3000kbps loss over 1000 metres of cable ?

Following on from my struggle with BT to supply a reasonable broadband connection, yesterday I visited my accountant, who lives very close to me as the crow flies, although the actual distance that the cabling takes is rather longer.

My neighbour who lives at the top of my road (closer to the exchange) who is with BT Broadband manages to sync at 5120kbps with a 6dB noise margin. My accountant lives even closer to the exchange, but about only 1000 metres cable length from my neighbour.

Yesterday my account let me look at his stats..... he was syncing at the full 8128kbps, with a SNR margin of 9dB. This is on g.dmt - the exchange doesn't get ADSL2+ until April. I estimate that he could probably get between 10000 and 12000kbs if the router was allowed to sync faster.

Now, my question is..... is a drop of over 3000kbps in speed normal over a line length of 1000 metres ? I know exactly the route that the cable takes, and that is about the right length.

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Edited by zebedeee (Tue 09-Feb-10 12:45:02)

Just did a quick test using MrSaffron's speed estimator.

It uses ADSL2+ but that shouldn't be too significant for this particular "test".

Entering a 45dB attenuation gives a max speed of 8000Kbps. Using an attenuation of 55dB (using 10dB=1Km which I believe is about the expected average) gives a max speed of 4250Kbps. So, if those figures are even remotely right then a drop of 3Mbps over 1Km is not out of the question.

This is a very rough and ready calculation but could show that 1Km could have a devastating effect on speeds.

of course its possible, in terms of copper distance 1000 metres is quite significant. Especially if you talking crow distance.

in regards to ian72 my opinion is the average is nearer to 14db per km.

Edited by Chrysalis (Tue 09-Feb-10 20:48:54)

I wasn't talking about crow distance, I was talking about the actual distance, and that was generously estimated.

Incidentally, my line attenuation is 38dB. Kitz estimates 7000kbps for that on g.dmt.

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Edited by zebedeee (Tue 09-Feb-10 22:38:57)

even in actual cable distance its not unreasonable 1km will equate to 3mbit of speed.

considering your attenuation your sync does seem low tho.

Edited by Chrysalis (Tue 09-Feb-10 23:34:35)

Does aluminium enter into this anywhere or was that totally replaced?

I think there's aluminium still in there, but I think it's between the cab and the exchange, so it should affect all of us. My accountant is as far from the exchange as I am from him.

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As you're now on Be if you use this link:

http://www.kitz.co.uk/routers/DMTv7.htm

This might help indicate why your sync is poor.

Andrue Cope
Brackley, UK

Just because he can

I think there's aluminium still in there, but I think it's between the cab and the exchange, so it should affect all of us.

Often more than one E-side cable between the cab and the exchange, one might be aluminium in part, and the other 0.5 copper.

Zarjaz

In reply to a post by Andrue:

As you're now on Be if you use this link:

http://www.kitz.co.uk/routers/DMTv7.htm

This might help indicate why your sync is poor.

I've already set the SNR margin - Be allows you to do this - you don't need DMT. I have mine set to 3dB. This allows a 3dB margin at night, which rises to about 7 or 8dB during the day, which equates to about 4900kbps.

Home ADSL: Be Unlimited LLU
Business ADSL:
Be LLU supplied by Andrews & Arnold
Orange 3G Business Everywhere Mobile BB