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' Icom Marine Ssb Antenna Grounding'


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  and antenna

             Icom Inc.
Congratulations on your purchase of an ICOM marine single sideband transceiver. You have
chosen one of the finest sideband sets available.

This special insert in your marine single sideband instruction and installation manual will
assist you in choosing the right antenna and getting the best range out of a good grounded
single sideband installation. Good antennas and good grounding are absolutely essential for
good single sideband range, and this is why this special report is included with your single
sideband transceiver.
If your ICOM SSB is going aboard a sailboat, you may                  Another antenna system for powerboat operation is the
either use an insulated backstay an insulated sidestay, or a          pre-tuned trap, 23-foot, aluminum whip from Morad, Inc.
non-resonant white fiber glass whip antenna off the stern             This antenna requires no automatic tuner­simply feed it
to make up your antenna system. Your best range will be               with coax out of the back of your SSB, and it works nicely
from an insulated backstay because of the long length of              on all of the pre-set marine frequencies. This antenna
the antenna "radiator" which is that portion within the top           system must usually be tuned up by a technician, and it
and bottom insulators. Have your rigger put the top                   usually is not as popular as the non-resonant, white fiber
insulator about two feet down from the tip of the mast.               glass whip used in conjunction with the ICOM tuner.
Have your rigger install the bottom insulator at about eye-           Although both are good performers, the ICOM tuner and
level when you're standing back aft. (This length between             the white fiber glass non-resonant whip is usually the easier
insulators should not exceed 120' or be less than 23'.) If            way to go.
you decide to go for the non-resonant whip antenna, such
as a Shakespeare or Morad, the antenna usually goes at                We suggest you check with the dealer that sold you your
the extreme stern and mounts either vertically or raked               transceiver if you would like to purchase the ICOM auto-
back at about a 45-degree angle.                                      matic tuner as well as a resonant or non-resonant whip
                                                                      antenna assembly. Dealers that sell ICOM equipment
These non-resonant antennas may be tuned by the                       usually have these accessories on hand.
ICOM automatic antenna tuner that matches the ICOM
SSB transceiver. The tuner goes back aft, in the lazarett. It         THE IMPORTANCE OF GROUNDING
is completely weather-protected and can easily take the               Please read this! If you are looking for "super range" with
punishment of being aft and below deck where you're                   your new ICOM SSB, we have some tricks that will give
probably also going to store wet life preservers, foul                you the same kind of range as globe-circling cruise ships,
weather gear and the like. The tuner interconnects with the           super tankers, solo sailors, the Navy and the Coast Guard.
ICOM SSB. Full details are in the tuner instruction/installa-         Surface area to the sea water and the use of copper foil
tion manual. We suggest you use "GTO-15" high voltage                 exclusively throughout your RF ground system is the com-
lead-in wire from the single wire output of the tuner to              bination that gives you commercial-type "super range."
your insulated backstay or to your non-resonant whip.                 The sea water acts like a diving board or side of a pool for
This high voltage wire won't break down in wet weather or             a diver and a swimmer ­ it gives your signal a solid surface
sunlight. Use stainless steel hose clamps to attach the wire          to push off from. This is technically called a "counter-
to the insulated backstay. If you decide to use a non-                poise", and it's the absolute necessary "other-half" of your
resonant whip, attach the single wire with a lug to the               antenna system that must be achieved for your overall sin-
feedpoint at the base of the whip.                                    gle sideband system to work well.

More about the importance of grounding in a moment.                   It's not that hard to develop your own sideband RF ground
                                                                      system in just about a day's time, and you may even find
For those of you with a powerboat, a whip antenna                     that most of the RF ground system is already installed so
approximately 20 feet long is what you'll be using with               you have little to do but to tie everything together with
your new ICOM SSB. The most common and preferred set-                 copper foil. Read on, please, and let us show you how
up consists of the white fiber glass 21-foot, non-resonant            easy it can be.
whip antenna that is automatically tuned with the ICOM
automatic antenna tuner. Similar to sailboat installations,           NON-TECHNICALLY SPEAKING
the tuner is hidden out of the way in the flying bridge area          If you plan to have a technician or a technical friend install
or below deck near the base of the whip. GTO-15 wire                  your sideband system, have him skip this part and begin
interconnects the whip to the automatic tuner. The tuner is           reading at "Antenna Ground Principles, Technically
fed with coax (RG 213) and a control line from the back of            Speaking." If you plan to do the installation yourself, and
the ICOM SSB wherever you plan to hide the auto-tuner.                this is the first one you've done, read on!
Remember, the ICOM automatic tuner is fully automatic,
so you can put it completely out of sight!

