Advanced Qualification · A-007 Feedlines and matching · A-007-007-011
Which antenna system and operating frequency are most suitable for Near Vertical Incidence (NVIS) communications?
- AA horizontal antenna at a height of half wavelength and an operating frequency the optimum working frequency
- BA vertical antenna and a frequency below the maximum usable frequency
- CA vertical antenna and a frequency above the lowest usable frequency
- DA horizontal antenna less than 1/4 wavelength above ground and a frequency below the current critical frequency
Correct answer: D — A horizontal antenna less than 1/4 wavelength above ground and a frequency below the current critical frequency. From the official ISED question bank, verified word for word.
Why
To bounce signals straight up for short-range coverage, you need a horizontal antenna mounted very low, under a quarter wavelength high, which forces the radio waves upward instead of out to the horizon. The full explanation — and one for every question — is in Pro.
Practise this section
Feedlines and matching is section A-007 of the Advanced exam: Feedlines and matching at the advanced level: transmission line theory, impedance transformation, stubs and matching networks.
Drill A-007 — free, no account