QAM
From MythTV Official Wiki
Quadrature amplitude modulation (QAM) is 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. [1]
Oftentimes, the author is writing in the context of HDTV transmission. The other forms being OTA and satellite service.
