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Comcast’s Digital Switchover

I wrote this as a response to a discussion on LinkedIn, but thought I’d post it here too, in case anyone was interested.


Because of the switchover to all digital for over-the-air broadcasts back in June of 2009, all TVs made since 2008 had to have digital (ATSC) tuners built-in.

Most of these digital tuners also support tuning “clear” (unencrypted) QAM signals, which is what most digital cable providers use. Comcast has to send local channels unencrypted, so you will never need a cable box to view those channels as long as your TV has an ATSC/QAM tuner. If your TV doesn’t have this tuner, you will need to get a box from Comcast to continue receiving channels.

Some channels send a virtual channel number with their signals. WGAL does this so that their channel shows as 8.1 on your TV, even though it’s broadcast on channel 58.1. Other channels don’t do this, so without the Comcast box to translate the numbers, they will show up on odd channels. I believe that WGN, for example, is currently on channel 17.5. Since Comcast moves around their channels fairly often, it’s a good idea to do regular rescans if you’re plugging directly into the TV. The Comcast box will continue using the channel numbers that you’re used to (5 for WGAL, 20 for WGN, etc.).

For the encrypted channels (right now this is everything above 24, but Comcast has told me that it will soon be everything but the locals), you’ll need to either rent a cable box from Comcast, or rent a CableCard from Comcast and plug it into a CableCard-supported TV.

Comcast is moving to all-digital because digital channels take up much less bandwidth than analog channels do. This will let them carry more HD channels, more channels with 5.1 surround sound, and even provide faster internet service. It also makes it much easier for them to control access to the channels (and I believe this is the real reason for the switch). For analog cable, a tech would have to go out to the box in your neighborhood and physically install/remove a “trap” to block the signals. With everything digital, it’s the cable box itself (or CableCard) that gives/removes access to certain channels, so they can do it all from their office with the click of a mouse.

  1. aaron
    April 13, 2012 at 7:31 PM

    good write up. At work we sell our own TV service. We recently went all digital and added a bunch of HD channels. It has been really difficult to explain this transition to the ederly (and even people in my department). We’ve also run into people with HDTV “monitors” aka hd capable TVs without digital tuners. Also some TVs have odd ways of switching tuners and can really be confusing to residents. example: above channel 100 you have to type channel 99 to switch the tuner rather than hitting channel down. also the channel.1 etc really confuses people. I recoomended using boxes in the planning stages but that was shot down by the rest of the team. it really simplifies things and I understand why comcast offers them, though I do not agree with them requiring them.

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