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Irish Shark
Play Like A Champion Today
MVM
join:2000-07-29
Las Vegas, NV

Irish Shark to bryant313

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Re: [NV] Heat Throwing Off Modem Signal Levels?

said by bryant313:

whatever it may be this is not the first time this has happened so hopefully the problem can get resolved

Has this happened when it is 80 or lower outside? Or is this just happening during the precious weeks?

A MODEM is not a very scientific measurement tool. The readings can/are not exact.

According to the DOCSIS specs on Cable MODEM operational levels, the MODEM must work with a DS signal level of +8 to +58 dBmV. ISPs set the lower and upper limits on a much more conservative level.

So your reading of 56.2dBmV still has some room left before you start seeing the MODEM acting up.

Now you are reporting lags and slow page loads.

Do you have any critical errors in the MODEM log?
lilstone87
join:2009-04-09
Chesapeake, VA

lilstone87

Member

Your right about modem isn't the best at judging signal levels, but if there is that much swing in power levels on a modem. Good chance it's a cable issue on down the line somewhere. Because if the modem is reporting that much of a swing in levels, it would point to a problem with the modem itself, if the modem was old. As for at 56db being room before the modem acts up, please look at the requirements of D3 modems, and the max levels when using a D3 modem. As I know with D3 modems bonding on the upstream the max is 51db, before the modem will have problems bonding on the upstream. Also I am sure even with a D2 modem max is probably only around 53-55db, and he's reporting power level swings up to 56db.

Anyways not to say a modem can't work at levels that high, just don't expect the performance to be good. Also with him complaining of lag now, its possible. As he's reporting big swings in upstream power levels. All I can suggest to him about lag problem, is start running steady traceroutes.
bryant313
join:2011-05-24
Las Vegas, NV

bryant313 to Irish Shark

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to Irish Shark
no errors in my modem logs the internet is running fine today i am still having a tech visit though
bryant313

bryant313 to lilstone87

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well if its the modem this will be the 3rd modem swap in less than a year

Irish Shark
Play Like A Champion Today
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join:2000-07-29
Las Vegas, NV

Irish Shark to lilstone87

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Cisco Manual On This MODE>
I guess we all will see if the thing gets fixed. I have seen other folks with this same issue, but I never saw what fixed it.

Since you have this MODEM, you are more of an expert than me, since I not even sniffed this MODEM.

That Particular MODEM has various limits depending on the modulation and number of Upstream that are bonded.

I do not have the foggiest how his MODEM is connecting. However the manual from Cisco has the chart above.

The FAQ (»Cox HSI Forum FAQ »What should my modem signal levels be?) has this:

Upstream (Transmit): 40-52 dBmV. A value within the range +40 to +52 dBmV is within spec with the low to mid 40's the most common. If the cable modem is going offline, and the upstream signal strength is at or above +52dBmV, then a poor upstream path is probably the problem.

I think the levels in the 40's are what Cox wants to see on their network.
bryant313
join:2011-05-24
Las Vegas, NV

bryant313

Member

thank you for the info its much appreciated yeah i am curious myself what they will do if anything for this issue

news
@videotron.ca

news

Anon

Re: [NV] Heat Throwing Off Modem Signal Levelthe center s?

Temperature changes (high heat, very cold) will affect dwnstream signal but not upstream. Upstream variations means attenuation on low frequencies, caused by corossion, bad connector (partially short) or loose connector, cable squirrel chew, staple in cable, bad tap... Upstream isn't suppose to change much... An aluminium braid lost inside a brand newconnector touching the center pin can cause 10 dB upstream variation...
videonex
join:2001-07-22

videonex

Member

said by news :

Temperature changes (high heat, very cold) will affect dwnstream signal but not upstream. Upstream variations means attenuation on low frequencies, caused by corossion, bad connector (partially short) or loose connector, cable squirrel chew, staple in cable, bad tap... Upstream isn't suppose to change much... An aluminium braid lost inside a brand newconnector touching the center pin can cause 10 dB upstream variation...

Extreme heat like they have had in Las Vegas recently will cause many of the very things you mention to happen. Your's is really the best explanation so far. I have found that corroded connections are usually the culprit. The metals expanding in the heat exaggerate the corrosion and line resistance in the upstream frequency range increases and in turn the modem ups it's output power to compensate.

I've found a shotgun approach by replacing any connectors, barrels and splitters located outside will usually cure the issue.
bryant313
join:2011-05-24
Las Vegas, NV

bryant313

Member

even with all the cable lines and splitters inside and outside the home being new?

less than a year
videonex
join:2001-07-22

videonex

Member

Yes. Partially because it's quick and the least expensive but it's also the culprit much more often than not.

Hopefully your tech comes at the hottest part of the day. If he does the connection replacement first, the modem upstream power will show an immediate improvement if it has been solved.

If not then you move on to checking tap and lines. Connections on the tap are the next most likely culprits.
bryant313
join:2011-05-24
Las Vegas, NV

bryant313

Member

that is the thing it is not a consistent number it varies a lot and is very random at what times it happens whether it be day or night

and on days like yesterday it did not change much only plus or minus like .3dBmv which i would say is normal but on other days like Friday Saturday and Sunday where it change anywhere from 5dBmv to 15dBmv

Irish Shark
Play Like A Champion Today
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join:2000-07-29
Las Vegas, NV

Irish Shark to news

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to news
One word: Wrong
bryant313
join:2011-05-24
Las Vegas, NV

bryant313

Member

cox tech came out today and the signals were spiked while he was here the modem and the hd boxes were all failing

so he plug every cable into his meter and tested every line in the home and at the street including the tap and there was no interference

and he saw that the neighbors signal was flucuating just like mine so he turned it over to maitence and we will see what happens tomorrow

dsttechs
@wideopenwest.com

dsttechs to Irish Shark

Anon

to Irish Shark
2 words: 100% correct

As in, News is 100% correct

Attenuation due to heat affects the higher downstream frequencies, not the lower upstream frequencies. Since the modems downstream levels were unaffected that rules out attenuation due to heat. Because this modem keeps turning up its transmit it sounds like it was trying to overcome some sort of unwanted noise.

Keep an eye on your upstream SNR (signal to noise ratio), if the problem persists let the tech know what its doing in relation to the upstream levels. If it is a noise issue in the plant it's probably affecting many modems and maintenance is probably already aware there is an issue.

Irish Shark
Play Like A Champion Today
MVM
join:2000-07-29
Las Vegas, NV

Irish Shark

MVM

said by dsttechs :

2 words: 100% correct

As in, News is 100% correct

Attenuation due to heat affects the higher downstream frequencies, not the lower upstream frequencies.

You and News are 0% correct. You are going backwards.

What scientific proof do you or News have that temperature changes affects the DL frequencies more than the Upload frequencies?