As I recall, Pate, German, and Smith came out with the NSA +/- 4 dB paper in 1982. The FCC had been using tuned dipoles at 3 meters for Class B and 10 meters for Class A for quite awhile, but would accept "other" antennas if properly corrected for. Any dispute would be settled with tuned dipoles at the above spec'd distances. Why 30 MHz? tuned dipoles any bigger (lower freq) were too delicate and broke often, if you could find any sources. They often had fixed section with a tunable end piece for a band. And try to scan a 30 MHz dipole in vertical... We had 3 meter pre-compliance chambers for frequency identification and measured at 3 and 10 m on the OATS for compliance data, until we got the first FCC recognized 3 meter chamber as an alternative test site done. And then we used the distance correction factor for Class A. But the various EU standards in effect then only accepted 10 meter data, not corrected but measured, so we either measure at the OATS or sent it out, until we built the 10 meter chambers. We did have a couple of 30 meter chambers at other locations, and I thought they were big until I stepped into a full size automotive SAC. I've been in what has been said to be the worlds biggest, but I don't count military chambers in comparisons with civilian chambers. Another rational used by one of the FCC engineers ran along the line of 3 meters is a SWAG for common house/apartment dimensions and 10 meters is common for office, commercial, etc. Why are the EU standards different than the FCC? It has taken many years of negotiation and compromise to get as close as they are today. But Immunity is still a non-USA concern, which might change with the toyota debacle since it involves significant safety concerns. Why might the USA not be interested in immunity? Could be the reciprocity mentioned in another email - 'what can get out, can also get in', but the USA counts on market forces to handle quality issues instead of standards to test for a minimum level of "quality" or immunity. Why the conducted to radiated break at 80 MHz? Some standards run the conducted up to 230 MHz. Some equipment will handle up to 1 GHz conducted testing. The 80 MHz radiated start may well be due to the calculations (theory) of getting a 0,+6dB "plane" wave over 16 points in a chamber, with affordable power amps. Not many of us can put a quarter million watts, or more, of RF power into a chamber to get the required field strength.
- Bill In the event of a national emergency, click on the following links to provide directions to your duly elected mis-representative. http://www.usa.gov/Contact/Elected.shtml or... https://writerep.house.gov/writerep/welcome.shtml http://www.senate.gov/general/contact_information/senators_cfm.cfm ________________________________ From: Ken Javor <[email protected]> To: "[email protected]" <[email protected]> Sent: Tue, March 9, 2010 1:19:39 PM Subject: Re: Radiated Immunity The RE measurement starting at 30 MHz is based on the ability to use a tuned dipole at three meters and have reasonable repeatability (NSA +/- 4 dB). 30 MHz is as low as you can go. Phone: (256) 650-5261 ________________________________ From: "Pettit, Ghery" <[email protected]> List-Post: [email protected] List-Post: [email protected] List-Post: [email protected] Date: Tue, 9 Mar 2010 10:13:32 -0800 To: "[email protected]" <[email protected]>, "[email protected]" <[email protected]> Conversation: Radiated Immunity Subject: 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]> - 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]>
