[TenTec] Station and AC Ground

[JAMES BRASSELL]

Thanks for the comments.  My comment to Martin about a direct strike is, 
'Forget it'.  In the case of a direct strike, there is no system that will 
absorb it.  You can mitigate the damage, but you cannot prevent it.  That's 
from experience where I had a direct strike on the tower that turned 
antennas to molten aluminum and fried everything in the shack and the house 
in general.  By the way, take a look at Martin's web site and what he has 
done.  Pretty impressive.  Thanks, again.

Jim, K4ZMV
----- Original Message ----- 
From: "Martin, AA6E" <martin.ewing at gmail.com>
To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
Sent: Tuesday, November 29, 2005 10:54 AM
Subject: Re: [TenTec] Station and AC Ground


> Jim,
>
> I'm surprised your grounds are equal "to the microvolt".  To me, that
> indicates that no current is flowing in either, not even reactive, or
> else they really are bonded together in some way.  A practical ground
> is going to have a resistance of a few ohms, in my experience.  And no
> two independent grounds will have the same resistance.  So a current
> of even a microamp will produce microvolts of differential.
>
> That's neither here nor there.  The thing to be concerned with is what
> happens under fault conditions.  What if there's a short in the wiring
> that delivers 100 amps into the protective AC ground?  (Let alone a
> lightning event.)  Under those conditions, you want to be sure that
> your ham gear is not in the loop.  If your 3rd wire AC ground goes to
> your rig, and your local radio ground is separate, you'll get a good
> fraction of the fault current going through the radio.  Bad!
>
> I solve this by running all my station AC through a Polyphaser PLDO
> protector, which is bolted to my single point ground plane.  That's
> where the 3rd wire AC meets my ham ground system.  I observed a
> fraction of a volt of AC between the grounds before connecting them.
> Now, any current surge will go from the 3rd wire to the SPG and my
> equipment should not see it. See
> http://blog.aa6e.net/2005/03/in-shack-ground-system.html .
>
> (The PLDO is there mainly to absorb voltage surges on the hot and
> neutral wires, not for grounding, but it does add discipline to the
> grounding situation.)
>
> 73 Martin AA6E
>
> On 11/29/05, JAMES BRASSELL <jimbrass at bellsouth.net> wrote:
>> 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 an
> d
>>  Voyager, and run 1500 watts into them on a regular basis without any RF 
>> problems.  What say you?
>>
>> Jim, K4ZMV
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>
>
> --
> martin.ewing at gmail.com
> http://blog.aa6e.net
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