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First Voice Radio Transmission

July 6th Fact-of-the-Day

Professor Reginald Aubrey Fessenden was the first person to successfully transmit human voice by radio. The transmission took place December 23, 1900, between a transmitter and receiver located on Cobb Island in Maryland. The transmission distance was 1,600 meters. Identical antennas supported by 15-meter masts were used on each end. The RF carrier was produced by a spark transmitter that produced 10,000 sparks per second. The carrier was amplitude-modulated by means of an asbestos-insulated carbon microphone inserted in series with the transmitting antenna feed-line. Sound-waves varied the microphone resistance which modulated the antenna current and consequently the amplitude of the radiated RF signal. The received voice signal was reportedly accompanied by disagreeable noise, but was said to have been perfectly intelligible. ©2005 Martek International All rights reserved.


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