CWI AXIS COLLIMATION

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