In this article for InCompliance magazine, instructor Arturo Mediano discusses how using higher quality components with low parasitics can actually cause problems in your system by ringing.
Successfully troubleshooting EMI/EMC problems isn't easy. You need time, you need a strategy, and you need to remain calm. Sometimes, you need a special "sixth sense" that only comes from experience because in some cases, your problems aren't even related with the EUT (equipment under test).
Article by instructor Arturo Mediano about near-field scanners.
I love near field probes because they let me "see" magnetic and electric fields with an oscilloscope or with a spectrum analyzer. They let locate sources of emissions in board, cables, and systems. Near-field scanners also let you see emissions, particularly all over a board. That's hard to do with a single probe.
Arturo Mediano is a professor at University of Zaragoza (Spain) and founder of The HF-Magic Lab®, a specialized laboratory for design, diagnostic, troubleshooting, and training in the EMI/EMC/SI and RF fields. He is also an instructor for Besser Associates (CA, USA) offering public and on site courses in EMI/EMC/SI/RF subjects.
Instructor Arturo Mediano has written an article for In Compliance magazine:
Digital and power electronic systems can reduce the radiated and conducted emissions profile using spread spectrum techniques. Typically, no more than 10-12dB can be obtained with those techniques but the result can be useful to comply with regulations...
Instructor Arturo Mediano has published an article with In Compliance magazine on reducing VHF EMI from a flyback power supply.
Usually, EMC design guidelines in flyback literature are related with the switching effects of the output transistor to minimize emissions for conducted tests in the 9 kHz to 30 MHz range. But failure in radiated emissions in the VHF range is typical when testing the product for EMC compliance.