I read in !emc-pstc that Enci <e...@cinepower.com> wrote (in <3.0.6.32.2 0020205082333.00aed...@mail.cinepower.com>) about 'ITE Class A vs B Emissions', on Tue, 5 Feb 2002: >I have often wondered exactly why there are two classes in EN55022. The >limits are pretty similar, does a 13dB difference in conducted emission QP >limits really make a difference above 5MHz? I know the 23dB difference ><5MHz (conducted emissions) helps with products that have a SMPS, for >example. In the radiated emissions the difference is 10dB. In the real >world is there really a need for two limits?
Probably not. The CISPR Class B limits were probably (even I am too young to know!) influenced by the situation in Germany in the 1950s, when their AM (only sort available) broadcasting was severely restricted to low powers and frequencies that no-one else wanted. Consequently, man-made noise had to be kept low as well. I suppose CISPR/H is considering a single set of limits, but that might be the Class B limits if people who want something else don't bother to take part in the work. Note that this is a matter of general interest, not just for ITE, so it should not be a matter for CISPR/I alone. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk After swimming across the Hellespont, I felt like a Hero. PLEASE do NOT copy news posts to me by E-MAIL! ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ 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: Michael Garretson: pstc_ad...@garretson.org Dave Heald davehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
