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Cable Modem Losing Connection

L

Laurel

Junior Member
I have a Motorola SB5120 Surfboard Cable Modem along with a SkyRocket VoiceIP box and a D-Link wireless router. I keep losing my connection to the internet and have to unplug the power to the cable modem (and sometimes unplug the cable). It seems to happen more frequently when VPN'd into the office.

Since my cable TV is coming in through the same cable and my cable TV almost never goes out, am I correct to assume my cable modem is not acting properly? or could it be my SkyRocket creating problems? Any suggestions or experiences with such items?

Thanks for any help!
 
"SkyRocket in flight *zoom* afternoon delight!..."

Ahem... back to the subject...

When it happens next time try unplugging and replugging the router instead of the modem and see if that fixes it. I know I have to reset my router like that every once in a while.
 
You are showing your age with that reply - number one hit (by a one hit wonder) in around 1979??? I will give it a shot!
 
Log into the modem (possibly 192.168.0.100) and check the signal levels. The down power level should be between -8 to +8 dB, and the up power level should be below 55dB. The signal-to-noise for up and down should be above 30.

Ideally you want the main coax feed from the pole to be grounded outside your home, then it should run into a 2-way splitter in the attic. One leg should go directly to the cable modem, and the other to a splitter for all of the tv's.
 
The next time you have a connection problem, verify you have block sync on the modem. If all the normal lights are on, the problem is with the other equipment, maybe the PC.

use this: 192.168.100.1
 
Any guesses on the default username/password for a Motola 5120? I cannot remember setting the username/password.

Thanks!
 
I had a similar problem a year ago with my modem. The cable company said it was my modem and they brought me a loaner and that fixed my problem so I bought a new one and gave them back their loaner. No problems since.

Good Luck
Smitty
 
My problems is mostly with not having a 100% signal on my wireless card. Using P2P (uses up all the ports?) Not have the same settings on both my card and my router. Oh yea, use some kind of encryption on your router.
 
I had a similar problem about a year ago, and Comcast came out and checked. It was because the initial installer used the wrong splitter between the PC and the TV lines. Changed the splitter - end of that problem.
 
Hopefully I can try all of these changes. The modem doesn't seem to like the admin/motorola password - still working on that situation. Could the cable company have changed the settings? Working online late last night and no problems. It definitely seems to be the cable modem (it is losing the connection - checking the lights). I'm very curious about the splitter - when they came out for the install, there was already a splitter in my attic and they just used the existing one. Wonder if it is incorrect. I'll keep everybody updated on my status (although I'll be out of town all next week and may not be able to test until I get back). Thanks for all the help!
 
To answer your original question: The internet signal and the TV signal are two different things. The internet signal can be crapped out and the TV is fine. You cannot judge one with the other.

pcgeek11
 
The type of splitter is important. The tech that fixed mine said that they had used the existing TV splitter - for TV and Cable Internet it is a different animal. It's worth a question.
 
point your browser to 192.168.100.1 and it should give you a status page, if the upstream is more than 50 then your signal is crap, down should be about 37 SNR should be 7 to -7
 
Originally posted by: Laurel
You are showing your age with that reply - number one hit (by a one hit wonder) in around 1979??? I will give it a shot!
Click to expand...

no he was quoting it from anchorman...right?:laugh:
EDIT: Awww shiz... 1 post above me was the exact sam thing... didn't see that.
 
The type of splitter is important. The tech that fixed mine said that they had used the existing TV splitter - for TV and Cable Internet it is a different animal. It's worth a question.
Click to expand...

There are a couple of important points here. First, splitters are the enemy, in general. A 2-way splitter gives you a 50% loss in signal strength on output, a 4-way 75%, etc. Signal strength is logarithmic, and I don't fully understand the effect of these loss levels on digital or analog signals, but the fact remains that signal-to-noise ratio is made worse by adding splitters.

Comcast recommends a "home run" to the cable modem, i.e. no more than a single good-quality 1 ghz. bandwidth splitter between the wall and the cable modem. Many people have more than this.

In our house we had eight splitters. I ran a line around all but one of them for the cable modem, and we've gotten good results, but the television signal was weak. I solved the whole problem by obtaining an amplified 8-way splitter which I mounted near the cable entry point. This particular unit (an Electroline) also has a 0-loss return path. The results were excellent, with improved signal strength and STNR to both the cable modem and the televisions. If you have a lot of splitters I recommend this route, as you can often get rid of all of them.
 
Originally posted by: Markbnj
Comcast recommends a "home run" to the cable modem, i.e. no more than a single good-quality 1 ghz. bandwidth splitter between the wall and the cable modem. Many people have more than this.
Click to expand...

Very good points Mark. That is essentially what Comcast put in, and then they just upgraded that when we went to digital TV w/HD. From that entry point, there is one divide - digital TV and digital internet. The Internet is a direct run to my router. The result is pretty good - I'm happy.

Result

 
Originally posted by: Markbnj
The type of splitter is important. The tech that fixed mine said that they had used the existing TV splitter - for TV and Cable Internet it is a different animal. It's worth a question.
Click to expand...

There are a couple of important points here. First, splitters are the enemy, in general. A 2-way splitter gives you a 50% loss in signal strength on output, a 4-way 75%, etc. Signal strength is logarithmic, and I don't fully understand the effect of these loss levels on digital or analog signals, but the fact remains that signal-to-noise ratio is made worse by adding splitters.

Comcast recommends a "home run" to the cable modem, i.e. no more than a single good-quality 1 ghz. bandwidth splitter between the wall and the cable modem. Many people have more than this.

In our house we had eight splitters. I ran a line around all but one of them for the cable modem, and we've gotten good results, but the television signal was weak. I solved the whole problem by obtaining an amplified 8-way splitter which I mounted near the cable entry point. This particular unit (an Electroline) also has a 0-loss return path. The results were excellent, with improved signal strength and STNR to both the cable modem and the televisions. If you have a lot of splitters I recommend this route, as you can often get rid of all of them.
Click to expand...

Actually, you lose 3db with a 2 way and 4db on a 4 way

 
The RF level is expressed in dBmV, 10LOG. If Channel 2 (54.00 MHz NTSC HRC) is measured at 10 dBmV and Channel 117 (750.00 NTSC HRC) is 13 dBmV, the Delta is 3 dB. 10 dB represents exactly 10x the power, 3 dB is 2x power.

The loss over a balanced 2-way splitter 3.5 dB, approximated at 4. An unbalanced 3-way is actually 2 2-way splitters, with losses of 7, 7, and 3.5 dB. A 4-way is 3 2-ways, 7 dB on each port. 8-way splitters have a loss of 11 dB. A directional coupler is effectively a 2-way with unbalanced outputs, most common is DC-8 (approx -1 dB on through leg, -8 on down leg). A balanced 3-way has a loss of 5 dB on each leg.

For the OP, if you verify the problem is with the service and not your equipment, contact the service provider and have them fix it.
 
Another item I just noticed:

Trying to complete some work before leaving on vacation, I was working late Saturday night from about 10 PM to 2 AM. Internet connection worked fine. I also worked Sunday morning from 7 AM to 11 AM and no problem. Then the connection started going haywire. I'm pretty certain my connections are always dropping during peak connection times in the neighborhood.

What problem would that signify?

PS - still cannot connect to 192.168.100.1. Asks for the user/password and nothing has worked so far. It would probably help me solve my problem if I could get into it.

Thanks for all the help (and I'm actually going on vacation starting tomorrow - won't be able to resolve this for another week or so).
 
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