Traditions are sometimes malleable over time and morph into something not originally envisioned. Think about Halloween trick-or-treating or the Easter Bunny!
IIRC FCC Part 15 started off with a 30m measurement distance which made 30MHz fields very close to a far field measurement which is what you want. We have to set the “way-back machine” for 1982 so my memory may not be totally accurate. With time, the EMC community realized that 10, 5 and even 3m measurement distances were so much cheaper to use when constructing a measurement area (OFS/OATS or Anechoic chamber) and the S/N ratio was much better giving cleaner results. Never mind if the results were representative of real-world interference or not. So now we are in a situation like Gert describes where theory and practice don’t really present a consistent story but such is life in the compliance world. …Marko ________________________________ From: ce-test, qualified testing bv - Gert Gremmen [mailto:[email protected]] Sent: Tuesday, March 09, 2010 12:11 PM To: [email protected] Subject: Re: [PSES] Radiated Immunity I go for tradition……and lack of innovation… and conservatism and protection of investments (of test houses). Transmission and receiving are reciprocal mechanisms. All arguments valid for immunity testing at 30 or 80 MHz are equally valid for emission testing and vice versa. Passive networks… As the OATS is a bad transmission line for low frequencies due to ground plane reflections and wave cancelling, so with immunity testing we put ferrite and foam on the floor… So we should do the same for emissions, shouldn’t we? Or don’t we believe in theory anymore ? Or should we remove the foam an ferrite and profit of the reflections by doubling the transmit field strength at the cost of changing the height of the send antenna ….. So the only technical valid argument is amplifier power and costs. Soon emission testing will start at 80 Mhz too, but soon is a large Time span in EMC-world…. Gert Gremmen Ce-test, qualified testing bv Van: [email protected] [mailto:[email protected]] Namens Pettit, Ghery Verzonden: dinsdag 9 maart 2010 19:14 Aan: [email protected]; [email protected] Onderwerp: RE: Radiated Immunity Conducted immunity is done up to 80 MHz in place of radiated immunity. It is difficult to generate a uniform field at lower frequencies in the space available in a typical lab with reasonable power requirements for the amplifier. As to why the break point for radiated emissions is 30 MHz? To quote Tevye, “Tradition!” Ghery S. Pettit From: [email protected] [mailto:[email protected]] On Behalf Of [email protected] Sent: Tuesday, March 09, 2010 7:13 AM To: [email protected] Subject: Radiated Immunity Can someone tell me why the Radiated Immunity testing is conducted from 80 Mhz to 2 Ghz while Radiated Emissions is conducted from 30 Mhz to 1 Ghz (or 5th harmonic), i.e. why the gap from 30 Mhz to 80 Mhz for Immunity? Robert Hanson - 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://www.ieeecommunities.org/emc-pstc 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://www.ieeecommunities.org/emc-pstc 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]> Important : This message is intended only for the recipient(s) identified above by the originator or forwarder of this message and may contain information that is confidential, proprietary and/or legally privileged. If you have any reason to believe or suspect that this message may have come to you in error, please notify the originator of this message of your receipt of it, refrain from sharing this message with anyone else, delete it from each computer or server on which it is stored (without copying it or printing it out) and take no other action based on its content. Thank you. - 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://www.ieeecommunities.org/emc-pstc 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://www.ieeecommunities.org/emc-pstc 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]>
