Tech Support > Computers & Technology > Internet & Broadband > Can someone explain about noise margins?
Can someone explain about noise margins?
Posted by BJH on December 5th, 2006


Hi all

I've just changed from a fixed 512k connection to 8M connection, I assume
this is what is called ADSL Max? I won't bore anyone with my reasons for
changing other than it got me away easily from Legend Communications (who
won't release MAC codes).

My noise marging with the 512K connection tended to be around 15dB

Since my new speed went 'live' today I've noticed that the noise margin has
dropped to 6dB.

I assume this is a function of the different connection type?

My current figures are:

Downstream
Noise Margin: 6dB
Output Power: 20dBm
Attenuation: 35dB

Upstream
Noise Margin: 26dB
Output Power: 10.5dBm
Attenuation: 17.5dB

Upstream: 448Kbps
Downstream: 6816 Kbps

Any comments/explanation on the above figures would be greatly appreciated.

--
Regards
Barry

Posted by K A Nuttall on December 5th, 2006


BJH wrote:

Ugh. Legend. Nightmare. Enough said.

BTW aim to keep the s/n ration at 6dB or above. They do this by
lowering the sync speed until the line is stable. S/N ratio is an
indicator of stability, so they target this value initially at 6dB, and
increase it in stages, if the disconnection rate doesn't improve. They
also set Interleave on problem lines.

As long as your line is stable, 6dB is fine. And you're probably
getting the best speed possible from your line.

--
K A Nuttall
www.yammer.co.uk
Re-type the e-mail address how it sounds, remove .invalid

Posted by Peter Crosland on December 5th, 2006


You are getting close to the theoretical maximum of 7MB. The up to 8MB is a
myth because with overheads etc. the real up to is about 7.1MB or
thereabouts,

Quite a good explanation of ADSL MAX can be found here.

http://portal.plus.net/support/broad... a8ba50191b51


Peter Crosland



Posted by BJH on December 5th, 2006


On Tue, 5 Dec 2006 11:42:11 -0000, Peter Crosland wrote:

Thanks Guys, that's good. I had a heart stopping moment about 15 mins ago
when the router 'lost' the connection.

I was logged on with the Legend user ID and password, but all I had to do
was switch off for a few minutes and reconnect with the new UserID and
password.

Now all fine and thanks again for the very clear explanations.

--
Regards
Barry

Posted by green on December 5th, 2006



"BJH" <barryh@kentra.co.uk.invalid> wrote in message
news:1pe0d4131a8pu$.dlg@ID-158254.user.individual.net...


Posted by green on December 5th, 2006



dont sweat it m8

mine goes every other day but alwsy comes back with an on/off router like
you did

bt "remotely stabilised mine" - from s/n of 6.6-7.5 - line going every
couple of hours

to sn above 10 sometimes 14 and a couple of days out of it

so they can "tweak" things

speed is down a bit but not fatal

i can only get 2.something meg but it will do me



"green" <green@green.com> wrote in message
news:1yddh.132864$Vu4.131608@newsfe10.phx...


Posted by Richard Tobin on December 5th, 2006


In article <45755b13$0$8717$ed2619ec@ptn-nntp-reader02.plus.net>,
Peter Crosland <g6jns@yahoo.co.uk> wrote:

The figures quoted also include those overheads, so he is still over a
megabit away from the maximum. If he had a perfect line, it would show
the downstream as 8128Kb/s.

-- Richard
--
"Consideration shall be given to the need for as many as 32 characters
in some alphabets" - X3.4, 1963.

Posted by NoNeedToKnow on December 5th, 2006


On 5 Dec 2006, "Peter Crosland" <g6jns@yahoo.co.uk> wrote:

or maybe (since the pn_session information is meant to be unique)
http://portal.plus.net/support/broad...ax_guide.shtml
(which will fit on newsreaders a bit better without wrapping/breaks).


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