The Radio Experiment7 1897, Marconi sent the first ever wireless communication over opensea. The experiment, witnessed a message transversed over theBristol Channel a distance of 6 kms. The message read "Are youready"
Transatlantic transmissions8 12 December 1901, using a 152.4-metre (500 ft) kite-supported antenna for reception, the message was received atSignal Hill in St Johns, Newfoundland (now part of Canada)signals transmitted by the companys new high-power stationat Poldhu, Cornwall. The distance between the two points wasabout 3,500 kilometres
Wave Propagation9 Ground Wave Sky Wave Space Wave
Sky Wave Propagation10 Radio waves radiated at a high angle and reflectedby these layers return to earth at a distance from thetransmitter.
Orbit Types12 There are three major orbits: geosynchronous orbit(GEO), middle earth orbit (MEO), and low earth orbit(LEO). The majority of communications satelites inuse are GEOs.
Low Earth Orbit (LEO)13 LEO satellites are much closer to the earth thanGEO satellites, ranging from 500 to 1,500 km abovethe surface. LEO satellites don’t stay in fixed position relative tothe surface, and are only visible for 15 to 20 minuteseach pass.
Medium Earth Orbit (MEO)15 A MEO satellite is in orbit somewhere between 8,000km and 18,000 km above the earth’s surface. MEO satellites are similar to LEO satellites infunctionality. MEO satellites are visible for much longer periods oftime than LEO satellites, usually between 2 to 8hours. MEO satellites have a larger coverage area thanLEO satellites.
Geostationary Earth Orbit (GEO)18 These satellites are in orbit 35,863 km above theearth’s surface along the equator. Objects in Geostationary orbit revolve around theearth at the same speed as the earth rotates. Thismeans GEO satellites remain in the same positionrelative to the surface of earth.• A GEO satellite’s distance from earth gives it a largecoverage area, almost a fourth of the earth’s surface.
Artificial Satellites20 The Soviet Union launched Sputnik 1 on Oct. 4,1957. The world’s first artificial satellite
Artificial Satellites21Sputnik-2 equipped with a rudimentary life support systemto keep its passenger, a dog named Laika
India’s First Satellite22Aryabhatta April 19, 1975 , Soviet Intercosmos rocket
How do Satellites Work23 Two Stations on Earth want to communicate throughradio broadcast but are too far away to useconventional means. The two stations can use a satellite as a relay stationfor their communication One Earth Station sends a transmission to thesatellite. This is called a Uplink. The satellite Transponder converts the signal andsends it down to the second earth station. This iscalled a Downlink.