What frequency range is occupied by a 3 kHz USB signal with the displayed carrier frequency set to 14.347 MHz?
The correct answer is B: 14.347 MHz to 14.350 MHz. The frequency range occupied by a 3 kHz USB signal with the displayed carrier frequency set to 14.347 MHz is 14.347 MHz to 14.350 MHz. USB uses the upper sideband, so the signal extends from carrier to (carrier + 3 kHz). For amateur radio operators, this helps understand SSB frequency ranges. Understanding this helps when operating SSB.
Exam Tip
3 kHz USB at 14.347 MHz = 14.347-14.350 MHz. Think 'U'SB = 'U'pper sideband = 'U'pper frequencies (carrier to carrier + 3 kHz). USB extends from 14.347 to (14.347 + 0.003) = 14.347-14.350 MHz. Not below carrier - above carrier.
Memory Aid
"3 kHz USB at 14.347 MHz = 14.347-14.350 MHz. Think 'U'SB = 'U'pper sideband = 'U'pper frequencies. USB extends from carrier to (carrier + 3 kHz). Upper sideband uses frequencies above the carrier."
Real-World Application
You operate USB on 20 meters with carrier at 14.347 MHz. Your 3 kHz USB signal occupies 14.347-14.350 MHz (from carrier to carrier + 3 kHz). USB uses the upper sideband, so the signal extends above the carrier frequency. This is the USB frequency range.
Key Concepts
Why Other Options Are Wrong
Option A: Incorrect. 14.347-14.647 MHz is way too wide - that's 300 kHz, not 3 kHz. USB extends only 3 kHz above carrier.
Option C: Incorrect. 14.344-14.347 MHz would be LSB (lower sideband) - USB extends above the carrier, not below.
Option D: Incorrect. 14.3455-14.3485 MHz is centered differently - USB extends from carrier to (carrier + 3 kHz), which is 14.347-14.350 MHz.
题目解析
The correct answer is B: 14.347 MHz to 14.350 MHz. The frequency range occupied by a 3 kHz USB signal with the displayed carrier frequency set to 14.347 MHz is 14.347 MHz to 14.350 MHz. USB uses the upper sideband, so the signal extends from carrier to (carrier + 3 kHz). For amateur radio operators, this helps understand SSB frequency ranges. Understanding this helps when operating SSB.
考试技巧
3 kHz USB at 14.347 MHz = 14.347-14.350 MHz. Think 'U'SB = 'U'pper sideband = 'U'pper frequencies (carrier to carrier + 3 kHz). USB extends from 14.347 to (14.347 + 0.003) = 14.347-14.350 MHz. Not below carrier - above carrier.
记忆口诀
3 kHz USB at 14.347 MHz = 14.347-14.350 MHz. Think 'U'SB = 'U'pper sideband = 'U'pper frequencies. USB extends from carrier to (carrier + 3 kHz). Upper sideband uses frequencies above the carrier.
实际应用示例
You operate USB on 20 meters with carrier at 14.347 MHz. Your 3 kHz USB signal occupies 14.347-14.350 MHz (from carrier to carrier + 3 kHz). USB uses the upper sideband, so the signal extends above the carrier frequency. This is the USB frequency range.
错误选项分析
Option A: Incorrect. 14.347-14.647 MHz is way too wide - that's 300 kHz, not 3 kHz. USB extends only 3 kHz above carrier. Option C: Incorrect. 14.344-14.347 MHz would be LSB (lower sideband) - USB extends above the carrier, not below. Option D: Incorrect. 14.3455-14.3485 MHz is centered differently - USB extends from carrier to (carrier + 3 kHz), which is 14.347-14.350 MHz.
知识点
USB, 3 kHz bandwidth, Frequency range, Upper sideband
Verified Content
Question from official FCC General Class question pool. Explanation reviewed by licensed amateur radio operators.