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bchandler02

join:2011-07-08
Oklahoma City, OK
reply to Ender3rd

Re: Forward Path Attenuators

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?


bspencer

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

Here are my downstream numbers:

Channel ID 199 200 201
Frequency 579000000 Hz 585000000 Hz 591000000 Hz

Signal to Noise Ratio 36 dB 37 dB 37 dB

Downstream Modulation QAM256 QAM256 QAM256

Power LevelThe Downstream Power Level reading is a snapshot taken at the time this page was requested. Please Reload/Refresh this Page for a new reading
-6 dBmV -6 dBmV -7 dBmV

Is QAM256 good?


bchandler02

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

Those downstream dbs, while within spec, are a little on the low side. They're fine, but lower than most would like. SNRs are decent.

This may end up being one of those times where an amp is actually a good solution. See what Cox says, CT1 here is a good resource and can uusally help alot.


bspencer

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

I tried to post a link to the amp I bought, but it seems that this forum doesn't allow links. If the other post shows up, sorry about double posting. I just ordered the Motorola Signal Booster 1-Port Cable Modem TV HDTV Amplifier with Active Return Cable Modem Boost. The only down side is that this amp apparently runs a little hot. I'll have to keep it in a well ventilated area away from anything that can catch fire. I agree that my downstream power level could also be increased which this amp will do as well. The Active Return should also hopefully lower my upstream power level. I'll post my results as soon as I get the unit. Thanks again for all the help. I do appreciate it.


bspencer

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

I just purchased »www.amazon.com/Motorola-Signal-B···duct_top. I'll post my results once I get it.



bbeesley
VIP
join:2003-08-07
Richardson, TX
kudos:5
reply to bspencer

said by bspencer:

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

not directly, Cox stores this information in their tools. You can PM a tech to look into it for you.

Also, what others have told you is correct, adding attenuation will raise your upstream power

the return power is set by the modem based on how well the CMTS can "hear" it. If there is more attenuation in the line, the return power goes up.


bbeesley
VIP
join:2003-08-07
Richardson, TX
kudos:5
reply to bspencer

said by bspencer:

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?

I have never seen an amp that only does return

also, generally speaking return amps are a bad idea because;
1. They are masking an issue, not resolving it
2. If you also have phone on an EMTA, when the amp looses power, your return level will jump and you could potentially loose service.
3. - and this is the most important - amps also amplify noise, not just good signal. The return carriers are particularly sensitive to noise impairments which manifest as packet loss. By putting in an amp you risk making your service even less stable.

Get the levels resolved. The techs should be able to easily do this and it will be your best long term fix for good, stable service.


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

I agree as well no amp should be used at all. If the cable line comes into the home/outside of home and immediately hits a 2 way splitter. One leg goes to the cable modem then the other leg goes to whatever else you need. If you can't get a decent signal with a setup like that then Cox needs to come out and fix the levels at the tap. If the tap is fine well then that leaves one thing, your drop. If you use an amp and have cox telephone as well then when the power goes out the MTA will lose sync due to the amp not having any power and basically sucking the life out of the cable signal with no power supply.

Anytime I've seen an amp used I've seen the downstream signal go up, but then sometimes the SNR gets worse (due to amping noise), and the upstream also goes up due to another component the modem has to "talk" through.

Cable modem and amps don't mix for me.



kilrathi
Premium
join:2005-04-22
Rockaway Park, NY
reply to digiblur

Yes but it does help if your downstream power level is too hot.



digiblur
Premium
join:2002-06-03
Louisiana

said by kilrathi:

Yes but it does help if your downstream power level is too hot.

Put it behind a splitter. That's rarely the problem though.

bspencer

join:2012-10-17
Foothill Ranch, CA

said by digiblur:

said by kilrathi:

Yes but it does help if your downstream power level is too hot.

Put it behind a splitter. That's rarely the problem though.

