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
27
3. Remember that the radiating part of the antenna starts at the coupler. The
location of the bottom portion of the antenna is important.
d. Vertical antennas have an omni directional radiation pattern, providing
equal performance in all directions.
4. 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;
therefore, it should be located so that the ends point in directions where
communications are not required.
5. The V antenna 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.
6. High voltages (sometimes exceeding 30,000 volts RF) are present on the
antenna. All parts of the antenna and coupler must be located or protected so
that there is no possibility of accidental contact.
7. Do not locate the antenna close to other antenna systems.
8. Make sure that the antenna is rigidly supported. The antenna will de-tune if
it sags or sways.
9. The connection from the coupler to the ground must be a small percentage
of the total length of the antenna. Do not let the length of the ground strap
exceed one meter. Use heavy gauge wire or strap for ground connection.
10. Whip antennas should be connected with the minimum length of wire. (Do
not exceed 0.6 meters).
11. Do not locate the coupler farther from the transceiver than necessary. If the
distance exceeds 10 meters (30 feet), we recommend you use low loss coaxial
cable, such as RG-8 or RG-213.
5.3 Ground Systems—General
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 difficulty of adjusting the
coupler. A good ground is essential.