No, your message is clear, what I am saying is that the emissions below 30Mhz cause the majority of the interference problems to consumer electronics and that's not being addressed.
Ralph Cameron ----- Original Message ----- From: "Ken Javor" <[email protected]> To: "Ralph Cameron" <[email protected]>; "dan kwok" <[email protected]> Cc: "EMC-PCST (E-mail)" <[email protected]> Sent: Monday, January 15, 2001 10:34 PM Subject: Re: Site Correlation > I must have been unclear in my previous message. The purpose of controlling > cable cm CE is to control the resultant cable-induced RE, which are > controlled to protect tunable antenna-connected radio receivers, period. > There was never any other purpose for controlling CE or RE. > > Ken Javor > > ---------- > >From: "Ralph Cameron" <[email protected]> > >To: "Ken Javor" <[email protected]>, "Dan Kwok" <[email protected]> > >Cc: "EMC-PCST \(E-mail\)" <[email protected]> > >Subject: Re: Site Correlation > >Date: Mon, Jan 15, 2001, 8:51 PM > > > > > Perhaps what you state is correct Ken but there has been a supposition that > > RE , induced or other wise when converted to conducted current does not > > effect other devices connected to those same conductors whether they be > > power, incoming TV or telephone cables etc. All these conductors intercept > > RE and their effects have been eliminated in 90% of cases( I have > > personally suppressed ) , by suppresseing the common mode signals.Over 300 > > successes is a significant statistic. > > > > Ralph Cameron > > > > > > . > > ----- Original Message ----- > > From: "Ken Javor" <[email protected]> > > To: "Dan Kwok" <[email protected]>; "Ralph Cameron" <[email protected]> > > Cc: "EMC-PCST (E-mail)" <[email protected]> > > Sent: Monday, January 15, 2001 5:42 PM > > Subject: Re: Site Correlation > > > > > >> > >> Mr. Kwok's theories are logical and no doubt bear on the subject, but > > there > >> is a historical angle that bears inspection. About the time FCC limits > > for > >> IT equipment were being drawn up (late '70s) PCs were not yet on > > everyone's > >> desktop. Most of the business equipment that would have been envisioned > > to > >> be qualified to USC Title 47, Part 15, Subpart J would have been > > stand-alone > >> items such a copier, with the only cable connection being ac power. The > >> report which documents the development of the CE and RE limits/test > > methods > >> found in the above mentioned FCC limits specifically states that 30 MHz > > was > >> picked as the cutoff between CE and RE for the reason of radiation > >> efficiency per Mr. Kwok's surmise, but also because 30 MHz was the lowest > >> frequency at which a 3 m OATS measurement would provide the desired > >> accuracy. > >> > >> Ken Javor > >> > >> P.S. Said report also demonstrated that the CE limit below 30 MHz > > sufficed > >> to control RE from the power cable to levels sufficient to protect against > >> cable radiation-induced rfi. > >> > >> ---------- > >> >From: Dan Kwok <[email protected]> > >> >To: Ralph Cameron <[email protected]> > >> >Cc: "EMC-PCST (E-mail)" <[email protected]> > >> >Subject: Re: Site Correlation > >> >Date: Mon, Jan 15, 2001, 2:49 PM > >> > > >> > >> > > >> > Hello Ralph: > >> > > >> > That's a good question. At one time, I pondered the same question > >> > myself. There are obviously plenty of communication systems operating > >> > under 30 MHz. I suppose there are reasons why CISPR or CISPR 22 does not > >> > specify radiated emissions below 30 MHz. I can suggest one possibility. > >> > Perhaps others here will come up with more. > >> > > >> > For a fixed cable of length L, the ratio of L/lambda gets progressively > >> > small for frequencies much less than 30 MHz with most commercial EUTs. > >> > If we consider the cable part of dipole antenna, the reduction in > >> > frequency has a diminishing effect on the antenna's radiation > >> > resistance. Given a constant current, the radiated power would decrease > >> > with decreasing radiation resistance. At 550 KHz (bottom of the AM > >> > broadcast band in North America), the 1/4 wavelength is 136 meters. Even > >> > if the antenna's reactance is ignored, one would need very long cables > >> > driven by a significant CM noise voltage at this frequency to radiate > >> > much energy. > >> > > >> > -- > >> > ------------------------------------------------------------------------ > >> > Daniel Kwok > >> > Principal EMC Engineer > >> > Intetron Consulting, Inc. > >> > Vancouver, Canada > >> > Phone (604) 432-9874 > >> > Email [email protected] > >> > Web http://www.intetron.com"; > >> > > >> > > >> > Ralph Cameron wrote: > >> >> > >> >> Ken: > >> >> > >> >> I like the idea of setting a limit to common mode currents on attaching > >> >> cables but mI wonder why CISPR has chosen to start such measurements at > >> >> 30Mhz when most of the common mode currents are the result of switching > >> >> products and are generated harmonically from the fundamental and as > > such > >> >> propagate from the low Khz range up through 30Mhz. is there no > > consideration > >> >> for those who occupy the spectrum below 30Mhz? > >> >> > >> > > >> > ------------------------------------------- > >> > This message is from the IEEE EMC Society Product Safety > >> > Technical Committee emc-pstc discussion list. > >> > > >> > To cancel your subscription, send mail to: > >> > [email protected] > >> > with the single line: > >> > unsubscribe emc-pstc > >> > > >> > For help, send mail to the list administrators: > >> > Jim Bacher: [email protected] > >> > Michael Garretson: [email protected] > >> > > >> > For policy questions, send mail to: > >> > Richard Nute: [email protected] > >> > > >> > > >> > >> ------------------------------------------- > >> This message is from the IEEE EMC Society Product Safety > >> Technical Committee emc-pstc discussion list. > >> > >> To cancel your subscription, send mail to: > >> [email protected] > >> with the single line: > >> unsubscribe emc-pstc > >> > >> For help, send mail to the list administrators: > >> Jim Bacher: [email protected] > >> Michael Garretson: [email protected] > >> > >> For policy questions, send mail to: > >> Richard Nute: [email protected] > >> > >> > >> > > > ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. 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