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Broadband Disconnects


Broadband Disconnects

A bit of advice if i May.

I have a zoom x2 adsl modem with a Belkin Pre-M Mimo router(wireless).

I am currently (as in the last week/2 weeks) experiencing lots of disconnects particualry in the evenings (the only time i use it) though.

My snr and Attuation were always at the limits (Snr around 7-10 and attenuation 50-60).

However in the last 2 weeks i am getting disconnects regulary - sometimes it has trouble reconnecting and holding synch and sometimes it just reconnects slower, and slower until it reaches the max my line is guaranteed (512, though i can often get 1mb synch).

I've been asked to do the standard checks - (when i had this problem a year ago i did all the standard checks - it did not make any difference, i gave up reporting it and a few weeks later the problem seemed to disappear. I am certain its not the filters. I am fairly confident its not the equipment though i have no way of testing that anyway.

Plugging into the master socket in the past increased my snr to around 15-20 but increased attenuation to 65/70 - however I cannot test the line here as to test it properly i would need to leave it for a few weeks, and our master socket is in our hallway which has no power sockets and is already narrow. It would also mean trailing a lot of wires for the power and for my parents pc to get access to the internet (they connect via ethernet).

In any case, this problem has *only* happened in the last week/2 and on 1 occasion i lost connection around 11pm, and when i checked in the morning it had had 121 connection attempts. Due to my live being interleaved /maxdsl'd I expect 2-3 dc a day, but 20/30 can't be right?

Any help appreciated.
Plusnet Staff
Plusnet Staff
Posts: 12,169
Thanks: 18
Fixes: 1
Registered: 04-04-2007

Broadband Disconnects


If you are getting that many disconnections then I would very much recommend test it from the master socket, you should notice in a few hours whether it makes any difference or not. The reason being that if we raised it as a fault and an engineer came out and found the wiring to be the cause they may charge you a call out fee.

If you have a router then there's no need to take the PC as well, if the router logs the disconnections then just connect it up to the master socket for a few ours in the evening and see if it disconnects. If it logs the same amount of disconnections you know it's not the wiring, if it stays connected then it probably is the wiring.

Chances are though that the line is just sync'ing at too high a rate which is why it keep decreasing in speed when it loses sync. Increasing the target SNR to 12dB may help, although it will decrease the speed a little to improve the stability should there not be any problems with the wiring.

Broadband Disconnects

If you snr goes up that much at the master socket it suggest that there is something wrong with your wiring as there should be very little difference.The quality of the filters can make a big difference as well a lot of old ones were designed for 512K not 8 meg and changing to a new one can make a massive difference I bought new ones and it made 8bd difference.

Can you disconnect the extensions? If you can try a extension cable they are cheap enough and see if you get better results.

Has anything changed recently like any new electrical equipment added moved etc? You can sometimes get changes due to the weather or temperature.
Posts: 25
Registered: 22-08-2007

Broadband Disconnects

I have the same problem raised query with support and they strengthned my signal so far stability is good but speed is halved. Getting 4mb connect speed when its usually 7.7/6, my Snr seems high to yours I live under 2km from my exchange.

voyager 105 reports

down 4096 up 256
snr local is 25 remote 12
attennutation local 25.5 remote 12.5

Still testing connection I'll see by Monday if things improve.
I will try new filters but I don't think it will be any major difference as all was fine until this month.

Broadband Disconnects

Looks like CSC increased your target SNR to 12, as you say this will reduce your sync rate but should increase your stability.

The below is hugely simplified (and probably flawed) summary of noise on digital transmissions-

If you can imagine any kind of signal, be it telephone, television, broadband, radio etc. then there will be noise or interference on the transmission medium. Digital transmission can usually ignore this interference as the signal will be one of two discrete values, and these can usually be picked out despite any noise.

If you want to imagine this visually, a perfect digital signal should be a squarish wave like this-

1) Low level, 2) High level, 3) Rising edge, 4) Falling edge.

In theory this should be perfectly square, but no electronics are capable of instantaneously changing voltage.

In practice a digital signal might look a bit like this-

Although there is obvious noise, a receiving device can still see "level changes" between the two states and should be able to filter for a good quality signal.

The problem comes when the SNR (Signal Noise Ratio) on the signal drops so low that the amplitude (signal strength) of the noise is too close to that of the signal. This makes it hard for for the receiving device to isolate one from the other and spot genuine level changes.

Under these circumstances any additional noise spikes will probably corrupt the signal and cause your broadband to lose sync.

PlusNet are able to set a "target SNR" for your line which will force the exchange to sync at a speed where noise amplitude is sufficiently reduced over that of the signal for your modem/router to tell them apart. Unfortunately this also has the effect of reducing sync speed as alphakk1 states.