[TowerTalk] Antenna to Shack Ground Connection

[Patrick Greenlee]

Your story seems to support the old rule of thumb.  Lightning hit all 
around but not directly on to the tower.

Lots of folks think lightning rods (and other  structures such a towers 
etc.) are intended to attract lightning to protect other objects from 
being hit.  Not so, gentle reader, as the primary purpose of lightning 
rods is to drain away static charges such as accumulate and thereby 
prevent a lightning strike.  If the grounded system is hit by lightning 
then the protection system has failed its primary goal. A secondary 
consideration is surviving the strike so as to continue with its primary 
purpose of draining charge and preventing strikes in the immediate area.

The videos we recently watched showing guys climbing tall towers let us 
see some of the charge draining structures.  Some looked like metal 
modern art impressionistic porcupines among other styles.  The shared 
attribute of the charge draining structures was their radius of 
curvature. Sharp points and edges to allow charges to more easily drain 
away. The electric field vector strength is inversely proportioned to 
the radius of curvature of the conductor.  Sharp points "amplify" the 
field strength leading to more ionization and better conduction to drain 
the static charge.

Patrick   NJ5G

On 1/28/2015 10:13 PM, Roger (K8RI) on TT wrote:
> On 1/28/2015 1:57 PM, Patrick Greenlee wrote:
>
> Not a debunking, but maybe a modification<:-))
>
> I have a 100' 45G that had a 30'  mast extension in the center of a 
> 200 X 200 lot. One multiple strike abt 6, or 7 years ago hit all 
> around us except to the S, yet it ignored my system that was almost in 
> the center of the strike zone.
>  http://www.rogerhalstead.com/ham_files/Tower29.htm  I was in a bit 
> better shape back then.  Yet as I've mentioned a number of times, it 
> took 17 visually verified hits in 6 years and nothing in the 8 years 
> since.  Oh!  That strike did a lot of damage in the neighborhood.
>
> The only thing predictable about lightening, is its unpredictability.
>
> 73
>
> Roger (K8RI)
>
>
>> The old rule of thumb for lightning protection from over head 
>> dissipation devices (high metal roofs, lightning rods, grounded 
>> towers, etc. is a 30 degree cone angle.  This is NOT a guarantee but 
>> a tendency.  I think more is better and would not find fault with a 
>> ground wire a ways above coax or control leads but would encourage 
>> ground rods along the way so as to not encourage a great deal of 
>> coupling between lightning generated ground wire and "other" 
>> conductors below it.
>>
>> Patrick  NJ5G  (now stand by for a total debunking of my comments...)
>>
>>
>> On 1/28/2015 12:30 PM, David Gilbert wrote:
>>>
>>> I don't have the expertise to be sure about it, but it always seemed 
>>> to me that it would be best to run the ground wire (grounded at both 
>>> ends and maybe a few places in between) in the same trench as the 
>>> coax ... but some distance above them ... in order to provide a sort 
>>> of shielding effect for the coax against induced currents from 
>>> nearby lighting bursts.  I was once told that the electric utilities 
>>> run a ground line at the top of utility poles above the actual power 
>>> lines for a similar purpose.
>>>
>>> Possibly induced currents in the ground wire would still couple to 
>>> the coax anyway, but I certainly don't see how running the ground 
>>> wire with the coax would be any worse than running them separately.
>>>
>>> 73,
>>> Dave   AB7E
>>>
>>>
>>>
>>> On 1/28/2015 8:43 AM, Cox, Norman R. wrote:
>>>> Dear Group:
>>>>
>>>>      I am now ready to connect the tower grounding rod network to  
>>>> the shack grounding system.  The crank-up tower is about 30 feet 
>>>> from the shack.  Is it preferable to run the ground connection 
>>>> between the two along with signal cables?  Or is it better to run 
>>>> the grounding connection not so close to the signal cables?  I've 
>>>> seen people do it both ways, and can see a possible benefit either 
>>>> way, but a lightning strike could throw either idea out the window.
>>>>
>>>> Thanks,
>>>>
>>>> Norm
>>>> KE0ZT
>>>>
>>>>
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