Radio Waves - Propagation Of Radio Waves, Transmission Of Radio Waves, Modulating A Sound Wave
marconi frequencies electromagnetic band
Radio waves are a form of electromagnetic radiation with long wavelengths and low frequencies. The radio section of the electromagnetic spectrum covers a fairly wide band and includes waves with frequencies ranging from about 10 kilohertz to about 60,000 megahertz (which correspond to wavelengths between 98,000 ft, or 30,000 m, and 0.2 in, or 0.5 cm). The commercial value of radio waves as a means of transmitting sounds was first appreciated by the Italian inventor Guglielmo Marconi in the 1890s. Marconi's invention led to the wireless telegraph, the radio, and eventually to such variations as the AM radio, FM radio, and CB (citizen's band) radio.
Additional Topics
Radio waves travel by three different routes from their point of propagation to their point of detection. These three routes are through the troposphere, through the ground, and by reflection off the ionosphere. The first of these routes is the most direct. A radio wave generated and transmitted from point A may travel in a relatively straight line through the lower atmosphere to a second point, B…
The radio wave that leaves a transmitting antenna originates as a sound spoken into a microphone. A microphone is a device for converting sound energy into electrical energy. A microphone accomplishes this transformation by any one of a number of mechanisms. In a carbon microphone, for example, sound waves entering the device cause a box containing carbon granules to vibrate. The vibrating carbon …
The simple transmission scheme outlined above cannot be used for commercial broadcasting. If a dozen stations all transmitted sounds by the mechanism described above, a receiving station would pick up a garbled combination of all transmissions. To prevent interference from a number of transmitting stations, all broadcast radio waves are first modulated. Modulation is the process by which a sound w…
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