Advanced Qualification · A-007 Feedlines and matching · A-007-003-006
A quarter-wave stub, for use at 15 MHz, is made from a coaxial cable having a velocity factor of 0.8. Its physical length will be:
- A 4 m (13.1 ft)
- B 12 m (39.4 ft)
- C 8 m (26.2 ft)
- D 7.5 m (24.6 ft)
Correct answer: A — 4 m (13.1 ft). From the official ISED question bank, verified word for word.
Why
At 15 MHz, a full wavelength in free space is 20 metres, so a quarter-wave section is normally 5 metres. The full explanation — and one for every question — is in Pro.
Practise this section
Feedlines and matching at the advanced level: transmission line theory, impedance transformation, stubs and matching networks.