Deep Dive: G7B11
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.
Why Other Answers 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.
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 Example
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.
Source & Coverage
Question Pool: 2023-2027 Question Pool
Subelement: G7B
Reference: 2023-2027 Question Pool · G7 - Practical Circuits
Key Concepts
Verified Content
Question from the official FCC General Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the G7B topic.