Re: QAM v. ATSC tuners

jim.e.dimoni@xxxxxxxxxxxxxxxxxxx wrote:
I'd like to get this clear also.

I have 2 "old" sets and one new. None HD.

None mention "QAM" but all have switches to allow receiving
unscrambled cable channels (2-76). I therefore assume QAM is
specifically HD - maybe not.

Looking at new HDTV some mention QAM, some only ATSC & NTSC.

My question - what determines if a set will receive the 2-76 cable
channels, or is it assumed that all new sets do via the std NTSC tuner
and a switch? -- AND the same assumption holds for the ATSC tuner in
receiving cable channels that somewhere there is a switch?

thx


On 16 Apr 2007 13:59:47 GMT, rlewart@xxxxxxxxxxxxxxxxxx (Cass Lewart)
wrote:

From my engineering days I remember that QAM stands for Quadrature
Amplitude Modulation, a method to squeeze more bits per second into a limited bandwidth transmission line. ATSC is a standard used for HD over the air transmission. Some people refer to QAM tuners and ATSC tuners as 2 different items, some use the terms for the same tuner. Which is correct? If these are 2 different items what are the inputs and outputs?
Cass

For some time now TVs sold in the US have featured the option of analog/NTSC over the air and analog "Cable Ready" reception. In many cases the type of reception can be selected from a menu with the set's infrared remote control.

ATSC is digital, but not necessarily high definition. ATSC signals are further divided by resolution and scan type. The number designates vertical resolution from the 480i standard definition to the 720i, 720p and 1080i high definition. The "i" and "p" designate interlaced scan (alternating lines before returning to the top to fill in the remaining lines) like was used in NTSC signals or a progressive scan which displays EVERY line in the picture before restarting at the top of the screen. Be alert that there WILL be TVs that can display "digital" "SD" or even "Enhanced" pictures without having the ability to display in high definition.

Sets labeled "High Definition Ready" may be able to display high definition images, but require an external cable converter, satellite receiver, external tuner or high definition (HD OR Blu-ray) disk player to display ANY programming.

As the analog broadcast cut off approaches, progressively smaller sets manufactured for sale in the US MUST have digital tuners IF they include analog tuners. "High Definition Ready" monitors aren't required to have either type of tuner. Basically, if the TV has ANY over the air tuner at all it has to have a ATSC/digital tuner.

QAM is the digital equivalent to "Cable Ready", but be aware that many channels on you local system, particularly out of town channels and channels that are "exclusively" on cable may require a rental converter OR rental "CableCard" to be viewed. As with analog, the channel guide and pay per view programming ordered with a remote require the external rental converter.
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