QAM & HDTV Antenna Question - AVS Forum
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post #1 of 14 Old 05-16-2007, 12:46 PM - Thread Starter
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I hope I posted this in the right place. I've done some searching but have not come up with a good answer.

I have an HDTV antenna which I hooked up to my neighbors HDTV. With it we picked up 10 HD stations ota. I am looking to buy a HDTV but cannot decide whether I need it to have 1 or 2 rf inputs. If the HDTV has a QAM tuner, will I most likely get all the HD stations without having to use the antenna? Or will there probably be a few that I can only pick up with the antenna and not with QAM?

Has anyone else ran into this situation that can tell me what they discovered? Thanks for any help you can give.
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post #2 of 14 Old 05-16-2007, 01:11 PM
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Well, QAM is the tuner, you still need an antenna or cable to send the signal to the TV so it can receive the signal with the QAM tuner. So, you really only need just one RF input. I run both cable and and antenna and simply flick an AB switch to watch one or the other.
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post #3 of 14 Old 05-16-2007, 01:32 PM
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Check the local reception forum for a thread for your area to see what others get around you. If your cable company carries all your locals, you could get away with just QAM, if you can get all your locals via antenna with no issues you can use ATSC, if you have a mix you'll either want a dual input TV or use an A/B switch as Kid Red does.

http://www.avsforum.com/avs-vb/forumdisplay.php?f=45

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post #4 of 14 Old 05-16-2007, 02:37 PM
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Note that if a TV has both ATSC and QAM tuners, but only one RF input, it may require you to do a new channel scan (which can be time-consuming) whenever you switch the input between antenna and cable. Apparently Kid Red doesn't have this problem, probably because his TV saves both the antenna and cable channel lists, but not all TVs can do this.
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post #5 of 14 Old 05-16-2007, 03:41 PM - Thread Starter
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Thanks, that is what I was wondering. I was going to try an a/b switch on my neighbors TV but it required you to rescan everytime the input changed. This did result in a very long time thus making it unacceptable. How would I be able to tell if the TV I want to get is able to save the antenna and cable list? Or for those of you that use an a/b switch, what type of HDTV do you have?

Thanks!
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post #6 of 14 Old 05-16-2007, 04:21 PM
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If you can get a set with 2 RF ins its nice.

As you can get both OTA and QAM channels(cable).
In most cases cable only carrys the major local channels so you may miss out on some of the sub channels.

If you end up with a cable box some will have built in OTA tunners that will intergrate local OTA channels in with you regular cables channels so that somthing to look at.


Its always good to have a backup. If the cable gos out you can always get OTA signal...
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post #7 of 14 Old 05-16-2007, 04:36 PM - Thread Starter
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I was looking at the Sony KDL46XBR3 primarily because it has two RF inputs, one is listed as Antenna (RF1) and the other listed as cable (RF2). I'm guessing that I can hook up my HDTV antenna to RF1 and pick up OTA channels and use the QAM tuner to pick up any QAM channels. Anyone have this line of Sony HDTV's that can verify this?

I'm still interested to know of any TV's that people use an a/b switch on without having to recan the channels everytime you change the input. Please list them if yours can do this.

Thanks again!
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post #8 of 14 Old 05-16-2007, 08:59 PM
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Check the display section for specifics on televisions.

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post #9 of 14 Old 05-17-2007, 04:24 AM
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If you are going to do both cable and OTA it would be more convenient to have 2 RF inputs, there could be cases of the OTA and cable channels that overlap.
So a rescan might be needed when you change inputs.

Another option (which you probably don't want to do ) is use a STB for cable and the ATSC tuner for the OTA stations.
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post #10 of 14 Old 05-17-2007, 05:10 AM
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Quote:
Originally Posted by jtbell View Post

Note that if a TV has both ATSC and QAM tuners, but only one RF input, it may require you to do a new channel scan (which can be time-consuming) whenever you switch the input between antenna and cable. Apparently Kid Red doesn't have this problem, probably because his TV saves both the antenna and cable channel lists, but not all TVs can do this.

Mine stores 2 lists and the switch between antenna and cable (VBS vs QAM for the digital portion of the ATSC tuner) is relatively simple. What I HATE is that when you rescan one it erases what was previously scanned on it ... in other words, if you have an antenna with a rotor, you cannot populate the list, even manually. OUCH!
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post #11 of 14 Old 05-17-2007, 05:41 AM - Thread Starter
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Thanks for all the replies so far. I've done some research and found out that on some HDTV's that have 2 RF inputs, that only one can be active at a time. Also once you switch over from cable to OTA it clears the memory and a rescan is still needed.

