🔍 Key Concepts

• Basic radar signal path: transmitter → TR cell → mixer/local oscillator → IF amplifier → video detector → video amplifier → display (CRT) • How range-scaling changes the display (sweep length and range marks) but not the underlying received signal path • What kind of fault would cause a central blank spot that changes with range scale rather than total loss of all echoes

💭 Think About

• Think about which components, if defective, would affect all echoes at all ranges versus only a specific area (like the center) of the screen • Ask yourself: if the transmitter or TR cell failed, what would the whole picture look like? Would changing the range scale make a central blank hole get smaller? • Consider which part of the chain deals specifically with turning detected RF echoes into the brightness pattern on the CRT, and whether a fault there could affect only a small central area

✅ Before You Answer

• Verify which components (TR cell, local oscillator, IF amplifier) are mainly involved in frequency conversion and RF/IF amplification, not shaping the actual picture on the CRT • Check which circuit is responsible for handling detected video and feeding it to the CRT, and whether a failure there is likely to show up as a localized, range-dependent blank area • Be sure your choice explains why the blank spot changes size when you change range scale, not just why echoes might be weak or missing in general