Hi James,
I'm no expert, but this is what I understand about grounding. Maybee others
can fill in some gaps.
Should a lightning strike the AC wires, the AC ground is not enough to
dissipate the current before it reaches the radio chasis. Even .001 ohms
between the AC ground and the RF gound will create a huge voltage
difference, and the station chassis will become the fuse.
For instance, a cloud to ground strike has between 10 million and 1 billion
volts. All that could hit the ground system but for discussion lets say it
has at least volts 500,000 Volts by the time it gets into the ground system
looking for a way to dissipate itself, the current at .001 ohms is an
instantaneous 500 Million amps...
That much current & voltage will likely fry something inside the radio. So
the idea is to direct that stuff away from the station.
Best is to use a large wire from the AC Main ground DIRECT to the RF
Grounding system. Following the grounding guidelines really works.
I've had strikes and the radios have survived so far. I lost two PC network
cards, and a network router from the EMP induced into the cat 5 cable, so,
I'm going wireless from now on.
In reality, there is NO way to prevent the voltage on the ground system from
going very high during a direct lighting hit or to really guarantee that it
won't harm some equipment. But a well grounded station is much more likely
to survive intact.
The purpose for tying everything together with heavy gauge wire ( like #6 or
#O ) is to prevent the voltage of any one area in the electrical/antenna
system from rising too far above any other area of the system during the
lighting strike. It's Ok if the voltage rises, As long as EVERYTHING else
goes up with it at the same instant and it has a very low ohm path to
dissipate itself. The more grounding rods, the faster the voltage will
dissipate and the less the voltage will rise...
Best wishes,
Rich
K5SF
>From: "JAMES BRASSELL" <jimbrass@bellsouth.net>
>Reply-To: Discussion of Ten-Tec Equipment <tentec@contesting.com>
>To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
>Subject: [TenTec] Station and AC Ground
>Date: Tue, 29 Nov 2005 09:37:24 -0500
>
>Hey, All.
>
>Just a quick observation and question. I have read many posts on this site
>about having the station and AC mains grounds tied together. For my
>observation, when you have a separate station ground (and I do; a good one)
>and all pieces of equipment are tied to that ground and the ground wire
>from the AC plug is tied to the equipment chassis then you have effectively
>tied the AC mains ground to the station ground. I have measured from the
>AC mains ground to the station ground and it is zero ohms, with no voltage
>(to the microvolt between them). I have looked in the equipment and the AC
>ground is tied directly to the chassis, not through a board. My question
>is, if the equipment is grounded and you have a good AC mains ground is
>that not tying the mains and station grounds together? I could see where
>one might have a problem if the ground in the equipment was achieved
>through a circuit board and the equipment was not otherwise grounded. I
>feed two verticals, GAP Titan and
> Voyager, and run 1500 watts into them on a regular basis without any RF
>problems. What say you?
>
>Jim, K4ZMV
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