I totally agree Glenn and was about to reply to Jon's response with a
similar answer, except I saw your comments and yours are right on.
On another point:
I disagree with the theory of disconnecting equipment from the coaxes/cables
as a good method to avoid lightning problems in lieu of providing a proper
grounding system. Disconnecting equipment, as I have pointed out
previously, with some disagreement from others ;-), opens your house/shack
up to arc-over at the open connections and possibly resulting in fire. I've
had my antenna farm and lightning protection system in place since 1994 with
all equipment continuously plugged-in with out any problems. A properly
designed and installed lightning protection system will allow you to keep
your station on-the-air 24x7, as I do. 4 Packet radios, IC-4KL, IC-781,
PCs, more. All antennas are always connected to both radios and ring rotor
controllers. I operate in all kinds of wx, and ignore it as an operating
issue. Lightning storms approach my tower/property and literally go around
the property, often splitting (or morphing) so as to avoid my tower and
property, then re-converging and proceeding when past the property. It's a
very interesting site. In a big storm, where there's lots of lightning, it
looks miraculous.
Skimping on this lightning protection stuff just doesn't make sense to me -
never has.
Bill, N3RR
www.erols.com/n3rr
----- Original Message -----
From: "Glenn Little" <glittle@awod.com>
To: "Jon Ogden" <na9d@speakeasy.net>; "Bill Hider (N3RR)" <n3rr@erols.com>;
<towertalk@contesting.com>; <brewerj@squared.com>
Sent: Wednesday, September 18, 2002 6:00 PM
Subject: Re: [Towertalk] creating ground "surround" of house: Obstacle
> If the grounds are not tied together, you will get a difference in
> potential between the two grounds. If the grounds are tied together, the
> difference of potential will be minimum. If everything is tied together
and
> a lightning strike occurs, everything elevates to the same level and
> everything is happy. If the grounds are not tied together and a strike
> occurs, the two "grounds" will elevate to different points. A difference
of
> potential and current flow. Not at all good. If the tower takes the hit
> (probable) and is connected to the house by anything conductive and the
> house is not at the same ground potential as the tower, dammage will occur
> as the energy attempts to equalize. To ground the tower to the house
> requires ground rods placed along the path at twice the distance of the
> ground rod length. The ground wire should be bonded to the rods along the
> path. To be done properly, the rods are driven to about 18 inches below
> grade and the ground wire (#2 AWG or larger) is trenched to the depth of
> the rods and welded. References for this are Motorola's R-56 manual for
> site selection and MIL-HDBK-419A.
>
> In my past job, I evaluated sites for lightning probabilities. If
> everything is bonded together, minimum damage during a strike. I anything
> was not attached to the system bonded ground, it was usually toast after a
> strike.
>
> YMMV.
>
> 73
> Glenn
> WB4UIV
>
> At 06:42 AM 9/18/02 -0500, Jon Ogden wrote:
> >on 9/16/02 11:56 PM, Bill Hider (N3RR) at n3rr@erols.com wrote:
> >
> > > Now, sometimes the tower is located so far from the shack (house) that
the
> > > impedance in the coax shield
> > > over that long run (say several hundreds of feet) is so large that
you'd
> > > think the lightning would dissapate before
> > > it got to your shack. Well, maybe it would and maybe it wouldn't.
Why not
> > > be safe and provide a path for the lightning
> > > that YOU know is the one you want it to take? Add that measure of
> > > protection. In your case, 70 ' just doesn't come
> > > close to being far enough to ignore this, in my opinion.
> >
> >This whole thing seems to be a bit of debate between people. To connect
the
> >tower to the house ground or not to.
> >
> >Most people I have talked to do not connect the tower ground to house
> >ground. The simplest reason, is you want to keep lightning strike energy
> >AWAY from the house. A big, long wire connecting 70 feet or more of
length
> >is going to have a lot of inductance to lightning and won't do much good
> >anyhow.
> >
> >The reason for tying electrical grounds together is for safety reasons as
> >you want all "ground" points to be at the same potential relative to the
hot
> >wire in the electrical circuit. Otherwise, you can create major problems
as
> >ground is not always "ground." Tying electrical grounds together fixes
> >that.
> >
> >This is a different purpose for the tower ground. In fact, I personally
> >think that keeping the ground separate is a very good thing as you want
to
> >keep al lightning strike AWAY from your house electrical system.
> >
> >The best protection of shack and equipment is as one person said to
> >disconnect everything. Sure, but it's not always practical. So the
> >alternative is to bite the bullet and drop the big bucks for surge
> >suppressors. One of the guys that helped me put up my tower told me in
no
> >uncertain terms to do this. He said EVERY line coming from the tower
going
> >into the house needs to be protected. The surge arrestors should be as
> >close to ground as possible and grounded right near the tower.
> >
> >So yesterday I ponied up the big bucks and spent the money to get the
> >arrestors for every line. Cable Experts sells the ICE, Alpha Delta and
> >Polyphaser models. The ICE ones that I bought cost $40 to $46 each and
look
> >to have a pretty good design.
> >
> >73,
> >
> >Jon
> >NA9D
> >
> >-------------------------------------
> >Jon Ogden
> >NA9D (ex: KE9NA)
> >
> >Life Member: ARRL, NRA
> >Member: AMSAT, DXCC
> >
> >http://www.qsl.net/ke9na
> >
> >"A life lived in fear is a life half lived."
> >
> >_______________________________________________
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an
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>
> --------------------------------------------------------------------------
-
> Glenn Little glittle@awod.com QCWA LM 28417
> Amateur Callsign: WB4UIV wb4uiv@amsat.org AMSAT LM 2178
> QTH: Goose Creek, SC USA (EM92xx) ARRL TAPR
> --------------------------------------------------------------------------
-
>
>
> _______________________________________________
> Self Supporting Towers, Wireless Weather Stations, see web site:
http://www.mscomputer.com
> Call 888-333-9041 to place your order, mention you saw this ad and take an
additional 5 percent off
> any weather station price.
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