How close to the upper edge of a band’s phone segment should your displayed carrier frequency be when using 3 kHz wide USB?
The correct answer is B: At least 3 kHz below the edge of the band. How close to the upper edge of a band's phone segment your displayed carrier frequency should be when using 3 kHz wide USB is at least 3 kHz below the edge of the segment. USB extends above the carrier, so you need 3 kHz clearance below the edge to prevent out-of-band operation. For amateur radio operators, this ensures legal operation. Understanding this helps when operating near band edges.
Exam Tip
USB near upper edge = at least 3 kHz below edge. Think 'U'SB = 'U'pper sideband extends 'U'pper, so need clearance 'B'elow edge. USB extends above carrier, so need 3 kHz clearance below upper edge. Not above edge, not 1 kHz - just 3 kHz below.
Memory Aid
"USB near upper edge = at least 3 kHz below edge. Think 'U'SB = 'U'pper sideband extends 'U'pper, so need clearance 'B'elow. USB extends above carrier, so need 3 kHz clearance below upper edge. Ensures legal operation."
Real-World Application
The upper edge of the phone segment is 14.350 MHz. You operate 3 kHz USB. Your carrier must be at least 14.347 MHz (3 kHz below the edge) so your signal (which extends 3 kHz above the carrier) doesn't go above 14.350 MHz. This ensures legal operation.
Key Concepts
Why Other Options Are Wrong
Option A: Incorrect. 3 kHz above the edge would put you out of band - USB extends above the carrier, so you need clearance below the edge, not above.
Option C: Incorrect. 1 kHz above the edge would put you out of band - you need 3 kHz clearance below the edge for 3 kHz USB.
Option D: Incorrect. 1 kHz below the edge isn't enough - you need 3 kHz clearance for 3 kHz USB bandwidth.
题目解析
The correct answer is B: At least 3 kHz below the edge of the band. How close to the upper edge of a band's phone segment your displayed carrier frequency should be when using 3 kHz wide USB is at least 3 kHz below the edge of the segment. USB extends above the carrier, so you need 3 kHz clearance below the edge to prevent out-of-band operation. For amateur radio operators, this ensures legal operation. Understanding this helps when operating near band edges.
考试技巧
USB near upper edge = at least 3 kHz below edge. Think 'U'SB = 'U'pper sideband extends 'U'pper, so need clearance 'B'elow edge. USB extends above carrier, so need 3 kHz clearance below upper edge. Not above edge, not 1 kHz - just 3 kHz below.
记忆口诀
USB near upper edge = at least 3 kHz below edge. Think 'U'SB = 'U'pper sideband extends 'U'pper, so need clearance 'B'elow. USB extends above carrier, so need 3 kHz clearance below upper edge. Ensures legal operation.
实际应用示例
The upper edge of the phone segment is 14.350 MHz. You operate 3 kHz USB. Your carrier must be at least 14.347 MHz (3 kHz below the edge) so your signal (which extends 3 kHz above the carrier) doesn't go above 14.350 MHz. This ensures legal operation.
错误选项分析
Option A: Incorrect. 3 kHz above the edge would put you out of band - USB extends above the carrier, so you need clearance below the edge, not above. Option C: Incorrect. 1 kHz above the edge would put you out of band - you need 3 kHz clearance below the edge for 3 kHz USB. Option D: Incorrect. 1 kHz below the edge isn't enough - you need 3 kHz clearance for 3 kHz USB bandwidth.
知识点
USB, Band edge, 3 kHz clearance, Upper edge
Verified Content
Question from official FCC General Class question pool. Explanation reviewed by licensed amateur radio operators.