An AFC system keeps the receiver tuned to...

🔍 Key Concepts

• AFC (Automatic Frequency Control) keeps a receiver locked on to a signal even if there is small drift. • How a superheterodyne receiver works: incoming RF, local oscillator, mixer, IF (intermediate frequency). • Which stage’s frequency you can change to keep the IF frequency constant when the received signal drifts.

💭 Think About

• In a superheterodyne radar receiver, which signal is actually mixed with the incoming radar echo to produce the IF? • If the transmitted/received radar frequency drifts slightly, which oscillator can you adjust so that the difference (the IF) remains the same? • Think about which component is designed to be tunable/adjustable in normal receiver operation, rather than being a fixed resonant device.

✅ Before You Answer

• Identify which component in the list is the frequency source that can be tuned in a receiver (not the fixed RF power source). • Confirm which stage’s frequency change will directly maintain a constant IF frequency as the incoming RF frequency changes. • Eliminate any components that are primarily power-generating or RF switching/duplexing hardware, rather than tuning elements.

An AFC system keeps the receiver tuned to the transmitted signal by varying the frequency of the:

Magnetron.

IF amplifier stage.

Local oscillator .

Cavity duplexer.

🔍 Key Concepts

💭 Think About

✅ Before You Answer