DECT phone noise ONLY when microfilter involved?

I've been going mad, and I call upon the forum to please help me, before I go over the edge! The problem we have is annoying, makes the phone unuasable, and all the regular paths have been explored as far as I can tell.

We've had O2 "business" broadband for quite a while now. We have a new home, and I removed the bellwire early on to improve ADSL reception. When we moved in and dug out our very old DECT phones, they were rubbish. Noisy, feint voice, just terrible. So we ditched them and put in our regular old phone...

More recently we tried some brand new DECT phones. Panasonic and AN Other brand I can't recall.

When the DECT phone is plugged into the wall socked, any wall socket (we have the master and one extension) the line is fine.

When we plug the phone into a microfilter, regardless of brand (I shelled out on a new XF-1e as apparently they do amazing things) we get a great deal of line noise, and the phone is extremely quiet. Unusably quiet voices, and unbearably loud "noise" (hiss).

Now, this happens even if we disconnect and switch off the modem and all other wireless enabled products in the house.

No microfilter, perfect, microfilter, unusable.

Our regular old plug in BT phone works whatever the microfilter situation.

It seems that the microfilter(s) cause the noise, but six (yes, six) microfilters, including a brand new one, cannot be faulty. Where do I go from here?!

Edited by deleted (Wed 17-Mar-10 07:29:56)

Have you tried whilst plugged into the test socket inside the bt master socket?
As you have not said that you already have done, i would advise you to if you have not, just to rule out the faceplate and the internal wiring ,
2,If there is no change try the same again, but using a corded phone,
let us know how you get on

Edited by tommy45 (Wed 17-Mar-10 07:43:13)

We don't actually have a master BT socket (as in the proper BT faceplate) but I have connected it at the first socket in the house (non-brand BT "master" socket with no test socket) and at that point also disconnected the extension lead. The result was the same using this socket as the extension socket upstairs.

That the old analogue wireless phones were dire is no surprise so let's just rule them out.

You say you have tried 6 different filters so that pretty much eliminates the filters as being faulty.

You have tried with the modem/router disconnected and turned off.

So imo the only thing remaining which could be to blame is your nice new DECT phone. Can you borrow a different one to try? If not then Argos sell them and offer a no quibble money back guarantee if you decide you don't want what you bought.

Tried talking to ADSLNation, they have in the past being fairly good at knowing what the oddities people have come across are.

Also try taking a filter and the phone to someone elses home, and if they work there, then probably something odd with your wiring

I should have mentioned I have tried with another DECT handset which was purchased last year, just cant recall the brand. Same issue.

It's just totally baffling the line is clear without a filter, noisy with one. And then only with DECT.

Have you tried double-filtering the phone?

John.

Are you sure it is a Master? As it is no branded - probably not BT then it may not be a real master. Is there a hidden master somewhere else.

I have tried double, triple, even daisy chaining all the damned things together out of pure frustration.

No noticeable difference.

Yep. We have a slightly unusual home and I can remove the outer wall skins, it comes straight from the drop in cable to this master socket.

It didn't at first, the drop in cable (big black beast of a cable) used to stop outside and had an extension lead wired to it into the master socket.

How close, physically, is the phone to the micro filter? Have you tried separating the two with an extension lead?

Are you sure that there are just 2 wires from the drop wire connected and no others are in accidental contact. Can you take a picture of the box outer and inner (be careful as it can have 70V AC and 48V DC inside). Post the images on a suitable host and provide a link.

I've not tried an extra extension to move the DECT base unit away from the actual microfilter. Don't have one. Not sure how that could help? Any logic/thought behind this suggestion that you could share with me?

Just a thought, but an A/B reversal on the internal wiring will sometimes give a 'faint' fault.....

Time to open all the boxes and provide some clear photographic evidence .......

Hello.

Yep, certain of that. The wire was (oddly) hooked up outside the house to a white telephone extension lead, stuffed and taped into a clear plastic bag and stuck behind our external cladding. This extension then fed the master socket.

Apparently BT have an arrangement with the builders so they just wire up to the house, leave the wire there, and the electricians on site do the rest.

I can't take pictures just now, but the orange and white wires are now plugged directly into the 2 and 5 connections on the master socket, which the blue and white and white and blue wires come from to feed the extension (when it was connected).

