Extra exam question E4E05
Subelement E4, AMATEUR PRACTICES· Group E4E
What is used to suppress radio frequency interference from a line-driven AC motor?
- A.A high-pass filter in series with the motor’s power leads
- B.A brute-force AC-line filter in series with the motor’s power leads (correct answer)
- C.A bypass capacitor in series with the motor’s field winding
- D.A bypass choke in parallel with the motor’s field winding
WhyRadio frequency interference from a line-driven AC motor is suppressed with a brute-force AC-line filter in series with the motor's power leads. RFI from a line-driven AC motor is commonly suppressed with a brute-force AC-line filter installed in series with the motor's power leads, blocking the noise the motor's brushes or switching generate from propagating back onto the power line and radiating, answer B. A high-pass filter would let the higher-frequency noise straight through instead of blocking it, and bypass capacitors or chokes on the field winding aren't the standard fix for line-conducted motor noise.
Published 2026-08-28 · Last updated 2026-08-28 · Question text is verbatim from the 2024-2028 NCVEC Element 4 pool (public domain); the explanation above is original writing, see our methodology.
Related questions
- E4E01What problem can occur when using an automatic notch filter (ANF) to remove interfering carriers while receiving CW signals?
- E4E02Which of the following types of noise can often be reduced by a digital noise reduction?
- E4E03Which of the following types of noise are removed by a noise blanker?
- E4E04How can conducted noise from an automobile battery charging system be suppressed?
- E4E06What type of electrical interference can be caused by computer network equipment?