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AM broadcasting
Videos
AM broadcasting is radio broadcasting using amplitude modulation transmissions. It was the first method developed for making audio radio transmissions, and is still used worldwide, primarily for mediu
Lee de Forest used an early vacuum-tube transmitter to broadcast returns for the Hughes-Wilson presidential election returns on November 7, 1916, over 2XG in New York City. Pictured is engineer Charles Logwood.
Lee de Forest used an early vacuum-tube transmitter to broadcast returns for the Hughes-Wilson presidential election returns on November 7, 1916, over
Nellie Melba making a broadcast over the Marconi Chelmsford Works radio station in England on June 15, 1920.
Nellie Melba making a broadcast over the Marconi Chelmsford Works radio station in England on June 15, 1920.
Farmer listening to U.S. government weather and crop reports using a crystal radio in 1923. Public service government time, weather, and farm broadcas
Farmer listening to U.S. government weather and crop reports using a crystal radio in 1923. Public service government time, weather, and farm broadcasts were the first radio "broadcasts".
1938 Zenith Model 12-S vacuum-tube console radio, capable of picking up mediumwave and shortwave AM transmissions. "All Wave" receivers could also pic
1938 Zenith Model 12-S vacuum-tube console radio, capable of picking up mediumwave and shortwave AM transmissions. "All Wave" receivers could also pick up the third AM band: longwave (LW).
Amplitude modulation
Videos
Amplitude modulation is a signal modulation technique used in electronic communication, most commonly for transmitting messages with a radio wave. In amplitude modulation, the instantaneous amplitude
One of the crude pre-vacuum tube AM transmitters, a Telefunken arc transmitter from 1906. The carrier wave is generated by 6 electric arcs in the vertical tubes, connected to a tuned circuit. Modulation is done by the large carbon microphone (cone shape) in the antenna lead.
One of the crude pre-vacuum tube AM transmitters, a Telefunken arc transmitter from 1906. The carrier wave is generated by 6 electric arcs in the vert
One of the first vacuum tube AM radio transmitters, built by Meissner in 1913 with an early triode tube by Robert von Lieben. He used it in a historic
One of the first vacuum tube AM radio transmitters, built by Meissner in 1913 with an early triode tube by Robert von Lieben. He used it in a historic 36 km (22 mi) voice transmission from Berlin to Nauen, Germany. Compare its small size with the arc transmitter above.
Figure 3: The spectrogram of an AM voice broadcast shows the two sidebands (green) on either side of the carrier (red) with time proceeding in the ver
Figure 3: The spectrogram of an AM voice broadcast shows the two sidebands (green) on either side of the carrier (red) with time proceeding in the vertical direction.