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From: "Hemon Dey"
References: <3DB611D8.C62D54F9@earthlink.net> <3DB78E6F.F4E0BA72@earthlink.net>
Subject: Re: Chip Ferrites
X-Newsreader: Microsoft Outlook Express 6.00.2600.0000
Date: Fri, 25 Oct 2002 09:34:37 +1300
NNTP-Posting-Date: Fri, 25 Oct 2002 09:34:38 NZDT
So I take it then nobody knows much about ferrites??? only about TEMPEST?
"Robert Baer" wrote in message
> Hemon Dey wrote:
> > You got me there, what's Tempest? do you have a link?
> > "Robert Baer" wrote in message
> > news:3DB611D8.C62D54F9@earthlink.net...
> > > Hemon Dey wrote:
> > > >
> > > > Hello post,
> > > >
> > > > I'm wondering if anybody out there knows much about ferrite beads
> > chip
> > > > ferrites. I'm making a custom module that has USB and RS232 devices
> > them.
> > > > The USB application note specifies the BLM18BB121SN from Murata
> > has
> > > > 120 ohm impedance at 100Mhz. How important is this impedance rating?
> > was
> > > > looking at getting a 75 ohm equivalent due to availability - does
> > anybody
> > > > see any problems doing this?
> > > >
> > > > I can't find an app note anywhere on what ferrite values to attach
> > the
> > > > RS232 lines (Rx,Tx, CTS, RTS) Any advice on the choice I should be
> > making?
> > > > surely there must be a scientific way about it ...
> > > >
> > > > Thanks for your help.
> > > > Hemon
> > >
> > > The only app i know of that may use ferrites for RS-232 lines is for
> > > Tempest.
> "Tempest" is a military EMI specification that virtually eliminates
> all forms of noise from the inside of a double shielded box (say with a
> computer in it) to the outside.
> Have not tried to find links on that.
> I understand the method is highly classified, and the specs may also
> be classified.
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