This video of so called "plasma radio" is popular lately on Russian blogs. The shown effect is very cool. Here is a short story to understand it:
Location: Brovary town, Russia.
Transmitter output: 150 kW
Also used: old Soviet antennas, 90 meteres (280 ft) long cable.
That's all what you need for UNSAFE experiments to receive radio waves.
In the area of the effect of radio waves very big potential difference emerges. Because of the modulation of the radio signal the electical spark arc starts vibrating with the human voice and begins to "speak".
The intensity of current in such "radio" can reach hundreds of ampers and it easily can molt metals.
Such electricity doesn't have any barriers, it can come through the thick tree.
Don't try this at home!