CE-1008
that the needle of the cable-wrap meter M1 goes into the red area of the scale whenever an electrical limit of 270 is
reached.
D.
POLARIZATION DIVERSITY CONTROL CIRCUITS (See Figure 1-6)
(1) The Antenna System is capable of any one of four modes of linear polarization: left-hand, right-hand,
left-hand 45 degrees, or right-hand 45 degrees. The mode is selected by operation of POLARIZATION SELECT switch
S6. Refer to Figure 1-6. When the desired mode is reached, all lights except the one for the selected mode will go out.
a.
The antenna polarization is selected by a motor-driven Polarization Diversity Mechanism which is
mounted by struts on the reflector and supports the antenna feed. This mechanism is controlled by a detent relay in the
antenna pedestal which is, in turn, controlled in the aforementioned manner by the controls on the Control Indicator. The
motor-driven Polarization Diversity Mechanism shaft, which supports the antenna, has four positions and will drive
through 135 degrees of actual rotation. It has stops in positions that are one fourth of this total rotation. There is a dual
function of movement which indicates a coarse position of the polarizer, and an indexing movement which operates at
four times the polarizer speed and determines a precise motor stop position. When the polarizer motor reaches the limit
of travel, a switch controlled by the Geneva mechanism causes a reversing relay to be actuated or deenergized,
depending on the direction of rotation. The antenna polarization control then causes the motor to drive in the opposite
direction. For example, if the antenna is directed in a horizontal position and the operator desires to drive it to vertical
position, the motor will then be driving out of one stop into another stop position. If it is desired to turn it in the reverse
direction (for example, to the right-hand circular), the motor drive will drive forward to the limit stop, reverse its direction
of rotation, and then return to the newly selected position, which is between vertical and horizontal polarization. Due to
the time interval between the fine and the coarse indexing switches on the motor-driven polarizer, it is necessary that the
detent relay be operated which, in turn, prevents the reversing relays and the Control Indicator from operating until the
motor itself has come to a complete index stop in either direction of rotation. This sequence assures that the polarizer
will stop only in the correct polarizing position.
E.
ELECTROMECHANICAL LINEAR ACTUATOR (BEAM BROADENER) AND INDICATOR CIRCUITS (See
Figure 1-7) - The Antenna System is provided with an electromechanical linear actuator (beam broadener) which consists
of a motor-driven mechanism to provide remotely selectable actuation of the linear movement of the antenna feed
support shaft relative to the focal point of the reflector. The primary effect of defocusing the antenna feed toward the
reflector from the focal point is to increase the phase error across the reflector, broadening the main lobe by several
degrees and reducing the gain of the antenna.
1-21
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