Analog vs. Digital

by Bob Seidel

There is a lot of exposure lately in the press and on TV about the upcoming change to Digital TV. You should be aware of this by now. The bottom line: If you have cable or satellite service, you don't have to do a thing. If you have a TV with an external antenna or rabbit ears, you will probably have to get a converter box - see a friend or someone you can count on to guide you in this.

But what is not explained is exactly what the difference between analog and digital is. If you are just a "turn on the switch and don't care what is behind the front panel" type, then read no further. But if you do want to know, let me try to explain it as basically as I can.

Radio (the electromagnetic spectrum) occurs naturally. It was not invented - it was always there. It covers everything from broadcast radio to light to infrared to microwaves, and so on. Early in the 20th century we learned to harness and use it. But there is no natural way to send information by radio waves - they just "are". We needed to find a way to use these radio waves to communicate.

The first attempts just involved turning on and off a radio signal. In the early days they generated the radio waves by using, literally, a large spark. This would generate a very broad and sloppy radio signal, but it could be detected and heard by receivers. Morse code, which was formerly used for telegraphs, was adopted for this use - most popularly by ships at sea. Later we learned how to refine the signals generated and received, primarily with the invention of the vacuum tube. But we still could not send information such as voice or music.

The breakthrough here was the invention of "modulation". Various forms of modulation evolved, including AM (Amplitude Modulation) and FM (Frequency Modulation) - either of these being able to put voice or music on the signal. And thus broadcast radio was born. TV is just more than one radio signal in a package - one signal for the picture and one signal for the audio.

But the biggest problem with these analog radio waves was that they have a bad tendency to mix together. A noisy motor for example in the vicinity could mix with a radio signal causing it to sound bad or completely cover it. Analog radio signals were also subject to significant losses due to the atmospheric conditions or when passed through long wires. That is why we got noisy or ghosty television pictures in the old days.

So how does digital change that? First of all, digital is in effect a modulation technique, not a change to the radio wave spectrum. Digital signals still use radio waves - if you put up a digital antenna on your TV and use the proper tuner or converter, you are still receiving analog radio wave signals, and a weak signal will always be a weak signal.

The difference is that computer-type hardware is on either end of the signal. The prime benefit is that very complex procedures can be put in place to ensure the integrity of the data - exactly what is sent is received. This eliminates all noise and will enable the exact video picture that was sent to be received. If the analog signal carrying this digital data is too weak or becomes corrupted then it stops working completely, rather than degrading. Digital signals also contain the ability to correct errors if received.

A second feature of digital is that it can contain a number of separate data channels simultaneously. I explained this briefly in past columns when talking about the new HDMI and digital audio cables. Just as when watching a DVD now, your future digital TV will allow you to have different audio languages or perhaps different video scenes, picture-in-picture, etc.

So digital is far more reliable (read: better picture and audio) and allows for a lot of nifty new features. For those old analog TV owners, it was time to convert - get over it! If you insist on staying with your old analog TV, the cost of converters is fairly inexpensive, especially considering the $40 rebate available.

Next year, we will all be digital and enjoying great pictures, sound, and new features.

(Bob Seidel is a local computer consultant in the Southport - Oak Island area. You can visit his Website at or e-mail questions or column ideas to him at For specific inquiries, please call Bob Seidel Consulting, LLC at 278-1007.)