(2)
Position controls on indicator as follows:
(a)
GAIN to PRESET.
(b)
SEC SCAN to 160 degrees. (Switch/indicator off).
(c)
TILT control to zero.
(d)
INT control midscale.
(e)
RANGE switch to 100.
(f)
AZIM and TGT ALRT switch/indicators off.
(g)
Set STAB switch to ON.
(h)
Select STBY. Allow 70 seconds warmup period.
(3)
After warmup, the desired mode may be selected (WX, CYC, MAP). The R/T unit will generate RF pulses for transmission and send them to the antenna via the waveguide. The reflected RF is returned to the R/T for amplification (Fig. 2).
(4)
The video output from the R/T unit is processed in the indicator and displayed on the CRT screen to show target returns. The display area can be changed to either an 80-degree or 160-degree presentation. In addition, the display can be frozen to allow closer observation of the returns. Range can be set from 10 to 300 nautical miles.
(5)
When the MAP pushbutton is selected, the radar system operates in the terrain mapping mode. The STC function is inoperable and noise/clutter appear in the 0-20 mile display area. Also, rotating the GAIN control out of PRESET position causes the noise and video in the display to increase/decrease. Varying the GAIN control setting in the MAP Mode may increase the definition of certain types of terrain targets.
(6)
When the CYC (cyclic) mode is selected, the system will display normal weather video for a half second alternating with a half second of contoured video, the highest level (red) is blacked out. The GAIN control reverts to the PRESET value when CYC is selected.
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34-41-0 Page 6 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. Feb 20/85
C. Functional Description.
(1)
Antenna
(a)
The antenna consists of a base assembly, an azimuth frame with radiator plate and waveguide components, and a stabilization chassis.
(b)
The flat-plate radiator of the antenna is driven by the azimuth motor through a total sweep angle of 160 degrees, or in SEC SCAN, a total sweep angle of 80 degrees. The azimuth motor is a stepper motor driven by two 120 Hz square waves (phase A and phase B) 90 degrees out of phase, at a stepping rate of 240 Hz. In the absence of drive signals, a drive dc voltage provides a high residual holding torque.
(c)
The rotor winding of a sweep-sense resolver that is mechanically linked to the azimuth assembly receives square wave reference signals from the indicator. The stator output is returned to the indicator for coincidence check of antenna radiator scan angle and displayed information.
(d)
The antenna stabilization system is used to automatically maintain the antenna scan parallel to the horizon regardless of airplane attitude. This is accomplished by using pitch and roll attitude inputs from the attitude reference system.
(e)
The antenna stabilization can be turned ON or OFF by the STAB switch on the indicator/control. When the switch is in the ON position, +23v dc is applied to the stabilization circuit in the R/T (Fig. 3). This allows pitch and roll signals from the attitude reference system to be connected to the isolation amplifiers in the stabilization amplifier.
(f)
Output from the pitch and roll amplifiers are applied to cosine and sine windings of the azimuth resolver in the antenna. The rotor of the resolver is driven by the azimuth motor. This generates the proper pitch and roll commands as a function of antenna position. The rotor output is applied to the R/T ELEV AMP and from there to the elevator motor in the antenna. A total of 40° of pitch attitude correction (including the +15° tilt) can be applied to the antenna. Pitch and roll amplifier gain pots are located under a pivoted cover plate on the front panel of the R/T.
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