Ed Hare spotted the same reference. His comment: "The net effect is that there will now be strong emissions that are strong across wide frequency ranges, not just on specific frequencies." Dave K1ZZ -----Original Message----- From: Bob Vallio [mailto:rbvallio@gmail.com] Sent: Monday, April 17, 2006 7:41 PM To: arrl-odv Subject: Spread Spectrum Noise from Switching Power Supplies Switching power supplies can generate some nasty RFI spurs. Now, some designers are turning toward "dithering" the power supply switching frequency courtesy of a built-in random number generator. With this approach, instead of having a lot of RFI on one frequency, the RFI will be thinned out and spread across a wide spectrum like cheese on a cracker. See: http://powerelectronics.com/mag/603PET07.pdf <http://powerelectronics.com/mag/603PET07.pdf> Apparently this is cheaper than building in filter components, hence improving the profit margin for the manufacturers