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Discussion in 'TiVo Series3 HDTV DVRs' started by JANNINO, Oct 17, 2007.
Im not AMF.... but attenuators are additive... stack em up and add the values together.
This is an interesting discussion. I've been trying to figure out the cause of some occasional pixelation with my S3. Originally I had signal strength readings in the 90's, and in fact, for some of the digital cable channels are still around that figure, but my local HD stations have gone from the 90's down to low 80's even dropping into the 70's.
After reading about the RS numbers above I checked mine.
On Tuner 2 I'm getting a fluctuating strength reading of 77-81 with an RS uncorrected number of 280 with a corrected number in the 5 million range. A SNR of 33
On Tuner 1 I'm getting a strength reading of 81 with an RS uncorrected of 0 and a corrected of 22. SNR is 33.
Based on the above I think a call to the cable company(Comcast) is in order as it looks like the signal quality is a bit too weak to drive both tuners adequately.
Any thoughts, or input?
Changing channels to reset the numbers shows that one channel in particular seems to have a real problem, within 1 minute of tune, it's already at 150000 corrected errors - problem with the cable company, or a problem with the station's signal..?? This particular station is where I get most of the pixelation issues, although I do get them on the others as well.
Yup... sounds like the cableco could do some optimizing and improve your situation. Signal strength below 80 will quite likely be a problem. The 90's would be much better. Can you describe your wiring between where the cable enters the house and the Tivo? Splitters can easily cause the problems you describe. Poor quality cables and loose fittings can also cause it. You might try unhooking your coax cables and reconnecting them making sure to snug them up good.
For that 280 uncorrected number... how long were you tuned to that channel. There is a tune time in the diagnostic menu too. Its the rate of uncorrected that is really important.
I'm not sure how long it was tuned to that channel for the 280 number. I recorded on that channel from 9-11pm and I checked the diagnostic screen at around 12am so I'm guessing it was around 3 hrs, although that tuner may have been tuned to the channel prior to 9pm. I'll check today and time it to see what the numbers read.
The line in from the pole is a straight shot with possibly 1 joiner at the roof and then it's fed through a grounding block. From there it feeds a 1GHz splitter with one output to a Moto cable amp that feeds an HDHR digital PC tuner and an un-amped feed straight to the S3. The lines within the house are all cut to length professionally terminated. I have not done a visual inspection on the line from the grounding block back to the pole yet, but baring more rain that is something I will do today.
I tried feeding the S3 an amplified signal but it seems to make no difference and in fact decreases the signal strength. The decrease is consistent with my testing this about a year ago when I first got the S3, an amplified signal actually made the signal quality worse with lower strength readings.
I also eliminated the splitter as a test and it makes no difference, the signal strength remains consistent with the current low 80's. When first tuning the channel I can see the number start off high, say an 86-87 very briefly, but then it settles very quickly back down to the very low 80's.
As I noted, last Sept, my readings were in the low to mid 90's, and although I've been through a few software revisions with the S3 I don't believe those revisions would cause any change in the tuner signal strength readings, and in fact, I did not have the pixelation problem back then either. This has been developing over the past few months so my assumption is that something has changed at the cable end as I believe my end has remained static.
Comcast has been upgrading my area to a 1GHz system over the past few months, but I don't believe there has been any "switchover" yet on any lines/equipment that may have caused this. There has been no visible change in the channel lineup and/or announcement from Comcast that the switch to 1GHz from 550MHz has been done. The actual "change" is supposed to happen in Dec.
I'll post some timed readings later today. Meanwhile I'm going to call Comcast. My worry there is that they may test the line and say it's fine based on how well their equipment(STBs) works with the current signal, hopefully they will agree there is a problem.
Okay, ran a 1 hour test and got the following readings.
For the CBS station,
Uncorrected - 0
Corrected - 11
For the NBC station,
Uncorrected - 286
Corrected - 4558107
Current readings for ABC, 4276 secs since tune start,
Uncorrected - 1433
Corrected - 141404
For NBC again, 987 secs since tune start,
Uncorrected - 39
Corrected - 5163280
S3 never was tuned to the FOX station tonight. It seems to me I definitely have a signal problem. Comcast will be here in the AM...
Yup.... signal problem or bad tuner.
Could a tuner just go bad? That would seem like a longshot to me but I guess it's possible, the S3 has been flawless since last Sept other than this recent signal problem.
Well, Comcast has been and gone and they say the signal looks good, but, he said he was going to have their in-house "TiVo whiz kid" come out on Sunday. Today's guy was complaining about CableCARDs and TiVo from the minute he got here.
Its possible but its more likely that its a signal problem in my opinion. You could change channels until you get the problem ones on the 'other' tuner and check the numbers there. If they are similar on both tuners then you have eliminated the tuner as a problem.
Yes, I've been playing around with that right now.
Another indicator to me that it's a signal problem is that the recordings made from an HDHR networked tuner also exhibit some signal anomalies, while they don't manifest in exactly the same way - a pixiedust like artifact on the S3 shows up as just a brief flash on the HDHR recording, which could be due to different software encoding/decoding on the PC side - is does seem to prove that the signal is in question.
I doubt it. These are pieces of silicon. They usually either work from the start or are defective and don't work [reliably] at all.
That's my take on it as well, it either works from the getgo or it doesn't work right at all. I've considered that one of the CCs may have gone bad, but then again, they're just a piece of silicon as well and in fact shouldn't have any impact on signal quality/level anyways.
Well, hopefully the "TiVo whiz-kid" will show up Sunday and have some ideas.
I've also been having severe pixelation on only one of my two tuners in the TiVo HD. While I have split the cable coming in, my S3 is perfect (same split point) and one of the two tuners on my TiVoHD is fine. The other is, well, unwatchable.
Signal strength hops all over everywhere, but only on the 2nd tuner. (68 to 93 is a typical series of jumps in a 30 second period on the same channel).
First pics show the first tuner (Tuner 0),
and the last pic shows the second tuner (Tuner 1).
For tuner 1, I have uncorrected RS @ about 44 million and corrected RS at about 330 million.
I haven't received a call from Comcast today on whether their "TiVo whiz kid" is going to show up or not. Haven't noticed any problems yet today, but I've spent most of my time with Sunday Ticket. Great Minn/Dallas game.
If he doesn't show I'll be calling back in the AM.
Since your signal strength indicates 100... my recommendation would be to attenuate the signal until the 'good' tuner indicates 90's and see if that helps. You might be overloading the tuner. You could add an additional 2 way splitter to knock it down 3.5db.
I had the same issue. Tivo sent me a new box and it works fine. Must have been a manufacturing issue on some boxes.
How long had you had the S3 before it starting reflecting this behavior? I've had mine for over 13 mos and probably started to notice the issue after about 10-11 mos of use.
I had mine less than a month. It was probably like this from the beginning. Only affected a handful of channels, but was 100% reproducable on those channels. Note however that this seems to only be a Tivo HD issue from what I have gathered.
Me too - same situation.
First tuner (tuner 0) is fine all stations, second tuner (tuner 1) has severe pixelation and wildly varying signal strength on certain stations (always the same stations). I'm using FIOS w/ 2 Motorola cable, TivoHD.
Currently on 9.1 waiting to see if 9.2 fixes the problem.
- Fix seems to be to attenuate the signal so that your SNR is down to 31/32 (no more than that). Even though your signal strength drops to the 60's, it's okay.
- Fix is usually to get a good signal amplifier/cleaner, like the Viewsonics 8x.
In any case, the same symptoms can result from too hot (FIOS), and too weak/dirty (Comcast) a signal.