2.4ghz Spectrum Analyzer – Keep an Eye on Your WiFi

(If you want to get a shorter summary of this build explanation, my project was written about here and here , and you can find my original post on the subject here )

Over the summer, I got bored. To be precise, I got bored a lot. One of the times I got bored, I pulled out my magic parts bin, and found this:

Oooh a circuit board!

Hey! A radio module! That’s neat. I can use that to send data wirelessly. One problem: I only had one of them. That would be one lonely (or schizophrenic) radio module, talking to itself all day. So, I turned to my good friend, the datasheet (a lengthy document that exists for just about everything electronic, detailing everything about it), for ideas. You’d be surprised how many cool things you can learn from those hopelessly long, boring, behemoths of seemingly useless information (also, they are a remarkable cure for even the most persistent of insomnias). And after some painful sorting through confusing diagrams, lo and behold, I found an idea! Now, I know you’re jumping out of your chair because you can’t wait to hear this idea, but I want to harness that excitement to give a quick disclaimer: I said this blog was about programming, and it is, amongst other things. However, some of my favourite things to program are things I’ve built myself, and well, I have to build them first. So if you’re terrified of embedded electronics, if you don’t even know what embedded electronics are, or if you’re already completely lost, hang tight. I’ll try to make the rest of this post fairly accessible, and I hope to have my introduction to embedded electronics post available soon.

Now: back to the thrilling saga of the lonely wireless module. Well, I learned two big things from the datasheet. First, the module operates in the 2.4ghz range, which is neat. What this means is that this chip is used to send and receive data along some of the same frequencies (think of them like stations on a TV or radio) that WiFi routers, cordless house phones, bluetooth, RC cars, cameras, and many other things transmit on. Relating to this, I found the second cool thing, which is that this module has digital RSSI (Received Signal Strength Indicator). Acronym-free translation: I can tell it to go to any channel (station) on the airwaves (in the 2.4 range), and it will give me the total power of everything transmitting on that station in the area. Boom! I had my project. If I could make it scan through all of those channels really quickly, and then display it, I can make a poor man’s spectrum analyzer, a tool used to give the user a detailed picture of all the wireless things operating in the area. Commercial grade, fast versions of these sell for anywhere between $50 and $1000.

Stay tuned for part two (hardware), and part three (software)!


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