Re: FCC rule interpretation (add'l info)
On 6-Aug-01 John Woodgate j...@jmwa.demon.co.uk wrote In Europe, the limits are specified in dB(uV/m), but no-one has been daft enough to propose limits like 53.9790009... dB(uV/m). Folks HAVE been daft enough; 3 volts per meter is 129.542425 dBuV/m, right? Result of specifying in two systems, that's all. Anyway, if you're smart, you don't push the limit. What's the uncertainty of the equipment? +/- 1 dB for the generator, 1 dB for the measuring meter, if they're good. Sounds like a marketers decision, NOT the EMC engineer's! Cortland --- 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: http://www.rcic.com/ click on Virtual Conference Hall,
Re: FCC rule interpretation (add'l info)
I read in !emc-pstc that Hare, Paul ph...@pirus.com wrote (in 200108162322.f7gnm8304...@gemini2.ieee.org) about 'FCC rule interpretation (add'l info)', on Thu, 16 Aug 2001: As a side note, I've seen an FCC application where the second harmonic of the device was measured and reported to be at the limit (i.e. 54 dBuV/m). Since the second harmonic was the closest to the limit, the transmitter's power had been increased to a point at which there was zero margin (questionable philosophy considering manufacturing variabilities, I know). The limit is the limit, right?? Unfortunately, 54 dBuV/m is technically greater than 500 uV/m and the FCC wouldn't certify the device. A situation that discredits both parties. Squeezing up to an EMC limit is highly unwise, but 54 dB(uV/m) is 501.1872366... uV/m. Can we assume that the FCC can measure that precisely? In Europe, the limits are specified in dB(uV/m), but no-one has been daft enough to propose limits like 53.9790009... dB(uV/m). -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co..uk Eat mink and be dreary! --- 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: http://www.rcic.com/ click on Virtual Conference Hall,
RE: FCC rule interpretation (add'l info)
Stuart, As a side note, I've seen an FCC application where the second harmonic of the device was measured and reported to be at the limit (i.e. 54 dBuV/m). Since the second harmonic was the closest to the limit, the transmitter's power had been increased to a point at which there was zero margin (questionable philosophy considering manufacturing variabilities, I know). The limit is the limit, right?? Unfortunately, 54 dBuV/m is technically greater than 500 uV/m and the FCC wouldn't certify the device. I only make these comments since you have been using 54 and 74 dB in your postings... Paul Hare e: ph...@pirus.com Compliance Engineer w: 978.206.9179 Pirus Networks f: 978.206.9199 43 Nagog Park c: 508.450.0376 Acton, MA 01720 i: www.pirus.com -Original Message- From: Wismer, Sam [mailto:wisme...@ems-t.com] Sent: Thursday, August 16, 2001 1:16 PM To: Stuart Lopata; emc Subject: RE: FCC rule interpretation (add'l info) Not sure if you got my last response. Answer is no(IMO). If the idea is to be able to take peak measurements instead of average measurements to expedite the test, then I suggest you take your peak measurements and compare them to average limits. If the peak measurement meets both the calculated peak limit(5000 uv/m) and the stated average limit(500uv/m), then there is no need to make the average measurement. If, however, the peak measurement meets only the peak limit, you are still obligated to take an average measurement and compare it to the average limit. The stated limit always takes precedence over any derived limits. ~ Sam Wismer Lead Regulatory Engineer/ Radio Approvals Engineer LXE, Inc. (770) 447-4224 Ext. 3654 Visit Our Website at: http://www.ems-t.com http://www.ems-t.com/ -Original Message- From: Stuart Lopata [mailto:stu...@timcoengr.com] Sent: Thursday, August 16, 2001 10:51 AM To: emc Subject: Fw: FCC rule interpretation (add'l info) Does this imply that we can use 74 dBuV/m (at 3 meters) rather than the 54 dBuV/m limit if we took measurements employing peak detection? I left that last part out in the previous question.
RE: FCC rule interpretation (add'l info)
Stuart, You must meet both requirements. The part of the rules that also apply is 15.35 paragraph (b) If you made peak measurements, they cannot exceed the average limit (Table 15.209) and the peak measurement cannot exceed the average limit by more than 20 dB. If you only performed peak measurements and meet the average limit, then you don't need to make average measurements. When submitting a certification application, you are required to explain how you made your average measurements. 15.35 describes requirements of the average detector and how the measurements should be performed. Michael Peters -Original Message- From: Stuart Lopata [mailto:stu...@timcoengr.com] Sent: Thursday, August 16, 2001 10:51 AM To: emc Subject: Fw: FCC rule interpretation (add'l info) Does this imply that we can use 74 dBuV/m (at 3 meters) rather than the 54 dBuV/m limit if we took measurements employing peak detection? I left that last part out in the previous question.
