- I read through your EMF shielding tutorial, but am not familiar with
- the theory enough to apply it to a particular question.  It has
- often been said that putting a cellular phone inside a microwave,
- closing the door, and seeing if it will ring when called is a good way
- to test the integrity of the microwave's shielding/seals. I've been
- trying to understand the theory of how shields work in order to
- determine if this is true.
- - Cell phone seem to operate between 900-2000 MHz (.33m for 900 MHz,
- ~.15m wavelength for 1900 MHz)
- - Microwaves operate at around 2.45 GHz (~.122m wavelength)
- The answer seems dependent on whether or not microwave oven shielding
- also shields cellular phone frequencies, and I have not found a
- scientific consensus as to whether or not this is the case.
- In reading your explanation, I was drawn to the following formula as
- perhaps the answer to this:
- Thus, it would appear that if all other characteristics about the
- shield are kept constant, decreasing the frequency will increase the
- attenuation -- perhaps an effective shield for 2.45 GHz really isn't
- an effective shield for lower frequencies.
- However, this quote seems to imply that if an aperture is much smaller
- than the wavelength, the energy will not penetrate:
- | Fortunately, apertures with maximum dimensions that are much
- | smaller than a wavelength provide very little impedance to
- | the flow of currents on a conducting surface.
- So, it would seem that an effective shield for 0.122m would also
- shield for the longer wavelengths of the cell phone range very well.
- Would you be able to clarify which of these interpretations is
- correct? I believe I have tried calling a cell phone inside a
- microwave and had it both ring and not ring. This might be a neat
- practical example of the theoretical article you have online, perhaps
- as an appendix. Just a suggestion.
a guest Jul 26th, 2011 144 Never
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