Full-duplex repeaters transmit and receive simultaneously, requiring two separate frequency channels. The offset refers to the mathematical difference between the repeater's transmit (downlink) frequency and its receive (uplink) frequency.

Most repeaters follow a standardized band plan, which assigns predictable offset values. These offsets are often referred to simply by the shift, which can be either positive (+) or negative (-).

Some repeaters or nodes operate on a single simplex channel, where the transmit and receive frequencies are the same. This is designated with an “x”. If a repeater has a non-standard split or offset, it is noted with an “s”.

For “Rest of World” repeaters, offset designators are not used. Instead, repeater data includes both transmit and receive frequencies, and the offset is calculated and displayed automatically.