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High SNR & Missing Recordings

Discussion in 'TiVo Roamio DVRs' started by shortcut3d, Sep 18, 2013.

  1. Goober96

    Goober96 New Member

    300
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    Jun 28, 2005
    Anderson, SC
    What is the consensus on what are good numbers? Is a signal strength of 80 too low?
     
  2. kbmb

    kbmb Active Member

    1,286
    13
    Jun 22, 2004
    NH
    According to Tivo, 80-99 is the recommended, with 50-53 the minimum:
    http://support.tivo.com/app/answers/detail/a_id/150

    Although I saw signal level of 67 result in complete pixelation.

    -Kevin
     
  3. shortcut3d

    shortcut3d New Member

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    Sep 1, 2013
    No AMP. I may order a couple attenuators.
     
  4. astrohip

    astrohip Well-Known Member TCF Club

    10,049
    35
    Jan 6, 2003
    Houston &...
    Just to be clear... I have the occasional missing recording (3 so far). All due to "Signal not available". And I have on occasion flipped thru the channels and found one not tuned in.

    DVR Diagnostics on my Pro show all tuners, almost any channel, coming in around SNR 42-43dB, with signal strength of 100 all the time. Comcast/Houston, no TA.

    So I'm too hot?

    And the secret sauce seems to be buy some attenuators and drop my SNR to ~35dB?

    Thanks in advance.
     
  5. kbmb

    kbmb Active Member

    1,286
    13
    Jun 22, 2004
    NH
    Personally I would look LESS at the SNR and more at the signal. If you can drop the signal so that at least one channel hits 99 (even if it's for a few seconds).....then why worry about the SNR?

    Tivo even states on their page that you can have a signal that is "a bit beyond" the 100 and you should have excellent picture quality. Can't image that if you were to get the signal to be right around 100.....even with a high SNR that Tivo would cause the signal to go out. If so that's crazy.

    Problem is Tivo doesn't show beyond 100.....so it's a guessing game to get to under or at 100. I finally went with a 6dB attenuator and most all my channels are solidly at 100. However, I know (or am guessing) that I'm not far above because I have some channels hitting 97-99 at times.

    Even with this I have SNR numbers from 37-43dB. So far no issues.

    What's interesting is.....my old TivoHD never had a problem, and I was pumping the full signal into it.....no attenuation.

    -Kevin
     
  6. HarperVision

    HarperVision TiVo's Italian Cuz!

    5,275
    3
    May 14, 2007
    Paradise...
    If that's what you think then you don't understand how it all works. SNR means "signal to noise ratio" so no matter how high your signal level may be, if the "ratio" of noise to said signal is high enough past the threshold of what the equipment is designed for, then you're screwed, plain and simple. Inversely you can have a low level signal (70 something maybe) but a great signal to noise ratio and get a great picture tuned in.

    When I was in broadcast TV we spent a hell of a lot more time suppressing noise and harmonics of the signal by tuning the cavity and transmission lines with line flatteners and network analyzers than we did worrying about our power output and what it looked like on our power meters and spectrum analyzers. Increase the power, it just increases the noise, whereas decreasing noise had a better net effect.

    You're most likely seeing a side benefit from lowering the signal power input due to the higher signal creating things like more rf reflections, vswr, anomalies of any not so perfect connections, etc. which in turn naturally improves [edit] the snr.
     
  7. kbmb

    kbmb Active Member

    1,286
    13
    Jun 22, 2004
    NH
    Yup...then I don't have a clue.

    Please enlighten me.....if I have a signal on my Tivo of 99-100, what is a good SNR?


    -Kevin
     
  8. shortcut3d

    shortcut3d New Member

    36
    0
    Sep 1, 2013
    OMG... These missed recordings need to stop. Revenge was not record because it was not available and shows up as a conflict. Only two other shows were recording and I have a Plus. Not to mention it started recording then suddenly disappeared.
     
  9. HarperVision

    HarperVision TiVo's Italian Cuz!

    5,275
    3
    May 14, 2007
    Paradise...
    A good snr for TiVo is apparently 29-35db for QAM256. Technically a higher signal to noise ratio should always be better as long as it doesn't overload other parts of the circuit, and my guess is that's how TiVo designed it as well.
     
  10. moyekj

    moyekj Well-Known Member

    11,140
    28
    Jan 23, 2006
    Mission...
    FYI, signal levels are 100 for me on most channels with SNR in the range of 39-42 dB and so far I have not had any missed recordings (after several weeks). So while that may not be in TiVo's defined good range it still works for me. I think the other key specs that need attention are RS corrected/uncorrected errors. I get very low counts on those which is a good sign. If you see high numbers there then it's likely you will see macroblocking on occasion due to dropped bits for RS uncorrected errors and it's a sign of tuning difficulty. These signal and SNR numbers are quite significantly higher than I recall with my Elite, Premiere and S3 units. I did on occasion have Elite fail to tune any/all channels requiring a reboot to fix. Have not had that issue even once yet with my Roamio Pro.
     
  11. andyf

    andyf Active Member

    1,176
    2
    Feb 23, 2000
    Houston,...
    We're on the same cable system. I put a 10db attenuator inline and it didn't make a difference. Put a 16db attenuator in and the levels dropped down but it killed my MoCa connection so I'm back at 10db.

    I missed 3 recordings last Monday with the 10db attenuator, Hostages, Blacklist and Castle. fortunately Hostage and The Blacklist re-aired Saturday and I saw Castle on Xfinity Online. Haven't seen a No Signal since the update came down. (.2?)

    Also Comcast is doing some weird stutters from time to time. Pretty sure it's Comcast because I see it on my other TiVos too.
     
  12. shortcut3d

    shortcut3d New Member

    36
    0
    Sep 1, 2013
    I did the update last week and still got the same missed recording for Revenge last night. Again, it started recording and showed up in My Shows with a red circle, then disappeared at some point while watching another recording. The History says Not Available and is sorted under Conflicts. Only three other shows recorded at that time block.

    I disabled Tivo Suggestions as that's all I can think of at this point. This may be related to the 30 sec skip bug / no buffer bug, but I'm not getting the full symptoms.
     
  13. kbmb

    kbmb Active Member

    1,286
    13
    Jun 22, 2004
    NH
    I'm not sure if Tivo's SNR numbers are correct. I also have what Tivo would probably call a hot signal....signal 100 and SNR numbers of 40-43.

    I had to troubleshoot something so I brought my Comcast Motorola box downstairs and plugged in into the line used by Tivo. The Moto box showed 37.5 dB SNR.

    Wonder if Tivo boosts the signal internally?

    To the OP: I think the Not Available is now a known bug with back to back recordings:
    http://www.tivocommunity.com/tivo-vb/showthread.php?t=509715

    I too am like you, high signal and SNR.....great picture quality.

    -Kevin
     

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