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Borderline Attenuation

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Borderline Attenuation

Hi All,

I'm sure it's been asked many times before, but can someone give me a definitive answer to the question of will an attenuation of 46 be okay for a 2Mb upgrade.

I've followed other threads and they talk about a 4db increase once you have broadband, so this would seem to indicate that the actual is around 42.

What do you think?

Any help would be appreciated.

Andy
23 REPLIES
Alecto
Grafter
Posts: 2,886
Registered: 30-07-2007

Borderline Attenuation

46dB will definitely not be accepted for an upgrade to 2Mb.
BT are now mercilessly strict with applying the limit of 43dB and will not even try a line with a worse reading than that.

Presumably you've got the 46 from your router and it may be wrong, but it's unlikely to be too far out.
.
To check that the figure of 46dB is right, you can raise a ticket and ask Pn to check what the actual figure is with a "woosh test".

You can't do arithmetic on the figure to arrive at what it would be if such and such, you can only use the figure as it is measured. Cry
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Borderline Attenuation

I have 44dB on 2MB Smiley
Alecto
Grafter
Posts: 2,886
Registered: 30-07-2007

Borderline Attenuation

And I have 47dB on 2Mb, but neither of us would get 2Mb if we were trying to upgrade today. :roll:
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Borderline Attenuation

BT round my area are so Loving and Kind Smiley
Install a FacePlate instead of using filters so you can connect straight to the main socket. This will help you get 2mb
Community Veteran
Posts: 1,817
Thanks: 11
Registered: 30-07-2007

Borderline Attenuation

I had 44 to 45 and was regraded soo after connection as I pointed out how close it was to 43 and that the 4 either way could potentially make it ok.

A
hitachi
Grafter
Posts: 343
Registered: 05-04-2007

Borderline Attenuation

Its not really close, because of the way it is measured it is only half the signal strength.
Alecto
Grafter
Posts: 2,886
Registered: 30-07-2007

Borderline Attenuation

That's true, 1dB doesn't look much, but a 3dB difference is equal to losing half the strength of the signal.

As John Essex says in his tutorial about it,

So a loss of 3 dB is equal to almost exactly half the power being received.
Similarly, if you were to look at log tables and calculate other figures you would find that losses of:

10 dB = 1/10th of the power
20 dB = 1/100th of the power
30 dB = 1/1000th of the power.


Amazing that it works at all really. :roll:
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Borderline Attenuation

Thanks for all the replies. As someone referred to John Essex's post, it is this post that alerted me to the fact that being on broadband adds 4db to the attenuation reading, which is why I raised the question that this would imply that the reading on non-broadband would be about 42. Or am I deluding myself Cheesy
Plusnet Staff
Plusnet Staff
Posts: 12,169
Thanks: 18
Fixes: 1
Registered: 04-04-2007

Borderline Attenuation

Hi,

If memory serves correct the 43dB figure takes into account broadband being on the line. Because of the number of 2Mbps orders and regrades that have gone in at the borderline that ultimately didn't work or had intermittant sync issues tightening the limits was the sensible thing to do.

The good news is that when DSL Max arrives next year customers on 1Mbps or 512 will be able to switch to this and let the exchange kit decide exactly what speed a line can support. So if you have a good SNR but are over the 43dB attentuation then you may well see a speed increase, it might be to 1.5Mbps or it could be faster.

What the kit at the exchange does is determines at speed your line will support, so lets say it can do 1.7Mbps, and then round it down to the nearest 0.5Mbps (so you'd get a 1.5Mbps sync speed).
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Borderline Attenuation

Thanks for this helpful reply Dave. It is good news about the DSLMax for me because I have, I think, an excellent SNR of 33db, so hopefully this may be good news for me.

I'm mainly concerned because in very short order, < 2Mb will be as dial-up is now - supportable but not enjoyable - and with everyone else getting 8Mb and 24Mb then my requirements are just going to get lost in the shuffle - so I hope to try to get as good a connection as possible as I want to remain a teleworker.

Regards
Plusnet Staff
Plusnet Staff
Posts: 12,169
Thanks: 18
Fixes: 1
Registered: 04-04-2007

Borderline Attenuation

33dB is certainly nice and healthy so I would be surprised if you didn't see at least a 0.5Mbps increase.

There are other developments going on as well designed to help people like yourself (as you're far from alone).

First we have ADSL2+. The headlines with ADSL2+ is that it can deliver speeds up to 24Mbps for people nearest the exchanges, but it can also deliver (smaller speed increases for people further away). It does get to a point (based on line characteristics) where the speed on ADSL2+ is probably the same as ADSL but most would see a speed boost from ADSL2+.

The second technology is VDSL, or FTTC (Fibre to the cabinet). This is currently being trialled (in Rotherham I think). What happens is BT install a mini DSLAM in the green cabinet at the bottom of your road and then run fibre from the cabinet back to the exchange. For most people this significantly reduces the copper run (and it's generally the length of copper that determines the maximum speed a line can support, although there are other factors), so a shorty copper run means that people who are 4, 5, 6km away from their exchange may now only have a 1km copper run or less and can benefit from much faster speeds.

When are these technologies going to arrive? Well ADSL2+ is starting to appear now via LLU, BT Wholesale also have an internal trial going on, they are also trialling FTTC so expect to hear more next year.
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Borderline Attenuation

After looking at my router I get Downstream 56.6 and Upstream 31.5? Why the difference and will I ever get 2MB, thats why I joined PN in the first place. Thanks.
Plusnet Staff
Plusnet Staff
Posts: 12,169
Thanks: 18
Fixes: 1
Registered: 04-04-2007

Borderline Attenuation

WIth attentuation of 56.6dB your line is over the limit for 2Mbps. It needs to be under 43dB so it is quite a way over. With the changes in technology coming up you may see faster in the future but unfortunately not at the moment.

The reason for the different figures in upstream and downstream is because the are different speeds and use different frequencies so are affected differently by quality of the cable, line length, etc.
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Borderline Attenuation

Thanks Dave.

Sounds really exciting, but I must confess that I'm not holding my breath because I'm not urban, I'm semi-rural in a village of about 5,000 homes. So I dare say it might come one day, but not in the forseeable future.

Andy