Skywave

As the sky wave from a transmitter propagating electromagnetic wave is called that does not follow, in contrast to bump the curvature of the earth, but in a straight line like light "in the room " spreads. In a certain frequency range they can get back to Earth by reflections from the ionosphere by a great distance. Since the ionosphere has no hard reflecting surface, one must, strictly speaking, not by reflection but by refraction speak.

At high frequencies in the HF, VHF and radar range as well as the satellite radio is only the space wave of interest because the bump is absorbed after a very short distance. In the long and medium waveband both observed and can interfere with each other by interference. In this frequency range, the space wave is absorbed by the ionosphere during the day and did not come to the reflecting layer, which is why at night in these frequency ranges more stations can be received than in the daytime hours.

The space wave is short-wave broadcasting of major importance (→ reflection of short waves in the ionosphere ). The damping is low and between about 5 MHz and 30 MHz body waves off the ionosphere are reflected particularly well and move back to the surface. From there, the signal can be reflected again to the ionosphere. In this way, the radio waves can be received around the world worldwide. This reflection can be disrupted in a magnetic storm so that the space wave is no longer observable at a great distance.

Body waves of FM transmitters are hardly absorbed in the ionosphere and not or only very poorly reflected. For this reason, FM stations can be received as a rule only where the transmitting antenna is visible ( quasi-optical propagation ). In certain weather inversions, however, there may be overreaching. In addition, FM waves can be diffracted by obstacles and the more so the larger the wavelength.