Crackling Problem on Phone line when Modem Syncs ?

Hi,

I've recently been having problems with my Analogue Phone Line crackling and drop in
Upload and Download Speeds. I first noticed this after sluggish web page surfing and very slow Upload speeds, anyway after picking up the Analogue phone I could hear cracking. Phoned Nildram who said yes, I can hear it too, report it to BT. So I reported it to BT on 151. Nice lady at BT said she could hear it too so she booked me a visit from the BT Phone Line Engineer (BT Openreach). Nice BT man came in, checked the Master Socket, oh yes Crackling and went to check our local cabinet. All perfect, so to cut a long story short we found the crackling on the phone line only happens when the ADSL Modem is plugged in. Unplug the RJ11 from the Filter and cracking goes away, plug the RJ11back in, no cracking BUT ! As soon as the Netgear Modem Syncs with the Exchange and green line comes on the Modem Crackle Crackle. Unplug and a few seconds later, a perfectly clear Land Line. The nice BT Man said he would not charge me for the callout £150 but it was a Broadband problem so he could not help. I have raised a Ticket with Nildram but what is going on??

Is it a Relay problem, i.e does the BT PABX use two relays one for Analogue Phone and one for the ADSL Line or is it a ADSL Line Card problem at BT Exchange. Remember crackling only happens when the Modem Syncs which makes me suspect the Exchange. I am on my third ADSL Router, and half a dozen Filters and the result is always the same. Also the level of noise and cracking changes, totally random, like a bad connection or something stupid !!

Anybody have any ideas or experienced this themselves, something is very wrong.

Thanks very much - Simon

P.S. On a good day I can sync at 3.8 to 4Mb Download and 640 Upload but throughput is a lot lower.

Often, but not allways, an indication of particular type of line fault, but you will probably need a broadband skilled Openreach tech to locate it.
Your ISP wil be able to instigate the correct diagnostics process to identify and resolve the issue.

"BT PABX" are you referring to the exchange, or a PABX you have in your property?

Sounds like a fault, that would probably one day affect voice even when ADSL is not present, but needs reporting via ISP now. Assuming you have checked that its not a wiring issue such as a phone/device without a filter which can cause this.

I had this problem on and off for a year. Started off by thinking it was a line problem as it varied with time of day and weather. Also, the line noise problem reduced when I had low Synch speed, but when I was running at the speed my line should have supported it was sometimes the case that a phone call could result in drop of the ADSL2+ synch (I am on O2). This would set off a re-train which resulted in more loud crackling on the voice call whilst the modem synched (at a much lower speed).

Looking at the SN margin whilst a phone call was in progress I could see that the phone loop being closed resulted in the ADSL SN margin dropping by up to 6dB, hence causing the synch to be lost in some cases. From other posts on this forum I thought this was some sort of 'HF-Dis' line fault.

Thought I'd have to put up with it (O2 were really not keen to get a BT SFE out), and was resigned to hissy landline calls / running at a few megs lower than I thought I should have had. However, last weekend it got really bad again. So in a fit of pique I swapped my ADSL Nation XF-1e filter out for the cheapo filter that came with the O2 box..... and it completely cured the problem!

I hasten to add that I had tried four other filters (such as the one that came with my Netgear, and with my previous Orange box) before, but this didn't resolve the problem, so I thought that I had eliminated the filter as the problem; I had dismissed the O2 filters as cheap tat. In fact they seem to do the job better than anything. I now have a completely noise free landline, and I am getting faster speeds now than I have ever got.

So, before you get your ISP investigating, try a few different DSL filters. My experience shows that an expensive transistorised DSL filter may be much less reliable than a simple passive one.

I'm afraid your cheap filter is just masking the problem. Filters such as the XF-1e put minimal loading across the line and depend on a stable voltage to power the circuitry. If a line fault exits then the filter will not be able to function properly, this is not a fault of the filter but a fault on the line.

Your cheap filter has no circuit to power from the line voltage and is likely not designed to have the correct characteristics for the line. As a result actually connecting the filter is putting a load on the line that is masking the fault.

I had this last week. In my case though powercycling the router got rid of the crackling and I've not heard it since. I suspected melt water had got into the underground junction box outside my house.

I'm not sure how powercycling the router could clear it but so far it's remained clear.

Well, in theory if the router chooses different bins to put the signal then what you hear (which is effectively some kind of unbalanced stuff that gets round the filter) will change, or disappear.

I think I have a similar problem, I'm hoping it too will go away but I didn't want to re-sync because the problem caused my SNR target to become 15dB due to hundreds of re-syncs just as the thaw was beginning. Again it could have been due to excessive amounts of rain/melting snow getting in somewhere.

Hi,

Whilst not doubting what you are saying (and my post was in no way intended to put down your product) it is a sad fact that support for problems such as may be present on my line is nigh on impossible to obtain in cases where the voice service is provided by one party and the DSL service provided by another. It is easier for them to play off against each other and pass the buck rather than going to the effort of getting a SFE out to do a detailed investigation (or rather paying the large fee for an investigation to be undertaken).

As far as my cheap filter is concerned, it is doing the job it needs to do. I now have a clear line and a stable & fast DSL connection. In my circumstance the cheap filter is proving the better tool for the job. As an Engineer I'm well aware that the most expensive option is not always the best solution. It looks like my line just needs a sledgehammer solution rather than a technically elegant one.

If I'm ever able to get the line seen to please be assured I'll try the XF-1e again.

Hi Everyone,

Just want to thank everybody for their input and ideas. Just wanted to let people know what happened and what the fault was in case they have the same problem.

Well, the fault was reported to Nildram who tried various line test's and because of the nature of the noise when the Router/Modem was connected raised a Fault Ticket with BT. An order went out to change the Line Pair for the ADSL connections (Tie Pair) and this was done by BT on 25th Feb. On returning from a business trip a few days later with the Router left on the crackling had dissappeared and the internet was up, great !!

Not quite the end of it however, Nildram could not see me On-Line. Are you On-Line, sure I'm on line, no your not, yes I am! Ah another problem we now can't see you and so put you back onto your normal profile. Nildrams system was now looking at the wrong pair. Another BT Work Order went out and a few days later I had a call from BT Broadband Engineer. Great guy, I told him the full story and he said the reason they could not see the New Pair was probably because of a software issue with the ISP on their equipment. He said he would check out the line anyway to prove things were ok and turned up on the doorstep 30 minutes later with an ADSL Line Analyzer, very fancy, anyway the line was perfect as he suspected.

At the same time as they arrived I phoned Nildram Tech Support who in turn spoke to the BT Engineer Live at my premises. This turned out to be very useful and stop any confusion!! BT Engineers went away, made the report and a few days later Nildram told me they were working on a software fix and trying to find me on the Exchange. It took until this weekend but now everything is working very well, back to my old Profile, Nildram can see me again and No Cracking of the Line.

Many thanks to Nildram Tech Support and BT for finding this pain of a fault, very happy..

3.8Mb Downstream and 640Kb Upstream, oh and no crackling!!

Apparently the problem at the Exchange turned out to be a non Standard Connector or Block I was connected too. Well, you live and learn.

Cheers and thanks everyone.