For a target 25 miles away on the 25 mile range setting, what is the most appropriate pulse width and pulse repetition rate?

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Multiple Choice

For a target 25 miles away on the 25 mile range setting, what is the most appropriate pulse width and pulse repetition rate?

On a 25-mile range scale, you want enough energy in each pulse to reach a target at the far edge and enough time between pulses to hear that echo without overlap from the next pulse. The round-trip time for 25 miles is about 268 microseconds, so the pulse repetition interval should be greater than that (PRF under roughly 3.7 kHz). All the given choices meet the unambiguous-range requirement, but the energy in each pulse is increased with longer pulse width, which helps detect distant targets. Among the options, the longest pulse width is 1.0 microsecond, paired with a relatively low PRF of 500 pps, giving a PRI of 2000 microseconds—ample time for far-range echoes and more energy per pulse. This makes it the best match for a target at the far edge of the 25-mile scale. The other choices use shorter pulse widths (less energy) or a higher PRF (which tightens the unambiguous range and reduces the time available for far echoes).

On a 25-mile range scale, you want enough energy in each pulse to reach a target at the far edge and enough time between pulses to hear that echo without overlap from the next pulse. The round-trip time for 25 miles is about 268 microseconds, so the pulse repetition interval should be greater than that (PRF under roughly 3.7 kHz). All the given choices meet the unambiguous-range requirement, but the energy in each pulse is increased with longer pulse width, which helps detect distant targets. Among the options, the longest pulse width is 1.0 microsecond, paired with a relatively low PRF of 500 pps, giving a PRI of 2000 microseconds—ample time for far-range echoes and more energy per pulse. This makes it the best match for a target at the far edge of the 25-mile scale. The other choices use shorter pulse widths (less energy) or a higher PRF (which tightens the unambiguous range and reduces the time available for far echoes).

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