Some portable TVs only have an ATSC tuner, while others have both ATSC and NTSC tuners. While both tuner types receive over-the-air signals, NTSC is an older analog standard that has largely been co-opted by digital ATSC. An ATSC tuner delivers better audio and video quality in addition to supporting formats such as widescreen. If you want a portable TV capable of pulling in the greatest number of signals, go with one that includes both types of tuners.