Noise margin vs. speed

I recently upgraded my ADSL conneciton from 500kb to 2Mb. From what
I'd read here, I expected the noise margin to be reduced by about
12dB, but in fact it's barely changed (from 31.0dB to 29.5dB). I see
that the output power has increased from 16.5dBm to 19.0dBm - does
this explain it?

-- Richard

Richard Tobin wrote:
> I recently upgraded my ADSL conneciton from 500kb to 2Mb. From what
> I'd read here, I expected the noise margin to be reduced by about
> 12dB, but in fact it's barely changed (from 31.0dB to 29.5dB). I see
> that the output power has increased from 16.5dBm to 19.0dBm - does
> this explain it?
>
> -- Richard

Doubt it, I would personally wonder about the accuracy of the readings
your router is giving you...

On 7 Dec 2005 21:02:58 GMT, (E-Mail Removed) (Richard Tobin)
wrote:

> From what
>I'd read here, I expected the noise margin to be reduced by about
>12dB, but in fact it's barely changed (from 31.0dB to 29.5dB). I see
>that the output power has increased from 16.5dBm to 19.0dBm - does
>this explain it?

31 was probably a maximum displayable value (binary), the actual might
have been 39 dB - lose 12 from that then add on 2.5 for the extra
power and bingo, 29.5 dB.

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.

>I recently upgraded my ADSL conneciton from 500kb to 2Mb. From what
> I'd read here, I expected the noise margin to be reduced by about
> 12dB, but in fact it's barely changed (from 31.0dB to 29.5dB). I see
> that the output power has increased from 16.5dBm to 19.0dBm - does
> this explain it?
>
> -- Richard

It could be that your ISP had your line provisioned at 2Mb anyway, and
was just limiting it to 512 from their end - There are a few ISPs who do
that (including AOL). Obviously, there would be no change in noise
margin etc if this has been the case.

In article <(E-Mail Removed)>,
Phil Thompson <(E-Mail Removed)> wrote:

>31 was probably a maximum displayable value (binary), the actual might
>have been 39 dB - lose 12 from that then add on 2.5 for the extra
>power and bingo, 29.5 dB.

Possible, but given that it can do .5dB I would have expected the maximum
to be 31.5dB...

-- Richard