thin case

[Donut]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

is a computer case with .7mm thickness steel as good as a .8mm?
is there more emi/rfi in the thinner case?

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

donut wrote:
> is a computer case with .7mm thickness steel as good as a .8mm?
> is there more emi/rfi in the thinner case?
In all wires, or metal conductors, electricity follows the "Skin Effect"
in that all electron flow of electricity is in the first molecule of the
outermost skin.

The greater flow of a #4 guage wire, over a #14 guage wire is due to the
vastly greater skin area of the #4 wire.

If we are dealing with a flat area, there is no significant difference
between a 10 guage steel sheet, and a 6 guage steel sheet, provided they
are both used predominately in their flat sheet shape!

We often use screen mesh, in blocking EMI/RFI, and you might see
multiple layers of screen, folded, used as a gasket, in some computers
from the 1980's. The screen may permit emission of some higher
frequency energy.

In fact, if you examine your Microwave Oven, you will see the 'screen'
of punched holes in the door window, where the holes are smaller than
the wavelength of the tuned microwave frequency, effectively blocking
it, while allowing visual range 'light' frequencies to pass!

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

In article <44tkc.504828$B81.8946718@twister.tampabay.rr.com>,
Patrick <pberry26@yahoo.com> wrote:
>donut wrote:
>> is a computer case with .7mm thickness steel as good as a .8mm?
>> is there more emi/rfi in the thinner case?

The short answer is No. Is this a general inquery or are you trying
to solve a problem ?

What are you trying to shield ?

Are you trying to prevent interferance from getting in or out ?

Frequently interferance gets in or out via the wires you connect to
the PC, which is why VGA monitor cables and USB cables frequently hove
those lumps on them. If a consmer device causes interferance
in can come under FCC regulations.

FWIW I have the cover off my desktop PC right now. I just carried
an AM/FM radio over to it and tuned the bands. There is a tiny
bit of interference what drops to nothing at 6 ft seperation.


>In all wires, or metal conductors, electricity follows the "Skin Effect"
>in that all electron flow of electricity is in the first molecule of the
>outermost skin.

To be precice, the Skin Effect is only for alternating current, and it's
not "the first molecule. Frequency determines the current density
on the crosssection. It's insignificant until you get into the 10's
of Mhz.

>
>The greater flow of a #4 guage wire, over a #14 guage wire is due to the
>vastly greater skin area of the #4 wire.



>
>If we are dealing with a flat area, there is no significant difference
>between a 10 guage steel sheet, and a 6 guage steel sheet, provided they
>are both used predominately in their flat sheet shape!
>
>We often use screen mesh, in blocking EMI/RFI, and you might see
>multiple layers of screen, folded, used as a gasket, in some computers
>from the 1980's. The screen may permit emission of some higher
>frequency energy.
>
>In fact, if you examine your Microwave Oven, you will see the 'screen'
>of punched holes in the door window, where the holes are smaller than
>the wavelength of the tuned microwave frequency, effectively blocking
>it, while allowing visual range 'light' frequencies to pass!
>
>


--
Al Dykes
-----------
adykes at p a n i x . c o m

 

[Donut]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

if i get the thinner case i can save some money
but is i going to interfere with the tv reception?

asus a7n266vm
amd 2000+ xp
onboard video audio lan
wd 10gb
wd 30gb
mitsumi 3.5
sony cdrom

On 30 Apr 2004 10:42:38 -0400, adykes@panix.com (Al Dykes) wrote:

>In article <44tkc.504828$B81.8946718@twister.tampabay.rr.com>,
>Patrick <pberry26@yahoo.com> wrote:
>>donut wrote:
>>> is a computer case with .7mm thickness steel as good as a .8mm?
>>> is there more emi/rfi in the thinner case?
>
>The short answer is No. Is this a general inquery or are you trying
>to solve a problem ?
>
>What are you trying to shield ?
>
>Are you trying to prevent interferance from getting in or out ?
>
>Frequently interferance gets in or out via the wires you connect to
>the PC, which is why VGA monitor cables and USB cables frequently hove
>those lumps on them. If a consmer device causes interferance
>in can come under FCC regulations.
>
>FWIW I have the cover off my desktop PC right now. I just carried
>an AM/FM radio over to it and tuned the bands. There is a tiny
>bit of interference what drops to nothing at 6 ft seperation.
>
>
>>In all wires, or metal conductors, electricity follows the "Skin Effect"
>>in that all electron flow of electricity is in the first molecule of the
>>outermost skin.
>
>To be precice, the Skin Effect is only for alternating current, and it's
>not "the first molecule. Frequency determines the current density
>on the crosssection. It's insignificant until you get into the 10's
>of Mhz.
>
>>
>>The greater flow of a #4 guage wire, over a #14 guage wire is due to the
>>vastly greater skin area of the #4 wire.
>
>
>
>>
>>If we are dealing with a flat area, there is no significant difference
>>between a 10 guage steel sheet, and a 6 guage steel sheet, provided they
>>are both used predominately in their flat sheet shape!
>>
>>We often use screen mesh, in blocking EMI/RFI, and you might see
>>multiple layers of screen, folded, used as a gasket, in some computers
>>from the 1980's. The screen may permit emission of some higher
>>frequency energy.
>>
>>In fact, if you examine your Microwave Oven, you will see the 'screen'
>>of punched holes in the door window, where the holes are smaller than
>>the wavelength of the tuned microwave frequency, effectively blocking
>>it, while allowing visual range 'light' frequencies to pass!
>>
>>

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

In article <t0q490lilra8tcb48o98deea9o1bo6pbuo@4ax.com>,
donut <donut@glazed.com> wrote:
>if i get the thinner case i can save some money
>but is i going to interfere with the tv reception?
>
>asus a7n266vm
>amd 2000+ xp
>onboard video audio lan
>wd 10gb
>wd 30gb
>mitsumi 3.5
>sony cdrom
>
>On 30 Apr 2004 10:42:38 -0400, adykes@panix.com (Al Dykes) wrote:

I think the answer is that the thinkness of the metal won't make the
difference, other features of the case may. I doubt if you'll
have a problem.

