Communications and Media

Radio

The radius is a media that relies on sending signals of audio through waves of radius, although the term is also used for other forms of sending audio to distance and Internet radio. The radio is the technology that enables the transmission of signals by modulation (in frequency or amplitude) of electromagnetic waves. These waves do not require physical means of transportation, so it can spread through both air and empty space.

A radio wave arises when a charged particle (for example, an electron) is excited at a frequency situated in the radio frequency (RF) of electromagnetic spectrum . When the radio wave acts on an electrical conductor (the antenna), it induces motion of an electrical load (electric current), which can be transformed into audio signals or other signals carrying information.

It is difficult to attribute the invention of radio to a single person. In 1873, the Scottish physicist James Clerk Maxwell formulated the theory of electromagnetic waves, which are the basis of the radio. In 1888, the German physicist Heinrich Hertz discovered radio waves. In 1894, Nikola Tesla made his first public demonstration of radio transmission, and about the time, in 1895, Italian Guglielmo Marconi built the first radio system, and in 1901 was able to send signals to the other side of the Atlantic. The Spanish Julio Cervera Baviera , who served three months in 1898 in Marconi's private laboratory, according to research by a professor at the University of Navarra, is the inventor of the radio before Marconi invented wireless telegraphy Cervera.

The first regular entertainment broadcasts began in 1920 in Argentina. The first station on a regular basis and information is considered by many authors 8MK station (now WWJ) in Detroit (United States) belonging to The Detroit News that began operations on August 20, 1920. Although, many authors believe that KDKA in Pittsburgh began broadcasting in November 1920, it obtained a business license before it. In the 1920's, amplification by thermionic valve revolutionized both radio receivers and radio transmitters (Umble, pp. 06-06).

In 1933, Edwin Armstrong describes a system of high quality radio, less sensitive to the AM radio interference, using frequency modulation (FM). At the end of the decade, this procedure is established on a commercial basis, while riding in charge of Armstrong himself a station with this system.

In 1943, the Supreme Court of the United States gives to Tesla rights invention of radio and then to bring this suit for plagiarism of their patents. In the 1950's, wireless technology underwent a number of improvements that resulted in the widespread use of the transistor. In 1957, the company introduced the first recipient Regency transistor, small enough to be carried in a pocket and powered by a small battery. It was not reliable because the valves have no heat. For the next twenty years, transistors displaced valves almost completely, except for very high powers and frequencies.

Between the decades of the years 1960 and 1980, the radio enters a period of decline due to competition from television and the ...