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voiptalk

join:2010-04-10
Gainesville, VA

[Signals] Upstream Variation > 10db

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Background:

+ Have both a cable modem (SB6120) and an eMTA (502G).
+ These are on different cable drops in the house.

Problem:

+ Both the CM and the eMTA loose sync at the same time. They typically loose the signal and resync within a minute.
+ Occasionally, I will see video breakup on the TV when they drop out.
+ From the status page on the CM, my "typical" upstream signal level is 45. However, I see this floating up to 55+ and back again on a regular basis (hourly).
+ This has been happening since last November. At the worst, I was logging dropouts of up to 12 times a day. It is currently down to once or twice a day.

Troubleshooting so far:

+ Comcast has dispatched three times.
+ The main splitter outside (4-way) has been replaced 3 times.
+ All cables have been re-terminated.
+ I've worked with ComcastSteve, but this isn't something he can help with.
+ I have now "front ended" the outside main splitter with a 2-way. The cable modem hangs off of one output. This increased both the US and DS levels to a point where the CM is more tolerant of the signal fluctuation. That has helped a lot with the sync loss, but the levels are a bit hotter then they should be (hey, it helps).

+ I am convinced the dropouts are directly linked to wide variations in ambient temperature. The problem is mostly seen soon after sunset and sunrise.

Question:

I was hoping some of the experienced cable techs on the forum could provide some insight and thoughts on what to ask the techs on the next (4th) dispatch. Thanks!

I know somebody is going to ask, so here's my current levels.



news

@videotron.ca
10 dB upstream variations most of the time means corrosion, or bad or loose connectors, partially short connector. If your cable installation is ok, it can be caused by a defective tap at the pole where you are connected or any other tap upstream your tap, cracked cable, or bad attenuator in the return distribution amplfier.

Wide temperature variations will affect only high frequency signals (downstream), upstream isn't supposed to vary more than 2 or 3 dB max...

If the service techs did there job right, including going to the pole to chek if the cable drop is ok (no corrosion, no squirrel shew) and they cheked all the cable connectors to the cable modem, maybe it's time for them to open a ticket for a maintenance technician to look at the distribution line, taps...

voiptalk

join:2010-04-10
Gainesville, VA
said by news :

If the service techs did there job right, including going to the pole to chek if the cable drop is ok (no corrosion, no squirrel shew) and they cheked all the cable connectors to the cable modem, maybe it's time for them to open a ticket for a maintenance technician to look at the distribution line, taps...

Actually, I was just going to add another data point to my original post .....

The tech on the 2nd dispatch told me he was turning it out to maintenance. He was also foolish enough to point out the cabinets in the neighborhood the service is routed through (everything is buried, nothing overhead). I promptly went and put nylon cable ties on all the latches, so I would know if somebody had been out to check. Two months later, all my "tamper evident" ties are still on the latches! Nobody ever came out. Busted!


tshirt
Premium,MVM
join:2004-07-11
Snohomish, WA
kudos:5
Reviews:
·Comcast
Well you said it's happening less, so maybe line maintaince found and fixed something further up the line and thought it was totally fixed.
I agree that it is likely a loose connection... maybe swinging in the wind in an arial section, or intermitant shorts in a vault.

If it isn't fixed call it in, give them a week then call it in again.


news

@videotron.ca
reply to voiptalk
You said you have 2 cable modems with the same problem on two different cable drops (from the cable modems to the splitter I suppose). Habitually, there's only one cable drop from the pedestal (outside box) to the house. Did they change that cable? With an intermittent problem like yours and 3 tech visits, it will be a good thing to change the cable drop from the tap to the house, particularly in a underground system, cause you can't see by looking at it like an aerial drop if the cable is domaged or not.

voiptalk

join:2010-04-10
Gainesville, VA
said by news :

You said you have 2 cable modems with the same problem on two different cable drops (from the cable modems to the splitter I suppose). Habitually, there's only one cable drop from the pedestal (outside box) to the house. Did they change that cable?

Correct one service drop to the house ... into the "main" 4-way splitter in the box on the outside of the house. CM and EMTA on their own inside drops from there.

