Which of the following types of modulation is used for data emissions below 30 MHz?
The correct answer is B: FSK. Which of the following types of modulation is used for data emissions below 30 MHz is FSK. Frequency Shift Keying is commonly used for data below 30 MHz. For amateur radio operators, this is important for HF data operation. Understanding this helps when operating data modes on HF.
Exam Tip
Data emissions below 30 MHz = FSK. Think 'D'ata 'B'elow '3'0 MHz = 'F'SK. Frequency Shift Keying is commonly used for data below 30 MHz. Not DTMF/FM, not pulse modulation, not spread spectrum - just FSK.
Memory Aid
"Data emissions below 30 MHz = FSK. Think 'D'ata 'B'elow '3'0 MHz = 'F'SK. Frequency Shift Keying is commonly used for data below 30 MHz. Important for HF data operation."
Real-World Application
Data emissions below 30 MHz: FSK (Frequency Shift Keying) is commonly used. Modes like RTTY, PSK31, and other HF data modes use FSK. Spread spectrum isn't allowed below 30 MHz (only above 222 MHz). This is the modulation type - FSK is used for data below 30 MHz.
FCC Part 97.311Key Concepts
Why Other Options Are Wrong
Option A: Incorrect. DTMF tones modulating FM signal isn't used for data below 30 MHz - FSK is used. DTMF/FM isn't used.
Option C: Incorrect. Pulse modulation isn't commonly used for data below 30 MHz - FSK is used. Pulse modulation isn't used.
Option D: Incorrect. Spread spectrum isn't allowed below 30 MHz - spread spectrum is only above 222 MHz. Spread spectrum isn't allowed.
题目解析
The correct answer is B: FSK. Which of the following types of modulation is used for data emissions below 30 MHz is FSK. Frequency Shift Keying is commonly used for data below 30 MHz. For amateur radio operators, this is important for HF data operation. Understanding this helps when operating data modes on HF.
考试技巧
Data emissions below 30 MHz = FSK. Think 'D'ata 'B'elow '3'0 MHz = 'F'SK. Frequency Shift Keying is commonly used for data below 30 MHz. Not DTMF/FM, not pulse modulation, not spread spectrum - just FSK.
记忆口诀
Data emissions below 30 MHz = FSK. Think 'D'ata 'B'elow '3'0 MHz = 'F'SK. Frequency Shift Keying is commonly used for data below 30 MHz. Important for HF data operation.
实际应用示例
Data emissions below 30 MHz: FSK (Frequency Shift Keying) is commonly used. Modes like RTTY, PSK31, and other HF data modes use FSK. Spread spectrum isn't allowed below 30 MHz (only above 222 MHz). This is the modulation type - FSK is used for data below 30 MHz.
错误选项分析
Option A: Incorrect. DTMF tones modulating FM signal isn't used for data below 30 MHz - FSK is used. DTMF/FM isn't used. Option C: Incorrect. Pulse modulation isn't commonly used for data below 30 MHz - FSK is used. Pulse modulation isn't used. Option D: Incorrect. Spread spectrum isn't allowed below 30 MHz - spread spectrum is only above 222 MHz. Spread spectrum isn't allowed.
知识点
Data emissions, Below 30 MHz, FSK, Frequency Shift Keying
Verified Content
Question from official FCC Extra Class question pool. Explanation reviewed by licensed amateur radio operators.