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Old 11-11-2007, 10:56 AM   #361
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Just to add some more confusion. I am currently running a THD with 9.2J and have seen some macroblocking and sound drop outs. My Hitachi HDTV also has a SA cable card. My THD has a SA MCard. Using split screen, I am able to put the THD on one screen and the TV cable card on the other. I am seeing the same macroblocking on both screens. Apparently my problems are the cable or cable card (Comcast). The signal strength is 98-100, so I'm suspecting the broadcast.
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Old 11-11-2007, 06:16 PM   #362
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Installers are taught that a signal level of +5dB is excellent. That signal is fine for the Motorola boxes, but in many cases, it is too strong for the TiVo.
Your post is very informative. But it also has the tone of "apologizing" for TiVo. As I indicated in this posting the ANSI spec says a receiver should accept a signal anywhere in the range of -12 dBmV to +15 dBmV. If the TiVo HD can't do it, then it is a P.O.S.

I need to go back and re-read the ANSI spec. Maybe there's a section in there about going to the local Radio Shack and buying an in-line attenuator. Just in case.
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Old 11-11-2007, 07:58 PM   #363
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Originally Posted by Phantom Gremlin View Post
Your post is very informative. But it also has the tone of "apologizing" for TiVo. As I indicated in this posting the ANSI spec says a receiver should accept a signal anywhere in the range of -12 dBmV to +15 dBmV. If the TiVo HD can't do it, then it is a P.O.S.

I need to go back and re-read the ANSI spec. Maybe there's a section in there about going to the local Radio Shack and buying an in-line attenuator. Just in case.
Based on what I have heard, I believe there is more going on with FIOS than meets the eye. The action that needs to be taken to get good results is counterintuitive. The kind of things that have to be done for FIOS dont have to be done with typical copper cable. Instead of automatically declaring Tivo guilty, perhaps a look at FIOS would be another path to consider. As to Tivo's tuner capabilities, with TWC, at one time I was driving the S3 with a +10 signal and saw no adverse effects.

Taking another path... Does anyone have any technical info on the implementation of FIOS? Are they doing a block conversion on a chunk of optical spectrum to create the 54-860 Mhz spectrum? I cant envision a bunch of individual QAM and NTSC modulators in the ONT. If they are block converting... controlling the cumulative jitter would seem to be a challenge.
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Old 11-11-2007, 08:47 PM   #364
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It was marked at -8 per port? or was that its acutal effect? A 2way should be minus 3.5db. Sometimes they are labeled -4db.
As you said, -4.
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Old 11-11-2007, 09:49 PM   #365
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Pixelization with Verizon FiOS: How to Fix

Background

FiOS uses several different ONTs which provide an average signal level of +12dB to +18 dB to +24 dB. Output from the most widely used ONT (Motorola 612) is +18 dB on most channels. Output with older installations (Motorola 611) is up to +24dB.

For some reason, the output on many ONTs (or some COs?) is not linear. The output might be +14dB to +16dB on most channels, but +20 dB on others.

Verizon installers are instructed to add an attenuator to reduce the signal down to +5 dB. Some do, some don't, as the Motorola STBs and DVRs tend to work fine with mosts signals of +10 dB or less.

The Problem

Installers are taught that a signal level of +5dB is excellent. That signal is fine for the Motorola boxes, but in many cases, it is too strong for the TiVo.

With a signal level of +5dB, the majority of channels will be fine on the Tivo, but many may exhibit intermittent pixelization. On these channels, RS Corrected and RS Uncorrected errors increment rapidly, SNR fluctuates, and signal strength fluctuates between 100 and a lower number (such as 50).

Even with a signal level of +0dB, some channels may exhibit intermittent pixelization. In my experience, 90-95% of FiOS channels are fine with a signal level of +0 dB, but that signal level is still too strong on perhaps 5-10% of channels.

I attribute this to non-linear output from the ONT -- most channels may be +0dB but others in different frequency ranges may be +5dB higher (or more). It is these channels with higher signal levels that exhibit pixelization. FiOS uses the same frequency ranges for locals, RSNs, and other cable channels on every system across the country. It is common for the local HD channels to be in the frequencies with a higher signal level.

More often than not, calling Verizon FiOS support is not a solution, because installers take one look at the +5dB signal level and conclude that the signal is fine -- just as they are trained to do. Verizon installers do have attenuators, but they don't attenuate the signal further because they are trained on the requirements of the Motorola boxes, not the TiVos.

The Solution

The solution is to further reduce signal strength to -6dB or lower by adding an attenuator to the end of the coax cable. This does not affect the FiOS channels with lower signals levels, but it eliminates the pixelization on FiOS channels with higher signal levels. It takes about 60 seconds to install an attenuator.

Steps to Fix
  1. Order a pack of attenuators. These screw on to the end of the coax.

    http://www.smarthome.com/7800.html

  2. Find a channel with pixelization.

  3. Once you've found a channel with pixelization, open Settings -> System Information -> Diagnostics. With this screen, you can monitor your SNR and number of RS Corrected and RS Uncorrected errors.

    Your goal is to completely eliminate the RS Uncorrected errors and the fluctuation in the SNR. A few occasional RS Corrected errors are fine; it is the RS Uncorrected Errors that indicate pixelization.

  4. Disconnect the coax cable from the TiVo.

    Note the process of disconnecting and reconnecting the coax will result in a lot of RS Uncorrected and RS Corrected errors, but don't worry about that. Only worry about errors that increment after the cable is firmly connected.

  5. Most seem to require -10dB to -16dB of new attenuation. I would start with -16dB. Screw one -10dB attenuator and one -6dB attenuator onto the end of the coax cable. Then reconnect the coax back to the TiVo.

  6. Is the problem fixed? Wait 60 seconds. Have the RS Uncorrected errors stopped incrementing on the Diagnostics screen?

  7. If not, disconnect the coax again and repeat step four using one -10dB attenuator and one -2dB attenuator.

    Is the problem fixed? Wait 60 seconds. Have the RS Uncorrected errors stopped incrementing on the Diagnostics screen?

  8. If not, disconnect the coax again and repeat step four using a single -10dB attenuator.

    Is the problem fixed? Wait 60 seconds. Have the RS Uncorrected errors stopped incrementing on the Diagnostics screen?

  9. If not, disconnect the coax again and repeat step four using a single -6dB attenuator.

  10. By now, the problem will be fixed.

This is worth a try, but it's not a panacea. I've had the pixellation on FIOS on and off since the beginning of August, after having 5 months of zero pixellation from March - August. Nothing on my system changed in August to cause the problem. I've had numerous visits from Verizon, and the signal has been attenuated with a variable attenuator until the signal disappears completely, and the pixellation was reproducible on the same fixed set of channels at any signal strength.

Verizon IS working with TiVo on this -- according to their last communication with me on my trouble ticket, they're sending a senior tech with specialized monitoring equipment out to me shortly. That guy will apparently work directly with the TiVo engineers to troubleshoot the issue.

I know of a couple of other people in various parts of the country who have similar problems.
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Old 11-12-2007, 09:09 AM   #366
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Your post is very informative. But it also has the tone of "apologizing" for TiVo. As I indicated in this posting the ANSI spec says a receiver should accept a signal anywhere in the range of -12 dBmV to +15 dBmV. If the TiVo HD can't do it, then it is a P.O.S.

I need to go back and re-read the ANSI spec. Maybe there's a section in there about going to the local Radio Shack and buying an in-line attenuator. Just in case.
Then return it.

Alternatively, if you want to get it to work, add in-line attenuation to get the SNR down to 31/32.
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Old 11-12-2007, 12:08 PM   #367
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FIOS and HD Pixellation - attenuation through splitters

I've attenuated my signal down so SNR is around 32 - no more pixellation or macroblocking or RS incrementing.

Because I could not locally purchase attenuators, I took the signal down about 11db by running the signal serially through 3.5db and 7.5db splitters. Other than being inelegant, is there is any issue with using multiple splitters as compared to dedicated attenuators?
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Old 11-12-2007, 12:58 PM   #368
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I've attenuated my signal down so SNR is around 32 - no more pixellation or macroblocking or RS incrementing.

Because I could not locally purchase attenuators, I took the signal down about 11db by running the signal serially through 3.5db and 7.5db splitters. Other than being inelegant, is there is any issue with using multiple splitters as compared to dedicated attenuators?
Leaving all those unused taps open might allow egress or ingress and lead to interference... but there is always the old saying... if it aint broke, dont fix it. The engineer in me would want to do it with proper attenuators... or at least terminate the open outputs of the splitters.
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Old 11-12-2007, 01:06 PM   #369
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Good point on termination

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Originally Posted by SCSIRAID View Post
Leaving all those unused taps open might allow egress or ingress and lead to interference... but there is always the old saying... if it aint broke, dont fix it. The engineer in me would want to do it with proper attenuators... or at least terminate the open outputs of the splitters.
I terminated the open splits right from the start. Thanks.
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Old 11-12-2007, 01:14 PM   #370
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Originally Posted by TimAtkins1 View Post
I've attenuated my signal down so SNR is around 32 - no more pixellation or macroblocking or RS incrementing.

Because I could not locally purchase attenuators, I took the signal down about 11db by running the signal serially through 3.5db and 7.5db splitters. Other than being inelegant, is there is any issue with using multiple splitters as compared to dedicated attenuators?
The low-quality splitters might also screw with signal strength non-linearly, so you might find variability with some channels.

You can buy in-line attenuators at places like smarthome, for like $2 each. They come in -3db, -6db, -10db, -20db, and I think some others.

I bought a bunch and just fiddled with each Tivo until I got to the right SNR. I chose not to do it at the source, but for no particular reason other than I wanted as strong a signal as possible right to the destination. My "gut" felt better that way.
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Old 11-12-2007, 01:27 PM   #371
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The low-quality splitters might also screw with signal strength non-linearly, so you might find variability with some channels.

You can buy in-line attenuators at places like smarthome, for like $2 each. They come in -3db, -6db, -10db, -20db, and I think some others.

I bought a bunch and just fiddled with each Tivo until I got to the right SNR. I chose not to do it at the source, but for no particular reason other than I wanted as strong a signal as possible right to the destination. My "gut" felt better that way.
How much 'wiggle room' did you end up with? Can you take out 2db of attenuation or add 3-4db of attenuation and still work OK?
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Old 11-12-2007, 02:13 PM   #372
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How much 'wiggle room' did you end up with? Can you take out 2db of attenuation or add 3-4db of attenuation and still work OK?
It's pretty coarse, if that's what you mean. Taking out 3db vs. 6db often didn't make a ton of difference in SNR, so I tended to err on the more attenuation side of things.
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Old 11-12-2007, 04:11 PM   #373
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It's pretty coarse, if that's what you mean. Taking out 3db vs. 6db often didn't make a ton of difference in SNR, so I tended to err on the more attenuation side of things.
I was thinking of functioning properly vs SNR. So if you added or removed 3-6db of attenuation... would it still work 'ok' ie no pixelation or other 'problems'?
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Old 11-12-2007, 04:38 PM   #374
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I was thinking of functioning properly vs SNR. So if you added or removed 3-6db of attenuation... would it still work 'ok' ie no pixelation or other 'problems'?
Ah, I see. The magic number definitely seems to be 31 SNR. Anything higher, and you get pixellation/increasing RS Uncorrected. 31/32 was as high as I could get. 32/33 pixellation was back.

