In message <[email protected]>, dated Sat, 12 Feb 2011, Brian O'Connell <[email protected]> writes:
>The 10m fully anechoic chamber data indicates from +5dB to +11dB in >several frequencies; while the 10m OATS says the unit passes Class B, >min -4.2dB. > >Huh?!? What is the physics behind the difference between an outside >site and absorbers? Where are the Borg when you need them? There is always the possibility of such results. Neither a real OATS or a real FAR exhibits perfectly theoretical behaviour, and sooner or later, some products show that up. One possibility is that the EUT emits narrow focused beams of radiation at some frequencies. In electroacoustics, loudspeakers that do this (emit side-lobes) can be very difficult to measure repeatably. You might be able to use 3D emission contour plots to see what is happening. I've not tried at radio frequencies, but it can work for loudspeakers, and, after all, it's all waves, isn't it?(;-) Even if you find out why, it may not help, unless you are getting emissions through holes or narrow slots, where you stand a chance of eliminating them. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK Plural: data, criteria, phenomena. Singular: datum (different meaning: use 'data element' for a single item), criterion, phenomenon. 'Effect' is a noun, 'affect' is a verb (except in psychiatry). - ---------------------------------------------------------------- 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://product-compliance.oc.ieee.org/ 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 <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
