Re: EMI guard bands
The limit for RE is based as I said in an earlier message on the television band rf signal level required to get a specified base band video signal-to-noise ratio. The fact that the interference coupling mechanism is near field is not important, except of course as it affects measurement technique. -- From: Doug McKean dmck...@auspex.com To: EMC-PSTC Discussion Group emc-p...@majordomo.ieee.org Subject: Re: EMI guard bands Date: Fri, Dec 21, 2001, 10:48 AM John Woodgate wrote: I would be suspicious of that; it is a 'near-field' scenario, which means that the emission field strengths are complex and impossible to calculate. The Class B limits are related to a 10 m separation of source and potential victim, and that implies far-field conditions for emissions above about 5 MHz. That's true, but weren't the early measurements for Class B done at 3 meters? - 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 Healddavehe...@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 Healddavehe...@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.
Re: EMI guard bands
John Woodgate wrote: I would be suspicious of that; it is a 'near-field' scenario, which means that the emission field strengths are complex and impossible to calculate. The Class B limits are related to a 10 m separation of source and potential victim, and that implies far-field conditions for emissions above about 5 MHz. That's true, but weren't the early measurements for Class B done at 3 meters? - 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 Healddavehe...@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.
Re: EMI guard bands
The CE limits were designed entirely empirically but the RE limits were based on EIA TV standards that require a specified signal quality for a given rf input level. The RE limits were simply set X dB below that EIA specified level. My recollection is that the rf level specified would be a long way from a broadcast tower. -- From: John Woodgate j...@jmwa.demon.co.uk To: emc-p...@majordomo.ieee.org Subject: Re: EMI guard bands Date: Thu, Dec 20, 2001, 1:52 PM I read in !emc-pstc that Doug McKean dmck...@auspex.com wrote (in 006801c18988$24b4a2a0$3e3e3...@corp.auspex.com) about 'EMI guard bands', on Thu, 20 Dec 2001: Anywho, the answer I got back from him was that the limits were empirically derived in reference to interfering with television signals. So, the worst case (which turned out to be Class B) was a tv back to back across a wall from another device in an apartment complex. I would be suspicious of that; it is a 'near-field' scenario, which means that the emission field strengths are complex and impossible to calculate. The Class B limits are related to a 10 m separation of source and potential victim, and that implies far-field conditions for emissions above about 5 MHz. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk After swimming across the Hellespont, I felt like a Hero. --- 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 Healddavehe...@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 Healddavehe...@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.
Re: EMI guard bands
I read in !emc-pstc that Doug McKean dmck...@auspex.com wrote (in 006801c18988$24b4a2a0$3e3e3...@corp.auspex.com) about 'EMI guard bands', on Thu, 20 Dec 2001: Anywho, the answer I got back from him was that the limits were empirically derived in reference to interfering with television signals. So, the worst case (which turned out to be Class B) was a tv back to back across a wall from another device in an apartment complex. I would be suspicious of that; it is a 'near-field' scenario, which means that the emission field strengths are complex and impossible to calculate. The Class B limits are related to a 10 m separation of source and potential victim, and that implies far-field conditions for emissions above about 5 MHz. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk After swimming across the Hellespont, I felt like a Hero. --- 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 Healddavehe...@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.
Re: EMI guard bands
Thanks to all who responded. Yes, Ralph Showers. I kept the response from him for the longest time. But, after several program and hard drive crashes, it's lost. Thanks again. Regards, 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 Healddavehe...@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.
RE: EMI guard bands
I beleive his name is Dr. Ralph Showers. A very nice fellow. John Shinn, P.E. Manager, Lab. Operations Sanmina-SCI -Original Message- From: owner-emc-p...@majordomo.ieee.org [mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of Doug McKean Sent: Thursday, December 20, 2001 10:57 AM To: EMC-PSTC Discussion Group Subject: Re: EMI guard bands Historical bit of news ... I asked a similar question a couple of years ago here and was referred to a gentleman who was in the writing of the original FCC limits. Can't remember the man's name but he's a professor at Univ. Penn. if I remember correctly. Anywho, the answer I got back from him was that the limits were empirically derived in reference to interfering with television signals. So, the worst case (which turned out to be Class B) was a tv back to back across a wall from another device in an apartment complex. Regards, 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 Healddavehe...@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 Healddavehe...@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.
Re: EMI guard bands
Historical bit of news ... I asked a similar question a couple of years ago here and was referred to a gentleman who was in the writing of the original FCC limits. Can't remember the man's name but he's a professor at Univ. Penn. if I remember correctly. Anywho, the answer I got back from him was that the limits were empirically derived in reference to interfering with television signals. So, the worst case (which turned out to be Class B) was a tv back to back across a wall from another device in an apartment complex. Regards, 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 Healddavehe...@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.
