Skip zone

Transmitting at night is most effective for long-distance communication but the skip zone becomes significantly larger.

Very high frequency waves and higher normally travel through the ionosphere wherefore communication via skywave is exceptional.

In other words, a frequency exists for which vertically incident radio waves will always be refracted back to the Earth.

Skip zone is the subject of a film 'SKIPZONE' made in 1992 by UK artist, Peter Lee-Jones.

[citation needed] In the episode "Short Wave"[1] of Father Knows Best, the family hears a distress call from a small boat at sea.

Formation of a skip-zone using Proplab-Pro 3.
If the radio wave frequency is decreased, a point is reached where all waves (even vertically incident waves) are reflected back to the Earth.