I've been having trouble with my cable connection (Comcast) for some time
now. I've tried changing splitters to no avail.

My downstream specs:
Lock Status Locked
Modulation 256QAM
Channel ID 36
Symbol Rate 536.0537 Ksym/sec
Downstream Power 0.0 dBmV
SNR 33.3 dB


My Upstream specs:
Lock Status Locked
Modulation 16QAM
Channel ID 1
Symbol Rate 2560 Ksym/sec
Upstream Power 61.0 dBmV


I have done some homework and I know the 61.0 dBmV is way out of spec but I
don't really know that I can do about it. Any help would be greatly
appreciated!

Please remove the {at}nospam and replace it with @ for email.
chris_s1{at}nospam.comcast.net

Chris R. Speaker wrote:
Essentially your modem is screaming at the top of it's voice to be
heard.

Things that you can check in your house are:
+ Make sure the cable is RG6 not the older, thinner RG59
+ Make sure the cable is not damaged
+ The ideal set-up is a separate run from the "pole" to the house
just for your cablemodem, but if that's not what you have, make sure
there is only one splitter on the path to the cablemodem. If that
splitter is a 3-way, make sure it's on the leg of the splitter that has
the least signal drop.
+ If there is a splitter, it shouldn't be a cheap TV splitter. It
should have a wide frequency range.
+ There should be no amplifiers on the path from the cablemodem out
of the house.
+ If there is a filter located near the splitter, it should be on
the leg going to the runs to the TV, not on the run to the cablemodem,
or on the run into the house
+ The run to the cablemodem should be a piece of continuous cable,
not a couple of pieces spliced together
+ All connections should be corrosion free even if they're outside.

It's possible that everything in your house is perfect, and the problem
is outside your house. In that case, it's out of your hands, and you'll
need to get a technician sent out to your house. (Note that you don't
have to crawl around your attic or crawlspace to check all those other
things, either. The technician will be able to take care of any of those
issues if they're causing the problem, too. You also shouldn't have to
buy any new cable, connectors, splitters, filters, or whatever. Those
things will be provided by the cable company if you need them.)

--
Warren H.

==========
Disclaimer: My views reflect those of myself, and not my
employer, my friends, nor (as she often tells me) my wife.
Any resemblance to the views of anybody living or dead is
coincidental. No animals were hurt in the writing of this
response -- unless you count my dog who desperately wants
to go outside now.

Power Lawncare Tools for Spring Clean-up:
http://www.holzemville.com/mall/blackanddecker/

Check with a couple of neighbors and find out the Upstream power levels
on their modems, if they have more than 50 dBmV, then the cable company
have may have to adjust the reverse amplifier in your neighborhood.
Bottomline is - if nothing has changed in your home since you last had
good connection, it may not be something you can fix on your own.

"Check with a couple of neighbors and find out the Upstream power
levels
on their modems"

Or, call Comcast and say your connection is not working. Unplug your
modem before you call, so when they run a test, it will show offline.
Fib if they ask you to powercycle the modem and say you did.

Don't bother your neighbors unless Comcast is unwilling to fix the
problem.

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:

http://tinyurl.com/h7pg5 - Commscope RG-6 sheet (pdf)
http://tinyurl.com/kb7s4 - 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.