Line lengths - a couple of examples.

There have been a couple of threads about line length recently - I thought I would give a couple of examples of extreme installations.

In my Scottish house, where there is just ADSL Max available we get around 7600 kbps with attenuation under 10dB and SNR of around 4 or 5 dB. Transmitted power is also well down at about 11 dBm - most will see around 19 dBm. The line length is, from BTs records, 497m and the distance by road from house to exchange is just over 440m so when you allow for the amount taken up internal exchange wiring, up to the top of the pole, down the building, sag in overhead drops, slack underground cables &c it is a fairly accurate measurement.

I was asked to look at a friends connection (in Scotland) last week as they are only syncing around 3500 kbps. They are the second closest house to the exchange at around 200 m. Their line length is well over 3km with attenuation of around 45dB - the cable really does go around the houses and is subject to a lot of snow damage, we know the route it takes. The nearest house - just a few metres closer get full speed with attenuation of around 4 to 6 dB where the downstream power level is about 9dBm.

The friends are currently negotiating with BT to get three new poles installed - partly at their expense to overcome the line length and loss of service issues. They have a good case and are prepared to pay - and BT are willing to do it as they have had to reinstate the line three or four times over the past winter.

do you have any bits per bin plots from these low power cases, I'm wondering if the higher frequencies aren't in use if you're not getting full sync at 10 dB attenuation.

The sync, as far as I can remember, is sometime full speed or just under, 7600 is the throughput.

But I'm back in London now - had planned to go up this weekend but the house was snowed in so did not bother trying.

you don't get 7600 throughput on Max

I did say "around" - and trying to remember the figures when not in front of me.

I saw too many figures in the few days, high, low, fixed 512k links &c &c. I end up looking at a few different links for people with problems and they in turn keep an eye on things when I am not around.

Next time I am there, I will be running some external cat 5 - around 80 to 100 m from house to a barn where a small switch/hub will sit, followed by another 80 to 100m to another barn followed by a final link to the neighbours house.

One gets around 5Mb and the other - 20k dial up only! 600m by road but the lines follow totally different road but as both barns have power it should be able to provide a link in the 10s of Mbps.