OTA signal analysis

Discussion in 'TiVo Help Center' started by Wayne Rutherford, Dec 1, 2019.

  1. Wayne Rutherford

    Wayne Rutherford Member

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    Mar 19, 2018
    Can anyone tell me where to find the information to decipher the numbers i get in the diagnostics? What is an acceptable signal strength? What do SNR, RS Uncorrected, SR Corrected actually mean? Example: channel 25-2 strength=72%, SNR 29db, RS Uncorrected 0, RS Corrected 0 and is a GREAT picture! Channel 6-1 strength 60%, SNR 24 db, RS Uncorrected 642, RS Corrected 0 will have a good picture, then pixelate so bad you have to ff until it clears up. What does SNR mean and what values are good? What do RS Corrected/Uncorrected mean and what values are good. Best of all, WHERE do I find this information?
     
  2. V7Goose

    V7Goose OTA ONLY and Loving It!

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    The things you are asking about have been discussed MANY times in these forums, and unfortunately you will not find simple answers to all of your questions. My formal training and experience in the industries of avionics and broadcast radio and television is from the ancient time of analog, but the basic principles of radio signals have not changed:

    Signal strength and SNR numbers are RELATIVE numbers, not absolute things that can be compared between two different boxes. But at least they give you a place to start.

    On a Bolt, 72% signal strength is the MAXIMUM you will see, since the box has an automatic gain control (AGC) circuit that will actively reduce any stronger signal to prevent problems from overdriving the rest of the system. A Bolt will generally produce a perfect picture with any signal strength over 40% IF, AND ONLY IF, the rest of the signal is "clean".

    SNR means signal to noise ratio, and it is an indication of one aspect of how good the signal is. "Noise" comes from many things, and it generally means any part of the signal that is not the desired part. No electronic circuit is ever totally quiet, but the system can compare the base level of steady signal that is ALWAYS there with the variable part of the signal being received to produce an SNR number. By definition, you ALWAYS want a higher SNR ratio; ANY "noise" is bad, so less is better. Unfortunately, the variable part of the signal you are receiving is not always a good part of the signal that you want, so just having a high SNR number is not a guarantee of a good signal either.

    It is also important to remember that since the Noise part is generally at a fixed level the Ratio will always go down as the Signal strength drops. With a Bolt, 72% and SNR of 29 dB SHOULD be excellent (ignoring other possible signal quality problems), while 40% and SNR of 16 dB should be acceptable, along with anything in between.
     
    Last edited: Dec 1, 2019
  3. JoeKustra

    JoeKustra in the other Alabama TCF Club

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    Ashland, PA...
    RS: Reed–Solomon error correction - Wikipedia on a basic Roamio and Bolt, the count of Corrected will always display zero. I don't know if it works on the EDGE.

    Signal Strength: % is influenced by AGC (see my signature for abbreviations) but the happy number for OTA (again on a basic Roamio & Bolt) is 72%. For cable it is 90%. If the signal is too high or too low and AGC can not compensate, you may experience blocking errors and even loss of the video. I see V7Goose types faster than I do, so read that post.

    If your TV has diagnostics, like a Sony, expect different numbers. Long ago it was common to see real numbers that showed an actual measurement. But then people would replace tubes in their televisions also. In HAM radio, you may find signals measured in microvolts per dB of quieting, but that was 50 years ago for me. Now the only CE stuff with actual numbers (I think) is speakers and some receivers.
     
  4. Wayne Rutherford

    Wayne Rutherford Member

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    Mar 19, 2018
     
  5. Wayne Rutherford

    Wayne Rutherford Member

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    Mar 19, 2018
    Thank you. I have to find a happy place for my antenna. The towers are almost 180° from one another. I bought what was supposed to be an omnidirectional, but I will have to tinker to dial it in.
     
  6. mdavej

    mdavej Well-Known Member

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    Two directional antennas are better for that situation. Combine with a splitter in reverse. Aim each using the signal strength bar on your Tivo.
     
    kpeters59 likes this.
  7. Wayne Rutherford

    Wayne Rutherford Member

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    Mar 19, 2018
    Thanks. Good thing I got a trial period for an assessment. So you would use a regular splitter but in reverse?
     
  8. mdavej

    mdavej Well-Known Member

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    Yes
     

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