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bspencer

join:2012-10-17
Foothill Ranch, CA

Forward Path Attenuators

My upstream dbmV is at 55-58 and I have frequent cable modem drops. My downstream voltage and SNR are always good. I've heard mention of forward path attenuators (FPA), but I'm not sure how to use one or which one to get. How would I bring my upstream voltage into normal (40-45 dbmV) range by using an FPA. Do I need to first determine the frequency range of my upstream from COX? Also, does the FPA go out at the panel on the side of my house or can I use it right at my cable modem?

I greatly appreciate any help with this. Resetting the modem and router is getting real old....



DrDrew
That others may surf
Premium
join:2009-01-28
SoCal
kudos:15

Forward path anttenuators would do nothing for your upstream level problem. Call cox and have a tech get your levels fixed


bspencer

join:2012-10-17
Foothill Ranch, CA

What could COX possibly do to fix the levels? I've had them come out soooo many times and nothing gets resolved. As I type, my upstream level is at a nice 49 dbmV. However, it may change at any time and cause a disconnect. In your opinion, what other factors may be contributing to the high upstream power level? The connection that my cable modem is on is a dedicated one with no splitters at all. that was confirmed by a COX technician that was at my hous for a couple of hours crawliing through the attic and tracing all of my connections. So, there is no attenuator that can decrease the upstream power level?



DrDrew
That others may surf
Premium
join:2009-01-28
SoCal
kudos:15

An attenuator by definition ADDs resistance to the line. You need the line fixed, more than a 3 db swing in 24 hours is a problem. A broken or loose connector, short center conductor, or cracked cable will commonly cause the symptoms you see.
--
If it's important, back it up... twice. Even 99.999% availability isn't enough sometimes.



digiblur
Premium
join:2002-06-03
Louisiana
reply to bspencer

And the same is true for people putting an attenuator on their line to raise the upstream level. It does nothing except create a false reading on the cable modem.

But this is a totally different issue... this needs to be fixed.


bspencer

join:2012-10-17
Foothill Ranch, CA
reply to DrDrew

unfortunately, the cable box that has the neightborhood connections is in my front lawn and I believe that COX gets into that box often. I checked/reseated the cables ihn the box at the side of my house and replaced the cable going to my cable modem. I guess I'll have to grin and bear the cable company technician coming out again. Surprisingly, my upstream power level is at 58 dbmV as I type this message. I wonder why I'm still connected.



JeffinKenner

@cox.net
reply to bspencer

Every other night between 12am and 2am I seem to have issues with my upload speed dropping to nothing.

Channel ID 3
Frequency 31250000 Hz
Ranging Service ID 3626
Symbol Rate 2.560 Msym/sec
Power Level 42 dBmV
Upstream Modulation [3] QPSK
[2] 16QAM
[3] 64QAM

Ranging Status Success


bchandler02

join:2011-07-08
Oklahoma City, OK
reply to bspencer

They need to fix that, the signal is too weak. Your modem is working overtime to connect with an upstream that high. You need less blockage, not more.

Splitters, old lines, bad connections are the most common cause. Do you have access to your cable box? If so, take your modem and a laptop outside and connect directly at the line coming to your house and see what it reads there. If it is still high, call Cox. Show the tech the upload db, have them pull the historical graph, and don't sign off on them leaving until something is done about it.


bspencer

join:2012-10-17
Foothill Ranch, CA

That's a great idea. I'll try to get to that this weekend. I'll have to run an extension cord to the side of the house to power the cable modem. What's the highest you feel that the upstream power level should be - 55 dbmV?



DrDrew
That others may surf
Premium
join:2009-01-28
SoCal
kudos:15

35-50


bspencer

join:2012-10-17
Foothill Ranch, CA
reply to bchandler02

Is there a way for me to pull the historical graph?


bspencer

join:2012-10-17
Foothill Ranch, CA
reply to DrDrew

said by DrDrew:

35-50

It is interesting though that my upstream power level last night was at 58 and I didn't have a drop. I was sure I would. Any ideas of why it wouldn't have dropped?

bspencer

join:2012-10-17
Foothill Ranch, CA
reply to bchandler02

said by bchandler02:

They need to fix that, the signal is too weak. Your modem is working overtime to connect with an upstream that high. You need less blockage, not more.

