Can the ATSC Tunner in new TiVo get any Channels From Cable

gastrof

· #2 · Sep 15, 2007

Digital channels aren't broadcast "as is" (usually phrased as "in the clear") on cable.

Cable uses a different digital system called "QAM". Some digital TV tuners can do OverTheAir and QAM. Some can't do QAM.

I think the Series 3 and the TiVo HD need cable cards to get any digital cable channels, but I could be wrong.

If your cable system is the odd duck that uses OTA-type ATSC for digital (I don't even know if that's possible), then an ATSC tuner would get those channels. Again, tho', I don't think that's ever the case.

Reply

Save

Like

Mars

Discussion Starter · #3 · Sep 15, 2007

I'm asking about ATSC service.

If you don't know what that is please do not respond to this thread, leave room for others.

Reply

Save

Like

C

chip_r

· #4 · Sep 15, 2007

Mars said:
I know most cable co's have boxes for their digital channels. But will they be adding any ATSC channels taken off the air and rebroadcast "as is" on cable?

I believe Gatrof has answered your question. In short, an ATSC channel will never be rebroadcast "as is" on cable.

In lay terms, ATSC and QAM are two different ways to PACKAGE a channel. ATSC uses a modulation scheme called VSB and involves transmission towers and rabbit ears on your TV or TiVo. It's strictly a free-space way to communicate. Your local TV stations have antennas that broadcast channels with the VSB packaging.

QAM, on the other hand, is strictly used for cable transmission of digital signals.

So if your cable company decides it wants to pick up ABC in HD and ship it over cable, it first receives it over the air as ATSC (really meaning VSB) with rabbit ears, extracts the video signal (called baseband) and repackages the video signal into a QAM format for distribution on their cable system. The cable company at that point decides on the QAM frequency (channel number) to use for it's rebroadcast of the ABC in HD.

In reality, the cable company doesn't use rabbit ears. They likely pick it up via satellite directly and convert to QAM. The rabbit ears is just to illustrate how it could be done.

What makes it kind of confusing for some folks, is that the 1950's-sh NTSC packaging of video channels is identical for free-space and cable companies. That's what analog cable is today and why cable-ready TVs have existed for decades.

When ATSC came out, one would naturally expect it do the same. Unfortunately the VSB modulation scheme used by ATSC conflicts with the QAM format cable had been using for digital. So the cable companies just use QAM for any "new" additions. The high-def ATSC broadcasts are "new" and must go through the ATSC-to-QAM conversion described above to avoid the conflict.

See less See more

Reply

Save

Like

gastrof

· #5 · Sep 15, 2007

Mars said:
I'm asking about ATSC service.

If you don't know what that is please do not respond to this thread, leave room for others.

Please don't take that tone with me. We treat each other with respect here.

You were plainly told that ATSC is not the format that cable companies use on digital cable, and that if it's even possible, it'd be the "odd duck" cable company that does so.

Even OverTheAir channels are done as QAM on digital cable.

I explained to you that I believe the Series 3 and TiVoHD digital tuners do NOT do QAM, and that I believe they require cable cards to get ANY cable channels, including those QAM format ones that aren't even scrambled.

Perhaps if you'd read my reply carefully and allowed yourself to become informed you wouldln't have replied the way you did.

Perhaps you read the words, but it's apparent you didn't listen to what was being said. It was pretty plain.

Please ask more questions, and reply in similar fashion to others who answer them for you. That way, nobody will be inclined to answer you in the future.

By the way...

You're welcome.

See less See more

Reply

Save

Like

T

TydalForce

· #6 · Sep 15, 2007

The Series3 and the TiVoHD *can* receive unencrypted QAM channels without a CableCARD. Do a channel scan, and oodles of them will be picked up, many of which you can tune to.

As indicated above, the ATSC tuner won't receive anything from your Cable line, but the QAM tuner will.

However they may not have the numbers you expect. QAM channels, encrypted or not, tend to move around and get reassigned frequently. So if you find your QAM version of for example CNN, it may be on a different channel next month.

Many cable companies are broadcasting what's called PSIP data with their local "broadcast" stations, though. So let's say your local ABC affiliate's broadcast is on 6-1. If you do a channel scan, the PSIP data will associate the Cable rebroadcast of ABC with channel 6-1 so you can tune to it as you might expect to.

This seems to be mostly on a whim though; not everyone can get it.

Reply

Save

Like

wmcbrine

· #7 · Sep 15, 2007

I've heard that there are a few cable systems that use ATSC. It's not common, because they can fit twice as many bits into the same bandwidth with QAM256.

Reply

Save

Like

C

chip_r

· #8 · Sep 15, 2007

wmcbrine said:
I've heard that there are a few cable systems that use ATSC. It's not common, because they can fit twice as many bits into the same bandwidth with QAM256.

I could believe it. If they have the frequencies open on the cable there isn't a reason why that can't. But definately a minority since most cable cos. want to pack as many channels at they can over the cable. QAM256 is the way to go.

Reply

Save

Like

phox_mulder

· #9 · Sep 15, 2007

TydalForce said:
The Series3 and the TiVoHD *can* receive unencrypted QAM channels without a CableCARD. Do a channel scan, and oodles of them will be picked up, many of which you can tune to.

You can even do manual recordings on these channels.

You won't have guide data for these "in the clear" channels, so whatever you record won't have a user friendly title, but just the channel number and date/time recorded.

Because you don't have guide data, you can't use Season Passes or Wishlists to record any programs on these "in the clear" channels.

Cable Cards are required to map these channels to the channel the Cable Company reports the channel to be, and where TiVo expects the channel to be.

phox

Reply

Save

Like