Strange cap (1333kbps) and just a coincidence the margin has turned out at 9dB I guess.
Surely such an unusual sync speed (1333kbps) can only be a result of syncing according to a target margin?
I'd understand if the sync was 1250 or 1500, but 1333kbps???
My lines set to 15.0 mbps however I sync at 15562 kbps, give or take a few kbps. it never syncs dead on a speed.
Sometimes, although rarely this occurs...
DLM sets the line to a sync speed e.g. 7mbps.
If the person syncs in the morning, they can easily get 7mbps with a 6 / 7 db noise margin
However in the late evening, their noise margin drops and is 4 / 5 db at 7mbps.
If they connect at this time they will sync below 7 mbps.
This is because sky does not allow a user to connect at a speed which results in an SNR below 7db (I'm pretty sure sky use 7db noise margin instead of the standard 6db)
The point is they could not sync above 7mbps even if they tried to force their snr down to 1db with custom firmware.
In the above case, if they are syncing below the cap that DLM has set. Manually lowering the SNR will increase the speed, but only upto the physical cap.
So yep, noise margin targets are in place to some degree. However the target is never usually set above 7db, if the lines unstable a sync speed cap is applied that increases the noise margin naturally.
So people often sync with an SNR of 10db, 11db etc.
So yes. I would say it's a coinsidence.
If you ring up sky they CAN apply a higher SNR target although they are VERY reluctant to do this.
If you login to your my sky account you can see what speeds your line has been set to. Often you can sync around 0.5meg higher than the speed in mysky as it's generally a rounded figure.
EDIT: The user can ring up and ask sky to UNCAP the line. This removes any artificial speed cap that has been placed on the line
In this case the line will sync at whatever speed a 7db noise margin gives.
So this CAN occur like you suggested, however DLM does not automatically apply it.
Edited by ukhardy07 (Sun 28-Aug-11 18:18:17)