SG-231 MANUAL
SGC Inc. SGC Building, 13737 S.E. 26th St. Bellevue, WA. 98005 USA
© 11/00 SGC, Inc.
P.O. Box 3526, 98009 Fax: (425) 746-6384 Tel: (425) 746-6310
E-Mail: [email protected] Website: www.sgcworld.com
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Although it is not mandatory that ground foil be glued into place, we consider it a good
idea to keep the space below decks neat and orderly under all conditions.
If you are using a backstay antenna, try to visualize your ground as you look down
from the top of the mast. Ask yourself if you see 100 square feet of metal below you.
The closer to this figure you can get, the better your radiated signal will be. What you
are trying to do is make a large capacitor to the seawater. Consider the salt water of the
sea to be one plate of a capacitor, the ground system the other, and the hull to be the
dielectric.
On marine installations, you should also be aware of potential noise sources that may
need to be bypassed to ground. We have encountered just about every source of noise
imaginable in vessel installations. The best time to track down annoying noise sources
is when you are laying in a ground system. Not only will you get much better voice
communications, but Weatherfax, Navtex, and Loran reception will improve as well if
they are also tied into the ground system.
Particular attention should be paid to any device that uses an electric motor. This
means to turn on the water pressure pump, bilge pump, hot water forced air heater
fans, refrigeration, and auto pilot motors. A few small capacitors to ground (.01 micro
farads at 100 VDC) can resolve many issues. Bypassing of the vessel's alternator is also
a good idea.
5.3.3 Base Station Grounds
In areas of high ground conductivity, an effective ground can be made through a
grounding rod. The rod should be approximately 3 meters in length and should be
installed as close as possible to the coupler. It may be necessary to use several ground
rods bonded together to improve the ground contact. Water pipes are sometimes
recommended as grounds and may be used provided plastic pipe is not buried as part
of the system and the following conditions are met:
1. The water pipe is close to the coupler.
2. The water pipe enters the ground close to the coupler bonding point.
3. There are no joints or couplings in the pipe that will increase the resistance
path to ground.
4. The water pipe enters soil with good conductivity.
5. A low resistance contact is made to the water pipe.
Earth requiring a counterpoise
. Frequently the ground conductivity will not suffice to
provide satisfactory operation of the coupler—almost certainly the case with well-
drained sandy, rocky, or loamy soils. Therefore, a counterpoise (artificial ground) must
be used as the ground system.
Rooftop installation requiring a counterpoise
. In a rooftop installation where there is
no existing ground plane, the ideal ground would be a conducting surface extending
several wavelengths in all directions around the antenna. On a rooftop, this situation