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The early history of radio is the history of technology that produced radio instruments that use radio waves. Within the timeline of radio, many people contributed theory and inventions in what became radio.Radio development began as "wireless telegraphy". Later radio history increasingly involves matters of programming and content.
Various scientists proposed thatelectricity and magnetism, both capable of causing attraction and repulsion of objects, were linked. In 1802 Gian Domenico Romagnosi suggested the relationship between electric current and magnetism, but his reports went unnoticed. In 1820 Hans Christian Ørsted performed a widely known experiment on man-made electric current and magnetism. He demonstrated that a wire carrying a current could deflecta magnetized compass needle. Ørsted's experiments discovered the relationship between electricity and magnetism in a very simple experiment. Ørsted's work influenced André-Marie Ampère to produce a theory of electromagnetism. During its early development and long after wide use of the technology, disputes persisted as to who could claim sole credit for this obvious boon to mankind. Closelyrelated, radio was developed along with two other key inventions, the telegraph and the telephone.
In the late 19th century it was clear to various scientists and experimenters that wireless communication was possible. Various theoretical and experimental innovations led to the development of radio and the communication system we know today. Some early work was done by local effects and experiments ofelectromagnetic induction. Many understood that there was nothing similar to the "ethereal telegraphy" and telegraphy by induction; the phenomena being wholly distinct. Wireless telegraphy was beginning to take hold and the practice of transmitting messages without wires was being developed. Many people worked on developing the devices and improvements.
There are varying disputed claims about whoinvented radio, which in the beginning was called "wireless telegraphy". The key invention for the beginning of "wireless transmission of data using the entire frequency spectrum", known as the spark-gap transmitter, has been attributed to various men. Marconi equipped ships with lifesaving wireless communications and established the first transatlantic radio service. Tesla developed means toreliably produce radio frequency electrical currents, publicly demonstrated the principles of radio, and transmitted long distance signals.
The most common type of receiver before vacuum tubes was the crystal set, although some early radios used some type of amplification through electric current or battery. Inventions of the triode amplifier, motor-generator, and detector enabled audio radio. Theuse of amplitude modulation , with which more than one station can simultaneously send signals was pioneered by Fessenden and Lee de Forest.
To this day there is a small but avid base of fans of this technology who study and practice the art and science of designing and making crystal sets as a hobby; the Boy Scouts of America have often undertaken such craft projects to introduce boys toelectronics and radio, and quite a number of them having grown up remain staunch fans of a radio that 'runs on nothing, forever'. As the only energy available is that gathered by the antenna system, there are inherent limitations on how much sound even an ideal set could produce, but with only moderately decent antenna systems remarkable performance is possible with a superior set.
During the mid 1920s,amplifying vacuum tubes revolutionized radio receivers and transmitters. John Ambrose Fleming developed an earlier tube known as an "oscillation valve" . Lee De Forest placed a screen, the "grid" electrode, between the filament and plate electrode, creating the triode. The Dutch engineer Hanso Schotanus à Steringa Idzerda made the first regular wireless broadcast for entertainment from his home...
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