Hi,

I recently got cableinternet. I've got a motorola surfboard modem. My
question is, how long can the coaxcable from modem to wallsocket be? The
internetprovider says approx 1m, but because of the difficulty of running
another cable through the house, I've got it up to 20-25 meter till where
the cable enters the house. I've been told cabletechnicians also say that
the requirement of 1 meter is exaggerated . It worked great for the past
two weeks, but since today the connection is gone once in a while. The
lights on the modem indicate that it's searching for an upstream channel.
It's very difficult to get a connection once it's gone. When I connected
the modem close to the main socket, it found the connection, but it also
found it again later upstairs, only to loose it again after a few hours.

Is it likely that the cable is too long after all, even after two weeks of
error-free use?

TIA

Halfgaar
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Halfgaar wrote:
You have what is called 'ingress' noise on the upstream frequency. Call
your cable provider and tell them that you are having connectivity
problems. Such problems are pretty common on new installs.
And don't worry about the length of cable from the wall to the modem,
mine is about 10 feet.

Ron Hunter wrote:

But 20 meter is 6 times more than 10 feet.

I could call my provider, but the problem is that I already know what
they're going to say: "connect your modem as specified by the manual or you
won't get support... Call back when you've made the changes and the errors
remains".

BTW, the picture quality of lowfrequecy channels (e.g. 175 MHz) is as good
as high frequency ones (e.g. 719 MHz). And "as good" means that the quality
is good. This should indicate that the cable should also transport the
internet signal well enough, right? I mean, that the cable is not too long.

Halfgaar
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Ron Hunter wrote:

On a different newsgroup I've been told that the surfboard has the ability
to measure signal strength. By logging into 192.168.100.1 with http you can
see it. The specs are as follows:

Downstream:
Frequency 482000000 Hz Locked
Signal to Noise Ratio 32 dB
Power Level -16 dB

Upstream:
Channel ID 1
Frequency 43504000 Hz Ranged
Power Level 58 dBmV

That dude thought (he was not sure) that the signal strength needs to be 48
dB, he didn't say upstream or downstream. Are my specs OK?

Halfgaar
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Halfgaar wrote:

If the wall socket is the coax going back to the pole/ISP, my modem is 100'
from the grounding block and another 50' to the curb connection.

Never heard the 1m thing, unless it's 1m minimum. There are reasons for
that.

How long is the cable from the splitter to the outlet you're connected
to? Is it a 2-way splitter that outlet is connected to, or is it a
directional coupler (tap)?


CIAO!

Ed Nielsen
CENCOM
http://www.cencom94.com

Halfgaar wrote:

No. Input is a bit low (Needs to be above -15dBmV. Preferably above
-10dBmV) and the output is a bit high (Preferably below ~50dBmV).


CIAO!

Ed Nielsen
CENCOM
http://www.cencom94.com

Halfgaar wrote:

Ed Nielsen wrote:

That's the 20-25 meter part, from the splitter to me. The kind? I don't
really know. What's a directional coupler? I believe it's one with
different signal strengths on the two outputs. Does that say anything?

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$Bill wrote:

I meant from the the place where the coax enters the house to the modem.

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Ed Nielsen wrote:

The input level is not in dBmV, but in dB. Is that the same?

But anyway, my problem is not with input, but with output. When the modem
has difficulties, it hangs on establashing an outputsignal. So my output is
too high. Are there standard tricks to improve signaltranfer through the
coax?
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Halfgaar wrote:

That's 100' for me.

$Bill wrote:

That's even longer than I have here. Do you know your input/output signal
strenghts?

BTW, my outputlevel has dropped from 58 to 57. A little improvement....
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Halfgaar wrote:
Upstream shouldn't be greater than 44 dBmV according to my local cable
service. That high a number (58) indicates there is trouble on the
upstream side. You can't maintain connectivity with that high a value.
Tell them to FIX IT!

Ron Hunter wrote:

A Local cable provider here (not mine) says it should be between 40 and 55.
Mine has dropped now from 58 to 57 BTW, as you may have read. My provider
doesn't say anything about signal strength.

Before I tell them anything, I should try what the signalstrength is with
the modem at the beginning of the COAX cable. I'm afraid my cable is just
too long. But as I explained, running an extra cable through the house is a
huge amount of work and I don't even have the tools for it. Not to mention
the ugly site an extra cable through the living room is.

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In article <bm9tct$gb9$1@news3.tilbu1.nb.home.nl>, voor_achter@yahoo.remove.com
says...
A LAN with 1/4 inch coax cable ( 10 base T, RG 59u ) can be upm to 600 ft.
long.

It would be difficult to measure the difference in loss between a 3 ft. cable
and a 25 ft. cable.

So replacing your 25 ft. cable with a 3 ft. cable will have no effect on the
signal level.

Please call the service provider, tell them what the signal levels that you are
reading are, and have them fix their problem.

As I write this, my Downstream S/N = 35 dB., Power level = -1 dBmV., Upstream
Power level = 35 dBmV.

If you are also seeing a noisy TV picture on the lower channels, ( 2-3-4-5 ),
be sure to tell them this. ( You might have to call the TV support people to
get that part fixed, which might also correct the cable modem signal problem. )


--
Claude

Claude J Ortega wrote:

Yes, but that's dealing with lower frequencies I believe, which are less
easily distorted.

Are you saying that the signallevels will be about as much at the beginning
of the cable and that my signal problems are the fault of the
internetprovider? There's also a splitter in the way. If I tell them I
didn't connect the modem at the beginning of the cable, they probably won't
do a thing. And BTW, my COAX cable is not 25 ft, it's 20-25 meters. 25
meters is 75 feet.

As I said earlier in this post somewhere, the high frequency TV stations are
as good as the lower ones. And "as good as" means that they're good. There
are two or three stations with a bit of noise, but as far as I know, the
entire town suffers from that problem. It seems to be inherent to those
TV-stations.
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Halfgaar wrote:

They don't show up once the modem is connected, but I managed to
get them when the modem was up and still ranging (don't know how
accurate the numbers would be (Adelphia.net) :

Tx Power 50.2 dBmV
Rx Power -1.9 dBmV
Downstream SNR 32.3 dB
Tx Frequency 33000000 Hz
Rx Frequency 705000000 Hz

From DSL reports:

Coax Cable Signal (Attenuation) Loss per 100ft :

Loss at RG-59 RG-6 RG-11
1MHz 0.4dB 0.2dB 0.2dB
10MHz 1.4dB 0.6dB 0.4dB
50MHz 3.3dB 1.4dB 1.0dB
100MHz 4.9dB 2.0dB 1.6dB
200MHz 7.3dB 2.8dB 2.3dB
400MHz 11.2dB 4.3dB 3.5dB
700MHz 16.9dB 5.6dB 4.7dB
900MHz 20.1dB 6.0dB 5.4dB
1000MHZ 21.5dB 6.1dB 5.6dB

$Bill wrote:

I'm using RG-6 by the way.

Signal levels are in dBmV. Yes, there is a problem with the input as
well as the output. DOCSIS (the standard by which most cable modems and
cable internet systems are designed and built) calls for input levels to
be from -15 to +15dBmV and output levels to be between 8 and 58dBmV.
Somewhere between 40 and 50dBmV or so at the output is what most
industry engineers recommend, with the input level being between -10 and
+10dBmV.


CIAO!

Ed Nielsen
CENCOM
http://www.cencom94.com

Halfgaar wrote:

DOCSIS calls for upstream to be between 8 and 55dBmV. Most CATV
engineers recommend from ~40 to ~50 or so.

Ron Hunter wrote: