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From: email@example.com (Dale Chisholm)
Subject: Re: Chip Ferrites
Date: 25 Oct 2002 07:33:26 -0700
NNTP-Posting-Date: 25 Oct 2002 14:33:27 GMT
I've found the applications folks at "Fair-Rite Products" to be fairly
helpful. They seem to have a good grasp of how to use their stuff to
good advantage in standardized applications (like USB), and sometimes
have products available especially for that purpose.
Yeah, they have a vested interest in selling their products. But they
know that if they don't perform as expected there won't be many repeat
sales, and for products that literally sell for pennies it's the
repeat sales that make a business.
"Tempest" was an unclassified code-name for a classified program
dealing with identifying and eliminating compromising emissions from
military & gov't electronic equipment. (E.g., all the crypto in the
world is useless if somebody parked outside the gate can "read" your
message by recording the spark discharge spikes coming off the
commutator of the Teletype on which it's finally printed. Or he can
figure out whether you're processing payroll, or downloading cruise
missile target data, by observing which computer clock frequencies are
active.) Eventually it evolved into a comprehensive series of
specifications and guidelines covering shielding, filtering and
circuit design techniques to reduce emissions. It was active in the
1970's; maybe earlier - I didn't know the term was still in general
"Hemon Dey" wrote in message news:...
> Hello post,
> I'm wondering if anybody out there knows much about ferrite beads and chip
> ferrites. I'm making a custom module that has USB and RS232 devices in them.
> The USB application note specifies the BLM18BB121SN from Murata which has
> 120 ohm impedance at 100Mhz. How important is this impedance rating? I 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 to 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.
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