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Garbled Channels

Discussion in 'TiVo Roamio DVRs' started by evstok, May 16, 2017.

  1. evstok

    evstok New Member

    28
    1
    Jan 17, 2008
    Can anyone shed any light on why I would have a few garbled HD channels on an intermittent basis? Specifically, it is four channels in close proximity to each other (432, 434, 438 and 439). I've swapped cable cards without success. Comcast is blaming the Tivo (of course) but I'm not convinced since it is an intermittent problem. Here is an example of the diagnostics screen for channel 432 at a time when the signal is garbled:

    Tuner: 0
    Channel 432
    Frequency: 79000KHz
    Modulation: QAM 256
    Program Number 2
    Signal Source: Cable
    Connector Type: RF 2
    Channel Bits: 3176474
    Signal Strength: 98%
    Signal Lock: Yes
    Program Lock: Yes
    Search Complete: Yes
    SNR: 39dB
    RS Uncorrected: 137465667
    RS Corrected: 393361744
    RC State: Available
    Current Tuning Status: Tuned: Success
    Tune State: In progress
    etc.

    Any help would be appreciated.
     
  2. ThAbtO

    ThAbtO TiVoholic by the bay

    7,283
    60
    Apr 6, 2000
    SF Bay Area
    Try bringing the signal strength down a bit. It looks like its a bit high with the SNR 39%. Try a splitter with just 1 output to the Tivo, should be enough to bring it down to 37% or so.
     
    Last edited: May 16, 2017
  3. evstok

    evstok New Member

    28
    1
    Jan 17, 2008
    Plugged in the splitter but it didn't bring things down much. Signal strength at 97% and SNR still at 39dB.
     
  4. UCLABB

    UCLABB Well-Known Member

    1,352
    47
    May 29, 2012
    Riverside, CA
    My Plus typically has a signal strength of 99% and SNR of 39 and I have no problems. No RS uncorrected and few corrected. That's not saying your signal strength isn't too high, just that those numbers are not unusual. Just for the heck of it try another splitter.
     
  5. evstok

    evstok New Member

    28
    1
    Jan 17, 2008
    Two splitters and I'm at 96% signal strength and 38dB SNR. I have high signal strength on all of my channels but only 4 of them are having issues.
     
  6. ThAbtO

    ThAbtO TiVoholic by the bay

    7,283
    60
    Apr 6, 2000
    SF Bay Area
    That's a start.... How are the splitters installed?

    Do you have a splitter that is -6dB?
     
  7. evstok

    evstok New Member

    28
    1
    Jan 17, 2008
    Not sure if I follow. Splitters installed in sequence. Line from the wall to first splitter, line from first splitter to second and line from second splitter to Tivo. That's all the splitters I have at present. What makes no sense to me is that this is an intermittent problem. In the course of a couple of hours I go from a perfect, clear picture to garbled to no signal and back to everything being fine. Right now, for example, everything is fine and my signal and SNR numbers haven't changed meaningfully.

    Earlier when nothing was working I was at a Signal Strength of 98% and SNR of 39dB.
    Now everything is fine and I'm at a Signal Strength of 99% and SNR of 39dB.

    The only difference is that my RS Uncorrected is sitting at zero now. My RS Corrected is 900000+ and climbing.

    How can basically the same numbers provide such dramatically different results and why the seemingly random fluctuation?
     
  8. evstok

    evstok New Member

    28
    1
    Jan 17, 2008
    An update...

    There was a powered booster in my attic that all of the cable distribution was running through. I disconnected it and replaced it with an unpowered splitter. Strangely enough (at least to me) that had no impact at all on my signal strength or SNR. I purchased two attenuators... One 6dB and one 12dB. I tried them one at a time and in combination (6dB, 12 dB, 18db). All of this succeeded in lowering my signal strength dramatically... Down into the 70s or 80s. My SNR also dropped dramatically down into the upper 20s or low 30s. It did nothing to correct the problem however. Above 12dB the issues began to spread to other channels. I'm sort of at a loss at this point. Any thoughts?
     
  9. MikeBear

    MikeBear Member

    185
    17
    May 21, 2015
    Mid-Michigan
    Do you have a cable modem for internet, hooked into the same line that goes to your Tivo? Or how does the modem connect into the cable line from the street? I'm wondering if that connection is somehow causing this issue.

