Crystal radio is an interesting concept -- but note I didn't claim it was impossible, just highly inefficient and with mediocre power/range (I couldn't find sou

Crystal radio is an interesting concept -- but note I didn't claim it was impossible, just highly inefficient and with mediocre power/range (I couldn't find sources, but apparently it's typically 40uW with a ~1m? antenna). Remember that's for a (usually) 50kW station -- that's 1e-9 efficiency, or 0.0000001%. Realistically I'd expect you to be able scale this to 10k's receivers to up to about 0.001%. It's not realistic to increase this power significantly due to health/electronics concerns for persons living close to the source and massive consumption -- bringing the power near a single station to 4W would consume 5GW, about 1% of total US power consumption! Interesting to imagine a system with sightly higher frequencies (20Mhz?) dedicated to power transmission. It'd essentially be a hugely wasteful system (and expensive with high powered antennas everywhere to mitigate invsq law) which however might be able to power ultra low power sensors and gadgets. Some clever phase distribution (pseudorandom modulation should do it) system would allow location with ~15m accuracy too (even working indoors, although building refraction and reflections might be a little troublesome).