Harmful interference isn't promoted by any government, unless one happens to be a PLT/PLC/BPL seller, but that is off topic. However, FCC Part 15 limits are in my observation now set not by what it takes to cause interference, though that is a starting point, but by what industry will accept by way of limitation on its profits. In the United States the rule-making process carries a period of public comment and the FCC is exquisitely sensitive to Congressional pressure, so that one should (IMO) not rely on Part 15 or Part 18 to preempt interference, if that is one's goal. FCC limits, already assume that the risk of harmful interference is small, and are therefore increased beyond a level that insures reception is protected. When interference occurs, it is presumed, the aggrieved party will be able to pursue a complaint, a presumption without much merit these days.
It appears that other standards here -- DO-160 and MIL-STD 461 -- do incorporate a margin; they, however, may not be legally enforceable limits, but negotiable as you describe on a one-by one basis. I have had to point out that negotiations and customer insistence may with more rather than less stringent limits if, for example, one's EUT is to be installed line-of-sight to an aircraft radio antenna. Sometimes people forget where the antennas are. And some of us remember the "good old days" of VDE 0871! Cortland KA5S > [Original Message] > From: Get Gremmen <[email protected]> > To: <[email protected]> > Date: 7/4/2007 3:42:30 AM > Subject: RE: Internal Margins for Emissions Testing > > I have been reading this thread for a while, but missed an important > aspect. > > Engineers in our profession have been looking at limits as absolute > LIMITS, not to be exceeded by any device under any circumstances. > To meet this in practical situations, many approaches have been > suggested, most suggesting extra severe limits, where the discussion is > about how much more severe. > > Well in Europe, and this shows the strength of the EMC directive, the > bottom line is that equipment should not interfere. (simplified > essential requirement - 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 [email protected] 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] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email ______________________________________________________________________
