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uk.telecom.broadband (UK broadband) (uk.telecom.broadband) Discussion of broadband services, technology and equipment as provided in the UK. Discussions of specific services based on ADSL, cable modems or other broadband technology are also on-topic. Advertising is not allowed.

Any experience of 256k ADSL?



 
 
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  #1  
Old June 13th 05, 11:45 PM posted to uk.telecom.broadband
Trevor Morris
external usenet poster
 
Posts: 4
Default Any experience of 256k ADSL?

I have had an intermittent new 512 kb/s ADSL service via Zen for a couple of
weeks, using a Netgear DG834 ethernet router supplied by them. BT have
fitted a filtered faceplate to the master socket, with no improvement. When
working, downstream attenuation is 63 dB, with a noise margin from 1 to 5 dB
(usually 3 dB): upstream attn. 31.5 dB, noise margin 9-11 dB (from memory).
The connection works (synchronises) for between a few seconds to a few hours
at a time, up and down several times a day. I am reported to be 4.5 km from
the newly-enabled exchange (straight line), but the road distance (which the
phone lines more or less follow) is more like 9 km. This is the message
from Zen today:

"Following your report to our technical support team of a fault on the line
enabled for your ZenADSL service, BT engineers have carried out tests and
reported the results to us directly. We are advised that BT engineers are
unable to improve the current level of service provided, and as a result BT
Wholesale have offered the following options:

1. Your service can resume at the current level of service. If you choose to
retain the service, no future faults relating to this issue will be accepted
by BT.

2. If you do not wish to resume at the current level of service, BT
Wholesale can cancel the ADSL circuit. If the service was provisioned within
the last three months, we will provide a full refund of the activation
charge and monthly fees paid.

Please contact us as soon as possible to advise how you wish to proceed with
this order. If no reply is received within five days, BT Wholesale will
automatically resume service on the line and may revoke the option for a
refund if the service is ceased after this point."

This looks a bit odd insofar as Zen are not offering to try a step down to
their 256 k service, which might in theory work better, and I will phone
them about that tomorrow. But in the meantime, has anyone managed to get a
256 k service on a long line where 512 k was not reliable? Any views on my
chances?

Thanks,
Trevor Morris



  #2  
Old June 14th 05, 03:30 AM posted to uk.telecom.broadband
[email protected]
external usenet poster
 
Posts: 33
Default Any experience of 256k ADSL?

The CS person that advised you probably doesn't know the 256K service
could give you better performance. Call and tell them you want a
regrade to 256K, but make sure they don't just throttle your line to
256kb or something. It may be too late to take advantage of Zen's
DrayTek Vigor offer (last I was aware, Zen would accept a return and
give a refund on the -- somewhat marked up -- Vigor if your connection
didn't work out). The Vigor is a better router and optimised for long
lines so may hold the connection for longer, although I read that the
long line firmware is designed to handle poor attenuation, rather than
poor SNR, and the attenuation in your case seems okay. I would ditch
the Netgear router before doing anything drastic. Maybe try a
SpeedTouch?

Have you tried unplugging the faceplate and plugging the router
straight into the test socket on the master box (with no filter) to
isolate any extensions?

If it is not possible to test with the router due to location of pc,
put a phone on the appropriate extension, dial zero and listen for any
audible noise on the line, then repeat with the phone plugged straight
into the test socket on the main box (or with all extensions unplugged,
if they are not hard wired in to the back). There is a quiet line test
you can do, but this is adequate to pick up mains hum (eg if you have
extensions with untwisted alarm cable that run parallel to
mains/lighting circuits).

I can't see internal wiring accounting for such a significant amount of
signal loss, but if you can find and correct such a fault it may help
improve reliability.

I am over 10 k from the exchange and was getting a 24-26bd downstream
noise margin on 512k (now on 1MB and have not lost sync since
installation 4/5 days ago). Attenuation is pretty similar to yours,
59db, sometimes 62db.

In our case the line also follows one road for 90% of that distance,
but the line is entirely underground and only passes a handful of
premises and two street lights on the way, with no other potential
sources of interference during the route.

