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Posted: 1/19/2006 5:39:43 AM EDT
My cable service has been teh suck lately, intermittent connections, slow connections, the whole works.
Had one service call already and they ran a new cable from the junction box in the yard to the side of my house and put a signal booster on the splitter inside my house where the cable gets split 1 direction to the cable box and the other direction to the cable modem.

Thought all was fine but in the end nothing's really changed. Did some Googling and found out that if you have a motorola modem you can go to http://192.168.100.1/signal.html and check your signal strength and Signal to Noise Ratio. Well my SNR is 27-28dB, sometimes gets up to 29dB sometimes to 26dB, then craps out.

30db is considered the minimum for a good solid connection, the higher the number the better.

Could this be a bad cable modem? I have a feeling the cable company is going to blame the wiring inside my house on the problem instead of taking responsibility for the cabling on their end. I have another service call this afternoon, will see how it goes. DSL may be in my future
Link Posted: 1/19/2006 8:12:41 AM EDT
the answer is YES! My service call was 1-3 today, so this morning while waiting I swapped out my Motorola SB4200 and got an evil black Motorola SB5101 SNR is now 35db+

Made the cable company give me 3 weeks credit for Roadrunner

Link Posted: 1/19/2006 9:08:25 AM EDT
glad we could help
Link Posted: 1/19/2006 3:56:52 PM EDT
It was a bad modem only due to the fact it was reporting the wrong SNR. This was probably a symptom of other issues the modem may have been having. More than likely a bad tuner in the modem. You can't change the SNR by simply swapping a modem. If indeed it was an SNR issue you would still see the low SNR after a modem swap.

You really should not have an Amp on the line going to the modem. This can cause issues also. If this is the case, you have crappy signal coming in your house to begin with. Optimally the line is split before the amp to feed your modem.

The SB4200 was notoriously a troublesome modem. That SB5101 is a good modem. Just make sure that standby button doesn't get bumped if the modem tips over.
Link Posted: 1/19/2006 4:28:53 PM EDT
I tried a half dozen things trying to figure out the problem between the 1st service call and the second one I canceled just after getting the new modem, including connecting different computers to the same modem, another splitter (non powered), no splitter via a barrel nut connect the cable feed in directly to the modem. The SB4200's SNR never got out of the 26-28db range. Havent removed the signal amplifier with the new modem yet, but I'm willing to bet it'll have no effect as well.

Right now I'm just happy as hell!
Link Posted: 1/19/2006 4:35:24 PM EDT
old modem with problems:





new modem:

Link Posted: 1/19/2006 4:59:57 PM EDT
While a downstream level of 9 is not bad, it is not optimum. It should be below 7.

Your upstream is fine.

Where are you located?
Link Posted: 1/19/2006 5:56:45 PM EDT

Originally Posted By richhermes:
While a downstream level of 9 is not bad, it is not optimum. It should be below 7.

Your upstream is fine.

Where are you located?



raleigh area, NC, the 9 was the old modem, I'm now reading 8.3-8.4 dBmv on the new one (third pic)
Link Posted: 1/21/2006 8:48:03 PM EDT

Originally Posted By AssaultRifler:

Originally Posted By richhermes:
While a downstream level of 9 is not bad, it is not optimum. It should be below 7.

Your upstream is fine.

Where are you located?



raleigh area, NC, the 9 was the old modem, I'm now reading 8.3-8.4 dBmv on the new one (third pic)



Cool.
I'm down in Tampa, FL. I'm a lead tech for the cable modem division of the cable co. here. I deal mostly with commercial and corporate cable modem applications and our VoIP product.
Link Posted: 1/22/2006 5:48:52 AM EDT

Originally Posted By richhermes:


Cool.
I'm down in Tampa, FL. I'm a lead tech for the cable modem division of the cable co. here. I deal mostly with commercial and corporate cable modem applications and our VoIP product.



been running steady for last 3 days now,

Downstream Value
Frequency 609000000 Hz
Signal To Noise Ratio 35.7 dB
Power Level 8.3 dBmV


Upstream Value
Channel ID 3
Frequency 33008000 Hz
Power 37.0

Ask your techs to try replacing modems before replacing cable lines
Link Posted: 1/22/2006 8:56:44 AM EDT

Originally Posted By AssaultRifler:
Ask your techs to try replacing modems before replacing cable lines



Actually, that's what my guys do on a regular basis. Always do the easy stuff first!
Link Posted: 2/19/2006 3:26:08 PM EDT
Downstream Value
Frequency 579000000 Hz Locked
Signal to Noise Ratio 36 dB
Power Level 2 dBmV

Upstream Value
Channel ID 3
Frequency 34000000 Hz Ranged

Power Level 46 dBmV

Wow, that's pretty cool. I never knew about this utility. Looks like my downstream power level is pretty weak.
Link Posted: 2/19/2006 3:29:48 PM EDT
You cant think of it as weak, the lower number means that the system doesnt have to over amplify to get thru bad cable etc. If the number was higher that would indicate a problem.
Link Posted: 2/19/2006 4:18:33 PM EDT

Originally Posted By USMC88-93:
You cant think of it as weak, the lower number means that the system doesnt have to over amplify to get thru bad cable etc. If the number was higher that would indicate a problem.



So 2dBmV is good downstream, is the 46dBmV up ok?

I currently don't have any problems, just asking for my own edification.
Link Posted: 2/19/2006 4:29:49 PM EDT
On the docsis standard for cable modems, your downstream (or forward) needs to fall in the range of +7 to -7 dbmv. Upsteam (or reverse) would optimally not exceed 50dbmv. This all depends on the QAM your cable system runs on also. Any flunkie answering the phones at the cable Co. will know the ranges, but will be clueless on the QAM, so I would not bother calling them to ask.

Suffice it to say, +2 down and 46 up is a good signal.
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