General FAQ, InFocus General and Support Frequently Asked Questions

Q: What is SDTV?: A: SDTV is a subset of the ATSC 's standard for Digital Television. SDTV refers to digital video signals that are not as good as HDTV signals but provide a picture quality significantly better than NTSC signals. SDTV may have a 4:3 or 16:9 aspect ratio. The advantage of broadcasting SDTV instead of HDTV is the ability to broadcast several SDTV programs in the spectrum space that is taken up by a single HDTV program.
Q: What is QAM?: A: QAM stands for Quadrature Amplitude Modulation. It's a method used by some cable-TV operators for encoding digital cable signals (typically local broadcast channels). Later models of RCA HDTV's (for example, models ending in 41 or 151) are able to decode QAM signals so you won't need a cable box as long as these signals are "in the clear" (i.e., not scrambled or encrypted). A cable box may be needed for premium QAM cable channels.
Q: How do I know whether a channel is digital (ATSC) or analog (NTSC)?: A: The channel banner indicates whether the channel you're tuned to is analog or digital. Typically, digital channels will appear with a subchannel listed (e.g., 21-1, where "-1" is the subchannel number of channel 21) and analog channels will only have one channel (e.g., 21)
Q: What is HDTV?: A: HDTV is the highest form of digital television. An HDTV features an ATSC (American Television Standards Committee) integrated high-definition tuner with a built-in digital receiver/decoder, either 720 or 1080 scan lines, a wide aspect ratio (16:9), and 5.1 channel Dolby Digital sound. HDTV can refer to the type of TV or to the format of the program viewed on the HDTV. In order to watch HDTV, the broadcaster must be sending the program in the new ATSC format. The FCC (Federal Communications Commission) has mandated networks to change from the old broadcast system (known as analog or NTSC format) to the new ATSC format. The transition to digital TV is expected to be complete in 2007.
Q: What is a subchannel?: A: A broadcaster can send more than one signal on each channel (this is also known as "multicasting"). This smaller part of a signal is called a subchannel (sometimes called a minor channel). For example, primary programming could be broadcast channel 8, subchannel 1 (displayed as "8-1" in the channel banner); the weather forecast could be broadcast channel 8, subchannel 2 (displayed as "8-2"); and the weather radar could be broadcast on channel 8, subchannel 3 (displayed as "8-3").