Plastic does not make a good RF shield material [Digital Cameras]

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From: Paul J Gans on 26 Dec 2009 20:07

In rec.photo.digital Eric Stevens <eric.stevens(a)sum.co.nz> wrote:
>On Sat, 26 Dec 2009 00:29:40 -0800 (PST), RichA <rander3127(a)gmail.com>
>wrote:

>>Once again, plastic falls short. Lack of oversight of products today
>>is allowing companies to import shoddy RF-emanating products that are
>>a problem, from computers with plastic box housings to set-top HDTV
>>boxes. Plastic and aluminum SUCK as RF shields. Only steel or copper
>>work well. Below is an example of the problem.
>>
>>http://forum.getdpi.com/forum/showthread.php?t=12869

>Shielding is designed to keep RF in. Your problem is that you cannot
>keep RF out. You should know that your shielding will not keep out
>X-Rays or Cosmic Rays, either.

Good grief! You've given RichA something new to torment us with!

--
--- Paul J. Gans

From: John McWilliams on 26 Dec 2009 20:17

John A. wrote:
> On Sat, 26 Dec 2009 14:37:22 -0800, John McWilliams
> <jpmcw(a)comcast.net> wrote:
>
>> Eric Stevens wrote:
>>> On Sat, 26 Dec 2009 00:29:40 -0800 (PST), RichA <rander3127(a)gmail.com>
>>> wrote:
>>>
>>>> Once again, plastic falls short. Lack of oversight of products today
>>>> is allowing companies to import shoddy RF-emanating products that are
>>>> a problem, from computers with plastic box housings to set-top HDTV
>>>> boxes. Plastic and aluminum SUCK as RF shields. Only steel or copper
>>>> work well. Below is an example of the problem.
>>>>
>>>> http://forum.getdpi.com/forum/showthread.php?t=12869
>>> Shielding is designed to keep RF in. Your problem is that you cannot
>>> keep RF out. You should know that your shielding will not keep out
>>> X-Rays or Cosmic Rays, either.
>> That's why we recommend actual *tin* foil, not the ubiquitius aluminum
>> foil for protective caps/hats.
>
> Is it also because aluminum foil hats amplify incoming signals in
> bands reserved for government use?
>
> http://people.csail.mit.edu/rahimi/helmet/
>
> (Has such a study been done on tin foil hats?)

Dunno. But it's not radio signals he has to be chary of: It's the
controlling brain waves from aliens circling the earth in invisible
space ships....

--
john mcwilliams

From: RichA on 26 Dec 2009 22:03

On Dec 26, 4:14 pm, "U*U" <c...(a)freespeechstore.ca> wrote:
> "RichA" <rander3...(a)gmail.com> wrote in message
>
> news:b1761f8f-dde6-429f-b4ef-1f8eb9fd3b86(a)v25g2000yqk.googlegroups.com...
>
> > Once again, plastic falls short. Lack of oversight of products today
> > is allowing companies to import shoddy RF-emanating products that are
> > a problem, from computers with plastic box housings to set-top HDTV
> > boxes. Plastic and aluminum SUCK as RF shields. Only steel or copper
> > work well. Below is an example of the problem.
>
> >http://forum.getdpi.com/forum/showthread.php?t=12869
>
> Wrong Mr. Engineer, aluminum is used in RF shields, as is bronze, stainless
> steel, gold, tin and copper. Plastic can be coated with RF paint. So once
> again Rich/RichA shows he knows nothing about what he prattles on about.

CLUELESS! Steel or other ferrous material or copper is the only sure
way to guard against RF.
RF paint on plastic!!!

From: Eric Stevens on 27 Dec 2009 03:19

On Sun, 27 Dec 2009 01:07:51 +0000 (UTC), Paul J Gans
<gansno(a)panix.com> wrote:

>In rec.photo.digital Eric Stevens <eric.stevens(a)sum.co.nz> wrote:
>>On Sat, 26 Dec 2009 00:29:40 -0800 (PST), RichA <rander3127(a)gmail.com>
>>wrote:
>
>>>Once again, plastic falls short. Lack of oversight of products today
>>>is allowing companies to import shoddy RF-emanating products that are
>>>a problem, from computers with plastic box housings to set-top HDTV
>>>boxes. Plastic and aluminum SUCK as RF shields. Only steel or copper
>>>work well. Below is an example of the problem.
>>>
>>>http://forum.getdpi.com/forum/showthread.php?t=12869
>
>>Shielding is designed to keep RF in. Your problem is that you cannot
>>keep RF out. You should know that your shielding will not keep out
>>X-Rays or Cosmic Rays, either.
>
>Good grief! You've given RichA something new to torment us with!

I wonder how many holes have been punched through his brain while he
has been thinking about this new source of worry?

Eric Stevens

From: Bristolian on 27 Dec 2009 06:26

RichA wrote:
> On Dec 26, 4:14 pm, "U*U" <c...(a)freespeechstore.ca> wrote:
>> "RichA" <rander3...(a)gmail.com> wrote in message
>>
>> news:b1761f8f-dde6-429f-b4ef-1f8eb9fd3b86(a)v25g2000yqk.googlegroups.com...
>>
>>> Once again, plastic falls short. Lack of oversight of products today
>>> is allowing companies to import shoddy RF-emanating products that are
>>> a problem, from computers with plastic box housings to set-top HDTV
>>> boxes. Plastic and aluminum SUCK as RF shields. Only steel or copper
>>> work well. Below is an example of the problem.
>>> http://forum.getdpi.com/forum/showthread.php?t=12869
>> Wrong Mr. Engineer, aluminum is used in RF shields, as is bronze, stainless
>> steel, gold, tin and copper. Plastic can be coated with RF paint. So once
>> again Rich/RichA shows he knows nothing about what he prattles on about.
>
> CLUELESS! Steel or other ferrous material or copper is the only sure
> way to guard against RF.
> RF paint on plastic!!!

Tut! Tut! You have demonstrated your complete lack of knowledge about
anything to do with materials properties so often on here that it
beggars belief that you would continue in this vein.

For a start you need to define whether you are talking about radiated or
conducted RF because the protection methods needed for both are entirely
different. If radiated interference is the problem then shielding with a
path to ground is the ONLY solution. Any conductive metallic material
(including Aluminium) can be used with pretty much equal effectiveness.
Metallic coatings on plastic are also quite effective for low levels of
interference - a solution widely used in modern airliners and medical
instruments.

Where conducted interference is an issue the parasitic beads around
cables is the widely adopted method but over-all screened cables with
ONE END grounded is the better (but more costly) solution.

For the past ten years (at least) all electrical products manufactured
and/or sold within the EU have had to comply with strict rules about
both radiated and conducted RF emissions - both the levels they give out
and their susceptibility to received interference.

--
Regards

Bristolian