So attenuate until you hit that magic number!
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Old 11-12-2007, 05:29 PM   #375
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Tuner Specifications

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Your post is very informative. But it also has the tone of "apologizing" for TiVo. As I indicated in this posting the ANSI spec says a receiver should accept a signal anywhere in the range of -12 dBmV to +15 dBmV. If the TiVo HD can't do it, then it is a P.O.S.
That is the ANSI spec, and it means just what it says. The receiver should be able to receive a signal on a single carrier witin the -12 dBmV to +15 dBmV range with the specified bit errror rate (usually about 1 bit error per million or billion bits). This does NOT mean the receiver will be able to reliably receive any signal on any medium where the channel in question is within that range. Very few if any consumer grade receivers, for example, could manage to reliably receive a signal on one channel at 0 dBmV if the adjacent channels are both coming in at +25dB mV. Similarly, the amount of 2nd and 3rd order distortions in the receiver itself climb rapidly as the number of channels and the total input power increases. If the CATV plant in question is delivering a full +15 dBmV wall to wall on 170 carriers, then any receiver would croak. Indeed, that level of signal may be enough to actually damage or even destroy some receivers. It amounts to 0.36 watts, which is enough to make a 1/8 or even 1/4 watt resistor mighty hot on most circuit boards. Even if not, no receiver has a common mode rejection that high across the entire 50MHz - 1000MHz band, and those sorts of broadband levels will drive any receiver insane. It's a lot like trying to hear someone scream at you at a rock concert right in front of one of the stage monitors. No matter how loud they scream, you won't be able to understand them.

So is there an answer? Yes, there is. An optimum signal level would be where the lowest carrier in the band is 3dB higher than the lowest level at which the receiver can reliably receive that same channel. Any lower and the chances the signal may drift down to the point whrere reception becomes an issue start to rise sharply. There is no benefit whatsoever to increasing the signal level beyond this point. Therefore the best situation would be to arrange for the signal on the lowest level carrier to be about -9 dBmV and no higher than about -6 dBmV. The spectrum ideally should also be fairly flat. If the highest level carrier is more than 10dB higher than the lowest level carrier, then it is not unlikely your CATV provider may have a problem on their plant. Have them verify this. If not, then a tilt compensator may be in order. Since in the event the situation probably derives from being way at the end of the CATV cascade and having a very long subscriber drop, it's likely there may be a residential amplifier involved, and many high quality residential CATV amplifiers have variable tilt compensators built in.
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Old 11-12-2007, 05:38 PM   #376
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Inaccurate

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Alternatively, if you want to get it to work, add in-line attenuation to get the SNR down to 31/32.
This is not quite correct. It may be true for a CATV spectrum profile similar to yours the optimum signal level may be found when the S/N is about 32. This does not mean it will be optimum for everyone. The S/N is affected by a large number of factors and the optimum S/N depends on the total number of carriers, in-band flatness, noise level on the CATV plant, and the receiver sensitivity. The assumption your plant configuration is typical may or may not be true, and the typical plant profile may not relate to the CATV profile of any particular user. That said, they can try your recommendation as a starting point and refine it from there.
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Old 11-12-2007, 05:47 PM   #377
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That and more

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Leaving all those unused taps open might allow egress or ingress and lead to interference... but there is always the old saying... if it aint broke, dont fix it. The engineer in me would want to do it with proper attenuators... or at least terminate the open outputs of the splitters.
Actually, improperly terminated (i.e. loose) terminators will cause more ingress / egress than none at all, so make sure the terminators are tight. They need to be snug when tightened with a small wrench. It should not be possible to remove them with the fingers. Don't get too excited with the wrench, though, or you can break off a port.

There is another big reason to terminate any spliter ports, however: flatness. You would be appalled to see what unterminated ports will do the the signal levels on the other ports of a splitter. In some cases it can cause an attenuation of over 10dB to some parts of the spectrum, or even possibly just to one or two channels. It's also not possible to predict very well which part of the spectrum will be affected or how much. It depends on the lengths of the attached cables.
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Old 11-12-2007, 06:02 PM   #378
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Maybe

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Because I could not locally purchase attenuators, I took the signal down about 11db by running the signal serially through 3.5db and 7.5db splitters. Other than being inelegant, is there is any issue with using multiple splitters as compared to dedicated attenuators?
Yes, there can be - maybe. Of course the mere fact there are more connectors in the equation means there are more single points of failure, and connectors are right up there in the list of things most likely to cause problems. That's not to say they will, but they can. If the connectors are of good quality and their installation is done properly, they shouldn't cause many problems.

The problems they can cause include ingress and ghosting due to low return loss issues, especially if the connectors are bad or loose.

In addition, while the splitters are said to increase the "flat loss" (properly termed attenuation), the fact is their response is not flat. Every splitter looses more at higher frequencies than at low frequencies. At 50MHz, a hihg quality 2 way splitter will lose very close to 3.5 dB between the input and output. At 1000MHz, the number may exceed 4.5dB. Multiple splitters will of course loose even more at the high end compared to the low end. Now if your subscriber tap happens to be fairly close to an amplifier, then this isn't going to have a significantly bad impact. Indeed, it may even make the signal better, because close to an amplifier the high frequencies are also going to be high in level, and multiple splitters will provide some welcome - although not really necessary - tilt compensation. Further towards the end of the subscriber plant the high frequencioes are going to be much lower in level already than the low frequncies, and the additinal equalization from the splitters can cause the highest channels to be too low in level.
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Old 11-12-2007, 09:11 PM   #379
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Very few if any consumer grade receivers, for example, could manage to reliably receive a signal on one channel at 0 dBmV if the adjacent channels are both coming in at +25dB mV.
Your explanation is interesting in general cable terms. However the discussion I was replying to was in the context of FiOS and an ONT on the side of the house. I would expect the ONT output to be balanced to within a few dB. Also hopefully we don't need to worry about things like "tilt" since in most FiOS installations the coax is very short (compared to a cable plant).
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Old 11-12-2007, 09:31 PM   #380
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Your explanation is interesting in general cable terms. However the discussion I was replying to was in the context of FiOS and an ONT on the side of the house. I would expect the ONT output to be balanced to within a few dB. Also hopefully we don't need to worry about things like "tilt" since in most FiOS installations the coax is very short (compared to a cable plant).
It would seem a reasonable expectation... but is it met? Tilt could also come from the source itself or from off the shelf components with tilt compensation that isnt required. I certainly dont know.

I would like to find a good explanation of how FiOS generates its 50-860 Mhz output. Block converter? It could also be interesting to see what comes out of the ONT above 860 and below 50Mhz... given the shouting next to the concert speaker line of thought.
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Old 11-13-2007, 02:50 PM   #381
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Not just a FIOS problem ...

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...
Verizon installers are instructed to add an attenuator to reduce the signal down to +5 dB. Some do, some don't, as the Motorola STBs and DVRs tend to work fine with mosts signals of +10 dB or less.

The Problem

Installers are taught that a signal level of +5dB is excellent. That signal is fine for the Motorola boxes, but in many cases, it is too strong for the TiVo.

With a signal level of +5dB, the majority of channels will be fine on the Tivo, but many may exhibit intermittent pixelization. On these channels, RS Corrected and RS Uncorrected errors increment rapidly, SNR fluctuates, and signal strength fluctuates between 100 and a lower number (such as 50).
...
I have that problem on my new TiVo HD, however my cable company is RCN.

So, what constitutes too hot a signal in terms of the data I can read on my tivo's Diagnostics screen?

Channels that are causing intermittent pixelization problems for me have signal strengths in the range of 87-93 with occasional peaks up to 100. The signal to noise ratio (SNR) display for those channels sits around 35-36 dB. Might those values be considered too high? If so, what range of values should I be trying to hit when I start adding attenuation?