Re: EMI guard bands
I have a copy of a CBEMA (Computer and Business Equipment Manufacturers' Association) report from 1977 that includes the complete development of the CE and RE limits imposed by the FCC. The limits are based purely on the effect on a radio receiver. I have myself verified that the limits are well-placed in the conducted case. I think any concern about measurement accuracy should NOT be built into the limits. The limits themselves contain a lot of slop. The limits are based on maintaining a particular signal-to-noise ratio which in turn means a particular level of signal from the broadcast station. Also, different radios have different sensitivity when receiving the same rf input, that is for the same rf input to the front end, differing amounts of rfi cause the same amount of interference. I have myself verified this across a sample of over 30 radios with large variations from sample to sample but the mean was exactly 48 dBuV, which is the CBEMA-recommended and FCC mandated CE limit. With significant variation in the response of individual protected victims, an excessive focus on minor variations in the repeatability of measurements is unproductive and misplaced emphasis. Incidentally, several years ago I determined that the response of these radios to common mode rfi was 20 dB more sensitive than to differential mode rfi, because the storage capacitor in the radio's power supply acts as a filter to dm conducted interference. I proposed changing CE limits and measurements to reflect this difference in sensitivity, but no action was taken. -- From: rehel...@mmm.com To: emc-p...@majordomo.ieee.org Subject: RE: EMI guard bands Date: Thu, Dec 20, 2001, 6:03 AM After listening to this thread, it brings up a question that I have had over the years regarding limit lines and passing margins. Are there EMI guard bands already built into the limit lines? I find it very difficult to believe that a group of reasonable people developing a limit line would have determined that they had thought of every possible EMI interference issue and would not have built a safety margin into that limit. Does anyone have any historical development data or insights into the creation of limits? Bob Heller 3M Product Safety, 76-1-01 St. Paul, MN 55107-1208 Tel: 651- 778-6336 Fax: 651-778-6252 --- 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 Healddavehe...@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 Healddavehe...@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.
Re: EMI guard bands
I read in !emc-pstc that rehel...@mmm.com wrote (in of6c4e54e3.fd742a66-on86256b28.0040f...@mmm.com) about 'EMI guard bands', on Thu, 20 Dec 2001: Does anyone have any historical development data or insights into the creation of limits? See my direct response to the OP. Even if limits were originally 'best guess', over the years they have been altered if/when too many complaints of interference were received by the spectrum-control authorities. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk After swimming across the Hellespont, I felt like a Hero. --- 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 Healddavehe...@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.
Re: EMI guard bands
I read in !emc-pstc that CE-TEST cet...@cetest.nl wrote (in nfbbilofgmjcamhepkbaaeglceaa.cet...@cetest.nl) about 'EMI guard bands', on Thu, 20 Dec 2001: It's just for a few months now that CISPR/IEC are considering to implement measurement faults into the required margin. No, the subject has been under study for several years. Several reports have been circulated for voting. As far as my knowledge reaches, a margin for measurement errors in your equipment is officially not required, however silly that sounds. The subject is extremely complex; so complex, in fact that for practical purposes it may actually be uncomputable, but this concept is unacceptable to accreditation agencies so we have to continue to try to make it computable. Some errors are quite easily (if expensively) controlled, and equipment errors fall into this category - you just calibrate against national standard very frequently! Other errors are not controllable, such as the dependence of emissions in a given direction on the exact positioning of cables, and must be classified as 'uncertainty', which can be *estimated* but not *calculated*. If you could calculate it, it would not be uncertainty! There are ways of reducing uncertainty - such as repeated testing one sample and testing many samples, but these are very costly procedures. It is extremely difficult to reconcile the approach to this subject which is fundamental to metrologists and accreditation agencies with the practicality that demands justification for 'high accuracy at any cost'. Bear in mind that emission limits are justified pragmatically by the maintenance at acceptable levels of complaints of interference, not by appeal to some laws of physics. The levels adopted generally at present seem adequate for at least 10^6-1 out of 10^6 sites (Remember that even in a small country there are probably 10^8 'sites'). So an uncompensated measurement error that changes this figure to 10^6 - 1.001 does not seem worth spending USD10 000 to track down. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk After swimming across the Hellespont, I felt like a Hero. --- 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 Healddavehe...@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.
