Explanation: In this RADAR system, the local oscillator (klystron) operates at a higher frequency than the transmitter (magnetron), producing an Intermediate Frequency (IF) equal to the difference (3.060 GHz - 3.0 GHz = 60 MHz). If the magnetron drifts *higher* in frequency (e.g., to 3.001 GHz), the current IF will *decrease* (3.060 GHz - 3.001 GHz = 59 MHz). The Automatic Frequency Control (AFC) system must increase the klystron's frequency to bring the IF back to 60 MHz (e.g., to 3.061 GHz). In a reflex klystron, the repeller plate is negatively biased relative to the cathode. Making the repeller plate *more negative* increases the repulsive force on the electrons, causing them to spend less time in the repeller field (shorter transit time). This shorter transit time results in an *increase* in the klystron's output frequency. Therefore, to increase the klystron frequency to compensate for the higher magnetron frequency and maintain the 60 MHz IF, the AFC system must cause the klystron repeller plate to become **more negative**.