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[sheddyian]

Hello,

Bald Eagle thought it might be of interest for me to post about a problem I had when ADSL was first enabled for me, and what I did to fix (circumvent?) it.  I'd welcome comments on whether I did the right thing, and what might actually have been wrong.

So...

Last year, ordered Broadband from Talk Talk.  They are 1 of few ISPs who offer LLU at my local exchange.

I knew when it had been enabled as there was lots of noise on the line   So immediately switched on the Router (Talk Talk supplied DSL-2780) and fitted microfilter to the DECT base unit.

BUT, the line, which had for years previous, been very low noise, now had distinct hiss (I assumed ADSL noise) and speech quality, whilst not apalling, was far from being good.

I tried a different filter on the telephone, and also tried stacking two in series.  Made no difference.

I left it for a few days, but it was annoying, so thought I'd try a few experiments to see if anything could be improved.

Wiring was like this

incoming line > JCT box in attic > BT master socket > unused extension > unused extension > socket for DECT phone.  Total wire length can't be more than about 15 - 20 metres I'd guess.

The router modem was plugged into the BT master socket, via a microfilter as per instructions.  It isn't (wasn't *cough*) an NTE/5, just a plain BT branded master socket.

I tried replacing the master socket, as it was in a sorry condition and my suspicions were heaped upon it, but this made no difference.

Disconnecting the extension sockets gave me a significant boost in speeds
                Synch Speed      Attenuation      S/N Margin
                 UP      DWN         UP  DOWN     UP  DOWN
With extns  941    15524       11.6   23        11.8  10.9
Without      925    17380       11.5   22        12.5  11.8

Now, I'd already disconnected the ring wire, and had no previous problems with line quality - it's always been remarkably clear and crisp, quiet line was *really* quiet!

Using a BT plug and a junction box, I contrived a bodge that gave the extensions a pre-filtered signal from the one plug-in ADSL microfilter at the master socket, so ADSL was only available at the master socket.  On resetting everything, I was delighted to get a vastly improved voice quality on the telephone, and the modem resynched at the same "extensions disconnected" figures I quoted above (except S/N margin down was marginally lower)

I subsequently replaced my bodge with one of those pre-filtered NTE5 faceplates from ADSL nation, which has retained the noise-free voice line and good ADSL speeds. 

So, I was pleased to have sorted it out, but am curious as to what might have been causing the problem? As I said, I feel I've circumvented it rather than fixing it.  Why did I get so much ADSL noise on the voice phone, when it had it's own ADSL microfilter plugged in, and I tried several varieties in case of a faulty one?  (The microfilter that provided the bodged solution was one that had previously been used on the handset in question, so I am sure it was working OK)

Ian

(for amusement, I've attached a picture of my bodge that worked!)

[Bald_Eagle1]

Hi sheddyian,

I'm sure someone who knows will provide a proper explanation shortly.

In the meantime, if I have understood matters, you originally had unfiltered ADSL signal at all the extensions & DECT socket.

Creating your pre-filtered signal to the extensions seems basically the same as fitting a filtered faceplate where the telephone only signal starts at the faceplate.

I wonder if the ADSL signal was originally simply too close to the DECT phone & it being wireless, noise was picked up by the phone.
Once you filtered out the ADSL at the master socket the problem disappeared.

Prior to the Talk Talk LLU connection did you have a "standard" ADSL (lower frequencies) connection that did NOT cause this issue?

Paul.

[sevenlayermuddle]

Intersesting history.

Is there any chance one of the unused extensions may have been another master? 

I've nothing specific in mind with that question as I can't see how it could cause your exact symptoms, but a second master can certainly cause problems under some circumstances.  It's not inconceivable that such problems could then be affected by putting a filter between the two masters.

[sheddyian]

In the meantime, if I have understood matters, you originally had unfiltered ADSL signal at all the extensions & DECT socket.

Correct. And connecting the DECT phone via ADSL microfilter did not completely remove the ADSL noise.  Voice quality suffered.

Creating your pre-filtered signal to the extensions seems basically the same as fitting a filtered faceplate where the telephone only signal starts at the faceplate.

Agree.  Can't now remember if I'd already read about these and thus copied the idea, or if I'd been incredibly smart an invented one for myself without knowing they existed 

I wonder if the ADSL signal was originally simply too close to the DECT phone & it being wireless, noise was picked up by the phone.

Possibly.  I didn't try a standard handset.

Once you filtered out the ADSL at the master socket the problem disappeared.

