James It is to account for the lack of ground plane with its potential +6dB effect due to reflection found during height scanning
The FCC have already considered this in KDB558074 when allowing conducted spurious emissions measurements to be performed in lieu of radiated ones for some unlicensed transmitters, however, the FCC requirements are: 3. Add appropriate factor to model worst-case ground reflections For emissions < 30 MHz, add a factor of 6.0 dB; For emissions > 30 MHz and < 1000 MHz, add a factor of 4.7 dB. Regards Charlie From: Pawson, James [mailto:[email protected]] Sent: 16 October 2012 15:27 To: [email protected] Subject: [PSES] OATS vs FAR Radiated Emissions Limits We've just received EN 61000-6-3:2007 + A1:2011 which has added the ability to test radiated emissions in either an OATS, Fully Anechoic Room (FAR) or TEM waveguide. What puzzled me is the limits for the FAR @ 3m: 30MHz ~ 230MHz: 42 to 35dBuV decreasing linearly with the log of the frequency 230MHz ~ 1GHz: 42dBuV Checking a draft version of CISPR 32 also shows these same limits for an FAR. These limits are lower than those for an OATS at 3m. Does anyone know why the limits are lower and of a different characteristic? I'm guessing something to do with the lack of reflective ground plane in the FAR. Does anyone have any further information? Many thanks James ~~~~~~~~~~~~~~~~~~~~~ James Pawson Leading Hardware Engineer - EMC EchoStar Europe - ---------------------------------------------------------------- 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]<mailto:[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]<mailto:[email protected]>> Mike Cantwell <[email protected]<mailto:[email protected]>> For policy questions, send mail to: Jim Bacher <[email protected]<mailto:[email protected]>> David Heald <[email protected]<mailto:[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]>
