For which of the following modes is a Class C power stage appropriate for amplifying a modulated signal?
The correct answer is B: FM. For which of the following modes a Class C power stage is appropriate for amplifying a modulated signal is FM. Class C amplifiers can only amplify constant-envelope signals (like FM), not variable-envelope signals (like SSB or AM). For amateur radio operators, this is important for amplifier selection. Understanding this helps when choosing amplifier classes.
Exam Tip
Class C appropriate for = FM. Think 'C'lass 'C' = 'C'onstant envelope = 'F'M. Class C can only amplify constant-envelope signals like FM, not variable-envelope signals like SSB or AM. Not SSB, not AM - just FM.
Memory Aid
"Class C appropriate for = FM. Think 'C'lass 'C' = 'C'onstant envelope = 'F'M. Class C can only amplify constant-envelope signals like FM. Not SSB or AM - just FM."
Real-World Application
You use a Class C amplifier for FM operation. FM has a constant envelope (amplitude doesn't vary with modulation), so Class C can amplify it without distortion. SSB and AM have variable envelopes, so they require linear amplification (Class A, AB, or B). Class C is only appropriate for FM.
Key Concepts
Why Other Options Are Wrong
Option A (SSB): Incorrect. Class C can't amplify SSB - SSB has variable envelope, and Class C is non-linear. SSB requires linear amplification (Class A, AB, or B).
Option C (AM): Incorrect. Class C can't amplify AM - AM has variable envelope, and Class C is non-linear. AM requires linear amplification.
Option D: Incorrect. Since SSB and AM are not appropriate, 'all of the above' cannot be correct. Only FM is appropriate for Class C.
题目解析
The correct answer is B: FM. For which of the following modes a Class C power stage is appropriate for amplifying a modulated signal is FM. Class C amplifiers can only amplify constant-envelope signals (like FM), not variable-envelope signals (like SSB or AM). For amateur radio operators, this is important for amplifier selection. Understanding this helps when choosing amplifier classes.
考试技巧
Class C appropriate for = FM. Think 'C'lass 'C' = 'C'onstant envelope = 'F'M. Class C can only amplify constant-envelope signals like FM, not variable-envelope signals like SSB or AM. Not SSB, not AM - just FM.
记忆口诀
Class C appropriate for = FM. Think 'C'lass 'C' = 'C'onstant envelope = 'F'M. Class C can only amplify constant-envelope signals like FM. Not SSB or AM - just FM.
实际应用示例
You use a Class C amplifier for FM operation. FM has a constant envelope (amplitude doesn't vary with modulation), so Class C can amplify it without distortion. SSB and AM have variable envelopes, so they require linear amplification (Class A, AB, or B). Class C is only appropriate for FM.
错误选项分析
Option A (SSB): Incorrect. Class C can't amplify SSB - SSB has variable envelope, and Class C is non-linear. SSB requires linear amplification (Class A, AB, or B). Option C (AM): Incorrect. Class C can't amplify AM - AM has variable envelope, and Class C is non-linear. AM requires linear amplification. Option D: Incorrect. Since SSB and AM are not appropriate, 'all of the above' cannot be correct. Only FM is appropriate for Class C.
知识点
Class C amplifier, FM, Constant-envelope, Modulated signals
Verified Content
Question from official FCC General Class question pool. Explanation reviewed by licensed amateur radio operators.