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[westom]

Is it possible that there could be some interference affecting the UL frequencies ?

  Yes.  ADSL wire is twisted pair so that 80 Khz interference does not exist.  However if someone accidentally connected two phone wires to different (not paired) twisted wires, then ADSL interference could exist.  Just another of those 73 problems that get tested for by temporarily connecting a failing ADSL connection directly to the master socket - to learn if that problem (or so many others) still exists or disappears.

[hake]

Using a portable wireless on LW, I found that one of my PC's PSUs was spewing out a horrible noise at 210kHz.  It has been binned.  Isolating that faulty equipment has not, however, affected the upstream problem.

Are there any radio receivers which can scan the whole of the frequency range of an ADSL signal?  The LW range of available receivers only seems to cover 150kHz to 300kHz.

[westom]

Are there any radio receivers which can scan the whole of the frequency range of an ADSL signal?  The LW range of available receivers only seems to cover 150kHz to 300kHz.

  If a device creates noise at 100 Khz with enough strength to interfere with twiste pair ADSL, then it is also making noise in the 150+ Khz range. However relevant noise would more likely be on the ADSL pair from another pair of wires - not noise in the air.

  Another in the long list of 73 problems include an inadvertant grounding of one wire in the pair.  Until you have determined which side of the master socket is the problem, well, a 30Khz noise interference is only one of too many possible reasons.  Rather than take on all 73 problems one by one (which is what you are doing), first is shorten that list massively by determining which side of the master socket has that problem.

[sevenlayermuddle]

Hake,

I'd not worry tooooo.... much about the exact frequency of the noise.  If the interference signal were a perfect sinusoidal waveform, then it would only be detected at it's own resonant frequency.   But it's awfuly difficult to generate such a pure sinusoidal waveform even when you're trying to do so,  and it's most unlikely to occur by accident.

Much, much, much , more likely it's a spurious waveform, full of harmonics, that happens to be based on some particular frequency, like - say - 80 Khz.  That being the case, you'd detect signals of various strenghts at 2x, 4x, etc the basic frequency.

If you can 'home in' in some noise on your LW radio, that co-incides with the problems, then I'd not worry about the exact frequency.  However, bear in mind that LW radio signals tend to follow the curviture of the planet.  It's quite normal on a summer's eveing to detect crackle emanating from many (hundreds of) miles away.  Make sure the onset (&drop) conincides with the problem before taking too much notice off it.

[hake]

Gotcha!  I heaved the big chest of drawers out of the way to gain access to the master socket.  I connected direct to the test socket via an Exelcus passive microfilter and, bingo, the upstream bitrate is 224kbps (a few weeks ago it was 448kbps).

I am therefore confident that any problem is not in the cabling that I have installed.

What should I do next?

[westom]

I connected direct to the test socket via an Exelcus passive microfilter and, bingo, the upstream bitrate is 224kbps (a few weeks ago it was 448kbps).

   What are your 'signal to noise' or 'signal strength' dB numbers during good and bad operation?  Numbers are always important.

  Step back.  Just to be sure I understand what you posted.  First, connection to the master socket is without anything else in the house connected.

  Second, apparently you don't understand what the filter does.  Everything else in your house 'eats' DSL signals.  Your DSL modem must make a direct connection to the providers DSLAM.   Not through a filter.  That filter is normally between BT phone line and everything else in the house - to separate everything else from eating DSL signals.  Correct operation is ADSL modem connected directly to master socket and ISPs DSLAM.   Your test has nothing else connected to the master socket.

  Is an ADSL filter defective?  Your test - only modem connected and nothing else; not even a filter - is the test.

  Again, dB signal numbers are important.  However it sounds like you have a problem that must be solved by the ISP.  Any problem on the BT side of a master socket is 100% their problem.  Best you can do is have so much information that they cannot deny the problem.  Those dB numbers would help make your case (and might have made my reply more useful).  If a modem loses signal strength when it is the only item connected, then your problem can only be solved by the ISP.

  Now, is any (even the slightest) noise heard on other POTS phones at any time?  Any crackling, pops, or snaps – even faint?  And when?  If so, that is critical information (a symptom) to help identify and to confirm that the problem exists and when the problem is finally solved.

[hake]

I recollect that the upstream SNRM during a good spell (upstream speed 448kbps) was around 16db. The quiet line test is just that: quiet.  There is no audible noise and none has been heard during the many quiet line tests I have done over the past few weeks.

PlusNet's support has now taken the issue on board.

I have had variable line performance over the three years I have been on MaxADSL.  Disconnects were becoming more frequent over the past six months and the stats wobbling around more.  My main worry was intermittency and the difficulty of firm evidence.  Now, at last, I have a firmly demonstrable problem which was previously not the case.

[jeffbb]

HI
quote My main worry was intermittency and the difficulty of firm evidence.

As suggested in an earlier post by hpsauce quote  You could try Routerstats of course, see if that shows any more detail.

you can get it from here  http://vwlowen.co.uk/internet/files.htm

Regards Jeff

[westom]

I recollect that the upstream SNRM during a good spell (upstream speed 448kbps) was around 16db.

  You now have a benchmark.  Failure would probably be indicated by 10 dB. Your ADSL would still work - but has failed.  An example of why the numbers are so important.  A benchmark that says when Plusnet has 'really' fixed the problem and how to solve problems before cuaing  ADSL speed degradation.

  Also a method to determine if anything else in your house (when reconnected to the master socket) contributes to DSL signal degradation.

  My experience: you are about to deal with the hard part.  Get them to finally send out someone who really knows how ADSL works.  Some ISPs will do anything to avoid rolling a truck.  Some (if not many) understand nothing more than disconnected wires.  Good luck.