pulse generator (APG), located in the rotary joint,
transmits to the radar indicator azimuth information
corresponding to beam direction. Polarization of the
radiated energy can be remotely switched to either
linear or circular polarization. The reflector has a
modified parabolic shape designed to produce an
approximately cosecant squared beam in the elevation
plane. The reflector surface, covered with expanded
aluminum screen, is 16.1 feet wide and 9 feet high.
The antenna feedhorn, which mounts on the polarizer,
provides impedance matching between the waveguide
system and free space, and produces the desired feed
pattern to illuminate the reflector. A radome over
the horn aperture excludes moisture and foreign matter,
and provides a pressure seal.
pedestal assembly, the feedhorn and feedhorn support
boom, and the reflector assembly.
The base assembly provides a surface for mounting
the antenna to the ship. It also contains the azimuth
drive gearbox. The gearbox is driven by the azimuth
drive motor, which drives the pedestal in azimuth
through a pinion gear mated to a ring gear located
at the bottom of the cone-shaped pedestal assembly,
The azimuth drive circuits rotate the antenna through
360 degrees at speeds of 6 rpm and 12 rpm.
The reflector and the feedhorn support boom are
mounted on a trunnion, allowing the elevation angle
of the rf beam to be controlled by a jackscrew located
behind the reflector. The jackscrew is rotated by the
elevation drive gearbox, which is connected to two
dc motors. The rf energy to the feedhorn is routed
through elevation and azimuth rotary joints located
within the pedestal.
The AS-3263/SPS-49(V) antenna (fig. 2-46)
consists of three major sections: the antenna base and
Figure 2-46.AS-3263/SPS-49(V) antenna.