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SECTION 3
GENERAL
ANTENNA
CONSIDERATIONS
FOUNDATION
DESIGN
CONSIDERATIONS
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42S042G
FOUNDATION INSTALLATION
(120° MOUNT)
The pointing accuracy of the installed antenna is determined by the
stiffness of the mount, the reflector, and the foundation. Therefore,
antenna foundation preparation is an essential part of antenna
installation.
The foundation heading is critical to the performance of the
motorized antenna, but not to the performance of the non-motorized
antenna. The foundation heading establishes the center of azimuth
travel.
For a non-motorized antenna to be later upgraded to
motorization, the foundation heading must be installed initially as
though for a motorized antenna.
Proper electrical grounding shall be provided by the installing
contractor to meet local applicable codes. Depending on local soil
conditions, this may take the form of a buried grid or a suitable
copper stake. The antenna mount shall be electrically connected to
the ground.
Provisions must be made to provide suitable support for power, RF,
and control cables either by buried conduit or overhead raceway. If
conduit is supplied, it shall be at least 3 inches (7.6 cm) in diameter.
Lightning arrestors must be provided across all cables leaving the
antenna per applicable local codes and N.F.P.A. codes. (Refer to
Section 2 for information on required operational clearances.)
The antenna is designed to withstand an effective velocity pressure of
31 pounds per square (151.4 kg/m2) foot in any orientation, or 40
pounds per square foot (195.3 kg/m2) if stowed. These pressures
represent 110 and 125 mile per hour (176 and 200 km/h) winds
respectively at standard air at ground level. The foundation should be
designed to maintain the antenna integrity under these same loads,
with a safety factor of at least 1.5, and also to not allow the mounting
plane of the three antenna feet to tilt more than 0.02°.
The loading for the above conditions is presented in Tables 3-1 and 3-
2. Figure 3-1 depicts the sign conventions for the tables. The loads
for each mounting foot are listed in Table 3-1 and the resultant
foundation loads are listed in Table 3-2. If loads are required for
wind pressures other than those listed, they may be calculated from
the information in the tables using the following procedure:
1.
Subtract the corresponding Weight Only load components from the
load components for the orientation of interest.
SERIES 8060 6-METER EARTH STATION ANTENNA
3-1
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