Signal-Blocking Glove Box

Intro: Signal-Blocking Glove Box

Imagine you're headed out on a big road trip with your favorite songs blasting on the radio and a cool breeze is blowing in through the window. You've finally found peace... until your cellphone begins to ring. Sure, you could've turned it off, or maybe even taken out the battery (if the manufacturer will even allow it!), but what if you want real freedom from your phone without having to compromise it or, dare I say, leave it at home? With the Signal-Blocking Glove Box, you won't have to do either of the above. As a powerless RF-blocking container, you'll be free from the constant connectivity that distracts and ties you down to the modern world. Say goodbye to GSM, GPS, Bluetooth, WiFi, and NFC. The government can't track you and your peeps can't text you, but who needs 'em? You've got the open road...

STEP 1: How to Block RF Signals

In technical terms, the "Signal-Blocking Glove Box" is a Faraday cage. At its most basic, a Faraday cage is simply a conductive enclosure. The physical structure of the enclosure determines how effective it is at absorbing electric charge or attenuating RF signals. We're interested in the RF blocking aspects of the Faraday cage, so we'll need to figure out what kind of material we can use.

Most modern cell phones and other personal gadgetry contain a variety of radios that operate up to 2.4 gigahertz, the exception being 802.11ac for Wi-Fi which operates at 5 gigahertz. Let's use this higher measurement as our goal to ensure even greater success at attenuating the lower frequencies. In order to properly block a 5 GHz signal, we'll need to figure out the wavelength and how tight our enclosure needs to be, which we can do with the following equations:

λ = c / f

x = λ / 10

λ = wavelength in meters

c = velocity of light in meters per second

f = frequency in Hertz

x = maximum diameter in meters of any holes in the surface of our Faraday cage

Plugging everything in gives us:

λ = 299,792,458 / 5,000,000,000

λ = 0.0599584916 m

x = 0.0599584916 / 10

x = 0.00599584916 m (~6 mm)

In order to block a 5 GHz signal from entering or leaving our box, we'll need to make sure there are no holes or gaps greater than 6 mm in diameter. Ideally, the box would also have a conductive path to ground, but seeing as how we'll be stuffing ours into a plastic compartment within a moving vehicle, we'll have to do without (but this won't limit our RF blocking abilities; grounding would just be an added benefit)

I designed a self closing box that would fit snugly into my glove compartment. The compartment dimensions were about 10 inches wide by 7 inches deep by 4 inches tall, so I settled on making my box 9 by 6 by 4 inches to make things fit snugly while maximizing storage space. The box is pulled tightly closed by extension springs to ensure a tight, conductive seal is always made.

I used special RF blocking fabric (linked on the next page) as my conductive layer for the box, but it was by no means the only way. Aluminum foil is cheap, plentiful, and effective in layers, however the constant crinkling noise seemed unpleasant and the long term durability questionable.

STEP 2: Parts and Materials

conductive fabric (or aluminum foil)

(600mm x 600mm) acrylic sheet

(2x) extension spring

(20x) M3 x 12 screws

(2x) M3 x 20 screws

(22x) M3 nuts

double stick foam

STEP 3: Assemble Box

I cut my box out of 3mm thick black acrylic using a laser cutter. I've attached the file for my box above if you wish to copy it, but you could also easily modify a premade box. The most important feature is making sure the door of your box forms a tight compact seal to ensure a fully conductive shell around the interior. If you decide to make the box from my vector files, you can see how to assemble it above. If you decide to sew the interior shell with conductive fabric of your box, be sure to use a tight stitch; regular thread will work just fine too!

STEP 4: Installation

Installation is pretty straightforward, but it will certainly vary depending on the interior of your glove compartment. I affixed my box to the little shelf inside with double stick tape on the bottom of the box (Command strips to the rescue!). The door of the Faraday cage is physically attached to the glove compartment door by strings wrapped around the exterior screw heads. This way, the door to the interior box will open automatically with the glove compartment door, making it easier to use if you only have one hand free.

