Digital TV is something many of us use every day, and yet few of us understand the difference between digital and analogue TV. In 2009, the United States transitioned permanently from analogue to digital TV. A handful of other countries have done this and others plan to follow. During this transition, you may have heard things about how digital TV used less spectrum, or how it’s not fuzzy, but you may not completely understand why or how these things happen. Let’s take a closer look at what digital TV is and how it differs from analogue TV.
It is easy to think of the different types of TV like the different types of pictures. Think of having a physical print of a picture as analogue TV, and having a picture on your computer as digital TV. The digital copy is perfect in that it can be infinitely copied without losing quality, and it does not degrade over time. When you get a digital TV signal over-the-air, you get it in exactly the same quality it was at when it left the station. High-definition signals can even be transmitted over the air without losing quality. If you have a print of a photo, then it might be perfect quality at first. But it is susceptible to damage, and if it is copied the copy is usually lower quality. Analogue TV is like this – it is possible to get the same quality signal as is transmitted, but if you live far away from the broadcast tower, you may get a slightly degraded signal. Also, it is more susceptible to degradation and interference.
These differences are caused by the different types of signals. Analogue TV uses a waveform signal – it broadcasts a signal over a large range of spectrum, and sometimes the wave gets a bit messed up. Digital TV broadcasts signal as packets – small groups of 1s and 0s. Because the signal can only be a 1 or a 0, it is much harder to be interfered with. Also, it uses a smaller range of radio spectrum.
Of course, most people do not use over-the-air signals as I have talked about, but instead have their TVs wired to cable boxes (or satellite receivers). The cables you use to connect your TV to these sources have the same issues – they can be analogue or digital (though almost everything now is digital), but usually an analogue signal does not have as many interference problems when it is run through a cable.
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