Basic Qualification · B-006 Feedlines and antenna systems · B-006-008-002
A wire dipole has a resonant frequency of 3600 kHz. How can you change its resonant frequency to 3900 kHz?
- A Use larger diameter wire
- B Make it shorter
- C Make it longer
- D Install it as a sloper
Correct answer: B — Make it shorter. From the official ISED question bank, verified word for word.
Why
To raise the resonant frequency from 3600 kHz to 3900 kHz, you must make the antenna shorter because a shorter wire vibrates faster, just as a shorter guitar string produces a higher note. 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.