Advanced Qualification · A-007 Feedlines and matching · A-007-003-004
Assuming a velocity factor of 0.66 what would be the physical length of a typical coaxial stub that is electrically one quarter wavelength long at 14.1 MHz?
- A 20 metres (65.6 feet)
- B 2.33 metres (7.64 feet)
- C 0.25 metre (0.82 foot)
- D 3.51 metres (11.5 feet)
Correct answer: D — 3.51 metres (11.5 feet). From the official ISED question bank, verified word for word.
Why
At 14.1 MHz, a full wavelength in free space is about 21.3 metres, but a quarter wavelength is only 5.3 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.