[TowerTalk] w7ekb & ground rods

[Kelly Taylor]

In most cases, RF ground is a fallacy. The right length of conductor can
make it so that there's zero difference RF-wise between having it connected
and having it not connected to the ground rod. A ground conductor starts
rapidly losing effectiveness RF-wise at one-tenth a wavelength (about 6' on
10m) and longer.

Also, as part of an antenna system such as a vertical, a ground rod (for RF
purposes) is next to useless. (Important for lightning protection, yes, but
not for RF.) Radials are the way to provide RF current return: a ground rod
is mostly very well insulated from picking up return currents.

Dry soil has got to be less conductive than moist soil. I would think what
that means is multiplying the number of ground rods to make up for the lack
of conductivity, and perhaps encasing the rods in concrete or bentonite to
maximize whatever conductivity there is. You don't have to have the rods
vertical, either. You could lay them in trenches, and for concrete
encasement, you'd treat the ground rod much like you would rebar, suspending
it in the concrete during the pour.

73, kelly
ve4xt




On 1/19/15 10:45 AM, "Ken" <wa8jxm at gmail.com> wrote:

> It seems to me that the ground above my rock layer (@ 36-40²)  gets really dry
> during the summer.  Does that dry dirt have enough conductivity to be useful?
> I do not know the answer to that question.
> 
> Are there different answers depending on why we have the ground rod?  (RF
> ground, power line ground, or lightning protection)
> 
> Ken WA8JXM
> 
> 
>> On Jan 19, 2015, at 12:53 AM, Kelly Taylor <ve4xt at mymts.net> wrote:
>> 
>> It seems to me a valid question to ask on this thread: Do you gain anything
>> by, for example, drilling a hole to get a ground rod deeper?
>> 
>> If you think about it, the answer might not be so simple.
>> 
>> The point of a ground rod is to maximize electrical contact with the ground.
>> If you have to drill 48 inches of an eight-foot rod and don't employ some
>> kind of conductive filler (concrete, bentonite, etc.) to bond the rod to the
>> rock, how much better off are you than just putting in a 48-inch rod? Even
>> if you do use bentonite, is rock a good connection?
>> 
>> If that's the case, what would be wrong with cutting the eight-foot rod into
>> two 48-inch rods and driving them 96 inches apart?
>> 
>> The point of eight- or ten-foot ground rods is to get eight or ten feet of
>> contact area, not necessarily to get eight or ten feet deep, yes?
>> 
>> Just curious on all this.
>> 
>> 73, kelly
>> ve4xt
> 
>