The frequency is related to wavelength by the following equation:

**f = c/γ**

Where

**f**= frequency in Hz,

**c**is light velocity, and

**γ**represents wavelength in meters.

One rule of thumb often used for Faraday cages to prevent transmission is that the holes need to be no larger than 1/10 of the wavelength of the signal.

So for a 3G cell phone that operates at a frequency of 2.1 GHz (2.1 * 109 Hz), the wavelength = (3 * 108 m/sec) / (2.1 * 109 Hz) = .14 meters. Thus, for a Faraday cage to prevent this noise from entering, the holes in the cage should be smaller than .014 meters (or 1.4 cm).

Also, 60Hz line noise will have a wavelength of (3 * 108 m/sec) / 60 Hz = 5.4 meters or ~17.5 feet. This would mean that 1 foot holes would block 60Hz EM waves, but that is not the case when I build a faraday cage.

When we surround our electronics with a metal screen mesh from Home Depot, as seen below:

This does a wonderful job of blocking 60 Hz noise, but does not effect the 3G cell phones signal when I place it inside the cage! That seems to be the opposite of what that equation is stating. What is my confusion?

I should note that I ground our electronics to the Faraday cage, but I'm not sure where to ground the cell phone to the cage. Is this what is making the difference? I am wondering why?

Thanks!