Pulse Repetition Interval (PRI) is defined as what?

• A. The duration of a single pulse.
• B. The time between transmissions when the radar is idle.
• C. The complete full-cycle time from the beginning of one transmitted pulse to the beginning of the next.
• D. The number of pulses per second.

Answer: (C)

PRI is the complete cycle time from the start of one transmitted pulse to the start of the next. It includes the actual pulse duration plus the interval when the radar is idle between pulses, making it the period of the pulsed train. For example, if the PRF is 500 Hz, PRI = 1/500 s = 2 ms. If the pulse lasts 0.8 ms, the idle interval is 2 ms − 0.8 ms = 1.2 ms. This distinguishes PRI from the pulse duration (which is just the length of a single pulse) and from the pulse repetition frequency (how many pulses occur each second).