The
pulse repetition frequency (
PRF) is the number of pulses of a repeating signal in a specific time unit, normally measured in
pulses per second. The term is used within a number of technical disciplines, notably
radar. In radar, a radio signal of a particular
carrier frequency is turned on and off; the term "frequency" refers to the carrier, while the PRF refers to the number of switches. Both are measured in terms of
cycle per second, or
Hertz. The PRF is normally much lower than the frequency. For instance, a typical
World War II radar like the Type 7 GCI radar had a basic carrier frequency of 209 MHz (209 million cycles per second) and a PRF of 300 or 500 pulses per second. A related measure is the pulse width, the amount of time the transmitter is turned on during each pulse.