FCC Exam Question: 8-44F4

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?

A. The deflection coils need adjusting.
B. The centering magnets at the CRT neck need adjusting.
C. The waveguide compensation delay line needs adjusting.
D. The CRT filaments are weakening.
Correct Answer: C

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.

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Includes Elements 1, 3, 6, 7R, 8, and 9.