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SNR & Power Level on set top boxes
I recently discovered way to look at diagnostic pages of couple STB’s I have. Noticed downstream signal to noise ratio and power level, also upstream power level though terminology not exactly same as internet modem. I understand good ratings of these as it relates to internet modems, but wondered if same values would apply to set top boxes.
So question is can these valves be considered same with STB as with cable modem?
Accepted Solution
Tecknowhelp
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Cox mini box can work on 64 and 256 QAM. The higher the modulation, the less resilient to noise. Assuming it uses 256 QAM, here are some general signal specs:
Level: Should be -12 to +15 dBmV for QAM256
S/N: Should be 33 dB (or more) for QAM256 [This is more important than level]
Seconds: How long channel has been tuned.
Corr Bytes: How many bytes were detected in error and corrected since first tuned
Uncor Blks: How many data blocks that failed parity check, but could not be corrected.
Errs Avg/Inst: Average and Instantaneous Bit (byte? block?) Error Rates.
See links for more info.
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Don318
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Thanks Tecknowhelp,
Both units are more advanced units 9865 & 4742 operating at 256 QAM. Both in proper signal levels like 4 & 6 dBmV and around 38-39 dB S/N. Not yet sure how to get that data displayed by mini-box.
But your answer clears up question, basically same appropriate levels as cable modem. I’m learning here and this makes me think STB is basically a cable modem with channel tuners and hard drive for recording in some units. Also I now know I can use diagnostic page to evaluate incoming signal on STB as I have done in past on cable modem.
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Tecknowhelp
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Have you had any luck with MoCA? Is there a patch yet for MoCA 2.0?
I notice the video output on t he 4742(1920x1080p/24) is higher then 9865(1440x1080i/30). Any visual difference?
As I understand, the guide data is pushed every 24 hours on the downstream, or when Cox sends a activation signal. Upstream is possible by the equipment but Cox doesn't use it.
Kind of? The tuner doesn't use DOCSIS, so signal perimeters are wider. Think of it more like HAM radio, but over wire and with encryption. Scrambling is applying a filter to that signal using mathematical equations.
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Don318
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Yes looked at MoCA as that is what you helped me with in early May, which allowed me to learn how to get into diagnostic pages of the 9865 & 4742.
http://forums.cox.com/forum_home/tv_forum/f/4/t/13813.aspx
Not sure about patch for MoCA 2.0…. Visual the 4742 looks a little better but might be quality of TV it’s hook too. The 9865 is on a cheaper TV but newer. Simply hard to tell or I’m not capable of seeing difference.
Data I was referring to on mini-box is diagnostic pages like on first two boxes. Couldn’t find that on MoCA being Cisco mod. “DTA 250HD” that is on bottom of box.
Thanks for that explanation.
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