You have my vote, Dave - we've preached the point for years. The
National Electric Code also requires it, although I've not read the
section to see the exact verbiage.
Comments have appeared on TT concerning the distance from the house
service ground, and deleting the need at a certain distance. This offends
my "common sense" thinking, in that if a collection of coax and rotor
cable to the house is the only equalization path between large potentials
for even a nanosecond, it pretty presumptious to assume that any ground
dispersion field, no matter how elaborate, around the base of the tower
could guarantee anything more than perhaps an insurance discount.
With all of the expense of a field, one more run of heavy, solid copper
to the power company neutral seems eminently logical to me!
73,
Press Jones, N8UG, The Wireman, Inc., Landrum, SC, 29356
Sales (800)727-WIRE(9473) or orders@thewireman.com
Tech help (864)895-4195 or n8ug@thewireman.com
http://www.thewireman.com and the WIRELINE news
and bargain page. Our 22nd year!
On Fri, 10 Dec 1999 08:26:35 -0700 "Dave D'Epagnier"
<DAVED@ctilidar.com> writes:
>
> David, how far is your tower from the shack? I wonder about whether
> the
> tower ground should be connected to your house ground with something
> other
> than the shield of your coax cable(s). My thought is that if your
> tower is
> located a ways from the shack then as a charged cloud moves overhead
> (or if
> lightning strikes) the ground potentials at the tower ground and the
> shack
> ground will be different. This will cause current flow between the
> two and
> it'll take the least resistance path which will be down the shield
> of your
> coax cables. It seems like it would be better to keep everything
> more or
> less at the same potential by connecting both grounds together with
> some
> heavy wire/cable/strap, and placing ground rods between the tower
> and shack.
> That way most of the current (either from charge build up or during
> a
> lightning strike) flows along the ground cable instead of on your
> coax. Bob
> and I have gone round and round on this. He thinks it's a waste of
> money,
> I'm not so sure. Does anybody else on this list have a strong
> opinion one
> way or another about this?
>
> thanks,
> Dave
> K0QE
>
> ----------
> From: DavidC [SMTP:eDoc@netzero.net]
> Sent: Thursday, December 09, 1999 8:57 PM
> To: n7cl@mmsi.com; towertalk@contesting.com;
> aa0cy@nwrain.com
> Subject: Re: [TowerTalk] Three Lightning Protection
> Clarifications
> Please?
>
>
> Thanks to all for the very helpful review of lightning
> protection
> and grounding principles! Here is what I have learned from
> this
> and am about to apply.
>
> Context:
>
> The only reason I am extending the ground is because the
> shack
> entry point for antennas is 48 feet away from the service
> ground
> rod.
> I understand that I need to connect to that to avoid
> circulating
> currents.
> The tower will be heavily grounded so hopefully most of the
> energy
> will be absorbed there. The ground here is said to be
> Alkaline
> (sand,
> some clay and limestone) and the test I just ran confirms
> that.
>
> Plans:
>
> I will go with copper ground rods and avoid complications.
> The wire
> I
> have is stranded and each strand looks to be about #10.
>
> I am awaiting a reply from Harger as to the cost and part
> numbers I
> need for the CADweld moulds, starter and materials. I am
> told that
> Harger is 1/2 to 1/3 cheaper than all other sources.
>
> I will have a grounding panel just outside the shack wall,
> about 24"
>
> from the wall, through which all of the antenna and rotor
> lines will
> be
> routed. My one open-wire feedline will have both a
> disconnect knife
>
> switch and inline AEI lightning protection fuses. The coax
> and
> rotor
> wires will have Polyphaser and MOV protectors. The panel
> will be
> thoroughly bonded to the buried ground line that I will have
> extended
> from the service panel ground rod to the shack entry point
> 48 feet
> away.
>
> I think that about covers it.
>
> - Thanks! & 73, DavidC K1YP
>
>
>
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>
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