> 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.
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
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.
> Dale - WD4IFR
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