cancel
Showing results for 
Show  only  | Search instead for 
Did you mean: 
john46
Distinguished Sage
545 Views
Message 51 of 75

Re: Slow Internet - mods please assist.

normal default noise margin is 6dB
0 Ratings
Redtractor
Aspiring Contributor
532 Views
Message 52 of 75

Re: Slow Internet - mods please assist.

Hi TiRich et al,

Sorry to say , but your DL attenuation seems quite high at 55dB. And this will definitely limit your max speed achievable. You can google up the tables of atten vs distance and speed for ADSL as a bit of a guide. Your link runs at about 6dB noise margin and this indicates IMHO that it is running close to its max speed at this distance without excessive errors/ retrys. If more bps were sent over the link, the noise margin would decrease towards zero and at around 3dB would likely become unstable /  lost. To improve my link I simplified my house wiring and put a professional quality phone / ADSL splitter directly into the customer side of the BT master socket. I cabled to the modem with pro grade cat 5 cable and finished off with a pro grade RJ45 wall socket. Through this forum a Moderator helped by having the service released from its profile and it went from a profile limited 2Mbps and 12dB SNR to about 8Mbps and 5dB SNR.  Christmas TV is just rubbish, isn't it? Cheers, David.

john46
Distinguished Sage
524 Views
Message 53 of 75

Re: Slow Internet - mods please assist.

this link should help you see the average attainable speed with a 6dB noise margin and your attenuation http://www.kitz.co.uk/adsl/max_speed_calc.php
0 Ratings
TiRich
Contributor
506 Views
Message 54 of 75

Re: Slow Internet - mods please assist.

Thanks for the replys.

 

The house wirig has been optimised already - there is no internal wiring used, bell wires disconneted and the router is in the Master Socket with an ADSL Nation face plate and quality Belkin leads. 

 

The Kitz website shows what i am finding in proactice in that i am better off with a ADSL connection compated to a ADSL2 connection. 55dB on ADSL gives a 3000 IP Profile speed. 58dB on ADSL2 gives a 2822 IP Profile (I lose 3dB going to ADSL2 which is normal)

 

I am currently on a 2880 profile so agree there is little room for improvement in theory.

 

BUT

 

I have had real speeds (not profile) of 3200+ in the past and i still do not understand why the SNR is 6dB and then peaks better to 12dB! if i could get to the borrom of that i am sure there is more room for improvement. The graph is effectively upside down!

 

 

0 Ratings
john46
Distinguished Sage
501 Views
Message 55 of 75

Re: Slow Internet - mods please assist.

the 12 db margin is not what you want the correct default SNR is 6dB
Redtractor
Aspiring Contributor
492 Views
Message 56 of 75

Re: Slow Internet - mods please assist.

Hi - Something strange does happen to give you a 12dB result from time to time. IMHO I reckon it's one of 2 things. Interference which stops - already discussed. Or, sorry to say, the link speed drops. If your link was forced by sw to run at (say) 2Mbps then I would expect to see SNR improve like this and errors go to zero(ish). As you say, with 55 dB attenuation one can't expect much more speed than you are getting. The link speed I get is very close to what the model predicts now (thank you Sage for posting) . In my case after cleaning up the wiring and leaving the modem alone for approx 10 days there was one more bite of the cherry which increased the speed by a couple of hundred K and caused SNR to drop from about 6 to about 5dB and the errors to go up from about  a hundred to about a thousand a day. The link has been quite stable there since. So you might get a further small speed increase automagically. Cheers.

umpire
Distinguished Guru
488 Views
Message 57 of 75

Re: Slow Internet - mods please assist.

The connection speed will only change after a disconnection and reconnection.

Assuming the charts are showing correct information then the short changes to 12dB do to me indicate a temporary reduction in noise. It is just for a very short time though. If that reduction could be achieved constantly then the current connection noise margin would stay at 12dB, then after a reconnection it would go back to the default 6dB but with a faster connection speed.

One other point. Do we know what the noise margin was back when you had a faster connection speed? The DLM may have used 3dB to achieve the faster speed. You are currently telling the modem to use 6dB regardless of what the DLM thinks. My ADSL2+ line for example uses 3dB with a HomeHub4 as it is stable enough.

Try the noise margin on auto again and see what it selects?
umpire
Distinguished Guru
487 Views
Message 58 of 75

Re: Slow Internet - mods please assist.

Note that if you changed the noise margin to auto (assuming that will then use the DLM figure) then I think you would need to do a reconnect in order to apply it. The target noise margin is used at connection (sync) time to set the initial starting point.
umpire
Distinguished Guru
483 Views
Message 59 of 75

Re: Slow Internet - mods please assist.

Looking back at the chart, if you ignore the big peaks the noise margin is very stable. The line might be stable enough to run at 3dB at a slightly faster speed.

But as already mentioned if the error counts are too high the DLM will be sensible and change it back to 6dB.

On my line the DLM has left my margin at 3dB but after a couple of months recently changed it from fast path to interleaved. Probably due to the miserable weather and slightly higher error counts? 😄
0 Ratings
TiRich
Contributor
475 Views
Message 60 of 75

Re: Slow Internet - mods please assist.


@john46 wrote:
the 12 db margin is not what you want the correct default SNR is 6dB

The line is stable at 6dB but with temporary peaks to 12dB showing there is scope on the line if we can obtain the 12dB constant and then reconnect at 6dB at a higher sync speed.

0 Ratings