Can't find a better place to post this and hopefully there are clever electrickery versed people in here who can help.
For the last 5 or 6 days my phone line has been intermittently crackling and internet service has been dropping out or running at very restricted speeds. Like 160 kb/s instead of the normal 4000 kb/s - barely better than an old pre-dsl modem.
Trouble is every time I phone up BT and they run a line check they say they can't see a fault but if I want to pay for an engineer visit they'll be more than happy. In fact the crackling tends to disappear after I initiate a phone call so by the time I've explained the problem to the muppet in Mumbai it's ok again.
I strenuously refute any allegations that I've gone outside and removed the cover from the connection box outside on the house wall and checked the connections inside it or indeed those that I've removed the cover from the primary socket inside and checked those connections. Doing that would maybe make me liable for any subsequent faults so it would be a silly thing to do. Howver if hypothetically I had done so I couldn't find any problem.
I have however tried fitting an old but reliable corded phone directly into the main socket without the computer connected, there is no equipment fitted to any other socket, I've tried several different DSL filters but the problem persists.
So why might a bad phone line get better once you initiate a call?
Strategy to get BT to fix it?