Intro: RF Shield Out of Duct Tape
Like most people, I'm not too thrilled about everyone and their brother spying on me, attempting to hack into my electronics, etc. I'm also smart enough to realize that I really can't stop the all the different governments and their organizations from doing this, but it really torques me off when Google, Apple, and all the various apps load their spyware on my devices and keep turning the profiling and tracking apps back on every time they update their software.
I also worry when I'm traveling around with smart cards and/or a passport that can be remotely activated by some script kiddy walking around with a back pack collecting personal information.
So in the interest of increasing my personal security I created an RF shielded bag out of duct tape (Image 1) that works pretty well and will walk through the construction of the device.
For those of you who have seen my other Instructable, I can't do much by myself - my supervisor has to be around at all times to make sure I don't screw up. This time she was a little distracted (Images 2 & 3) by a nearly empty jar of peanut butter and she got really upset whenever I tried to pull the jar off her head so this instructable was written without close supervision. :-)
How do if your bag works??? After making the bag and folding it down, have somebody attempt to call your phone in an area where you have maximum reception/connection strength. Then turn on the Wi-Fi feature of your phone and attempt to text or email your phone using the Wi-Fi connection before putting the phone in the bag and then again after putting the phone in the bag.
I made my bag a little large so I could put my phone, passport, and several smart cards into it all at the same time.
Note: If you put your smart phone in the bag and leave it there for a long time, your battery will be discharged as your phone will try to connect to the local cell service.
Step 1: Materials
This is a relatively simple and in-expensive project to make. The necessary supplies are:
1) A role of aluminum duct tape
2) A role of fiber duct tape - any color
3) A sheet of heavy duty aluminum foil - approximately 24" long by 18" wide
4) An exacto knife
5) A permanent market
6) A ruler
Step 2: Theory Behind the Project and Getting Started
Although I'm not a member of the tin foil hat club, heavy duty aluminum foil is great stuff for providing RF shielding, it's only drawback is that it's doesn't hold up well to handling.
The idea is to use the aluminum foil as the foundation for the RF shield and use overlapping layers of aluminum duct tape to add strength and rigidity followed by the fibrous duct tape to add color and to camouflage the true intent of the bag - it looks like a small lunch bag made out of duct tape. No use drawing attention to the bag if you don't have to.
To begin the project, identify what you want the bag to hold - this will set the size. The dimensions that I used may not work for your phone or you may decide that you want to hold more stuff than I do, so adapt the sizes as necessary.
Step 3: Initial Layout
Start the project by cutting an 18" x 24" piece of heavy duty aluminum foil.
Use the marker to outline your phone and then outline size of anything else you want to store in the bag - on top of the phone. Notice in the photos above, the passport is wider than the phone and the phone is taller than the passport - take the larger of both of these measurements and measure out 1/4" to 1/2" beyond the size of the stuff to get an idea of the basic size of the bag.
This provides the basic outline of how big you will have to make your bag. Record the width and height on some paper for later reference
Now stack your phone and everything else the bag is to hold and measure the thickness and add another 1/4" to 1/2". Record this dimension also.
Step 4: Cutting the Aluminum Duct Tape
The next step is to cut strips of aluminum duct tape and coat both sides of the aluminum foil.
Before rushing off and cutting the tape though, a couple of thoughts to keep in mind:
You will cover the front of the aluminum foil with horizontal strips of tape and the back side of the foil with vertical strips. Each strip should overlap the the previous strip by 1/8" to 1/16" of an inch. By using this approach, all the seams are strengthened and the bag will not wear out as quickly.
I started out cutting 8 horizontal strips of aluminum tape and applied them (covering up my initial drawing) followed by 10 vertical strips of aluminum tape. When cutting the tape, use a cutting board to protect the table you are cutting on - aluminum tape is pretty tough and you might have to press pretty hard with the exacto knife to make the cuts. Also, don't have the sheet of aluminum foil under the tape as you are cutting it or you will cut the foil and have to start all over.
