Tech Support > Computers & Technology > Internet & Broadband > Noise Margin Problem
Noise Margin Problem
Posted by naza on February 25th, 2007


My broadband with sky has been running for 3 months but in the last
month i have been having problems with dropouts in the connection. It
goes like this. My normal Line attenuation is 50db downstream and
noise margin when my broadband was activated was around 8.0db. But
now, rarther then the noise margin increasing it decreases. it goes to
about 4.0db before i dont get a connection to anthing from my PC. So i
cant browser the internet, skype looses its connection and all that.
Sometime it survives until 3.5. When it hits 2.0 db it looses it IP
address and then the internet light goes off. Does anyone know what
the problem could be. I am fairly certian that the problem lies within
my house but not quite sure because it did run fine at first. At the
main socket i dont see much of an increase in speed but siginal is
good and noise margin is constant so no cut offs. The setup is as
follows: from the main socket one cable runs to a junction box. from
there 2 cables leave. one goes upstairs and the router is connected
there. The other runs into the living room and then from the living
room into a socket in the kitchen. So any ideas on what the problem
could be and a solution.
thanx

Posted by kraftee on February 25th, 2007


naza wrote:
What speeds you get would help.

A wild stab in the dark would be check all equipment attatched to the
telephone line is filtered & you could try removing the bell wire
connection from the back of the front plate on your master socket
(connection 3 if you didn't know). You could try walking around the
house with a pocket AM radio tuned to Radio5 to see if any electrical
equipment is starting to broadcast excessive RF but you may get a lot
of false leads before you hit the 'hotspot', that is if you have one
at all (remember it doesn't have to be in your house, it could be
anything upto a mile away).

It's perfectly normal for the SNR to drop (more noise compared to the
adsl signal) in the evenings & during electrical storms rebooting your
router would make adjustments for you, it would reduce your speed, so
you require less bandwidth which would bring the SNR up again.



Posted by Eeyore on February 25th, 2007




naza wrote:

No surprise there !

Have you fitted more CFLs recently or anything else that might radiate RF
electrical noise ?

Is there a pattern to the drop-outs ?

Graham


Posted by m on February 26th, 2007




naza wrote:

Looks like you have the problem faced by so many people.
Really anything in the house connected to your line can cause problems.
I recently improved a friend's (SKY)setup from a 130kb connection to
over 4Mb.
He had the modem in a phone socket half way around the house on cabling
which included the 'old' BT blue/orange/green/brown unpaired cable. This
is the death to broadband as the pairs are not laid in the cable
correctly. Even though he had filtered everything correctly, the problem
remained.
By unplugging the main socket faceplate and connecting the modem there
(with just one filter) and then installing a filtered faceplate on the
main socket we got up to full speed. Then I installed a 10m RJ11 cable
(obtainable from Maplin - don't be tempted with the hundreds of pounds
versions from P* W***d) from there specially direct to his PC with no
noticeable service degredation.

Brilliant now.

Mike


Posted by Eeyore on February 26th, 2007




m wrote:

Yes, cable that isn't twisted pair can really mess things up. Also if you have
entensions, the ring circuit will also 'unbalance' the ADSL signal.

Graham


Posted by naza on February 26th, 2007


Here are the speeds that i am getting.

ADSL Link Downstream Upstream
Connection Speed 2336 kbps 416 kbps
Line Attenuation 54.0 db 31.5 db
Noise Margin 10.3 db 14.0 db

I have subcribed to the 8meg service with sky. the max my line can do
is 5mb based upon the quailty and distance from the exchange. If that
is any help. No pattern in drop out. I do however use skype a lot and
normally be connected to the office for calls that last around and 1hr
sometimes and normally the sign that its about to go is that i get
breaks in the voice.
No new CFLs or products in the house.


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