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SNR Of zero

Gel
Seasoned Pro
Posts: 1,423
Thanks: 142
Fixes: 12
Registered: 02-08-2007

SNR Of zero

What causes a zero figure; never seen before? CN21 long line.

 

4. Board version: Plusnet Hub One
5. DSL uptime: 0 days, 10:27:59
6. Data rate: 910 / 3419
7. Maximum data rate: 917 / 3228
8. Noise margin: 6.4 / 0.0
9. Line attenuation: 36.7 / 61.7
10. Signal attenuation: 36.3 / 57.2
9 REPLIES
Community Veteran
Posts: 19,099
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Registered: 31-08-2007

Re: SNR Of zero

Has it ever had a different value at all? Have a look in the event log and see if there are any figures there when sync was achieved.
If no and none, then buggy firmware (or deliberately blocked). There was a time when the HH5A did not give any figures when used on ADSL. I'm sure someone mentioned that more recent firmware remedied that. And in case you are now wondering about firmware updates, it's a case of be patient and it will happen when it happens if there is one!

NorthPole
Aspiring Pro
Posts: 255
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Registered: 05-07-2013

Re: SNR Of zero

Happened to me once with a TP-Link router - not sure how it arises, but cured by a reboot!

Superuser
Superuser
Posts: 10,411
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Registered: 22-08-2007

Re: SNR Of zero

A zero SNRM could be correct if there is a lot of noise present.  Is the figure ALWAYS ZERO whenever you look?  If yes, then AO's buggy software is the likely answer, however if it is variable then there's a source of interference to be searched for! Buck2

A reboot of the router does not so much fix an issue such as this, but rather just masks the issue.  A resynch will always deliver the target SNRM - that might be at the expense of a slower synch speed.

For what its worth, I have seen routers report negative SNRM (up to -2dB which can be reported as a really big number) and still keep trucking.  I suspect that has been down to buggy software or an aberration of how the router has calculated the margin.

Community Veteran
Posts: 19,099
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Registered: 31-08-2007

Re: SNR Of zero

The implication of Gel's post is that it's permanently on 0.0   I doubt very much that sync would be maintained with a varying value that was reaching 0.0 for periods of any duration long enough to capture such an image from the Helpdesk page.

On the basis of the other figures in the stats, it's highly improbable that there is any interference at all.

Community Veteran
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Registered: 10-06-2010

Re: SNR Of zero

Some modems may get "stuck" in the sense that once the SNRM figure hits 0, goes negative or displays some really big number misrepresenting a negative number, then that will be the only figure they display until the DSL connection drops and re-connects.

A negative SNRM figure could also be correct if there's a lot of noise present.

Community Veteran
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Registered: 10-06-2010

Re: SNR Of zero

There were also some stats with a SNRM of 4.4 earlier: previous stats

Community Veteran
Posts: 19,099
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Registered: 31-08-2007

Re: SNR Of zero

Whilst there is absolutely nothing incorrect about what you've said, it is also highly improbable with the Hub One unless it's faulty which is a possibility.

Community Veteran
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Registered: 31-08-2007

Re: SNR Of zero

To add further to the above, I'm not sure why Gel started a new thread when continuing the previous one would have been more sensible with all the relevant history in one place.

@ejs Do modems with Lantiq chipsets commonly report negative SNRMs whilst managing to hold the connection?

Community Veteran
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Registered: 10-06-2010

Re: SNR Of zero


Anotherone wrote:

@ejs Do modems with Lantiq chipsets commonly report negative SNRMs whilst managing to hold the connection?


I don't know, sorry.

In general though, if the SNRM is really zero or negative, the error rate is likely to be much higher than what it would be with a more normal SNRM, which could result in the Internet connection being somewhere between much slower than usual to completely unusable.

On the other hand, if the SNRM is displayed as zero, but the Internet connection seems completely fine and running at full speed, then it would look more like some bug with displaying the SNRM.