What is the purpose of Near Vertical Incident Sky Wave (NVIS) communications?

The purpose of Near Vertical Incident Sky Wave (NVIS) communications is to alleviate "skip zones" in radio transmission. NVIS is a method used primarily in high-frequency (HF) radio communication, where signals are transmitted at steep angles towards the ionosphere. This enables the radio waves to effectively bounce back to the earth within relatively short distances, which is particularly useful for establishing communication in areas where direct line-of-sight paths are obstructed or where traditional radio propagation techniques may not be effective.

In NVIS, the signal is transmitted almost vertically, allowing the signal to cover a smaller radius. This is beneficial for local communication, especially in mountainous regions or in situations where longer distance transmission would result in signal fading or loss due to terrain. By utilizing NVIS, operators can effectively connect over distances that would otherwise be impacted by skip zones, which are areas where radio signals fail to reach due to the curvature of the Earth and the characteristics of skywave propagation.

Other options do not accurately reflect the primary purpose of NVIS. While NVIS does allow for some ground-to-ground communication, its main strength is in minimizing the effects of skip zones rather than enhancing communication speed or increasing satellite communication distances.