RE: EMI guard bands
It's just for a few months now that CISPR/IEC are considering to implement measurement faults into the required margin. Several reports have been circulated for voting. As far as my knowledge reaches, a margin for measurement errors in your equipment is officially not required, however silly that sounds. So you are allowed to go for the limit having measurement equipment with an accuracy of 10 dB as well as 1 dB, where the latter of course might be much more severe, depending on the polarity of the error. The only wise and required margin is that required by the 80/80 rule. I doubt however, that any of us can reliably prove it's measurement errors for radiated emissions are less then 6dB using a real life EUT. A recent survey of Goedbloed amongst accredited laboratories showed measurement differences of over 10 dB using a standard EUT, depending on frequency, OATS, SAR and FAR. This survey excluded variations in set up of the EUT, rotational variations and thoroughness of the test engineer in finding worst case ! EMI measurement is still a fuzzy discipline ! Gert Gremmen -Original Message- From: owner-emc-p...@majordomo.ieee.org [mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of douglas_beckw...@mitel.com Sent: woensdag 19 december 2001 16:50 To: Stone, Richard A (Richard) Cc: 'Gary McInturff'; Doug McKean; EMC-PSTC Discussion Group Subject: RE: EMI guard bands From: Douglas Beckwith@MITEL on 12/19/2001 10:50 AM Legally you are not required to have any margin, but you measurement uncertainty is usually 3-4db, so you would set the margin to allow for at least your measurement uncertainty. In my previous company we specified 6dB margin to Class A and 3dB margin to Class B. If you specifiy greater than 3dB to class B, your development costs to achieve that rise exponentially. Regards Doug Beckwith Mitel Networks Stone, Richard A (Richard) rsto...@lucent.com on 12/19/2001 08:06:06 AM Please respond to Stone, Richard A (Richard) rsto...@lucent.com To: 'Gary McInturff' gary.mcintu...@worldwidepackets.com, Doug McKean dmck...@auspex.com, EMC-PSTC Discussion Group emc-p...@majordomo.ieee.org cc:(bcc: Douglas Beckwith/Kan/Mitel) 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 Healddavehe...@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
RE: EMI guard bands
After listening to this thread, it brings up a question that I have had over the years regarding limit lines and passing margins. Are there EMI guard bands already built into the limit lines? I find it very difficult to believe that a group of reasonable people developing a limit line would have determined that they had thought of every possible EMI interference issue and would not have built a safety margin into that limit. Does anyone have any historical development data or insights into the creation of limits? Bob Heller 3M Product Safety, 76-1-01 St. Paul, MN 55107-1208 Tel: 651- 778-6336 Fax: 651-778-6252 --- 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 Healddavehe...@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.
RE: EMI guard bands
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 Healddavehe...@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 Healddavehe...@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
RE: EMI guard bands
We manufacture both Class A (ITE) and Class B (short range radio) devices and treat margins equally. Richard Woods Sensormatic Electronics Tyco International -Original Message- From: Stone, Richard A (Richard) [mailto:rsto...@lucent.com] Sent: Wednesday, December 19, 2001 8:06 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 Healddavehe...@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 Healddavehe...@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 Healddavehe...@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
RE: EMI guard bands
Richard, we make both. I don't relax the guard band. We might release a few beta's if we pass but are within that noise margin range, but the work continues to drop all signals to under the 3 db limit before I will sign the ECO to release it to production status. Theoretically at least I agree with you about the .1 as being a pass - hence the Beta unit release, although these are tracked and occasionally replaced. If I was only selling one product and didn't have to worry about variation in parts and manufacturing I would give up the guard band requirement. If rules and methods are put in place to address a problem and they do what they were intended to do, regardless of some level of uncertainty then we should quit mucking around with them and get onto other issues. If and only if they aren't resolving the issue should they rules/ methods more stringent, reduce the margin of uncertainty, or develop whole new methodologies. If it isn't broke don't fix it, but we like to fuss and make things better even when unnecessary just because we can, and it often costs alot of time and money. A sledge hammer is unnecessary to kill a fly - although it satisfies me a great deal! And now the firestorm of e-mails start. Gary -Original Message- From: Stone, Richard A (Richard) [mailto:rsto...@lucent.com] Sent: Wednesday, December 19, 2001 5:06 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 Healddavehe...@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 Healddavehe...@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
RE: EMI guard bands
From: Douglas Beckwith@MITEL on 12/19/2001 10:50 AM Legally you are not required to have any margin, but you measurement uncertainty is usually 3-4db, so you would set the margin to allow for at least your measurement uncertainty. In my previous company we specified 6dB margin to Class A and 3dB margin to Class B. If you specifiy greater than 3dB to class B, your development costs to achieve that rise exponentially. Regards Doug Beckwith Mitel Networks Stone, Richard A (Richard) rsto...@lucent.com on 12/19/2001 08:06:06 AM Please respond to Stone, Richard A (Richard) rsto...@lucent.com To: 'Gary McInturff' gary.mcintu...@worldwidepackets.com, Doug McKean dmck...@auspex.com, EMC-PSTC Discussion Group emc-p...@majordomo.ieee.org cc:(bcc: Douglas Beckwith/Kan/Mitel) 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 Healddavehe...@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 Healddavehe...@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 Healddavehe...@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
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 Healddavehe...@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 Healddavehe...@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 Healddavehe...@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.
