Basic Qualification · B-008 Interference and suppression · B-008-005-009
A nearby high-power HF broadcast station in the 31-metre band is interfering with your reception on the 40-metre and 30-metre bands. What type of filter is needed on the receiver to minimize interference?
- A Low-pass
- B High-pass
- C Band-reject
- D Band-pass
Correct answer: C — Band-reject. From the official ISED question bank, verified word for word.
Why
A band-reject filter is the right choice because it blocks a specific range of frequencies while letting others pass, which stops the strong 31-metre broadcast signal from drowning out your 40-metre and 30-metre reception. 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.