Antenna and Wave Propagation

Hertz was the pioneer and father of radio, his invention remained a laboratory curiosity until 20-year-old Guglielmo Marconi of Bologna, Italy, went on to add tuning circuits, big antenna and ground systems for longer wavelengths, and was able to signal over large distances. In mid-December 1901 he startled the world by receiving signals at St. Johns, Newfoundland, from a transmitting station he had constructed at Poldhu in Cornwall, England.Guglielmo Marconi ¿s square conical antenna at Poldhu, England, in 1905 for sending transatlantic signals at wavelengths of 1000s of meters. Shown in fig. below. Rarely has an invention captured the public imagination as Marconi ¿s wireless did at the beginning of the 20th century. With the advent of radar during World War II, centimeter wavelengths became popular and the entire radio spectrum opened up to wide usage. Thousands of communication satellites bristling with antennas now circle the earth in low, medium, and geostationary orbits. The geostationary satellites form a ring around the earth similar to the rings around Saturn.