I’m still wondering why the emissions standards don’t just come out with a statement such as:
“All DUTs will be designed with at least 0.5Kg of ferrite. The type, composition and placement will be left up to the Original Equipment Manufacturer.” :-) At least that way, we’ll all be in the same boat; and nobody will need to worry about having to explain to their management why they need to add $5 to $10 to the product cost for a piece of sintered rust. Alternatively, we could send our management to classes for “ferrophobia”. Chris Maxwell Nettest _____ From: [email protected] mailto:[email protected]] On Behalf Of Pettit, Ghery Sent: Tuesday, March 22, 2005 11:20 AM To: Geetha Balasubramanian; Grasso, Charles; Bob Richards ; [email protected]; [email protected] Subject: RE: Radiated Emission Testing Geetha, 1. RF semi-anechoic chambers are acceptable for testing as long as they meet the volumetric normalized site attenuation requirements in the standards. The FCC does accept chamber measurements as long as these requirements are met. 2. 1.6 dB margin is pretty slim. As noted previously, labs may vary by 6 dB and nobody is terribly surprised. A signal 1.6 dB under the limit in one lab could be 4 dB over the limit in another. 3. You list 6 frequencies, and only six frequencies from the first test. This is one of my objections to the current standards which only require that the 6 worst signals be listed. A difference between two labs can cause different lists to be provided with minor changes in signal amplitude. Our labs provide a much larger list. 4. You question the frequencies from the lab in Taiwan, but not the frequencies from the lab in the US. How would 43 MHz and 52.38 MHz come from 4 MHz and 12 MHz clocks if harmonics are the only way to generate emissions (which, by the way, they are not). I think you got bit by the problem of repeatability between labs. Also, there is a significant time difference between the two measurements and you could have changes in the product that you are completely unaware of. Have your parts vendors changed any of their processes? Have there been die shrinks on any of your semi-conductor parts? Too much information is not available in this message to make a solid determination, but passing by only 1.6 dB in the first instance leaves you very vulnerable to failing at a later date simply due to differences in the labs (facilities, precise techniques, etc.). Unless the FCC and VCCI read these messages they are unlikely to find out about your BSMI test results. However (and I’m not a lawyer, nor do I play one on TV, nor did I stay in a Holiday Inn Express last night), if your product were found to cause harmful interference in the US and the FCC found that you had non-compliant data and knew of a fix that you weren’t shipping, they might not look kindly on your actions. You don’t need to go retrofit product in the field, but I would recommend (and this is a business decision for your company to make) that you ship the ferrite with future product. Hope this helps. Now, go make some ferrite vendor happy. Ghery S. Pettit (note, the opinions expressed are my own and not necessarily those of my employer) _____ ---------------------------------------------------------------- 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/listserv/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: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc ---------------------------------------------------------------- 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/listserv/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: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
