Sites differences are really curious, would love to work on that one! So the noise source, my SWAG, use o'cope to measure the ac/rf difference between primary and secondary, that is switching side to rectified side of transformer. Use several caps in parallel to decouple that down to about 1/4 of the original reading. Hint, it is easiest to measure the more DC or stable levels of each side. 2nd hint, on primary side, if dot convention means that end is started first so that it is inner most winding, then that needs to be the switched end of the primary winding. Do the same for the DC modulators, Or place honking big ferrites on AC and all outputs. If that works, I'll tell what I think is going, but havn't figured out how to demonstrate it, yet. ps. you want caps directly across, not each side to reference plane, which is actually two in series. That works out to half the capacitance and twice the inductance - the wrong way to go for EMC.
Attitude is Mind over Matter. If you don't Mind, it doesn't Matter... This email has been displayed using 100% recycled electrons and 100% pure virgin photons. --- On Sat, 2/12/11, Brian O'Connell <[email protected]> wrote: > From: Brian O'Connell <[email protected]> > Subject: RE: OATS vs anechoic > To: [email protected] > Date: Saturday, February 12, 2011, 6:22 PM > Just finished 2d OATS site - was not > able to detect much of anything. > > Went back to indoors fully anechoic, where the noise plot > is deafening. > > This is a simple 100W unit with one main ac/dc converter > and (6) dc current modulators. Construction is mostly > plastic, with exception of metal base plate. As it is Class > II construction, there is no ground wire. > > Bad stuff is at 40-80MHz and 200-500MHz. Did some isolation > troubleshooting - looks like the input power cord is the > main radiator. > > The EMC engineers at all three sites are both baffled and > fascinated and want a sample unit to play with. I am very > happy that they are amused, but I have to ship a product and > cannot afford to support the Southern California EMC > industry. > > thanks, > Brian > > > -----Original Message----- > > From: [email protected] > [mailto:[email protected]]On > Behalf Of Brian > > O'Connell > > Sent: Saturday, February 12, 2011 12:25 PM > > To: [email protected] > > Subject: OATS vs anechoic > > > > > > Good People, > > > > Have tested at several sites. All are 'big' names and > have a > > good reputation. > > > > The 10m fully anechoic chamber data indicates from > +5dB to > > +11dB in several frequencies; while the 10m OATS says > the > > unit passes Class B, min -4.2dB. > > > > Huh?!? What is the physics behind the difference > between an > > outside site and absorbers? Where are the Borg when > you need them? > > > > Brian > > > > - > > > ---------------------------------------------------------------- > > This message is from the IEEE Product Safety > Engineering > > Society emc-pstc discussion list. To post a message > to the > > list, send your e-mail to <[email protected]> > > > > All emc-pstc postings are archived and searchable on > the web at: > > http://product-compliance.oc.ieee.org/ > > Graphics (in well-used formats), large files, etc. > can be > > posted to that URL. > > > > Website: http://www.ieee-pses.org/ > > Instructions: http://listserv.ieee.org/request/user-guide.html > > List rules: http://www.ieee-pses.org/listrules.html > > > > For help, send mail to the list administrators: > > Scott Douglas <[email protected]> > > Mike Cantwell <[email protected]> > > > > For policy questions, send mail to: > > Jim Bacher: <[email protected]> > > David Heald: <[email protected]> > > > > > > - > ---------------------------------------------------------------- > This message is from the IEEE Product Safety Engineering > Society emc-pstc discussion list. To post a message to the > list, send your e-mail to <[email protected]> > > All emc-pstc postings are archived and searchable on the > web at: > http://product-compliance.oc.ieee.org/ > Graphics (in well-used formats), large files, etc. can be > posted to that URL. > > Website: http://www.ieee-pses.org/ > Instructions: http://listserv.ieee.org/request/user-guide.html > List rules: http://www.ieee-pses.org/listrules.html > > For help, send mail to the list administrators: > Scott Douglas <[email protected]> > Mike Cantwell <[email protected]> > > For policy questions, send mail to: > Jim Bacher: <[email protected]> > David Heald: <[email protected]> > - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://product-compliance.oc.ieee.org/ Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
