Does ATSC QAM mean it has a built in HD tuner ?

I think so....and cable non-scrambled hi-def. My computer card picks up Comcast non-scrambled hi-def QAM channels, and I think it would do the same thing for over the air, if I hooked an over the air antenna to it.

I'm no expert though.

Dave

Yes, it will pick up HD OTA
QAM (quadrature amplitude modulation) is capability to tune from those digital cable feeding
(cut&paste)
A QAM tuner is a electronic tuning device. The qam tuner is used in digital television sets and other electronic equipment, such as vcrs and dvrs. QAM stands for "quadrature amplitude modulation". Qam is the format by which digital cable channels are encoded and transmitted by the cable companies. A qam tuner can tune non-encrypted, digital cable channels, without using a cable box (set top box). If your set has a built in qam tuner, you can simply plug the cable from the cable company, directly into your TV set. This will allow you to watch non-encrypted programming. (Encryption is used for programs such as HBO and Showtime).
Regards
Thuan

Over-the-air and cable HD transmissions use different modulation schemes. ATSC (Advanced Television Systems Committee) is the standard for over-the-air transmissions and uses a 8 VSB (vestigial sideband) modulation scheme. As someone else pointed out, cable systems use QAM (quadrature amplitude modulation).

Bottom line is that the set you saw in the ad can receive both over-the-air HD transmissions and unencrypted cable HD transmissions.

Thank you all for the help!

Comcast, with exception of a very few analogue channels still being broadcast that must for NSTC form, both scrambles and encrypts all its digital channels that are transmitted in QAM format. No way to look at digital transmision with one of their boxes.

One other thought on receiving unencrypted QAM channels. Most cable companies don't provide mapping information for their digital cable channel numbers.

I use Cox in New Orleans. For example, CBS HD is mapped to Cox channel 704. If I want to watch it as an unencrypted QAM I have to search for it and remember the native channel number. Last time I tried this it was 53.110. The cable companies frequently move the QAM channels without warning. It can become a pain to periodically rescan and hunt down your favorite channels. The cable's set top box or Cablecards provide the mapping to the stable cable-assigned channel numbers (like 704).

The FCC requires that all cable carriers transmit network HD signals as clear QAMs, but they don't have to make it easy.