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. 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
