PDA

View Full Version : HDTV/Cable System



Joe Pelonio
06-14-2009, 7:18 PM
My mother-in-law is in an adult family home where she's had a little 12" Old Fashioned CRT TV which has taken a turn for the worst, and needed a new one. Now days about all you can get are the HD, LCD or Plasma, so we found a good price on a LCD 19" and took it over. Now at age 90 she really can't tell much difference in picture quality but it was amazingly bad on many channels compared to the old TV. A few are beautiful, others are un-watchable, most have snowy pictures. After talking to the manufacturer tech support people I found out something interesting that I don't remember hearing before. The HDTV is worse if you don't have an HD converter box.

Her connection is just the coax coming in from a splitter outside the home.

I'll now have to see if I cahn arrange for the Cable people (Comcast) to bill my account here for a box that will be located in a nearby city. Luckily they serve both cities but I don't know if they allow that.

Jim Becker
06-14-2009, 7:26 PM
Some of the newer TVs do not display Standard Definition media very well and some do a great job. (Sharp Aquos, for example, does a fairly good job) In addition, there are often settings that can be tweaked to make an SD signal display better on many 16:9 format TVs. But of course, High Definition stations are going to look better than anything...

Joe Pelonio
06-14-2009, 7:52 PM
This one is an Aquos, but after the "tweaking" that the tech support guy had me do the improvement was very little. He said that the coax is the worst
way to go, even the non-HD box using the audio and video inputs is better
on these.

Jim Becker
06-14-2009, 8:19 PM
Sorry, I missed that part in your original post...correct. Coax is NOT the way to hook up to a cable box of any kind. In order of preference, top to bottom...HDMI, Component Video, A/V, Coax.

Tim Morton
06-14-2009, 9:12 PM
You are right, coax is the worst...480i is the max signal that will pass thru the coax.

Have you tried over the air using a digital converter box?

You can go to the AVS forums and search for solutions...
might be worth a look.

Good Luck!!!

Joe Pelonio
06-14-2009, 9:40 PM
Have you tried over the air using a digital converter box?

Good Luck!!!
That won't work for one reason, she loves to watch the Mariners games, which are available only via cable on Fox Sports NW. Looks like we'll have to pay for a box.

Tim Wagner
06-15-2009, 12:39 AM
Well I am no comunications expert, but we have Cox cable in cleveland with HDDVR's and they are connected with coax going to the box and HDMI coming into the tv. They display 1080I and look truly awsome. 1080i on the hd channles that is. the others are digital and look fairly well i geuss.

tim.

Tim Morton
06-15-2009, 6:44 AM
Well I am no comunications expert, but we have Cox cable in cleveland with HDDVR's and they are connected with coax going to the box and HDMI coming into the tv. They display 1080I and look truly awsome. 1080i on the hd channles that is. the others are digital and look fairly well i geuss.

tim.


thats because the box is the HD converter...try running coax out of the box and into the TV and watch it degrade;)

Eric DeSilva
06-15-2009, 10:57 AM
480i is the max signal that will pass thru the coax.

Where did that come from? It's totally wrong...

Coax carries modulated RF fine. So, for example, plenty of UHF antennas are connected to converter boxes and HDTVs via coax and do 1080i as well as anything else. So, in fact, coax carries 1080i quite well.

The cable television issue is that, once upon a time, they carried modulated RF duplicating the over-the-air (OTA) channels on the low end of their cable coax. That meant you could plug it into a television and the TV decoding circuitry would effectively pretend the coax was an antenna and you would get the OTA channels via coax without a box. Cable television systems do not do this for HD broadcasts, however. So, even if you have an HDTV capable of demodulating OTA HD, you won't get anything from the CATV coax without a set top box (STB) or a cable card.

You can, however, get an external antenna, connect it via coax to your HDTV, and get a darn fine HDTV signal from OTA sources--assuming they are there to pick up.

