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A361 Antenna Elevation Parking Control
MX-7974/ASA-69 Radar Interface Unit

Aviation Electronics Technician 1 (Organizational)
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warm-up time, the WARM-UP section will extinguish, and the STBY section illuminates. This tells the operator that the system is ready for use. Press the HV push button now to apply the radar operating power. When the operating power is applied, the HV ON section will illuminate. Press the push button to alternately select HV ON and STBY. FTC SWITCH.— This switch controls the receiver’s fast time constant circuitry. With this switch in the FTC position, the targets displayed have strong leading edges and attenuated trailing edges. This improves the display when the target is near a landmass. LOAD SWITCH.— This switch controls the waveguide switch on the ante ma unit. When the ANT section is illuminated, the RF energy is actually radiated by the antenna. In the DUMMY mode of operation, the RF energy is fed into the dummy load on the antenna. In this mode, there is no radiation out of the antenna CAUTION Ensure the radar system is in STBY prior to selecting or deselecting DUMMY Load to avoid damaging equipment. PWR SWITCH.— This is the system power switch. It applies power to the system and starts the warm-up period. RCVR GAIN KNOB.— This knob controls the receiver gain of the system. The operator will adjust the gain until the radar noise levels are matched between the forward and aft radars. VIDEO TEST SWITCH.— This switch will select the video self-test circuitry in its respective RT for an overall performance check. If the PULSE push button is in the LONG position, the display should show simulated targets 1 nautical mile apart. In the OFF position, the system is in the normal mode of operation. STC DEPTH KNOB.— This knob will vary the amount of receiver attenuation for close-in targets. It is used in conjunction with the STC RANGE knob. STC RANGE KNOB.— This knob varies the range to which the intensity of target return is effectively reduced. It will vary the range between 0 and 20 nautical miles. If both the DEPTH and the RANGE knobs are rotated fully clockwise, close-in targets could be blanked from the display. AFC/MAN SWITCH.— This switch selects either the AFC mode or the manual tuning mode of operation. In the AFC position, the local oscillator has the automatic frequency control circuitry connected to it. With this switch in the MAN position, the operator can manually tune the local oscillator. If the system is manually tuned correctly, there should be no difference in the video in either position. The system is locked in the fixed-mode of operation if this switch is in the MAN position, regardless of the position of the FREQ push button. MAN TUNE KNOB.— This is the knob the operator rotates to manually tune the local oscillator when the AFC/MAN switch is in the MAN position. FAIL LIGHTS.— There are two lights located on the control panel to indicate there is a problem with the system. One is the RT light, and the other is the APP light. The RT light will illuminate when the receiver-transmitter BITE circuitry detects a failure in the RT. The APP light will illuminate when the BITE circuitry detects a failure in the antenna position programmer. C-7557/ASA-69 Radar Scan Converter Control The radar scan converter (fig. 3-6) and associated components provide the interface between the data processing system and the APS-115 radar set. It also Figure 3-6.-C-7557/ASA-69 radar scan converter control 3-6







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