Thread: Does noise margin change depending on speed profile?

Quote: Originally Posted by dub45 Yes in theory but don't forget his internal wiring could be in a mess True, but surely that would deteriorate the signal and up the noise?

The op has not told us exactly what the issue was that lead to UTV changing his profile. The attenuation figure would suggest that he is living very close to the exchange. The SNR figure would suggest that give that proximity to the exchange there must be an issue of line quality somewhere. That problem may be contributing to the already low snr figure.

Quote: Originally Posted by Grommet Modems are normally set to "Rate Adaptive" mode by the operator, which means that the modem will be set to a maximum speed (probably 7Mbps in this case) but can re-synch at lower speeds if noise is introduced onto the line. It sounds as if there is some RF interference somewhere that is causing the op's line to degrade on occasion. I doubt if UTV (or eircom) have actually provisioned...

Quote: Originally Posted by Karsini I've seen some people's modems constantly sync at 6144/512 or 5120/512 so this would make me think that there are multiple profiles. I'd just find it highly unlikely that a modem would, on its own accord, sync at exactly 5 or 6 megs. It depends on the modem manufacturer. The various synch speeds are defined within the modem firmware. The max profile is set by the operator, the modem then...

Crosstalk would do nothing except lower signal margin. Aka it's not noticeable until the signal margin spikes down towards 0. The fact that the speed issues only appear in the evenings, and stop by 1am, means that contention/backhaul issues in some form or other are the problem. The line is grand. Btw, I've found the signal margin changes unpredictably when sync rate is changed. As good as the Kitz website is, the "rule of...

Quote: Originally Posted by Grommet Modems are normally set to "Rate Adaptive" mode by the operator, which means that the modem will be set to a maximum speed (probably 7Mbps in this case) but can re-synch at lower speeds if noise is introduced onto the line. It sounds as if there is some RF interference somewhere that is causing the op's line to degrade on occasion. I doubt if UTV (or eircom) have actually provisioned...

Quote: Originally Posted by Grommet EDIT: come to think of it - if your exchange was only enabled in June then there is no way the link between the DSLAM and the BRAS would be anywhere near full already. So almost certainly not congestion there. Absolutely . Another possibility and one that would be have been masked by the congestion upstream would be 'Crosstalk' . In other words too many people out your direction from the exchange...