QAM=quadrature amplitude modulation... GOOGLE it to define it.
Yes, you can decode them if they are unscrambled.
Yes, you can decode them if they are unscrambled.
What is a QAM tuner?
I am getting a HDTV with built in QAM tuner. My local Comcast cable company pumps out HDTV unscrambled on channels 703, 704, etc. I get basic analogue cable now. Will the Qam tuner allow me to pick up the HDTV signals without renting their cable box?
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Yes.
QAM is the modulation method of choice for cable HDTV. It's different than modulation used for over-the-air digital TV (DTV). The reason cable uses QAM is because it allows them to place twice as many HD channels in the same bandwidth, without any loss of image and sound quality.
Many (but not all) cableco's pass local HD channels in the clear using QAM. With a QAM capable tuner, you can receive those channels with any basic cable subscription. Comcast & TWC are the most prominent of the cableco's who pass local HD in the clear. Cox is the most prominent that does not pass local HD in the clear.
All cableco's scramble digital tier HD channels (ESPN HD, INHD, etc.) and premium HD channels (HBO, Showtime, etc.), and can only be received using a cableco supplied STB.
This will change somewhat in the very near future, as CableCARD equipment hits the market this summer. CableCARD STB's & HDTV's will have conditional access to allow receiving all subscribed channels, HD & otherwise; you buy the hardware of choice and the cableco rents you the access card. PPV, VOD, and other two-way dependent services, like on screen programming guides will not be available with the initial versions of CableCARD equipment.
| I am getting a HDTV with built in QAM tuner. My local Comcast cable company pumps out HDTV unscrambled on channels 703, 704, etc. I get basic analogue cable now. Will the Qam tuner allow me to pick up the HDTV signals without renting their cable box? |
QAM is the modulation method of choice for cable HDTV. It's different than modulation used for over-the-air digital TV (DTV). The reason cable uses QAM is because it allows them to place twice as many HD channels in the same bandwidth, without any loss of image and sound quality.
Many (but not all) cableco's pass local HD channels in the clear using QAM. With a QAM capable tuner, you can receive those channels with any basic cable subscription. Comcast & TWC are the most prominent of the cableco's who pass local HD in the clear. Cox is the most prominent that does not pass local HD in the clear.
All cableco's scramble digital tier HD channels (ESPN HD, INHD, etc.) and premium HD channels (HBO, Showtime, etc.), and can only be received using a cableco supplied STB.
This will change somewhat in the very near future, as CableCARD equipment hits the market this summer. CableCARD STB's & HDTV's will have conditional access to allow receiving all subscribed channels, HD & otherwise; you buy the hardware of choice and the cableco rents you the access card. PPV, VOD, and other two-way dependent services, like on screen programming guides will not be available with the initial versions of CableCARD equipment.
I wonder why they didn't use QAM technology for the over-the-air broadcasts as well. Wouldn't that free up bandwidth?
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IB
I have a Zenith C32V37 which has a QAM tuner. But when I try to detect cable HD, it asks me whether to use STD, HRC, or IRC. Which one is used by Comcast, specifically in Aurora, Illinois? How can I tell?
In experience with QAM in this area, STD and IRC were identical. HRC didn't work. YMMV
It basically is how the bandwidth is allocated for channel assignments.
It basically is how the bandwidth is allocated for channel assignments.
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Does anybody know about Charter in WI (QAM or not)
| Originally posted by Ken H Many (but not all) cableco's pass local HD channels in the clear using QAM. With a QAM capable tuner, you can receive those channels with any basic cable subscription. Comcast & TWC are the most prominent of the cableco's who pass local HD in the clear. Cox is the most prominent that does not pass local HD in the clear. |
Here in Aurora, the major broadcast HD channels (WBBM, WMAQ, WLS, WGN, WTTW) are carried in-the-clear by Comcast. My HDTV can display them even though I have not specifically paid for HDTV service.
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QAM isn't suitable for OTA. There was talk of using COFDM (which uses QAM and QPSK) ...
Do a search for 8VSB vs COFDM or VSB vs COFDM if you're really curious.
