Television+and+News+Media

=The Television=

Home | Radio | Regulation | Television and News Media |

Technologies in television have dramatically altered both politics and culture in America and the world in profound ways. Just think how different our country would be if F.D.R. were unable to communicate to the masses with his famous "Fireside Chats", or what might of happened if the country had not seen the presidential debates between John Kennedy and Richard Nixon. Thinking of these examples, imagine what current politics would be like if these technologies did not exist. Our world, and specifically our political scene, has been irrevocably changed as a result of technologies in radio and television. Technology evolved a lot in order to accomplish these historical feats. The Television was a result of the discovery of the Cathode Ray Tube.

The history of television is long and complex, and for a time followed two parallel lines. The first developments in television technology followed electromechanical designs, and were started as early as the late 1800's. Beginning in the 20th century, discoveries in the now defunct electronic television took off and eventually eclipsed those of electromechanical scientists.

The first true success in the development of “seeing the telegraph” came in 1884 when Paul Nipkow, a German Physicist, received a patent for his design. Incorporated into his design were the achievements of earlier physicist in their own attempts to design a television. Nipkows design included the use of an electron tube to amplifying the weak signal being broadcast by stations, and the correct use of selenium in a photo tube combined with a scanning disk, two features later developed for more successful devices. His scanning disk was a single row of holes arranged so that they spiral inward toward the center from a point near the edge. The disk revolves in front of a light-sensitive plate on which a lens forms an image; each hole passes across, or “scans,” a narrow, ring-shaped sector of the image. the holes trace contiguous concentric sectors, so that in one revolution of the disk the entire image is scanned. When the light-sensitive cell is connected in an electric circuit, the variations in light cause corresponding fluctuations in the electric current. The image can be reproduced by a receiver whose luminous area is scanned by a similar disk synchronized with the disk of the transmitter. Nipkows revolutionary design lead to him receiving a patent for the first successful television and gave way for the birth of what is now the most common household item, the TV.

The development of the photo tube by Nipkow gave way for the development of the mechanical disk-scanning method designed by J.L. Baird and C. F. Jenkins in 1926. Using this method images were produced of 60 to 100 scanned lines broadcasted over the airwaves. However, shortly there after the electronic scanning process superseded the mechanical process which was patented by V.K. Zworykin in 1928. During the following months the television saw further laboratory development until it began reaching the market in 1945 after the Second World War.

As years passed more and more improvements met the television. The modern scanning process operates like the eyes do in reading a page of printed matter, line by line. A complex circuit of horizontal and vertical deflection coils controls this movement and causes the electronic beam to scan the back of a mosaic of photoelectric cells in a 525-line zigzag 30 times each second. (The 525-line 30-frame-per-second system is used in the United States, Japan, and elsewhere; many other countries use similar but incompatible systems.) Because of how our eyes are we only need to see about 30 transmitted images a second to get the effect of motion. Through the development of interlaced scanning certain lines are scanned each 1/60 sec and the rest the next 1/60 sec or faster based on the developer and the technology.

It can only be estimated as to the where or how far the development of the television will go as every day we push for a faster, sharper, brighter image.

There are three major ways that television signals are transmitted. The first one is by modulated electromagnetic waves traveling through the air. The second way is by fiber optic or coaxial cables. The third way is by satellite.

In the first method, electrical signals are amplified. When these signals are sent to an antenna, an electromagnetic wave is created by oscillating charges, and the signal is modulated in the same way as simple radio transmissions are modulated. Frequencies for these waves are either in the VHF (very high frequency) range or UHF (ultra high frequency) range. Click here to see a list of frequency ranges. These waves travel through the air to antennas at the house where the television is located. The changing frequency of the waves induces a modulated current in the antenna which carries the signals to the television.

The second method television signals are transmitted is by coaxial or fiber optic cables. This method is actually similar to the original antenna method, because the signals travel to a large community antenna owned by the cable company, and then it is transmitted to the homes of the subscribers through coaxial or fiber optic cables. The advantage of this method is that the single, large community antenna can pick up a greater range of channels.

A third method that television signals are transmitted is from a communications satellite. A communications satellite is a structure in space which is capable of receiving transmitted signals from earth, amplifying them, and rebroadcasting them back to earth. This method is extremely useful in long-distance communication. Many satellites are in geosynchronous orbits above earth, meaning that they move at the same angular velocity as earth's surface, thus, they stay above the same spot on earth all the time. These communications satellites can be used to broadcast to either one of the community antennas as used in the cable method, or to small satellite dishes at the home where the television is located. However, signals are often scrambled, so the subscriber needs to purchase a decoder so that they can receive a clear signal.