How Do Radio Repeaters Work ?
Repeaters help with the problem of line of sight in conventional communications. If two radios want to communicate with a hilltop in the way, then there is no line of sight. One way to overcome this is placing a repeater (or base station) at the top of the hill. One radio communicates up to the repeater, this is called uplink, and then the repeater repeats that transmission down to the radio on the other side of the hill, this is called downlink.