Marvin, There is work on-going in CISPR SC G to create limits at 3 meters for Class B devices of a certain size or less. Given the speed with which changes occur, and then are adopted, I wouldn't count on this happening any time soon. The 10 meter limits will not go away for larger systems, or for Class A devices.
CISPR 22 does allow testing at shorter distances when measurements cannot be made at 10 meters due to ambient signals or other reasons. Some companies have taken this to be a blanket approval to test at 3 meters. Some countries, notably Taiwan, insist on 10 meter measurements if at all possible. While you can make measurements at distances less than 10 meters, you are taking a risk as the 1/R distance factor doesn't really work and the field generally falls off more slowly. As a result, a product may appear to pass at 3 meters and fail at 10 meters. The rate of falloff is not constant, but varies with frequency and the size of the EUT. Caveat tester! Hope this helps. Ghery S. Pettit, NCE Intel Corporation Member, USNC IEC / CISPR SC G TAG -----Original Message----- From: Wolak, Marvin [mailto:marvin.wo...@marconi.com] Sent: Friday, October 06, 2000 1:56 PM To: EMC-PSTC Newsgroup (E-mail) Subject: Antenna Distance Is 10m emissions testing going away or unnecessary? What does the future hold? (Please indicate degree of uncertainty when projecting future changes.) We are a global company and must meet all international requirements as well as Bellcore. The reason I ask this is that I keep hearing via third parties that some test lab or other is claiming that they do all certification testing in a 3m / 5m chamber. Regards, Marvin Wolak Marconi Communications marvin.wo...@marconi.com ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson: pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson: pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
