What type of digital TV tuner you need depends on where you live and how you’re able to receive digital signals. This might be via over-the-air, cable, or satellite broadcasts. For over-the-air, or terrestrial DTV broadcasts, you’ll need either a stand-alone tuner or an integrated DTV (i.e., one that includes a built-in DTV tuner). You may also wish to consider a satellite HDTV tuner, even if you don’t have satellite, as these also tend to come equipped with analog and digital terrestrial tuner functions. An analog tuner is listed as an NTSC (National Television System Committee) tuner and is the same unit used in regular TVs and VCRs. This may be a handy feature to have, to ensure you can get all your existing channels plus whatever digital channels might be available. An ATSC (Advanced Television Standard Committee) tuner is a fancy name for an over-the-air, HDTV, or digital TV tuner.

JUST BECAUSE YOU HAVE a digital-ready TV doesn’t mean you can watch HDTV. You need a digital tuner.

HDTV over cable currently comes in a few different forms. In some cases, the cable company may retransmit the terrestrial (off-air) broadcast signal. A terrestrial tuner with Cable-8VSB capability will tune these channels, which are at different frequencies than some off-air channels. This is temporary, and eventually those cable companies must change to a system called QAM. Some cable companies are already using QAM, and of those, some are scrambling only their premium channels. Their customers can connect an integrated HDTV with QAM tuning capability directly to the cable, without a cable box, and receive the unscrambled channels. The cable companies likely require an HDTV cable box, which may also have a corresponding fee, to view premium and pay-per-view channels. You’ll have to call your local cable company to find out. Future "digital cable-ready" displays will connect directly to the cable line, without a cable box, for all high-definition channels, premium or otherwise. These displays will include a slot for a security access smart-card, called CableCARD, provided by the local cable company. Only a couple of companies are offering such a TV. Cable companies are expected to have their systems in place sometime this year.

Once you’ve figured out what tuning functions you’ll need, you’ll want to pay attention to what connections are available. For example, you may need two antenna inputs if you want to use both a rooftop antenna and cable signals. Multiple audio and video outputs provide more flexibility when connecting the tuner to your audiovisual system. You’ll definite ly need a digital audio output to con nect the HDTV signal’s 5.1-channel Dolby Digital audio soundtrack to your surround-sound processor. There are two types of digital audio connectors. The type you need depends on the type of inputs on your surround processor. The 5.1 analog Dolby Digital outputs available on some tuners might be useful if you have an older Dolby Digital–ready surround processor.

When you get to the high-definition video connection, what you need depends on what type of connection is on the TV. Most displays will have either a three-wire component (Y, Pr, Pb) or a computer-type RGB connection. Either is fine, so long as it matches with the display. A digital link like FireWire (IEEE-1394), DVI or HDMI between the tuner and display would be a step up in quality. FireWire transfers the compressed digital video signal from the tuner to the display or to a recording device like a D-VHS recorder. The display decompresses the signal.

This connection is most common on newer stand-alone terrestrial tuners, but it should soon proliferate, thanks to a recent government ruling on compatibility standards.

DVI and HDMI, on the other hand, are connections that transmit the signal after it’s been decompressed. Both are compatible with each other, which means an HDMI-equipped TV can be connected to a DVI-equipped tuner box. When both the tuner and TV incorporate HDMI, however, the signal can also carry digital audio and control signals to the TV. DVI carries just the video signal and requires a separate audio connection. If you route your audio signals through a separate surround processor, HDMI may not be all that necessary.
The best but unfortunately least- abundant feature to find in a digital tuner is a DVR (digital video recorder), which incorporates a high-capacity computer hard drive for storing audio and video information. The advantages of a DVR are plentiful (see Digital TV Editor Mike Wood’s review of the ReplayTV DVR in this issue). The type of DVR is determined by the on-screen programming guide, which allows you to select programs for recording, tailor the displayed schedule according to your favorite shows, and search the program guide for types of content, actors or titles. Most important is the size of the hard drive. The bigger the drive, the more programming time it can store at higher quality before it fills up.

The die-hard enthusiast may also be concerned with output rates. The general goal is to have an output rate that matches with the TV’s native resolution (see the feature on displays, on page 51 in this issue). Average users will have much less need for this type of feature. Most if not all tuners will output signals at high definition’s 1080i scan rate, which is compatible with nearly all displays.
 
TVs used to be an all-in-one-box solution. Technology marches forward, however, and requires changes along the way. These days, it might still make a good deal of sense to purchase a display without a digital tuner, but the reasons are quickly dwindling. Either way, get a tuner so you can start enjoying the plethora of digital television programming that’s available.

Related Product Directories:

 Digital Tuners
In order for you to watch HDTV broadcasts, you need an HDTV tuner. This list includes terrestrial, satellite and even cable digital tuners.

 Video Processors
Many digital TVs already come with a video processor built-in. But if your analog sources still don’t look good, you might try one of the external models listed here.