can determine the collimation error between the TX
The borescope operator may have to give several
axis and the boresight axis. Extreme care must be
marks at each offset position to obtain a good average
exercised in taking each power reading to obtain
power reading. Figure 4-8 shows the TX axis beam-
accuracy with this method.
pattern plot-method graph.
CWI AXIS COLLIMATION
Figure 4-8.—Beam-pattern plot-method graph.
The beam-pattern plot method of measurement is
used to determine the error between the CWI axis and
the borescope axis of the AN/SPG-51C/D radar.
There is no requirement for test equipment aboard
ship during the performance of this test.
The procedures for determining CWI axis error
are similar to those for the track-transmit axis, except
that the CWI radar is used.
The test setup aboard ship consists of placing the
CWI transmitter in RADIATE, pointing the radar an-
tenna toward the tower, and centering the CWI optical
target 8 in the borescope.
4-8
In the tower, the average power meter is con-
nected through the calibrated attenuator (X-band) to
the X-band waveguide line going to antenna Don the
tower array. The attenuator is adjusted to allow the
C WI power to be read conveniently on the power
meter (in decibels or milliwatts, as preferred). After
establishing a reference point (maximum power read-
ing) by coaching the director operators aboard ship,
the CWI power at the tower as the antenna (director)
is held stationary in one axis (traverse or elevation)
and moved off target in the other axis is plotted. The
offset readings in roils are given by the borescope
observer aboard ship.
A power plot curve is drawn and the 3-decibel
down points are connected by a horizontal line. The
bisector of this line intercepts the mils axis of the
