Hi,
I had problems with a customer who had an HF start plasma table with the PC some 20'-30' away.
The winning strategy was to put ferrites on the cable, but in three locations, approximately equal distance apart.
I reasoned that the cable was behaving like an antenna. By putting ferrites on it, it broke the antenna from one long
one to four shorter ones.
The customer tried one at each end and while it helped it still wasn't right until he put a third one on.
Craig