RF Engineering
What Is NVIS? Near Vertical Incidence Skywave for Regional and Emergency Radio
Near vertical incidence skywave, or NVIS, is a high frequency technique that sends the signal almost straight up so it reflects off the ionosphere and returns over a wide area beneath the antenna, with no skip zone and no need for line of sight. It is how you hold a reliable radio net across rugged or remote country, which makes it central to regional and emergency communication in Australia. This guide explains how NVIS works, the band it uses, why the frequency has to follow the ionosphere up by day and down by night, a worked frequency choice, why the antenna is mounted low, and where it fits for emergency services, mining and pastoral operations.