Repeaters
Repeaters extend the range of transmission by receiving and automatically rebroadcasting a transmission using an antenna located in a high location, normally the top of a mountain, tall building or radio tower. Sometimes a transmission range of over 100 kilometres can be achieved through the use of a repeater. The repeater function on a UHF CB radio is normally referred to as 'duplex' or a 'range extender' function.
Read more about this topic: UHF CB