Question re: grounding for lightning protection

[WRTC928]

What is the logic behind bonding your lightning ground to the house ground? Lightning always wants to go to the earth, so grounding your antenna and coax makes sense. You give the lightning an easy path to the earth, and hopefully it will take it. I also understand why it's recommended that you bond the common ground for your equipment to the house ground. The powered equipment is part of the same circuit as all the other electrical equipment in the house and you want to keep it at the same potential. However, I don't follow the reasoning of bonding the two together. It seems to me that the most logical solution for protecting against lightning is to give the electrical buildup a way to get to the earth without directing it into your house; i.e., a lightning ground separate from the equipment ground. Yet everything I read recommends bonding the lightning ground to the house ground, so there must be some reason that I don't understand.

[LeoG]

9 minutes ago, AdmiralCochrane said:

Disconnect/open loops because EMF.

 

 

Lightning strike between my house and neighbor's house took out 2 window AC's and 3 TV's at the neighbor's house, but just a light ballast and the power filter board on my HF rig.  If I had had the HF rig disconnected from the power supply it would have just been the light ballast.  Power poles are your friend.

Lighting is just like tornadoes.  Destroying one while barely touching the one next door.  Could have been grounding, or just dumb luck.  People struck by lighting can survive or become crispy kritter piles of dust.

[WRKC935]

27 minutes ago, LeoG said:

So why isn't the tower bonded to the electrical ground through the coax which is attached to the chassy which is grounded through the ground line in the power outlet?  No matter how much you ground anything because of the resistance of wire they'll always be at a different potential?

Yes, there is always going to be a difference.  You bond because coax connectors are NOT high current rated. The circular mills of the shield conductor is also not sufficient to minimize the resistance of the conductor.  This is why you don't use split bolts and crap to do your grounding.  It's all CadWeld or 15 ton compression lugs / connections.  

 

[AdmiralCochrane]

13 minutes ago, LeoG said:

Lighting is just like tornadoes.  Destroying one while barely touching the one next door.  Could have been grounding, or just dumb luck.  People struck by lighting can survive or become crispy kritter piles of dust.

It was all about EMF and loops that absorbed it.  Any luck involved was whether the loop was tuned/angled to the wave that passed thru it.

[SteveShannon]

1 hour ago, LeoG said:

That right there should protect the radio.  But I know nothing will protect with a direct hit.  Dissipating charge should be accomplished with the wire sizes as they are.
 

That won’t protect the radio at all. Electrons don’t stop instantly and between the antenna connector and the power input there’s a lot of components that are at a different potential than the coax shield and center conductor. 

1 hour ago, LeoG said:

I'm just thinking about my situation.  The main electrical connection to all 4 bays in the building I'm in is at the opposite side of where my antenna is.  That's 170' of conductor needed to make the connection from where the cable enters the building to the bond where the electrical box is.  25'+100'+45'. 
 

Yes, it’s not cheap. 

1 hour ago, LeoG said:

And as to having a ground rod for each leg of the tower why can't the 3 or 4 legs be connected by copper wire and then go to a single ground rod?  The ground loop around the tower is doing essentially just that but just increasing the cost substantially.  And would that change between a steel tower and an aluminum tower since aluminum conducts better?

Tying all of the legs to a single ground rod requires changing the path of the discharge. Having a ground for each provides a straight path to ground, plus having more rods reduces the impedance going to the ground. In an engineered ground system such as a substation you might even see a ground mat, chemicals, and other things done to minimize the resistance and create a large bed of equal potential.