Which method is used to eliminate stationary objects from the PPI presentation?

Using a discriminator as a second detector is a method employed to eliminate stationary objects from the PPI (Plan Position Indicator) presentation. This process works by differentiating between stationary and moving signals. The discriminator effectively filters out signals that remain constant over time, which are typically those from stationary objects, such as land or other fixed structures. This enables the radar system to focus on moving targets, which are of greater interest in many applications, such as air traffic control or maritime navigation.

In contrast, removing the discriminator from the unit would negate the ability to filter out unwanted signals, resulting in a cluttered display. Calibrating the IF (Intermediate Frequency) circuit and the local oscillator are important for ensuring accurate operation and signal processing but do not directly address the issue of eliminating stationary objects from the PPI presentation.