On 9/3/12 9:15 AM, Jim W7RY wrote:
All your tower and shack grounding questions answered here:
http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CCIQFjAA&url=http%3A%2F%2Fwww.radioandtrunking.com%2Fdownloads%2Fmotorola%2FR56_2005_manual.pdf&ei=ZtdEUOzCGureigLcroHgAg&usg=AFQjCNEOc2r04mGLmXraEPGmEoqznH6KJQ&sig2=KVPI276L2uOjwU9r6NuFeA
Interesting.. they've got the same IEEE docs, but they don't give much
rationale for things, other than citing other specs (IEEE, TIA, etc.)
pg 4-12 Here's a potential reason for multiple rods... Contact with
unfrozen soil
And they recommend the use of Ufer grounds for new construction.
What's odd is for ground rings, they have a thing about rods.. if you
have rods they have to be no more than a certain distance apart. Can't
use just one rod or two... I'm going to guess that's because the
purpose of a ground ring is to make the voltage uniform within the ring.
Changing the local resistance to the surrounding soil in one place
will reduce that effect.
Page 4-24 does talk about radials, to be used where there is high soil
resistivity or bedrock and to help dissipate lightning impulses with
lower current density. But that isn't for the ground bond wire between
antenna site and shack.
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