I have Comcast cable service, and I'm using their broadband service as well.  My modem is an RCA model DCM235.

My problem is that my broadband service fails - intermittently throughout the day, then comes back all by itself.  I had this problem from shortly after installation.  The installer ran a separate cable from the box on the exterior of my home to where my computer is, and the original line goes to my VCR.

When the problem first began, I had service techs out but they almost never showed up when the system was down.  I understand that it's hard to fix what ain't broken.  Finally, one time a tech showed up when it was down and said that there was a grounding problem somewhere on other side of my wall - that is, it was a cable company problem, not something in my house.

Well, apparently not, because shortly after that, my VCR bit the dust, and when I disconnected it from the cable, my broadband service was flawless.  

Hmm...

So, I replaced the VCR.  Things went along well for a couple of months.  Now it's doing it again.  When my broadband service crashes, all it takes to restore service is for me to disconnect the cable going to the VCR for a few seconds to a minute or two, then everything comes back up, I plug the VCR cable back in, and we're good to go.  Until the next time.

Do I have a bad cable modem?  WTF is going on?  I'm ready to sacrifice a chicken here to get rid of the voodoo spell.

did you see where he put the filter in?
If so, swap the lines if you can and see if it helps. maybe the splitter he put in is bad.

You most likely have a weak or fluctuating cable signal for some reason. You are going to have to get a tech support person that will listen and insist they fix it.

I went through much the same thing you did. I used to run a splitter between a VCR and a cable modem (RCA DCM 215), and had much the same problems. At one point it got so bad that if I had the VCR hooked up the modem could never pick up a signal.....but when run direct from the wall it was fine.

IMHO the problem is definitely on the side of the cable company. In my case, it was actually a bad wire running from the junction box on the side of the road and under the street. Caused the signal to degrade to the point where the higher freq functions (cable modem, digital cable) wouldn't work very well. Once they replaced the wire there (which was a complete CF....imagine coming home with no warning to find a bunch of guys standing next to a backhoe and a four foot deep hole in your lawn!), things got a lot better.

You should call Comcast again, and ask them to send out service techs to check the line signal both inside and outside of the house. When the check the line at the junction box they should be able to detect any signal strength/dropoff issues.

I had the same problem with Comcast when I lived in Virginia...some of my TV channels were messed up, and my Internet would go down fairly often, too.  When a technician came out to hook up a neighbor's cable (I lived in a condo), he found that the splitter my cable was connected to had corroded, and the cable was barely connected...it's amazing that I had any service at all.  He replaced the splitter, and my problems went away.  Hope this helps!

I have a great deal of experience with this.  A broken cable, either underground or above ground will give you intermittent signal strength as temperature fluctuates and the cable expands and contracts.  They had to replace about 180 feet of cable at my last house to fix this.  Another problem that it is hard to get the cable company to own up to is that too many users on a hub will kill the signal strength.  This will appear at peak-use times.  You must start by having a cable tech. verify your signal strength.  YOU are paying for a certain amount of signal and they MUST provide it.  

Too many TV taps will kill your signal strength.  Look at the channels on TV.  Are the upper channels more snowey than the lower ones?  This is a very good indicator.  Scientific atlanta makes a very good line amplifier that just about anyone can install.  This is what I had to do at my house, and at my last house.  You install it on the main line and then all you your remaining taps go into your house.  It acts as your splitter and amplifier.  This will clear up the upper channels, providing that you have a clean, but slightly weak signal at the tap. You must use good grade cable and high grade connectors.  Not gold ones, but ones that have a gas tight crimp on the shield.  If your clamps are Radio-shack grade, you probably have bad connections in the house.


After all of that is verified, cable modems do degrade.  Call them up and make them send you another one, especially if it is under warranty.  Learn how to do a trace route and how to ping the provider to see if you are really on line, how many packets are dropped, your bit rate, and where the signal may be getting lost.

Lastly, switch to DSL, if it is an option.  I use Cox and Qwest for cable and DSL.  Cox (cable) will never admit the problem is their fault.  Recently there was an outage on the entire west coast and their recorded phone message stated that.  I called to find out when they would be back on line and they said there wasn't an outage.  What dicks!  Even after getting it back 3 days later, my incoming signal was lessened and that is when I had to get the line amplifier out of the closet.  I hate those fuckers, and their tech. support people are dumber than a bag of hammers.

Good luck, IM with questions.