[Kenwood] Lightning protection wire antennas WA8OPR

[Robert Rode]

...Guys, I know ur talking about wire antennas, a thot,..with  tri bander
on tower, tower grounded, coax disconnected from station, lightning hit
tower near top, and still came in, through the rotor wires, never thot of
that. burned up every thing attached to station ground, knocked circuit
breaker right out of fuse box, welded plug into wall socket,.later took
tower down for different reason, saw 3 black burns in steel near top,..all
this was "at ground potential".. W9ESX/Robert


On Wed, May 14, 2014 at 11:15 AM, Kenneth G. Gordon <
kgordon2006 at frontier.com> wrote:

> On 14 May 2014 at 11:41, Terry Clinard wrote:
>
> > Can someone answer this question:
>
> Maybe...
>
> > Decided to purchase two old style heavy duty knife switches with
> porcelain
> > bases.  The gap between the heavy duty copper contacts is a bout 2.5
> inches.
>
> OK.
>
> > The live end of the antenna wire is attached to the center knife rocker
> and one
> > of the side psots is connected to the transceiver.  Obviously when the
> knife
> > switch is opened it disconnects the antenna.  My question is should the
> opposite
> > knife post be attached to an earth ground?
>
> IMHO, yes. For the following reason: it has been pretty much proven by
> experiment (and you can find this info on the web somewhere) that
> GROUNDED and elevated metal objects tend to make lightning AVIOD them.
>
> In fact, a high, well-grounded, metal object, like a BC tower, provides
> protection against lightning strikes for a significant area around it. A
> sort of
> "safety zone".
>
> I have seen photos of lightning strikes which have, very obviously, flowed
> around a grounded and elevated metal structure. The strike is "bent" in the
> photos.
>
> The safety zone around such a grounded metal object is fairly wide too. As
> I
> remember it, that zone is as much in radius as the antenna or tower is
> tall.
>
> The only antenna I presently own is a 55' tall vertical, which is always
> at DC
> ground for this very reason.
>
> There have been lightning strikes all around my location, but so far, no
> damage has occurred to any piece of equipment I have here.
>
> > This then puts the wire in the air
> > directly to ground.
>
> Yes. Is good.
>
> >  Now with the antenna going to true ground raises the
> > negative potential of the wire in the air.
>
> That is not necessarily true.
>
> Do some research on lightning research. There is plenty of info out there
> on
> it.
>
> >  I am thinking that one does not want
> > to do this, because now you have created a high (55 foot) negative
> conductive
> > path for lightning to target.  Should the antenna be grounded or simply
> turned
> > off with the 2.5" knife switch air gap?
>
> First of all, a 2.5" air-gap would not be even noticeable to a lightning
> strike.
> We are talking about several hundred thousands, perhaps millions, of volts
> at
> 10s of thousands of amperes. A 2.5" gap in such conditions is simply
> laughable.
>
> Secondly, as I have tried to make clear above, research proves that
> lightning
> AVOIDS a properly-grounded, elevated metal object.
>
> I think you would do far better to make absolutely certain you have an
> EFFECTIVE ground system.
>
> Mine consists of several 8 foot ground rods, driven to within a few inches
> of
> their ends, all tied together with welding cable, PLUS as many radials as I
> could put down, all tied to the rods. And the purpose of the welding cable
> is
> not to be able to carry significant current, but to reduce the
> circuit-resistance
> to minimum.
>
> Also, be aware that some designs of antenna couplers automatically assure a
> continuous DC ground.
>
> This is another reason to have an effective ground system.
>
> Ken W7EKB
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