[time-nuts] GPS-Attached Equipment Lightning Protection

[SAIDJACK at aol.com]

Hello Alan,
 
>rod. The likelihood of getting any significant voltage on the  center
>conductor I would think would be very small.
 
A lightning strike is not your normal static discharge. The magnetic, and  
electromagnetic energy released by a strike is humongous. We had to go to 3000W  
fast TVS diodes to achieve an acceptable level of protection from proximity  
strikes. I heard that a strike 100 meters away can still fry your antenna  
circuits.
 
>The most likely scenario is for
>induced voltages/current on  the braid due to nearby strikes. This should be
>grounded in a way that  does not allow the whole ground system that it is
>connected to to to be  "pulled up".


Yes, this is the case, but it's easy to induce a couple 100 Volts into  the 
center conductor through the exposed elements of the antenna. Also,  grounding 
can be an issue, since the earth has a fairly  high resistance as well. Have 
you seen the video where a strike hits a  soccer game, and all of the players 
fall over at the same time even though the  strike actually happened 10's of 
Meters away?
 
Average strikes have about 30,000 Amps and up to 200 Million Volts, with  
some super-bolts reaching 300,000 Amps. That's a lot of current going through an  
RG-8 cable. This kind of current can bring up the ground potential around 
your  house, let alone generate a lot of voltage on the antenna cable.
 
bye,
Said







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