Ridiculously high line attenuation (177dB)

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DanielMole

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#73106 9-Dec-2010 14:45

I've been living in this house for 2 years now, and we have always had a pretty good line but a few drops a week.

So a couple of weeks ago I had a look in my router config and was blown away by the ridiculous figures for line attenuation.

122 down and 177 up. yeah.

I live in Papanui, Chch, about 200m from a cabinet.

So now that its the holidays I've decided to actually do something about it. What are the factors that usually cause high attenuation?

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#415064 9-Dec-2010 14:53

Line quality

Check the wiring in your house

John

DanielMole

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#415066 9-Dec-2010 14:56

Cheers for the reply, I had a quick look in the wiring box and there's electrical connector blocks joining cables instead of proper gel crimps, looks like I found the problem :)

cyril7

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#415067 9-Dec-2010 14:57

You modem however is still syncing at near full speed, which suggests that the attenuation figure is erroneous, purhaps a firmware bug in the modem that has shown or calculated it incorrectly.

You say you are having occasional dropouts, I suggest you check you house wiring as John suggests, there could be a rouge Phone without a filter, or maybe and alarm panel playing havoc.

Cyril

DanielMole

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#415386 10-Dec-2010 09:11

WTF

So I put in completely new run of cat5e from the demarc to the master jack, and the attenuation is 122/170. I guess that the router is just reporting it wrong. Although another thing I noticed is the noise level went UP and output power DOWN. That's bad right?

cyril7

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#415398 10-Dec-2010 09:31

Hi, your noise margin and power levels look good and consistent with a 4-8dB line attenuation as is the sync speed, at the end of the day if the attenuation was as high as being reported then the modem would never work. Typically modems can only report to around 65dB attenuation, after that they bottom out, your sync speed would normally be down to around 1Mb/s, much higher than 65dB and they stop working all together.

So as I say you modem is telling porkies, see if you can borrow a mates modem, preferably a Broadcom based one, ie Thompson (as supplied by Telecom) Dynalink, or TPlink and compare.

Cyril

webwat

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#415514 10-Dec-2010 13:18

Thats noise margin (signal to noise), not the actual noise level, so lower noise at same speed would show up as better noise margin. I guess you have replaced those electrical connectors with a Cat5 joiner now? Blue wires are the DSL/phone wires that have to be connected.

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DanielMole

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#415519 10-Dec-2010 13:30

webwat: Thats noise margin (signal to noise), not the actual noise level, so lower noise at same speed would show up as better noise margin. I guess you have replaced those electrical connectors with a Cat5 joiner now? Blue wires are the DSL/phone wires that have to be connected.

Nah I just ran a clean line from demarc to the master jack, so no joins :)

But yes I used proper gel crimps to join the cable at the demarc.

cyril7

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#415521 10-Dec-2010 13:34

What other wiring is connected to the line, ie is there any other lines spanning off from the demarc, and others from the master jack, or is it just the one master socket and thats all.

Cyril

coffeebaron

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#415526 10-Dec-2010 13:55

DanielMole: Although another thing I noticed is the noise level went UP and output power DOWN. That's bad right?

This is good - greater noise margin, so line is cleaner. Lower output power, as it doesn't need to crank the power up as much as before.

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DanielMole

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#415627 10-Dec-2010 16:22

coffeebaron:
DanielMole: Although another thing I noticed is the noise level went UP and output power DOWN. That's bad right?

This is good - greater noise margin, so line is cleaner. Lower output power, as it doesn't need to crank the power up as much as before.

Ah, thanks for clarifying that :)

DanielMole

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#416093 12-Dec-2010 11:27

Right, installed a xDSL master splitter today.

Sync speed dropped :(

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cyril7

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#416155 12-Dec-2010 14:28

how exactly did you install it, and how much did it drop by.

Cyril

DanielMole

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#416162 12-Dec-2010 14:55

cyril7: how exactly did you install it, and how much did it drop by.

Cyril

I put the splitter in the demarc, orange pair to line in, blue pair to cat5e that runs to the phone jack, and green pair to cat5e that runs to my dsl jack.

It went down from about 17500 to 16700. This is a crappy belkin router too.

cyril7

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#416169 12-Dec-2010 15:14

What are the rest of the line stats. I take it there are no other connections to the direct line, ie the line from the street goes to the orange port of the filter and no where else. And there is nothing other than the modem attached to the green port.

Cyril

DanielMole

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#416170 12-Dec-2010 15:16

cyril7: What are the rest of the line stats. I take it there are no other connections to the direct line, ie the line from the street goes to the orange port of the filter and no where else. And there is nothing other than the modem attached to the green port.

Cyril

Yep thats exactly right.

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