Ideally one would want a good margin between the emissions of the EUT and the limit to which it must comply. There can be differences due to site variations and EUT configurations or just different samples which have already been discussed. I am comfortable with 6dB of margin. That is 6dB below the required limit(Class A, B, doesn't matter). 3dB of margin is an acceptable pass, but not comfortable and the emission should be seriously investigated. Anything less than that is an issue. A margin of less than 3dB could quickly be over the limit with a different sample or another site. I think it is a very high expectation to want 10dB below the class B limit. Unless there is evidence to suggest that the level may be significantly higher with another sample, site, etc., than 3 or 6dB should be adequate.
Patrick Webb Compliance Engineer -----Original Message----- From: Stone, Richard A (Richard) [mailto:rsto...@lucent.com] Sent: Wednesday, December 19, 2001 7:06 AM To: 'Gary McInturff'; Doug McKean; EMC-PSTC Discussion Group Subject: RE: EMI guard bands Does anyone make Class A AND Class B products? if so, do you allow for a much smaller margin on the B since its approx. 10 db quieter than A to start with. or do you treat them equally. Also Oats site to Oats site can differ as much as +/- 4 db do to many factors. any comments? Richard, -----Original Message----- From: Gary McInturff [mailto:gary.mcintu...@worldwidepackets.com] Sent: Tuesday, December 18, 2001 1:19 PM 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:dmck...@auspex.com] 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson: pstc_ad...@garretson.org Dave Heald davehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson: pstc_ad...@garretson.org Dave Heald davehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson: pstc_ad...@garretson.org Dave Heald davehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson: pstc_ad...@garretson.org Dave Heald davehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org 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.
