[sdiy] Ferrite beads on module power inputs

[Paul Perry]

Something that I have found suprising, is the amount of HF noise that can be 
generated by a 'simple' power supply diode rectifier.
I put the quotes around 'simple' because, in the real world, you find all 
manner of unexpected things happening - that is why you see so many wall 
warts with the lead threaded through a ferrite ring, in a desperate last 
minute atempt to get RF to stop radiating. The RF noise comes from very very 
narrow spikes generated as the diodes reverse (I think.) Pretty near 
invisible on the scope, but certainly pervasive, and gave me a lot of grief.

Too late for me now.. but this article looks useful:
http://www.smpstech.com/mtblog/diode_recovery_emi.html

paul perry Melbourne Australia