Deep Dive: G4A04
The correct answer is B: A pronounced dip. The effect on plate current of the correct setting of a vacuum-tube RF power amplifier's TUNE control is a pronounced dip. When the amplifier is properly tuned to resonance, plate current dips to a minimum. For amateur radio operators, this is how you tune a tube amplifier - tune for minimum plate current. Understanding this helps when tuning amplifiers.
Why Other Answers Are Wrong
Option A: Incorrect. Plate current doesn't peak when properly tuned - it dips. Peak current indicates mistuning. Option C: Incorrect. Plate current does change when tuning - it dips at resonance. No change would indicate the control isn't working. Option D: Incorrect. Plate current doesn't oscillate when properly tuned - it dips to a steady minimum. Oscillation indicates instability.
Exam Tip
Correct TUNE setting = pronounced dip in plate current. Think 'T'UNE = 'T'ube 'U'nity 'N'ulls current (dips). When properly tuned to resonance, plate current dips to minimum. Not peak, not no change, not oscillation - just dip.
Memory Aid
Correct TUNE setting = pronounced dip in plate current. Think 'T'UNE = 'T'ube 'U'nity 'N'ulls current. When properly tuned to resonance, plate current dips to minimum. Standard tuning procedure for tube amplifiers.
Real-World Example
You tune a vacuum tube RF power amplifier. As you adjust the TUNE control, plate current changes. When you reach the correct setting (resonance), plate current dips to a pronounced minimum. This is how you know the amplifier is properly tuned. Tune for minimum plate current.
Source & Coverage
Question Pool: 2023-2027 Question Pool
Subelement: G4A
Reference: 2023-2027 Question Pool · G4 - Amateur Radio Practices
Key Concepts
Verified Content
Question from the official FCC General Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the G4A topic.