Subelement F: Installation, Maintenance & Repair— Topic 44: Equipment Faults-1
Question 8-44F4
Element 8 (RADAR)While the vessel is docked the presentation of the pier is distorted near the center of the PPI with the pier appearing to bend in a concave fashion. This is a primary indication of what?
Explanation
The described concave bending of a straight pier near the center of the PPI display is a classic symptom of an error in the radar's zero-range calibration. The waveguide compensation delay line (or a similar zero-mileage adjustment) is critical for synchronizing the start of the radar's display sweep with the exact moment the radar pulse leaves the antenna.
If this delay line is misadjusted, the radar will incorrectly calculate the range to very close targets. This causes distortion, especially for nearby objects, making straight features like a pier appear bent or concave. The other options relate to display aesthetics (brightness, centering) or overall sweep linearity, not this specific type of range-related distortion near the center of the screen.
Related Questions
8-44F2 Range rings on the PPI indicator are oval in shape. Which circuit would you suspect is faulty?8-44F3 What would be the most likely defective area when there is no target video in the center of the CRT and the blank spot gets smaller in diameter as your range scale is increased?8-44F5 In a RADAR using digital video processing, a bright, wide ring appears at a fixed distance from the center of the display on all digital ranges. The transmitter is operating normally. What receiver circuit would you suspect is causing the problem?8-44F6 The raster scan RADAR display has missing video in a rectangular block on the screen. Where is the most likely problem area?8-45F1 A circuit card in a RADAR system has just been replaced with a spare card. You notice the voltage level at point E in Fig. 8F12 is negative 4.75 volts when the inputs are all at 5 volts. The problem is: