Ken Javor wrote >> I didn't know what the 20 H rule was either, just assumed everyone else did... <<
See http://www.qsl.net/wb6tpu/si-list4/0391.html page 9 of http://www.ansoft.com/thewave/Shielding_and_Decoupling.pdf http://factaee.elfak.ni.ac.yu/fu2k12/fu04.html and others (search on "20H rule.") RF between two equally sized planes does radiate from the slot formed at the edge - but RF on a small plane over a larger one also radiates from the slot around the smaller. We don't want to put patch antennas on a board while trying to avoid other problems. Thus the controversy. Cortland KA5S - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc