Hi Jeff:
Back in the days when people had ordinary telephones and AM radio stations were common, it was a “known thing” that cables near an AM radio transmitter could develop common mode voltages up to 3 Vrms. If the phone did not have perfect earth balance at the AM frequency, there would be a common-mode-to-differential conversion that would create a differential RF signal on the phone line pair. Any non-linearity in the phone circuit, such as a diode, would demodulate the differential AM RF signal, with the result that the AM radio music/voice could be clearly heard in the telephone handset. I’m describing this to you because it is the only situation where I have personally seen a performance degradation due to common mode RF on a cable. Hearing AM radio broadcasts in ordinary phones was a common problem. CISPR has extended this principle to a range of frequencies that is larger than the AM band, and to performance degradation that that includes digital malfunctions as well. Presumably they had their reasons for this, but I do not know the rationale. All I can say is that I hope the real-world example I described above gives you some idea of what CISPR may be concerned about. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 (USA) <mailto:j...@randolph-telecom.com> j...@randolph-telecom.com <http://www.randolph-telecom.com> http://www.randolph-telecom.com From: Jeff Keyzer [mailto:j...@mightyohm.com] Sent: Thursday, March 25, 2021 1:21 PM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: [PSES] rationale behind conducted immunity levels in EN 55035 / IEC 61000-4-6 Hello all, I am looking for background information on the rationale behind the conducted immunity test levels defined in EN 55035 / CISPR 35 and IEC 61000-4-6. Specifically, in 55035:2016 table 2, clause 2.1 calls for a test level of 3V rms from 0.15 to 10MHz. It also defines a slope that reduces the signal level above 10MHz. What is the technical rationale behind 3V rms being the desired immunity level for ITE equipment? Second, why does the voltage level taper above 10MHz in 55035, as opposed to 55024, where the test remains constant from 150kHz - 80MHz? IEC 61000-4-6 also calls for 1V, 3V, 10V rms test levels and calls for 80% AM modulation "to simulate actual threats". Is the rationale behind this documented somewhere? What threats were considered? I suspect this is a rabbit hole, but curiosity (and a concerned client) has gotten the best of me. -- Jeff Keyzer MightyOhm LLC j...@mightyohm.com <mailto:j...@mightyohm.com> - ---------------------------------------------------------------- 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 <emc-p...@ieee.org <mailto:emc-p...@ieee.org> > All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) <http://www.ieee-pses.org/list.html> List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <sdoug...@ieee.org <mailto:sdoug...@ieee.org> > Mike Cantwell <mcantw...@ieee.org <mailto:mcantw...@ieee.org> > For policy questions, send mail to: Jim Bacher <j.bac...@ieee.org <mailto:j.bac...@ieee.org> > David Heald <dhe...@gmail.com <mailto:dhe...@gmail.com> > - ---------------------------------------------------------------- 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 <emc-p...@ieee.org> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <sdoug...@ieee.org> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.com>