Are you in a built up area? If it is a rural location (I assume so from
the activation date, our exchange was only enabled May) and there are
no built up areas between you and the exchange or other infrastructure
that could be contributing to interference, then the SNR seems
particularly poor for your circumstances and BT may need to replace
some bad cable.

What speed were you connecting at over dialup? We were achieving 45kb,
which hardly ever dropped. Anything less than 35kb would indicate
problems with the line (I would connect at 33kb when dialing from the
upstairs extension, down to electromagnetic induction on the cheap
extension line from a mains lighting circuit).

  #3  
Old June 14th 05, 07:38 AM posted to uk.telecom.broadband
Mark Carver
external usenet poster
 
Posts: 480
Default Any experience of 256k ADSL?

Trevor Morris wrote:
I have had an intermittent new 512 kb/s ADSL service via Zen for a couple of
weeks, using a Netgear DG834 ethernet router supplied by them. BT have
fitted a filtered faceplate to the master socket, with no improvement. When
working, downstream attenuation is 63 dB, with a noise margin from 1 to 5 dB
(usually 3 dB): upstream attn. 31.5 dB, noise margin 9-11 dB (from memory).
The connection works (synchronises) for between a few seconds to a few hours
at a time, up and down several times a day. I am reported to be 4.5 km from
the newly-enabled exchange (straight line), but the road distance (which the
phone lines more or less follow) is more like 9 km. This is the message
from Zen today:


[snip]

This looks a bit odd insofar as Zen are not offering to try a step down to
their 256 k service, which might in theory work better, and I will phone
them about that tomorrow. But in the meantime, has anyone managed to get a
256 k service on a long line where 512 k was not reliable? Any views on my
chances?


256k will only offer an advantage if Zen/BT actually drop the sync speed to
the same (or to be exact 288k). ISTR that Zen's 256 service is normally
provided at this lower sync speed, other ISP's 256 services are provided at
578 or higher, and the speed 'crippled' within the network.

If your noise margin is currently 3dB at 512, in theory dropping the sync
speed to 288 should add 6dB to it. Indeed the upstream sync speed is already
at 288 and as you've observed you do get a 9dB figure.

In short ask Zen to provision the line at a 256(288) speed.

--
Mark
Please replace invalid and invalid with gmx and net to reply.
  #4  
Old June 14th 05, 10:37 AM posted to uk.telecom.broadband
Trevor Morris
external usenet poster
 
Posts: 4
Default Any experience of 256k ADSL?

wrote in message
oups.com...
The CS person that advised you probably doesn't know the 256K service
could give you better performance. Call and tell them you want a
regrade to 256K, but make sure they don't just throttle your line to
256kb or something.


I did that initially, but Zen wanted to charge me 15 to regrade unless BT
confirmed that 512 would not work. I called Zen CS just now and they are
going to try the 256 k idea on BT and let me know...

It may be too late to take advantage of Zen's
DrayTek Vigor offer (last I was aware, Zen would accept a return and
give a refund on the -- somewhat marked up -- Vigor if your connection
didn't work out). The Vigor is a better router and optimised for long
lines so may hold the connection for longer, although I read that the
long line firmware is designed to handle poor attenuation, rather than
poor SNR, and the attenuation in your case seems okay. I would ditch
the Netgear router before doing anything drastic. Maybe try a
SpeedTouch?


I have a USB modem I can try, but if line noise is the problem, it's hard to
imagine anything beating the Netgear's ability to work with a 1 dB margin...


Have you tried unplugging the faceplate and plugging the router
straight into the test socket on the master box (with no filter) to
isolate any extensions?


Yes - tried all that, and the router has always sat next to the master
socket
with its new BT face plate - made no difference (in fact I think it has
synchronised less reliably than with the dangly add-on filter).


If it is not possible to test with the router due to location of pc,
put a phone on the appropriate extension, dial zero and listen for any
audible noise on the line, then repeat with the phone plugged straight
into the test socket on the main box (or with all extensions unplugged,
if they are not hard wired in to the back). There is a quiet line test
you can do, but this is adequate to pick up mains hum (eg if you have
extensions with untwisted alarm cable that run parallel to
mains/lighting circuits).