If anyone uses an A/B switch and does not have to rescan (without having to buy an external tuner), please let me know.

If a rescan is still going to be needed I will opt at buying a HDTV with only 1 RF input. Hopefully the QAM will pick up all the HD channels that the antenna does. If not then I'll put in the switch and will just have to rescan when I change over.

This is how I think I will have it set up:

Split cable from outlet 3 ways. One goes into an A/B switch with one side connected to Antenna and the other directly into RF input, one to cable box, and one to Series 2 Tivo. Then use composite cables out to my cable box and Tivo. This way I'll only have to switch to the RF input when I want to watch HD and can rescan between OTA and QAM.

Thanks again as this can be confusing for a newbie. Great community here and look forward to learning even more.
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post #12 of 14 Old 05-17-2007, 05:45 AM
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Quote:
Originally Posted by brettatk View Post

I was looking at the Sony KDL46XBR3 primarily because it has two RF inputs, one is listed as Antenna (RF1) and the other listed as cable (RF2). I'm guessing that I can hook up my HDTV antenna to RF1 and pick up OTA channels and use the QAM tuner to pick up any QAM channels. Anyone have this line of Sony HDTV's that can verify this?

You are on the right track - get a TV like that - with 2 RF inputs. Any kind of switching of the RF inputs between OTA and cable is inconvenient at best.

I think most/all TVs that have 2 RF inputs work like that Sony, including my 30XS955 - OTA (ATSC and NTSC) on one and cable (QAM and NTSC) on the other.
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post #13 of 14 Old 05-18-2007, 06:34 AM
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Quote:
Originally Posted by brettatk View Post

Thanks for all the replies so far. I've done some research and found out that on some HDTV's that have 2 RF inputs, that only one can be active at a time. Also once you switch over from cable to OTA it clears the memory and a rescan is still needed.

With my 2 input Sony, and single input Element, I do not have to rescan. I did have to scan once for each input; a unique list is kept for the OTA (8VSB modulation) and cable (64QAM and 256QAM modulation.
Quote:
Originally Posted by brettatk View Post

If anyone uses an A/B switch and does not have to rescan (without having to buy an external tuner), please let me know.

If a rescan is still going to be needed I will opt at buying a HDTV with only 1 RF input. Hopefully the QAM will pick up all the HD channels that the antenna does. If not then I'll put in the switch and will just have to rescan when I change over.

See above for rescan issue; I don't think that QAM will pick up all the signals that the antenna does; I know here in Greenville SC that a coathanger will get a few digital channels that Charter does not have.
Quote:
Originally Posted by brettatk View Post

This is how I think I will have it set up:

Split cable from outlet 3 ways. One goes into an A/B switch with one side connected to Antenna and the other directly into RF input, one to cable box, and one to Series 2 Tivo. Then use composite cables out to my cable box and Tivo. This way I'll only have to switch to the RF input when I want to watch HD and can rescan between OTA and QAM.

I'm not sure I completely understand your need, but it sounds like you will have 4 sources for the set, Tivo, Antenna, cable via component, and cable(for QAM). With a single RF connector, a pair of A/B/C switches with the devices. Using 1 and 2 for switches, A, B, C, common for ports,

Antenna to 2A
Cable to 1 common
1A to 2B
1B to Tivo
1C to cable box
Tivo to 2C
2 common to set RF
Cable box to component on set

If the cable box is RF out only, you'll need an A/B/C/D for switch 2. IF you have a set with 2 RF inputs, and your Tivo and cable box are RF out, those outputs will go to the antenna, not cable, input on the set after the switch.

Clear as mud? Comments from others?

Good Luck!
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post #14 of 14 Old 05-20-2007, 05:43 AM
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Quote:
Originally Posted by jtbell View Post

Note that if a TV has both ATSC and QAM tuners, but only one RF input, it may require you to do a new channel scan (which can be time-consuming) whenever you switch the input between antenna and cable. Apparently Kid Red doesn't have this problem, probably because his TV saves both the antenna and cable channel lists, but not all TVs can do this.

Yes it does, it's a Vizio. I had read that TVs WON'T save the scans so I was pleasantly surprised to just hit the B switch and choose cable or air in the menu.
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