Any advice on this would be greatly appreciated. Thanks.
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Old 11-13-2007, 03:05 PM   #382
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I have that problem on my new TiVo HD, however my cable company is RCN.

So, what constitutes too hot a signal in terms of the data I can read on my tivo's Diagnostics screen?

Channels that are causing intermittent pixelization problems for me have signal strengths in the range of 87-93 with occasional peaks up to 100. The signal to noise ratio (SNR) display for those channels sits around 35-36 dB. Might those values be considered too high? If so, what range of values should I be trying to hit when I start adding attenuation?

Any advice on this would be greatly appreciated. Thanks.

The peaks to 100 would be what would concern me. The final arbitor as to when its 'right' would be the RS Uncorrected value staying at zero and no visable pixelation. Given the peaks to 100, I would suggest attenuating 3 to 6 db and see what happens. 'Typical wisdom' would be to look for stable mid 80 to mid 90's signal strength with SNR around 34db. Note that typical wisdom can be wrong so its just a starting point. FiOS is one proof point of this.
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Old 11-13-2007, 03:40 PM   #383
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I have that problem on my new TiVo HD, however my cable company is RCN.

So, what constitutes too hot a signal in terms of the data I can read on my tivo's Diagnostics screen?

Channels that are causing intermittent pixelization problems for me have signal strengths in the range of 87-93 with occasional peaks up to 100. The signal to noise ratio (SNR) display for those channels sits around 35-36 dB. Might those values be considered too high? If so, what range of values should I be trying to hit when I start adding attenuation?

Any advice on this would be greatly appreciated. Thanks.
The magic SNR for FIOS is 31/32. Not sure if that would also work for other "hot" cable connections, but it's worth a try, as it's easy to test.
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Old 11-16-2007, 11:00 AM   #384
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My experience, in case it helps anyone...

Two Tivo S3 on Comcast in Sacramento. Pixelation started on one Tivo about two months ago and has gotten progressively worse. The other tivo is fine. Finally, watching Sunday Night Football was unbearable. And, I was starting to get some pixelation on downloaded content (tivocast). So, I figured it must be the HDD. However, I checked signal strength on ESPN-HD and it was a little low (SNR 29-30, Signal 63-69). I decided to upgrade the hard drive to see if that would help anyway. Went from a Seagate barracuda 750gb to seagate barracuda 1TB. All pixelation is gone. And here's the annoying thing. The signal strength now shows perfect on all channels. This seems an incredible coincidence. I checked just before and just after changing the HDD and signal went from marginal to perfect. I'm pretty much convinced my HDD was the primary issue but I don't understand the signal strength wierdness.

Key thing: the HDD might be the problem for more folks than we might think, even if the signal strength looks a bit marginal.
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Old 11-16-2007, 12:28 PM   #385
bkdtv
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Originally Posted by PaulRuby View Post
My experience, in case it helps anyone...

Two Tivo S3 on Comcast in Sacramento. Pixelation started on one Tivo about two months ago and has gotten progressively worse. The other tivo is fine. Finally, watching Sunday Night Football was unbearable. And, I was starting to get some pixelation on downloaded content (tivocast). So, I figured it must be the HDD. However, I checked signal strength on ESPN-HD and it was a little low (SNR 29-30, Signal 63-69). I decided to upgrade the hard drive to see if that would help anyway. Went from a Seagate barracuda 750gb to seagate barracuda 1TB. All pixelation is gone. And here's the annoying thing. The signal strength now shows perfect on all channels. This seems an incredible coincidence. I checked just before and just after changing the HDD and signal went from marginal to perfect. I'm pretty much convinced my HDD was the primary issue but I don't understand the signal strength wierdness.

Key thing: the HDD might be the problem for more folks than we might think, even if the signal strength looks a bit marginal.
Sounds like your previous drive upgrade caused some sort of interference.
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Old 11-16-2007, 12:53 PM   #386
PaulRuby
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Originally Posted by bkdtv View Post
Sounds like your previous drive upgrade caused some sort of interference.
Yes it does... But it took a year to go bad. Was great for ~8 months then spent 4 months getting to the unbearable point. Now is great again with the 1TB drive. I sprung for the more expensive 24-7 version of the drive (NS instead of AS suffix) so I hope that means it'll survive longer than a year.
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Old 11-17-2007, 12:23 AM   #387
Berone
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Originally Posted by bkdtv View Post
Pixelization with Verizon FiOS: How to Fix

Background

FiOS uses several different ONTs which provide an average signal level of +12dB to +18 dB to +24 dB. Output from the most widely used ONT (Motorola 612) is +18 dB on most channels. Output with older installations (Motorola 611) is up to +24dB.

For some reason, the output on many ONTs (or some COs?) is not linear. The output might be +14dB to +16dB on most channels, but +20 dB on others.

Verizon installers are instructed to add an attenuator to reduce the signal down to +5 dB. Some do, some don't, as the Motorola STBs and DVRs tend to work fine with mosts signals of +10 dB or less.

The Problem

Installers are taught that a signal level of +5dB is excellent. That signal is fine for the Motorola boxes, but in many cases, it is too strong for the TiVo.

With a signal level of +5dB, the majority of channels will be fine on the Tivo, but many may exhibit intermittent pixelization. On these channels, RS Corrected and RS Uncorrected errors increment rapidly, SNR fluctuates, and signal strength fluctuates between 100 and a lower number (such as 50).

Even with a signal level of +0dB, some channels may exhibit intermittent pixelization. In my experience, 90-95% of FiOS channels are fine with a signal level of +0 dB, but that signal level is still too strong on perhaps 5-10% of channels.

I attribute this to non-linear output from the ONT -- most channels may be +0dB but others in different frequency ranges may be +5dB higher (or more). It is these channels with higher signal levels that exhibit pixelization. FiOS uses the same frequency ranges for locals, RSNs, and other cable channels on every system across the country. It is common for the local HD channels to be in the frequencies with a higher signal level.

More often than not, calling Verizon FiOS support is not a solution, because installers take one look at the +5dB signal level and conclude that the signal is fine -- just as they are trained to do. Verizon installers do have attenuators, but they don't attenuate the signal further because they are trained on the requirements of the Motorola boxes, not the TiVos.

The Solution

The solution is to further reduce signal strength to -6dB or lower by adding an attenuator to the end of the coax cable. This does not affect the FiOS channels with lower signals levels, but it eliminates the pixelization on FiOS channels with higher signal levels. It takes about 60 seconds to install an attenuator.

Steps to Fix
  1. Order a pack of attenuators. These screw on to the end of the coax.

    http://www.smarthome.com/7800.html

  2. Find a channel with pixelization.

  3. Once you've found a channel with pixelization, open Settings -> System Information -> Diagnostics. With this screen, you can monitor your SNR and number of RS Corrected and RS Uncorrected errors.

    Your goal is to completely eliminate the RS Uncorrected errors and the fluctuation in the SNR. A few occasional RS Corrected errors are fine; it is the RS Uncorrected Errors that indicate pixelization.

  4. Disconnect the coax cable from the TiVo.

    Note the process of disconnecting and reconnecting the coax will result in a lot of RS Uncorrected and RS Corrected errors, but don't worry about that. Only worry about errors that increment after the cable is firmly connected.

  5. Most seem to require -10dB to -16dB of new attenuation. I would start with -16dB. Screw one -10dB attenuator and one -6dB attenuator onto the end of the coax cable. Then reconnect the coax back to the TiVo.

