The reduction on the level on radiated emissions might come from the CISPR 20, As you might know CIPSR 35 is a combination of CISPR 24 and CISPR 20.
Sincerely, Dieter Paasche Senior Product Developer, Electrical CHRISTIE 809 Wellington Street North Kitchener, ON N2G 4Y7 Phone: 519-744-8005 ext.7211 www.christiedigital.com<http://www.christiedigital.com/> This e-mail message (including attachments, if any) is confidential. Any unauthorized use, distribution or disclosure is prohibited. If you have received this e-mail message in error, please notify the sender by reply e-mail or telephone and delete it and any attachments from your computer system and records. From: Joe Randolph <j...@randolph-telecom.com> Sent: Thursday, March 25, 2021 1:58 PM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] rationale behind conducted immunity levels in EN 55035 / IEC 61000-4-6 CAUTION:This email originated from outside of the organization. Do not click links or open attachments unless you recognize the sender and know the content is safe. 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) j...@randolph-telecom.com<mailto:j...@randolph-telecom.com> http://www.randolph-telecom.com<https://nam11.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.randolph-telecom.com%2F&data=04%7C01%7CDieter.Paasche%40christiedigital.com%7C30ad8bdd7e6542fbe4c808d8efb78292%7Cdf46f062ad2c407688e6c675c789a0d8%7C0%7C0%7C637522918751734875%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=Nd8efb9uM7GI1w3%2BvqBtCbUGSISn5ove3ekTU8SXaf4%3D&reserved=0> From: Jeff Keyzer [mailto:j...@mightyohm.com] Sent: Thursday, March 25, 2021 1:21 PM To: EMC-PSTC@LISTSERV.IEEE.ORG<mailto: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. 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