Noisy line - bad filters

Just thought i would share my experiance.

Our BT line was Noisy (Static) expecially when the weather changed. So the internet was very often on-off-on-off .....
But worse - the router would splash audable network and dialup noise onto any phone call so we had to turn it off while making calls.

Browsing various forums suggested that the filters (dead or dying)) and maybe router (capacitor noise) needed upgrading....and our line needed checking.

BT man came and checked all the connections from Grren box to our house and replaced a small section of Al wire. Noisy line now much better.

More intresting is that there is now no audible noise from the router while making calls. (Router and filters had not been changed)

So when you have network noise while making a phone call - It may not be filters at fault.

Edited by deleted (Mon 10-Oct-11 12:13:31)

It may not be filters, but changing those before an engineer visit is wise, since if they find they are faulty you get an expensive call out charge.

The issue with filters is generally poor joints, or capacitor break down. The joint issue sounds very likely on the line, since poor joints cause the DSL noise to bleed down into the audio range.

bleed noise down into the audio range

I was reading somewhere that when the higher frequency bands have too much interference then the network system uses or borrows some of the lower frequencies
- hence the audible noise. Do you think that this is a correct anaylsis of whats happening or could the combination of adnormal capacitances and high impedance 'faults' have an effect on lowering the frequencies into the audio range.

ADSL will not use below 100Khz for downstream
25 to 100Khz is kept for the upstream.

Phone audio is only around 3 to 4KHz.

So there is no borrowing of the audio to improve ADSL.

If most people can only hear 14Khz-18Khz then what network noise are we hearing if the lowest the upsteam data frequency is 25Khz.

Bad joints can cause this, i.e. the small gaps act a little like a crystal radio in shifting things down the frequency spectrum.