What you guys all seem to be conflating is carrying a demodulated digital HD signal. Once something has demodulated the signal from RF and turned it into 1's and 0's of digital, you want to move the signal from box to box in the digital domain. That means HDMI or DVI. It makes little sense to turn it into HD, then convert it back to analog to go from box to TV.

Brad Wood
06-15-2009, 11:41 AM
to another part of your OP, you should be able to have the bill sent to you for service at a different address.

We have cable running in to all our locations here in Clark County and the bills come to me - I use the word "bills" and not "bill" because God forbid their system would be able to consolidate all the services into one bill.... but I digress

Lee DeRaud
06-15-2009, 11:45 AM
Her connection is just the coax coming in from a splitter outside the home.This sounds more like a cable problem than a TV problem.

First thing I'd check is that splitter: they used to make splitters that worked fine for normal analog and most cable systems, but didn't have anything like the bandwidth to handle newer digital cable feeds. For the channels her old set could handle, it probably didn't matter. (IIRC, the old ones cut off at 300MHz, the new ones at 800MHz-1GHz.)

Regardless, I'd get the cable company out to check the signal strength (1) coming in from the street and (2) at the back of the set...might have to put an amplifier on her leg of the feed.

(But something doesn't sound right...her cable system is running HD channels in without any encryption?!?)

Frank Hagan
06-15-2009, 12:19 PM
(But something doesn't sound right...her cable system is running HD channels in without any encryption?!?)

The new TV might have the right tuner to decode the HD signal; many cable systems include HD channels with the basic tier (Verizon FiOS does, for instance.)

Standard def content always looks worse on LCD or plasma than it does on a CRT set. Its why I haven't plunged ahead for a flat screen. I'm waiting for my 36" Toshiba set to die.

The other issue is that we still refer to sets by their "diagonal" measurement. Standard def has an aspect ratio that is almost square, 4:3 I think. Flat panels have an aspect ratio that is much more rectangular, at 16:9 or something like that. The net result is that unless you use a setting to mangle the image by zooming it or stretching it, you have two black bars on either side of the image. And your effective picture size is REALLY about 10" smaller than the diagonal dimension (depending on what size you start out with, of course, but the 10" is a good rule of thumb).

To replace a 12" set, and see standard def in the normal 4:3 aspect ratio with the same pic height and width, you would need a 19 - 22" wide screen set. To replace my 36" set, I need to go to at least a 46" set. Or, I can deform the picture and stretch it, like all the sports bars do (why people aren't throwing beer mugs at the screen, I don't know). Zoom and stretch are crimes against humanity, and should be outlawed by international convention (well, maybe not, but I shudder every time I see a BIG, BAD picture).

Dan Mages
06-15-2009, 1:25 PM
Hi Joe,

As I understand your original post, your mom has a 19" TV that is connected to the cable supplier via coax with no cable box, is this correct? If this is the case, then you have two choices, deal with the picture, or have Comcast install and HD cable box. However, this will only improve the picture on HD channels unless the cable box upconverts the signal. While Comcast is there, you can have them test the wires and splitters to make sure you are getting the best signal.

Dan

Eric DeSilva
06-15-2009, 1:28 PM
Let me try this from the ground up.

In the beginning, everyone got standard definition (SD) over-the-air (OTA). People had televisions which had tuners inside them that demodulated the OTA signals into NTSC video. (I say this because today, you can also buy a "monitor," which is different because it does not have a tuner inside it and therefore is not a TV.)

You can put the radiofrequency (RF) signal you get OTA on coaxial cable and pipe it around--i.e., from an antenna in your attic to the TV itself. The tuner in the TV is still examining modulation in a specific frequency band and demoduating that to create an NTSC signal. When cable TV (CATV) came around, the easiest thing to do was to get people to hook up their cable to the back of their TV instead of a coax from an antenna. The CATV system modulated a bunch of channels on the coax in addition to what you would get over-the-air. Because the signal wasn't dependent upon the vagaries of distance and power, it seemed like a better signal.

As CATV attempted to expand, they increased the number of signals they were modulating onto the cable. At some point, it becomes much more efficient to do this by digitizing the signal instead of transmitting RF type modulations. Enter "digital cable." Here's the problem. The CATV company digitizes their signal, but still has a bunch of customers who just run the cable into the back of their TV. The solution is to digitize the signals above the normal reception range of the TV. People who still plugged their coax directly into their TVs still got the modulated RF "low tier" signals, and those who used a set top box (STB) got the "high tier" digital signals. The STB converted the digital signals into a format that then got transmitted directly to your TV. In rare cases, that was still coax--remember setting your CATV box (or VCR) to "output channel 2" or "output channel 3" and then tuning into that channel? Since that was really putting a square peg into a round hole--since it relied on the tuner in the TV to demodulate a remodulated signal, other ANALOG transmission technologies got implemented--Video coax using RCA, S-Video, RGB, etc. These technologies moved a demodulated analog signal from one box to another. Since they were not relying on the tuner in the TV, they could also be used to transmit higher quality video signals--remember "progressive scan" DVD players?

Enter High Definition. HD is a digital format, but it has nothing to do with digital cable. HD is transmitted OTA and can be received on HDTVs with rabbit ears or other antennas (note I say "TVs"--not monitors). Once, TVs used to be analog devices, in the sense that the scan pulses were actually analog. Today's LCDs and plasmas are digital in the sense that they actually have discrete pixels. Doesn't take much science to figure out that taking a digital HD signal, converting to analog (e.g., component video), piping it to your LCD, and then having the LCD convert it back into digital pixels isn't the best idea. So, they came up with digital transmission formats--DVI, DVI-HDCP, HDMI. (To Lee's point, the content industry had a huge problem, however, in that digital outputs have the ability to permit people to make digital copies that are perfect. So, there are limits on the types of conversions that can take place and you have to conform to certain protocols in order to get the super secret handshake that allows you to build things that decoded encrypted HDMI or DVI-HDCP signals. But, its all "unencrypted" in the sense that HD OTA is, in fact, free over the air. Anyone can pick up the signal.)

So, most CATV companies haven't changed much. When HD started getting broadcast OTA, they took the HD signal, generally compressed it digitally, and then put it on their digital tier and had their digital STBs demodulate it. They did not, however, put HD RF modulated signals on the coax cable for analog users. What this means is that even if you have an HDTV, if you run the coax directly into your set, you will still only get SD OTA and whatever else SD the CATV company has modulated onto the wire. This is where the OP's problem comes in. The solutions are really one of three things--live with the SD version of the HD signal for OTA broadcasts, get a OTA antenna and let your TV decode OTA HD, or spring for a digital CATV STB (or a cable card).

Something to consider. With Friday's analog to digital switch, most SD OTA broadcasts terminated on Friday at noon. That means that the CATV companies no longer have an SD version of the local channels to run. So, those are gone. They provide HD versions, but those are typically digital and require a digital STB.

Some people say SD broadcasts look terrible on HD or that they look better on CRTs, etc. There is no rule here. A digital television, when faced with an SD signal, has to convert the SD to digital to display it. In so doing, they have to interpolate pixels where there is no "value" because the resolution exceeds the NTSC specification. Some TV circuitry does that better than others. Some people prefer a bit of noise that "blurs" the signal a bit. In a lot of ways, its personal preference. Same goes with black bars. HD is 16:9, SD is 4:3. You can squeeze/stretch/zoom or black bar. What you prefer is what you prefer. I stick with the black bars, because I think short wide people look funny. Others get used to it.

Dan Mages
06-15-2009, 1:45 PM
Let me try this from the ground up.

In the beginning, everyone got standard definition (SD) over-the-air (OTA). People had televisions which had tuners inside them that demodulated the OTA signals into NTSC video. (I say this because today, you can also buy a "monitor," which is different because it does not have a tuner inside it and therefore is not a TV.)

You can put the radiofrequency (RF) signal you get OTA on coaxial cable and pipe it around--i.e., from an antenna in your attic to the TV itself. The tuner in the TV is still examining modulation in a specific frequency band and demoduating that to create an NTSC signal. When cable TV (CATV) came around, the easiest thing to do was to get people to hook up their cable to the back of their TV instead of a coax from an antenna. The CATV system modulated a bunch of channels on the coax in addition to what you would get over-the-air. Because the signal wasn't dependent upon the vagaries of distance and power, it seemed like a better signal.

As CATV attempted to expand, they increased the number of signals they were modulating onto the cable. At some point, it becomes much more efficient to do this by digitizing the signal instead of transmitting RF type modulations. Enter "digital cable." Here's the problem. The CATV company digitizes their signal, but still has a bunch of customers who just run the cable into the back of their TV. The solution is to digitize the signals above the normal reception range of the TV. People who still plugged their coax directly into their TVs still got the modulated RF "low tier" signals, and those who used a set top box (STB) got the "high tier" digital signals. The STB converted the digital signals into a format that then got transmitted directly to your TV. In rare cases, that was still coax--remember setting your CATV box (or VCR) to "output channel 2" or "output channel 3" and then tuning into that channel? Since that was really putting a square peg into a round hole--since it relied on the tuner in the TV to demodulate a remodulated signal, other ANALOG transmission technologies got implemented--Video coax using RCA, S-Video, RGB, etc. These technologies moved a demodulated analog signal from one box to another. Since they were not relying on the tuner in the TV, they could also be used to transmit higher quality video signals--remember "progressive scan" DVD players?

Enter High Definition. HD is a digital format, but it has nothing to do with digital cable. HD is transmitted OTA and can be received on HDTVs with rabbit ears or other antennas (note I say "TVs"--not monitors). Once, TVs used to be analog devices, in the sense that the scan pulses were actually analog. Today's LCDs and plasmas are digital in the sense that they actually have discrete pixels. Doesn't take much science to figure out that taking a digital HD signal, converting to analog (e.g., component video), piping it to your LCD, and then having the LCD convert it back into digital pixels isn't the best idea. So, they came up with digital transmission formats--DVI, DVI-HDCP, HDMI. (To Lee's point, the content industry had a huge problem, however, in that digital outputs have the ability to permit people to make digital copies that are perfect. So, there are limits on the types of conversions that can take place and you have to conform to certain protocols in order to get the super secret handshake that allows you to build things that decoded encrypted HDMI or DVI-HDCP signals. But, its all "unencrypted" in the sense that HD OTA is, in fact, free over the air. Anyone can pick up the signal.)

So, most CATV companies haven't changed much. When HD started getting broadcast OTA, they took the HD signal, generally compressed it digitally, and then put it on their digital tier and had their digital STBs demodulate it. They did not, however, put HD RF modulated signals on the coax cable for analog users. What this means is that even if you have an HDTV, if you run the coax directly into your set, you will still only get SD OTA and whatever else SD the CATV company has modulated onto the wire. This is where the OP's problem comes in. The solutions are really one of three things--live with the SD version of the HD signal for OTA broadcasts, get a OTA antenna and let your TV decode OTA HD, or spring for a digital CATV STB (or a cable card).

Something to consider. With Friday's analog to digital switch, most SD OTA broadcasts terminated on Friday at noon. That means that the CATV companies no longer have an SD version of the local channels to run. So, those are gone. They provide HD versions, but those are typically digital and require a digital STB.

Some people say SD broadcasts look terrible on HD or that they look better on CRTs, etc. There is no rule here. A digital television, when faced with an SD signal, has to convert the SD to digital to display it. In so doing, they have to interpolate pixels where there is no "value" because the resolution exceeds the NTSC specification. Some TV circuitry does that better than others. Some people prefer a bit of noise that "blurs" the signal a bit. In a lot of ways, its personal preference. Same goes with black bars. HD is 16:9, SD is 4:3. You can squeeze/stretch/zoom or black bar. What you prefer is what you prefer. I stick with the black bars, because I think short wide people look funny. Others get used to it.

Great overview, however, you omitted QAM tuner (http://en.wikipedia.org/wiki/ClearQAM)capabilities found in most HDTVs. QAM tuner capability allows you to plug the coax directly into the back of the TV and receive unencrypted digital cable signals, including HD.

I did a quick check on Sharp's website. This TV is capable of 720p HD picture and has a QAM tuner. The big question is whether Comcast in your area gives you the HD cannels as part of the unencrypted package, or as a premium service, like they do around here. If it is the former, you might just have to have her upgrade to a digital cable package, if it is the latter, then you will have to add the HD package and a cable box.

Dan

Lee DeRaud
06-15-2009, 2:16 PM
Something to consider. With Friday's analog to digital switch, most SD OTA broadcasts terminated on Friday at noon. That means that the CATV companies no longer have an SD version of the local channels to run. So, those are gone. They provide HD versions, but those are typically digital and require a digital STB.Huh? Just because they went all-digital doesn't mean they went all-HD. Every local station I know of is still transmitting SD on one or more of their digital slots. And IIRC the cable companies are required to provide analog feeds (decoded/modulated versions of the digital SD feed) on basic cable for awhile longer (sometime in 2011?).

Lee DeRaud
06-15-2009, 2:36 PM
The other issue is that we still refer to sets by their "diagonal" measurement. Standard def has an aspect ratio that is almost square, 4:3 I think. Flat panels have an aspect ratio that is much more rectangular, at 16:9 or something like that. The net result is that unless you use a setting to mangle the image by zooming it or stretching it, you have two black bars on either side of the image. And your effective picture size is REALLY about 10" smaller than the diagonal dimension (depending on what size you start out with, of course, but the 10" is a good rule of thumb).

To replace a 12" set, and see standard def in the normal 4:3 aspect ratio with the same pic height and width, you would need a 19 - 22" wide screen set. To replace my 36" set, I need to go to at least a 46" set. Or, I can deform the picture and stretch it, like all the sports bars do (why people aren't throwing beer mugs at the screen, I don't know). Zoom and stretch are crimes against humanity, and should be outlawed by international convention (well, maybe not, but I shudder every time I see a BIG, BAD picture).Need to brush up on your math a bit...

If you're going to watch a 4:3 picture on a 16:9 set, it needs to be 22% bigger diagonally than a 4:3 set to get the same size picture: the 12" 4:3 set becomes a 15" 16:9 set. (Although there are still plenty of 15" 4:3 LCD TVs available out there.)

To replace your 36", you nominally need a 44", but I suspect your 36" is more like 34"-35" 'viewable' size, so a 42" will do nicely. (There's still a decent price jump going from 42" to 46". And actually the LCDs tend to look bigger than a same size CRT...I have no idea why.)

Eric DeSilva
06-15-2009, 2:42 PM
you omitted QAM tuner (http://en.wikipedia.org/wiki/ClearQAM)capabilities found in most HDTVs. QAM tuner capability allows you to plug the coax directly into the back of the TV and receive unencrypted digital cable signals, including HD.

... The big question is whether Comcast in your area gives you the HD cannels as part of the unencrypted package, or as a premium service, like they do around here.

I did reference the HD tuner--the difference between an "HD monitor" and an "HD Television." The tuner is what allows you to pull in HD OTA with just an antenna and without a separate box. They used to market HD tuner boxes for HD monitors that were separate until the FCC cracked down and forced more companies to produce HDTVs instead of HD monitors.

This is not an encryption issue--it is that the CATV version of what digital means is different. QAM will not decode CATV digital. You can get a cablecard to put in some TVs that will decode CATV digital. But, no CATV company that I know of transmits digital HD in analog. Some might put it in a non-premium tier, but its still transmitted digitally and you will still need something to decode CATV digital--either a digital STB or cable card.

