Few questions about SNR margin

Hi there,
Sometimes router is opened or re-booted it begins with 30.3db SNR
margin which is great. But somedays it's opened it begins with 10.5db
SNR margin. And with the router stays opened after few days passes,
SNR decreases about low to 10db from 30.3db.

I want to ask:
1-Why does SNR margin value reduce/decrease after a few days with
router stays open steady without ANY reboot or turn off?
2-Is low SNR effect performance? (downloading speed)

Thanks in advance.

On Mon, 18 Jun 2007 02:34:28 -0700, kimiraikkonen
<(E-Mail Removed)> wrote:

>1-Why does SNR margin value reduce/decrease after a few days with
>router stays open steady without ANY reboot or turn off?

The SNR margin will go up and down at different times of day depending
on line noise. Usually there is more line noise in the evening so the
margin will be lower then.


>2-Is low SNR effect performance? (downloading speed)

The initial download speed negotiated will be based on whatever the
SNR is at the time, Thereafter that connection will be sustained at
that speed until line noise causes the SNR margin to drop below an
acceptable threshold (usually about 4) at which time the connection
will drop and have to be re-negotiated.


Jim.

On Jun 18, 5:14 pm, James Egan <j...@jegan.com> wrote:
> On Mon, 18 Jun 2007 02:34:28 -0700, kimiraikkonen
>
> <kimiraikkone...@gmail.com> wrote:
> >1-Why does SNR margin value reduce/decrease after a few days with
> >router stays open steady without ANY reboot or turn off?
>
> The SNR margin will go up and down at different times of day depending
> on line noise. Usually there is more line noise in the evening so the
> margin will be lower then.
>
> >2-Is low SNR effect performance? (downloading speed)
>
> The initial download speed negotiated will be based on whatever the
> SNR is at the time, Thereafter that connection will be sustained at
> that speed until line noise causes the SNR margin to drop below an
> acceptable threshold (usually about 4) at which time the connection
> will drop and have to be re-negotiated.
>
> Jim.

Is it normal decreasing SNR margin value day to day with no router
turn off?

"kimiraikkonen" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed) oups.com...
> On Jun 18, 5:14 pm, James Egan <j...@jegan.com> wrote:
>> On Mon, 18 Jun 2007 02:34:28 -0700, kimiraikkonen
>>
>> <kimiraikkone...@gmail.com> wrote:
>> >1-Why does SNR margin value reduce/decrease after a few days with
>> >router stays open steady without ANY reboot or turn off?
>>
>> The SNR margin will go up and down at different times of day depending
>> on line noise. Usually there is more line noise in the evening so the
>> margin will be lower then.
>>
>> >2-Is low SNR effect performance? (downloading speed)
>>
>> The initial download speed negotiated will be based on whatever the
>> SNR is at the time, Thereafter that connection will be sustained at
>> that speed until line noise causes the SNR margin to drop below an
>> acceptable threshold (usually about 4) at which time the connection
>> will drop and have to be re-negotiated.
>>
>> Jim.
>
> Is it normal decreasing SNR margin value day to day with no router
> turn off?

That's the idea, the speed will increase and the SNR margin will decrease to
a point where communications reliability begins to fall, and there it will
stop. I my experience this usually happens at an SNR mrgin of about 7dB.
If your line is intermittently noisy the speed will stay low and the SNR
margin remain rather higher, as being the best compromise.

-- Graham J

On Mon, 18 Jun 2007 10:49:51 -0700, kimiraikkonen
<(E-Mail Removed)> wrote:

>Is it normal decreasing SNR margin value day to day with no router
>turn off?

In a normal situation it fluctuates up and down. It shouldn't just
keep going down.

You shouldn't look at the SNR margin in isolation. Does it keep going
down while the download speed stays the same?


Jim.