Deep Dive: E8B09
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.
Why Other Answers 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.
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 Example
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.
Source & Coverage
Question Pool: 2024-2028 Question Pool
Subelement: E8B
Reference: FCC Part 97.307
Key Concepts
Verified Content
Question from the official FCC Extra Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the E8B topic.