Which mode is most commonly used for voice communications on the 160-, 75-, and 40-meter bands?
The correct answer is B: Lower sideband. Lower sideband (LSB) is most commonly used for voice communications on the 160-, 75-, and 40-meter bands. These bands are below 10 MHz, where LSB is the standard convention. For amateur radio operators, understanding this convention ensures compatibility - everyone uses LSB on these bands. This is an important operating convention that allows proper communication.
Exam Tip
160m, 75m, 40m = Lower sideband. Think 'L'ower 'S'ideband for 'L'ower frequencies (below 10 MHz). LSB is standard for 160m, 75m, and 40m. USB is for higher frequencies (14 MHz and above).
Memory Aid
"160m, 75m, 40m = Lower sideband. Think 'L'ower 'S'ideband for 'L'ower frequencies. LSB convention: 160m, 75m, 40m use LSB. USB is for 20m, 15m, 12m, 10m, VHF/UHF (14 MHz and above)."
Real-World Application
You operate SSB on 40 meters (7 MHz). Everyone uses lower sideband on this band - it's the standard convention. If you transmitted upper sideband, your signal would be on the wrong side of the carrier, and other operators wouldn't be able to copy you properly. LSB ensures compatibility on these lower frequency bands.
Key Concepts
Why Other Options Are Wrong
Option A (Upper sideband): Incorrect. USB is used on frequencies above 10 MHz (20m, 15m, 12m, 10m), not on 160m, 75m, and 40m. LSB is standard below 10 MHz.
Option C (Suppressed sideband): Incorrect. This describes the technique, 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 LSB is used on 160m, 75m, and 40m.
题目解析
The correct answer is B: Lower sideband. Lower sideband (LSB) is most commonly used for voice communications on the 160-, 75-, and 40-meter bands. These bands are below 10 MHz, where LSB is the standard convention. For amateur radio operators, understanding this convention ensures compatibility - everyone uses LSB on these bands. This is an important operating convention that allows proper communication.
考试技巧
160m, 75m, 40m = Lower sideband. Think 'L'ower 'S'ideband for 'L'ower frequencies (below 10 MHz). LSB is standard for 160m, 75m, and 40m. USB is for higher frequencies (14 MHz and above).
记忆口诀
160m, 75m, 40m = Lower sideband. Think 'L'ower 'S'ideband for 'L'ower frequencies. LSB convention: 160m, 75m, 40m use LSB. USB is for 20m, 15m, 12m, 10m, VHF/UHF (14 MHz and above).
实际应用示例
You operate SSB on 40 meters (7 MHz). Everyone uses lower sideband on this band - it's the standard convention. If you transmitted upper sideband, your signal would be on the wrong side of the carrier, and other operators wouldn't be able to copy you properly. LSB ensures compatibility on these lower frequency bands.
错误选项分析
Option A (Upper sideband): Incorrect. USB is used on frequencies above 10 MHz (20m, 15m, 12m, 10m), not on 160m, 75m, and 40m. LSB is standard below 10 MHz. Option C (Suppressed sideband): Incorrect. This describes the technique, 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 LSB is used on 160m, 75m, and 40m.
知识点
Lower sideband, LSB, 160m, 75m, 40m, SSB conventions
Verified Content
Question from official FCC General Class question pool. Explanation reviewed by licensed amateur radio operators.