The ITU regulations give an indication where the CISPR levels are coming from;-
The ITU-R (BS.412) recommendation for minimum useable field strength in urban areas is 54dbuV/m (for FM stereophonic service) and defines a radio-frequency co-channel protection against steady state interference of 45dBuV/m. Hence, the maximum level of steady state interference that a radio receiver will operate successfully (i.e. you can still listen to your loacl radio station) in, is 45dBuV/m. Given that the class A limit is 40dB at 10m for unintentional transmitters, it gives a level of protection against interference to radio services. regards Andy __________________________________ Andy White, Consulting EMC Engineer/Staff, Xerox EMC Competency Center, El Segundo, CA e-mail: andy.wh...@cax.usa.xerox.com __________________________________ -----Original Message----- From: John Allen [mailto:john.al...@racalradio.com] Sent: Friday, May 28, 1999 4:33 AM To: emc-p...@ieee.org; 'Douglas McKean' Subject: RE: History Class ... Hi Doug In addition to Lou's comments, I believe that the lower limits in these bands have lot to do with the fact they cover the commercial TV & Radio broadcasting Bands I, II, III & IV/V - don't forget that a major driving force in the preparation of the standards was to protect such services from interference. If you look into the older national versions of such standards you may well - e.g. as in Germany (I think!) - find that the national restrictions vary according to the specific frequency bands used for such purposes in those countries. Regards John Allen ---------- From: Douglas McKean[SMTP:dmck...@corp.auspex.com] Reply To: Douglas McKean Sent: 27 May 1999 21:45 To: emc-p...@ieee.org Subject: History Class ... Anyone have a clue where the limits (frequency and amplitude) for CISPR-22 came from? For instance ... Radiated Limits for Class A at 10 meters Frequency Quasi-Peak limits MHz dBuV 30 - 230 40 230 - 1000 47 Why the 40 dBuV/m limit from 30 - 230 MHz? Or any other similar standard limits for that matter? Regards, Doug McKean --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators). --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators). --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