Yes, line noise virtually eliminated, speech quality now excellent. I'd say the line isn't *quite* as quiet as it was pre-ADSL, but it's barely detectable unless you're listening for it.

Prior to the Talk Talk LLU connection did you have a "standard" ADSL (lower frequencies) connection that did NOT cause this issue?

Talk Talk (ADSL2+ LLU) was the first ADSL service on this line, ever. Previously only analogue voice and dial-up.

Thanks!

Ian

[sheddyian]

Intersesting history.

Is there any chance one of the unused extensions may have been another master?

I'm reasonably sure they're all secondary sockets, except the first in the chain, as I put them in some years ago, and I understood what was meant to go where 

That being said, I may have made a mistake, and I haven't checked to confirm there is only one master.

Ian

[sheddyian]

Just to follow up, in case anyone is interested.  I checked all the sockets on my line, and only the first socket is a master, so that's all correct.

Although I'd disconnected the ring wire at the master, it was connected the rest of the way through on each extension, so I've now disconnected that as well.  As the extensions are wired through a filtered faceplate, I'm doubtful this will make any difference, but it won't hurt.

I did spot something I'd forgotten about though, and which may have been responsible for my original problem of ADSL noise at the handset :

I'd thought that all of the sockets were daisy-chained.  In fact, the 2nd unused socket had 3 cables, with the daisy chain in and out, plus a 3rd dog leg that used to go up to a bedroom, but had been cut off part way along.  This was still connected to the telephone system, so could have been acting as an aerial or causing reflections?  Anyway, it's now disconnected.

So, my problematic wiring was like this :

line in > jct box > master > unused skt > unused skt > dect phone skt
                                                             !
                                                             !
                                          rogue unterminated
                                                    wire

Would that have caused ADSL noise on the phone handset, despite the correct use of a microfilter?

Anyway, it's academic as putting in a filtered faceplate resolved the ADSL noise problem. 

I have just rebooted the modem on the optimistic chance that my wiring improvements just now will have gained me further bandwidth... well, it did, but only from 21023 to 21098.  I think this is within margin of error

Ian

[burakkucat]

Just to follow up, in case anyone is interested.

Of course we are interested! 

In fact, the 2nd unused socket had 3 cables, with the daisy chain in and out, plus a 3rd dog leg that used to go up to a bedroom, but had been cut off part way along.

Ah, ha. A bridged tap. It's doubtful that it was the audible noise source but it would have had a detrimental effect on an xDSL signal due to its loading of the line.

Just wondering . . . Have you now re-decorated that internal window-sill? 

[sheddyian]

Ah, ha. A bridged tap. It's doubtful that it was the audible noise source but it would have had a detrimental effect on an xDSL signal due to its loading of the line.

Wonder what caused it then?

I'm about 10 minutes walk from the exchange, surely it's not that the signal is so strong it was swamping the filter?    (Note that, despite being on the 6db profile, I typically get 20k not 24k sych down - distance?)

Just wondering . . . Have you now re-decorated that internal window-sill? 

No, but I have cleaned the windowsill!  There'd been a leak in the roof, and that's partly what made me suspect the original master socket was to blame, as it was a bit corroded inside!

I knew I should have posted the "after" picture as well!  Not only did I fit a shiny new filtered faceplate, I applied some Flash liquid and a sponge to the paintwork.  Sadly the latter didn't improve my signal 

[burakkucat]

Wonder what caused it then?

    A mystery.

I'm about 10 minutes walk from the exchange, surely it's not that the signal is so strong it was swamping the filter? 

No.    Whatever the reason may have been, it certainly wouldn't have been that.

No, but I have cleaned the windowsill!

Did "Senior Management" approve? 

I knew I should have posted the "after" picture as well!  Not only did I fit a shiny new filtered faceplate, I applied some Flash liquid and a sponge to the paintwork.

Excellent work! 

[sheddyian]

>I'm about 10 minutes walk from the exchange, surely it's not that the signal is so strong it was swamping the filter? 

No.    Whatever the reason may have been, it certainly wouldn't have been that.

I'm pleased I made the problem go away, and at least it didn't go away on it's own, but it bugs me that I don't really know why it happened!

>No, but I have cleaned the windowsill!

Did "Senior Management" approve? 

"Have you finished messing around in there yet?" 

Actually, after the shiny faceplate and the flash & sponge combo, I did get "that looks much better", and later, "you know, it does seem faster"

So I think I win 

Ian