Kitz Forum
Broadband Related => ADSL Issues => Topic started by: jaydog on July 28, 2008, 05:24:42 PM
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I used to be able to get a sync of 4800 which allowed 4mb speeds.
My SNR was increased from 6 to 9 because it kept disconnecting.
Whats the maximum speed I can get with an SNR of 9? Because I have possibly found a way to stop my disconnections and crap sync, however the SNR increase may now be stopping me going to my max of 4mb.
Any ideas?
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Theres too many variables and you cant go just off the SNR. You have to look at the whole picture.
The target SNR (which is different from but related to the SNR Margin) will have been increased for a reason.
Every line will have SNR fluctuations throughout the day, usually its worse in the evenings and to be expected. Some lines fluctuate more than others, generally those that are further from the exchange.
If its in relation to your thread here (http://forum.kitz.co.uk/index.php?topic=2542.msg73532#msg73532), then as a very rough guide, then the increased target SNR may have brought your max sync speed down by anywhere around 1200 kbps give or take a few hundred kbps either way.
Remember though the DLM will have increased your target SNR for a reason (http://forum.kitz.co.uk/index.php?topic=2490.msg72852#msg72852), and the more you mess and disconnect, then the more it will think your line is unstable.. and therefore increase the target SNR further. Reducing the target SNR could make your line unstable again.
You also have to remember that the more people there are using their connections, then the more chance of cross-talk from the other lines - not much you can do about this Im afraid. Ive seen the SNR drop on my own line over the years.. down to no other reason I can think of other than crosstalk.
5 years or so ago, I was probably the only one in the street that had adsl.. now just about every house has it.
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is it possible i could go from a 3700 sync to a 4800 sync with an snr of 9 though?
my max sync on a snr of 6 was 5400.
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Unless your SNR Margin increases dramatically - then no.
The amount of SNR Margin (which is the "spare") is what dictates your maximum sync speed.
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is there anyway to get my snr back to what it was? seems stupid that because i had problems once, my max speed is now limited.
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Contact your ISP who should be able to request this from BT.
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Hi
I am new to this stuff.
Can you not change your snr with dmt tool?
Could be wrong in which case tell me to bugger off not a prob :-\
regards
Squeeek
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Hi and welcome
Yes, youre correct, you can - but only if you have one of the supported routers... and unfortunately more router manufacturers seem to be withdrawing DMT tweak support (http://www.kitz.co.uk/routers/DMTv7.htm) :/
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DLM will only raise your target SNR if your speed is comfortably in excess of the FTR. FTR is the 'fault threshold' speed that was established during your initial 10 day period.
So, it soundle like maybe your line has 'improved' at some time? Maybe you fitted an I-Plate or, as I did (same thing really) cut the bell wire? If that's the case then to get your line working optimally your ISP would need to persuade BT to restart the 10 day period and establish a new FTR that's appropriate for your improved line. If they don't do that then DLM will keep raising your target margin, and reducing your speed back down towards FTR, every time it thinks it's seen any instability.
Unfortunately, I don't think BT often (ever) respond to a request for resetting FTR. I certainly wouldn't pin your hopes on any off-shore ISP helpdesk even understanding the question, let alone getting BTW to act upon it.
Whatever you do, never do anything that might cause your modem to resync ten time inside an hour because, if your current sync speed is comfortably in excess of FTR, you'll immediately trigger a reaction by DLM that raises your margin by up to 6dB. Here speaks the voice of experience :(
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Unfortunately, I don't think BT often (ever) respond to a request for resetting FTR.
A friend of mine had a real antique "mess" of 1930's and 1950's phone wiring resulting in a "locked" 15dB margin and speeds below 2meg.
After sorting out his wiring his line is "capable" of a rock-solid 8128/448 but BT, despite numerous requests, point blank refuse to reset anything so the target SNRM stays at 15dB.
So he just uses DMT to force it. It actually syncs and stays stable for days at 8128 and the actual SNRM is then around 10dB as he has a good line with spare speed capacity.
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In my case, I cut the bell wire and jumped from ~2mbs to ~3.5mbs on a 9dB margin. I then 'tried a few things', like swapping different filters, and trying master skt vs extensions. Before long (inside an hour) I'd tried ten such things things and, Wallap, my speed was back where it used to be thanks to a 15dB margin.
I did persuade my ISP to persuade BT to reset the margin back to 9dB but 48 hours later, for reasons I never fugured out, it shot back up again. And has stayed there. I haven't (yet) got a tweakable modem.
