Are those levels reported by

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November 9, 2011 at 12:01 am #6448
FrankAZ

    Are those levels reported by the Ceton’s tuner diagnostics, or are you calculating them from a measurement elsewhere and your knowledge of the coax network? In themselves those figures are not too terrible though of course 0dBmV would be better.

    I have the good fortune to have two Ceton cards, one in each of two machines. One card is a gen 1 from August 2010, the other a gen2 from earlier this year. When I connect them to the very same cable with the same dongle etc I see very different signal levels reported by the two Ceton cards. There is about a 7dB difference. I tried RMA exchanging the gen 2 unit with Ceton and the replacement gen 2 unit showed exactly the same lower signal levels as the first. I mention this because it seems that the Ceton card, or at least the two gen 2 ones and the gen 1 one I have used, report different levels for the same cable. It may be that your measurement of -11dBmV is off, and you are actually seeing something less which would be expected to produce errors.

    Have you tried calculating backwards/forwards from the signal levels reported by your Cable Modem or Tuning Adapters to check? In my case I determined that the low signals being reported by the gen 2 Ceton cards were actually not low and I just put up with a reported low signal and enjoy good video. Don’t forget to account for a passive splitter inside the Ceton card which divides the signal at the dongle to each of the 4 tuner modules. That will amount to a 7dBmV drop between the coax cable and the tuners.

    My service provider is Cox in Phoenix. They seem to launch all the HD channels at about the same signal level, +/- 2 dBmV so I don’t see a lot of variation from channel to channel. Years ago I did though – it varied horribly by > 8dBmV between adjacent channel numbers, and then I realized that channel numbers were no relation to actual RF frequency. When I compared good vs. bad channels by frequency I found that I was seeing a more periodic rise/fall in signal levels. The culprit turned out to be a bad coax drop to my home. It was buried under some loose stone gravel and people walking on the gravel had caused the stones to puncture the sheath and irrigation water to flood the dielectric. Signal reflections for different frequencies must have been causing constructive or destructive interference at nodes along the cable and my equipment was seeing this as a rising and falling in signal level. You might want to get your cable provider to look into that – it is a simple test they are accustomed to doing and if they find a problem they can replace the drop quickly.

    Frank.