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Sync Times

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Sync Times

Before i moved house, my router use to be able to power up and sync with the exchange within about 5 seconds. On that exchange i was just inside the 5km limit so could only get a 512kb connection.

Now that i have moved, my line is virtually next door to the exchange, its been tested by BT who said its got an attenuation of 13 and noise level of 37, however the sync now takes alot longer... sometimes up to 15 seconds.

Speed tests give me 485 kbps and i can download at up to 60kb/s

Its not exactly a problem, but i wondered will different exchanges sync at different times, or does it take longer during peak hours, or does it have any other issues such as distance from exchange etc?
4 REPLIES
Community Veteran
Posts: 6,983
Thanks: 8
Registered: 10-04-2007

Sync Times

Do you have any figures for your line conditions and how do they compare with your old line?
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Sync Times

Not really, all i know is the new line is waaaay faster yet slower to connect... bit wierd.
Community Veteran
Posts: 14,469
Registered: 30-07-2007

Sync Times

My guess is your current exchange may be using slightly different equipment to your old one so the sync part (as apposed to the logon to PlusNet part) may be different.
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Sync Times

When negotiating a sync, it is not just the signal detection that is done.
The tx power at the exchange and the tx power from your modem are varied until the best compromise between transmit power and signal are achieved.
Generally, power starts at maximum and is decreased in steps until packet drops occur and then is raised back to the previous level +1.
As you are closer to the exchange with low attenuation and good SNR, there are more reduction steps in the tx power, so it takes longer to sync.
The power negotiation is there, as more power means more noise is generated on the line, hence the requirement for the compromise.

Conversely, users with high attenuation and poor SNR figures are liable to see long sync times due to inconsistent results of the power stepping.

Some modems will let you see the Tx power. A Samsung modem I used to have, even indicated the far end (exchange) equipment.