Faraday cages and radio / microwave transmission

[Humberto]

• Will spanish burglar bars disrupt wireless communication signals? Like if you place an iBurst modem in front of spanish burglar bars, will the burglar bars act as a Faraday cage and disrupt the signal?
• To my knowledge, the reason why the inside of a car is a safe place during a thunderstorm is because the car is a Faraday cage. This being the case, why can one use a cellphone inside a car? From http://en.wikipedia.org/wiki/Faraday_cage:
  
  

  The reception or transmission of radio waves, a form of electromagnetic radiation, to or from an antenna with in a Faraday cage are heavily attenuated or blocked by a Faraday cage.

 

[HavocXphere]

Will reduce but not block.

 

[b@nD]

Specifics

To my knowledge, the reason why the inside of a car is a safe place during a thunderstorm is because the car is a Faraday cage.

Do not think a car is a "Faraday Cage"
A proper Faraday Cage is somewhat more complex than that. ( and not just solid metal )

 

[ponder]

Do not think a car is a "Faraday Cage"
A proper Faraday Cage is somewhat more complex than that. ( and not just solid metal )

From controlled lightning test I've seen a car body works quite well. It's not a perfect Faraday cage but it works.

Ever watched those guys dress up in chainmail and stand between two mofo Van de Graaff generators? Same principal applies.

 

[Swa]

From controlled lightning test I've seen a car body works quite well. It's not a perfect Faraday cage but it works.

Ever watched those guys dress up in chainmail and stand between two mofo Van de Graaff generators? Same principal applies.

It's not really a Faraday cage example. The reason it works is because being surrounded by metal makes this the path of least resistance. Any other path followed inside the car would add to resistance and the lightning would have to then find a path leading back to the frame so it instead avoids this and takes a path through the frame as though it were solid.

Back to the topic: In order for a signal to be blocked there needs to be an obstacle larger than the wavelength with no openings larger than the wavelength. This is not a hard and fast rule though. As said the signal will only be reduced and true blocking only comes in when the obstacle is also thicker and of the right material. In your case though the building probably has a bigger effect on the signal and the window even with bars could help it.