Uplink/downlink frequency applies to the usage of a radio repeater. The uplink frequency is used by the central station transmitter. For example, my central station transmitter transmits at 469.5000 MHz, which is the repeater's uplink frequency. That is the frequency that the repeater uses to receive.
The downlink frequency is 468.5000 MHz, which is the frequency that the repeater transmits on. My central station receiver receives at this frequency.
So you see, your transmitter uses the repeater's uplink (receive) frequency, and your receiver uses the repeater's downlink (transmit) frequency.
