Basic Qualification · B-007 Radio wave propagation · B-007-001-002
Que permet la propagation par onde ionosphérique à incidence quasi verticale ("NVIS")?
- ADes communications à l'échelle d'un continent
- BDes communications HF à moyenne portée, notamment en terrain accidenté
- CDes communications HF mondiales par sauts multiples
- DDes communications régionales audessus de la fréquence critique
Correct answer: B — Des communications HF à moyenne portée, notamment en terrain accidenté. Question tirée de la banque officielle d'ISDE.
Why
Near vertical incidence sky-wave, or NVIS, sends radio signals almost straight up so they bounce off the ionosphere and return to Earth nearby, filling the gap between ground wave and long-distance sky wave. The full explanation — and one for every question — is in Pro.
Practise this section
Radio wave propagation is section B-007 of the Basic exam: How signals travel: the ionosphere and its layers, skip, ground wave, sporadic E, and which bands work when.
Drill B-007 — free, no account