Deep Dive: E1C09
The correct answer is B: 1.0. The highest modulation index permitted at the highest modulation frequency for angle modulation below 29.0 MHz is 1.0. Angle modulation (FM/PM) below 29 MHz is limited to a modulation index of 1.0. For amateur radio operators, this is important for HF operation. Understanding this helps ensure legal operation.
Why Other Answers Are Wrong
Option A (0.5): Incorrect. 0.5 is too low - the maximum is 1.0, not 0.5. 0.5 is too restrictive. Option C (2.0): Incorrect. 2.0 is too high - the maximum is 1.0, not 2.0. 2.0 exceeds the limit. Option D (3.0): Incorrect. 3.0 is way too high - the maximum is 1.0, not 3.0. 3.0 exceeds the limit.
Exam Tip
Angle modulation below 29 MHz = maximum modulation index 1.0. Think 'A'ngle 'M'odulation 'B'elow '2'9 MHz = '1'.0 maximum. Angle modulation below 29 MHz is limited to modulation index of 1.0. Not 0.5, not 2.0, not 3.0 - just 1.0.
Memory Aid
Angle modulation below 29 MHz = maximum modulation index 1.0. Think 'A'ngle 'M'odulation = '1'.0 maximum. Angle modulation below 29 MHz is limited to modulation index of 1.0. Important for HF operation.
Real-World Example
Angle modulation (FM/PM) below 29.0 MHz: The highest modulation index permitted at the highest modulation frequency is 1.0. This limits the frequency deviation or phase deviation to prevent excessive bandwidth. For example, with 3 kHz modulating frequency, maximum deviation would be 3 kHz (modulation index = deviation/modulating frequency = 3/3 = 1.0). 1.0 is the maximum modulation index.
Source & Coverage
Question Pool: 2024-2028 Question Pool
Subelement: E1C
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 E1C topic.