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Re: Putting in ground rod


 > From: mconway-at-deepthnk.kiwi.gen.nz (Mark Conway)
 > Subject: Re: Putting in ground rods; Best way to install       
 > ground rods?

This was some excellent information. Thanks Mark for posting this
up. More than a few people here are either building coil systems,
or upgrading to higher power levels. I have always said that
Tesla coils literally have to be hand built from the ground up.

 MC> Over on the radio amateur echo somebody was saying that this 
 MC> method <soaking the soil> is not the best for putting in     
 MC> ground rods as the soil does not make good contact with the  
 MC> rod as the water washes the soil away from the rod.

Just a heavy soaking is not going to hurt. The practice that I
think was specifically being advised against was pressurizing
a pipe with water and then using the water flow to assist in
getting the pipe into the soil.

Bruce N9EHA said:

 > the ARRL made mention..., that in many types of soils, most of 
 > what is left after using water pressure to make the hole, is   
 > stones.  All of the conductive earth is washed away. 

But, a good soaking brings particulate dirt and clay in close
contact to the conductor. 

Then quoting Gary Coffman KE4ZV
 
 > Lightning is RF, though most of its energy falls below 2 MHz, 
 > so the skin effect must be considered. That's why solid strap 
 > is preferred over round wire. Strap has a larger surface area, 
 > pound for pound, than round copper wires. Copper pipe can also
 > be used, but it's surface area will be half that of copper
 > strap with a width equal to the pipe circumfrence. 

This is why I used 15 foot long by 3 inch wide copper strap for
the center of my new ground. Again quoting Gary Coffman:

 > Woven braid conductors should be avoided for grounding runs    
 > because braid has about 5 times the impedance of smooth solid  
 > strap on a pound for pound of copper basis. There are a couple 
 > of reasons for this. First, the braid strands weave in and     
 > out, adding inductance, and second, because the skin effect    
 > tries to force currents to the surface, while the individual   
 > strands keep diving into the middle of the bundle, the         
 > currents try to flow from strand to strand along the outside   
 > of the braid. Since the mechanical connections of one strand   
 > to another are fairly loose, a high resistance path is formed.

This is a pretty good argument for using wide smooth strap in the
ground path. I have known for some time that strap performs
significantly better than round wire, and have said that the
widest possible strap is better than the skinny stuff (this is
easily experimentally verified). 

One other thing that I thought someone might mention, but
considering the different applications that grounding is used for
perhaps not; the use of salt in RF grounding applications. Rock
salt or water softener salt can be buried around the ground
conductor. A depression in the surface of the ground is left and
the area is given a good soaking before firing. A section of PVC
pipe could be partially buried around the ground conductor,
filled with salt, and then soaked before firing. The other way is
to perforate the end of a grounding pipe before planting it and
then rig up a simple gravity pump with a saturated saline
solution.

Salt plumes are fairly inexpensive and easy to build up in the
subsoil. They are non-toxic, with the exception perhaps of a tree
root passing directly through it. The presence of an established 
salt plume will really increase the local conductivity. Watering
the ground before firing makes an excellent connection between
the ground conductor and the salt plume. 

Richard Quick


... If all else fails... Throw another megavolt across it!
___ Blue Wave/QWK v2.12