Question
Which of the following can create intermittent loud roaring or buzzing AC line interference?
Answer Options
- A) Arcing contacts in a thermostatically controlled device
- B) A defective doorbell or doorbell transformer inside a nearby residence
- C) A malfunctioning illuminated advertising display
- D) All these choices are correct
Correct Answer: D
Explanation
Intermittent loud roaring or buzzing interference on the radio bands is a classic signature of electrical arcing or sparking, often involving a device cycling on or off. The arcing generates high-frequency broadband noise, which can be radiated by power lines acting as large antennas.
Common sources of this arcing-type interference include: arcing contacts in a thermostatically controlled device (like a furnace or water heater); sparking from a defective doorbell or doorbell transformer (due to the low voltage/high current circuit); and switching or arcing components in a malfunctioning illuminated advertising display (neon or fluorescent signs). Therefore, all these choices are correct.
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