Increasing PRF generally has what effect on the radar's unambiguous range?

• A. It increases the maximum unambiguous range
• B. It has no effect
• C. It reduces the maximum unambiguous range
• D. It doubles angular coverage

Answer: (C)

Unambiguous range is limited by how long you wait between emitted pulses. If an echo returns after the next pulse has already been sent, you can’t tell which pulse it came from, causing range ambiguity. The time between pulses is the inverse of the pulse repetition frequency (PRF), so a higher PRF shortens that window. The farthest distance you can measure without ambiguity is R = c / (2 × PRF). Therefore, increasing PRF reduces the maximum unambiguous range (doubling PRF halves the range). This is why higher PRF improves speed/ Doppler decisions but narrows how far you can unambiguously range.