Basic Qualification · B-008 Interference and suppression · B-008-002-004
What sound is heard from a public address system if audio rectification of a nearby CW transmission occurs?
- A Audible, possibly distorted speech
- B Muffled, severely distorted speech
- C A steady whistling
- D On-and-off humming or clicking
Correct answer: D — On-and-off humming or clicking. From the official ISED question bank, verified word for word.
Why
When a continuous wave (CW) transmission hits a public address system, the equipment acts like a crude radio detector, turning the radio signal into an electrical pulse. The full explanation — and one for every question — is in Pro.
Practise this section
When things interfere: harmonics, overload, RFI to and from your station, filters, ferrites and how to fix the neighbour's TV.