What parameter determines the sweep frequency of a radar indicator?

The pulse repetition frequency (PRF) is the parameter that determines the sweep frequency of a radar indicator. PRF refers to the number of pulse transmissions made by the radar system in one second. When a radar system transmits pulses at a specific frequency, it establishes the rate at which the radar can update the information it displays on the indicator, which in turn affects how fast the radar can sweep across its designated area.

As the pulse repetition frequency increases, the radar can provide more rapid updates, allowing for a higher sweep frequency on the indicator. This is crucial for tracking fast-moving objects and ensuring that the radar system can accurately display the position of targets in real-time.

The other options mentioned, transmission voltage, signal modulation frequency, and antenna gain, do not directly determine the sweep frequency. While they play significant roles in radar operation—affecting the power of the signal, the characteristics of the transmitted waveform, and the efficiency of radar signal reception, respectively—none of these parameters specifically controls the rate at which the display sweeps across the monitored area. This makes pulse repetition frequency the correct choice for determining the sweep frequency of a radar indicator.