How will DTV differ from today's TV?

Wider aspect ratio
When television was first being developed the relative size of the picture width and height was set to a ratio of 4 to 3. This was very close to motion picture film at the time -- tv experimenters saw that as accepting a reasonable standard. When television started cutting into movie audiences, movie companies started experimenting with wider screens as a way to differentiate themselves from tee-vee. With the new digital television standard, tv manufacturers are once again taking the screen proportions typical of motion pictures... this time choosing a ratio of 16 by 9.

Multi-channel audio
The standard allows for "5.1" channel audio. Each video signal can be accompanied by left, center, right, left rear, and right rear sound plus a low-frequency-only subwoofer channel. It's another steal from the motion picture industry, this time Dolby Labs' digital audio system.

Multiple channels
By using agressive data compression techniques developed for computers, DTV will be able to carry much more information on a single television channel than the current NTSC signal can. One of the breakthroughs in DTV is that this extra information may be used in several ways. A station may decide to broadcast a single High Definition TV signal, with a much crisper picture than is possible on present consumer television sets. Another station might decide to transmit multiple signals, each of which will have picture quality about the same as todays. The information doesn't need to be a television signal. Many stations will probably use some of their bandwidth to send data unrelated to their television programming. Many stations are looking forward to this as another way to make money.

Improved picture quality
Many of the picture flaws seen in current television will be absent. "Ghosts" and snow will not appear on an DTV set. The digital system will be able to correct, or at least conceal, any errors that get picked up between the transmitter and the viewer's set. On the down side if there are too many transmission problems the error correction will fail and the viewer will see no picture at all.

Currently, critical viewers can notice many problems with colors in NTSC television. Examples are colors appearing where they shouldn't -- patches of swirling rainbows on tweed coats, and indistinct and jittery edges of brightly colored objects. These picture flaws are a result of the compormises made when color was introduced. Advanced television will not have these picture flaws -- but introduce new digital imperfections.

How large will an DTV set look in my home?

The advertised size of a television sets in the U.S. is the size of the viewable picture, measured diagonally. These diagonal measurements can be misleading when comparing conventional and DTV sets. Here's a scale drawing comparing a 25" standard set -- a popular size -- with a theoretical 25" DTV screen:

As you can see, a wide-screen DTV set will seem quite a bit smaller than an NTSC set of the same advertised size. One way to compare NTSC and DTV sets more fairly is to compare the diagonal measurement of the NTSC screen with the width of the DTV screen. Continuing the example, a 28" or 29" (advertised) DTV set will appear approximately as large as a 25" NTSC set:

The lesson? Bring a tape measure to the store when shopping for an DTV set. Be sure to check how deep the set is also; first-generation DTVs will have very long picture tubes. You'll also need a strong friend or two to help lug the thing home. The new sets will be HEAVY.

What are the DTV assignments for your state?

See the tables at Doug Lung's R.F. TECHNOLOGY PAGE.