Putting a smartphone in a tinfoil shoebox

Modern smartphones are great tracking devices, thanks to GPS and mobile data technology.

Throw in voice calls and SMSs, and it is near impossible to escape anyone if you have a smartphone on you (unless you ignore them).

Many professions require an employee to carry a company-tracked device with them at all times, which can be exploited by an employer.

This is an issue for some, especially if you want to play a few rounds of golf undisturbed.

One solution to constant tracking is a homemade Faraday cage – which means it is time to roll out the tinfoil.

Faraday cage

A Faraday cage is an enclosure used to block electromagnetic fields, such as cellphone signals.

A variant of the Faraday cage is the Faraday shield, which can be created by surrounding a device with a continuous covering of conductive material.

This is commonly used to protect sensitive devices from radio interference, or for security reasons.

Faraday shields can be used to protect smartphones from being remotely accessed, and can shield car remote signals from being compromised.

Users can also purchase Faraday bags, which shield devices from outside signals – including Bluetooth, cellular, RFID, Wi-Fi, and GPS signals.

The myths

There are several myths surrounding Faraday cages, of which how to build one and which common devices double-up as a shield are widespread.

To see which ones hold true, we tested common Faraday-cage-related information found online.

Our goal was to place a smartphone inside a “homemade” cage and prevent it from receiving a call.

This is what went down.


Placing a device in a microwave will shield it from electromagnetic fields, according to reports.

We tested this by placing a smartphone in two different microwaves, both of which were turned off, and then calling the phone.

The smartphone was able to receive calls while inside the microwave – meaning that while it may prevent the passage of certain electromagnetic radiation, it won’t stop a phone call.


Tinfoil Box

Another option punted online is a small box covered in tinfoil.

We constructed a DIY shield using a shoebox and several layers of heavy aluminium foil, ensuring there were no gaps between the container’s lid and body.

Placing the smartphone in the box, we called it several times – and received all the calls.

Tinfoil Box

Chip packet

In 2017, an Australian man prevented his employer from tracking the location of his company-issued device by placing it in an empty packet of crisps.

The device was unable to report his position, and he took advantage of his makeshift Faraday shield to play golf on company time.

The same was not true for our smartphone, however, as our tests saw the device receive all calls successfully.

Lays crisps packet

Biscuit tin

A near-airtight container made of tinplate (steel coated with a thin layer of tin) is a promising candidate for a Faraday cage, due to the thickness of its construction.

Our tests proved this theory correct, as our smartphone was unable to receive any calls while in a biscuit tin.

Three biscuit tins were tested, and all acted as Faraday cages – shielding the smartphone from receiving phone calls.

It must be noted that blocking a mobile call does not mean the container works to protect against all signals.

Biscuit tin

Now read: South African renewable energy myths dispelled

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Putting a smartphone in a tinfoil shoebox