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SNR presence with not plugged it

Discussion in 'TiVo Roamio DVRs' started by dlongnecker, Feb 19, 2014.

  1. dlongnecker

    dlongnecker New Member

    24
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    Dec 30, 2006
    I've been trying to troubleshoot the problem with my new Roamio not getting authorized for about 3 weeks. While both Tivo and Comcast are trying to be helpful, its not going anywhere. (I'm getting all channels but the premium ones and VOD freezes.).

    Tivo claims my SNR is too high. Its at the 42 level. Tried putting attenuators in place, to get it down to 36, but then I lose my internet connection.

    For grins, I wanted to see what my SNR on the TIvo is when absolutely nothing is plugged into it but the HDMI cable and Power. Right now, SNR is 19. Switched cable cards, it is 19. This is with nothing plugged into the coax. All other electronics, except for the TV turned off.

    Does it seem unusual that I start out with a 19 SNR level with nothing plugged in?
     
  2. kbmb

    kbmb Active Member

    1,292
    15
    Jun 22, 2004
    NH
    Where are you putting the attenuators and what is losing internet....the Tivo or the whole network?

    -Kevin
     
  3. StevesWeb

    StevesWeb Grumpy Old Geek

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    Dec 26, 2008
    Geek Hill,...
    No, when the input to an amplifier is open it is going to sit there amplifying noise.

    I am deeply skeptical of claims that a superior signal to noise ratio will cause a TV tuner to malfunction. I believe what is actually happening in some cases is that the signal level is too high. Adding splitters reduces signal level. Adding more noise to a signal is not an improvement, whether the data being modulated is analog or digital.

    So, when a TiVo tech says the SNR is too good I consider an indication of his ignorance of what the term means and how it relates to TV tuner performance. Maybe the peak to peak signal level is too high.

    It will often be the case that strong signals also have high (desirable) signal to noise ratios, this may be how this false correlation got started.

    Ignore the SNR, it is a red herring.
     
  4. CrispyCritter

    CrispyCritter Purple Ribbon Wearer

    3,647
    1
    Feb 28, 2001
    North...
    I agree with most of your analysis, but you left out an important adjective phrase. The TiVo tech is saying the SNR as reported on the TiVo is too good. We don't know that the TiVo SNR is a true signal-to-noise-ratio and I strongly suspect it isn't. It's some mixed up number that has a strong signal strength component.

    There have been many folks in this forum that have been helped by reducing the signal strength (either attenuators or getting the cable company to fix it) after noticing the the SNR as reported on the TiVo is that high. In practice it seems to be a quite valuable diagnostic number, even if it shouldn't be called "SNR".
     
  5. shamilian

    shamilian Member

    442
    0
    Mar 26, 2003
    NJ
    Just use the Signal Strength value.

    Get it in the mid to high 90s and that should be good.
    (over 100% and your signal may be clipped)

    The SNR value is not useful and no one knows how it is computed.
     
  6. StevesWeb

    StevesWeb Grumpy Old Geek

    704
    0
    Dec 26, 2008
    Geek Hill,...
    Good point. It does seem what is really helping in such cases is reducing signal level. It certainly is possible to overdrive the input on a tuner.
     
  7. dtivouser

    dtivouser Tivoless TCF Club

    1,813
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    Feb 10, 2004
    SoCal
    The Tivo rep had me unplug the coax from my Romaio. When it still showed 15db, he said that's a defect and RMA'ed my Tivo. The replacement fixed almost all of the problems I was having.

    Call Tivo and tell them about this.
     
  8. lgnad

    lgnad Pantless Mofo

    691
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    Feb 14, 2013
    Massachusetts
    Where were you putting the attenuators? Where your signal comes into your property, or right "in front" of the tivo?

    Some alternate ideas:

    Getting all channels but premium could be a pairing/authorization issue. It took the cablecard hotline group THREE tries to get my Roamio right a few days ago. First call got me con:, second val: the third try got me my full channel lineup.

    Does on-demand freeze immediately after starting, or randomly?
    If it freezes right away, there have been threads about needed ing to add authorization to your account with Comcast. Something about adding it under the "bolt-ons" section... Search for the thread on here.
     
  9. triftraf

    triftraf New Member

    90
    0
    Jan 26, 2006
    I am having problems where my new roamio stops tuning all channels on all 6 tuners. First time I called TiVo they told me to get attenuators cause my signal strength is 100 and SNR is 45. I have not done this cause I had a premiere on the same coax and never had any probs.

    It has happened a couple times now for me on the roamio. My SNR is 11 when no coax attached. Anybody know what the acceptable value is when no coax? I assumed it should go to 0.

    The premier which is now relocated to a different area of the house drops from 35SNR and 90% SS to 0 when the coax is pulled.
     
