I read in !emc-pstc that Ken Javor <[email protected]> wrote (in <bad41a21.1ef6%[email protected]>) about 'FCC Limits' on Tue, 29 Apr 2003: > I am interested in opinions on the matter of the FCC changing their > CE limits to include frequencies down to 150 kHz. My concern is > predicated on the following assumptions: > > a) CISPR 22 controls to 150 kHz because European radios broadcast > down to that frequency. That is called the long wave band
>. Quite right. Well, almost, we are supposed to call it 'ow Frequency' now. > In > North America, AM broadcasts are confined to the medium wave band. > The 450 kHz cut off includes the AM band IF. The preferred IF in Europe is 450 kHz, since that minimises problems with image interference even for the French LF stations. > > b) (Most?) European single phase power is 220 Volts, 50 Hz. The > transformers in radio power supplies have a different turns ratio > than for American single phase power at 120 Volts. 230 V now. but with tolerances that admit 220 V. > > c) In my experience, a generic 50/60 Hz transformer works just as > well at 150 kHz as it does at the power line frequency. That is astonishing. At 150 kHz, I would expect a power transformer to look like a network of capacitors. > > In view of the above, it is not obvious to me why the FCC adopted > CISPR 22 CE limits. Does anyone know if LW broadcasts are planned > for North America? If that were to happen, the CISPR 22 limits at > 150 kHz would need to be reduced roughly 6 dB, to account for the > reduced turns ratio in power supplies built for North American > power. European transformers would attenuate power line ripple > more than American transformers would. I don't see why, since the capacitances are the dominant transfer router. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk Interested in professional sound reinforcement and distribution? Then go to http://www.isce.org.uk 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: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