The water that your boat sits in is the ultimate ground           copper plumber's tape. Three-inch is better. Note: A three
counterpoise. There's none better. Commercial AM broad-           inch strip mounted three inches away from another three
cast stations on the coast usually put their giant antenna        inch strip of copper foil looks like a nine inch strip to a
system in the mud flats of a local bay for good range.            radio wave.

Some boat suppliers put ground foil and ground screen in          It's going to take you about a day to work this foil below
the cabin overhead. This is true on expensive powerboats,         decks and below the water line picking up anything and
and is sometimes found in a few sailboats. While this type        everything of ground potential. If you can get at your keel
of overhead RF ground system is better than nothing, it           bolt, or tap a screw into the keel, your grounding is done.
still lacks the capability of coupling with the ocean or lake     Lead incapsulated keels are the ultimate in grounds, and
as the ultimate water ground system. A far better RF              you may need nothing further.
ground system would be the following:
                                                                  In powerboats, since there's no keel, you're going to need
           1.   100 sq. ft. area of foil below water line         to come up with at least 100 square feet of RF ground
           2.   Metal water tanks                                 surface below the water line. This means you must pick up
           3.   Lead keel                                         as many ground potentials below the water line as possi-
           4.   Foil radials                                      ble. We usually use a stainless steel hose clamp to grab
           5.   Interconnected through-hull                       each underwater metal source.
           6.   Engine block
           7.   Metal oil-catch pans                              Now let's take a look at grounding from a slightly more
           8.   Steering system hydraulics                        technical point of view. Don't worry, we won't get over-
                                                                  technical, and it's easy to read and understand. If you're
That's right, we list the engine block as last as a good          letting a technical friend of technician put in your equip-
underwater counterpoise. Engine blocks do not have an             ment, make sure they read over this section several times.
extremely large amount of surface area that is flat and           The facts here are based on hundreds of hours of doing
close to the water your boat is sitting in. The whole idea is     and undoing, different types of ground systems. In all
surface area­and this is why a keel bolt, underwater tanks,       cases, following these techniques will give you the results
through-hulls, and anything else flat and next to the water       that you want and that's long range and the loudest
does such a good job. Now we know your next question,             signal on the band.
"But doesn't a good ground actually have to be in contact
with the water?" Not at all! At radio frequencies (RF), your      ANTENNA GROUND PRINCIPLES,
underwater ground counterpoise sees the water in a                TECHNICALLY SPEAKING
capacitive way, which gives just as good a ground effect          The marine antenna system for low, medium, and high
as if it were actually touching the water!                        frequency applications will utilize both the seawater as
                                                                  well as that shiny white fiber glass antenna radiator for its
Now here's another very important point, no round wires           entire operation. Like two kids on a teeter-totter, the sys-
for RF ground! Even if you use welding wire the size of           tem works well if there is a balance between the antenna
your thumb, you cannot achieve a good ground counter-             radiator and the seawater ground. This balanced antenna
poise with round wire. In our "Technically Speaking"              system may electrically be compared to a dipole antenna
section, we'll tell you why, but, in non-technical terms,         system­one-half wavelength long on the frequency band
round wires tend to cancel out at radio frequencies, and          of operation with voltage and current loops equally
they look invisible as a ground counterpoise interconnect.        distributed throughout the half-wave length system. In
This is why copper foil must be used between the chassis          marine applications where a vertical antenna is used, this
of your transceiver to your ship's RF ground, as the chas-        system is more precisely referred to as a Hertz antenna set-up.
sis of the automatic antenna tuner to ship's RF ground.           The white fiber glass whip is tuned to an electrical
Round wires won't work--only copper foil will!                    one-quarter wavelength and the ground system will make
                                                                  up the other one-quarter wavelength. We technically call
Your better marine electronic stores that sell ICOM equip-        the RF ground system a "counterpoise," and the antenna
ment will also sell three-inch wide, super-thin, copper           the "radiator."
foil for grounding. In a pinch, you can use one-inch wide

