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Re: [RFI] Lightning Protection

To: "Roger (K8RI)" <k8ri@rogerhalstead.com>
Subject: Re: [RFI] Lightning Protection
From: dalej <dj2001x@comcast.net>
Date: Mon, 2 Jul 2012 13:26:53 -0500
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>
Drip loop is a better name for them, although I didn't loop for that reason, 
the tower is a ways away from the house.  I do have drip loops in the dish coax 
which enters the house directly from the dish antenna.  In my case I guess they 
would be a service loop incase I need the extra coax.  

My tower ground is a series of 3 rods outside the concrete base and they are 
all connected together to form a ring using the heavy solid copper wire that's 
used for service grounds to main breaker box, my remote antenna switch is also 
bonded to that ground system.  I also have a run of that same wire which 
connects to my station ground and goes under the turf to the tower ground.  
It's about a 30 foot run or so.  I hope it will be ok and I hope it will never 
be needed.  

73
Dale k9vuj



On 02, Jul 2012, at 12:48, Roger (K8RI) wrote:

> On 7/2/2012 9:44 AM, dalej wrote:
>> 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.
> 
> I call those drip loops to keep water/moisture out of the coax.
> I ground the coax shield at both the top and bottom of the tower so I 
> don't worry about the lightning having to jump anywhere and my system 
> has taken many direct strikes.  Most of those strikes do nothing, but I 
> have had a couple that removed the plating (and weatherproofing) from 
> every connector up there and with 6 antennas that is a lot of 
> connectors.  17 if I counted correctly with power dividers and rotator 
> loops.  They were just bare brass (with a very rough finish).  The 
> weatherproofing  which was the self sealing tape covered with regular 
> Scotch 66 tape looked like sheets of expanded metal.
> That was when I realized the fallacy in believing a good job of weather 
> proofing will always keep water out of the coax.
> 
> 73
> 
> Roger (K8R)
> 
> 
>> 
>> 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
>>>> 
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> 
> 
> 
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