Developer Forum

I have broadband cable internet service from Comcast and I've been very
happy with it until this past week. I've been having intermitant
service to the net and it's really bugging me! It will work fine and
the online light will be on the external modem and then it will just be
off and no internet for my family (and biz). Then, it will just come
back on again after a few minutes, maybe stay on for hours then off
again for awhile.

I've talked to Comcast and we did a powerdown reset on the computer and
modem and he could tell on his end what my modem was trying to do (but
not succeeding in doing = to get online) and he said that the signal
was good to the house and that many people on my street were on at that
very moment w/o any complaints. He had me test the cable channels and
they were all fine as well. A new (mega thick) line was run to our
house just a few months back (worked fine after the cable was
installed). So he said it must be the modem.

We own our modem so they offered to have us signup for their rental
service ($3?/mo) but he wasn't sure if there would be a service
/installation fee to deliver and set it up. I told him I'd just buy
another one myself.

Am I smart in doing this or should I just pay their fee and have them
do it so the servicing is all on them? I worry (and have heard about)
about them using some cheap modems that actually don't work as reliably
or as fast as the Moto Surfboard SB5100 that I now have. Yes, the irony
of that last staement about my modem being reliable has hit me!

I have some info (an error log and some specific numbers but I'm not
sure which ones are relevent here) from a Motorola diagnostics site if
that could help anybody help me.

Before I fork over my money on a new modem could it be anything else?

Thanks so much for the help!!!!

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.

In article < XXXX@XXXXX.COM >,



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

--
I know that you believe that you understood what you think I said, but I am
not sure you realize that what you heard is not what I meant.
-- Robert McCloskey, State Department spokesman (attributed)

[This followup was posted to comp.dcom.modems.cable and a copy was sent
to the cited author.]

In article < XXXX@XXXXX.COM >,
XXXX@XXXXX.COM says...

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 *** 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.

--
If there is a no_junk in my address, please REMOVE it before replying!
All junk mail senders will be prosecuted to the fullest extent of the
law!!
http://www.yqcomputer.com/ ~andyross

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.

In article < XXXX@XXXXX.COM >,



Hi. Thanks! I'll go there

Cheers, George

--
I know that you believe that you understood what you think I said, but I am
not sure you realize that what you heard is not what I meant.
-- Robert McCloskey, State Department spokesman (attributed)

In article < XXXX@XXXXX.COM >,



I posted a very similar problem to this group a few weeks ago, received
a number of useful responses. Broadbandreports.com FAQs and forums are
full of reports from others with similar problems, and good
troubleshooting tips.
Since I own my modem (Moto SB5100) I decided to contact Motorola tech
support just to see what their story might be. When I read off values
from the modem signal and log pages (which were somewhat better than
yours), they said "those levels are terrible." Called Comcast, they sent
a tech out, who put his signal meter on the line, claimed all was
"within spec," and snugged up connections (no splitter in line, have a
direct drop from the pole to the modem, separate from the video
service). I showed him the modem's configuration pages with signal
levels and logs with "3-critical" errors of every kind. He was curious
how I was able to get that information on screen; he'd never seen _that_
before, how did I do that? So, I knew I was sunk. Trying to convince
Comcast something should be bumped up on their end, even just a bit,
looks like a hopeless effort.
--
Chuck Reti
Detroit MI

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

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?