So, I agree, tweaking target SNR with DMTool (or other means) seems the only way to get speed back. But not everybody is going to be able to do so, either owing to lack of knowledge ot unsuitability of routers. Wouldn't it be better if the DLM algorithms actually catered for the possibility that a line might actually 'improve' following the ten day period?
BTW - I just noticed that the original item on this thread goes back to July so my comments may be less appropriate tha n I reallised. Ooops, do I look silly now? :-[
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>> Ooops, do I look silly now?
Not at all - interesting discussion.
What isnt evident from this thread is that jaydog had had several other queries in other threads which he'd done all the usual bellwire stuff etc.
IIRC he also had a router which wasnt DMT tweakable but was with an ISP who are ameinable to attempting to lower the Target SNR.
TBH though and I cant recall without going through a pile of old posts, I think he had variable SNR there may have been a reason why I wasnt sure if it would be a good idea or not in his case since he still suffered from the odd disconnects long after attending to his internal wiring.
I think what some people do forget is that the DLM has higher profiles for a reason... and that some lines just do need a larger 'spare' SNR in order to remain stable.
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A few of years ago when DMT tool was released, the news of DMT tweaking to increase your sync speed spread like wild-fire across many many forums.
The downside there wasnt any information anywhere how to use it.. and any info about it was in German.
You can imagine the scenario:
- Forum or Blog Post :- "BT users can use this tool on their Home hubs to get higher speeds".
- So off goes the 'average BT user' who wouldnt have a clue about SNR, target SNR and the DLM.
- They grab DMTtool.. 'ooooh what does this slider do'..... "oooh look now I can sync 1.Mb higher - great".
- Now DMTtool on the ST based routers unlike some of the others can permanently set this change and...
- Then one week later you get the same people phoning up BT helpdesk "My connection is rubbish - its disconnecting every half hour".
- BT helpdesk wont know theyve been DMT tweaking they'll still see that the DLM is set at 12/15dB..
- so they call out an Openreach engineer, which the ISP has to foot the £150 bill for.
The above may seem like an exaggeration and whilst Ive shortened the process.. this in fact is exactly what did happen 100s of times over and it caused a massive headache for BT helpdesks... so much so that BT called a halt to it and requested that Thomson remove the DMT code from their routers - which Thompson happily obliged to. :/
The unfortunate thing is that DMT tweaking has always been available in many routers long before the advent of DMT tool. I remember it being there in my first router that I bought in 2003... DMTtool just made it easy for a more novice to change the settings.. and because of this action you now have a couple of fairly major router manufacturers who have withdrawn any form of DMT tweaking code from their firmwares.
I'm not blaming DMTtool - its an excellent piece of software worthy of much credit.
One of the reasons I wrote the DMT tutorials in the first place is because there was no info in English anywhere at the time on how to use it.. nor how to get the default settings back to normal.
What is unfortunate is that it was released into the UK on certain forums or blogs as a cure-all to get higher speeds... and too many users used it without having a clue what they were doing.... and blindly went ahead and permanently made changes in their router without RTFM.... then went bleating to BT. :mad:
So now because of that, a very useful feature has been removed for all - even those that use it sensibly. :'(
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Hi
So from now on there is no way to tweak even when its done sensibly . :(
Jeff
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Thomson/Speedtouch routers have been neutered, but there are several other makes of router which can still be tweaked, such as the Netgear DG834GT (particularly good with the unofficial DGTeam firmware).
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D Link's Broadcom routers such as the DSL-2740B can be tweaked with DMTv8 :)
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Thanks for that . At the moment I am on an st330 modem. It performed ok . but now for some reason I have been getting disconnections and my snrm has shot up, connection speed down profile down :(. The stats from st330 not really good enough to pinpoint problem . I will need to get a router asap.so that I can see what's going on. I will be raising new topic for advice .
Jeff
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I read that the ST330s used to perform badly on ADSL Max, have you got the latest firmware on it?
I believe that the older firmware was causing the issues you are describing.
Have a quick read of this:-
http://www.kitz.co.uk/adsl/frogstats.php#44
Gives an explanation of getting stats and the issues it was causing...
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It used to perform very well. I had connections speeds up to 7.2Mbps on a line with 34db attenuation and an snrm of 5. no errors for most of the day would start getting errors in evening when snrm would drop to about 2 or 3. its in the last 3 weeks that its got bad .Mind you with tiscali as my ISP I am still connecting at 5Mbps or better ,which is way way way above the DL speed available most of the evening and week end.I am getting all my data together for my next topic. Yes the firmware is ok I think 330 1.0.12 1999-2004.