I can't see internal wiring accounting for such a significant amount of
signal loss, but if you can find and correct such a fault it may help
improve reliability.


The line is a second one fitted for the previous owner's dial-up service, so
has no extensions, mains wires etc anywhere near it. Can't hear mains
harmonics, though it is a bit hissy (but that could be the DECT phone...)
Keeping the power plug
away from the router helps, but there seems to be no other local source of
noise that I can find. Am taking an oscilloscope there tomorrow to see
what is going on.


I am over 10 k from the exchange and was getting a 24-26bd downstream
noise margin on 512k (now on 1MB and have not lost sync since
installation 4/5 days ago). Attenuation is pretty similar to yours,
59db, sometimes 62db.

In our case the line also follows one road for 90% of that distance,
but the line is entirely underground and only passes a handful of
premises and two street lights on the way, with no other potential
sources of interference during the route.

Are you in a built up area? If it is a rural location (I assume so from
the activation date, our exchange was only enabled May) and there are
no built up areas between you and the exchange or other infrastructure
that could be contributing to interference, then the SNR seems
particularly poor for your circumstances and BT may need to replace
some bad cable.


It is rural (Gower), with a lot of overhead power lines, HV and mains, mixed
in with telephone poles...

What speed were you connecting at over dialup? We were achieving 45kb,
which hardly ever dropped. Anything less than 35kb would indicate
problems with the line (I would connect at 33kb when dialing from the
upstairs extension, down to electromagnetic induction on the cheap
extension line from a mains lighting circuit).


Funnily enough, when I first got dial-up there last September, it ran at 28
kb. Then after some BT work on wires up poles around the village I got 44
kb before the ADSL service was set up, but since adding a filter it has
dropped to 31 kb.

Love BT's heart-warming "take it or leave it within 5 days or you're dead"
offer, though....

Thanks for the reply - I will report what happens!

TM


  #5  
Old June 14th 05, 10:42 AM posted to uk.telecom.broadband
Trevor Morris
external usenet poster
 
Posts: 4
Default Any experience of 256k ADSL?

"Mark Carver" wrote in message
...
Trevor Morris wrote:
I have had an intermittent new 512 kb/s ADSL service via Zen for a couple
of weeks, using a Netgear DG834 ethernet router supplied by them. BT
have fitted a filtered faceplate to the master socket, with no
improvement. When working, downstream attenuation is 63 dB, with a noise
margin from 1 to 5 dB (usually 3 dB): upstream attn. 31.5 dB, noise
margin 9-11 dB (from memory). The connection works (synchronises) for
between a few seconds to a few hours at a time, up and down several times
a day. I am reported to be 4.5 km from the newly-enabled exchange
(straight line), but the road distance (which the phone lines more or
less follow) is more like 9 km. This is the message from Zen today:


[snip]

This looks a bit odd insofar as Zen are not offering to try a step down
to their 256 k service, which might in theory work better, and I will
phone them about that tomorrow. But in the meantime, has anyone managed
to get a 256 k service on a long line where 512 k was not reliable? Any
views on my chances?


256k will only offer an advantage if Zen/BT actually drop the sync speed
to the same (or to be exact 288k). ISTR that Zen's 256 service is
normally provided at this lower sync speed, other ISP's 256 services are
provided at 578 or higher, and the speed 'crippled' within the network.

If your noise margin is currently 3dB at 512, in theory dropping the sync
speed to 288 should add 6dB to it. Indeed the upstream sync speed is
already at 288 and as you've observed you do get a 9dB figure.

In short ask Zen to provision the line at a 256(288) speed.

--
Mark


Have just done that - they are passing the request to BT Wholesale - I still
think it is odd that BT did not suggest that solution themselves... (Zen did
not want to try it free of charge without confirmation from BT that 512
would not work any better, which they now have.)

Thanks!
TM



 




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