[Top] [All Lists]

[TowerTalk] Grounding

To: <>
Subject: [TowerTalk] Grounding
From: "Dale Sanders" <>
Date: Fri, 16 Nov 2012 17:05:11 -0600
List-post: <">>
> Over the years of being an electrical engineer and a "ham", I've heard 

> so many stories about how this ham or that ham was grounding his 

> station to prevent lightning strikes or handle a lightning strike.  

> Let me go on record that if "the finger of God" decides it your turn 

> to be touched, nothing, I repeat, NOTHING will stop damage from a 

> strike.  I work in the broadcast and wireless industries where 

> grounding is literally a science.  We use established standards for 

> grounding systems at the towers and there is still damage from lightning


> In any lightning strike, even a 2" solid piece of copper takes on the 

> characteristics of a light bulb filament.  I see all this discussion 

> of all the capacitances and impedances, and all these highly technical 

> discussions when the people that install grounding for these 

> commercial facilities use the following guidelines.  These are time
proven, well researched solutions that are in use worldwide by engineers
responsible for million dollar equipment and sites.


> 1.         Single point grounding.  Use one ground field or system and

> everything gets grounded to it.

> 2.         You put enough copper in the ground to get to a <25 ohm, and in

> case of telecom, <5ohm resistance at the ground field connection 

> point.  I doesn't matter what type of soil you have or where you are.  

> You still have to put enough conductor into the ground to get to those 

> low resistance figures. ...and it doesn't matter if it's simple or 

> something exotic.  It's all about the resistance.  A difference of as
little as 5 ohms can divert the energy in a lightning bolt.

> 3.         Measure the resistance into the ground with a "Megger" or with

> clamp-on type ground meter.  I realize these are expensive tools but 

> there are guys in your area that probably have them and use them on a 

> regular basis.  Ask around amongst the local hams, the wireless 

> companies, the telephone companies, or any local tower companies.  

> There are even grounding companies out there that would take a reading 

> on a system for little or nothing.  Seek and ye shall find.


> BTW -- You do not have to use exothermic welds exclusively for your 

> ground connections.  One of the companies that make crimp on grounding 

> connectors is "Burndy".  These clamps are designed to get away from 

> Cadwelding but still require the use of a 12 ton crimper to bond the 

> connection.  Again, these can be rented.  Since I work in this 

> industry, I have access to all of this stuff and I'm sure there are 

> others that you can find that can assist you in your system.  I've 

> helped many hams in my area by loaning them a crimper or a CadWelder 

> and the associated "shots" that are required to make a connection.

Whatever you use, DO NOT scrimp on the connections in your grounding system.
The old

Clamp on grounding connectors from Home Depot "ain't" gonna cut it.


> The key to a ground system is the conductor connecting the tower, 

> radios, whatever to the ground field.  It MUST be of a lower resistance 

> than any other piece of conductor in the system.  In most systems 

> where we install an MGB (Main ground bar) we utilize one or 2 pieces 

> of 750 or larger grounding conductors to connect to the ground field.  

> This gives you the low resistance path to ground for EMP, a nearby 

> strike, or a strike that takes place miles away but still can energize 

> the ground or neutral conductor coming from the utility (remember that the
ground cable is a conductor too).



> In my set up, I have 14 ground rods driven into the ground 8 ft deep 

> under the concrete base of my tower.  The bottom section of my tower 

> is bonded to those rods (which are bonded together) with a 4 pieces of 

> copper braid that are cadwelded (exothermic) to the tower legs.  From this
point, I have an 8"

> x 3" x 1/4" ground bar mounted with a piece of 750 cable running 

> inside to my MGB (see above). It is cadwelded to the braid and to the
tower leg.


Everything in my shack is grounded to 

> that MGB, including the negative of the battery bank and the utility 

> ground.  This places the grounds in my home, shack, and tower on the 

> same ground plain electrically (single-point grounding).  In other 

> words, if you do not tie all the grounds to a single point, then you 

> run the risk of having varied resistances at each grounding point.  

> Remember now, that lightning will take the lowest resistance path to 

> ground....make sure that, if your tower is the target, then the ground 

> directly below it has the lowest resistance path of any path in your

 If you don't then  the lower resistance path will be the one that the
lightning will follow.


> Remember that we're not always able to eliminate lightning strikes, but

> trying to manage the path of the lightning so that it doesn't come 

> into your shack or home.  If you need further clarification, Google

> grounding.  It's the grounding system that is used in critical systems 

> worldwide.  P=Producer, A=Absorber, N=Non Isolated, and I=Isolated.

> Remember to ground your radios to the "I" or isolated side of the MGB.

> The large, low resistance cables connecting the MGB set up in the PANI 

> manner will always be connected dead-center between the A and N 

> sections of the ground bar.


There's not enough room here to explain the PANI theory, you'll have to
research that on your own.


> If you have any questions, feel free to ask.  I'll answer and help out 

> as time and work allows.


> '73

> Dale - WD4IFR



TowerTalk mailing list

<Prev in Thread] Current Thread [Next in Thread>