Faraday Cage Grounded Or Ungrounded
 

I am assuming that a microwave oven is a Faraday cage. Since it keeps
the radiation trapped, bouncing around inside to heat up the food
instead of you. I am betting you would loose signal on a cell phone
completley if it were placed inside of a microwave with the door
closed. This should work even with the oven unplugged from the wall
outlet, which then would be ungrounded.

The electric field inside a Faraday cage is zero, regardless of what
the outside is doing or is connected to. But the reverse is also true.
The charges that are built up from components inside of the Faraday
cage are trapped to bounce around like the radiation inside of a
microwave. So that makes me think it needs to be grounded. On the
other hand, if the shell of a microwave is grounded. Then what keeps
the radiation inside from going to ground instead of bouncing around
and cooking your food?

AC/DC wrote:
I am assuming that a microwave oven is a Faraday cage. Since it keeps
the radiation trapped, bouncing around inside to heat up the food
instead of you. I am betting you would loose signal on a cell phone
completley if it were placed inside of a microwave with the door
closed. This should work even with the oven unplugged from the wall
outlet, which then would be ungrounded.

The electric field inside a Faraday cage is zero, regardless of what
the outside is doing or is connected to. But the reverse is also true.
The charges that are built up from components inside of the Faraday
cage are trapped to bounce around like the radiation inside of a
microwave. So that makes me think it needs to be grounded. On the
other hand, if the shell of a microwave is grounded. Then what keeps
the radiation inside from going to ground instead of bouncing around
and cooking your food?

http://www.google.ca/search?q=microw...e+Search&meta=

There was considerable debate whether the cell phones in the
hijacked planes could have actually worked at all. I've had problems
even in a wood framed house with stucco wire around it.


On a radio related note, it appears LIGHTBULBS may become a source
of interference for wireless networks.

http://www.geek.com/news/geeknews/20...0617012210.htm

For those with deficient, URL wrapping browsers:

http://tinyurl.com/328yp



A more permanent solution may be found he


Mozilla download
http://www.mozilla.org/

Netscape download
http://channels.netscape.com/ns/browsers/default.jsp


mike

On a radio related note, it appears LIGHTBULBS may become a source
of interference for wireless networks.

http://www.geek.com/news/geeknews/20...0617012210.htm

For those with deficient, URL wrapping browsers:

http://tinyurl.com/328yp

A more permanent solution may be found he

Mozilla download
http://www.mozilla.org/

Netscape download
http://channels.netscape.com/ns/browsers/default.jsp

mike


I recently purchased a pack of the small screw-in fluorescent bulbs and
the package contained a statement to the effect that although they had
been approved by the FCC they may cause interference to radios, wireless
networks, remote controllers etc.

A quick check with a portable HF receiver disclosed that they do indeed
radiate wide spectrum noise, although at a low enough level that I have
not noticed a problem when using an outdoor antenna with co-ax feed.

Dave

Dave

Dave Holford wrote:

I recently purchased a pack of the small screw-in fluorescent bulbs and
the package contained a statement to the effect that although they had
been approved by the FCC they may cause interference to radios, wireless
networks, remote controllers etc.

A quick check with a portable HF receiver disclosed that they do indeed
radiate wide spectrum noise, although at a low enough level that I have
not noticed a problem when using an outdoor antenna with co-ax feed.

Some years ago there were rules concerning the use of dimmers near
radio telescopes because of the noise. All this stuff is accumulative.

How can any device that causes interference be type approved by UL
or the CSA? There may be some monetary incentives going on that we
aren't aware of.




mike

"m II" wrote in message
news:lS9Ac.48479$Ds.19843@clgrps12...
Dave Holford wrote:

I recently purchased a pack of the small screw-in fluorescent bulbs and
the package contained a statement to the effect that although they had
been approved by the FCC they may cause interference to radios, wireless
networks, remote controllers etc.

A quick check with a portable HF receiver disclosed that they do indeed
radiate wide spectrum noise, although at a low enough level that I have
not noticed a problem when using an outdoor antenna with co-ax feed.

Some years ago there were rules concerning the use of dimmers near
radio telescopes because of the noise. All this stuff is accumulative.

How can any device that causes interference be type approved by UL
or the CSA? There may be some monetary incentives going on that we
aren't aware of.



I can't speak for CSA, but UL doesn't cover RF radiation, only safety issues
and other concerns of insurance companies.

As for the RF noise, FCC Part 15 applies to all such devices. Part 15 rules
allow for really quite a bit of RF garbage (100mW on AMBCB can create quite
a havoc, especially when it's connected to a nice long antenna like your
electrical wiring). I believe all the small fluorescent stuff uses a
switching power supply, similar in function to the one in your computer.
This means square waves.. and square waves mean beaucoup RF radiation up to
who knows how far in the spectrum.

In article ,
"Brenda Ann Dyer" wrote:

"m II" wrote in message
news:lS9Ac.48479$Ds.19843@clgrps12...
Dave Holford wrote:

I recently purchased a pack of the small screw-in fluorescent bulbs and
the package contained a statement to the effect that although they had
been approved by the FCC they may cause interference to radios, wireless
networks, remote controllers etc.