    Or is there a Moca connection somewhere that could be backfeeding the signal in a way that causes this?
     
  10. evstok

    evstok New Member

    28
    1
    Jan 17, 2008
    The cable modem splits off from the four way splitter in the attic. A separate line runs from the four way to the TiVo. The only MOCA network is the one generated by the TiVo itself to communicate with a pair of minis.
     
  11. MikeBear

    MikeBear Member

    185
    17
    May 21, 2015
    Mid-Michigan
    Do you live in a house, or an apartment? Do you have a Moca blocker filter on the incoming line before your splitter? If not, maybe it's picking up a neighbors setup and somehow doing this? Also, is all your cabling RG-6, or is there some RG-59 in there? If there is some RG-59, I recommend that you replace it with RG-6

    Amazon.com: Filter, MoCA "POE" for Cable TV & OTA coaxial networks ONLY: Home Audio & Theater

    P.s. you aren't somehow combining your cable coax's with an OTA tv antenna, are you?
     
  12. evstok

    evstok New Member

    28
    1
    Jan 17, 2008
    No, strictly cable. No OTA antenna. It is a house not an apartment. I can't speak to the RG-6 vs RG-59 question. I honestly don't know. The house was built 12 years ago if that would indicate one way or the other. No MOCA blocker that I'm aware of.
     
  13. MikeBear

    MikeBear Member

    185
    17
    May 21, 2015
    Mid-Michigan
    You probably NEED a Moca blocker at the entrance point (attic splitter input? if that's the first connection from the street) of your cable line. If you don't have one, it can cause this issue. They are cheap, click on the Amazon link to see what I'm talking about. Though they are available elsewhere.
     
    Last edited: May 19, 2017
  14. evstok

    evstok New Member

    28
    1
    Jan 17, 2008
    I appreciate the info. I've tried every imaginable configuration of signal booster, splitter, attenuator etc without success. I'll try the Moca blocker and if that doesn't work I guess I'll give up and call Comcast. Could you suggest any brick and mortar stores where I might be able to pick one up? I searched Best Buy without success. If not I guess I'll get it from Amazon.
     
  15. MikeBear

    MikeBear Member

    185
    17
    May 21, 2015
    Mid-Michigan
  16. evstok

    evstok New Member

    28
    1
    Jan 17, 2008
    I went through my entire list of channels in order to see if I could find every one that is out and see if there is any pattern to it. I don't know if this means anything at all but here is what I found:

    The following channels are so disrupted that they do not come in at all and generate V53 errors:
    432 - Frequency 79000KHz
    434 - Frequency 79000KHz
    220 - Frequency 79000KHz
    217 - Frequency 79000KHz

    The following channels are very badly garbled but do not generate an error message:
    439 - Frequency 85000KHz
    438 - Frequency 85000KHz
    201 - Frequency 85000KHz
    202 - Frequency 85000KHz
    203 - Frequency 85000KHz
    204 - Frequency 85000KHz
    205 - Frequency 85000KHz
    207 - Frequency 85000KHz

    Every other channel is fine. It seems as though that grouping has to mean something but perhaps not.
     
  17. MikeBear

    MikeBear Member

    185
    17
    May 21, 2015
    Mid-Michigan
    Hard to tell. I still think the Moca filter is your next best possibility to hopefully cure the issue. IF that doesn't work, you definitely need to call out a cable tech to check from the pole to your devices and see what they can find.
     
  18. evstok

    evstok New Member

    28
    1
    Jan 17, 2008
    You're probably right. I gave up and have a tech coming out Monday afternoon. We'll see what he's able to do.

    Strangely enough, I saw a Comcast truck roll through my neighborhood this morning and at the moment at least all my problems are gone. Probably a coincidence.
     
  19. ThAbtO

    ThAbtO TiVoholic by the bay

    7,283
    60
    Apr 6, 2000
    SF Bay Area
    The filter will not help as it only blocks internet data from spreading to outside along the cable system and has nothing much to do on channels.
     
  20. evstok

    evstok New Member

    28
    1
    Jan 17, 2008
    I was half-joking earlier about the Comcast truck that rolled through my neighborhood this morning but (knock on wood) I'm starting to think I may have been right. Maybe I wasn't the only one who was experiencing difficulties. No issues at all today. Fingers crossed.
     
    MikeBear likes this.

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