There are different types of sources for tuners and it took me a while to decipher which I need, plus more importantly, information specific to where I live. Here is what I have found (keep in mind I live in the Toronto area in Ontario Canada)…
This is the old analog cable that everyone can pickup using the old “rabbit-ear” antennas on grandpa’s first TV. This is also the standard definition signal we get when connect our TV directly to the cable provider. This has been phased out in the US as of June 2009, however there are still many channels available both over the air and through cable providers in Canada. NTSC is scheduled to be abandoned in Canada in August 2011. These are the typical channels I remember as a kid like 3 (Global), 7 (CityTV), 29 (Fox), etc.
This is pretty much the HD version of NTSC. It isn’t used by any cable providers that I know of, however it is broadcasted freely through the air. I purchased a cheap $20 antenna, connected it directly to the TV and pointed it out my bedroom window then was instantly picking up free HD channels. I have since upgraded to a $90 antenna, and mounted it on a pole on the side of my house. At last check I am getting over 20 HD channels through this antenna. At my last house (only a block away) I had the antenna mounted in the attic and was getting about 18 HD channels. These channels are represented with a decimal (usually lower than 60 from what I have found) like 41.1 (Global), 9.1 (CityTV), 29.1 (Fox), etc.
To see what kinds of signals you can get from your area I highly recommend checking this site…
This is the equivalent to ATSC for cable providers. This comes in either “Clear QAM” or “Encrypted QAM” options from the cable provider. The “Encrypted QAM” channels require the use of a cable box rented or purchased from the cable company. The “Clear QAM” is more like the channels from old NTSC but can be received without the need of a cable box. It is hit and miss if your cable provider has any channels in “Clear QAM” as none of the Canadian providers have any information on their websites and the customer service people have never heard of it. Even with every channel being able to have HD, the cable providers still broadcast mostly old SD (standard definition). You can usually determine the number of available “Clear QAM” channels available by connecting the cable directly to your TV (without a rented box) and doing an ATSC channel scan. I know Rogers almost only broadcasts their Galaxy Music channels over “Clear QAM” whereas Cogeco also includes several basic cable package channels. At last check I was getting about 50 “Clear QAM” channels at my house (not including the tonne of music channels). These channels also come in with a decimal (but are typically higher that those of ATSC) like 81.3 (Global), 81.7 (CityTV), 81.24 (Fox), etc.
From my experience (I haven’t been able to find anything in writing) but it apears that all tuners that have ATSC also support “Clear QAM” and visa-vera.
Other Areas (not available to me)…
This is an American only option that allows “Encrypted QAM” to be used by renting a PCMCIA style card from the cable provider then using the tuner (or digital box) of your choice. I guess in other parts of the world the cable companies pay the salaries of employees to the regulatory bodies (CRTC here in Canada) which then force us to use the garbage digital boxes only available through the cable company which they can then make more money on (excuse my bitter rant). Anyway, I recently discovered that these tuners without the card from the cable company will still work with ATSC and “Clear QAM”.
There are different flavours of this standard which are available in Europe. I am not to knowledgeable on them however one should be aware that they exist and are not compatible with other standards.
This is yet another standard available in Japan & Latin America of which again is not compatible with other standards.
I hope this clarifies any questions with my post regarding Tuners for Windows Media Center.