I plan on installing the amp as follows:

Wall---Splitter---Amp---Cable Modem


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

said by bspencer:

said by digiblur:

said by kilrathi:

Yes but it does help if your downstream power level is too hot.

Put it behind a splitter. That's rarely the problem though.

I plan on installing the amp as follows:

Wall---Splitter---Amp---Cable Modem

whats the splitter for? Previously you said your modem was on a direct line with no splits...
--
If it's important, back it up... twice. Even 99.999% availability isn't enough sometimes.

bspencer

join:2012-10-17
Foothill Ranch, CA

said by DrDrew:

whats the splitter for? Previously you said your modem was on a direct line with no splits...

The best quality line in my house happens to go directly from the street to my cable phone modem. I split that line and attached my cable modem.


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

Is the phone modem showing the same signals? Is the splitter just a 2 way splitter? Did cox install both and the splitter?


bspencer

join:2012-10-17
Foothill Ranch, CA

said by DrDrew:

Is the phone modem showing the same signals? Is the splitter just a 2 way splitter? Did cox install both and the splitter?

I haven't been able to view the signal on the phone modem. I installed the splitter, but it was one that the technician left for me in case I needed it for anything else.

bchandler02

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

That alone could be a MAJOR part of your problem. Between the wall and the modem there should be no splitter. Cable modems should have a direct line ran for them.

In your box outside, you should either have 1) a direct line to your cable modem, if no other cox services (jacks) used, or 2) incoming line --> 2 way splitter --> 1 to cable modem, the other to everything else (and an additional splitter if needed)


bspencer

join:2012-10-17
Foothill Ranch, CA

said by bchandler02:

That alone could be a MAJOR part of your problem. Between the wall and the modem there should be no splitter. Cable modems should have a direct line ran for them.

In your box outside, you should either have 1) a direct line to your cable modem, if no other cox services (jacks) used, or 2) incoming line --> 2 way splitter --> 1 to cable modem, the other to everything else (and an additional splitter if needed)

Hopefully this can still be overcome by using the Active Return amp.

bspencer

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

Today my upstream is showing as follows. However, I'm sure that 58 dBmV will be right around the corner sometime.

Channel ID 3
Frequency 35580000 Hz
Ranging Service ID 882
Symbol Rate 2.560 Msym/sec
Power Level 49 dBmV
Upstream Modulation [2] QPSK
[3] 16QAM

Ranging Status Success

Still interested in whether 16QAM is good or can be improved.


bspencer

join:2012-10-17
Foothill Ranch, CA

1 edit
reply to bspencer

I received and installed my Active Return amp. Here are my signal strengths now.

Downstream
Channel ID 199 200 201
Frequency 579000000 Hz 585000000 Hz 591000000 Hz
Signal to Noise Ratio 37 dB 37 dB 38 dB
Downstream Modulation QAM256 QAM256 QAM256
Power 5 dBmV 5 dBmV 5 dBmV

Upstream
Channel ID 3
Frequency 35580000 Hz
Ranging Service ID 882
Symbol Rate 2.560 Msym/sec
Power Level 42 dBmV
Upstream Modulation [2] QPSK [3] 16QAM

I feel that these are really good signals. I'll let you know if I experience cable modem resets.

I've seen my upstream QAM be as high as 64 even when I didn't have the amp installed. Any idea what that value means and how to get the best possible value? I read the FAQ at »Comcast High Speed Internet FAQ »What is QAM? and it would seem that the higher the QAM, the better.


lilstone87

join:2009-04-09
Portsmouth, VA
kudos:3

With 64QAM on the upstream, there is about twice as much available bandwidth on the upstream channel. However 64QAM doesn't play nice with noise, so the modem will drop to 16QAM. As 16QAM works better when there is a active noise issue appearing.



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

Cox would be at my house everyday replacing pieces if I had to use an amp to get my modem signals right. There should be no reason that an amp is required.