Signal strength and DNR (signal to noise ratio) . . .

Discussion in 'TiVo Roamio DVRs' started by Expidia, Nov 1, 2020.

  1. Nov 1, 2020 #1 of 17
    Expidia

    Expidia Albany, NY

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    Now that my system has been corrected and is working again from the mini's not seeing the Romio I can tweak it a little . . . I just ordered 5 new 2500 Mhz splitters to replace the 1,000 MHz spitters after Spectrum swapped out my Holland 2,100's when they came through my house in 2019 for a dropping internet signal issue and installed their 1,000 Mhz splitters. The system was working so I left their splitters in place. In checking my signal strength it was 100% and since the Tivo diagnostic screen does not read above 100% it could again be pulling in a signal much higher and hotter than 100%. I'm the last house on my street and Spectrum says that can cause a hot signal. I used to use an array of two or 3 splitters to pad down a hot signal at this first two way splitter where the signal comes in just before my Romio from the street. But now I just went back to using Attentuators. I have 3 of them. 3 DB, 6 DB and 10 DB. Using them alone or in combination allows me to lower a hot signal. Just by adding the 6 DB I was able to bring my signal down to 96-98% . This pic shows the attentuator being added to the splitter (I'm upgrading this splitter to a 2500 Mhz) One side goes to the Romeo and the other run is feeding 3 TV's.

    I have not been perusing this forum for awhile as my system has been running good past 2 years. But please let me know if using attenuators is passe'. My SNR is 39-40 db which is slightly high over the Tivo spec of 29-35 SNR. varying with each of the 6 tuners.
    I'll address this SNR number if it gives me any issues down the road.
     

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    Last edited: Nov 1, 2020
  2. Nov 1, 2020 #2 of 17
    dlfl

    dlfl Cranky old novice

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    LOL attenuators are not passe’ although they aren’t necessarily de rigor or du jour. :D

    They are like crutches and bandages: Not a la mode, but appropriate when necessary. I prefer attenuators over splitters — much smaller and probably more uniform over the bandwidth.

    In general, don’t fix it if it ain’t broke. But your 39 dB is a little on the high side, so maybe an additional 3db would be in order. I and many.others have found that 37 dB is perfectly acceptable, despite TiVo’s stated limit. I have read that there is an effect where hot signals, although not hot enough to impact video performance, can damage tuners over a long period of operation.
     
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  3. Nov 1, 2020 #3 of 17
    JoeKustra

    JoeKustra in the other Alabama TCF Club

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    As long as your Signal Strength is below 100% I would not do anything to attenuate the signal. The meter only goes to 100% and problems can happen when it goes over 100%.

    I might have someone watch your RS Corrected and Uncorrected while you wiggle the connections. A few errors are ok, but zero is better. Those number move in real time, so you can watch them move. After thirty days I have zero errors with a Signal of 90% on all channels. But if it's not broke, don't fix it.
     
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  4. Nov 1, 2020 #4 of 17
    DeltaOne

    DeltaOne Mount Airy, MD

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    I also use attenuators to bring the signal down below 100%. I think you're doing it just right.

    I put all six tuners on different channels...the six we most often watch. Then check the diagnostics screen for each channel's value. That'll give you a guide to get just the right attenuation.

    I've found it's good to check the signal levels every 3 to 4 months. At times I've had to add or subtract an attenuator to keep the signal strength right where I want it.
     
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  5. Nov 1, 2020 #5 of 17
    Expidia

    Expidia Albany, NY

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    Here is what I'm getting swapping around the attentuators . . .

    None - signal 99% (at least I know is not way over 100%) SNR 39

    3 DB = 87% signal and SNR 34 DB

    3+6 = 74% signal and SNR 29 DB

    6 DB = 98% signal and 39 SNR

    I'm thinking just using the 3 DB with an 87% signal and SNR 34 DNR
    Although when my 2500 Mhz splitters get here (replacing the 1,000 that are on there now) these numbers could change again.
    ** Which is more important to be inline with Tivo's recommended specs signal % or SNR DB? Is it better to be closer on the SNR or the Signal strength?
    I can't seem to tweak both of those to be in spec at the same time with the same DB attenuators.
     
  6. Nov 1, 2020 #6 of 17
    Expidia

    Expidia Albany, NY

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    Good advice. Once I get the new 2500 splitters installed I'll wiggle each connection while my wife watches the numbers to try and get it down to zero. I did not realize they change in real time.
     
  7. Nov 1, 2020 #7 of 17
    JoeKustra

    JoeKustra in the other Alabama TCF Club

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    They are reset to zero when the box does a restart or you place it into Standby. On a basic Roamio, RS Corrected never goes over zero. That's a really old bug.
     
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  8. Nov 1, 2020 #8 of 17
    dlfl

    dlfl Cranky old novice

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    Are you sure about those numbers? Doesn’t make sense that you get higher SNR and signal with 6 dB vs. 3 dB.

    RS errors also get reset to zero when you first tune to a particular channel.
     
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  9. Nov 1, 2020 #9 of 17
    Expidia

    Expidia Albany, NY

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    Yep, just ran them again. I'm just tracking tracking the first page but the SNR with the 6DB is 39 and the SNR with the 3 DB is 34. Thats why I was trying various combinations.
     
  10. DeltaOne

    DeltaOne Mount Airy, MD

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    74% and 87% are too low.

    I don't see how a 6 dB gives you a stronger signal than a 3 dB?

    TiVo will tell you the sweet spot is 35 dB. Of course, the signal strength and dB rise and fall together.
     
  11. WVZR1

    WVZR1 Active Member

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    The WV...
    There's such a +/- tolerance and taking a 'mislabeling/packaging' problem into consideration, most anything is possible.
     
  12. mdavej

    mdavej Well-Known Member

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    Dumb question, but what is DNR?
     
  13. Expidia

    Expidia Albany, NY

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    If you mean SNR it means “signal to noise ratio”.
     
  14. Expidia

    Expidia Albany, NY

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    Ok good. I’ll swap the attenuator to the 6 dB which will put me at 98% and 39 SNR ratio. Nope that was no good. I have the 3 dB back in now. 96% signal and 38 dB on channel 48. This is as good as in going get with mixing around the 3,6 and 10 dB attenuators I have in stock.
     
    Last edited: Nov 1, 2020
  15. mdavej

    mdavej Well-Known Member

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    I have no idea. You put it in your thread title and a couple of other posts. Is it a typo or a new acronym I’ve never heard of?
     
  16. JoeKustra

    JoeKustra in the other Alabama TCF Club

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    I think it means if this thread needs life saving actions none should be taken. I have one. ;)
     
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  17. Expidia

    Expidia Albany, NY

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    Sorry my bad! I can't correct the title but I'll check some of the other threads and change them.
     

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