Re: [TowerTalk] Station grounding on granite

[Gary Schafer <garyschafer@comcast.net>]

You would not want to use aluminum strap in contact with copper. It will 
corrode away the aluminum in a short time.

Burying copper wire for a ground is a good thing to do. However a very 
long run will do little good. The inductance of a long run gets too high 
and the long length of wire becomes useless. It is much better to use 
shorter runs out in different directions. Build a buried radial system 
just like you would for a vertical antenna.

73
Gary  K4FMX


ny6dx@netscape.net wrote:
> Martin as an electrician and a cert. lighting ground installer in New York 
> might I suggest the following.
>    First when seccureing your wire for lightning use only copper or aluminium 
> nails and straps.all others will not work.Second do not bend sharp angles in 
> the ground wire(sweeps only)the speed at wich lightning travels will cause it 
> not to make a sharp turn.
>    As for being on granite if you run a bare copper ground(#4 
> recommended)burried 2 ft or so run it as long as possible.the increase in the 
> surface area in contact with the ground will help disipate the charge.Hope this 
> helps NY6DX
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> Martin Ewing <martin@aa6e.net> wrote:
>
>
> > Folks,
> >
> > Having invested in a SteppIR, a roof-top tower, a
> > rotor, and several wire antennas, I find I have a lot
> > of copper running out to the sky from my shack.  Too
> > much to easily disconnect when I hear thunder.  Time
> > to think about a better protective ground system.
> >
> > Inside the shack, I am thinking of a single-point
> > ground plane near the feedline entrances.  All
> > connections including AC power, telephone, computer,
> > SteppIR/rotor control, etc. pass through surge devices
> > on that plane, and all equipment is hopefully
> > connected by low inductance strapping to the SPG.
> >
> > My problem is how to get a good "earth ground" for the
> > SPG.  My house is on a granite ledge with only 1-2 ft
> > of soil nearby. We are about 80 ft from salt water,
> > but that doesn't help. The house does have lightning
> > rods with 3 or 4 downleads (more on this in a moment).
> > The 20-ft rooftop tower is connected to a lightning
> > rod ground, but feedlines are not.
> >
> > I was wondering how the lightning rod grounds were set
> > up, so I partly excavated one.  The results are
> > visible on my web site:
> > http://www.aa6e.net/aa6e/grounding .
> >
> > Is this approach - dual buried horizontal ground rods
> > - good enough even for home protection?  Should I do
> > something like this for my station? (The shack is not
> > near any of the existing ground connections.)
> >
> > It's clear that not even an "excellent" ground
> > connection can prevent kilovolt surges from a near
> > hit, because that is what happens to the earth itself.
> > And full protection from a direct hit to the house is
> > hard to achieve (IMO) no matter how you try in a
> > typical home retrofit. The whole shack should be
> > inside a grounded metal box...
> >
> > My philosophy now is to concentrate on the SPG system
> > and not to obsess on the low-Z ground, which must be
> > pretty hard to realize over rock.  (I would put in
> > something like what I see on the existing lightning
> > rod system.) If the SPG is really good, and the
> > equipment is all referred to that carefully, then it
> > shouldn't matter if the whole system floats up and
> > down by kilovolts.  (Hopefully the op is elsewhere!)
> >
> > The "kilovolt" scenario doesn't quite catch the full
> > impact of a direct hit to the antenna.  10,000 amps
> > into a one ohm ground (?) is 10 kV.  No one expects
> > the Spanish Inquisition! (i.e., worst-case event)
> >
> > I would appreciate suggestions, especially from anyone
> > who has faced a similar problem -- and survived the
> > worst.
> >
> > 73, Martin, AA6E
> >
> > p.s. Fortunately here in CT, we have fairly low
> > lightning incidence.  Even so, we had a close strike a
> > couple of years ago.  A BIG crack, and both my close
> > neighbors lost their telephones and other electronics.
> > We had no troubles here.  My tower was down then;
> > maybe our lightning rods actually caught one. Thank
> > you, Ben Franklin.
> >
> >
> > _______________________________________________
> >
> > See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA.
> >
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>
>
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>
> See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA.
>
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_______________________________________________

See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA.

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