# Designing device to reflect my laptop's wifi signal.

#### Man10

Joined Jul 31, 2018
147
If I use aluminium foil to extend the range of the wifi signal that my laptop generates by reflecting the wifi signal, my laptop can generate a wifi signal, how thick should the aluminium foil be?

#### WBahn

Joined Mar 31, 2012
28,182
It not thickness that matters nearly as much as size, shape, and position.

At 2.4 GHz, the wavelength of the signal is about 5". That means that if you move your reflector just over an inch you go from reinforcing the non-reflected signal to canceling it out. This is even more sensitive at 5 GHz.

#### Man10

Joined Jul 31, 2018
147
Does the amount reflected depend on thickness, at all?

#### WBahn

Joined Mar 31, 2012
28,182
Does the amount reflected depend on thickness, at all?
Not much. The skin depth of pure aluminum at 2.4 GHz is only about 2 µm. This is why aluminized mylar film can be used as reflectors and shields above a certain frequency.

#### Man10

Joined Jul 31, 2018
147
Not much. The skin depth of pure aluminum at 2.4 GHz is only about 2 µm. This is why aluminized mylar film can be used as reflectors and shields above a certain frequency.
So if I make the aluminium layer thicker, it will reflect a greater proportion of rf energy?

#### BobTPH

Joined Jun 5, 2013
6,302
Not measurably.

#### Man10

Joined Jul 31, 2018
147
So if I increase the thickness of the aluminium foil, it will reflect a greater proportion of the energy of the radio waves, but not measurably?

#### WBahn

Joined Mar 31, 2012
28,182
Correct.

#### Man10

Joined Jul 31, 2018
147
So if I place the aluminium foil at a different distance, the aluminium foil will reflect a greater proportion of rf energy or a smaller proportion of rf energy?

#### WBahn

Joined Mar 31, 2012
28,182
So if I place the aluminium foil at a different distance, the aluminium foil will reflect a greater proportion of rf energy or a smaller proportion of rf energy?
The amount of energy it reflects won't change much. How the reflected energy interacts with the rest of the energy will change.

Get some aluminum foil and start seeing what happens.

#### Man10

Joined Jul 31, 2018
147
Not much. The skin depth of pure aluminum at 2.4 GHz is only about 2 µm. This is why aluminized mylar film can be used as reflectors and shields above a certain frequency.
What is skin depth?

#### Man10

Joined Jul 31, 2018
147
The amount of energy it reflects won't change much. How the reflected energy interacts with the rest of the energy will change.

Get some aluminum foil and start seeing what happens.
So at certain distances, constructive interference will occur between wifi signal and reflected waves, and the wifi signal will travel at maximum range, at other distances destructive interference will occur between wifi signal and reflected waves and the wifi signal will travel over the minimum distance?

#### WBahn

Joined Mar 31, 2012
28,182
Pretty much.

#### Man10

Joined Jul 31, 2018
147
So if I place my laptop 1 wavelength from the aluminium foil, the wifi signal will travel over the maximum distance?

#### WBahn

Joined Mar 31, 2012
28,182
So if I place my laptop 1 wavelength from the aluminium foil, the wifi signal will travel over the maximum distance?
Since we are talking about wavelengths in the 2.5" or 5" range, where do you measure from? What part of your laptop?

It all depends on what the actual radiation pattern is and what the shape of your aluminum foil is.

Again, get some aluminum foil and start experimenting. Asking question after question is not going to get you anywhere.

#### Man10

Joined Jul 31, 2018
147
I did get some aluminium foil and start experimenting. I started this post to learn how to design the reflector.

#### Man10

Joined Jul 31, 2018
147
I place a stack of aluminium foil against the laptop. So the aluminium foil is touching the laptop and the distance from the laptop to the aluminium foil is zero inches. I noticed if I place my cell phone on 1 side of the aluminium foil and the laptop is on the other side of the aluminium foil, my cell phone still gets a strong signal. If I place the aluminium foil 1 wavelength from the laptop and the aluminium foil is between the laptop and cell phone will the cell phone not receive a signal?

#### WBahn

Joined Mar 31, 2012
28,182
I place a stack of aluminium foil against the laptop. So the aluminium foil is touching the laptop and the distance from the laptop to the aluminium foil is zero inches. I noticed if I place my cell phone on 1 side of the aluminium foil and the laptop is on the other side of the aluminium foil, my cell phone still gets a strong signal. If I place the aluminium foil 1 wavelength from the laptop and the aluminium foil is between the laptop and cell phone will the cell phone not receive a signal?
Try it and see.

You'll find that radiation patterns are not nearly as easy to describe as you think they are.

#### Alec_t

Joined Sep 17, 2013
13,332
I noticed if I place my cell phone on 1 side of the aluminium foil and the laptop is on the other side of the aluminium foil, my cell phone still gets a strong signal.
Your cell phone will also be receiving signals reflected from furniture and the walls of any room you are in, so it's unlikely the foil will block them completely.