TELECOM 247

HI,

I have an ADSL line with BT. Were about 3 miles from the exchange, in a
fairly remote house out in the country.

Ive recently gone from a 512Kbps service to an up to 8Mb and after the
initial test fortnight got a princely speed increase to... 576kbps.

Ive changed the old Belkin modem for a Netgear DG834 which is supposed
to be good with noisy lines, and incidentally allows me to monitor the
line noise stats.

After watching it for a week or so, its obvious that the noise margin is
cyclic and much worse during the hours of darkness: I get around 14dB
margin +/- 2dB between 7:00 and about 15:30 then it drops off to 4dB
+/-6dB(!) for the rest of the time.

I know about extra noise during daylight hours due to the sun heating
things up, but I hadnt come across this one.

Any ideas on the cause, and even better a solution?

In any case, this line is mainly for business use during daylight, but
the abysmal nighttime noise levels have led to the 576kbps speed limit -
can anything be done to get this increased so I can get a decent speed
during the day (steady 12-14dB margin) but accept lots of dropouts at
night(-2-10dB margin)?

On 28/12/2007 10:05, PCPaul wrote:


Your fixed 512Kbps service would have always had a line rate of 576Kbps
anyway.


Christmas lights?

On Fri, 28 Dec 2007 10:05:15 GMT, PCPaul wrote:


Birds roosting on the overhead, thus putting strain on a joint etc.?

--
Cheers

Peter

PCPaul wrote:

The basic background RF signal is cyclical, which is demonstratable by
tuning in on a weak am radio signal during the day & then at night
(this led to the urban myth that the old Radio Luxembourg had a gian
dish on its roof causing the peak/trough effect). There is little
you can do about it other than make sure that there isnt a point of
weakness in your premises.

Has the line got any extensions on it? If so you could do the old
trik off removing the bell wire fron the back of the master (IDC 3) as
that can act like an aeriel picking up signals, feeding them back yo
your master socket & straight onto your DSL signal reducing your
bandwidth/speed. Other than that there isnt a lot more you can do,
that is other than turning off the router when not at work, so it only
syncs when you have the better SNR.

On Fri, 28 Dec 2007 10:24:56 +0000, Andy Burns wrote:


Hmm.. hadnt considered that one, but as far as I can see there arent
any near the run of the line, and none at all near the router/modem.

I guess Ill just have to wait and see about that one in the New Year!

On Fri, 28 Dec 2007 11:52:26 +0000, kraftee wrote:

I can try removing the bell wire.

I was under the impression that after the test period they set a
maximum for the DSLAM to even try and sync at, based on the line
characteristics. Ive never seen a connection at higher than 576K,
regardless of when it is first turned on.

In fact when I installed it it was during the day and the first set of
stats showed a nice steady 14dB noise margin but still a 576Kbps speed.

Is there anything else I could do to try and improve on that?

PCPaul wrote in message
news:vT3dj.69051$c 1.4515@text.news.blueyonder.co.uk...

Like you, I am about three miles from my exchange and use a DG834.

Maybe like you, I see the noise margin degrade during the evening period. At
6AM it is about PLUS 6dB, at 6PM it can be as low as MINUS 1dB.

Unlike you, my connect speed is 2.5 to 3.0Mbps - so maybe Im lucky and/or
you arent.

Id guess that the variation is due to crosstalk over the four or so miles
of cable, and that it gets worse in the evenings as that is when there is
more data traffic to crosstalk. I doubt that it is to do with actual
darkness as at this time of the year, 6AM is dark - plus that at the height
of summer, when 6PM is still bright daylight, the degradation profile is
just the same!

I got the DG834 for the reason you mention, and find that it works well down
to zero dB margin, but will fail, about every ten minutes, when the margin
becomes negative and so, initially, I tried to minimise how often I used the
system between 6 and 9PM. This wasnt too difficult as, like yourself, this
is primarily a work connection. If the line did drop, I would disconnect
next morning (disconnect via router dialog and then physically disconnect
the power lead and phone line from the router) for a couple of minutes and
then reconnect. This meant that I spent very little time with a poor
profile - and this seems to have stuck - hence my 2.5Mbps service. The only
other thing I did was to swap over the phone line pair. This makes quite a
difference to the drop rate here and has had the same effect for others.
Might be worth a try. (If it works for a while than reverts, BTW, swap them
again as - most likely - some oik has been up the pole/in the cabinet and
has re-swapped your pair!)

BTW, there is a bug in the DG834 software whereby it reports -1dB as
+2,147,483,648dB Noise Margin. If only!

My Line Attenuation is -53dB, what is yours?

HTH

On Fri, 28 Dec 2007 14:39:37 +0000, Peter Able wrote:


I use Routerstats Lite to monitor it - it does go negative sometimes,
and it does seem to manage to hang on right down to 0dB. I guess the
reputation it has for being good on noisy lines is deserved!


Thatd be right :-(


I havent seen it in summer, so I cant tell. It definitely starts to
drop at about 15:30 and stays very poor right through to 07:00 though. I
can see kids back from school causing more traffic from 15:30 until most
adults give up by about 02:00, but surely there arent that many people
online from 02:00 to 07:00, and Id expect P2P traffic to be fairly
constant...


Ill try that.


Presumably swap the wires in the pair, not try and switch to the spare
pair in the BT cable?

Ill give it a go.


Seems to be dead at the moment (I set it up to allow log in remotely from
my IP only, and on a weird port number..) so I cant find it. I have a
feeling it was in the high -40s.


I guess Ill have to keep resetting it first thing in the morning and see
if the rate increases. We wanted to up the speed so we could start using
VoIP for some calls, but its too crap for that when its running like
this...