Transformer coupling and properly grounding
your end-fed antenna will offer you four
benefits: (1) Greater signal levels across a
larger bandwidth (impedance smoothing), (2)
Less electrical noise pickup from local sources
(common mode rejection), (3) Greater protection
to your equipment (constant static bleed and
near-strike (DC only) shunting).
Shown here are 4 possible ways to connect your
transformer (balun wired as an unun) to the
antenna and the radio. (Note that the first
example uses a coax connector at the
transformer and the subsequent figures show
the coax as being hard wired - both are
acceptable and are options for your particular
requirements.) The sketches are pretty much
self explanatory. Technically, they are shown in
the order of functional preference.
If you have trouble reading these sketches, you may "right click"
them to your clipboard and paste them to a .jpg viewer. Please give
full credit if reused elsewhere.
Here is a graphical illustration of a typical
installation. The details will be different, but the
principles are the same. The primary point is to
mount the xfmr as close to the system ground as
possible. Mounting it directly to the first ground
rod is text book-ideal. An alternate would be to
eliminate the vertical component of the antenna
and mount the xfmr to the insulator above it and
run a heavy ground up to it. This will depend on
how much the vertical wire is exposed to
near-field electrical noise from your home.
Here is an example of good RF "ground farm"
practice. As opposed to many socio-religious
beliefs, in this case, more is better! There will be
a point of diminishing returns, but generally
speaking, one ground rod is not going to be
optimal. Experimental and empirical testing is
the only way to determine what will be best for
You may get a relative ground conductivity test
as shown below. Most electrical service entry
points are grounded to the fresh water (cold
water) feed pipe. Homes with plastic well pipes
will have some other code-complient grounding
system. Either way, you should consider
"bonding" your ground farm with the
house/utility grounds. (And you'll need a
licensed electrician to properly perform this
kind of system upgrade.) Regarding RF
grounding: some soils will indicate a few dozen
ohms/foot and others will offer thousands of
ohms. You'll have to do some measurements
with an ohm meter to get a "feel' of what your
ground farm will be like. But remember, this is
only a "test indication" that will give you a "feel"
of your soil quality. You will also learn how
conditions change with seasons and weather.
Disclaimer: Remember, you are dealing with
earth (signal) grounds only. Never tamper with,
or intrude upon, or compromise your electrical
service grounds in any way. If in doubt, consult
your utility company and/or a licensed
electrician for bonding information. Also,
lightning is completely unpredictable. A direct
strike or a close near-strike may damage your
equipment, start fires, or cause personal injury,
or death. Use common sense and be careful !
The above sketch is just for illustrative purposes to point out that soil is not a very good conductor of
electricity, no matter where you live, and no matter what kind of chemicals you "seed" the soil with.
The above test will give a good indication of just how resistive soil can be and an interesting exercise
to conduct during various seasons and/or weather conditions. Of course DC ohms measurements are
pretty meaningless at RF frequencies where electrical current flow behaves much differently, but you
will gain a "feeling" for what grounding is all about and why Ground Bonding is so important..
With a Balun Feed