RE: EMI guard bands
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:gary.mcintu...@worldwidepackets.com] 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: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 Healddavehe...@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 Healddavehe...@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 Healddavehe...@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.
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 Healddavehe...@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 Healddavehe...@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.
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 Healddavehe...@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.
Re: EMI guard bands
Tania and Amund, IMHO, the margin of compliance should be at least equal to or greater than the measurement uncertainty. Measurement uncertainty for radiated emissions is generally in the range of 3 to 4 dB for most labs. Jim Hulbert Pitney Bowes Tania Grant taniagr...@msn.com To: am...@westin-emission.no, emc-p...@majordomo.ieee.org Sent by: cc: owner-emc-pstc@majordom Subject: Re: EMI guard bands o.ieee.org 12/17/2001 01:38 PM Please respond to Tania Grant 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! Education (repeated brainwashing of as many 'powerful company managers) has been my response;-- but that often takes time. In those cases, there is a written memoranda signed by me explaining why that kind of approach is not correct. taniagr...@msn.com - Original Message - From: am...@westin-emission.no To: emc-p...@majordomo.ieee.org Sent: Sunday, December 16, 2001 11:20 AM Subject: SV: EMI guard bands Cecil, When thinking of EMI guard band (margins), I put the following into mind: 1. variation in production (a couple of dB) 2. uncertainly during measurements (5-6 dB at lower frequencies like 30MHz) 3. variation from labs to labs (I don't know 4-6 dB ?? ) I think 6-8dB should give you a good feeling. Amund -Opprinnelig melding- Fra: owner-emc-p...@majordomo.ieee.org [mailto:owner-emc-p...@majordomo.ieee.org]Pa vegne av cecil.gitt...@kodak.com Sendt: 10. desember 2001 13:46 Til: emc-p...@majordomo.ieee.org Emne: EMI guard bands From: Cecil A. Gittens I am in the process of putting a document together for products that are tested for Radiated Conducted Emissions that should have a Guard-band of 6 dB for FCC or CISPR22 class A or B. Does it depend if the product is class A or B? Does anyone have any pointers or suggestions? Thanks. --- 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 Healddavehe...@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 Healddavehe...@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
Re: EMI guard bands
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! Education (repeated brainwashing of as many 'powerful company managers) has been my response;-- but that often takes time. In those cases, there is a written memoranda signed by me explaining why that kind of approach is not correct. taniagr...@msn.com - Original Message - From: am...@westin-emission.no To: emc-p...@majordomo.ieee.org Sent: Sunday, December 16, 2001 11:20 AM Subject: SV: EMI guard bands Cecil, When thinking of EMI guard band (margins), I put the following into mind: 1. variation in production (a couple of dB) 2. uncertainly during measurements (5-6 dB at lower frequencies like 30MHz) 3. variation from labs to labs (I don't know 4-6 dB ?? ) I think 6-8dB should give you a good feeling. Amund -Opprinnelig melding- Fra: owner-emc-p...@majordomo.ieee.org [mailto:owner-emc-p...@majordomo.ieee.org]Pa vegne av cecil.gitt...@kodak.com Sendt: 10. desember 2001 13:46 Til: emc-p...@majordomo.ieee.org Emne: EMI guard bands From: Cecil A. Gittens I am in the process of putting a document together for products that are tested for Radiated Conducted Emissions that should have a Guard-band of 6 dB for FCC or CISPR22 class A or B. Does it depend if the product is class A or B? Does anyone have any pointers or suggestions? Thanks. --- 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 Healddavehe...@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 Healddavehe...@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 Healddavehe...@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.
RE: EMI guard bands
Cecil, We design our products for -10 dB limit, accept -8 dB for a lab prototype pre-production) and allow -6 dB for production units. We feel this is not conservative based on past history of measurement uncertainty and production variations. Jim -Original Message- From: owner-emc-p...@majordomo.ieee.org [mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of cecil.gitt...@kodak.com Sent: Monday, December 10, 2001 7:46 AM To: emc-p...@majordomo.ieee.org Subject: EMI guard bands From: Cecil A. Gittens I am in the process of putting a document together for products that are tested for Radiated Conducted Emissions that should have a Guard-band of 6 dB for FCC or CISPR22 class A or B. Does it depend if the product is class A or B? Does anyone have any pointers or suggestions? Thanks. --- 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 Healddavehe...@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 Healddavehe...@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.
