In article ,
"John Doe" wrote:



So then, what is the reason that they drive a separate ground rod in when
they install a commercial tower whose legs are in concrete?

Howard W3CQH



There is a GIANT difference between RF Grounding and Lightning
Protection. Don't even think of confussing the two....

You wrote:

There is a GIANT difference between RF Grounding and Lightning
Protection. Don't even think of confussing the two....

And there's a third reason and set of requirements for grounding which
is different from both of those -- AC safety ground. Its requirements
are dictated by the NEC and local electrical codes, and it shouldn't be
confused with either of the other two.

Roy Lewallen, W7EL

On Wed, 11 Jul 2007 11:35:11 -0700, Roy Lewallen wrote:


And there's a third reason and set of requirements for grounding which
is different from both of those -- AC safety ground. Its requirements
are dictated by the NEC and local electrical codes, and it shouldn't be
confused with either of the other two.

Is there such a thing as a ground that is good for both AC safety ground
and lightning protection ... or, both of those plus RF ground?

Rick (W-A-one-R-K-T) wrote:
On Wed, 11 Jul 2007 11:35:11 -0700, Roy Lewallen wrote:


And there's a third reason and set of requirements for grounding which
is different from both of those -- AC safety ground. Its requirements
are dictated by the NEC and local electrical codes, and it shouldn't be
confused with either of the other two.

Is there such a thing as a ground that is good for both AC safety ground
and lightning protection ... or, both of those plus RF ground?

Sure. One way to do it is to make a proper AC safety ground, a good
lightning ground, and an effective RF ground, then bond them all
together (provided it's permitted by code).

Roy Lewallen, W7EL

Roy Lewallen wrote in
:

Rick (W-A-one-R-K-T) wrote:
On Wed, 11 Jul 2007 11:35:11 -0700, Roy Lewallen wrote:


And there's a third reason and set of requirements for grounding
which is different from both of those -- AC safety ground. Its
requirements are dictated by the NEC and local electrical codes, and
it shouldn't be confused with either of the other two.

Is there such a thing as a ground that is good for both AC safety
ground and lightning protection ... or, both of those plus RF ground?

Sure. One way to do it is to make a proper AC safety ground, a good
lightning ground, and an effective RF ground, then bond them all
together (provided it's permitted by code).

Roy,

Isn't equipotential bonding part of making three independent earth
systems work compatibly with each other, to be a single system that is
effective for each of the purposes?

Owen

Roy Lewallen, W7EL

"Owen Duffy" wrote in message
...
Roy Lewallen wrote in
:

Rick (W-A-one-R-K-T) wrote:
On Wed, 11 Jul 2007 11:35:11 -0700, Roy Lewallen wrote:


And there's a third reason and set of requirements for grounding
which is different from both of those -- AC safety ground. Its
requirements are dictated by the NEC and local electrical codes, and
it shouldn't be confused with either of the other two.

Is there such a thing as a ground that is good for both AC safety
ground and lightning protection ... or, both of those plus RF ground?

Sure. One way to do it is to make a proper AC safety ground, a good
lightning ground, and an effective RF ground, then bond them all
together (provided it's permitted by code).

Roy,

Isn't equipotential bonding part of making three independent earth
systems work compatibly with each other, to be a single system that is
effective for each of the purposes?

Owen

Roy Lewallen, W7EL


Owen

Equipotential bonding is the process whereby all exposed conductive parts
are connected together so that they are all at the same (usually earth)
potential. Cross connecting three independent earthing systems could well be
used to ensure that a system as a whole was properly grounded for power,
lightning and RF. However, you have to bear in mind that for some power
purposes, a high ohmic value is required in the earth circuit to prevent
lethal current flowing in event of a fault. Under these circumstances it
would be wrong to cross connect all the earths together. It is important to
study the design criteria for the power circuits and protection devices
before making any changes to an existing installation.

Mike G0ULI

"Mike Kaliski" wrote in
:

Owen

Equipotential bonding is the process whereby all exposed conductive
parts are connected together so that they are all at the same (usually
earth) potential. Cross connecting three independent earthing systems

The problem is that in the event of a lightning strike, nothing is at earth
potential!

Owen