A quick check with a portable HF receiver disclosed that they do indeed
radiate wide spectrum noise, although at a low enough level that I have
not noticed a problem when using an outdoor antenna with co-ax feed.

Some years ago there were rules concerning the use of dimmers near
radio telescopes because of the noise. All this stuff is accumulative.

How can any device that causes interference be type approved by UL
or the CSA? There may be some monetary incentives going on that we
aren't aware of.



I can't speak for CSA, but UL doesn't cover RF radiation, only safety issues
and other concerns of insurance companies.

As for the RF noise, FCC Part 15 applies to all such devices. Part 15 rules
allow for really quite a bit of RF garbage (100mW on AMBCB can create quite
a havoc, especially when it's connected to a nice long antenna like your
electrical wiring). I believe all the small fluorescent stuff uses a
switching power supply, similar in function to the one in your computer.
This means square waves.. and square waves mean beaucoup RF radiation up to
who knows how far in the spectrum.

I'll add that any FCC type acceptance allows a device to generate noise
only to a certain level depending on frequency so the closer your radio
is to it the more likely you will hear it.

--
Telamon
Ventura, California

These are ion the same ISM frequency as microwave ovens (2450 mHz as I
recall). Satellite radio is the closest licensed service that may be
affected. A part 15/ISM device may not cause interference to a
licensed service.

BTW, these are the equivalent of 2 microwave ovens running with the
doors open. I doubt they'll be deployed in habitated spaces.

On Wed, 16 Jun 2004 22:54:07 -0400, Dave Holford
wrote:





On a radio related note, it appears LIGHTBULBS may become a source
of interference for wireless networks.

http://www.geek.com/news/geeknews/20...0617012210.htm

For those with deficient, URL wrapping browsers:

http://tinyurl.com/328yp

A more permanent solution may be found he

Mozilla download
http://www.mozilla.org/

Netscape download
http://channels.netscape.com/ns/browsers/default.jsp

mike


I recently purchased a pack of the small screw-in fluorescent bulbs and
the package contained a statement to the effect that although they had
been approved by the FCC they may cause interference to radios, wireless
networks, remote controllers etc.

A quick check with a portable HF receiver disclosed that they do indeed
radiate wide spectrum noise, although at a low enough level that I have
not noticed a problem when using an outdoor antenna with co-ax feed.

Dave

Dave

In article ,
Brenda Ann Dyer wrote:

"m II" wrote in message
news:lS9Ac.48479$Ds.19843@clgrps12...
Dave Holford wrote:

I recently purchased a pack of the small screw-in fluorescent bulbs and
the package contained a statement to the effect that although they had
been approved by the FCC they may cause interference to radios, wireless
networks, remote controllers etc.

A quick check with a portable HF receiver disclosed that they do indeed
radiate wide spectrum noise, although at a low enough level that I have
not noticed a problem when using an outdoor antenna with co-ax feed.

Some years ago there were rules concerning the use of dimmers near
radio telescopes because of the noise. All this stuff is accumulative.

How can any device that causes interference be type approved by UL
or the CSA? There may be some monetary incentives going on that we
aren't aware of.



I can't speak for CSA, but UL doesn't cover RF radiation, only safety issues
and other concerns of insurance companies.

As for the RF noise, FCC Part 15 applies to all such devices. Part 15 rules
allow for really quite a bit of RF garbage (100mW on AMBCB can create quite
a havoc, especially when it's connected to a nice long antenna like your
electrical wiring). I believe all the small fluorescent stuff uses a
switching power supply, similar in function to the one in your computer.
This means square waves.. and square waves mean beaucoup RF radiation up to
who knows how far in the spectrum.

I purchased some GE brand compact fluorescents recently and on the card
in the packaging has a warning.

.... "This product complies with Part 18 of the FCC Rules but may
cause interference to radios, televisions, wireless telephones, and
remote controls. Avoid placing this product near these devices.
If interference occurs, move product away from the device or
plug either into a different outlet. Do not install this product
near maritime safety equipment or other critical navigation or
communications equipment operating between .45 - 30 MHz. ..."

Part 18 is Industrial/Scientific/Medical regs, ie. microwave ovens,
induction stove burners, etc.

Mark Zenier Washington State resident

In article ,
David wrote:
These are ion the same ISM frequency as microwave ovens (2450 mHz as I
recall). Satellite radio is the closest licensed service that may be
affected. A part 15/ISM device may not cause interference to a
licensed service.

Part 18 covers a whole series of bands, mostly HF and Microwave, and
a pretty much blanket use of LF. (For LF, the important part is how
much crud you put back into the powerline). For HF, the bands are
6.78 MHz +/- 15 kHz,
13.56 MHz +/- 7 kHz,
27.12 MHz +/- 163 Khz. (Yup, Citizens Band)

It's got my favorite line that I've found so far in the regs.

18.306a "ISM equipment operating on a frequency specified in (paragraph)
18.301 is permitted unlimited radiated energy in the band specified for
that frequency". (You're not allowed to modulate any information on it,
though).

Mark Zenier Washington State resident

How can any device that causes interference be type approved by UL
or the CSA? There may be some monetary incentives going on that we
aren't aware of.

because the responsibility of UL and CSA is purely safety. They
measure temperatures, leakage current etc. They neither know or care
about Radio Frequency energy.