Hey, guys, "I think" and "I assume" are not warm and fuzzy words when
talking about this subject. Follow the specifications. Do what you are
supposed to do. But let's get some solid advise about what is
necessary.
Follow ANSI/EIA/TIA-222-F, dated June 10, 1996. If you own a tower, you
should have a copy of it in your home library. Read it and heed it.
Many jurisdictions require your PE stamped construction drawings to
state compliance with it before issuing a building permit. If they do
and you "got by" without it, I wouldn't brag about it, I'd worry.
Use the proper equipment to measure your ground resistance. A megger is
the appropriate piece of equipment for this purpose, not a digital (or
analog) vom.
Read the PolyPhaser book. Go to their home page. Get the facts.
Many posts have been made here on the relevant URLs. Go to the PVRC
home page and click on the hyperlinks. (http://www.pvrc.org)
But, please use engineering sense (common sense isn't good enough) when
dealing with such leathal items like lightning protection for a tower.
Bill, N3RR
John Allen wrote:
>
> I think that a digital ohm meter would work.
>
> One ham I know runs a wire (#10 or larger?) a few hundred feet
> to a brook where he gets a good ground. I works very well for him.
>
> I have 3 8 foot rods at the base of the tower into fairly poor
> and dry soil and no salt or conductivity enhancer. I was hit by
> lightning - a direct hit on the tower - the following resulted:
>
> 1. antennas were disconnected, but the 6M coax was about 6 inchs away
> from the side of a rack cabinet.
>
> 2. All of the bolts holding the Rohn 45 sections together were
> loosened by several turns!!! EXCEPT the sections that had aluminum
> conductive grease at the junction (Hint: do the inside of the bottom
> of each section instead of the outside of the top of each section and
> you will have much less grease on your clothes when done.) The clamp
> screws on the ground rods were also very loose.
>
> 3. The 6M coax arc'd over the 6 inch space to the (grounded) rack.
> (How do I know? - there is a 1/2 inch dia molten spot on the N
> connector and a matching burn spot on the steel rack.
>
> 4. The power supplies in the rack and the 6 and 2 M (tube) amps were
> fine. But the 6M and 2M ICOM 551/251 xcvrs are HISTORY
> (unrepairable, totalled).
>
> 5. The current went from the rack to the above rigs and also into
> the shack's power/neutral line.
>
> 6. Everything connected to the phone line that wasn't a phone (ie
> answering machine, modem) was fried.
>
> 7. Random other appliances (only a few) were fried. Including a
> Cuisinart food proccessor and a subwoofer and the ac side bypass caps
> of my audio power amp.
>
> So don't laugh when you see someone worry about the ground resistance
> of tower grounding and don't laugh when you see someone move all of
> the coaxes 6 or more feet away from the shack entrance.
>
> 73, John K1AE, ex K1FWF
>
> > A short time ago someone indicated they had measured the resistance
> > on their ground rods. How does one do this? Can it be done with
> > something as simple as a digital volt meter? What two points do
> > you measure between? I don't live in a particularly sandy area but
> > have no idea if my ground rods (6) will actually help if lightning
> > should visit.
> >
> > Thanks,
> > 73 Wayne AJ5M ehayes@vnet.ibm.com
> >
> >
> > --
> > FAQ on WWW: http://www.contesting.com/towertalkfaq.html
> > Submissions: towertalk@contesting.com
> > Administrative requests: towertalk-REQUEST@contesting.com
> > Problems: owner-towertalk@contesting.com
> >
> >
>
> --
> FAQ on WWW: http://www.contesting.com/towertalkfaq.html
> Submissions: towertalk@contesting.com
> Administrative requests: towertalk-REQUEST@contesting.com
> Problems: owner-towertalk@contesting.com
--
FAQ on WWW: http://www.contesting.com/towertalkfaq.html
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com
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