Advanced Qualification · A-007 Feedlines and matching · A-007-005-010
In amateur work, what is the surface error upper limit you should try not to exceed on a parabolic reflector?
- A 0.1 lambda
- B 0.25 lambda
- C 5 mm (0.2 in) regardless of frequency
- D 1% of the diameter
Correct answer: A — 0.1 lambda. From the official ISED question bank, verified word for word.
Why
A surface error limit of 0.1 lambda ensures the reflected radio waves stay in step, or in phase, so they combine to form a strong signal rather than cancelling each other out. 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.