Re: [FL] Bad signal levels and constant T3 timeouts

Hey, I see this thread is about a week old now, so it may be resolved already, but I thought I would chime in. I've been a field technician for another MSO for over 8 years, so I may be able to give you a bit of insight.

Based off of the info in your previous post:

said by dsbm :

These are my signal levels now:

Downstream:
Frequency: 111000000 Hz (111 MHz)
SNR: 32.0 dB
Power Level: -2.8 dBmV

Upstream:
Frequency: 31500000 Hz (31.5 MHz)
Power Level: 55.0 dBmV

On further inspection, I was able to get these signal levels by plugging the modem into the outlet that my TV is using:

Downstream:
Frequency: 111000000 Hz (111 MHz)
SNR: 32.1 dB
Power Level: 6.8 dBmV

Upstream:
Frequency: 31500000 Hz (31.5 MHz)
Power Level: 47.0 dBmV

That's quite a difference.

This information tells me several things. First, look at the Downstream Power Level. This is a reading of the RF signal level at the input port of your cable modem. At its usual location, this level is pretty low, and your Upstream Power Level is *very* high - which is bad bad bad! Essentially, what is happening is that due to the low signal levels, your cable modem is having to *SCREAM* at the CMTS to be heard, and even then it's not always getting through. This is what's causing the timeouts.

Now looking at those same stats at the new location, they look excellent, well within spec. This leads me to believe that your tap levels and service drop are fine, and that the problem is somewhere in your internal wiring.

There is a 9dB difference between your CM's normal location, and the location where your TV is hooked up. This raises a couple of possibilities:

1) There are multiple splitters between your service drop and the cable modem. Each splitter introduces signal loss, so when you have a cascade of 2 of more splitters, it can become a problem. 9dB is more loss than I would expect to see from a single splitter, but is very close to what I would expect from, say, a 2-way followed by a 4-way.

Based off this, it seems likely that your TV outlet is hooked up to the first splitter in a cascade, but the outlet feeding your modem is on the 2nd, or possibly even 3rd. *IF* all your splitters are at the demark, where they should be, this is an easy problem to fix. A tech should be able to use a tone and probe kit to identify the line feeding your CM and reconfigure your splitters to give it more signal. However, there may be splitters in a crawlspace, attic, inside a wall, etc, that are not immediately apparent, that's where it gets a bit tricky. But still, any experienced tech should be able to figure it out.

2) Second possibility - the actual cable line between your demark and the outlet feeding the CM is bad. This could be any number of things - physical damage from animals or weed-eaters, a poorly installed fitting, old age, or obsolete cable are the things that come to mind immediately.

One thing I would definitely recommend is checking the connector behind the wall plate, and the F-81 connector in the wallplate. A lot of techs neglect to do this, and an old or poorly installed connector can cause all kinds of problems - signal loss, ingress, etc. Obsolete cable is also a likely culprit - older homes are often wired with RG-59 coax cable, which is smaller in diameter and has less shielding than current RG-6 cables. It could be as simple as replacing a connector, or it could involve replacing the actual cable.

So those are the 2 most likely scenarios IMO... Either one of which should be fairly easy for a decent tech to figure out. It sounds like your previous techs have either been inexperienced, uneducated, or unmotivated - maybe some combination of those things.

Anyway, I know its frustrating for you to have a problem like this, and to have to come to a forum to get help that your service provider should be giving you. I apologize on behalf of those of us who actually take pride in our jobs and try to help our customers, instead of just blowing them off...

I hope this helps, and if there's anything else I can do, please don't hesitate to let me know. I'll do my best to assist.

Sincerely,
Tech 7118

permalink · 2008-06-24 19:49:04 · Print ·


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