[TowerTalk] [Bulk] Re: RF Ground is a Myth

[Randy]

On 1/21/2015 9:15 AM, Jim Lux wrote:
> On 1/21/15 5:29 AM, Patrick Greenlee wrote:
>> I have a triangular tower with legs on 14 ft centers, yes, 14 feet, not
>> inches.  I built it with three separate concrete foundations, one per
>> leg.  It is currently tilted over so one leg is not touching its
>> concrete embedded mechanical connection/mount.
>>
>
>>
>> Am I missing something?  Will a simple ohm meter test give a reasonable
>> measure of Ufer ground quality, sufficient to decide the question of
>> whether or not multiple copper clad ground rods need to be installed and
>> interconnected?
>
> You need to use an AC source for the measurement: a DC source will 
> cause polarization and the reading will be low resistance at first and 
> then rise (think as if it were an electrolytic capacitor). The other 
> thing is that a typical solid state multimeter uses such low 
> current/voltage that you're going to see strange readings.
>
> if you have something like a 12-24V AC transformer around (12.6V 
> filament transformer, landscape lighting, bell transformer), you can 
> use it: measure voltage and current, and you can go from there.  You 
> can even use 110V (with an isolation transformer from the line, please!)
>
>
>
>
>>
>> Is it too much of a leap of faith or otherwise to assume the inter-leg
>> resistance is an adequate predictor of tower mount to Mother Earth
>> conductivity?
>>
>
> Nope.. that's pretty much how they do it.

Jim, I am glad you mentioned using AC as a source. I once observed a 
crew from the electric company installing new ground rods. They used a 
device that had a "zero center" meter on it to measure the ground rod's 
"resistance", and, as I recall, the "AC source" must have been somewhere 
around 1 Hz or so, based on my observation of the meter swinging back 
and forth. The rod they used were threaded on each end, and they could 
couple on another section and drive it further down if they didn't like 
the readings they got.

As for the electrolytic action...that's my understanding as to why 
multiple ground rods are used, and why the separation between them-- in 
the event of a strike, the ground around the rod rapidly loses its 
ability to further "charge" the ground around it (and dissipate the 
energy) because of electrolytic action, and a rod too near to it would 
suffer the same effect.

Randy
KZ4RV

>
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk at contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>


-- 
I am using the free version of SPAMfighter.
SPAMfighter has removed 2174 of my spam emails to date.
Get the free SPAMfighter here: http://www.spamfighter.com/len

Do you have a slow PC? Try a Free scan 
http://www.spamfighter.com/SLOW-PCfighter?cid=sigen