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Home > Archive > Electrical code Compliance > January 2007 > Black poly blocks RF
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| Author |
Black poly blocks RF
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| My name is Bob 2006-12-19, 9:25 am |
| Hi,
I am a member of an internet forum with a guy claiming that black poly
(standard black plastic) blocks RF. I am not sure if he is on drugs or is
some kind of super physicist, because he is very confident but IMHO is
talking rubbish.
He is extracts of what he has said (I only cut out parts that don't
contribute to his argument):
"I just wanted to drop off my 2 cents cause this topic happens to be under
my area of expertise.
When manufactures claim something is RF shielded, it means that most of the
electrical components are cover with a high carbon content polymer (aka
black plastic!). It's that simple. However, it's very difficult to shield
all the RF emitting from the power cord connection, so usually no ballast is
perfectly shielded.
There's an easy solution if you are having RF interference problems.
Surround the area/room/cabinet that contains the ballast with a layer or two
of black poly. Remember, black plastic absorbs RF like a sponge, where as
metal reflects it like a mirror. Wet wood absorbs RF like a champ too but
that's not as easy to work with as black poly.
"
"What about there very nature makes plastics non-conductive? High carbon
content plastics do indeed attenuate RF emissions because carbon is
conductive to EM radiation in most pratical spectral bands. So yes, black
poly will attenuate most RF signals!"
"Infinite resistance! Well that sounds like the perfect material to
attenuate a signal with!
But seriously, I have the same black poly as you do. Your ohm meter measures
a material's ability to conduct a DC electrical signal which is completely
different from a material's ability to conduct an electromagnetic wave.
You'll need a spectrum analyzer; UHF antena; function generator; and a
little more insight on the nature of photons to be able to measure a
material's resistance to an electromagnetic wave.
You should really trust me on this one because as it turns out the electrons
in the carbon atom get really excited when they get hit with photons that
are about 100 nanometers to several feet in length. This causes them to jump
to a higher energy state and absorb some of the energy from the wave in
doing so. An RF signal is just a stream of photons that are a couple
centimeters to serveral feet in length. Hence, plastics containg carbon
atoms attenuate RF signals. Isn't that great!
"
"It would take a layer of black poly an inch thick to completely block a
cell phone signal"
Am I woefully misinformed or does he have a point?
Thanks.
| |
| hrhofmann@att.net 2006-12-20, 1:25 pm |
| He is about 95% full of hot air.
My name is Bob wrote:
> Hi,
>
> I am a member of an internet forum with a guy claiming that black poly
> (standard black plastic) blocks RF. I am not sure if he is on drugs or is
> some kind of super physicist, because he is very confident but IMHO is
> talking rubbish.
>
> He is extracts of what he has said (I only cut out parts that don't
> contribute to his argument):
>
> "I just wanted to drop off my 2 cents cause this topic happens to be under
> my area of expertise.
>
> When manufactures claim something is RF shielded, it means that most of the
> electrical components are cover with a high carbon content polymer (aka
> black plastic!). It's that simple. However, it's very difficult to shield
> all the RF emitting from the power cord connection, so usually no ballast is
> perfectly shielded.
>
> There's an easy solution if you are having RF interference problems.
> Surround the area/room/cabinet that contains the ballast with a layer or two
> of black poly. Remember, black plastic absorbs RF like a sponge, where as
> metal reflects it like a mirror. Wet wood absorbs RF like a champ too but
> that's not as easy to work with as black poly.
> "
>
> "What about there very nature makes plastics non-conductive? High carbon
> content plastics do indeed attenuate RF emissions because carbon is
> conductive to EM radiation in most pratical spectral bands. So yes, black
> poly will attenuate most RF signals!"
>
> "Infinite resistance! Well that sounds like the perfect material to
> attenuate a signal with!
>
> But seriously, I have the same black poly as you do. Your ohm meter measures
> a material's ability to conduct a DC electrical signal which is completely
> different from a material's ability to conduct an electromagnetic wave.
>
> You'll need a spectrum analyzer; UHF antena; function generator; and a
> little more insight on the nature of photons to be able to measure a
> material's resistance to an electromagnetic wave.
>
> You should really trust me on this one because as it turns out the electrons
> in the carbon atom get really excited when they get hit with photons that
> are about 100 nanometers to several feet in length. This causes them to jump
> to a higher energy state and absorb some of the energy from the wave in
> doing so. An RF signal is just a stream of photons that are a couple
> centimeters to serveral feet in length. Hence, plastics containg carbon
> atoms attenuate RF signals. Isn't that great!
> "
>
> "It would take a layer of black poly an inch thick to completely block a
> cell phone signal"
>
> Am I woefully misinformed or does he have a point?
>
> Thanks.
| |
|
| My name is Bob wrote:
> Hi,
>
> I am a member of an internet forum with a guy claiming that black poly
> (standard black plastic) blocks RF. I am not sure if he is on drugs or is
> some kind of super physicist, because he is very confident but IMHO is
> talking rubbish.
>
> He is extracts of what he has said (I only cut out parts that don't
> contribute to his argument):
>
> "I just wanted to drop off my 2 cents cause this topic happens to be under
> my area of expertise.
>
> When manufactures claim something is RF shielded, it means that most of the
> electrical components are cover with a high carbon content polymer (aka
> black plastic!). It's that simple. However, it's very difficult to shield
> all the RF emitting from the power cord connection, so usually no ballast is
> perfectly shielded.
>
> There's an easy solution if you are having RF interference problems.
> Surround the area/room/cabinet that contains the ballast with a layer or two
> of black poly. Remember, black plastic absorbs RF like a sponge, where as
> metal reflects it like a mirror. Wet wood absorbs RF like a champ too but
> that's not as easy to work with as black poly.
> "
>
> "What about there very nature makes plastics non-conductive? High carbon
> content plastics do indeed attenuate RF emissions because carbon is
> conductive to EM radiation in most pratical spectral bands. So yes, black
> poly will attenuate most RF signals!"
>
> "Infinite resistance! Well that sounds like the perfect material to
> attenuate a signal with!
>
> But seriously, I have the same black poly as you do. Your ohm meter measures
> a material's ability to conduct a DC electrical signal which is completely
> different from a material's ability to conduct an electromagnetic wave.
>
> You'll need a spectrum analyzer; UHF antena; function generator; and a
> little more insight on the nature of photons to be able to measure a
> material's resistance to an electromagnetic wave.
>
> You should really trust me on this one because as it turns out the electrons
> in the carbon atom get really excited when they get hit with photons that
> are about 100 nanometers to several feet in length. This causes them to jump
> to a higher energy state and absorb some of the energy from the wave in
> doing so. An RF signal is just a stream of photons that are a couple
> centimeters to serveral feet in length. Hence, plastics containg carbon
> atoms attenuate RF signals. Isn't that great!
> "
>
> "It would take a layer of black poly an inch thick to completely block a
> cell phone signal"
>
> Am I woefully misinformed or does he have a point?
>
> Thanks.
>
>
>
Black poly doesn't as far as I am aware, contain carbon atoms which are
not chemically bound to the polimers, so the idea of carbon atoms being
excited to a higher energy state by a radio wave is pretty far fetched!
Designing antennas for use at millimetric wavelengths, as I do, I can
assure you that any plastic as thin as black poly will have almost no
affect on the passage of radio waves. We use plastic in our radome
covers, and, while we do take care to match the thickness of the plastic
to the wavelength of the transmission to ensure minimum attenuation, the
affect of the plastic on the power of the transmissionis utterly minimal.
Basically, your friend is so full of shit his eyes are brown.
Sean
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