Basic Internet Connectivity And Modem Help

[ggbal]

I have a Arris TM722G. It directly connects to the cable outlet. I have a TV in the other room. I found that the the TV signal lost sounds or pixelated when I use upload something using the internet. Then I did the speedtest (speedtest.comcast.com). I noticed that at the end of download test and the whole upload test, the TV will experience the same sound lost or pixelated. 

My understanding is that cable internet runs different frequency than TV signal. So how come the internet, particularly uploading, affect the TV signal? And how I can fix that?

[JayInAlg]

There are several things that can cause this.

Loose coax cables or poor shielding or loose / corrorded F connectors including cheap coax jumpers with poor shields & connectors, especially those cheap ones with the gold ends.  Cheap splitters with poor isolation or shielding also will cause these issues.  Splitters must be high quality with good isolation and shielding.

High upstream power levels can cause interference on the TV side.

With your browser go into http://192.168.100.1 and post the downstream power levels, upstream power levels and SNR readings.

Go over every inch of your coax for damage, check every F connector that it's snug and that the shield is firmly attached to the connector, replace any coax jumpers that could be questionable with RG6 jumpers with compression fittings.  Replace all cheapie splitters.

[ggbal]

downstream: power 12.45-13.41 dBmv, SNR 36.17 - 37.09 dB

upstream: power 42.75-43.00 dBmv, freq: 25.30 - 37 MHz

I thinking whether I should put a high-pass filter on the TV cable since almost all the time it is uploading causes the interference. Will this help?

[JayInAlg]

A high pass filter will break your cable box, it needs the 5-50mhz return path to talk back to the system.

Your downstream is a little high which is not good, are you in a MDU or single family home?  If your in a home, do you have a drop amp or booster somewhere in the home?

[ggbal]

yes, there is a 3x8 RF distribution drop amp. 

[JayInAlg · Accepted solution]

Put a 2 way splitter ahead of the amp and feed the eMTA directly on one leg, and the amp's input on the other leg.  That is standard practice.  The recommendation is not amp the modem unless absolutely necessary and under a Comcast tech's direction.

[ggbal]

I will try that. 

BTW, since cabel modem and TV are in different frequency, why does the modem interfere TV?

[ggbal]

Also what kind of 2-way splitter should I use? Will the regular passive filter be ok or have to use active filter since you will not be a short distance from drop to the outlet?

[JayInAlg]

It could be cross or intermodulation from the drop amp or a cabling or fitting fault.  It's still easy to get adjacent channel interference.  There's only a handful of upstream channels.

[ggbal]

This did it. I added a splitter before the amp. Now the interference is gone, The downstream power is ~1dBmv now. Thanks, JaylnAlg.

[JayInAlg]

Good, that signal to the eMTA is now closer to where it should be.