Could a dodgy master socket cause this problem? Wondering if I should perhaps try invested in an NTE5 style, seeing as we didn't have one fitted in the first place?

In reply to a post by BernieSteak:

I've not tried an extra extension to move the DECT base unit away from the actual microfilter. Don't have one. Not sure how that could help? Any logic/thought behind this suggestion that you could share with me?

The Dect phone/base station is in itself a radiation transmitter. It could be messing up the microfilter.

In reply to a post by Stevenage_Neil:

In reply to a post by BernieSteak:

I've not tried an extra extension to move the DECT base unit away from the actual microfilter. Don't have one. Not sure how that could help? Any logic/thought behind this suggestion that you could share with me?

The Dect phone/base station is in itself a radiation transmitter. It could be messing up the microfilter.

Very, very unlikely, because (a) the power output of DECT phones is very small, and (b) the frequency of DECT phones (2400MHz) is a long way away from broadband (2.2 MHz max).

In reply to a post by BernieSteak:

Apparently BT have an arrangement with the builders so they just wire up to the house, leave the wire there, and the electricians on site do the rest.

I think you've just explained the source of your problem. Builders are notorious for using the wrong wire for phones (alarm wire instead of solid twisted pair) and for getting the wiring wrong. Get it checked out by someone who knows what they are doing.

BT I assume?

From the drop wire now there are two wires, blue and white coming to terminals 2 and 5 and from them (when connected) the blue/white and white/blue wires go off to the one wired extension.

I'll have one last shot at this.

How close is the DECT phone's power brick to the filter?

Switch mode power supplies often generate broad spectrum noise and it is just possible that the ferrite cores in the filter inductors are helping with picking up some of this. I still don't know why you'd actually hear it though as that implies other problems somewhere - dodgy joints being the most likely.

For the master socket the power point for the DECT phone is about 10 feet away on another wall.

I'm glad I'm not the only one flummoxed by this!

It is very very strange. To rule out the DECT psu can you try it using the standard phone + filter but with the DECT phone powered up.

I really can't see how things like A & B reversal or incorrect wire type could possibly lead to the symptoms you have.

In reply to a post by kwikbreaks:

I really can't see how things like A & B reversal or incorrect wire type could possibly lead to the symptoms you have.

Ditto.

In reply to a post by kwikbreaks:

I really can't see how things like A & B reversal or incorrect wire type could possibly lead to the symptoms you have.

The use of a non-twisted cable could lead to higher radiation of RF from the wiring, and all DECT phones have audio amplifiers in them which can be affected by signals which are not far out of the audio range. These audio amplifiers have an automatic gain control to prevent feedback between the earpiece and the microphone, and it doesn't take much to push them over the edge, and you can get feedback, which is often heard as a rushing sound or an echo.

P.S. The use of stranded cable rather than solid core can cause bad connections when IDC connectors are used.

Edited by deleted (Thu 18-Mar-10 10:59:01)

In reply to a post by zebedeee:

The use of a non-twisted cable could lead to higher radiation of RF from the wiring, and all DECT phones have audio amplifiers in them which can be affected by signals which are not far out of the audio range. These audio amplifiers have an automatic gain control to prevent feedback between the earpiece and the microphone, and it doesn't take much to push them over the edge, and you can get feedback, which is often heard as a rushing sound or an echo.

P.S. The use of stranded cable rather than solid core can cause bad connections when IDC connectors are used.

yes yes I know all that (although you seem to put a lot more faith in 4 or 5 twists per meter than I do) but that still doesn't explain why the problem only occurs when there is a filter in circuit even when there is no ADSL signal present - you need an awfully long length of cable for 3kHz to radiate very much.

Well, you assumed in one of your posts that the fault occurred with no ADSL router connected, but I've seen no confirmation of that from the OP.

In reply to a post by zebedeee:

Well, you assumed in one of your posts that the fault occurred with no ADSL router connected, but I've seen no confirmation of that from the OP.

First post

In reply to a post by BernieSteak:

Now, this happens even if we disconnect and switch off the modem and all other wireless enabled products in the house.

I stand corrected, sorry !

Makes it more puzzling doesn't it?

I wonder if we really have the entire story or if something is accidentally omitted.

Certainly the ferrite cored inductors in the filters could make passable antennas but what is the source of the RF noise and what is rectifying it? Maybe a bad joint because of using multicore wire as you suggested but I doubt that.