Most of the RF in a PC is in the GHz range, well above the TV bands.

>
>>In article <44tkc.504828$B81.8946718@twister.tampabay.rr.com>,
>>Patrick <pberry26@yahoo.com> wrote:
>>>donut wrote:
>>>> is a computer case with .7mm thickness steel as good as a .8mm?
>>>> is there more emi/rfi in the thinner case?
>>
>>The short answer is No. Is this a general inquery or are you trying
>>to solve a problem ?
>>
>>What are you trying to shield ?
>>
>>Are you trying to prevent interferance from getting in or out ?
>>
>>Frequently interferance gets in or out via the wires you connect to
>>the PC, which is why VGA monitor cables and USB cables frequently hove
>>those lumps on them. If a consmer device causes interferance
>>in can come under FCC regulations.
>>
>>FWIW I have the cover off my desktop PC right now. I just carried
>>an AM/FM radio over to it and tuned the bands. There is a tiny
>>bit of interference what drops to nothing at 6 ft seperation.
>>
>>
>>>In all wires, or metal conductors, electricity follows the "Skin Effect"
>>>in that all electron flow of electricity is in the first molecule of the
>>>outermost skin.
>>
>>To be precice, the Skin Effect is only for alternating current, and it's
>>not "the first molecule. Frequency determines the current density
>>on the crosssection. It's insignificant until you get into the 10's
>>of Mhz.
>>
>>>
>>>The greater flow of a #4 guage wire, over a #14 guage wire is due to the
>>>vastly greater skin area of the #4 wire.
>>
>>
>>
>>>
>>>If we are dealing with a flat area, there is no significant difference
>>>between a 10 guage steel sheet, and a 6 guage steel sheet, provided they
>>>are both used predominately in their flat sheet shape!
>>>
>>>We often use screen mesh, in blocking EMI/RFI, and you might see
>>>multiple layers of screen, folded, used as a gasket, in some computers
>>>from the 1980's. The screen may permit emission of some higher
>>>frequency energy.
>>>
>>>In fact, if you examine your Microwave Oven, you will see the 'screen'
>>>of punched holes in the door window, where the holes are smaller than
>>>the wavelength of the tuned microwave frequency, effectively blocking
>>>it, while allowing visual range 'light' frequencies to pass!
>>>
>>>
>


--
Al Dykes
-----------
adykes at p a n i x . c o m

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

On Fri, 30 Apr 2004 13:48:34 GMT, donut <donut@glazed.com> wrote:

>is a computer case with .7mm thickness steel as good as a .8mm?
>is there more emi/rfi in the thinner case?

No, thickness isn't an issue for emi/rfi at .7mm., but a larger issue
might be how much of that case isn't covered by metal, like a side window,
large openings in front behind plastic bezel.

The biggest issue to me would be that .7mm makes for a flimsy case. .8mm
isn't all that great either, all the cases for my own systems have 1.0mm
in steel... I have one 1.0mm aluminum and won't buy another Al that's
thinner than 1.2mm, as it needs be thicker for same rigidity as steel. If
the cases you're looking at are very small as is possible with that
all-integrated board, at least the smaller size in combination with a lot
of folds and/or creases in the metal may reduce the impact of the thin
metal. Then again a very small case may not have very good cooling for
the 2 HDDs you mentioned.

 

[yogi]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

I would be looking at the thicker case as the thinner the case the
more drummy it will sound with the case and CPU fans. As well as what
has been said by others, the thicker the case the more rigid it will
be.

Cheers

On Fri, 30 Apr 2004 13:48:34 GMT, donut <donut@glazed.com> wrote:

>is a computer case with .7mm thickness steel as good as a .8mm?
>is there more emi/rfi in the thinner case?



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[Donut]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

what do you use to cover the openings that is not needed?

On Fri, 30 Apr 2004 18:38:26 GMT, kony <spam@spam.com> wrote:

>On Fri, 30 Apr 2004 13:48:34 GMT, donut <donut@glazed.com> wrote:
>
>>is a computer case with .7mm thickness steel as good as a .8mm?
>>is there more emi/rfi in the thinner case?
>
>No, thickness isn't an issue for emi/rfi at .7mm., but a larger issue
>might be how much of that case isn't covered by metal, like a side window,
>large openings in front behind plastic bezel.
>
>The biggest issue to me would be that .7mm makes for a flimsy case. .8mm
>isn't all that great either, all the cases for my own systems have 1.0mm
>in steel... I have one 1.0mm aluminum and won't buy another Al that's
>thinner than 1.2mm, as it needs be thicker for same rigidity as steel. If
>the cases you're looking at are very small as is possible with that
>all-integrated board, at least the smaller size in combination with a lot
>of folds and/or creases in the metal may reduce the impact of the thin
>metal. Then again a very small case may not have very good cooling for
>the 2 HDDs you mentioned.

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

On Sat, 01 May 2004 18:50:38 GMT, donut <donut@glazed.com> wrote:

>what do you use to cover the openings that is not needed?
>

Personally I use aluminum tape, commonly found at hardware stores in the
HVAC or tape isle. Since aluminum tape is electrically conductive you'd
want to be sure it's applied to a clean surface and it's adhesive is
holding well, or apply to outer wall of case instead of interior wall,
minimizing chance it could come off and create a short. FWIW, I've never
had any come off, it holds quite well.