# ATSC Tuner/Digital..why do cable or fiber companies insist on set top box ?



## westwood wizard (Dec 22, 2005)

I understand the FCC requirement regarding the broadcast format for television channels only applies to any channel that is transmitted terrestrially. Thus, an ATSC tuner would be needed if you wanted to receive these channels over the air. It could be integrated or it could be through a separate set top box/decoder. 

However, here is what I do not understand with respect to the cable companies. Almost all televisions, vcrs and dvd players/recorders for as long as I can remember have had an integrated NTSC tuner. The cable companies have had their base package of 70 - 100 channels available via the coaxial cable without the need for their set top box as long as you had your own NTSC tuner. You only need their set top box for the so called digital tiers/pay per view/sports packages and any HDTV programming which I will refer to generically as true digital programming because these include the local networks which will be required to broadcast in only digital format by 2009 regardless of definition level (SD, ED, HD, does not matter ...the important aspect is their signal will only be transmitted digitally...cable and satellite can convert these to analog if they wish for the end user).

However, I keep reading that people say the ATSC tuner will only be useful for OTA broadcast. Why ? The cable companies could transmit the same 70 - 100 channels though the coaxial cable in digital format without a set top box as long as the end user has an ATSC tuner built in or their own ATSC decoder box. Yes, I know about Cable Card but it is only important to cable companies in order to control the various levels of programming. Cable companies have for a long time not required set top box for the analog tier which includes the most popular channels anyway. Why would the equivalent digital tier not be made made available without the requirement of a set top box so that people can take advantage of having an ATSC tuner especially in multiple rooms where they may not want the rental fees that add up for addition set top boxes/cable cards and are okay with the basic tier of service which most people are at least in rooms where television is not going to be viewed all the time. This has been the beauty of the NTSC tuner and cable service one advantage over satellite.

Cable companies are not going to have a choice anyway. They have to make available local channels and those channels will only be broadcast digitally in 2009. I suppose the cable companies could still convert those to analog and then require a set top box or additional programming fee for those who want the local channels in digital format as they are doing now although this would not be fair.


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## KyL416 (Nov 11, 2005)

Digital Cable doesn't use ATSC for their signal, they use a system called QAM, or something similar.

And for the record, there ARE televisions that are Cable Card/Digital Cable ready. They feature a slot where the cable company inserts an authorization card into the TV so you can recieve digital channels, except PPV, without a Set Top box. Also, many cable providers send select digital channels, like the local HD channels, and whatever multicast channels they carry in the clear, so any Digital Cable ready TV can recieve them without a cable card.

As for converting the digital local channels, and downconverting the HD Locals, to analog for those who do not desire a set top box, the cable companies want to do that, but there are some people who want to prevent that, details about that are being discussed here:
http://www.dbstalk.com/showthread.php?t=58612


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## Geronimo (Mar 23, 2002)

Actually your NTSC tuner ws not giving you all those old cable channels. Cable channels have bee different that OTA for some time.


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## Jim5506 (Jun 7, 2004)

Geronimo said:


> Actually your NTSC tuner was not giving you all those old cable channels. Cable channels have been different that OTA for some time.


Actually it was.

That is why there is either a switch or a software mode that allows you to change from antenna to cable on your "cable ready" TV. The antenna setting has channels from 2 to 69, and the cable usually has channels from 2 to 125 or somewhere thereabouts. Most of the additional channels are located between channels 4 & 5, below channel 7 or above channel 13, areas denied to broadcast but available to cable because the signal is restricted to the cable wire (not broadcast OTA).

With the advent of digital cable you must have a STB to convert the digital channels to the NTSC or direct input that your TV can interpret.

Yes, cable companies mostly use QAM or scrambled QAM for digital cable, that is why some ATSC tuners that are capable of seeing QAM can be used in cable, except of course for the scrambled channels, they require an STB or a cable card. But these are not the old cable channels.


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## westwood wizard (Dec 22, 2005)

KyL416 said:


> Digital Cable doesn't use ATSC for their signal, they use a system called QAM, or something similar.
> 
> And for the record, there ARE televisions that are Cable Card/Digital Cable ready. They feature a slot where the cable company inserts an authorization card into the TV so you can recieve digital channels, except PPV, without a Set Top box. Also, many cable providers send select digital channels, like the local HD channels, and whatever multicast channels they carry in the clear, so any Digital Cable ready TV can recieve them without a cable card.
> 
> ...


I am waiting for Cable Card 2.0 before I buy a television with a CableCard slot. It is my understanding that Cable Card 1.0 televisions will not be able to get a firmware update ?


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## westwood wizard (Dec 22, 2005)

Jim5506 said:


> Actually it was.
> 
> That is why there is either a switch or a software mode that allows you to change from antenna to cable on your "cable ready" TV. The antenna setting has channels from 2 to 69, and the cable usually has channels from 2 to 125 or somewhere thereabouts. Most of the additional channels are located between channels 4 & 5, below channel 7 or above channel 13, areas denied to broadcast but available to cable because the signal is restricted to the cable wire (not broadcast OTA).
> 
> ...