Edited by kwikbreaks (Fri 19-Mar-10 10:34:58)

"When the DECT phone is plugged into the wall socked, any wall socket (we have the master and one extension) the line is fine.

When we plug the phone into a microfilter, regardless of brand (I shelled out on a new XF-1e as apparently they do amazing things) we get a great deal of line noise, and the phone is extremely quiet. Unusably quiet voices, and unbearably loud "noise" (hiss)."

Sounds back to front to me if the line is ADSL enabled.........

Edited by deleted (Fri 19-Mar-10 11:03:34)

In reply to a post by kwikbreaks:

Makes it more puzzling doesn't it?

I wonder if we really have the entire story or if something is accidentally omitted.

I think you're right. I still think there's a wiring fault somewhere. What I'd like to see done is to disconnect all the indoor wiring, attach a master socket to the incoming pair, and then connect the DECT base unit via the ADSL Nation filter. While he's doing that, he could check the polarity of the A & B wires (that only needs a £5 meter which you can get from Maplins or a host of DIY stores).

It does, doesn't it ? I wonder if this will turn out to be a line card fault at the exchange ?

You have tried new filters, another DECT phone, problem exists whether the router is connected or not. You have removed the ringwires.

All the wiring has been disturbed. Not very difficult for one wire in one IDC to have become a problem.

I would suggest that you go round the sockets remove all the wires except those in terminals 2 & 5. Before you put the socket back together reseat the wires in terminals 2 & 5. If there is anywhere that there are more than two wires in any IDC connector that also could be a problem area. From what I understand you have a master and one extension so there should not be more than 2 wires in any IDC.

Also check that the same colour wire is in terminal 2 in the master as is in terminal 2 of the extensions and the same for terminal 5.

Sorry for the lack of feedback lately. We've had a house full of sick little and big people.

Anyway... I've taken photos, and I have removed the extension lead too during my endless "I'll try this combination then..." fault finding mission.

Someone mentioned the polarity of the incoming cables. Does this make a difference? The advice I read elsewhere suggested that as long as the correct two were connected to the correct points it didn't matter if they were "reversed"?

If it might matter, can someone suggest the correct meter to buy from the local Maplin?

I've taken it right down to only having the master socket wired up and using the X1-Fe filter and still the difference is there. Telephone is fine without the filter, noisy with it.

I've got pictures but lost my damned card reader so can't do it.

Can you confirm that if you plug your phone directly into an unfiltered, ADSL enabled "master" socket that it works fine, but when you add an ADSL filter you get a "hissing" sound and low volume?

I'm doubting my own sanity so I wont say "yes" right off the bat. I'll check it again and report back ASAP.

In reply to a post by BernieSteak:

Someone mentioned the polarity of the incoming cables. Does this make a difference? The advice I read elsewhere suggested that as long as the correct two were connected to the correct points it didn't matter if they were "reversed"?

If it might matter, can someone suggest the correct meter to buy from the local Maplin?

The polarity can be important under certain circumstances. A suitable meter would be the N20AX at £6.99, or the UZ82D at £9.99. The first one is digital, and the second one is an analogue meter. The A wire is positive with respect to the B wire, so a digital meter should not display a minus sign when the red probe is on the A wire, and the black lead on the B wire. On the analogue meter, the needle should move when the red + wire is connected to the A wire. You should set the meters to the 100V DC range, and you should read about 50V DC across the wires when the phone is on the hook.

Edited by deleted (Sun 21-Mar-10 00:02:30)

A & B would be on which connectors when they're numbered only. I do not have the "A/B" style master socket.

I'm sure I have a voltmeter somewhere, if not I'll try and get to Maplins.

Thanks for all the advice.

The A wire usually goes to pin 5 and the B wire to 2. You may find this useful.

'The polarity can be important under certain circumstances.'

My point was that an A/B reversal, if on the extension wiring may give faint problems with cordless phones. The OP seems to have ruled this out now. I'd love to go have a look at this one.

