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[Black Sheep]

If ip75 wanted to, he/she could pm me their post code and I could attempt to confirm the actual route, and total length ? If they trawl back through my postings, they'll see it's all done in the strictest confidence. 

[ip75]

That would be fantastic, thank you! PM sent.

[ip75]

Black Sheep has very kindly confirmed for me that the line route to my cabinet is sensible and appears to be around 220m, so hopefully the line will do significantly better than the estimate. I have now ordered the 40/10 service from Sky with an install date of the 10th, when I'll find out for sure.

[NewtronStar]

Black Sheep has very kindly confirmed for me that the line route to my cabinet is sensible and appears to be around 220m

Thats good news and Black Sheep is an excellent member even though he gets the odd anti-bt stone thrown at him from time to time he has thick and honorable skin 

[tickmike]

Yes, either the line takes a crazy route underground between the cabinet and the DP (adding at least 500m I reckon), or the estimate is wrong, or there's something else I've missed!

A chap in my village has the fibre cab near his front door yet his line goes 400 metre's around to his back door via 3 roads

[Black Sheep]

Black Sheep has very kindly confirmed for me that the line route to my cabinet is sensible and appears to be around 220m

Thats good news and Black Sheep is an excellent member even though he gets the odd anti-bt stone thrown at him from time to time he has thick and honorable skin 

Odd ?? Odd, I say !!! It's a full-time job dodging them half-charlies !! 

[ip75]

Having mulled this over a little bit, and putting some addresses into the DSL checker, I have a theory, for what it's worth. As I said, I'm on a 220m line to cabinet 6, with a top FTTC estimate of 46. My neighbour is on a different cabinet, cabinet 2, which I reckon is about 800m away. His estimate is 40. So, I wonder if the estimate I'm getting for my address is based on the distance from cabinet 2, despite the fact that I'm really connected to cabinet 6.

Incidentally, I found a house just up the road which is connected to cabinet 2, at a minimum distance of 650m from that cabinet, which has an estimate of the full 80mbps, which also seems wrong, so that's some more evidence that the records around here are not quite right.

[Black Sheep]

As I mentioned in the PM to you, ip75, the prints* I have vision of were slightly 'hazy' around your DP. There is definitely a cable that heads back to PCP6 from the DP, but there is also another cable that I couldn't pin-point as to what its function was, that connects to the main UG spine cable running along the main road ??

It's a long-shot but not completely unheard of ......I'm wondering if that DP has been 'fed' via two different Cabs in the past ?? You do comment that two different site-engineers have confirmed that you are 'fed' from PCP6 though, so I hope the 'haziness' falls in the positive camp which means you will enjoy pretty much full synch speeds ?

* Unless you are in the Lancs & Cumbria/ Manchester patches, my view of the network and all its joint, ducts, boxes, CP's etc etc .......... is quite limited. I have to access a different on-line system that still give decent info, just not with the ease-of-use or depth, that the local network records afford.

[Black Sheep]

In other words ...... ^^^^ is my disclaimer. 

[ip75]

Oh, that's interesting - but yes, I've been told a few times before by engineers (when I had a line fault a couple of years ago) that I'm on cab 6. The house I mentioned that had an 80 estimate despite being on cabinet 2 *might* actually be connected to the same DP (it's very close to it), so your theory of a DP fed by two cabinets sounds like a good one.

[ip75]

Well, I was connected today to Sky's 40/10 service, which went very smoothly - it's a self install, and I already had the VDSL capable Sky router. My ADSL connection dropped, and about 10 minutes later it reconnected with FTTC speeds.

The Sky router shows me the following stats (this is all you can get from it):

Broadband Link    Downstream  Upstream
---------------------------------------
Connection Speed  39998 kbps  9999 kbps
Line Attenuation  11.0 dB     0.0 dB
Noise Margin      33.6 dB     31.31 dB

which looks like it could probably do 80/20 quite easily; plenty of margin there and line attenuation is relatively low, although I'm probably the first person on the cabinet so things might get a little worse as more lines are connected (although I have an idea that there are only around 50-60 lines in the cabinet).

So it looks like there really is some anomaly with the estimate from the FTTC checker in this case!

[WWWombat]

Yeah - that looks extremely healthy: that's a lot of spare noise margin, and it'll be interesting to see how that changes as take-up rises. Note that there isn't anyone on http://www.mydslwebstats.co.uk/ with a margin as high as that; people capped at 40Mbps are seeing SNRM values of 18-20dB.

My rule of thumb for what an extra 3dB of noise margin is worth in the downstream direction:
- For speeds around 20Mbps, 3dB is worth 3Mbps
- For speeds around 40Mbps, 3dB is worth 6Mbps
- For speeds of 60Mbps or more, 3dB is worth 11Mbps.

I reckon that makes your attainable speed around 120Mbps. A thoroughly reasonable result for no crosstalk on 200m of copper.

[ip75]

I guess it's possible that the Sky router calculates the overall margin differently to the Huawei modem, although I think the Sky router also uses a Broadcom chip. I actually find the modem side of the Sky router very good - I got a faster and more stable connection on ADSL than I did with any other router I tried.

I'll keep an eye on the margin as more lines are added. I'm tempted to move up to 80/20 but it's pretty expensive on Sky - I'll wait for the novelty of 40/10 to wear off first....

[WWWombat]

Unless you are doing something serious, or have a very big family, I doubt you'll see the need for the increase, beyond the bragging rights.

For some extra comparisons, my new line has an attenuation of 8.2dB on about 100m of copper - but I suspect it is 0.4mm stuff. That currently does 80/20 with attainable levels of 98/32 - but the cabinet is definitely well used, and has been there for 4 years.

My previous line had attenuation of 17dB, which was around 350-400m of copper; it started out easily attaining 80/20 3 years ago, but the attainable gradually dropped to leave us on 78/20 at the end of last year.

[ip75]

Hmm. So the connection has been fine for the last couple of days. However, I have noticed that when I'm on the phone, the downstream noise margin drops by 1dB, and the upstream noise margin drops by 4dB. Which doesn't cause any kind of problem. However, when I hang up, the upstream margin very briefly drops by a further 14db (so from 31dB before the call to 13dB at the end).

The margins are high so this doesn't cause a problem at all at the moment, but I fear it may do if I was on an 80/20 service.

Does anyone know what kind of fault this could be? Does it sound like an HR fault? The line stays quiet throughout.