS prohibited more than one neutral to ground bond in a
> system, and has always required earth electrodes for every
> building. As
> you noted earlier, the addition of a transformer establishes a new
> system, where there must be a neutral to ground bond. I have great
> respect for those who produced and update NEC (although the
> section on
> Antennas is pretty dated, and seems focused solely on the
> possibility of
> wires falling on power lines).
NEC is written from the standpoint of protecting people, not necessarily
equipment. Granted, more often than not, when it comes to
grounding/bonding, what's good for protecting people is usually also helpful
(but not necessarily ideal) for protecting equipment. Providing good 60 Hz
protection isn't necessarily so good when it comes to lightning protection.
So, while following NEC's minimums is a requirement, including bonding
any/all ground electrodes and not establishing new ones willy-nilly as hams
often do, going well above and beyond NEC is necessary in order to protect
your antenna systems and radio equipment from lightning- and surge-induced
damage.
Although it's been mentioned here many times over, R56 and the Polyphaser
book are good reads and cover the basics and beyond. I also have papers and
construction guidelines from Qwest, AT&T, et al that detail grounding
requirements for microwave sites and central offices which are very good.
Somewhere I also have a hardcopy of something from the DoD or one of the
branches of the military; I should try to find and scan that. While I don't
agree 100% with everything in any/all of them, these are about the best
references you'll find regarding protecting communications facilities from
lightning damage.
--- Jeff WN3A
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