"A good ground is one of the most essential parts of a solid
HAM station." There are various reasons for this statement. First and
foremost is for the safety of your family, home, and HAM equipment.
Lightening NOT ONLY KILLS radios but can start house fires! A
protruding antenna or tower into the atmosphere dramatically increases
your odds of a lightening strike. Statistically however, most lightening
damage comes from the AC power and telephone lines running into your
home.
An understated fact of significance to HAM Radio is that a
good ground WILL increase receiver sensitivity and transmit
propagation. I've, personally, observed a decrease in surrounding
ambient noise levels, from as much as S9 to S4 drop, on 75/40 meters
when I shifted from a "cold water iron pipe 12 AWG wire ground" to a RF
ground system stated in this paper. HF antenna(s) work BEST when they
work against a "proper" counter-poise ground reference.
RF grounding is as mis-understood and as difficult to understand
as "impedance." Both are very real, hard to measure, and cannot tangibly
be seen in operation. The term that is used in RF grounding is
"skin effect."
In a ground system the vast majority of electrons run along the "outer
most surface or skin of the conductor. A good RF ground has the least
amount of resistance to electrons being conducted to ground via the most
amount of conducting surface area (skin)
that is practical.
The goal of a good RF ground system is to obtain as "little" resistance
as possible between the "antenna/tower-to-ground" and the
"radio-to-ground". Thus the more conductive surface area
the larger the path for
electrons to earth ground. You could argue that multi-stranded
cable/wires have more overall wire surface area but the touch areas of
the wires negated skin effect conductance. Do not confuse current
carrying capability with grounding skin affect they are two very
different elements of electrical conductivity.
A typical laboratory/aerospace test system ground measures
<12 ohms from "Unit-Under-Test to earth ground". A very very
GOOD cold water iron pipe ground may measure as little as 35 ohms and
that's if the water pipes are NOT PVC. [BEWARE --most new home
construction use PVC pipes for water and sewage. Even in older homes the
water service provider should have installed more than a 5' section of
plastic pipe between the water mains and your home water line
feeder -- this is to eliminate electrolysis/galvanic action within
the piping system.]
Making a ground measurement is very difficult and most HAM's
do not have a Megger(TM) generator type instrument to conduct a valid
resistance measurement. This paper will attempt to "assist" in providing
knowledge and examples of "reasonably good" RF ground systems that are
within the economical range of most HAM's and that can achieve <20
ohms. How good a ground system you want installed is directly
proportional to the amount of effort and funds you want to invest in the
safety/operation of your station.
Disclaimer: Will installing
these grounding methods written here prevent a loss of equipment from a
lightening hit, NO! What it will do is help in minimizing
damages. Are the methods in this paper the "best"? This is a loaded
question that few understand but all HAMs seem to be experts on.
When getting into these philosophical arguments I resign myself to
just listen to what these self proclaimed experts profess and either
improve my knowledge or shake my head in despair and walk away -- you
cannot improve self-proclaimed experts knowledge. PolyPhaserTM has
a much more elaborate ground system plans but I cannot afford nor do I
have the acreage to install a PolyPhaser ground system (designed for the
infinite budget commercial world).