STEP 5: Final Thoughts

I'm quite happy with the mechanism and the effectiveness of the box (I've successfully failed to call myself during every test!). If you plan on making your own Faraday cage, let me know and show off your work in the comments!

Comments

[CraftAndu]

This is clever!

[idrawbooks]

Why is simply turning the phone off not an option? I'm not trying to be a smartass, just not sure what the difference is.

[dsantil71]

ur phone can be remotely turned on without u even knowing it!

[dsantil71]

just like ur the webcam on pc or laptop can! Especially when surfing at free WiFi hotspots! The easiest trick to disable it - a 1/2 inch square of black cardstock taped over it! They can hack it all they want & won't see a thing.

[Rimwulf]

unless your not using a vpn it is unlikely for someone to hack phone unless they were already inside like the phone companies also its a numbers game there's just too many people to hack just by some random fact your hit or unless you check- "install from untrusted sources" . people like the government can get access with a warrant taking them only minutes get the information needed because your phone company can access it. none wireless internet is safer.

[MichaelR5]

They are correct, as insane as it sounds, but it is possible that with the phone powered off, firmware in the phone can still activate the GPS and send a signal. I have not confirmed this myself, but working in Information Security, computing hardware and software, and previously as an Electronics Technician, I know and have read enough to be confident of that. There are some in the industry who believe it is the NSA who forced features like that to be placed in some devices. I don't know about that. But, the switches on an iPhone for example, (because I have one and have looked at the programming side a little), are not hardware enabled, but software. For example, you can turn the side switch to "silent" and have it still make sounds, if they're programmed to ignore it. Same is true for the power. I've been thinking about making a lead-lined book safe to stuff things like the phone and chipped credit cards in.

[windshadow]

When president bush visited the soviet union all members of the party were instructed to "remove the batteries from their phones". Any electronic device can be hacked and remotely controlled or used as a surveillance device.

[goofylunatic]

Even phones that are turned off can continue to operate in low power states that can be remotely turned back on by those with the means. The Faraday cage method here ensures 100% communication blockage to the device, incoming and outgoing. Helpful if you are truly worried about big brother tracking you.

Using a "Cage" to fall off the "Grid". Nice.

[quader4]

It's to prevent unauthorized tracking. People with the know-how can track any phone's GPS even if its turned off.

By blocking the signal, you're putting them out of commission.

[MichaelR5]

This is useful, but it will eat up your cell phone battery if you leave it powered on and place it where it can't get signal, because they're designed to try finding a signal by boosting power. The battery will run down much, much faster when you don't have a signal, than if you do. Use it to keep your credit cards with chips, your hand, after your company "chips" you, or other RFID items. But turn off your cell phone if you want to save your battery for when you remove it from the glove box.

[bremus]

Agreed. This would be very bad for your phone, It would be in sealed box, using up all the battery, and get extremely hot.

[dsantil71]

I would hope people who would use this would be smart enough to turn their phone off. I know I would, lol.

[bremus]

Someone smart would know that a turned off phone can't receive a signal elminating the need to be placed in a signal blocking box.

[woodNfish]

If you can't remove the battery from your phone, you can never truly turn off your phone, and it can be tracked.

[Grayhawk845]

Even if you can remove your battery your phone has another internal battery that keeps everything in a sync sort of, like unplugging your computer. BIOS has a small watch type battery that keeps the internal clock running. Your de-batteried phone still has power unfortunately

[windshadow]

Great tutorial Aleator777. I wondered about this for some time. Do you thing a few layers of foil Brick coffee bags would accomplish the same thing for a more portable version.

Now if you could design a small cover for the tiny gps installed in every car after the inception of computer chips.

[garethllewelyn]

This would work to block EZPass signals too I think.

Good clear "bl

[aethersquall]

I actually thought this *exact* same thing.

[Aleator777]

Oh yeah. Thanks!

[sleeepy2]

A buddy of mine is a truck driver, and his company tracks his location at all times through his phone. He made one of these so he could pop home to use the bathroom when it was necessary. They call him after and ask what happened to his signal, and he feigns ignorance. They think he keeps hitting cellular dead zones!