The 2.5 millimeter or 122 GHz band is a portion of the EHF (microwave) radio spectrum internationally allocated to amateur radio use on a secondary basis. The amateur radio band is between 122.250 GHz and 123.000 GHz. Amateur satellite operations are not permitted, and the ITU's allocation is the same in all three ITU regions.
The 122 GHz band coincides with a molecular resonance of oxygen which causes significant atmospheric propagation losses, similar to the 60 GHz band.
List of notable frequencies
References
2.5-millimeter band Wikipedia(Text) CC BY-SA