Eric DeSilva
06-15-2009, 2:47 PM
Huh? Just because they went all-digital doesn't mean they went all-HD. Every local station I know of is still transmitting SD on one or more of their digital slots. And IIRC the cable companies are required to provide analog feeds (decoded/modulated versions of the digital SD feed) on basic cable for awhile longer (sometime in 2011?).

Yes it does. There is *NO* specification for digital, non-HD. There was a provision that permitted compressed analog in HD digital allotments, but those are either now fully digital or secondary. In other words, OTA SD should be dead except for secondary low power television stations that can be kicked off the air at pretty much any moment.

Hence, I'm not sure what digital SD feed you are talking about. The CATV systems must carry the locals. If the locals are analog SD because they are licensed secondary, they might still be around--but not for long, like I said. All the networks and primaries ceased SD transmission as of noon Fri. There is *no* requirement that CATV provide downrezzed HDTV.

EDIT: I just double checked something. Apparently CATV cos do have to carry both analog and digital must carry signals until sometime in 2012 unless they have gone all-digital. So, if they require everyone to have a box, they can drop the analog version. I also gather there were a few CATV cos that actually did rebroadcast the QAM on coax in the clear, so you could get the HD signal via coax. I gather that was pretty rare, and it is certainly not a requirement. Makes me wonder, however, they can get the SD version of the HD signal for rebroadcast without violating copyright.

Lee DeRaud
06-15-2009, 3:49 PM
There is *NO* specification for digital, non-HD. There was a provision that permitted compressed analog in HD digital allotments, but those are either now fully digital or secondary. In other words, OTA SD should be dead except for secondary low power television stations that can be kicked off the air at pretty much any moment.

Hence, I'm not sure what digital SD feed you are talking about. The CATV systems must carry the locals. If the locals are analog SD because they are licensed secondary, they might still be around--but not for long, like I said. All the networks and primaries ceased SD transmission as of noon Fri. IIRC, you can split an HD frequency slot into multiple (6?) SD slots. For example, the local ABC affiliate (KABC) puts out three or four separate digital SD channels in addition to the HD. They had been doing that for a couple of years before Friday's changeover. Visually, the only difference between the old "channel 7" and its digital copy (107 on the cable, I think the DTV converter boxes call it 7.1) was a slightly different logo down in the corner. The others (7.2, 7.3) have different programming.

(I am not talking about a "secondary low power" station: this is the network-owned ABC station in Los Angeles.)

Here's s snippet directly from the FCC's "dtv.gov" website:

For example, rather than being limited to providing one analog program, a broadcaster is able to offer a super sharp “high definition” (HD) digital program or multiple “standard definition” (SD) digital programs simultaneously through a process called “multicasting.” Multicasting allows broadcast stations to offer several channels of digital programming at the same time, using the same amount of spectrum required for one analog program. So, for example, while a station broadcasting in analog on channel 7 is only able to offer viewers one program, a station broadcasting in digital on channel 7 can offer viewers one digital program on channel 7-1, a second digital program on channel 7-2, a third digital program on channel 7-3, and so on. This means more programming choices for viewers. Further, DTV can provide interactive video and data services that are not possible with analog technology.

Tim Morton
06-15-2009, 5:28 PM
Where did that come from? It's totally wrong...

Coax carries modulated RF fine. So, for example, plenty of UHF antennas are connected to converter boxes and HDTVs via coax and do 1080i as well as anything else. So, in fact, coax carries 1080i quite well.

The cable television issue is that, once upon a time, they carried modulated RF duplicating the over-the-air (OTA) channels on the low end of their cable coax. That meant you could plug it into a television and the TV decoding circuitry would effectively pretend the coax was an antenna and you would get the OTA channels via coax without a box. Cable television systems do not do this for HD broadcasts, however. So, even if you have an HDTV capable of demodulating OTA HD, you won't get anything from the CATV coax without a set top box (STB) or a cable card.

