Howto on Cable Modem Connection

Have a question or want to start a discussion? Post it! No Registration Necessary.  Now with pictures!

Threaded View


A friend of mine has Comcast Internet, and is experiencing numerous
"stalling" occurrences during her Internet sessions. Her XP Pro PC is
hardwired to a Linksys BEFW11S4 router, which also feeds a laptop and
a TiVo wirelessly. Router is connected to a SurfBoard modem.

I tried to trace the route of the incoming cable back to the entrance
point on the house today (having some problems because the entire
basement has a drop ceiling). It appears the incoming cable runs to a
Regal DS4DGH10 splitter. From there, a lead goes to a Regal GRS3DGH
110db EMI Isolator, and the lead to the cable modem takes off from
there.

She called Comcast this week, and the tech who showed up said he
couldn't find anything wrong (he didn't look at anything in the
basement, though). The TiVo, which is using a DLink USB wireless
adapter, was showing Poor (24%) to Marginal (28%) connectivity most of
the time I was there, with an occasional jump to Fair (58%).

I downloaded a firmware upgrade for the Linksys router, and the
download speed started out at 113 kbps, and gradually went up, never
breaking 200 kbps. Applied the upgrade, but no change. Noticed the
Internet light was flashing constantly on the router, which looks odd
to me (my Linksys WRT54G, on a DSL line, has a constant Internet
light).

Any suggestions as to what might be wrong gratefully appreciated.
John Jones, Detroit

Re: Howto on Cable Modem Connection


On Fri, 10 Feb 2006 19:16:22 GMT, John Jones

Quoted text here. Click to load it
Comcast lights flash.

Quoted text here. Click to load it


Re: Howto on Cable Modem Connection


John Jones wrote:
Quoted text here. Click to load it

Access the cable modem statistics page at 192.168.100.1 and check signal
to noise ratios and signal levels.  The cable modem faq at
www.dslreports.com will provide the basis for determining if there are
line quality issues from the signal levels.

Q

Re: Howto on Cable Modem Connection


Best to not go through more than one splitter.

Re: Howto on Cable Modem Connection


wrote:

Quoted text here. Click to load it

Finally had a chance Sunday to do this. Stats are:

Downstream
SNR: 36 dB
Power Level: -1 dBmV

Upstream
Power Level: 56 dBmV

According to the FAQ, only the Upstream Power Level number looks bad.
Guess I'll start looking for the right kind of splitter to feed the
cable modem, and do some rewiring.
John Jones, Detroit

Re: Howto on Cable Modem Connection


John Jones wrote:
Quoted text here. Click to load it

It is always best to split the line only once prior to the modem and the
installation techs know this.  the 56 dbmv is certainly not good, shoot
for 35-40 dbmv range.  If you are doing your own wiring, consult the faq
for coax specs.  Radio Shack is *not* the best source.  Buy the best
coax type you can afford, and know that the connectors and install
techniques have a significant influence on signal quality.  IOW, you
might contract a professional installer.

Q

Re: Howto on Cable Modem Connection


I have a cable connection also and I also had a BEFW11S4 router. I switched
to a WRT54GS router. It made a difference.
Steve

Quoted text here. Click to load it



Re: Howto on Cable Modem Connection


wrote:

Quoted text here. Click to load it

I happen to have a new WRT54G router laying around, so I may try
swapping it into her network if I can't find anything else wrong. I
still think her cable wiring isn't right, so I want to change that
first.
John Jones, Detroit

Re: Howto on Cable Modem Connection


John Jones wrote:
Quoted text here. Click to load it

I responded above, but you toggled a memory cell or two: you have 56
dBmv upstream at the modem.  A typical double splitter is -3dBmv loss.
Unless you have a bunch of splitters in front of your modem, the 56dBmv
is from my experience as a customer indicative of a line drop issue that
only the ISP's techs can correct.

Re: Howto on Cable Modem Connection


I agree!  The 56dBmv upstream sounds like a level issue between him and the
node.    I had a 55dBmv for quite some time and experiences random
disconnects.   It took several attempts to get Comcast to find a problem at
the node.   I now have a 36dBmv upsteam, 8dBmv downstream and a 39dB SNR.
I'm very happy with them.



Quoted text here. Click to load it



Re: Howto on Cable Modem Connection


wrote:

Quoted text here. Click to load it

The incoming line goes through one splitter, then a second one. The
cable modem is connected to the second one. I'm thinking I'll try to
locate a good splitter to replace the first one with, and connect the
cable modem to the proper tap on that. If that doesn't help, I'll tell
my friend to have Comcast get involved again.
John Jones, Detroit

Re: Howto on Cable Modem Connection


On Fri, 10 Mar 2006 14:42:02 GMT, John Jones

Quoted text here. Click to load it

In your search for the perfect splitter, consider dropping by your
local cable office. So far, everywhere I've lived, they gladly hand
out splitters as well as reasonable lengths of terminated cable, just
for asking.


Re: Howto on Cable Modem Connection


"Bill M." wrote:
Quoted text here. Click to load it


    Here in Los Angeles, the field tachnicians are generous
"judiciously".  If you're a customer, they'll give you up to 100'
of RG6 quad-shield cable and they'll even cut it and attach
connectors.  That's because it's in their interest to keep
you happy and using good cable that prevents leakage into
and out of their network.  But the business office can't be
bothered.  In such instances, it helps to just walk into the
field ops truck yard and speak to a supervisor and explain
that you're a customer and sound you know what you're
doing.  Using terms like "RG6 quad-shield",
"Snap-N-Seal F-connector", "2-way splitter good for
1 gigahertz" does help.  I once did that.  At first the techs
denied that they had any splitters in their trucks.  But after
a brief conversation, they were giving me stuff that I hadn't
even asked for.

*TimDaniels*

Re: Howto on Cable Modem Connection


Quoted text here. Click to load it
The smarter cable office have learned (are learning) that giving out a
20 splitters that costs them $1 in bulk can save a service call that
costs $200 (after accounting for overheard).

After an installer in Chapel Hill, NC dropped off a cable modem for a
new house I mentioned getting a powered splitter to handle all the
prewired drops. He handed me a new one from his truck. :)

Site Timeline