How HDTV Works? - Buying an HDTV

The DTV transition is not the first change to the TV signal. In 1946, the National Television System Committee (NTSC) began setting standards for American broadcasting. In 1953, NTSC standards changed to allow color television, and in 1984, they changed to allow stereo sound.
Those changes were different from the DTV switch because they were backwards compatible -- you could watch the new signal on your trusty old TV. With DTV, you'll need some new gear, and the gear you choose will affect whether you can receive and view high-definition video. You can learn about buying a DTV set in How Digital Television Works -- here, we'll focus on HDTV.
When you start shopping, keep in mind that HDTV requires three parts:

• A source, such as a local, cable or satellite HDTV station
• A way to receive the signal, like an antenna, cable or satellite service
• An HDTV set

Photo courtesy Consumer Guide Products If you purchase an HDTV-ready set, you'll need a receiver before you can watch high-definition broadcasts.

Most people start with the set. You can choose:

• An integrated HDTV, which has a digital tuner, also known as an ATSC tuner, built in. If a station near you is broadcasting in HDTV, you can attach an antenna to an integrated set and watch the station in high definition.
• An HDTV-ready set, also called an HDTV monitor, which does not have an HDTV tuner. HDTV-ready sets often have NTSC tuners, so you can still watch analog TV with them. This is the option for you if you want to have HDTV capabilities later on but aren't ready for the financial commitment now. Your picture quality will still be better than on your old TV, but it won't be high definition until you get an HDTV receiver.

Designing and building an HDTV that could display all of the ATSC formats would be virtually impossible. For this reason, HDTVs have one or two native resolutions. When the TV receives a signal, it will scale the signal to match its native resolution and de-interlace the signal if necessary. A good rule of thumb is to choose a set that has a native resolution matching the signals you plan to use most often. Film fans will generally want displays with the highest possible resolution. Sports fans will generally want displays with the highest possible progressive frame rate.

Photo courtesy Consumer Guide Products An HDTV-ready plasma TV

If you receive a signal that has a significantly lower resolution than your screen can display, all the extra pixels won't help it look better. This is why some people who have bought HDTVs have been dismayed at the quality of the picture - the existing analog signal just doesn't have enough detail to look good on a high-definition set. As broadcasters change to a digital signal, this problem will improve substantially.
In the next section, we'll look at the options for getting a signal to your TV as well as the compatibility of your existing home entertainment equipment.

via: http://electronics.howstuffworks.com/hdtv3.htm