  6. Is the problem fixed? Wait 60 seconds. Have the RS Uncorrected errors stopped incrementing on the Diagnostics screen?

  7. If not, disconnect the coax again and repeat step four using one -10dB attenuator and one -2dB attenuator.

    Is the problem fixed? Wait 60 seconds. Have the RS Uncorrected errors stopped incrementing on the Diagnostics screen?

  8. If not, disconnect the coax again and repeat step four using a single -10dB attenuator.

    Is the problem fixed? Wait 60 seconds. Have the RS Uncorrected errors stopped incrementing on the Diagnostics screen?

  9. If not, disconnect the coax again and repeat step four using a single -6dB attenuator.

  10. By now, the problem will be fixed.
My FIOS installation to a new S3 went flawlessly. I followed instructions from another thread to walk the installer through the process. Unfortunately I only verified that I had signal - I didn't check for pixelezation. Later in the day I started seeing the problem and started testing things. It was bad - on almost all channels, but worst on the HD channels. On the worst channels the signal bounced from 100 to 72 to 0 and all around that. The SNR bounced from 32 to 38, and the RS uncorrected was rising constantly. As I was unwilling to use FIOS without Tivo I only have 15 days to fix it or dump it. Calling FIOS tech support yielded the "we don't support Tivo" response. Trying to find attenuators locally was a flop and I didn't have time to order online. Fortunately I occasionally work for CBS and a tech at the broadcast center hooked me up. I got two 10 db and two 6 db attenuators from him, and there was already a 3 db that the installer used. The CBS tech told me that if I used 20 db of attenuation I wouldn't get any signal at all. So I followed the directions above - first 16 db and then working down to 6 db. The best was at 16, but there was still pixellezation. So I went up to 20 db. The tech I spoke to was wrong. While the signal still jumps around from the low 70's to 90 and the SNR jumps from 31 to 35, the RS uncorrected is 0. I'll continue to test it over the next few days, but now it looks good. The best part is the message I got from Verizon tonight making sure that everything went well after the installation. Yeah, you can bet I'll be returning that call! Thanks, bkdtv, for posting this information - happy to have the new service and Tivo!
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Old 11-17-2007, 12:12 PM   #388
kpepling
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I installed my attenuators and I was able to lower my SNR but no matter what I do it will not stay stable. It jumps around from 31-32 and I still get some pixelization. I don't have any real drop outs just some issues where the picture gets messy but not the sound. That is using 16db and when I tried 20db I got an unstable picture.
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Old 11-17-2007, 12:57 PM   #389
bkdtv
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Originally Posted by kpepling View Post
I installed my attenuators and I was able to lower my SNR but no matter what I do it will not stay stable. It jumps around from 31-32 and I still get some pixelization. I don't have any real drop outs just some issues where the picture gets messy but not the sound. That is using 16db and when I tried 20db I got an unstable picture.
You might need more or less attenuation. You'll rarely get the right amount on the first try.

There is a 3-4dB range that will eliminate pixelization. Too much attenuation will give you a weak signal, too little attenuation won't resolve the problem on all channels.

You might try 18dB and 14dB.
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Old 11-19-2007, 01:25 PM   #390
rlintacoma
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Pixelation and missing channels fixed easily

I was really concerned about the pixelation problem which was particularly bad on one or two channels and by some HD channels which mysteriously disappeared last week.

Poking around on this thread, it seems lots of people have the problem and are having mixed results getting it fixed. I guess I am one of the lucky ones and both problems were fixed with a short visit from the Comcast tech.

My cable ran from the wall through my rather expensive surge protector and then into TIVO. It has done this since I first got an HD TV and when I used Comcast's crappy Motorola cable box/DVR. But the pixelation problem began about a month ago. The tech took the cable out of the surge protector and put high end connectors on the cable. My pixelation is gone. And my missing channels came back as well. His explanation: the surge protector was causing the pixelation problems and the better connectors fixed the missing channels. I don't know if he knows what he is talking about or not, but my problems went away.
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