The tower doesn't even have to be close. The idea of tying all grounds
together is to have all equipment to rise (and fall) to the same
voltages at the same time.
As for induced voltages, a strike a mile distant can induce as much as a
thousand volts per meter into a piece of wire, so imagine one in the
neighbor's yard. Signal strength falls as the square of the distance,
so what's a 100 yards compared to 1700 @ 1000 volts/meter. That's a
ratio of 170:1. or a strike in the neighbor's yard could induce as
much as 28,900 times as much voltage in a meter of wire.
Sounds like a good reason for a good grounding system and why most
damage is from nearby strikes. There's a lot more nearby strikes than
direct hits.
73
Roger (K8RI)
On 1/30/2015 10:17 AM, john@kk9a.com wrote:
Even with no connection, if the tower is close to the house everything
inside will be vulnerable due high voltages induced into electrical system
from a lightning strike.
John KK9A
To: Towertalk <towertalk@contesting.com>
Subject: Re: [TowerTalk] Fwd: Antenna to Shack Ground Connection
From: Bill Turner <dezrat@outlook.com>
Date: Wed, 28 Jan 2015 17:36:56 -0800
At the risk of starting a flame war (wouldn't be the first time), I
have to question the purpose of running a ground wire from the tower
to the shack.
What is it you are trying to accomplish? Or putting it another way,
what current are you expecting to flow between your tower and your
shack?
If your tower takes a direct lightning strike, won't a small
percentage of the strike find its way into this ground wire, and since
the wire to earth connection is not zero ohms, some of the strike will
find its way into your shack?
Even if you disconnect your coax and rotator cables during a storm,
this ground wire leaves your shack vulnerable, doesn't it?
Does not sound good to me but if there is a good reason, I want to
hear it.
Bill W6WRT
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73
Roger (K8RI)
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