I’m not sure how I discovered the EMF Explorer, but building one has been on my list of things to do for years now. About eight months ago, I even purchased the parts to build several of them, but never got around to it. A couple of weeks ago, I read about a workshop at DEFCON to build one, but I found out about it too late, and I couldn’t sneak into the workshop. Last night, however, I finally built one.
What is an EMF Explorer? According to the designer, Darcy Neal—who describes themselves as a new media artist, cyborg, and educator—the EMF Explorer is an “electromagnetic frequency sensing circuit that lets you listen to the world of hidden electromagnetic frequencies all around you!” Here’s the scematic:
As you can see, it’s a pretty simple circuit. The 100 mH inductors act as pickup coils, and the electromagnetic signals they pick up are amplified by the op amps and output to the headphone jack. To use it, you simply bring the coils close to something that you suspect is emitting electromagnetic waves, as shown in this video:
The Explorer shown in the video was made from a kit that you can buy from Make: magazine. It’s actually on sale now for $30. Since I had all the parts, I made my own:
Since this is just a prototype, I left off the power switch and LED. That’s why there’s no battery in the second battery holder. You might also notice that I used a 14-pin IC socket instead of an 8-pin socket. The reason for that is that is what I had in my junk box.
The prototype board is worth mentioning, too. I was originally going to build this on some perf board that I had, but in pawing through my junk box, I came across the Adafruit Perma-Proto Half-sized Breadboard PCB. Each row of holes on this board connect to one another, just like on a a no-solder prototype board. Building a circuit on this board is much easier than if I had tried making it on a board on which I had to connect all the components myself. Adafruit charges $4.50 for this board, but, of course, you can get cheaper ones on Amazon.
A badge for ham radio?
One of the things that I’ve been impressed by in attending hacker conferences over the past three or four years are the badges. At DEFCON, there was even a Badge Life Village. Some of them are even useful. For example, the badge I got at KernelCon is a mini-weather station.
I think that ham radio is missing the boat by not having cool badges like this. So, what I’m thinking is that a version of the EMF Explorer could be made into a badge for Dayton 2027 (and/or other ham radio events).
To do this, I think we’d need two things:
- Artwork appropriate for ham radio
- A PCB design incorporating this artwork.
Anyone interested in helping me with this project? I think that I know enough about KiCAD to actually do the PCB design, but I wouldn’t mind having some help with that, and I certainly am not a good enough graphic designer to come up with some cool artwork. If you’re at all interested, please send me an email.