Questions to do with Noise Margin

Soldato
Joined
25 Jul 2006
Posts
3,529
Location
Taunton
for the past few months we have been having a lot of problems with out phone line and internet connectivity, normaly the lack of a internet connection and i think i have found the culprit. a lot of the time our noise margin is less then 10 which i have read to be pretty awful

6dB or below is bad and will experience no synch or intermittent synch problems
7dB-10dB is fair but does not leave much room for variances in conditions
11dB-20dB is good with little or no synch problems* (but see note below)
20dB-28dB is excellent
29dB or above is outstanding

questions i have is how does this noise level fluxuate (i.e. what would cause it to go up and down)?
would a phone being on dial tone increase the noise level?
is there any way i could improve this number?
 
I'm presuming your on adsl max?
Post your stats from your router/modem.
That table only applys to fixed line products e.g 512 Kbps, 1 Mbps, 2 Mbps
Due to the way adsl max works the target snr always starts at 6 which is perfectly normal as it means your squeezing as much out of the line as possible.
Everyone's snr takes a slight hit usualy at night due to more interference/the ground being warmer and so on.
The length of the line and quality of the cable from your premises to the exchange affect it lots too which is out of your control.

The phone won't really affect things provided your using a decent filter.
First thing you can try is taking the front off your master socket and plugging your router straight into the test socket.
If that improves your connection stats that will mean your internal wiring/extensions are to blame.
Also take a look here which is well worth doing for the small time it takes to do.
 
cheers for the reply, the only reason i ask about the phone is if my connection drops for severaly hours which it normally does daily, if i leave the phone on dial tone it will connect, but then obviosuly no-one can call as line will be engaged.

i've followed that guide before and it makes no difference to the state or my connections, just like plugging the router straight into the test socket doesnt gurantee a connection.

ADSL Link Downstream Upstream
Connection Speed 864 kbps 416 kbps
Line Attenuation 15.5 db 31.5 db
Noise Margin 14.8 db 14.0 db

thing is the noise started off as 7.something then when the page refreshed 5 seconds later it had doubled. any reason for that?

and yes meant to be on 8MB

edit: heres some more that i took last week
Date: 26th July 2007
Time: 19:17:56

ADSL Link Downstream (Kbps) /Upstream (Kbps)
Connection Speed 160 /416
Line Attenuation(db) 52.0 /31.5
Noise Margin(db) 5.1 /13.0
Speed Test 138 /285

Date: 26th July 2007
Time: 20:38:51

ADSL Link Downstream (Kbps) /Upstream (Kbps)
Connection Speed 1600 /416
Line Attenuation(db) 50.0 /31.5
Noise Margin(db) 22.0 /13.0
Speed Test 1371 /328

Date: 30th July 2007
Time: 01:54:01

ADSL Link Downstream (Kbps) /Upstream (Kbps)
Connection Speed 1728 /416
Line Attenuation(db) 49.0 /31.5
Noise Margin(db) 25.6 /14.0
Speed Test 1486 /352

Date: 30th July 2007
Time: 21:54:52

ADSL Link Downstream (Kbps) /Upstream (Kbps)
Connection Speed 416 /416
Line Attenuation(db) 49.0 /31.5
Noise Margin(db) 7.6 /13.0
Speed Test 353 /297

Date: 30th July 2007
Time: 22:21:22

ADSL Link Downstream (Kbps) /Upstream (Kbps)
Connection Speed 5600 /416
Line Attenuation(db) 48.0 /31.5
Noise Margin(db) 10.8 /13.0
Speed Test 4822 /342

Date: 31st July 2007
Time: 19:02:17

ADSL Link Downstream (Kbps) /Upstream (Kbps)
Connection Speed 832 /416
Line Attenuation(db) 50.0 /31.5
Noise Margin(db) 2.3 /14.0
Speed Test 722 /340

Date: 1st August 2007
Time: 22:26:59

ADSL Link Downstream (Kbps) /Upstream (Kbps)
Connection Speed 512 /516
Line Attenuation(db) 52.0 /31.5
Noise Margin(db) 8.7 /13.0
Speed Test 442 /337

Date: 2nd August 2007
Time: 00:04:16

ADSL Link Downstream (Kbps) /Upstream (Kbps)
Connection Speed 288 /416
Line Attenuation 52.0 /31.5
Noise Margin 10.2 /13.0
Speed Test 248 /304
 
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Well if your still getting the same results with just the router plugged into the test socket on its own its not going to be your phone.
I'm fairly sure theres a physical fault on your line somewhere between your house and your exchange as the huge changes in your line attenuation should never ever be happening like the results you,ve posted. Its probaly a loose joint somewhere causing it all.
I don't even think a crap/faulty router could cause things to be as bad as what your line is at the moment though thats the last thing you could try ;/
Get on to your isp and quote them the info you recorded from last week so they can send out an bt open reach engineer to fix it once and for all.
 
thing is this has happened with 2 different isps, 2 different routers, 2 different sets of internal cabling (within the house), never the same any 2 days in a row, not weather controlled - so doesnt leave much else. im glad at least someone was able to diagnose it. but thing is a BT engineer has come out before and he couldnt find a fault.
 
Have you tryed the router in different rooms/plugged into different electric sockets to double check its not local interference/dirty electric power nearby causing it as a last ditch resort?
Apart from that I don't know what to suggest apart from hammering on at your isp even more to get bt open reach engineers out again, again and again till its fixed. Quite often adsl faults are not found first time by them so keep at it.
 
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when you say that my line attentuation shouldnt flux that much are you saying that with reference to the very 1st reading in the post above of 15.5 as i've heard that is a bug with the router that does sometimes happen or are you actually referring to the fact that it fluxuates from 48-52?
 
Even if thats a bug for the 15.5 no the 48-52 change is pretty large and should not be happening as often as what your line is doing.
Same goes for your sync rates as thier all over the place too and are quite shocking.
Its a long long shot but have you thought of trying a decent mains conditioner as your usual belkin surge protector etc is no where near as good at reducing rfi/dirty mains power from interfering with the adsl.
 
you think that it may be poor electrical connection causing the changes in connection statistics?
 
I still personaly think its going to be a fault somewhere on the line from your house to the exchange or in the cabinet box near by but yeah theres a small remote posibility it could be something as silly as your boiler etc causing some of the problems or a hell of a lot of rf interference in your house/nearby from someone using radios/rowing machines/street lights etc.
Someone I know posted about bad sync rates/disconnections and it turned out it was his boiler causing it when it clicked on and off.
He fitted a mains conditioner on the plug his router used and it fixed his problems.
Keep on at your isp and get bt out a few more times before considering getting one as it might not help in the slightest.
I can't link it for obvious reasons but do a google for Tacima 6 Way Mains Conditioner.
If you do decide to get one, worst case scenario your have a spare 6 way Mains Conditioner/surge protector out of it which you can always put to use.
 
ok well thank you very much for the advice, ill get back to you once i have heard back from sky bout sending out a BT engineer, hopefully that will be tomorrow.
 
right an update: Have contacted both Sky and BT, BT have sent me one email back saying that they will try to help, this was 2 days ago and have not heard from them since, i 1st contacted them a weekago. Sky on the other hand has not contacted me at all which i find appauling.

but i have some more symptons to add to my list, when our wireless phone is used it cuts off the internet connection although the line is filtered twice, once at the master socket and once in the kitchen socket, and yet it still does this. could the seconds filter be interfeering with the 1st?

i need to test to see if it does it with the wired phone in my room, so back shortly with another update.
 
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