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Re: [TowerTalk] A different question (I think) on SPG

To: "Jim Brown" <>, "Tower Talk List" <>
Subject: Re: [TowerTalk] A different question (I think) on SPG
From: "Gene Fuller" <>
Date: Wed, 4 Aug 2010 16:16:45 -0400
List-post: <">>
I can't resist chipping in with my experience at the other end of the 
"protection" spectrum.
I put up a 100 foot commercial tower (200 lb 20 foot sections) about 40 
years ago. Guyed with heavy duty power company galvanized strand and power 
company egg insulators, broken into non-resonant lengths, first guyed at 
30-60-90, now 30-70-90 to allow clearance for TH-6 @ 45 feet  on a side 
Out of a combination of ignorance and naivete I just used several good 
ground rods (2x6' and 2x8') at the tower and one 8' outside the shack 
window. Not a thing done to the house systems. Equipment each "grounded" to 
a heavy wire, to a strap to the "station" ground rod. I may be courting 
disaster, but I've never had a problem. Fourty years ago, but no longer as 
much, the tower was 30-40 feet above the trees and heavy lightning storms 
have come down my street on numerous occasions. I see two possible 
mitigating factors. All coax and control lines are burrued at least 6" for 
about 200 feet from the tower to the house. Also, I theorize that the 
combination of antennas and guywires are effectively creating  a "point 
discharge" protection system. Point discharge protection seems to have 
escaped discussion.
I'm sure we we all know of cases of severe damage by lightning. I feel very 
lucky to have escaped, but based on 40 years of good luck I'm hesitant to 
change anything.
Gene / W2LU

----- Original Message ----- 
From: "Jim Brown" <>
To: "Tower Talk List" <>
Sent: Wednesday, August 04, 2010 3:21 PM
Subject: Re: [TowerTalk] A different question (I think) on SPG

> On Wed, 4 Aug 2010 10:48:59 -0700, Dick Dievendorff wrote:
>>I (will) have a main panel on the garage wall.  The power company ground 
>>is right there.  It's not much of a ground rod.
> That's a good reason to improve on it by adding more, separated by the
> distance equal to the length of the rod.
>>There's a sub panel up in the radio room over the garage. That sub panel 
>>connected to the main panel with four wires, 2 black and one white neutral
>>for 220, and a separate green ground wire. Neutral is attached to the 
>>ground wire only at the main panel.
> Very good.
>>The radio equipment will be connected to one heavy conductor (a copper or
>>aluminum bar) within the shack.
>>The tower is a bit more than 100 feet away.  It has several ground rods. 
>>lightning hits, the tower and its antennas are the most likely first
>>I'm planning to put some PolyPhaser lightning arrestors inline to the
>>antenna coax, and through that effort the coax shield will be bonded to 
>>tower's ground system.
> As K1TTT noted a few weeks ago, those arrestors should be very close to 
> the
> protected equipment. Good practice is to a beefy conductive ground panel
> (copper or other good conductor) where they enter the building next to the
> gear, with that panel well bonded to ground.
>>Are you advocating a separate wire 100+' heavy copper wire to connect the
>>tower's ground system to the power company ground rod outside the garage?
> No. I would treat the tower as a separate location. Bonding as noted
> previously. At the AT&T site, the tower was right next to the building, 
> and
> their budget was infinite. That proximity demanded that the tower be 
> bonded to
> the building, and the budget allowed them to do it VERY well. :)  In 
> addition,
> they designed the building, the layout of the building and the tower, and 
> the
> grounding arrangement before they started digging holes in the ground. 
> When
> you do it that way, it's a LOT easier to do it very well, and with fewer
> compromises.
>>Is this "single point ground"?  Looks like multiple paths to ground to me.
> Again, you are getting hung up on the words single point ground, which are
> confusing and lead to fuzzy thinking.
>>Is there a reason to run a separate wire from the shack ground plate to 
>>power company ground rod, or would it suffice to connect it to the green
>>wire inside the sub panel, which has a green wire to the main panel and 
>>to the power company ground rod.  Isn't that more "single point" than a
>>separate parallel ground line?
> Please take the words "single point ground" out of your vocabulary. It is
> confusing things.  Go back and read what I've written a half dozen times
> before. :) All ground electrodes associated with your house/shack MUST be 
> tied
> together by the shortest practical path. That's power, shack, telco, CATV,
> building steel if there is any, metallic plumbing if there is any. All the
> gear in your shack should be bonded together by short fat copper. One big
> conductor, or more big conductors in parallel to lower the impedance, 
> should
> take a junction of those shack bonds to the nearest junction of the earth
> electode bonds. All of the gear in your shack must also be bonded to the 
> green
> wire at the local power outlet(s).
> Don't lose sight of the fundamental reason for all of this, which is to
> minimize the DIFFERENCE IN POTENTIAL between equipment that is 
> interconnected,
> to prevent current from flowing THROUGH equipment, and to direct it away 
> from
> equipment.
> Another point. The more things are spread out, the more difficult it is to
> minimize the potential difference between them. That's because connecting
> wires have inductance, and the current from a strike will induce voltage 
> and
> current on them. To maximize lightning safety we want to minimize that
> distance. The safest layout from a lightning protection point of view 
> would
> have power entry, telco, CATV, and the ham shack all right next to each 
> other.
> Few of us have the luxury of that kind of layout, so we must make the best 
> of
> what we have, or what we can do at reasonable cost (including the cost of
> keeping the XYL happy).
> 73, Jim K9YC
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