🔍 Key Concepts

• Frequency discriminator function in a radar receiver’s automatic frequency control (AFC) system • How a klystron local oscillator is tuned/controlled in older marine radar sets • Which stages in the receiver chain (RF, IF, magnetron) are involved in frequency correction vs. signal amplification or generation

💭 Think About

• Ask yourself: which component in a marine radar system actually gets its frequency pulled or tuned by a DC control (error) voltage to stay on the correct frequency? • Which of these options (repeller, IF grids, RF grids, magnetron) would change the oscillation frequency when a control voltage is applied, instead of just changing gain? • Is the discriminator’s error voltage more likely to correct the transmitter’s magnetron frequency directly, or the local oscillator used in the receiver’s mixer stage?

✅ Before You Answer

• Identify which device in the list works as a tunable local oscillator in classic marine radar receivers • Verify which elements (grids vs. repeller vs. magnetron) are normally used for automatic frequency control (AFC), not just amplification • Be sure you separate the roles of transmitter source (magnetron), local oscillator (klystron), and amplifier stages (RF/IF) before choosing your answer