What circuit is used to select one of the sidebands from a balanced modulator?
The correct answer is B: Filter. The circuit used to select one of the sidebands from a balanced modulator is a filter. Balanced modulators produce double-sideband output; a filter selects either the upper or lower sideband. For amateur radio operators, this is how SSB is generated. Understanding this helps when designing SSB transmitters.
Exam Tip
Select sideband from balanced modulator = filter. Think 'S'elect 'S'ideband = 'S'elective 'F'ilter. Balanced modulators produce double-sideband; filter selects upper or lower sideband. Not carrier oscillator, not IF/RF amplifier - just filter.
Memory Aid
"Select sideband from balanced modulator = filter. Think 'S'elect 'S'ideband = 'S'elective 'F'ilter. Balanced modulators produce double-sideband; filter selects upper or lower sideband. Essential for SSB generation."
Real-World Application
A balanced modulator produces double-sideband output (USB and LSB). A filter (crystal or mechanical) selects either the upper sideband or lower sideband, rejecting the other. This is how SSB is generated - balanced modulator plus filter. The filter is essential for sideband selection.
Key Concepts
Why Other Options Are Wrong
Option A (Carrier oscillator): Incorrect. Carrier oscillator generates the carrier, it doesn't select sidebands. Carrier oscillator is for modulation, not sideband selection.
Option C (IF amplifier): Incorrect. IF amplifier amplifies intermediate frequency, it doesn't select sidebands. IF amplifier is for amplification, not sideband selection.
Option D (RF amplifier): Incorrect. RF amplifier amplifies RF signals, it doesn't select sidebands. RF amplifier is for amplification, not sideband selection.
题目解析
The correct answer is B: Filter. The circuit used to select one of the sidebands from a balanced modulator is a filter. Balanced modulators produce double-sideband output; a filter selects either the upper or lower sideband. For amateur radio operators, this is how SSB is generated. Understanding this helps when designing SSB transmitters.
考试技巧
Select sideband from balanced modulator = filter. Think 'S'elect 'S'ideband = 'S'elective 'F'ilter. Balanced modulators produce double-sideband; filter selects upper or lower sideband. Not carrier oscillator, not IF/RF amplifier - just filter.
记忆口诀
Select sideband from balanced modulator = filter. Think 'S'elect 'S'ideband = 'S'elective 'F'ilter. Balanced modulators produce double-sideband; filter selects upper or lower sideband. Essential for SSB generation.
实际应用示例
A balanced modulator produces double-sideband output (USB and LSB). A filter (crystal or mechanical) selects either the upper sideband or lower sideband, rejecting the other. This is how SSB is generated - balanced modulator plus filter. The filter is essential for sideband selection.
错误选项分析
Option A (Carrier oscillator): Incorrect. Carrier oscillator generates the carrier, it doesn't select sidebands. Carrier oscillator is for modulation, not sideband selection. Option C (IF amplifier): Incorrect. IF amplifier amplifies intermediate frequency, it doesn't select sidebands. IF amplifier is for amplification, not sideband selection. Option D (RF amplifier): Incorrect. RF amplifier amplifies RF signals, it doesn't select sidebands. RF amplifier is for amplification, not sideband selection.
知识点
Balanced modulator, Sideband selection, Filter, SSB generation
Verified Content
Question from official FCC General Class question pool. Explanation reviewed by licensed amateur radio operators.