[RFI] w7ekb & ground rods

[Jim Brown]

On Mon,1/19/2015 10:01 AM, Mike King - KM0T wrote:
> For what it's worth, you will find the ground rod resistance calculations in
> the IEEE Green Book, that's where the rule of thumbs come from on ground rod
> spacing verses length.  Lots of other good grounding stuff there too.

Yes, and that's an excellent reference on grounding. I own it, and 
studied it long enough ago that I'd forgotten what I'd seen where. :)
> -----Original Message-----
> From: RFI [mailto:rfi-bounces at contesting.com] On Behalf Of EDWARDS, EDDIE J
> Sent: Monday, January 19, 2015 11:24 AM
> To: 'Rik van Riel'; rfi at contesting.com
> Subject: Re: [RFI] w7ekb & ground rods
>
> Rik,
>
> In quick scan couldn't find anything on NEC Article 250 supporting your
> statement.  Did you find anything in 250?  I only found a reference to "6 ft
> minimum" distance, but that might be old reference and depend on length of
> the ground rod.  This makes sense for NEC since it's worried more about AC
> electrical safety not RF grounding.  In comm buildings R56 calls for using
> both an underground ground ring/buss and bonded ground rods as a single
> system bonded together.

NEC has always been especially lax about the requirements for grounding 
electrodes. One of the reasons for that is that BONDING is far more 
important than the earth connection with respect to safety. Another is 
that the nature of the earth varies so widely from one place to another. 
Remember that NEC is a GUIDELINE code, written by a group of excellent 
engineers, for local jurisdictions to use as they see fit. It's a very 
good code, and is updated every three years.

> However, your statement about rods closer than twice the length being
> unproductive is true.  It is a waste of money and has little effect on
> ground resistance, but I doubt it does much harm if any overall.  And the
> "two-times length" maximum is also true.
>
> I'd rather have any and all above ground, bonding connections from/to each
> service (AC, cable TV, ham radio, telephone) as short of a run as possible
> to the earth (e.g. buried, bonded ground rods) even if that meant the 8 ft
> rods were only 6-8 ft apart.  This would be required for an RF single point
> ground system as I know it.
>
> These are interesting NEC links for those with time on their hands:

I didn't watch the video, but the slide show content is quite good.

73, Jim K9YC