Fundamentals of Radio Wave Propagation and NVIS Communication

Radio wave propagation describes how radio signals travel through various modes, including line of sight, surface waves, and ionospheric reflection. Line of sight is direct transmission ideal for VHF and above. Surface waves follow Earth’s contour at lower frequencies, supporting ground wave communication. Ionospheric propagation involves signal refraction by charged particles, enabling long-distance communication via skywaves. The critical frequency marks the limit for signal reflection, while NVIS (Near Vertical Incidence Skywave) uses high-angle transmission for reliable coverage in mountainous or skip zones, especially useful for regional and emergency communications.