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From: Robert Baer
X-Mailer: Mozilla 4.75 [en] (Win98; U)
Subject: Re: Chip Ferrites
Date: Thu, 24 Oct 2002 06:08:25 GMT
NNTP-Posting-Date: Wed, 23 Oct 2002 23:08:25 PDT
Organization: EarthLink Inc. -- http://www.EarthLink.net
Hemon Dey wrote:
> You got me there, what's Tempest? do you have a link?
> "Robert Baer" wrote in message
> > Hemon Dey wrote:
> > >
> > > Hello post,
> > >
> > > I'm wondering if anybody out there knows much about ferrite beads and
> > > ferrites. I'm making a custom module that has USB and RS232 devices in
> > > The USB application note specifies the BLM18BB121SN from Murata which
> > > 120 ohm impedance at 100Mhz. How important is this impedance rating? I
> > > looking at getting a 75 ohm equivalent due to availability - does
> > > see any problems doing this?
> > >
> > > I can't find an app note anywhere on what ferrite values to attach to
> > > RS232 lines (Rx,Tx, CTS, RTS) Any advice on the choice I should be
> > > 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
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