Comcast / Motorola sb5100 cable modem dropping connection...

They always say that... Don't take that as a given, as the tech you're speaking to has no idea what other people are complaining about.

Ask your neighbors if they're having the same problem.

A_C

Can you access the modem to see the levels yourself?

Does any of this help any?

///////////////////////////// Downstream Value Frequency 687000000 Hz Locked Signal to Noise Ratio 36 dB Power Level -10 dBmV The Downstream Power Level reading is a snapshot taken at the time this page was requested. Please Reload/Refresh this Page for a new reading

Upstream Value Channel ID 3 Frequency 31000000 Hz Ranged Power Level 52 dBmV ////////////////////////////////////

ERROR LOG Time Priority Code Message

2006-05-10 13:34:47 3-Critical R005.0 Started Unicast Maintenance Ranging - No Response received - T3 time-out 2006-05-10 12:24:22 3-Critical R002.0 No Ranging Response received - T3 time-out 2006-05-10 12:23:57 3-Critical T001.0 SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing 2006-05-10 12:23:43 3-Critical D005.0 TFTP failed - request sent - No Response 2006-05-10 12:22:33 3-Critical R007.0 Unicast Ranging Received Abort Response - Re- initializing MAC 2006-05-10 12:21:54 3-Critical R002.0 No Ranging Response received - T3 time-out

at a glance you seem to be riding on the end of the power level specs. Here are suggested working ranges for solid operation. Values are from mine:

Motorola Surboard SB5120 QAM 256 (Working range) Down Power -4 dBmV (-10 and +10 dBmV) SNR 37 dB (higher than 33dB) Up Power 48 dBmV (30 and 55dBmV)

Anytime you lose the connection, get the values.

First of all thanks so much for the help!!

I only get these values when I'm online by connecting to a Moto site I saw in one of these posts. When my modem goes ofline I can't get these numbers

Does it look like the modem is bad or is it saying that I'm getting a fairly weak (barely strong enough) signal?

Thanks again!!

OK, maybe we're on to something. I checked all the connections again but this time ran the cable to the modem directly from the wall w/o going through the splitter that they installed when they hooked up my dvr box in the same room. My down power level went up 3 dbs to -7. Seems a little low but not right on the bottom like it was. I'll try it like this for awhile and see if I get dropped. Maybe the modem is actually fine and they need to do something about the signal splitter.

On the signal splitter it says 2-way splitter 5-1000mhzand on each of the two split connectors it says -3.5 db. Not sure what that means exactly but is it a coincidence that my signal rose 3 db w/o it? Can I just get a different value splitter?

Thanks agin!!

John

You should have a splitter coming into the house and you want the cable modem to go direct to that splitter using preferably RG6.

Run your TVs off the other legs of that splitter (you may even use another splitter off one of the TV lines [I do] without any major issues).

As far as the TV in the same room as the modem, I'd run another RG6 line for it.

Basically you want nothing else on your modem leg.

SBill - PMFJI. I have a similar setup, viz., incoming feed split into two -3.5db channels.

Question: Can I install an amplifier on the non-modem channel to feed three TVs in the house, or will that cause problems? I've wired the modem line with a 50' length of RG6, but haven't actually hooked up my SF5120 as yet and called Comcast to set up service.

TIA

George

When the modem is offline, what lights are blinking? If the receive light just blinks continuously, it is trying to find the downlink signal (receive signal strength or too much noise.) If the receive light is solid, but the send light is blinking, it is trying to establish the uplink (same potential problems as downlink.)

For a weak incoming signal, you can use a broadband compatible RF amplifier. These allow the upstream signal to pass with minimal loss. It should be placed as close to where the cable comes into your house as possible. I would avoid the Radio Shack crap amps and get the Motorola

484095-001-00 amp if you can find it. A Google search will find alot of sites. It's also commonly available at Circuit City, but at full price.

I don't see why not, but i'm running 3 TV legs off my 1-4 splitter and one of the legs has a 1-8 splitter on it feeding 7 TVs/VCRs/PCs and I have no problems with it. You may not need an amplifier.

You may want to check some of the websites out devoted to this sort of thing - like broadbandreports.com etc.

Hi. Thanks! I'll go there

Cheers, George

Andrew, and everyone else, thanks for all thew responses!

When the modem is offline (no online light) the recieve light sometimes blinks first then usually turns solid and the send light blincks about once per second. The PC/activity light blincks at a faster rate and sometimes I've seen it solid. Obviously, the power light is on. Then for seemingly no rhyme or reason the online light will come on and everything is fine.

I thought the problem was fixed yesterday when was mainly on especially after removing the 2 way splitter from the wall connection (moden on one end and TV on the other). That bumped my signal about

3dbs and I stayed online longer than anytime in the last week. Then right b4 an ebay auctiuon was about to end (!!!) the modem went offline for the rest of the night. Then , this morning it's back on. I'm going to rework a splitter connection at the street/house connection and get another 3dbs. That should get my modem signal to about -4 or -5. Does it have anything to do with people coming back from work and using Comcast and lowering the signal (although I have lost the connection in the day time as well)? Are the numbers I posted too low and it's a Comcast signal problem? What's the minimum signal requirements for a reliable signal?

Thanks again for the help!!!

John

I just saw a manual on the 5100 that states it's operating range as -15

This is not fun! What do you think?

I may just buy the newer Moto 5120 at Wal-mart for under $60 and then if I still have problems get Comcast out here to increase the signal. Is it normal in some cases where the computer is not getting a strong enough signal for them to just run a seperate line to the house or is that always treated as more money either for the installation and/or monthly charges?

While the -10dBmV downstream is perfectly fine, I would be a little concerned about the +52dBmV transmit level. Two possibilities are: 1) Temperature. It is possible that as the day progresses, the increase in temperature increases the attenuation of the cable sufficiently to push that transmit power beyond its limit, which typically is about 56-58dBmV.

2) At some point, noise is getting into the return path, which causes your cable modem to transmit at a higher level than it otherwise would. The 2 biggest types of noise that can disrupt the upstream path are ingress and impulse noise. Ingress is stuff leaking into the cable system from the outside world. The most common causes of leakage are loose/substandard/corroded connectors, poorly shielded cable, substandard passive devices (splitters, taps). These are all part of the drop system. Impulse noise can be electrical noise getting into the cable system if there is insufficient filtering at some point where the 2 have something to do with each other, such as a cable modem plugged directly into a wall outlet without the benefit of a surge power strip. Vacuum cleaners and blow dryers (things that cause sparklies on your TV when turned on) are also sources of impulse noise.

Something is causing your cable modem to shout loud enough to be heard by the CMTS. Sounds like sometimes it has to shout so loud that it can't be heard.

I would call and have a tech come out and figure out why your transmit is as high as it is.

CIAO!

Ed N.

snipped-for-privacy@gmail.com wrote:

Redid some splitters/connections. So far I'm still online just fine and here are the newest readings: Downstream Value Frequency 687000000 Hz Locked Signal to Noise Ratio 38 dB Power Level -2 dBmV The Downstream Power Level reading is a snapshot taken at the time this page was requested. Please Reload/Refresh this Page for a new reading

Upstream Value Channel ID 3 Frequency 31000000 Hz Ranged Power Level 44 dBmV

That 44dBmV is a beautiful thing!

CIAO!

Ed N.

snipped-for-privacy@gmail.com wrote:

I don't think the 5120 is any newer than the 5100. They just justed two different chipsets and gave them different model numbers.

Yes, those are all good levels.