What type of modulation varies the instantaneous power level of the RF signal?
The correct answer is D: Amplitude modulation. The type of modulation that varies the instantaneous power level of the RF signal is amplitude modulation. AM varies the amplitude (power level) of the carrier based on the modulating signal. For amateur radio operators, this is a fundamental modulation type. Understanding this helps when operating AM.
Exam Tip
Varies instantaneous power level = amplitude modulation. Think 'A'mplitude 'M'odulation = 'A'mplitude 'M'odified to convey information. AM varies the amplitude (power level) of carrier based on modulating signal. Not power modulation, not phase, not frequency - just amplitude modulation.
Memory Aid
"Varies instantaneous power level = amplitude modulation. Think 'A'mplitude 'M'odulation = 'A'mplitude 'M'odified. AM varies the amplitude (power level) of carrier based on modulating signal. Standard modulation type."
Real-World Application
Amplitude modulation: The instantaneous power level (amplitude) of the RF carrier is varied based on the audio signal. As the audio changes, the carrier amplitude changes. This is amplitude modulation - the power level is changed to convey information. AM is the oldest modulation type.
Key Concepts
Why Other Options Are Wrong
Option A (Power modulation): Incorrect. Power modulation isn't a standard term - amplitude modulation is the correct term. Power is related to amplitude, but the term is AM.
Option B (Phase modulation): Incorrect. Phase modulation varies phase, not power level - AM varies amplitude/power. Phase modulation is different.
Option C (Frequency modulation): Incorrect. Frequency modulation varies frequency, not power level - AM varies amplitude/power. Frequency modulation is different.
题目解析
The correct answer is D: Amplitude modulation. The type of modulation that varies the instantaneous power level of the RF signal is amplitude modulation. AM varies the amplitude (power level) of the carrier based on the modulating signal. For amateur radio operators, this is a fundamental modulation type. Understanding this helps when operating AM.
考试技巧
Varies instantaneous power level = amplitude modulation. Think 'A'mplitude 'M'odulation = 'A'mplitude 'M'odified to convey information. AM varies the amplitude (power level) of carrier based on modulating signal. Not power modulation, not phase, not frequency - just amplitude modulation.
记忆口诀
Varies instantaneous power level = amplitude modulation. Think 'A'mplitude 'M'odulation = 'A'mplitude 'M'odified. AM varies the amplitude (power level) of carrier based on modulating signal. Standard modulation type.
实际应用示例
Amplitude modulation: The instantaneous power level (amplitude) of the RF carrier is varied based on the audio signal. As the audio changes, the carrier amplitude changes. This is amplitude modulation - the power level is changed to convey information. AM is the oldest modulation type.
错误选项分析
Option A (Power modulation): Incorrect. Power modulation isn't a standard term - amplitude modulation is the correct term. Power is related to amplitude, but the term is AM. Option B (Phase modulation): Incorrect. Phase modulation varies phase, not power level - AM varies amplitude/power. Phase modulation is different. Option C (Frequency modulation): Incorrect. Frequency modulation varies frequency, not power level - AM varies amplitude/power. Frequency modulation is different.
知识点
Amplitude modulation, Instantaneous power level, RF signal, Modulation types
Verified Content
Question from official FCC General Class question pool. Explanation reviewed by licensed amateur radio operators.