Editing Skywave (section)

===Near-vertical skywaves===

Skywaves directed almost vertically are referred to as [[Near vertical incidence skywave|''near-vertical-incidence skywaves'' (''NVIS'')]]. At some frequencies, generally in the lower [[shortwave]] region, the high angle skywaves will be reflected directly back towards the ground. When the wave returns to ground it is spread out over a wide area, allowing communications within several hundred miles of the transmitting antenna. NVIS enables local plus regional communications, even from low-lying valleys, to a large area, for example, an entire state or small country. Coverage of a similar area via a line-of-sight VHF transmitter would require a very high mountaintop location. NVIS is thus useful for statewide networks, such as those needed for emergency communications.<ref>{{cite book |editor=Silver, H.L. |year=2011 |title=The ARRL Handbook for Radio Communications |edition=88th |publisher=American Radio Relay League |location=Newington, CT}}</ref> In short wave broadcasting, NVIS is very useful for regional broadcasts that are targeted to an area that extends out from the transmitter location to a few hundred miles, such as would be the case in a country or language group to be reached from within the borders of that country. This will be much more economical than using multiple FM (VHF) or AM broadcast transmitters. Suitable antennas are designed to produce a strong lobe at high angles. When short range skywave is undesirable, as when an AM broadcaster wishes to avoid interference between the ground wave and sky wave, [[anti-fading antennas]] are used to suppress the waves being propagated at the higher angles.