Below are the questions asked during the live event, along with their respective answers.
Q: With all the sub-assemblies inside the product box, is cavity resonance likely?
A: It is true that a box filled to the brim with subassemblies (high packing factor) is unlikely to resonate, but I have seen boxes with great spaces left inside. A particular instance was a remote control sub-assembly designed to fit in a 1U high (1.75″) box that was placed in a 4U (7″) high box because the customer wanted room for future expansion.
Q: Could you explain some experience about common mode and differential mode EMI?
A: Not sure if I understand the question, other than to state that differential mode noise (noise picked up as the intended current runs its course [maybe through direct rectification of mains followed by switched high voltage dc]) tends to be lower frequency and is impressed back onto the copper wires of the mains supply. This would be picked up during a conducted emissions test.
Q: Can the conducted noise also be affected by this kind of test?
A: Yes, you will notice that the mains filter fitted to most equipment is designed to attenuate both types of noise, differential and common mode. Differential noise is mainly low frequency and so was not dwelt upon as the webinar concentrated on radiated (higher frequency) emissions.