The 9-centimeter band is a portion of the SHF (microwave) radio spectrum internationally allocated to amateur radio and amateur satellite use. The amateur radio band, in ITU regions 1 and 2, is between 3.300 GHz and 3.500 GHz, and it is available only on a secondary basis. The amateur satellite band is between 3.400 GHz and 3.410 GHz, and it is only available in ITU Regions 1 and 2, on a non-interference basis to other users (ITU footnote 5.282). In Germany and Israel, the band 3.400 - 3.475 GHz isalso allocated to the amateur service on a secondary basis (ITU footnote 5.431).
In CEPT's "European Common Allocation Table", footnote EU17 allocates 3.40 GHz to 3.41 GHz to European amateurs on a secondary basis.
In the US, the FCC is recommending removing the amateur service from this band in order to make room for the 5G cellular system. There have been many objections to this proposal by Amateur Radio operators, including the ARRL.
3.332 - 3.339 GHz and 3.3458 - 3.3525 GHz are used by radio astronomers for spectral line observations. Amateur stations voluntarily avoid using these frequencies when in geographic proximity to a radio telescope. ITU footnote 5.149 encourages all radio communications in the band to take practical steps to avoid harmful interference to radio astronomy observations in those frequency ranges.
The Swedish Post and Telecom Authority (PTS) does not consider 3.4 GHz to be an amateur band, and has therefore auctioned it off for 5G test use. Temporary permits in the 3.400 - 3.401 GHz range are currently issued however.
The Ministerio de Asuntos Económicos y Transformación Digital does not allow 3.4 GHz to be used by amateurs. Currently this band is used by 5G services.