If either a one-quarter wavelength antenna or ground              be laminated inside the fiber glass layers as the hull is
system is missing or inadequate, radio reception and              under construction. Thin sheets of copper foil could also
transmission range will be severely reduced. How good             be used in the manufacturing process of the hull. Even the
was your car radio reception when someone broke off               conducting mesh that holds together cement hulls can be
your whip antenna? The same degradation of range also             used quite nicely as a ground counterpoise system.
takes place when there is little or no RF ground system for
the whip to work against in a marine installation.                Copper foil and grounding screen is available from most
                                                                  marine electronic distributors as well as marine electronic
Imagine a swimmer making a flip turn, but not having the          dealers. Thickness of the screen and foil is not important,
side of the pool to push off from. The same thing happens         the most common foil is generally one to four mills thick
with radio wave transmissions on single sideband. The             and comes in three-inch wide rolls of just about any length
most powerful antenna will not radiate a signal if it has not     you want. Copper window screen (if you can find it)
counterpoise to push off the signal from.                         is usable, thickness is not important. Radio frequency
                                                                  energy travels on the outside of this conducting surface
In technical terms, the less RF ground, the higher the            called skin effect, eliminating the need for thick
radiation resistance of the antenna system. This radiation        grounding materials.
resistance will lead to substantial power loss and single
sideband equipment will not only perform poorly, but also         Since grounding foil and screen is relatively expensive,
get quite hot in the transmitter section. An inadequate           most boat builders will simply leave out this grounding
single sideband RF ground will also lead to "hot mikes"           process and expect the customer to provide their own RF
where the operator actually receives a radio frequency            ground once the boat is finished. This is a shame­it's so
burn each time the mike is held next to his mouth. Poor RF        easy to build in when the hull is under construction, and
grounding will also lead to erratic movement of analogue          far more difficult to add after the vessel is fully completed.
dial instruments, bizarre behavior of automatic pilots
while transmitting on the sideband set, and may even              The copper foil and screen does not actually need to con-
cause burn-outs of tiny integrated circuits in companion          tact seawater in order to create the ground system. Radio
marine electronic gear aboard. Isolating your RF ground-          frequency energy passes quite nicely through fiber glass,
ing system from your DC grounding system will prevent             so an incapsulated ground system works just as well as
these unwanted occurrences.                                       one that is actually exposed to the seawater. Incapsulated
                                                                  lead keels with a half-inch of resin also work well. Any RF
SURFACE AREA                                                      ground system that is capacitively coupled to the seawater
For marine SSB radios a good radio frequency ground sys-          is enhanced by the seawater itself.
tem will consist of a minimum of 100 square feet of metal
below the waterline. Now we know you're going to jump             Developing the ground system for radio frequency appli-
out of your chairs when you read this, but don't be over-         cations (as opposed to DC circuits) requires that all ground
whelmed. There are plenty of underwater metals that we            connections be interlaced using copper foil. Round ground
might attach to in order to obtain this amount of counter-        wires are out! Wires actually look like inductive trapcir-
poise below the waterline. Lead keels incapsulated within         cuits at certain radio frequencies, and will appear invisible
fiber glass will make excellent surface area grounds in sail-     as an effective way of coupling your set to your ground
boat applications. The tough part will be getting to the          system. That's right, copper foil must be run from below
lead keel or the exposed keel bolt.                               the waterline ground system and attached directly to each
                                                                  piece of low and high frequency radio gear.
In other marine installations, stainless steel tanks, copper
hydraulic lines, and through-hulls, will help make up the         While this may also seem to be an insurmountable prob-
RF ground counterpoise system.                                    lem in running foil, rather than wire, foil handles quite
                                                                  nicely, even in tight places. The foil is easily soldered to
Boat manufacturers have the capabilities of adding a              the below waterline ground system, and then routed up
terrific RF ground system when the hull is being laid up.         the side of the hull into the area of the NAV station. It may
Lightweight copper screen is one of the best ways to              be glassed into the hull, painted over, glued in, or even left
provide a good surface area ground. Copper screen could           resting on the side of the hull. The foil may be bent in