RE: FCC rule interpretation (add'l info)
Section 15.35(b) details the two detectors and associated limits. See below: (b) On any frequency of frequencies above 1000 MHz, the radiated limits shown are based upon the use of measurement instrumentation employing an average detector function. When average radiated emission measurements are specified in the regulations, including emission measurements below 1000 MHz, there is also a limit on the radio frequency emissions, as measured using instrumentation with a peak detector function, corresponding to 20 dB above the maximum permitted average limit for the frequency being investigated unless a different peak emission limit is otherwise specified in the rules in this part, e.g., see §15.255. Unless otherwise specified, measurements above 1000 MHz shall be performed using a minimum resolution bandwidth of 1 MHz. Measurement of AC power line conducted emissions are performed using a CISPR quasi-peak detector, even for devices for which average radiated emission measurements are specified. You have to meet both. The nature of the signal is unimportant in this respect. Both limits apply. Ghery Pettit Intel -Original Message- From: umbdenst...@sensormatic.com [mailto:umbdenst...@sensormatic.com] Sent: Thursday, August 16, 2001 10:37 AM To: emc-p...@majordomo.ieee.org; stu...@timcoengr.com Subject: RE: FCC rule interpretation (add'l info) Stuart, Are you confusing the requirement to meet a peak limit while also meeting the average limit? The FCC imposes a condition on meeting a limit where an average detector is specified. If you have a pulsed system, the system must meet the average limit and at the same time not be more than 20 dB higher in peak detection. This does not mean you can add 20 dB to the average limit for any signal condition. Is this issue the origin of the question? Best regards, Don Umbdenstock Sensormatic -- From: Stuart Lopata[SMTP:stu...@timcoengr.com] Reply To: Stuart Lopata Sent: Thursday, August 16, 2001 10:50 AM To: emc Subject: Fw: FCC rule interpretation (add'l info) Does this imply that we can use 74 dBuV/m (at 3 meters) rather than the 54 dBuV/m limit if we took measurements employing peak detection? I left that last part out in the previous question. --- 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: http://www.rcic.com/ click on Virtual Conference Hall, --- 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: http://www.rcic.com/ click on Virtual Conference Hall,
RE: FCC rule interpretation (add'l info)
Stuart, Are you confusing the requirement to meet a peak limit while also meeting the average limit? The FCC imposes a condition on meeting a limit where an average detector is specified. If you have a pulsed system, the system must meet the average limit and at the same time not be more than 20 dB higher in peak detection. This does not mean you can add 20 dB to the average limit for any signal condition. Is this issue the origin of the question? Best regards, Don Umbdenstock Sensormatic -- From: Stuart Lopata[SMTP:stu...@timcoengr.com] Reply To: Stuart Lopata Sent: Thursday, August 16, 2001 10:50 AM To: emc Subject: Fw: FCC rule interpretation (add'l info) Does this imply that we can use 74 dBuV/m (at 3 meters) rather than the 54 dBuV/m limit if we took measurements employing peak detection? I left that last part out in the previous question. --- 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: http://www.rcic.com/ click on Virtual Conference Hall,
RE: FCC rule interpretation (add'l info)
Not sure if you got my last response. Answer is no(IMO). If the idea is to be able to take peak measurements instead of average measurements to expedite the test, then I suggest you take your peak measurements and compare them to average limits. If the peak measurement meets both the calculated peak limit(5000 uv/m) and the stated average limit(500uv/m), then there is no need to make the average measurement. If, however, the peak measurement meets only the peak limit, you are still obligated to take an average measurement and compare it to the average limit. The stated limit always takes precedence over any derived limits. ~ Sam Wismer Lead Regulatory Engineer/ Radio Approvals Engineer LXE, Inc. (770) 447-4224 Ext. 3654 Visit Our Website at: http://www.ems-t.com http://www.ems-t.com/ -Original Message- From: Stuart Lopata [mailto:stu...@timcoengr.com] Sent: Thursday, August 16, 2001 10:51 AM To: emc Subject: Fw: FCC rule interpretation (add'l info) Does this imply that we can use 74 dBuV/m (at 3 meters) rather than the 54 dBuV/m limit if we took measurements employing peak detection? I left that last part out in the previous question. attachment: Sam_Wismer.vcf
Re: FCC rule interpretation (add'l info)
There appears to be an implicit assumption that peak vs. average detection yield a 20 dB difference. I don't understand that. If the signal is cw, like a clock, it won't make any difference what detector you are using. if the signal has some modulation, then the peak/average detector output ratio will depend on the modulation, right? What am I missing? -- From: Stuart Lopata stu...@timcoengr.com To: emc emc-p...@majordomo.ieee.org Subject: Fw: FCC rule interpretation (add'l info) List-Post: emc-pstc@listserv.ieee.org Date: Thu, Aug 16, 2001, 9:50 AM Does this imply that we can use 74 dBuV/m (at 3 meters) rather than the 54 dBuV/m limit if we took measurements employing peak detection? I left that last part out in the previous question.
Fw: FCC rule interpretation (add'l info)
Does this imply that we can use 74 dBuV/m (at 3 meters) rather than the 54 dBuV/m limit if we took measurements employing peak detection? I left that last part out in the previous question.
