So what is this thing? Basically it's a handheld device that allows you to "hear" RF sources. Regular rf receivers single out a particular frequency and decode it into some type of information. This device on the other hand picks up everything and plays it as audio without any decoding.

When you turn it on you immediately hear a whole forest of sounds; rapid blips from wifi, the intermittent chirps of airport radar, the drone of a microwave oven, and so on. It's like gaining access to a whole world of sound that ordinarily cannot be heard.

The design is based on the AD8318 demodulator chip, I bought a breakout board from Amazon. This chip has an RF input, and outputs a logarithmic amplitude signal. I take that signal and run it through various amplifiers and filters to turn it into something audible.

The other off the shelf part is a TSA900 antenna. It's broadband (900MHz-12GHz) and directional which is perfect for my project.

The most important part of the project is probably the schematic, so here it is. I've done my best to annotate it and explain how it works.

The project files can be downloaded HERE. Included are: Solidworks files, STLs, STEP Files, gerbers, the schematic, and BOM.

Note: that I changed the PCB to match my reworked version but I didn't actually re-spin the board so no guarantees ;)

This is my original concept. It had the signal from the AD8318 feeding into a TEENSY 4.0, and would use a DAC to produce audio output. It would also display information on an LCD.

It looked cool, but the digital electronics didn't serve much of a purpose so I eventually scrapped those, going full analog. The PCB antenna was slightly warped, so I added a frame around it. I also wanted to add an AM-stop filter. Unfortunately this required a huge re-design to make the space. ..and I didn't even end up needing it. The image next to the file download shows the final result.