Deep Dive: T8A11
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.
Why Other Answers 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.
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 Example
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.
Source & Coverage
Question Pool: 2022-2026 Question Pool
Subelement: T8A
Reference: 2022-2026 Question Pool · T8 - Signals and emissions
Key Concepts
Verified Content
Question from the official FCC Technician Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the T8A topic.