Earth
Ground
Most of us overlook the importance of hooking good
earth grounds to our antennas and our radios. Some think
if lightning hits, its going to do what it wants to do.
Probably right! Lightning protection is not why I am
stressing the earth ground. Good earth grounds serve two
purposes. One they protect against lightning (by routing
current to the ground instead of our radios). Secondly,
they discharge stray RF energy. There are a few things
this does for us. First, it makes our receiver quieter
(less static). Secondly it prevents RF from building up
on the station equipment and distorting our audio (So
many CBers have this problem!). Have you every heard
someone who's audio would distort when they would talk?
The number one cause of this is strong RF currents
running on the radio chassis and mic (more power and the
problem gets worse!). Also grounding stray RF energy
cuts down on interference to TVs, Phones etc. Plus, if
you are using a vertical antenna (1/2,5/8 Wave) you can
improve the performance by lowering the angle of
radiation by using ground rods and radials running on
the surface of the earth under your antenna. This is a
total must if you are co-phasing verticals.
So what constitutes a good ground? Well, it depends
on a few things. First, inspect the soil where you have
your ground rods (or will you will be putting them). If
your soil is rocky or sandy, you better buy a few ground
rods and a bag of rock salt. Rocky and sandy soil is a
poor conductor and has a high resistance to ground. If
you soil is high in mineral or ash content (nice dark
top soil deep down for many feet) then you have a nice
low resistance to ground. There are two places where you
will need to a make good ground. One from the antenna,
so the ground should be directly (or as close as
possible) underneath the antenna. Figure 1 shows where
to place the ground rods around your tower, but if you
have your antennas mounted on your roof, still run a
wire to three ground rods shaped like a triangle.
Figure 1 - Three ground rods located around the
base of the tower. The ground wire runs down the tower
from the antenna, and splits into three, and runs to
each ground rod. Solder the wires to the rods!
The other ground should run from the back of your
radio chassis. Actually, all the station equipment
should be grounded together with a heavy copper wire
(coax braid is good). This should run to a ground as
short as possible, preferable out the window to the
ground directly. You must keep this ground under 9ft
long (102") or the effect of a long wire will
impede the RF from grounding. If you must have a longer
ground wire (really, try not to, this is important), run
a separate wire off the back of the radio (where the
normal ground is hooked) that is 102" inches long.
just let the wire hang to the floor and then run it
across the floor (don't roll it up). This is called a
"counterpoise". You should have three ground
rods outside the window, shaped like a triangle like you
have around your tower.
If your soil is rocky or sandy, drive your ground
rods, pull them back out and dump the rock salt into the
holes where the ground rods go. Then, fill the holes up
with water to dilute the salt and let it flow in the
ground surrounding the rods. This will greatly improve
the conductivity of the earth. Remember to replenish the
salt ever year, it disapates into the ground over time.
Ground rods should be copper about 6 - 8 feet long. You
should have at least three ground rods, located about 6
feet from each other. You will need at least 6 ground
rods in total, 3 for the antenna and the other 3 for the
radio ground. Solder the wires onto the ground rods (to
prevent static ground noise).
If the antenna you are using is a vertical, it would
be helpful to place "radials" off of one of
the ground rods. You do this by taking a shovel and
driving the tip into the ground, rock it back and forth
opening up a V shape in the soil (no deeper than 1
inch). Do this at least 8 directions from one of the
ground rods (if possible). Radials should be as longs as
possible (36 feet is best). Drop the radial wire into
the channels you built with the shovel and stomp the
channel shut with your foot or the shovel to seal the
wire into the ground (to hold it down and so you do nail
it with your lawn mower!). This is a great way to
improve the DX capability of the vertical! Figure 2
shows a view looking straight down on the tower. You can
see how the radials should lay.
Figure 2 - Looking straight down on tower. You can
see the radials, but after you install them, they should
be buried under the ground about 1/2 inch (no more than
1 inch deep). This will improve the radiation pattern of
the vertical antenna. If you are not using a vertical
antenna, just go with the three ground rods. Make sure
they are about six feet away from each other.
The connection to your antennas should be a good one
with the largest practical conductor size. You should
hook the ground close to or on the shield of the coax
(on the collar of the PL-259). Connect the ground wire
to the chassis of you radio, hooking it firmly to metal.
If the connection is loose, it will cause more static
noise on your receiver! Do not expect to notice a huge
difference (or a immediately detectable difference) from
doing this. But remember, when you are trying to talk to
a DX station with the faintest signal, even that slight
bit means hearing or not hearing that DX station.