A 10 dB margin? That's easy for the guy doing the test to say! Heck; why not 20dB?! For the designer who is sweating bullets trying to keep within cost and size requirements, however, this may be quite another matter.
Considering the original specifications are somewhat arbitrarily derived in the first place, it seems to me a more pragmatic approach is warranted that meets the spirit of the regulations, rather than just overdesigning to meet ill-defined "worse case" scenarios that may or may not actually exist. Bob Wilson TIR Systems Ltd. Vancouver. -----Original Message----- From: Greilich, Jeff [mailto:[email protected]] Sent: February 28, 2002 10:00 AM To: [email protected] Subject: Safety Margins based on NSA premises Et Al: Another important point to consider on safety margins is how the site performed for Normalized Site Attenuation (NSA) when applicable. A +/-4dB variation is the maximum allowable for NSA based on the premise that 1.5 dB is attributable to the site uncertainty and 2.5 dB is attributable to instrumentation uncertainty. Considering these uncertainties, if a mere 3 dB of margin is considered as "safe", it is conceivable that the same EUT could be measured 8 dB different at another site (i.e. the FCC's Site). However, if a 10 dB margin is achievable, this automatically factors out site conjugate uncertainties and provides an additional 2 dB margin for a worst-case scenario. Regards, Jeffrey W. Greilich EMC Technical Manager Automotive System Laboratory, Inc. 27200 Haggerty Road, Suite B-12 Farmington Hills, MI 48331 (248) 848-2771 (Office) ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [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://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list" ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [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://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
