SNR on Connection

[Tacitus]

Not iDNet related but could be of general interest.

I've just rebooted my router and on connection it showed the following:

noise margin downstream: 15 db
output power upstream: 11 db
attenuation downstream: 55 db

Within 5 minutes that had dropped to 11dB downstream and it remains around that for the rest of the day unless it gets hit by a sudden noise burst which forces a resync

A BT Speedtest shortly afterwards 09.53am gives the following:

Your DSL connection rate: 2304 kbps(DOWN-STREAM),  448 kbps(UP-STREAM)
IP profile for your line is - 1750 kbps
Actual IP throughput achieved during the test was - 1598 kbps

The profile should probably update to 2000 kps in the next few days.  I think 2290 is the trigger point.

Now the question!  Why does the snr suddenly drop from 15 to 11dB?  Is this simply a noisy line - although at present it's not showing any of the huge errors I sometimes get around morning and teatime'ish. 

At present, more often than not it manages to stay up for over 24 hours, occasionally it will manage a whole week!

[Rik]

The drop indicates there was even more noise on the line later than when you rebooted, Tac. At the time the modem negotiates a connection, it will get the best possible speed for its target noise margin and the prevailing noise conditions. After that, fluctuations reflect a change in ambient noise, sometimes giving a higher noise margin, sometimes lower. Some routers are more prone to wild swings, eg Netgear.

[Sebby]

Yep, definitely varying noise is the reason.

[Tacitus]

Yep, definitely varying noise is the reason.

Thanks Seb & Rik.  I thought that might be the case, although a quiet line test doesn't show any *obvious* noise.  In the past though it always started at 11dB dropping to 6 or so over the day.  I'm assured the target snr hasn't been fixed at a higher level, so on the assumption that is true (it came from the script monkeys) it must be the automatic system setting the higher level.  It is gradually getting worse though.

I'm on the lookout for a 2Wire at present to see if that makes much difference. I suspect it will, but how much remains to be seen.

Incidentally what does it mean if they are BNIB boxed?  Can't quite see the relevance of the Institute for the Blind, if that is the case.

[Rik]

We're not talking about audible noise here, Tac, but RF noise in the MW band. Hence you'll often see me recommending people wander about with a de-tuned radio to search for noise sources.

BNIB - best guess, brand new in box?

[Tacitus]

We're not talking about audible noise here, Tac, but RF noise in the MW band. Hence you'll often see me recommending people wander about with a de-tuned radio to search for noise sources.

I really must put my brain in gear.....  Given the state of the line I was looking for audible noise.  Or even listening for it.... 

BNIB - best guess, brand new in box?

Line I said, bit early yet for putting my brain in gear........     

Interesting the MW radio trick as this suggests quite a bit of noise from the modem itself.

[Rik]

Modems radiate some noise, but you're interested in the wiring up to that point more (but also check out the computer's power supply and the monitor).

[Tacitus]

Modems radiate some noise, but you're interested in the wiring up to that point more (but also check out the computer's power supply and the monitor).

I've ruled out most things but resiting the modem might be worth a try.  Inconvenient, but at least I'll have  covered everything.

[Rik]

Always worth a try, though it probably isn't going to solve the problem, unfortunately.

[Tacitus]

Always worth a try, though it probably isn't going to solve the problem, unfortunately.

I agree, but I can't say I didn't try.   

[kinmel]

SNR is a nightmare for some of us, mine yoyo s about all over the place. 

With an Attenuation of 59.4, my  present SNR is 8dB, sync'd at 4544 and yet by midnight SNR will be down to about 2dB, fortunately the good old 2700HGV usually manages to hang in there and keep the sync above 4512.

The 2700HGV is certainly worth a try. I would lend you one, but the  postage to you and back is about £10 and you can get one to keep from ebay for that.

Edit: On Ebay search for "Business Hub" as well as for "2700HGV"

[Rik]

You're doing better than me, Alan, I'm synced at 3488 on a 57db line.

[Glenn]

Twice the speed of mine, with a similar nm, mines currently 59.9

[Rik]

It makes you want to spit, doesn't it, Glenn.

[Glenn]

  I'm resigned to the fact my line won't get quicker.

[Glenn]

I might ask support if they can get BT to reduce the target margin down to 9 from 12 again

[Rik]

I'm resigned to the fact my line won't get quicker.

Me too - no point in worrying about it, my option is to move if I want a better performance.

[Rik]

I might ask support if they can get BT to reduce the target margin down to 9 from 12 again

I have mine pegged at 9, it seems to work best for me.

[g7pkf]

He's not with idnet. (well the original poster)

wonder what support he will get?   

mines set to 15

[Rik]

That is high.

Tac will get Demonic support, of course.

[Tacitus]

That is high.

Tac will get Demonic support, of course.

Ho ho!!

Are the BT BUSINESS HUB 2700HGV GATEWAY VERSION 2.0 the ones to go for?

[Rik]

They will do nicely.

[Tacitus]

They will do nicely.

Good!  I'm now the proud owner of the above - or will be when it arrives.  £21 - ostensibly brand new so it should be OK.

Expect more pleas for help in setting it up....   

[Rik]

Was that with carriage? It seems slightly high...

[Glenn]

Here is all you need to know to get it working http://www.idnetters.co.uk/forums/index.php?topic=8927.0