Free power from a radio tower to power a radio? (Experimenters)

[Omega-TI]

The project below looks interesting to me from a "playing around & experimenting" aspect. Has anyone here had experience with this sort of project? It reminds me of Nikola Tesla's early experiments. I would not be interested in lighting an LED, but instead to charge a low powered battery for a cheap radio... yeah I know additional circuitry would be required.

Go to 15:30 for the project.

 

[RFI-EMI-GUY]

You could harvest HF band RF energy from a longwire antenna. There was study by US Navy indicating that the combined power is quite high at times of day. Not sure how effective a diode rectifier would be as the voltages will all be non-coherent and out of phase. Maybe a full wave bridge of 4 Shottkey diodes coupled to a supercapacitor would yield some significant charge. You could then power a small uC timer and keyer to switch the antenna to a CW transmitter and beacon out some message until the capacitor or battery depletes and then revert to harvesting power once again. The message could be the joules of energy last harvested. Be sure to have some sort of surge protection or the experiment will end quickly.