Amateur radio frequency band
The 23 centimeter, 1200 MHz or 1.2 GHz band is a portion of the UHF (microwave) radio spectrum internationally allocated to amateur radio and amateur satellite use on a secondary basis. The amateur radio band is between 1240 MHz and 1300 MHz. The amateur satellite band is between 1260 MHz and 1270 MHz, and its use by satellite operations is only for up-links on a non-interference basis to other radio users (ITU footnote 5.282). The allocations are the same in all three ITU regions.
Most modes of communication used in amateur radio can be found in the 23 cm band. Some of the more common modes include voice, data, EME (moonbounce), as well as ATV.
History.
The 23cm band was born after the World War II, at the International Radio Conference celebrated in Atlantic City, in 1947. The band was defined from 1215 to 1300 MHz and was allocated exclusively for radio amateur use.
In the 1979 World Administrative Radio Conference held in Geneva (WARC-79), the band was reduced to 1240 - 1300 MHz and downgraded to secondary allocation for amateur use. The primary allocation to the radiolocation service has highest priority. 
Agenda Item AI-9.1b at the 2023 World Radio Conference (WRC-23) considered further constraints on 23cm to protect the Radio Navigation Satellite Service (RNSS), which is also a primary user of the band. RNSS systems include Glonass, Compass and Galileo which use this frequency range to supplement their more standard GNSS frequencies. 
In November 2023 ITU-R Recommendation M.2164 was published, giving guidance for amateur and amateur satellite usage.
List of notable frequencies.
Frequencies in the 23 cm band are harmonized by International Telecommunication Union region.
Region 3.
In 2008 the IARU Region-1 Cavtat Conference designated 1240.000-1240.750 MHz as an alternative centre for narrowband activity and beacons. This is a mitigation for sharing with existing aviation radars and Primary users, or for potential
issues with the European Galileo system.
References.
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