Quadrature Amplitude Modulation: A modulation scheme which conveys data by changing (modulating) the amplitude of two carrier waves. These two waves, usually sinusoids, are out of phase with each other by 90° and are thus called quadrature carriers—hence the name of the scheme.

When you open Windows Media Center TV Pack for the first time on a computer that has a Quadrature Amplitude Modulation (QAM) tuner installed, and you choose to set up your TV signal, one of the optional configuration steps will prompt you to scan for channels. When the channel scan completes, you may find a smaller than expected number of QAM channels listed in the Electronic Programming Guide (EPG).

For more information about how to remove a channel from the EPG if you receive a “No TV signal” error message when you tune to the channel, click the following article number to view the article in the Microsoft Knowledge Base:

955485 Error message when you open Windows Media Center TV Pack and tune to a channel that is listed in the Electronic Program Guide: “No TV Signal”