When coating the foil with the aluminum tape, be aware the glue on the tape is extremely adhesive and doesn't let go of whatever it sticks to easily. I found that if you pull about 1 inch of the paper backing off the tape and position it then slowly pull the paper backing off as you smooth the tape down it works best. Removing all the paper backing then trying to get a perfect layout was really difficult (4th photo is an example of this).
Once the front and back of the foil is covered with the aluminum tape it's time to begin the final layout for this project.
Step 5: Final Layout and Initial Folds
The next step is the final layout of the folds that will be made to create the bag.
To start I laid out a rectangle about 4" from the bottom edge of the foil. The rectangle was drawn close to the center (from the right and left edge) of the foil. The dimension of the rectangle was 3 3/4" by 6" (see the second photo).
Once the rectangle is laid out, extend the rectangle lines to the edges of the foil - these lines are your folding lines and all other folding and cutting lines will be based on these lines.
The next lines to lay out are the lines for the sides of the bag - in my example, these lines are 1 1/2" inches out from the right, left, and bottom lines (see image 2)
The next step is to measure the overlap for the two sides of the bag. Remember, we don't want to leave any holes or slots, so overlapping the bag base and one face is essential. Since the width of the bag is 3 3/4", I decided to 1/2" to the right and left side of each side of the bag that will be the overlap seam. This meant adding one additional mark on the foil - 2 1/4" out from the last mark (1 1/2" side marking).
Using the straight edge, bend along each of the marks on the right and left side. Once that is done, cut along the outer right and left edge marks - removing all the excess foil (as shown in image 4).
Once all the excess foil has been removed, you should be able to form a square tube (image 5).
Now unfold the tube and fold the bottom up along the lines (image 6).
Step 6: Assembling the Aluminum Bag
The next step will be to cut two slits on the bottom of the bag (image 1 above). Start on the 2nd line from the bottom and cut to the bottom end of the foil - this cut is along the inner fold on each side.
The next cut will be horizontal (image 2) and will go along the bottom line on the foil from the inner right and left fold lines to the next fold lines - cut from the previous cut point towards the edge of the foil.
Next cut from the 2nd line from the bottom to the cut you just made using the next pair of lines out. This should provide a nice square flap (image 2).
Now you should have a right and left side L shaped flap on the two sides that will form the front face of the bag. These flaps can be cut off at the second line (image 3). The center flap should not be cut at this time.
In the last image (image 4) the two side flaps have been folded over and the tabs have been folded in also.
This next step is very difficult if you have big hands - cut a small piece of foil tape and carefully fold the sides of the bag back, remove the protective paper, and press the tape against the inside bottom of the bag - taping the flaps together.
Next fold the center flap up and over the bag and gently press it into place (it won't stay), stretch a piece of the aluminum tape across the seam from the bottom to the top of the bag, add about 1" to the length of the tape, cut it and overlay the flap, seam, and wrap over the top of the bag.
Next you will seal the inside of the flaps with tape. Again, this is difficult if you have big hands. Peel about 1" of paper back from the foil tape and carefully fasten it to the bottom of the bag and slowly pull the tape back and press it in place on the inside of the bag (images 8 & 9).
The last step with the foil tape is to cover the bottom and sides of the bag where the seams are - I stretched a piece of the tape across the bottom and about 3" up the sides of the bag, cut it, and then carefully centered the tape so there would be about 1/4" of tape overlapping each side of the bag, which I then folded down to seal any remaining seams (images 10 & 11)
Step 7: Finishing Up...
You can use the bag now but I prefer to add some color. Pick your favorite color of duct tape - my son is partial to camo but he didn't have any left so I raided my wifes' stock.
I generally only use gray or grey - depending on which country you are reading this from ;-) but for this project selected a baby blue.
Tape the sides first leaving about 1 1/2" of aluminum showing at the top. Then slowly add layers across the faces and bottom until you are satisfied with the look of the back.
The last image is a test with my phone in the bag sitting next to the wireless router - I started across the room and gradually got closer as I tested it. I also tried to call the phone multiple time - no success.
Step 8: Final Notes
As with my last Instructable - thanks for reading! All questions, comments, suggestions, and criticisms are always welcome - I might not get back to you but I will read everything.
And for my American friends - have a safe Memorial Day weekend.