This will NOT `help` you but I wanted to let you know that I have a very similar problem. Since the first connecting of a Router to my telephone line - Ihave had the same noise/interferance problerm.
I also have tried `every` combination of microfilters and changing microfilter brands etc. - nothing that I have tried worked - the ONLY thing that stops the noise/interferance is to turn off the Router - which I do to make/take telephone calls.
I narrowed the problem down to the Router fairly quickly and obtained a replacement - that ALSO had the same problem! - I borrowed a Router of a different manufacturer - [somehow configured by a friend to `work on my ISP]- that also had the same noise/interference so I thought that I had `eliminated everything EXCEPT `faulty` internal wiring.
I called in a telephone engineer [B.T.] who checked out my Incoming AND Internal wiring - NO FAULT was found - nor could he diagnose what was happening regarding the noise/interferance!! - so I am `stuck` with having to turn off the Router when making/taking telephone calls.
Sorry that this is no help - BUT I wanted to let you know that - in my case - the `problem` could NOT be resolved!.
As an Engineer [Heating] - I am not used to `unsolvable` problems - I know how frustrating this is for you - "Good Luck" - CHRISMUR.

Edited by deleted (Mon 22-Mar-10 21:21:37)

What you describe is almost certainly a high resistance fault. If you report the problem through your ISP you should get an ADSL trained engineer - some of these guys actually have opposable thumbs and may even find the fault and fix it.

I agree entirely, and I think this could be the OP's problem too.

Except he says it is the same with the router turned off. I suppose it is vaguely possible that the DSLAM is faulty and continues to transmit even in the absence of a signal from the client but even then it doesn't expain why the noise can only be heard with a filter plugged in unless the loading of the phone stops the transmission???

My own theory remains that the problem is caused by the switch mode psu for the dect phone despite the distance - it is maybe radiated by the mains wiring. That would require two dodgy ones of course according to what the o/p said....

Edited by kwikbreaks (Tue 23-Mar-10 09:20:30)

In reply to a post by kwikbreaks:

Except he says it is the same with the router turned off.

Yes, but he also later said that he wasn't totally sure that this was the case, and was going to take another look.

In reply to a post by kwikbreaks:

My own theory remains that the problem is caused by the switch mode psu for the dect phone despite the distance - it is maybe radiated by the mains wiring. That would require two dodgy ones of course according to what the o/p said....

Yep, I was under the impression that he'd tried at least two different types of DECT phone. One thing that occurred to me - would noise pickup from adjacent pairs in the cable be enough to cause a problem if there was an HR joint somewhere ?

In reply to a post by zebedeee:

One thing that occurred to me - would noise pickup from adjacent pairs in the cable be enough to cause a problem if there was an HR joint somewhere ?

So crosstalk causes an HR fault in the line to show up but only with a filter in circuit?

Maybe but I reckon the odds are comparable with those for it being a joke perpetrated by an alien in a UFO parked on the lawn and hidden by a SEP field.

I'm not even convinced I could solve this one on site so I reckon I'm going to stop taking guesses based on the certainly incomplete and possibly incorrect information posted here.

Still cannot find my card reader for showing you guys the connections. But I have checked them and they appear "clean" and simple (no crossed wires etc).

I haven't been able to get out and get a voltmeter to test the incoming cable just yet to see if that's reversed, but most of you guys don't seem to think that will make a great difference.

What I have been able to do is shoot some quick video on my iPhone with and without the filter attached taken at the master socket, so show you guys (mostly so you can hear) what the situation is like.

I used two DECT phones, the first is a magicbox phone: http://www.johnlewis.com/230649923/Product.aspx and the second is a Panasonic: http://www.johnlewis.com/230588206/Product.aspx The Panasonic is MUCH worse than the Magicbox, but you can (hopefully) hear a difference on both with and without the filter.

Might have to turn up your volume a fair amount.

Distance from plug, base unit, to master wall socket: http://www.youtube.com/watch?v=BhPCUlTgpSc

First phone (magicbox) with no filter involved: http://www.youtube.com/watch?v=KDVZH5tl5Ds

Quite a big difference, but you can still hear the dial tone.

First phone (magicbox) with filter involved: http://www.youtube.com/watch?v=rnl3I1cE36w

Second phone (Panasonic) with no filter involved: http://www.youtube.com/watch?v=0zvmZbZc4v4

HUGE difference between these two, I struggled to get the iPhone to pick up the feint dial tone / white noise...

Second phone (Panasonic) with no filter involved: http://www.youtube.com/watch?v=EiuK_nKl_Y0

The bangs/pops are the phone earpiece hitting the iPhone microphone.

This is with ALL router, computers, wireless devices in the house switched off and unplugged.

Here's some photos of the socket (master) and extension.

