It seems like there are two issues here. The first would be the variability for identical products using the same test setup at the same test lab. I think that's what this thread is about so far.
The second issue would be the variability for a given product and test setup at different test labs. For the second situation, I've heard that 6 dB is about all you can count on, when you set up and do the test yourself. 15 dB or so if the lab or someone else does it. So how much does the second issue matter? Only if your test results are challenged I suppose. Two more cents George -----Original Message----- From: Gary McInturff [mailto:[email protected]] Sent: Tuesday, December 18, 2001 10:19 AM To: Doug McKean; EMC-PSTC Discussion Group Subject: RE: EMI guard bands I hold with the 3 db under class B, as well as A. The only effective argument, in my mind, is the uncertainty of measurement issue. Beyond that I find that if I have 3 db everywhere my measurements next time down with that product or with one off the shelf have also been compliant. So if pragmatic repeated measurements is telling me I'm in then I am not going to spend the time and money to make even more sure that I am in. The goal is to not interfere with communications not to be invisible at all costs. If it ain't broke I'm not fixing it. Obviously, others disagree. By the way if a customer requests it, they get what they want, if they want to pay for it, and I have never rejected products with a 3 db band - and they haven't bitten me yet either. My couple cents Gary -----Original Message----- From: Doug McKean [mailto:[email protected]] Sent: Monday, December 17, 2001 3:15 PM To: EMC-PSTC Discussion Group Subject: Re: EMI guard bands "Tania Grant" wrote: > > Amund, > > My minimum criteria and recommendation has always been at least 6dB. > However, how many engineering managers, upon finding a 1.5 dB margin in > their favor, rule "ship it"! <nod> Although in some markets, there are customers who require -6dB under the Class A limit. Although if I had it my way, I'd make it about -10dB under the limit. - Doug McKean ------------------------------------------- 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: Michael Garretson: [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: No longer online until our new server is brought online and the old messages are imported into the new server. ------------------------------------------- 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: Michael Garretson: [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: No longer online until our new server is brought online and the old messages are imported into the new server. ------------------------------------------- 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: Michael Garretson: [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: No longer online until our new server is brought online and the old messages are imported into the new server.
