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Subelement O: RADAR— Topic 92: Range, Pulse Width & Repetition Rate

Question 3-92O2

Element 3 (GROL)

When a RADAR is being operated on the 6 mile range setting what is the most appropriate pulse width and pulse repetition rate?

Explanation
For effective radar operation on a short range setting like 6 miles, two key parameters are critical: 1. **Pulse Width (PW):** A shorter pulse width provides better range resolution, allowing the radar to distinguish between closely spaced targets. For close ranges, high resolution is paramount to see fine details. A 0.25 µs pulse is appropriately short for this purpose. Longer pulses (1.0 µs, 2.0 µs) would smear targets together, reducing detail, while an extremely short pulse (0.01 µs) might lack sufficient energy for reliable detection even at 6 miles. 2. **Pulse Repetition Rate (PRR):** A higher PRR provides more frequent updates to the display and increases the number of echoes received from targets, improving detection reliability. For a 6-mile range, a PRR of 1,000 pps is suitable. It ensures a good refresh rate and avoids "second-time around" echoes, as the maximum unambiguous range ($c / (2 \times PRR)$) is 93 miles, well beyond the 6-mile setting. Lower PRRs (500 pps) would result in slower updates.

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