What is EME (Earth-Moon-Earth) or Moonbounce in Amateur Radio?

What is EME (Earth-Moon-Earth) or Moonbounce in Amateur Radio?

EME (Earth-Moon-Earth) or Moonbounce is an interesting but quite challenging way to contact another amateur radio station using VHF or higher bands. Due to the distances involved, it requires high powers, high gain antennas and sensitive receivers. Moon acts as a reflector of the signals, though a poor one resulting in low received signals. The problem is to sieve it out of the galactic noise especially when moon crosses the plane of the Milky Way twice a month.

The antenna has to be steerable in addition to having high gain in order to track the path of the moon. Moon surface typically reflects only about 6% of the signal it receives. The loss of signal also depends on the distance of the moon from earth, which is higher in apogee than in perigee. There could be some Doppler shift in the signal frequency due to the relative motion of moon and earth. CW and FT8 modes are used more often though SSB contacts are also possible on Moonbounce.