On 6/11/2012 1:14 PM, Jeff Liebermann wrote:
On Mon, 11 Jun 2012 11:47:02 -0400, "Michael A. Terrell"
wrote:

On 6/10/2012 8:31 PM, Jeff Liebermann wrote:

Incidentally, your header shows a peoplepc.com email address and an
Earthlink ISP, neither of which offer cable service. How did you
manage that?

You subscribe through TW Cable or Brighthouse like I do. They
offered a choice of Road Runner, AOL or Earthlink when I signed the
contract.

Thanks. I didn't know that. On the left coast, we have mostly
Comcast, which offers ummmm.... Comcast. Locally, AOL and Earthlink
both resell DSL. However, they can be purchased with a "bring your
own ISP" contract that will work with any means of connectivity.


They were forced to offer other choices, since AOL owns
TWC/Brighthouse and most of the RR fiber optic backbone. AOL was the
obvious choice, and since Earthlink was one of the largest ISPs they
only had to add one other service to satisfy the regulators. I'm not
sure that you can still get Earthlink from Brighthouse for new accounts.
I haven't seen it in their ads in some time.


They used a directional coupler instead of a splitter when
they installed my cable modem. I can't get to it right now to tell you
how many dB drop right now.

Locally, Comcast uses splitters. The only time I've seen directional
couplers used is when the line level is to high and the installer
wants to drop the receive level to the cable modem, while not
introducing any additional loss to the return path.

Brighthouse currently uses S.A./Cisco Webstar modems in this area.
192.168.100.1 will display the current data.

That's the most common IP address for cable modem diagnostics. The
same IP is used by Comcast modems. I haven't found it in the
CableLabs specs, but outgoing traffic to 192.168.100.1 is apparently
trapped by cable modem firmware, and redirected to the internal web
server, instead of going out to the internet.

If you have problems accessing the SNR values, try this work around:
http://kd6cae.livejournal.com/234572.html
http://www.broadbandreports.com/forum/r26111757-CISCO-DPC2100R2-signal-status-page

Name CISCO DPC2100R2
Modem Serial Number 224656807
Cable Modem MAC Address xx:xx:xx:xx:xx:xx
Hardware Version 2.1
Software Version dpc2100rx-v202r1256-110513Uas-TWC
Receive Power Level -4.9 dBmV
Signal to Noise Ratio 37.7 dBmV
Transmit Power Level 41.5 dBmV
Cable Modem Status Operational

Looks good.

For reference, the cable modem is designed to work with -15 to +15dBmV
receive power, but it's usually best to keep it between -8 and +8dBmV.
Upstream power should be at the lower end of 37 to 55dBmV. It's a
measure of upstream line loss. You're fine.

SNR (signal to noise ratio) isn't measured in dBmV. Did you edit the
above diagnostic output? It should be greater than 30dB SNR. I've
seen the SNR vary erratically as a result of ingress and crappy
connections, while the other numbers remain fairly constant. That's
my guess what is happening with the OP's setup.


I only edited the MAC Address, for security reasons.

Directional couplers provide better isolation from the garbage sent
upline by crappy TV tuners. I worked in CATV for years, and tested
hundreds of samples of 2 to 8 way splitters for return loss in our lab.

I'm used to using a Fireberd to measure the BER on digital
communication systems. FPQSK was real fun when we first added it to our
telemetry products. The units are those selected by SA, long before
Cisco bought that divison. At one time we built the SA Telemetry
receiver that they had cloned from our 1200 series.