What do you mean, “Clear QAM?”

The TV industry loves to confound you with strange abbreviations. One of the weirdest is QAM, pronounced “kwam.” It sounds vaguely Australian, doesn’t it?

What’s worse is that if you search for QAM, you find out that it means “Quadrature amplitude modulation” which doesn’t help your search for understanding unless you’re a physics teacher. Then you start hearing terms like “Clear QAM” and your head begins to spin, your eyes roll back in your head, and you start wondering if there’s anything good on TV.

Relax, we’re here to help.

Of course you’ve heard of AM and FM, and you know they are different, and maybe you never cared to know more than that. It’s enough to know that if you’re broadcasting, you can use AM or FM. Well, you can also use QAM. It’s just another way of sending a signal through a wire or over the air. Unlike AM or FM, it uses fancy math tricks to fit a lot more information in a relatively small space. That’s why it’s the default method used by cable companies to send your TV pictures to you.

In the beginning, there was Clear QAM. In this case, “Clear” just means “not encrypted.” Back when cable TV started, all signals were sent over the wire without any special need for passwords or decoding equipment. If your TV was “cable-ready you could hook up a cable to it and the TV could find the channels. This worked for about 20 years.

By the 1990s, though, cable companies started entering into very complex contracts with providers like HBO, who insisted that some sort of anti-piracy measures be put in place. Cable boxes were built that decoded “Encrypted QAM” signals, in other words signals that you couldn’t get through your average TV. These signals needed special passwords and other stuff to make them work.

For the most part, though, you always had the option of just hooking your cable directly to the TV to get locals and maybe a few other channels that still used Clear QAM. Cable systems were obligated to give subscribers some sort of box-free option. That changed in October of last year when the FCC ruled that cable providers could stop providing any Clear QAM feeds as long as they had some way to get data to people without charging them for a cable box. For example, they could use a standard system (like CableCard or Tru2Way) that let people buy their own equipment. Many cablesystems already uses systems like this and so a lot of Clear QAM systems have already disappeared.

About the Author

Stuart Sweet
Stuart Sweet is the editor-in-chief of The Solid Signal Blog and a "master plumber" at Signal Group, LLC. He is the author of over 8,000 articles and longform tutorials including many posted here. Reach him by clicking on "Contact the Editor" at the bottom of this page.