Should I have my line maxed now?

[#1]

A couple of years ago I asked to have dsl max enabled on my line. It is a long line (5.1km). To cut the story short, after a discussion with Dave T it was decided against doing it as my downstream noise margin was pretty low at 11db. Actual stats were as below.
ZyXEL 660HW
noise margin downstream: 11 db
attenuation downstream: 55 db
noise margin upstream: 24 db
attenuation upstream: 31 db
A couple of routers later I now have a Netgear 834g V4. No other changes made to hardware, wiring etc. at the house. The noise margin stats are now considerably better, though attenuation is a bit worse. Figures are now as below.
Netgear 834G V4
noise margin downstream: 20.7 db
attenuation downstream: 63.0 db
noise margin upstream: 24.0 db
attenuation upstream: 31.5 db
Would it now be worth attempting to enable dsl max on my line again? It seems to be consistently at these figures and the BT checker says I may be able to now get 1.5 meg if maxed (currently fixed 512k). To be honest, this router seems to be far more stable than any other I've ever had.
Opinions please from community and staff.
Thanks
Trev

[#2]

Hi Trev,
The increase in attenuation when moving to your Netgear is a *bad thing*.
That to me would suggest either a fault with the router or some reporting weirdness.  It makes it look like your house has magically moved further away from the exchange!
Are you wired into your master socket via a filter?

[#3]

Hi James,
To be honest every router I've had has reported attenuation differently. When first on ADSL had a 3COM (forget the model) and this reported about 60db downstream. Then had the ZyXEL 660HW which reported 55db, but then started getting worse. Wasn't sure at the time if it was the router or line so got a Thomson Speedtouch 585 V6, which reported 61-62db. This router didn't seem the most reliable in the world so got the Netgear, with the results as shown, and seems to be rock solid at the same time. Remember this is also over a period of several years, so I've not just bought a load of routers in the last few months or anything (3 routers in 2 years though!). I think there may have been a reporting anomaly with the ZyXEL if anything as the others are similar.
My wiring has always been the same. Solid core phone cable from Master socket to extension socket, then filter on extension. I may have changed filter at some point (seem to have gained a few of them over the years!) but I can't think when I would have done so.
Trev

[#4]

Assuming the Netgear numbers are more or less correct you may be able to get a bit more speed by going to max. However the thing you need to do first is to monitor your noise margin and errors over 24 hours - RouterStats will do that for you with that router http://www.vwlowen.co.uk/internet/files.htm
The point here is the degree to which your noise margin drops overnight - if it only drops about 3dB then you may be able to get  about 1500kbps stable rate according to this http://www.dslzoneuk.net/maxspeed.php

[#5]

Thanks very much for that. I will download and monitor, and report the results back. From what I've seen from random checks over the last couple of months I'm optimistic actually, but there's nothing like a proper test to see.
Trev

[#6]

How did you determine your line length? At 5.1km I am surprised that you ever got close to 55dB line attenuation. Mine has been reported at around 4 - 4.3 km, this came from stats produced on a BT Engineer's laptop, but there was some variation in both the line length and attenuation. This variation should not happen unless there has been any maintenance on your line or the equipment it is connected to at the exchange. I believe that in my case the variation in statistics was over a short period and was indicative of a possible problem with the exchange equipment, which once resolved gave me a much more stable connection, but still with an attenuation of 63dB.
My connection is stable at ~1.5Mbps, and has been as high as 2Mbps. But if your line really is 5.1km then BT are likely to have the view that your line is barely capable of operating under ADSLmax and suggest you consider a fixed speed product. It is probably worthwhile getting upgraded to 1M fixed, possible 2M. I'm sure there are others on this forum who can give advice based on wider knowledge and experience than my limited knowledge.

[#7]

A few years ago there was an engineer's number that could be called that gave an estimate of line length (don't think it's possible now but I may be wrong). 5.1km is the length this estimated the line at. The actual length may be different, though with my physical distance from the exchange it is probably roughly correct.
maranello, what is your downstream margin?
Trev

[#8]

Hi Trev, my d/s noise margin varies, which is to be expected as the amaount of noise varies throughout the day. The target noise margin is 6dB, which is what my router reports when it first achieves sync. At a speed of 1.8Mbps or below the noise margin doesn't vary a great deal, but if I sync at higher speeds the margin variation is greater and the connection is more prone to getting dropped.
I have read  that some routers will only report the downstream line attenuation up to 63dB, which is what I get. If your line is ~1km longer than mine then your line will be more susceptible to noise and you may need to have a higher target noise margin to get a stable connection. The target margin is set by BT, and if your line drops frequently then increasing the noise margin in increments of 3dB is how BT tries to stabilise it. However, each 3dB increase in the target margin can reduce your sync speed by up to ~800kbps.
PS I don't know how much of the above applies if you are on a fixed speed product.

