Andy writes:
If the Faraday cage had perfect conductivity and were
seamless, it would work pretty well. However, using REAL
materials, the EM energy is only attenuated so many db,
depending on the material. Additionally, every discontinuity
such as a seam or change in material, sets up circulating
currents which retransmit the field on the inside of the cage,
with the attenuation depending on the thickness, the material,
the length of the discontinuity, and a dozen other things...
In other words, it ain't gonna work in the real world like it
works in the textbook.... A Faraday cage is a theoretical
concept which works on paper, but cannot be produced
in nature...... Besides, you would suffocate fairly quickly...
You can prove this by tuning a transistor radio to a local
AM station, then wrapping it in aluminum foil..... Damn little
effect , if any. Wrap it in several overlapping layers and try to
make it seamless..... it still won't get rid of that damn rap music...
... that's why the elevator you mentioned doesn't give a million
db of attenuation to the cell phone.
Andy (retired from Raytheon Electromagnetics Lab)
Regarding your second mention, about the TTL circuitry....
More than likely , there is enough electrical noise flying about
at a level greater than the cell tower signal in your receiver, to
keep the receiver from processing it. Hence, you will probably
get a "no signal" indication on you little cell phone indicator.
It probably doesn't work well around arc welders, either....
The basis of jammers is to prevent your receiver from processing
the cell tower signal. It doesn't take much energy to do this, since
we are talking about field strengths in the microvolt level.
