Lets talk about getting grounded!

[linkclan]

In my travels as a data center electrician, the consensuses is to establish a multi-point grounding system with a bonded loop necessary to reduce or eliminate noise and stray EMF associated with separate grounding points.

This said, I see in this community the standard is to drive a rod or two or three at any point where lightning or utility surge may become an issue. This is okay except that you still have a grounding conductor which travels through your feed line back to your equipment which may or may not have a dedicated grounding electrode. In this instance, there could be trouble as the ground(Terra firma) begins to form an inductive loop and brings with it noise and the possibility of confusing an EMF strike into finding a secondary path to ground(right through your equipment).

I may be over thinking it here but for me, it makes sense to carry a grounding conductor from the shack electrode to the tower electrode(s) and also bond it to your main service entrance grounding point.

It seems like a lot of extra work here and like I said, I may be over thinking it but... Stuff happens and I like nice stuff.

Thoughts....

[gil]

Hello,

I have a ground rod with a lightning arrester on the line.. Not that I am sure it would work and lightning could go up my coax to my room... To find nothing... Because I unplug my radios when not in use ;)

Gil.

[cockpitbob]

Just outside my shack I have 2 ground rods 10' apart.  They come straight into my shack on heavy braid to ground my shack.  Any coax feed lines have a lightning arrestor that directly connects their shields to that ground.  If the antenna gets hit by lightning the center conductor, of course, will be grounded by the arrestor's gas discharge tube.

My 12V power supply's negative output is isolated from AC power ground, so this is a single point (no loop) grounding system.

I know lots of hams with shacks on the 2nd story and have no ground other than the AC ground in the house's wiring.  Not ideal, especially in the case of a lightning strike, but they operate just fine.

[Rob_ma]

You want to maintain a single point of ground for both RF and lightning protection. Easier said than done in a residential setting but keep your grounds as short as possible, don't daisy chain them, and tie them all back to a single point. The ground systems in data centers are a single point of ground in that the main conductor (which is often the metal cable tray that runs over the equipment) has the same ground potential at all points. Every point along the ground system is the electrical equivalent of any other point and all equipment and their racks are bonded to the ground main system.

At your coax entry point you want to create a low impedance to ground so that lightning will prefer the ground path you've created rather than the coax into your home. If you consider the distance the lightning has jumped from the cloud to ground you can see that there are no guarantees that the 1/32" spark gap in your lightning arrestor will always direct the energy to ground.   :)  Lightning has magnetic field components that will cause voltage potentials in metallic objects some distance from the actual strike. Most of the time equipment damage is from nearby strikes and the rapid rise in magnetic field in the area of it. Direct strikes are more catastrophic and you need to do more work to flow that large amount of energy to ground.

The reason for single point of ground is that when all ground points are tied to the same point and the electromagnetic surge from a lightning strike occurs all grounded points rise and fall in potential (voltage) at the same time. A change in potential allows current to flow and if there is no potential difference between two objects then the surge current won't flow. That is the theory a Faraday cage is based on.

All you can do is reduce the chances - not totally eliminate it in real life. If your antenna system, electrical system, and equipment are all at the same ground potential via a single point of ground then you decrease the chance of damaging current flowing in your equipment from a nearby strike.

- Rob