
36
factory operation the system must be carefully selected, then installed cor-
rectly. The unbalanced antennas used with the automatic antenna tuner use
the ground (counterpoise) as half of the antenna system. The ground forms
an "image" antenna and is a critical part of the system. It is essential to consid-
er both the ground and the antenna when designing the system installation.
6
6..2
2
A
An
ntte
en
nn
na
a L
Lo
oc
ca
attiio
on
n
The figures in Section 4 illustrate several different antenna installations.
The following points should be carefully considered when designing the
antenna system.
1.
The antenna should be located in a position free of obstructions,
particularly in the desired direction of communication.
2.
The antenna should be kept as far away as possible from buildings,
trees and vegetation. If metallic masts or supports are used, arrange
the insulators so the antenna is spaced at least 2 meters from the mast.
3.
Remember that the radiating part of the antenna starts at the tuner.
The location of the bottom portion of the antenna is very important.
4.
Vertical antennas have an omni-directional radiation pattern and
will provide equal performance in all directions.
5.
Horizontal wire antennas have maximum radiation broadside to the
antenna when the frequency is less than 1/4 wavelength. As the
frequency increases beyond 1/4 wavelength, lobes will appear in the
radiation pattern with the principal lobes becoming closer to the
plane of the antenna as the length increases. At all times, radiation
will be minimal at the end of the antenna and should be located so
the ends point in directions where communications are not required.
6.
The "V" construction minimizes the directivity of the horizontal
antenna and is recommended for all around coverage. In addition,
the "V" antenna is a compromise between vertical and horizontal
polarization and will give good results for communications with land
or marine mobiles using vertical whip antennas.
7.
High voltages (sometimes exceeding 30,000V RF) are present on the
antenna. All parts of the antenna and tuner must be located or
protected so that there is no possibility of accidental contact.
8.
Do not locate the antenna close to other antenna systems.
SGC Inc. SGC Building, 13737 S.E. 26th St. Bellevue, WA 98005 USA
P.O. Box 3526, 98009 Fax: 425-746-6384 Tel: 425- 746-6310 or 1-800-259 7331
E-mail: [email protected] Web site: http://www.sgcworld.com
© 1998 SGC Inc
SG-230 Manual