Twice the techs have put their test set directly on the amp in the cabinet ... then taken a reading at the house. They say the service drop is good. But, I always stress to them that I agree the signal looks good to you now, but it drops out. They seem extremely reluctant to turn it out to maintenance without specific evidence of a problem.

I'm keeping a spreadsheet of the dropout times and duration ... along with a screen shot of the CM signal levels.

I understand intermittent problems can be hard to isolate, but after 3 dispatches I'm getting a bit frustrated.

Thanks for everybody's input.


gar187er
I do this for a living

join:2006-06-24
Dover, DE
kudos:4
reply to voiptalk
said by voiptalk:

said by news :

If the service techs did there job right, including going to the pole to chek if the cable drop is ok (no corrosion, no squirrel shew) and they cheked all the cable connectors to the cable modem, maybe it's time for them to open a ticket for a maintenance technician to look at the distribution line, taps...

Actually, I was just going to add another data point to my original post .....

The tech on the 2nd dispatch told me he was turning it out to maintenance. He was also foolish enough to point out the cabinets in the neighborhood the service is routed through (everything is buried, nothing overhead). I promptly went and put nylon cable ties on all the latches, so I would know if somebody had been out to check. Two months later, all my "tamper evident" ties are still on the latches! Nobody ever came out. Busted!

that means nothing....9/10 i dont need to go to the tap in front of someones house to fix their issue....its further upstream...
--
I'm better than you!

voiptalk

join:2010-04-10
Gainesville, VA
reply to voiptalk

Excellent Response from Comcast

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The troops arrive!
Hat's off to Comcast for an excellent response to my problem. Once it was escalated and flagged as being a chronic problem, they certainly went into action and have been taking all the right steps to resolve the issue.

On the 4th dispatch, the tech put new connectors on both ends of the service drop to the house. That definitely made an improvement. I did not see any level fluctuation or errors after that.

The next day (today), maintenance shows up to take a look at it.

Now this evening, I get a call from a maint. tech that is dedicated to my problem and gave me his cell phone number to call direct, if there are more problems. He also said that he changed out the amplifier in cabinet, just in case that was causing the problem.

So, bottom line ... stellar response from Comcast. TBD if it is permanently resolved, but I feel confident they are committed to fixing it. Thanks guys!

Gruhnade

join:2011-07-12
reply to voiptalk

Re: [Signals] Upstream Variation > 10db

This sounds like the problem that ive been having.

Ok last year around july/august I had comcast hsi internet installed. I suffered from timeouts throughout the day/night. Had a tech come out and he saw the timouts switched out the modem with no avail. The tech requested for someone to come and replace the temp line to a permanent line coming to the house. The timeouts still occured. Now when it began getting colder I noticed the timeouts ceased completely for the whole winter so i just figured the problem had fixed itself. Now as of about it 2-3 weeks ago as it is starting to warm up/get more humid the timeouts are back in full force. Has anyone heard of anything like this before? The heat/humidity affecting connection stability? An does anyone have any ideas on what could be causing it specificially?

Just a quote from my intial post

Comcast steve asked me to have the tech coming out to check the tap for moisture etc. Anything else you remember asking/or them telling you so i can try to get all the bases covered and the problem resolved quickly Thanks.


telcodad
Premium
join:2011-09-16
Lincroft, NJ
kudos:15

1 recommendation

I also had a similar problem, until a few weeks ago.

I found that whenever it rained, my modem's downstream channel power levels would increase by several dBs after 1 or 2 days. This was also the case with the TV channels on higher frequency carriers. Then, as things dried-out, the levels seemed to go back down.

At it's worst, the levels for some of the carriers were getting down to -15 dBmV, so I called Comcast to have a technician come by and troubleshoot this. The tech ended up replacing the ground block and the connectors at each end of my drop line. That seemed to fix the wet/dry problem.

However, after that, I saw that the power levels would go down as the outside temperature increased and back up as it dropped. During the latest warm days of Winter, the carrier levels were starting to drop below -10 dBmV again. I figured that it must be a line amp or something, and was just about to call again when suddenly the problem disappeared.

So maybe someone else in the neighborhood had complained, or maybe a tech installing a new service for someone on my street saw the issue and fixed it.

Now I'm only seeing a daily variation of 4 db or less, so I'm happy!