You can, however, get an external antenna, connect it via coax to your HDTV, and get a darn fine HDTV signal from OTA sources--assuming they are there to pick up.

What you guys all seem to be conflating is carrying a demodulated digital HD signal. Once something has demodulated the signal from RF and turned it into 1's and 0's of digital, you want to move the signal from box to box in the digital domain. That means HDMI or DVI. It makes little sense to turn it into HD, then convert it back to analog to go from box to TV.


you cannot take output a 1080i signal from a set top HD cable box to your TV using coax cable...maybe i said it wrong the first time.

Craig Coney
06-15-2009, 11:14 PM
Joe,
Around here, Comcast is advertising free HD without a converter box. Did you by any chance scan for the HD channels? I went with satellite before they offered this, the picture quality wasn't acceptable even out of their converter boxes at the time.

Joe Pelonio
06-15-2009, 11:36 PM
(But something doesn't sound right...her cable system is running HD channels in without any encryption?!?)
Yes, some of the channels that are crap down low 4,5,7 can be found again at HD channel locations 104, 105, 107 and are beautiful. The PBS on 9 is not recognizable, and the HD version on 109 is not much better. Here we have a DVR on a non-HD TV and the HD channels are about the same quality as non HD versions but are rectangular. Without a box we get only 1-99 but on the DVR go up to 998 now. That's only in my shop, we have two others with little mini-boxes that get up to 591. It takes a alot of effort to sort it out.

Joe Pelonio
06-15-2009, 11:42 PM
EDIT: I just double checked something. Apparently CATV cos do have to carry both analog and digital must carry signals until sometime in 2012 unless they have gone all-digital. So, if they require everyone to have a box, they can drop the analog version. I also gather there were a few CATV cos that actually did rebroadcast the QAM on coax in the clear, so you could get the HD signal via coax. I gather that was pretty rare, and it is certainly not a requirement. Makes me wonder, however, they can get the SD version of the HD signal for rebroadcast without violating copyright.
That I can verify, the cable company did tell me a few weeks ago that if we had any sets on just coax they would send us a free digital adapter box. That me be what's causing the problem on that HD set, I had forgotten about it. Maybe she hadn't watched it since the changeover since it was Friday and we switched sets Saturday morning!

Joe Pelonio
06-15-2009, 11:44 PM
Joe,
Around here, Comcast is advertising free HD without a converter box. Did you by any chance scan for the HD channels? I went with satellite before they offered this, the picture quality wasn't acceptable even out of their converter boxes at the time.
I had it scan for whatever it found, and it identified 100+ analog and 200+ digital channels. Identifying and being able to watch are not the same, though. I had some work to do today so have yet to call but will try tomorrow.

Mike Henderson
06-15-2009, 11:49 PM
I have cox cable and I get HD with the standard cable service (I don't have any cable boxes and run the cable directly into my TV). That is, on channel 4 (for example) I used to get the local analog SD channel 4. But when channel 4 went HD, I started getting it as HD on my new flat screen. The old SD is still there as channel 4 but the HD version is channel 4-1 (at least that's how it displays on my TV). There's also a 4-2 which is a weather channel of channel 4. Channel 7 is Channel 7 (SD), Channel 7-1 (HD), Channel 7-2 (advertising shows - infomercials) and channel 7-3 (weather).

I need to do another "scan" of the cable (scan function on the TV) to see if there's any new HD channels that have shown up since the last time I scanned.

Mike

[I don't know how this is done in the frequency spectrum. As Eric points out, the standard analog (SD) channels are broadcast in 6 MHz channels using vestigial side band. Those channels are contiguous (except for the gap between 6 & 7) and have to stay where they are in order for old TVs to receive the signal properly. So channel 4 is broadcast on 67.25MHz using VSB. The thing I don't know is where is channel 4-1 and 4-2 broadcast? Must be outside the standard analog over-the-air bandwidth. Anyone know?? Maybe in the new frequency bands that the HD would have over-the-air??? Maybe between analog channel 6 and 7?]