to accomplish a 90-degree turn. If the foil must absolutely        We usually ground everything with foil at the navigation
pass through a small hole, it may be rolled up in a not-so-        station. This would include the casing of the wind
tight configuration and squeezed through the orifice.              and speed equipment, pilot control box, GPS, sideband,
Avoid a concentric type, for that type tends to cancel oscil-      radar, VHF, and just about everything else that lights up.
lating radio frequencies. Flat is best.                            The more grounding you provide for your central electron-
                                                                   ics, the less problems you will have with stray RF.
There are several sticky marine compounds that will allow
the foil to adhere to the underside of a hatch, or to the side     The ground foil must also run to remote tuners. This
of a hull. Almost anything will work, and there is little          includes the tuner on your Loran antenna set-up as well as
danger of any substantial amounts of voltage developing            the ICOM single sideband tuner that's usually several feet
on your ground foil run. The ground foil and your                  away from the equipment. These tuners may be all the
complete RF ground system, which run inside the hull,              way back aft, adding another dimension to your ground
also will not substantially change your corrosion exposure         foil run. It's best to run the foil from the RF ground source
to the seawater. Galvanic corrosion problems occur                 directly to your tuner, rather than stringing everything out
when dissimilar metals are immersed in seawater. The               in series like Christmas tree lights. Now picture one
ground system is not actually immersed, its coupling is            ground foil run from the keel bolt to the electronics, and a
only capacitive.                                                   second ground foil run from the keel bolt back aft to the
                                                                   sideband tuner and your stern-mounted Loran whip.
Electrolysis is another form of corrosion where stray              These tuner ground circuits are mandatory for any type of
currents may begin to eat up underwater metals. Good               reliable operation. If you try to run an ICOM sideband set
wiring techniques for your 12-volt system independent of           with a remote tuner that is undergrounded, you stand the
your RF ground system will eliminate electrolysis.                 chance of not only burning up your equipment, but also
                                                                   damaging other electronics onboard with stray RF. If it's
Now let's get back to finding a spot to terminate that three-      not easy to run ground foil from your central below the
inch wide copper foil that emanates from the below water-          waterline ground source back aft, then try to figure out
line ground system. Most manufacturers of Loran weather            another way to do it. It has to be done!
fax and marine single sideband sets don't provide an
easy way of adding ground foil to the stern end of their           You can also pick up additional ground counterpoise sur-
electronics! The best method is to run the foil up to the          face area by adding substantial metals along the way in
back of the equipment and use existing sheet metal                 your copper foil run. Stainless steel hose clamps make it
screws to make a firm connection. Where a ground post              easy to pick up through-hull bronze fittings, water tanks,
stud with nuts and a washer are provided, all the                  copper hydraulic lines, bilge pump valves and copper
better­run the foil up to the stud, double it back on itself       lines, small underwater grounding lightning plates, and
several times for strength, punch a hole in it, and then           anything else that may give you some additional under-
make the connection. Never negate all your hard work of            water surface area.
running the foil by using a small jumper wire to intercon-
nect the foil to the radio set-up. You will be putting a           Mariners with sailboats with poured incapsulated lead
"weak link" in your ground system at radio frequencies.            keels as well as metal hull vessels have the easiest time
                                                                   in obtaining a good ground counterpoise. If the keel is
We usually accordion up the excess foil in back of the             visible, a second nut on the exposed thread will anchor on
equipment so that we might remove the equipment for                the ground foil. We usually seal this connection to prevent
servicing with the foil attached. If you put the bends in the      deterioration from the bilge water. It may also be recom-
right spot, the foil will resume its natural collapsed state       mended by local experts to tie in the aluminum mast to
when the equipment is put back in place. Watch out for             this close proximity keel bolt for lightning protection. The
the sharp corners on the ground foil, they are capable of          run from the mast to the keel bolt must be smooth, direct,
piercing through the plastic protective covering on electri-       and without sharp turns in order to pass lightning energy
cal wires. Make sure that red and black voltage carrying           effectively into the underwater lead. Again, consult local
wires are not allowed to rub up against the side of the            lightning experts.
ground foil.

Steel-hulled vessels are easily attached to with foil by
scraping away any protective coating from the hull, and
making a low resistant good surface area contact. Again,
seal this connection well. Non-metal hull or keel boats
require yards and yards of foil to be run below the water-
line, anywhere you can, and picking up any other large
below the waterline tanks and tubes.

If you follow
                If you follow these steps, you will have an outstanding single sideband signal that can be
these steps,
                heard around the world. The difference between a good and bad ground is easily noticed on
you will have
                transmission as well as reception. Since your ground counterpoise is actually a part of your
an outstand-
                complete antenna system, pay just as much attention to RF grounding as you did to putting
i     n      g
                up that white fiber glass whip or going to your insulated backstay.
single side-
band signal
that can be
heard around
the     world.
The     differ-
ence between
a good and
bad ground is
e a s i l y
noticed     on
as well as reception. Since your ground counterpoise is
actually a part of your complete antenna system, pay just
as much attention to RF grounding as you did to putting
up that white fiber glass whip or going to your insulated

Count on us!

               Icom Inc.
               6-9-16, Kamihigashi, Hirano-ku, Osaka 547, Japan · ©2000 by Icom Inc MA-4648 7.00

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