Which of the following can create intermittent loud roaring or buzzing AC line interference?
The correct answer is D: All these choices are correct. Which of the following can create intermittent loud roaring or buzzing AC line interference includes: arcing contacts in a thermostatically controlled device, a defective doorbell or doorbell transformer inside a nearby residence, and a malfunctioning illuminated advertising display. All three can create this interference. For amateur radio operators, this is important for troubleshooting interference. Understanding this helps when identifying interference sources.
Exam Tip
All three can create intermittent loud roaring/buzzing AC line interference: arcing contacts, defective doorbell, malfunctioning display. When all listed sources can create this interference, 'all of the above' is usually the answer. All are valid interference sources.
Memory Aid
"All three can create intermittent loud roaring/buzzing AC line interference: Arcing contacts, Defective doorbell, Malfunctioning display. Think 'A'll 'A'C 'I'nterference sources. All three are valid interference sources. Important for troubleshooting interference."
Real-World Application
Intermittent loud roaring or buzzing AC line interference: It can be created by arcing contacts in a thermostatically controlled device, a defective doorbell or doorbell transformer inside a nearby residence, and a malfunctioning illuminated advertising display. All three can cause this type of interference. This is what can create it - all these sources.
Key Concepts
Why Other Options Are Wrong
Option A: While correct, this is incomplete. Defective doorbell and malfunctioning display can also create this interference.
Option B: While correct, this is incomplete. Arcing contacts and malfunctioning display can also create this interference.
Option C: While correct, this is incomplete. Arcing contacts and defective doorbell can also create this interference.
题目解析
The correct answer is D: All these choices are correct. Which of the following can create intermittent loud roaring or buzzing AC line interference includes: arcing contacts in a thermostatically controlled device, a defective doorbell or doorbell transformer inside a nearby residence, and a malfunctioning illuminated advertising display. All three can create this interference. For amateur radio operators, this is important for troubleshooting interference. Understanding this helps when identifying interference sources.
考试技巧
All three can create intermittent loud roaring/buzzing AC line interference: arcing contacts, defective doorbell, malfunctioning display. When all listed sources can create this interference, 'all of the above' is usually the answer. All are valid interference sources.
记忆口诀
All three can create intermittent loud roaring/buzzing AC line interference: Arcing contacts, Defective doorbell, Malfunctioning display. Think 'A'll 'A'C 'I'nterference sources. All three are valid interference sources. Important for troubleshooting interference.
实际应用示例
Intermittent loud roaring or buzzing AC line interference: It can be created by arcing contacts in a thermostatically controlled device, a defective doorbell or doorbell transformer inside a nearby residence, and a malfunctioning illuminated advertising display. All three can cause this type of interference. This is what can create it - all these sources.
错误选项分析
Option A: While correct, this is incomplete. Defective doorbell and malfunctioning display can also create this interference. Option B: While correct, this is incomplete. Arcing contacts and malfunctioning display can also create this interference. Option C: While correct, this is incomplete. Arcing contacts and defective doorbell can also create this interference.
知识点
Intermittent loud roaring or buzzing, AC line interference, Arcing contacts, Defective doorbell, Malfunctioning advertising display
Verified Content
Question from official FCC Extra Class question pool. Explanation reviewed by licensed amateur radio operators.