I just backed this project! Why? Because for $400, I get one of the most flexible and inexpensive SDR's on the market. Not only do I get that, I also get in-depth documentation and guides on how to use it. I've been wanting a nice SDR for some time now, ever since I saw the OpenBTS demo using the Ettus Research USRP1. Unfortunately, the USRP1 is, to me, too limited to justify the price. Additionally, there is a very steep learning curve if you're a beginner like me. I'm still interested in cell phone networks, though, and with the pending release of the bladeRF, I will finally have a chance to play around with the technology.
Today, I hacked a multi-function audio player (commonly known as a "boom box") to add an external audio input. This hack isn't really done yet (I still have to solder everything up, drill a hole, add the 1/8" jack, etc.), but I have pictures of what I've done.
Essentially, I started out by poking around the live circuit with my oscilloscope. I didn't get very far with that, so I decided to look up the datasheet for the identical DIP chips that looked like they were the amp chips. After reading the bits I needed, I saw that the chips were indeed amplifiers (with one for each channel). After tracing some circuit paths, I managed to find a good point to input the signal. I connected some wires to those points, found a point for ground, and connected it to an 1/8" jack in my iPhone.
I was able to play Derezzed REALLY loud before it started getting distorted.
Sorry there's no video, but the music player I was using also happens to be my video camera, phone, calendar, and video player (among other things). Also, my normal video camera wasn't available. Click "Continue Reading" to see the pictures.