To the Ferrite discussion: I've refrained from responding to the ferrite question because of being away but I would confirm what Amand states. I use powdered iron FT240-43 from Fair-Rite as they make them for Amidon and have the properties desired to reduce common mode signals appearing on connecting cables to consumer devices- VCR, TV sets, Hi-Fi speaker cables etc.
I have treated over 300 cases of RF getting into telephones ( via the phone cable connection) , VCRs via the sheath on the TV cable , modems, speaker cables etc. Success in siolating the offending RF ( 500Khz- over 30Mhz ) has been in ecess of 90%. I say if it works, don't know kit,. 20 years ago I had an EMC engineer characterise the attenutaion over the above frequency range and Mix 43, with init. perm of 850 was the best compromise. As Amand states Mix 77 would work better below 500Khz. The minimum attenutaion was 15dB and approached 27dB at 35Mhz . At 30 dB it provided rejection of RF common mode signals of 25dB. It is important that between 8-9 tuuns be used and spaced over the surface of the toroid to flatten the attenuation curve. Many telephone filters made by AT&T and others I have found to have a very peaked response over the HF range and will work sometimes and sometimes not. The nice thing about external devices like this are they don't degrade performance in any way, are re-useable, quite economical and easy to install. It is also important to keep the toroids as close as possible to the device being protected in order to minimize pickup due to re radiation. This is a simple procedure which many manaufacturers overlook , yet could save them a bundle in returned product and in some cases litigation. The components can be used to suppress incoming RF our outgoing.from the product. I started out doing this type of suppression free of charge but after using several hundred toroids ( the 2.4 " O.D. ones for power line cables) I started to recover my costs. These thinbgs really do work. Ralph Cameron EMC Consutling and Suppression of Consumer Electronics ( After sale) ----- Original Message ----- From: <[email protected]> To: <[email protected]> Sent: Wednesday, March 14, 2001 5:22 PM Subject: Re: Ferrites experience ....... last comment > > Hi all, > > Many thanks to all of you who participated in this ferrite discusson. I have > leard a lot about ferrites the last 10 days. > > In my special case, I would like to give you some information: > > We had a problem with conducted emisson on the DC supply line to a telecom > product. The harmonic switching frequency was 160kHz and our problems was in > the range 160kHz-5MHz. We used a toroid (DC cable five turns in the Toroid)and > we managed to decrease the noise about 10-15dB in the frequency range 1-5MHz. > The toroid had an outer/inner diameter of 61mm/36mm (a big one). We used a > toroid with material 43 and its permeability is approximate 850. Material 43 > has its application areas from 30-200MHz, so we should have had a toroid with > an other material. > I think a toroid with a material 77 (permeability 2000) could have helped us > with the 160kHz-1MHz band. Next time ..... > > One last comment, try to avoid snap-on ferrites. Remember the air gap, you will > have a large increase in the impedance even if you use strips to tighten it > together. Use the solid ones .... > > See you later. > > Best regards > Amund Westin, Oslo/Norway > > > > On 6 Mar 2001 19:16:37 -0000 [email protected] wrote: > > > >Hi all, > > > >During conducted emission test, we have 150kHz power supply switching > >distrubance on the 48VDC-line, and we can not insert capacitors,chokes or any > >filters on the line. > > > >Do you have any experience using ferrites to suppress noise in the band > 100kHz - > > 5MHz ? > > > >We have used ferrites with success on I/O-lines during radiated emission, but > >no experience on DC-lines (use LISN). > > > >Best regards > >Amund Westin, Oslo / Norway > > > >-- > >Get your firstname@lastname email for FREE at http://Nameplanet.com/?su > > > >------------------------------------------- > >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: > > http://www.rcic.com/ click on "Virtual Conference Hall," > > > > > > > -- > Get your firstname@lastname email for FREE at http://Nameplanet.com/?su > > ------------------------------------------- > 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: > http://www.rcic.com/ click on "Virtual Conference Hall," > > ------------------------------------------- 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: http://www.rcic.com/ click on "Virtual Conference Hall,"