Splitters, old lines, bad connections are the most common cause. Do you have access to your cable box? If so, take your modem and a laptop outside and connect directly at the line coming to your house and see what it reads there. If it is still high, call Cox. Show the tech the upload db, have them pull the historical graph, and don't sign off on them leaving until something is done about it.

I hope that it's high at the box as trying to isolate the problem in the house will not be fun.

bchandler02

join:2011-07-08
Oklahoma City, OK
reply to bspencer

35-50 is right. 55 is the absolute max, anything above will cause drops. As far as I know, only Cox can see the historical graphs on their end.

Do you have any other Cox services? How are they working?


bspencer

join:2012-10-17
Foothill Ranch, CA

said by bchandler02:

35-50 is right. 55 is the absolute max, anything above will cause drops. As far as I know, only Cox can see the historical graphs on their end.

Do you have any other Cox services? How are they working?

I have COX television and telephone. They are both working fine. As a matter of fact, I moved my Cable Modem to the same cable line that my phone converter is on as that is, according to COX, a direct connect.
Expand your moderator at work


DrDrew
That others may surf
Premium
join:2009-01-28
SoCal
kudos:15
reply to bspencer

Re: Forward Path Attenuators

said by bspencer:

said by DrDrew:

35-50

It is interesting though that my upstream power level last night was at 58 and I didn't have a drop. I was sure I would. Any ideas of why it wouldn't have dropped?

The CMTS in the headend changed the negotiated upstream channel to a slower one that can handle lower SNR and higher transmit levels. The CMTS in the headend also made up the difference by accepting a lower receive level on it's end.

Neither situation is good and will have spotty performance
--
If it's important, back it up... twice. Even 99.999% availability isn't enough sometimes.

bspencer

join:2012-10-17
Foothill Ranch, CA
reply to bspencer

The information at »Cable Modems and Wiring Issues »Upstream Power is Too High (>55) suggests a 2-way amplifier. Has anyone had experience with these. Do you think that it would reduce my upstream power level?



DrDrew
That others may surf
Premium
join:2009-01-28
SoCal
kudos:15

said by bspencer:

The information at »Cable Modems and Wiring Issues »Upstream Power is Too High (>55) suggests a 2-way amplifier. Has anyone had experience with these. Do you think that it would reduce my upstream power level?

It won't fix the problem that is making your upstream change so much.

If it were steady and high, an amp might be a solution, but yours fluctuates. An amp would be a bandaid that won't fix your underlying problem, you could have spotty performance still.
--
If it's important, back it up... twice. Even 99.999% availability isn't enough sometimes.


Ender3rd

join:2001-07-15
Connecticut
reply to bspencer

I struggled with borderline-high upstream power levels and frequent disconnects for a period of time following a severe storm in my area. I took a screenshot of the modem "Signal" page and then did what was suggested in the thread above and moved my modem to the basement and connected it at the tap to check the levels right off the street. I took another screenshot in that configuration and had clear proof that the high upstream power level was not due to my residential wiring.

Cox support on the phone confirmed my poor upstream level and also checked other customers' modem signal levels and confirmed that the upstream was poor on the entire street.

When the Cox technician arrived, he looked at my screenshots then connected his gear at both places and confirmed the poor signals at the tap. He checked levels at the drop outside my house and again at the pole where my drop originates from and confirmed the poor signals from the street.

At that point he called in to have a truck rolled and they arrived later in the day and worked backwards from my pole until they found the problem. They found it pretty quickly and it was corrected. Life has been good since then!

Keep documenting the time and duration of every outage as well as out of range signal levels until it's fixed. If the disconnects continue for more than several days call and request credit for incomplete service until it is corrected. That seems to get a lot of attention if it goes on for too long.

Hope it gets resolved quickly!

Ender
--
Politicians are the only people in the world who create problems and then campaign against them. (Charlie Reese)


bchandler02

join:2011-07-08
Oklahoma City, OK

Agree this is a good approach. If your area has a local executive escalations line (OKC does), get them involved. Call daily for status updates until resolved, and request credit each day.


bspencer

join:2012-10-17
Foothill Ranch, CA
reply to bspencer

Thanks for the information. It's much appreciated.


bspencer

join:2012-10-17
Foothill Ranch, CA
reply to bspencer

So that I don't have to worry about what may occur at the street level, I may go with an Active Return Amplifier. It's specifically designed to reduce high upstream power levels by only amplifying the reverse signal (signal from your house) to your ISP.



