KenAF
join:2006-01-23
Arlington, VA
1 edit | reply to deblin
Re: [TIVO] Signal Quality problems
said by deblin  :There is definitely a difference between the 1st and 2nd tuners. The signal levels on the two tuners can differ slightly. You can confirm this by tuning a channel on one tuner, looking at the signal level, and then tuning that same channel on the other tuner and comparing the signal level. On my TiVo there is a slight difference.
It is possible that you've applied just barely enough attenuation for one tuner and therefore not quite enough for the other. |
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HenryFarpolo
Premium
join:2003-08-31
Andover, MA
| reply to toups
Deblin, This is the process I followed when I had the same problem you are having. It worked and I have not had a problem since. You may not have to start as high as 20db, but it doesn't hurt. This was posted on the TIVO forum;
Steps to Fix
1. Order a pack of attenuators. These screw on to the end of the coax.
»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. Some require as much as -20dB. I would start with -20dB and work your way down.
Screw one -20dB 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, or you aren't getting a picture, disconnect the coax again and repeat using one -10dB attenuator and one -6dB 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 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?
9. If not, disconnect the coax again and repeat using a single -10dB attenuator.
Is the problem fixed? Wait 60 seconds. Have the RS Uncorrected errors stopped incrementing on the Diagnostics screen?
10. If not, disconnect the coax again and repeat using a single -6dB attenuator.
11. By now, the problem should be fixed. |
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toups
join:2001-11-02
Boxborough, MA
| reply to deblin
Could be a bad connection. I've had specific channels drop out when the coax connector was not well connected. What happens is that the signal is reflected from a poor connection and can set up a standing wave pattern. Hence, only certain specific channels may be affected.
I've run into this problem when I made some cables using the screw on type-F connectors that then subsequently were pulled loose.
Try checking all of the coax connections to see that the cable is not loose. |
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deblin
Dark Side of the Moon
Premium,MVM
join:2001-09-01
Middletown, DE
1 edit | reply to deblin
I think the signal problems also seem to be frequency specific. E.g. the broadcast channels in the ~500-ish MHz range seem to be the worst.
Even with this 15 dB attenuation on the coax, I'm seeing 86-90 signal strength and 0 "RS corrected". This is on channel 551 @ 717 MHz.
Perhaps there's just some interference being induced in my house somehow on the 500-600 MHz range, which is being amplified by the tivo causing the problems? Would the frequency range be related to the temperatures?
Edit: likewise, channel 550 (135 MHz) seems fine. Signal strength 77 almost constantly with very little fluctuation occasionally up to 81. Again, zero RS corrected. |
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deblin
Dark Side of the Moon
Premium,MVM
join:2001-09-01
Middletown, DE
| reply to wfdavis
Thanks for the info. I'll have to check the splitter in the basement.
As we have only one other TV, I"m thinking of disconnecting the other runs to other parts of the house and capping those unused ports with F-terminators to cut down the noise.
As I understand this stuff, if the signal is very hot, you're amplifying noise along with the "good" signal. So if you amplify too much, you can end up amplifying the noise. So perhaps I have more noise now for some reason and the internal amplification by the S3 Tivo is causing the pixelation. By attenuating, I bump the noise (and the good parts of the signal down) and allow the Tivo to amplify and do its error correction. Just a theory I guess...
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He who is not contented with what he has, would not be contented with what he would like to have. -Socrates |
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wfdavis
join:2000-07-24
Collingswood, NJ
| reply to deblin
Hi Deblin,
I thought I would jump in here and add my 2 cents for what it's worth. I to started have major pixlation and loss of sound on channel 681 A&E HD with my Tivo series 3 about 3 weeks ago. It started intermittently and slowly got worse. The signal was fluctuating 60 to 80 and the SNR was as low as 29. At that point the channel was unwatchable. Long story short I finally checked all the cable connections by grabbing them and making sure everything was tight from the 8 port VZ splitter to my TV and whola! Problem solved. Signal up 80-95 and SNR 33-35. No pixelation. The connector at the 8 port splitter had a slight short. Like everyone says the Tivo 3 is very sensitive to signal strength.
Hope this helps
Wfdavis |
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deblin
Dark Side of the Moon
Premium,MVM
join:2001-09-01
Middletown, DE
| reply to KenAF
There is definitely a difference between the 1st and 2nd tuners.
I tuned 510 on the 2nd tuner for 180 seconds and there were 110 "RS corrected".
Doing the same for the 1st tuner resulted in 377.
Granted, this is a short sample time, but I've noticed this trend as I've been watching these RS numbers for both tuners.
Perhaps the signals strength is higher for tuner1 due to the way the signal is split internally in the Tivo. So the attenuation I'm doing is having less of an effect on the first tuner?
--
He who is not contented with what he has, would not be contented with what he would like to have. -Socrates |
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deblin
Dark Side of the Moon
Premium,MVM
join:2001-09-01
Middletown, DE
1 edit | reply to KenAF
Hmm I've seen the signal quality hit as high as 90 on the 514 channel, though rarely.
Very few RS corrected (the show isn't HD on that channel at the moment, does that matter?) and 0 uncorrected...could be the temps are going up today? Although not really, it's only 15 outside haha
So am I right that 15 dB of attenuation knocks the signal down by a factor of over 31? 
A = 10*logb10(Pin/Pout)
Is the formula I found that seems to ring a bell from college. 
15 = 10*logb10(x)
(15/10) = logb10(x)
10^(15/10) = x
31.6227... = x
That seems insane, but it's still tuning channels... |
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deblin
Dark Side of the Moon
Premium,MVM
join:2001-09-01
Middletown, DE
| reply to JeepMatt
Having had to deal with sub-par DVRs, I'm not going to ditch the Tivo unless I absolutely have no other recourse :P
So anyone know what the signal quality should be when the proper attenuation is in place? Should I be looking for a MAX of X for all the channels I watch then?
