I haven’t written much on subjects pertaining to communications, yet. To be honest, there’s better sources than me, like the Brushbeater blog for one. Off grid communications are a big interest of mine though, and I do have a fair amount of lessons learned I can share. If these subjects are of interest to you as well, I can’t recommend the Brushbeater communications courses enough.
Tonight I built my first Farraday cage/ signal blocker and thought it was an interesting and easy project. A Farraday cage is basically a container to block harmful electromagnetic pulses, either natural or man made, from damaging sensitive electronics. It is a sealed metallic, electrically continuous container line with electrically insulating materials. While all that might be a mouthful, it was actually simple to build with household items.
The items you will need are as follows:

  • A metal container. I picked up a 12” diameter bow tin from Wally World on clearance for $.87.
  • Aluminum Duct (not duck) tape. This is a special metal tape for sealing seams in duct work, it’s in the hardware section. Cost me about $4.
  • If your container is painted, a sheet of sand paper.
  • Insulating material to line the container with. I used some left over foam mat and vinyl cove base that I had left over from a construction project. I’ve been told you can even do this with card board so any insulator will work.
  • Some sort of glue or silicone to stick the insulating material to the container lid.
  • Tools to do it

First prepare the container. In my case I removed the bow and ribbon and scraped off the excess glue. I then taped all the seams with the duct tape.

Next I sanded the paint off the top of the container so it had good metal on metal contact with the lid.

Once this was done I added more tape to the area I just sanded to add a very tight seal that is electrically continuous. At this point I checked it with a meter. This is an optional step but I was curious. A reading of 0 ohms indicates no resistance at all. My probes measured 0.1 before the test, and in the photo you can see that I am getting that same measurement. This means there is zero resistance, indicating I have a very solid connection between the lid and the container.

This tight connection is important because as a signal blocker it has to have a very tight seal to block out signals. I tested this by placing my phone inside then trying to call it. Before I taped the top of the container I could still reach my phone, but after I couldn’t.
It was now time to line the container. First I measured and cut the cove base to length and width.

Then I traced the outline of the container on the foam pieces and cut them to fit as well.

After this I used my liquid nails and glued the top piece to the lid and placed some handy weights I had laying around on it to help get the glue stuck on.

I now have a completed Farraday cage to store my sensitive electronics in. This is my first build and if anyone reading this has more experience I would appreciate any advice if you see something I could do better.