Warren Wrote: "+ Make sure the cable is RG6 not the older, thinner RG59 "
Actually, RG-59 and RG-6 are very similar when it comes to upstream losses. RG-6 has much less loss/100ft at high frequencies (above
400MHz), but there's only about 1/2dB difference at subband frequencies:
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- Commscope RG-6 sheet (pdf)
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- Commscope RG-59 sheet (pdf)
Otherwise, great advice. The problem with RG-59 is that it is more likely to be damaged or poor quality, because it has been exposed to weather and other hazards over the years.
"All connections should be corrosion free even if they're outside. "
That is the 2nd most common cause of high modem transmit levels. Old connectors that were not installed properly, no weather seal, waterlogged centerconductors. The most common cause I see is junk splitters, FYI.
You may want to take a look at your tap (where your house connects to the pole), if you are in an area served with aerial cable. If it is labeled with a 26 or 23, it means the modem will have to transmit higher than if it is a 14 or 11. If it is a 26, you really need to make sure the modem is split ahead of everything else in the house. This is how all installations should be in an ideal world, but we all know how that works. The engineers who design the systems don't live in our world, so they continue to use these high value taps. :)
Anyway, you need to have someone come out and take a look at things. Any tech worth his pay should be able to see a problem right away.