When I worked at FCC I remember being told the interference limits were such that a "TASO Grade 3" quality picture would be maintained as a minimum. Not sure if TASO is the right acronym but it's correct phonetically...
On Oct 17, 2012, at 9:45 AM, Ken Javor wrote: > What is arbitrary and capricious about setting EMI limits just below a level > that provides a minimum quality standard? > > Ken Javor > Phone: (256) 650-5261 > > > From: Bill Owsley <[email protected]> > Reply-To: Bill Owsley <[email protected]> > Date: Wed, 17 Oct 2012 09:39:13 -0700 (PDT) > To: John Woodgate <[email protected]>, "[email protected]" > <[email protected]> > Subject: Re: [PSES] OATS vs FAR Radiated Emissions Limits > > Way back in the old days, so goes the tale as it was told to me, for the > FCC,broadcast receivers were determined to have a certain level of > sensitivity for reliable reception of the intended broadcast. So Limits were > set capriciously and arbitrarily just below that sensitivity level. > Measuring distance was determined in a similar fashion, 3 meters being the > home environment, and 10 meters being the work or non-home environment. I > vaguely recall a 30 meter distance. All this are tales of the dark side when > there were only OATS and testing was all day long in the blistering summer > sun, or all night while feeding mosquito's. > > The automotive industry declined to play along and took care of themselves, > as did the military, and the airlines, > And they do have some near field testing and get to use comfortable test > environments like indoors for a large portion. > > We got so envious of those comfortable conditions, we ginned up a fine story > about ambients interfering with our tests, and weather interfering with test > time, etc. that we got to build a 3 meter chamber, the first one recognized > by the FCC as an alternative to the OATS. > > > > > > > > From: John Woodgate <[email protected]> > To: [email protected] > Sent: Wednesday, October 17, 2012 8:45 AM > Subject: Re: [PSES] OATS vs FAR Radiated Emissions Limits > > > In message > <of583e7385.c0c56cf9-on86257a9a.0040152b-86257a9a.00418...@mmm.com>, dated > Wed, 17 Oct 2012, [email protected] writes: > > > And has any of this OATS, SAR, FAR, and TEM cell data differences been > > correlated to actual interference problems? Is the EMC industry crying > > "wolf"? > > The only practicable way to check is to look at the number of complaints of > interference, but many countries now don't collect them, and the number of > interference cases probably exceeds the number of complaints by a large > factor. > > It is certain that if any manufacturer or industry association heard any > alarmist cries, representations would be made for speedy changes. > > > > Limits and test methods should be based in reality. They should not be > > academic exercises. For example, much of the world's products are in the > > near-field of each other (cockpits, OR, control rooms, etc.). Why aren't > > there near field test procedures? Yes, I know the problems but those are > > just excuses. Methods need to be developed (and alas, I'm not smart enough). > > The problems are not excuses, any more than an inability to develop > anti-gravity is an excuse. Ye canna change the laws o'physics, Cap'n! > Near-field measurements are horribly non-repeatable and, in almost all cases, > cannot be relied on in a regulatory context. > -- OOO - Own Opinions Only. See www.jmwa.demon.co.uk > <http://www.jmwa.demon.co.uk/> > The longer it takes to make a point, the more obtuse it proves to be. > John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK > > - > ---------------------------------------------------------------- > 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 > <[email protected]> > > All emc-pstc postings are archived and searchable on the web at: > http://www.ieee-pses.org/emc-pstc.html > > Attachments are not permitted but the IEEE PSES Online Communities site at > http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used > formats), large files, etc. > > 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 <[email protected]> > Mike Cantwell <[email protected]> > > For policy questions, send mail to: > Jim Bacher: <[email protected]> > David Heald: <[email protected]> > > > > > > - > ---------------------------------------------------------------- > > 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 > <[email protected]> > > All emc-pstc postings are archived and searchable on the web at: > http://www.ieee-pses.org/emc-pstc.html > > Attachments are not permitted but the IEEE PSES Online Communities site at > http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used > formats), large files, etc. > > 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 <[email protected]> > Mike Cantwell <[email protected]> > > For policy questions, send mail to: > Jim Bacher <[email protected]> > David Heald <[email protected]> > > - > ---------------------------------------------------------------- > 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 > <[email protected]> > All emc-pstc postings are archived and searchable on the web at: > http://www.ieee-pses.org/emc-pstc.html > Attachments are not permitted but the IEEE PSES Online Communities site at > http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used > formats), large files, etc. > 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 <[email protected]> > Mike Cantwell <[email protected]> > For policy questions, send mail to: > Jim Bacher <[email protected]> > David Heald <[email protected]> - ---------------------------------------------------------------- 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 <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. 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 <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
