Signal strength vs HD picture quality (OTA)

Discussion in 'TiVo Series3 HDTV DVRs' started by Mars Rocket, Nov 11, 2007.

  1. Mars Rocket

    Mars Rocket Loosely wound

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    Sinnoh region
    I put up an antenna on my roof so I could get the local CW station in HD (comcast here only carries the non-digital signal for that station.) I aimed the antenna by eye, based on information from antennaweb.org.

    My TiVo shows a signal strength of 85 for the station in question, and I'm wondering if there's any point in me trying to aim it better and maybe get a slightly higher number. It may not be possible to get anything better, and re-aiming it would be a major pain in the a** because I'd have to climb up on the roof, make a small change, then come down and see what the result was, then repeat until things were optimal.

    Is there going to be much difference between an 85 and a 90 or maybe 95 signal strength? The station looks fine to me in the short time I've been able to view HD content from it.
     
  2. phox_mulder

    phox_mulder I get paid 2watch TV

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    Digital is either there or it's not.

    Higher signal strengths will mean you'll have picture and sound longer during rain or snow storms.

    85 is a pretty good number, IMHO.


    phox
     
  3. moyekj

    moyekj Well-Known Member

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    Signal strength doesn't really mean much. SNR is more important. For OTA if you are getting 20+ dB that seems to be good enough for Tivo. OTA uses 8VSB modulation which tolerates lower SNR ratio compared to QAM which usually needs 34+ dB or so to ensure clean signal.
     
  4. aaronwt

    aaronwt UHD Addict

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    Northern...

    My OTA signal strength goes up during rain and snow storms. That's when I have absolutely no reception issues.
     
  5. Mars Rocket

    Mars Rocket Loosely wound

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    Is there any way to tell what my SNR is from the TiVo, or do I need specialized equipment for that?
     
  6. moyekj

    moyekj Well-Known Member

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    Tune to stations of interest and then visit the Diagnostics menu. For digital channels (OTA ATSC & cable QAM) you will see SNR numbers there for each tuner updating in real time along with Signal strength and a bunch of other info.
     
  7. SCSIRAID

    SCSIRAID Active Member

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    Vero Beach, FL
    Exactly. The end goal would be to keep the RS Uncorrected value at zero and the RS Corrected rate as low as possible. Mid 20's SNR for Digital OTA should do that.

    Im 20 miles from antenna farm and with an attic antenna I get SNR's around 28-30 and RS Unc = 0.
     
  8. Mars Rocket

    Mars Rocket Loosely wound

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    Looking at it just now I see an SNR of 29-30, but the RS Unc is now 27 and RS Corr. is 241. This is after 180 seconds with a SD show, if it matters.
     
  9. SCSIRAID

    SCSIRAID Active Member

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    Vero Beach, FL
    180 seconds isnt really enough time to tell but 27 is a lot higher that I would expect. Watch it for an hour and then look at RS Uncorrected. Multipath can result in errors even if you have good signal 'strength'.
     
  10. TAsunder

    TAsunder Debates Ghee vs Gi

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    Madison, WI
    The concept of digital being there or not is kind of a misnomer as it relates to OTA. All it really implies is that if your incoming stream is steady and perfectly pure, there will be no quality loss. The stream can get interrupted by a lot of things and waver in/out, which will cause massive pixelation and other problems. A signal can vary quite a bit despite seemingly being an 85. It really depends on other factors than the signal strength indicator. I've had stations at over 90 that still have major problems, and I've had stations at 75 with no problems.
     
  11. MickeS

    MickeS Active Member

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    I heard that rain, snow and some fog are usually very good conditions for signals to travel in. For satellite reception it's another matter.

    I thionk a signal strength of 85 sounds fine, so unless you have other issues, leave it alone. I had less than that and got a perfect signal.
     
  12. Mars Rocket

    Mars Rocket Loosely wound

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    Mar 24, 2000
    Sinnoh region
    As it happens, the errors I saw all occurred within the first few seconds after tuning the channel. It went up to about 180 uncorrected and 2450 corrected almost immediately and then there were 0 additional errors over the next hour+. I'm just going to leave things as they are, except for maybe shortening the cable from the antenna (it's about 50 feet longer than necessary at the moment).

    Thanks for all the info in this thread.
     

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