Grace, Do they make a fully compliant 3 meter semi-anechoic chamber? I wasn't aware that a 3 meter chamber passed the NSA requirements down to 30Mhz. The purpose of having a Test Standard is to standardize on a method in which testing is performed so the results can be repeated at other test sites and hopefully have the same or similar results. When you stray from what the standard calls out, then you take the risk of your results being brought into question. I think your biggest problem with testing at 3 meter is going to be with near field below 100Mhz. Because of the common differences seen when testing a product at 3 meter verses 10 meter, I think there will always be a high level of doubt in your test results. In my opinion, "compliance testing" can only be confidently done at a 10 meter OATS or equivalent. BTW, the note in section 10.2.1 is a method to test signals that fall near or on a high ambient. Most all OATS have at least a few areas with high ambient and this section gives them a work around at only those frequencies. It is not intended to allow full testing at distances than 10 meter. In a chamber you wouldn't have any ambient signals so you couldn't use this section to justify 3 meter testing. I am very curious to know the confidence level of 3 meter chambers are. Maybe some who have such chambers will post. The Other Brian. _____
From: [email protected] [mailto:[email protected]] On Behalf Of Grace Lin Sent: Monday, June 18, 2007 1:43 PM To: [email protected] Subject: RE Measurement Distance per EU Dear Members, Is 3m measurement distance for radiated emission not accepted by EU? I propose a 3m full compliant chamber. A chamber manufacturer informs me that EU only accepts 10m measurement distance. I checked EN 55022: 1998 incorprating Corrigendum Nol 1 and A1 and A2. Clause 6 states: "The EUT shall meet the limits of Table 5 or Table 6 when measured at the measuring distance R in accordance with the methods described in Clause 10. ... " The title of Table 5 is: "Table 5 - Limits for radiated disturbance of class A ITE at a measuring distance of 10m". The title of Table 6 is: "Table 6 - Limits for radiated disturbanc eof class B ITE at a measuring distance of 10m". Subclause 10.2.1 states: " 10.2.1 Antenna-to-EUT distance Measurements of the radiated field shall be made with the antenna located at the horizontal distance from the boundary of the EUT as specified in Clasue 6. NOTE If the field-strength measurement at 10m cannot be made because of high ambient noise levels, or fo rother reasons, measurement of class B EUT's may be made at a closer distance, for example 3m. An inverse proportionality factor of 20 dB per decade should be used to normalize the measured data to the specified distance for determining compliance. Care should be taken in the measurement of large EUTs at 3m at frequencies near 30 MHz, due to near field effects. " I look forward to your comments. Best regards, Grace Lin Crestron Electronics, Inc. www.crestron.com - ---------------------------------------------------------------- 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/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] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc Notice: This communication may contain confidential information intended for the named recipient(s)only. If you received this by mistake, please destroy it and notify us of the error. Thank you. ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email ______________________________________________________________________ - ---------------------------------------------------------------- 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/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] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
