What Is The Fundamental Idea Of Radio And Television Transmission?

Radio waves sent out by radio stations are reflected by the ionosphere (a part of the atmosphere which extends from 60 to 500 km above the earth) and can be received anywhere on the earth. Due to slight absorption in the ionosphere, the radio signals received at far off places are rather weak. At night the radio reception improves because the layers of the ionosphere are not exposed to sunlight and are more settled.

High-frequency waves carrying television signals penetrate the ionosphere and are not received like radio signals. Television transmission is there-fore accomplished on a 'line-of-sight' basis. This explains why television programmes can only be received over a limited range. The curvature of the earth limits the range of television reception. However, geostationary satellites are being used these days for television (and telephone) links between places anywhere on the earth.