Specifications

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The ground system (also called a counterpoise) is a key part of the overall
antenna system and is the primary cause of poor performance and the diffi-
culty of adjusting the tuner. A good ground is essential.
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Connect the tuner directly to the frame of the vehicle. Ensure that a heavy
strap is used from the tuner ground lug and that the connections are cleared
of all paint and dirt so that the shiny metal is exposed. SGC always recommends
that two grounding bolts with star washers be used to insure no ground resis-
tance is encountered. Make sure that the grounding point is not insulated
from other parts of the vehicle by non-metallic couplings, bushings, fiber-
glass panels, etc. Modern vehicle assembly techniques which use spot welding
may not always adequately connect various body parts. Use an ohm meter and
insure your vehicle is electrically bonded.
Another area to watch is trunk lids and hoods. Because many body parts are
dip painted, they may float above the RF ground when assembled. Use of short
heavy braid to insure all doors and hatches are grounded is good installation
practice. Although this is tedious work, the benefit is that once completed you
will have a much superior radiated signal and lower noise floor on receive.
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A metal hulled vessel in salt water provides an almost ideal ground. The tuner
should be connected directly to the hull using the shortest possible ground
strap or 2 to 3 inch wide 2 mil copper foil. Make sure that the contact point is
free from paint and dirt. Ensure a good contact area for minimum resistance.
Wooden and fiberglass hulled vessels present more of a grounding problem. It
is normally necessary to bond all large metallic parts such as the stove, fuel
tanks, engine, propeller shaft, etc., and sometimes an external grounding
plate should be connected to the hull. The bonding and grounding plate
should take into consideration the problems of electrolysis. Severe damage
may result if dissimilar metals are connected together.
Our experience is that sacrificial zincs, which double as radio grounds, may
help, but are not by themselves a complete solution. If you use one (or more)
of these devices, remember to provide for a large physical counterpoise in
addition.
SGC Inc. SGC Building, 13737 S.E. 26th St. Bellevue, WA 98005 USA
P.O. Box 3526, 98009 Fax: [phone] Tel: [phone] or 1-800-259 7331
E-mail: [e-mail] Web site: http://www.sgcworld.com
© 1998 SGC Inc
SG-235 Manual