This is the DJBB Maggie - a simple device for listening to electromagnetic radiation in the world around you. Hold it up to your phone, computer, router, or anything with electricity to hear some interesting buzzes, bleeps, and the occasional radio or walkie-talkie signal. Similar to the Priezor LOM.
I recorded audio from 4 antenna designs in the table below. I have a sample of the same source for each: holding it by a router, sweeping it around a Macbook, and holding a phone in the middle of it while opening apps and scrolling around. They were all recorded into my Zoom H1n with NO pre-amp, and the gain knob set to 7/10. They were all normalized and phase corrected before upload, but otherwise not processed.
The last test is a frankenstein coil made up of what I had left of a few different spools.
*Note on Magnet Wire I tested with a few gauges, and I suggest 32 AWG. I would not go larger than ~30 AWG, but go as small as you'd like.
Larger (lower AWG number) = Fewer
3D print the top and bottom piece. I used PETG and a 0.6 mm nozzle, but anything should work. models here.
Cut 2 pieces of wire - about 15 cm.
Solder these wires to the L and R pins on your aux jack. These are the 2 pins on the bottom of the jack. The single in in the middle is ground, which we don't need.
NOTE - You could also skip the aux jack and solder an aux cable directly if modularity isn't important to you.
Pop the aux connector in its home, and route the wires like so.
Snap on the other shell, insert the nuts into their inset holes, and screw it together.
Wind the magnet wire around the shell. You want the two ends to terminate near the 2 aux jack wires.
Note the little channel that can be used to get the top coil wire back down to the aux jack wires.
Use a small piece of sandpaper to sand off the coating on the two ends of the magnet wire (so the solder sticks).
You may have success melting it off with a hot soldering iron instead, but I never did.
Shove the soldered wires into the space within the shell. Secure with hot glue, or whatever you have.
Apply hot glue, resin, superglue, or whatever to the outside of the wire windings to hold everything in place. You don't want the wire to unwind somehow.
Plug in your aux cord and you're ready to go. Plug it into a pre-amp -> audio recording device if you can, but it also seems to work by plugging straight into something like a Zoom H1 and turning the gain up. This is what I usually do.
One very important thing to note is that this thing produces stereo audio that has extreme phase issues. YOU MUST FLIP THE PHASE OF ONE OF THE CHANNELS after recording.If you don't, it'll sound neat in headphones, and absolutely silent in mono. There is probably another way to wire it to avoid this issue, but I haven't experimented with that yet.
Here are a few ideas of things to try recording:
If you're into DIY audio devices like this, perhaps check out my guide on making a pair of contact mics.
And there you have it. Your own lil' thing to record electromagnetic sounds for not-too-much-money.