[TowerTalk] Does prevailing grounding scheme promote large ground loop?

[Roger (K8RI) on TT]

Remember, a lightning strike a mile away can induce as much as a 
thousand volts per meter in a conductor.  It doesn't necessarily need a 
physical connection to the strike.

I would add that the pulse from a nearby lightning strike propagates 
through a building at speeds different than the induced voltages in the 
wiring, let alone the wiring from different sources so it's possible, or 
even quite likely to have voltage differentials in the thousands of 
volts between ends of the house, or even adjacent wires in the same room 
with many thousands of joules capable of starting fires, let alone 
frying delicate electronic equipment.

It's different for every home and every strike. Even the magnetic fields 
can induce voltages that are lethal to equipment and sometimes, humans. 
   Any conductor can turn into something carrying lethal voltages.

My one rig used for weather watching/nets is well protected, but I still 
set it up for locked cross band repeat so the only thing I'm touching is 
the HT.

73

Roger (K8RI)

On 7/25/2016 Monday 5:32 PM, Jim Brown wrote:
> On Mon,7/25/2016 5:51 AM, jimlux wrote:
>> What you want is everything that is "near" each other connected with 
>> good conductors that are similar in length (so the inductance is 
>> similar, and the voltage rise from the pulse is similar).
>>
>> If you have one piece of gear with a 10 foot cable to the lightning 
>> impulse. And another piece of gear on the bench connected with a 100 
>> foot cable to the lightning impulse, and then you interconnect the 
>> two with a short jumper, you can see that there might be a problem.
>
>
> The problem with this (and any) analysis of a lightning event is that 
> it is FAR more complicated than anything we can compute, simply 
> because the voltages and currents induced in any system (stuff wired 
> together) will be different in each conductor depending on WHERE the 
> strike is, the physical geometry of the conductors that make up that 
> system, how energy from the strike gets to the earth, etc.
>
> Remember that in any given lightning event, voltages/currents are 
> likely to couple into our system (our home) via the power system, via 
> the CATV system, via the telephone system, via our antennas, and 
> directly onto all the wiring within our home. Voltages/currents will 
> be very different between those multiple systems by virtue of THEIR 
> geometry, how they are earthed and bonded, and THEIR proximity to the 
> strike.
>
> 73, Jim K9YC
>
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk at contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk


-- 

73

Roger (K8RI)


---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus