- April 11, 2007 at 10:13 am #6887wdcxParticipant
Total posts : 451
Broadcast began in Italy:
Thank you, Mr. Marconi!
Gugliemo Marconi, born on 25 April 1874 in Bologna, Italy, had the incredible foresight and intuition to create the reality of wireless communication. Triumphant in things that many people before him had attempted but
never succeeded, Marconi knew how to take advantage of his success by becoming, at just 23 years of age, the chief of a first-class international industry and one of the most important personalities in the history of technological development.
Enjoy.April 12, 2007 at 1:24 pm #15242Ermi RoosGuest
Total posts : 45366
Marconi was a great inventor, but he was not the one who invented wireless communications. Several other people designed wireless telegraphy equipment before Marconi. There were people working on wireless communications even before Hertz performed his 1888 experiment that proved the existence of the electromagnetic waves predicted by Maxwell. The earlier wireless devices used induction, and had very little range.
What Marconi did was find an important new use for existing wireless inventions. It was “known” by the leading scientists in 1901 that light was made up of electromagnetic waves, and that radio waves traveled in a straight line, just like light waves. It was therefore considered to be impossible to transmit beyond the horizon. It had been demonstrated that wireless signals can go over hills, but this had been accounted for by the diffraction of the radio waves. It was certainly considered to be impossible to send a wireless signal across the Atlantic. Over a distance of 1800 miles, there is a “hill” about 100 miles high due to the curvature of the earth. In his 1901 experiment, Marconi demonstrated that, by using vertical polarization of the electric field, the signal travels along the surface of the earth, provided that the carrier frequency is low enough. Today, this is known as groundwave propagation. Some people did not believe that Marconi’s 1901 experiment actually worked, because that would have meant that the laws of physics were violated. In modern times, conventional scientific opinion has usually been correct, but this is an example of when it was not.
Marconi’s antennas were electrically short vertical antennas over ground, similar in principle to what is used for Part 15 AM today. He had to use electrically short antennas because the wavelengths he used were very long.
For the first two decades of the Twentieth Century, the principal mode of radio communications was telegraphy at low frequencies. Later, most low-frequency, long distance, communications was replaced by HF telegraphy and telephony. Today, of course, satellites are used.April 13, 2007 at 8:41 pm #15248RattanGuest
Total posts : 45366
“Nine months after his death, the US Supreme Patent Court determined that Tesla, not Marconi, should be considered the father of wireless transmission and radio, a somewhat belated` victory for the deceased inventor.”
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