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Attenuation

will2012
Grafter
Posts: 110
Registered: ‎03-12-2012

Attenuation

Hi
I have played with a couple of filters on my line, and have noticed something rather odd; when I use my usual Speedtouch filter, my attenuation is 47.3 db, so say the router logs. However, when I swap that for an apparently unbranded filter, the attenuation drops to 44.0db. What could be causing this?
All telephone equipment was reconnected, nothing else was changed. I even reconnected the Speedtouch filter and sure enough, it went back up to 47.3db.
Will
32 REPLIES
Community Veteran
Posts: 4,915
Thanks: 139
Fixes: 25
Registered: ‎14-07-2009

Re: Attenuation

Faulty Speedtouch filter?  The attenuation should not change.
will2012
Grafter
Posts: 110
Registered: ‎03-12-2012

Re: Attenuation

Quote from: will2012
Hi
I have played with a couple of filters on my line, and have noticed something rather odd; when I use my usual Speedtouch filter, my attenuation is 47.3 db, so say the router logs. However, when I swap that for an apparently unbranded filter, the attenuation drops to 44.0db. What could be causing this?
All telephone equipment was reconnected, nothing else was changed. I even reconnected the Speedtouch filter and sure enough, it went back up to 47.3db.
Will

I have also noticed that when I use the filter which achieves the lower attenuation figure, under 'mode' in the router logs it says 'G.DMT2 ANNEX A' whereas when using another brand new filter, it connects with mode 'G.DMT2+ ANNEX A' again with the higer attenuation figure.
I assume therefor that there was a fault with that filte in some way causing it to connect using ADSL, rather than ADSL2. Interesting that there was no difference in either the sync speed, or the download speed using a speed tester.
Community Veteran
Posts: 4,915
Thanks: 139
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Registered: ‎14-07-2009

Re: Attenuation

Oh, that changes everything.  ADSL2+ uses higher frequencies that ADSL.  The reported attenuation is some sort of average value over all frequencies so if the frequency range is different then the average can be different.  I think you should concentrate your attention on the sync rate you achieve.   
will2012
Grafter
Posts: 110
Registered: ‎03-12-2012

Re: Attenuation

Do you think that as there appears to be no difference in sync speed between adsl and adsl2 on my line, I should let Plusnet know, given as I am only 2.5km away from the exchange? The phone lines follow the road exactly to a box a few metres away from where the exchange is located, so I know the distance is correct.
adie:quote
Community Veteran
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Registered: ‎14-07-2009

Re: Attenuation

Your attenuation (either way) seems a little high for 2.5km.  Have you tried your router in the Test Socket (ask if you don't know what that is).
Community Veteran
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Registered: ‎14-07-2009

Re: Attenuation

Oh, and what sync speed do you actually get?
will2012
Grafter
Posts: 110
Registered: ‎03-12-2012

Re: Attenuation

Quote from: ReedRichards
Your attenuation (either way) seems a little high for 2.5km.  Have you tried your router in the Test Socket (ask if you don't know what that is).

Yes, i have tried it in the test socket, it made no difference. Our router is connected via a small extension, but is very near the main socket 2-3 metres). The sync speeds at the moment are 5945 down and 776 up. Looking at the log they have deteriorated since 4pm at which time they were 6593 down and 784 up. I assumed this was because it was beginning to go dark.
will2012
Grafter
Posts: 110
Registered: ‎03-12-2012

Re: Attenuation

It has now stopped connecting on ADSL2 altogether.
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Registered: ‎14-07-2009

Re: Attenuation

Quote from: will2012
Yes, i have tried it in the test socket, it made no difference.

No difference to the attenuation or the sync rate or both?  I ask because some people make the mistake of just running a speed test, not realising that speed test results can take days to catch-up with a change in sync rate.  And did you check that connecting to the test socket rendered your extensions dead?  That would not happen if they were wired 'unofficially'.
Take a look at the calculator here http://www.kitz.co.uk/adsl/max_speed_calc.php .  If you put in 47dB you get around your current line rates(s) but the estimated line length is 3.5km.  So try to make absolutely sure you are not using a bad cable to your router that gives you a poor electrical contact.     
Plusnet Alumni (retired) orbrey
Plusnet Alumni (retired)
Posts: 10,540
Registered: ‎18-07-2007

Re: Attenuation

Aside from the additional diagnostics being suggested above (which it would definitely be worth following through on Smiley ) I can see you've raised a fault, thanks for that. The line is definitely dropping so we'll get on that for you, and if the tests that you went through when raising the issue didn't change the situation or the symptoms then you've pretty much proved it's a line fault. We'll update you as soon as there's any more information available.
will2012
Grafter
Posts: 110
Registered: ‎03-12-2012

Re: Attenuation

Hi Matt,
Thanks very much for your reply.
Yes, i'm sure there is something wrong somewhere. I followed all your tests but without joy. The line seems quiet though, no noise really. The only noise is white noise which I can only hear when the cordless phone is on loudspeaker, so I presume it is poor amplification etc, rather than line noise.
I cannot understand why it keeps connecting on normal adsl for no reason, with no change in sync speed or actual recorded download speed. There must be some difference in sync speeds between the two surely?
Hi Reed,
Thanks again for your reply.
There was no change in sync speed or attenuation when I tried the test socket. It did disconnect my small extension which is wired using one of the twisted pair in a cat5e cable. I did not realise the recorded download speed could take days to catch up with a change in sync speed, why is that?
It is definitely not 3.5km. As I say the phone cables actually follow the road until a few metres away from the exchange when they go underground. Well past this exchange is the fuel station I fill up at. Resetting the trip computer at that fuel station and driving home the trip just changes to two miles exactly as I hit my drive. It is no where near 3.5km to the exchange. 2.5 is probably still too long, nearer 2 I should think.
Thanks,
Will
Luzern
All Star
Posts: 3,518
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Registered: ‎31-07-2007

Re: Attenuation

I dunno, but I think the Kitz tester is based on pre ADSL2. When I was put on ADSL 2/2+  it went from 43 to dB. I am ~2.9 kms from exch.
No one has to agree with my opinion, but in the time I have left a miracle would be nice.
will2012
Grafter
Posts: 110
Registered: ‎03-12-2012

Re: Attenuation

Plusnet have found a battery connect fault on my line. From my basic research this may be fooling the line somehow into thinking it is longer than it actually is. Whether they proceed to fix the fault or not is anyones guess. I shall wait and see.
Community Veteran
Posts: 19,102
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Registered: ‎31-08-2007

Re: Attenuation

A battery contact fault, as explained in your other thread, will affect the broadband signal that you receive. The information from the modem/router such as attenuation is likely to be meaningless.
If I could make 2 suggestions. First, always post full modem/router stats rather than just selected figures, this gives a clearer picture of what sort of problems may exist. And 2nd, it's gets more confusing when you have two threads that are essentially the same problem as there may be information that might appear in the 2nd one relevant to the first that could easily get overlooked. As it's your fault (and thread) you can include in it whatever you want without feeling you have to start another thread.