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Downstream SNR

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Downstream SNR

Hi guys ,since i regraded to 2mb from 1mb my downstream snr dropped from 28db to 13db.

Nothing has changed my end. whats going on ?


2mb line
Downstream Rate: 2272 kbps
Upstream Rate: 288 kbps
Current Noise Margin: 13.0 dB (Downstream), 31.0 db (Upstream)
Current Attenuation: 29.0 dB (Downstream), 16.0 db (Upstream)
Current Output Power: 7.1 dB (Downstream), 11.6 db (Upstream)

1mb (original activation speed)
Downstream Rate: 1152 kbps
Upstream Rate: 288 kbps
Current Noise Margin: 30.0 dB (Downstream), 31.0 db (Upstream)
Current Attenuation: 29.0 dB (Downstream), 16.0 db (Upstream)
Current Output Power: 13.9 dB (Downstream), 11.4 db (Upstream)

for some reason my downstream has lost a lot of power, is that what happens when the upgrade you.

13db is borderline for a nice stable error free connection isn't it.

Moderators note by John (johnessex) All capital title reduced to lower case.
7 REPLIES
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Downstream SNR

This is indeed correct.

The higher the speed, the more your SNR value will drop.

Attuation should remain constant, whilst SNR will change depending on the sync rate of your line. The SNR value can be used to tell how stable your line may be at X speed.

The SNR quoted is OK for 2Mb, but may pose stability problems. There is little or nothing that can be done or investigated, unless you are actualy seeing connection problems as a result.
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ahh ok.

I thought as much.

maybe if i re-terminate my phone wires i mught go up a db or 2.

EDIT:

undid all my wires reterminated connection to master socket and BT point, managed to get anohter db...so now running 14bd down snr.

thats fine..

no errors from router :-)
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Downstream SNR

any ideas?
since being upgraded to 2mb i have had probs with dropped connections, first off i thought i would shift the usb modem to a powered usb hub, this helped a bit for a day or two but now the problem has reappeared, evrything was fine before the upgrade, I tried a router and got the following info:
downstream snr 14.9
up 27.0
Line attenuation 48.1
up 30
data rate down 2272
up 288
don't mean a lot to me but maybe someone can help.

any advice is welcomed
Thanks
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Downstream SNR

Line attenuation of 48.1 is too high for a 2mg service I was told it had to be 43db or lower thats why you are having probelms. Ring PN customer services or raise a ticket.
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Downstream SNR

Is there a table of acceptable SNR and attenuation vs. line speed?
We're on a long 1Mb line, getting 63dB attenuation and less than 6dB SNR margin. We get periods of disruption - is that to be expected and would we be better off downgrading to 500k?

Anahata
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Downstream SNR

Go to this post. All you need to know his here
http://portal.plus.net/central/forums/viewtopic.php?t=12400
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Downstream SNR

Thanks. That confirms that our line is below limits for 1Mb, which was not made clear by my reply from CS when I raised a ticket a few weeks ago.

Anahata