The CE limits were designed entirely empirically but the RE limits were based on EIA TV standards that require a specified signal quality for a given rf input level. The RE limits were simply set X dB below that EIA specified level. My recollection is that the rf level specified would be a long way from a broadcast tower.
---------- >From: John Woodgate <[email protected]> >To: [email protected] >Subject: Re: EMI guard bands >Date: Thu, Dec 20, 2001, 1:52 PM > > > I read in !emc-pstc that Doug McKean <[email protected]> wrote (in > <[email protected]>) about 'EMI guard > bands', on Thu, 20 Dec 2001: >>Anywho, the answer I got back from him was that >>the limits were empirically derived in reference to >>interfering with television signals. So, the worst >>case (which turned out to be Class B) was a tv >>back to back across a wall from another device >>in an apartment complex. > > I would be suspicious of that; it is a 'near-field' scenario, which > means that the emission field strengths are complex and impossible to > calculate. The Class B limits are related to a 10 m separation of source > and potential victim, and that implies far-field conditions for > emissions above about 5 MHz. > -- > Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk > After swimming across the Hellespont, I felt like a Hero. > > ------------------------------------------- > 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: > Michael Garretson: [email protected] > Dave Heald [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: > No longer online until our new server is brought online and the old > messages are imported into the new server. > ------------------------------------------- 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: Michael Garretson: [email protected] Dave Heald [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: No longer online until our new server is brought online and the old messages are imported into the new server.
