Regarding the second part of question #3: “How were the charge and discharge time constants selected for the first QP detectors and why were they changed over the years? How was the bandwidth selected? [Note: the 9 kHz bandwidth was the prevalent bandwidth of radio receivers for sound broadcast reception at the time. EdB] “
Ed answers the question himself concerning BW. In order to get the best signal quality, the receiver bandwidth should match the broadcast signal BW. The same applies to assessing the effect of rfi. 9 kHz and 120 kHz mirror broadcast radio reception in the AM and FM bands (LF – Europe only, MF, and VHF). A very real problem arises when using these BW (and by extension QP detector) in assessing TVI. There were in the past dithered clocks provided so that the spectral distribution of harmonics would fall outside any one 120 kHz BW, and thus the QP detector would average the harmonic content that fell in a BW, and it would be smaller than if the frequency had been fixed with all harmonic amplitude contained in one BW. The dithering worked with 120 kHz BW, but didn’t move a signal outside a broadcast TV channel, and there were reports that the dithered clock harmonics were actually more disruptive to TV reception than if the harmonics had been fixed in frequency. Ken Javor Phone: (256) 650-5261 ________________________________ From: <ralph.mcdiar...@ca.schneider-electric.com> List-Post: emc-pstc@listserv.ieee.org List-Post: emc-pstc@listserv.ieee.org List-Post: emc-pstc@listserv.ieee.org Date: Tue, 23 Mar 2010 12:18:25 -0700 To: <EMC-PSTC@LISTSERV.IEEE.ORG> Subject: Re: the QP detector Here is a link to an interesting historical note on the Quasi-peak Detector. Hopefully, someone on this forum can answer one or more of the questions at the end of the article to enlighten the rest of us. http://www.ieee.org/organizations/pubs/ ewsletters/emcs/summer01/pp.bronaugh.htm <http://www.ieee.org/organizations/pubs newsletters/emcs/summer01/pp.bronaugh.htm> <http://www.ieee.org/organizations/pubs newsletters/emcs/summer01/pp.bronaugh.htm> _______________________________________ _____________________________________________ Ralph McDiarmid | Schneider Electric | Renewable Energies Business | CANADA | Compliance Engineer - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <emc-p...@ieee.org> All emc-pstc postings are archived and searchable on the web at http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <emcp...@socal.rr.com> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher <j.bac...@ieee.org> David Heald <dhe...@gmail.com> - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <emc-p...@ieee.org> All emc-pstc postings are archived and searchable on the web at http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <emcp...@socal.rr.com> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher <j.bac...@ieee.org> David Heald <dhe...@gmail.com>