Note: VSB apprantly allows for more available bandwidth (over COFDM) ... however bandwidth seemed to be the last thing people were concerned about (coverage, cost of operation, multipath issues, comparability to NTSC coverage, license fees, etc. etc.)
| Originally posted by inky blacks I wonder why they didn't use QAM technology for the over-the-air broadcasts as well. Wouldn't that free up bandwidth? |
Do a search for 8VSB vs COFDM or VSB vs COFDM if you're really curious.
Note: VSB apprantly allows for more available bandwidth (over COFDM) ... however bandwidth seemed to be the last thing people were concerned about (coverage, cost of operation, multipath issues, comparability to NTSC coverage, license fees, etc. etc.)
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Check in the HDTV Locals forum.
If they are doing HD, they are using QAM, but the issue is 'are the locals in the clear'?
You can also call them and ask, but the garden variety CSR will not know; get a hold of the Charter local engineering department.
| Originally posted by sterno3 Does anybody know about Charter in WI (QAM or not) |
If they are doing HD, they are using QAM, but the issue is 'are the locals in the clear'?
You can also call them and ask, but the garden variety CSR will not know; get a hold of the Charter local engineering department.
QAM has no error-correction which is required for OTA reception thats why 8VSB is used for OTA HD.
Does anyone know where I can find a list of OTA boxes with built in QAM tuners?
The few OTA HD STBs that support QAM only do so for the few unencrypted HD channels. Some cable systems unencrypt the local HD channels only others encrypt everything.
Please excuse a really silly question, but Inky Black's original message indicated that he has basic analog cable. Does the fact that Comcast uses QAM to broadcast some of their HD channels "in the clear" imply that they can be received by a customer with a QAM tuner. . .even without subscribing to "digital cable?" Comcast in my area has the Motorola 6208 STBs available for $5 /month. Like Inky Black, I only subscribe to analog cable. If I pick up the 6208, will I be able to receive any QAM channels they broadcast in the clear without subscribing to digital cable?
Someone please educate me on the vagaries of digital transmission via the cable system! Is it basically an analog system that requires analog to digital converters (essentially modems) to transmit and/or receive a "digital" signal?
Thanks!
Someone please educate me on the vagaries of digital transmission via the cable system! Is it basically an analog system that requires analog to digital converters (essentially modems) to transmit and/or receive a "digital" signal?
Thanks!
I tried out an LG 3510A last month. CC has them in stock. Connected to Comcast in central NJ I was able to receive all of the Philly HD stations that Comcast was re-transmitting as well as ESPN-HD and INHD. I also received some PPV content which would come and go from time to time. I think it may have depended upon what my neighbors were paying for. I took the box back because I was unsatisfied with it operation. I think the next generation will be better.
The Comcast HD content is transmitted in digital format. There is no conversion from analog to digital. The signal is there. I didn't need to inform Comcast that I had the QAM tuner. In central NJ they are broadcasting the basic HD service in the clear. Hope this helps.
The Comcast HD content is transmitted in digital format. There is no conversion from analog to digital. The signal is there. I didn't need to inform Comcast that I had the QAM tuner. In central NJ they are broadcasting the basic HD service in the clear. Hope this helps.
harristl,
Yes, if your HDTV has a QAM tuner then you can receive unscrambled HDTV signals from cable TV.
Yes, if your HDTV has a QAM tuner then you can receive unscrambled HDTV signals from cable TV.
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Cable uses error detection and correction for digitial video both SD and HD. You do get errors with cable just a lot less than you'll usually get with OTA. I don't think you would enjoy watching digital cable without error detection and correction. 8VSB and QAM are just modulation techniques. By themselves they have nothing to do with the data being sent, which may include schemes for error detection and correction.
| Originally posted by Joxer QAM has no error-correction which is required for OTA reception thats why 8VSB is used for OTA HD. |
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The HDTV STB Synopsis.
| Originally posted by zyvo23 Does anyone know where I can find a list of OTA boxes with built in QAM tuners? |
I got my 51HX93 today and have been unable to pick up any digital signals through basic analouge cable service via my QAM tuner. Oh well.
Megawave antenna a bust. Not one usable digital station. Will try the Radio Shack powered antenna next.
IB
Megawave antenna a bust. Not one usable digital station. Will try the Radio Shack powered antenna next.
IB
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