I should add too that I changed the wiring slightly to achieve a more stable connection as I couldn't work with it disconnecting every 5 minutes, and this may explain the jump in attenuation. The first set of stats was master socket --> filter ---> router and phone. Now I have it set up so that master socket --> filter ---> second filter ---> router and phone.

But you have lost 11mb in your connection and your attenuation has jumped 50db - this is NOT right.

You are not even syncing at 1mb now, and previously you were syncing at almost 12mb and had a 26db attenuation, now your attenuation is 78db???? Whatever you did with the wiring I would undo it!

What you appear to have is what is called an intermittent "HR dis" amongst BT technicians. This is a corroded joint which not only causes big jumps in the attenuation figures, but it can also act as a crude rectifier, which is why you can hear noises from the ADSL signals which are normally out of audible range. You should get your ISP to ask BT to send out an ADSL special investigations team, who will use special equipment to look for dodgy joints in the cable. The joint will eventually fail completely, and it will stop your phone service too.

Thanks again for the replies. Sorry that I have yet to post test socket stats - I was called away to work today and so haven't had time - travelling for 10 hours today!

Kyomii, I seem to have a choice :P I can either have the high speeds and disconnects every few minutes, or the low speeds and disconnects every few hours. Hence why I chose to put the extra filter in - it lowers the speed but increases the stability.

Zebedeee, thanks for the info - I'm going to call O2 tomorrow and suggest that to them, seeing as 'leaving it with them' is unsurprisingly not getting things done fast. Hopefully they'll get an engineer sent out.

The thing is adsl does not require a filter, so the best thing you can do is to plug directly into the test socket with a good professional filter and leave the phone plugged OUT and see what it syncs at and how stable it is.

I cannot for one minute understand why a double filter on the phone would add 50db to the attenuation or have you got your modem double filtered?

If so, this is not necessary, plug your modem in the single filter, then attach another filter then plug your phone in, after you have tried the test socket. There is no point ringing 02 until you have tried directly from the test socket with a new filter with just the modem plugged in.

You should never have 2 filters between a router and the BT linebox, see this >>>

http://usertools.plus.net/tutorials/id/13

"If you follow the route to the ADSL modem you will see that you have passed through 2 Filter / Splitters. This will cause you severe problems because at the first Filter / Splitter at the master socket you are passing through the Low Frequency part. Remember that the ADSL part of the system is at a much higher frequency than the phone system.

What will happen here is that the high frequencies of the ADSL signal will be severely attenuated by at least 30dB with a good filter and the signal reaching your modem will be very weak -- in most cases too weak to work at all -- although, if you are close to the telephone exchange you may find it works but you suffer from dropouts."

Post deleted by Zebedeee

Edited by deleted (Mon 12-May-08 22:18:13)

Not sure that is strictly true.
In some places I've read that the ADSL side of a filter isn't 'filtered' - i.e. it's only the voice side that gets changed.

I've also read that 'double filtering' has been shown to help in some circumstances.

While my study is being revamped I've been working for a few weeks in another room - and I'm using double filtering successfully. I was seeing more noise spikes with my router connected via different wiring so tried adding an extra filter to an already filtered (face place filter) line. If doesn't seem to have helped my situation - but it's certainly no worse.

the ADSL side of a filter is indeed a pass through.

Double filtering can help with a noisy or sensitive phone device.

If someone does double filtering without knowing what they're at then there is a fair chance they plug filter A into the wall, filter B into filter A then the modem into the ADSL port of filter B, thus filtering the ADSL once and the phone twice.

I was about to say that in my deleted post, but wonderob's link seemed to illustrate a filter wrongly connected, i.e. with an ADSL device fitted to a filtered line. The ADSL side of a filter is indeed straight through.