The specific allocation is 1400 to 1427 MHz. It is reserved for radio astronomy (the hydrogen line is at 1420.4 MHz), passive (receive only) Earth exploration s

The specific allocation is 1400 to 1427 MHz. It is reserved for radio astronomy (the hydrogen line is at 1420.4 MHz), passive (receive only) Earth exploration satellites and passive space research. In the US, 1240 to 1400 MHz is allocated to radar. GNSS downlinks at 1240 to 1300 MHZ are not protected in the US.