seems that most dried wood is non conductive so wood does not shield
well for rfi or emi


hmmm might have to add a layer of thin metal on the inside to minimize
leakage

copper always looks good but i wonder if the patina that develops
will change the way it shields


maybe there is a wood that has some conductive qualities even in the
dried state

faraday tree

On Thu, 30 Jun 2016 18:11:54 -0700, Electric Comet
wrote:


seems that most dried wood is non conductive so wood does not shield
well for rfi or emi


hmmm might have to add a layer of thin metal on the inside to minimize
leakage

copper always looks good but i wonder if the patina that develops
will change the way it shields


maybe there is a wood that has some conductive qualities even in the
dried state

faraday tree

Ironwood?

Seriously, if you insist on such nonsense, use a separate shield or
metallic paint on the interior. A better solution is to design what's
going inside such that it doesn't need shielding.

On 6/30/2016 9:11 PM, Electric Comet wrote:

seems that most dried wood is non conductive so wood does not shield
well for rfi or emi


hmmm might have to add a layer of thin metal on the inside to minimize
leakage

copper always looks good but i wonder if the patina that develops
will change the way it shields


maybe there is a wood that has some conductive qualities even in the
dried state

faraday tree


Self-adhesive copper foil can be bought in sheets from virtually any
company that sells stained-glass supplies. I've never seen it in sizes over
12"X12" but if one looked hard enough bigger stuff is probably out there.
If using small sheets joining them together is easy with a bit of flux and
solder. Back in ancient days when I occasionally built wooden enclosures
for rf-sensitive audio gear I used similar foil for shielding and in the
wooden computer case I built I covered everything inside with copper. My
foil was bought in Japan and was, at a guess, 60cm wide and 10m long but
had no adhesive backing and had to be glued down with contact cement.

Electric Comet wrote in news:nl4g0j$ri3$2
@dont-email.me:


seems that most dried wood is non conductive so wood does not shield
well for rfi or emi


hmmm might have to add a layer of thin metal on the inside to minimize
leakage

copper always looks good but i wonder if the patina that develops
will change the way it shields


maybe there is a wood that has some conductive qualities even in the
dried state

faraday tree

LOL at faraday tree. Trees are good conductors of lightning
discharges, but otherwise I can't think of one that conducts.

RFI/EMI is a difficult subject. You need a conductive material,
and any gaps or holes have to be smaller than the wavelength
of the signal you're trying to contain (or block out, as the
case may be). Unfortunately, that means the holes/gaps have
to be small in both directions - a long, thin gap like you
might get at the joint of a lid and a houseing can be an
excellent radiator of RFI.

You could put solid metal sheet (copper, aluminum, steel) in
as a shield, or metal mesh/screen, or conductive paint.
Whatever you use has to be well grounded to your circuit
ground to work well for EMI. This can be a problem with
paint. Tarnish on copper is only a problem if it prevents
a good ground path from existing.

Any wires that come out of your enclosure can be excellent
conductors of EMI/RFI, including the power cord. RFI can
usually be solved with a small cap to ground, but it can
be a real bear getting EMI off a power cord.

Beware that if you have an oscillator running at high freqs
(100 MHz, say) and your shielding is close to it and not
very rigidly fixed, it can detune your oscillator and cause
various weird problems.

John

On Fri, 1 Jul 2016 10:32:38 -0400, BenignBodger
wrote:

On 6/30/2016 9:11 PM, Electric Comet wrote:

seems that most dried wood is non conductive so wood does not shield
well for rfi or emi


hmmm might have to add a layer of thin metal on the inside to minimize
leakage

copper always looks good but i wonder if the patina that develops
will change the way it shields


maybe there is a wood that has some conductive qualities even in the
dried state

faraday tree


Self-adhesive copper foil can be bought in sheets from virtually any
company that sells stained-glass supplies. I've never seen it in sizes over
12"X12" but if one looked hard enough bigger stuff is probably out there.
If using small sheets joining them together is easy with a bit of flux and
solder. Back in ancient days when I occasionally built wooden enclosures
for rf-sensitive audio gear I used similar foil for shielding and in the
wooden computer case I built I covered everything inside with copper. My
foil was bought in Japan and was, at a guess, 60cm wide and 10m long but
had no adhesive backing and had to be glued down with contact cement.

Foil is also available with a conductive adhesive. I used it at a
PPoE to try different shielding techniques. The eventual solution was
conductive (nickel-filled) paint.

In article , says...

On 6/30/2016 9:11 PM, Electric Comet wrote:

seems that most dried wood is non conductive so wood does not shield
well for rfi or emi


hmmm might have to add a layer of thin metal on the inside to minimize
leakage

copper always looks good but i wonder if the patina that develops
will change the way it shields


maybe there is a wood that has some conductive qualities even in the
dried state

faraday tree


Self-adhesive copper foil can be bought in sheets from virtually any
company that sells stained-glass supplies. I've never seen it in sizes over
12"X12" but if one looked hard enough bigger stuff is probably out there.
If using small sheets joining them together is easy with a bit of flux and
solder. Back in ancient days when I occasionally built wooden enclosures
for rf-sensitive audio gear I used similar foil for shielding and in the
wooden computer case I built I covered everything inside with copper. My
foil was bought in Japan and was, at a guess, 60cm wide and 10m long but
had no adhesive backing and had to be glued down with contact cement.

