Tonight, the HAARP transmitter in Alaska was used to direct exceedingly powerful radio pulses (around 4 Gigawatts effective radiated power) at the moon at a frequency of 6.7925 MHz and I could easily receive the echoes from the two second bursts here on earth with my amateur radio rig.

Waterfall spectrogram of radio echoes from the moon.

Waterfall Spectrogram of Moon Echos.

Waterfall Spectrogram of Moon Echos. Click to view larger.