That's my understanding as well. Ralph McDiarmid, AScT Compliance Engineering Group Xantrex Technology Inc.
> -----Original Message----- > From: [email protected] [mailto:[email protected]] > Sent: August 24, 2004 8:07 AM > To: [email protected]; > [email protected]; [email protected] > Subject: RE: Average Detection > > > One of the earliest posts to this question (I have since deleted that > post) mentioned the incorrectness of averaging after the > logarithmic detector. Averaging after the log detector, I > believe, does not correctly average the signals. However, > this appears to be standard and accepted practice. Even the > common technique of averaging multiple signal measurements in > decibels, such as five different PC's, is not correct. The > technically correct method is to convert the measurements > into linear units, average them, then convert to decibels. > Any comments on this? > > Dave Cuthbert > Micron Technology > > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of Charles Grasso > Sent: Monday, August 23, 2004 7:38 PM > To: Ralph McDiarmid; [email protected] > Subject: RE: Average Detection > > > There is some variance as to the appropriate > VBW setting to make an accurate average measurement. > As I recall there is (and I have forgotten what it is) > a ratio that must be maintaied between the RBW and the VBw > settings. Our Spectrum Analyzer uses a 30Hz bandwidth setting > (for conducted emissions) but one lab mentioned that a 1kHz > VBw should be the minimum. > > Chas Grasso > > -----Original Message----- > From: [email protected] > [mailto:[email protected]]On Behalf Of Ralph McDiarmid > Sent: Monday, August 23, 2004 9:45 AM > To: '[email protected]' > Subject: RE: Average Detection > > > It's my understanding that the 10Hz VBW provides a filter > time-constant approximating that of an average detector. > > Ralph McDiarmid, AScT > Compliance Engineering Group > Xantrex Technology Inc. > > > > -----Original Message----- > > From: [email protected] > > [mailto:[email protected]] On Behalf Of Tom Cokenias > > Sent: August 23, 2004 6:51 AM > > To: Ridler, Samantha; '[email protected]' > > Subject: Re: Average Detection > > > > > > Hello Samantha, > > > > For analyzers that do not incorporate an average detector, > the FCC has > > specified settings of RBW 1 MHz and VBW of 10 Hz for average > > measurements in other parts of the Rules for measurements > above 1 GHz. > > They have been accepting these settings for many years for spread > > spectrum and now 802.11 radios operating under 15.247 of the Rules. > > > > best regards > > > > Tom Cokenias > > > > T.N. Cokenias Consulting > > P.O. Box 1086 > > El Granada CA 94018 > > > > tel 650 726 1263 > > fax 650 726 1252 > > > > cell 650 302 0887 > > > > At 8:21 AM +0100 8/23/04, Ridler, Samantha wrote: > > >Hello All > > > > > >FCC part 18 requires the use of an Average detector. For > > measurements > > >above 1GHz on a HP8593E EMC (Spectrum) analyser, would > > using a Video > > >Average of 100 or more be equivalent to taking a > measurement with an > > >Average detector? > > > > > > > > >It has been suggested to me by a test house that this is the > > case, but > > >I have not managed to find any rationale for this. > > > > > >The setup for the Analyser in question during the measurent was as > > >follows if this helps: SPAN = 2GHz, RBW =1MHz, VBW = 3MHz, > > SWEEP =40ms > > > > > >Many thanks. > > > > > >Samantha Ridler BEng MIEE > > >Compliance Engineer > > > > > >---------------------------------------------------------------- > > >This message is from the IEEE Product Safety Engineering Society > > >emc-pstc discussion list. Website: http://www.ieee-pses.org/ > > > > > >To post a message to the list, send your e-mail to > [email protected] > > > > > >Instructions: > > >http://listserv.ieee.org/listserv/request/user-guide.html > > > > > >List rules: http://www.ieee-pses.org/listrules.html > > > > > >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://www.ieeecommunities.org/emc-pstc > > > > ---------------------------------------------------------------- > > This message is from the IEEE Product Safety Engineering Society > > emc-pstc discussion list. Website: http://www.ieee-pses.org/ > > > > To post a message to the list, send your e-mail to [email protected] > > > > Instructions: > > http://listserv.ieee.org/listserv/request/user> -guide.html > > > > > > List rules: > > http://www.ieee-pses.org/listrules.html > > > > 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://www.ieeecommunities.org/emc-pstc > > ---------------------------------------------------------------- > This message is from the IEEE Product Safety Engineering Society > emc-pstc discussion list. Website: http://www.ieee-pses.org/ > > To post a message to the list, send your e-mail to [email protected] > > Instructions: > http://listserv.ieee.org/listserv/request/user> -guide.html > > > List rules: > http://www.ieee-pses.org/listrules.html > > 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://www.ieeecommunities.org/emc-pstc This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html 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://www.ieeecommunities.org/emc-pstc This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html 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://www.ieeecommunities.org/emc-pstc