I've done most testing with the extension disconnected, but it really doesn't seem to make any difference at all. Certainly nothing I can detect by ear alone!

Flickr images, master socket wired up only: http://www.flickr.com/photos/oxleywoodsphotos/446615...

Master with extension: http://www.flickr.com/photos/oxleywoodsphotos/446615...

Extension: http://www.flickr.com/photos/oxleywoodsphotos/446693...

Doubt these add much to the conundrum, but maybe there's a clue I can't see and someone else can?!

First observation, thats a cheap and nasty 'master' socket.

Reverse the polarity on the incoming pair, then reconnect the extension as it is, blue to two, and white/blue to 5.

You mentioned ages ago that theres a joint on the feed pair, is there any way you can move the master up to the joint and connect there, ruling out the current wire feeding the master ?

Do you think a new socket might be a wise investment? I'm not at all surprised it's cheap and nasty, the builders will cut every cost possible I'm sure.

I already removed the "bridge" outside the house so the drop wire is coming straight in. The wire reaches easily inside the house, no idea why they felt the need to add some connections and wire to the equation!

I'll have a go at reversing the polarity and see if that makes any difference too.

Small update, next step I feel is a call to either O2 support or BT. But not sure who is the first port of call?

I swapped the crappy "master socket" for an NTE5a type. No huge difference, but the line is generally louder and clearer when no microfilter is involved. My broadband speed also seems to have picked up. May be coincidence, but before and after saw a jump of around 500 kbps or more download speed. Nice side benefit.

What it has shown though is this fault is NOT purely DECT related as I had thought. I can now hear a significant difference on the trust old BT Duet 200 phone, previously I couldn't notice anything with the naked ear (not a phrase I thought I'd ever use!).

Once again this testing was carried out at the master socket with the ADSL off, routers, computers, all wireless devices off, nothing else plugged in.

I didn't invest in a voltmeter yet, but when installing the new master socket I tried the two feeds from the drop wire both ways around (blue and white are active, and I switched those two over and tested for any audible difference).

So, tried swapping EVERYTHING in the house, from the master socket inwards. No ADSL microfilter, telephone line clear as a bell. ADSL microfilter, noisy line, and unusably quiet dialtone/voice.

So, any suggestions on where to go from here?

Since your problem involves broadband hardware, your best approach is via O2. If Openreach send out a phone guy in response to a voice fault callout, he will probably run a mile when he sees that it involves broadband hardware. I would suspect a line card fault, but as someone who has had BTO guys on and off my premises over a 5-month period, I wish you luck

Hi

came very late to this while searching for my own problem....( buzzing on receive of BT synergy DECT AM phone, regardless if theres a DSL filter or not )

Anyway, this sounds like a sidetone problem to me. The hiss is coming from the mic circuits of the DECT phone. Normally this should not be heard, as it goes upstream only. The sidetone circuit in the phone ( all phones have one ) attempts to identify what on the line is from its own mic circuit, and subtract this from whats on the line ( ie to end up with just the speech from the remote end ).

To do this it relies on the impedance of the line being what it expects. It sounds like the DSL filter is presenting a different impedance, in the 0 - 4KHz region, , and so the sidetone cancellation in the phone isn't working properly.

This is a compatiblity issue really, but you could try changing the impedance a bit to see if this helps. eg try adding a 22nF cap across the line at the phone connect point ( ie after the filter ) - min 250V - , or adding a resistor in series eg 100R ).

hope this helps

D139 ( ex PBX design engineer )

Right then.

After too, too long, we have a working phone line. After backing off every time the £130 callout fee threat came over the phone, I finally bit the bullet and a BT engineer called early in the week.

They tested the line, noisy and quiet by default, much worse with ADSL microfilter.

Checked at the cabinet down the road, still a bad line.

Checked at the exchange and apparently better. But not great.

They changed some stuff, did some work at the frame, very little (if any) change in quality.

They replaced our ADSL equipment at the exchange for all new stuff (apparently). Still the same issue.

Had ONE clear call where our call was "intercepted". BT doing a lot of head scratching.

Today back the exchange they changed out something more significant, apparently very rare, might have been the card, not sure.

Then did something again with the ADSL gear.

And we have a very good quality phone line. Superb.

ADSL seems a little slower than before, so not sure if O2 can tweak a setting or two on that, but the phone works great.

Post deleted by billford