In a message dated 7/1/01 3:22:38 PM Eastern Daylight Time, [email protected]
writes:
<< I have chosen to ground the antenna in a separate ground stake, with no
connection to the main station gnd. >>
This strikes me (no pun intended) as a very good idea.
In broadcast practice, our masts are normally earthed to as effective a
ground system as we can possibly achieve. Even so, however, when lightning
does strike the tower, the whole earth system rises above local terrestrial
average potential for a brief moment. During that interval, current will
attempt to flow--no, let me amend that--current WILL flow through any
convenient conductive path away from the immediate vicinity.
When the potential of the station earth is raised this way, the resulting
current often passes through equipment on its way out to the electric mains
and their ground system, telephone lines and other cables, etc. Heavy-duty
commercial gear is designed to handle a certain amount of this mistreatment
by Mother Nature, but even so, damage is a common result.
At home, however, I've had personal experience with what happens when the
local ground gets elevated above the potential of the rest of the world by a
relatively small nearby strike (about 25kA). Satellite receivers, computer
modems, videocassette recorders, etc., are not nearly as sturdy as a
broadcast transmitter!
Therefore, if your provide a preferred path to earth that is as independent
of your radio shack's ground system as possible, the chances of protecting
your ham equipment are significantly improved.
73,
John
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