# Radio waves vs material & shape

1. Jun 8, 2013

### bikespot

What happens when radio waves of around 1900mhz (cell phone) is confined in an aluminum box. Will the waves be able to pass through the box to the outside.

What would be the best way to get the waves to the outside of the box with only modifying the box. If i cut a hole would that improve how much signal is escaping the box . Also depending on the size of the hole and the shape. What about a non conductive coating on the aluminum...

Last edited: Jun 8, 2013
2. Jun 9, 2013

### bikespot

Would the waves just bounce off the walls of the aluminum box. What if there was a hole in the box.

Basiclly im trying to still have the aluminum box but have as much signal pass through it as possible.

3. Jun 9, 2013

### marcusl

Your cellphone will work with much reduced performance in a box with an opening--basically the more metal you put around and near it, the worse it will perform. If you need a mostly-enclosed box, then add a slot that is onehalf the wavelength λ. This will act as a radiator (antenna) that will permit some radiation to escape. You can compute wavelength from frequency as $$\lambda=\frac{c}{f}$$ where f is the frequency and c is the speed of light. Since you are perturbing the phone antenna's by putting metal near it, and since the slot is in its near field region, I wouldn't expect very good performance.

Last edited: Jun 9, 2013
4. Jun 9, 2013

### Naty1

bikespot..
Faraday cages are used to block electromagnetic radiation and protect interior electronics..even from lightning strikes......you might find this discussion of Faraday Cages of interest.....has some practical insights

http://en.wikipedia.org/wiki/Faraday_box

while they discuss exterior electromagnetic waves, obviously internally generated waves are blocked/transmitted similarly.

5. Jun 9, 2013

### physwizard

A solid metal box should not allow electromagnetic waves to escape unless the metal is too thin like a coating or something. If you make a hole or holes in the box whose size is much larger than the wavelength then the waves can escape.

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