I received a question that is right up my alley. A reader wanted some information about TV signals and the digital transition:
“How were TV broadcasts transmitted before 2009 and the digital change, and what are the differences?”
Awesome question and one I have some experience with. I was working in TV back during the big digital transition and participated in several phone banks designed to help viewers understand what was happening with the transition. The digital transition was quite expensive for TV stations, but they had no option. The government mandated that signals switch to digital.
I guess the first question is, what were we transitioning from? TV moved away from transmitting analog signals to digital signals. Both signals carry information like audio and video. Analog signals are used in their original forms. For example, a VCR or a cassette tape record analog information. You can’t really speed up the transfer process and it takes however long the original recording was to copy the information. If you want to copy a two-hour VHS program to another VHS tape, it’s going to take two hours.
When a signal is digital, it is compressed and can be transferred much faster and also without degradation. A copy of a copy of a copy of a VHS tape is going to look horrible. I can transfer the digital signal again and again without losing quality.
Digital signals carry much more information. In the same amount of bandwidth an old analog TV signal used to take up, a digital signal can fit several channels of high-definition signals. HD signals offer far more detail than analog signals. Digital signals can easily include surround sound, multiple languages, closed captioning, descriptions for the visually impaired, and more.
HD broadcasts are in the 16 x 9 format, the same as movies in the theater. There’s no need to chop off part of the picture for broadcast.
To receive a digital signal, you need a digital receiver. Old analog TVs can’t pick them up. So you need a converter of some kind. That can be a separate converter box that you buy or a service provided by the converter included with your cable or satellite package.
One downside of digital signals is that they are all or nothing. With analog signals, you could receive a fuzzy TV signal. With digital, it is all or nothing. Digital is also line-of-site. Buildings, trees, and other objects can block your signal. Many living in rural, wooded, and mountainous communities lost their ability to pick up over-the-air signals.
Because digital signals use less bandwidth, the government has been selling off airwave space to be used for the increasing demand for wireless phone and Internet communication.
Bottom line, digital signals carry more information and take up less bandwidth.