line attenuation

gforces

Hi -

I recently got eircom broadband and my line attentuation is showing at 56/31db. Can anyone say whether this is good or bad? or whether it could have a bearing on an upgrade to a 2Mb line?

JNive

that is a horrible attenuation and my guess is your max speed wont be much above 512K,

Generally, anything above 50dB makes for a very weak and unreliable signal, for 2MBit you would want under 40db realistically, with at least 15dB SNR

CyberGhost

is there anything we can do about it?


Down Up
SNR 12.5 dB 10.0 dB
ATEN 48 dB 26 dB

TimTim

Dig up the road and replace the cable?

Don't see any other way.

JNive

even that might not be enough, you may end up digging/replacing all the way to the exchange LOL.

TimTim

If your going to do that, mind digging up the rest of the country and replacing all the copper with fibre?

And put in man sized ducting so its easy to replace.

gforces

JNive wrote:

that is a horrible attenuation and my guess is your max speed wont be much above 512K,

Generally, anything above 50dB makes for a very weak and unreliable signal, for 2MBit you would want under 40db realistically, with at least 15dB SNR

Well, my speeds on irishisptest are around 860kbps at best. Right now my speed is showing at 992/128 on the router, but this can fluctuate.
Overall, though, the line doesn't seem too bad but I'll be watching closely when I receive my 'upgrade' to 2Mb.

Infini

TimTim wrote:

Dig up the road and replace the cable?

Don't see any other way.

Might as well get fibre optic cable layed while your at it, you'd get killer speeds then.

CyberGhost

k guys, be at home tomorrow, I'll need an access so I can install the lines

Infi, you want fiber eh? k, how much speed should I sign you up for?

OfflerCrocGod

JNive wrote:

that is a horrible attenuation and my guess is your max speed wont be much above 512K,

Generally, anything above 50dB makes for a very weak and unreliable signal, for 2MBit you would want under 40db realistically, with at least 15dB SNR

After all that horsesh*t I'll tell the truth.

I have ATEN of 52dB/31dB and yet always connect at 2048 and get downloads of 205 to 210 when maxed - and they stay there. Even with torrents.

Oh and my SNR is 6.5dB/0.0dB according to the expert I should be lucky to expect ~50K. My pings are normal as well.

Solair

Just checked mine

Downstream:
relative capacity occupation: 21%
noise margin downstream: 42.0 db
output power upstream: 1.5 dbm
attenuation downstream: 26.5 db

Upstream:

relative capacity occupation: 18%
noise margin upstream: 28.0 db
output power downstream: 18.0 dbm
attenuation upstream: 18.0 db

Connected to Wellington Road exchange in Cork.
BT Ireland Home Plus DSL.

(you can check it from the web configurator utility on the Zyxel modem/router that BT Ireland provides and im sure from plenty of other modems too)

DemonOfTheFall

OfflerCroc theres no need to be so harsh on JNive. What he said about attenuation over 50 dB being awful is true. In general with attenuation that high people will have terrible DSL.

I've seen plenty of pages all over the net which say that 56dB is a ****load of attenuation.

OfflerCrocGod

DemonOfTheFall wrote:

OfflerCroc theres no need to be so harsh on JNive. What he said about attenuation over 50 dB being awful is true. In general with attenuation that high people will have terrible DSL.

Ye but I think he was just repeating what everyone else here is saying and that is annoying when it's plain wrong - my broadband is just fine no high pings or slow speeds, it's just like normal.

tea

DemonOfTheFall wrote:

I've seen plenty of pages all over the net which say that 56dB is a ****load of attenuation.

It is a high attentuation, and close to the point where the modem won't sync at all, but its not necessarily a big deal. In most cases, at 56db, the service should work fine - its just more likely to work badly than for a lower attenuation.

So I vote that you're both right!

nutzboutstuff

How far do you guys live from your exchanges? in my parents house its 29db/15db, thats in clondalkin, although i almost have LOS to the exchange. The same goes for my flat in ranelagh. Both lines on average can pull down two 80KB/s at a time without problem, still kinda slow when i'm used to 2x4Mb/s in work, and soon to include 2Mb/s symmetric wireless backup!

Solair

This kinda explains everything:

Noise Margin (AKA Signal to Noise Margin or Signal to Noise Ratio)
Relative strength of the DSL signal to Noise ratio. 6dB is the lowest dB manufactures specify for modem to be able to sync. In some instances interleaving can help raise the noise margin to an acceptable level. The higher the number the better for this measurement.

6dB or below is bad and will experience no sync or intermittent synch problems
7dB-10dB is fair but does not leave much room for variances in conditions
11dB-20dB is good with no synch problems
20dB-28dB is excellent
29dB or above is outstanding

Line Attenuation

Measure of how much the signal has degraded between the DSLAM and the modem. Maximum signal loss recommendation is usually about 60dB. The lower the dB the better for this measurement.

20dB and below is outstanding
20dB-30dB is excellent
30dB-40dB is very good
40dB-50dB is good
50dB-60dB is poor and may experience connectivity issues
60dB or above is bad and will experience connectivity issues

Output Power

How much power modem (upstream) or DSLAM (downstream) is using. Maximum recommended is about 15dB. The lower the power the better for this measurement.

jonski

Mine is 34/20 , so rosy I guess . Thanks for that information , most helpful .

JNive

OfflerCrocGod

If you werent so god damn blind you might notice is said GENERERALLY.

You are lucky, and transmission technology has MANY variables and all material is different, so please think before you speak and try telling those with 45dB attentuation and dial-up like speeds that its a load of horsesh*t.

If you dont think people should give advice, then why be here

JoyPad

OfflerCrocGod wrote:

I have ATEN of 52dB/31dB and yet always connect at 2048 and get downloads of 205 to 210 when maxed - and they stay there. Even with torrents.

Oh and my SNR is 6.5dB/0.0dB according to the expert I should be lucky to expect ~50K. My pings are normal as well.

No offense, but ever thought your modem might be reporting these values wrong? Ever tried a different modem on that line?

You shouldn't draw conclusions from one measurement. You need to take 10 measurements, eliminate the odd value (obviously measurement error), and average the rest.


Cheers,
JP

BugBlaster

I also get this attenuation, did a isp speed test. My connect is only 864k dn and 94k up. I'm happy with that seeing as i'm six miles from the exchange!

lucernarian

JoyPad wrote: »

No offense, but ever thought your modem might be reporting these values wrong? Ever tried a different modem on that line?

You shouldn't draw conclusions from one measurement. You need to take 10 measurements, eliminate the odd value (obviously measurement error), and average the rest.


Cheers,
JP

No offense, but if the modem is able to connect at its proper speed, then even if the stats are wrong, the line is obviously guaranteed to be good enough to handle 2048/256 if there are no disconnects.

And attenuation values don't vary within the same modem really. SNR values can vary within the modem, so yes refreshing the page can be helpful for an average. On netopia modems, I've never seen the SNR vary by more than 5dB, and less than that if the FW was upgraded.

For the record, there was a post here on boards from someone who had 2048/256, though with a poor SNR of about 6-8dB, on a line which was over 5km long and with a modem reported attenuation of 61dB. That's the record for 2mbps that I know of.