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See digital television for more technical details, or DTV transition in the United States for specific information related to the analog-to-digital switchover

In the United States, digital television broadcasts, or DTV, can be received via cable, via internet, via satellite, or via free over-the-air (OTA) digital terrestrial television - much like analog television broadcasts have been. Full-power analog television broadcasts, however, are required by U.S. federal law to cease by June 12, 2009. Low-power, Class A, and TV Translator stations are not currently required to cease analog broadcasts. Also by law, digital broadcasts - when transmitted as OTA signals or over cable systems - must conform to ATSC standards.[1]; it is unclear whether satellite operators are free to use their own proprietary standards; and many standards exist for internet television (most are proprietary).



The U.S. opted to adhere to ATSC standards for broadcast digital television. These standards define, among other things, format and transmission criteria that ensure consistency, accessibility, and fairness for consumers and equipment manufacturers alike in the U.S., as well as international compatibility.


Format standards

The five main ATSC formats of DTV currently broadcast in the U.S. are:

Most digital television sets sold in the U.S. use a display with a 16:9 aspect ratio to optimally display HDTV-formatted content. Lower-resolution sources like regular DVDs may be upscaled to the native resolution of the TV. Most television broadcasts, as of 2007, were in standard definition.

In North America, FOX, MyNetworkTV (both owned by the News Corporation), ABC, and ESPN (ABC and ESPN are both owned by Disney) currently broadcast 720p content. NBC, Universal HD (both owned by the NBC Universal subsidiary of General Electric and Vivendi), CBS, The CW (co-owned by CBS and Time Warner), HBO (owned by Time Warner), Showtime (owned by CBS), Starz! (owned by Liberty Media), MOJO HD, HDNet,MTV2 (owned by Viacom) ,TNT (owned by Time Warner), CNN (also owned by Time Warner), Discovery HD Theater(owned by Discovery Communications) and the Public Broadcasting Service currently broadcast 1080i content. In Canada, virtually all over-the-air HD stations broadcast 1080i, as do most cable specialty channels. For list of local over the air HD channels visit a web site like

Transmission standards

Cable and satellite

Currently, most Americans get digital television broadcasts via cable or satellite. By law, digital cable television broadcasts must follow the same ATSC standards as OTA digital broadcasts; however, cable operators typically use a different modulation scheme than OTA transmissions (QAM instead of 8VSB). Digital television sets (equipped with ATSC tuners) are capable of viewing a baseline set of unencrypted digital programming, known as basic cable, which typically include local network television affiliates. According to FCC regulations, the remaining encrypted channels must be viewable with a receiver equipped with a CableCARD, in theory eliminating the need for any proprietary set-top box.


Digital television transmissions over-the-air (OTA) are now available in most metropolitan areas in the U.S., often carrying both standard-definition and high-definition (HDTV) transmissions of the same stations[2]. In fact, by the analog shut-off date of June 12, 2009, all Full Power OTA stations in the U.S. will, by law, have to either transmit their broadcasts digitally, or shut down.

Many stations have already used the switch to digital transmission as an opportunity to transition from 480i broadcasts to digital HD OTA broadcasts (either in 720p or 1080i), though this change is voluntary.

Within a distance of 35 to 40 miles from the broadcast stations, it is possible that no equipment more special than perhaps a simple antenna (such as "rabbit ears") may be necessary to receive a DTV broadcast signal OTA -- at least some of the time for some of the channels. Any television equipped with an ATSC tuner may display DTV broadcasts properly. Some customers are already discovering that terrain, trees, rain, snow, wind, and even the movement of people around the room interfere with reception to one degree of another, from signals breaking up to total loss of signal. (Few ATSC-equipped televisions or converter boxes have internal antennas, in contrast to analog sets available in years past).

Transition from analog to digital OTA broadcasts in 2009

It is estimated that as of April 2007, 28% of American households had an HDTV set, a total of 35 million sets, and that 86% of owners were highly satisfied with the HDTV programming[3] Some extimate that by the end of 2010, 59% of American TVs will be HDTVs. All TV stations currently broadcast in both digital and analog and major networks broadcast in HD in most markets.

While many in the industry wanted a flexible or delayed deadline, the FCC forced the issue at the behest of Congress. Congress wanted to reclaim the spectrum for emergency services. They also wanted to auction off the 76-88 MHz frequencies and old analog channels 60 to 69, and channels 52 to 59 by mandating DTV tuners be phased in to all new TV sets, beginning with the largest. Many dates were proposed, but Congress finally fixed February 17, 2009 (later extending it until June 12, 2009), in law as the maximum end date for analog television authorizations.[4] Because this date comes after the NCAA's Bowl Championship Series and the NFL's Super Bowl XLIII, there will be less of a chance of an acute hardware shortage from people waiting until the last minute to purchase an ATSC tuner than there would have been with a January 1 cutoff. The original deadline of January 1, 2006 was abolished when it was realized that TV stations and customers would not be able to meet the earlier deadline.

Early rollout of transition

On May 8, 2008, FCC Chairman Kevin J. Martin announced the agency would test run the transition to digital television in Wilmington, North Carolina, beginning September 8, 2008. This test run was to work out problems that might have occurred before the complete transition.

See also


  1. ^ FCC. The Digital TV Transition FAQs
  2. ^ AntennaWeb
  3. ^ WKYC's Director's Cut with Frank Macek: News: HDTV Penetration at 28%
  4. ^ 47 USC 309(j)(14)(A) [1] as amended by section 3002 of S.1932 signed into law February 8, 2006

External links


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