The Amateur Radio Service has secondary status to the primary radiolocation service. Domestically, Amateur Radio is afforded primary status in the 1800-1900 kHz segment. In ITU Region 1, the radiolocation service is exclusive in the segment 1800-1810 kHz. Amateur Radio is exclusive from 1810-1850 kHz. The segment 1850-2000 kHz is allocated to the fixed and mobile services with no amateur operation.
Radiolocation services are secondary.
Voluntary band plans have developed over time to provide coordination of the various operating activities. The ARRL recommends the segment 1800-1840 kHz for CW, RTTY, and narrow band modes. The 1840-2000 segment should be reserved for phone, CW, SSTV, and other wideband modes. From 1830-1850 kHz, only intercontinental QSO's should occur so your neighbor can work the DX without local interference. Voluntary cooperation with these recommendations aids all amateurs and helps keep the frustation level down.