I cannot bear to bear that bear.I can't bear to watch. I have a heavy load to bear. There is a bearing on my axle. Is that animal a bear? Does the use of bear have a bearing on language?
YesSo if I had a powerful enough transmitter and fired a focused beam of radio waves at 2.8 gigahertz at a. Solid Wall made of mild steel, and not ground, the radio waves would pass through the wall and a receiver on the other side would detect the signal?
Just to learn how radios work.Yes
your waves are attenuated , so still there , but smaller.
Its "just" a mater of detecting,
refer back to Xrays .
when you started this , it was a general question, a though experiment ?
It now seems to be turning into how do I make a ray gun pointing through a wall ,
What are your intentions ?
Kind of depends on what you mean by "block" . What your application. What I am thinking about is Cu a conductor but put something in a Cu Faraday cage and ground it will block rf by shunting it to ground, as long as the wave length is longer than any holes in the box.Will metal block all frequencies of radio waves, or are there some frequencies metals won't block? For example will lower frequencies, penetrate metals better? Is attenuate a more accurate term than block?
Your typical Cu Faraday cage doesn't work by shunting current to ground. If that was necessary RF shielding in airplanes wouldn't work. A "perfect" Faraday cage does not block EM radiation but it can attenuate /reduce the in/out going signals to acceptable but not totally undetectable levels.Kind of depends on what you mean by "block" . What your application. What I am thinking about is Cu a conductor but put something in a Cu Faraday cage and ground it will block rf by shunting it to ground, as long as the wave length is longer than any holes in the box.
We will assume the emitting source is placed at a reasonable distance from the wall of the enclosure (inside) such that we are concerned with far field radiation (radiation that has escaped the antenna; 1/6 wavelength is often used as an approximate distance for predominance of radiation field in shielding applications) propagating outwards towards the enclosing shield wall.
The attenuation provided by the shield results from three mechanisms: (1) reflection of an electromagnetic wave when it encounters an impedance disontinuity, e.g., the air to metal impedance discontinuity as the wave encounters the shield (2) absorption within the shield material of portions of the wave energy not reflected as it transfers some energy in heating the shield and (3) possible additional reflections within the shield and at the impedance discontinuity as any remnant of the wave encounters another metal (typical shield material) air boundary. The diagram below is for a wave approaching from outside; simply reverse the label, i.e., let "inside of enclosure" in the diagram be "outside of enclosure."
Electromagnetic radiation is primarily shielded by reflection via mobile charge carriers (electrons or holes) which interact with the radiation. High conductivity of the shield is not required, e.g. on the order of 1 ohm is usually sufficient. Electrical conductivity is not the criterion for shielding (though conductivity enhances shielding) though, since that would require connectivity in the conduction path, e.g., to ground.
by Jake Hertz
by Jake Hertz
by Jake Hertz
by Jake Hertz