As the 12 o'clock display position poinds to True North (0 degrees), the Heading Flash is needed to display the ships heading.

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DSP - Digital Signal Processing of a RADAR signal makes it easy to implement filters to enhance weak target returns, so Answer B. is correct.

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Due to aliasing, the sample frequency used must be at least twice the frequency of the signal being processed. This is known as the Nyquist Theorem.

Aliasing is the reason stage-coach wheels sometimes appear to turn backwards in western movies. This happens when the sampling frequency (the number of frames per second of the movie or TV camera) is less than twice the sampled frequency (the number of wheel spokes going by every second.)

Answer C. is the correct answer.

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Answer B. is wrong because the targets must be adjacent to each other.

Answer C. is wrong because RADAR stands for RAdio Direction And Range-finding. Elevation is not part of the acronym.

Answer D. is wrong because RADAR's primary function is, again, RAdio Direction And Range-finding. Sizing is not part of the acronym.

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When an RC integrator is driven by a square wave with a period much shorter than the time constant (RC), the output waveform takes the shape of a triangle wave.

To understand why this happens, let's consider the behavior of an RC integrator. An RC integrator consists of a resistor (R) and a capacitor (C) connected in series. When a voltage input signal is applied, the capacitor charges and discharges according to the time constant (τ = RC), which is the product of the resistance and capacitance.

In the case of a square wave with a period much shorter than the time constant, the input voltage changes rapidly from one state to another before the capacitor has enough time to fully charge or discharge. As a result, the capacitor cannot fully respond to the input changes, and its voltage output increases or decreases gradually, creating a linear ramp-like waveform. This ramp waveform, when plotted, resembles a triangle.

Mnemonic: "Gradual Rise, Gradual Fall"

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How do you eliminate stationary objects such as trees, buildings, bridges, etc., from the PPI presentation?

Use a discriminator as a second detector.

To eliminate stationary objects such as trees, buildings, bridges, etc., from the PPI (Plan Position Indicator) presentation in a radar system, you can use a technique called "MTI" (Moving Target Indication). The MTI technique uses a discriminator as a second detector to filter out signals from stationary objects, leaving only the signals from moving targets.

Here's how it works: The radar receiver uses two detectors, one after the other. The first detector captures the radar returns as usual. The second detector, known as the discriminator, compares the current radar returns with the previous ones. It identifies and removes signals that remain stationary or have very slow changes over time (indicative of stationary objects like buildings and trees).

The remaining signals with significant changes are likely coming from moving targets, such as vehicles or aircraft. By eliminating stationary returns, the PPI presentation becomes clearer and allows radar operators to focus on detecting and tracking moving targets more effectively.

Note: The "Second Dicriminator" referred-to in this question is NOT to be confused with the discrimantor that compares the Magnetron and Klystron frequencies to drive the AFC - Automatic Frequency Control.

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