[I went and did some research. The HD channels are probably on one of the old UHF channels. They identify themselves so the system can display them in order by channel number, even though the frequency of each channel is significantly different. So on my TV, the analog channel 4 is still at 67.25MHz, but channel 4-1 is probably some UHF channel at a significantly higher frequency.]

Frank Hagan
06-16-2009, 2:27 AM
Need to brush up on your math a bit...

If you're going to watch a 4:3 picture on a 16:9 set, it needs to be 22% bigger diagonally than a 4:3 set to get the same size picture: the 12" 4:3 set becomes a 15" 16:9 set. (Although there are still plenty of 15" 4:3 LCD TVs available out there.)

To replace your 36", you nominally need a 44", but I suspect your 36" is more like 34"-35" 'viewable' size, so a 42" will do nicely. (There's still a decent price jump going from 42" to 46". And actually the LCDs tend to look bigger than a same size CRT...I have no idea why.)

I'll agree with the first part, at least mathmatically, but not the second. The calculator at Cnet.com (http://reviews.cnet.com/4520-7608_7-1016109-4.html) does show that to get the same size diagonal picture on a 16:9 set I need to buy a 44", so you're right. The "cheater dimension" (whether a 4:3 36" set is REALLY 36" or 35 or 34) is probably the same "cheater dimension value" on the new flat screen ... unless the marketers have suddenly got religion, and all 52" sets actually have 52" of diagonal viewing surface. So I'll disagree with the second part.

But there's something else I've noted on this topic, and why I saw 10" more is a better rule or thumb. Look at the "maximum viewing distance" for CRT and LCD sets. They have an interesting chart at that same link showing the minimum and maximum viewing distance for 4:3 and 16:9 sets.

A 19" 4:3 set has a maximum viewing distance of 7.6'. Guess what the smallest size you need for that same maximum viewing distance in a 16:9 set? A 30" set ... about 10" larger. A 32" 4:3 set has a maximum viewing distance of 12.8 feet ... and to get the smallest set with a maximum viewing distance of 12.8 feet in a 16:9 set: 55".

You CAN sit closer to a 16:9 set and do better than with a 4:3 CRT set, but for optimum viewing at family room distances, about 8 - 12' normally, you need a bigger 16:9 set than just the diagonal.

Its one reason so many people are disappointed when they get a flat screen TV. That and the lousy picture quality compared to their CRT set from RCA they bought in 1975.

Lee DeRaud
06-16-2009, 10:38 AM
I'll agree with the first part, at least mathmatically, but not the second. The calculator at Cnet.com (http://reviews.cnet.com/4520-7608_7-1016109-4.html) does show that to get the same size diagonal picture on a 16:9 set I need to buy a 44", so you're right. The "cheater dimension" (whether a 4:3 36" set is REALLY 36" or 35 or 34) is probably the same "cheater dimension value" on the new flat screen ... unless the marketers have suddenly got religion, and all 52" sets actually have 52" of diagonal viewing surface. So I'll disagree with the second part.The quoted dimensions for LCD screens are actually the same as the viewable size, unlike CRTs. I don't think it was a marketing thing so much as the physical construction and mounting requirements of LCD panels make it possible to use the whole area, unlike CRTs which were sized by the maximum tube dimension. (Or it may have been some kind of regulatory thing: at some point awhile back they started advertising CRTs as 'X" diagonal (Y" viewable)'.)

As for the rest of it: the way I computed it was to compare the vertical dimension of 4:3 screens (0.6 x diagonal) with the vertical dimension of 16:9 screens (0.49). That ratio is 1.224 or slightly more than 22% bigger.

If there is some rational reason why seating distances would be different for the same image on the two screens, I'd love to hear it. I suspect it's more of a question of people wanting to sit closer to the big screens to get the "movie" experience...in other words, totally psychological.

Eric DeSilva
06-16-2009, 11:37 AM
I'll be damned. I thought that was transitional only. I think I'd rather have the HD...