Basic Qualification · B-008 Interference and suppression · B-008-003-010
What can cause parasitic oscillations in a stage?
- AUnwanted positive feedback
- BUnwanted negative feedback
- COscillator drift
- DPower supply instability
Correct answer: A — Unwanted positive feedback. From the official ISED question bank, verified word for word.
Why
Parasitic oscillations happen when a tiny part of an output signal loops back into the input and gets stronger instead of weaker, which is exactly what unwanted positive feedback does. The full explanation — and one for every question — is in Pro.
Practise this section
Interference and suppression is section B-008 of the Basic exam: When things interfere: harmonics, overload, RFI to and from your station, filters, ferrites and how to fix the neighbour's TV.
Drill B-008 — free, no account