Measuring power network frequency using junk you have in your closet

I've been using a transformer & resistor voltage divider direct into audio in to decode Decabit signals (a form of ripple control aka audio frequency load control): https://web.archive.org/web/20140127003936/http://www.anime-...

I'll test if this antenna methods works as an alternative. I'd feel more comfortable sharing with others if mains voltages are eliminated entirely.

Good to give mains respect. It can deliver kilowatts of power without breaking a sweat, and breakers are slow enough you could see multiple joules of energy into your device. It's an expert magic smoke emancipator.

Disagree on the surprise that the setup worked, though. Mains is only regulated to a few % in frequency from what I've read. But you can see 0.05 Hz deviations (or 1%aka 1000 ppm). Even a junky crystal at ~100ppm is an order of magnitude better. A 10 ppm oscillator isn't hard to find, so the computer is likely somewhere in the middle. The math all checks out.