CoxTech1
VIP
join:2002-04-25
Chesapeake, VA
kudos:77

It's generally better to at least try to troubleshoot the source of the signal issue before trying to work around it with an amplifier. Amplifiers are a useful tool for solving signal related problems however if they are used without first trying to identify the cause of the issue the results may not be favorable. If the problem really is just weak signal that cannot be addressed otherwise they work great.


bspencer

join:2012-10-17
Foothill Ranch, CA

said by CoxTech1:

It's generally better to at least try to troubleshoot the source of the signal issue before trying to work around it with an amplifier. Amplifiers are a useful tool for solving signal related problems however if they are used without first trying to identify the cause of the issue the results may not be favorable. If the problem really is just weak signal that cannot be addressed otherwise they work great.

I agree that the real problem should be fixed. In my case it's been a moving target. I've had COX technicians out many, many times but the issue always returns. Rather than having to wonder if someone else in the neighborhood made a service call and a technican moved my connection at the street or somehow else caused an issue, I would rather just put something in that I can control. If I go with an Active Return Amplifier, will it affect my downstream power level? Is there a certain type of Active Return Amplifier that I need to buy so that only the upstream power level is affected?

bspencer

join:2012-10-17
Foothill Ranch, CA
reply to DrDrew

said by DrDrew:

said by bspencer:

The information at »Cable Modems and Wiring Issues »Upstream Power is Too High (>55) suggests a 2-way amplifier. Has anyone had experience with these. Do you think that it would reduce my upstream power level?

It won't fix the problem that is making your upstream change so much.

If it were steady and high, an amp might be a solution, but yours fluctuates. An amp would be a bandaid that won't fix your underlying problem, you could have spotty performance still.

Seems like an Active Return Amplifier may be a nice bandaid - »www.cabletvamps.com/Info/cable-m···vels.htm. I do agree that it's not fixing the cause of the problem, but, at the same time, I have had great signals for months and then, because of a technician coming out to fix a neighbors issue, my signals went bad. So, to avoid having to worry about what happens external to my house, I may just use the Active Return Amplifier. I believe that it will lower my upstream power level and not affect my downstream power level. Is this a correct assumption?


DrDrew
That others may surf
Premium
join:2009-01-28
SoCal
kudos:15

A return amp will change the signal STRENGTH output, which you can see, but you don't know the current signal QUALITY which is measured by SNR (signal to noise), MER (modulation error rate) and BER (bit error rate) or what they will change to with the addition of an amplifier.

What ever problem is causing the signal STRENGTH to fluctuate may also be causing problems with the signal QUALITY. Often just increasing strength doesn't improve reliability because the QUALITY has a problem that doesn't get better and may even get worse with amplification. The signal going into the amp MAY be too high since it's close to the modem transmitter and/or the problem is causing odd signal reflections/distortions after the amp.

Yelling louder doesn't always mean the listener can understand the message any better.
--
If it's important, back it up... twice. Even 99.999% availability isn't enough sometimes.


bchandler02

join:2011-07-08
Oklahoma City, OK
reply to bspencer

I have no direct experience using amps, but my general thought on them is they cause more problems than they solve except in extremely rare cases. If your levels are truly that weak by design, an amp is good. Otherwise, it will just cause problems.

You have to remember - amps amplify the good AND the bad.

Your upstream MAY be high because of a dirty line. Unfortunately you cannot see upstream SnR on your end, but Cox can.

Can you post your full signals for up and down? It may shed some additional light.



digiblur
Premium
join:2002-06-03
Louisiana
reply to bspencer

I remember several years ago having a 25 dBmv upstream for a couple of weeks. No issues, must have been a very clean channel.


bspencer

join:2012-10-17
Foothill Ranch, CA
reply to bspencer

Here are my upstream numbers for reference.

Channel ID 3
Frequency 35580000 Hz
Ranging Service ID 882
Symbol Rate 2.560 Msym/sec
Power Level 58 dBmV

Upstream Modulation
[2] QPSK
[3] 16QAM

Ranging Status Success

What does 16QAM signify and what is considered a good value here?