  10. kbmb

    kbmb Active Member

    1,292
    15
    Jun 22, 2004
    NH
    On my Roamio Basic, with coax I get roughly 92-99% signal and ~38 dB SNR. When I pull the coax, signal goes to - and SNR is either 9 or 15 dB.

    With the coax in, the OOB SNR is ~400 dB (no ideas why this number is so different on the Basic compared to the Pro)

    Without the coax the OOB SNR is ~45 dB

    BTW...haven't had any tuning problems. I'm on Comcast NE with NO tuning adapter.

    EDIT:
    Checked my Pro:

    With coax, signal levels 94-100%, SNR 37-40 dB. OOB SNR 32 dB.

    Without coax, signal levels -, SNR 11-22 dB. OOB SNR 124 dB ?!?!

    Haven't had tuning issues with this one either.

    -Kevin
     
  11. CrispyCritter

    CrispyCritter Purple Ribbon Wearer

    3,647
    1
    Feb 28, 2001
    North...
    There are major differences between the Roamio and Premiere response to signal strength. The Roamio is much more sensitive. People have said that the Roamio has an internal amplifier to split the signal over the 6 tuners.

    Lots of people have been helped with attenuators when their SNR is that high; it's a reasonable thing to try.
     
  12. CrispyCritter

    CrispyCritter Purple Ribbon Wearer

    3,647
    1
    Feb 28, 2001
    North...
  13. kbmb

    kbmb Active Member

    1,292
    15
    Jun 22, 2004
    NH
    I would at a minimum, throw a 2 or 3-way splitter in front of the Tivo to bring the SNR down under 100. Once you find how much you need, then you can order attenuators.

    -Kevin
     
  14. triftraf

    triftraf New Member

    90
    0
    Jan 26, 2006
    I did call TiVo again about this today. This tech says I may have fried my unit with too much signal. Since I'm within my 30 days on my Roamio Pro - they are RMA-ing it...

    After getting off the phone - I did put a 2way splitter on it (-3.5db) - and it reduced signal to high 90's and lowered the SNR a little. So, I'm wondering do I even need an attenuator if I just add a splitter?

    The TiVo rep suggested I wanted signal in the 70's... Which I know on Premier or older boxes sometimes I had issues when the signal was in the low 70's... So that sounds pretty low...
     
  15. steve614

    steve614 what ru lookin at?

    10,722
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    May 1, 2006
    Dallas, TX
    You can't compare the signal as reported between different model TiVos. They may not be using the exact same parameters in measuring the signals.
     
  16. kbmb

    kbmb Active Member

    1,292
    15
    Jun 22, 2004
    NH
    Well according to this page on Tivo, the unit should have protected itself if signal too high:

    http://support.tivo.com/app/answers/detail/a_id/150

    As for the splitter, as far as I know it's doing the same thing an attenuator would do.....so if it's working for you, just leave it on.

    -Kevin
     
  17. mae

    mae member

    245
    1
    Dec 10, 2001
    USA
    If you use a splitter as an attenuator, you should cap any unused ports with a 75 ohm terminator to avoid other problems.
     
  18. dlongnecker

    dlongnecker New Member

    24
    0
    Dec 30, 2006
    From the outside wall to my tivo, it goes through three splitters. I have tried various attenuators in different locations, but no success. I am now on my sixth cable card and about my 20th call to comcast. I do call the comcast CABLECARD number...once in awhile it is connected to someone who obviously doesn't know what he is doing, so I hang up and call again.

    So right now my two problems are. 1 no premium channels and 2 VOD freezes after 5 seconds. I have asked all the questions about things turned on, etc. but no help.
     
  19. boulderskies

    boulderskies Member

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    Aug 23, 2013
    How do I find the SNR on a basic Roamio?

     
  20. jmbach

    jmbach der Neuerer

    1,557
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    Jan 1, 2009
    What cableCARD are you using. (brand and firmware version) I have read in different threads that the VOD freeze after 5 seconds is a "feature" option that needs to be added on at the head end. ( http://www.tivocommunity.com/tivo-vb/showthread.php?p=9809508#post9809508) The no premium channel problem is a pairing problem. I have Charter and when I have replaced the drive in my TiVo(s) with a new image, I lose the pairing. In my area they use Motorola M-Cards. These cards have a habit of generating new data ids when the drive is replaced or if you eject the card and reinsert it. The Charter techs check the S/N, Host ID, and cableCARD ID which does not change. All they want to do is send hits to the card and have me reboot the TiVo. I tell them about the Data ID and they either tell me it does not matter or lie to me that it is the same. Then they want to roll a truck. In the end I either call back or ask for the next supervisor above the person I am talking to. Eventually I get to someone who listens and does check the Data ID. Why I know they lie? Because when I finally get someone to check the Data ID, it is different and as soon as they change it to what my M-Card Data ID is, I am back up, paired, and have all my premium channels.
    From what I have read in the threads, the Cisco/Scientific Atlanta cards don't have this issue.
     

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