Right now the United States is in the process of converting all television transmissions from analog signal to digital signal. Switching from analog to digital offers numerous improvements and advantages. One of the primary advantages is the amount of data that can be broadcast. When using a digital signal you can broadcast far more actual data than you can using an analog signal over the same amount of bandwidth. There is also a large movement to High Definition TV; to be able to take advantage of the benefits of HDTV it is imperative that the US switches to digital transmissions.
To transmit a signal for HDTV can require up to five times as much data as a standard television signal. In the frequency range allocated for television broadcast there is not enough open bandwidth to transmit that much data via an analog signal. To accommodate more HDTV transmissions more and more transmissions in the US will have to be digital.
It is possible to greatly increase the amount of compression applied to the data within the signal with digital transmissions as compared to analog transmissions. Digital transmissions use the Mpeg 2 standard of compression; with this compression technology it is possible to compress the data as much as 55 to 1. The standard is what is known as a “lossy" standard, which does mean that there is some quality lost. However the final quality is still far superior to the NTSC standard currently used for analog television transmissions. The Mpeg 2 standard is already the standard compression used for DVD's and digital satellite stations.
The final quality of a digital signal is far superior to an analog signal for several reasons. First as stated earlier the Mpeg 2 is a superior technology to the NTSC and creates a better product before it is transmitted. Secondly digital signals do not allow for any loss of quality during the transmission. Analog transmissions are transmitted as a wave signal, which allows for signal degradation during the transmission. Digital signals are a series of 1's and 0's and only require that the signal be strong enough to be received. As long as the signal is received then the data will be a perfect reproduction of the data that was originally transmitted. With an analog signal though as the signal power decreases so does the quality. The weaker the signal the lower the quality of the image that is reproduced by the television receiver at the other end of the signal. This is what causes static and “snow" when you watch anything broadcast with an analog signal. Because of the improved quality and improved flexibility in broadcast format there are many good reasons for the US to make the switch to digital. Over the next several years more and more stations will change to a digital signal instead of analog. Soon there will be few if any stations still broadcasting an analog signal.
By Steve Welker
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