[time-nuts] GPS antenna selection - lightning
albertson.chris at gmail.com
Sat Aug 6 13:13:50 EDT 2016
If you are looking for info in lightening. University of Florida has a
huge collection and also points to many other places on the web. They
actually do testing there, lightening occurs so reliably almost every day
in summer. Their test tower gets many hits
But really, for practical purposes Ben Franklin got it pretty close to
right. Give the lightening a good low impedance path to ground.
On Sat, Aug 6, 2016 at 8:00 AM, Clay Autery <cautery at montac.com> wrote:
> Is the 1987 version the latest issue available for free?
> Clay Autery, KY5G
> MONTAC Enterprises
> (318) 518-1389
> On 8/6/2016 8:46 AM, Glenn Little WB4UIV wrote:
> > Cone of protection is addressed.
> > Volume 1 is theory, volume 2 is application.
> > The military requires 1/0 cable exterior to the building, commercial
> > practice is #2AWG.
> > Ground rod spacing is address.
> > Overall a very good reference based on practical experience and backed
> > with theory.
> > 73
> > Glenn
> > WB4UIV
> > On 8/6/2016 1:19 AM, Bill Hawkins wrote:
> >> Hi Glenn,
> >> Your advice is excellent.
> >> Seems like every time we have a lightning discussion there is no
> >> distinction between an EMP and a direct hit.
> >> I started work in 1960 at a blasting cap plant in upstate New York. The
> >> powder magazines were protected by tall masts according to the "cone of
> >> protection" theory. The angle of the cone varied between 45 and 60
> >> degrees. The earth ground resistance of the mast was measured by a
> >> hand-cranked device that looked like a megger but read earth resistance
> >> to less than a tenth of an ohm. Had the lightning but never lost a
> >> magazine.
> >> You say MIL-HDBK-419 covers EMP. Does it also cover cone of protection
> >> for direct hits?
> >> I was fascinated by the idea that a simple capacitor discharge into an
> >> inductor could be greatly enhanced by reducing the diameter of the
> >> inductor with a conventional explosive, described in one of Stephen
> >> Coonts' books, if my failing memory recalls correctly. And so I learned
> >> what I could about EMP. Never built anything, just interesting behavior.
> >> Best regards,
> >> Bill Hawkins
> >> -----Original Message-----
> >> From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of Glenn
> >> Little WB4UIV
> >> Sent: Friday, August 05, 2016 9:47 PM
> >> To: Discussion of precise time and frequency measurement
> >> Subject: Re: [time-nuts]GPS antenna selection - lightning
> >> A very good reference for EMP protection is MIL-HDBK-419.
> >> This is downloadable for a number of web sources.
> >> It is about 600 pages and is in two volumes.
> >> This discusses a number of different sources of EMP such as nuclear and
> >> lightning.
> >> A lot is for protection of military industrial complexes, but, there is
> >> a lot that pertains to us.
> >> I worked for a military complex that assembled nuclear missiles.
> >> The site was built to this handbook specs.
> >> We had no EMP related damage at the site.
> >> Number one rule, bond all grounds together. If something on your
> >> property takes a hit, you want everything on your property to elevate to
> >> the same level and the same rate.
> >> If you have multiple, non bonded grounds, there is a different reference
> >> for each ground. This is a major source for disaster.
> >> I spent seven years in lightning mitigation. I was told by professionals
> >> that I was wrong. The third time that their tower was struck, destroying
> >> all of the lights and attached equipment, they followed my
> >> recommendations. That was ten years ago. The three hits were within four
> >> months of each other. The site has been free of destructive hits since
> >> then.
> >> 73
> >> Glenn
> >> WB4UIV
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Redondo Beach, California
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