Which mode is most commonly used for voice communications on frequencies of 14 MHz or higher?
The correct answer is A: Upper sideband. Upper sideband (USB) is most commonly used for voice communications on frequencies of 14 MHz or higher. This includes 20 meters, 15 meters, 12 meters, 10 meters, and VHF/UHF bands. USB is the standard for these frequencies. For amateur radio operators, understanding this convention helps ensure compatibility - everyone uses USB on these bands, allowing proper communication. This is an important operating convention.
Exam Tip
14 MHz and higher = Upper sideband. Think 'U'pper 'S'ideband for 'U'pper frequencies (14 MHz+). USB is standard for 20m, 15m, 12m, 10m, and VHF/UHF. LSB is for lower frequencies (below 10 MHz).
Memory Aid
"14 MHz and higher = Upper sideband. Think 'U'pper 'S'ideband for 'U'pper frequencies. USB convention: 20m, 15m, 12m, 10m, VHF/UHF use USB. LSB is for 160m, 80m, 40m (below 10 MHz)."
Real-World Application
You operate SSB on 20 meters (14 MHz). Everyone uses upper sideband on this band - it's the standard convention. If you transmitted lower sideband, your signal would be on the wrong side of the carrier, and other operators wouldn't be able to copy you properly. USB ensures compatibility on 14 MHz and higher frequencies.
Key Concepts
Why Other Options Are Wrong
Option B (Lower sideband): Incorrect. LSB is used on frequencies below 10 MHz (160m, 80m, 40m), not on 14 MHz and higher. USB is standard above 10 MHz.
Option C (Suppressed sideband): Incorrect. This describes the technique (suppressing one sideband), not which sideband is used. Both USB and LSB are suppressed sideband modes.
Option D (Double sideband): Incorrect. DSB transmits both sidebands, which is inefficient. SSB (single sideband) is standard, and USB is used on 14 MHz and higher.
题目解析
The correct answer is A: Upper sideband. Upper sideband (USB) is most commonly used for voice communications on frequencies of 14 MHz or higher. This includes 20 meters, 15 meters, 12 meters, 10 meters, and VHF/UHF bands. USB is the standard for these frequencies. For amateur radio operators, understanding this convention helps ensure compatibility - everyone uses USB on these bands, allowing proper communication. This is an important operating convention.
考试技巧
14 MHz and higher = Upper sideband. Think 'U'pper 'S'ideband for 'U'pper frequencies (14 MHz+). USB is standard for 20m, 15m, 12m, 10m, and VHF/UHF. LSB is for lower frequencies (below 10 MHz).
记忆口诀
14 MHz and higher = Upper sideband. Think 'U'pper 'S'ideband for 'U'pper frequencies. USB convention: 20m, 15m, 12m, 10m, VHF/UHF use USB. LSB is for 160m, 80m, 40m (below 10 MHz).
实际应用示例
You operate SSB on 20 meters (14 MHz). Everyone uses upper sideband on this band - it's the standard convention. If you transmitted lower sideband, your signal would be on the wrong side of the carrier, and other operators wouldn't be able to copy you properly. USB ensures compatibility on 14 MHz and higher frequencies.
错误选项分析
Option B (Lower sideband): Incorrect. LSB is used on frequencies below 10 MHz (160m, 80m, 40m), not on 14 MHz and higher. USB is standard above 10 MHz. Option C (Suppressed sideband): Incorrect. This describes the technique (suppressing one sideband), not which sideband is used. Both USB and LSB are suppressed sideband modes. Option D (Double sideband): Incorrect. DSB transmits both sidebands, which is inefficient. SSB (single sideband) is standard, and USB is used on 14 MHz and higher.
知识点
Upper sideband, USB, 14 MHz and higher, SSB conventions
Verified Content
Question from official FCC General Class question pool. Explanation reviewed by licensed amateur radio operators.