Communication takes many forms such as speech, writing, television, radio, etc. In this project, the subject of radio is used to serve as our tool in talking about communication theory. Radio basically transmits intelligence signal without wires from one point to another by means of electromagnetic wave. These electromagnetic waves are radiation of energies from a transmitting source. These waves consist of some sinusoidal functions that are composed of sine waves. The following picture shows an electromagnetic wave. We can apply the materials from trigonometry to communication since data are transmitted in term of sinusoidal functions. The Java page will serve the purpose of broaden the student's view on trigonometry and its use in the field of communication.
The above wave is very similar to any sine or cosine waves. The
first electromagnetic waves of radio were conceived by James Clerk Maxwell
in 1864. He published his first paper to show that an electrical disturbance
result from a changing in voltage or current should travel at the speed
of light.
The following is the overview on the history of radio:
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Early 1800s Faraday and Henry independently developed the theories
of current travel |
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1820s Oersted proves that current-flowing wire sets up a magnetic
field |
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1864 Maxwell writes a paper to the effect that electrical disturbance
should travel at the light speed |
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1883 Edison makes observation regarding the direction of current
travel |
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Late 1880s Hertz produces the first electromagnetic wave |
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1895 Marconi produces the first practical wireless telegraph system |
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1896 Marconi receives first wireless patent |
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March 1899 Marconi sends signal across the English Channel |
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12 December 1901 Marconi sends the first trans-Atlantic signal |
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1905 First diode produced by Fleming |
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1906 Fessenden sends the first human speech |
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1907 DeForest invents triode |
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1909 Marconi shares Nobel Prize in Physics |
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April 1912 Sarnoff broadcasts the first news about the SS Titanic |
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1912 Armstrong invents the superheterodyne circuit |
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1916 Sarnoff submits idea for a radio music box |
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WWI Schottky experiments with the tetrode |
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1919 Eccles introduces the terms diode and triode |
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1924 Hull creates the 4-electrode tube |
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1925-33 Armstrong invents FM |
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1926 Tellegen adds suppresser grid to create the pentode |