HDTV

The standard-analog or NTSC-Television, (National Television Standards Committee) transmits only the video signal, containing no other information. But a major problem with analog signals is that between the transmitter and your Television set many things can interfere, thus distorting the picture you see. From a plane flying far overhead, to hilly terrain, tall buildings and even atmospheric conditions, all are obstacles that can interrupt the signal.

Advantages Of HDTV Television

HDTV Television signals are made up of coded instructions - the same 'bits' of 'ones and zeros' that make your computer work, and give life to your 'CD's' and 'DVD's' - which are transmitted to your Digital Receiver, (aka: Tuner, Decoder or Set-Top-Box "STB") which in turn deciphers the code. Your receiver isn't concerned with the signal strength, or what conditions exist between you and the transmitter. As long as the signal gets to the receiver, it can read the code and reproduce a near-perfect picture.

HDTV Television eliminates "snow" and "ghosting" caused by the weak signals from distant or blocked transmitting towers. If your analog TV set is not receiving a strong, undistorted signal from the tower, you will not get a perfectly clear picture.

Both HDTV Television and analog Televisin signals get weaker the farther they travel away from the transmitting tower. On an analog TV, the picture slowly deteriorates from bad to worse for more distant receivers. However, the picture on a HDTV Television set will stay perfect until the signal becomes too weak for the receiver to distinguish between a (1) and a (0), at which point the image disappears completely. HDTV Television displays pictures that contain significantly more detail, resulting in much 'crisper' pictures. Images viewed on TV screens are made up of small picture elements known as 'pixels.' Each of these pixels is made up of three, closely spaced 'dots' of color - red, blue and green. Combined together on the TV's phosphor screen, and viewed from a distance, the colors are seen as one. The phosphor at each of these dots emits light directly proportional to the intensity from the electron beam that hits it, as it scans across the screen.

On traditional, NTSC TV's 256 levels of intensity are possible for each of the three colors. The result is a range of 16.8 million colors for each pixel. The pixels in the analog system are slightly 'taller' than their width. Get up close to an analog screen - especially the larger projection sets - and you can easily see the red, blue and green rectangles. This is why distortion is sometimes seen on traditional, NTSC TV's.

The pixels in HDTV Television sets are square; they are also smaller, and spaced closer together. There can be (4 1/2) HDTV pixels in the same space that a single NTSC pixel requires. The result is that HDTV Television can display at least 4.5 times more detail than NTSC-analog TV.

HDTV Television sets are sold in two 'Aspect Ratios.' Aspect Ratio refers to the ratio between the horizontal (width) measurement and the vertical (height) measurement of the screen. This ratio is also used in reference to how the picture is transmitted and displayed on the screen.

The two aspect ratios used in HDTV Television are (4:3) and (16:9). That is, (4) units wide by (3) units high, and (16) units wide by (9) units high respectively.

HDTV Television vs.Standard Definition Television

As already stated, the ATSC has assigned (18) formats to Digital TV. At the current time, in HDTV Television we are primarily concerned with just two: 1080-i and 720-p. "True" HDTV Television may have, either 1080 interlaced lines, or 720 progressive-scanned lines. (Higher resolutions may be introduced in the future; for instance 1080-p, which is not currently used because of high manufacturing costs).