There was a paper in the 1987 IEEE International Symposium on EMC by a guy >from DEC talking about issues relating to building an OATS. His final point was data showing that 1/R didn’t work from 3 meters to 10 meters and that the error could be as large as 7 dB, in the direction Bill points out. Pass at 3, fail at 10.
Ghery From: [email protected] [mailto:[email protected]] On Behalf Of Bill Owsley Sent: Friday, November 20, 2009 2:55 PM To: Bill Stumpf; Derek Walton Cc: Grace Lin; [email protected] Subject: Re: 3-meter Chamber Site Comparison Ah.... But back in the day when mini-towers were first coming out.we found we could pass that 3 meters and fail at 10 meters. And then discovered that these amazing technical marvels were launching plane waves that did not roll off the usual expected 10.5 dB. Around about that time I think there was IEEE EMC article about electromagnetic missles or some such fanfare. Now the military actually has a microwave crowd control device that gives the target a sensation of being set on fire. It's amazing what you can do with the flat side of a mini-tower when energized just right. ps. another pound of spring fingers solved that problem. - 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 --- On Fri, 11/20/09, Derek Walton <[email protected]> wrote: From: Derek Walton <[email protected]> Subject: Re: 3-meter Chamber Site Comparison To: "Bill Stumpf" <[email protected]> Cc: "Grace Lin" <[email protected]>, [email protected] List-Post: [email protected] List-Post: [email protected] List-Post: [email protected] Date: Friday, November 20, 2009, 12:38 PM Hi Bill, I take exception when you say data taken at 3m will often show surprising difference if measured at 10m even if set up identically My observations, with typical small objects not great big things, is that emissions are very close at both distances apples to apples.... What does change is that the mast height at which the emission maximizes changes.. Also, 10 metre testing MISSES emissions from EUTs at higher mast heights. IMHO it reaffirms my opinion that the current tests are regulatory, and not oriented towards problem mitigation. It's time we got back to just doing whats necessary to stop practically observed problems. Darn, that turned into a soapbox fast.... Happy holidays, Derek. Bill Stumpf wrote: > Grace, > Any good Calibrated Noise Emitter at the correct frequency range is a good source for checking your OATS or chamber. There are "Round Robin" programs offered by a couple groups that can anonymously show results of your lab compared to other labs participating. When testing actual products what must be remembered is that every EUT will look different from one site to the next due to setup and test distance, among other variables. Also, EUT's are generally "distributed" RF sources and data taken at 3m will often show surprising difference if measured at 10m even if set up identically. Bill > > ------------------------------------------------------------------------ > *From:* [email protected] <http://us. c396.mail.yahoo.com/mc/[email protected]> [mailto:[email protected] <http://us.mc 96.mail.yahoo.com/mc/[email protected]> ] *On Behalf Of *Grace Lin > *Sent:* Friday, November 20, 2009 6:54 AM > *To:* [email protected] <http://us.mc 96.mail.yahoo.com/mc/[email protected]> > *Subject:* 3-meter Chamber Site Comparison > > Dear Members, > I am asked to perform site comparison and would like to hear your comments. > Should I purchase a signal source? If yes, do you have any reference? I do have a COM-POWER comb generator and don't know if it is good enough for the purpose. > Should I use an EUT for site comparison? > Thank you. > Best regards, > Grace Lin > - > ---------------------------------------------------------------- > 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] <http://us.mc396.mai .yahoo.com/mc/[email protected]> <mailto:[email protected] <http://us.mc396.mail.yahoo.com/mc/[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] < ttp://us.mc396.mail.yahoo.com/mc/[email protected]> <mailto:[email protected] <http://us mc396.mail.yahoo.com/mc/[email protected]> >> > Mike Cantwell <[email protected] <ht p://us.mc396.mail.yahoo.com/mc/[email protected]> <mailto:[email protected] <http://us.m 396.mail.yahoo.com/mc/[email protected]> >> > > For policy questions, send mail to: > Jim Bacher <[email protected] <http:/ us.mc396.mail.yahoo.com/mc/[email protected]> <mailto:[email protected] <http://us.mc 96.mail.yahoo.com/mc/[email protected]> >> > David Heald <[email protected] <http:/ us.mc396.mail.yahoo.com/mc/[email protected]> <mailto:[email protected] <http://us.mc3 6.mail.yahoo.com/mc/[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] <http://us.mc396.mai .yahoo.com/mc/[email protected]> <mailto:[email protected] <http://us.mc396.mail.yahoo.com/mc/[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] < ttp://us.mc396.mail.yahoo.com/mc/[email protected]> <mailto:[email protected] <http://us mc396.mail.yahoo.com/mc/[email protected]> >> > Mike Cantwell <[email protected] <ht p://us.mc396.mail.yahoo.com/mc/[email protected]> <mailto:[email protected] <http://us.m 396.mail.yahoo.com/mc/[email protected]> >> > > For policy questions, send mail to: > Jim Bacher <[email protected] <http:/ us.mc396.mail.yahoo.com/mc/[email protected]> <mailto:[email protected] <http://us.mc 96.mail.yahoo.com/mc/[email protected]> >> > David Heald <[email protected] <http:/ us.mc396.mail.yahoo.com/mc/[email protected]> <mailto:[email protected] <http://us.mc3 6.mail.yahoo.com/mc/[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] <http://us.mc396.mai .yahoo.com/mc/[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] <ht p://us.mc396.mail.yahoo.com/mc/[email protected]> > Mike Cantwell <[email protected] <http://us.mc396.mail.yahoo.com/mc/[email protected]> > For policy questions, send mail to: Jim Bacher: <[email protected] <http:/ us.mc396.mail.yahoo.com/mc/[email protected]> > David Heald: <[email protected] <http:// s.mc396.mail.yahoo.com/mc/[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. 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