You are likely thinking of the tin plate shielding boxes.  The only supplier
that I've found for these is
http://www.tekoenclosures.com/enclosures/RF-index.html.  They sell direct
and appear to accept orders for small quantities.

I've never ordered from them, but have it bookmarked for a couple future
projects.


Jack




-----Original Message-----
From: pic microcontroller discussion list
[mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Jesse Lackey
Sent: Wednesday, June 04, 2003 12:32 AM
To: PICLIST@MITVMA.MIT.EDU
Subject: [EE]: RF screens / shields ... suppliers? necessary?


Hello all,

I have a project where there is significant digital next to sensitive
analog (mic preamp) on a small board.  I'd like to put a screen or
shield of some sort between the two.  There are already separate grounds
and it is inside a metal box.

I see occasionally in tv sets and the like aluminum (?) shields or
screens covering a particularly sensitive (or radiating!) sections of
circuitry.  My question is ... are these available anywhere?  Or are
they typically something that is made in a metal shop along with
whatever chassy metalwork that needs to be done?

If I have them made, is any particular types of metal better or worse
than others?  Right now I'm thinking of just a vertically mounted
"strip" or "wall", kind of like a tennis net, say, between the two board
sections.

I'm not 100% sure its necessary, this design is a radical reworking of
an (aging) existing product, which used two layers, and I'm using four,
and am getting significantly better performance already.  But if a 25c
piece of metal can get me another 2db, I'll take it!  Also I have seen
these screens over crystals/clock gen circuits in other audio A/D
products and maybe it would help this one too.

I have access to an audio precision 2 (amazing piece of equipment) so a
does-it-improve-things yes/no test is easy to do.

Thanks for any advice!
Jesse

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