The 4 millimeter band is a portion of the EHF (microwave) radio spectrum internationally allocated to amateur radio and amateur satellite use. The amateur radio and amateur satellite band is between 76.0 GHz and 81.0 GHz. Amateurs operate on a primary basis between 77.5 GHz and 78.0 GHz and on a secondary basis in the rest of the band. Also, 81.0 GHz to 81.5 GHz is allocated by ITU footnote 5.561A to the amateur and amateur-satellite services on a secondary basis. The ITU's allocations are the same in all three ITU regions.
Until 2006, 75.5 GHz to 76.0 GHz was also allocated by the ITU to amateurs on a primary basis. In response to this change, CEPT added footnote EU35 to the "European Common Allocation Table", which provides a continued allocation of this segment to European amateurs.