Why do AC cords make so much difference?

Hdm, I wouldn't know as have not had a ground in over twenty years....The ground in my house only extends as far as kitchen, baths and laundry....

Has anyone here measured the capacitance between primary and secondary of a toroid transformer as opposed to an EI core? You will find about ten times as much capacitance with the toroid compared to a twin bobbin EI core which allows a sneak path for all sorts of RF nasties....Some IBM folks presented a study a few years ago to the IEEE of noise on power lines in major metropolitan areas and found huge spikes at 5mhz and 50mhz rather than the 27Mhz citizen's band they were expecting....With the profusion of toroid transformers, most of them center tapped to save on diodes, the noise is put right back into the neutral through the ground.......The vehicle I use to deal with RF noise is high capacitance and low self-inductance.....