Which of the following phone emissions uses the narrowest bandwidth?
The correct answer is A: Single sideband. The phone emission that uses the narrowest bandwidth is single sideband. SSB uses only one sideband (typically 2.4-3 kHz), making it the narrowest bandwidth phone mode. For amateur radio operators, this is why SSB is popular on HF. Understanding this helps when selecting operating modes.
Exam Tip
Narrowest bandwidth phone emission = single sideband. Think 'S'SB = 'S'ingle 'S'ideband = 'S'limmest bandwidth. SSB uses only one sideband (2.4-3 kHz), making it narrowest. Not vestigial sideband, not phase modulation, not frequency modulation - just SSB.
Memory Aid
"Narrowest bandwidth phone emission = single sideband. Think 'S'SB = 'S'limmest bandwidth. SSB uses only one sideband (2.4-3 kHz), making it narrowest. Most efficient phone mode for HF."
Real-World Application
Phone emissions bandwidth comparison: SSB uses 2.4-3 kHz (narrowest), vestigial sideband uses more, phase modulation uses more, FM uses 5-15 kHz (widest). SSB's narrow bandwidth makes it efficient for HF operation, allowing more stations in the same spectrum. SSB is the narrowest bandwidth phone emission.
Key Concepts
Why Other Options Are Wrong
Option B (Vestigial sideband): Incorrect. Vestigial sideband is wider than SSB - it includes part of the other sideband, making it wider. VSB isn't the narrowest.
Option C (Phase modulation): Incorrect. Phase modulation is wider than SSB - PM typically uses more bandwidth than SSB. PM isn't the narrowest.
Option D (Frequency modulation): Incorrect. Frequency modulation is much wider than SSB - FM typically uses 5-15 kHz, much wider than SSB. FM isn't the narrowest.
题目解析
The correct answer is A: Single sideband. The phone emission that uses the narrowest bandwidth is single sideband. SSB uses only one sideband (typically 2.4-3 kHz), making it the narrowest bandwidth phone mode. For amateur radio operators, this is why SSB is popular on HF. Understanding this helps when selecting operating modes.
考试技巧
Narrowest bandwidth phone emission = single sideband. Think 'S'SB = 'S'ingle 'S'ideband = 'S'limmest bandwidth. SSB uses only one sideband (2.4-3 kHz), making it narrowest. Not vestigial sideband, not phase modulation, not frequency modulation - just SSB.
记忆口诀
Narrowest bandwidth phone emission = single sideband. Think 'S'SB = 'S'limmest bandwidth. SSB uses only one sideband (2.4-3 kHz), making it narrowest. Most efficient phone mode for HF.
实际应用示例
Phone emissions bandwidth comparison: SSB uses 2.4-3 kHz (narrowest), vestigial sideband uses more, phase modulation uses more, FM uses 5-15 kHz (widest). SSB's narrow bandwidth makes it efficient for HF operation, allowing more stations in the same spectrum. SSB is the narrowest bandwidth phone emission.
错误选项分析
Option B (Vestigial sideband): Incorrect. Vestigial sideband is wider than SSB - it includes part of the other sideband, making it wider. VSB isn't the narrowest. Option C (Phase modulation): Incorrect. Phase modulation is wider than SSB - PM typically uses more bandwidth than SSB. PM isn't the narrowest. Option D (Frequency modulation): Incorrect. Frequency modulation is much wider than SSB - FM typically uses 5-15 kHz, much wider than SSB. FM isn't the narrowest.
知识点
Phone emissions, Narrowest bandwidth, Single sideband, SSB
Verified Content
Question from official FCC General Class question pool. Explanation reviewed by licensed amateur radio operators.