🔍 Key Concepts

• Operation of a reflex klystron and the role of the repeller electrode • How frequency tuning is achieved in microwave oscillators • Difference between mechanical tuning of a cavity and electrical tuning by changing voltages

💭 Think About

• Think about which part of the reflex klystron directly controls the transit time of electrons between the cavity and the reflecting element. • Ask yourself: which adjustment would cause a small change in oscillation frequency without physically changing the cavity dimensions? • Consider what an AFC (automatic frequency control) system does compared with the basic built‑in tuning method of the klystron itself.

✅ Before You Answer

• Identify which option relates to the repeller electrode, a key element in reflex klystron operation. • Distinguish between mechanical tuning (changing cavity shape/size) and electrical tuning (changing electrode voltage). • Verify which method is commonly used for fine, not coarse, frequency adjustments in a reflex klystron.