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Old 14-Aug-2015, 1:06 AM   #15
rabbit73
Retired A/V Tech
 
Join Date: Aug 2012
Location: S.E. VA
Posts: 2,569
Not too crazy, it's the nature of the beast.

Many things can cause errors in the digital stream. The BER (Bit Error Rate/Ratio) can be increased by a weak signal, multipath reflections (Static or Dynamic), and by electrical interference, as you found out. Any or all can be present at any time.

The FEC (Forward Error Correction) can correct a limited number of errors in the digital stream. Once that limit is exceeded, you reach the Digital Cliff, where you experience pixelation, picture freeze and finally dropout.

Forum member mulliganman was having an unacceptable number of uncorrected errors with his TiVo Roamio. This is his Diagnostics Screen readings before improvements:
Quote:
Originally Posted by mulliganman View Post
I went into the DVR diagnostics menu on the Roamio to get some info for all channels. Here is what it shown (as setup in the diagram I posted):

Channel 3-1 signal strength 55%, 22 dB SNR, RS Corrected 0, RS Uncorrected 66

Channel 3-2 signal strength 55%, 22dB SNR, RS Corrected 0, RS Uncorrected 60

Channel 3-3 signal strength 57%, 23 dB SNR, RS Corrected 0, RS Uncorrected 81

Channel 10-1 signal strength 67%, 27dB SNR, RS Corrected 0, RS Uncorrected 30

Channel 21-1 signal strength 52%, 21 dB SNR, RS Corrected 0, RS Uncorrected 132

Channel 21-2 signal strength 52%, 21 dB SNR, RS Corrected 0, RS Uncorrected 30

Channel 21-3 signal strength 52%, 21 dB SNR, RS Corrected 0, RS Uncorrected 60

Channel 27-1 signal strength 60%, 24 dB SNR, RS Corrected 0, RS Uncorrected 6

Channel 33-1 signal strength 60%, 24 dB SNR, RS Corrected 0, RS Uncorrected 0

Channel 33-2 signal strength 60%, 24 dB SNR, RS Corrected 0, RS Uncorrected 120

Channel 33-3 signal strength 60%, 24 dB SNR, RS Corrected 0, RS Uncorrected 45

Channel 49-1 signal strength 45%, 18 dB SNR, RS Corrected 0, RS Uncorrected 6

Channel 49-2 signal strength 45%, 18 dB SNR, RS Corrected 0, RS Uncorrected 0
and this is after improvements:
Quote:
Originally Posted by mulliganman View Post
I believe the coax from the 91XG to the attic amp to be less than 25 feet, so I made the following change as you suggested: 91XG > downlead > LNA 100 > AC7 ch 49 input. The C2V went into the other input of the AC7. I did a rescan, then as soon as I had a chance a little while later I went back into the DVR diagnostics menu on the Roamio. Here are the results:

Channel 3-1 67% signal strength, 27 dB SNR, RS Corrected 0, RS Uncorrected 0

Channel 3-2 65% signal strength, 27 dB SNR, RS Corrected 0, RS Uncorrected 0

Channel 3-3 67% signal strength, 27 dB SNR, RS Corrected 0, RS Uncorrected 0

Channel 10-1 72% signal strength, 29 dB SNR, RS Corrected 0, RS Uncorrected 0

Channel 21-1 72% signal strength, 29 dB SNR, RS Corrected 0, RS Uncorrected 0

Channel 21-2 72% signal strength, 29 dB SNR, RS Corrected 0, RS Uncorrected 0

Channel 21-3 72% signal strength, 29 dB SNR, RS Corrected 0, RS Uncorrected 0

Channel 27-1 72% signal strength, 29 dB SNR, RS Corrected 0, RS Uncorrected 0

Channel 33-1 67% signal strength, 27 dB SNR, RS Corrected 0, RS Uncorrected 0

Channel 33-2 67% signal strength, 27 dB SNR, RS Corrected 0, RS Uncorrected 0

Channel 33-3 67% signal strength, 27 dB SNR, RS Corrected 0, RS Uncorrected 0

Channel 49-1 62% signal strength, 25 dB SNR, RS Corrected 0, RS Uncorrected 0

Channel 49-2 62% signal strength, 25 dB SNR, RS Corrected 0, RS Uncorrected

I was surprised to see improvements in signal strength and the RS Uncorrected numbers across the board. I'm not sure if the "0" for the RS Uncorrected is just temporary because I had rescanned or not. I had never seen that on any channels other than 49-1 or 49-2 when looking at in the DVR Diagnostics menu on the Tivo Roamio (I had a similar setup just the LNA 100 after the AC7 combiner but didn't see the same results). Maybe someone else can jump in with an explanation of what they think is going on or if I should leave the LNA 100 as the only amplification on my setup.
Attached Images
File Type: jpg TivoDiagScr (2).jpg (186.8 KB, 572 views)
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Last edited by rabbit73; 14-Aug-2015 at 1:31 AM.
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