Why Did Old TVs Get Static?

If you’re old enough to remember an old clunker of a TV you probably also remember all TV static when you weren’t properly tuned into anything. Even if you’ve never seen a CRT TV, you’re probably at least a little familiar with TV static, considering how often it is used as a shorthand for errors in media. It’s a reality we all just kind of accepted, but why did old TVs get static anyway?

Analog Television

Analog televisions separate video and sound into separate signals. That’s why you had to plug in three cables to get them working. Yellow was for video while red and white were for the right/left audio channels. If your system couldn’t do stereo sound, audio was only one plug. 

Your TV gets video input from a composite video signal. When you put an image on a screen, it is broken up into pixels. When your TV receives a composite video signal, it receives the following information to apply to each pixel: intensity, horizontal-retrace signals, and vertical-retrace signals. Intensity is pretty simple; it just determines the brightness of the pixel. 

When an analog TV displays an image, it “paints” the screen pixel by pixel. It does this from left to right, starting at the top row of pixels. Once it reaches the end of a row, it goes down one row and back to the left side of the screen. This happens until we get to the bottom right corner of your screen. Then it returns to the top left corner and repeats the process–60 times per second. Horizontal retrace signals are indicators for when we go back from the right to the left side to paint the next row. Vertical retrace signals are for when we start over, and move back up to the top of the screen. 

You can think of this process like typing on a document. Each character is a pixel, and the cursor is your TV. At the end of each line, it goes back to the left side of the page and down one row. The only difference is once you finish the page. Imagine that instead of starting a new page, you just overwrite what was already on the page. Do one page 60 times per second.

Radio Waves

Composite video signals can be sent to your television through radio waves. Radio waves are just radiation—something you may have realized just by looking at the words. The thing about the radio waves your TV or radio tunes into is that we dictate the information in those waves. This is done by manipulating the frequency and amplitude of the signal. How often the signal is pulsed (turned on and off) can also contain information. Tuning into a specific channel basically tells your TV to only interpret signals coming from a specific band. 

Here’s the thing about radiation, though: it’s everywhere. So when you don’t tell your TV to tune into a channel (or tune into like an “in-between” channel), it just picks up random radiation. Static, simply, is actually just your TV trying to interpret ambient radiation in the same way that it interprets your late-night news. Some of that radiation is actually left over from the Big Bang itself. Nutty.

Why Don’t We Get Static Anymore?

In 1996, America began moving away from analog television to digital. This began with the Telecommunications Act of 1996, and analog televisions were officially retired by 2009. 

The reason our digital TVs don’t pick up radio static is a lot less flashy. Simply, the antenna of a digital TV just picks up a signal or it doesn’t. When there’s nothing to show, the TV just tells you there’s nothing going on since it’s not trying to interpret random data.

See if you know your TV here.