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He who is not contented with what he has, would not be contented with what he would like to have. -Socrates |
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JeepMatt
Delaware Fios
Premium
join:2001-12-28
Wilmington, DE
 ·Verizon FIOS
| reply to deblin
Deb-
Sorry to hear you're still having problems. Honestly, back during my first tour with FIOS TV, I couldn't take the Tivo issues anymore - and it was on Ebay the next day. 
--
"ONE team - ONE city - ONE dream!!" |
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deblin
Dark Side of the Moon
Premium,MVM
join:2001-09-01
Middletown, DE
1 edit | reply to KenAF
Ok so at least I know it's not the hdd failing.
The reported signal strength from the Tivo on the first tuner is toggling between 77 and 81, and 86, though more so between 77 and 81.
Still too hot?
*edit* that was for the problematic channel (514) from last night that took so many errors.
On 680 (SCIFIHD) the tuner is hovering between 90 and 86 signal strength. |
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KenAF
join:2006-01-23
Arlington, VA
4 edits | reply to deblin
said by deblin :Tuner 1 was on channel 516 (507000 KHz) for a few hours and has over 50,000 "RS uncorrected" now.  And over a million "RS corrected". The other tuner was on 680 (SCIFIHD) for the last ~3+ hours and has 0 "RS uncorrected" and 18 "RS corrected". Is my Tivo dying or what?  What does TiVo report your signal level at now?
I would go a little higher. Maybe 15dB attenuation?
Attenuation doesn't solve the problem for everyone. Nobody really knows why. It's always possible that Verizon did something on their end (like an equipment replacement) that causes problems for the TiVo but not necessarily the Motorola DVR.
You know your TiVo's hard drive is dying when you get pixelization, lost frames, and dropouts without the errors. A failing hard drive doesn't cause signal errors, though, and such large numbers of signal errors always cause picture problems. |
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deblin
Dark Side of the Moon
Premium,MVM
join:2001-09-01
Middletown, DE
| reply to deblin
Tuner 1 was on channel 516 (507000 KHz) for a few hours and has over 50,000 "RS uncorrected" now. And over a million "RS corrected".
The other tuner was on 680 (SCIFIHD) for the last ~3+ hours and has 0 "RS uncorrected" and 18 "RS corrected".
Is my Tivo dying or what?
--
He who is not contented with what he has, would not be contented with what he would like to have. -Socrates |
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deblin
Dark Side of the Moon
Premium,MVM
join:2001-09-01
Middletown, DE
| reply to deblin
The first tuner is definitely taking a ton more errors. Like 50/second sometimes pretty regularly.
After 10-15 minutes, tops, the first tuner had taken 15000 "corrected" RS, though luckily still 0 uncorrected. The other tuner had only taken like 250 corrected RS (and 0 uncorrected).
Seems odd...
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He who is not contented with what he has, would not be contented with what he would like to have. -Socrates |
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deblin
Dark Side of the Moon
Premium,MVM
join:2001-09-01
Middletown, DE
| reply to guppy_fish
Ah right. Ok, so what am I doing with 12 dB?
Am I right that the "RS Uncorrected" causes pixelation/audio dropouts/etc, but "RS Corrected" are ok? E.g. a fixed checksum mismatch?
I'm not able to watch each channel to look for the pixelation. So I was thinking of tuning each channel for 5-10 mins each and keeping an eye on the RS Uncorrected #.
Currently, the 2 tuners are on 511 and 514 and there are ~3000 corrected on tuner 0 (ch 511) and 122 on tuner 1 (channel 514). Uncorrected is 0 on both.
Weird, the channels are only 6 Mhz away but one is taking a ton more errors (even if they are corrected).
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He who is not contented with what he has, would not be contented with what he would like to have. -Socrates |
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guppy_fish
Premium
join:2003-12-09
Lakeland, FL | reply to deblin
db is logarithmic not linear
3db is cutting the signal in half |
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deblin
Dark Side of the Moon
Premium,MVM
join:2001-09-01
Middletown, DE
| reply to keyboards
I understand...but 9 dB didn't help either. I've got both 6s in there now for 12. Seems ok so far, but it's intermittent so who knows.
I know going from 9 to 12 seems like a lot, but I guess it's not that big a difference.
1/9 => 1/12 is .11111 to .08333
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He who is not contented with what he has, would not be contented with what he would like to have. -Socrates |
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keyboards
join:2001-02-14
Doylestown, PA
·Verizon FIOS
 ·Comcast
| reply to deblin
said by deblin :I'm trying a 3 and 6 together (9 for the math impaired  ) According to the tech, 8 dB failed her test, but I'm able to see at least one channel just fine. hmm. The tech is testing for Motorola levels, not TIVO - as others have stated in this thread. TIVO apparently has a front end amplifier that is going into overload on the FiOS signal and requires much more attenuation than the Motorola boxes.
--
REMEMBER: Stupidity should be painful !! |
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deblin
Dark Side of the Moon
Premium,MVM
join:2001-09-01
Middletown, DE
| reply to deblin
I'm trying a 3 and 6 together (9 for the math impaired )
According to the tech, 8 dB failed her test, but I'm able to see at least one channel just fine. hmm.
--
He who is not contented with what he has, would not be contented with what he would like to have. -Socrates |
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deblin
Dark Side of the Moon
Premium,MVM
join:2001-09-01
Middletown, DE | reply to deblin
And it's still doing it with a 3 dB attenuator too. |
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