Basic Qualification · B-006 Feedlines and antenna systems · B-006-005-007
If the characteristic impedance of the transmission line does not match the antenna input impedance then:
- A the antenna will not radiate any signal
- B standing waves are produced in the transmission line
- C heat is produced at the junction
- D the SWR reading falls to 1:1
Correct answer: B — standing waves are produced in the transmission line. From the official ISED question bank, verified word for word.
Why
When the transmission line's characteristic impedance does not match the antenna's input impedance, some of the radio energy sent down the line bounces back toward the transmitter instead of being radiated. The full explanation — and one for every question — is in Pro.
Practise this section
Getting the signal out: antennas, feedlines, SWR, baluns, matching, and why antenna length depends on frequency.