is reduced further, the radio waves penetrate through the ionosphere. For a particular angle of incidence, the point of reception (B) is at the minimum distance from transmitter. The shortest distance between the transmitter and the point of reception of the sky wave along the surface is called as the skip distance . The ground waves get attenuated as they move away from the transmitter.
At a particular point (A), there is no reception ground wave. The zone (in between A and B) where there is no reception of electromagnetic waves neither ground nor sky is known as skip zone or skip area (Figure . (b)). iii) Space wave propagation The process of sending and receiving information signal through space is called space wave communication (Figure .
(c)). The electromagnetic waves of very high frequencies above MHz are called as space waves. These waves travel in a straight line from the transmitter to the receiver. Hence, it is used for a line of sight communication (LOS).
The communication systems like television telecast, satellite communication and RADAR are based on space wave propagation. - - - - - - - - Unit electronics and Communication i) Weather satellites: They are used to monitor the weather and climate of Earth. By measuring cloud mass, these satellites enable us to predict rain and dangerous storms like hurricanes, cyclones etc. ii) Communication satellites: They are used to transmit television, radio, internet signals etc.
Multiple satellites are used for long distance communication. iii) Navigation satellites: These are employed to determine the geographic location of ships, aircrafts or any other object. . .
FIBRE OPTIC COMMUNICATION The method of transmitting information from one place to another in terms of light pulses through an optical fiber is called fiber optic communication. It works on the principle of total internal reflection. Rh Rh R h h 42217 km . SOME IMPORTANT COMMUNICATION SYSTEMS There are a large number of communication systems available in the market for varied purposes.