Tuning out static from digital switch

Sun., Feb. 24, 2008

Diane Werts Newsday

The digital conversion

Here's what this doesn't mean for you and me.

Myth No. 1: I need a new set to watch TV after next year's analog shut-off date.

Not true, mostly. Cable and satellite subscribers can keep watching on any old TV. These providers do the video translation to feed their signals to either your new digital set or your old analog one, via set-top box. They'll make sure you can see the channels they want you to pay for.

Antenna users with traditional NTSC-tuner sets, however, won't be able to see digital signals without adding gizmos. NTSC sets just don't speak ATSC language. But these viewers can get ATSC-to-NTSC conversion boxes at retailers for around $50. And the government is offering $40 discount coupons (see www.dtv2009.gov or call 888-DTV-2009).

Myth No. 2: I need a high-def set to watch digital signals.

Nope. HD and digital are two separate things. All HD signals are by definition digital, but all digital signals are not necessarily high-def.

This is obvious in the standard-definition subchannels already being broadcast via digital signals by some stations. ATSC sets can receive these over the air for free, though they aren't broadcast in HD-quality. (Multiple HD signals won't fit into a one-channel slice of spectrum.) Antenna-using NTSC sets can't receive or display these signals at all. Again, different languages spoken.

Cable/satellite systems, however, can carry digital signals to even analog TV sets by translating them as they're piped into homes. Purchased converter boxes will do the same thing.

Myth No. 3: Any digital set will display an HD picture.

No way. Inexpensive new sets may say "digital" and "ATSC," but that only means they can receive and display any new broadcast signal, but not necessarily with high-def clarity.

Currently, the highest HD-quality ATSC broadcast signal is called 1080i (for 1,080 lines of resolution, interlaced, with every other screen line refreshed at a time). The NTSC standard reaches only 480i. Many ATSC-tuner sets, especially smaller ones, display at 720p (for progressive display, all lines refreshed at the same time). ATSC broadcast standards allow for resolution as low as 480p.

Myth No. 4: To receive digital broadcasts via antenna, I need a widescreen, flat-panel TV set.

Not true. Some ATSC-tuner digital TVs use flat panels in the familiar 4x3 screen shape; these display 16x9 widescreen pictures in letterbox form. Other digital TVs are bulky, old-style tube sets, often in 16x9 format, sometimes in HD. For a TV to directly receive digital broadcasts via antenna, it simply needs to have an ATSC tuner, regardless of the set's shape or clarity.

Myth No. 5: Digital TV sets always provide perfect reception.

If only. One dirty little secret of ATSC is that you have either a great picture or none at all. Digital doesn't do snowy pictures or ghosting. The further you are from the transmission tower, the greater your chance of getting no reception. Homes currently using rabbit-ears antenna for adequate-but-not-great NTSC reception may require rooftop antennas to get any ATSC picture at all.

In less than a year, on Feb. 17, 2009, the American TV transition to digital broadcasting from analog broadcasting will be complete. This government-mandated analog “shut-off” paves the way for a brave new technical future of high-definition video, surround sound and multiple channels in one signal. You’ve been hearing breathless boasts about the high-tech wonders to come.

But you’ve also been hearing plenty of misinformation about digital technology and what it means to you, Jane and John Viewer. Some are claiming old TVs won’t work at all and you’ll need to buy expensive flat-panel digital sets. Others say you’ll have to pony up for high-def to keep watching anything.

Neither of these statements is true. Nor are many other dire warnings and wildfire rumors about the analog-to-digital transition.

Here’s the much-simplified story behind the switch-over.

In analog TV, local stations have always broadcast using the NTSC technical standard. This sends both picture and sound via radio waves spread across oodles of space on the federally apportioned spectrum of broadcast frequencies (like those megahertz-numbered radio stations).

Digital broadcasting uses the ATSC technical standard, developed over the past two decades. It’s a much more versatile and efficient method, using the same binary system of information delivery as computers. ATSC signals fit a more compact portion of the broadcast spectrum, yet offer better picture and sound, as well as the capacity to transmit several program streams in one channel space.

The government mandated local stations to start digital broadcasting several years ago, while still beaming their old analog signals to ease the transition. But the feds want the analog spectrum back for first-responders and wireless-provider auctions. So as of next Feb. 17, no more analog signals will beam for old TV sets to pick up via antenna. Only digital signals will be broadcast.