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March 22nd 04, 09:49 PM

On 22 Mar 2004 13:19:46 -0800, (g subs)
wrote:
how do you ground an antenna , if you live in a hight rise building
here in chicago, most of the building are sourrunded by concrete and
there is no open soil, i have cold water pipe here , can that work ?
or should i get some ground rods and drive it thru the concrete to
make my ground?

Hi OM,

There is no inherent advantage to ground except if you live in a high
lightning prone area (and your building would take care of that
liability anyway).

Being elevated above the sod presents you with a situation where you
are already "floating" with respect to ground. This implies that any
antenna you construct will be composed of the balanced dipole, or with
a radiator and counterpoise. This last is simply an artifice because
the difference between the two hardly matters.

On the flip side, there are a lot of metallic conductors that do
attach to ground, lo so far below, that will complicate issues of
resonance and patterns (and perhaps add losses, what with the usual
brick, concrete, wood, and interior furnishings being within the
field). As you are in very little control over these matters, you
must learn to adjust (that is why we have tuners).

These metallic conductors will include the ground wire of the three
wire AC system, and you do need to use it purposefully. It is a
SAFETY ground, not an RF ground. The two may be mixed through
deliberation or certainly through accident (or call it luck, but not a
luck to count on). It would be better to be deliberate and do the RF
ground thing through employing dipoles (vertical as well horizontal)
or monopoles with radials (more likely one counterpoise which comes
very close to that vertical dipole thingy). You can tie RF ground to
your SAFETY ground (at one point only! more can bring grief). Make
sure your equipment ties there too (usually enforced through common
construction techniques and the three prong plug if code has not been
violated).

73's
Richard Clark, KB7QHC

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