Cracking noise margin

http://home.clara.net/jrm64/images/snr.png

What's that all about then

Netgear DG834G

Just got a 2MB regrade yesterday, I was surprised it passed BT due to my
SNR being consistantly over 45db and a very low noise margin when I was
on 1MB. However everything seems to be ok, getting good speeds during
the day, but last night it was very erratic, this morning back to
normal. Maybe contention kicking in, never had a problem before with
512 or 1MB.

--
Regards
James[M]

In article <(E-Mail Removed)>, (E-Mail Removed)
says...

> http://home.clara.net/jrm64/images/snr.png
>
> What's that all about then
>
> Netgear DG834G
>
> Just got a 2MB regrade yesterday, I was surprised it passed BT due to my
> SNR being consistantly over 45db and a very low noise margin

That should be attenuation over 45db

--
Regards
James[M]

James <(E-Mail Removed)> wrote in
news:(E-Mail Removed):

> Just got a 2MB regrade yesterday, I was surprised it passed BT due to my
> SNR being consistantly over 45db and a very low noise margin when I was
> on 1MB. However everything seems to be ok, getting good speeds during
> the day, but last night it was very erratic, this morning back to
> normal. Maybe contention kicking in, never had a problem before with
> 512 or 1MB.
>

That huge figure just means it's gone into negative territory - it's
interpreting the sign bit as a number. God knows how you can get negative
SNR margin though... I used to get that on a DG834G too - SNR margin
varies wildly. SNR margin on my current router (Speedtouch 580) doesn't
vary so much.

--
Phil
http://www.philipchung.co.uk/

On Wed, 14 Sep 2005 11:21:47 +0100, James <(E-Mail Removed)> wrote:

>What's that all about then
>Netgear DG834G

the answer is in the question :-)

>Just got a 2MB regrade yesterday, I was surprised it passed BT due to my
>SNR being consistantly over 45db and a very low noise margin when I was
>on 1MB.

and now its negative, but the Netgear web page screws up the display
of a -ve number.

Time for a bit of faceplate filtering or other wiring hygiene I
suspect.

Phil
--
Tiscali - dialup speeds at Broadband prices, see
http://bbs.adslguide.org.uk/postlist...&Board=tiscali

AOL - the unlimited ISP of choice for heavy downloaders.

In article <(E-Mail Removed)>,
(E-Mail Removed) says...

> On Wed, 14 Sep 2005 11:21:47 +0100, James <(E-Mail Removed)> wrote:
>


> Time for a bit of faceplate filtering or other wiring hygiene I
> suspect.


Thanks, I've actually got a faceplate, it's the original one from the
original install in 2001, prior to getting the 2MB regrade I tried
allsorts to improve the SNR, even plugging the router directly into
faceplate, cutting out the extension. It didn't make any difference.

My SNR varied wildly from 01 to 31db when on 1MB, I've been monitoring
it for a few weeks now. When it drops into single figures a router
reboot normally gets it back up to 20+db. I'll give it a restart a
little later on.

Thanks
--
Regards
James[M]

In article <Xns96D17838EAFF0pelhamnet@127.0.0.1>, (E-Mail Removed)
says...

> James <(E-Mail Removed)> wrote in
> news:(E-Mail Removed):
>

> That huge figure just means it's gone into negative territory - it's
> interpreting the sign bit as a number. God knows how you can get negative
> SNR margin though... I used to get that on a DG834G too - SNR margin
> varies wildly. SNR margin on my current router (Speedtouch 580) doesn't
> vary so much.

Thanks for that, I'll take these figures off the router with a large
pinch of salt methinks


--
Regards
James[M]

In an earlier contribution to this discussion,
James <(E-Mail Removed)> wrote:

> http://home.clara.net/jrm64/images/snr.png
>
> What's that all about then
>
> Netgear DG834G
>
> Just got a 2MB regrade yesterday, I was surprised it passed BT due to
> my SNR being consistantly over 45db and a very low noise margin when
> I was on 1MB. However everything seems to be ok, getting good speeds
> during the day, but last night it was very erratic, this morning back
> to normal. Maybe contention kicking in, never had a problem before
> with 512 or 1MB.

If you *really* had an SNR of that, the signal would be at a few megavolts!

Does your router have a status page which reports CRC and other related
errors? If so, have a look at that when the speed drops, and see whether the
error rate has suddenly gone up. The throughput speed can drop dramatically
if each frame has be sent umpteen times before arriving intact.
--
Cheers,
Tim
______
Please reply to newsgroup. Reply address is invalid.

In article <(E-Mail Removed)>, (E-Mail Removed) says...


> Does your router have a status page which reports CRC and other related
> errors? If so, have a look at that when the speed drops, and see whether the
> error rate has suddenly gone up. The throughput speed can drop dramatically
> if each frame has be sent umpteen times before arriving intact.


There does not appear to be anything on the router to monitor errors
[not that I can see anyway]. I've been doing some large downloads from
8am till 2pm, and have been getting a sustained 220K/Sec give or take a
a bit. Will try again this evening out of curiosity.

Just rebooted the router and my noise margin is now 21db, that's more
like it

--
Regards
James[M]

On 14 Sep 2005 14:56, James <(E-Mail Removed)> wrote:

>There does not appear to be anything on the router to monitor errors
>[not that I can see anyway].

One would hope it is in there somewhere... The Ebuyer sub-25 quid units
I have in use (and the Dabs Value ones) using Conexant hard/software do
provide such stats, but having said that, the more expensive kit may be
"hiding" the information, or one has to use Telnet to see it, perhaps ?


--
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