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Author Topic: ADSL Connection goes up and down  (Read 20722 times)

SlowConnector

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Re: ADSL Connection goes up and down
« Reply #30 on: September 24, 2012, 02:44:17 PM »

Thanks for explaining, I understand how the attenuation place a cap on my download speed.

However, I am not sure I understand whether line attenuation recorded by my router is fixed (by my distance from the exchange), or whether it varies with my IP profile, as I note that line attenuation for my connection seems to vary between 33-40db.

If I understand correctly, when I was on a 15db profile, line attenuation was about 35db, so if I went to a 6db profile, then attenuation on my line was reduced to 40db as recorded by my router.
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roseway

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Re: ADSL Connection goes up and down
« Reply #31 on: September 24, 2012, 02:55:23 PM »

Attenuation is a value which is calculated by the router, based on the conditions which exist at the time. It's a sort of average of the attenuations of all the individual tones which make up the ADSL signal, but it's possibly also weighted to take more account of the tones which have high bitloading than those which have low bitloading. So when you upgrade from ADSL to ADSL2+ (for example) higher frequency tones are used, which results in a higher average attenuation.

Quote
when I was on a 15db profile, line attenuation was about 35db, so if I went to a 6db profile, then attenuation on my line was reduced to 40db as recorded by my router.

You mean 'increased' I presume. :)  This could be accounted for by the fact that, on the 6 dB profile, more high frequency tones were in use.
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Jonnyteg

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Re: ADSL Connection goes up and down
« Reply #32 on: September 24, 2012, 02:59:52 PM »

Line attenuation is relative to the loss of the dsl signal on your  pair.   The longer the line is the higher the attenuation, other factors come into play like the gauge of the conductor and quality of pair.

Also if your unlucky you may even have some aliminum in your pair which again will increase loss.

The 'E' side of your pair will have the biggest affect on this.   

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kitz

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Re: ADSL Connection goes up and down
« Reply #33 on: September 24, 2012, 03:24:20 PM »

>> I understand how the attenuation place a cap on my download speed.

Its not that attenuation places a cap, attenuation gives an indication of the physical condition and length of your line from the exchange.  The longer the line then the more attenuated the line will be ie the signal strength is reduced.  Think someone shouting across a crowded room, the further you are away from that person the less chance you have of hearing what they are saying. You could say in very simplistic terms that Attenuation is a measurement of the amount of signal deterioration.

>>>  I note that line attenuation for my connection seems to vary between 33-40db.

Attenuation as reported by your router can vary slightly for a few different reasons.
1) Some routers report attenuation at a specific frequency.
2) Some routers report attenuation across what tones are in use.
3) Some routers report attenuation across all tones that are available for use.

Therefore its not unusual to see slight increases in attenuation as your sync speed increases.  However Ive just noticed your line was reporting 40dBm when on the 8Mb 15dB profile (first post).

If you want a little bit more info theres some here:-
What is attenuation.
Decibels in the context of adsl
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