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Re: Grounding Rod Troubles
Tesla List wrote:
>
> Original Poster: Adam <psycho-at-tradewind-dot-net>
>
> Today I tried to drive a 5/8" by 8' bonded copper ground rod into the
> ground. I tried digging, soaking, soaking, digging, cursing, digging,
> cursing, swearing, and soaking, and it simply would not go in far enough
> (only three feet). My soil is way too rocky for this.
>
> the guy at home depot, however, told me that an electrical ground
> doesn't have to go straight down, it can be bent, angled, and twisted in
> all three dimensions: all that matters is that the rod is 8 ft. long.
>
> Is this true? Can I just shape the rod into something like this:
>
> |
> |------Ground level
> | |------| |
> |-----| |----|
>
> Or does anyone know a better way to do it (there must be one)?
>
> I'm in Northern New Jersey, and I know there are a couple other coilers
> around here, so what do you guys do?
>
> Thanks a lot,
> Adam
The guy at Home Depot, of course, doesn't have much experience with RF.
For a safety ground (which is what they sell those rods for), it is
pretty much the total buried length that is important. For instance, a
UFER ground (quite common here in California) is essentially the
grounding wire bonded into the concrete slab, which in turn is in
contact with the ground.
Even for a safety ground, depth is important... The idea is to get the
rod down to where the soil is always moist (i.e. a conductor).
For RF, you have a slightly different goal in mind, that is, low RF
impedance. A crummy ground close to you is actually better for RF than a
good ground connected with 100 ft of wire.
What you want is a good low impedance RF ground (much like they use in
electrical substations). The trick here is lots of wires in the ground.
It doesn't matter much how long they are, as long as you've covered a
goodly area. (An extreme obvious example is that if you buried a 1000 ft
spool of wire, intact, it doesn't do very much for you as a ground.)
In fact, the RF ground can even be insulated wire (on standoffs a few
feet above the "real" ground for that matter. It could even be the side
or roof of your room. For practical safety reasons, you want to make
sure that there is a direct metallic connection (i.e. a wire) between
the real ground and your RF ground (in case you get a power line short
to your RF ground, the breaker will trip). And, whatever "you" are going
to be touching, standing on, sitting on, etc. should be connected to the
RF ground by a low impedance (e.g. short, wide) connection. (Ask the
radio amateur who has gotten the "RF zap" from a transmitter that is DC
grounded, but is actually floating RF, wise.)