The 2-millimeter band is a portion of the EHF (microwave) radio spectrum internationally allocated to amateur radio and amateur satellite use. The band is between 134 GHz and 141 GHz.
Due to the lack of commercial off the shelf radios, amateurs who operate on the 2 mm band must design and construct their own equipment, and those who do, often attempt to set communication distance records for the band.
The International Telecommunication Union allocates 134 GHz to 141 GHz to amateur radio and amateur satellites. Amateurs operate on a primary basis between 134 GHz and 136 GHz and on a secondary basis in the rest of the band. As such, amateurs must protect the radio astronomy and radiolocation services from harmful interference, which share the band with amateurs between 136 GHz and 141 GHz. The ITU's allocations are the same in all three ITU Regions.
The allocation was introduced as a result of changes at ITU's World Radiocommunication Conference 2000. Prior to this the amateur allocation was 142-144 GHz Primary and 144-149 GHz Secondary.
The first 2 mm distance record, and still standing longest distance achieved on the band, was set by US stations WA1ZMS and W4WWQ, who established contact at 114.4km (71.1miles) on February 26, 2006.
The longest distance achieved on 2 mm in the United Kingdom was 35.6km (22.1miles) between stations G8ACE and G8KQW on January 16 2016.
In Australia, the 2 mm distance record was 19km (12miles) set by stations VK3CV and VK3NH on June 11, 2020.