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Drop in speed/sn ratio

frank39
Grafter
Posts: 118
Registered: 19-03-2009

Drop in speed/sn ratio

I have, in the last week or so, suffered a dramatic loss in download speed ( from ca 12M to less than 500k) on on or two occasions.  In each case it as been accompanied by a drop in s/n from ca 3 to 0.5 or less.  A router reboot or a disconnect/reconnect restores the normal conditions.  I have had a pretty solid connection for the last 9 months or so.
Is this something novel that I should worry about or is it just engineers working in my exchange.
I'm using an early TN582n router with 10.2.1.8 firmware.
Just noticed the service status report, I'm on exchange 01295 - is that the cause.
8 REPLIES
Community Veteran
Posts: 4,854
Thanks: 121
Fixes: 24
Registered: 14-07-2009

Re: Drop in speed/sn ratio

Quote from: frank39
Is this something novel that I should worry about or is it just engineers working in my exchange.

I'm afraid it is far more likely to be the former than the latter.  Does your router sync rate actually fall or just the download speed measured in a speed test?  Have you just put the Xmas lights up? 
frank39
Grafter
Posts: 118
Registered: 19-03-2009

Re: Drop in speed/sn ratio

Sync rate remains high and the ping is normal at under 50ms, just the S/N and the speed test falls, the fault appeared before the christmas lights went up.
Community Veteran
Posts: 4,854
Thanks: 121
Fixes: 24
Registered: 14-07-2009

Re: Drop in speed/sn ratio

I guess that your SNR drops so low that you get lots of errors so your effective speed becomes low although your router doesn't lose sync.  See if you can find something electrical in your house that will cause your SNR to increase if you switch it off.  I would start with the Xmas lights, just to be sure.   
frank39
Grafter
Posts: 118
Registered: 19-03-2009

Re: Drop in speed/sn ratio

Could it just be an old and tired filter?
And why does a disconnect/ reconnect fix it?  (Rhetorical question)
Community Veteran
Posts: 4,854
Thanks: 121
Fixes: 24
Registered: 14-07-2009

Re: Drop in speed/sn ratio

Quote from: frank39
why does a disconnect/ reconnect fix it?

Presumably because it forces the router back to its target SNR.
Quote from: frank39
Could it just be an old and tired filter?

Some electrical devices can work okay until they get too hot with use then start to malfunction.  But filters don't get hot and it they wear-out they don't recover - so a filter seems an unlikely culprit, given the symptoms. 
Plusnet Alumni (retired) orbrey
Plusnet Alumni (retired)
Posts: 10,540
Registered: 18-07-2007

Re: Drop in speed/sn ratio

Hi there,
Can't see any disconnections and your profile doesn't appear to have changed since at least October so it doesn't look like any sort of line fault. Is there any chance you could test an alternative router at all, or if not possibly test yours on a different broadband line to see if the same fault happens then? That would go a fair way to proving if it's the router at fault or not.
frank39
Grafter
Posts: 118
Registered: 19-03-2009

Re: Drop in speed/sn ratio

Thanks Matt,
I am minded to swap routers as you suggest.  I will wait until the fault reappears so that I can get a feel for the frequency before making the swap.  The alternative is a TG585v7,
Is the snr as displayed by the router a live reading of the current noise level or is it a value set elsewhere - that is can I use it to detect the addition/removal of a noise source in my house?
Frank
Community Veteran
Posts: 38,460
Thanks: 1,027
Fixes: 62
Registered: 15-06-2007

Re: Drop in speed/sn ratio

The downstream SNR is a live reading.
The upstream can be but isn't always