What is the approximate bandwidth required to transmit a CW signal?
The correct answer is B: 150 Hz. The approximate bandwidth required to transmit a CW signal is 150 Hz. CW (Morse code) is essentially an unmodulated carrier that's keyed on and off. The bandwidth needed depends on the keying speed - faster keying needs slightly more bandwidth, but typical CW operation uses about 100-200 Hz. For amateur radio operators, CW's extremely narrow bandwidth makes it the most spectrum-efficient mode, allowing many stations to operate in a small frequency range. This narrow bandwidth also makes CW excellent for weak-signal work.
Exam Tip
CW bandwidth = 150 Hz. Think 'C'W = 'C'ontinuous 'W'ave = 'C'ompact 'W'idth (~150 Hz). Narrowest of all modes. Just enough for keying speed, making it extremely spectrum-efficient.
Memory Aid
"CW bandwidth = 150 Hz. Think 'C'W = 'C'ontinuous 'W'ave = 'C'ompact 'W'idth (~150 Hz). Narrowest bandwidth of all modes. Extremely spectrum-efficient."
Real-World Application
On a crowded band, CW operators can fit many stations in a small range because each uses only about 150 Hz. You might have CW stations every 200-300 Hz, while SSB stations need 3 kHz spacing and FM stations need 15 kHz. CW's narrow bandwidth makes it ideal for weak-signal work and efficient spectrum use.
Key Concepts
Why Other Options Are Wrong
Option A (2.4 kHz): Incorrect. 2.4 kHz is much wider than CW - that's more like SSB bandwidth. CW uses only about 150 Hz.
Option C (1000 Hz): Incorrect. 1000 Hz (1 kHz) is wider than typical CW. CW uses about 150 Hz for normal keying speeds.
Option D (15 kHz): Incorrect. 15 kHz is FM bandwidth, not CW. CW is the narrowest mode at about 150 Hz.
题目解析
The correct answer is B: 150 Hz. The approximate bandwidth required to transmit a CW signal is 150 Hz. CW (Morse code) is essentially an unmodulated carrier that's keyed on and off. The bandwidth needed depends on the keying speed - faster keying needs slightly more bandwidth, but typical CW operation uses about 100-200 Hz. For amateur radio operators, CW's extremely narrow bandwidth makes it the most spectrum-efficient mode, allowing many stations to operate in a small frequency range. This narrow bandwidth also makes CW excellent for weak-signal work.
考试技巧
CW bandwidth = 150 Hz. Think 'C'W = 'C'ontinuous 'W'ave = 'C'ompact 'W'idth (~150 Hz). Narrowest of all modes. Just enough for keying speed, making it extremely spectrum-efficient.
记忆口诀
CW bandwidth = 150 Hz. Think 'C'W = 'C'ontinuous 'W'ave = 'C'ompact 'W'idth (~150 Hz). Narrowest bandwidth of all modes. Extremely spectrum-efficient.
实际应用示例
On a crowded band, CW operators can fit many stations in a small range because each uses only about 150 Hz. You might have CW stations every 200-300 Hz, while SSB stations need 3 kHz spacing and FM stations need 15 kHz. CW's narrow bandwidth makes it ideal for weak-signal work and efficient spectrum use.
错误选项分析
Option A (2.4 kHz): Incorrect. 2.4 kHz is much wider than CW - that's more like SSB bandwidth. CW uses only about 150 Hz. Option C (1000 Hz): Incorrect. 1000 Hz (1 kHz) is wider than typical CW. CW uses about 150 Hz for normal keying speeds. Option D (15 kHz): Incorrect. 15 kHz is FM bandwidth, not CW. CW is the narrowest mode at about 150 Hz.
知识点
CW bandwidth, Morse code, Narrow bandwidth, Spectrum efficiency
Verified Content
Question from official FCC Technician Class question pool. Explanation reviewed by licensed amateur radio operators.