Basic Qualification · B-008 Interference and suppression · B-008-005-004
Why should the impedance of a filter match the transmission line where it is inserted?
- A To preserve the balance of the line
- B To minimize noise in the receiver
- C To prevent spurious emissions
- D To avoid unwanted reflection
Correct answer: D — To avoid unwanted reflection. From the official ISED question bank, verified word for word.
Why
When a filter's impedance does not match the transmission line, the radio signal hits a mismatch and bounces back toward the source instead of moving forward. 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.