Possibly a wee bit harshly stated, but otherwise correct as previous posters have noted. That said, the other issues are beam width of antennas (unspecified in most standards) and "bore-sighting" (uspecified in most (all?) standards). If I remember correctly, the proposed CISPR 22 standard for emissions above 1 GHz does not have a height scan or bore sighting. Is this correct?
With respect, Brent DeWitt > -----Original Message----- > From: [email protected] [mailto:[email protected]]On Behalf Of Dward ATCB > Sent: Saturday, October 01, 2005 5:54 PM > To: [email protected]; [email protected] > Cc: [email protected] > Subject: RE: Above 1 GHz EMI testing with horn antenna > > > Just because someone does something and 'gets away with it' does > not mean it > is right nor within the rules. The standards say raise and lower the > antenna 1-4 meter. That is what it means. Until such time as > the standards > and rules are written for a different antenna height, the only > way that you > can say you comply with the rules is to do what it says i.e. > raise and lower > the antenna 1-4 meters. IF you do not raise and lower the antenna 1-4 > meters then you are not compliant to the rules. It is as simple as that. > > > Dennis Ward > Evaluation Engineer > American TCB > Certification Resource for the Wireless Industry www.atcb.com > 703-847-4700 fax 703-847-6888 > direct - 703-880-4841 or 209-966-2145 > NOTICE: This E-Mail message and any attachment may contain privileged or > company proprietary information. If you received this message in error, > please return to the sender. > > > -----Original Message----- > From: [email protected] [mailto:[email protected]] On Behalf Of > Eric Lifsey > Sent: Saturday, October 01, 2005 12:29 PM > To: [email protected] > Cc: [email protected] > Subject: Re: Above 1 GHz EMI testing with horn antenna > > Circa 1995 I saw plotted emission data taken at a semi-anechoic > chamber in Austin, Texas, that justified reducing the scan > height to a maximum of around 1.4 meters (IIRC) for emissions in > the GHz range. > > However, when I ran the first 1-2 GHz emissions measurements > where I worked I found maximums at 2.5 meter heights. (Using an > octave horn.) I suspect the other lab tested a physically small > source which would hide the effect of a real EUT of random > dimensions and apetures. > > I mounted the horn with a slight downward tilt to help insure > that the EUT emissions would be collected at the higher antenna > elevation and as frequency approached 2 GHz. The measurement > distance was 3 meters within a compact shielded room with cone > absorbers. This chamber was used primarily to pre-scan > emissions below 1 GHz at the time. > > IMO the best approach as suggested by others is to scan per the > written requirements. I'd add that I would have preferred to > collect emissions from greater than 3 meters to avoid the > concerns of the narrow field of illumination/sensitivity in the > octave horn. > > Best Regards, > Eric Lifsey > > [email protected] said: > > Hello, > > > > A discussion has come up about the need to raise the horn > > antenna up to 4 > > meters when doing an EMI test above 1 GHz. ANSI states that the > > antenna height > > should be adjusted between 1-4 meters to maximize the emissions. > > Some labs > > are only doing this test at 1 meter or maybe 2 meters high, > > (probably to > > reduce cable loss issues). Normally, the emissions are worst > > case below 2 > > meters, but how can one be absolutely sure, without checking? > > What is the legal > > requirement for the antenna height? These questions apply to > > unintentional > > radiators, where measurement above 1 GHz is required. > > > > Regards, > > Tim Pierce > > > > - > > 2005 IEEE Symposium on Product Safety Engineering > > 3-4 October Schaumburg, IL > > http://www.ieee-pses.org/symposium > > > > ---------------------------------------------------------------- > > This message is from the IEEE Product Safety Engineering Society > > emc-pstc discussion list. Website: http://www.ieee-pses.org/ > > > > To post a message to the list, send your e-mail to > > [email protected] > > > > Instructions: > > http://listserv.ieee.org/listserv/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: > > > > Richard Nute: [email protected] > > Jim Bacher: [email protected] > > > > All emc-pstc postings are archived and searchable on the web at: > > > > http://www.ieeecommunities.org/emc-pstc > > > > > --- > http://www.relia.net/~elifsey/ > > - > 2005 IEEE Symposium on Product Safety Engineering > 3-4 October Schaumburg, IL > http://www.ieee-pses.org/symposium > > ---------------------------------------------------------------- > This message is from the IEEE Product Safety Engineering Society > emc-pstc discussion list. Website: http://www.ieee-pses.org/ > > To post a message to the list, send your e-mail to [email protected] > > Instructions: http://listserv.ieee.org/listserv/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] > > All emc-pstc postings are archived and searchable on the web at: > > http://www.ieeecommunities.org/emc-pstc > > - > 2005 IEEE Symposium on Product Safety Engineering > 3-4 October Schaumburg, IL > http://www.ieee-pses.org/symposium > > ---------------------------------------------------------------- > This message is from the IEEE Product Safety Engineering Society > emc-pstc discussion list. Website: http://www.ieee-pses.org/ > > To post a message to the list, send your e-mail to [email protected] > > Instructions: http://listserv.ieee.org/listserv/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] > > All emc-pstc postings are archived and searchable on the web at: > > http://www.ieeecommunities.org/emc-pstc > -- > No virus found in this incoming message. > Checked by AVG Anti-Virus. > Version: 7.0.344 / Virus Database: 267.11.9/116 - Release Date: 9/30/2005 > -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.344 / Virus Database: 267.11.9/116 - Release Date: 9/30/2005 - 2005 IEEE Symposium on Product Safety Engineering 3-4 October Schaumburg, IL http://www.ieee-pses.org/symposium This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/listserv/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] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