You guys are overthinking this. Copper is expensive overkill for
shielding. Grocery-store aluminum foil works fine and you can stick it
down with hot glue, double-stick tape, contact cement, or whatever else
you like. If you have an opening you need to shield, aluminum screen
from your average hardware store is plenty for the sort of openings you
typically find in computer cases--it's better than what is used in most
store-bought computers.

On 7/2/2016 4:48 AM, J. Clarke wrote:
In article , says...

On 6/30/2016 9:11 PM, Electric Comet wrote:

seems that most dried wood is non conductive so wood does not shield
well for rfi or emi


hmmm might have to add a layer of thin metal on the inside to minimize
leakage

copper always looks good but i wonder if the patina that develops
will change the way it shields


maybe there is a wood that has some conductive qualities even in the
dried state

faraday tree


Self-adhesive copper foil can be bought in sheets from virtually any
company that sells stained-glass supplies. I've never seen it in sizes over
12"X12" but if one looked hard enough bigger stuff is probably out there.
If using small sheets joining them together is easy with a bit of flux and
solder. Back in ancient days when I occasionally built wooden enclosures
for rf-sensitive audio gear I used similar foil for shielding and in the
wooden computer case I built I covered everything inside with copper. My
foil was bought in Japan and was, at a guess, 60cm wide and 10m long but
had no adhesive backing and had to be glued down with contact cement.

You guys are overthinking this. Copper is expensive overkill for
shielding. Grocery-store aluminum foil works fine and you can stick it
down with hot glue, double-stick tape, contact cement, or whatever else
you like. If you have an opening you need to shield, aluminum screen
from your average hardware store is plenty for the sort of openings you
typically find in computer cases--it's better than what is used in most
store-bought computers.



But aluminum foil will not develop that blueish green patina over time
like copper will.

On Sat, 2 Jul 2016 05:48:06 -0400, "J. Clarke"
wrote:

In article , says...

On 6/30/2016 9:11 PM, Electric Comet wrote:

seems that most dried wood is non conductive so wood does not shield
well for rfi or emi


hmmm might have to add a layer of thin metal on the inside to minimize
leakage

copper always looks good but i wonder if the patina that develops
will change the way it shields


maybe there is a wood that has some conductive qualities even in the
dried state

faraday tree


Self-adhesive copper foil can be bought in sheets from virtually any
company that sells stained-glass supplies. I've never seen it in sizes over
12"X12" but if one looked hard enough bigger stuff is probably out there.
If using small sheets joining them together is easy with a bit of flux and
solder. Back in ancient days when I occasionally built wooden enclosures
for rf-sensitive audio gear I used similar foil for shielding and in the
wooden computer case I built I covered everything inside with copper. My
foil was bought in Japan and was, at a guess, 60cm wide and 10m long but
had no adhesive backing and had to be glued down with contact cement.

You guys are overthinking this. Copper is expensive overkill for
shielding. Grocery-store aluminum foil works fine and you can stick it
down with hot glue, double-stick tape, contact cement, or whatever else
you like. If you have an opening you need to shield, aluminum screen
from your average hardware store is plenty for the sort of openings you
typically find in computer cases--it's better than what is used in most
store-bought computers.

The problem with aluminum foils is that the seams have to be
connected. Aluminum quickly forms an oxide that's non-conductive.
Since aluminum, (particularly foil) doesn't solder well that doesn't
help, either. If you can solve the seam problem, aluminum is
excellent.

On Thu, 30 Jun 2016 18:11:54 -0700
Electric Comet wrote:


seems that most dried wood is non conductive so wood does not shield
well for rfi or emi

decided to make two enclosures

the first one will enclose the device
then i will place a copper mesh over that
the second box will enclose the mesh and the first box

this way it will look like a solid wood enclosure

On Mon, 11 Jul 2016 18:52:39 -0700, Electric Comet
wrote:

On Thu, 30 Jun 2016 18:11:54 -0700
Electric Comet wrote:


seems that most dried wood is non conductive so wood does not shield
well for rfi or emi

decided to make two enclosures

the first one will enclose the device
then i will place a copper mesh over that
the second box will enclose the mesh and the first box

this way it will look like a solid wood enclosure

The mesh must be continuous, with no seams and any openings have to be
as small as possible. This can be a real PITA, without the
complications of your Russian doll. Conductive paint is a whole lot
easier. ...almost as easy as punctuation and starting sentences with
upper case characters.

On Mon, 11 Jul 2016 22:14:55 -0400, wrote:

On Mon, 11 Jul 2016 18:52:39 -0700, Electric Comet
wrote:

On Thu, 30 Jun 2016 18:11:54 -0700
Electric Comet wrote:


seems that most dried wood is non conductive so wood does not shield
well for rfi or emi

decided to make two enclosures

the first one will enclose the device
then i will place a copper mesh over that
the second box will enclose the mesh and the first box

this way it will look like a solid wood enclosure

The mesh must be continuous, with no seams and any openings have to be
as small as possible. This can be a real PITA, without the
complications of your Russian doll. Conductive paint is a whole lot
easier. ...almost as easy as punctuation and starting sentences with
upper case characters.

Better yet make a faraday cage.....