G4WHO wrote :

BT also have a wonderful little pair of boxes which duplexes two BT lines

onto

one physical pair of cables. If someone near you has had one fitted

depending on

the technology used this could increase the noise on the phone lines.

Last year I started hearing approximately one-second ticks with a double
tick on the minute on all radio frequencies up to 5 MHz, including 136. I
thought at first MSF was running amok but it was coming from overhead phone
lines running alongside my property and was somehow linked with a nearby
cellphone installation. I moaned to BT who said they could do nothing about
it  - "everything was within spec"  and it was somehow my fault for living
too close by.  What with this sort of thing and the broadband noise now
covering 160m over large areas of the country for hours on end I'm
beginning to think my amateur radio days are over!