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Re: [RFI] Lightning Protection

To: dj2001x@comcast.net,RFI@contesting.com
Subject: Re: [RFI] Lightning Protection
From: Missouri Guy <n0tt1@juno.com>
Date: Mon, 2 Jul 2012 18:02:37 +0000
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>
I agree on the vaporization.  The installer deliberately made the
loops, then cut off the excess coax and installed the connectors.  
The dish is grounded directly via a #12 copper wire to a ~4ft 
ground rod...no loops there...that's good.

Yes, interesting discussion on lightning,

73,
Charlie, N0TT
 
On Mon, 2 Jul 2012 12:10:03 -0500 dalej <dj2001x@comcast.net> writes:
> I suspect during a direct strike the coax would be vaporized so loops 
> probably won't do much.  It was a way to take care of extra coax up 
> there.  I always like to have a little more in case I make changes, 
> which I do from time to time. If you go to my QRZ page and arrow 
> down you can see the antennas and the loops.  The cover page they 
> aren't installed because that picture is old, like me :)
> 
> I'm learning a lot with this discussion about mother nature's sparks 
> and how to properly ground a tower.  
> 
> 73
> Dale, K9vuj
> 
> 
> On 02, Jul 2012, at 10:50, Missouri Guy wrote:
> 
> > Hmmm...loops in coax.  I always wondered why
> > the "pro" installers put loops in the coax feeds.  This
> > is on my satelite internet feed.  The same kind of loops
> > are on my Dish Network antenna feedlines.  There's
> > one just below the dish and one fastened to the pole.
> > 
> > So, is this for lightning "protection" or is it just a "service 
> loop"?
> > Maybe both?  
> > 
> > See photo here:
> > 
> http://i913.photobucket.com/albums/ac332/MissouriGuy/th_LOOPSINCOAX.jpg
> > 
> > 73,
> > Charlie, N0TT
> > 
> > On Mon, 2 Jul 2012 08:44:26 -0500 dalej <dj2001x@comcast.net> 
> writes:
> >> I put large loops in my coax at the top of the tower.  The idea 
> being 
> >> the lightning striking the antenna goes down the coax and won't 
> make 
> >> the bend so it just shoots out the coax and not down to the rig.  
> I 
> >> suppose it's not very effective, but I had some extra up there so 
> I 
> >> figured why not.
> >> 
> >> Interesting discussion about lightning. 
> >> 
> >> 73
> >> Dale, k9vuj
> >> 
> >> 
> >> 
> >> On 02, Jul 2012, at 8:08, Kim Elmore wrote:
> >> 
> >>> No, not effective. Again, because *everything else* is in corona 
> 
> >> (tower legs, rivets, weld sputters, bolt threads, nut shoulders, 
> 
> >> joints of all kinds) and because lightning propagation isn't 
> driven 
> >> by small variations in the local electric field, which is all 
> these 
> >> devices can accomplish. Lightning begins well aloft in the cloud, 
> 
> >> when the e-field approaches 1 M V/m and propagates at the very 
> high 
> >> e-field at the tip of the stepped leader. The downward 
> propagating 
> >> stepped leader is typically met 100-200 m above the surface by an 
> 
> >> upward-propagating streamer, which is caused by the local e-field 
> 
> >> induced by the stepped leader. All of this happens faster (think 
> 
> >> relativistic speeds) than corona currents can diffuse away from 
> the 
> >> source.
> >>> 
> >>> Kim N5OP
> >>> 
> >>> 
> >>> 
> >>> 
> >>> On Jul 1, 2012, at 23:21, "KD7JYK DM09" <kd7jyk@earthlink.net> 
> >> wrote:
> >>> 
> >>>> "I asked them about these corona brushes and was told that they 
> 
> >> are 
> >>>> ineffective. Once the electric field exceeds about 50-100 kV 
> per 
> >> meter, 
> >>>> everything -- grass, trees, fences, antennas -- are all in 
> corona 
> >> and the 
> >>>> air is about as "saturated" with corona ionization as it can 
> get. 
> >> These 
> >>>> corona brushes have no effect"
> >>>> 
> >>>> Several of htese at a site won't lower the potential in the 
> >> immediate area 
> >>>> preventing charges in the 50-100 kV per meter range?
> >>>> 
> >>>> I see the diasharge brushes on remote sites, radar, repeaters, 
> 
> >> surveillance, 
> >>>> even airports surrounded by towers with brush arrays a few tens 
> 
> >> of feet 
> >>>> across?
> >>>> 
> >>>> Not effective at all?  What about a row of air teminals on a 
> >> house?
> >>>> 
> >>>> Kurt
> >>>> 
> >>> _______________________________________________
> >>> RFI mailing list
> >>> RFI@contesting.com
> >>> http://lists.contesting.com/mailman/listinfo/rfi
> >> 
> >> _______________________________________________
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> >> 
> >> 
> > 
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> 
> 
> 
 
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