What is deviation ratio?
The correct answer is B: The ratio of the maximum carrier frequency deviation to the highest audio modulating frequency. Deviation ratio is the ratio of the maximum carrier frequency deviation to the highest audio modulating frequency. This is a key parameter in FM system design.
Deviation ratio = Maximum frequency deviation / Highest modulating frequency. It's similar to modulation index but is specifically defined for the maximum conditions. The deviation ratio helps determine bandwidth requirements and signal characteristics. A higher deviation ratio means more frequency deviation relative to the modulating frequency, which typically results in wider bandwidth and more sidebands. Deviation ratio is an important specification in FM system design.
Exam Tip
Deviation ratio = Max deviation / Highest modulating frequency. Remember: Deviation ratio is the ratio of maximum carrier frequency deviation to the highest audio modulating frequency.
Memory Aid
"**D**eviation **R**atio = **M**ax **D**eviation / **H**ighest **M**odulating **F**requency (think 'DR = MD/HMF')"
Real-World Application
You're designing an FM system with maximum deviation of 5 kHz and highest audio frequency of 3 kHz. The deviation ratio is 5 / 3 = 1.67. This ratio helps you determine the bandwidth requirements and understand how the FM signal will behave.
FCC Part 97.307Key Concepts
Why Other Options Are Wrong
Option A: Incorrect. Deviation ratio isn't the ratio of modulating frequency to carrier frequency. It's deviation divided by modulating frequency.
Option C: Incorrect. Deviation ratio isn't the ratio of carrier frequency to modulating frequency. It's about deviation, not carrier frequency.
Option D: Incorrect. Deviation ratio isn't about the ratio of highest to average modulating frequency. It's about maximum deviation relative to highest modulating frequency.
题目解析
The correct answer is B: The ratio of the maximum carrier frequency deviation to the highest audio modulating frequency. Deviation ratio is the ratio of the maximum carrier frequency deviation to the highest audio modulating frequency. This is a key parameter in FM system design. Deviation ratio = Maximum frequency deviation / Highest modulating frequency. It's similar to modulation index but is specifically defined for the maximum conditions. The deviation ratio helps determine bandwidth requirements and signal characteristics. A higher deviation ratio means more frequency deviation relative to the modulating frequency, which typically results in wider bandwidth and more sidebands. Deviation ratio is an important specification in FM system design.
考试技巧
Deviation ratio = Max deviation / Highest modulating frequency. Remember: Deviation ratio is the ratio of maximum carrier frequency deviation to the highest audio modulating frequency.
记忆口诀
**D**eviation **R**atio = **M**ax **D**eviation / **H**ighest **M**odulating **F**requency (think 'DR = MD/HMF')
实际应用示例
You're designing an FM system with maximum deviation of 5 kHz and highest audio frequency of 3 kHz. The deviation ratio is 5 / 3 = 1.67. This ratio helps you determine the bandwidth requirements and understand how the FM signal will behave.
错误选项分析
Option A: Incorrect. Deviation ratio isn't the ratio of modulating frequency to carrier frequency. It's deviation divided by modulating frequency. Option C: Incorrect. Deviation ratio isn't the ratio of carrier frequency to modulating frequency. It's about deviation, not carrier frequency. Option D: Incorrect. Deviation ratio isn't about the ratio of highest to average modulating frequency. It's about maximum deviation relative to highest modulating frequency.
知识点
Deviation ratio, Frequency deviation, Modulating frequency, FM parameters
Verified Content
Question from official FCC Extra Class question pool. Explanation reviewed by licensed amateur radio operators.