[#9]

On a fixed speed line it is the actual noise margin at that speed, simple as that. Looks like I have a bit of leeway as far as a maxed line target margin would be concerned, so if the line stays somewhere similar overnight there seems to be a fair chance that my line could work at a higher speed. All being logged now, so I'll check the results tomorrow.
Trev

[#10]

Right, done 24 hours of logging using RouterStats now. I've never logged for that long before, quite interesting results.
The only thing that changed at all was the downstream noise margin. Attenuation 63db throughout, no other changes to logged figures.
Keeping reasonably short and without supplying the whole log here are the results.
Start 11:40 yesterday - consistently 20.6-20.8db, rising to about 21db by 15:00.
15:59 started dropping, went to 18.9db, down to 18.2 by 16:30, then back to 20.5 for a few mins, then back to 18.5 with a single reading of 15.9.
This was the period of time the street lights were coming on, so I'm guessing it may have been this.
Then 16:40 back to 20.2-20.4db.
Down to the high 19s from 17:30 to 18:00, then back around 20.4.
Kept in the mid to high 20s with the odd drop into the 19s until 1:00am when the router reset itself. I'll forgive it as it had around 400 hrs uptime.
After restart between 20.6 and 21db for several hours.
8:38, sudden drop to 18.6db going down to 17.8db after a few mins, hovered between 17.8 and 18.1.
Can't link this to anything obvious in the house or externally.
9:51 back up to 20.6db just as suddenly.
stayed between 20.6 and 20.8db for rest of test period.
Roughly, most of time in high 20s, period of time in low 18s, another period of time around 18.0db. Had a single reading of 15.9db.
Opinions as to whether this line could handle better than the 512 it is currently on please?
As far as I can see my options are:
Request fixed speed upgrade to 1 or 2 meg.
Request line to be maxed.
Do nothing.
Trev

[#11]

You won't get a fixed speed over 512kbps as the BT rules are geared to the attenuation.
i would recommend going for max.

[#12]

Thanks for your advice.
I've put in a request for the line to be maxed (27757395).
(wonders how much it would cost for a fibre link from Sheffield to Worksop...)
I'll post any developments of interest here.
Trev

[#13]

Progress report....
Got up this morning to find my line had been regraded, which was bang on when I was told it would be so thanks to CS for that. Was surprised to discover the router appears to have resynced without dropping the line! As a result I thought best to restart it and then go through some initial checks.
Well, so far it's synced at 1856, which is higher than I expected, still 63db attenuation. Noise margin currently 6.9db and steady for the first couple of hours I've checked it. Not anything like enough time to be meaningful yet though.
Thought I'd have a quick check on download speed. Still around 480kbps at it was before regrade, so I thought I better check this out. BT speed tester says IP profile is 1500 which is correct (if the line stays OK), but checking Plusnet it says the data rate is 500. I'm guessing the reason for the 480 download speed is there somewhere.
It's all been up just a few hours so systems have to sort themselves out and the training period has only just begun but things look at least potentially promising even if I don't have a faster download speed yet, so it is possible to sometimes get more than 512 out of a 5km line (though Kitz estimates at 4.5km).
Fingers crossed.
Trev
[Edit] Plusnet now reporting 1500 too. Speed up to 520 so far.

[#14]

Hi Trev,
There's a chance you might need to reboot to see the benefit of the 1500Kbps profile.

[#15]

When the 17070 test still gave an estimate of line length, mine was reported as 5·3 km, which tallied with the recorded distance if I drove to the exchange.
When I first had broadband, it was limited to 512k - I later found out from a tame BT guy that there was a lot of aluminium cable in the route. I didn't have a router that gave stats then, so I don't know the attenuation. About a year or so later the aluminium was replaced with copper, and now my attenuation is 52dB and sync is 5200.
In answer to your question, then, yes one can certainly exceed 512k on a 5 km line, but your stats suggest to me that you don't have an all-copper route.