Are you saying that some ATSC tuners might be able to receive at least some of the Digital Cable Channels even today ?


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## harsh (Jun 15, 2003)

westwood wizard said:


> I am waiting for Cable Card 2.0 before I buy a television with a CableCard slot. It is my understanding that Cable Card 1.0 televisions will not be able to get a firmware update ?


Cablecard 1.0 is one-way towards the subscriber. Cablecard 2.0 is two-way opening up the door for interactive content.


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## harsh (Jun 15, 2003)

westwood wizard said:


> Are you saying that some ATSC tuners might be able to receive at least some of the Digital Cable Channels even today ?


No. Some Cablecard ready televisions allow you to use the built-in QAM tuner without a Cablecard. ATSC and QAM are apples and oranges.


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## harsh (Jun 15, 2003)

Geronimo said:


> Actually your NTSC tuner ws not giving you all those old cable channels. Cable channels have bee different that OTA for some time.


Same tuner, different frequencies. It is still NTSC regardless of what frequency it is cast on.

The goal for cable is to do away with analog as soon as possible as they can use that same bandwidth to cast five SD channels or one HD channel plus an SD or two.


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## Jim5506 (Jun 7, 2004)

westwood wizard said:


> Are you saying that some ATSC tuners might be able to receive at least some of the Digital Cable Channels even today ?


YES. There are ATSC tuners (I believe the Samsung SIR-T451 for 1) that can also receive QAM signals.


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## harsh (Jun 15, 2003)

Jim5506 said:


> YES. There are ATSC tuners (I believe the Samsung SIR-T451 for 1) that can also receive QAM signals.


It is important to note that QAM is not one of the ATSC schemes. Support for QAM without support for Cablecard probably won't get you very far. In my area you can get the HD locals (block converted into the upper 80's and lower 90's) without a cablecard, but that's about it.

For the isatiable, look up Vestigial Side Band (ATSC) versus Quadrature Amplitude Modulation.


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## Michael P (Oct 27, 2004)

> Support for QAM without support for Cablecard probably won't get you very far.


 I've read posts over the the AVS forums where cable subs with their own QAM receivers have received not only all the local stations, but surprisingly some RSN activity as well (it's been reported that SportsTime Ohio's feeds have been "in the clear" over at least one cable system in the Greater Cleveland area). Not too many subscribers know about these tuners (some are PC cards) so for now the cable companies can add "hidden" channel (hidden to their STB's but viewable on the QAM "FTA" receivers).


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## KKlare (Sep 24, 2004)

Jim5506 said:


> The antenna setting has channels from 2 to 69, and the cable usually has channels from 2 to 125 or somewhere thereabouts. Most of the additional channels are located between channels 4 & 5, below channel 7 or above channel 13, areas denied to broadcast but available to cable because the signal is restricted to the cable wire (not broadcast OTA).


A few add-ons: The original range was 2 to 83 but was cut to 69 and now to about 50. The gap between 4 and 5 is small (2 MHz?) and while enough to allow both in the same broadcast market it is not enough for a 6 MHz channel. It is above 6 and below 7 that gets cable 14 to 22, IIRC. Above 13 gets cable 23 and upward into the UHF.
A side note, it looks like ATSC channels are not assigned 3 in a row. My guess is some harmonic interference/crosstalk. It is hard to know how they can cram that much cleanly in the 6 MHz slot and get ~15 Mbits/sec. Remember analog used less with sound beginning at about 4.5 MHz and had some side band below the "center" frequency and the color signals were centered up 3.5... MHz up, IIRC.
-Ken


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## harsh (Jun 15, 2003)

KKlare said:


> The gap between 4 and 5 is small (2 MHz?) and while enough to allow both in the same broadcast market it is not enough for a 6 MHz channel.


It is actually 4MHz (CATV A-8). This is probably enough for several SD DTV channels (or maybe one HD and one SD). Someone would have to declare what OTA channel number to assign to that frequency.


> It is above 6 and below 7 that gets cable 14 to 22, IIRC.


There are some optional cable channels that appear below 2 (CATV T-7 to T-14). CATV 95-99 (A-5 to A-1) appear below CATV 14 in between 6 and 7 too. None of this applies to ATSC because cable doesn't use ATSC.


> A side note, it looks like ATSC channels are not assigned 3 in a row.


This has more to do with adjacent market overlap. You cannot exceed the old 6MHz bandwidth. The UHF DTV frequencies will eventually be brought back to their respective VHF frequencies and the higher UHF stations (>50) will probably be moved down to new VHF frequencies (they could keep their UHF numbers, I suppose).


> It is hard to know how they can cram that much cleanly in the 6 MHz slot and get ~15 Mbits/sec.


It is well known how they cram 600Mbps (2Mb/frame x 30 frames/second) into 6MHz (actually 3MHz or less): MPEG2 compression.


> Remember analog used less with sound beginning at about 4.5 MHz and had some side band below the "center" frequency and the color signals were centered up 3.5... MHz up, IIRC.


The NTSC signal layout with its video carrier, color carrier and audio carrier is out the door with ATSC. The sound and color picture ride in a single non-segregated subcarrier as an MPEG2 compressed stream.


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