What is near vertical incidence skywave (NVIS) propagation?
Propagation near the MUF
Short distance MF or HF propagation at high elevation angles✓الإجابة الصحيحة
Long path HF propagation at sunrise and sunset
Double hop propagation near the LUF
الشرح
NVIS works by launching energy almost straight up on a frequency below the vertical incidence critical frequency, so it is returned steeply and lands in a circle a few hundred kilometers across with no skip zone. It is a short-range technique for MF and lower HF, not a long-path or near-MUF technique.