Purposefully block your cell phone signals.
Let's say it's your university examination season and you want to study undisturbed for some time or, your relatives are annoying you by calling every now and then or, you don't want to talk to anyone but at the same time you don't want to hurt someone's feelings by hanging up in the face or by rejecting their calls or, maybe your girlfriend wouldn't stop calling you... Whatever the case may be, It could be pretty hard to ignore calls and come up with some legitimate reason at the same time. BUT not after this instructable...
The most forgivable Excuse for not picking (or not receiving any calls in the first place) calls is definitely a USER NOT REACHABLE or an OUT OF COVERAGE message from the service provider. Why would someone argue if you're out of coverage?? But in this connected world, one can only be out of coverage if he is living underground or something... Well, In this instructable, I'll show you guys how to create your very own personal and portable Unreachable Area. Micheal Faraday got your back.
Also, this project will help you understand why your phone loses signal in a closed type elevator.
Step 1: A Little Bit of Science and History About Faraday Shield/cage
A Faraday cage or Faraday shield is an enclosure used to block electromagnetic fields(cell phone signals are electromagnetic signals). A Faraday shield may be formed by a continuous covering of conductive material or in the case of a Faraday cage, by a mesh of such materials. Faraday cages are named after the English scientist Michael Faraday, who invented them in 1836.
A Faraday cage operates because an external electrical field causes the electric charges within the cage's conducting material to be distributed such that they cancel the field's effect in the cage's interior. This phenomenon is used to protect sensitive electronic equipment from external radio frequency interference (RFI). Faraday cages are also used to enclose devices that produce RFI, such as radio transmitters, to prevent their radio waves from interfering with other nearby equipment. They are also used to protect people and equipment against actual electric currents such as lightning strikes and electrostatic discharges (or crazy people playing with high voltage Tesla coils) since the enclosing cage conducts current around the outside of the enclosed space and none passes through the interior.
image source: Wikipedia
Step 2: Gather All the Components
This little project can easily be made using some household junk.
- Sneak into your girlfriend's/sister's room and find the box of her most expensive shoes. Throw away the shoes because you won't be needing them and keep the box, that's what you'll be needing. do this at your own risk!... You need to find a fairly intact shoebox or any cardboard box of approximately the same size will do.
- white hobby Glue.
- loaded Stapler.
- aluminum foil
- A shielded cable. It's not absolutely necessary to use shielded cable, you can use solid copper wire too but shielded cable worked best for me. Usually, good quality USB cables are shielded find a spare one in your box of cables (Every house hold have at least one box of cables :P ) and cut the USB connectors on both ends strip open the outer insulation and you'll see a wire mesh surrounding the inner wires (the purpose of the mesh is similar. It acts as a Faraday cage and prevents any exterior electrical interference while transferring data).
- xacto knife/hobby knife.
- access to mains earth connection (be very careful while working around mains make sure which of the connection is earth according to your local standard electrical connection rules. In India green wire is the earth connection red is Hot i.e. 220VAC and black is neutral. Also, make sure the switch is in off position because the project does not require any power only earth connection is needed for which you don't have to turn on the power switch as it is directly connected to ground. If you absolutely have no idea on how to work with mains then, stay away or ask an adult or experienced personnel for help)
- and last but not the least A roll of Electrical tape.
Step 3: Okay Let's Build It
- Cut a piece of aluminum foil large enough to cover all the faces of your shoe box/cardboard box.
- Apply glue on all the outer faces along with the lid of the shoe box/cardboard box.
- Start sticking aluminum foil on the exterior surfaces of the box. Try keeping the foil in as one single piece as possible. if any tears or gaps arrises, use some more aluminum foil as a patch on the torn areas. make sure all of the outer faces are wrapped in a single piece of aluminum foil. All the faces must have a good electrical connection when the lid is closed.
- Make sure no open spaces are left on the exterior of the box and the whole box needs to be electrically conductive when the lid is closed.
- Strip off the outer insulation of shielded USB cable and twist the outer mesh as shown. you snip inner wires or you can strip them off twist them together along with the mesh wire.
- Use stapler pins to connect the wire to the aluminum foil on any of the exterior faces of the foil covered box. make sure it makes a good electrical connection.
- Strip the insulation off of the free end of the wire and twist the wires as before.
- Connect the free end to the ground/earth connection of the mains power socket. ( I taped the free end of the wire to the metallic shaft of a screwdriver because I couldn't find anything else to insert in the plug and the wire alone was just too flimsy it kept falling off the earth/ground connection.) AGAIN BE CAREFUL WHILE WORKING WITH MAINS SOCKET. DO NOT ATTEMPT IT IF YOU HAVE NO IDEA HOW IT WORKS. ASK AN ADULT OR EXPERIENCED PERSONNEL FOR HELP. MAKE SURE THE POWER SWITCH IS ALWAYS OFF.
- Put your mobile phone in the box and close the lid and try calling on that phone. If everything is connected properly and there're no gaps in foil wraps, then you'll hear an "UNREACHABLE" message.
There you have your very own out of coverage area or Faraday cage. Now you can ignore calls without being rude to someone.
You can improvise by wrapping the inside of the box and connecting it to outer wrap.
You can also use a metal box or tin foil food box and connect it to earth instead of wrapping up a cardboard box in foil but for some reason, it didn't work for me.
SO, The closed elevators in the malls are similar to the foil wrapped box, they too are connected to earth which makes them a FARADAY CAGE and due to this Faraday cage effect, your phone loses signal in the elevator.
I recorded a Video of it working (next step) :)
Step 4: YAY... IT WORKS...
I blurred out mine and my mom's contact number for obvious reasons.
It'll not work if there's a signal leakage in the box.
Notice how I connected the wire to the ground terminal and also the power switch is in off position.
the OUT OF REACH message might vary for different service providers. in my case (BSNL) message states "THE PERSON YOU'RE TRYING TO REACH IS EITHER SWITCHED OFF OR MOVED OUT OF COVERAGE AREA"
also when you put your phone on flight mode, your network reports your number as switched off.
DISCLAIMER: This project is meant for educational and informational purposes only and I'll not be responsible for any damages.