Which of the following can cause shielded cables to radiate or receive interference?
The correct answer is B: Common-mode currents on the shield and conductors. Which of the following can cause shielded cables to radiate or receive interference is common-mode currents on the shield and conductors. Common-mode currents cause shielded cables to radiate. For amateur radio operators, this is important for reducing interference. Understanding this helps when troubleshooting cable radiation.
Exam Tip
Shielded cable radiation cause = common-mode currents on shield and conductors. Think 'S'hielded 'C'able 'R'adiation = 'C'ommon-'M'ode 'C'urrents. Common-mode currents cause shielded cables to radiate. Not low inductance ground, not braided shielding, not differential-mode - just common-mode currents.
Memory Aid
"Shielded cable radiation cause = common-mode currents on shield and conductors. Think 'S'hielded 'C'able = 'C'ommon-mode. Common-mode currents cause shielded cables to radiate. Important for reducing interference."
Real-World Application
Shielded cables: They can radiate or receive interference when common-mode currents flow on the shield and conductors. Common-mode currents (currents flowing in the same direction on all conductors) can cause the cable to act as an antenna. This is the cause - common-mode currents.
Key Concepts
Why Other Options Are Wrong
Option A: Incorrect. Low inductance ground connections at both ends doesn't cause radiation - common-mode currents do. Low inductance ground isn't the cause.
Option C: Incorrect. Use of braided shielding material doesn't cause radiation - common-mode currents do. Braided shielding isn't the cause.
Option D: Incorrect. Tying all grounds to common point causing differential-mode currents isn't the cause - common-mode currents cause radiation. Differential-mode isn't the cause.
题目解析
The correct answer is B: Common-mode currents on the shield and conductors. Which of the following can cause shielded cables to radiate or receive interference is common-mode currents on the shield and conductors. Common-mode currents cause shielded cables to radiate. For amateur radio operators, this is important for reducing interference. Understanding this helps when troubleshooting cable radiation.
考试技巧
Shielded cable radiation cause = common-mode currents on shield and conductors. Think 'S'hielded 'C'able 'R'adiation = 'C'ommon-'M'ode 'C'urrents. Common-mode currents cause shielded cables to radiate. Not low inductance ground, not braided shielding, not differential-mode - just common-mode currents.
记忆口诀
Shielded cable radiation cause = common-mode currents on shield and conductors. Think 'S'hielded 'C'able = 'C'ommon-mode. Common-mode currents cause shielded cables to radiate. Important for reducing interference.
实际应用示例
Shielded cables: They can radiate or receive interference when common-mode currents flow on the shield and conductors. Common-mode currents (currents flowing in the same direction on all conductors) can cause the cable to act as an antenna. This is the cause - common-mode currents.
错误选项分析
Option A: Incorrect. Low inductance ground connections at both ends doesn't cause radiation - common-mode currents do. Low inductance ground isn't the cause. Option C: Incorrect. Use of braided shielding material doesn't cause radiation - common-mode currents do. Braided shielding isn't the cause. Option D: Incorrect. Tying all grounds to common point causing differential-mode currents isn't the cause - common-mode currents cause radiation. Differential-mode isn't the cause.
知识点
Shielded cables, Radiate or receive interference, Common-mode currents, Shield and conductors
Verified Content
Question from official FCC Extra Class question pool. Explanation reviewed by licensed amateur radio operators.