Re: QAM v. ATSC tuners
- From: Bernie <bernie@xxxxxxxxxxxxx>
- Date: Mon, 23 Apr 2007 20:37:24 -0500
Let me try to answer the question simply. All of your old TV's have an NTSC tuner. They can receive over-the-air analog broadcasts AND they can receive analog signals provided by your cable company. Analog signals from your cable company are usually channel numbers below 100.
Your cable company controls which stations appear at which numbers when you are using your analog tuner. In your case they map OTA channels 2-6 to their cable channels 2-6. In my case they also do that with channels 8, 11, and 13 since those are the major broadcast stations in this area and it is the most obvious thing to do.
The major stations in your area should now be broadcasting a digital signal OTA in addition to their analog signal. They MAY also be broadcasting an HD digital signal. Your ATSC tuner will tune those digital OTA signals.
Within the next two years the OTA analog signals will disappear. Our old, NTSC TV's will no longer work with an OTA signal. Converter boxes to tune ATSC signals should become available at reasonable prices. BUT, cable companies will probably continue to provide analog versions of some stations, so if you have cable and an older NTSC TV it will continue to work for as long as your cable company provides that signal.
Your ATSC tuner will display over-the-air digital signals. If you want to display the digital signals provided by your cable company you must have a TV with a QAM tuner. To receive scrambled digital cable channels (which is most of the digital cable channels) you also need a cablecard or a descrambler from the cable company. The cable company provides two types of descrambler boxes. One type is a simple "set top box" that will tune all of the analog and digital channels. The other is a Digital Video Recorder. Despite whatever complaints you will read about the various DVR's, if you have cable you will want to get one. They change the way you watch television, making all your shows appear when it is convenient for you.
To get HD you must be able receive digital signals, either over the air via an ATSC tuner, or via cable via a QAM tuner, and of course you need a display that is capable of displaying the high definition images.
Satellite services are similar in that they require a "set top box".
Bernie
On 4/23/2007 2:00 PM, 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 QuadratureAmplitude 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
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