What is the frequency deviation for a 12.21 MHz reactance modulated oscillator in a 5 kHz deviation, 146.52 MHz FM phone transmitter?
The correct answer is B: 416.7 Hz. The frequency deviation for a 12.21 MHz reactance modulated oscillator in a 5 kHz deviation, 146.52 MHz FM phone transmitter is 416.7 Hz. The deviation is reduced by the multiplication ratio: 5 kHz / 12 = 416.7 Hz (since 146.52 / 12.21 ≈ 12). For amateur radio operators, this explains how multipliers affect deviation. Understanding this helps when designing FM transmitters.
Exam Tip
Oscillator deviation = final deviation / multiplication ratio = 5 kHz / 12 = 416.7 Hz. Think 'O'scillator 'D'eviation = 'O'utput 'D'eviation divided by 'M'ultiplication. Deviation is reduced by multiplication ratio. Not 101.75 Hz, not 5 kHz (final), not 60 kHz - just 416.7 Hz.
Memory Aid
"Oscillator deviation = final deviation / multiplication ratio = 416.7 Hz. Think 'O'scillator 'D'eviation = 'O'utput divided by 'M'ultiplication. Deviation is reduced by multiplication ratio. How multipliers affect deviation."
Real-World Application
A 146.52 MHz FM transmitter: Final deviation = 5 kHz, multiplication ratio = 12 (146.52 / 12.21 ≈ 12). Oscillator deviation = 5 kHz / 12 = 416.7 Hz. The reactance modulated oscillator at 12.21 MHz has 416.7 Hz deviation, which is multiplied to 5 kHz at 146.52 MHz. This is how multipliers affect deviation.
Key Concepts
Why Other Options Are Wrong
Option A (101.75 Hz): Incorrect. 101.75 Hz is too low - calculation gives 416.7 Hz, not 101.75 Hz. Calculation error.
Option C (5 kHz): Incorrect. 5 kHz is the final deviation, not the oscillator deviation - oscillator deviation is reduced by multiplication ratio. 5 kHz is the output, not input.
Option D (60 kHz): Incorrect. 60 kHz is way too high - oscillator deviation is less than final deviation, not more. 60 kHz is too high.
题目解析
The correct answer is B: 416.7 Hz. The frequency deviation for a 12.21 MHz reactance modulated oscillator in a 5 kHz deviation, 146.52 MHz FM phone transmitter is 416.7 Hz. The deviation is reduced by the multiplication ratio: 5 kHz / 12 = 416.7 Hz (since 146.52 / 12.21 ≈ 12). For amateur radio operators, this explains how multipliers affect deviation. Understanding this helps when designing FM transmitters.
考试技巧
Oscillator deviation = final deviation / multiplication ratio = 5 kHz / 12 = 416.7 Hz. Think 'O'scillator 'D'eviation = 'O'utput 'D'eviation divided by 'M'ultiplication. Deviation is reduced by multiplication ratio. Not 101.75 Hz, not 5 kHz (final), not 60 kHz - just 416.7 Hz.
记忆口诀
Oscillator deviation = final deviation / multiplication ratio = 416.7 Hz. Think 'O'scillator 'D'eviation = 'O'utput divided by 'M'ultiplication. Deviation is reduced by multiplication ratio. How multipliers affect deviation.
实际应用示例
A 146.52 MHz FM transmitter: Final deviation = 5 kHz, multiplication ratio = 12 (146.52 / 12.21 ≈ 12). Oscillator deviation = 5 kHz / 12 = 416.7 Hz. The reactance modulated oscillator at 12.21 MHz has 416.7 Hz deviation, which is multiplied to 5 kHz at 146.52 MHz. This is how multipliers affect deviation.
错误选项分析
Option A (101.75 Hz): Incorrect. 101.75 Hz is too low - calculation gives 416.7 Hz, not 101.75 Hz. Calculation error. Option C (5 kHz): Incorrect. 5 kHz is the final deviation, not the oscillator deviation - oscillator deviation is reduced by multiplication ratio. 5 kHz is the output, not input. Option D (60 kHz): Incorrect. 60 kHz is way too high - oscillator deviation is less than final deviation, not more. 60 kHz is too high.
知识点
Reactance modulated oscillator, Frequency deviation, 416.7 Hz, Multiplication ratio
Verified Content
Question from official FCC General Class question pool. Explanation reviewed by licensed amateur radio operators.