“One of the higher-frequency harmonics inevitably created by any real-world DAC during playback will then be the original fundamental, which should leak to the environment as a short-range radio transmission via the ad-hoc antenna formed by the physical wires and circuit traces in the audio output path.”
Sometimes I think I’m a smart guy…and then I read of people doing shit like this.
I once programmed my TI-84 calculator to do exactly this! The only missing thing was a circuit to convert the audio jack output voltage into the needed form for an antenna. I had the CS know-how but no EE know-how, so I never got it to work. It was fun to dream about confusing my high school's clocks though. (Sadly, the other obstacle was that the clocks only listened for the signal overnight, which improved their chances of detecting the weak broadcast out of far-away Colorado.)
This is pretty darn cool, but I have to say I was somewhat let down by the WWVB signal. I was expecting the entire audible range instead of simply the extracted data. That being said, that's also really darn cool.
Ha, there's one radio clock in my house that I still keep going for sentimental reasons... it's had a rough time setting itself for a few years, likely due to its placement in the house.
I'll have to test this out sometime, what a fun idea!