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[TowerTalk] entrance panels for grounding

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Subject: [TowerTalk] entrance panels for grounding
From: (Bob Wanderer)
Date: Tue, 28 Dec 1999 09:52:23 -0800
I would still recommend protecting the dc cables
from the battery.  PolyPhaser (and there are probably
other sources as well) makes units for this purpose
in low current and  30 and 50 Amp models and for
different voltages too.

As you pointed out, the name of the game is induction.
What you are trying to do in this case is prevent any
surge energy induced on your cables from getting into
the equipment.

Insofar as single point grounding is concerned, induction
can be an issue if your AC Mains entrance and ground rod
are a significent distance from the ham shack.  Using the
lowest inductance medium possible reduces the voltage
differential in that scenario.

73Bob AA0CY

From:  Mark .[]
Sent:  Monday, December 27, 1999 10:32 PM
Subject:  RE: [TowerTalk] entrance panels for grounding

4th attempt to post....

Ed asked:

<< I would think you'd want the equipment chas-sis  to remain grounded.  
That way the equipment and AC ground is the same potential at all times, and 
a local rise in potential won't result in surge into the AC power cord 
feeding the unground "floating" equipment.

If you isolate the equipment from ground, you should also unplug every AC 
power cord to prevent the above type of surge from happening.  Of course a 
good surge arrester would help, but I'd think that grounded equipment would 
reduce the need to rely on the suppressor.  Wouldn't it? 73, de ed -K0iL >>

Hello Ed,

More good questions!
If the equipment were adjacent to conductors that were dissipating direct 
strike current, such as on the tower, where the potential for side-flash 
between metallic objects is large, then I would say yes, I would want the 
objects to be grounded to rise and fall with the enormous electrical 
However, in the shack, I should (hopefully) be dealing with reduced, induced 
surges on lines from magnetic pulse in the near field of a strike. From what 
I have been able to gather about lightning energy, it always finds the least 
inductive path to ground, and I don't want my equipment to become any part 
of that path.
If lightning strikes my shack, instead of the lightning rod at 126' on top 
of the mast of the tower, then I may have to rely on insurance!  I'm 
counting on the rod to take the strike since the tower is only spaced 40' 
from my home.

  Ed, I think you just got me convinced to install a second air terminal 
above the shack roofline and bond it to the panel ground conductor.
  Another thing that works in my favor is that the only thing I have plugged 
into the wall is a battery charger. All the other hamshack gear runs 
directly off of a large, group 8D battery. I have a small inverter for the 
rotator. Essentially, I am always on emergency power, hopefully further 
protecting the gear and enhancing readiness.

  There are varied opinions on how best to protect your gear and I am 
certainly no expert in the field so I may be missing something. So I read as 
much as I could here on TowerTalk and in other sources and applied a 
solution that made the most sense to me.
  From time-to-time, industry professionals in many fields will take the 
time to post absolute gems of knowledge here, making TowerTalk so valuable.



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