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Re: LF: Lightning

To: [email protected]
Subject: Re: LF: Lightning
From: [email protected]
Date: Sun, 1 Jul 2001 17:41:18 EDT
Reply-to: [email protected]
Sender: <[email protected]>
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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